KR101727677B1 - Laser annealing apparatus and laser annealing method using multiple laser beams - Google Patents

Abstract

A laser annealing apparatus and a laser annealing method using a plurality of laser beams are disclosed. The laser annealing apparatus disclosed in the present application is a laser annealing apparatus for performing a heat treatment by irradiating a laser beam to an object to be processed mounted on a stage and comprises three or more laser light sources for emitting pulsed laser beams, And an image lens unit for irradiating the annealing laser beam emitted from the beam homogenizer to a predetermined region of the object to be processed do.

Description

[0001] The present invention relates to a laser annealing apparatus and a laser annealing method using a plurality of laser beams,

The present invention relates to laser annealing, and more particularly to a laser annealing apparatus and a laser annealing method using a plurality of laser beams.

In order to fabricate an IGBT (Insulated Gate Bipolar Transistor), which is a type of power device, a predetermined semiconductor process is first performed on the front surface of a semiconductor substrate, then the rear surface of the semiconductor substrate is thinly ground, . Then, an annealing process is performed by irradiating a laser beam on the back surface of the semiconductor substrate in a process for activating impurities after ion implantation.

In order to achieve good activation of impurities by the laser annealing process, it is necessary to be effectively heated to a predetermined depth of the semiconductor substrate by the laser beam. However, since the laser beam used in the conventional laser annealing process has a narrow pulse width, the depth reaching the laser beam inside the semiconductor substrate is small and the time to be heated by the laser beam is short, There is a problem that it is difficult to activate.

According to an embodiment of the present invention, there is provided a laser annealing apparatus and a laser annealing method using a plurality of pulsed laser beams.

In one aspect of the present invention,

A laser annealing apparatus for performing a heat treatment by irradiating a laser beam onto an object to be processed mounted on a stage,

Three or more laser light sources each emitting a pulsed laser beam;

A beam homogenizer that combines the pulsed laser beams emitted from the laser light source to form an annealing laser beam that travels on one optical path; And

And an image lens unit for irradiating the predetermined area of the object with the annealing laser beam emitted from the beam homogenizer.

The depth at which the annealing laser beam reaches the object can be adjusted by changing the interval between the pulses of the laser beams constituting the annealing laser beam.

The time intervals between the pulses of the laser beams are all the same or at least some of the time intervals of the laser beams may be different from other time intervals. Further, the intensity of the laser beams constituting the annealing laser beam may all be the same, or at least some of the laser beams may be different in intensity from other laser beams.

Each of the pulsed laser beams may have a full width at half maximum (FWHM) of 1300 ns or less, for example. The laser annealing apparatus may further include moving means for moving at least one of the stage and the annealing laser beam. The object to be processed may include a semiconductor substrate.

In another aspect,

A laser annealing method for performing a heat treatment by irradiating a laser beam to an object to be processed mounted on a stage,

Emitting three or more pulsed laser beams;

Forming an annealing laser beam that combines the pulsed laser beams to travel through one optical path; And

And irradiating the annealing laser beam onto a predetermined region of the object to be processed.

And moving at least one of the object to be processed and the annealing laser beam.

The depth at which the annealing laser beam reaches the object can be adjusted by changing the time interval between pulses of the laser beams constituting the annealing laser beam. Here, the time intervals between the pulses of the laser beams are all the same, or at least some time intervals of the time intervals of the laser beams may be different from other time intervals. Further, the intensity of the laser beams constituting the annealing laser beam may all be the same, or at least some of the laser beams may be different in intensity from other laser beams.

The impurity implanted into the semiconductor substrate can be activated by irradiation of the annealing laser beam.

According to the embodiment of the present invention, the annealing laser beam, in which the pulses are formed by the combination of the intervals between the pulses, the half width of each of the pulses and the intensity of the beam, etc. according to the annealing condition, Next, the annealing process can be smoothly performed by heating the inside of the object to a desired range.

1 schematically shows a laser annealing apparatus according to an exemplary embodiment of the present invention.
FIG. 2 shows pulses of the first, second, third, and fourth laser beams emitted from the four laser light sources shown in FIG. 1, respectively, with respect to time.
FIG. 3 is a time chart of pulses of the annealing laser beam formed by combining the first, second, third, and fourth laser beams shown in FIG.
FIG. 4 is a graph showing the relationship between the depth of the silicon wafer and the depth of the silicon wafer when the annealing laser beam, which is formed by combining the first, second, third and fourth laser beams emitted from the four laser light sources at regular time intervals between pulses, FIG.
Figure 5 illustrates pulses of an annealing laser beam according to another exemplary embodiment of the present invention.
Figure 6 illustrates pulses of an annealing laser beam according to another exemplary embodiment of the present invention.
Figure 7 illustrates pulses of an annealing laser beam according to another exemplary embodiment of the present invention.
FIG. 8 shows pulses of the first, second, third, and fourth laser beams emitted from the four laser light sources shown in FIG. 1, respectively, in accordance with another exemplary embodiment of the present invention.
FIG. 9 shows the pulses of the annealing laser beam formed by combining the first, second, third and fourth laser beams shown in FIG. 8 in time.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments illustrated below are not intended to limit the scope of the invention, but rather are provided to illustrate the invention to those skilled in the art. In the drawings, like reference numerals refer to like elements, and the size and thickness of each element may be exaggerated for clarity of explanation. Further, when it is described that a certain material layer is present on a substrate or another layer, the material layer may be present directly on the substrate or another layer, and there may be another third layer in between. In addition, the materials constituting each layer in the following embodiments are illustrative, and other materials may be used.

1 schematically shows a laser annealing apparatus according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the laser annealing apparatus 100 according to the present embodiment is an apparatus for annealing a workpiece 10 by irradiating a laser beam onto a workpiece 10 mounted on a stage S. Here, as the object to be processed 10, for example, a semiconductor substrate (a silicon wafer as a specific example) may be used. However, the present invention is not limited thereto.

The laser annealing apparatus 100 includes a plurality of laser light sources, a beam homogenizer 300, and an image lens unit 400. The plurality of laser light sources may include, for example, four laser light sources, i.e., first, second, third, and fourth laser light sources 101, 102, 103, 1 shows a case where a plurality of laser light sources include four laser light sources 101, 102, 103 and 104, but the present embodiment is not limited thereto. That is, the plurality of laser light sources may include three laser light sources or five or more laser light sources. Hereinafter, a case where a plurality of laser light sources include four laser light sources 101, 102, 103, and 104 will be described as an example.

The first, second, third and fourth laser light sources 101, 102, 103 and 104 can emit the first, second, third and fourth laser beams L1, L2, L3 and L4, respectively. Here, the first, second, third, and fourth laser beams L1, L2, L3, and L4 may be pulsed laser beams, respectively. Specifically, the first laser beam L1 may be a pulsed laser beam in which a first pulse (P1 in Fig. 2) is periodically emitted, and the second laser beam L2 may be a second pulse (P2 May be a pulsed laser beam emitted periodically. 2). The third laser beam L3 may be a pulsed laser beam that periodically emits a third pulse (P3 in Fig. 2), and the fourth laser beam L4 may be a fourth pulse (P4 in Fig. 2) May be a pulsed laser beam that is emitted periodically. The first, second, third, and fourth pulses P1, P2, P3, and P4 may each have a pulse width of, for example, 1300 ns or less. Here, the pulse width means a full width at half maximum (FWHM), which is a pulse width corresponding to half of the maximum intensity value of the laser beam.

 The first, second, third, and fourth laser beams L1, L2, L3, and L4 are arranged such that the first, second, third, and fourth pulses P1, P2, P3, (T1 in Fig. 3). Although not shown in the figure, the sequential emission of the laser beams L1, L2, L3, and L4 can be performed using a predetermined optical element such as an AOM (Acousto-Optic Modulator) or the like. The first, second, third and fourth laser beams L1, L2, L3 and L4 emitted from the laser light sources 101, 102, 103 and 104 may be laser beams of a predetermined wavelength, have. However, the present invention is not limited to this, and the first, second, third, and fourth laser beams L1, L2, L3, and L4 may have different wavelengths.

The first, second, third, and fourth laser beams L1, L2, L3, and L4, which are emitted from the first, second, third, and fourth laser light sources 101, 102, 103, And may be incident on the beam homogenizer 300. On the other hand, the reflection mirror 200 may include a scanning unit that scans the incident beam while driving in the x-axis and y-axis directions, for example. Although not shown in the figure, a predetermined optical system may be additionally disposed between the laser light sources 101, 102, 103, and 104 and the reflective mirror 200. For example, a beam expanding telescope (BET) for adjusting the size of the incident beam may be provided on the optical path between the laser light sources 101, 102, 103, and 104 and the reflective mirror 200.

The beam homogenizer 300 combines a plurality of incident laser beams L1, L2, L3, and L4 and advances the laser beams onto a single optical path. The beam homogenizer 300 can also serve to uniform the intensity of the beam. The first, second, third and fourth laser beams L1, L2, L3 and L4 emitted from the laser light sources 101, 102, 103 and 104 and reflected by the reflecting mirror 200 are incident on the beam homogenizer 300 Then, the laser beam L may be emitted as an annealing laser beam L which is combined and travels on one optical path.

The image lens unit 400 adjusts the annealing laser beam L emitted from the beam homogenizer 300 to a desired size and irradiates the laser beam L to a predetermined position on the object 10 mounted on the stage S . Here, the annealing laser beam L emitted from the image lens unit 400 reaches the predetermined depth from the surface or the surface of the object 10 to heat the object 10 to perform the annealing process.

In the laser annealing apparatus 100 according to the present embodiment, by controlling the intervals between the pulses of the first, second, third and fourth laser beams L1, L2, L3 and L4, And the fourth laser beams L1, L2, L3, and L4 are combined with each other, the depth of the annealing laser beam L reaching the inside of the object 10 can be adjusted. For example, if the intervals between the pulses of the first, second, third and fourth laser beams L1, L2, L3 and L4 are increased, the first, second, third and fourth laser beams L1, L2, L3, and L4 are formed, the pulse width of the annealing laser beam L is substantially increased, so that the laser beams L1, L2, L3, and L4 The depth of the laser beam reaching the object 10 can be increased. As described above, the range of heat extraction can be adjusted by reaching the annealing laser beam L to a desired depth in the object 10, and thus the desired annealing process can be performed smoothly.

FIG. 2 is a diagram illustrating the pulses of the first, second, third and fourth laser beams L1, L2, L3 and L4 emitted from the four laser light sources 101, 102, 103 and 104 in the laser annealing apparatus 100 shown in FIG. (P1, P2, P3, P4), respectively. Referring to FIG. 2, the first, second, third and fourth laser beams have first, second, third and fourth pulses, respectively. The first, second, third and fourth pulses (L1, L2, L3, L4) are sequentially emitted with a predetermined time interval (t1 in Fig. 3). FIG. 2 shows a case where the first, second, third and fourth pulses P1, P2, P3 and P4 all have the same shape. Accordingly, in FIG. 2, the first, second, third and fourth pulses P1, P2, P3 and P4 have the same pulse width W1 and beam intensity.

FIG. 3 is a time chart showing a state in which first, second, third and fourth pulses P1, P2, P3 and P4 emitted at a predetermined time interval t1 shown in FIG. 2 are combined . The pulses P1, P2, P3 and P4 shown in FIG. 3 are generated by combining the first, second, third and fourth laser beams L1, L2, L3 and L4, And pulses of the annealing laser beam L. 3, the annealing laser beam L irradiating the object 10 is irradiated with the first, second, third and fourth pulses P1, P2, P3 and P4 at a constant time interval t1 It has a form that comes out sequentially. Here, the pulse of the annealing laser beam L formed by combining the first, second, third and fourth pulses P1, P2, P3 and P4 has a width W substantially equal to the width of the first, Is larger than the pulse width W1 of each of the third and fourth pulses P1, P2, P3, and P4. Generally, as the pulse width of the laser beam increases, the depth at which the laser beam reaches the inside of the object to be processed 10 becomes larger. Therefore, compared with the case where any one of the first, second, third, and fourth laser beams L1, L2, L3, and L4 is irradiated onto the object to be processed 10, The depth of the laser beam reaching the inside of the object to be processed is larger when the object to be processed 10 is irradiated with the annealing laser beam L formed by combining the first to fourth laser beams L1, L2, L3, .

FIG. 4 is a graph showing a temperature distribution according to the depth of a silicon wafer when an annealing laser beam including first, second, third and fourth laser beams emitted from four laser light sources at a constant pulse interval is irradiated onto the silicon wafer Respectively. 4 shows the measured results when the four pulse shapes are all the same, the half width of each pulse is 0.2 mu s (i.e., 200 ns), and the energy density of each of the laser beams is 4 J / cm < ^{2 &} gt ;. Table 1 below shows the maximum temperature according to the depth of the silicon wafer from the results shown in Fig. In Table 1, for example, -6 mu m means a position at a depth of 6 mu m from the surface of the silicon wafer.

Position (탆) Max. Temperature (K) Surface 4500 -2 3500 -4 2700 -6 2100 -8 1700 -10 1150

Referring to FIGS. 4 and Table 1, the first, second, third and fourth laser beams emitted at a constant pulse interval are combined to form an annealing laser beam having a pulse width broader than that of each of the pulses have. Therefore, the annealing process can be performed by heating the inside of the silicon wafer by reaching the annealing laser beam from the surface of the silicon wafer to a deep depth. Here, by controlling the pulse intervals of the first, second, third and fourth laser beams, it is possible to control the depth at which the annealing laser beam reaches the inside of the silicon wafer, whereby the heat generated by the annealing laser beam The annealing process can be performed by adjusting the range of diffusion.

Figure 5 shows the pulses of the annealing laser beam in time according to another exemplary embodiment of the present invention. FIG. 5 shows a state where four first, second, third, and fourth pulses P1, P2, P3, and P4 sequentially outputted at a predetermined pulse interval t2 are formed in a composite state, The pulses of the first, second, third and fourth laser beams (L1, L2, L3 and L4 in FIG. 1) are combined to form pulses of the annealing laser beam L traveling in one optical path.

5, the first, second, third, and fourth pulses P1, P2, P3, and P4 are sequentially emitted at a constant time interval t2, 3 is larger than the interval t1 between the pulses shown in Fig. Thus, the annealing laser beam L including the pulses P1, P2, P3, and P4 of the type shown in Fig. 5 is incident on the surface of the object 10 to a deeper depth, It can be seen that the beam reaches and the object to be processed can be heated.

In the above embodiments, the four pulses P1, P2, P3 and P4 are outputted at a constant time interval t1 or t2. However, the pulses P1, P2, P3 and P4 May vary in various ways.

Figure 6 illustrates pulses of an annealing laser beam according to another exemplary embodiment of the present invention. 6, the first, second, third, and fourth pulses P1, P2, P3, and P4 that are sequentially emitted while varying the intervals between pulses are formed in a composite state. P1, P2, P3, and P4 are formed by combining the first, second, third, and fourth laser beams (L1, L2, L3, and L4 in FIG. 1) to form pulses of an annealing laser beam .

Referring to FIG. 6, the first, second, third, and fourth pulses P1, P2, P3, and P4 are sequentially output at predetermined time intervals. Here, the interval t1 between the first pulse P1 and the second pulse P2, the interval t2 between the second pulse P2 and the third pulse P3, and the interval t2 between the third pulse P3 and the fourth pulse The intervals t3 of the pulses P4 may be different from each other. 6, the first, second, third, and fourth pulses P1, P2, P3, and P4 have the same shape. However, the first, second, third, Some of the fourth pulses P1, P2, P3, P4 may have a different form from the other pulses.

Figure 7 illustrates pulses of an annealing laser beam according to another exemplary embodiment of the present invention. FIG. 7 shows the first, second, third, and fourth pulses P1, P2, P3, and P4 sequentially formed at different time intervals t1. These pulses P1, P2, P3 and P4 are generated by combining the first, second, third and fourth laser beams (L1, L2, L3, L4 of FIG. 1) And pulses of the laser beam L.

Referring to FIG. 7, the first, second, third and fourth pulses P1, P2, P3 and P4 are sequentially output at a predetermined time interval t1. Here, the second and fourth pulses P2 and P4 may have different forms from the first and third pulses P1 and P3. More specifically, the pulse width W1 of the second and fourth pulses P2 and P4 may be different from the pulse width S2 of the first and third pulses P1 and P3, have. 7 illustrates an example in which four pulses P1, P2, P3, and P4 are output at the same time interval t1. However, some pulse intervals may be different from other pulse intervals.

FIG. 8 shows pulses of the first, second, third, and fourth laser beams emitted from the four laser light sources shown in FIG. 1, respectively, in accordance with another exemplary embodiment of the present invention. 9 shows the pulses of the annealing laser beam formed by combining the first, second, third, and fourth laser beams shown in FIG. 8 with time.

Referring to FIG. 8, the first, second, third and fourth laser beams L1, L2, L3 and L4 emitted from the four laser light sources 101, 102, 103 and 104 are emitted simultaneously, And fourth pulses P1, P2, P3, and P4. In this case, by combining the first, second, third and fourth pulses P1, P2, P3 and P4, the first, second, third and fourth pulses P1 , P2, P3, and P4, respectively, can be obtained. Accordingly, it is possible to form an annealing laser beam having a high energy density by combining a plurality of laser beams having a low energy density, so that an annealing process requiring a laser beam having a high energy density can be performed smoothly.

As described above, the annealing laser beam, in which the pulses are formed by a combination of the pulses, the half width of each of the pulses, and the intensity of the beam, according to the annealing condition, reaches the desired depth in the object, The annealing process can be smoothly performed by heating the inside of the object to a desired range.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined by the appended claims.

100 .. Laser annealing device
101. A first laser light source
102. A second laser light source
103. Third laser light source
104. The fourth laser light source
200 .. reflection mirror
300 .. Beam homogenizer
400 .. Imaging Lens Unit
L1 .. First laser beam
L2 .. Second laser beam
L3 .. Third laser beam
L4 .. Fourth laser beam
L .. annealing laser beam
W .. The object to be processed
S .. Stage

Claims (15)

A laser annealing apparatus for performing a heat treatment by irradiating a laser beam onto an object to be processed mounted on a stage,
Three or more laser light sources each emitting a pulsed laser beam;
A beam homogenizer that combines the pulsed laser beams emitted from the laser light source to form an annealing laser beam that travels on one optical path; And
And an image lens unit which irradiates the annealing laser beam emitted from the beam homogenizer to a predetermined region of the object to be processed,
And adjusts the depth at which the annealing laser beam reaches within the object by changing the distance between the pulses of the laser beams constituting the annealing laser beam. delete The method according to claim 1,
Wherein the time intervals between the pulses of the laser beams are all the same or at least some time intervals of the time intervals of the laser beams are different from other time intervals. The method according to claim 1,
Wherein the intensity of the laser beams constituting the annealing laser beam are all the same or at least some of the laser beams are different in intensity from other laser beams. The method according to claim 1,
Wherein each of the laser beams includes a pulse having a full width at half maximum (FWHM) of 1300 ns or less. The method according to claim 1,
And moving means for moving at least one of the stage and the annealing laser beam. The method according to claim 1,
Wherein the object to be processed comprises a semiconductor substrate. A laser annealing method for performing a heat treatment by irradiating a laser beam to an object to be processed mounted on a stage,
Emitting three or more pulsed laser beams;
Forming an annealing laser beam that combines the pulsed laser beams to travel through one optical path; And
And irradiating the annealing laser beam onto a predetermined region of the object to be processed,
Wherein the depth of reach of the annealing laser beam in the object is adjusted by changing a time interval between pulses of the laser beams constituting the annealing laser beam. 9. The method of claim 8,
And moving at least one of the object to be processed and the annealing laser beam. delete 9. The method of claim 8,
Wherein the time intervals between the pulses of the laser beams are all the same or at least some of the time intervals of the laser beams are different from the other time intervals by a laser annealing method 9. The method of claim 8,
Wherein the intensity of the laser beams constituting the annealing laser beam is all the same or at least some of the laser beams are different in intensity from other laser beams. 9. The method of claim 8,
Wherein each of the laser beams comprises a pulse having a half-width (FWHM) of 1300 ns or less. 9. The method of claim 8,
Wherein the object to be processed comprises a semiconductor substrate. 15. The method of claim 14,
And impurities injected into the semiconductor substrate are activated by irradiation of the annealing laser beam.

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