CN1892420B - Mask for continuous lateral solidification technology and method for forming polycrystalline silicon layer by using same - Google Patents

Abstract

The invention discloses a mask applied to a continuous transverse solidification technology, which is used for generating a polycrystalline silicon film with dispersed crystallization boundaries. The mask of the present invention comprises at least: a first region, a second region and a third region. The first area and the third area are transparent, and the second area is light-shielding. The first region surrounds the second region, and the first region and the second region have substantially the same peripheral shape. The third region and the first region have the same peripheral shape, and the third region, the first region and the second region are arranged in parallel in a predetermined direction. The invention has the advantages that the polysilicon patterns in at least two grain directions can be designed by utilizing the concept of pattern graph complementation on the mask, and the perfect grain boundary can be obtained by controlling the pattern area of a plurality of shading areas and light-transmitting areas on the mask.

Description

Mask for continuous lateral solidification technique and method for forming polysilicon layer using same

technical field

The invention relates to a mask used in polysilicon thin film technology, in particular to a mask for producing a polysilicon thin film with dispersed crystal boundaries by continuous lateral solidification technology, specifically a mask and the formed polysilicon.

Background technique

Thin Film Transistor (TFT) has been widely used in active liquid crystal displays, and the materials used in thin film transistors generally include amorphous silicon (amorphous-silicon) and polysilicon (poly-silicon).

In the manufacture of liquid crystal displays, polycrystalline silicon materials have many characteristics superior to amorphous silicon materials. For example, polysilicon has larger grains, and electrons are easy to move freely in polysilicon, so the electron mobility (mobility) of polysilicon is higher than that of amorphous silicon. The response time of polysilicon thin film transistors made of polysilicon is faster than that of amorphous silicon thin film transistors. In a liquid crystal display with the same resolution, the substrate area occupied by the polysilicon thin film transistor (poly-Si TFT) is smaller than that occupied by the amorphous silicon thin film transistor, which improves the aperture ratio of the liquid crystal panel. Under the same brightness, a liquid crystal display (poly-Si TFT LCD) using polysilicon thin film transistors can use a low-wattage backlight source to meet the requirements of low power consumption.

At present, most of the low temperature polysilicon (Low Temperature Poly-Silicon; LTPS) processes are used to produce polysilicon thin films on substrates. The low temperature polysilicon process uses an excimer laser (Excimer Laser) as a heat source. When laser light is irradiated on a substrate with an amorphous silicon film, the amorphous silicon film absorbs the energy of the excimer laser and transforms into a polysilicon film.

Sequential Lateral Solidification (SLS) technology is a polysilicon formation technology developed using excimer laser annealing. Use a laser to generate a laser with a specific shape through a mask. After the first laser crystallizes the laterally grown grains, the second laser irradiation overlaps with a part of the first crystallization area. By irradiating the amorphous silicon area, the second After the silicon film in the area irradiated by the second laser beam starts to melt, long columnar crystal grains will grow out of the first crystalline polysilicon film as a seed crystal.

FIG. 1A is a schematic side sectional view of a polysilicon thin film fabricated using a continuous lateral solidification method. As shown in FIG. 1A , an amorphous silicon film 11 is formed on a substrate 10 by chemical vapor deposition (CVD) or sputtering, and a mask 2 is disposed above the amorphous silicon film 11 . As shown in FIG. 1B , the mask 2 includes a plurality of elongated light-transmitting regions 21 and a plurality of elongated light-shielding regions 22′. A laser light source will step and scan in parallel to the direction parallel to the short axis of the long strip pattern in the light-transmitting region 21 and the light-shielding region 22, so as to step and irradiate different regions on the amorphous silicon film 11 to gradually obtain lateral growth. Polysilicon pattern.

FIG. 1C is a schematic diagram of the structure of the polysilicon pattern obtained through the mask 2 . The grain boundary 111 (grain boundary) obtained from the polysilicon obtained by the mask 2 is perpendicular to the direction of grain growth. According to the experimental results, it is shown that when the channel of the thin film transistor is parallel to the grain growth direction, the electrical performance is better. On the contrary, if the channel of the transistor is perpendicular to the grain growth direction, the electrical performance is poor. Therefore, the thin film transistor channels on the panel must be arranged in a single direction, which is very inconvenient for circuit design.

Therefore, how to solve the problem of circuit layout design affected by the crystallization direction encountered in the SLS process is one of the efforts of relevant practitioners.

Contents of the invention

The purpose of the present invention is to provide a polysilicon thin film mask, which can be applied to the continuous lateral solidification technology to produce a polysilicon thin film with dispersed crystal boundaries.

Another object of the present invention is to provide a mask applied to the continuous lateral solidification technique to produce polysilicon patterns with at least two grain orientations.

The invention provides a mask applied to the continuous lateral solidification technique to produce a polysilicon film with dispersed crystal boundaries. The mask of the present invention at least includes: a first area, a second area and a third area. Wherein the first area and the third area are light-transmitting, and the second area is light-shielding. The first area surrounds the second area, and the first area and the second area have substantially the same peripheral shape. The third area has the same peripheral shape as the first area, and is arranged parallel to the first area and the second area in a predetermined direction.

The present invention also provides a method for forming a polysilicon layer using a mask, characterized in that it comprises:

A laser crystallization process for the first time, providing a laser beam to scan an amorphous silicon film through the mask; changing the relative position of the mask and the scanning direction of the laser beam; and a second The laser crystallization process provides a laser beam to scan the amorphous silicon film through the mask; wherein, when the laser is irradiated on the irradiation area of the amorphous silicon film for the second time, it is along the The first region of the mask moves toward the third region.

In summary, the mask in the application of SLS technology disclosed by the present invention utilizes the concept of complementarity of patterns on the mask to design polysilicon patterns that can produce at least two grain directions, and by controlling the multi-silicon pattern on the mask The size of the pattern area of the light-shielding area and the light-transmitting area to obtain a perfect grain boundary.

Description of drawings

FIG. 1A is a schematic side sectional view of a polysilicon thin film manufactured using a continuous lateral solidification method;

FIG. 1B is a schematic front view of the mask used in FIG. 1A;

FIG. 1C is a schematic diagram of the polysilicon pattern structure obtained through the mask in FIG. 1B;

FIG. 2 is a schematic top view of a mask according to a preferred embodiment of the present invention;

3 is a schematic flow chart of forming a polysilicon layer in SLS technology using the mask disclosed by the present invention;

4A to 4B are schematic diagrams of polysilicon patterns formed by the mask in FIG. 2;

FIG. 4C is a schematic diagram of a polysilicon pattern channel configuration formed using the mask in FIG. 2;

5A to 5B are schematic diagrams of polysilicon patterns formed by the mask in FIG. 2;

FIG. 6 is a schematic diagram of the pattern of another preferred embodiment of the mask disclosed in the present invention;

7A to 7B are schematic diagrams of polysilicon patterns formed by the mask in FIG. 6;

FIG. 8 is a schematic diagram of another preferred embodiment of the mask disclosed in the present invention;

9A to 9B are schematic diagrams of polysilicon patterns formed by the mask in FIG. 8;

FIG. 10 is a schematic diagram of the pattern of another preferred embodiment of the mask disclosed in the present invention.

Explanation of main component symbols

10 Substrate 11 Amorphous silicon film 2 Mask

21 Translucent area 22 Shading area 111 Grain boundary

3 mask 31 first area 32 second area

33 third area 3a thin film transistor channel 3b gate line

4 mask 41 first area 42 second area

43 Third area 5 Mask 51 First area

52 Second area 53 Third area 6 Mask

61 The first area 62 The second area 63 The third area

64 Fourth Area 65 Fifth Area 66 Sixth Area

67 Seventh area 68 Eighth area

Detailed ways

The invention discloses a mask applied to continuous lateral solidification (SLS) to produce a polysilicon film with dispersed crystal boundaries. The mask of the present invention will be described in detail below with reference to the accompanying drawings and multiple specific embodiments.

FIG. 2 is a schematic top view of a mask according to a preferred embodiment of the present invention. The mask 3 in FIG. 2 at least includes: a first region 31 , a second region 32 , and a third region 33 . Wherein, the first area 31 and the third area 33 are light-transmitting, and the second area 32 is light-shielding.

The first region 31 surrounds the second region 32 , and the first region 31 and the second region 32 have substantially the same peripheral shape. The third region 33 has the same peripheral shape as the first region 31 , and in this embodiment, the peripheral shapes of the above three regions are rectangular structures. Moreover, the third area 33 is arranged parallel to the first area 31 and the second area 32 in a predetermined direction.

The mask of the present invention is applied in the continuous lateral solidification technique described in the prior art in FIG. 1A to achieve the purpose of producing a polysilicon film with dispersed crystal boundaries. FIG. 3 is a schematic flow chart of applying the mask disclosed by the present invention to form a polysilicon layer in SLS technology, at least including:

Step S301: providing a laser beam to scan through the first region 31 or the third region 33 of the mask 3 to perform a first laser crystallization process on an amorphous silicon film;

Step S302: Change the relative position of the mask 3 and the scanning direction of the laser beam. The method of changing the relative position of the mask 3 and the scanning direction of the laser beam includes: moving the mask 3 or moving the scanning direction of the laser beam. circumstances change;

Step S303: Provide a laser beam to scan through the mask 3 to perform a second laser crystallization process on the same amorphous silicon film. Wherein, the secondary irradiation of the laser on the irradiation area of the amorphous silicon thin film corresponds to step 301, moving along the first area 31 of the mask 3 to the third area 33, or moving from the third area 33 to the first area 31 .

FIG. 4A and FIG. 4B show the polysilicon film manufactured through the above-mentioned mask 3 and the process. FIG. 4A shows the polysilicon pattern present on the amorphous silicon film after the first laser crystallization process is completed in step S301. Since the molten crystalline silicon has the characteristic of growing crystal grains from a low temperature, a polycrystalline silicon pattern with dispersed grain boundaries as shown in FIG. 4A is formed. When the process enters the second laser crystallization process in step S303, and the light-shielding area and the light-transmitting area on the mask 3 are exactly opposite, the polysilicon pattern as shown in FIG. 4B will be completed.

In the above step S302, the relative positions of the mask 3 and the scanning direction of the laser beam are changed, and when the moving direction is moving along the direction from the first area 31 to the third area 33 of the mask 3, the result shown in FIGS. 4A to 4B can be obtained. polysilicon pattern; if it moves from the third region 33 to the direction of the first region 31, the polysilicon pattern as shown in Figure 5A to Figure 5B will be obtained. The mask pattern disclosed in the present invention is used to obtain grain boundary dispersion, at least For polysilicon patterns with crystal grains crystallized in two directions, no matter what the laser irradiation sequence is, as long as different regions are irradiated sequentially, the desired purpose of the present invention can be obtained.

The mask pattern designed in the present invention is to design different light-shielding areas and light-transmitting areas through the concept of similar figure complementarity. It is worth mentioning that in order to make the grain boundaries of the polysilicon pattern multi-directional and at the same time make the grain growth uniform and perfect, the size design of the mask pattern of the present invention is ingenious. Taking the mask 3 in FIG. 2 as an example, the area of the third area 33 is between the area of the first area 31 and the area of the second area 32 . This is to cause the laser to irradiate the light-transmitting area repeatedly when the position of the mask and the laser is moved in the first laser process and the second laser crystallization process. Since the boundary of the shading area of the second area 22 is a lower temperature area when the amorphous silicon melts, it will crystallize faster, resulting in an increase in the probability of poor crystal grain crystallization. Therefore, the laser repeatedly irradiates the light-transmitting area to remelt the local area to achieve Grain boundary growth is more perfect for the purpose.

The mask disclosed by the present invention can grow crystalline thin films in two directions, and can obtain uniform and good electrical properties in conjunction with double-gate thin film transistors. 4C is a schematic diagram of a TFT channel (channel) 3a and a gate line (gate line) 3b configured by using a mask 3 to form a polysilicon pattern.

The mask disclosed in the present invention is applied in the continuous lateral solidification technology to obtain a polysilicon film with dispersed crystal boundaries, and the shape of the pattern used on the mask is not limited. As long as the pattern design can simultaneously produce at least two directions and any frame shape can be applied to the mask pattern of the present invention. FIG. 6 and FIG. 8 are schematic diagrams of patterns of other two preferred embodiments of the mask disclosed in the present invention. Mask 4 among Fig. 6 comprises first area 41, second area 42 and the 3rd area 43, the design of relative position and optical characteristic are identical with above-mentioned mask 3, only the first area 41 of mask 4, the second area 42 and the third area 43 have a circular shape. The polysilicon pattern shown in FIGS. 7A-7B can be obtained by applying the mask 4 in the SLS process. Similarly, using the mask 5 in FIG. 8 , the outer shapes of the first region 51 , the second region 52 and the third region 53 are triangular, and the polysilicon pattern as shown in FIGS. 9A-9B can be obtained.

The number of light-shielding regions and light-transmitting regions in the mask pattern in the mask disclosed in the present invention is not limited. As long as the pattern design can produce at least two directions at the same time, multiple frames of the same shape can be applied to the mask pattern of the present invention. FIG. 10 is a schematic diagram of another preferred embodiment of the mask disclosed in the present invention. Mask 6 among Fig. 10 comprises: a first region 61, a second region 62, a third region 63, a fourth region 64, a fifth region 65, a sixth region 66, a seventh region 67 , and an eighth area 68 . Wherein the first area 61, the third area 63, the fourth area 64, the seventh area 67, and the eighth area 68 are light-transmitting areas; the second area 62, the fifth area 65, and the sixth area 66 are light-shielding areas, The basic peripheral shape of the above-mentioned area is a rectangle.

The design concept is the same as that of other embodiments, the difference in area size between each region of the pattern in the mask 6 is used to repeatedly irradiate the light-transmitting region with the laser. For example, the area of the sixth area 66 is between the area of the second area 62 and the area of the fourth area 64 , and the area of the eighth area 68 is between the area of the fourth area 64 and the area of the fifth area 65 .

Compared with the prior art, the mask applied in the SLS technology disclosed by the present invention has the following characteristics and advantages:

1. Utilizing the complementary concept of patterns on the mask to design polysilicon patterns that can produce at least two crystal grain directions.

2. By controlling the pattern size of multiple light-shielding areas and light-transmitting areas on the mask, perfect grain boundaries can be obtained.

The above detailed description is a specific description of the preferred embodiments of the present invention. The above embodiments are not intended to limit the scope of protection of the present invention. All equivalent implementations or changes that do not depart from the technology of the present invention should be included in the protection of this case. in range.

Claims (9)

1. A mask applied to continuous lateral solidification technology, characterized in that the mask is used to produce a dispersed polysilicon film with a crystal boundary, and the mask comprises: - the first area is transparent; a second region that is completely shaded, wherein said first region completely surrounds said second region, said first region and said second region have substantially the same peripheral shape; and a third area, which is transparent, has the same peripheral shape as the first area, and the third area is arranged in parallel with the first area and the second area in a predetermined direction, The area of the third area is between the area of the first area and the area of the second area. 2. The mask of claim 1, further comprising: A fourth area is transparent; wherein, the second area completely surrounds the fourth area, and the second area and the fourth area have the same peripheral shape. 3. The mask of claim 2, further comprising: A fifth area is completely light-shielding; wherein, the third area completely surrounds the fifth area, the third area has the same peripheral shape as the fifth area, and the The area of the fifth region is between the area of the second region and the area of the fourth region. 4. The mask of claim 3, further comprising: A sixth area is transparent; wherein, the fifth area completely surrounds the sixth area, and the fifth area and the sixth area have the same peripheral shape. 5. The mask according to claim 1, wherein the peripheral shapes of the first region and the second region are triangular. 6. The mask according to claim 1, wherein the peripheral shapes of the first region and the second region are circular. 7. The mask according to claim 1, wherein the peripheral shapes of the first region and the second region are oval. 8. The mask according to claim 1, wherein the peripheral shapes of the first region and the second region are rectangles. 9. A method for forming a polysilicon layer using a mask as claimed in claim 1, comprising: A first laser crystallization process, providing a laser beam to scan an amorphous silicon film through the mask; changing the mask and the scanning direction of the laser beam, moving either the mask or the scanning direction of the laser beam; and A second laser crystallization process, providing a laser beam to scan the amorphous silicon film through the mask; Wherein, when the laser light is irradiated on the irradiated area of the amorphous silicon film for the second time, it moves along the direction of the first area of the mask to the third area.

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