KR20040031276A - laser annealing apparatus and method for crystallizing the using - Google Patents

Abstract

The present invention relates to a laser annealing apparatus and a silicon crystallization method using the same to improve the reliability and characteristics of the device through heated nitrogen (N ₂ ) injection during the crystallization of silicon using a laser beam, a laser for generating a laser beam A beam generator, a homogenizer for uniformly irradiating the energy density of the laser beam, an XY stage positioned corresponding to the laser beam generator and moving by a predetermined distance along the X axis or the Y axis, and the XY stage; A mask including a plurality of slits positioned between the laser beam generators and passing a laser beam, a mask moving stage connected to one side of the mask to move the mask by a predetermined distance, and heated to a substrate to which the laser beam is irradiated Including a nitrogen gas supply device for supplying nitrogen gas .

Description

Laser annealing apparatus and silicon crystallization method using the same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display (LCD), and more particularly, to a laser annealing apparatus suitable for improving the reliability and characteristics of a device and a silicon crystallization method using the same.

As the information society develops, the demand for display devices is increasing in various forms.In recent years, liquid crystal display (LCD), plasma display panel (PDP), electro luminescent display (ELD), and vacuum fluorescent display (VFD) have been developed. Various flat panel display devices have been studied, and some are already used as display devices in various devices.

Among them, LCD is the most widely used as a substitute for CRT (Cathode Ray Tube) for the use of mobile image display device because of the excellent image quality, light weight, thinness, and low power consumption, and mobile type such as monitor of notebook computer. In addition, it is being developed in various ways, such as a television for receiving and displaying broadcast signals, and a monitor of a computer.

Thus, although various technical advances have been made in order for the liquid crystal display device to serve as a screen display device in various fields, the task of improving the image quality as the screen display device has many advantages and arrangements.

Therefore, in order to use a liquid crystal display device in various parts as a general screen display device, the key to development is how much high definition images such as high definition, high brightness, and large area can be realized while maintaining the characteristics of light weight, thinness, and low power consumption. It can be said.

Such a liquid crystal display device may be broadly divided into a liquid crystal panel displaying an image and a driving unit for applying a driving signal to the liquid crystal panel, wherein the liquid crystal panel includes first and second glass substrates having a space and are bonded to each other; It consists of a liquid crystal layer injected between the said 1st, 2nd glass substrate.

The first glass substrate (TFT array substrate) may include a plurality of gate lines arranged in one direction at a predetermined interval, a plurality of data lines arranged at regular intervals in a direction perpendicular to the gate lines, and A plurality of pixel electrodes formed in a matrix form in each pixel region defined by crossing each gate line and data line, and a plurality of thin films that transmit signals of the data line to each pixel electrode by being switched by signals of the gate line The transistor is formed.

The second glass substrate (color filter substrate) includes a black matrix layer for blocking light in portions other than the pixel region, an R, G, B color filter layer for expressing color colors, and a common electrode for implementing an image. Is formed. Of course, the common electrode is formed on the first glass substrate in the transverse electric field type liquid crystal display device.

The first and second glass substrates are bonded by an actual material having a predetermined space and a liquid crystal injection hole by a spacer, and a liquid crystal is injected between the two substrates.

In this case, in the liquid crystal injection method, the liquid crystal is injected between the two substrates by osmotic pressure when the liquid crystal injection hole is immersed in the liquid crystal container by maintaining the vacuum state between the two substrates bonded by the reality. When the liquid crystal is injected as described above, the liquid crystal injection hole is sealed with a sealing material.

On the other hand, in order to increase the mobility of the thin film transistor, which is a switching element, in order to increase the density and large area of the liquid crystal display and to fabricate the display portion and the driving circuit portion on the same substrate, an amorphous silicon hydride thin film transistor (a- Si: H TFT) hardly satisfies the increase in mobility.

Recently, a polysilicon thin film transistor (Poly Si TFT) has attracted much attention as a method to effectively solve this problem. Due to the high mobility of polycrystalline silicon TFTs, peripheral circuits can be integrated on glass substrates, thus attracting much attention in terms of reducing production costs.

That is, silicon may be classified into amorphous silicon and crystalline silicon according to states.

Generally, it is possible to form a thin film by depositing amorphous silicon on a substrate at a low temperature, so that a switching device of a liquid crystal panel mainly using glass having a low melting point as a substrate. I use it a lot.

However, the amorphous silicon thin film has difficulty in deteriorating electrical characteristics and reliability of the liquid crystal panel driving device and increasing the display device large area.

Therefore, commercialization of large-area, high-definition and panel image driving circuits, integrated laptop computers, and wall-mounted liquid crystal display devices has excellent electrical characteristics (for example, high field effect mobility (30 cm2 / VS) and high frequency operation). Characteristic and low leakage current (pixel) driving device application is required, which requires the application of high-quality poly crystalline silicon (poly crystalline silicon).

In particular, the electrical properties of the polycrystalline silicon thin film are greatly influenced by the grain size. In other words, as the grain size increases, the field effect mobility increases.

Therefore, a method of polycrystallizing amorphous silicon has become a big issue in consideration of this point, and recently, SLS (Sequential Lateral Solidification), which manufactures huge polycrystalline silicon by inducing lateral growth of silicon crystals by irradiating a laser with an energy source. Technology has been proposed.

The SLS technology takes advantage of the fact that silicon grain grows in the direction perpendicular to the interface between the liquid silicon and the solid silicon, and appropriately controls the size of the laser energy and the shift of the irradiation range of the laser beam. By growing the silicon grain by a predetermined length, the amorphous silicon thin film is crystallized.

Meanwhile, the method for forming the polycrystalline silicon thin film is an LPCVD method for depositing polycrystalline silicon on a substrate by a chemical vapor deposition (CVD) method at 600 ° C. or higher, and after depositing the amorphous silicon thin film by a CVD method on a substrate, 550 ° C. Solid phase crystallization method to crystallize by heat treatment at above temperature for a long time And a method of depositing the same.

Hereinafter, a conventional laser annealing apparatus and a silicon crystallization method using the same will be described with reference to the accompanying drawings.

1 is a schematic configuration diagram showing a conventional laser annealing equipment.

As shown in FIG. 1, a laser beam generator 11 for generating a laser beam 12 and a first direction for changing a traveling direction of the laser beam 12 emitted through the laser beam generator 11. And second and third reflectors 13, 14 and 15 and a homogenizer 16 for uniformizing the energy density of the laser beam 12 whose direction of travel from the third reflector 15 is changed. And a mask 17 which irradiates the laser beam 12 with uniform energy density from the homogenizer 16 onto a substrate on which an amorphous silicon thin film is deposited.

The laser beam generator 11 emits a laser beam 12 that is not processed by a light source, and passes through an attenuator (not shown) to adjust the energy of the laser beam 12.

In addition, at the position corresponding to the mask 17, the substrate 18 on which the amorphous silicon thin film is deposited is located on the X-Y stage 19 which is movable in the X-axis or the Y-axis.

In this case, in the related art, the laser beam generator 11 and the mask 17 are fixed at one position, so that the XY stage 19 is X-axis or Y-axis in order to crystallize all regions of the amorphous silicon thin film. By moving it in a small direction, it is possible to enlarge the crystal area.

In the above-described configuration, the mask 17 includes a plurality of slits A, which are transmission regions through which the laser beam 12 passes, and an absorption region B, which absorbs the laser beam 12, includes the slits A. It is composed between.

The width of the slit A formed in the mask 17 determines the size of the grains of the silicon crystals crystallized by the primary laser beam irradiation, and the interval between the slit A and the slit A is the side growth of the grain. Determine the size.

On the other hand, the silicon crystallization method using the conventional laser annealing equipment configured as described above are as follows.

2A to 2D are cross-sectional views showing a conventional silicon crystallization method.

As shown in Fig. 2A, an amorphous silicon film 20 is deposited on a substrate (18 in Fig. 1) using chemical vapor deposition (CVD) or the like.

At this time, the amorphous silicon film 20 contains a lot of hydrogen, the hydrogen is characterized by leaving the thin film by heat.

Therefore, the amorphous silicon film 20 is heat-treated to undergo dehydrogenation.

This is because, in the case where hydrogen is not removed in advance, the surface of the crystal thin film becomes very rough and its electrical properties are poor.

As shown in FIG. 2B, the laser beam is emitted from the laser beam generator (11 in FIG. 1) through a mask (17 in FIG. 1) provided with a plurality of slits A positioned on the amorphous silicon film 20. (12 of FIG. 1) is first investigated.

At this time, the irradiated laser beam 12 is divided by a plurality of slits (A in FIG. 1) formed in the mask 17 to partially liquefy the amorphous silicon film 20.

In this case, the energy level of the laser beam 12 uses a high melting region (complete melting regime) such that the amorphous silicon film 20 is completely melted.

When the completely melted and liquefied silicon is irradiated with the laser beam 12, the lateral growth of the silicon grain 21a proceeds at the interface between the amorphous silicon region and the liquefied silicon region. Lateral growth of grain occurs perpendicular to the interface.

As a result, partially crystallized regions occur in one block by the number of slits A constituted in the mask 17.

As shown in FIG. 2C, after irradiating the primary laser beam 12, the XY stage (19 of FIG. 1) is moved to several micrometers which is equal to or smaller than the lateral growth length of grain, and then the secondary laser beam ( 12). In this case, the portion of the amorphous silicon film 20 that contacts the second irradiated laser beam 12 is liquefied and then crystallized again.

At this time, the silicon grain 21a of the polycrystalline silicon region formed as a result of irradiating the primary laser beam 12 acts as a seed, and the lateral growth of the grain is formed in the silicon melting region.

After the irradiation of the secondary laser beam 12 is finished, the silicon grain 21b grows laterally in succession to the silicon grain 21a grown by the primary irradiation.

Therefore, the above-described process is repeated to crystallize the amorphous silicon film 20 corresponding to one block into the polycrystalline silicon film 21c as shown in FIG. 2D.

However, the above-described conventional laser annealing equipment and the crystallization method using the same have the following problems.

First, a lot of contamination occurs on the surface of the crystallized silicon exposed to the crystallization process time in the atmosphere.

Second, the cooling time of silicon is short, which increases the defects by decreasing the lateral growth length and increasing the thermal stress.

The present invention has been made to solve the conventional problems as described above, while increasing the grain size and reducing defects through the heating of nitrogen (N ₂ ) during crystallization of silicon using a laser beam, and at the same time pollution in the air It is an object of the present invention to provide a laser annealing equipment and silicon crystallization method using the same to prevent the improvement of the reliability and characteristics of the device.

1 is a schematic configuration diagram showing a conventional laser annealing equipment

Figure 2a to 2d is a process cross-sectional view showing a conventional silicon crystallization method

Figure 3 is a schematic diagram showing a laser annealing equipment according to the present invention

Figures 4a to 4e is a cross-sectional view showing a silicon crystallization method according to the present invention

5a to 5d are microstructures showing changes in SLG size with substrate heating

6 is a graph showing the results of SLG length and time to solidification according to substrate heating

7 is a schematic diagram illustrating the nitrogen supply device of FIG.

8 shows a laser beam irradiation area and a nitrogen blowing area;

Explanation of symbols for the main parts of the drawings

31 laser beam generator 32 laser beam

33: first reflector 34: second reflector

35: third reflector 36: homogenizer

37 mask 38 substrate

39: vacuum chuck 40: X-Y stage

41: mask moving stage 42: nitrogen supply device

43 amorphous silicon film

Laser annealing equipment according to the present invention for achieving the above object is a laser beam generating device for generating a laser beam, a homogenizer for uniformly irradiating the energy density of the laser beam, and the laser beam generating device A XY stage correspondingly positioned and moving a predetermined distance along the X axis or the Y axis, a mask including a plurality of slits positioned between the XY stage and the laser beam generator and passing through the laser beam, and connected to one side of the mask And a mask moving stage for moving the mask by a predetermined distance, and a nitrogen gas supply device for supplying heated nitrogen gas to the substrate irradiated with the laser beam.

Here, the nitrogen gas supply device is composed of a purifier for purifying the nitrogen gas supplied through the nitrogen supply line, and a heater for receiving and heating the nitrogen gas purified from the purifier to spray.

The apparatus may further include a plurality of reflectors positioned between the laser beam generator and the homogenizer to change a traveling direction of the laser beam.

In addition, the silicon crystallization method according to the present invention for achieving the above object comprises the steps of depositing an amorphous silicon film on a substrate, mounting the substrate on which the amorphous silicon film is deposited on an XY stage, a plurality of on top of the substrate Positioning a mask having two slits and irradiating a primary laser beam to the front surface; spraying heated nitrogen onto an amorphous silicon film irradiated with the primary laser beam; And crystallizing by irradiating the second laser beam.

Here, the nitrogen injection region blows larger than the region to which the primary laser beam is irradiated.

In addition, the substrate is vacuum-adsorbed to the X-Y stage by a vacuum chuck.

In addition, the mask is moved by a predetermined distance through the mask moving stage.

In addition, the heated nitrogen temperature is sprayed by heating to a substrate deformation temperature or more than room temperature.

Hereinafter, a laser annealing apparatus and a silicon crystallization method using the same according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a schematic diagram illustrating a laser annealing apparatus according to the present invention.

As shown in FIG. 3, the laser beam generator 31 generating the laser beam 32 and the first direction for changing the traveling direction of the laser beam 32 emitted through the laser beam generator 31 are changed. And second and third reflectors 33, 34 and 35, and a homogenizer 36 for uniformizing the energy density of the laser beam 32 whose direction of travel from the third reflector 35 is changed. And a mask 37 for irradiating the laser beam 32 having a uniform energy density from the homogenizer 36 to the substrate 38 on which the amorphous silicon thin film is deposited, and the mask 37 irradiated through the mask 37. Fixing the vacuum chuck 39 and the vacuum chuck 39 for supporting the substrate 38 on which the amorphous silicon thin film (not shown), which is crystallized by the laser beam 32, is deposited by vacuum adsorption. And the XY stage 40 which moves the board | substrate 38 to an X-axis direction or a Y-axis direction simultaneously with the said mask 37 When the mask movement stage 41 is connected to one side and moves the mask 37 at a predetermined distance (for example, about several μm) and the substrate 38 is irradiated with a laser beam 32 to crystallize. It is configured to include a laser beam 32, a nitrogen (N ₂₎ the supplied nitrogen supply 42 to heat the irradiated portion.

Here, the nitrogen supply device 42 blows the heated nitrogen (N ₂ ) larger than the region to which the laser beam 32 is irradiated to the region to which the laser beam 32 is irradiated.

The laser beam generator 31 emits a laser beam 32 that is not processed by a light source, and passes through an attenuator (not shown) to adjust the energy of the laser beam 31.

In addition, the substrate 38 on which the amorphous silicon thin film is formed is fixed to the position corresponding to the mask 37 by the vacuum chuck 39 on the X-Y stage 40.

At this time, in the present invention, since the laser beam generator 31 and the mask 37 are not fixed to one position as in the related art, they have a configuration that can be moved by a predetermined distance by the mask movement stage 41, and thus amorphous. In order to crystallize all regions of the silicon thin film, the crystal movement region can be enlarged by moving the mask movement stage 41 and the XY stage 40 minutely.

The mask 37 is fixed to the mask movement stage 41 by a predetermined method, and can be moved by a small distance of several μm under the control of the mask movement stage 41. Since the mask moving stage 41 is small in size, the time for moving and stopping is significantly smaller than that of the X-Y stage 42.

Therefore, in the process of crystallizing the amorphous silicon thin film in blocks, the micro distance movement of the laser beam 32 in one block is controlled by the movement of the mask 37 using the mask movement stage 41. That is, the region to which the laser beam 32 is irradiated within one block is defined as the movement of the mask 37 rather than the movement of the substrate.

At this time, since the movement range of the mask movement stage 41 is limited, the X-Y stage 40 is used only when the crystal region of the substrate 38 is moved in units of blocks.

In this way, the time taken to crystallize the thin film can be shortened much more than when only the X-Y stage 40 is used.

In the above-described configuration, the mask 37 includes a plurality of slits A, which are transmission regions through which the laser beam 32 passes, and an absorption region B, which absorbs the laser beam 32, includes the slits A. It is composed between.

The width of the slit A formed in the mask 37 determines the size of the grains of the silicon crystals crystallized by the primary laser beam irradiation, and the interval between the slit A and the slit A is the side growth of the grain. Determine the size.

4A to 4E are process cross-sectional views showing a silicon crystallization method according to the present invention.

As shown in FIG. 4A, an amorphous silicon film 43 is deposited on the substrate 38 using chemical vapor deposition (CVD) or the like.

At this time, the amorphous silicon film 43 contains a lot of hydrogen, the hydrogen is characterized by leaving the thin film by the heat.

Therefore, the amorphous silicon film 430 is heat-treated to undergo dehydrogenation.

This is because, in the case where hydrogen is not removed in advance, the surface of the crystal thin film becomes very rough and its electrical properties are poor.

Subsequently, the substrate 38 on which the amorphous silicon film 43 is deposited is vacuum-adsorbed onto the X-Y stage 40 using a vacuum chuck (39 in FIG. 3).

As shown in FIG. 4B, a mask 37 having a plurality of slits A is positioned on the substrate 38 on which the amorphous silicon film 43 is deposited, and the laser beam 32 is first irradiated. .

Here, the laser beam 32 is divided through the slit A formed in the mask 37 to partially melt the amorphous silicon film 43 in one block into a liquid silicon state.

Subsequently, when the irradiation of the laser beam 32 is stopped, the liquid silicon rapidly cools and the grains 44a grow at the boundary between the amorphous silicon and the liquid crystal silicon. At this time, the size of the grain (44a) can be controlled according to the width of the slit (A).

As shown in FIG. 4C, heated nitrogen (N ₂ ) is injected from the nitrogen supply device (42 in FIG. 3) to the entire surface of the substrate 38 to which the primary laser beam 32 is irradiated.

Here, the heated nitrogen (N ₂ ) blows to the area to which the laser beam 32 is irradiated larger than the area to which the laser beam 32 is irradiated.

At this time, the heated nitrogen (N ₂ ) temperature blown to the substrate 38 uses nitrogen (N ₂ ) heated within the substrate deformation temperature above room temperature.

As shown in FIG. 4D, the mask 37 is moved by a number μm corresponding to a distance equal to or smaller than the width of the grain 44a by using the mask moving stage 41 of FIG. 3.

Subsequently, the laser beam 32 is irradiated to the mask 37 moved at the minute distance. At this time, the laser beam 32 passes through the slit A moved by the mask 37 to melt a portion of the region of the grain 44a during primary irradiation and the amorphous silicon film 43 in the region adjacent thereto. do.

When the irradiation of the laser beam 32 is stopped again, the grain 44a formed by irradiating the primary laser beam acts as a seed to obtain grains 44b having side surfaces grown.

By repeating the above process, as shown in Fig. 4E, growth of one block of silicon grain is completed to crystallize the amorphous silicon film 43 into the polycrystalline silicon film 44c.

At this time, when the grains laterally grown in the respective regions collide with each other, the growth of the grains is stopped. Therefore, the size of the grain can be controlled by the interval between the slits (A) configured in the mask 37.

Next, when all of the crystallization of any one block is finished, the crystal growth process of the next block in which the crystal growth of silicon is not started is started.

In this case, when moving between blocks, the crystallization process may be performed by moving the X-Y stage 40 having a larger movement distance than the mask movement stage 41 to the X axis or the Y axis.

5A to 5D are microstructures illustrating changes in SLG size with substrate heating.

That is, the substrate heating temperature is 27 ° C in Fig. 5A, 100 ° C in Fig. 5B, 300 ° C in Fig. 5C, and 500 ° C in Fig. 5D.

As shown in FIGS. 5A and 5D, it can be seen that as the heating temperature of the substrate increases, the SLG size increases.

Figure 6 is a graph showing the results of the SLG length and the time taken to solidify according to the substrate heating.

As shown in FIG. 6, it can be seen that as the substrate is heated, the SLG length expansion is more than doubled and the time to solidification is reduced by more than twice as long as the defect due to thermal stress is reduced.

FIG. 7 is a schematic diagram illustrating the nitrogen supply apparatus of FIG. 3.

As shown in FIG. 7, a purifier 42a receives and purifies nitrogen N ₂ supplied through a nitrogen supply line, and a heater 42b receives and heats purified nitrogen from the purifier 42a. .

8 is a view showing a laser beam irradiation area and a nitrogen blowing area.

As shown in Fig. 8, the nitrogen blowing region II is made larger than the laser beam irradiation region I.

As described above, the silicon crystallization apparatus and the silicon crystallization method using the same according to the present invention have the following effects.

First, by adding a mask moving stage with a small size and smooth control, the micro distance is moved through the mask moving stage and crystallized.In block-to-block crystallization, the XY stage having a larger moving distance than the mask moving stage is X-axis or Y. The process time can be shortened because the moving time to the axis moves the crystallization process and the moving and stopping time is short.

Second, by blowing the heated nitrogen to the area irradiated with the laser beam, it is possible to reduce the possibility of contamination that may occur during the crystallization process time and to reduce oxygen contents and roughness by preventing oxidation.

Third, by increasing the cooling time of the silicon it is possible to reduce the defects caused by the increase in the lateral growth length and thermal stress (thermal stress) to obtain a high-quality polycrystalline silicon.

Claims (8)

A laser beam generator for generating a laser beam, Homogenizer for uniformly irradiating the energy density of the laser beam, An X-Y stage positioned corresponding to the laser beam generator and moving by a predetermined distance along the X-axis or the Y-axis; A mask comprising a plurality of slits positioned between the X-Y stage and the laser beam generator and passing through a laser beam; A mask moving stage connected to one side of the mask and moving the mask by a predetermined distance; And a nitrogen gas supply device for supplying heated nitrogen gas to the substrate irradiated with the laser beam. According to claim 1, The nitrogen gas supply device, A purifier for purifying nitrogen gas supplied through a nitrogen supply line, Laser annealing equipment comprising a heater for receiving the purified nitrogen gas from the purifier to heat and spray. The laser annealing apparatus as claimed in claim 1, further comprising a plurality of reflectors positioned between the laser beam generator and a homogenizer to change a traveling direction of the laser beam. Depositing an amorphous silicon film on the substrate; Mounting the substrate on which the amorphous silicon film is deposited on an X-Y stage; Placing a mask having a plurality of slits on the substrate and irradiating a first laser beam on the front surface thereof; Spraying heated nitrogen onto the amorphous silicon film irradiated with the primary laser beam; And crystallizing the nitrogen-injected amorphous silicon film by irradiating a secondary laser beam. The method of claim 4, wherein the nitrogen injection region blows larger than the region to which the primary laser beam is irradiated. 5. The method of claim 4, wherein the substrate is vacuum adsorbed to the X-Y stage by a vacuum chuck. The method of claim 4, wherein the mask moves by a predetermined distance through a mask moving stage. The silicon crystallization method according to claim 4 or 5, wherein the heated nitrogen temperature is sprayed by heating to a substrate deformation temperature or higher than room temperature.