CN100508170C - Method for forming polysilicon thin film device - Google Patents

Abstract

The invention discloses a method for forming a polycrystalline silicon thin film device, which comprises the following steps: providing a substrate; forming a polysilicon film on the substrate, wherein the polysilicon film has a plurality of silicon crystal grains arranged towards a grain growth direction; forming a plurality of thin film transistors, wherein each thin film transistor is provided with a channel region which is formed by a part of the polycrystalline silicon thin film; wherein at least one channel region has an equivalent parallel channel region with a channel direction parallel to the grain growth direction and an equivalent vertical channel region with a channel direction perpendicular to the grain growth direction. The invention provides a method for forming a polysilicon thin film device, which enables a thin film transistor on the polysilicon thin film device to present better electrical characteristic uniformity through the design of a channel region.

Description

Method for forming polysilicon thin film device

technical field

The present invention relates to a method for forming a polysilicon thin film device, in particular to a method for enabling a thin-film transistor (TFT) on a polysilicon thin film device to exhibit better electrical uniformity through the design of a channel region.

Background technique

In the semiconductor process, since the amorphous silicon (amorphous silicon) thin film can be formed on the glass substrate in a low temperature environment, the amorphous silicon thin film transistor is currently widely used in the field of liquid crystal displays. However, the mobility of electrons in amorphous silicon thin films is slower than that in crystalline silicon thin films, which makes amorphous silicon thin film transistor liquid crystal displays exhibit longer response times, and also limits their application in large-size panels. Therefore, both the industry and academia are devoted to the research and development of transforming low-temperature amorphous silicon thin films into polysilicon thin films by laser annealing, and producing polysilicon thin films with large-sized crystal grains.

The polysilicon film formed by sequential lateral solidification (SLS) has good periodic grain boundary arrangement. FIG. 1A is a schematic diagram of an existing system for forming a polysilicon thin film using continuous lateral solidification (SLS), which mainly includes: a laser generator 11 to generate a laser beam 12; and a photomask 13 arranged on the laser beam 12 On the traveling path, there are a plurality of light-transmitting regions 13a and a plurality of light-impermeable regions 13b above the mask. Each of the plurality of light-transmitting regions 13a is a strip region with a width W. The laser beams 12 passing through the plurality of light-transmitting regions 13a irradiate the amorphous silicon film 15 on the substrate 14 below the mask 13, so that a plurality of strips with a width of W on the amorphous silicon film 15 irradiated by the laser beam 12 Region 15a is melted. After removing the laser beam 12, each of the plurality of elongated regions 15a starts to solidify from both sides, and produces a main grain boundary (primary grain boundary) 16 parallel to the long side of the elongated region 15a in the elongated region 15a to form a polysilicon film with a grain length of 1/2W, as shown in FIG. 1B .

US Pat. No. 6,908,835 and No. 6,726,768 respectively disclose methods for forming polysilicon thin films by continuous lateral solidification by multiple laser irradiations, so as to provide larger-sized crystal grains.

However, the polysilicon film formed by continuous lateral solidification has a specific grain growth direction and periodic grain boundary arrangement. The electrical characteristics of the thin film transistor formed by the polysilicon film are mainly determined by the number of grain boundaries and the arrangement of the grain boundaries that the current passes through the channel. Different channel direction designs will make the current in the channel vertical or parallel to the grain growth direction, resulting in great electrical differences among thin film transistors formed on the same substrate with the same component parameters. Such electrical non-uniformity is particularly conspicuous for polysilicon thin-film devices (such as liquid crystal displays) that employ a large number of thin-film transistors with different channel directions.

To solve this deficiency, Jung proposed a method of manufacturing liquid crystal displays in US Patent No. 6,521,473, which uses a photomask 23 as shown in Figure 2A to form a 45-degree angle different from traditional lateral crystallization by a continuous lateral solidification process The polysilicon film 25 in the crystallographic direction is shown in FIG. 2B. Therefore, regardless of whether the transistor 27 is laid out horizontally or vertically, the current direction in the component channel will be at an angle of 45 degrees to the grain growth direction, so that the transistor component exhibits uniform electrical characteristics. However, the above-mentioned method will result in the inability to achieve crystallization in some areas of the panel, resulting in a decrease in the available area on the panel, which indirectly affects the throughput efficiency. Therefore, in order to overcome the lack of the above-mentioned technology, there is an urgent need for a method of forming a polysilicon thin film device. Through the design of the channel region, the thin film transistors on the polysilicon thin film device exhibit better uniformity in electrical characteristics.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for forming a polysilicon thin film device. Through the design of the channel region, the thin film transistors on the polysilicon thin film device exhibit better uniformity of electrical characteristics.

To achieve the above object, the present invention provides a method for forming a polysilicon film, comprising the following steps: providing a substrate; forming a polysilicon film on the substrate, wherein the polysilicon film has a plurality of silicon crystal grains arranged in a grain growth direction and forming a plurality of thin film transistors, each of the plurality of thin film transistors has a channel region formed with a part of the polysilicon film; wherein at least one channel region has a channel direction parallel to the grain growth direction, etc. an effective parallel channel region, and an equivalent vertical channel region whose channel direction is perpendicular to the grain growth direction.

Preferably, the polysilicon film has a plurality of major grain boundaries perpendicular to the grain growth direction and a plurality of minor grain boundaries parallel to the grain growth direction.

Preferably, the polysilicon film is formed by sequential lateral solidification (SLS) by at least one laser irradiation.

Preferably, the channel area is L-shaped, multiple L-shaped, fan-shaped or circle-shaped.

Preferably, the polysilicon thin film device is a liquid crystal display, a display driving circuit or a display pixel circuit.

By adopting the method for forming a polysilicon thin film device provided by the present invention, the thin film transistors on the polysilicon thin film device exhibit better electrical characteristic uniformity through the design of the channel region.

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments, but not as a limitation of the present invention.

Description of drawings

1A is a schematic diagram of a conventional system for forming a polysilicon thin film using continuous lateral solidification (SLS);

FIG. 1B is a top view of a polysilicon film formed by the system for forming a polysilicon film in FIG. 1A;

2A is a top view of a photomask used in a continuous lateral curing (SLS) process in US Patent No. 6,521,473;

FIG. 2B is a polysilicon film and transistor layout formed in US Patent No. 6,521,473;

3 is a top view of the transistor layout of the method for forming a polysilicon thin film device according to the first embodiment of the present invention;

4 is a top view of the transistor layout of the method for forming a polysilicon thin film device according to the second embodiment of the present invention;

5 is a top view of the transistor layout of the method for forming a polysilicon thin film device according to the third embodiment of the present invention; and

FIG. 6 is a top view of a transistor layout of a method for forming a polysilicon thin film device according to a fourth embodiment of the present invention.

11: Laser generator 12: Laser beam

13: Mask 13a: Translucent area

13b: Opaque area 14: Substrate

15: Amorphous silicon film 15a: Strip area

16: Main grain boundary 23: Mask

25: Crystalline silicon film 27: Transistor

35: Polysilicon film 36: Grain

361: Primary grain boundary 362: Secondary grain boundary

37: Transistor 371: First electrode

372: Second electrode 373: Channel area

CH _L equivalent parallel channel area CH _H : equivalent vertical channel area

45: Polysilicon film 47: Transistor

471: First electrode 472: Second electrode

473: Channel area CH _L : Equivalent parallel channel area

CH _H1 : Equivalent Vertical Channel Area CH _H2 : Equivalent Vertical Channel Area

55: Polysilicon film 57: Transistor

571: First electrode 572: Second electrode

573: channel area 65: polysilicon film

67: Transistor 671: First electrode

672: Second electrode 673: Channel area

Detailed ways

Below in conjunction with accompanying drawing, the feature, object and function of the present invention are described as follows.

In the present invention, a method for forming a polysilicon thin film device is disclosed. Through the design of the channel region, the thin film transistors on the polysilicon thin film device exhibit better electrical characteristic uniformity.

As shown in FIG. 3 , it is a top view of the transistor layout of the method for forming a polysilicon thin film device according to the first embodiment of the present invention. In the first specific embodiment, the method includes the following steps: providing a substrate (not shown in the figure); forming a polysilicon film 35 on the substrate, wherein the polysilicon film has a plurality of silicon crystals arranged in a grain growth direction grain 36; and form a plurality of thin film transistors 37, each of which has a channel region 373, and the channel region 373 is formed by a part of the polysilicon film; wherein at least one channel region 373 has a channel direction parallel An equivalent parallel channel region _CHL in the grain growth direction and an equivalent vertical channel region CHH in which the channel direction is perpendicular to the grain growth direction.

In this specific embodiment, the polysilicon film 35 has a plurality of primary grain boundaries 361 perpendicular to the grain growth direction and a plurality of secondary grain boundaries 362 parallel to the grain growth direction.

In this specific embodiment, the polysilicon film 35 is formed by sequential lateral solidification (SLS) by at least one laser irradiation.

In practical applications, the first electrode 371 and the second electrode 372 in FIG. 3 form a source/drain pair.

In the present invention, besides the L-shape (as shown in the first embodiment above), the channel area can also be multiple L-shape. Please refer to FIG. 4 , which is a top view of the transistor layout of the method for forming a polysilicon thin film device according to the second embodiment of the present invention. In the second specific embodiment, a plurality of thin film transistors 47 are also formed on the polysilicon film 45, and each of the plurality of thin film transistors has a channel region 473, and the channel region 473 is formed by a part of the polysilicon film; wherein at least A channel region 473 has an equivalent parallel channel region CH _L whose channel direction is parallel to the grain growth direction, a first equivalent vertical channel region CH H1 whose channel direction is perpendicular to the grain growth direction, and a first equivalent vertical channel region CH _H1 whose channel direction is perpendicular to the grain growth direction. The second equivalent vertical pass region CH _H2 in the growth direction. In addition, in practical applications, the first electrode 471 and the second electrode 472 in FIG. 4 form a source/drain pair.

It should be noted that although the present invention is described by the above-mentioned first and second specific embodiments, it is not limited thereto. Those having ordinary skill in the art can suggest other changes without departing from the scope of the present invention.

For example, as shown in FIG. 5 , it is a top view of the transistor layout of the method for forming a polysilicon thin film device according to the third embodiment of the present invention. In the third specific embodiment, a plurality of thin film transistors 57 are also formed on the polysilicon film 55, and each of the plurality of thin film transistors has a channel region 573, and the channel region 573 is formed by a part of the polysilicon film; wherein at least A channel area 573 is fan-shaped. The fan-shaped channel region 573 is formed by an equivalent parallel channel region CH _L whose channel direction is parallel to the grain growth direction, and an equivalent vertical channel region CH _H whose channel direction is perpendicular to the die growth direction.

In addition, in practical applications, the first electrode 571 and the second electrode 572 in FIG. 5 form a source/drain pair.

FIG. 6 is a top view of the transistor layout of the method for forming a polysilicon thin film device according to the fourth embodiment of the present invention. In the fourth specific embodiment, a plurality of thin film transistors 67 are also formed on the polysilicon film 65, and each of the plurality of thin film transistors has a channel region 673, and the channel region 673 is formed with a part of the polysilicon film; at least one of them The channel area 673 is in the shape of a circle. The ring-shaped channel region 673 is formed by an equivalent parallel channel region CH _L whose channel direction is parallel to the grain growth direction, and an equivalent vertical channel region CH _H whose channel direction is perpendicular to the die growth direction.

In addition, in practical applications, the first electrode 671 and the second electrode 672 in FIG. 6 form a source/drain pair.

The polysilicon thin film device formed by the method of the present invention can be not only a liquid crystal display, but also a driving circuit of a display or a pixel circuit of a display. Likewise, the application field of the polysilicon thin film device of the present invention is not limited thereto. Those having ordinary skill in the art can suggest other changes without departing from the scope of the present invention.

To sum up, the present invention provides a method for forming a polysilicon thin film device, through the design of the channel region, the thin film transistors on the polysilicon thin film device exhibit better uniformity of electrical characteristics.

Certainly, the present invention also can have other multiple embodiments, without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding Changes and deformations should belong to the scope of protection of the appended claims of the present invention.

Claims (10)

1. A method for forming a polysilicon thin film device, comprising the following steps: providing a substrate; forming a polysilicon film on the substrate, wherein the polysilicon film has a plurality of silicon grains arranged in a grain growth direction; forming a plurality of thin film transistors, each of the plurality of thin film transistors has a channel region, and the channel region is formed by a part of the polysilicon film; At least one channel region has an equivalent parallel channel region whose channel direction is parallel to the crystal grain growth direction, and an equivalent vertical channel region whose channel direction is perpendicular to the crystal grain growth direction. 2. The method for forming a polysilicon thin film device according to claim 1, wherein the polysilicon film has a plurality of major grain boundaries perpendicular to the grain growth direction and a plurality of minor grain boundaries parallel to the grain growth direction Grain boundaries. 3. The method for forming a polysilicon thin film device as claimed in claim 1, wherein the polysilicon thin film is formed by continuous lateral solidification by at least one laser irradiation. 4. The method for forming a polysilicon thin film device as claimed in claim 1, wherein the channel region is L-shaped. 5. The method for forming a polysilicon thin film device as claimed in claim 1, wherein the channel region is in a multiple L-shape. 6. The method for forming a polysilicon thin film device as claimed in claim 1, wherein the channel region is fan-shaped. 7. The method for forming a polysilicon thin film device as claimed in claim 1, wherein the channel region is in a ring shape. 8. The method for forming a polysilicon thin film device as claimed in claim 1, wherein the polysilicon thin film device is a liquid crystal display. 9. The method for forming a polysilicon thin film device as claimed in claim 1, wherein the polysilicon thin film device is a driving circuit of a display. 10. The method for forming a polysilicon thin film device as claimed in claim 1, wherein the polysilicon thin film device is a pixel circuit of a display.

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