JP2002158185A - Method and apparatus for laser annealing, and method and apparatus for manufacturing thin film transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for leaser annealing which allows the radiation of excimer laser beam at a constant and desired fluence from start to end and which can uniform the grain diameters of polysilicon. SOLUTION: A pulsatory excimer laser beam B is oscillated toward amorphous silicon 7 on a glass substrate 5. The rise and fall of the excimer laser beam B is not necessarily sharp. An optical path along which the excimer laser beam B irradiates the amorphous silicon 7 is cut off between the pulses of the excimer laser beam B. By this method, the excimer laser beam B can irradiate the amorphous silicon 7 at a constant and desired fluence from start to end, and the grain diameters of polysilicon formed by the laser annealing can be uniformed. Furthermore, the uniform performance of a thin film transistor can be achieved by irradiation with the excimer laser beam on the amorphous silicon 7 in the manufacture of the thin film transistor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for irradiating an amorphous silicon semiconductor on a light-transmitting substrate with a laser beam.
The present invention relates to a laser annealing method for converting an amorphous silicon semiconductor into a polycrystalline silicon semiconductor, a device therefor, a method for manufacturing a thin film transistor, and a device therefor.

[0002]

2. Description of the Related Art At present, an insulated gate thin film transistor (TF) formed of amorphous silicon (a-Si) which is an amorphous silicon semiconductor.
T) as a pixel switch (Liquid C
rystal Display (LCD) is used.

In order to realize a high-definition, high-speed, high-performance liquid crystal display, an electric field mobility (μF
E) Amorphous silicon thin film transistors as low as 1 cm ² / Vs or less have insufficient performance. On the contrary,
In a polycrystalline silicon semiconductor prepared by a laser annealing method in which amorphous silicon is irradiated with an excimer laser beam, the electric field mobility in an experimental stage is 100 cm ² / Vs to 20 cm.
A material of about 0 cm ² / Vs can be obtained. For this reason, it is expected that the liquid crystal display has higher functions such as higher definition, higher speed, and integrated formation of a driving circuit.

Further, the excimer laser method is a method in which amorphous silicon on a glass substrate is irradiated with an excimer laser to form polysilicon. Specifically, the beam size on the surface of the amorphous silicon is, for example, 250 mm in length and 0.4 mm in width, and this pulse beam is oscillated at 300 Hz to gradually move the region irradiated with each pulse. Then, the amorphous silicon on the glass substrate is changed to polysilicon.

A factor that determines the electric field mobility of a polysilicon thin film transistor is the grain size of the polysilicon. This largely depends on the energy density of a laser beam to be irradiated, which is called fluence. That is, as the fluence increases, the grain size of polysilicon increases, but the electric field mobility is 100 cm ² /
To obtain high-performance polysilicon of Vs or higher, F1
It is necessary to have a higher fluence than a certain fluence.

However, when the fluence is increased more than F1, the grain size of the polysilicon further increases, but becomes a fine crystal grain at a certain fluence value, ie, F2. Desirable thin film transistor characteristics cannot be obtained with simple polysilicon.

Further, the grain size of polysilicon can be determined by etching the polysilicon with an etchant and observing the grain size with a scanning electron microscope (FE-SEM). Using this method, the fluence of the laser beam is selected in a region where the grain size of polysilicon is relatively large, that is, between F1 and F2. With this selection, a polysilicon thin film transistor having a desired electric field mobility can be obtained even if the oscillation intensity of the laser beam changes to some extent.

[0008]

However, in the above-described laser annealing apparatus, a low-speed shutter is used for emitting a laser beam. For this reason, in the transition period of passage and shielding of the laser beam by the shutter, the laser beam does not change sharply, and the intensity of the laser beam on the glass substrate changes.

That is, as shown in FIG. 4, it takes, for example, 1 to 2 seconds to pass and block the laser beam by the shutter. During this time, the laser beam is partially blocked by the shutter. Therefore, there is a problem that a laser beam having a lower intensity than the intensity during the irradiation is irradiated onto the glass substrate at the start and end of the irradiation of the laser beam. Therefore, at the start and end of laser beam irradiation, it is not possible to obtain polysilicon having a desired particle size.

[0010] Therefore, it is necessary to start and end the irradiation of the laser beam in a portion where there is no pixel transistor or transistor for a driving circuit, which is a constraint in manufacturing a liquid crystal display. For example, when the laser beam irradiation is stopped near the center of the glass substrate due to a trouble of the laser beam, the laser beam irradiation cannot be restarted accurately from the stopped position, and this glass substrate has to be discarded.

When the laser beam irradiation pitch is made fine in order to increase the particle size in a part of the glass substrate, the laser beam irradiation is temporarily stopped, and the moving speed of the stage on which the glass substrate is placed is reduced. It is necessary to restart the irradiation at a desired position after the change, but also in this case, there arises a problem that the particle size of the first and last regions of the laser beam irradiation changes, and such a process cannot be realized.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and a laser annealing method capable of irradiating a laser beam with a constant desired energy density from the beginning to the end and maintaining a constant grain size of a polycrystalline silicon semiconductor. , A device thereof, a method of manufacturing a thin film transistor, and a device thereof.

[0013]

According to the present invention, a pulsed laser beam is applied to the amorphous silicon semiconductor on a light transmitting substrate having a thin film of an amorphous silicon semiconductor deposited on one principal surface. This is a laser annealing method for converting the amorphous silicon semiconductor into a polycrystalline silicon semiconductor, wherein an optical path of the amorphous silicon semiconductor irradiated with the laser beam is interrupted between laser beam pulses.

In this configuration, a pulsed laser beam is oscillated toward the amorphous silicon semiconductor deposited on one main surface of the translucent substrate. At this time, since the rise and fall of the laser beam are not necessarily steep, the optical path for irradiating the amorphous silicon semiconductor on the light-transmitting substrate with the laser beam is intercepted between the laser beam pulses, so that the light is transmitted. Irradiation of the laser beam onto the amorphous silicon semiconductor on the conductive substrate has a constant desired energy density from the beginning to the end, so that the grain size of the polycrystalline silicon is constant.

Further, when the amorphous silicon semiconductor during the production of the thin film transistor is irradiated, the performance of the thin film transistor becomes constant.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a laser annealing apparatus according to an embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 3, the laser annealing apparatus shown in FIGS. 1 to 3 is formed of polysilicon 2 which is a polycrystalline silicon semiconductor on an array substrate 1, and is a polycrystalline silicon active matrix type liquid crystal display.
(Insulated gate type thin film transistor (ThinFil) used as a pixel switch of (Liquid Crystal Display: LCD)
m Transistor (TFT) is a manufacturing apparatus for manufacturing TFT3.

Further, the laser annealing apparatus uses an amorphous silicon (a-) amorphous silicon semiconductor deposited on an undercoat layer 6 formed on one main surface of a glass substrate 5 which is a light-transmitting substrate. An excimer laser beam B which is a pulsed laser beam using xenon chloride (XeCl) or the like is irradiated toward the thin film of Si) 7,
The amorphous silicon 7 on the glass substrate 5 is laser-annealed, and the amorphous silicon 7 is
To

Here, the size of the glass substrate 5 is 400 m.
mx 500 mm. In addition, the undercoat layer 6
It is formed by a plasma CVD method using SiN _x and SiO _x . Further, the amorphous silicon 7 is also formed by the plasma CVD method.

Further, this laser annealing apparatus has the structure shown in FIG.
As shown in FIG. 1, a laser oscillator 11 which is a laser oscillation means for oscillating an excimer laser beam B is provided. The laser oscillator 11 passes through a first module 21 and a second module 31 of an optical system to form a pulsed excimer laser toward the amorphous silicon 7 on the glass substrate 5 placed on the stage 53 in the annealing chamber 51. Beam B
Is output and irradiated. Here, this laser oscillator 11
At the start and end of excimer laser beam B oscillation,
An excimer laser beam B having an intensity lower than the intensity during oscillation is oscillated.

Further, the laser oscillator 11 has a laser body 12, and a detector 13 as an oscillation source of the excimer laser beam B is mounted in the laser body 12. This detector 13 has a photodiode (P
hoto diode). The laser beam oscillated by the detector 13 is
The optical path is totally reflected, for example, in a 90 ° direction by a total reflection mirror 14 arranged in front of the optical path 13. This total reflection mirror 14 is provided in the laser main body 12.

A laser tube 15 as a laser oscillation tube is provided in front of the optical path of the laser beam whose optical path is refracted by the total reflection mirror 14. The laser tube 15 is provided in the laser main body 12, and turns the laser beam oscillated from the detector 13 into an excimer laser beam B. In addition, this laser tube
A laser oscillator is provided for each of the 15 optical paths ahead and behind.
Resonator mirrors 16a and 16b for resonating the excimer laser beam B oscillating from 11 are provided. Then, the laser main body 12 located in front of the optical path of the resonator mirror 16b through which the excimer laser beam B passing through the laser tube 15 passes.
On one side surface, a protect window 17 for extracting the excimer laser beam B passing through the resonator mirror 16b to the outside of the laser main body 12 is attached. An anti-reflection coat is applied to one main surface of the protect window 17 on the side of the resonator mirror 16b.

Further, the other main surface of the protection window 17 is provided with a first module 21 for drawing in the excimer laser beam B oscillated from the laser oscillator 11 and controlling the transmittance of the excimer laser beam B. . In the first module 21, an optical path of the excimer laser beam B, for example, 90 mm ahead of the optical path of the excimer laser beam B passing through the protection window 17.
A first mirror 22 that totally reflects light in degrees is provided. The first mirror 22 is provided in the first module 21.

A variable attenuator 23 is mounted in front of the optical path of the excimer laser beam B reflected by the first mirror 21. The variable attenuator 23 is provided in the first module 21 and adjusts the transmittance of the excimer laser beam B. The variable attenuator 23 includes an attenuator 24 capable of changing the transmittance of the excimer laser beam B in a range of 0% to 90%, and a compensating plate for correcting an optical path of the excimer laser beam B passing through the attenuator 24. And a compensator 25. The excimer laser beam B incident on the variable attenuator 23 is
After the transmittance is changed by the attenuator 24, the transmittance of the changed excimer laser beam B is corrected by the compensator 25 to the light path before the light enters the attenuator 24. Further, the attenuator 24 and the compensator 25 are formed of quartz or the like, and can be rotated in conjunction with each other in directions facing each other.

A telescope 26 is provided in front of the optical path of the excimer laser beam B passing through the variable attenuator 23. This telescope 26
It is provided in the first module 21 and includes a plurality of lenses, for example, two lenses, and adjusts the size of the excimer laser beam B incident on the LAH 32, that is, the beam size. Further, a second mirror 27 is disposed in front of the optical path of the excimer laser beam B that has passed through the telescope 26 to reflect the optical path of the excimer laser beam B at, for example, 90 °. This second mirror 27 is
, And totally reflects the incident excimer laser beam B.

Further, a second module 31 adjacent to the first module 21 is mounted in front of the optical path of the excimer laser beam B totally reflected by the second mirror 27. The excimer laser beam B reflected by the second mirror 27 is the excimer laser beam B
Into a long axis homogenizer that adjusts the long axis of the laser, that is, LAH32. This LAH 32 is disposed in the second module 21 and has an excimer laser beam B
A first LH and a second LH (not shown) for zooming the long axis of the lens, and a condenser lens (not shown) for correcting the waveform of the excimer laser beam B whose long axis has been zoomed by the first LH and the second LH. have.

A short axis homogenizer for adjusting the short axis of the excimer laser beam B, that is, the SAH 36, is provided in front of the optical path of the excimer laser beam B whose long axis has been adjusted by the LAH 32. This S
The AH 36 is provided in the second module 31 and includes a first SH and a second SH (not shown) for zooming the short axis of the excimer laser beam B, and the first SH and the second SH. And a condenser lens (not shown) for correcting the waveform of the excimer laser beam B whose short axis has been zoomed.

Further, a short-axis slit is provided in front of the optical path of the excimer laser beam B whose short axis has been adjusted by the SAH36.
Forty are arranged. The short axis slit 40 is provided in the second module 31.

A shutter 41 is provided in front of the optical path of the excimer laser beam B passing through the short-axis slit 40 so as to block the excimer laser beam B for 100 nsec or more and 1 msec or less. This shutter 41
Is located in the second module 31 and is located at or near the narrowest place where the short axis of the excimer laser beam B is focused by the LAH 32. As a result, the shutter 41 is connected to the amorphous silicon 7 on the glass substrate 5 placed on the stage 53 and the laser oscillator.
11 on the optical path of the excimer laser beam B.

Further, this shutter 41 is a laser oscillator
A trigger signal of the excimer laser beam B oscillated from 11 is received, and based on the trigger signal, a pulse motor (not shown) is used to pass or cut off the excimer laser beam B between pulses of the excimer laser beam B. That is, it turns. Also, this shutter 41
The excimer laser beam B is passed or cut off when it reaches a position where laser annealing of the amorphous silicon 7 on the glass substrate 5 placed on the stage 53 is started. Further, in the shutter 41, the stage 53 on which the glass substrate 5 is placed is accelerated before the designated coordinates for irradiating the excimer laser beam B, and moves to a uniform speed, and the stage 53 reaches the designated coordinates. This shutter at the time
The trigger to open and close 41 works.

As shown in FIG. 2, the shutter 41 has a disk portion 42 which is a disk-shaped disk for blocking the excimer laser beam B. The disk portion 42 has at least one, for example, four slits 43 formed by cutting out along the radial direction. Each of these slits
The reference numerals 43 are formed at positions equidistant from one another along the circumferential direction, and have the same shape. Each of the slits 43 has an area of one slit 43 and a disc portion.
The ratio of the area to the area 42 is almost equal to the ratio between the oscillation time of the pulse of the excimer laser beam B and the non-oscillation time.

Further, each slit 43 is substantially fan-shaped, with both sides extending near the center of the disk portion 42, and
Is formed so that the ratio of the arc length of the outer circumference to the arc length of the disk portion 42 is substantially equal to the ratio of the oscillation time of the pulse of the excimer laser beam B to the non-oscillation time. Each slit 43 is formed such that the ratio between the angle between both sides and the angle between the slits 43 is substantially equal to the ratio between the oscillation time of the pulse of the excimer laser beam B and the non-oscillation time.

When the disk part 42 is rotated and the slit 43 of the disk part 42 is rotated to a predetermined position, the excimer laser beam B passing through the short-axis slit 40 is rotated by the slit 42. It is attached to the pedestal 44 so as to be rotatable around the central axis so as to pass through 43.

A field lens 45 for adjusting the short axis of the excimer laser beam B and the steepness in the time waveform of the excimer laser beam B is disposed in front of the optical path of the excimer laser beam B passing through the shutter 41. Has been established. The field lens 45 is provided in the second module 31. Further, a third mirror 46 for reflecting the optical path of the excimer laser beam B at, for example, 90 ° is disposed in front of the optical path of the excimer laser beam B passing through the field lens 45.
The third mirror 46 is disposed in the second module 31, and totally reflects the incident excimer laser beam B. Further, a projection lens 47 called a so-called 5X lens is provided in front of the optical path of the excimer laser beam B passing through the third mirror 46. The projection lens 47 is provided in the second module 31.

An annealing chamber 51 is provided in front of the optical path of the excimer laser beam passing through the projection lens 47 as atmosphere control means for internally laser-annealing the amorphous silicon 7 on the glass substrate 5. An annealing window 52 for irradiating an excimer laser beam B from the outside to the inside is provided on one side surface of the annealing chamber 51. The annealer window 52 is provided at a position where the excimer laser beam B passing through the projection lens 47 is incident.

In the annealing chamber 51, a glass substrate 5 is provided on the upper surface, and a stage 53 for scanning, ie, moving, the glass substrate 5 in the plane direction is attached. This stage 53 is mounted on the glass substrate 5
Can be scanned in respective directions that intersect at right angles to each other, that is, the horizontal direction.

Here, the atmosphere on the glass substrate 5 placed on the stage 53 is adjusted by an inert gas such as nitrogen gas by the annealing chamber 51. further,
The stage 53 is formed such that the entire surface of the thin film of the amorphous silicon 7 on the glass substrate 5 placed on the stage 53, that is, the entire region is irradiated with the excimer laser beam B passing through the anneal window 52. The stage 53 moves at a constant speed from a position where laser annealing of the amorphous silicon 7 on the glass substrate 5 placed on the stage 53 is started.

Next, the configuration of a liquid crystal display manufactured by the above laser annealing apparatus will be described.

First, the liquid crystal display includes an array substrate 1, and the array substrate 1 includes a glass substrate 5 formed of glass. The glass substrate 5 has a substantially transparent insulating property having a light transmitting property. On one main surface of the glass substrate 5, an insulating undercoat layer 6 for preventing diffusion of impurities from the glass substrate 5 is formed.

Then, on the undercoat layer 6,
An island-shaped polysilicon 2 is formed. The polysilicon 2 is irradiated with an excimer laser beam B toward the amorphous silicon 7 deposited on the glass substrate 5,
The amorphous silicon 7 is formed by laser annealing. The film thickness of the amorphous silicon 7 before the formation of the polysilicon 2 is about 50 nm by the spectral ellipsometry.

On the undercoat layer 6 including the polysilicon 2, a gate insulating film 63 is formed of a silicon oxide film having an insulating property.

Then, on the gate insulating film 63, a molybdenum-tungsten alloy (MoW) or the like is formed.
A gate electrode 64 and an auxiliary capacitance line 65 are formed. The storage capacitor line 65 forms a storage capacitor 66 having a MOS structure using the polysilicon 2. Then, the thin film transistor 3 is formed by the polysilicon 2, the gate insulating film 63, and the gate electrode 64. Here, the thin film transistor 3 is formed by a photolithography technique.

On both sides of the polysilicon 2, a source region 67 and a drain region 68 are formed. Further, the polysilicon 2 located below the gate electrode 64 becomes the channel region 69.

On the gate insulating film 63, the gate electrode 64 and the auxiliary capacitance line 65, an interlayer insulating film 71 made of a silicon oxide film or the like is formed. The first contact holes 72a and 72b penetrating the interlayer insulating film 71 and the gate insulating film 63 and communicating with the source region 67 and the drain region 68 are formed in the interlayer insulating film 71 and the gate insulating film 63.
Is open.

Further, a source electrode 73 and a drain electrode 74 formed as a second wiring layer are formed on the interlayer insulating film 71.
And a signal line (not shown) for supplying an image signal. The source electrode 73, the drain electrode 74, and the signal line are formed of a low-resistance metal such as aluminum (Al). The source electrode 73 is conductively connected to the source region 67 via the first contact hole 72a. Similarly, the drain electrode 74 is conductively connected to the drain region 68 via the first contact hole 72b.

Then, a protective film 75 is formed on the interlayer insulating film 71, the source electrode 73 and the drain electrode 74. On this protective film 75, color filters 76 of three colors of each color, for example, red, blue and green are formed. The protective film 75 and the color filter 76 are provided with a second contact hole 77 which is in contact with the drain electrode 74.

Further, on the color filters 76, pixel electrodes 78, which are transparent conductor layers, are arranged in a matrix. The pixel electrode 78 is conductively connected to the source electrode 73 via the second contact hole 77.

The opposing substrate 55 faces the pixel electrode 78.
The counter electrode 56 is formed on one main surface of the counter substrate 55 facing the pixel electrode 78.

Further, a liquid crystal 79 is provided between the pixel electrode 78 of the array substrate 1 and the counter electrode 56 of the counter substrate 55.

Next, a method of manufacturing a liquid crystal display manufactured by the laser annealing apparatus will be described.

First, an undercoat layer 6 is formed on one main surface of the glass substrate 5 by forming a silicon oxide film or the like by a plasma CVD method or the like.

Next, on this undercoat layer 6, 5
Plasma CV of amorphous silicon 7 with a thickness of 0 nm
The film is formed by the method D or the like.

Then, the amorphous silicon 7 is heat-treated at 500 ° C. for 10 minutes in a nitrogen atmosphere to reduce the hydrogen concentration in the amorphous silicon 7.

Thereafter, the glass substrate 5 on which the undercoat layer 6 and the amorphous silicon 7 are formed is placed on a stage.
The stage 53 is scanned on the glass substrate 5
While moving the laser, an excimer laser beam B is oscillated from the laser oscillator 11, and the excimer laser beam B is irradiated toward the amorphous silicon 7 on the glass substrate 5, and the amorphous silicon 7 is laser-annealed. The silicon 7 is turned into a desired polysilicon 2 having a crystal grain size of, for example, about 0.3 μm.

At this time, a 300 Hz
The wavelength of the excimer laser beam B oscillated at 308 n
m, and the irradiation size of the excimer laser beam B is a linear beam of 250 mm × 0.4 mm. Also,
The fluence of the excimer laser beam B on the glass substrate 5 is set to 350 mJ / cm ^2, and the overlap of the excimer laser beam B is set to 95%. Further, the stage 53 on which the glass substrate 5 is set is 6 m
Move at m / s.

Here, based on the trigger signal of the pulse of the excimer laser beam B, the oscillation timing of the excimer laser beam B is fed back to the shutter 41 to synchronize the excimer laser beam B with a region other than the rising and falling regions. To rotate the shutter 41. As a result, while the fluence of the excimer laser beam B passing through the shutter 41 is kept constant, the amorphous silicon 7 on the glass substrate 5 is laser-annealed.

Further, a gate insulating film 63 is formed on the glass substrate 5 containing the polysilicon 2 by a plasma CVD method or the like.

Next, on the gate insulating film 63,
The first wiring layer is formed by a sputtering method, and the first wiring layer is etched to form the gate electrode 64 and the auxiliary capacitance line 65.

Thereafter, a source region 67 and a drain region 68 are formed on both sides of the polysilicon 2. The source region 67 and the drain region 68 are formed on both sides of the polysilicon 2 by ion doping with an impurity such as boron (B) or phosphorus (P) using a resist at the time of etching the gate electrode 64 as a mask. It is formed by doping.

At this time, the undoped polysilicon 2 located below the gate electrode 64 becomes the channel region.
It becomes 69.

Next, an interlayer insulating film 71 made of SiO ₂ is formed on the gate insulating film 63, the gate electrode 64, and the auxiliary capacitance line 65, and a low-resistance metal containing Al as a main component is formed on the interlayer insulating film 71. Is formed by a sputtering method or the like to form a source electrode 73, a drain electrode 74, and a signal line.

Then, a protective film 75 is formed on the interlayer insulating film 71, the source electrode 73, and the drain electrode 74.
A color filter 76 is formed thereon.

Further, an ITO (Ind
After a transparent conductor layer such as ium tin oxide is formed, the pixel electrode 78 is formed by etching.

Thereafter, the opposing substrate 55 and the array substrate 1 are disposed so as to oppose each other. An opposing electrode 56 is formed on one main surface of the opposing substrate 55 facing the array substrate 1.

The counter substrate 55 and the array substrate 1
The liquid crystal 79 is injected between them.

As described above, according to the above-described embodiment, the excimer laser beam B oscillated from the laser oscillator 11 is output in the form of a pulse, and therefore does not oscillate between pulses of the excimer laser beam B. There is blank time.
Therefore, the shutter 41 is closed during the blank time between the pulses of the excimer laser beam B, and the excimer laser beam B irradiated to the amorphous silicon 7 on the glass substrate 5 is irradiated.
Is interrupted between the pulses of the excimer laser beam, so that the amorphous silicon 7 on the glass substrate 5 can be irradiated with the excimer laser beam B from the beginning to the end with a constant desired fluence.

The rise and fall of the excimer laser beam B are not always steep. Therefore, by cutting off the rising and falling of the excimer laser beam B in the optical path where the excimer laser beam B is irradiated to the amorphous silicon 7 on the glass substrate 5, the amorphous silicon 7 on the glass substrate 5 The irradiation of the excimer laser beam B can be performed at a constant desired fluence from the beginning to the end.

Thus, the particle size of the polysilicon 2 formed by irradiating the amorphous silicon 7 on the glass substrate 5 with the excimer laser beam B and subjecting the amorphous silicon 7 to laser annealing can be made constant. The amorphous silicon 7 on the glass substrate 5 can be laser-annealed with a uniform particle size from the place where the irradiation of the beam B starts to the place where the irradiation ends.

Therefore, polysilicon 2 having a desired particle size can be uniformly formed at a desired position up to the vicinity of the end on glass substrate 5. Therefore, the shutter 41
By irradiating the amorphous silicon 7 for manufacturing the thin film transistor 3 with the excimer laser beam B blocked by the above, the performance of the thin film transistor 3 can be made constant, and the thin film transistor 3 having excellent thin film transistor characteristics can be manufactured.

As a result, the thin film transistor 3 having high mobility can be manufactured with a high yield over substantially the entire main surface of the glass substrate 5, and the thin film transistor 3 having a drive circuit integrated type and other high-functionality can be used up to the end of the glass substrate 5. Large liquid crystal displays can be manufactured in large quantities with good yield.

Since the shutter 41 for passing and blocking the excimer laser beam B is a disk portion 42 provided with slits 43 at positions equidistantly spaced from each other along the circumferential direction, by rotating the disk portion 42 , The passage and blocking of the excimer laser beam B can be performed accurately and easily.

Further, by providing four slits 43 in the disk portion 42, the rotation speed of the disk portion 42 when the excimer laser beam B is cut off can be reduced, so that the load of the pulse motor for rotating the disk portion 42 is reduced. Can be reduced.

Since the excimer laser beam B is output in a pulse form, the ratio between the area of one slit 43 and the area between the slits 43 is determined by the oscillation time and non-oscillation time of the excimer laser beam B pulse. A fan-shaped slit 43 is provided in the disk portion 42 so as to be substantially equal to the ratio of the disk portion.
By rotating 42 in synchronization with the oscillation frequency of the excimer laser beam B, the amorphous silicon 7 on the glass substrate 5 can be irradiated with the excimer laser beam B at a constant desired fluence from the beginning to the end. Therefore, the amorphous silicon 7 on the glass substrate 5 can be appropriately laser-annealed.

Further, the extension of both sides of one slit 43 passes near the center of the disk portion 42, and the ratio of the arc length of the outer periphery of the slit 43 to the arc length of the disk portion 42 is determined by the ratio of the excimer laser beam B pulse. A slit 43 is provided in the disk portion 42 so as to be substantially equal to the ratio between the oscillation time and the non-oscillation time, and the disk portion 42 is rotated in synchronization with the oscillation frequency of the excimer laser beam B, so that Irradiation of the excimer laser beam B to the amorphous silicon 7 can be performed at a constant desired fluence from the beginning to the end. Therefore, the amorphous silicon 7 on the glass substrate 5 can be appropriately laser-annealed.

Since the excimer laser beam B contracts most in the optical system at the short-axis slit 40, the excimer laser beam B passing through the shutter 41 immediately after the short-axis slit 40 or passing through the short-axis slit 40 immediately. By arranging them at the passing positions, the optical path of the excimer laser beam B can be cut off without applying a load to the mechanical system.

Further, since the four slits 43 are provided at equally spaced positions on the disk portion 42, the number of rotations of the pulse motor for rotating the shutter 41 is reduced to 1/4 of the laser oscillation frequency of the excimer laser beam B. be able to.
As a result, the passage and cutoff of the excimer laser beam B can be easily controlled by rotating the disk part 42 and instantaneously shifting the phase of the disk part 42.

Then, the pulse signal of the pulse of the excimer laser beam B is received by a pulse motor for rotating the disk part 42 of the shutter 41, and the disk part 42 by this pulse motor is received.
Of the excimer laser beam B, the oscillation timing of the excimer laser beam B is fed back to the pulse motor, and the excimer laser beam B is blanked by the disc portion 42 of the shutter 41, and the excimer laser beam B rises and falls. B, and further, the disk portion 42 is rotated to change the phase of the disk portion 42, and the passage of the excimer laser beam B by the slit 43 of the disk portion 42 is synchronized with the optical path of the excimer laser beam B. This makes it easy to control the passage and cutoff of the excimer laser beam B by the disk unit 42.

Further, since the output of the excimer laser beam B is 300 Hz, the excimer laser beam B is cut off by the shutter 41 for 100 nsec or more and 1 msec or less, so that the blank time of the excimer laser beam B, the rise and the fall The falling time can be cut off accurately.

In the above-described embodiment, the shutter 41 for passing and blocking the excimer laser beam B by rotating the disk portion 42 provided with four slits 43 at positions equally spaced from each other has been described. The configuration is not limited to such a configuration, and any configuration may be used as long as the excimer laser beam B can be accurately passed and cut off during the blank time between pulses of the excimer laser beam B and at the time of rising and falling. Therefore, a non-mechanical shutter such as an optical shutter combining an electro-optic crystal and a polarizing plate or a shutter using the Franz-Keldysh effect may be used.

[0080]

According to the present invention, an amorphous silicon semiconductor on a light-transmitting substrate is irradiated with a laser beam, and the optical path through which the amorphous silicon semiconductor is irradiated with a laser beam By cutting off during that time, the rise and fall of the laser beam to the amorphous silicon semiconductor becomes sharp, and the irradiation of the laser beam to the amorphous silicon semiconductor on the light-transmitting substrate is constant from the beginning to the end. Since the desired energy density is obtained, the grain size of the polycrystalline silicon semiconductor can be made constant.

Further, by irradiating an amorphous silicon semiconductor when manufacturing a thin film transistor, the performance of the thin film transistor can be made constant.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a laser annealing apparatus of the present invention.

FIG. 2 is an explanatory view showing a shutter of the laser annealing apparatus according to the first embodiment;

FIG. 3 is a sectional view showing a liquid crystal display manufactured by the laser annealing apparatus.

FIG. 4 is a graph showing laser intensity versus time of an excimer laser beam used in a conventional laser annealing apparatus.

[Explanation of symbols]

2 Polysilicon as Polycrystalline Silicon Semiconductor 5 Glass Substrate as Transparent Substrate 7 Amorphous Silicon as Amorphous Silicon Semiconductor 11 Laser Oscillator as Laser Oscillator 41 Shutter 42 Disk 42 as Disk 43 Slit 53 Stage B Laser Excimer laser beam as beam

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Claims (8)

[Claims] 1. A light-transmitting substrate having a thin film of an amorphous silicon semiconductor deposited on one main surface thereof is irradiated with a pulsed laser beam toward the amorphous silicon semiconductor to thereby form the amorphous silicon semiconductor. A laser annealing method for converting a semiconductor into a polycrystalline silicon semiconductor, wherein an optical path for irradiating the amorphous silicon semiconductor with the laser beam is interrupted between pulses of the laser beam. 2. A laser beam is cut off by rotating a disk in which a ratio of an area of one slit to an area between the slits is substantially equal to a ratio of an oscillation time of a laser beam pulse to a non-oscillation time. The laser annealing method according to claim 1, wherein: 3. The extension of both sides of the slit passes near the center of the disk, and the ratio between the arc length of the outer periphery of the slit and the arc length of the disk is substantially equal to the ratio between the oscillation time and the non-oscillation time of the pulse of the laser beam. 2. The laser annealing method according to claim 1, wherein the laser beam is cut off by rotating an equal disk. 4. A non-crystalline silicon semiconductor is polycrystalline by irradiating a laser beam to the amorphous silicon semiconductor on a light-transmitting substrate having a thin film of an amorphous silicon semiconductor deposited on one main surface. A laser annealing apparatus for forming a silicon semiconductor, comprising: a stage on which the light-transmitting substrate is installed; and oscillating the laser beam toward an amorphous silicon semiconductor on the light-transmitting substrate installed on the stage. A laser oscillating means, a shutter disposed on the optical path of the laser beam between the amorphous silicon semiconductor on the translucent substrate mounted on the stage and the laser oscillating device, and capable of blocking the laser beam A laser annealing apparatus characterized by comprising: 5. A laser beam is output in a pulse shape, and the shutter has at least one or more substantially fan-shaped slits, and the ratio of the area of one slit to the area between the slits is a laser. 5. The laser annealing apparatus according to claim 4, wherein the disk is a rotatable disk substantially equal to the ratio of the oscillation time of the beam pulse to the non-oscillation time. 6. A laser beam is output in a pulse shape. The shutter is a rotatable disk having a substantially fan-shaped slit, and both sides of the slit extend near the center of the disk, and an arc on the outer periphery of the slit is provided. 5. The laser annealing apparatus according to claim 4, wherein the ratio between the length and the arc length of the disk is substantially equal to the ratio between the oscillation time of the pulse of the laser beam and the non-oscillation time. 7. A method for manufacturing a thin film transistor using an amorphous silicon semiconductor as a polycrystalline silicon semiconductor, comprising using the laser annealing method according to claim 1. 8. An apparatus for manufacturing a thin film transistor using an amorphous silicon semiconductor as a polycrystalline silicon semiconductor, the apparatus including a laser annealing apparatus according to claim 4.