JP2006074018A - Laser crystallization apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser crystallization apparatus capable of correcting a magnification and an image surface position of an image formation optical system and capable of forming a crystal grain of a desired size at a desired position with a good reproducibility. <P>SOLUTION: The laser crystallization apparatus comprises: a light source 2a; a phase shifter 3 which modulates a laser beam from the light source 2a; an illumination system 2 which is provided between the light source 2a and the phase shifter 3 and homogenizes a light intensity of the laser beam from the light source 2a and illuminates the phase shifter 3 with this homogenized light; a stage 6 which supports a non-single-crystal semiconductor 5; an image formation optical system 4 which is provided between the non-single-crystal semiconductor 5 on the stage 6 and the phase shifter 3 and is provided with plural optical members L1 to L10, 4c for forming an image of the modulated laser beam at a desired part on the non-single-crystal semiconductor 5; and temperature adjustment portions 10 to 17, 20 to 22, 42 to 48 which adjust temperatures of the optical members L1 to L10, 4c by heating or cooling the optical members of the image formation optical system 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laser crystallization apparatus that generates a crystallized semiconductor film by irradiating a polycrystalline semiconductor film or an amorphous semiconductor film with laser light having a predetermined light intensity distribution.

  Thin-film-transistors (TFTs) used as switching elements for selecting display pixels of liquid-crystal displays (LCDs) are amorphous silicon and polycrystalline silicon (TFT). poly-Silicon).

  Polycrystalline silicon has higher electron or hole mobility than amorphous silicon. Therefore, when the transistor is formed using polycrystalline silicon, the switching speed is faster and the response of the display is faster than when the transistor is formed using amorphous silicon. In addition, it is possible to configure the peripheral LSI with thin film transistors. Furthermore, there is an advantage that the design margin of other parts can be reduced. Further, when peripheral circuits such as a driver circuit and a DAC are incorporated in the display, the peripheral circuits can be operated at higher speed.

  Since polycrystalline silicon consists of a collection of crystal grains, for example, when a TFT transistor is formed, a crystal grain boundary is formed in the channel region, and this crystal grain boundary serves as a barrier and mobility of electrons or holes compared to single crystal silicon. Becomes lower. In addition, in many thin film transistors formed using polycrystalline silicon, the number of crystal grain boundaries formed in the channel portion is different among the thin film transistors, and the variation causes a problem of display unevenness if the liquid crystal display device is used. . Therefore, recently, in order to improve the mobility of electrons or holes and to reduce the variation in the number of crystal grain boundaries in the channel portion, a large-grained crystallized silicon having a size capable of forming at least one channel region has been developed. Producing crystallization methods have been proposed.

Conventionally, as this kind of crystallization method, a phase shifter that is placed in parallel with a polycrystalline semiconductor film or a non-single crystal semiconductor film is irradiated with excimer laser light to generate a crystallized semiconductor film. Annealing) method is known. Details of the phase control ELA method are disclosed in Non-Patent Document 1, for example.
Surface Science Vol.21, No.5, pp.278-287, 2000

  In the phase control ELA method, light having a reverse peak pattern (a pattern in which the light intensity is the lowest at the center and the light intensity rapidly increases toward the periphery) is lower than that of the periphery at the point corresponding to the phase shift portion of the phase shifter. An intensity distribution is generated, and light having this reverse peak light intensity distribution is irradiated to a non-single-crystal semiconductor film (polycrystalline semiconductor film or amorphous semiconductor film). As a result, a temperature gradient occurs in the melted region in accordance with the light intensity distribution in the irradiated region, and crystal nuclei are formed in the part that first solidifies or does not melt corresponding to the point where the light intensity is the lowest. Crystals grow laterally from the nucleus toward the periphery, and single crystal grains having a large grain size are generated.

In Patent Document 1, an imaging optical system is arranged between a phase shifter having a line-and-space pattern with a phase difference of 180 degrees and a substrate to be processed. Then, the crystallized semiconductor film is generated on the substrate to be processed by irradiating the substrate to be processed with the light having the light intensity distribution of the reverse peak pattern generated through the phase shifter through the imaging optical system. .
JP 2000-306859 A

  In order to realize the position and size of crystal grains industrially and with good reproducibility, the magnification (reduction magnification or equal magnification) and image plane position (focal position) of the imaging optical system corrected for aberrations are not changed, or It is necessary to be able to correct the magnification and the image plane position. For example, in the case of a 10 mm square mask pattern used for manufacturing 4 μm crystal grains, the magnification of the imaging optical system changes from 1 / 5.000 to 1 / 4.995 (change of 0.1%). The irradiation area size changes from 2 mm square to 2.002 mm square on the substrate to be processed.

  In this case, for example, if the left end of the irradiation area of 2 mm square is taken as a reference, the crystal grain position is shifted to the right by 2 μm (0.002 mm) at the right end. As a result, a mask pattern alignment error occurs during the TFT manufacturing process performed in the process after laser crystallization. Also, when the image plane position of the imaging optical system changes, the depth of focus (DOF) fluctuates, and a desired light intensity distribution cannot be obtained on the substrate to be processed. As a result, crystal grains of a desired size are formed. I can't.

  The present invention has been made in view of the foregoing problems, and can reduce the magnification and image plane position fluctuations of the imaging optical system and correct the image plane position in accordance with the image plane position fluctuations. Another object of the present invention is to provide a laser crystallization apparatus capable of forming crystal grains of a desired size at a desired position with good reproducibility.

  In order to solve the above problems, in the first embodiment of the present invention, a non-single crystal semiconductor is irradiated with laser light to locally melt the non-single crystal semiconductor, and crystal grains that crystallize in the solidification process are grown. A laser crystallization apparatus comprising: a light source (2a); a spatial intensity modulation optical element (3) that modulates the intensity and phase of laser light from the light source; and the light source and the spatial intensity modulation optical element. An illumination system (2) for uniforming the light intensity of the laser light from the light source and illuminating the spatial intensity modulation optical element with the uniformed light; and a stage for supporting the non-single crystal semiconductor (5) ( 6) and a laser beam that is provided between the non-single crystal semiconductor on the stage and the spatial intensity modulation optical element, and is modulated by the spatial intensity modulation optical element to a desired portion on the non-single crystal semiconductor. Multiple for imaging An imaging optical system (4) having a learning member (L1-L10, 4c) and a temperature adjusting unit (10-17) for adjusting the temperature of the optical member by heating or cooling the optical member of the imaging optical system , 20-22, 42-48), and a laser crystallization apparatus.

  According to a second aspect of the present invention, there is provided a laser crystallization apparatus that irradiates a non-single crystal semiconductor with a laser beam, locally melts the non-single crystal semiconductor, and grows crystal grains that crystallize in the solidification process. A light source (2a), a spatial intensity modulation optical element (3) that modulates the intensity and phase of laser light from the light source, and a laser from the light source provided between the light source and the spatial intensity modulation optical element. An illumination system (2) for illuminating the spatial intensity modulation optical element with the uniformed light, a stage (6) for supporting the non-single crystal semiconductor, and a non-single crystal on the stage A plurality of optical members provided between a semiconductor and the spatial intensity modulation optical element for imaging a laser beam modulated by the spatial intensity modulation optical element at a desired site on the non-single crystal semiconductor; And holding the optical member An imaging optical system (4) having a holding member and a temperature at which the optical member of the imaging optical system is heated or cooled, or the temperature of the optical member is adjusted by heating or cooling the holding member. Based on the adjustment unit (10-17, 20-22, 42-48), the temperature sensor (22) for detecting the temperature of at least one of the optical member and the holding member, and the detected temperature from the temperature sensor. Position adjusting means (6, 6) that relatively moves the stage and the imaging optical system along the optical axis of the imaging optical system to adjust the relative position between the imaging optical system and the non-single crystal semiconductor. 10). And a laser crystallization apparatus.

  According to the present invention, the magnification of the imaging optical system and the fluctuation of the image plane position can be reduced, and the image plane position can be corrected according to the fluctuation of the image plane position. It can be formed at a desired site on the crystalline semiconductor with good reproducibility.

  Important terms used herein are defined below. “Crystallization” refers to crystal growth starting from a crystal nucleus in the process of melting a film to be crystallized and solidifying the melt. “Lateral growth” means that the growth of crystal grains proceeds laterally along the film surface in the process of melting the crystallization target film and solidifying the melt. “Light intensity distribution” or “beam profile” refers to a two-dimensional intensity distribution of light incident on a crystallization target film. “Laser fluence” is a measure of the energy density of laser light at a certain position, and refers to the amount of energy per unit area, specifically the average intensity of laser light measured in the light source or irradiation area. Say.

  “Attenuator” refers to an optical element that attenuates the intensity of laser light. “Homogenizer” is an optical element that divides incident light into multiple parts, superimposes the divided lights in the same shape, determines the cross-sectional dimension of the laser light on a specific surface, and makes the light intensity uniform. That means. In addition, the “homogenized surface” refers to a specific surface on which light passing through the homogenizer converges. The “spatial intensity modulation optical element” refers to a photomask for modulating the phase of light and modulating the light intensity. In a laser crystallization apparatus, a spatial intensity modulation optical element is called a “phase shifter” and is distinguished from a phase shift mask used in an exposure process of a photolithography process. The phase shifter is formed, for example, by forming a step on a quartz substrate by etching.

  “Image plane” refers to a plane on which light passing through the imaging optical system of the laser crystallization apparatus converges. The surface on which the light that has passed through the primary imaging optical system (homogenizer, condenser lens, mask, etc.) of the projection type laser crystallization apparatus converges to form an image is particularly called a “primary image plane”. A primary image plane refers to a phase shifter plane and / or a homogenized plane when it coincides (completely overlaps) with a phase shifter plane and / or a homogenized plane. A surface on which light passing through a secondary imaging optical system (such as a reduction lens) of a projection type laser crystallization apparatus converges to form an image is particularly called a “secondary image plane”. In other words, the “secondary image plane” refers to a plane on which an image formed on the primary image plane is transferred to the substrate side.

  "Telecentric optical system" or "telecentric lens optical system" means that the aperture stop is at the focal position of the lens and the principal ray is parallel to the lens optical axis on the object side, the image side, or both sides of the object / image. An optical system. “Aperture stop” refers to a light-shielding frame provided in the optical system or in the vicinity of the optical system in order to limit a region through which light rays around the optical axis pass.

  In the laser crystallization apparatus of the present invention, the temperatures of a plurality of optical members constituting an imaging optical system for imaging a laser beam modulated by a spatial intensity modulation optical element on a desired site on a non-single crystal semiconductor are adjusted. A temperature adjustment unit for adjustment is provided. As a result, the temperature adjustment unit can reduce the magnification of the imaging optical system and the fluctuation of the image plane position, and can correct the image plane position according to the fluctuation of the image plane position. Can be formed at a desired position with good reproducibility.

  Embodiments of the present invention will be described with reference to the accompanying drawings. As shown in FIG. 1, a laser crystallization apparatus 1 of the present embodiment includes a projection illumination system 2, a spatial intensity modulation optical element 3 (phase shifter or diffractive optical element), and an imaging optical system 4. A substrate stage 6 that movably supports the substrate 5 to be processed is provided. The substrate stage 6 has a built-in XYZ-θ drive mechanism (not shown), and is aligned in each of the X-axis, Y-axis, and Z-axis directions for alignment with the optical systems 2, 3, and 4. While being moved, it is rotated θ around the Z axis.

As shown in FIG. 2, the illumination system 2 includes, for example, a KrF excimer laser light source 2a that oscillates laser light having a wavelength of 248 nm as a light source that outputs energy light that melts the amorphous silicon film on the substrate 5 to be processed. ing. The light source 2a incorporates an attenuator (not shown). The attenuator attenuates the laser light oscillated from the light source 2a and adjusts its light intensity level to, for example, about 1 J / cm ² to prevent the optical members of the illumination system 2 and the imaging optical system 4 from being burned. . As the light source 2a, an XeCl excimer laser light source that oscillates a laser beam having a wavelength of 308 nm, or another appropriate light source capable of emitting an energy beam that melts the object to be crystallized such as a YAG laser light source is used. You can also.

  The laser beam 70 is emitted from the light source 2a, then passes through the beam expander 2b, is enlarged, and enters the first fly-eye lens 2c. Thus, a plurality of virtual light sources are formed on the rear focal plane of the first fly-eye lens 2c. The light beams from these virtual light sources illuminate the incident surface of the second fly's eye lens 2e in a superimposed manner via the first condenser optical system 2d. As a result, more virtual light sources are formed on the rear focal plane of the second fly-eye lens 2e than on the rear focal plane of the first fly-eye lens 2c.

  Light beams from a plurality of virtual light sources formed on the rear focal plane of the second fly-eye lens 2e illuminate the spatial intensity modulation optical element 3 in a superimposed manner via the second condenser optical system 2f. Here, the first fly-eye lens 2c and the first condenser optical system 2d constitute a first homogenizer. The laser light emitted from the light source 2a is made uniform with respect to the incident angle on the phase shifter 3 by the first homogenizer.

  The second fly's eye lens 2e and the second condenser optical system 2f constitute a second homogenizer. With this second homogenizer, the light intensity at each in-plane position on the phase shifter 3 can be made uniform with respect to the laser light having the uniform incident angle from the first homogenizer. Thus, the illumination system 2 illuminates the phase shifter 3 with the laser beam having a substantially uniform light intensity distribution.

  The laser light 70 is phase-modulated or diffracted by the phase shifter 3 and is incident on the substrate 5 to be processed via the imaging optical system 4. Here, the phase shifter 3 and the substrate to be processed 5 are optically conjugate with respect to the imaging optical system 4. In other words, the substrate 5 to be processed is set to a surface optically conjugate with the phase shifter 3 (image surface of the imaging optical system 4).

  As shown in FIG. 3, the imaging optical system 4 is entirely covered with protective covers 41a and 41b. In the protective covers 41a and 41b, the first lens groups L1 to L3, the aperture stop 4c, and the second lens groups L4 to L10 are arranged in order. Each of the optical members L1 to L10, 4c is supported by the lens holder 42 in a state where the optical axes are aligned with each other and at a suitable distance from each other.

  An entrance window 40a is fitted into the upper protective cover 41a, and an exit window 40b is fitted into the lower protective cover 41b. The first lens groups L1 to L3 are arranged on the incident window 40a side (phase shifter 3 side), and the second lens groups L4 to L10 are arranged on the emission window 40b side (processed substrate 5 side). ing. The modulated laser light 70 enters the imaging optical system 4 from the entrance window 40a, and sequentially passes through the first lens groups L1 to L3, the aperture stop 4c, and the second lens groups L4 to L10, and then exits the exit window 40b. Through the imaging optical system 4.

  The imaging optical system 4 is an optical system for reducing the illumination intensity of the laser light from the light source onto the substrate 5 to be processed. Although the imaging optical system 4 of the present embodiment projects a laser beam in a reduced scale, the present invention is not limited to this, and may be an equal magnification projection or an enlarged projection.

  Since the lens groups L1 to L10 of the imaging optical system 4 are made of reduced telecentric lenses, the second lens groups L4 to L10 are smaller in size than the first lens groups L1 to L3. Thus, since the second lens groups L4 to L10 have a small heat capacity, they are more easily heated than the first lens groups L1 to L3 and more easily cooled. In correspondence with the lens size, the diameter of the lower protective cover 41b is made smaller than that of the upper protective cover 41a.

  The aperture stop 4c is disposed between the first lens group L1 to L3 and the second lens group L4 to L10. The aperture stop 4c has, for example, a plurality of aperture stops having different sizes of openings (light transmission portions), and the plurality of aperture stops 4c are attached to the laser light path in an exchangeable manner. Or you may use the iris diaphragm which can change the magnitude | size of an opening part continuously as the aperture stop 4c. In any case, the size of the aperture of the aperture stop 4c (that is, the image-side numerical aperture NA of the imaging optical system 4) is set so as to generate a required light intensity distribution on the semiconductor film of the substrate 5 to be processed. Has been.

  The imaging optical system 4 of the present embodiment employs a double telecentric lens optical system. As shown in FIG. 5A, in the double-sided telecentric lens optical system, since the principal ray 30 is parallel to the lens optical axis on both the object side and the image side, the object-side work 31 has moved in the vertical direction in the figure. Even in this case, the size of the image 32 does not change. Therefore, in the double-sided telecentric lens optical system, even if the back focus changes, the magnification does not change in principle.

  Further, an image side telecentric lens optical system can be used as the imaging optical system 4 in place of the double telecentric lens optical system. In the image-side telecentric lens optical system, as shown in FIG. 5B, only the image-side principal ray 30 is parallel to the lens optical axis, so that the object-side workpiece 31 moves in the vertical direction in the figure. The size of the image 32 changes. Accordingly, in the image side telecentric lens optical system, the magnification changes when the back focus changes.

The substrate 5 to be processed is obtained by sequentially forming a base film and a non-single crystal film on a flat glass substrate for a liquid crystal display, for example, by chemical vapor deposition (CVD). The base insulating film is an insulating film such as SiO ₂ , which prevents the non-single crystal film and the glass substrate from coming into direct contact with each other to prevent foreign substances such as Na from entering the amorphous silicon film. Is prevented from being directly transferred to the glass substrate. The non-single-crystal film is an amorphous semiconductor film or a polycrystalline semiconductor film having a predetermined thickness (for example, about 50 nm).

The non-single crystal film may be a non-single crystal semiconductor film or a metal film. On the amorphous silicon film, an insulating film such as a SiO ₂ film is formed as a cap film. The cap film is heated by a part of the light beam incident on the amorphous silicon film, and stores the heated temperature. This heat storage effect is that when the incidence of the light beam is interrupted, the high temperature portion of the irradiated surface of the amorphous silicon film cools relatively rapidly, but this temperature gradient is relaxed and the large grain size is reduced in the lateral direction. Promotes crystal growth. The substrate 5 to be processed is positioned and held at a predetermined position on the substrate stage 6 by a vacuum chuck or an electrostatic chuck. In addition, the to-be-processed substrate 5 generally has a curvature and a deflection of about ± 5 μm to ± 10 μm as an error in flatness.

  Thus, in the laser crystallization apparatus according to the present embodiment, light of a beam profile having a so-called reverse peak pattern (V-shaped two-dimensional pattern) is irradiated onto the non-single crystal semiconductor film on the substrate 5 to be processed. As a result, a temperature gradient is generated in the melted region in the irradiated region in accordance with the beam profile, and a crystal nucleus is formed in a portion that first solidifies or does not melt corresponding to the point where the light intensity is the lowest. The crystal grows laterally from the starting point.

  By the way, in a laser crystallization apparatus, an imaging optical system 4 with a reduction magnification is often used. For example, when the imaging optical system 4 having a reduction magnification of 1/5 is used, it becomes easy to manufacture a phase shifter or a diffractive optical element as the spatial intensity modulation optical element 3 (when an equal-magnification imaging optical system is used). This is because the size is 5 times that of Further, the light irradiation energy per unit area incident on the homogenizer (2c, 2e) and the spatial intensity modulation optical element 3 in the illumination system 2 is reduced to 1/25 as compared with the case where an imaging optical system having the same magnification is used. This is because the damage given to the homogenizer (2c, 2e) and the spatial intensity modulation optical element 3 is small.

  In addition, the imaging optical system 4 forms a light intensity distribution in the range of several μm defined by the spatial intensity modulation optical element 3 on the substrate 5 to be processed at a reduced magnification or an equal magnification without aberration or distortion. Usually, it is composed of 10 or more optical lenses. When an excimer laser light source is employed as the light source 2a, the optical material used for the lenses L1 to L10 of the imaging optical system 4 is synthetic quartz or calcium fluoride (fluorite).

Here, the thermal conductivity of calcium fluoride is 9.71 (W / (m · ° C)), and the thermal conductivity of synthetic quartz is 1.35 (W / (m · ° C)). Therefore, it is assumed that the temperature change caused by light irradiation is larger in the lens made of synthetic quartz than in the lens made of calcium fluoride. Further, the thermal expansion coefficient of calcium fluoride is about 2 × 10 ⁻⁵ / ° C., and the temperature coefficient of its refractive index is about −1 × 10 ⁻⁵ / ° C. On the other hand, the thermal expansion coefficient of synthetic quartz is about 4 × 10 ⁻⁶ / ° C., and the temperature coefficient of its refractive index is about 1 × 10 ⁻⁵ / ° C.

  Considering the temperature characteristics of such an optical material, in the imaging optical system 4, for example, a change in image plane position (focal position) of several μm with respect to a lens temperature change of 1 ° C. A change in the imaging position of several μm along the optical axis is estimated. For example, in the case of a crystallization apparatus using excimer laser light, it is said that there is an imaging optical system in which the image plane position (imaging position) changes by about 10 μm with respect to a lens temperature change of 1 ° C.

  By the way, in a conventional crystallization apparatus (an apparatus prior to the phase control ELA method), an elongated long beam (for example, 500 μm × 300 mm or the like) is uniformly irradiated onto a substrate to be processed. In this case, since the positioning of the crystal grains is not performed in the first place, even if a change in the crystal grain position of several μm occurs due to, for example, a change in magnification of the imaging optical system, there is no problem.

  On the other hand, in the laser crystallization apparatus of the present invention, it is required to accurately irradiate a desired portion of a substrate to be processed with a position accuracy of micron order. For this reason, the change in magnification and the change in image plane position (primary image plane position, secondary image plane position, focus position) of the imaging optical system described above become a problem even if they are slight. For example, when a 2 μm monochrome pattern is transferred through an imaging optical system having an image-side numerical aperture NA = 0.12 using laser light having a wavelength of 308 nm, the numerical aperture of the illumination system and the imaging optical system If the numerical aperture on the incident side is equal, the depth of focus (DOF) of the imaging optical system is about ± 10 μm to ± 20 μm. When using a diffractive optical element as the spatial intensity modulation optical element and controlling the light intensity distribution on the substrate 5 to be processed on the micron order, the depth of focus is further reduced, and depending on conditions, the depth of focus is as narrow as 5 μm or less. In some cases.

  Therefore, the laser crystallization apparatus 1 of the present embodiment includes a plurality of temperature adjustment units in order to adjust the temperatures of the optical members L1 to L10, 4c of the imaging optical system 4, as shown in FIG. These temperature adjustment units adjust the temperature of the optical members L1 to L10, 4c, thereby correcting the magnification of the imaging optical system 4 and correcting the image plane position with high accuracy. In the present embodiment, the following three temperature adjustment units are exemplified.

The first temperature adjustment unit is an air cooling mechanism that directly cools the optical members L1 to L10, 4c with the refrigerant gas. The air cooling mechanism includes a refrigerant gas supply source 11, a valve 12, pumps 13 and 14, a gas inlet 43a, an upper space 43, an internal flow path 44 of the lens holder 42, a lower space 45, and a gas outlet 45a. The refrigerant gas supply source 11 accommodates, for example, a low-temperature (room temperature or lower) inert gas (for example, nitrogen (N ₂ ) gas, helium (He) gas) or air as the refrigerant gas. The discharge port of the feed pump 13 communicates with the gas inlet 43a of the upper protective cover 41a, and the intake port of the exhaust pump 14 communicates with the gas outlet 45a of the lower protective cover 41b. In this embodiment, the refrigerant gas is discharged from the exhaust pump 14 into the atmosphere. However, the exhaust gas can be connected to the supply source 11 to form a circulation circuit, and the refrigerant gas can be reused.

  The gas inlet 43a communicates with the upper space 43 (directly above the lens L1), and the upper space 43 communicates with the space between the lenses L1 to L10 one after another via the internal flow path 44 of the lens holder 42. Further, the lowermost inter-lens space communicates with the lower space 45 (directly below the lens L10) via the internal flow path 44, and the lower space 45 communicates with the gas outlet 45a. As shown in FIG. 4, the internal flow path 44 is wide open.

  The refrigerant gas is the inlet 43a → the upper space 43 → the internal flow path 44 → the space between the lenses L1 and L2 → the internal flow path 44 → the space between the lenses L2 and L3 → the internal flow path 44 → the space between the lenses L3 and L4 → the internal flow path. 44 → Space between lenses L4 and L5 → Internal flow path 44 → Space between lenses L5 and L6 → Internal flow path 44 → Space between lenses L6 and L7 → Internal flow path 44 → Space between lenses L7 and L8 → Internal flow path 44 → The space between the lenses L8 and L9 → the internal flow path 44 → the space between the lenses L9 and L10 → the internal flow path 44 → the lower space 45 → the outlet 45a passes through the imaging optical system 4 in this order, and the optical members L1 to L10, Cool 4c directly.

  The second temperature adjustment unit is a liquid cooling mechanism that indirectly cools the optical members L1 to L10, 4c with the refrigerant liquid. This liquid cooling mechanism includes a heat exchanger 15, a pump 16, a valve 17, a supply pipe 47, an internal flow path 46 of the lens holder 42, and a return pipe 48. The heat exchanger 15 exchanges heat between the refrigerant liquid (for example, cooling water) and another heat exchange fluid, and cools the refrigerant liquid to a predetermined temperature below room temperature. The outlet side of the heat exchanger 15 communicates with the supply pipe 47 via the pump 16 and the valve 17, and the inlet side of the heat exchanger 15 communicates with the return pipe 48. The supply pipe 47 communicates with the uppermost internal flow path 46 of the lens holder 42, and the return pipe 48 communicates with the lowermost internal flow path 46 of the lens holder 42. As shown in FIG. 4, the internal flow path 46 is formed in an annular shape so as to surround the holding portions 42 h that hold the lenses L <b> 1 to L <b> 10 at each stage. The lens holder 42 functions as a heat exchange jacket by these internal flow paths 46. When the coolant liquid is allowed to flow through the internal flow path 46, not only the lenses L1 to L10 that are in contact with the holding portion 42h are indirectly cooled, but the entire imaging optical system 4 is efficiently cooled.

  When a large number of laser shots are shot on a large LCD substrate, the lens temperature of the imaging optical system rises. In particular, the temperature of the small second lens groups L4 to L10 tends to rise rapidly, but these are cooled directly or indirectly by the above-described first and second temperature adjustment units, so that these temperature rises are suppressed. Is done. However, since it is difficult to completely suppress the thermal displacement of the imaging optical system, the imaging optical system 4 and the substrate 5 to be processed are used for correcting the magnification of the imaging optical system and correcting the image plane position. The relative position needs to be adjusted. In other words, the control unit 10 moves the substrate stage 6 in the Z-axis direction based on the temperature detected by the temperature sensor 22, so that the substrate to be processed (non-single crystal semiconductor) along the optical axis of the imaging optical system 4. 5 is aligned with the imaging optical system 4. Thereby, the laser beam 70 is accurately irradiated to a desired portion of the non-single crystal semiconductor on the substrate 5 to be processed.

  The third temperature adjustment unit is a heating mechanism that indirectly heats the second lens groups L4 to L10 with the heater 20. This heating mechanism includes a heater 20, a power source 21, and a temperature sensor 22 wound around the outer periphery of the lower protective cover 41b. As the temperature sensor 22, for example, a thermocouple attached in contact with the lens L5 can be used. Since the second lens groups L4 to L10 are smaller in size than the first lens groups L1 to L3, the second lens groups L4 to L10 are easy to be overheated or overcooled because the heat capacity is small. When the lens groups L4 to L10 are overcooled, condensation tends to occur on the lens surface, and the laser crystallization process cannot be performed stably and normally. Therefore, when the lens temperature is detected by the temperature sensor 22 and the detected temperature is below a predetermined threshold, the second lens group L4 to L10 is heated by the heater 20.

  As described above, in the laser crystallization apparatus 1 of the present embodiment, the temperatures of the optical members L1 to L10, 4c of the imaging optical system 4 are adjusted. As a result, the magnification and image plane position of the imaging optical system 4 can be corrected, and crystal grains of a desired size can be formed at a desired position on the substrate 5 with good reproducibility.

  In addition, in the 2nd temperature adjustment parts 15-17 of this embodiment, although the optical members L1-L10 and 4c are cooled using cooling water, it is optical using warm water for the 2nd temperature adjustment parts 15-17. The members L1 to L10, 4c may be heated. The control unit 10 may control the first temperature adjustment units 11 to 13 and the second temperature adjustment units 15 to 17 based on the detected temperature from the temperature sensor 22.

  Further, the temperature sensor 22 of the present embodiment directly detects the lens temperature by making contact with the lens L5. However, the temperature sensor is attached so as to contact the lens holder 42, and the temperature of the lens holder 42 is detected. Also good. In this case, the control unit 10 obtains the lens temperature by converting the lens holder detection temperature into the lens temperature using a predetermined reference data table. Furthermore, a Peltier element may be attached to the lens holder or the protective cover, and the optical member may be indirectly cooled via the lens holder or the like.

Next, a case where a thin film transistor is manufactured using the laser crystallization apparatus of this embodiment will be described with reference to FIGS. As shown in FIG. 6A, a base film 51 (for example, SiN having a film thickness of 50 nm and a SiO ₂ film having a film thickness of 100 nm is laminated on an insulating substrate 50 (for example, alkali glass, quartz glass, plastic, polyimide, etc.). And the like, and a substrate 5 to be processed on which an amorphous semiconductor film 52 (for example, Si, Ge, SiGe, etc. having a film thickness of about 50 nm to 200 nm) is formed using a chemical vapor deposition method or a sputtering method is prepared. To do. The laser crystallization apparatus 1 is used to irradiate a predetermined region on the surface of the amorphous semiconductor film 52 with laser light 70 (for example, KrF excimer laser light or XeCl excimer laser light).

Thus, as shown in FIG. 6B, a polycrystalline semiconductor film or a single crystallized semiconductor film 54 having a crystal with a large grain size is generated. Next, as shown in FIG. 6C, the polycrystalline semiconductor film or the single crystallized semiconductor film 54 is processed into an island-shaped semiconductor film 55 that becomes a region for forming a thin film transistor, for example, by using a photolithography technique. Then, a SiO ₂ film having a thickness of 20 nm to 100 nm is formed as a gate insulating film 56 on the surface by using a chemical vapor deposition method or a sputtering method. Further, as shown in FIG. 6D, a gate electrode 57 (for example, silicide or MoW) is formed on the gate insulating film, and impurity ions 72 (in the case of an N-channel transistor) using the gate electrode 57 as a mask. Phosphorus and boron in the case of a P-channel transistor are ion-implanted. Thereafter, annealing is performed in a nitrogen atmosphere (for example, 450 ° C. for 1 hour) to activate the impurities and form the source 62 and the drain 63 in the island-shaped semiconductor film 55. Next, as shown in FIG. 6E, an interlayer insulating film 59 is formed to make contact holes, and a source electrode 64 and a drain electrode 65 connected to a source 62 and a drain 63 connected by a channel 61 are formed.

  In the above process, the channel 61 is formed in accordance with the position of the large grain crystal of the polycrystalline semiconductor film or the single crystallized semiconductor film 54 generated in the process shown in FIGS. 6A and 6B. . Through the above steps, the TFT 60 can be formed in the polycrystalline transistor or the single crystal semiconductor. Polycrystalline transistors or single crystal transistors thus manufactured can be applied to driving circuits such as liquid crystal display devices (displays) and EL (electroluminescence) displays, and integrated circuits such as memories (SRAM and DRAM) and CPUs. is there.

  Next, a laser crystallization apparatus according to another embodiment will be described with reference to FIG. The laser crystallization apparatus of the present embodiment includes a temperature adjustment unit for adjusting the temperatures of a plurality of optical members (only lenses L1 to L6 are illustrated) constituting the telecentric lens imaging optical system 4A. . The temperature adjusting unit is a holding member adjusting unit for adjusting the temperature of the holding member (that is, the outer cylinder) 83d that holds the optical members L1 to L6, and the heater 91 and the Peltier element arranged so as to contact the holding member 83d 92.

  The heater 91 has a heating function, and the Peltier element 92 has a cooling function, and each of them indirectly adjusts the temperature of the lenses L1 to L6 by heat conduction. The temperature adjustment unit has an atmosphere adjustment function for adjusting the temperature of the atmosphere by circulating a gas having a predetermined temperature in the gap between the lenses L1 to L6. For example, the temperature adjustment unit includes a gas supply unit 93 that allows an inert gas (for example, nitrogen gas, helium gas) 93 a that has been adjusted to a predetermined temperature to flow into the laser beam path of the imaging optical system 3. . The inert gas 93a supplied from the gas supply unit 93 flows through the gap between the lenses L1 to L6, and is then discharged to the outside of the imaging optical system 4A.

  Further, the temperature adjustment unit, for example, a temperature sensor 94 for measuring the temperature of the lens L5, and a control unit 95 for controlling the heater 91, the Peltier element 92, and the gas supply unit 93 based on the output from the temperature sensor 94, respectively. And have. As the temperature sensor 94, for example, a thermocouple attached so as to be in contact with the lens L6 can be used. The control unit 95 adjusts the temperature and flow rate of the inert gas 93 a supplied from the gas supply unit 93.

  As described above, in the laser crystallization apparatus of this embodiment, the imaging optical system is controlled by controlling at least one of the heater 91, the Peltier element 92, and the gas supply unit 93 based on a command from the control unit 95. The temperatures of the lenses L1 to L6 constituting 4A are adjusted. As a result, the magnification and image plane position of the imaging optical system 4A can be corrected, and crystal grains of a desired size can be formed at the desired position with good reproducibility.

  In the above description, the heater 91 and the Peltier element 92 disposed so as to be in contact with the holding member 83d are used as the holding member adjusting portion for adjusting the temperature of the holding member 83d. However, the present invention is not limited to this, and various modifications can be made to the specific configuration of the holding member adjusting portion. For example, as shown in FIG. 7, a circulating unit 96 that circulates cooling water or hot water around the holding member 93d can be used as the holding member adjusting unit. In order to adjust the temperature of the holding member 83d, the circulation unit 96 supplies water cooled or heated to a predetermined temperature around the holding member 83d, and collects the supplied cooling water or hot water.

  In this embodiment, the temperature of the optical member (for example, the lens L5) is measured by the temperature sensor 94, and the temperature of the optical members (the lenses L1 to L6) of the imaging optical system 4A is adjusted based on the measured temperature. However, the present invention is not limited to this. For example, a temperature sensor is attached so as to be in contact with the holding member 83d, the temperature of the holding member 83d is measured by this temperature sensor, and the temperature of the optical members (lenses L1 to L6) of the imaging optical system 4A is based on the measured temperature. Can also be adjusted.

  In addition, as indicated by the dashed arrows in FIG. 7, the control unit 95 determines the temperature of the temperature sensor 94 (or the holding member 83d) for measuring the temperature of the optical members (lenses L1 to L6) of the imaging optical system 4A. The position of the substrate (non-single crystal semiconductor) 5 along the optical axis of the imaging optical system 4A is moved by moving the substrate stage 6 based on the output from a temperature sensor (not shown) for measurement. Can also be adjusted.

  Next, a case where the laser crystallization apparatus of this embodiment is used for manufacturing a circuit of a liquid crystal display device will be described with reference to FIG. In the active matrix liquid crystal display device 50, a large number of thin film transistors (TFTs) 60 are formed on an insulating substrate such as glass or plastic in order to drive each pixel individually. Among silicon films used for TFT source, drain, and channel regions, amorphous silicon (a-Si) films have a low formation temperature and can be formed relatively easily by a vapor phase method. Therefore, it is generally used as a semiconductor thin film used for the TFT 60. However, a-Si films are inferior in physical properties such as conductivity to poly-Si films (the mobility in a-Si films is two orders of magnitude higher than that in poly-Si films). There is a disadvantage that it is low).

Therefore, by using the laser crystallization apparatus 1 of the present embodiment to irradiate a desired portion of the a-Si film with laser light having a predetermined power (one shot is about 1 J / cm ² ), the source 62 of the TFT 60, Crystalline silicon (poly-Si) is formed one after another in regions to be the drain 63 and the channel 61. Here, in the laser crystallization apparatus 1 of the present embodiment, since the telecentric imaging optical system is thermally stabilized, the imaging optical system 4 is not displaced with respect to the substrate 5 to be processed. Further, since the control unit 10 adjusts the position of the non-single crystal semiconductor 5 along the optical axis of the imaging optical system 4 based on the output of the temperature sensor 22, the laser light 70 changes from the first TFT to the last TFT. The desired part is irradiated with high accuracy until it reaches.

  The liquid crystal display device 50 includes a transparent substrate 52, a pixel electrode 53, a scanning line 54, a signal line 55, a counter electrode 56, a thin film transistor 60, a scanning line driving circuit 57, a signal line driving circuit 58, a liquid crystal controller 59, and the like. Yes. That is, in the liquid crystal display device 50, the TFT 60 shown in FIG. 6E is used in a peripheral circuit portion that requires high-speed operation such as the scanning line driving circuit 57 and the signal line driving circuit 58.

The liquid crystal display device 50 can realize a system display including active elements such as a peripheral circuit unit and a memory circuit unit. The TFT 60 is formed in a structure as shown in FIG. 6E, and constitutes a peripheral circuit portion such as a scanning line driving circuit 57 and a signal line driving circuit 58 that are required to operate at high speed. In peripheral circuit portions such as the scanning line driving circuit 57 and the signal line driving circuit 58, the source end position of the source region S or the drain end position of the drain region D is formed within 0.05 to 0.2 μm from the crystal growth end position. A TFT can be used. That is, the peripheral circuit can be constituted by a TFT having excellent characteristics with a mobility (μmax) of 300 cm ² / V · s or more.

  The display device thus manufactured can realize a system display including active elements such as peripheral circuits and memory circuits. This display device is also effective in reducing size and weight. In the above embodiment, an example of an active matrix liquid crystal display device has been described. However, the present invention is not limited to this, and the present invention can also be applied to the manufacture of an organic EL display device.

It is a schematic diagram which shows the outline | summary of a laser crystallization apparatus. It is an internal perspective view which shows the outline | summary of the illumination system of a laser crystallization apparatus. It is a block sectional view showing a telecentric lens optical system as a principal part of a laser crystallization apparatus concerning an embodiment of the present invention. It is a top view which shows a telecentric lens optical system seeing from an optical axis direction. (A) is a schematic diagram which shows a both-side telecentric lens optical system, (b) is a schematic diagram which shows an image side telecentric lens optical system. It is a cross-sectional schematic diagram which each shows the to-be-processed object in each process at the time of manufacturing an electronic device using the laser crystallization apparatus of this invention. It is a block sectional view showing a telecentric lens optical system as a principal part of a laser crystallization apparatus concerning other embodiments of the present invention. It is a block top view which shows the outline | summary of a display apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser crystallization apparatus 2 Illumination system 2a Laser light source 2b Beam expander 2c, 2e Fly eye lens 2d, 2f Condenser optical system 3 Spatial intensity modulation optical element (phase shifter or diffractive optical element)
4 Imaging optical systems L1 to L10 Lens group (optical member)
4c Aperture stop 5 Substrate 6 Substrate stages 10-17, 20-22, 42-48 Temperature adjustment unit 91 Heater 92 Peltier element 93 Gas supply unit 94 Temperature sensor 95 Control unit

Claims (19)

A laser crystallization apparatus for irradiating a non-single crystal semiconductor with laser light to locally melt the non-single crystal semiconductor and growing crystal grains that crystallize in the solidification process.
A light source;
A spatial intensity modulation optical element that modulates the intensity and phase of laser light from the light source;
An illumination system that is provided between the light source and the spatial intensity modulation optical element, uniformizes the light intensity of the laser light from the light source, and illuminates the spatial intensity modulation optical element with the uniformized light;
A stage for supporting the non-single crystal semiconductor;
Provided between the non-single crystal semiconductor on the stage and the spatial intensity modulation optical element, and for imaging a laser beam modulated by the spatial intensity modulation optical element at a desired site on the non-single crystal semiconductor An imaging optical system having a plurality of optical members;
A temperature adjusting unit that adjusts the temperature of the optical member by heating or cooling the optical member of the imaging optical system;
A laser crystallization apparatus comprising: The imaging optical system has a holding member that contacts only the peripheral edges of the plurality of optical members and supports the optical members;
The holding member has an internal flow channel formed so as to surround a periphery of the optical member,
The laser crystallization apparatus according to claim 1, wherein the internal flow path communicates with a supply source that supplies a refrigerant fluid. The laser crystallization apparatus according to claim 2, further comprising a circulation channel that circulates a refrigerant fluid between the supply source and the internal channel. The laser crystallization apparatus according to claim 1, wherein the temperature adjustment unit includes a heater that heats the holding member. The temperature adjustment unit is
A refrigerant gas supply source;
A gas inlet communicating with each of the refrigerant gas supply source and the imaging optical system;
An upper space communicating with the gas inlet and exposing an optical member closest to the light source among the plurality of optical members;
A gas outlet communicating with the inside of the imaging optical system;
A lower space that communicates with the gas outlet and exposes the optical member closest to the stage among the plurality of optical members;
An internal flow path formed in the holding member and communicating with the space between the optical members, the upper space and the lower space, respectively.
The laser crystallization apparatus according to claim 2, wherein: 6. The laser crystallization apparatus according to claim 5, wherein the refrigerant gas is nitrogen gas or helium gas. 6. The laser crystallization apparatus according to claim 5, further comprising control means for controlling a flow rate of the refrigerant gas supplied to the space between the optical members. The temperature adjustment unit includes a temperature sensor that detects the temperature of at least one of the optical member and the holding member;
The laser crystallization apparatus according to claim 2, further comprising a control unit that causes the temperature adjustment unit to perform temperature adjustment based on a temperature detected from the temperature sensor. The optical member includes a first telecentric lens group disposed on the light source side, a second telecentric lens group disposed on the non-single crystal semiconductor side, the first telecentric lens group, and the second telecentric lens group. The laser crystallization apparatus according to claim 1, further comprising: an aperture stop disposed between the telecentric lens group. The laser crystallization apparatus according to claim 1, wherein the imaging optical system is either a double-sided telecentric lens optical system or an image-side telecentric lens optical system. A laser crystallization apparatus for irradiating a non-single crystal semiconductor with laser light to locally melt the non-single crystal semiconductor and growing crystal grains that crystallize in the solidification process.
A light source;
A spatial intensity modulation optical element that modulates the intensity and phase of laser light from the light source;
An illumination system that is provided between the light source and the spatial intensity modulation optical element, uniformizes the light intensity of the laser light from the light source, and illuminates the spatial intensity modulation optical element with the uniformized light;
A stage for supporting the non-single crystal semiconductor;
Provided between the non-single crystal semiconductor on the stage and the spatial intensity modulation optical element, and for imaging a laser beam modulated by the spatial intensity modulation optical element at a desired site on the non-single crystal semiconductor And an imaging optical system having a holding member for holding the optical member,
A temperature adjusting unit that adjusts the temperature of the optical member by heating or cooling the optical member of the imaging optical system or heating or cooling the holding member;
A temperature sensor for detecting the temperature of at least one of the optical member and the holding member;
The stage and the imaging optical system are relatively moved along the optical axis of the imaging optical system based on the detection temperature from the temperature sensor, and the imaging optical system and the non-single crystal semiconductor are relatively moved. Position adjusting means for adjusting the position;
A laser crystallization apparatus comprising: The holding member has an internal flow channel formed so as to surround a periphery of the optical member,
The laser crystallization apparatus according to claim 11, wherein the internal flow path communicates with a supply source that supplies a refrigerant fluid. The laser crystallization apparatus according to claim 12, further comprising a circulation channel that circulates a refrigerant fluid between the supply source and the internal channel. The laser crystallization apparatus according to claim 11, wherein the temperature adjustment unit includes a heater for heating the holding member. The temperature adjustment unit is
A refrigerant gas supply source;
A gas inlet communicating with each of the refrigerant gas supply source and the imaging optical system;
An upper space communicating with the gas inlet and exposing an optical member closest to the light source among the plurality of optical members;
A gas outlet communicating with the inside of the imaging optical system;
A lower space that communicates with the gas outlet and exposes the optical member closest to the stage among the plurality of optical members;
An internal flow path formed in the holding member and communicating with the space between the optical members, the upper space and the lower space, respectively.
The laser crystallization apparatus according to claim 12, comprising: The laser crystallization apparatus according to claim 15, wherein the refrigerant gas is nitrogen gas or helium gas. 16. The laser crystallization apparatus according to claim 15, further comprising control means for controlling a flow rate of the refrigerant gas supplied to the space between the optical members. The optical member includes a first telecentric lens group disposed on the light source side, a second telecentric lens group disposed on the non-single crystal semiconductor side, the first telecentric lens group, and the second telecentric lens group. The laser crystallization apparatus according to claim 11, further comprising: an aperture stop disposed between the telecentric lens group. 12. The laser crystallization apparatus according to claim 11, wherein the imaging optical system is either a double-sided telecentric lens optical system or an image-side telecentric lens optical system.

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