JP2003332236A - Method and device for crystallizing semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the throughputs of a method and device for crystallizing semiconductor even when a CW solid-state laser is used. <P>SOLUTION: The device for crystallizing semiconductor is provided with a plurality of laser sources 71 and 72, a focusing optical system 73, and a synthesizing optical system 74 which leads the laser beams emitted from the laser sources 71 and 72 to the focusing optical system 73. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a semiconductor crystallization method and apparatus.

[0002]

2. Description of the Related Art A liquid crystal display device includes an active matrix driving circuit including a TFT. The system liquid crystal display device also includes an electronic circuit including a TFT in a peripheral region around the display region. Low-temperature poly-Si is a TFT of a liquid crystal display device and a TFT of an electronic circuit in a peripheral area of a system liquid crystal display device.
Suitable for forming. Further, low-temperature poly-Si is expected to be applied to a pixel driving TFT in an organic EL and an electronic circuit in a peripheral area of the organic EL. The present invention relates to a semiconductor crystallization method and apparatus using a CW laser (continuous oscillation laser) for manufacturing a TFT with low-temperature poly-Si.

In order to form a TFT of a liquid crystal display device using low temperature poly-Si, conventionally, an amorphous silicon film is formed on a glass substrate, and the amorphous silicon film on the glass substrate is irradiated with an excimer pulse laser to form an amorphous film. The crystalline silicon was crystallized.
Recently, a crystallization method has been developed in which an amorphous silicon film on a glass substrate is irradiated with a CW solid laser to crystallize the amorphous silicon.

In the crystallization of silicon by the excimer pulse laser, the mobility is about 150 to 300 (cm ² / Vs), whereas in the crystallization of silicon by the CW laser, the mobility is 400 to 600 (cm). ² / Vs) can be realized, and it is particularly advantageous for forming a TFT of an electronic circuit in the peripheral area of the system liquid crystal display device.

In crystallization of silicon, the silicon film is scanned with a laser beam. In this case, a substrate having a silicon film is mounted on a movable stage, and scanning is performed while moving the silicon film with respect to a fixed laser beam.
As shown in FIG. 10, in the excimer pulse laser,
For example, it is possible to scan with a laser beam having a beam spot X of 27.5 cm × 0.4 mm, and a beam width of 27.
When scanning is performed at 5 cm and a scan speed of 6 mm / s, the area scan speed is 16.5 cm ² / s.

On the other hand, as shown in FIG. 11, in the CW solid state laser, for example, the laser power is 10 W, the width of the beam spot Y is about 400 μm, and the scanning speed is 50.
When scanning is carried out at cm / s, the effective melt width capable of good crystallization becomes 150 μm at the beam spot of 400 μm, so that the area scan speed is 0.75 cm ² / s. As described above, crystallization by the CW solid-state laser makes it possible to obtain high-quality polysilicon, but has a problem of low throughput.

[0007]

Crystallization by a CW solid-state laser makes it possible to obtain high-quality polysilicon, but it has a problem that the area scan speed is low and the throughput cannot be sufficiently increased.

It is an object of the present invention to provide a semiconductor crystallization method and apparatus capable of increasing the throughput even when a CW solid state laser is used.

[0009]

According to the semiconductor crystallization method of the present invention, a semiconductor crystal of a substrate is irradiated with laser beams emitted from a plurality of laser sources through a focus optical system to melt and crystallize the semiconductor film. Method,
The plurality of laser beams are irradiated onto the substrate without overlapping each other, and scan the semiconductor film in parallel with each other, and the melting traces are positioned so as to overlap each other.

The semiconductor crystallization method according to the present invention is
A semiconductor crystallization method of irradiating a semiconductor film of a substrate with laser beams emitted from a plurality of laser sources through a focus optical system to melt and crystallize the semiconductor films, which is formed by laser beams emitted from the laser sources. The plurality of beam spots are characterized in that they overlap each other at least at a part thereof.

Further, the semiconductor crystallization apparatus according to the present invention is
A plurality of laser sources, a focus optical system, and a combining optical system that guides laser beams emitted from the plurality of laser sources to the focus optical system are provided, and the combining optical system is disposed after the first laser source. A λ / 2 plate, a beam expander arranged after at least one of the first and second laser sources, and a polarization beam splitter for combining the laser beams emitted from the first and second laser sources. It is characterized by

According to these configurations, by irradiating the amorphous semiconductor of the substrate with the laser beams emitted from the plurality of laser sources through the focusing optical system, the beam spot to be emitted can be increased. Since the beam width increases and the melt width increases, the area scan speed increases even if the scan speed required to obtain high-quality polysilicon is constant. Thus, high quality polysilicon can be obtained with high throughput.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view showing a liquid crystal display device according to an embodiment of the present invention. The liquid crystal display device 10 is configured by inserting a liquid crystal 16 between a pair of glass substrates 12 and 14 facing each other. The electrodes and the alignment film are glass substrates 12, 14
Can be provided. One glass substrate 12 is T
It is an FT substrate, and the other glass substrate 14 is a color filter substrate.

FIG. 2 is a schematic plan view showing the glass substrate 12 of FIG. The glass substrate 12 has a display area 18 and a peripheral area 20 around the display area 18. Display area 18
Includes a large number of pixels 22. In FIG. 2, one pixel 22 is shown in a partially enlarged manner. The pixel 22 includes sub-pixel regions RGB of three primary colors, and each sub-pixel region RGB has T
The FT 24 is formed. The peripheral region 20 has a TFT (not shown), and the TFT in the peripheral region 20 is the display region 18
Are arranged more densely than the TFT 24.

The glass substrate 12 of FIG. 2 is a 15 type QXGA.
It constitutes a liquid crystal display device and has a size of 2048 × 153.
It has 6 pixels 22. 2048 pixels are arranged in the direction (horizontal direction) where the three primary color sub-pixel regions RGB are arranged,
The number of sub-pixel areas RGB is 2048 × 3. 1536 pixels are arranged in a direction (vertical direction) perpendicular to the direction (horizontal direction) in which the sub-pixel regions RGB of the three primary colors are arranged. In the semiconductor crystallization described later, the peripheral region 2
At 0, laser scanning is performed in the direction parallel to each side, and at the display area 18, laser scanning is performed in the direction of arrow A or arrow B.

The reason is that the TFTs are densely arranged in the A and B directions and the TFTs are sparsely arranged in the direction perpendicular to the A and B directions. This is because the number of laser scans is smaller and the throughput is higher.

FIG. 3 is a schematic plan view showing a mother glass 26 for making the glass substrate 12 of FIG. The mother glass 26 is adapted to collect a plurality of glass substrates 12. In the example shown in FIG. 3, one mother glass 26 to 4
It is designed to collect two glass substrates 12, but 1
It is also possible to collect four or more glass substrates 12 from one mother glass 26.

FIG. 4 shows the TFT 24 of the glass substrate 12 of FIG.
6A and 6B are diagrams showing a process of forming a TFT in the peripheral region 20. In step S1, an insulating film and an amorphous silicon film are formed on the glass substrate. In step S2, the amorphous silicon film is crystallized to become polysilicon. In step S3, a necessary silicon portion such as a silicon portion to be a TFT is left, and unnecessary portions of the polysilicon and the amorphous silicon film are removed to perform TFT separation.
In step S4, a gate electrode, a drain electrode, an interlayer insulating film, a contact hole, etc. are formed. In step S5, an insulating film and an ITO film are further formed,
The glass substrate 12 is completed. The ITO film serves as a pixel electrode forming the pixel 22.

FIG. 5 is a diagram showing a state where an amorphous silicon film (semiconductor film) is crystallized by a laser beam.
The amorphous silicon film 36 is formed on the glass substrate 12 with an insulating film such as SiO ₂ sandwiched between the glass substrate 12 and XY.
XY with vacuum chuck and mechanical stopper of stage 38
It is fixed to the stage 38. The amorphous silicon film 36 is irradiated with the laser beam LB, the XY stage 38 is moved in a predetermined direction, and scanning is performed. First, the amorphous silicon 36 in the peripheral region 20 of the glass substrate 12 is focused and irradiated with a laser beam to melt and solidify the amorphous silicon and crystallize it into polysilicon. Then, the amorphous silicon in the display region 18 of the glass substrate 12 is focused and irradiated with a laser beam to melt and solidify the amorphous silicon and crystallize it into polysilicon. The reason is that when performing laser scanning by crossing, when crystallizing with a weak laser light corresponding to the display area after crystallizing with a strong laser light like the peripheral area, the crystallinity of the crossing part is strong This is because crystallization by intense laser light becomes insufficient in the reverse order. This is because if it is amorphous and well crystallized to some extent, light absorption becomes small.

The TFT in the peripheral area 20 is the TFT in the display area 18.
Since they are arranged more closely than the FT 24, high quality polysilicon is required. Therefore, the laser scanning of the peripheral region 20 is performed with a laser beam having a relatively high power at a relatively low scanning speed, and the TFT 24 in the display region 18 does not need to be polysilicon of such high quality. A relatively low-power laser beam (or a sub-beam obtained by dividing the laser beam) is used at a relatively high scanning speed.

FIG. 6 is a diagram showing a laser device 70 used for crystallizing the semiconductor in the peripheral region 20. Laser device 7
0 is used with the XY stage 38 of FIG. 5 for crystallization. The laser device 70 has two laser sources (continuous oscillation (CW) laser oscillators) 71 and 72, a common focus optical system 73, and a laser beam LB emitted from the two laser sources 71 and 72 to the focus optical system 73. And a synthetic optical system 74 for guiding.

The focus optical system 73 has a lens 75 having a substantially semi-cylindrical shape, a lens 76 having a substantially semi-cylindrical shape arranged so as to be orthogonal to the lens 75, and a convex lens 7.
It consists of 7. The focus optical system 73 causes the beam spot of the laser beam LB to have an elliptical shape.

The combining optical system 74 includes a λ / 2 plate 78 disposed after the first laser source 71, a beam expander 79 disposed after the second laser source 72, and first and second laser beams. The polarization beam splitter 80 is configured to combine the laser beams LB emitted from the laser sources 71 and 72. 81 is a mirror.

In this way, the laser beam LB emitted from the plurality of laser sources 71, 72 is constituted by the combining optical system 74,
The combined laser beam LB is applied to the amorphous semiconductor 36 of the glass substrate 12 through the focus optical system 73 to crystallize the amorphous semiconductor 36. Beam expander 79
Is for adjusting the divergence angle of the laser beam LB.
That is, the laser beams L of the plurality of laser sources 71, 72
If the divergence angle of B is uneven, even if one of the laser beams LB is focused by the focus optical system 73, the other laser beam LB may not be focused, so the beam expander 79 causes the laser beam LB. The two laser beams LB are brought into focus by adjusting the divergence angle. The beam expander 79 may be arranged in the optical path of the other laser beam LB. Alternatively, they may be arranged on both optical paths of the two laser beams.

The laser beams LB emitted from the first and second laser sources 71 and 72 are vertically linearly polarized light, and the laser beams LB emitted from the first laser source 71 are polarized by the λ / 2 plate 78. The plane is rotated by 90 degrees and becomes a horizontally linearly polarized light. Therefore, λ / 2 is emitted from the first laser source 71.
Laser beam LB passing through plate 78 and second laser source 7
The laser beam LB emitted from 2 is the polarization beam splitter 8
0 is introduced, and the two laser beams LB are almost overlapped with each other and travel toward the amorphous semiconductor 36. The manner of change of the linearly polarized light is shown in more detail in FIG.

Each laser beam LB is focused by the focus optical system 7.
An elliptical beam spot is formed through 3. Figure 8
As shown in FIG. 5, the beam spots of the combined laser beam LB are formed so that the beam spots of the individual laser beams LB overlap with each other, forming a cocoon-shaped beam spot BS. This is achieved, for example, by slightly shifting either angle of the mirror 81. That is,
Laser beam L emitted from a plurality of laser sources 71, 72
Each of B forms an elliptical beam spot, and the plurality of elliptical beam spots overlap each other in the major axis direction.

In the example, SiO ₂ is plasma CVD
Was formed on the glass substrate 12 to a thickness of 400 nm, and amorphous silicon 36 was formed thereon to a thickness of 100 nm by plasma CVD. The laser uses a continuous wave of Nd: YV04 solid-state laser. In one example, when using a single laser source, laser power of 10 W, 400 μm × 2
A beam spot of 0 μm is formed. With a single laser source, an area scan of 200 cm ² / s can be achieved by scanning with a laser width of 400 μm and a scan speed of 50 cm / s. Then, of the laser irradiation width of 400 μm, the stripe-shaped portion of the amorphous semiconductor 36 having a width of 150 μm is well melted and crystallized, and exhibits a flow type grain boundary. TF is formed in the polysilicon region composed of this flow type grain boundary.
When T is made, high mobility characteristics with a mobility of 500 (cm ² / Vs) can be obtained.

Two laser sources 7 as shown in FIG.
The beam spot of the laser beam LB emitted from 1, 72 and combined is 600 μm × 20 μm. When the laser power is 10 W, the spot width is 600 μm, and the scanning speed is 50 cm / s, the laser irradiation width is 600 μm.
Of m, a stripe-shaped portion of the amorphous semiconductor 36 having a width of 350 μm was particularly well melted and crystallized, and a region showing a flow type crystal grain boundary was obtained. The high quality crystallized 350 μm wide stripes were more than twice as large as the high quality crystallized 150 μm wide stripes using a single laser source. That is, the mutual heating of the two beam spots allowed expansion of the beam spot size and the effective melt width (width of high quality crystallized).

FIG. 7 is a diagram showing a modification of the laser device 70. The laser device 70A of FIG. 7 includes two units of optical system. The optical system of each unit includes the same optical members as the laser device 70 of FIG. The optical system of the first unit is shown in FIG.
The subscript a is attached to the numeral representing the optical member, and the subscript b is attached to the numeral representing the optical member in FIG. 6 in the optical system of the second unit. The beam expander 79 can be provided as appropriate.

The optical systems of the two units are arranged close to each other,
A beam spot BS formed by a two-unit optical system is arranged so as to be displaced in a direction perpendicular to the scanning direction and a direction parallel to the scanning direction. In this configuration, 350μ each
The effective melt width region of m was arranged so that the traces of the scan had an overlap of 50 μm, and the effective melt width was 650 μm.

FIG. 9 is a diagram showing another example of the beam spot. The three beam spots BS are arranged so as to be displaced in a direction perpendicular to the scanning direction and a direction parallel to the scanning direction.
The three beam spots are displaced from each other in the scanning direction and are irradiated onto the substrate without overlapping each other. However,
The three beam spots scan the semiconductor film in parallel with each other, and when viewed in the scanning direction, the three beam spots are overlapped and positioned so that their melting widths (melt widths) overlap each other. Also, three or more beam spots BS
Can be displaced in a direction perpendicular to the scanning direction and a direction parallel to the scanning direction.

[0033]

As described above, according to the present invention,
Throughput can be increased even when a CW solid-state laser is used.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a schematic plan view showing the glass substrate of FIG.

FIG. 3 is a schematic plan view showing a mother glass for making the glass substrate of FIG.

4 is a TFT of the glass substrate of FIG. 2 and TF of a peripheral region.
It is a figure which shows the process of forming T.

FIG. 5 is a diagram showing crystallization of a semiconductor film by a laser beam.

FIG. 6 is a diagram showing a laser device used for crystallizing a semiconductor in a peripheral region.

FIG. 7 is a diagram showing a modification of the laser device.

FIG. 8 is a diagram showing an example of a beam spot.

FIG. 9 is a diagram showing an example of a beam spot.

FIG. 10 is a diagram illustrating a crystallization method using a conventional excimer pulse laser.

FIG. 11 is a diagram illustrating a crystallization method using a conventional CW laser.

[Explanation of symbols]

12, 14 ... Glass substrate 16 ... Liquid crystal 18 ... Display area 20 ... Peripheral area 22 ... Pixel 24 ... TFT 26 ... Mother glass 30 ... CW laser oscillator 36 ... Amorphous silicon film 73 ... Focus optical system 74 ... Synthetic optical system 78 ... λ / 2 plate 79 ... Beam expander 80 ... Polarizing beam splitter

Continued front page    (72) Inventor Tatsuya Utsuka             2-14-1, Nishiwaseda, Shinjuku-ku, Tokyo Stock             Ceremony Company Japan Laser F-term (reference) 5F052 AA02 BA02 BA07 BA11 BA13                       BB02 BB04 BB07 CA10 DA02                       DB03 FA00 JA01

Claims (3)

[Claims] 1. A semiconductor crystallization method for irradiating a semiconductor film of a substrate with laser beams emitted from a plurality of laser sources through a focus optical system to melt and crystallize the semiconductor film, wherein the plurality of laser beams are mutually A method for crystallizing a semiconductor, characterized in that the semiconductor films are irradiated without overlapping, and the semiconductor films are scanned in parallel with each other, and melting traces thereof are positioned so as to overlap with each other. 2. A semiconductor crystallization method for irradiating a semiconductor film of a substrate with laser beams emitted from a plurality of laser sources through a focus optical system to melt and crystallize the semiconductor films, the laser emitting from the laser sources. A semiconductor crystallization method, wherein a plurality of beam spots formed by a beam overlap each other at least at a part thereof. 3. A plurality of laser sources, a focus optical system, and a combining optical system for guiding a laser beam emitted from the plurality of laser sources to the focus optical system, wherein the combining optical system comprises a first laser. Λ / placed after the source
Two plates, a beam expander arranged after at least one of the first and second laser sources, and a polarization beam splitter for combining the laser beams emitted from the first and second laser sources. And a semiconductor crystallization device.