JP2005333117A - Laser irradiation apparatus and method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser irradiation device which can irradiate laser light of a uniform energy density on an object to be irradiated without complicating an optical system. <P>SOLUTION: The laser device comprises: a laser oscillator; an optical system which repeatedly scans a beam spot formed by the laser light oscillated from the laser oscillator in one axis direction of the surface of the object to be irradiated; and a position control means which moves a position relative to the laser light of the object to be irradiated in the direction of crossing the one axis direction of the surface. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laser irradiation apparatus used for crystallization of a semiconductor film. Further, the present invention relates to a method for manufacturing a semiconductor device.

  A thin film transistor (TFT) using a polycrystalline semiconductor film has a mobility of two orders of magnitude higher than that of a TFT using an amorphous semiconductor film, and the pixel portion of a semiconductor display device and its peripheral drive circuit are formed on the same substrate. It has the advantage that it can be integrally formed. The polycrystalline semiconductor film can be formed over an inexpensive glass substrate by using a laser annealing method.

  Lasers are roughly classified into two types, pulse oscillation and continuous oscillation, depending on the oscillation method. A pulsed laser typified by an excimer laser has a laser beam energy output per unit time of about 3 to 6 digits higher than that of a continuous wave laser. Therefore, by shaping the beam spot (irradiation area where the laser beam is actually irradiated on the surface of the irradiated object) into a rectangular shape of several centimeters square or a linear shape with a length of 100 mm or more, by an optical system, The throughput of laser light irradiation can be increased. For this reason, it has become the mainstream to use a pulsed laser for crystallization of the semiconductor film.

  Here, “linear” does not mean “line” in a strict sense, but means a rectangle (or oval) having a large aspect ratio. For example, an aspect ratio of 2 or more (preferably 10 to 10000) is called a linear shape, but the linear shape is still included in a rectangular shape.

  However, the semiconductor film crystallized using pulsed laser light in this way is formed of a collection of a plurality of crystal grains whose positions and sizes are random. Unlike in the crystal grains, there are innumerable recombination centers and trap centers due to an amorphous structure, crystal defects, and the like at the interface (crystal grain boundary) of the crystal grains. When carriers are trapped in this trapping center, the grain boundary potential rises and becomes a barrier against the carriers, so that there is a problem that the carrier transport property is lowered.

  Against the background of the above problems, a technique related to crystallization of a semiconductor film using a continuous wave laser has attracted attention in recent years. In the case of a continuous wave laser, unlike a conventional pulsed laser, a semiconductor film is irradiated with laser light while scanning in one direction, and a crystal is continuously grown in the scanning direction. A collection of crystal grains made of a single crystal extending along the length can be formed.

  By the way, in order to increase the throughput of laser annealing, it is necessary to form a beam spot into a linear shape by an optical system even when using continuous wave laser light. What is important in the formation of the beam spot is how the energy density distribution in the long axis direction (also referred to as the long side direction) of the beam spot can be made uniform. This is because the distribution of energy density in the major axis direction affects the crystallinity of the semiconductor film crystallized by laser annealing, and thus affects the characteristics of the semiconductor element formed using the semiconductor film. . For example, when the energy density in the major axis direction of a beam spot has a Gaussian distribution, the characteristics of a semiconductor element formed using the beam spot also vary with a Gaussian distribution. Become. Therefore, in order to ensure the uniformity of the characteristics of the semiconductor element, it is desirable to make the energy density distribution in the major axis direction of the beam spot more uniform. In addition, the distribution of the energy density in the major axis direction of the beam spot has a merit that the beam spot can be elongated longer in the major axis direction and throughput can be improved.

  However, in order to make the energy density of the linear beam spot in the major axis direction uniform, it is necessary to use an optical system such as a cylindrical lens or a diffractive optical element. The optical system for making these energy densities uniform requires a sophisticated optical design in consideration of the wavefront and shape of the beam spot, so that there is a problem that adjustment is complicated.

Further, the crystallization of the semiconductor film can be performed more efficiently as the absorption coefficient of the laser beam with respect to the semiconductor film is larger. In the case of a YAG laser or a YVO ₄ laser, the second harmonic wave having a shorter wavelength than the fundamental wave has a much higher absorption coefficient for a silicon film with a film thickness of several tens to several hundreds nm that is usually used in a semiconductor device. Therefore, in general, laser crystallization of a semiconductor film in a manufacturing process of a semiconductor device uses harmonics and hardly uses a fundamental wave. Conversion from the fundamental wave to the harmonic can be performed by using a nonlinear optical element.

  However, since a continuous wave laser has a lower output of laser light per unit time than a pulsed laser, the density of photons with respect to time is also low, and thus the conversion efficiency to harmonics in a nonlinear optical element is low. Specifically, although depending on the mode characteristics and time characteristics of incident light, the conversion efficiency of a pulsed laser is about 10 to 30%, whereas the conversion efficiency of a continuous wave laser is 0.2 to 0. About 3%. Further, in the case of a continuous wave laser, since the load is continuously applied to the nonlinear optical element, there is a problem that the resistance of the nonlinear optical element to the laser beam is significantly lower than that of the pulsed laser.

Therefore, a continuous wave laser has a weaker laser beam output per unit time than a pulsed laser, and it is difficult to increase the beam spot area and increase the throughput. For example, a continuous wave YAG laser can output a fundamental wave of 10 kW, while a second harmonic output of only about 10 W can be obtained. In this case, in order to obtain an energy density necessary for crystallization of the semiconductor film, the area of the beam spot must be reduced to about 10 ⁻³ mm ² . As described above, the continuous wave laser has a lower throughput than the pulsed excimer laser, and this contributes to a decrease in economy in mass production.

  In view of the above-described problems, the present invention proposes a laser irradiation apparatus that can irradiate an irradiated body with a linear laser spot having a uniform energy density in the major axis direction without complicating the optical system. Is an issue. Another object of the present invention is to propose a laser irradiation apparatus capable of continuously growing crystal grains in a direction intersecting with the long axis of a linear beam spot. It is another object of the present invention to provide a laser irradiation apparatus that can improve the throughput of laser irradiation on an object to be irradiated.

  In addition, in view of the above-described problems, the present invention can irradiate a semiconductor film with a linear laser spot having a uniform energy density in the long axis direction without complicating the optical system. The proposal of Another object of the present invention is to propose a laser irradiation apparatus capable of continuously growing crystal grains in a direction intersecting with the long axis of a linear beam spot. Another object is to propose a method for manufacturing a semiconductor device, which can improve the throughput of laser irradiation on a semiconductor film.

  In one embodiment of the present invention, a laser beam oscillated from a laser oscillator is scanned at high speed in one axis direction using an optical system, and a pseudo linear beam spot (hereinafter referred to as a pseudo linear beam spot) is obtained. It is characterized by forming. In this specification, the pseudo-linear beam spot is a spot formed by scanning a laser beam on a line connecting the first point and the second point, and the first point is irradiated with the laser beam. This is a beam spot formed by scanning the laser beam on the second point before the melted region is solidified. That is, the region irradiated with the pseudo-linear beam spot is melted for a certain period of time as if irradiated with a linear beam.

  Then, the laser beam is scanned so as to trace a plurality of straight lines arranged at equal intervals one by one using an optical system or means for moving the position of the irradiated object relative to the optical system and the laser beam. The first quasi-linear beam spot and the second quasi-linear beam spot, which are formed by tracing adjacent straight lines out of a plurality of straight lines, are part of each other in the direction intersecting the long axis of the quasi-linear beam spot. To overlap. Further, before the irradiated object in the first pseudo-linear beam spot formed earlier is solidified, the laser beam is scanned to form a second pseudo-linear beam spot to be formed next. . As a result, the crystal grains of the irradiated object can be extended in the direction intersecting the long axis of the pseudo-linear beam.

  One form of the laser irradiation apparatus of the present invention includes a laser oscillator, an optical system that scans laser light oscillated from the laser oscillator so as to reciprocate on a straight line, and forms a quasi-linear beam spot, and a quasi-linear beam And means for moving the relative position of the irradiated object with respect to the laser beam in a direction crossing the long axis of the beam spot. A first irradiated region to be irradiated with the pseudo-linear beam spot, and a second irradiated region to be irradiated with the pseudo-linear beam spot after the first irradiated region is irradiated, The irradiated object is moved by the moving means so as to partially overlap, and the laser beam irradiated at the pseudo-linear beam spot is absorbed by the first irradiated object region, so that the first irradiated object region becomes Prior to melting and solidifying, the irradiation position of the pseudo-linear beam spot is moved from the first irradiated region to the second irradiated region by the moving means.

  In one embodiment of the laser irradiation apparatus of the present invention, a laser oscillator, an optical system that scans laser light oscillated from the laser oscillator so as to reciprocate on a straight line, and a relative position of an irradiated object with respect to the laser light are determined. And means for moving in a direction crossing the scanning direction of the laser beam. The optical system and the moving means scan the laser beam on the irradiated object so as to follow a wave shape or a sawtooth line, and the second direction change from the first turning point of the wave shape or the sawtooth line. When scanning to the third turning point via the point, when the first turning point is irradiated with the laser beam, and when the third turning point is irradiated with the laser beam The second beam spot is partially overlapped, and the laser beam is irradiated from the first turning point to the third beam before the irradiated laser beam is irradiated at the first beam spot and the irradiated object is solidified. It scans to a turning point.

  One embodiment of the laser irradiation apparatus of the present invention includes a laser oscillator and an optical system that scans laser light oscillated from the laser oscillator so as to trace a plurality of straight lines arranged at equal intervals one by one. A first pseudo-linear beam spot formed by scanning to trace the first straight line among the plurality of straight lines, and a second formed by scanning to trace the second straight line adjacent to the first straight line. The quasi-linear beam spot partially overlaps and forms a second quasi-linear beam spot by scanning the laser beam before the irradiated object in the first quasi-linear beam spot solidifies. It is characterized by doing.

  One embodiment of the laser irradiation apparatus of the present invention includes a laser oscillator and an optical system that scans laser light oscillated from the laser oscillator so as to trace a wave shape or a sawtooth line. The first beam centered on the first turning point when scanning from the first turning point of the wave shape or sawtooth line to the third turning point via the second turning point The laser beam is scanned so that the spot and the second beam spot centered on the third turning point partially overlap, and the laser beam is irradiated before the irradiated object in the first beam spot is solidified. The light is scanned from the first turning point to the third turning point.

  In one embodiment of a method for manufacturing a semiconductor device of the present invention, a first scan of laser light is performed along a first direction in order to melt a first region of a semiconductor film. In order to melt the second region of the film, the laser beam is scanned in the second direction along the second direction, the first region partially overlaps the second region, and the second scan is performed. During this time, at least a part of the first region is in a molten state.

  According to one embodiment of a method for manufacturing a semiconductor device of the present invention, a semiconductor film is scanned with a laser beam so as to trace a wave shape or a sawtooth line, and the first direction change point of the wave shape or the sawtooth line is changed. When scanning to the third turning point via the two turning points, the first beam spot centered on the first turning point and the second beam centering on the third turning point The laser beam is scanned from the first beam spot to the second beam spot before the beam spot partially overlaps and the semiconductor film portion irradiated by the first beam spot is solidified. It is characterized by.

  In one embodiment of the method for manufacturing a semiconductor device of the present invention, the semiconductor film is scanned with the laser light so as to trace a comb-like line, and the second and third lines are scanned from the first corner of the comb-like line. When scanning to the fourth corner via the corner, the first beam spot centered on the first corner and the second beam spot centered on the fourth corner are partially overlapped. In addition, the laser beam is scanned from the first beam spot to the second beam spot before the semiconductor film portion irradiated by the first beam spot is solidified.

  When the laser beam irradiation apparatus or the semiconductor device manufacturing method as described above is used, the solid-liquid interface can be continuously moved in one direction in the irradiated body.

  For example, in the case of a continuous wave laser beam, the time from when the semiconductor film is melted by laser beam irradiation until it is completely solidified is approximately 100 ns as described in Non-Patent Document 1. In this case, the quasi-linear beam spot may be formed by setting the scanning frequency of the laser beam in the uniaxial direction to 10 MHz or more. With the above configuration, before the melted region of the semiconductor film in the quasi-linear beam spot is completely solidified, the next quasi-linear beam spot is irradiated to the region partially overlapping with the melted region of the semiconductor film. The solid-liquid interface can be continuously moved in the direction intersecting with the long axis of the quasi-linear beam spot. As a result of continuously moving the solid-liquid interface, for example, a set of crystal grains having a width in the direction intersecting the major axis of the pseudo-linear beam spot of 10 to 30 μm and a width in the major axis direction of about 1 to 5 μm. Can be formed. Then, by forming single crystal grains that extend long along the direction intersecting the long axis of the quasi-linear beam spot, a TFT having few crystal grain boundaries that intersect with the direction in which carriers move is obtained. It becomes possible to form.

Surface Science Vol. 24, no. 6, pp. 375-382, 2003

  Note that the scanning frequency of the laser beam in the uniaxial direction for forming the quasi-linear beam spot ensures the total energy of the laser beam irradiated to an arbitrary point to such an extent that the semiconductor film can be melted. The upper limit should be decided so that it can be done.

  The laser beam used in the present invention is not limited to continuous oscillation. For example, the laser crystallization may be performed by setting the oscillation frequency of pulsed laser light to 100 MHz or more and using a frequency band significantly higher than a frequency band of several tens to several hundreds Hz that is normally used. It is said that the time from when the semiconductor film is irradiated with laser light by pulse oscillation until the semiconductor film is completely solidified is several tens to several hundred ns. Therefore, by setting the scanning frequency of the laser beam to several tens to several hundreds of MHz, the next pseudo linear beam spot can be obtained before the melted region of the semiconductor film in the pseudo linear beam spot is completely solidified. Can be irradiated to a region partially overlapping with the melted region of the semiconductor film. Therefore, since the solid-liquid interface can be continuously moved in the semiconductor film, a semiconductor film having crystal grains continuously grown in the direction intersecting with the long axis of the pseudo-linear beam spot is formed. . Specifically, a set of crystal grains having a width in the direction intersecting with the major axis of the quasi-linear beam spot of 10 to 30 μm and a width in the major axis direction of about 1 to 5 μm can be formed. By forming single crystal grains that extend long along the direction intersecting the long axis of the quasi-linear beam, a TFT having few crystal grain boundaries that intersect the direction in which carriers move is formed. It becomes possible.

  When a remarkably high oscillation frequency as described above is used, the pulse width is inevitably shortened to the order of ps (pico second) or less in accordance with the oscillation frequency. Accordingly, even if the laser beam is irradiated from a direction perpendicular to the substrate, a secondary effect that interference caused by light reflection on the back surface of the substrate can be suppressed can be obtained. Interference can be suppressed when the time during which the light returning to the semiconductor film after reciprocating on the glass substrate of about 1 mm and the light newly incident on the semiconductor film is mixed is a pulse width on the order of ps. This is because it can be significantly shortened. In a pulse oscillation laser using a normal oscillation frequency, the pulse width is 10 ns to several 100 ns, and the distance traveled by light during this period is about 3 m to 100 m. However, when using a significantly higher oscillation frequency, the pulse width is on the order of ps. For example, the distance traveled by light during a period of 10 ps is about 3 mm, and the distance is significantly shorter than that of a pulsed laser having a normal oscillation frequency. Therefore, the time in which the light returning to the semiconductor film after reciprocating on the glass substrate of about 1 mm and the light newly incident on the semiconductor film are mixed is short, and interference can be easily suppressed. Therefore, it is not necessary to irradiate the semiconductor film obliquely with respect to the semiconductor film in consideration of the influence of interference, and the laser light can be irradiated from a direction perpendicular to the substrate. Therefore, the optical design becomes easy and the energy distribution of the obtained beam spot can be made more uniform. In addition, when the laser beam is irradiated obliquely, it is difficult to perform uniform laser annealing because the irradiation condition of the laser beam changes depending on the scanning direction of the irradiated object. In this case, in order to perform uniform laser annealing, it is necessary to perform laser annealing only by scanning in one direction, and throughput must be sacrificed. However, when a remarkably high oscillation frequency is used, the laser beam can be irradiated vertically, so that the irradiation condition of the laser beam does not change depending on the scanning direction. Therefore, the uniformity of laser annealing is not impaired even if the irradiation object is scanned so as to reciprocate.

  Further, when crystallization is performed using a conventional pulsed laser, impurities such as oxygen, nitrogen, and carbon tend to segregate at the crystal grain boundaries. In particular, when crystallization using laser light and crystallization using a catalyst metal are combined, the catalyst metal that could not be gettered may be segregated. In the present invention, since the solid-liquid interface can be continuously moved, as in the zone melting method, segregation of impurities with a positive segregation coefficient can be prevented, and the semiconductor film can be purified and the solute concentration can be made uniform. it can. Therefore, characteristics of a semiconductor element using the semiconductor film can be improved and variation in characteristics can be suppressed.

In the present invention, a continuous wave gas laser or solid state laser can be used. Examples of gas lasers include Ar laser and Kr laser, and solid-state lasers include YAG laser, YVO ₄ laser, YLF laser, YAlO ₃ laser, Y ₂ O ₃ laser, glass laser, ruby laser, alexandrite laser, and Ti: sapphire laser. Etc.

In the present invention, a laser capable of pulse oscillation at a frequency of 100 MHz or more can be used. If oscillation at the above frequency is possible, Ar laser, Kr laser, excimer laser, CO ₂ laser, YAG laser, Y ₂ O ₃ laser, YVO ₄ laser, YLF laser, YAlO ₃ laser, glass laser, ruby laser Alexandrite laser, Ti: sapphire laser, copper vapor laser or gold vapor laser can be used.

  Note that the method for manufacturing a semiconductor device of the present invention can be used for a method for manufacturing an integrated circuit or a semiconductor display device. Examples of the semiconductor display device include a liquid crystal display device, a light emitting device including a light emitting element represented by an organic light emitting element in each pixel, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display), and the like. Can be mentioned.

  Conventionally, when a linear beam spot is formed using only an optical system, there has been a limit to uniform energy distribution in the major axis direction in the beam spot. In the case of the present invention, the quasi-linear beam spot is formed by scanning the beam spot at high speed in one axis direction so that adjacent spots overlap each other. Therefore, the energy distribution in the major axis direction of the quasi-linear beam spot can be made more uniform without complicating the optical system than in the case of the conventional linear beam spot. Therefore, the crystallinity of the semiconductor film in the major axis direction of the quasi-linear beam spot can be made more uniform, and variations in characteristics of semiconductor elements formed using the semiconductor film can be suppressed.

  In addition, when there is a limit to the uniform energy distribution in the long axis direction as in the prior art, it becomes difficult to extend the linear beam spot longer in the long axis direction, which hinders improvement in throughput. In the case of the present invention, the width of the quasi-linear beam spot in the major axis direction is further increased by increasing the scanning speed of the laser beam in the major axis direction while ensuring the total energy of the laser beam irradiated to an arbitrary point. Can be long. Therefore, the throughput of laser irradiation can be further increased without complicating the optical system.

  Further, when forming a linear beam spot as in the prior art, it is necessary to use a cylindrical lens as an optical system for condensing laser light. In the present invention, the beam spot for forming the quasi-linear beam spot may have a circular shape. When a circular beam spot is used, a spherical lens can be used as an optical system for condensing laser light. Since the spherical lens is generally more accurate than the cylindrical lens, it is possible to form a beam spot having a higher energy density and a shorter diameter. Therefore, in the present invention, the width in the minor axis direction of the pseudo-linear beam spot can be shortened and the width in the major axis direction can be made longer than in the case of the conventional linear beam spot. Can be further enhanced.

  Further, by continuously moving the solid-liquid interface in the direction intersecting with the long axis of the quasi-linear beam spot, large crystal grains can be formed. Accordingly, since at least one islanded semiconductor film can be formed within one crystal grain size, a carrier is not trapped at a crystal grain boundary, and a semiconductor device in which carrier transport characteristics are not deteriorated can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different modes, and those skilled in the art can easily understand that the modes and details can be variously changed without departing from the spirit and scope of the present invention. Is done. Therefore, the present invention is not construed as being limited to the description of this embodiment mode. In addition, the shape of the beam spot in the following embodiments and examples is not limited to a circle, and may be an ellipse or a square.

(Embodiment 1)
First, the formation of the quasi-linear beam spot used in the present invention will be described with reference to FIG. FIG. 1A shows a state in which a quasi-linear beam spot 100 is formed by scanning a laser beam spot 101 in a uniaxial direction or linearly as indicated by a solid arrow. .

  In FIG. 1A, the quasi-linear beam spot 100 is formed by scanning the beam spot 101 so as to reciprocate. However, the present invention is not limited to this configuration, and the quasi-linear beam spot 100 may be formed by scanning the beam spot 101 only in one direction. FIG. 1A shows a state in which the beam spot 101 is scanned from left to right in FIG. 1A and then scanned again from right to left. However, the present invention is limited to this configuration. Not. In the present invention, the beam spot 101 only needs to be scanned at least once at an arbitrary point in the pseudo-linear beam spot 100.

  For example, when the irradiated object is a semiconductor film, the beam spot 101 may be irradiated again with a laser beam until an arbitrary point of the semiconductor film melted by the laser beam irradiation is completely solidified. Make it as fast as possible. That is, in the case of FIG. 1A, the beam spot 101 is scanned at the left end in the uniaxial direction before the region melted by the beam spot 101 at the right end in the uniaxial direction in the pseudo-linear beam spot 100 is not completely solidified. Thus, the scanning speed of the beam spot 101 may be set. By doing so, it is possible to form a quasi-linear beam spot that is melted linearly for a certain period of time.

  Further, when forming a quasi-linear beam spot with a pulse oscillation beam spot, scanning is performed so that adjacent beam spots overlap each other.

  The scanning speed of the laser light in the uniaxial direction is such that the total energy of the laser light irradiated to any one point can be secured to such an extent that the semiconductor film can be melted.

  In this embodiment, an example is shown in which the quasi-linear beam spot 100 is formed by scanning the beam spot 101 only in one axis direction, but the present invention is not limited to this configuration. As a result, if the pseudo-linear beam spot 100 can be formed, the beam spot may be scanned in two or more directions.

  In the present invention, the quasi-linear beam spot 100 is further scanned in a direction crossing the uniaxial direction, in other words, in a direction crossing the long axis of the quasi-linear beam spot 100. In FIG. 1B, the quasi-linear beam spot 100 shown in FIG. 1A is scanned in the direction intersecting the long axis as indicated by the dashed arrow to form the quasi-linear beam spot 103. It shows how it is doing.

  The region in the quasi-linear beam spot 100 is in a state where the semiconductor film is not completely solidified. Therefore, before the semiconductor film irradiated with the quasi-linear beam spot 100 is solidified, the semiconductor film is irradiated with the quasi-linear beam spot 103 that partially overlaps the quasi-linear beam spot 100. Can move the solid-liquid interface continuously.

  FIG. 1C shows a state in which the above operation is repeated and the semiconductor film is crystallized. In FIG. 1C, the laser beam spot 101 is scanned so as to trace a plurality of straight lines facing each other at equal intervals as indicated by arrows, and the semiconductor film 102 which is an object to be irradiated is crystallized. To do. At this time, a quasi-linear beam spot 100 formed so as to trace a certain straight line and a quasi-linear beam spot 103 formed so as to trace the next straight line are partially separated as shown in FIG. The quasi-linear beam spot is scanned so as to overlap each other. As a result, single crystal grains extending long along the scanning direction indicated by the broken arrow can be formed. Specifically, the regions along one long side of each of the pseudo-linear beam spot 100 and the pseudo-linear beam spot 103 are overlapped.

  The scanning speed of the laser light is set to a speed at which the pseudo linear beam spot 103 can be formed before the irradiated object irradiated with the laser light in the pseudo linear beam spot 100 is solidified. More precisely, among the plurality of beam spots for forming the pseudo-linear beam spot 100, the pseudo-linear beam spot 103 is formed before the irradiated region melted at any beam spot is solidified. One of a plurality of beam spots is irradiated so as to overlap the irradiated object region. By carrying out like this, the crystal grain of a to-be-irradiated body can be made to grow continuously to one direction, and a large grain size can be formed.

  The time required for the silicon to be solidified by irradiation with the laser is about 100 ns. Therefore, when the irradiated object is silicon, the pseudo-linear beam spot 103 is preferably formed within 100 ns after the pseudo-linear beam spot 100 starts to be formed.

  Next, the structure of the laser irradiation apparatus of this invention is demonstrated. FIG. 2 shows an embodiment of the laser irradiation apparatus of the present invention. 2 includes a laser oscillator 201, a condensing optical system 202, a mirror 203, an acoustooptic element 204, an fθ lens 205, a stage 206, an X-axis direction position control unit 209, Y-axis direction position control means 210.

As the laser oscillator 201, an oscillator that can continuously oscillate laser light or an oscillator that can oscillate laser light at a frequency of 100 MHz or more can be used. In this embodiment, it is assumed that, for example, a continuous wave YVO ₄ laser with an output of 10 W is used, and a laser beam having a circular shape with a cross section of 1 mm in diameter is oscillated from the laser oscillator 201.

  The laser light oscillated from the laser oscillator 201 enters the condensing optical system 202. The condensing optical system 202 only needs to be an optical system that can condense laser light. For example, a spherical lens or a Fresnel lens can be used. In the present embodiment, it is assumed that in the condensing optical system 202, the circular cross section of the laser beam is reduced from 1 mm to 0.1 mm in diameter. The laser beam condensed by the condensing optical system 202 is reflected by the mirror 203 and enters the acoustooptic device 204.

  The acoustooptic device 204 periodically modulates the refractive index by applying a sound wave having a high frequency such as an ultrasonic wave, so that the incident laser light can be deflected at a high period in GHz. Therefore, by using the acoustooptic device 204, it becomes possible to repeatedly scan the beam spot in a uniaxial direction with a high period. In this embodiment, an acousto-optic element is used as an optical system for repeatedly scanning a beam spot in one axis direction, but the present invention is not limited to this configuration. Any optical system that can repeatedly scan a beam spot in a uniaxial direction with a high period may be used. For example, a polygon mirror or a resonant scanner can be used.

  The laser beam deflected by the acoustooptic device 204 is incident on the fθ lens 205. The fθ lens 205 can collect the deflected laser light so as to always focus on the irradiated object. The stage 206 can place an object to be irradiated. FIG. 2 shows an example in which a semiconductor film 208 formed over a substrate 207 is used as an object to be irradiated. The laser beam is focused on the semiconductor film 208 placed on the stage 206 by the fθ lens 205, so that a beam spot periodically scanned in the uniaxial direction can be formed. The locus of the beam spot periodically scanned in the uniaxial direction is shown as a quasi-linear beam spot 211 in FIG.

  A process in which the quasi-linear beam spot 211 is formed by the laser light deflected by the acoustooptic device 204 will be described with reference to FIG. 3A to 3C are diagrams in which the laser beam deflected by the acoustooptic device 204 and the fθ lens 205 illustrated in FIG. As shown in FIGS. 3A to 3C, the laser beam indicated by the solid line arrow is deflected by the acousto-optic element 204, condensed by the fθ lens 205, and focused on the semiconductor film 208. It is out.

  If it is assumed that the refractive index of the acoustooptic device 204 is modulated in the order of FIGS. 3A, 3B, and 3C, the laser light is directed toward the deflection direction indicated by the white arrow. Deflected. Along with the deflection of the laser beam, a region in the semiconductor film 208 where the laser beam is focused, that is, a beam spot, is scanned in a uniaxial direction.

  In the pseudo-linear beam spot 211, it is necessary that the semiconductor film 208 is not completely solidified. Therefore, it is necessary to scan the beam spot in a uniaxial direction at a speed satisfying the above condition. . In the case of the laser irradiation apparatus shown in FIG. 2, the scanning speed in the uniaxial direction of the beam spot can be controlled by the frequency of the sound wave applied to the acoustooptic device 204.

  In the present embodiment, it is assumed that the refractive index in the acoustooptic device 204 is modulated with a period of 80 MHz. Further, in this embodiment, it is assumed that a beam spot having a diameter of 5 μm is formed on the surface of the semiconductor film 208 by the fθ lens 205. When the quasi-linear beam spot 211 is formed under the above conditions, the width of the quasi-linear beam spot 211 in the minor axis direction can be 5 μm, and the width in the uniaxial direction, that is, the major axis direction can be about 400 μm.

  In the laser irradiation apparatus shown in FIG. 2, the X-axis direction position control means 209 that can move the position of the stage 206 in the X-axis direction is used to cross the quasi-linear beam spot 211 in a direction intersecting the uniaxial direction ( It is possible to scan in the direction intersecting the long axis of the quasi-linear beam spot. That is, the relative position of the irradiated object with respect to the laser light can be moved in the direction indicated by the dashed arrow in FIG. The moving speed of the X-axis direction position control means 209 is much slower than the scanning speed of the beam spot 101 in the uniaxial direction. Thereby, scanning as shown in FIG. 1C is realized. The X-axis direction position control means 209 moves the stage 206 at a constant speed in a direction crossing the long axis of the pseudo-linear beam spot. In addition, the laser irradiation apparatus shown in FIG. 2 further includes Y-axis direction position control means 210 that can move the position of the stage 206 in the Y-axis direction orthogonal to the X-axis direction.

  In FIG. 2, the relative position of the quasi-linear beam spot 211 with respect to the stage 206 is controlled using two position control means, that is, an X-axis direction position control means 209 and a Y-axis direction position control means 210. The present invention is not limited to this configuration. The laser irradiation apparatus of the present invention only needs to have at least the X-axis direction position control means 209. In addition to the X-axis direction position control unit 209, the stage 206 may have a position control unit that can rotate in a plane including the stage 206.

  In this embodiment, the acousto-optic element 204 and at least the X-axis direction position control means 209 are used to scan the laser light so as to trace a plurality of straight lines arranged at equal intervals as shown in FIG. Crystallize 208.

  In the present embodiment, the stage 206 is scanned in the X-axis direction at a scanning speed of, for example, 100 mm / s or more using the X-axis direction position control means 209. When it is desired to irradiate the entire surface of the semiconductor film 208 with laser light, the pseudo-linear beam spot 211 is scanned in the major axis direction using the Y-axis direction position control unit 210, and again using the X-axis direction position control unit 209. The operation of scanning the quasi-linear beam spot 211 in the X-axis direction may be repeated. Further, the position of the quasi-linear beam spot 211 with respect to the stage 206 may be controlled by moving the optical system itself. In that case, it is not necessary to move the stage, and the optical system indicated by 201 to 205 in FIG. 2 may be moved in the X-axis direction and the Y-axis direction.

  Note that in the case of using an oscillator that can oscillate laser light as the laser oscillator 201, the length of the pseudo-linear beam spot 211 in the major axis direction is limited by the frequency of pulse oscillation. Therefore, the quasi-linear beam spot 211 needs to be designed in consideration of the frequency of pulse oscillation. Specifically, the diameter of the beam spot formed on the surface of the irradiated object is d [μm] in the uniaxial direction, the width of the quasi-linear beam spot 211 in the uniaxial direction is L [μm], and If the deflection cycle is f [MHz], the pulse oscillation frequency F [MHz] may satisfy the following equation (1).

  For example, if the diameter d in the uniaxial direction of the beam spot is 10 μm, the width L in the uniaxial direction of the quasi-linear beam spot 211 is 200 μm, and the deflection period f of the acoustooptic device 204 is 10 MHz, It can be seen that the frequency F should be 400 MHz or higher.

  In the laser irradiation apparatus shown in FIG. 2, the condensing optical system 202 is not necessarily required. However, by using the condensing optical system 202, the size of the cross section of the laser light incident on the acoustooptic element 204 can be suppressed, and thus a smaller acoustooptic element 204 can be used. An optical system such as the mirror 203 for deflecting the optical path of the laser light is not essential, and may be provided as needed. Further, although the fθ lens 205 is not necessarily required, the speed and size of the beam spot scanned in the uniaxial direction in the pseudo-linear beam spot 211 can be made constant by using the above optical system.

  Further, the optical system used in the laser irradiation apparatus of the present invention is not limited to that shown in FIG. 2, and a designer may appropriately add an appropriate optical system as necessary.

(Embodiment 2)
In this embodiment mode, a laser beam scanning method different from that in Embodiment Mode 1 is described with reference to FIG. Therefore, the second embodiment is the same as the first embodiment except for the laser beam scanning method. The laser irradiation apparatus shown in FIG. 2 is used.

  In FIG. 11, reference numerals 1101 and 1102 denote quasi-linear beam spots, 1103 and 1104 denote beam spots, and 1105 denotes a semiconductor film which is an object to be irradiated. Also in the scanning of the beam spot shown in FIG. 11, a pseudo linear beam spot is formed as in the first embodiment. Similarly to the first embodiment, the quasi-linear beam spot is also a region along one long side of each quasi-linear beam spot 1101 and the next quasi-linear beam spot 1102 formed subsequently. Are scanned so that they overlap each other.

  In FIG. 11A, the laser beam is scanned so as to follow a sawtooth line or in a jagged manner. In FIG. 11B, the laser beam is scanned so as to trace a wavy line, and in FIG. 11C, the laser beam is scanned so as to trace a comb-like line. As shown in FIGS. 11A and 11B, when the laser beam is scanned in a jagged or wavy shape, the portions that become both ends of the pseudo-linear beam spot are hereinafter referred to as turning points. 11A and 11B, when the quasi-linear beam spots 1101 and 1102 are partially overlapped, the beam spot 1103 centered on a certain turning point and the next next turning point are centered. If the beam spot 1104 to be partially overlapped, the quasi-linear beam spots 1101 and 1102 naturally overlap each other. In FIG. 11B, there is no arrow at the turning point of the wavy line, and there is only an arrow just before the turning point. However, in practice, the quasi-linear beam spot is formed by reciprocating the laser beam between the turning point of the wave-shaped line and the next turning point.

  FIG. 11C shows a modification of the scanning method shown in FIG. In FIG. 1C, the beam spot 101 is not scanned after the pseudo linear beam spot 100 is formed and before the pseudo linear beam spot 103 is formed. On the other hand, FIG. 11C illustrates an example in which the irradiated object is continuously irradiated with laser light even after the pseudo linear beam spot 1101 is formed and before the pseudo linear beam spot 1102 is formed. In order to make the distribution of energy density irradiated to the semiconductor film 1105 uniform with the scanning method of FIG. 11C, the scanning speed is increased or the output of the laser beam is weakened at both ends of the pseudo-linear beam spot. . By doing so, the total energy of the laser light absorbed at both ends of the pseudo-linear beam spot can be made the same level as the region irradiated with the other laser light.

  In the case of the scanning method shown in FIGS. 11A and 11B, at least once, from the turning point that is the center of the beam spot 1103, the direction that is the center of the beam spot 1104 through one turning point. The laser beam is scanned up to the turning point. Therefore, in order to continuously grow crystal grains in a direction intersecting with the long axis of the quasi-linear beam spot, the laser beam is scanned to the beam spot 1104 before the semiconductor film 1105 irradiated with the beam spot 1103 is solidified. do it. Then, as a result, the pseudo-linear beam spot 1102 can be formed before the irradiated object irradiated at the pseudo-linear beam spot 1101 is solidified, and is fixed in the direction intersecting the long axis of the pseudo-linear beam spot. The liquid interface can be moved. That is, a crystal having a large grain size can be formed.

  In the case of FIG. 11C, the comb that is the center of the beam spot 1104 passes through the second and third corners from the first corner of the comb-like line that is the center of the beam spot 1103. The laser beam is scanned up to the fourth corner of the tooth-like line. Therefore, in order to continuously grow crystal grains in a direction intersecting with the long axis of the quasi-linear beam spot, the laser beam is scanned to the beam spot 1104 before the semiconductor film 1105 irradiated with the beam spot 1103 is solidified. do it. Then, as a result, the pseudo-linear beam spot 1102 can be formed before the irradiated object irradiated with the pseudo-linear beam spot 1101 is solidified, and is fixed in the direction intersecting the long axis of the pseudo-linear beam spot. The liquid interface can be moved. That is, a crystal having a large grain size can be formed.

  In addition, the quasi-linear beam spot 1101 is irradiated with the laser beam 1103 the earliest. On the other hand, in the quasi-linear beam spot 1102, the beam spot 1104 is irradiated with the laser beam the latest. Therefore, in order to continuously grow crystal grains in a direction intersecting with the long axis of the quasi-linear beam spot, the laser beam is scanned to the beam spot 1104 before the semiconductor film 1105 irradiated with the beam spot 1103 is solidified. do it. Then, as a result, the pseudo-linear beam spot 1102 can be formed before the irradiated object irradiated with the laser beam in the pseudo-linear beam spot 1101 is solidified, and intersects the long axis of the pseudo-linear beam spot. The solid-liquid interface can be moved in the direction. That is, a crystal having a large grain size can be formed.

  The scanning method shown in FIG. 11 can be realized by moving the acoustooptic device 204 and the X-axis direction position control means 209 in FIG. 2 with good timing. The acoustooptic device 204 deflects light at a constant period. Various scans as shown in FIG. 11 can be performed by moving the X-axis direction position control means in accordance with a certain period of the acousto-optic element 204. The scanning method shown in FIGS. 11A and 11B is performed by moving the stage with X-axis direction position control means while scanning the laser light with the acousto-optic element. Further, the scanning method of FIG. 11C is performed by moving the stage with the X-axis direction position control means when the laser beam is positioned at the end of the pseudo-linear beam spot.

(Embodiment 3)
Next, another embodiment of the present invention will be described.

  First, the formation of the quasi-linear beam spot used in the present invention will be described with reference to FIG. FIG. 4A shows a state in which a pseudo linear beam spot 300 is formed by scanning a laser beam spot 301 in one direction as indicated by a solid arrow.

  FIG. 4A shows a state in which the beam spot 301 is scanned only in one direction to form a quasi-linear beam spot 300, unlike the case of the first embodiment. As shown in FIG. 4A, by scanning the beam spot 301 only in one direction, the total time during which the laser beam is irradiated is made uniform at any one point in the pseudo-linear beam spot 300. Can do. 4A shows a state in which the beam spot 301 is scanned from the left to the right in FIG. 4A, the present invention is not limited to this configuration. In the present invention, the beam spot 301 only needs to be scanned at least once at an arbitrary point in the pseudo-linear beam spot 300.

  In the case of FIG. 4A, the scanning speed of the beam spot 301 is such that the region melted by the beam spot 301 at the left end in the uniaxial direction in the pseudo-linear beam spot 300 is not solidified completely. The scanning speed of the beam spot 301 may be set so that the beam spot 301 is scanned at the right end.

  Also in this embodiment, similarly to Embodiment 1, the scanning speed of the laser light in one direction is set so that the total energy of the laser light applied to any one point is such that the semiconductor film can be melted. It is assumed that it can be secured.

  Note that in this embodiment mode, an example is shown in which the quasi-linear beam spot 300 is formed by scanning the beam spot 301 only in one direction, but the present invention is not limited to this configuration. As a result, if the quasi-linear beam spot 300 can be formed, the beam spot may be scanned in two or more directions.

  The quasi-linear beam spot 300 is further scanned in a direction intersecting with one direction, in other words, in a direction intersecting with the long axis of the quasi-linear beam spot 300. In FIG. 4B, the quasi-linear beam spot 300 shown in FIG. 4A is scanned in the direction intersecting with the long axis of the quasi-linear beam spot 300 as indicated by the dashed arrow, and the quasi-linear beam spot 300 is scanned. A mode that the linear beam spot 303 is formed is shown.

  The region in the quasi-linear beam spot 300 is in a state where the semiconductor film is melted without being completely solidified. Therefore, the semiconductor film is irradiated with the quasi-linear beam spot 303 before the quasi-linear beam spot 300 is irradiated and the semiconductor film is solidified, whereby the solid-liquid interface can be continuously moved in the semiconductor film. it can. At this time, the pseudo-linear beam spots 300 and 303 are made to partially overlap.

  FIG. 4C and FIG. 12 show how the semiconductor film is crystallized by repeating the above operation. While the laser beam spot 301 is scanned so as to trace a plurality of straight lines facing each other at equal intervals, the semiconductor film 302 that is an object to be irradiated is crystallized by the laser light. At this time, as shown in FIG. 4B, the pseudo-linear beam spot 300 and the subsequently formed pseudo-linear beam spot 303 are partially overlapped with each other, and further irradiated with the pseudo-linear beam spot 300. Before the irradiated object is solidified, a quasi-linear beam spot 303 is formed. As a result, single crystal grains extending long along the scanning direction indicated by the broken arrow can be formed. Specifically, in adjacent quasi-linear beam spots, regions along one long side of each quasi-linear beam spot are overlapped. When the irradiated object is silicon, the solidification time of silicon is about 100 ns, so that the quasi-linear beam spot 303 is formed within 100 ns after the quasi-linear beam spot 300 starts to be formed.

  FIG. 12 shows various laser beam scanning methods. 12A traces a sawtooth or jagged line, FIG. 12B traces a wavy line, and FIG. 12C traces a comb-shaped line. Scan the light. Also at this time, as in FIG. 4C, a certain quasi-linear beam spot 1201 and the next quasi-linear beam spot 1202 are partially overlapped, and the object irradiated with the quasi-linear beam spot 1201 is also overlapped. The quasi-linear beam spot 1202 is formed before the irradiated portion is solidified.

  When the pseudo-linear beam spots 1201 and 1202 are partially overlapped by the scanning method of FIGS. 12A and 12B, the beam spot 1203 centered on a certain turning point and the next next direction If the beam spot 1204 centering on the turning point is partially overlapped, the quasi-linear beam spots 1201 and 1202 partially overlap naturally.

  FIG. 12C is a modification of FIG. 4C, in which the irradiated object is irradiated with laser light during the formation of the pseudo linear beam spot 1201 after the pseudo linear beam spot 1201 is formed. It is. In order to make the distribution of energy density irradiated to the semiconductor film 1205 uniform by the scanning method of FIG. 12C, the scanning speed is increased or the output of the laser beam is weakened at both ends of the quasi-linear beam spot. . By doing so, the laser energy absorbed at both ends of the quasi-linear beam spot can be made comparable to the region irradiated with the other laser light.

  In the pseudo-linear beam spot 1201, the beam spot 1203 is irradiated with the laser beam earliest. On the other hand, in the quasi-linear beam spot 1202, the laser beam 1204 is irradiated with the latest laser beam. Specifically, in FIGS. 12A and 12B, the laser beam passes from a turning point that is the center of the beam spot 1203 to a turning point that is the center of the beam spot 1204 through one turning point. Is scanned. In the case of FIG. 12C, from one corner of the comb-like line that is the center of the beam spot 1203 to the corner of the comb-like line that is the center of the beam spot 1204 via the two corners. The laser beam is scanned. Therefore, in order to continuously grow crystal grains in the direction intersecting with the long axis of the quasi-linear beam spot, the laser beam is scanned to the beam spot 1204 before the semiconductor film 1205 irradiated with the beam spot 1203 is solidified. do it. Then, as a result, the pseudo-linear beam spot 1202 can be formed before the irradiated object irradiated with the pseudo-linear beam spot 1201 is solidified, and a crystal having a large grain size can be formed.

  The time from the irradiation of the laser light to the solidification of silicon is about 100 ns. Therefore, when the semiconductor film 1205 that is an irradiation object is silicon, the laser beam may be scanned to the beam spot 1204 within 100 ns after the irradiation with the beam spot 1203.

  Next, the structure of the laser irradiation apparatus of this Embodiment is demonstrated. FIG. 5 shows one mode of a laser irradiation apparatus of this embodiment mode. The laser irradiation apparatus shown in FIG. 5 includes a laser oscillator 401, a condensing optical system 402, a polygon mirror 403, an fθ lens 404, a stage 405, an X-axis direction position control unit 408, and a Y-axis direction position control. Means 409.

  As the laser oscillator 401, as in Embodiment 1, an oscillator that can continuously oscillate laser light or an oscillator that can oscillate laser light at a frequency of 100 MHz or more can be used. The laser light oscillated from the laser oscillator 401 enters the condensing optical system 402. The condensing optical system 402 only needs to be an optical system that can condense laser light, as in the case of the first embodiment. For example, a spherical lens or a Fresnel lens can be used. The laser beam condensed by the condensing optical system 402 enters the polygon mirror 403.

  Since the polygon mirror 403 is a rotating body having a series of planar reflecting surfaces around it, the incident laser light can be repeatedly deflected in the same direction. Therefore, by using the polygon mirror 403, it becomes possible to repeatedly scan the beam spot in a uniaxial direction with a high frequency.

  The laser beam deflected by the polygon mirror 403 enters the fθ lens 404. The fθ lens 404 can collect the deflected laser light so as to always focus on the irradiated object. The stage 405 can place an irradiated object. FIG. 5 shows an example in which a semiconductor film 407 formed over a substrate 406 is used as an irradiation object. A laser beam is focused on the semiconductor film 407 placed on the stage 405 by the fθ lens 404, so that a quasi-linear beam spot periodically scanned in the uniaxial direction can be formed. The locus of the beam spot periodically scanned in the uniaxial direction is shown as a quasi-linear beam spot 410 in FIG.

  A process in which a quasi-linear beam spot 410 is formed by the laser light deflected by the polygon mirror 403 will be described with reference to FIG. 6A to 6C are diagrams in which the laser light deflected by the polygon mirror 403 and the fθ lens 404 shown in FIG. 5 is scanned over the semiconductor film 407. As shown in FIGS. 6A to 6C, the laser beam indicated by the solid line arrow is deflected by the polygon mirror 403, condensed by the fθ lens 404, and focused on the semiconductor film 407. Yes.

  Then, when the polygon mirror 403 is rotated in the order of FIG. 6A, FIG. 6B, and FIG. 6C, the angle of one reflecting surface 411 of the polygon mirror 403 changes, and the laser light is outlined. It is deflected in the deflection direction indicated by the arrow. Along with the deflection of the laser beam, a region where the laser beam is focused on the semiconductor film 407, that is, a beam spot is scanned in a uniaxial direction. As the rotation of the polygon mirror 403 proceeds, the laser beam is deflected on the next reflecting surface connected to the reflecting surface 411, so that the beam spot can be repeatedly scanned in the same direction. is there.

  In the pseudo-linear beam spot 410, the semiconductor film 407 needs to be in a state of not being completely solidified. Therefore, the beam spot needs to be scanned in a uniaxial direction at a speed satisfying the above conditions. . In the case of the laser irradiation apparatus shown in FIG. 5, the scanning speed in the uniaxial direction of the beam spot can be controlled by the rotation period of the polygon mirror 403. Further, the length of the pseudo linear beam spot 410 in the major axis direction can be controlled by the width of the reflecting surface 411 of the polygon mirror 403 in the rotation direction.

  In the laser irradiation apparatus shown in FIG. 5, the quasi-linear beam spot 410 is intersected with the uniaxial direction by using the X-axis direction position control means 408 that can move the position of the stage 405 in the X-axis direction ( It is possible to scan in the direction intersecting the long axis of the quasi-linear beam spot. The moving speed of the X-axis direction position control means 408 is much slower than the scanning speed of the beam spot 301 in the uniaxial direction. For this reason, scanning as shown in FIG. 4C is realized. The X-axis direction position control means 408 moves at a constant speed in a direction crossing the long axis of the pseudo-linear beam spot. Thereby, a crystal having a large grain size can be formed. In addition, while the quasi-linear beam spot is formed, the scanning method shown in FIGS. 12B and 12C is enabled by moving the stage in the X-axis direction. Further, the laser irradiation apparatus shown in FIG. 5 further includes Y-axis direction position control means 409 that can move the position of the stage 405 in the Y-axis direction perpendicular to the X-axis direction.

  In FIG. 5, the relative position of the quasi-linear beam spot 410 with respect to the stage 405 is controlled using two position control means, that is, an X-axis direction position control means 408 and a Y-axis direction position control means 409. The present invention is not limited to this configuration. The laser irradiation apparatus of the present invention only needs to have at least the X-axis direction position control means 408. In addition to the X-axis direction position control means 408, a position control means that can rotate the stage 405 in a plane including the stage 405 may be provided.

  When it is desired to irradiate the entire surface of the semiconductor film 407 with a laser beam, the pseudo linear beam spot 410 is scanned in the X-axis direction using the X-axis direction position control means 408 and then simulated using the Y-axis direction position control means 409. The operation of scanning the linear beam spot 410 in the major axis direction may be repeated. Further, the position of the quasi-linear beam spot 410 with respect to the stage 405 may be controlled by moving the optical system itself. In that case, it is not necessary to move the stage, and the optical system indicated by 401 to 404 may be moved in the X-axis direction and the Y-axis direction.

  Note that in the case of using an oscillator that can oscillate laser light as the laser oscillator 401, the length of the quasi-linear beam spot 410 in the major axis direction is limited by the frequency of pulse oscillation. Therefore, the pseudo-linear beam spot 410 needs to be designed in consideration of the frequency of pulse oscillation. Specifically, as in the case of the first embodiment, the pulse oscillation frequency may satisfy the above-described equation (1). Note that f in the equation is the period of deflection in the acoustooptic device 204 in the first embodiment, but is the period of rotation of the polygon mirror in this embodiment.

  In the laser irradiation apparatus shown in FIG. 5, the condensing optical system 402 is not necessarily required. However, by using the condensing optical system 402, a pseudo-linear beam spot 410 having a shorter width in the short axis direction and a longer width in the long axis direction can be formed, and throughput can be improved. . In addition, an optical system for changing the optical path of the laser beam, such as a mirror, is not essential, and may be provided as appropriate. Further, although the fθ lens 404 is not always necessary, the speed and size of the beam spot scanned in the uniaxial direction in the pseudo-linear beam spot 410 can be made constant by using the above optical system.

  Further, the optical system used in the laser irradiation apparatus of the present invention is not limited to that shown in FIG. 5, and a designer may add and use an appropriate optical system as necessary.

  This embodiment can be combined with Embodiments 1 and 2 as far as practicable.

(Embodiment 4)
In the first to third embodiments, the laser beam is scanned linearly using an optical system, and the stage is moved in a direction intersecting the scanning direction of the laser beam, thereby two-dimensionally lasering the irradiated object. The form which irradiates light was demonstrated. In this embodiment, an example in which a laser beam is scanned two-dimensionally on an irradiated object using only an optical system without using a means for moving the stage is given.

  FIG. 13 shows a laser irradiation apparatus of this embodiment mode. The laser irradiation apparatus includes a laser oscillator 1301, a condensing optical system 1302, a first deflection optical system 1311, a second deflection optical system 1303, and an fθ lens 1304. The first deflecting optical system and the second deflecting optical system may be any optical system that can repeatedly scan a laser beam in one direction with a high period. For example, a polygon mirror, a resonant scanner, and an acousto-optic element may be used. is there. In FIG. 13, an acousto-optic element is used as the first deflection optical system 1311 and a polygon mirror is used as the second deflection optical system 1303. Reference numeral 1305 denotes a stage, and a substrate 1306 provided with a semiconductor film 1307 is placed on the stage 1305.

  By combining the first deflecting optical system 1311 and the second deflecting optical system 1303, laser light can be applied in a uniaxial direction and can be scanned in a direction intersecting the uniaxial direction. First, a laser beam is scanned in a uniaxial direction by the first deflection optical system. A second deflecting optical system is provided so that the laser beam deflected in the uniaxial direction by the first deflecting optical system is further deflected in a direction intersecting the uniaxial direction. By doing so, it is possible to form a beam spot 1310 having a larger area than the quasi-linear beam spot formed by using only one deflection optical system.

  If the first deflection optical system scans with a width of M in a uniaxial direction and the second deflection optical system scans with a width of N in a direction crossing the uniaxial direction, sides of length M and N A quadrangular beam spot 1310 can be formed.

  Various scanning methods can be considered in the beam spot 1310. FIG. 14A is a top view illustrating a beam spot 1310 irradiated to the semiconductor film 1307. FIGS. 14B to 14E show an example of a laser beam scanning method for forming the beam spot 1310. These scanning methods are the same as those shown in the first to third embodiments. In FIG. 14B, scanning is performed on a plurality of straight lines arranged in parallel, and FIG. 14C is a sawtooth line or a jagged line. In FIG. 14D, scanning is performed on a wavy line, and FIG. 14E is scanning on a comb-shaped line. In this embodiment, laser light is scanned two-dimensionally using a combination of the first deflection optical system and the second deflection optical system. By appropriately controlling the two deflection optical systems, various scans can be performed in addition to those shown in FIGS. 14B to 14E. The relationship between the quasi-linear beam spot 1401 shown in FIG. 14 and the next quasi-linear beam spot 1402 is the same as in the first and second embodiments. The pseudo-linear beam spots 1401 and 1402 partially overlap, and the pseudo-linear beam spot 1402 is formed before the semiconductor portion irradiated by the pseudo-linear beam spot 1401 is solidified. Thereby, inside the beam spot 1310, crystal grains can be grown in a direction intersecting with the long axis of the quasi-linear beam spot, and crystal grains with a large grain size can be obtained.

  Only the first deflection optical system and the second deflection optical system can crystallize only part of the semiconductor film 1307. If it is desired to crystallize the entire surface of the semiconductor film, the X-axis direction position control means 1308 and the Y-axis direction position control means 1309 may be used. Alternatively, the irradiated object may not be moved, and the optical system itself indicated by reference numerals 1301 to 1304 and 1311 in FIG.

  In this embodiment, as long as it is within the range indicated by the beam spot 1310, the X-axis and Y-axis position control means are not required, and the semiconductor film as the irradiated object can be crystallized. Further, a crystalline semiconductor film in which crystal grains are grown in one direction can be obtained. Therefore, this embodiment is suitable for a manufacturing method in which a plurality of semiconductor elements are formed over one substrate and then individually separated to manufacture a plurality of ID chips.

  In the laser irradiation apparatus shown in FIG. 13, the condensing optical system 1302 is not always necessary. However, by using the condensing optical system 1302, the size of the cross section of the laser light incident on the first deflection optical system 1311 can be suppressed, so that the smaller first deflection optical system 1311 can be used. . Further, although the fθ lens 1304 is not always necessary, the speed and size of the laser light scanned in the beam spot 1310 can be made constant by using the fθ lens 1304.

  The optical system used in the laser irradiation apparatus of the present invention is not limited to the one shown in FIG. 13, and a designer may add and use an appropriate optical system as needed.

  This embodiment can be combined with Embodiments 1 to 3 within a feasible range.

  Next, a method for manufacturing a semiconductor device of the present invention will be described with reference to FIGS.

  First, as shown in FIG. 7A, a base film 501 is formed over a substrate 500. As the substrate 500, for example, a glass substrate such as barium borosilicate glass or alumino borosilicate glass, a quartz substrate, a stainless steel substrate, or the like can be used. In addition, substrates made of plastics typified by PET, PES, PEN, and flexible synthetic resins such as acrylic generally tend to have lower heat-resistant temperatures than the above-mentioned substrates. Any material that can withstand the processing temperature can be used.

  The base film 501 is provided to prevent an alkali metal such as Na or an alkaline earth metal contained in the substrate 500 from diffusing into the semiconductor film and adversely affecting the characteristics of the semiconductor element. Therefore, the insulating film is formed using an insulating film such as silicon oxide, silicon nitride, or silicon nitride oxide that can suppress diffusion of alkali metal or alkaline earth metal into the semiconductor film. In this embodiment, a silicon nitride oxide film is formed to a thickness of 10 nm to 400 nm (preferably 50 nm to 300 nm) using a plasma CVD method.

  Note that the base film 501 may be a single layer or a stack of a plurality of insulating films. In the case of using a substrate containing an alkali metal or an alkaline earth metal, such as a glass substrate, a SUS substrate, or a plastic substrate, it is effective to provide a base film from the viewpoint of preventing impurity diffusion. However, when diffusion of impurities does not cause any problem, such as a quartz substrate, it is not necessarily provided.

  Next, a semiconductor film 502 is formed over the base film 501. The thickness of the semiconductor film 502 is 25 nm to 100 nm (preferably 30 nm to 60 nm). Note that the semiconductor film 502 may be an amorphous semiconductor or a polycrystalline semiconductor. If the semiconductor film 502 is a polycrystalline semiconductor film, it can be recrystallized by irradiating laser light according to the present invention, and a crystalline semiconductor film composed of crystals with a large grain size can be obtained. As the semiconductor, not only silicon but also silicon germanium can be used. In the case of using silicon germanium, the concentration of germanium is preferably about 0.01 atomic% to 4.5 atomic%.

  Next, as shown in FIG. 7B, crystallization is performed by irradiating the semiconductor film 502 with laser light using the present invention.

  In the case of performing laser crystallization, it is preferable to add heat treatment at 550 ° C. for 4 hours to the semiconductor film 502 in order to increase the resistance of the semiconductor film 502 to the laser before laser crystallization. For laser crystallization, a continuous wave laser or a pulsed laser having an oscillation frequency of 100 MHz or more can be used.

Specifically, a known continuous wave gas laser or solid-state laser can be used. Examples of gas lasers include Ar laser and Kr laser, and solid-state lasers include YAG laser, YVO ₄ laser, YLF laser, YAlO ₃ laser, Y ₂ O ₃ laser, glass laser, ruby laser, alexandrite laser, and Ti: sapphire laser. Etc.

If pulse oscillation can be performed at a frequency of 100 MHz or more, an Ar laser, a Kr laser, an excimer laser, a CO ₂ laser, a YAG laser, a Y ₂ O ₃ laser, a YVO ₄ laser, a YLF laser, a YAlO ₃ laser, a glass laser Ruby laser, alexandrite laser, Ti: sapphire laser, copper vapor laser or gold vapor laser can be used.

For example, when a solid-state laser capable of continuous oscillation is used, a crystal having a large grain size can be obtained by irradiating laser light of second to fourth harmonics. Typically, it is desirable to use the second harmonic (532 nm) or the third harmonic (355 nm) of a YAG laser (fundamental wave 1064 nm). Specifically, laser light emitted from a continuous wave YAG laser is converted into a harmonic by a non-linear optical element to obtain, for example, laser light with an output of about 4 to 8 W. Then, a linear pseudo beam spot is formed by scanning the beam spot in a uniaxial direction, and the semiconductor film 502 is irradiated. Energy density may be about 0.01 to 100 MW / cm ² (preferably 0.1~10MW / cm ^2). The scanning speed of the laser beam for forming the quasi-linear beam spot is about 1 × 10 ⁶ to 1 × 10 ⁷ cm / sec. In this embodiment, it is 2 × 10 ⁶ cm / sec. Then, irradiation is performed with the scanning speed of the pseudo-linear beam spot in the direction intersecting the long axis being about 10 to 2000 cm / sec. In this embodiment, crystallization is performed with an energy of 5 W, a quasi-linear beam spot size of 400 μm in the major axis, 10 to 20 μm in the minor axis, and a scanning speed in the direction crossing the major axis of 35 cm / sec.

  By scanning the quasi-linear beam spot in the direction indicated by the white arrow as shown in FIG. 7B, the solid-liquid interface can be continuously moved in the direction of the white arrow. it can. Therefore, crystal grains continuously grown in the scanning direction of the quasi-linear beam spot are formed. By forming single crystal grains that extend long along the scanning direction, it is possible to form a TFT with few crystal grain boundaries that intersect the direction in which carriers move.

  Note that laser light may be irradiated in an inert gas atmosphere such as a rare gas or nitrogen. Thereby, roughness of the semiconductor surface due to laser light irradiation can be suppressed, and variation in threshold voltage caused by variation in interface state density can be suppressed.

  By irradiating the semiconductor film 502 with the laser light, the semiconductor film 503 with higher crystallinity is formed.

  Next, as illustrated in FIG. 7C, the semiconductor film 503 is patterned to form island-shaped semiconductor films 507 to 509, and the island-shaped semiconductor films 507 to 509 are used to represent the TFT. Various semiconductor elements are formed.

  Although not shown, for example, when a TFT is manufactured, a gate insulating film is formed so as to cover the island-shaped semiconductor films 507 to 509. For the gate insulating film, for example, silicon oxide, silicon nitride, silicon nitride oxide, or the like can be used. As a film formation method, a plasma CVD method, a sputtering method, or the like can be used.

  Next, after forming a conductive film over the gate insulating film, the conductive film is patterned to form a gate electrode. Then, using a gate electrode or a resist film formed and patterned as a mask, an impurity imparting n-type or p-type conductivity is added to the island-shaped semiconductor films 507 to 509 so that the source region, the drain, Regions, LDD regions and the like are formed.

  A TFT can be formed by the series of steps described above. Note that the method for manufacturing a semiconductor device of the present invention is not limited to the above-described TFT manufacturing process. By using a semiconductor film crystallized using the present invention as an active layer of a TFT, variations in element mobility, threshold voltage, and on-current can be suppressed.

  Further, a crystallization step using a catalytic element may be provided before crystallization with laser light. Nickel (Ni) can be cited as a catalyst element. Besides this, germanium (Ge), iron (Fe), palladium (Pd), tin (Sn), lead (Pb), cobalt (Co), platinum Elements such as (Pt), copper (Cu), and gold (Au) can be used. When a crystallization process using a laser beam is performed after a crystallization process using a catalytic element, the crystal formed during the crystallization using the catalytic element remains on the side closer to the substrate without being melted by the laser beam irradiation. Then, crystallization proceeds using the crystal as a crystal nucleus. Therefore, crystallization by laser light irradiation tends to progress uniformly from the substrate side toward the surface of the semiconductor film, and the crystallinity of the semiconductor film can be improved more than in the case of only the crystallization process by laser light. The surface roughness of the semiconductor film after crystallization by light can be suppressed. Accordingly, variation in characteristics of semiconductor elements formed later, typically TFTs, can be further suppressed, and off-current can be suppressed.

  Note that the crystallinity may be further increased by laser light irradiation after the catalyst element is added and heat treatment is performed to promote crystallization. Further, the heat treatment step may be omitted. Specifically, after adding a catalyst element, laser light may be irradiated instead of heat treatment to improve crystallinity.

  Note that in this embodiment, an example in which the present invention is used for crystallization of a semiconductor film is shown, but the present invention may be used to activate an impurity element doped in a semiconductor film.

  This embodiment can be combined with Embodiments 1 to 4 as far as practicable.

  In this example, unlike Example 1, an example in which laser crystallization is combined with a crystallization method using a catalytic element will be described.

  First, the process up to forming the semiconductor film 502 is performed with reference to FIG. Next, as shown in FIG. 8A, a nickel acetate salt solution containing 1 to 100 ppm of Ni in terms of weight is applied to the surface of the semiconductor film 502 by spin coating. Note that the addition of the catalyst is not limited to the above method, and the catalyst may be added by sputtering, vapor deposition, plasma treatment, or the like. And it heat-processes at 500-650 degreeC for 4 to 24 hours, for example, 570 degreeC and 14 hours. By this heat treatment, a semiconductor film 520 in which crystallization is promoted in the vertical direction from the surface coated with the nickel acetate salt solution toward the substrate 500 is formed (FIG. 8A).

  In the heat treatment, for example, RTA (Rapid Thermal Anneal) using lamp radiation as a heat source or RTA (gas RTA) using heated gas is performed at a set heating temperature of 740 ° C. for 180 seconds. The set heating temperature is the temperature of the substrate measured with a pyrometer, and this temperature is set as the set temperature during heat treatment. As another method, there is a heat treatment for 4 hours at 550 ° C. using a furnace annealing furnace, which may be used. The lowering and shortening of the crystallization temperature is due to the action of a catalytic metal element.

  In this embodiment, nickel (Ni) is used as a catalytic element. In addition, germanium (Ge), iron (Fe), palladium (Pd), tin (Sn), lead (Pb), cobalt (Co ), Platinum (Pt), copper (Cu), and gold (Au).

  Next, as shown in FIG. 8B, the semiconductor film 520 is crystallized by using the present invention. Laser crystallization can be performed under the conditions described in Example 1.

By irradiating the semiconductor film 520 with the laser light, the semiconductor film 521 with higher crystallinity is formed. Note that it is considered that the semiconductor element 521 crystallized using the catalytic element contains the catalytic element (here, Ni) at a concentration of about 1 × 10 ¹⁹ atoms / cm ³ . Next, gettering of the catalytic element present in the semiconductor film 521 is performed.

  First, an oxide film 522 is formed on the surface of the semiconductor film 521 as illustrated in FIG. By forming the oxide film 522 having a thickness of about 1 nm to 10 nm, the surface of the semiconductor film 521 can be prevented from being roughened by etching in a later etching step. The oxide film 522 can be formed using a known method. For example, it may be formed by oxidizing the surface of the semiconductor film 521 with an aqueous solution in which sulfuric acid, hydrochloric acid, nitric acid, and the like are mixed with hydrogen peroxide water or ozone water, or plasma treatment in an atmosphere containing oxygen Alternatively, it may be formed by heat treatment, ultraviolet irradiation or the like. In addition, an oxide film may be separately formed by a plasma CVD method, a sputtering method, a vapor deposition method, or the like.

Next, a gettering semiconductor film 523 containing a rare gas element at a concentration of 1 × 10 ²⁰ atoms / cm ³ or more is formed with a thickness of 25 to 250 nm on the oxide film 522 by a sputtering method. The gettering semiconductor film 523 preferably has a lower film density than the semiconductor film 521 in order to increase the etching selectivity between the semiconductor film 521 and the semiconductor film 521. As the rare gas element, one or more selected from helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) are used.

  Next, heat treatment is performed using a furnace annealing method or an RTA method to perform gettering. In the case of performing furnace annealing, heat treatment is performed at 450 to 600 ° C. for 0.5 to 12 hours in a nitrogen atmosphere. When the RTA method is used, the lamp light source for heating is turned on for 1 to 60 seconds, preferably 30 to 60 seconds, and this is repeated 1 to 10 times, preferably 2 to 6 times. The emission intensity of the lamp light source is arbitrary, but the semiconductor film is instantaneously heated to 600 to 1000 ° C., preferably about 700 to 750 ° C.

  By the heat treatment, the catalytic element in the semiconductor film 521 moves to the gettering semiconductor film 523 as indicated by an arrow by diffusion and is gettered.

Next, the gettering semiconductor film 523 is removed by etching. Etching can be performed by dry etching without using plasma with ClF ₃ , or wet etching with an alkaline solution such as an aqueous solution containing hydrazine or tetramethylammonium hydroxide ((CH ₃ ) ₄ NOH). At this time, the oxide film 522 can prevent the semiconductor film 521 from being etched.

  Next, after the oxide film 522 is removed with hydrofluoric acid, the semiconductor film 521 is patterned to form island-shaped semiconductor films 524 to 526 (FIG. 8D). Various semiconductor elements typified by TFTs can be formed using the island-shaped semiconductor films 524 to 526. In the present invention, the gettering step is not limited to the method shown in this embodiment. Other methods may be used to reduce the catalytic element in the semiconductor film.

  In the case of this example, the crystal formed during the crystallization with the catalytic element remains unmelted by laser light irradiation on the side closer to the substrate, and the crystallization proceeds using the crystal as a crystal nucleus. Therefore, crystallization by laser light irradiation is likely to proceed uniformly from the substrate side to the surface, and the crystal orientation is easily aligned, so that surface roughness can be suppressed compared to the case of Example 1. Therefore, variations in characteristics of semiconductor elements formed later, typically TFTs, can be further suppressed.

  Note that in this embodiment, the structure in which the crystallinity is further enhanced by laser light irradiation after the catalyst element is added and then heat treatment is performed to promote crystallization has been described. The present invention is not limited to this, and the heat treatment step may be omitted. Specifically, after adding a catalyst element, laser light may be irradiated instead of heat treatment to improve crystallinity.

  This example can be combined with Embodiments 1 to 4 and Example 1 as long as practicable.

  In this example, an example different from Example 2 in which the crystallization method of the present invention is combined with a crystallization method using a catalytic element will be described.

  First, the process up to forming the semiconductor film 502 is performed with reference to FIG. Next, a mask 540 having an opening is formed over the semiconductor film 502. Then, as shown in FIG. 9A, a nickel acetate salt solution containing 1 to 100 ppm of Ni in terms of weight is applied to the surface of the semiconductor film 502 by spin coating. Note that the addition of the catalyst is not limited to the above method, and the catalyst may be added by sputtering, vapor deposition, plasma treatment, or the like. The applied nickel acetate salt solution is in contact with the semiconductor film 502 at the opening of the mask 540 (FIG. 9A).

  Next, heat treatment is performed at 500 to 650 ° C. for 4 to 24 hours, for example, 570 ° C. for 14 hours. By this heat treatment, a semiconductor film 530 in which crystallization is promoted as shown by a solid arrow is formed from the surface coated with the nickel acetate salt solution (FIG. 9A). The heat treatment method is not limited to this, and the other heat treatment methods described in Embodiment 2 may be used. The catalyst elements listed in Example 2 can be used.

  Next, after removing the mask 540, as shown in FIG. 9B, the semiconductor film 530 is crystallized using the laser irradiation apparatus of the present invention. Laser crystallization can be performed under the conditions described in Example 1. By irradiating the semiconductor film 530 with the laser light, the semiconductor film 531 with higher crystallinity is formed.

Note that as shown in FIG. 9B, the catalyst element (Ni in this case) is contained in the semiconductor film 531 crystallized using the catalyst element at a concentration of about 1 × 10 ¹⁹ atoms / cm ^3. It is thought that. Next, gettering of the catalytic element present in the semiconductor film 531 is performed.

  First, as shown in FIG. 9C, a masking silicon oxide film 532 is formed to a thickness of 150 nm so as to cover the semiconductor film 531, an opening is provided by patterning, and a part of the semiconductor film 531 is exposed. Let Then, phosphorus is added to provide the gettering region 533 in which phosphorus is added to the semiconductor film 531. In this state, when heat treatment is performed in a nitrogen atmosphere at 550 to 800 ° C. for 5 to 24 hours, for example, 600 ° C. for 12 hours, the gettering region 533 in which phosphorus is added to the semiconductor film 531 functions as a gettering site, The catalytic element remaining in the semiconductor film 531 is segregated in the gettering region 533 to which phosphorus is added.

Then, by removing the gettering region 533 to which phosphorus is added, the concentration of the catalytic element in the remaining region of the semiconductor film 531 can be reduced to 1 × 10 ¹⁷ atoms / cm ³ or less. Next, after removing the masking silicon oxide film 532, the semiconductor film 531 is patterned to form island-shaped semiconductor films 534 to 536 (FIG. 9D). Various semiconductor elements typified by TFTs can be formed using the island-shaped semiconductor films 534 to 536. In the present invention, the gettering step is not limited to the method shown in this embodiment. Other methods may be used to reduce the catalytic element in the semiconductor film.

  In the case of this example, the crystal formed during the crystallization with the catalytic element remains unmelted by laser light irradiation on the side closer to the substrate, and the crystallization proceeds using the crystal as a crystal nucleus. Therefore, crystallization by laser light irradiation is likely to proceed uniformly from the substrate side to the surface, and the crystal orientation is easily aligned, so that surface roughness can be suppressed compared to the case of Example 1. Therefore, variations in characteristics of semiconductor elements formed later, typically TFTs, can be further suppressed.

  This embodiment can be combined with Embodiments 1 to 4 and Embodiments 1 and 2 within a feasible range.

  A structure of a pixel of a light-emitting device, which is one of semiconductor display devices formed using the present invention, will be described with reference to FIGS.

  In FIG. 10, a base film 6001 is formed over a substrate 6000, and a transistor 6002 is formed over the base film 6001. The transistor 6002 includes an island-shaped semiconductor film 6003, a gate electrode 6005, and a gate insulating film 6004 sandwiched between the island-shaped semiconductor film 6003 and the gate electrode 6005.

  As the island-shaped semiconductor film 6003, a polycrystalline semiconductor film crystallized by using the present invention is used. Note that the island-shaped semiconductor film may be made of silicon germanium as well as silicon. When silicon germanium is used, the concentration of germanium is preferably about 0.01 to 4.5 atomic%. Further, silicon to which carbon nitride is added may be used.

For the gate insulating film 6004, silicon oxide, silicon nitride, or silicon oxynitride can be used. A film in which these layers are stacked, for example, a film in which SiN is stacked on SiO ₂ may be used as the gate insulating film. The gate electrode 6005 is formed using an element selected from Ta, W, Ti, Mo, Al, and Cu, or an alloy material or a compound material containing the element as a main component. Alternatively, a semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorus may be used. Further, instead of a single conductive film, a conductive film composed of a plurality of layers may be stacked.

  The transistor 6002 is covered with a first interlayer insulating film 6006, and a second interlayer insulating film 6007 and a third interlayer insulating film 6008 are stacked over the first interlayer insulating film 6006. . The first interlayer insulating film 6006 can be formed using a single layer or a stack of silicon oxide, silicon nitride, or silicon oxynitride films by a plasma CVD method or a sputtering method.

The second interlayer insulating film 6007 can be formed using an organic resin film, an inorganic insulating film, a siloxane resin, or the like. Note that a siloxane resin corresponds to a resin including a Si—O—Si bond. Siloxane has a skeleton structure formed of a bond of silicon (Si) and oxygen (O). As a substituent, an organic group containing at least hydrogen (for example, an alkyl group or an aromatic hydrocarbon) is used. A fluoro group may be used as a substituent. Alternatively, an organic group containing at least hydrogen and a fluoro group may be used as a substituent.
In this embodiment, non-photosensitive acrylic is used. As the third interlayer insulating film 6008, a film that hardly transmits a substance that causes deterioration of the light-emitting element such as moisture or oxygen as compared with other insulating films is used. Typically, it is desirable to use, for example, a DLC film, a carbon nitride film, a silicon nitride film formed by an RF sputtering method, or the like.

  In FIG. 10, reference numeral 6010 denotes a first electrode, 6011 denotes an electroluminescent layer, 6012 denotes a second electrode, and a portion where the first electrode 6010, the electroluminescent layer 6011, and the second electrode 6012 overlap is a light emitting element. This corresponds to 6013. One of the transistors 6002 is a driving transistor that controls current supplied to the light-emitting element 6013, and is connected to the light-emitting element 6013 directly or in series via another circuit element. The electroluminescent layer 6011 has a structure in which a light emitting layer alone or a plurality of layers including a light emitting layer are stacked.

  The first electrode 6010 is formed over the third interlayer insulating film 6008. An organic resin film 6014 used as a partition is formed over the third interlayer insulating film 6008. In this embodiment, an organic resin film is used as the partition. However, an inorganic insulating film, a siloxane resin, or the like can be used as the partition. The organic resin film 6014 has an opening 6015, and a light-emitting element 6013 is formed by overlapping the first electrode 6010, the electroluminescent layer 6011, and the second electrode 6012 in the opening.

  A protective film 6016 is formed over the organic resin film 6014 and the second electrode 6012. As with the third interlayer insulating film 6008, the protective film 6016 is a film that hardly transmits a substance that causes deterioration of the light-emitting element such as moisture and oxygen compared to other insulating films, such as a DLC film, A carbon nitride film, a silicon nitride film formed by an RF sputtering method, or the like is used.

  Also, the end of the organic resin film 6014 in the opening 6015 is rounded so that the electroluminescent layer 6011 formed on the organic resin film 6014 partially overlaps so that there is no hole in the end. Is desirable. Specifically, it is desirable that the radius of curvature of the curve drawn by the cross section of the organic resin film in the opening is about 0.2 to 2 μm. With the above structure, coverage of an electroluminescent layer or a second electrode to be formed later can be improved, and the first electrode 6010 and the second electrode 6012 are short-circuited in a hole formed in the electroluminescent layer 6011. Can be prevented. Further, by relaxing the stress of the electroluminescent layer 6011, defects called “shrink” in which a light emitting region is reduced can be reduced, and reliability can be improved.

  Note that FIG. 10 illustrates an example in which a positive photosensitive acrylic resin is used as the organic resin film 6014. The photosensitive organic resin includes a positive type in which a portion exposed to energy rays such as light, electrons, and ions is removed, and a negative type in which the exposed portion remains. In the present invention, a negative organic resin film may be used. Alternatively, the organic resin film 6014 may be formed using photosensitive polyimide. When the organic resin film 6014 is formed using negative acrylic, an end portion of the opening 6015 has an S-shaped cross-sectional shape. At this time, it is desirable that the radius of curvature at the upper end and the lower end of the opening is 0.2 to 2 μm.

  Note that one of the first electrode 6010 and the second electrode 6012 corresponds to an anode and the other corresponds to a cathode.

  For the anode, other light-transmitting oxide conductive materials such as indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), and zinc oxide to which gallium is added (GZO) can be used. . Indium tin oxide containing ITO and silicon oxide (hereinafter referred to as ITSO) or indium oxide containing silicon oxide mixed with 2 to 20% zinc oxide (ZnO) may be used. In addition to the light-transmitting oxide conductive material as an anode, in addition to a single layer film made of, for example, one or more of TiN, ZrN, Ti, W, Ni, Pt, Cr, Ag, Al, etc., titanium nitride and A stack of a film containing aluminum as its main component, a three-layer structure of a titanium nitride film, a film containing aluminum as its main component, and a titanium nitride film can be used. However, when light is extracted from the anode side with a material other than the light-transmitting oxide conductive material, the light-transmitting oxide film is formed to have a film thickness that allows light to pass (preferably, about 5 nm to 30 nm).

As the cathode, a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a low work function can be used. Specifically, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, alloys containing these (Mg: Ag, Al: Li, Mg: In, etc.), and compounds thereof ( In addition to CaF ₂ and CaN, rare earth metals such as Yb and Er can be used. In the case where an electron injection layer is provided in the electroluminescent layer 6011, another conductive layer such as Al can be used. When light is extracted from the cathode side, other light-transmitting oxide conductive materials such as indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), and gallium-added zinc oxide (GZO) are used. It is possible to use. Indium tin oxide containing ITO and silicon oxide (hereinafter referred to as ITSO) or indium oxide containing silicon oxide mixed with 2 to 20% zinc oxide (ZnO) may be used. In the case of using a light-transmitting oxide conductive material, it is preferable to provide an electron injection layer in the electroluminescent layer 6011 to be formed later. In addition, without using a light-transmitting oxide conductive material, light can be extracted from the cathode side by forming the cathode with a film thickness that allows light to pass therethrough (preferably, about 5 nm to 30 nm). In this case, a light-transmitting conductive layer may be formed using a light-transmitting oxide conductive material so as to be in contact with or under the cathode so as to suppress the sheet resistance of the cathode.

  Note that FIG. 10 illustrates a structure in which light emitted from the light-emitting element is emitted to the substrate 6000 side; however, a light-emitting element having a structure in which light is directed to the opposite side of the substrate may be used.

  Actually, when completed up to FIG. 10, a protective film (such as a film having a layer that melts when thermocompression-bonded, an ultraviolet curable resin film, etc.) having high airtightness and low degassing so as not to be exposed to the outside air, It is preferable to package (enclose) with a translucent cover material. At that time, if the inside of the cover material is made an inert atmosphere or a hygroscopic material (for example, barium oxide) is arranged inside, the reliability of the light emitting element is improved.

  Note that although a light-emitting device is used as an example of a semiconductor display device in this embodiment, a semiconductor display device formed using the manufacturing method of the present invention is not limited thereto.

  This embodiment can be combined with Embodiments 1 to 4 and Embodiments 1 to 3 within a feasible range.

The figure which shows a mode that the pseudo linear beam spot is formed by scanning a beam spot in a uniaxial direction. The figure which shows one form of the laser irradiation apparatus of this invention. The figure which shows the process in which a pseudo linear beam spot is formed with the laser beam deflected in the acousto-optic device. The figure which shows a mode that the pseudo linear beam spot is formed by scanning a beam spot in a uniaxial direction. The figure which shows one form of the laser irradiation apparatus of this invention. The figure which shows the process in which a pseudo linear beam spot is formed with the laser beam deflected in the polygon mirror. 4A and 4B illustrate a method for manufacturing a semiconductor device of the present invention. 4A and 4B illustrate a method for manufacturing a semiconductor device of the present invention. 4A and 4B illustrate a method for manufacturing a semiconductor device of the present invention. FIG. 10 illustrates a pixel structure of a light-emitting device which is one of semiconductor display devices formed using the laser irradiation apparatus of the present invention. The figure which shows a mode that the pseudo linear beam spot is formed by scanning a beam spot in a uniaxial direction. The figure which shows a mode that the pseudo linear beam spot is formed by scanning a beam spot in a uniaxial direction. The figure which shows one form of the laser irradiation apparatus of this invention. The figure which shows a mode that the pseudo linear beam spot is formed by scanning a beam spot in a uniaxial direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Pseudo linear beam spot 101 Beam spot 102 Semiconductor film 103 Pseudo linear beam spot 201 Laser oscillator 202 Condensing optical system 203 Mirror 204 Acousto-optic element 205 fθ lens 206 Stage 207 Substrate 208 Semiconductor film 209 X-axis direction position control means 210 Y-axis direction position control means 211 Pseudo linear beam spot 300 Pseudo linear beam spot 301 Beam spot 302 Semiconductor film 303 Pseudo linear beam spot 401 Laser oscillator 402 Condensing optical system 403 Polygon mirror 404 fθ lens 405 Stage 406 Substrate 407 Semiconductor film 408 X-axis direction position control means 409 Y-axis direction position control means 410 Pseudo linear beam spot 500 Substrate 501 Base film 502 Semiconductor film 503 Semiconductor film 507 Island-like semiconductor film 52 Semiconductor film 521 Semiconductor film 522 Oxide film 523 Semiconductor film 524 Island-like semiconductor film 530 Semiconductor film 531 Semiconductor film 540 Mask 532 Silicon oxide film 533 Gettering region 534 Island-like semiconductor film 6000 Substrate 6001 Base film 6002 Transistor 6003 Island-like Semiconductor film 6004 Gate insulating film 6005 Gate electrode 6006 First interlayer insulating film 6008 Third interlayer insulating film 6007 Second interlayer insulating film 6010 First electrode 6011 Electroluminescent layer 6012 Second electrode 6013 Light emitting element 6014 Organic resin Film 6015 Opening 6016 Protective film 1101 Pseudo linear beam spot 1102 Pseudo linear beam spot 1103 Beam spot 1104 Beam spot 1105 Semiconductor film 1201 Pseudo linear beam spot 1202 Pseudo linear beam spot 1203 Beam spot 1204 Beam spot 1205 Semiconductor film 1301 Laser oscillator 1302 Condensing optical system 1303 Second deflection optical system 1304 fθ lens 1305 Stage 1306 Substrate 1307 Semiconductor film 1308 X-axis direction position control means 1309 Y-axis direction position control means 1310 Beam spot 1311 First deflection optical system 1401 Pseudo linear beam spot 1402 Pseudo linear beam spot

Claims (25)

A laser oscillator;
An optical system that scans the laser light oscillated from the laser oscillator so as to reciprocate on a straight line to form a quasi-linear beam spot;
Means for moving the relative position of the irradiated object with respect to the laser beam in a direction intersecting with the long axis of the pseudo-linear beam spot;
A first irradiated region to be irradiated with the laser beam in the pseudo-linear beam spot, and a second in which the pseudo-linear beam spot is formed following the irradiation of the first irradiated region. The irradiated body region is moved by the means so as to partially overlap,
Before the first irradiated region is solidified, the means moves the position of the pseudo linear beam spot from the first irradiated region to the second irradiated region. A featured laser irradiation device. A laser oscillator;
An optical system that scans the laser light oscillated from the laser oscillator so as to reciprocate on a straight line;
Means for moving a relative position of the irradiated object with respect to the laser beam in a direction crossing a scanning direction of the laser beam;
By the optical system and the means, the laser beam is scanned on the irradiated body so as to trace a wave shape or a sawtooth line,
When scanning from the first turning point of the wave shape or the sawtooth line to the third turning point via the second turning point,
The first beam spot when the first turning point is irradiated with the laser beam and the second beam spot when the third turning point is irradiated with the laser beam partially overlap each other. West,
A laser that scans the laser light from the first turning point to the third turning point before the irradiated object irradiated by the first beam spot is solidified. Irradiation device. A laser oscillator;
An optical system that scans the laser light oscillated from the laser oscillator so as to reciprocate on a straight line;
Means for moving a relative position of the irradiated object with respect to the laser beam in a direction crossing a scanning direction of the laser beam;
The optical system and the means scan the laser beam so that a plurality of straight lines arranged at equal intervals are traced one by one,
By scanning the laser light so as to trace the first straight line among the plurality of straight lines, a first irradiated region to be irradiated with the laser light and a second adjacent to the first straight line By scanning the laser beam so as to trace a straight line, the second irradiated object region irradiated with the laser beam is partially overlapped,
A laser irradiation apparatus that irradiates the second irradiated region with the laser beam before the first irradiated region is solidified. A laser oscillator;
An optical system that scans the laser light oscillated from the laser oscillator so as to reciprocate on a straight line;
Means for moving a relative position of the irradiated object with respect to the laser beam in a direction crossing a scanning direction of the laser beam;
By the optical system and the means, the laser beam is scanned on the irradiated body so as to trace a wave shape or a sawtooth line,
When scanning from the first turning point of the wave shape or the sawtooth line to the third turning point via the second turning point,
The first beam spot when the first turning point is irradiated with the laser beam and the second beam spot when the third turning point is irradiated with the laser beam partially overlap each other. West,
A laser irradiation apparatus that scans the laser beam within 100 ns from the first turning point to the third turning point. A laser oscillator;
An optical system that scans the laser light oscillated from the laser oscillator so as to reciprocate on a straight line;
Means for moving a relative position of the irradiated object with respect to the laser beam in a direction crossing a scanning direction of the laser beam;
The optical system and the means scan the laser beam so that a plurality of straight lines arranged at equal intervals are traced one by one,
When the laser beam traces a first straight line of the plurality of straight lines, a first irradiated region to be irradiated with the laser light, and a second adjacent to the first straight line. When tracing a straight line, the second irradiated object region irradiated with the laser beam is partially overlapped,
A laser irradiation apparatus that scans the laser light within 100 ns from the first irradiated region to the second irradiated region.   6. The laser irradiation apparatus according to claim 1, wherein the optical system is an acousto-optic element, a polygon mirror, or a resonant scanner.   7. The laser irradiation apparatus according to claim 1, wherein a speed at which the optical system scans the laser beam is faster than a speed at which the object is moved by the means. A laser oscillator;
An optical system that scans the laser light oscillated from the laser oscillator so as to trace a plurality of straight lines arranged at equal intervals one by one,
A first pseudo linear beam spot formed by scanning to trace the first straight line among the plurality of straight lines, and a second straight line adjacent to the first straight line are scanned and formed. The second quasi-linear beam spot partially overlaps,
The laser beam is scanned before the irradiated object irradiated with the first quasi-linear beam spot is solidified to form the second quasi-linear beam spot. Irradiation device. A laser oscillator;
An optical system that scans the laser light oscillated from the laser oscillator so as to trace a plurality of straight lines arranged at equal intervals one by one,
A first pseudo linear beam spot formed by scanning to trace the first straight line among the plurality of straight lines, and a second straight line adjacent to the first straight line are scanned and formed. The second quasi-linear beam spot partially overlaps,
Before the irradiated object irradiated by the first quasi-linear beam spot is solidified, the laser beam is scanned to start forming the second quasi-linear beam spot. Laser irradiation device. A laser oscillator;
An optical system that scans the laser light oscillated from the laser oscillator so as to trace a plurality of straight lines arranged at equal intervals one by one,
A first pseudo linear beam spot formed by scanning to trace the first straight line among the plurality of straight lines, and a second straight line adjacent to the first straight line are scanned and formed. The second quasi-linear beam spot partially overlaps,
The laser irradiation apparatus, wherein the laser beam irradiation is performed within 100 ns from the start of forming the first quasi-linear beam spot to the formation of the second quasi-linear beam spot. A laser oscillator;
An optical system that scans the laser light oscillated from the laser oscillator so as to trace a wave shape or a sawtooth line;
When scanning from the first turning point of the wave shape or the sawtooth line to the third turning point via the second turning point,
The laser beam is scanned so that the first beam spot centered on the first turning point and the second beam spot centered on the third turning point partially overlap,
Laser irradiation, wherein the laser beam is scanned from the first turning point to the third turning point before the irradiated object irradiated by the first beam spot is solidified. apparatus. A laser oscillator;
An optical system that scans the laser light oscillated from the laser oscillator so as to trace a wave shape or a sawtooth line;
When scanning from the first turning point of the wave shape or the sawtooth line to the third turning point via the second turning point,
The laser beam is scanned so that the first beam spot centered on the first turning point and the second beam spot centered on the third turning point partially overlap,
A laser irradiation apparatus that scans the laser beam within 100 ns from the first turning point to the third turning point.   13. The optical system according to claim 8, wherein the optical system includes a first optical system that scans the laser light in a first direction and the laser light in a direction that intersects the first direction. A laser irradiation apparatus comprising: a second optical system that scans a laser beam.   The laser irradiation apparatus according to claim 13, wherein each of the first optical system and the second optical system is an acousto-optic element, a polygon mirror, or a resonant scanner.   15. The laser irradiation apparatus according to claim 8, further comprising means for moving a relative position of an irradiation object with respect to the laser light. In any one of Claims 1 to 15,
The laser irradiation apparatus is characterized in that the laser light is pulse-oscillated from the laser oscillator, and the frequency of the pulse oscillation is 100 MHz or more. In any one of Claims 1 to 15,
The laser irradiation apparatus, wherein the laser light is continuously oscillated from the laser oscillator. In order to melt the first region of the semiconductor film, the laser beam is scanned in the first direction along the first direction,
After the first scan, in order to melt the second region of the semiconductor film, the laser beam is scanned in a second direction along a second direction,
The first region partially overlaps the second region;
A method for manufacturing a semiconductor device, wherein at least part of the first region is in a molten state during the second scanning.   19. The crystal of the semiconductor film according to claim 18, wherein the crystal of the semiconductor film continuously grows from the first region to the second region through a region where the second region partially overlaps the first region. A method for manufacturing a semiconductor device.   In Claim 18 or Claim 19, when irradiating a part of the second region with the laser beam, a part of the first region overlapping the part of the second region is A method for manufacturing a semiconductor device, wherein the semiconductor device is melted by first scanning.   In any one of Claims 18 to 20, the first region and the second region are linear, the first direction is the same direction as the second direction, 1. The method for manufacturing a semiconductor device, wherein the first region partially overlaps the second region along the first direction. In a method for manufacturing a semiconductor device in which a semiconductor film is crystallized by irradiating the semiconductor film with laser light,
The semiconductor film is scanned with the laser beam so as to trace a wave shape or a sawtooth line,
When scanning from the first turning point of the wave shape or the sawtooth line to the third turning point via the second turning point,
A first beam spot centered on the first turning point and a second beam spot centered on the third turning point partially overlap;
Fabrication of a semiconductor device, wherein the laser beam is scanned from the first beam spot to the second beam spot before the semiconductor film irradiated by the first beam spot is solidified. Method. In a method for manufacturing a semiconductor device in which a semiconductor film is crystallized by irradiating the semiconductor film with laser light,
The semiconductor film is scanned with the laser beam so as to trace a comb-like line,
When scanning from the first corner of the comb-like line to the fourth corner via the second and third corners,
A first beam spot centered on the first corner and a second beam spot centered on the fourth corner partially overlapping;
Fabrication of a semiconductor device, wherein the laser beam is scanned from the first beam spot to the second beam spot before the semiconductor film irradiated by the first beam spot is solidified. Method. 24. In any one of claims 18 to 23,
A method for manufacturing a semiconductor device, wherein the laser light is continuously oscillated. 24. In any one of claims 18 to 23,
The method for manufacturing a semiconductor device, wherein the laser beam is pulse-oscillated, and the frequency of the pulse oscillation is 100 MHz or more.

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