JP2004342875A - Laser annealing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a high-quality annealed product with a high yield by conducting a feedback control based on the information about an annealed state detected at the position where an annealing process is performed by a laser annealing device. <P>SOLUTION: A laser beam which has been emitted from the laser light source 300 of a semiconductor laser and is changed and adjusted for a space intensity distribution by means of a space light modulation means 316 is irradiated on a film-like object 150 to be annealed by means of a laser irradiation means. At the same time, an annealing process is conducted by scanning over the object 150 with the laser beam while moving the object 150 and the laser beam relatively with each other by a scanning means 152 and 330. At that time, a feedback control is conducted with respect to the space light modulation means 316 and/or the scanning means 152, 330, on the basis of the information on the annealed state measured at an annealing position by an annealing controlling means as a monitor, thereby to make the annealing process appropriate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser annealing apparatus that realizes large crystal grain formation by performing feedback control while monitoring an annealing state while performing an annealing process by irradiating an object with a laser beam.
[0002]
[Prior art]
In general, from the viewpoint of miniaturization and cost reduction of flat panel displays such as liquid crystal displays (LCD) and organic EL (electroluminescence) displays, not only thin film transistors (TFTs) for pixel display gates but also drive circuits and A system-on-glass (SOG) -TFT in which a signal processing circuit, an image processing circuit, and the like are directly formed on a glass substrate of an LCD has attracted attention.
[0003]
Amorphous silicon (a-Si) has been used for such a TFT for a pixel display gate, but polysilicon (Poly-Si) having high carrier mobility is required for the SOG-TFT. However, since the deformation temperature of glass is as low as 600 ° C., a crystal growth technique using a high temperature of 600 ° C. or higher cannot be used for forming a polysilicon film. Therefore, the polysilicon film is formed by forming an amorphous silicon film at a low temperature (100 to 300 ° C.), then thermally melting the amorphous silicon film by pulse irradiation with a XeCl excimer laser having a wavelength of 308 nm, and crystallizing in the cooling process. Excimer laser annealing (ELA) is used. By using this ELA, a polysilicon film can be formed without thermally damaging the glass substrate.
[0004]
A conventional laser annealing process for converting amorphous silicon (a-Si) to polysilicon (Poly-Si) is performed by irradiating the a-Si film with XeCl excimer laser light having a wavelength of 308 nm. The absorption coefficient of this XeCl excimer laser with respect to a-Si for light having a wavelength of 308 nm is 1 × 10 ⁶ cm ^-1 Therefore, the input energy is absorbed very close to the surface (<1 nm).
[0005]
For this reason, in the excimer laser annealing, a large temperature gradient is generated in the depth direction in the Si layer melted by absorption of laser energy and heat propagation, and a partial melting state shown in FIG. 24, for example, may occur.
[0006]
In this case, the heat mainly diffuses in the direction of the substrate, and the a-Si remaining without melting causes a phase transition to the crystalline phase between the solid phases at 800 ° C. Therefore, the boundary between the molten Si phase and the a-Si phase Conclusion nucleus is generated in the part. The generated crystal nuclei start from that point and grow in the upward direction of the figure along the temperature gradient. The crystal growth is stopped in a state where the crystal grains grown from the adjacent crystal nuclei collide and the crystal grains are small and there are many crystal grain boundaries.
[0007]
Here, high charge mobility is required for high performance of the TFT. Since the crystal grain boundary is a barrier to movement for electrons, it is important to generate crystal grains with few crystal grain boundaries, that is, large crystal grains, in order to increase the charge mobility.
[0008]
Therefore, in the excimer laser annealing, as shown in FIG. 25, when the output of the excimer laser is increased and the remaining a-Si phase is made into an island shape, the number of generated crystal nuclei is reduced and each crystal grain grows greatly. It becomes.
[0009]
In the excimer / laser annealing, as shown in FIG. 26, when the output of the excimer laser is further increased and the a-Si phase is completely melted, a supercooling state in which crystallization does not occur even when the temperature is lower than the melting point. When the temperature is lowered, crystal nuclei are generated all at once, and the entire state is filled with fine crystal grains.
[0010]
FIG. 27 shows the relationship between the laser intensity and the crystal grain size described above qualitatively. As the laser intensity increases, the crystal grain size increases from the partially melted (a) state to the molten state (b) in which the remaining a-Si phase is converted into islands, but the a-Si is completely As soon as the melting laser intensity is exceeded, a completely molten state (c) is reached, and the crystal grain size is refined at once. On the other hand, the output stability of the excimer laser is poor, and intensity fluctuations of about 10 to 15% (illustrated by hatching in FIG. 27) are unavoidable. Therefore, the crystal grain size obtained by excimer laser annealing is effectively limited to about 0.3 μm at present. This is also the limit that the crystal growth direction is the vertical direction (vertical direction toward FIGS. 24 and 25).
[0011]
To solve these problems, an annealing method has been devised in which the substrate is slowly scanned so that the a-Si is completely melted so as not to cause a supercooled state, and crystal growth is controlled in the lateral direction.
[0012]
In this annealing method, crystal nuclei are generated from the a-Si layer not irradiated with the laser as shown in FIG. 28, but the crystal growth is obliquely upward from the crystal nuclei at the bottom of the boundary between the a-Si and the molten layer due to the temperature gradient. move on. This is considered to be due to a temperature gradient in the depth direction, and the solid-liquid interface is slanted in the oblique direction, and crystal growth proceeds perpendicularly to the oblique solid-liquid interface.
[0013]
In any case, the size of the crystal grain boundary is limited by the collision with the crystal grain from the opposite side to the film thickness. This is essentially caused by a large temperature gradient in the depth direction of the molten layer (for example, see Non-Patent Document 1).
[0014]
Therefore, as a solution to the problem of lateral crystal growth of excimer laser, high output Nd: YVO with high laser output stability (1%) ₄ Laser annealing with a laser beam of 532 nm has been devised.
[0015]
Nd: YVO ₄ The absorption coefficient for a-Si of 532 nm light of the laser is 5 × 10 ⁴ cm ^-1 Therefore, a film thickness of 460 nm is required to absorb 90% of the input energy. This Nd: YVO ₄ Since the laser 532 nm light has an absorption coefficient that is about 1.5 orders of magnitude less than that of the excimer laser wavelength 308 nm, as shown in FIG. 29, the temperature gradient in the depth direction is flatter at 532 nm when compared with the same film thickness. Thus, the solid-liquid interface tends to stand vertically. For this reason, the growth distance in the horizontal direction is long and a large crystal grain boundary is generated (see, for example, Patent Document 1).
[0016]
[Non-Patent Document 1]
Masayoshi Matsumura, Surface Science Vol. 21, No. 5, pp 278-287, 2000
Accepted March 28, 2000
[Patent Document 1]
JP 2001-144027 A
[0017]
[Problems to be solved by the invention]
As described above, when annealing is performed in a state where the temperature gradient in the depth direction of the film thickness in the a-Si film is flat and the solid-liquid interface is set up vertically, the side of the crystal film grown from the solid-liquid interface is Since the growth distance in the direction can be long, a large grain boundary can be generated. For this purpose, it is necessary to proceed the annealing process while controlling the inclination and moving speed of the solid-liquid interface with a laser annealing apparatus.
[0018]
However, the conventional laser annealing equipment is only incidental laser crystallization and accidental crystallization is performed. Information on the solid-liquid interface state and crystallinity is detected at the annealed position, and this information is fed back. No laser annealing apparatus that can adjust the laser output, laser intensity distribution, scanning speed, and the like.
[0019]
In consideration of the above-mentioned facts, the present invention detects information on the annealing state at a position where the object is irradiated with a laser beam and performs the annealing process, and performs an appropriate annealing process by performing feedback control based on this information. It is an object of the present invention to newly provide a laser annealing apparatus that can be used.
[0020]
[Means for Solving the Problems]
A laser annealing apparatus according to claim 1 of the present invention includes a laser light source that emits a laser beam, a laser irradiation unit that irradiates a film-like annealing target with the laser beam emitted from the laser light source, Spatial light modulation means for changing and adjusting the spatial intensity distribution of the laser beam applied to the object, scanning means for relatively moving and scanning the annealing object and the laser beam, and the laser beam annealing object And annealing control means for performing feedback control on at least one of the spatial light modulation means and the scanning means based on information measured as an annealing state monitor at the position where the annealing treatment is performed by irradiating And
[0021]
By configuring as described above, the state where the object is annealed at the position where the annealing object is irradiated by irradiating the object to be annealed with the laser beam is monitored, and based on the information when this monitoring is performed, By performing feedback control for optimizing the annealing process on at least one of the spatial light modulation unit and the scanning unit, a high-quality product subjected to the annealing process can be manufactured with a high yield.
[0022]
According to a second aspect of the present invention, in the laser annealing apparatus according to the first aspect, the laser light source is a solid-state laser.
[0023]
With the configuration described above, the laser light source can be stably driven at a high output, so that the laser annealing process can be performed quickly and stably.
[0024]
A third aspect of the present invention is the laser annealing apparatus according to the first aspect, wherein the laser light source is a semiconductor laser.
[0025]
By configuring as described above, stability in driving the laser light source is improved, and even if the output of each semiconductor laser element is small, the total number is increased or decreased to increase the output or compare Therefore, the adjustment can be easily performed to set the output to be low, and the semiconductor laser light source is inexpensive, so that the product can be manufactured at low cost.
[0026]
According to a fourth aspect of the present invention, in the laser annealing apparatus according to the third aspect, the laser light source is a GaN-based semiconductor laser.
[0027]
By configuring as described above, the stability in driving the GaN-based laser light source is further improved, and the output of each GaN-based semiconductor laser element can be relatively strong among the semiconductor lasers. Adjustment can be easily made by increasing or decreasing the output to be higher or setting to a relatively lower output, and the GaN-based semiconductor laser light source is cheaper, so that the product can be manufactured at a lower price.
[0028]
According to a fifth aspect of the present invention, there is provided the laser annealing apparatus according to any one of the first to fourth aspects, wherein the annealing control means has a crystallinity in a crystallization region within a projection range of the laser beam being annealed. Measure the Raman spectrum information from the Raman scattered light emitted in response to the analysis, analyze the quality of the crystal and the position of the solid-liquid interface, and the crystallization state for at least one of the spatial light modulation means and the scanning means Or it is comprised so that the feedback control which optimizes the movement state of a solid-liquid interface may be performed.
[0029]
With the above-described configuration, in addition to the operation and effect of the invention according to any one of claims 1 to 4, the laser beam is irradiated on the object to be annealed and the annealing process is performed. Using the laser beam for annealing, information on the Raman spectrum is measured from the Raman scattered light emitted according to the crystallinity in the crystallization region within the projection range of the annealing laser beam, and the quality and stability of the crystal are measured. Analyzing the position of the liquid interface, and performing feedback control required to maintain the crystal quality above a predetermined standard for at least one of the spatial light modulation means and the scanning means, and the annealed high quality Products can be manufactured with high yield.
[0030]
In addition, since this annealing control means shares the laser beam emitted from the laser light source for annealing and for the Raman excitation light, compared to a laser light source for Raman excitation light separately provided, The configuration can be simplified.
[0031]
According to a sixth aspect of the present invention, in the laser annealing apparatus according to any one of the first to fourth aspects, the annealing control means is emitted from a laser light source for Raman excitation light at a position where annealing treatment is performed. When the laser beam with a wavelength different from that of the annealing laser beam is irradiated, information on the Raman spectrum is measured from the Raman scattered light emitted according to the crystallinity in the crystallization region, and the crystal quality and the position of the solid-liquid interface are measured. And at least one of the spatial light modulation means and the scanning means is configured to perform feedback control for optimizing the crystallization state or the movement state of the solid-liquid interface.
[0032]
With the above-described configuration, in addition to the operation and effect of the invention according to any one of claims 1 to 4, the laser beam is irradiated on the object to be annealed and the annealing process is performed. Using a laser beam having a wavelength different from that of the annealing laser beam emitted from the laser light source for Raman excitation light, Raman is emitted in accordance with the crystallinity in the crystallization region within the projection range of the annealing laser beam. To measure Raman spectral information from scattered light, analyze the quality of the crystal and the position of the solid-liquid interface, and maintain the quality of the crystal above a predetermined standard for at least one of the spatial light modulation means and the scanning means By performing the necessary feedback control, it is possible to manufacture high-quality products that are annealed with a high yield.
[0033]
In addition, by using a laser beam having a wavelength different from that of the annealing laser beam emitted from the laser light source for Raman excitation light, the annealing laser beam has a spatial intensity distribution in order to form a temperature gradient. When the pump light intensity changes, the Raman efficiency changes greatly, making it difficult to make a relative comparison of the Raman signal intensity difficult. By using the laser beam for annealing and a laser beam of a different wavelength as the Raman pump light, a Raman signal is obtained. It is possible to make a relative comparison of strengths and to grasp the state of the annealed part in more detail.
[0034]
According to a seventh aspect of the present invention, in the laser annealing apparatus according to any one of the first to fourth aspects, the annealing control means is uniform at a wavelength different from that of the annealing laser beam emitted from the reflectance measurement laser light source. When the laser beam for reflectivity measurement with high light intensity is reflected to the position where the annealing treatment is performed, the crystallized part and the melted part detected by measuring different reflection intensities at the crystallized part and the melted part Analyzing the movement speed data of the crystallization zone, the melting zone, and the crystallization zone obtained from the two-dimensional information with the part, and at least one of the spatial light modulation means and the scanning means is in a crystallization state or a solid state. It is configured to perform feedback control for optimizing the movement state of the liquid interface.
[0035]
By configuring as described above, in addition to the operation and effect of the invention according to any one of claims 1 to 4, the laser beam is irradiated to the object to be annealed and the annealing process is performed. On the other hand, when the reflectance measurement laser beam having a uniform light intensity at a different wavelength from that of the annealing laser beam emitted from the reflectance measurement laser light source is reflected, the crystallized portion and the melted portion Different reflection intensities were measured, and the state of the solid-liquid interface at the boundary between the crystallization zone and the melting zone, obtained from the two-dimensional information of the crystallization zone and the melting zone, By analyzing the data of the moving speed and performing feedback control required to maintain the crystal quality above a predetermined standard for at least one of the spatial light modulation means and the scanning means, the annealed high quality Made The it can be produced at a high yield.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
In the following, an embodiment in which the laser annealing apparatus of the present invention is applied to low-temperature polysilicon TFT formation will be described in detail with reference to the drawings.
[0037]
In the low-temperature polysilicon TFT formation process in which the laser annealing apparatus according to this embodiment is used, first, as shown in FIG. 18A, on a transparent substrate 150 made of glass or plastic (including a film or the like). , Silicon oxide (SiO _x ) An insulating film 190 is deposited and SiO _x An amorphous silicon film 192 is deposited on the insulating film 190.
[0038]
The amorphous silicon film 192 is polycrystallized by laser annealing to form a polysilicon film. Thereafter, using a photolithography technique, for example, as shown in FIG. _x A polysilicon TFT including a polysilicon gate 194, polysilicon source / polysilicon drain 196, gate electrode 198, source / drain electrode 200, and interlayer insulating film 202 is formed through the insulating film 190.
[Configuration of laser annealing equipment]
As shown in FIG. 1, the laser annealing apparatus according to the present embodiment includes a flat plate stage 152 that holds and holds a transparent substrate 150 on which an amorphous silicon film as an object is deposited. . The stage 152 constitutes a scanning unit that relatively moves and scans the annealing object and the laser beam.
[0039]
Two guides 158 extending along the stage moving direction are installed on the upper surface of the thick plate-shaped installation table 156 supported by the four legs 154. The stage 152 is arranged so that the longitudinal direction thereof faces the stage moving direction, and is supported by a guide 158 so as to be reciprocally movable. The laser annealing apparatus is provided with a driving device (not shown) for driving the stage 152 along the guide 158.
[0040]
A U-shaped gate 160 is provided at the center of the installation table 156 so as to straddle the movement path of the stage 152. Each end of the U-shaped gate 160 is fixed to both side surfaces of the installation table 156, respectively. A scanner 162 is provided on one side of the gate 160, and a plurality of (for example, two) detection sensors 164 for detecting the front and rear ends of the transparent substrate 150 are provided on the other side. . The scanner 162 and the detection sensor 164 are respectively attached to the gate 160 and fixedly arranged above the moving path of the stage 152. The scanner 162 and the detection sensor 164 are connected to a controller (not shown) that controls them.
[0041]
In this laser annealing apparatus, the annealing state is monitored at a position where the scanner 162 and the stage 152 and their control system are irradiated with GaN-based semiconductor laser light (405 nm) on the a-Si film. The crystallinity measured at the annealing position shown in FIG. 2 is used to realize large crystal grain formation by performing feedback control for promoting crystal growth in the lateral direction of the a-Si film based on the crystallinity information measured as An annealing control means for performing feedback control based on the information is configured.
[0042]
In the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position, as a laser light source 300, an optical fiber module for integrating and projecting light having a wavelength of 405 nm emitted from a GaN semiconductor laser in the optical fiber 301. Use a light source. The laser light source 300 may be configured to emit an annealing laser beam having an arbitrary wavelength within a wavelength range of 350 nm to 450 nm.
[0043]
In the case of a laser light source using a semiconductor laser, even if the output of each semiconductor laser element is small, it is easy to make adjustments to increase or decrease the total number of these to increase the output or to set a relatively low output. Can be done. Further, since the semiconductor laser light source is inexpensive, the product can be manufactured at a low price.
[0044]
In particular, if a GaN-based semiconductor laser is used, the stability in driving a GaN-based laser light source is further improved, and the output of each GaN-based semiconductor laser element can be relatively strong among the semiconductor lasers. Increase or decrease the total number to make the output higher, or easily adjust to set to a relatively low output (adjustment of power scaling), and the GaN-based semiconductor laser light source is cheaper, making the product cheaper Can be manufactured.
[0045]
Further, the laser light source 300 is a laser light source using an LD-excited solid-state laser, Nd: YVO. ₄ SH ₆ Laser, Nd: YAGSH ₆ A laser or a Pr: YLF laser may be used. When this solid-state laser is used as a laser light source, the laser light source can be driven stably with high output.
[0046]
As the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position, a laser beam with a wavelength of 405 nm projected from the optical fiber 301 of the laser light source 300 as the optical fiber module light source is used as the beam shaping optical system 302. The beam is shaped by the above-described method, passed through a spatial light modulator 316 that is a spatial light modulation means, bent to a projection lens 308 by a dichroic mirror 304, and projected from above onto the surface of the a-Si film with a desired beam pattern by the projection lens 308. Laser irradiation means is provided.
[0047]
In the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position shown in FIG. 2, the spatial light modulator 316 as the spatial light modulation means is used to change the incident light beam according to the data. It can be constituted by a digital micromirror device (DMD) which is a spatial light modulation element that modulates each pixel and forms a light beam in a predetermined spatial distribution.
[0048]
The spatial light modulator (DMD) 316 is connected to a controller (not shown) having a data processing unit and a mirror drive control unit. The data processing unit of this controller generates a control signal for driving and controlling each micromirror in the region to be controlled for each spatial light modulator 316 based on the input data. This data is data representing the density of each pixel in binary (whether or not dots are recorded). The mirror drive control unit controls the angle of the reflection surface of each micromirror for each spatial light modulator 316 based on the control signal generated by the data processing unit.
[0049]
As shown in FIG. 6, the spatial light modulator (DMD) 316 is configured such that a micromirror (micromirror) 62 is supported on a SRAM cell (memory cell) 60 and supported by a support column. ) Is a mirror device configured by arranging a large number of (for example, 600 × 800) micromirrors in a grid pattern. Each pixel is provided with a micromirror 62 supported by a support column at the top, and a material having a high reflectance such as aluminum is deposited on the surface of the micromirror 62. The reflectance of the micromirror 62 is 90% or more. A silicon gate CMOS SRAM cell 60 manufactured on a normal semiconductor memory manufacturing line is disposed directly below the micromirror 62 via a support including a hinge and a yoke, and is entirely monolithic (integrated type). ).
[0050]
When a digital signal is written in the SRAM cell 60 of the spatial light modulator (DMD) 316, the micromirror 62 supported by the support is centered on the diagonal line with respect to the substrate side on which the spatial light modulator (DMD) 316 is disposed. And tilted within a range of ± α degrees (for example, ± 10 degrees). FIG. 7A shows a state in which the micromirror 62 is tilted to + α degrees in the on state, and FIG. 7B shows a state in which the micromirror 62 is tilted to −α degrees in the off state. Therefore, the light incident on the spatial light modulator (DMD) 316 is controlled by controlling the inclination of the micromirror 62 in each pixel of the spatial light modulator (DMD) 316 in accordance with the data signal as shown in the figure. Is reflected in the tilt direction of each micromirror 62.
[0051]
FIG. 7 shows an example of a state in which a part of the spatial light modulator (DMD) 316 is enlarged and the micromirror 62 is controlled to + α degrees or −α degrees. On / off control of each micromirror 62 is performed by a controller (not shown) connected to a spatial light modulator (DMD) 316. A light absorber (not shown) is arranged in the direction in which the light beam is reflected by the micromirror 62 in the off state.
[0052]
The spatial light modulator (DMD) 316 is preferably arranged with a slight inclination so that the short side thereof forms a predetermined angle θ (for example, 1 ° to 5 °) with the sub-scanning direction. FIG. 8A shows the scanning locus of the reflected light image (irradiation beam) 53 by each micromirror when the spatial light modulator (DMD) 316 is not tilted, and FIG. 8B is the spatial light modulator (DMD). The scanning trajectory of the irradiation beam 53 when 316 is inclined is shown.
[0053]
In the spatial light modulator (DMD) 316, a large number (for example, 600 sets) of micromirror arrays in which a large number (for example, 800) of micromirrors are arranged in the long side direction are arranged. However, as shown in FIG. 8B, by tilting the spatial light modulator (DMD) 316, the pitch P of the scanning trajectory (scanning line) of the irradiation beam 53 by each micromirror. ₂ However, the pitch P of the scanning line when the spatial light modulator (DMD) 316 is not tilted. ₁ It becomes narrower and the resolution can be greatly improved. On the other hand, since the tilt angle of the spatial light modulator (DMD) 316 is very small, the scanning width W when the spatial light modulator (DMD) 316 is tilted. ₂ And the scanning width W when the spatial light modulator (DMD) 316 is not tilted. ₁ Is substantially the same.
[0054]
Further, laser irradiation (multiple exposure) is performed by overlapping the same scanning line by different micromirror arrays. Thus, by performing multiple exposure, a minute amount of the laser irradiation position can be controlled, and high-definition annealing can be realized. Further, the joints between the plurality of laser light sources 300 arranged in the main scanning direction can be connected without a step by controlling a very small amount of laser irradiation position.
[0055]
Note that the same effect can be obtained by arranging the micromirror rows in a staggered manner at a predetermined interval in the direction orthogonal to the sub-scanning direction instead of tilting the spatial light modulator (DMD) 316.
[0056]
In the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position in this laser annealing apparatus, the spatial light modulator (DMD) 316 is used for the a-Si film on the substrate 150. As shown by an imaginary line LP in FIG. 3, the distribution of the light energy projected onto the fine band-shaped range is strong at the front end side in the transport direction of the substrate 150 and weakened as it goes toward the rear end side in the transport direction. Adjustment is made so that the energy intensity has a gradient, and control is performed so as to obtain an ideal temperature distribution in the depth direction (film thickness direction) in the a-Si film as shown in FIG. It becomes possible.
[0057]
That is, in the annealing control means that performs feedback control based on the crystallinity information measured at this annealing position, the distribution of light energy with respect to the a-Si film is imagined in FIG. 3 using the spatial light modulator (DMD) 316. As indicated by the line LP, when the substrate 150 is strong at the front end side in the transport direction and weakens as it goes toward the rear end side in the transport direction, the front end in the transport direction where the laser beam in the a-Si film is projected and melting is started. The temperature gradient in the melted portion from the melting start position on the side (upstream in the transport direction) to the position of the solid-liquid interface LS on the rear end side in the transport direction (downstream in the transport direction) is shown by a solid line TL in FIG. In addition, the temperature can be controlled to decrease smoothly from the melting start position to the position of the solid-liquid interface LS.
[0058]
Thus, when heating control is performed so as to exhibit a temperature gradient in which the temperature smoothly decreases from the melting start position to the position of the solid-liquid interface LS, the melted laser beam in the a-Si film must be used. It can be controlled to grow a crystal from a crystal nucleus generated at the solid-liquid interface LS.
[0059]
Thus, for example, the crystal grows from the crystal nucleus generated in the partially cooled place (the part other than the solid-liquid interface LS) between the melting start position and the position of the solid-liquid interface LS, thereby preventing lateral crystal growth. And the formation of large crystal grains can be prevented from being hindered.
[0060]
In this heating control, the temperature gradient is set so that crystal nuclei are not generated in portions other than the solid-liquid interface LS even when the portion melted by the laser beam in the a-Si film is cooled by various factors. It is desirable to do.
[0061]
As described above, the a-Si film in the projection range of the light beam on which the light beam having the spatial distribution formed to give the temperature gradient by the spatial light modulator 316 is transported in the projection range of the light beam. It is heated and melted at the part from the melting start position on the front end side to the position of the solid-liquid interface LS, and crystallized with heat radiation in the crystallization area SA from the solid-liquid interface LS to the rear end side in the transport direction within the projection range of the light beam. To do.
[0062]
As shown in FIG. 3, since 405 nm light is irradiated to the crystallization area SA within the projection range of the light beam, this 405 nm light functions as Raman excitation light and depends on the crystallinity from the crystallization area SA. Raman scattered light RL is emitted. The Raman scattered light is 518 cm from the excitation light. ^-1 The shifted wavelength is, and as shown in FIG. 5, the spectrum half-width becomes narrower as the crystallinity becomes better.
[0063]
The Raman scattered light RL is collected by the projection lens 308, passes through the dichroic mirror 304, and is projected by the lens 310 onto the slit member 312 having the slit 314 formed therein. The Raman scattered light RL transmitted through the slit 314 is reflected by the concave mirror 318 and converted into a parallel beam, and enters the diffraction grating 320.
[0064]
The Raman scattered light RL diffracted by the diffraction grating 320 is reflected by the concave mirror 322 and imaged on the CCD 324. The longitudinal direction in the slit image of the Raman scattered light RL imaged on the CCD 324 corresponds to the spatial position on the a-Si film, and the short direction is developed on the wavelength axis by the diffraction grating.
[0065]
That is, when 405 nm light having an intensity pattern (intensity gradient) as shown by an imaginary line LP in FIG. 3 is projected onto the a-Si film, the light energy is absorbed and the temperature and phase state of the a-Si film are As shown in FIG. Due to thermal diffusion or movement of the substrate 150 provided with the a-Si film in the scanning direction, the temperature gradient sequentially moves and crystallization progresses.
[0066]
Therefore, as shown in FIG. 3, in the 405 nm beam projection pattern (within the light beam projection range), crystallization occurs in the crystallization area SA that is a part of the 405 nm beam projection pattern.
[0067]
Since 405 nm light is also projected onto the crystallization area SA, this 405 nm light functions as Raman excitation light and exhibits a Raman spectrum corresponding to the crystal quality.
[0068]
The pattern of the Raman scattered light generated in the crystallization area SA is projected onto the slit 314 of the slit member 312 by the projection lens 308 and the lens 310. The projection image transmitted through the slit 314 is decomposed into a spectrum as described above, and is detected as a spectrum pattern shown in FIG. 5 on the CCD light receiving surface.
[0069]
In FIG. 5, the X axis corresponds to the positional relationship in the X axis direction (scanning direction) of a-Si that is the longitudinal direction of the slit 314, and the Y axis corresponds to the wavelength of the Raman scattered light. .
[0070]
The information (data) of the Raman spectrum image output from the CCD 324 as shown in FIG. 5 is transmitted to the control unit 326, and the polysilicon pattern in the crystallization area SA within the 405 nm light projection area is output from the output pattern of the data. The crystal quality and the position of the solid-liquid interface LS are analyzed.
[0071]
The control unit 326 generates a control signal based on the information on the analyzed crystal quality and the position of the solid-liquid interface LS, and transmits the control signal to the spatial light modulator 316 and the stage driving unit 330 for feedback. By performing control (also performing control to adjust the laser output of the laser light source 300 as necessary), the movement state and the crystallization state of the solid-liquid interface LS are appropriately controlled, and the crystal is grown in the lateral direction. Increase grain size.
[0072]
In the feedback control performed by the control unit 326, for example, when the quality of the polysilicon crystal falls below a predetermined reference, a control signal is transmitted to the stage driving unit 330, and the stage 152 is moved in the normal transport direction. And then moving it again in the normal transport direction by moving it a predetermined distance in the opposite direction to recrystallize the portion where the quality of the crystal formed on the substrate 150 has fallen below a predetermined reference, so that an appropriate Crystals can be grown. As a result, the yield of manufacturing the substrate 150 as a product subjected to the annealing treatment can be improved.
[0073]
Further, in the feedback control performed by the control unit 326, for example, a control signal is transmitted to the stage driving unit 330 so that the moving speed of the solid-liquid interface LS becomes a predetermined speed, or the solid-liquid interface LS is controlled. An appropriate crystal can be stably grown on the substrate 150 by controlling to sequentially adjust the moving speed and the speed at which the stage 152 transports the substrate 150 or the like.
[0074]
Further, in the feedback control performed by the control unit 326, when the quality of the polysilicon crystal falls below a predetermined reference, for example, a control signal is transmitted to the spatial light modulator 316, and the spatial light modulator 316 transmits the spatial signal. An appropriate crystal can be grown by changing and adjusting the intensity pattern (intensity gradient) of the light beam having a wavelength of 405 nm formed by distribution.
[0075]
In other words, the control unit 326 controls the crystallization by performing the feedback control as described above, thereby facilitating the lateral growth of the crystal as compared with the conventional laser annealing process without the control. Can be increased in size.
[0076]
In addition, in order to provide feedback to laser drive control based on information obtained by monitoring the annealing position during the annealing process in the laser annealing apparatus, the laser light source 300 is configured with a semiconductor laser having excellent drive controllability. It can be realized for the first time. Further, it is impossible when an excimer laser is used as a laser light source as in the prior art. Therefore, in the laser annealing apparatus, the crystalline state and the solid-liquid interface state are immediately evaluated, and the results are fed back to the laser drive control for the laser light source 300 using the semiconductor laser, thereby stabilizing the high-quality Si. A crystal film can be realized.
[Other examples of laser annealing equipment]
Next, the structure of the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position in the laser annealing apparatus shown in FIG. 19 will be described.
[0077]
In the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position shown in FIG. 19, a fiber array light source 3000 is used as the laser light source, and one row is aligned along the main scanning direction orthogonal to the sub-scanning direction. Alternatively, it is configured by using a beam shaping optical system 3002 for shaping a laser beam irradiated from laser emitting units arranged in a plurality of rows into a light beam having a desired beam intensity. The other configuration is equivalent to the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position shown in FIG.
[0078]
As shown in FIG. 9A, the fiber array light source 3000 includes a large number of laser modules 64, and one end of the multimode optical fiber 30 is coupled to each laser module 64. An optical fiber 31 having the same core diameter as that of the multimode optical fiber 30 and a cladding diameter smaller than that of the multimode optical fiber 30 is coupled to the other end of the multimode optical fiber 30. ) Are arranged in a line along the main scanning direction orthogonal to the sub-scanning direction to constitute the laser emitting portion 68. The light emitting points can be arranged in a plurality of rows along the main scanning direction.
[0079]
As shown in FIG. 9B, the emission end of the optical fiber 31 is sandwiched and fixed between two support plates 65 having a flat surface. Further, a transparent protective plate 63 such as glass is disposed on the light emitting side of the optical fiber 31 in order to protect the end face of the optical fiber 31. The protection plate 63 may be disposed in close contact with the end surface of the optical fiber 31 or may be disposed so that the end surface of the optical fiber 31 is sealed. The exit end portion of the optical fiber 31 has a high light density and is likely to collect dust and easily deteriorate. However, the protective plate 63 can prevent the dust from adhering to the end face and can also delay the deterioration.
[0080]
In this example, in order to arrange the emission ends of the optical fibers 31 with a small cladding diameter in a line without any gaps, the multimode optical fiber 30 is placed between two adjacent multimode optical fibers 30 at a portion with a large cladding diameter. Two exit ends of the optical fiber 31 coupled to two adjacent multi-mode optical fibers 30 where the exit ends of the optical fibers 31 coupled to the stacked multi-mode optical fibers 30 are adjacent to each other at a portion where the cladding diameter is large. Are arranged so as to be sandwiched between them.
[0081]
For example, as shown in FIG. 10, an optical fiber 31 having a length of 1 to 30 cm and having a small cladding diameter is coaxially connected to the tip of the multimode optical fiber 30 having a large cladding diameter on the laser light emission side. Can be obtained by linking them together. In the two optical fibers, the incident end face of the optical fiber 31 is fused and joined to the outgoing end face of the multimode optical fiber 30 so that the central axes of both optical fibers coincide. As described above, the diameter of the core 31 a of the optical fiber 31 is the same as the diameter of the core 30 a of the multimode optical fiber 30.
[0082]
In addition, a short optical fiber in which an optical fiber having a short cladding diameter and a large cladding diameter is fused to an optical fiber having a short cladding diameter and a large cladding diameter may be coupled to the output end of the multimode optical fiber 30 via a ferrule or an optical connector. Good. By detachably coupling using a connector or the like, the tip portion can be easily replaced when an optical fiber having a small cladding diameter is broken, and the cost required for the irradiation head maintenance can be reduced. Hereinafter, the optical fiber 31 may be referred to as an emission end portion of the multimode optical fiber 30.
[0083]
The multimode optical fiber 30 and the optical fiber 31 may be any of a step index type optical fiber, a graded index type optical fiber, and a composite type optical fiber. For example, a step index type optical fiber manufactured by Mitsubishi Cable Industries, Ltd. can be used. In the present embodiment, the multimode optical fiber 30 and the optical fiber 31 are step index type optical fibers, and the multimode optical fiber 30 has a cladding diameter = 125 μm, a core diameter = 25 μm, NA = 0.2, an incident end face. The transmittance of the coat is 99.5% or more, and the optical fiber 31 has a cladding diameter = 60 μm, a core diameter = 25 μm, and NA = 0.2.
[0084]
In general, in laser light in the infrared region, propagation loss increases as the cladding diameter of the optical fiber is reduced. For this reason, a suitable cladding diameter is determined according to the wavelength band of the laser beam. However, the shorter the wavelength, the smaller the propagation loss. In the case of laser light having a wavelength of 405 nm emitted from a GaN-based semiconductor laser, the cladding thickness {(cladding diameter−core diameter) / 2} is set to infrared light in the wavelength band of 800 nm. The propagation loss hardly increases even if it is about ½ of the case of propagating infrared light and about ¼ of the case of propagating infrared light in the 1.5 μm wavelength band for communication. Therefore, the cladding diameter can be reduced to 60 μm.
[0085]
However, the cladding diameter of the optical fiber 31 is not limited to 60 μm. The clad diameter of an optical fiber used in a conventional fiber light source is 125 μm, but the depth of focus becomes deeper as the clad diameter becomes smaller. Therefore, the clad diameter of a multimode optical fiber is preferably 80 μm or less, more preferably 60 μm or less. Preferably, it is 40 μm or less. On the other hand, since the core diameter needs to be at least 3 to 4 μm, the cladding diameter of the optical fiber 31 is preferably 10 μm or more.
[0086]
The laser module 64 is configured by a combined laser light source (fiber light source) shown in FIG. This combined laser light source includes a plurality of (for example, seven) chip-like lateral multimode or single mode GaN-based semiconductor lasers LD1, LD2, LD3, LD4, LD5, LD6, arrayed and fixed on the heat block 10. And LD7, collimator lenses 11, 12, 13, 14, 15, 16, and 17 provided corresponding to each of the GaN-based semiconductor lasers LD1 to LD7, one condenser lens 20, and one multi-lens. Mode optical fiber 30. The number of semiconductor lasers is not limited to seven. For example, as many as 20 semiconductor laser beams can be incident on a multimode optical fiber having a cladding diameter = 60 μm, a core diameter = 50 μm, and NA = 0.2. In addition, the number of optical fibers can be further reduced.
[0087]
The GaN-based semiconductor lasers LD1 to LD7 all have the same oscillation wavelength (for example, 405 nm), and the maximum output is also all the same (for example, 100 mW for the multimode laser and 30 mW for the single mode laser). As the GaN-based semiconductor lasers LD1 to LD7, lasers having an oscillation wavelength other than the above 405 nm in the wavelength range of 350 nm to 460 nm may be used. A suitable wavelength range will be described later.
[0088]
As shown in FIGS. 12 and 13, the above-described combined laser light source is housed in a box-shaped package 40 having an upper opening together with other optical elements. The package 40 includes a package lid 41 created so as to close the opening thereof. After the deaeration process, a sealing gas is introduced, and the package 40 and the package lid 41 are closed by closing the opening of the package 40 with the package lid 41. The combined laser light source is hermetically sealed in a closed space (sealed space) formed by 41.
[0089]
A base plate 42 is fixed to the bottom surface of the package 40. The heat block 10, a condensing lens holder 45 that holds the condensing lens 20, and the multimode optical fiber 30 are incident on the top surface of the base plate 42. A fiber holder 46 that holds the end is attached. The exit end of the multimode optical fiber 30 is drawn out of the package from an opening formed in the wall surface of the package 40.
[0090]
Further, a collimator lens holder 44 is attached to the side surface of the heat block 10, and the collimator lenses 11 to 17 are held. An opening is formed in the lateral wall surface of the package 40, and wiring 47 for supplying a driving current to the GaN-based semiconductor lasers LD1 to LD7 is drawn out of the package through the opening.
[0091]
In FIG. 13, in order to avoid complication of the drawing, only the GaN semiconductor laser LD7 among the plurality of GaN semiconductor lasers is numbered, and only the collimator lens 17 among the plurality of collimator lenses is numbered. doing.
[0092]
FIG. 14 shows a front shape of a mounting portion of the collimator lenses 11-17. Each of the collimator lenses 11 to 17 is formed in a shape obtained by cutting a region including the optical axis of a circular lens having an aspherical surface into a long and narrow plane. This elongated collimator lens can be formed, for example, by molding resin or optical glass. The collimator lenses 11 to 17 are closely arranged in the arrangement direction of the light emitting points so that the length direction is orthogonal to the arrangement direction of the light emitting points of the GaN-based semiconductor lasers LD1 to LD7 (left and right direction in FIG. 14).
[0093]
On the other hand, each of the GaN-based semiconductor lasers LD1 to LD7 includes an active layer having a light emission width of 2 μm, and each of the laser beams B1 in a state parallel to the active layer and a divergence angle in a direction perpendicular to the active layer, respectively, for example A laser emitting ~ B7 is used. These GaN-based semiconductor lasers LD1 to LD7 are arranged so that the light emitting points are arranged in a line in a direction parallel to the active layer.
[0094]
Accordingly, in the laser beams B1 to B7 emitted from the respective light emitting points, the direction in which the divergence angle is large coincides with the length direction and the divergence angle is small with respect to the elongated collimator lenses 11 to 17 as described above. Incident light is incident in a state where the direction coincides with the width direction (direction perpendicular to the length direction). That is, the collimator lenses 11 to 17 have a width of 1.1 mm and a length of 4.6 mm, and the horizontal and vertical beam diameters of the laser beams B1 to B7 incident thereon are 0.9 mm and 2. 6 mm. Each of the collimator lenses 11 to 17 has a focal length f. ₁ = 3 mm, NA = 0.6, and lens arrangement pitch = 1.25 mm.
[0095]
The condensing lens 20 is formed by cutting a region including the optical axis of a circular lens having an aspheric surface into a long and narrow shape in parallel planes, and is long in the arrangement direction of the collimator lenses 11 to 17, that is, in a horizontal direction and short in a direction perpendicular thereto. Is formed. The condenser lens 20 has a focal length f. ₂ = 23 mm, NA = 0.2. This condensing lens 20 is also formed by molding resin or optical glass, for example.
[0096]
In the fiber array light source 3000 configured as described above, the laser beams B1, B2, B3, B4, B5, B6, and the like emitted from each of the GaN-based semiconductor lasers LD1 to LD7 constituting the combined laser light source, and Each of B7 is collimated by the corresponding collimator lenses 11-17. The collimated laser beams B <b> 1 to B <b> 7 are collected by the condenser lens 20 and converge on the incident end face of the core 30 a of the multimode optical fiber 30.
[0097]
In this example, the collimator lenses 11 to 17 and the condenser lens 20 constitute a condensing optical system, and the condensing optical system and the multimode optical fiber 30 constitute a multiplexing optical system. That is, the laser beams B1 to B7 condensed as described above by the condenser lens 20 enter the core 30a of the multimode optical fiber 30 and propagate through the optical fiber to be combined with one laser beam B. The light is emitted from the optical fiber 31 coupled to the output end of the multimode optical fiber 30.
[0098]
In each laser module, when the coupling efficiency of the laser beams B1 to B7 to the multimode optical fiber 30 is 0.85 and each output of the GaN-based semiconductor lasers LD1 to LD7 is 30 mW (when a single mode laser is used). Can obtain a combined laser beam B with an output of 180 mW (= 30 mW × 0.85 × 7) for each of the optical fibers 31 arranged in an array. Therefore, the output from the laser emitting unit 68 in which 100 optical fibers 31 are arranged in an array is about 18 W (= 180 mW × 100).
[0099]
In the laser emitting section 68 of the fiber array light source 3000, light emission points with high luminance are arranged in a line along the main scanning direction as described above. A conventional fiber light source that couples laser light from a single semiconductor laser to a single optical fiber has a low output, so a desired output could not be obtained unless multiple rows are arranged. Since the combined laser light source used in the form has a high output, a desired output can be obtained even with a small number of columns, for example, one column.
[0100]
For example, in a conventional fiber light source in which a semiconductor laser and an optical fiber are coupled on a one-to-one basis, a laser having an output of about 30 mW (milliwatt) is usually used as the semiconductor laser, and the core diameter is 50 μm and the cladding diameter is 125 μm. Since a multimode optical fiber having a numerical aperture (NA) of 0.2 is used, if an output of about 18 W (watt) is to be obtained, 864 (8 × 10 8) multimode optical fibers must be bundled. The area of the light emitting region is 13.5mm ² (1 mm × 13.5 mm), the luminance at the laser emitting portion 68 is 1.3 (MW (megawatt) / m). ² ), Brightness per optical fiber is 8 (MW / m) ² ).
[0101]
In contrast, in the present embodiment, as described above, an output of about 18 W can be obtained with 100 multimode optical fibers, and the area of the light emitting region at the laser emitting portion 68 is 0.3125 mm. ² (0.025 mm × 12.5 mm), the luminance at the laser emission unit 68 is 57.6 (MW / m). ² Thus, the brightness can be increased by about 44 times compared to the conventional case. Also, the luminance per optical fiber is 288 (MW / m ² The brightness can be increased by about 36 times compared with the conventional case.
[0102]
Further, in the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position shown in FIG. 19 described above, the laser beam is emitted from the laser emitting units arranged in one or a plurality of rows along the main scanning direction. In place of the fiber array light source 3000 configured to irradiate the light, a plurality of fiber light sources that are combined with laser beams emitted from a plurality of GaN-based semiconductor lasers in the optical fiber and then emitted from the output end of the optical fiber are provided. Each of the light emitting points at the exit end of the optical fiber is composed of a fiber bundle light source arranged in a bundle shape (a bundle of optical fibers that can be bundled in various cross-sectional shapes such as a circle, a rectangle, and a polygon) Then, the laser beam emitted from the fiber bundle light source is applied using the beam shaping optical system 3002. It may be configured to shape the beam intensity of the light beam.
[0103]
Further, in the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position shown in FIG. 19, the fiber array light source 3000 is used as the laser light source and 1 along the main scanning direction orthogonal to the sub-scanning direction. It is configured using a beam shaping optical system 3002 for shaping a laser beam emitted from the laser emitting portions arranged in a row into a light beam having a desired beam intensity.
[0104]
Further, the fiber array light source 3000 is configured to be driven and controlled for each semiconductor laser by the LD controller 3001, and in the same manner as the one provided with the spatial light modulator (DMD), the light having the wavelength of 405 nm formed in the spatial distribution. The configuration is such that spatial light modulation is possible to form a beam intensity pattern (intensity gradient) in a required spatial distribution. In this manner, as indicated by the imaginary line LP in FIG. 3 described above, the intensity of the light energy is increased in the beam projection pattern so as to increase strongly on the front end side in the conveyance direction of the substrate 150 and decrease toward the rear end side in the conveyance direction. It can be made to have a gradient.
[0105]
That is, in the fiber array light source 3000, the light beam projected from the output end thereof is output by the LD controller 3001 that is a control means of each semiconductor laser (which may be configured as an optical fiber module light source) to give a predetermined light beam. By forming the spatial light modulation formed in the spatial distribution, the desired spatial intensity distribution is formed as appropriate. Further, the control unit 326 feedback-controls the LD controller 3001 based on the crystallinity information measured at the annealing position, thereby controlling the movement of the solid-liquid interface and the crystallization state.
[0106]
The other actions and effects are equivalent to the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position shown in FIG.
[0107]
Next, the structure of the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position in the laser annealing apparatus shown in FIG. 20 will be described.
[0108]
In the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position shown in FIG. 20, apart from the laser light source 300 that projects the laser beam for annealing, the Raman excitation light having a different wavelength is projected. Means are provided.
[0109]
In the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position shown in FIG. 20, a laser beam for Raman excitation light having a wavelength different from that of the laser beam emitted from the laser light source 300 is emitted. A laser light source 332 is provided.
[0110]
The laser light source 332 for Raman excitation light includes, for example, light having a wavelength of 460 nm to 1000 nm, solid laser light, solid laser SHG light, semiconductor laser SHG light, semiconductor laser light, light with a wavelength of 488 nm, and wavelength of 532 nm as Raman excitation light. Light having a wavelength of 632 nm, light having a wavelength of 680 nm, light having a wavelength of 780 nm, or light having a wavelength of 800 nm.
[0111]
As shown in FIG. 20, the laser beam for Raman excitation light emitted from the laser light source 332 for Raman excitation light is shaped into a desired light beam by the beam shaping optical system 334 and reflected by the half mirror 336. Thus, the light passes through the dichroic mirror 304 and is projected from above onto the surface of the a-Si film in a desired beam pattern by the projection lens 308.
[0112]
The merit of using the annealing laser light projected from the laser light source 300 and the Raman excitation light laser beam 332 emitted from the Raman excitation light laser beam 332 as light of different wavelengths is as follows. That is, the annealing laser light has a spatial intensity distribution in order to form a temperature gradient. In addition, since Raman scattering is a non-linear phenomenon, the Raman efficiency changes greatly when the excitation light intensity changes, making it difficult to make a relative comparison of Raman signal intensity.
[0113]
Therefore, by using Raman excitation light whose intensity can be controlled independently of the laser annealing light, it is possible to make a relative comparison of Raman signal intensities and to grasp the state of the annealed portion in more detail.
[0114]
The other configuration of the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position shown in FIG. 20 is based on the crystallinity information measured at the annealing position shown in FIG. This is equivalent to an annealing control means for performing feedback control. In addition, in the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position shown in FIG. 20, the Raman excitation light laser beam emitted from the Raman excitation light laser light source 332 is used. Except for the operation and effect of the above, the same operation and effect as those shown in FIG.
[0115]
Next, the structure of the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position in the laser annealing apparatus shown in FIG. 21 will be described.
[0116]
In the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position shown in FIG. 21, the fiber array light source 3000 and the beam shaping optical system 3002 are used and have a wavelength different from that of the laser beam for annealing. A laser light source 332 as an annealing control means for projecting Raman excitation light, a beam shaping optical system 334, and a half mirror 336 are provided on the optical path.
[0117]
The other structure of the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position shown in FIG. 21 is based on the crystallinity information measured at the annealing position shown in FIG. This is equivalent to the annealing control means for performing feedback control or the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position shown in FIG. Further, in the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position shown in FIG. 21, the action and effect obtained by using the fiber array light source 3000, and the annealing laser shown in FIG. Except for the operation and effect obtained by using the laser light source 332 as a means for projecting Raman excitation light having a wavelength different from that of light, the same operation and effect as those shown in FIG.
[0118]
Next, the structure of the annealing control means for performing feedback control based on information obtained by measuring the solid-liquid interface state based on the reflectance measured at the annealing position in the laser annealing apparatus shown in FIG.
[0119]
Annealing control means for performing feedback control based on information obtained by measuring the solid-liquid interface state based on the reflectance measured at the annealing position shown in FIG. 22 includes a scanner 162 and a stage 152 in the laser annealing apparatus and portions of these control systems. The a-Si film is based on information obtained by measuring the solid-liquid interface state by reflectivity measured as a monitor of the annealing state at the position where the GaN semiconductor laser light (405 nm) is irradiated to the a-Si film and annealing is performed. There is provided a configuration for realizing large crystal grain formation by performing feedback control for promoting crystal growth in the horizontal direction.
[0120]
In the annealing control means for performing feedback control based on the crystallinity information measured at the annealing position, as a laser light source 300, an optical fiber module for integrating and projecting light having a wavelength of 405 nm emitted from a GaN semiconductor laser in the optical fiber 301. Use a light source.
[0121]
An annealing control means for performing feedback control based on the crystallinity information measured at the annealing position causes a laser beam with a wavelength of 405 nm projected from the optical fiber 301 of the laser light source 300, which is an optical fiber module light source, to be emitted by the beam shaping optical system 302. The beam is shaped, passed through a spatial light modulator 316, bent into a projection lens 308 by a dichroic mirror 304, and projected from above onto the surface of the a-Si film with a desired beam pattern by the projection lens 308.
[0122]
Thus, the a-Si film is heated and melted by the light beam having a spatial distribution formed by the spatial light modulator 316 and crystallized together with the heat radiation.
[0123]
The annealing control means for performing feedback control based on the crystallinity information measured at the annealing position is configured as a separately provided reflectance measurement laser light source 338 (for example, a laser light source that emits a light beam having a wavelength of 633 nm). ) Is shaped into a predetermined light beam by the beam shaping optical system 340, reflected by the half mirror 342, transmitted through the dichroic mirror 304, and a-Si with a desired beam pattern by the projection lens 308. Projected from above onto the surface of the membrane.
[0124]
The light beam emitted from the reflectance measuring laser light source 338 projected from above onto the surface of the a-Si film in this manner is used for the annealing position of the Si film (a-Si region, molten Si region, and , A portion with a crystallized region of polysilicon) is reflected according to each surface state, and is formed as a reflected image on the CCD 346 by the projection lens 308 and the lens 344. The light beam emitted from the reflectance measurement laser light source 338 and reflected by the Si film passes through the dichroic mirror 304 and the half mirror 342 on the optical path.
[0125]
Here, regarding the reflectance that the light beam emitted from the laser light source 338 for reflectance measurement reflects according to each surface state at the annealing position of the Si film, generally, a substance having a complex refractive index n-ik, air, The opposite rate R at the boundary surface of R = {(n−1) ² + K ² } / {(N + 1) ² + K ² }. Further, n and k of crystalline Si and molten Si are, for example, n for a light beam with a wavelength of 633 nm for reflectance measurement. _c = 3.88, k _c = 0.019, n _l = 2.82, k _l = 5.28. Here, the subscript c represents crystallized Si, and l represents molten Si.
[0126]
Therefore, in crystalline Si, the surface reflectance R _c = 0.348, R for molten Si _l = 0.7344, and the reflection intensity of the light beam for reflectance measurement is greatly different between the crystallized portion and the melted portion.
[0127]
Therefore, the crystallization portion when the light beam with uniform light intensity emitted from the reflectance measurement laser light source 338 is reflected on the region irradiated with the annealing laser beam (annealing position), and The state of the reflection intensity of the light beam that differs from the melted portion is detected by the CCD 346 as two-dimensional image information (data) of the crystallized portion and the melted portion. Image information (data) detected by the CCD 346 is transmitted to the control unit 328.
[0128]
The control unit 328 acquires data on the moving speed of the crystallization zone, the melting zone, and the crystallization zone (that is, the moving speed of the solid-liquid interface LS) from the image information (data), analyzes this data, and if necessary, The control signal for the spatial light modulator 316 and the stage driving unit 330 is generated, and the control signal is transmitted to the spatial light modulator 316 or the stage driving unit 330 to perform feedback control. The spatial intensity distribution of the light beam for laser annealing and the a-Si substrate moving speed are optimized, the solid-liquid interface LS movement is controlled, and crystal Si is appropriately grown in the lateral direction to enlarge the crystal grains.
[0129]
In the feedback control performed by the control unit 328, for example, when the solid-liquid interface LS becomes a wavy curve, or when the solid-liquid interface LS is inclined with respect to the conveyance direction (scanning direction) of the substrate 150, for example. Spatial light modulation to increase the light energy supplied to the part of the solid-liquid interface LS that is delayed toward the rear end side in the transport direction and to decrease the light energy supplied to the part that is advanced toward the front end side in the transport direction The container 316 is controlled so that the solid-liquid interface LS is adjusted to a straight line perpendicular to the transport direction.
[0130]
Furthermore, in the feedback control performed by the control unit 326, for example, if the speed at which the stage 152 conveys the substrate 150 is too fast relative to the moving speed of the solid-liquid interface LS, heat is not sufficiently distributed to the a-Si film. By transmitting a control signal to the stage driving unit 330 and performing control to adjust the conveyance speed of the substrate 150 to an appropriate speed, an appropriate crystal can be stably grown on the substrate 150.
[0131]
In other words, the control unit 326 controls the crystallization by performing the feedback control as described above, thereby facilitating the lateral growth of the crystal as compared with the conventional laser annealing process without the control. Can be increased in size.
[0132]
Next, the structure of the annealing control means for performing feedback control based on information obtained by measuring the solid-liquid interface state based on the reflectance measured at the annealing position in the laser annealing apparatus shown in FIG. 23 will be described.
[0133]
The annealing control means for performing feedback control based on information obtained by measuring the solid-liquid interface state based on the reflectance measured at the annealing position shown in FIG. 23 is configured using the fiber array light source 3000 and the beam shaping optical system 3002. .
[0134]
In addition, the other structure in the annealing control means for performing feedback control based on information obtained by measuring the solid-liquid interface state based on the reflectance measured at the annealing position shown in FIG. 23 was measured at the annealing position shown in FIG. This is equivalent to an annealing control means that performs feedback control based on information obtained by measuring the solid-liquid interface state based on the reflectance.
[0135]
In the annealing control means for performing feedback control based on information obtained by measuring the solid-liquid interface state based on the reflectance measured at the annealing position shown in FIG. 23, the LD controller 3001 in the fiber array light source 3000 is driven for each semiconductor laser. As in the case of providing a spatial light modulator (DMD), a light beam having a wavelength of 405 nm having a spatial distribution formed so as to have an appropriate spatial intensity distribution (intensity pattern (intensity gradient)) is emitted. .
[0136]
That is, in the fiber array light source 3000, the light beam projected from its output end is appropriately spatially intensified by output control by the LD controller 3001 that is a control means of each semiconductor laser (which may be configured as an optical fiber module light source). Shaped as a light beam with distribution. Further, based on the information regarding the position of the solid-liquid interface LS, the control unit 326 performs feedback control of the LD controller 3001 and the stage driving unit 330, and appropriately executes movement control of the solid-liquid interface LS and control of the crystallization state. To do.
[0137]
The other actions and effects are the same as those of the annealing control means for performing feedback control based on information obtained by measuring the solid-liquid interface state based on the reflectance measured at the annealing position shown in FIG.
[Operation of laser annealing equipment]
Next, the operation of the laser annealing apparatus will be described.
[0138]
As shown in FIG. 1, in this laser annealing apparatus, a stage 152 as a scanning unit that adsorbs a substrate 150 that is an object to be annealed to the surface and scans the object to be annealed and a laser beam relatively moved. However, it is moved at a constant speed from the upstream side to the downstream side of the gate 160 along the guide 158 by a driving device (not shown). When the front end of the substrate 150 is detected by the detection sensor 164 attached to the gate 160 when the stage 152 passes under the gate 160, the exposure start position is determined from this, and the laser light source 300 (3000) is driven and controlled. Then, the laser annealing process is started.
[0139]
At this time, in the case of including the spatial light modulator (DMD) 316, a control signal is transmitted from the mirror drive control unit to the spatial light modulator (DMD) 316 and the micromirror of the spatial light modulator (DMD) 316 is transmitted. Each of them is controlled to be turned on and off, and the laser light emitted from the laser light source 300 to the spatial light modulator (DMD) 316 is reflected on the a-Si film surface of the substrate 150 by reflecting when the micromirror is turned on. Imaged and laser annealed. In this manner, the laser light emitted from the laser light source 300 is turned on / off for each pixel, and the substrate 150 is irradiated with laser in approximately the same number of pixels (irradiation area) as the number of used pixels of the spatial light modulator (DMD) 316. And annealed.
[0140]
In this laser annealing apparatus, the substrate 150 is moved along with the stage 152 at a required speed, whereby the substrate 150 is sub-scanned in the direction opposite to the stage moving direction, and the scanner 162 is used as illustrated in FIGS. 16 and 17. A band-shaped irradiated region is formed.
[0141]
Further, in the case of including the spatial light modulator (DMD) 316, as shown in FIGS. 15A and 15B, for example, the spatial light modulator (DMD) 316 includes 800 micromirrors in the main scanning direction. When 600 microarrays are arranged in the sub-scanning direction, the controller controls so that only a part of micromirrors (for example, 800 × 10) are driven. Also good.
[0142]
Here, as shown in FIG. 15A, a micromirror array arranged at the center of the spatial light modulator (DMD) 316 may be used. As shown in FIG. A micromirror array located at the end of the modulator (DMD) 316 may be used. In addition, when a defect occurs in some of the micromirrors, the micromirror array to be used may be appropriately changed depending on the situation, such as using a micromirror array in which no defect has occurred.
[0143]
Since the data processing speed of the spatial light modulator (DMD) 316 is limited and the modulation speed per line is determined in proportion to the number of pixels used, only a part of the micromirror array is used. The modulation speed per line is increased.
[0144]
In this laser annealing apparatus, when the sub-scan of the substrate 150 by the scanner 162 is completed and the rear end of the substrate 150 is detected by the detection sensor 164, the stage 152 is moved along the guide 158 by the driving device (not shown). Is returned to the origin on the uppermost stream side, and moved again along the guide 158 from the upstream side to the downstream side of the gate 160 at a constant speed.
[0145]
Since this laser annealing apparatus uses a high-quality semiconductor laser as a laser light source instead of the excimer laser that is a gas laser, there are the following advantages 1) to 6).
[0146]
1) A polysilicon film with a stabilized light output and a uniform crystal grain size can be produced with good reproducibility.
[0147]
2) Since the semiconductor laser is a solid semiconductor laser, it can be driven for tens of thousands of hours and has high reliability. In addition, the semiconductor laser is less likely to break the light emitting end face, is highly reliable, and can achieve a high peak power.
[0148]
3) Compared with the case of using an excimer laser, which is a gas laser, the size can be reduced and the maintenance becomes very simple. Moreover, energy efficiency is as high as 10% to 20%.
[0149]
4) Since a semiconductor laser is basically a laser capable of CW (continuous) driving, the repetition frequency and pulse width (duty) can be freely set according to the absorption amount and heat generation amount of amorphous silicon even in the case of pulse driving. Can be set to For example, an arbitrary repetitive operation from several Hz to several MHz can be realized, and an arbitrary pulse width of several psec to several hundred msec can be realized. In particular, the repetition frequency can be up to several tens of MHz, and continuous crystal grain boundaries can be formed as in the case of CW driving. In addition, since the repetition frequency can be increased, high-speed annealing is possible.
[0150]
5) Since the semiconductor laser can be driven CW and the annealed surface can be scanned in a predetermined direction with continuous laser light, the direction of crystal growth can be controlled, and continuous crystal grain boundaries can be formed. A polysilicon film having carrier mobility can be formed.
[0151]
Further, in this laser annealing apparatus, when the fiber array light source 3000 in which the emission ends of the optical fibers of the combined laser light source are arranged in an array is used as the laser light source, the following advantages 1) to 3) are obtained. is there.
[0152]
1) Generally, in a laser annealing apparatus, an annealing surface (exposed surface) is 400 mJ / cm. ² ~ 700mJ / cm ² However, in this embodiment, by increasing the number of fibers to be arrayed and the number of laser beams to be combined, it is easy to increase the output and increase the light density with multiple beams. Can be achieved. For example, if the fiber output of one combined laser light source is 180 mW, a high output of 100 W can be stably obtained by bundling 556 lines. In addition, the beam quality is stable and the power density is high. Therefore, it is possible to cope with the future increase in the film formation area and high throughput of the low-temperature polysilicon.
[0153]
2) The exit end of the optical fiber can be attached in a replaceable manner using a connector or the like, and maintenance is facilitated.
[0154]
3) Since it is a small multiplexing module that combines a small semiconductor laser, the light source unit can be much smaller than the excimer laser.
[0155]
Furthermore, when the cladding diameter of the output end of the optical fiber is made smaller than the cladding diameter of the incident end, the diameter of the light emitting portion is further reduced, and the fiber array light source 3000 can have high brightness. Thereby, a laser annealing apparatus having a deeper focal depth can be realized. For example, in the case of annealing at an ultrahigh resolution with a beam diameter of 1 μm or less and a resolution of 0.1 μm or less, a deep focal depth can be obtained, and high-speed and high-definition annealing is possible.
[0156]
【The invention's effect】
According to the laser annealing apparatus of the present invention, information on the annealing state is detected at a position where the object is irradiated with the laser beam and the annealing process is performed, and feedback control is performed based on this information to perform an appropriate annealing process. It has the effect of making it possible.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an external appearance of a laser annealing apparatus according to an embodiment of the present invention.
FIG. 2 is an optical path diagram showing an annealing optical path provided with an annealing control means for performing feedback control based on crystallinity information measured at an annealing position according to an embodiment of the present invention.
FIG. 3 is a schematic perspective view showing an essential part of an annealing control means for performing feedback control based on crystallinity information measured at an annealing position according to an embodiment of the present invention.
FIG. 4 is an explanatory diagram showing a relationship between a temperature gradient at an annealing position and a solid phase and a molten phase (liquid phase) of an a-Si film in the laser annealing apparatus according to the embodiment of the present invention.
FIG. 5 is an explanatory diagram illustrating the state of Raman scattered light according to crystallinity in an annealing control unit that performs feedback control based on crystallinity information measured at an annealing position according to an embodiment of the present invention;
FIG. 6 is a partially enlarged view showing a configuration of a digital micromirror device (DMD) in the laser annealing apparatus according to the embodiment of the present invention.
7A and 7B are explanatory diagrams for explaining the operation of the DMD. FIG.
FIGS. 8A and 8B are plan views showing the arrangement of scanning beams and the scanning lines in a case where the DMD is not inclined and in a case where the DMD is inclined. FIG.
9A is a perspective view showing a configuration of a fiber array light source in the laser annealing apparatus according to the embodiment of the present invention, and FIG. 9B is a partially enlarged view of FIG. 9A.
FIG. 10 is a diagram showing a configuration of a multimode optical fiber.
FIG. 11 is a plan view showing a configuration of a combined laser light source.
FIG. 12 is a plan view showing the configuration of a laser module.
13 is a side view showing the configuration of the laser module shown in FIG.
14 is a partial side view showing the configuration of the laser module shown in FIG. 16. FIG.
FIGS. 15A and 15B are diagrams showing examples of DMD usage areas; FIGS.
FIG. 16 is a plan view for explaining an annealing method for annealing a transparent substrate by one scanning by a scanner.
FIGS. 17A and 17B are plan views for explaining an annealing method for annealing a transparent substrate by a plurality of scans by a scanner. FIGS.
FIGS. 18A and 18B are views for explaining a low-temperature polysilicon TFT formation process; FIGS.
FIG. 19 is an optical path diagram showing an optical path of annealing control means for performing feedback control based on crystallinity information measured at an annealing position using a fiber array light source in the laser annealing apparatus according to the embodiment of the present invention. .
20 performs feedback control based on crystallinity information measured at an annealing position using a spatial light modulator and a laser light source for Raman excitation light in a laser annealing apparatus according to an embodiment of the present invention. It is an optical path diagram which shows the optical path of an annealing control means.
FIG. 21 shows an annealing for performing feedback control based on crystallinity information measured at an annealing position using a fiber array light source and a laser light source for Raman excitation light in the laser annealing apparatus according to the embodiment of the present invention; It is an optical path diagram which shows the optical path of a control means.
FIG. 22 shows an annealing control for performing feedback control based on information obtained by measuring a solid-liquid interface state by a reflectance measured at an annealing position using a spatial light modulator in a laser annealing apparatus according to an embodiment of the present invention. It is an optical path diagram which shows the optical path of a means.
FIG. 23 shows an annealing control means for performing feedback control based on information obtained by measuring a solid-liquid interface state by a reflectance measured at an annealing position using a fiber array light source in a laser annealing apparatus according to an embodiment of the present invention. It is an optical path figure which shows the optical path of.
FIG. 24 is an explanatory view showing a state of partial melting by conventional excimer laser annealing.
FIG. 25 is an explanatory diagram showing a state in which crystal grains are grown with the remaining a-Si phase as islands by conventional excimer laser annealing.
FIG. 26 is an explanatory diagram showing a state in which the a-Si phase is completely melted by conventional excimer laser annealing to be in a supercooled state, and is entirely filled with fine crystal grains.
FIG. 27 is an explanatory diagram qualitatively showing the relationship between laser intensity and crystal grain size in conventional excimer laser annealing.
FIG. 28 is an explanatory diagram showing a state in which the size of a crystal grain boundary is limited by collision with crystal grains from the opposite side to the film thickness in the conventional annealing method for controlling the crystal growth in the lateral direction.
FIG. 29 shows Nd: YVO in the conventional annealing method for controlling the crystal growth in the lateral direction. ₄ It is explanatory drawing which shows the state which makes the temperature gradient with respect to the depth direction flat with 532 nm light of a laser, makes a solid-liquid interface stand upright, and grows a grain boundary greatly in a horizontal direction.
[Explanation of symbols]
150 substrates
152 stages
162 Scanner
300 Laser light source
301 optical fiber
302 Beam shaping optical system
304 Dichroic mirror
308 Projection lens
310 lens
312 Slit member
314 slit
316 spatial light modulator
318 Concave mirror
320 diffraction grating
322 Concave mirror
326 control unit
328 control unit
330 Stage drive unit
332 Laser light source for Raman excitation light
334 Beam shaping optical system
336 half mirror
338 Laser light source for reflectance measurement
340 Beam shaping optical system
342 half mirror
344 lens
346 CCD

Claims (7)

A laser light source for emitting a laser beam;
Laser irradiation means for irradiating the film-like annealing object with the laser beam emitted from the laser light source;
Spatial light modulation means for changing and adjusting the spatial intensity distribution of the laser beam applied to the annealing object;
Scanning means for relatively moving and scanning the object to be annealed and the laser beam;
Feedback control for at least one of the spatial light modulation unit and the scanning unit is performed based on information measured as an anneal state monitor at a position where the annealing target is irradiated with the laser beam and the annealing process is performed. Annealing control means to perform,
A laser annealing apparatus comprising: The laser annealing apparatus according to claim 1, wherein the laser light source is a solid-state laser. The laser annealing apparatus according to claim 1, wherein the laser light source is a semiconductor laser. The laser annealing apparatus according to claim 3, wherein the laser light source is a GaN-based semiconductor laser. The annealing control means measures the Raman spectrum information from the Raman scattered light emitted according to the crystallinity in the crystallization region within the projection range of the laser beam being annealed, and the quality of the crystal It is configured to analyze the position of the solid-liquid interface and perform feedback control to optimize the crystallization state or the movement state of the solid-liquid interface for at least one of the spatial light modulation unit and the scanning unit. The laser annealing apparatus according to any one of claims 1 to 4, wherein: When the annealing control means irradiates a laser beam having a wavelength different from that of the laser beam for annealing emitted from the laser light source for Raman excitation light at a position where the annealing process is performed, the crystallinity in the crystallization region is increased. In response, the information of the Raman spectrum is measured from the Raman scattered light emitted, the quality of the crystal and the position of the solid-liquid interface are analyzed, and at least one of the spatial light modulation means and the scanning means is crystallized. 5. The laser annealing apparatus according to claim 1, wherein the laser annealing apparatus is configured to perform feedback control for optimizing the state or the movement state of the solid-liquid interface. The annealing control means reflects the reflectance measurement laser beam having a uniform light intensity at a wavelength different from that of the annealing laser beam emitted from the reflectance measurement laser light source to a position where the annealing treatment is performed. Movement of crystallized zone, melted zone, crystallized zone obtained from two-dimensional information of crystallized zone and melted zone detected by measuring different reflection intensities of crystallized zone and melted zone It is configured to analyze velocity data and perform feedback control to optimize the crystallization state or the movement state of the solid-liquid interface for at least one of the spatial light modulation unit and the scanning unit. The laser annealing apparatus according to any one of claims 1 to 4.

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