JPH11305258A - Method and device for manufacturing semiconductor crystal film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polycrystal film having large crystal grains over a large area allowed to be used for a liquid crystal display device with high productivity by moving the end face of a shielding plate at a crystal growth speed. SOLUTION: The shielding plate 402 is formed on the surface of a film 403 so as to shield laser beams 401. A fixed phase 403a and a liquid phase 403b are generated on the film 403 irradiated by laser beams 402 based on the laser beams 401 and the shielding plate 402 shielding the beams 401. At the time, the plate 402 is moved in the direction of an arrow 404 during the irradiation of laser beams 401. A boundary between the fixed phase 403a and the liquid phase 403b is moved in a similar direction 406 in accordance with the movement of the plate 402. Finally the plate 402 completely shields the beams 401. In order to obtain a polycrytal film having large crystal grains, it is important to synchronize the irradiation time of laser beams 401 with the movement of the plate 402. Namely the boundary 405 between the fixed phase 403a and the liquid phase 403b formed by a temperature gradation area due to the plate 402 is moved at a speed suited to crystal growth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor crystal film for forming a polycrystalline semiconductor film on a large area at a low temperature and an apparatus for manufacturing a semiconductor crystal film.

[0002]

2. Description of the Related Art Applied products using a polycrystalline semiconductor are receiving attention. In particular, liquid crystal display devices using polycrystalline silicon have been manufactured. Liquid crystal display devices have conventionally been manufactured using drive elements using amorphous semiconductors, but polycrystalline semiconductors have come to be used in order to realize low cost and high performance.

A polycrystalline semiconductor has less carrier traps in an element than an amorphous semiconductor, and is expected to have a higher speed and higher performance. In a liquid crystal display device, a display device integrated with a driving circuit, which cannot be realized by an amorphous semiconductor, can be obtained. The liquid crystal display device integrated with a driving circuit has a feature that a driving circuit for driving a pixel of the display device can be created simultaneously with a manufacturing process of a semiconductor element array in the pixel. Therefore, peripheral IC chips required for a liquid crystal display device using an amorphous semiconductor are not required.

[0004] Since a polycrystalline semiconductor has less carrier traps than an amorphous semiconductor, an element having high mobility can be obtained. In this sense, the shape can be reduced in the case of a polycrystalline semiconductor element while obtaining the same driving performance as an amorphous semiconductor. Therefore, high definition of a liquid crystal display device using a polycrystalline semiconductor can be realized. As described above, it can be understood that the use of a polycrystalline semiconductor can improve the performance of an applied product thereof.

A feature of the polycrystalline semiconductor is that it is composed of crystal grains and grain boundaries. The grain boundaries are almost amorphous, and are a main cause of carrier traps when considering device operation. Therefore, in order to further improve the performance of the polycrystalline semiconductor, it is necessary to control the size of the crystal grains. In the case of a polycrystalline film having large crystal grains, the number of crystal parts occupying the film increases, so that electrical characteristics can be improved.

A technique for forming a polycrystalline semiconductor film includes an annealing method using excimer laser irradiation (hereinafter referred to as ELA).
Law). This is a method in which an amorphous film is used to start polycrystallization using ELA. Next, a conventional method will be described with reference to FIG.

FIG. 1 shows an example of a method for manufacturing a polycrystalline film using the ELA method. Starting film 10 on substrate 101
2a is formed. A shielding plate 104 for blocking the laser beam 103 is provided on the film 102a at a distance d. Since the laser beam 103 is partially blocked by the shielding plate 104, the film 102a corresponding to the vicinity of the geometric edge of the shielding plate is divided into two regions. Further, the width of the shielding plate in the depth direction of the drawing is sufficiently larger than the width of the laser beam. Since the laser is not irradiated below the shielding plate 104, the film has a solid phase 102a, but has a liquid phase 105 in a region irradiated with the laser. Since a temperature gradient is generated between the solid phase 102a and the liquid phase 105 near the edge of the shielding plate 104, there is a region where the liquid phase is near the surface and the solid phase is on the substrate side as shown in FIG. .

In the region where the temperature gradient is generated by the shield plate 104, the solid phase 102a becomes a crystal nucleus and a crystal grows in the direction shown by the arrow. This crystal grows up to the boundary 106 between the laser beam irradiation area defined by the laser beam irradiation diameter and the part not irradiated. In this manner, a crystal grows by one irradiation of the laser beam 103. At this time, the boundary 106 corresponds to the above-described grain boundary of the polycrystalline film.

In the prior art, a polycrystalline film having large crystal grains is formed by continuously applying the method using the shielding plate 104 shown in FIG. 1 as shown in FIG. FIG. 2 is a view of the laser beam 201 and the shielding plate 202 viewed from the side.

[0010] As shown in FIG.
Reference numeral 1 denotes a film 203 partially shielded by a shielding plate 202.
a. A region 201a where the laser beam is blocked by the shielding plate and a portion 201b where the laser beam is not blocked are formed.
A solid phase 203a and a liquid phase 203b are formed near the edge of the shielding plate 202 because of the temperature gradient described with reference to FIG. In addition, a boundary 204 defined by the irradiation diameter of the laser beam 201 exists.

The laser beam 201 is applied to the film 20 in a pulsed manner.
Irradiate 3 FIG. 2B is a diagram showing a state in which the irradiation of the laser beam 201 has been completed. The boundary 205 between the solid phase 203a and the liquid phase 203b generated in FIG. 2A grows to form a grain boundary 206 shown in FIG. 2B, and the growth ends.

Next, as shown in FIG. 2C, a shielding plate 202 is set at a position where the grain boundary 206 formed in FIG.
Irradiate 01. As described with reference to FIG.
It grows to the position 207 to the right of the second laser irradiation.

By repeating the above steps, a large crystal is grown. In principle, the crystal can be made as large as possible, but in reality, the crystal growth is hindered by impurities in the film 203, defects formed in the solid phase at the boundary 205 between the solid phase and the liquid phase, and the like. Is formed. However,
As a result, a polycrystalline film having large crystal grains can be obtained.

The feature of the conventional example shown in FIG. 2 is that the shielding plate 202 moves during the intermittent laser beam irradiation. That is, after the irradiation of the laser beam 201 is completed,
The crystal growth proceeds to a certain distance, for example, 206 in FIG.
The shielding plate 202 moves, and the next irradiation of the laser beam 201 is performed. When the crystal grains are made large, it is necessary to move the shielding plate 202 so as to cancel a grain boundary generated by laser beam irradiation, for example, the boundary of 206 in FIG. 2B. Therefore, it is necessary to move the shielding plate according to the length of the crystal grown by one laser beam irradiation.

The crystal grown by a single laser beam irradiation depends on the temperature gradient generated by the shielding plate 202, which is at most 1 μm. In order to increase the size of crystal grains, it is necessary to move the shielding plate with a stepping of about 1 μm. Further, since it is necessary to surely erase a grain boundary formed by one irradiation at the time of the next laser beam irradiation, stepping accuracy is also required.

When a large-area polycrystalline semiconductor is required as in a liquid crystal display device, sufficient productivity cannot be obtained with such stepping dimensions and stepping accuracy. Further, as shown in FIG. 3, there is a method of substantially growing a crystal 302 by scanning a laser beam 301. FIG. 3A shows an initial state, and FIG. 3B shows a state in which a laser beam is scanned. This is mainly a method of realizing crystallization using an electron beam as a technique for crystallizing crystalline silicon. Similarly, a method of growing a crystal by scanning a laser beam 301 on a starting material exists as a conventional technique. In this case, the scanning speed of the laser beam needs to be as high as 10 m / s or more.

In this case, it is necessary to scan the laser beam accurately and at high speed. However, it is difficult to scan a large area laser beam with high accuracy and high speed as in a liquid crystal display device.

[0018]

In the conventional method for producing a polycrystalline film by laser beam irradiation, high-speed scanning of a laser beam at a crystal growth rate of 10 m / s or more cannot be performed accurately. In addition, a large-area film using a polycrystalline film having large crystal grains in a liquid crystal display device cannot be obtained with high productivity.

According to the present invention, there is provided a method for growing a polycrystalline film having a large crystal grain, such as that used for a TFT, with a high productivity over a large area, such as a liquid crystal display device. The purpose is to:

[0020]

In order to achieve the above object, a method of manufacturing a semiconductor crystal film according to claim 1 includes a step of forming a non-single-crystal semiconductor film on a substrate, and a step of forming the non-single-crystal semiconductor film on the substrate. Forming a solid-liquid interface for melting and regrowing the non-single-crystal semiconductor film by transmitting a part of the energy beam from an end face of the shield plate to grow a crystal, and wherein the crystal is grown. Is characterized in that the end face is moved at the crystal growth speed.

According to a second aspect of the present invention, there is provided an apparatus for manufacturing a semiconductor crystal film, comprising: a table capable of holding a substrate having a non-single-crystal semiconductor film formed on a surface thereof; An energy beam irradiating means capable of irradiating an energy beam for crystal growth by forming a solid-liquid interface where a part of the non-single-crystal semiconductor film melts and re-grows through an end face of the shielding plate. Wherein the end face of the shielding plate is moved at the crystal growth speed. In the method or apparatus for manufacturing a semiconductor crystal film as described above, the end face of the shielding plate moves at the crystal growth rate, so that the sharp end face of the energy beam transmitted from the end face of the shielding plate becomes solid-liquid interface at the crystal growth rate. Fine-grained speed control that enables high-speed movement while irradiating the camera has become possible.

According to a third aspect of the present invention, in the semiconductor crystal film manufacturing apparatus according to the second aspect, the shielding plate is a rotating body that rotates on the table. In particular, when rotating in a direction perpendicular to the crystal growth direction, a stable rotation speed of the rotating body can be used, and high-speed speed control can be ensured.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention uses a shielding plate capable of blocking an energy beam (including an energy beam such as an electron beam, but is hereinafter referred to as a laser beam as a representative). By the shield moving at high speed in the crystal growth direction within the laser beam irradiation time,
The main point is that the laser beam can be scanned at an accurate crystal growth rate because the taper moves at a high speed.

In addition, since the shielding plate is moved at a high speed, the productivity is improved over a large area such as used for a liquid crystal display device without requiring complicated optical considerations. A high polycrystalline film growth method can be realized.

A method for manufacturing a polycrystalline film according to the present invention will be described with reference to FIG. Shield plate 4 so as to block laser beam 401
02 is placed on the membrane 403. The solid phase 403a and the liquid phase 403b are applied to the film 403 irradiated with the laser beam by the laser beam 401 and the shielding plate 402 for blocking the laser beam 401.
Occurs. At this time, the shielding plate 402 is
It moves in the direction of arrow 404 during 01 irradiation. Solid phase 40
The boundary 405 between 3a and the liquid phase 403b moves in the same direction 406 in accordance with the movement of the shielding plate 402. FIG. 4B shows this state. The shielding plate 402 grows to the right side of FIG. Finally, the shielding plate 402 completely blocks the laser beam 401 as shown in FIG. At this time,
The crystal growth forms a grain boundary as indicated by 407 and ends. Therefore, the crystal grows to a size approximately equal to the length L of the laser beam 401. At this time, the length Ls of the shielding plate 402 needs to be longer than the length L of the laser beam 401.

In order to obtain a polycrystalline film having large crystal grains according to the present invention, it is important to synchronize the irradiation time of the laser beam 401 with the movement of the shielding plate 402. That is, the solid phase 403a and the liquid phase 4 formed by the temperature gradient region by the shielding plate 402
It is important that the boundary 405 with 03b moves at a speed suitable for crystal growth.

The laser beam length L and the shielding plate length Ls
The size relationship is also important. That is, it is necessary that L ≦ Ls. This means that, when L> Ls, the crystallized film 403 is again irradiated with the laser beam 401, and the phase changes from liquefaction to solidification, which causes the generation of grain boundaries. Therefore, the shielding plate 4 is used to prevent the once crystallized region from being irradiated with the laser beam 401 again.
02 needs to block the laser beam 401.

By performing polycrystallization under the above-described conditions, crystal grains substantially equal to the laser beam length L can be obtained. Since the laser beam length L can be made uniform at least about several μm, crystal grains of at least several μm can be obtained by one laser beam irradiation.

[0029]

(Embodiment 1) Next, a method for obtaining a polycrystalline silicon film in a large area for use in a liquid crystal display device will be described with reference to FIG. Amorphous silicon 502 on a substrate 501
Is deposited. As the laser beam 503, for example, Xe
A gas laser such as Cl or KrF is used. Optically, the length of the shape of the laser beam 503 is L, the width is W,
The fluence in this region is adjusted so as to be constant.
On the other hand, the shielding plate 504 is made of the amorphous silicon film 502.
Install at a more appropriate distance. At this time, the shielding plate 50
4, the length Ls and the width Ws of the laser beam 503 need to satisfy the conditions of L ≦ Ls and W ≦ Ws.

The shielding plate 504 is moved at a speed suitable for crystal growth so as to block the entire irradiation area of the laser beam 503. Assuming that the crystal growth rate is V, the irradiation time of the laser beam 503 needs to be L / V. As a result, a polycrystallized film 502a is formed at the portion where the shielding plate 504 has passed, corresponding to the irradiation area of the laser beam 503. By overlapping the grain boundaries of the obtained polycrystalline film so as to be irradiated again with the laser beam 503, the crystal grains can be further enlarged.

By repeating the above steps, the remaining amorphous silicon film 502b is also polycrystallized. The prior art requires stepping the laser beam irradiation and the movement of the shielding plate intermittently, and is not suitable for polycrystallization in a large area. In the present invention, crystallization efficiency is remarkably improved since crystal grains substantially equal to the laser beam shape capable of obtaining a uniform fluence are obtained. According to the present invention, the efficiency of polycrystallization is improved by moving the shielding plate in accordance with the crystallization speed. In the prior art, the laser irradiation intensity was modulated by a shielding plate to form a temperature gradient region, and the efficiency could not be improved because the region depended on crystal growth in this region. On the other hand, according to the present invention, the crystal growth portion, for example, 405 in FIG. 4 is moved in accordance with the crystal growth speed, so that the efficiency can be greatly improved.

(Embodiment 2) A second embodiment of the method of moving the shielding plate 504 shown in FIG. 5 will be described with reference to FIG. In order to move the shielding plate at high speed, mechanical wear or the like is considered. As a method for solving this, there is provided a method of rotating the shielding plate 601 about the rotation shaft 602 as shown in FIG. The laser beam is rotated in the direction shown in FIG. 6 so that the laser beam shape 603 can be blocked as shown in the first embodiment. Thus, as described with reference to FIG. 4, the film can be polycrystallized by synchronizing the rotation time with the laser beam irradiation time. In this case, the rotation shielding plate 601 and the laser beam sequentially proceed with polycrystallization so as not to lose their positional relationship.

FIG. 6B is a diagram for explaining conditions for defining the shape of the rotary shield 601 and the shape of the laser beam 603. The rotary shield plate 601 has a laser beam shape 603
Must be large enough to completely hide the image.

FIG. 7 shows a case where the rotary shield plate shown in FIG. 6 is provided on both sides of the laser beam. A rotary shield plate defined in FIG. 6 and a rotary shield plate 70 having a laser beam shape.
1 are provided on the left and right of the laser beam shape 702.

When the number of the rotary shield plate 701 is one, the end of the shield plate 703 is rotated as shown in FIG.
02, so that the crystal growth direction is
03 toward the normal direction 704. To avoid this,
By providing the rotation shielding plates 701 on both sides, the laser beam can be grown in the long side direction as shown in FIG. 7B.

[0036]

According to the present invention, the efficiency can be greatly improved by moving the crystal growth portion in accordance with the crystal growth speed. Thus, not only can a polycrystalline film having large crystal grains be easily obtained, but also a polycrystalline film can be efficiently obtained in a large area region.

[Brief description of the drawings]

FIG. 1 illustrates a conventional polycrystallization technique.

FIG. 2 illustrates the principle of a conventional polycrystallization technique.

FIG. 3 is an explanation of a conventional technique.

FIG. 4 illustrates the principle of the present invention.

FIG. 5 is an explanatory view of Embodiment 1 of the present invention.

FIG. 6 is an explanatory diagram of a high-speed moving shielding plate according to a second embodiment of the present invention.

FIG. 7 is an explanatory view of a high-speed moving shielding plate according to a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 501 substrate 502 amorphous silicon 503 laser beam 504 shielding plate

Claims (3)

[Claims] A non-single-crystal semiconductor film is formed on a substrate, and a part of an energy beam is transmitted through the non-single-crystal semiconductor film from an end face of a shield plate to melt and regrow the non-single-crystal semiconductor film. Forming a solid-liquid interface and growing a crystal, wherein the end face of the shielding plate is moved at the speed of the crystal growth. 2. A table capable of holding a substrate having a surface on which a non-single-crystal semiconductor film is formed, a shielding plate movable on the table while maintaining a constant interval, and a part of the shielding plate from an end face. An energy beam irradiating means capable of irradiating an energy beam for transmitting an energy beam for crystal growth by forming a solid-liquid interface through which the non-single-crystal semiconductor film melts and grows again, wherein the end face of the shielding plate Is an apparatus for manufacturing a semiconductor crystal film, wherein the semiconductor crystal film is moved at the crystal growth speed. 3. The apparatus according to claim 2, wherein the shielding plate is a rotating body that rotates on the table.