JP2004103628A - Laser annealing device and method of laser-annealing tft substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser annealing device which is capable of emitting a continuous oscillation laser beam linear through a simple optical system, accurately irradiating only a target region with a laser beam, and obtaining a polycrystalline silicon film substantially equivalent to a single crystal film without causing thermal damage to the silicon film and a substrate. <P>SOLUTION: The laser beam is split into halves and deflected by a prism, and the split laser beams are made to overlap with each other while the directions of polarization of the split laser beams are made to cross each other at right angles, the overlapping laser beams are set uniform in energy distribution in the deflecting direction and condensed through a cylindrical lens or formed through a combination of a Powell lens and a cylindrical lens into a linear beam in the direction perpendicular to the deflecting direction. The linear beam is made to irradiate a plurality of target regions as continuously scanning the regions without stopping a stage, so that the polycrystalline silicon film having characteristics substantially equivalent to those of a single crystal silicon film is formed on only the target regions irradiated with the linear laser beam. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is suitable for irradiating a laser beam to an amorphous or polycrystalline semiconductor film formed on an insulating substrate to improve film quality, enlarge crystal grains, or perform single crystallization. About.
[0002]
[Prior art]
At present, a liquid crystal panel forms an image by switching a thin film transistor formed of an amorphous silicon film on a substrate such as glass or fused quartz. If it becomes possible to simultaneously form a driver circuit for driving a pixel transistor on this substrate, a dramatic reduction in manufacturing cost and improvement in reliability can be expected. However, at present, since the silicon film forming the active layer of the transistor has poor crystallinity, the performance of a thin film transistor represented by mobility is low, and it is difficult to manufacture a circuit that requires high speed and high function. In order to manufacture these high-speed and high-performance circuits, high mobility thin film transistors are required, and in order to realize this, it is necessary to improve the crystallinity of the silicon thin film.
[0003]
As a method for improving the crystallinity, excimer laser annealing has been receiving attention. This method uses an amorphous silicon film (having a mobility of 1 cm) formed on an insulating substrate such as glass. ² / Vs or less), the mobility is improved by irradiating an excimer laser to change the amorphous silicon film into a polycrystalline silicon film. However, the polycrystalline film obtained by excimer laser irradiation has a crystal grain size of about several 100 nm and a mobility of 100 cm. ² / Vs, which is insufficient for application to a driver circuit for driving a liquid crystal panel.
[0004]
Non-Patent Document 1 and Patent Document 1 describe an annealing method using a continuous wave laser to solve this problem.
[0005]
[Non-patent document 1]
F. Takeuchi, Performance of poly-Si TFTs Fabricated by a Stable Scanning CW Laser Crystallization, AM-LCD'01 (TFT4-3)
[Patent Document 1]
JP-A-10-64842
[0006]
[Problems to be solved by the invention]
In the above prior art, a diode-pumped continuous oscillation YVO ₄ The second harmonic of the laser is crystal-grown by scanning on an amorphous silicon thin film formed on a glass substrate, and 500 cm ² / Vs. When such a degree of mobility is obtained, a drive circuit with sufficient performance can be formed, and a system-on-panel can be realized.
[0007]
The above diode excited continuous oscillation YVO ₄ In the case of a solid state laser, such as the second harmonic of a laser, the emitted beam has a Gaussian distribution. In the case of a high-power laser such as an excimer laser, the laser oscillates in a multi-mode, and in any case, there is a problem in application to laser annealing that requires irradiation with a uniform energy density over the entire irradiation region. . For this reason, it is common to install a beam homogenizer in which a plurality of lens arrays are combined as disclosed in Japanese Patent Application Laid-Open No. H10-64842, for example, to make the energy density distribution uniform.
[0008]
However, the above technique is a combination of a plurality of lens arrays and is a very complicated and large-scale optical system, which has caused an increase in the cost of the apparatus. In addition, the diode-excited continuous oscillation YVO ₄ In the case of a solid-state laser such as the second harmonic of a laser, the coherence is higher than that of an excimer laser, and it is difficult to obtain a beam having a uniform energy density distribution with a homogenizer combined with a lens array. was there.
[0009]
An object of the present invention is to solve the above-mentioned drawbacks of the prior art, to obtain a linear beam having a uniform energy density distribution with an optical system having a simple structure, and to stably obtain a high-quality silicon thin film. An object of the present invention is to provide an annealing method, a laser annealing apparatus, and a TFT substrate obtained by the method and the apparatus.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the laser annealing method of the present invention converges a solid-state laser beam having a Gaussian distribution type energy distribution into a linear beam with a cylindrical lens in the width direction. In addition, the beam is divided into two in the longitudinal direction by refraction or reflection means, and the polarization directions of the divided beams are adjusted so as to form 90 degrees with each other, so that the beam diameter becomes １ ／ of the beam diameter before division. Then, the obtained linear beam is reduced and projected by an objective lens as necessary, and is irradiated in the amorphous or polycrystalline silicon thin film while scanning in the width direction of the laser beam.
[0011]
Further, in order to achieve the above object, the laser annealing apparatus of the present invention has a cylindrical lens for condensing in the width direction as a beam homogenizer for forming a laser beam into a linear shape, An optical system comprising: a beam splitting unit that splits a laser beam into two in a direction orthogonal to each other); a polarization direction adjusting unit that adjusts the polarization directions of the split beams so as to be orthogonal; and a unit that overlaps the split beams. It has a system and scans the obtained linear beam on a target substrate.
[0012]
Further, in order to achieve the above object, the laser annealing apparatus of the present invention has an optical system composed of a Powell lens for expanding laser light in one direction and a cylindrical lens for condensing light in a direction orthogonal to one direction. Then, the obtained linear beam is scanned on a target substrate. The Powell lens is disclosed in U.S. Pat. No. 4,826,299.
[0013]
Further, the flat display device of the present invention is a flat display device in which a transistor circuit having a high-performance silicon thin film manufactured by applying the laser annealing method is formed by the laser annealing device.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration of a laser annealing apparatus according to one embodiment of the present invention. The glass substrate 1 is mounted on an XYθ stage 2. The XYθ stage 2 fixed on a surface plate (not shown) provided with a vibration isolation mechanism is provided with linear scales 3 and 4 for detecting position coordinates in the X and Y directions, respectively.
[0015]
The annealing optical system includes a laser oscillator 6 for oscillating a continuous wave laser beam 18, a shutter 7 for preventing the laser beam 18 from being carelessly illuminated, a beam expander 8 for expanding the beam diameter of the laser beam 18, Variable transmittance filter 9 for adjusting the output (energy) of laser light 18, EO (electro-optic) modulator 10 for ON / OFF of laser light 18 and temporal modulation as required, and its power supply 21 A beam shaping optical system 11 for compressing the laser beam 18 in one direction and converting it into a linear beam, an electric rectangular slit 12 for cutting out only a necessary portion of the linearly formed laser beam 18, and an electric rectangular slit 12. An objective lens 13 for projecting the transmitted laser light 18 onto the glass substrate 1 and a slit reference light source for confirming the irradiation position and shape of the laser light 18 4. An epi-illumination light source 15 for illuminating the glass substrate surface, a CCD camera 16 for observing the glass substrate 1 surface or capturing an alignment mark as needed at the time of alignment, opening and closing the shutter 7, and controlling the transmittance variable filter 9. A control device 22 for adjusting transmittance, controlling the EO modulator power supply 21, controlling the electric rectangular slit 12, controlling the stage 2, processing signals from the linear scales 3 and 4, processing images captured by the CCD camera 16, and the like. It is composed of FIG. 1 shows only the electrical connections between the linear scales 3 and 4, the control device 22, the EO modulator 10, and the power supply 21.
[0016]
The laser oscillator 6 generates a continuous wave light of ultraviolet or visible wavelength. In particular, a laser diode-pumped YVO is used because of its large output and stability. ₄ The second harmonic of the laser is optimal. However, without being limited to this, it is possible to use harmonics of an argon laser, a YAG laser, a plurality of semiconductor lasers connected by a fiber, or the like.
[0017]
The shutter 7 is provided so as not to be carelessly irradiated with the laser light 18 while the glass substrate 1 is being conveyed or positioned, and is not used for turning on / off the laser light 18 during laser annealing. The beam expander 8 expands the beam diameter in order to prevent damage to an optical element, particularly a crystal such as a Pockels cell constituting the EO modulator 10, but uses a Pockels cell that can withstand a high energy density. If so, it is not necessary to use it.
[0018]
The continuous wave laser light 18 oscillated by the laser oscillator 6 passes with the shutter 7 open, the beam diameter is expanded by the beam expander 8, and is incident on the EO modulator 10. At this time, in consideration of the power resistance of the EO modulator 10, the beam diameter is expanded by the beam expander 8 to a size close to the effective diameter of the EO modulator 10. When the EO modulator 10 having a laser beam 18 oscillated from the laser oscillator 6 having a beam diameter of about 2 mm and an effective diameter of 15 mm is used, the magnification of the beam expander 8 is preferably about 3 to 5 times.
[0019]
The laser beam 18 whose beam diameter has been expanded by the beam expander 8 enters the EO modulator 10. The EO modulator 10 uses a Pockels cell 61 (hereinafter, referred to as a crystal) and a polarization beam splitter 62 in combination, as shown in FIGS.
[0020]
When the laser beam 18 is linearly polarized, a laser beam transmitted through the crystal 61 is applied by applying a voltage V1 (normally 0 V) to the crystal 61 via an EO modulator power supply (not shown) as shown in FIG. The polarization direction of 18 is stored as it is without rotation, and is incident on the polarization beam splitter 62 as S-polarized light and is set to be deflected by 90 degrees. That is, in this state, since the laser beam 18 is output after being deflected by 90 degrees, it does not enter the subsequent optical system, and the laser beam 18 is turned off on the glass substrate 1.
[0021]
Further, as shown in FIG. 3, by applying a voltage V2 capable of rotating the polarization direction of the laser beam 18 passing through the crystal 61 by 90 degrees, the polarization direction of the laser beam 18 passing through the crystal 61 is rotated by 90 degrees. Then, the light enters the polarization beam splitter 62 as P-polarized light. At this time, the laser light 18 passes through the polarization beam splitter 62 and goes straight. That is, in this state, the laser beam 18 goes straight and enters the subsequent optical system, so that the laser beam 18 is turned on on the glass substrate 1.
[0022]
FIG. 4 shows the relationship between the voltage applied to the crystal 61 and the transmittance T1 of the laser beam 18 transmitted through the EO modulator 6. As can be seen from this figure, by changing the voltage applied to the crystal 61 between V1 (normally 0 V) and V2, the transmittance of the laser beam 18 passing through the EO modulator 6 is set to T1 (normally 0). It can be set arbitrarily between T2 (here, the maximum transmittance, that is, 1). That is, the transmittance of the laser beam 18 passing through the EO modulator 6 can be arbitrarily set between 0 and 1. However, here, it is assumed that there is no reflection or absorption on the surface of the crystal 61 or the polarizing beam splitter 62.
[0023]
From these facts, as shown in FIG. 5, the output of the laser beam 18 incident on the EO modulator 10 (input to the EO modulator 10) is fixed at P0, and the applied voltage to the crystal 61 is V1, V2, V3, V1. As a result, stepwise pulse outputs of the outputs P2 and P3 are obtained as the laser output from the EO modulator 10. Here, the output P2 is obtained by the product of the input P0 to the EO modulator 10 and the transmittance T2 when the voltage V2 is applied, and the output P2 is obtained by the product of P0 and the transmittance T3 when the voltage V3 is applied. . Naturally, by continuously changing the voltage applied to the crystal 61, the output of the transmitted laser light 2 can be changed continuously, and as a result, the pulsed laser light 2 having an arbitrary time change can be obtained. Can be done.
[0024]
Here, the EO modulator 10 has been described by combining the Pockels cell 61 and the polarization beam splitter 62, but various types of polarizing plates can be used. In the following description, the combination of the crystal 61 and the polarizing beam splitter 62 (or the polarizing plate) is referred to as the EO modulator 10.
[0025]
In addition to the EO modulator 10, an AO (acousto-optic) modulator can be used. However, since the AO modulator generally has a lower driving frequency than the EO modulator, there are cases where high-speed rise and fall are required and cases where it is not suitable for cutting out pulse light having a small pulse width. By using a modulator such as the EO modulator 10 or the AO modulator in this manner, irradiation with a laser oscillator is started at an arbitrary time while laser light is always output from the laser oscillator, and irradiation is performed at an arbitrary time. Can be finished.
[0026]
The laser beam 18 turned on by the EO modulator 10 is formed into a linear beam by a beam forming optical system. Usually, an output beam from a gas laser oscillator or a solid-state laser oscillator has a circular and Gaussian energy distribution, and therefore cannot be used for laser annealing of the present invention as it is.
[0027]
If the oscillator output is sufficiently large, it is possible to obtain an arbitrary shape with a substantially uniform energy distribution by widening the beam diameter sufficiently and cutting out the required shape from a relatively uniform central portion. The surrounding area is discarded, and most of the energy is wasted. The beam shaping optical system 11 is used to solve this drawback and convert the Gaussian distribution into a uniform distribution.
[0028]
As shown in FIG. 6, the beam shaping optical system 11 includes a half-wave plate 31, a prism 32, and a cylindrical lens 33. The half-wave plate 31 is adjusted so that the polarization direction of the linearly polarized light incident on the prism 32 is rotated by 90 degrees, and is installed so that exactly half of the incident laser light is transmitted. The laser beams 18 whose halves are orthogonal to each other in polarization direction pass through the prism 32, are divided into two at the vertex of the prism 32, and are deflected in directions overlapping each other.
[0029]
At this time, each of the split beams corresponds to a portion 41 (shown by hatching in FIG. 6) that has passed through the half-wave plate 31 and a portion 41 ′ that has not passed, and the deflection directions are orthogonal to each other. Is set to Another half-wave plate (not shown) is installed in front of the beam forming optical system 11, and the polarization direction of the laser beam 18 incident on the beam forming optical system 11 is rotated. The wavelength plate 31 can be adjusted so that the polarization direction is rotated by 90 degrees.
[0030]
The apex angle of the prism 32 is designed so that the two split beams just overlap on the surface of the motor-operated rectangular aperture slit 12 described later. At the same time, light is converged by the cylindrical lens 33 in a direction orthogonal to the direction deflected by the prism 32. As the cylindrical lens 33, a lens having a focal length at which light is condensed at the surface of the motor-operated rectangular aperture slit 12 is selected.
[0031]
As shown in FIG. 7A, the laser beam originally having a Gaussian distribution gradually overlaps immediately after passing through the prism while maintaining the relationship that the deflection direction is orthogonal to the other half, and the motorized rectangular aperture slit The 12 surfaces completely overlap as shown in FIG. Here, the beam diameter is 1 / e of the energy density at the center of the beam. ² It stipulates that
[0032]
As a result, since the deflection directions of the divided beams are orthogonal to each other, they do not interfere with each other even when they overlap, and a beam having a substantially uniform energy distribution is formed as shown in FIG. 7C. . The energy distribution in the direction orthogonal to the distribution shown in FIG. 7 is substantially Gaussian as a result of being collected by the cylindrical lens 33. In other words, a linear beam having a size substantially equal to one half of the beam diameter incident on the beam shaping optical system 11 in the longitudinal direction and a size condensed by the cylindrical lens 33 in the width direction is obtained. The energy density at this time is about 121% at the center and about 114% at the periphery with respect to the energy density at the center when condensing only by the cylindrical lens.
[0033]
Consider a case where the beam is expanded to a beam diameter of 10 mm by the beam expander 8, enters the beam forming optical system 11, and the two split beams overlap at a position 1000 mm away from the position of the prism 32. Since one of the two split beams only needs to be deflected by 2.5 mm, the deflection angle is 2.5 milliradians. Assuming that the material of the prism is quartz, the refractive index is 1.46.
[0034]
In the case of a prism having a small deflection angle, the following relationship holds between the deflection angle ε, the prism ridge angle σ, and the prism refractive index n.
ε = (n−1) σ
That is, σ = 5.43 mrad is obtained from ε = 2.5 mrad and n = 1.46. This corresponds to 0.31 degrees, and the vertex angle α of the prism is 179.38 degrees from α = 180−2σ.
[0035]
When a cylindrical lens having a focal length of 1000 mm is used, a width of 100 microns can be obtained by setting the divergence angle of the incident beam to 0.1 milliradian.
[0036]
The laser beam 18 condensed linearly by the beam shaping optical system 11 is cut off an unnecessary portion of the laser beam by the electric rectangular aperture slit 12 to be shaped into a desired rectangular shape, and is formed on the glass substrate 1 by the objective lens 13. Reduced projection is performed. Assuming that the magnification of the objective lens 13 is M, the image of the motorized rectangular aperture slit 12 or the size of the laser beam 18 passing through the motorized rectangular slit 12 is projected at the reciprocal of the magnification, ie, 1 / M. Here, by using a 20 × objective lens, a linear beam having a length of 250 μm and a width of 5 μm can be obtained on the surface of the glass substrate 1.
[0037]
When irradiating the glass substrate 1 with the laser beam 18, the laser beam 18 is pulse-irradiated to a desired position while moving the stage 2 in the XY plane. If this occurs, the power density of the condensed laser light 18 fluctuates and the irradiation shape deteriorates, so that the intended purpose cannot be achieved. For this reason, the focus position is detected by an auto-focus optical system (not shown) so that irradiation can always be performed at the focus position if necessary. If the focus position deviates from the focus position, the stage 2 is moved in the Z direction (height direction). Driving or driving the optical system in the Z direction (height direction) is controlled so that the focal position (projection position of the electric rectangular aperture slit 12 surface) always coincides with the surface of the glass substrate 1.
[0038]
The surface of the glass substrate 1 irradiated with the laser light 18 can be observed by a monitor (not shown) by illuminating the surface of the glass substrate 1 with illumination light from the epi-illumination light source 15 and imaging the CCD camera 16. In the case of observation during laser irradiation, a laser cut filter is inserted in front of the CCD camera 16 so that the laser beam reflected on the surface of the glass substrate 1 causes halation or obstruction of the CCD camera 16 in extreme cases. To prevent damage.
[0039]
The alignment of the sample substrate 1 is performed by taking an image of an alignment mark formed on the glass substrate 1, a corner portion of the glass substrate or a specific pattern at a plurality of positions by the objective lens 13 and the CCD camera 16, and controlling the device 22 as needed. By performing image processing such as value conversion processing and pattern matching processing, calculating their position coordinates, and driving the stage 2, the processing can be performed on the XYθ3 axes.
[0040]
In FIG. 1, although the objective lens 13 is represented by one, a plurality of objective lenses are mounted on the electric revolver, switching is performed by a signal from the control device 22, and an optimal objective lens is selectively used according to the processing content. be able to. That is, it is possible to use an objective lens that is optimal for alignment when the sample is loaded, fine alignment as necessary, laser annealing, observation after the processing, and alignment mark formation described later.
[0041]
Alignment can be performed by providing a dedicated optical system (lens, imaging device, and illumination device). However, by sharing the optical system for laser annealing with the alignment optical system, detection on the same optical axis and laser Irradiation becomes possible, and alignment accuracy is improved.
[0042]
Next, a laser annealing method according to an embodiment of the present invention, which is performed using the laser annealing apparatus of the present invention, will be described with reference to the drawings. Here, the substrate to be annealed is a glass substrate having a thickness of about 0.3 to 1.0 mm with an amorphous silicon thin film having a thickness of 40 to 150 nm formed on one main surface via an insulating thin film. Alternatively, a polycrystalline silicon thin film crystallized into a polycrystalline silicon thin film by scanning an excimer laser beam over the entire surface of the amorphous silicon thin film is formed. Here, the insulator thin film is SiO2 or SiN or a composite film thereof having a thickness of 50 to 200 nm.
[0043]
A glass substrate 1 on which a polycrystalline silicon thin film annealed by an excimer laser is formed is placed on a stage 2. As shown in FIG. 8, the glass substrate 1 includes a pixel portion 101 and drive circuit portions 102 and 102 ', and alignment marks 103 and 103' are formed at two positions on the outer edge. These alignment marks 103 and 103 'may be formed by a photo-etching technique, but it is wasteful to carry out a photoresist process only for this purpose. For this reason, the laser beam 18 used for laser annealing is sequentially shaped into, for example, a vertically long and a horizontally long rectangle by the rotation of the beam shaping optical system 11 and the electric rectangular slit 12, and the polycrystalline silicon thin film is removed. Or by irradiating a fixed width and a fixed distance at a high energy density and processing it into a rectangular shape to obtain the alignment marks 103 and 103 '. In this case, it is necessary to perform pre-alignment in advance at a corner or the like of the glass substrate 1.
[0044]
After detecting the positions of the alignment marks 103 and 103 ′ and correcting the positions of XYθ, the stage 2 or the optical system is moved according to the design coordinates as shown by the arrow in FIG. The laser beam 18 turned on by the modulator 10 is condensed and irradiated by the objective lens 13.
[0045]
Irradiated regions are, for example, portions 102 and 102 'for forming a driver circuit for driving each pixel, and more specifically, an annealing region (104, 105, 106, 107, and 108 in the enlarged view of FIG. 8). , 109, 110). Irradiation is performed sequentially while reciprocating the glass substrate 1 a plurality of times as necessary. Depending on the configuration of the apparatus, relative scanning may be performed by moving the optical system.
[0046]
The size of each of the annealing regions 104 to 110 is, for example, 4 mm × 200 μm, and the rectangular regions are set at a pitch of 250 μm. On the other hand, the size of the laser beam to be irradiated is 250 μm × 5 μm. That is, the laser beam is formed in a rectangular (linear) shape having a length of 250 μm and a width of 5 μm as shown in FIG.
[0047]
The energy density at this time is 50 × 103 to 500 × 103 W / cm ² The degree is suitable, but varies depending on the thickness of the silicon film, whether it is amorphous or polycrystalline, and the like. Since it is 250 μm that can be annealed in one scan, irradiation of 16 one-way scans or 8 reciprocal scans is required to anneal the required width (4 mm). The size of the laser beam is determined by the output of the laser oscillator 6. If the output of the oscillator 6 is sufficiently large, it is possible to irradiate a larger area and reduce the number of scans. Alternatively, the longitudinal direction can be increased by making the shape of the irradiated beam smaller in the converging width.
[0048]
While the glass substrate 1 is relatively moved at a speed of 500 mm / s, irradiation is performed at a pitch of 250 μm and a length of 200 μm as shown in FIG. That is, the laser beam irradiation is started at the irradiation start position, the stage is relatively moved by 200 μm while the laser beam irradiation is continued, and the laser beam irradiation is stopped at the irradiation end position. The stage is moving continuously.
[0049]
Next, at the point where the stage has moved by 250 μm, irradiation is started again. When the stage has moved by 200 μm, irradiation is stopped, and this is repeated as many times as necessary. During that time, the stage does not stop and continues to move at a constant speed. As a result, an annealing region of approximately 250 μm × 200 μm (more precisely, an annealing region of 250 μm × 205 μm in consideration of the width of the laser beam to be irradiated) is formed at a pitch of 250 μm, which will be described in detail later. Crystal grains grow in the direction in which the laser light has moved. When the irradiation width is set to be exactly 200 μm, the EO modulator 10 may be controlled so that the scanning distance of the laser beam becomes 195 μm.
[0050]
Here, the procedure of turning on / off the laser light 18 by the EO modulator 10 while relatively scanning the substrate and irradiating the same is shown in FIG. 8 by a distance of 250 micron pitch while scanning in the X direction. An example in which irradiation is performed at 1024 locations by 200 microns will be described with reference to FIG.
[0051]
The linear scale 3 attached to the X axis of the stage 2 generates a pulse signal at regular intervals according to the movement of the stage 2 in the X direction. When the generated signal is a sine wave, one cycle may be converted to a one-pulse rectangular wave and used. The position of the stage can be detected by counting the pulse signals. The pulse signal generated by the linear scale 3 is generated, for example, by a high-accuracy linear scale, for example, one pulse for every 0.1 μm of movement. When the pulse interval is large, it is also possible to electrically divide the pulse into a small pulse interval.
[0052]
The stage requires a certain distance (acceleration area) from the stop state to a certain speed. Assuming that the stage speed at the time of laser irradiation is 500 mm / s, an acceleration region of about 50 mm is necessary, and a position 50 mm or more, for example, 60 mm left from the irradiation start position (left side of the annealing region 104 in FIG. 8) as the acceleration region. (Xs in FIG. 9) and stop.
[0053]
Here, the count is started after clearing C1 (counter 1) for counting the signal from the linear scale 3, and the stage drive is started. The counter 1 counts a pulse signal generated according to the movement of the stage, and outputs a gate ON signal when the stage reaches the irradiation start position X1, that is, when the number of pulses n1 (600,000 pulses) corresponding to the movement of 60 mm is counted. . With this signal, the gate to the EO modulator power supply 21 is opened, and the signal to the EO modulator power supply 21 can be transmitted. At this point, the stage speed has finished accelerating and has reached a certain speed.
[0054]
Upon receiving this gate ON signal, C3 (counter 3) outputs an ON signal of the EO modulator power supply 21 and clears the count to start counting. Thereafter, the pulse number n3 (2500 pulses) corresponding to the irradiation pitch is obtained. Each time it counts, it outputs an ON signal to the EO modulator power supply 21.
[0055]
On the other hand, C4 (counter 4) receives the ON signal to the EO modulator power supply 21, clears the count, starts counting, and counts the pulse number n4 (2000 pulses) corresponding to the annealing length of 100 microns. An OFF signal is output to the EO modulator power supply 21. This operation is repeated each time the counter 3 generates an ON signal to the EO modulator power supply 21.
[0056]
The EO modulator power supply 21 applies the polarization of the laser beam 18 to the Pockels cell 61 from the time the EO modulator power supply ON signal is received to the time the EO modulator power supply OFF signal is received (time to pass 200 microns at 500 mm / s: 400 microseconds). A voltage whose direction rotates 90 degrees is applied. As a result, the laser beam 18 is output for the same time as the voltage applied to the Pockels cell 61, and is irradiated onto the substrate 1.
[0057]
On the other hand, C2 (counter 2) receives the gate ON signal from counter 1 to clear the count, counts the EO modulator power OFF signal of counter 4 and counts the number of pulses n2 (1024 pulses) corresponding to the number of annealing regions. At the time of counting, the gate is closed. Thus, the EO modulator power supply 21 does not receive the EO modulator power supply ON signal or the EO modulator power supply OFF signal, and the EO modulator power supply 21 does not operate.
[0058]
According to the above procedure, the first laser annealing of the driver circuit area 102 shown in FIG. 8 is completed. However, the driver circuit area is actually several millimeters wide and the entire scanning cannot be performed by one scan. Therefore, the above-described procedure is repeated while moving in the Y direction at a constant pitch (250 microns in this embodiment). Thus, it is possible to irradiate the laser beam 18 with high accuracy without being affected by the fluctuation of the stage speed at all. However, when scanning is repeated, there may be cases where annealing overlaps in the scanning direction or where laser irradiation is not performed.However, layout is performed so that transistors are not formed in the portion where the scanning parts are connected. It is desirable to design.
[0059]
Here, the behavior of the polycrystalline silicon thin film when irradiated with the laser beam 18 will be described. As described above, in the present embodiment, the substrate on which the polycrystalline silicon thin film annealed by the excimer laser is formed on the glass substrate 1 is used as an object to be annealed.
[0060]
The polycrystalline silicon thin film obtained by annealing with an excimer laser is an aggregate of fine crystal grains 120 and 121 having a crystal grain size of 1 micron or less (several 100 nm) as shown in FIG. When the area shown in the drawing is irradiated with laser light, the fine crystal grains 120 outside the laser irradiation area remain as they are, but the fine crystal grains (for example, the crystal grains 121) in the laser irradiation area are melted.
[0061]
Thereafter, the solidified and recrystallized rapidly by passing through the laser irradiation area. At this time, in the melted silicon, the crystal grains that follow the crystal orientation of the seed crystal grow in the scanning direction of the laser beam according to the temperature gradient, with the crystal grains remaining around the melted portion as the seed crystal. Further, since the growth rate of the crystal grains differs depending on the crystal orientation, only the crystal grains having the crystal orientation with the highest growth rate ultimately continue the crystal growth.
[0062]
That is, as shown in FIG. 11, a crystal grain 122 having a crystal orientation with a slow growth rate is suppressed by the growth of surrounding crystal grains 124 and 126 having a crystal orientation with a fast growth rate, and crystal growth stops. The crystal grains 123 and 124 having a crystal orientation with a medium growth rate continue to grow, but the growth of the crystal grains 125 and 126 having a higher growth rate is suppressed, and the growth is eventually stopped. Eventually, only the crystal grains 125, 126, and 127 having the crystal orientation with the highest growth rate continue to grow.
[0063]
These crystal grains 125, 126, and 127 which have continued to grow to the end are independent crystal grains in the strict sense, but have almost the same crystal orientation, and the melted and recrystallized portion is practically almost It can be regarded as a single crystal.
[0064]
By irradiating the polycrystalline silicon thin film with the laser light as described above, only the portion irradiated with the laser light is annealed in an island shape, and only crystal grains having a specific crystal orientation grow, and in a strict sense, This means that the regions 125 to 127 which are in a crystalline state and have properties almost similar to a single crystal are formed. In particular, in a direction that does not cross the crystal grain boundary, the crystal may be considered substantially a single crystal. At this time, the mobility of the silicon film is 400 cm. ² / Vs or more, typically 500 cm ² / Vs.
[0065]
By repeating this procedure while relatively scanning the glass substrate 1 and sequentially irradiating a laser beam to a portion that needs to be annealed, all the regions where the transistors of the driver circuit are formed are regions having properties almost similar to a single crystal. Can be converted to Further, in a region having a property close to that of a single crystal, as shown in FIG. 11, crystal grains are grown in a certain direction. By matching the growth directions of the grains, it is possible to prevent a current from flowing across the grain boundaries.
[0066]
Therefore, as shown in FIG. 12, the laser irradiation region 301 may be positioned so that portions composed only of crystal grains having a distant growth rate become active layers (active regions) 302 and 303 of the driving transistor. Good. After the impurity diffusion step and the photo-etching step, the portions other than the confined regions 302 and 303 are removed, and the gate electrode 305 via the gate insulating film as shown in FIG. The transistor is completed by forming the drain electrode 306.
[0067]
Here, the active region 303 has crystal grain boundaries 304 and 304 ′. However, since the current flows between the source electrode 306 and the drain electrode 307, the current does not cross the grain boundaries 304 and 304 ', and a mobility substantially equivalent to that of a single crystal can be obtained. .
[0068]
As described above, the portion that has been melted and recrystallized by the laser annealing according to the present invention has a mobility that is the same as that obtained by annealing using an excimer laser, by matching the direction of current flow with the direction not crossing the crystal grain boundaries. The improvement can be made twice or more as compared with the crystalline silicon thin film. This mobility is a value sufficient to form a driver circuit for driving liquid crystal at high speed.
[0069]
On the other hand, the switching transistor in the pixel portion is formed in a region of the polycrystalline silicon thin film 103 which has just been annealed by excimer laser. Since the polycrystalline film obtained by annealing with a Kisima laser has small crystal grains and random crystal directions, the mobility is smaller than the crystal grains obtained by laser annealing of the present invention, but the switching transistor in the pixel portion is used. Enough to use.
[0070]
In some cases, an amorphous silicon film can be sufficiently used as a switching transistor in a pixel portion. In this case, an amorphous silicon thin film is formed on the glass substrate 1, and the laser annealing method of the present invention may be performed on a portion where a drive circuit is to be formed without performing annealing using excimer laser.
[0071]
That is, first, the melted silicon is irradiated with the laser beam 18 and becomes a fine polycrystalline state in the process of solidifying, and the crystal grains formed at this time become seed crystals, and the polycrystal formed by the excimer laser irradiation. As in the case where the silicon film in the state is irradiated with the laser beam 18, crystals having various crystal orientations grow, but only the crystal grains in the direction of the highest growth rate continue to grow, and substantially, A polycrystalline silicon film that can be regarded as a single crystal can be formed.
[0072]
After the laser annealing for the drive circuit region 102 shown in FIG. 8 is completed, the drive circuit region 102 'is annealed. In this case, the substrate may be rotated by 90 degrees or the scanning direction may be deflected by 90 degrees. May be. In the latter case, it is necessary to rotate the beam shaper (the cylindrical lens 11 in FIG. 1) by 90 degrees and switch the width direction and the length direction of the rectangular slit.
[0073]
However, in the glass substrate 1 shown in FIG. 8, if transistors that require high-speed operation can be combined in one of the driving circuit regions 102 and 102 ′, for example, the driving circuit region 102, only the driving circuit region 102 It is only necessary to perform the laser annealing of the present invention.
[0074]
That is, the active layer (active region) of the transistor formed in the drive circuit region 102 is made of polycrystalline silicon including crystal grains having no crystal grain boundary in the direction in which current flows, and a high-speed transistor can be obtained. In order to form a transistor that does not require such a high speed operation in the drive circuit region 102 ', the active layer (active region) of the transistor is formed of a polycrystalline silicon film composed of fine crystal grains merely annealed by an excimer laser. Is done. In this case, there is no need to rotate the substrate or rotate the scanning direction and the direction of the linear beam, and the area to be annealed can be reduced, thereby greatly improving the throughput.
[0075]
Alternatively, if the drive circuit region 602 requiring high mobility can be grouped on one side outside the pixel region 601, the active layer (active region) of all the transistors for the drive circuit forms a crystal grain boundary in the direction of current flow. A transistor which is formed of polycrystalline silicon including crystal grains not provided and operates at high speed can be obtained. Further, it is not necessary to rotate the substrate or rotate the scanning direction and the direction of the linear beam, which is preferable from the viewpoint of improving the throughput. However, needless to say, a plurality of alignment marks are required.
[0076]
In the description of the present embodiment, in order to detect the position or the amount of movement of the stage, it has been described by counting signals from a linear scale (linear encoder) installed on the stage. However, the present invention is not limited to this. Instead, in order to detect the stage position, an output signal from a length measuring device using laser interference, a rotary encoder installed on a motor shaft for driving the stage, or the like can be used.
[0077]
The manufacturing process of the TFT substrate including the procedure described above can be summarized as follows. That is, as shown in FIG. 18, an insulating film is formed on a substrate, an a-Si (amorphous silicon) film is formed, excimer laser annealing is performed, and then the laser annealing of the present invention is applied to a transistor constituting a drive circuit. Is performed only on the active layer portion and its periphery.
[0078]
The laser annealing step of the present invention will be described in more detail. As shown in FIG. 19, a substrate that has been subjected to excimer laser annealing is mounted on the laser annealing apparatus of the present invention, and pre-alignment is performed on the end face or corner of the substrate, and An alignment mark is formed by the above method. After detecting the alignment mark and performing alignment (fine alignment), laser annealing is performed only on the active layer portion of the transistor constituting the drive circuit and its periphery in accordance with the design data.
[0079]
When the alignment mark is formed by other means by a photoresist process or the like at the time of mounting on the laser annealing apparatus, the steps of pre-alignment and alignment mark formation are unnecessary. After repeating the process until all the desired regions are annealed, the substrate is unloaded. Thereafter, based on the alignment marks 103, 103 'or the origin coordinates calculated from the alignment marks 103, 103', only the necessary portions of the polycrystalline silicon film are left in an island shape by a photoetching process.
[0080]
Thereafter, through a photoresist process, impurity diffusion and activation of a diffusion region are performed through formation of a gate insulating film and formation of a gate electrode. Thereafter, through a photoresist process such as formation of an interlayer insulating film, formation of a source / drain electrode, formation of a protective film (passivation film), a drive circuit and a pixel portion 101 are formed, and a TFT substrate is completed.
[0081]
Note that the alignment marks 103 and 103 'are used for alignment in at least one photoresist step after performing the laser annealing of the present invention. Thereafter, an alignment mark newly formed in the above-described photoresist process may be used. The transistor illustrated in FIG. 13 is merely an example, and the transistor is not limited to this example. Although various structures are possible for the transistor, it is apparent that transistors having various structures can be formed without departing from the gist of the present invention.
[0082]
On the other hand, the switching transistor in the pixel portion is formed in the region of the polycrystalline silicon thin film 103 which has just been annealed by the excimer laser. That is, on the basis of the alignment mark or the origin coordinates calculated from the alignment mark, the gate insulating film formation, gate electrode formation, impurity diffusion, activation of the diffusion region, source / drain electrode formation, and the formation of a barrier film are performed. The TFT substrate is completed through a photo resist process.
[0083]
After that, an alignment film is formed on the completed TFT substrate, a rubbing process is performed, and a liquid crystal material is sealed by overlaying a power filter, and an LCD (panel) process is assembled together with a backlight, etc. A liquid crystal display device having a driver circuit formed on a glass substrate (a so-called system-on-panel) is completed.
[0084]
As an example of a product on which a liquid crystal display device manufactured by applying the laser annealing of the present invention is mounted, a display portion of a liquid crystal television 401 as shown in FIG. 14A, a mobile phone as shown in FIG. In addition to the display unit 402, the display unit of the notebook computer 403 as shown in FIG. 14C, the display unit of various instruments stored in the dashboard of the car, the display unit of the portable game machine, and the like. .
[0085]
Next, another embodiment of the present invention will be described with reference to FIG. FIG. 15 shows a beam shaping optical system 11 having a different structure from that shown in FIG. 6, for obtaining a linear beam. The beam shaping optical system 11 is formed by a prism 71, a cylindrical lens 72, a half-wave plate 74, and plane mirrors 75 and 76. It is configured. The incident linearly polarized laser light 18 passes through the prism 71, is divided into two parts by the vertex of the prism 71, and is deflected in a direction overlapping with each other. The two split beams 73 and 73 'are separated once after overlapping, reflected by the plane mirrors 75 and 76, and overlap again.
[0086]
At a position where the split beams are completely separated, only one beam (73 in FIG. 15) passes through the half-wave plate 74. The half-wave plate is adjusted so that the polarization direction of the transmitted beam is rotated exactly 90 degrees. Another half-wave plate (not shown) is installed in front of the beam shaping optical system 11, and the polarization direction of the laser beam 18 incident on the beam shaping optical system 11 is rotated, so that the half wave shown in FIG. The wavelength plate 74 can be adjusted so that the polarization direction is rotated by 90 degrees.
[0087]
The apex angle of the prism 71 is designed so that the two split beams 73 and 73 ′ are reflected by the plane mirrors 75 and 76 and then completely overlap on the electric rectangular opening slit surface 35. The cylindrical lens 72 has a focal length that converges on the surface of the electric rectangular aperture slit 12 only in the direction orthogonal to the direction in which the laser beams 73 and 73 ′ transmitted through the prism 71 are deflected, that is, in the width direction. Is selected.
[0088]
As shown in FIG. 7A, a laser beam having a Gaussian distribution originally passes through a prism, is divided into two parts, overlaps once, is separated, reflected by plane mirrors 75 and 76, and one is reflected by the other. 7A. The polarization gradually overlaps while maintaining the relationship that the polarization direction is orthogonal to the one, and completely overlaps with the electric rectangular opening slit surface 35 as shown in FIG. 7B. Here, the beam diameter is 1 / e of the energy density at the center of the beam. ² It stipulates that
[0089]
In this embodiment, the half-wave plate 74 is inserted after the incident laser beam 18 is divided into two by the prism 71 and completely separated from each other. However, as in the first embodiment, the half-wave plate 74 can be placed in front of the prism. good. At this time, it is necessary to adjust the end of the half-wave plate so as to coincide with the vertex of the prism.
[0090]
As a result, since the polarization directions of the divided beams are orthogonal to each other, they do not interfere with each other even when they are overlapped, and a linear beam having a substantially uniform energy distribution is formed as shown in FIG. 7C. You. The energy distribution in the direction (width direction) orthogonal to the distribution shown in FIG. 7 is substantially Gaussian as a result of being collected by the cylindrical lens.
[0091]
That is, a linear beam having a size equal to １ ／ of the beam diameter incident on the beam shaping optical system 11 in the longitudinal direction and a size condensed by the cylindrical lens 33 in the width direction can be obtained. At this time, the energy density at the center is approximately 121% of the energy density at the center when condensed only by the cylindrical lens, and the energy density at the periphery is 114%, which is a substantially uniform distribution.
[0092]
The laser beam 18 condensed linearly by the beam shaping optical system 11 is cut off an unnecessary portion of the laser beam by the electric rectangular aperture slit 12 as necessary, and is shaped into a desired rectangular shape. The image is reduced and projected on the substrate 1. Assuming that the magnification of the objective lens 13 is M, the size of the image of the electric rectangular aperture slit 12 or the size of the laser beam 18 passing through the surface of the electric rectangular slit 12 is projected as the reciprocal of the magnification, that is, 1 / M. When a linear beam of 5 mm in the longitudinal direction and 100 μm in the width direction is generated by the beam shaping optical system 11, a 20 × objective lens is used to make the surface of the glass substrate 1 250 μm in the longitudinal direction and 5 μm in the width direction. A linear beam will be obtained.
[0093]
The procedure of annealing with this linear beam, the behavior of the irradiated portion, and the like are as described above, and a polycrystalline silicon film having characteristics sufficient for forming a drive circuit is obtained in the portion irradiated with the laser. At this time, the mobility of the silicon thin film is 400 cm. ² / Vs or more, typically 500 cm ² / Vs.
Next, another embodiment will be described with reference to FIG. FIG. 16 shows a beam shaping optical system 11 having a configuration different from those shown in FIGS. 6 and 15, and includes an optical element called a Powell lens 78 and a cylindrical lens 79. Powell lens 78 is described in U.S. Pat. No. 4,836,299 as "Linear Deriving Lens".
[0094]
The Powell lens 78 broadens the beam one-dimensionally, and converts the distribution of the incident laser beam 18 in FIG. 16A so that the central portion is coarse and the peripheral portion is dense, thereby forming a Gaussian distribution. When a laser beam enters, it is converted into a substantially uniform distribution. On the other hand, FIG. 16B shows a side view of FIG. 16A, and the laser beam 18 passes through the Paulel lens 78 as parallel light and is collected by the cylindrical lens 79.
[0095]
For a laser beam 18 having a Gaussian distribution and a beam diameter of 2 mm and a divergence angle of 0.4 mrad, a Powell lens 78 that spreads to 5 mm at a projection distance of 500 mm is used. In accordance with the curvature, the beam diameter is widened while changing the distribution so that the central part is coarse, that is, the energy density is reduced, and the peripheral part is dense, that is, the energy density is increased. By arranging it so as to coincide with the surface 35, a beam in the longitudinal direction of 5 mm is obtained. As a result, the energy density decreases at the center of the Gaussian distribution and increases at the periphery, so that the diffusion direction (that is, the longitudinal direction of the linear beam) shown in FIG. A uniform energy distribution results.
[0096]
On the other hand, by arranging a cylindrical lens having a focal length of 500 mm in a direction orthogonal to the diffusion direction, light can be condensed to a width of about 200 microns. The laser beam 18 condensed linearly by the beam shaping optical system 11 is cut off an unnecessary portion of the laser beam by the electric rectangular aperture slit 12 as necessary, and is shaped into a desired rectangular shape (linear shape). The image is reduced and projected on the glass substrate 1 by the lens 13. Assuming that the magnification of the objective lens 13 is M, the image of the electric rectangular opening slit 12 or the size of the laser beam 18 passing through the electric rectangular slit surface 35 is projected with the reciprocal of the magnification, that is, 1 / M.
[0097]
Here, by using a 20 × objective lens, a linear beam of 250 μm in the longitudinal direction and 10 μm in the width direction can be obtained on the surface of the glass substrate 1. Annealing is performed by scanning the linear beam on the substrate 1. The annealing procedure and the behavior of the irradiated portion are as described above.
[0098]
In FIG. 16, the Powell lens 78 and the cylindrical lens 79 are separately arranged. However, as shown in FIG. 20, exactly the same effects can be obtained by using the optical element 80 formed integrally. Further, although the Paulel lens 78 has several shapes, it basically has the same function and can be used similarly.
[0099]
【The invention's effect】
As described above, according to the laser annealing apparatus and the laser annealing method of the present invention, it is possible to obtain a linear beam having a uniform energy distribution with an optical system having a simple structure. Crystal grains such as a silicon thin film can be grown in a desired direction to form a polycrystalline silicon thin film having crystal grains of a size.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a schematic configuration of a laser annealing apparatus according to one embodiment of the present invention.
FIG. 2 is a perspective view of an EO modulator used in one embodiment of the present invention.
FIG. 3 is a perspective view of an EO modulator used in one embodiment of the present invention.
FIG. 4 is a graph showing a relationship between an applied voltage and transmittance in an EO modulator.
FIG. 5 is a graph showing a relationship between a laser input, an applied voltage, and a laser output in the EO modulator.
FIG. 6 is a plan view and a side view showing a configuration of a beam shaping optical system according to an embodiment of the present invention.
FIG. 7 is an explanatory diagram of a beam shape formed by a beam forming optical system according to one embodiment of the present invention.
FIG. 8 is a perspective view illustrating a laser irradiation area when performing laser annealing according to the present invention.
FIG. 9 is a time chart showing a stage movement and laser irradiation timing according to another embodiment of the present invention.
FIG. 10 is a plan view showing a crystal state before performing an annealing method in one embodiment of the present invention.
FIG. 11 is a plan view showing a crystal state after performing an annealing method in one embodiment of the present invention.
FIG. 12 is a plan view of a substrate showing a positional relationship between a region where a laser annealing method according to the present invention is performed and a drive circuit active region.
FIG. 13 is a plan view of a substrate showing a configuration of a drive circuit transistor formed by performing a laser annealing method according to the present invention.
FIGS. 14A to 14C are perspective views showing examples of products to which a liquid crystal display device including a TFT substrate to which laser annealing according to the present invention is applied is applied.
FIG. 15 is a plan view and a side view showing a configuration of a beam shaping optical system according to another embodiment of the present invention.
FIG. 16 is a plan view and a side view showing a configuration of a beam shaping optical system according to another embodiment of the present invention.
FIG. 17 is a perspective view illustrating a laser irradiation region when performing laser annealing according to the present invention.
FIG. 18 is a flowchart showing a liquid crystal display device manufacturing process to which the laser annealing method of the present invention is applied.
FIG. 19 is a flowchart showing a laser annealing step of the present invention.
FIG. 20 is a plan view and a side view of an optical element applicable as a beam shaping optical system of the laser annealing apparatus of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... Stage, 3/4 ... Linear scale, 6 ... Laser oscillator, 7 ... Shutter, 8 ... Beam expander, 9 ... Continuous transmittance filter, 10 ... EO modulator, 12 ... Electric rectangular slit, DESCRIPTION OF SYMBOLS 13 ... Objective lens, 21 ... EO modulator power supply, 22 ... Control device, 31 ... 1/2 wavelength plate, 32, 71 ... Prism, 33, 72, 79 ... Cylindrical lens, 61 ... Pockels cell, 62 ... Polarization beam splitter 78, Powell lens, 101, pixel area, 102, drive circuit area, 103, alignment mark, 104-110, annealed area, 125, 126, 127, crystal grains grown by laser annealing, 304, crystal grain boundary, 305 ... gate electrode, 306 ... source electrode, 307 ... drain electrode, 401 ... liquid crystal television, 40 2: Mobile phone, 403: Notebook PC

Claims (7)

Stage means capable of mounting and moving a substrate, position detecting means for detecting the position of the stage, laser light source means for generating continuous wave laser light having a circular and Gaussian distribution in spatial distribution, and the laser A modulating means for turning on / off (passing / non-passing) the continuous wave laser light generated from the light source means, and the continuous wave laser light passing through the modulating means is uniform in the longitudinal direction and Gaussian in the width direction. Forming optical means for forming a linear or band-shaped laser beam having a distribution, irradiation optical means for irradiating the linear or band-shaped laser beam onto the substrate, and control means for controlling the stage means and the modulation means When the position detected by the position detecting means coincides with a preset position, the control means sets the modulating means in the laser beam passing state, whereby the scanning is performed. Laser annealing apparatus, which comprises irradiating a continuous wave laser beam in an arbitrary area while continuously moving the over-di unit. 2. The laser annealing apparatus according to claim 1, wherein the shaping optical unit is composed of a prism, a half-wave plate, and a cylindrical lens, and divides the continuous wave laser beam by the prism and deflects the split beam. Laser annealing, wherein one of the beams split into two by the half-wave plate is superposed by rotating one of the polarization directions by 90 degrees, and condensed by a cylindrical lens in a direction orthogonal to the direction of deflection. apparatus. 2. A laser annealing apparatus according to claim 1, wherein said shaping optical means is composed of a Powell lens and a cylindrical lens. A laser annealing apparatus. 4. The laser annealing apparatus according to claim 3, wherein the shaping optical means is constituted by an optical element in which a Powell lens and a cylindrical lens are integrated into one body, and the Powell lens portion spreads the distribution uniformly in one direction. A laser annealing apparatus wherein light is condensed by a cylindrical lens portion in a direction perpendicular to the laser beam. 5. A laser annealing apparatus according to claim 1, wherein said laser light source means is an oscillator for generating a second harmonic of a laser diode pumped continuous wave YVO4 laser. An insulating substrate having an amorphous silicon film or a polycrystalline silicon film formed on one main surface is placed on a stage, and laser light is applied to an arbitrary region of the amorphous silicon film or the polycrystalline silicon film on the insulating substrate. A laser annealing method, wherein the laser light has a uniform distribution in one direction, and is a continuous wave light formed into a linear or band shape having a Gaussian distribution in a direction orthogonal to the one direction. A laser annealing method comprising irradiating the continuous oscillation laser light only to a region to be irradiated with the laser light while the insulating substrate is continuously moved. A TFT substrate, wherein the mobility of the active region of the thin film transistor constituting the driving circuit is 400 cm ² / Vs or more, and the mobility of the active region of the pixel portion thin film transistor is 200 cm ² / Vs or less.

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