JPH09293687A - Laser annealing method of low-temperature polysilicon thin film transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize polycrystalline Si of different mobility by annealing at a time by a method wherein a laser beam is made to form a pattern prescribed in shape on a substrate, the laser beam is relatively moved to the substrate, and all target area which is turned to polysilicon is irradiated with a laser beam. SOLUTION: A laser beam projected from an excimer laser oscillator 21 is made to form the images of points in a far field at required positions in required phase by a Fourier transform-type phase hologram provided between a lens 70 and a substrate 31, and the intensity distribution of the laser beam is optionally shaped corresponding to the required mobility of a target part which is required to turn to polysilicon. The laser beam is made to form a shaped pattern on the substrate 31, and the laser beam is relatively moved against the substrate 31 to irradiate all target area which is turned to polysilicon. By this setup, polycrystalline Si of various mobility can be obtained at the same time by annealing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention converts an amorphous silicon film formed on a substrate, for example, an amorphous silicon film of a thin film transistor formed in a peripheral driving circuit portion and a central pixel portion of a liquid crystal panel into a polysilicon by laser irradiation. The present invention relates to a laser annealing method.

[0002]

2. Description of the Related Art A liquid crystal display using a thin film transistor using amorphous silicon as a semiconductor film as a switching element has been put into practical use, but the pixel size has been reduced with the progress of high definition, and the occupied area of the thin film transistor portion has been reduced. In order to make it as small as possible, development is underway to replace amorphous silicon with polysilicon which has a higher operating speed. Furthermore, even circuits for driving thin film transistors are being formed using thin film transistors using polysilicon, and polysilicon is becoming a key material in liquid crystal displays.

Solid phase growth method and laser annealing method are known as means for obtaining a polysilicon film. However, since it is difficult to lower the annealing temperature by the solid phase growth method, an amorphous silicon layer formed on a substrate such as a glass substrate as shown in FIG. 8 is annealed by a laser and melted and recrystallized. A laser annealing method has been proposed, which does not require heating the whole to a high temperature, and is expected as a method for manufacturing a low temperature polysilicon thin film transistor (polycrystalline Si-TFT) in which inexpensive glass can be used as a substrate. In the figure, 1 is a driving IC, 2 is a portion for forming a pixel, and 3 is a thin film transistor (T
FT) forming portion, 11 is a laser beam spot, and 12 is an arrow indicating the scanning direction of the laser beam.

Since an extremely large laser output is required to irradiate the entire area of the amorphous layer at one time, conventionally, a method has been adopted in which rectangular beams are irradiated by superimposing them at each step and annealing the entire area. However, there is a problem that the crystallinity is different between the overlapped portion and the other portion, and the characteristics of the thin film transistor based on this are not uniform, so that the liquid crystal screen becomes uneven.

Therefore, the excimer laser annealing technique shown in FIG. 5 is drawing attention. Here, XeCl (wavelength 308 nm) and KrF (wavelength 248) are used as excimer lasers.
nm), ArF (wavelength 193 nm) or the like, and introduces the laser beam into the chamber through an optical system including a beam homogenizer. The chamber has a pump for controlling a vacuum or a constant atmosphere, a gas system, and beam scanning includes moving the stage on which the substrate is placed, moving the optical system, or a combination of both. The laser beam with which the substrate is irradiated has a uniform irradiation intensity, and thin line and rectangular beam shapes are used.

Generally, a combination of a beam homogenizing optical system and a cylindrical lens is used as a beam shaping optical system for producing a uniform intensity distribution like a linear laser beam, but a beam homogenizer expands a small part of the laser beam. Since it is overlapped with other portions largely, there is a problem that they interfere with each other to form interference fringes and the intensity distribution is not uniform.
It is also very difficult to create an arbitrary intensity distribution other than the uniform intensity distribution.

Further, the excimer laser is a short-pulse discharge-excited laser, and since the discharge instability and the oscillation moat is not sufficiently formed in the resonator, the beam profile for each pulse and the center of gravity of the beam become unstable. Has become.
Further, the beam profile and the center of gravity of the beam change over a long period due to wear of the discharge electrode. Therefore, in the beam homogenizer, if the center of gravity of the beam shifts, the beam cannot be divided from the center. Further, unless the beam profile is as designed, even if they are superposed, a uniform intensity distribution cannot be obtained.

As described above, in the excimer laser annealing technique, the conventional beam homogenizing optical system cannot form a stable and uniform intensity distribution with respect to the short pulse laser and realizes a stable linear beam. Since it was difficult, stable annealing was difficult.

In order to solve such a problem, it has been proposed that the laser annealing apparatus has a Fourier transform type phase hologram type hologram as an important element constituting the beam shaping optical system.

[0010]

By the way, in the TFT characteristics, the mobility changes depending on the energy density as shown in FIG. 6, and the mobility changes depending on the number of shots as shown in FIG. Therefore, 1) the driving IC of the portion where the driving circuit is formed needs a higher mobility than the thin film transistor (TFT) forming portion 3 of the portion 2 where the pixel is formed. It is necessary to irradiate an excimer laser having a relatively low energy density on the thin film transistor formation portion of the portion where the GaN is formed, and to select irradiation energy according to the required mobility. 2) The driving IC unit is plasma CVD / α-Si: H
When it is formed by a film, it contains a large amount of hydrogen, so if you suddenly irradiate a laser with a high energy density, hydrogen will bump and destroy the film. It is necessary to scan in two steps so that hydrogen is expelled and then melted and solidified. Furthermore, 3) since the driving IC section is located on the upper side and the side of the liquid crystal panel, the laser beam with which the substrate is irradiated has a uniform irradiation intensity and is a thin line beam parallel to any one side of the rectangular substrate for annealing. Therefore, it is necessary to anneal the drive ICs on one side and then rotate the fine beam or the substrate 90 degrees to anneal the drive ICs on the other side.

Therefore, a first object of the present invention is to provide a laser annealing method capable of simultaneously annealing polycrystalline Si having different mobilities by an excimer laser beam. A second object of the present invention is to provide a laser annealing method using an excimer laser having a multi-step beam intensity and capable of performing a multi-step annealing that needs to be performed by a plurality of scans by a single excimer laser irradiation. To provide. A third object of the present invention is to provide a method capable of laser-annealing a driving IC portion extending in two directions of a liquid crystal panel without rotating a fine beam or a substrate by 90 degrees.

[0012]

In order to achieve the first object of the present invention, an excimer is used to manufacture a low temperature polysilicon thin film transistor by polycrystallizing an amorphous silicon film on a substrate for forming a thin film transistor by laser irradiation. The Fourier transform phase hologram is used to image the laser beam emitted from the laser oscillator at multiple points in the far field at a desired position and at a desired phase. A shaping step of shaping the siliconized portion so as to correspond to a desired mobility change, and forming an image of the laser beam on a substrate in a predetermined shaping pattern, and moving the laser beam relative to the substrate. And an irradiation step of irradiating the entire area of the portion to be poly-siliconized. That.

The Fourier transform type phase hologram is shown in FIG.
As shown in FIG. 3, the laser beam incident through the lens can be diffracted to be designed so that a spectrum according to a desired irradiation pattern can be image-formed, which will be described in detail below. , If the intensity distribution of the laser beam emitted from the excimer laser oscillator is changed stepwise in the relative movement direction, multiple points in the far field are connected to multiple straight lines parallel to each other at arbitrary phases. The second object can be achieved by using a Fourier transform phase hologram having an imaged pattern.

Further, the laser beam for annealing the peripheral portion extending in a strip shape in the XY axis directions is formed by the Fourier transform phase hologram from the linear component extending in the X axis direction and the linear component extending in the Y axis direction at the peripheral portion width. Become L
The laser beam angle with respect to the substrate is shaped by shaping the shape or the necessary widths of both the peripheral portions extending in the XY-axis direction in a band shape from the X-axis component and the Y-axis component that cross over the necessary width, By moving in the XY axis directions without changing, the peripheral portion extending in the XY axis directions in a band shape can be annealed.
The third object of the present invention can be achieved.

The laser beam for annealing the peripheral portion extending in a band shape in the XY axis directions is L-shaped by the Fourier transform type phase hologram and is composed of a linear component parallel to the X axis and a linear component parallel to the Y axis of the peripheral portion. The beam can be shaped into a fine line beam, and in this case, the beam is scanned in an oblique direction with respect to the XY axes, whereby the peripheral portion extending in a band shape in the XY axis direction can be annealed.

In order to anneal the pixel forming portion of the liquid crystal panel, the laser beam can be shaped into a spot beam array corresponding to the pixel pitch by the Fourier transform type phase hologram.

As the laser beam irradiation device, the modes listed below can be selected and used according to the situation.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. 1 is an LCD liquid crystal panel having a substrate of 12 inches, and has a portion 2 for forming pixels in the central portion as shown in FIG. A source drive circuit portion 1A and a gate drive circuit 1B having a portion 1 forming a circuit are formed of a plasma CVD / α-Si: H film in order to obtain high mobility. In this case, it is preferable that the laser beam for irradiating the peripheral portion having the drive circuit has an intensity distribution increased stepwise in the relative movement direction. Therefore, as a laser beam for dehydrogenation pre-annealing, 200 mJ / cm ² and 2
A linear beam of 30 mJ / cm ² is arranged in front and rear, and a rectangular beam for crystallization annealing of 260 mJ / cm ² (irradiation intensity for high mobility) is combined to form an image, while 200 mJ of dehydrogenation preannealing is performed. / Cm
The linear beam of ² to continuously irradiate the pixel portion 200 mJ / cm ² (low mobility irradiation intensity) is imaged form.

If a laser beam having the above pattern is used, the amorphous silicon portion contains a large amount of hydrogen, but since a laser having a gradually increasing energy density is continuously irradiated by one scanning, Hydrogen in the amorphous film is released without bumping and dehydrogenation is performed. Next, when the amorphous film is irradiated with a rectangular laser beam for crystallization annealing, the amorphous film is melted and solidified to become polysilicon. On the other hand, the pixel portion is 200 mJ / cm at the same time as the scanning for polysiliconization of the peripheral portion.
A linear beam of ² (irradiation intensity for low mobility) is irradiated to form polysilicon.

Therefore, according to the present embodiment, since it is possible to simultaneously form a plurality of uniform fine lines and rectangular beams having different irradiation intensities from one laser oscillator, a plurality of steps are performed. The laser annealing process can be performed with one scanning. Also, if you want to irradiate the drive circuit and pixels with different irradiation intensity,
Instead of a uniform beam of uniform intensity, regions of high and weak irradiation intensity are formed, and by shaping the beam of uniform intensity within each region, the drive circuit and pixels can be adjusted to their optimum intensity. Therefore, the annealing treatment can be performed by one scanning.

Embodiment 2 FIG. 2 is a 12-inch LCD liquid crystal panel similar to that shown in FIG. 1, which has a portion 2 for forming pixels in the central portion as shown in FIG. A peripheral portion extending in a strip shape has a portion 1 forming a drive circuit, and a source drive circuit portion 1A and a gate drive circuit 1B thereof are formed. The laser beam that anneals the peripheral portion extending in the XY-axis band shape has a tilted shape 11A that is composed of the X-axis component and the Y-axis component that cross the necessary widths of both the peripheral portions extending in the XY-axis direction. Have The inclination angle and the length thereof are based on the length in the X-axis direction of the drive circuit in which the length of the X-axis direction component of the thin line beam is the Y-axis direction when the direction of each side of the substrate is the XY-axis direction. It is preferable that the length of the Y-axis direction component of the thin wire is longer than the length of the drive circuit having the X-axis direction as the longitudinal direction in the Y-axis direction.
As shown in FIG. 7, this beam shape may be an L-shape 11B having a straight line component extending in the X-axis direction and a straight line component extending in the Y-axis direction at the peripheral portion width. Again,
When the direction of each side of the substrate is the X and Y axis directions, the length of the X axis direction component of the L-shaped beam is longer than the length of the X axis direction of the drive circuit having the Y axis direction as the longitudinal direction. It is preferable that the length of the Y-axis direction component be longer than the length in the Y-axis direction of the drive circuit whose longitudinal direction is the X-axis direction.

In the case of FIGS. 2 and 3, it is possible to anneal the peripheral portion extending in a strip shape in the XY axis directions by moving the laser beam angle with respect to the substrate in the X and Y axis directions without changing the angle. it can.

As shown in FIG. 2, the laser beam for annealing the portion forming the above-mentioned pixel is composed of a spot beam train corresponding to the pixel pitch. A spot beam row is formed so that one spot beam can irradiate only the portion forming a TFT in one pixel and at least all the pixel TFTs arranged in one row can be collectively irradiated. As a result, the entire pixel portion can be annealed with less energy (splitting due to spotting) compared to a uniform beam.

In FIG. 4, a laser beam for annealing a peripheral portion extending in a strip shape in the XY axis directions is X-rayed in the peripheral portion.
An L-shaped thin line beam composed of a straight line component parallel to the axis and a closed straight line component to the Y axis.
This is performed in an oblique direction with respect to the axis, and the peripheral portion extending in a strip shape in the XY axis directions is annealed. The thin-line beam has two thin-line components parallel to each side of the substrate, and the length of each is the length of the X-axis direction component of the L-shaped beam when the direction of each side of the substrate is the XY axis direction. The length of the Y-axis direction component of the beam is longer than the length of the drive circuit having the axial direction as the longitudinal direction, and the length of the component of the beam in the Y-axis direction is X as the longitudinal direction of the drive circuit.
It should be longer than the axial length. According to this method, the driving circuit around the pixel can be annealed with one L-shaped beam, so that it is not necessary to rotate the conventional beam or substrate. In addition to the L-shape and the slanted shape, any shape such as a cross can be shaped as the laser beam.

According to the present invention, since the laser beam having various shapes and intensity distributions can be shaped by the Fourier transform type phase hologram, an appropriate annealing pattern can be executed. For example, since multi-step intensity simultaneous irradiation annealing can be performed, the number of times of scanning can be reduced, the annealing time can be shortened, and the throughput can be improved. Further, since the annealing can be performed with the irradiation intensity suitable for the drive circuit and the pixel, the performance of each part can be improved and the variation can be reduced. Since an L-shaped or oblique beam can be formed and oblique scan annealing is possible, the driving circuit around the pixel can be annealed without rotating the beam and the substrate, and the throughput is improved. In addition, since the stage mechanism for rotation is not necessary, the reliability of the device is improved. Since the spot beam irradiation annealing is possible, a large area can be annealed by a low-power laser oscillator, the throughput is improved, and the reliability of the annealing apparatus is increased.

【Example】

The principle and apparatus shown in the following examples are specific examples of the Fourier transform type phase hologram used in the above embodiment and the laser annealing apparatus including the same.

Embodiment 1 FIG. 10 is a block diagram showing the structure of an apparatus for realizing a laser annealing method according to another embodiment of the present invention.
70 is a lens, 71 is a Fourier transform type phase hologram
Reference numeral 72 is a beam shaping optical system composed of a lens 70 and a hologram 71. That is, the lens 70 and the hologram 71 are a beam shaping optical system 72 for obtaining a linear laser beam having a uniform laser intensity distribution in the longitudinal direction on the annealing object 31.
Is composed.

Next, the operation will be described. The laser light emitted from the laser oscillator 21 passes through a beam shaping optical system 72 including a lens 70 and a hologram 71.
At this time, the laser light is irradiated onto the substrate 31 by the lens 70. However, as shown in FIG.
The hologram 71 provided between and is spatially modulated so as to have a number of overlapping irradiation spots aligned on the substrate 31. The hologram 71 can arrange each irradiation spot at an arbitrary position on the substrate 31 with an arbitrary intensity. For example, FIG. 12 (a)
As shown in FIG. 12B, a hologram 71 having irradiation spots arranged in a straight line is used, and when the irradiation spots are adjusted so as to overlap each other as shown in FIG.
Above, a beam having a uniform laser irradiation intensity distribution in the longitudinal direction can be obtained, and stable laser annealing can be performed.

FIG. 13 is a principle diagram showing the overlapping of a plurality of spots generated by the hologram 71. In order to obtain a uniform intensity distribution, the overlapping irradiation spots as shown in FIG. Must be arranged at intervals smaller than the full width at half maximum of and partially overlap each other. As the distance between the centers of adjacent irradiation spots, that is, the overlapping interval is smaller, the number of irradiation spots that are superposed on the same point is increased, so that the intensity distribution uniformity is improved. However, if the laser beams are superposed at a distance narrower than the spatial coherence distance, interference fringes may adversely affect the uniformity, and therefore the superposition distance may not be narrow.

As the hologram 71, a designed pattern, that is, a phase hologram having a high diffraction efficiency, which is a ratio of energy of light diffracted into a plurality of irradiation spots arranged in a straight line, is used to improve light utilization efficiency. by this,
The energy of several 10% of the laser output becomes available for the actual annealing process.

Next, a method of spatially modulating laser light by the hologram 71 will be described. For example, reference A. E. FIG. S
As shown in iegman "LASERS", the diffraction image of light propagating through the optical system represented by the ABCD ray matrix can be calculated as follows.

[0032]

[Equation 1] When the input image u (x1) is superposed with a modulation plate whose phase changes at the spatial frequency a, the diffraction image becomes as follows.

[0033]

[Equation 2] G (x2-Bλa) on the right side is obtained by moving g (x2), which is a diffraction image when the modulator is not inserted, by Bλa. The other terms on the right side are terms that change only the phase. When the modulation plates having the input image u (x1) spatial frequency a are superposed, an image appears at a position shifted by Bλa, and when the modulation plates in which the components of the spatial frequency a1 and the spatial frequency a2 are superposed with equal intensity are superposed, Bλa1 and Bλa2 2 at different positions
Two statues appear. From this, by inserting a phase hologram as a modulator having a phase distribution created by superimposing several spatial frequency components into the optical system, several images can be created at positions corresponding to each spatial frequency. . As long as the distance between the images is incoherent to each other, the phase of the images does not interfere with any value,
As shown in FIG. 2, by inserting such a hologram 71 into the condensing optical system including the lens 70, the substrate 31
By forming a plurality of irradiation spots aligned on a straight line and arranging these irradiation spots so as to overlap each other, an arbitrary irradiation intensity distribution suitable for annealing can be created.

The phase distribution pattern of the hologram 71 is determined by superimposing the spatial frequencies corresponding to the positions of the respective irradiation spots, that is, the transfer patterns. The phase distribution pattern of the hologram 71 can also be determined by calculating with a computer. The hologram 71 can also be manufactured by quantizing a smooth phase distribution in several steps.
In this embodiment, the hologram 71 is designed to superimpose various spatial frequencies at arbitrary initial phases. In such a hologram 71, even when the phase is quantized,
The initial phase to be superposed can be used as a parameter for optimization so as to minimize the quantization error, and the hologram 71 with high diffraction efficiency and low noise can be patterned.

FIG. 14 is a diagram for explaining the patterning method of the hologram 71 of the phase hologram type according to this embodiment, and FIG. 14 (a) shows the phase in a part of the hologram 71 divided into a plurality of cells. Shows an enlarged phase distribution pattern calculated by a computer by quantizing 2 to 0 degrees and 180 degrees, and 74 is a phase 0 degree part,
75 is a phase 180 degree part. Further, FIG. 14B shows the entire phase distribution pattern of the hologram 71. In this way, the entire hologram is divided into a large number of cells, each of which is quantized in two steps and superposed to optimize the quantization error using the initial phase as a parameter to determine the phase. Patterning. When manufacturing holograms for lasers, the materials that can be used are limited. However, if the phase is quantized and the pattern is determined by a computer as in this embodiment,
Actual production is relatively easy even with limited materials.

FIG. 15 is a diagram for explaining a method of manufacturing the hologram 71. 711 is a phase shift film, 712 is a phase shift part, 713 is a refractive index changing part, 714 is a phase shift film 711 and a phase shift part 712. , Or a substrate such as synthetic quartz on which the refractive index changing portion 713 is formed. FIG.
(a) shows a method of forming a phase distribution by attaching a phase shift film 711 to the substrate 714. In such a phase hologram, the amount of phase shift is determined by the film thickness of the phase shift film 711, but the control of the film pressure is compared. Since it is easy, the phase error is small. FIG. 15B shows a method of etching a substrate 714 made of synthetic quartz or the like and forming a phase shift portion 712 by an etching groove to form a phase distribution. The light resistance strengths shown in FIG. Since there is no interface between the substrate and the phase shift film which is extremely low, the light resistance strength of the hologram can be improved. FIG. 15 (c) shows a method of forming a phase shift portion by forming a refractive index changing portion 713 on a substrate 714 such as synthetic quartz, and the interface is also eliminated by this method. The strength can be improved.

As described above, according to the laser annealing apparatus of this embodiment, the hologram-based optical system can overcome the drawbacks of the beam homogenizer optical system and is suitable for annealing an object to be annealed. Since laser irradiation can be performed with a laser irradiation intensity distribution, stable and uniform laser annealing can be performed.

Embodiment 2 FIG. 16 is a diagram showing irradiation spots on an object to be annealed by an apparatus for realizing a laser annealing method according to another embodiment of the present invention. The structure of the laser annealing apparatus according to this embodiment is basically the same as that according to the first embodiment shown in FIG.

With the hologram according to the first embodiment,
Although a uniform intensity distribution is obtained in the longitudinal direction of the linear beam,
Since the intensity distribution in the width direction reflects the intensity distribution of a single irradiation spot as it is, the region having the allowable intensity in laser annealing is limited to a narrow range. When annealing is performed with such a laser beam, it may be necessary to perform highly accurate alignment in order to keep the one row of thin film transistor forming sections within this allowable range.
Therefore, the hologram according to this embodiment is configured to form a plurality of irradiation spots on two parallel straight lines, respectively, as shown in FIG.

Next, the operation will be described. Using a hologram for generating irradiation spots as shown in FIG. 16 (a), the irradiation spots are overlapped in the longitudinal direction to form a linear beam as shown in FIG. 16 (b), and two beams are formed. The linear beams of are also adjusted so that they overlap each other at an overlapping distance of about half width of the intensity distribution of one irradiation spot. As a result, as compared with the intensity distribution in the width direction of one linear beam on the object to be annealed formed in Example 1 shown in FIG.
As shown in FIG. 7 (b), the two linear beams overlap each other at the overlapping distance, and the range having a uniform intensity distribution is widened also in the width direction. As a result, the alignment accuracy of the irradiation position can be relaxed and stable annealing can be performed. Furthermore, by overlapping many parallel linear beams, the uniform intensity region in the width direction can be expanded, and the alignment accuracy of the irradiation position can be relaxed.

Embodiment 3 FIG. 18 is a block diagram showing the structure of an apparatus for realizing a laser annealing method according to another embodiment of the present invention.
In the figure, the same reference numerals as those shown in FIG. 10 denote the same or corresponding components. The structure of the laser annealing apparatus according to this embodiment is basically the same as that according to the first embodiment shown in FIG.

In the first embodiment, the hologram 71 is the lens 70.
While it was placed behind, in this example,
The hologram 71 is arranged at the focal position on the front side of the lens 70.

Next, the operation will be described. In the arrangement of the hologram 71 and the lens 70 according to this embodiment shown in FIG. 18, the chief rays of the laser beams divided by the hologram 71 are made parallel to the original optical axis by the lens 70. Therefore, the principal rays of all the laser beams incident on the substrate 31 can be vertically incident on the substrate 31. If the incident angle of light with respect to the substrate 31 is different, the light reflectance and the light absorptance of the substrate 31 change, and even if the irradiation intensity distribution is uniform, the light energy absorbed by the substrate 31 is uniform. And the annealing may become non-uniform. On the other hand, by adopting the arrangement shown in FIG. 19, since all the chief rays of the laser beam incident on the substrate 31 are incident at the same angle, the influence of the light incident angle is eliminated and uniform and stable annealing is possible. become.

Embodiment 4 FIG. 19 is a block diagram showing the structure of an apparatus for realizing a laser annealing method according to another embodiment of the present invention.
In the figure, the same reference numerals as those shown in FIG. 1 denote the same or corresponding components, and 80 is for expanding the beam width of the laser beam at least in the direction perpendicular to the longitudinal direction of the linear beam shape. It is a concave cylindrical lens. 19A shows a plan view of the laser annealing apparatus according to this embodiment, and FIG. 19B shows a side view thereof.

In the first to third embodiments, the laser light emitted from the laser oscillator is shaped into a linear beam shape as it is. Therefore, when the beam divergence angle from the laser oscillator is large, the transistor forming portion is formed. However, there is a problem in that it is not possible to condense light into a width smaller than the column spacing, and it is not possible to manufacture a high-definition liquid crystal display by reducing the column spacing in the transistor forming portion.

This embodiment is made in order to solve such a problem, and for this purpose, a cylindrical lens 80 having a concave surface is provided.

Next, the operation will be described. The laser light emitted from the laser oscillator 21 is propagated through the concave cylindrical lens 80, the convex lens 70, and the hologram 71, is shaped into a linear beam, and is applied to the transistor forming portion on the substrate 31 which is the object to be annealed. However, in the middle of this process, the laser light is expanded by the concave cylindrical lens 80 in the direction perpendicular to the longitudinal direction of the linear beam.

Generally, when the light is condensed by using the convex lens having the focal length f, the minimum converging width ω0 is represented by ω0 = f · (α · λ / D).

Here, λ is the wavelength of the laser light, D is the width of the beam when the laser light is incident on the convex lens, and α is a constant determined by the profile and divergence angle of the laser beam.

Therefore, in order to reduce the converging width ω0, it is necessary to reduce the focal length f of the convex lens or the wavelength λ of the laser light. Alternatively, it is necessary to increase the width D of the laser beam when entering the convex lens.

However, when the focal length f is reduced, the aberration of the convex lens increases, and the converging width increases. In addition, since the distance between the convex lens 70 and the substrate 31 becomes closer, there is an adverse effect such that scattered matter from the substrate 31 adheres to the convex lens 70. Further, if the wavelength of the laser light is reduced, it becomes difficult to select the lens material, and the stability of the laser oscillator 21 deteriorates.

When a laser beam having a beam width d incident on the concave cylindrical lens 80 is incident on the convex cylindrical lens 80 by the concave cylindrical lens 80, the beam width is expanded to be D, and α determined by the beam divergence angle is determined. The beam divergence angle can be increased. That is, the converging width can be reduced even with the laser oscillator 21 having a large beam divergence angle. Further, when the laser beams having the same α are used, the minimum converging width ω0 can be reduced to d / D, and the column width of the fine transistor forming portion can be reduced accordingly.

In this embodiment, the cylindrical lens 80 having a concave surface is used in order to increase the beam width incident on the convex lens 70. However, when the overlapping pitch is sufficiently small, the direction parallel to the longitudinal direction of the linear beam is used. When a uniform linear beam can be obtained even if the beam width is expanded and the converging width is reduced, an ordinary concave lens may be used instead of the concave cylindrical lens.

Embodiment 5 FIG. 20 is a block diagram showing the structure of an apparatus for realizing a laser annealing method according to another embodiment of the present invention.
In the figure, the same reference numerals as the reference numerals shown in FIG. 19 denote the same or corresponding components, 81 is a reflecting mirror, and 82 is the beam width at least in the direction perpendicular to the longitudinal direction of the linear beam shape. It is a convex cylindrical mirror for. FIG. 20 (a) shows a plan view of the laser annealing apparatus according to this embodiment, and FIG. 21 (b) shows a side view thereof. In this embodiment, a convex cylindrical mirror 82 is used instead of the concave cylindrical lens of the fourth embodiment.

Next, the operation will be described. As described above, by increasing the beam width of the incident laser light, the converging width can be reduced even in the laser oscillator 21 having a large beam divergence angle, and when the laser beam having the same divergence angle is used, the minimum The converging width can be reduced, and the column width of the fine transistor forming portion can be reduced by this amount. The laser light emitted from the laser oscillator 21 is reflected by the reflection mirror 81, then propagates through the convex cylindrical mirror 82, the lens 70, and the hologram 71, is shaped into a linear beam, and is a substrate that is an annealing target. The transistor formation portion on 31 is irradiated, but in the middle of this, the laser beam is expanded by the convex cylindrical mirror 82 in the direction perpendicular to the longitudinal direction of the linear beam. As a result, similarly to the twelfth embodiment, when the laser light having the beam width d incident on the concave cylindrical mirror 82 is incident on the convex cylindrical mirror 82 by the concave cylindrical mirror 82, the beam width is expanded to be D. Α determined by the beam divergence angle can be increased, that is, the beam divergence angle can be increased. That is, the laser oscillator 2 having a large beam divergence angle
Even with 1, the converging width can be reduced. When using laser beams having the same α, the minimum converging width ω0 is d / D.
The column width of the fine transistor forming portion can be reduced by that much.

Embodiment 6 FIG. 21 is a block diagram showing the structure of an apparatus for realizing a laser annealing method according to another embodiment of the present invention.
In the figure, the same reference numerals as those shown in FIG. 19 denote the same or corresponding components, and 83 denotes a concave cylindrical shape for expanding the beam width at least in the direction perpendicular to the longitudinal direction of the linear beam shape. A beam expander including a lens and a convex cylindrical lens, or a convex cylindrical mirror and a concave cylindrical mirror. 21A shows a plan view of the laser annealing apparatus according to this embodiment, and FIG. 21B shows a side view thereof. In this embodiment, a beam expander 83 including a concave cylindrical lens and a convex cylindrical lens for expanding the beam width in a direction perpendicular to the longitudinal direction of the linear beam shape is used instead of the concave cylindrical lens of the fourth embodiment. To use.

Next, the operation will be described. The laser light emitted from the laser oscillator 21 propagates through the beam expander 83, the lens 70, and the hologram 71, is shaped into a linear beam, and is applied to the transistor forming portion on the substrate 31 which is the object to be annealed. During this process, the laser light is expanded by the beam expander 83 in the direction perpendicular to the longitudinal direction of the linear beam, and as in the twenty-first embodiment, the laser light having the beam width d incident on the beam expander 83 is projected by the beam expander 83 into a convex lens. When the beam is incident on 70, by expanding the beam width to D, α determined by the beam divergence angle can be increased, that is, the beam divergence angle can be increased. That is, the converging width can be reduced even with the laser oscillator 21 having a large beam divergence angle. Also,
When the laser beams having the same α are used, the minimum converging width ω0 can be reduced to d / D, and the column width of the fine transistor forming portion can be reduced by this amount. Further, in this embodiment, when the laser light is incident on the lens 70, it becomes a parallel beam having a wide beam width, so that the concave cylindrical lens 80 as in the case of using the concave cylindrical lens of the fourth embodiment. The incident beam width does not change depending on the distance between the
It is possible to irradiate the transistor forming portion with a stable light collecting width.

Embodiment 7 FIG. 22 is a block diagram showing the structure of an apparatus for realizing a laser annealing method according to another embodiment of the present invention.
In the figure, the same reference numerals as those shown in FIG. 19 denote the same or corresponding constituent elements, and 84 denotes a mirror pair for assembling an unstable resonator at least in the direction perpendicular to the longitudinal direction of the linear beam shape. Is. 22 (a) shows a plan view of the laser annealing apparatus according to this embodiment, and FIG. 22 (b) shows a side view thereof.

In the first embodiment and the like described above, when the beam divergence angle from the laser oscillator is large, even if the laser beam emitted from the laser oscillator is shaped into a linear beam, the column spacing of the transistor forming portions is increased. There is a problem that it is not possible to condense light in a smaller width, and it is impossible to manufacture a high-definition liquid crystal display by reducing the column interval of the transistor formation portion. The laser annealing apparatus according to this embodiment is provided with an unstable resonator 84 for reducing the beam divergence angle in the direction perpendicular to the longitudinal direction of the linear beam shape in order to solve such a problem.

Next, the operation will be described. The laser light emitted from the laser oscillator 21 having the unstable resonator 84 is propagated through the lens 70 and the hologram 71 and shaped into a linear beam, which is then transferred to the transistor forming portion on the substrate 31 which is the annealing processing target. Is irradiated.

As described above, in general, when the light is condensed using the convex lens having the focal length f, the minimum converging width ω
0 is represented by ω0 = f · (α · λ / D).

Here, λ is the wavelength of the laser light, D is the width of the beam when the laser light is incident on the convex lens, and α is a constant determined by the profile and divergence angle of the laser beam.

In order to reduce the converging width ω0, the focal length f of the convex lens and the wavelength λ of the laser light are reduced, or the width D of the laser beam when entering the convex lens is increased, or the focal length is increased. Assuming that f, the wavelength λ of the laser light, and the width D of the laser beam when entering the convex lens do not change, it is necessary to reduce the beam divergence angle.

In the laser annealing apparatus according to the first embodiment, etc., the divergence angle is considered to be small in the ordinary laser oscillator in order to make the converging width of the linear beam as small as possible.
The beam in the direction perpendicular to the electrode direction is often configured to be the width direction of the linear beam. However, when a stable resonator is used, there is a limit to the small divergence angle in this direction, so the converging width cannot be made sufficiently small.

The laser annealing apparatus according to this embodiment is provided with an unstable resonator 84 for suppressing the beam divergence angle of the laser beam in the direction perpendicular to the electrode direction, and also in the direction perpendicular to the longitudinal direction of the linear beam shape. It is arranged to be perpendicular to the electrode direction. As a result, the divergence angle of the beam emitted from the unstable resonator 84 is sufficiently smaller than the divergence angle of the beam emitted from the stable resonator, so that the converging width is reduced accordingly and the fine transistor forming portion is formed. The column width of can be reduced.

Embodiment 8 FIG. 23 is a block diagram showing the structure of an apparatus for realizing a laser annealing method according to another embodiment of the present invention.
In the figure, the same reference numerals as those shown in FIG. 19 designate the same or corresponding components, and 85 is a mirror pair for forming an unstable resonator in axial symmetry with respect to the laser optical axis. FIG. 23 (a) shows a plan view of the laser annealing apparatus according to this embodiment, and FIG. 23 (b) shows a side view thereof.

In the seventh embodiment, the unstable resonator is constructed in order to reduce the beam divergence angle of the laser beam in the direction perpendicular to the electrode direction. However, the laser annealing apparatus according to this embodiment has an axially symmetrical unstable type. The resonator 85 is provided.

Next, the operation will be described. The laser light emitted from the laser oscillator 21 in which the axially symmetric unstable resonator 85 is incorporated is shaped into a linear beam that is propagated through the lens 70 and the hologram 71, and is formed on the substrate 31 that is an annealing processing target. Is irradiated to the transistor formation part of the. If the superposition pitch is sufficiently small, a uniform linear beam can be obtained even if the beam divergence angle with respect to the longitudinal direction of the linear beam and the parallel direction is reduced. The column width of the fine transistor forming portion can be reduced by using the axially symmetric unstable resonator 85.

Embodiment 9 FIG. 24 is different from the above embodiment in that the substrate 1 of the hologram 71 is different.
A pair of vertical and horizontal cylindrical lenses 70 on the side
And a pair of cylindrical lenses 70 are provided for controlling the vertical and horizontal widths of the beam formed on the substrate 1 by the laser beam shaped by passing through the hologram 71.
The adjustment is made. Here, the laser beam incident on the hologram 71 is 40 mm in the longitudinal direction of 84 mm.
The light is diffracted and dispersed into 0 to 800 peaks so that uniform intensity can be obtained, and a fine line beam having a width of 50 μm can be imaged on the substrate 1.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a multi-step strength simultaneous annealing method according to an embodiment of the present invention.

FIG. 2 is a schematic view of an annealing method by oblique beam and spot beam irradiation according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram of an annealing method by L-shaped beam irradiation of a third embodiment of the present invention.

FIG. 4 is a schematic diagram of a diagonal scan annealing method according to a fourth embodiment of the present invention.

FIG. 5 is a schematic diagram of a conventional excimer laser annealing apparatus.

FIG. 6 is a graph showing energy density dependence of TFT characteristics.

FIG. 7 is a graph showing the shot number dependence of TFT characteristics.

FIG. 8 is a perspective view and a partially enlarged schematic view of a liquid crystal panel annealed by the method of the present invention.

FIG. 9 is a conceptual diagram showing the function of a Fourier transform type phase hologram used in the present invention.

FIG. 10 is a block diagram showing a first configuration of a laser annealing apparatus that realizes a laser annealing method in the embodiment of the present invention.

11 is a block diagram showing a configuration of a beam shaping optical system in the laser annealing apparatus shown in FIG.

12 is a diagram showing a plurality of irradiation spots generated by the beam shaping optical system of the laser annealing apparatus shown in FIG.

13 is a diagram showing intensity distributions of a plurality of irradiation spots generated by the beam shaping optical system of the laser annealing device shown in FIG.

14 is a diagram showing patterning of a phase hologram used in the beam shaping optical system of the laser annealing device shown in FIG.

15 is a diagram showing a method of manufacturing a phase hologram used in the beam shaping optical system of the laser annealing device shown in FIG.

FIG. 16 is a diagram showing a plurality of irradiation spots generated by a beam shaping optical system used in a laser annealing apparatus that realizes a laser annealing method according to an embodiment of the present invention.

17 is a diagram showing the intensity distribution of a plurality of irradiation spots in the width direction of the linear beam generated by the beam shaping optical system of the laser annealing apparatus shown in FIG.

FIG. 18 is a configuration diagram showing a second configuration of the beam shaping optical system used in the laser annealing apparatus that realizes the laser annealing method according to the embodiment of the present invention.

FIG. 19 is a plan view and a side view showing a third configuration of a laser annealing apparatus that realizes a laser annealing method according to an embodiment of the present invention.

20A and 20B are a plan view and a side view showing a fourth configuration of the laser annealing apparatus that realizes the laser annealing method according to the embodiment of the present invention.

FIG. 21 is a plan view and a side view showing a fifth configuration of the laser annealing apparatus that realizes the laser annealing method according to the embodiment of the present invention.

22A and 22B are a plan view and a side view showing a sixth configuration of the laser annealing apparatus that realizes the laser annealing method according to the embodiment of the present invention.

FIG. 23 is a plan view and a side view showing a seventh configuration of the laser annealing apparatus for realizing the laser annealing method according to the embodiment of the present invention.

FIG. 24 is a perspective view showing an eighth configuration of the laser annealing apparatus that realizes the laser annealing method according to the embodiment of the present invention.

[Explanation of symbols]

 21 Laser oscillator 70 Lens 31 Substrate (or object to be annealed) 31a Amorphous silicon film 31b Substrate 71 Hologram (Fourier transform phase hologram) 84,85 Unstable resonator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H01L 21/336 H01L 29/78 627G (72) Inventor Hidetada Tokioka 2-2 Marunouchi, Chiyoda-ku, Tokyo Sanryo Electric Co., Ltd. (72) Inventor Taro Yoshino 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Sanryo Electric Co., Ltd. (72) Yasushi Eguchi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Sanryo Electric Co., Ltd.

Claims (6)

[Claims] 1. A laser beam emitted from an excimer laser oscillator is used to manufacture a low temperature polysilicon thin film transistor by converting an amorphous silicon film on a substrate for forming a thin film transistor into polysilicon by laser irradiation.
A Fourier transform type phase hologram is used to image multiple points in the far field at a desired position and at a desired phase, and the beam intensity distribution can be changed to the desired mobility change of the part to be polysiliconized in any shape. A shaping step for shaping the laser beam in a corresponding manner, and forming an image of the laser beam on a substrate with a predetermined shaping pattern, moving the laser beam relative to the substrate, and covering the entire region to be poly-siliconized. A laser annealing method comprising: an irradiation step of irradiating. 2. The Fourier transform type phase hologram comprises:
The laser beam emitted from the excimer laser oscillator is
A laser beam pattern having a pattern in which a plurality of points are imaged in the far field so that the intensity distribution changes stepwise in the relative movement direction, and a laser beam pattern in which the intensity distribution changes in multiple steps on the substrate is shaped. The laser annealing method according to claim 1. 3. The annealed portion is formed of an α-Si: H film, and the laser beam combines a linear beam pattern and a rectangular beam pattern to increase the irradiation intensity distribution stepwise in the relative movement direction. Item 3. The laser annealing method according to Item 2. 4. A substrate on which a thin film transistor is formed is a liquid crystal panel, which has a portion for forming a pixel in a central portion and a portion for forming a drive circuit in a peripheral portion extending in a strip shape in the XY axis directions. Then, the laser beam that anneals the peripheral portion extending in a band shape in the XY axis directions is composed of a linear component extending in the X axis direction and a linear component extending in the Y axis direction at the peripheral portion width by the Fourier transform phase hologram. The laser beam angle with respect to the substrate is changed by combining the shape or the X-axis component and the Y-axis component that cross the necessary widths of both the peripheral portions extending in the XY-axis direction in a strip shape, and / or shaping it into an inclined shape. Without moving the X-axis without moving the X-axis.
A laser annealing method characterized in that a peripheral portion extending in a band shape in the Y-axis direction is annealed. 5. A liquid crystal panel as a substrate on which a thin film transistor is formed, which has a portion for forming a pixel in the central portion and a portion for forming a drive circuit in a peripheral portion extending in a strip shape in the XY axis directions. Then, the laser beam that anneals the peripheral portion extending in a band shape in the XY axis directions is L-shaped by the Fourier transform type phase hologram and is composed of a linear component parallel to the X axis and a linear component parallel to the Y axis of the peripheral portion. A laser annealing method characterized in that the laser beam is shaped into a fine line beam, the beam is scanned in an oblique direction with respect to the XY axes, and a peripheral portion extending in a band shape in the XY axis directions is annealed. 6. The laser annealing method according to claim 4, wherein the laser beam for annealing the portion forming the pixel comprises a spot beam array corresponding to the pixel pitch.