JPH10333185A - Semiconductor device and its manufacture, and tft type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the semiconductor device which can decrease a leak current and make variance of transistor characteristics small by stabilizing the boundary surface between a gate insulating film and a polycrystalline silicon film and is simple in manufacture process by forming an amorphous silicon film containing hydrogen between a polycrystalline silicon film and a gate insulating film. SOLUTION: A two-layered structure film is laminated on a glass substrate 1 in the order of the polycrystalline silicon film 13' and amorphous silicon film 13. Then the gate insulating film 15 is formed on the amorphous silicon film 13, a gate electrode 16 is formed on the gate insulating film 15, and an inter-layer insulating film 17 is formed on the gate electrode 16. A source-drain wire electrode 19 is connected to the amorphous silicon film 13 through the inter-layer insulating film 17. Namely, this semiconductor device has the boundary surface between the gate insulating film 15 and polycrystalline silicon film 13 stabilized with hydrogen that the amorphous silicon film 13 contains since the amorphous silicon film 13 containing the hydrogen is formed between the polycrystalline silicon film 13' and gate insulating film 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device for stably forming a channel of a transistor using a polycrystalline silicon film, a method of manufacturing the same, and a TFT type liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, TFT type liquid crystal display devices have been widely used in personal computers, electronic cameras, and the like. . Further, in order to further improve the characteristics, a transistor using an amorphous silicon film has been developed to a transistor using a polycrystalline silicon film.

Hereinafter, an example of a method of manufacturing a conventional semiconductor device of a TFT type liquid crystal display device using the above-mentioned polycrystalline silicon film will be described with reference to the drawings. FIG.
(C) is a sectional view showing an outline of a process of a method of manufacturing a TFT type liquid crystal display device using a conventional polycrystalline silicon film. T
The FT element is formed by first forming a silicon dioxide film 2 having a thickness of about 200 nm on a surface of a glass substrate 1 by a chemical vapor deposition method.
After forming an amorphous silicon film 3 having a thickness of nm, the glass substrate 1 was heated to about 450 ° C. in a vacuum to degas hydrogen and the like taken in during the amorphous silicon film forming step. Thereafter, a heat treatment is performed by excimer laser light irradiation or a rapid surface heating method, etc., so that the amorphous silicon film is polycrystallized 3 ', and a photoresist pattern 4 is formed thereon (FIG. 2).
(A)). Next, using the photoresist pattern 4 as a mask, the polycrystalline silicon film 3 ′ is etched to remove the photoresist 4 and form a gate insulating film 5 using a silicon dioxide film to a thickness of about 100 nm. An aluminum (Al) wiring is formed to form a gate electrode 6. Next, impurities such as boron or phosphorus are implanted by an ion implantation method,
The source / drain 10 of the transistor is formed (FIG. 2)
(B)). Then, an interlayer insulating film 7 using a silicon dioxide film is formed.
Is formed to a thickness of about 350 nm, and a contact hole 8 for wiring connection and a wiring electrode 9 are formed in a predetermined pattern by etching (FIG. 2C).

[0004]

In the conventional structure, the amorphous silicon film 3 is taken into the amorphous silicon film at the time of excimer laser beam irradiation or rapid surface heating for polycrystallization 3 '. In order to prevent bumps in the gas such as hydrogen, it is necessary to perform a treatment in advance to remove hydrogen and the like taken in the amorphous silicon film by heating in a vacuum.
Although the mobility μ is large, the interface between the gate insulating film 5 in the channel portion of the transistor and the polycrystalline silicon film 3 ′ is unstable,
There is a problem that the leak current is large and the variation in transistor characteristics is large.

To solve such problems, transistors having an offset structure or transistors having an LDD structure are effective. However, the process of forming them is complicated, the productivity is low, and the manufacturing margin is low. small. In view of the above problems, the present invention can stabilize the interface between a gate insulating film and a polycrystalline silicon film, reduce leakage current and reduce variations in transistor characteristics, simplify the manufacturing process, and provide a large manufacturing margin. It is an object of the present invention to provide a semiconductor device, a method for manufacturing the same, and a TFT liquid crystal display device.

[0006]

According to a first aspect of the present invention, there is provided a semiconductor device comprising: a substrate; a two-layer structure film laminated on the substrate in the order of a polycrystalline silicon film and an amorphous silicon film; A source / drain formed by injecting impurities into the film;
A gate insulating film formed on the amorphous silicon film, a gate electrode formed on the gate insulating film, an interlayer insulating film formed on the gate electrode, and an amorphous silicon film formed through the interlayer insulating film. And a source / drain wiring electrode connected thereto.

According to the first aspect of the present invention, since the amorphous silicon film containing hydrogen is formed between the polycrystalline silicon film and the gate insulating film, the interface between the gate insulating film and the silicon film is amorphous. Can be stabilized by hydrogen contained in the porous silicon film,
The manufacturing method is simple, the manufacturing margin is large, and leakage current and variation in transistor characteristics due to instability of the channel surface can be reduced, thereby improving image quality and improving the yield of transistor formation. be able to.

According to a second aspect of the present invention, there is provided a TFT type liquid crystal display device.
A pixel region having a first transistor whose source / drain has a two-layer structure of a polycrystalline silicon film and an amorphous silicon film;
A drive circuit having a second transistor whose source and drain are made of a polycrystalline silicon film and driving the first transistor in the pixel region. TF according to claim 2
According to the T-type liquid crystal display device, when a driving circuit is simultaneously formed in the TFT-type liquid crystal display device, a transistor using a polycrystalline silicon film can realize an important improvement in response speed as an electronic circuit, and The pixel region is capable of reducing leakage current and variation in transistor characteristics of a transistor of a pixel formed in a lattice shape, improving image quality and improving a transistor formation yield, and is easy to manufacture. There is a similar effect.

According to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor device.
Forming a polycrystalline silicon film on the substrate, forming an amorphous silicon film on the surface of the polycrystalline silicon film, forming a gate insulating film, and forming a gate electrode on the gate insulating film Forming a source / drain by injecting impurities into the polycrystalline silicon film; forming an interlayer insulating film on the gate electrode; and providing a wiring electrode for wiring to the source / drain through the interlayer insulating film. And a step of forming

According to the method of manufacturing a semiconductor device according to the third aspect, the same effect as that of the first aspect is obtained. According to a fourth aspect of the present invention, in the method of manufacturing a semiconductor device according to the third aspect, the polycrystalline silicon film is formed by heat-treating the amorphous silicon film. According to the method of manufacturing a semiconductor device according to the fourth aspect, the same effect as that of the third aspect is obtained.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a semiconductor device.
The method according to claim 3 or 4, further comprising, after the step of forming the gate insulating film, etching the gate insulating film, the amorphous silicon film, and the polycrystalline silicon film into a predetermined pattern. According to the method of manufacturing a semiconductor device according to the fifth aspect, in addition to the same effect as the third or fourth aspect, the process can be simplified.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a semiconductor device.
In claim 3, claim 4, or claim 5, the thickness of the amorphous silicon film formed between the polycrystalline silicon film and the gate insulating film is between 5 nm and 20 nm. According to the method of manufacturing a semiconductor device according to the sixth aspect, the same effect as that of the third, fourth, or fifth aspect is obtained, and the effectiveness is large because the film thickness is between 5 nm and 20 nm.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor device of a TFT type liquid crystal display device according to an embodiment of the present invention and a method of manufacturing the same will be described below with reference to FIG. FIG. 1 (a)
FIGS. 1C to 1C are cross-sectional views schematically showing steps of a method of manufacturing a TFT liquid crystal display device according to an embodiment of the present invention. First, a silicon dioxide film 2 having a thickness of about 200 nm is formed on a surface of a glass substrate 1 by a chemical vapor deposition method, and then an amorphous silicon film 13a having a thickness of about 50 nm is formed by a plasma CVD method. After the formation, the glass substrate 1 is heated to about 450 ° C. in vacuum to degas the hydrogen and the like taken in during the amorphous silicon film forming step, and then heat-treated by excimer laser light irradiation. Then, the amorphous silicon film is polycrystallized. Thereafter, an amorphous silicon film 13 having a thickness of about 10 nm is formed on the surface of the polycrystallized polycrystalline silicon film 13 'by a plasma CVD method, and a photoresist pattern 14 is formed (FIG. 1A). . Next, using the photoresist pattern 14 as a mask, the amorphous silicon film 13 and the polycrystalline silicon film 13 'are etched to remove the photoresist 14, and then the gate insulating film 15 such as a silicon dioxide film is
After being formed to a thickness of 00 nm, an aluminum (Al) wiring is formed to form a gate electrode 16. Next, an impurity such as boron or phosphorus is implanted by an ion implantation method to form a source / drain 20 of the transistor in the polycrystalline silicon film 13 '(FIG. 1B). Thereafter, an interlayer insulating film 17 is formed to a thickness of about 350 nm using a silicon dioxide film or the like, and a contact hole 18 for wiring connection and a wiring electrode 19 are formed in a predetermined pattern by etching (FIG. 1C). ). Form source / drain electrodes and wiring.

FIG. 1C shows a schematic cross section of a TFT type liquid crystal display device formed by the manufacturing method of this embodiment.
A two-layer structure film in which a polycrystalline silicon film 13 'and an amorphous silicon film 13 are laminated in this order on the substrate 1;
3 ′, a source / drain 20 formed by implanting impurities, a gate insulating film 15 formed on the amorphous silicon film 13, and a gate electrode 1 formed on the gate insulating film 15.
6 and the interlayer insulating film 1 formed on the gate electrode 16.
7 and a source / drain wiring electrode 19 connected to the amorphous silicon film 13 through the interlayer insulating film 17.

As described above, since the amorphous silicon film 13 containing hydrogen is formed between the polycrystalline silicon film 13 'and the gate insulating film 15 by the above-described structure, the gate insulating film 15 and the polycrystalline silicon film 13 ′ Can be stabilized by hydrogen contained in the amorphous silicon film 13, the manufacturing method is simple, the manufacturing margin is large, and the leakage current and transistor characteristics caused by the instability of the channel surface are increased. Can be reduced, and the image quality can be improved and the yield of transistor formation can be improved.

When a driving circuit (not shown) is simultaneously formed in a TFT type liquid crystal display device, the source / drain 20 has a two-layer structure of a polycrystalline silicon film 13 'and an amorphous silicon film 13. And a driving circuit having a second transistor whose source / drain is made of a polycrystalline silicon film and driving the first transistor in the pixel region.

With this, the transistor using the polycrystalline silicon film can improve the response speed, which is important as an electronic circuit, and the pixel region can reduce the leakage current of the transistor of the pixel formed in a lattice and reduce the transistor characteristics. Can be reduced, the image quality can be improved, and the transistor formation yield can be improved.

In the embodiment, the thickness of the amorphous silicon film 13a to be polycrystallized is 50 nm, and the thickness of the amorphous silicon film 13 formed on the surface of the polycrystalline silicon film 13 'is 10 nm.
Although the thickness is set to nm, the present invention is not limited to this, and it has been found from experiments that the thickness of the amorphous silicon film formed on the surface of the polycrystalline silicon film is preferably between 5 nm and 20 nm. That is, when the thickness of the amorphous silicon film 13 is reduced, the mobility μ is improved, but the leakage current and the variation in transistor characteristics are increased, and when the thickness of the amorphous silicon film 13 is increased, the mobility μ is reduced. However, variations in leakage current and transistor characteristics are reduced. In addition, since the mobility μ is improved when the thickness of the polycrystalline silicon film 13 ′ is reduced, the respective thicknesses may be determined according to target characteristics. If the thickness of the amorphous silicon film 13 formed on the surface of the polycrystalline silicon film 13 'is less than 5 nm, the leakage current increases and the variation in transistor characteristics increases. If the thickness of the amorphous silicon film 13 exceeds 20 nm, the mobility μ sharply decreases, so that the polycrystalline silicon film 1
Experiments have confirmed that the effect of the transistor using 3 'is lost.

Furthermore, in the above-described embodiment, the gate insulating film 15 is formed after the amorphous silicon film 13 and the polycrystalline silicon film 13 'are formed by etching in a predetermined pattern. For this purpose, after forming a gate insulating film 15 such as a silicon dioxide film, the gate insulating film 15, the amorphous silicon film 13, and the polycrystalline silicon film 13 'may be etched and formed in a predetermined pattern. It is clear that the same effect is obtained in the case described above.

[0020]

According to the semiconductor device of the first aspect, since the amorphous silicon film containing hydrogen is formed between the polycrystalline silicon film and the gate insulating film, the interface between the gate insulating film and the silicon film is reduced. Since it can be stabilized by hydrogen contained in the amorphous silicon film, the manufacturing method is simple, the manufacturing margin is large, and variations in leak current and transistor characteristics due to instability of the channel surface are reduced. It is possible to improve image quality and the yield of transistor formation.

According to the TFT type liquid crystal display device of the present invention, when a driving circuit is formed simultaneously in the TFT type liquid crystal display device, an important response as an electronic circuit is provided by the transistor using the polycrystalline silicon film. In addition to the improvement in speed, the pixel region can reduce the leakage current of the transistors of the pixels formed in a grid and reduce the variation in transistor characteristics, thereby improving the image quality and the transistor formation yield and manufacturing. It is easy and has the same effect as the first aspect.

According to the method of manufacturing a semiconductor device according to the third aspect, the same effect as that of the first aspect is obtained. According to the method of manufacturing a semiconductor device according to the fourth aspect, the same effect as that of the third aspect is obtained. According to the method of manufacturing a semiconductor device according to claim 5,
In addition to the effects similar to those of the third and fourth aspects, the steps can be simplified.

According to the method of manufacturing a TFT type liquid crystal display device of the present invention, the same effect as that of the third, fourth or fifth aspect can be obtained, and the film thickness can be between 5 nm and 20 nm. Greater effectiveness.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process and outline of a semiconductor device of a TFT type liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a manufacturing process and outline of a semiconductor device of a conventional TFT type liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Silicon dioxide film 13 Amorphous silicon film 13 'Polycrystalline silicon film 14 Photoresist 15 Gate insulating film 16 Gate electrode 17 Interlayer insulating film 18 Contact hole 19 Wiring electrode 20 Source / drain of transistor

Claims (6)

[Claims] 1. A substrate, a two-layer structure film laminated on the substrate in the order of a polycrystalline silicon film and an amorphous silicon film, and a source film formed by injecting impurities into the polycrystalline silicon film.
A drain; a gate insulating film formed on the amorphous silicon film; a gate electrode formed on the gate insulating film; an interlayer insulating film formed on the gate electrode; A semiconductor device comprising: a source / drain wiring electrode connected to an amorphous silicon film. 2. A pixel region having a first transistor whose source / drain has a two-layer structure of a polycrystalline silicon film and an amorphous silicon film, and a second transistor whose source / drain is made of a polycrystalline silicon film And a driving circuit for driving the first transistor. A step of forming a polycrystalline silicon film on the substrate;
Forming an amorphous silicon film on the surface of the polycrystalline silicon film, forming a gate insulating film, forming a gate electrode on the gate insulating film, and adding impurities to the polycrystalline silicon film. Implanting to form a source / drain;
A method of manufacturing a semiconductor device, comprising: a step of forming an interlayer insulating film on the gate electrode; and a step of forming a wiring electrode for wiring to a source / drain through the interlayer insulating film. 4. The method according to claim 3, wherein the polycrystalline silicon film is formed by heat-treating the amorphous silicon film. 5. The semiconductor device according to claim 3, further comprising, after the step of forming the gate insulating film, a step of etching and forming the gate insulating film, the amorphous silicon film, and the polycrystalline silicon film in a predetermined pattern. Manufacturing method. 6. The semiconductor device according to claim 3, wherein the thickness of the amorphous silicon film formed between the polycrystalline silicon film and the gate insulating film is between 5 nm and 20 nm. Manufacturing method.