JP2003158135A - Manufacturing method of thin film transistor and manufacturing method of display device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resolve a problem in the manufacturing method of a thin film transistor employing a polycrystalline silicone film that a contaminated natural oxidized silicone film is formed on the surface of the film by exposed in an atmosphere in a clean room and when laser annealing is effected under this condition, a contaminated substance is drawn into the polycrystalline silicone film whereby a transistor characteristic is deteriorated and the grain size of a crystal is reduced when crystalizing is effected under a condition that the natural oxidized silicone film is removed, further, abrasion is caused in the silicone film when a laser energy is increased to enlarge the grain size of the crystal. SOLUTION: The natural oxidized silicone film on the surface of the amorphous silicone film after dehydration is removed by fluoroacid solution whereby the contaminated substance is prevented from being drawn into the silicone film. Thereafter, an oxidized film is formed on the surface to effect laser anneal whereby the reduction of grain size of a crystal and abrasion are prevented.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a thin film transistor (TF) provided on an insulating film formed on a glass substrate.
T), or a manufacturing method of a display device provided with a thin film integrated circuit to which they are applied. In particular, the present invention relates to a method for manufacturing an active liquid crystal display device (liquid crystal display) equipped with a thin film integrated circuit.

[0002]

2. Description of the Related Art Recently, a semiconductor device having a thin film transistor on an insulating substrate such as glass, for example, an active liquid crystal display device using the thin film transistor for driving pixels has been developed. Thin film silicon semiconductors are generally used for thin film transistors used in these devices. Among thin film silicon semiconductors, there is one made of polycrystalline silicon having crystallinity. This polycrystalline silicon thin film transistor has an electron mobility larger than that of an amorphous silicon thin film transistor by two digits or more. It has the advantage that the drive circuits can be integrated on the same substrate. In recent years, in the field of liquid crystal display devices, the development of a technology for manufacturing a thin film transistor array with a built-in drive circuit using this polycrystalline silicon thin film transistor on a glass substrate that is inexpensive and easy to have a large area has been actively developed and put into practical use. .

A method of manufacturing a thin film transistor for an active matrix array used in a conventional liquid crystal display device will be described with reference to the drawings.

First, as shown in FIG. 2A, the glass substrate 1
1, a silicon oxide film to be the buffer layer 12 is formed by the plasma CVD method. After that, the amorphous silicon (a-Si) 13 is deposited by the plasma CVD method without taking out the glass substrate on which the silicon oxide thin film is formed into the atmosphere. Next, heat treatment is performed at 400 to 450 ° C. for about 60 minutes in a nitrogen atmosphere to reduce hydrogen in the a-Si film. At this time, the natural oxide film 21 is formed on the amorphous silicon film. The a-Si film is polycrystallized by excimer laser annealing to form a polycrystal silicon (poly-Si) film 14. At this time, an XeCl excimer laser having a wavelength of 308 nm is used as the excimer laser.

Next, as shown in FIG. 2 (b), after processing the poly-Si film into a desired shape, a mask for impurity implantation is formed with a photoresist 23 to form impurities (phosphorus) in the source and drain regions 14c. Ion). Next, a silicon oxide film to be the gate insulating film 15 is formed. afterwards,
LDD region 1 is formed on the thin film transistor by forming the gate electrode 16.
Impurities (phosphorus ions) are implanted to form 4b. The region 14a in which impurities are not implanted is intrinsic polycrystalline silicon and serves as a channel region.

Next, as shown in FIG. 2 (c), after the silicon oxide film 17 to be an interlayer insulating film is formed, the implanted impurities are activated at 500 to 600 ° C. under a reduced pressure nitrogen atmosphere.
Annealing is performed at the temperature of. Next, contact holes are opened in the insulating film on the source and drain regions, and SD wirings (Al / Ti) 18 and 19 are formed.

Finally, the protective insulating film 2 made of silicon nitride
By forming 0 and annealing in a hydrogen atmosphere, dangling bonds in the polycrystalline silicon thin film are compensated by hydrogen, the characteristics are improved, and the thin film transistor is completed.

[0008]

After the amorphous silicon film is deposited or after dehydrogenation, the amorphous silicon film is exposed to the atmosphere, so that the amorphous silicon film is contaminated (organic substances,
A silicon oxide film formed by boron, alkali metal, etc. is formed. If crystallization is performed in this state, contaminants will be taken into the poly-Si film. This causes deterioration of transistor characteristics and reliability.

If this silicon oxide film is removed with a hydrofluoric acid solution and laser annealing is performed while the surface remains water repellent, the poly-Si crystal grain size becomes small. Also, if the laser energy is increased to obtain a large particle size, the film will ablate.

[0010]

The natural oxide film on the surface of the amorphous silicon film after dehydrogenation is removed with a hydrofluoric acid solution, and then an oxide film having a film thickness of 1 to 10 nm is formed on the surface. By doing so, it becomes possible to prevent the contaminants from adhering to the silicon film and to irradiate the laser energy under the same conditions as when the natural oxide film is present.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A method of manufacturing a thin film transistor according to claim 1 of the present invention comprises a step of depositing an amorphous silicon film on a glass substrate and a step of desorbing hydrogen contained in the amorphous silicon film. To heat the amorphous silicon film at a temperature of 400 ° C. or higher, and the native silicon oxide film formed on the amorphous silicon film is washed with an ozone solution and then removed with a hydrofluoric acid solution. And a step of forming a silicon oxide film having a film thickness of 1 to 10 nm on the surface of the amorphous silicon film, and irradiating the amorphous silicon film on which the silicon oxide film is formed with a laser beam. And a step of forming a crystalline silicon film.

The method of manufacturing a thin film transistor according to a second aspect of the present invention is characterized in that a silicon oxide film is formed on the surface of the amorphous silicon film using an ozone solution.

In the method of manufacturing a thin film transistor according to a third aspect of the present invention, a step of removing the natural silicon oxide film with a hydrofluoric acid solution, washing the hydrofluoric acid solution with pure water, and forming a silicon oxide film with an ozone solution. The process is continuously performed by one cleaning device.

A method of manufacturing a thin film transistor according to a fourth aspect of the present invention is characterized in that the silicon oxide film is formed on the surface of the amorphous silicon film by heating at a temperature of 200 ° C. to 600 ° C. in an oxidizing atmosphere. To do.

A method of manufacturing a thin film transistor according to a fifth aspect of the present invention is characterized in that a silicon oxide film is formed on the surface of the amorphous silicon film by plasma discharge in an oxidizing atmosphere.

A method of manufacturing a thin film transistor according to a sixth aspect of the present invention is characterized in that a silicon oxide film is formed on the surface of the amorphous silicon film by irradiating strong light in the ultraviolet region in an oxidizing atmosphere. .

The invention according to claim 7 of the present invention is claim 1
7. A method of manufacturing a display device, including the method of manufacturing a thin film transistor according to any one of items 1 to 6.

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) First, as shown in FIG. 1A, a silicon oxide film serving as a buffer layer 12 is formed on a glass substrate 11. Thereafter, the amorphous silicon (a-Si) film 13 is deposited on the glass substrate by the plasma CVD method without taking out the glass substrate on which the silicon oxide thin film is formed into the atmosphere. Next, the glass substrate 11 on which the silicon oxide film and the amorphous silicon film are formed is taken out into the air, and in order to reduce hydrogen in the a-Si film, it is heated at 400 to 450 ° C. in a nitrogen atmosphere in a heat treatment furnace. Heat treatment is performed for about 60 minutes. At this time, the native silicon oxide film 21 is formed on the amorphous silicon film.

Next, the natural silicon oxide film 21 on the a-Si film is washed with an ozone solution having a concentration of about 20 ppm, and the natural silicon oxide film 21 is removed with a hydrofluoric acid solution having a concentration of 1%. After the hydrofluoric acid solution remaining on the a-Si film is washed off with pure water, the surface of the a-Si film is washed with an ozone solution to form a silicon oxide film 22 having a film thickness of 1 to 10 nm on the surface.

Subsequently, the remaining ozone solution is washed away with pure water, and the substrate is dried. Next, the a-Si film is polycrystallized by excimer laser annealing to form a poly-Si film 14. At this time, an XeCl excimer laser with a wavelength of 308 nm is used as the excimer laser.

Next, as shown in FIG. 1B, after the poly-Si film is processed into a desired shape, a mask for impurity implantation is formed with a photoresist 23, and impurities (source) are formed in the source and drain regions 14c. (Phosphorus ion) is implanted. After forming a silicon oxide film to be the gate insulating film 15, a gate electrode 16 is formed, and impurities (phosphorus ions) are implanted into the thin film transistor to form the LDD region 14b. The region 14a in which impurities are not implanted is intrinsic polycrystalline silicon and serves as a channel region.

Next, as shown in FIG. 1C, after forming a silicon oxide film 17 to be an interlayer insulating film, annealing is performed at a temperature of 500 to 600 ° C. in a reduced pressure nitrogen atmosphere to remove the implanted impurities. Activate. Next, contact holes are opened in the insulating film on the source and drain regions, and SD wiring (Al /
Ti) 18 and 19 are formed.

Finally, the protective insulating film 2 made of silicon nitride
0 is formed, annealing is performed in a hydrogen atmosphere, and dangling bonds in the polycrystalline silicon thin film are compensated by hydrogen to improve the characteristics and complete the thin film transistor.

(Embodiment 2) First, as shown in FIG. 1A, a silicon oxide film to be a buffer layer 12 is formed on a glass substrate 11. Thereafter, the amorphous silicon (a-Si) film 13 is deposited on the glass substrate by the plasma CVD method without taking out the glass substrate on which the silicon oxide thin film is formed into the atmosphere. Next, the glass substrate 11 on which the silicon oxide film and the amorphous silicon film are formed is taken out into the atmosphere, and 400 to 450 ° C. under a nitrogen atmosphere in a heat treatment furnace in order to reduce hydrogen in the a-Si film. Heat treatment is performed for about 60 minutes. At this time, the natural oxide film 21 is formed on the amorphous silicon film.

Next, using an ozone solution having a concentration of 20 ppm,
After cleaning the native oxide film 21 on the Si film, the native silicon oxide film 21 is removed with a hydrofluoric acid solution having a concentration of 1%.

Next, heat treatment is performed in an oxidizing atmosphere (oxygen, ozone, a mixed gas of oxygen and nitrogen, etc.) at 200 to 600 ° C. for 5 minutes or more, and a silicon oxide film 22 having a thickness of 1 to 10 nm is formed on the surface. Form.

Next, the a-Si film is polycrystallized by excimer laser annealing to form a poly-Si film 14. At this time, an XeCl excimer laser having a wavelength of 308 nm is used as the excimer laser.

Next, as shown in FIG. 1 (b), after processing the poly-Si film into a desired shape, a mask for impurity implantation is formed with a photoresist 23, and impurities (impurities) are formed in the source and drain regions 14c. (Phosphorus ion) is implanted. Next, after forming a silicon oxide film to be the gate insulating film 15, a gate electrode 16 is formed, and the LDD region 14 is formed on the thin film transistor.
Impurities (phosphorus ions) are implanted to form b. The region 14a in which impurities are not implanted is intrinsic polycrystalline silicon and serves as a channel region.

Next, as shown in FIG. 1C, after forming a silicon oxide film 17 to be an interlayer insulating film, annealing is performed at a temperature of 500 to 600 ° C. in a reduced pressure nitrogen atmosphere to remove the implanted impurities. Activate. Next, contact holes are opened in the insulating film on the source and drain regions, and SD wirings (Al / Ti) 18 and 19 are formed.

Finally, the protective insulating film 2 made of silicon nitride
0 is formed, annealing is performed in a hydrogen atmosphere, and dangling bonds in the polycrystalline silicon thin film are compensated by hydrogen to improve the characteristics and complete the thin film transistor.

(Third Embodiment) First, as shown in FIG. 1A, a silicon oxide film to be a buffer layer 12 is formed on a glass substrate 11. After that, the amorphous silicon (a-Si) film 13 is deposited on the glass substrate by the plasma CVD method without taking out the glass substrate on which the silicon oxide thin film is formed into the atmosphere. Next, the glass substrate 11 on which the silicon oxide film and the amorphous silicon film are formed is taken out into the atmosphere, and 400 to 450 ° C. under a nitrogen atmosphere in a heat treatment furnace in order to reduce hydrogen in the a-Si film. Heat treatment is performed for about 60 minutes. At this time, the natural oxide film 21 is formed on the amorphous silicon film.

Next, using an ozone solution having a concentration of 20 ppm,
-The native oxide film 21 on the Si film is washed, and the native silicon oxide film 21 is removed with a hydrofluoric acid solution having a concentration of 1%.

Next, plasma discharge is performed in an oxidizing atmosphere (oxygen, ozone, a mixed gas of oxygen and nitrogen, etc.) to form a silicon oxide film 22 having a film thickness of 1 to 10 nm on the surface.

Next, the a-Si film is polycrystallized by excimer laser annealing to form a poly-Si film 14. At this time, an XeCl excimer laser having a wavelength of 308 nm is used as the excimer laser.

Next, as shown in FIG. 1 (b), after processing the poly-Si film into a desired shape, a mask for impurity implantation is formed with a photoresist 23 to form impurities (phosphorus) in the source and drain regions 14c. Ion). After forming a silicon oxide film to be the gate insulating film 15, the gate electrode 1
6 is formed, and impurities (phosphorus ions) are implanted into the thin film transistor to form the LDD region 14b. The region 14a in which impurities are not implanted is intrinsic polycrystalline silicon,
It becomes the channel region.

Next, as shown in FIG. 1C, after forming a silicon oxide film 17 to be an interlayer insulating film, the implanted impurities are activated at 500 to 600 ° C. under a reduced pressure nitrogen atmosphere.
Annealing is performed at the temperature of. Next, contact holes are opened in the insulating film on the source and drain regions, and SD wirings (Al / Ti) 18 and 19 are formed.

Finally, the protective insulating film 2 made of silicon nitride
0 is formed, annealing is performed in a hydrogen atmosphere, and dangling bonds in the polycrystalline silicon thin film are compensated by hydrogen to improve the characteristics and complete the thin film transistor.

(Embodiment 4) First, as shown in FIG. 1A, a silicon oxide film serving as a buffer layer 12 is formed on a glass substrate 11. After that, the amorphous silicon (a-Si) film 13 is deposited on the glass substrate by the plasma CVD method without taking out the glass substrate on which the silicon oxide thin film is formed into the atmosphere. Next, the glass substrate 11 on which the silicon oxide film and the amorphous silicon film are formed is taken out into the atmosphere, and 400 to 450 ° C. under a nitrogen atmosphere in a heat treatment furnace in order to reduce hydrogen in the a-Si film. Heat treatment is performed for about 60 minutes. At this time, the natural oxide film 21 is formed on the amorphous silicon film.

Next, using an ozone solution having a concentration of 20 ppm,
-The native oxide film 21 on the Si film is washed, and the native silicon oxide film 21 is removed with a hydrofluoric acid solution having a concentration of 1%. next,
In a oxidizing atmosphere (oxygen, ozone, mixed gas of oxygen and nitrogen, etc.), strong light of 100 W or more is irradiated with an average power having a wavelength in the ultraviolet range to form a silicon oxide film 22 having a film thickness of 1 to 10 nm on the surface. .

Next, the a-Si film is polycrystallized by excimer laser annealing to form a poly-Si film 14. At this time, an XeCl excimer laser with a wavelength of 308 nm is used as the excimer laser. Next, as shown in FIG. 1B, after processing the poly-Si film into a desired shape, a mask for impurity implantation is formed with a photoresist 23 to form the source and drain regions 14.
Impurities (phosphorus ions) are implanted into c. Gate insulating film 15
After forming a silicon oxide film to be the above, a gate electrode 16 is formed, and an impurity (phosphorus ion) is implanted to form the LDD region 14b in the thin film transistor. The region 14a in which impurities are not implanted is intrinsic polycrystalline silicon and serves as a channel region.

Next, as shown in FIG. 1C, after the silicon oxide film 17 to be an interlayer insulating film is formed, the implanted impurities are activated at a temperature of 500 to 600 ° C. under a reduced pressure nitrogen atmosphere. This is done by annealing. Next, a contact hole is opened in the insulating film on the source and drain regions,
SD wirings (Al / Ti) 18 and 19 are formed.

Finally, the protective insulating film 2 made of silicon nitride
0 is formed, annealing is performed in a hydrogen atmosphere, and dangling bonds in the polycrystalline silicon thin film are compensated by hydrogen to improve the characteristics and complete the thin film transistor.

If a liquid crystal display device is manufactured using the thin film transistors manufactured by these manufacturing methods, a liquid crystal display device with high definition and high aperture ratio can be obtained. In addition, the thin film transistor produced by these manufacturing methods can be applied to the organic EL display device, and a thin, high-luminance, high-contrast organic EL display device can be realized.

[0045]

The natural silicon oxide film on the surface of the amorphous silicon film after dehydrogenation is first washed with an ozone solution to remove organic contamination and the like, and the surface of the amorphous silicon film is made completely hydrophilic. A chemical solution such as hydrofluoric acid spreads uniformly on the film.

Further, by completely removing (water repellent state) the silicon oxide film with a hydrofluoric acid solution, it is possible to prevent contaminants from being taken into the silicon film during laser annealing, and to form a film having a thickness of 1 to 1 on the surface. By performing laser annealing after forming a 10 nm oxide film, a polycrystalline silicon film with a large crystal grain size can be obtained even if the laser energy is lower than when irradiating without the silicon oxide film (water repellent state). be able to.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process of an n-type TFT according to an embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of a conventional n-type TFT.

[Explanation of symbols]

11 glass substrate 12 buffer layer (silicon oxide) 13 Amorphous silicon 14 Polycrystalline silicon 14a Intrinsic polycrystalline silicon (channel region) 14b Low-concentration impurity implantation region (LDD region) 14c High concentration impurity implantation region (SD region) 15 Gate insulating film (silicon oxide) 16 Gate electrode (MoW alloy) 17 Interlayer insulation film (silicon oxide) 18, 19 SD wiring (Al / Ti) 20 Protective insulation film (silicon nitride) 21 Natural silicon oxide film 22 Silicon oxide film 23 Photoresist

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H092 JA25 KA04 MA25 MA30 MA37                       NA21                 5F052 AA02 BB07 CA02 DA02 DB03                       EA15 JA01                 5F110 AA30 BB01 CC02 DD02 DD13                       FF02 GG02 GG13 GG45 HJ01                       HJ23 HL03 HL04 HL11 HM15                       NN03 NN23 NN24 PP03 PP31                       PP35 QQ09 QQ23 QQ24                 5G435 AA17 BB12 CC09 KK05 KK09                       KK10

Claims (7)

[Claims] 1. A step of depositing an amorphous silicon film on a glass substrate, and a step of depositing the amorphous silicon film at a temperature of 400 ° C. or higher in order to release hydrogen contained in the amorphous silicon film. A step of heating, a step of cleaning the native silicon oxide film formed on the amorphous silicon film with an ozone solution and then a hydrofluoric acid solution, and a film thickness of 1 on the surface of the amorphous silicon film. A method of manufacturing a thin film transistor, comprising: forming a silicon oxide film having a thickness of 10 nm; and irradiating the amorphous silicon film having the silicon oxide film formed thereon with laser light to form a polycrystalline silicon film. 2. The method of manufacturing a thin film transistor according to claim 1, wherein a silicon oxide film is formed on the surface of the amorphous silicon film using an ozone solution. 3. The step of removing the natural silicon oxide film with a hydrofluoric acid solution and the step of rinsing the hydrofluoric acid solution with pure water to form a silicon oxide film with an ozone solution are successively performed by one cleaning device. The method of manufacturing a thin film transistor according to claim 1 or 2, characterized in that. 4. The method of manufacturing a thin film transistor according to claim 1, wherein the silicon oxide film is formed on the surface of the amorphous silicon film by heating at a temperature of 200 ° C. to 600 ° C. in an oxidizing atmosphere. 5. The method of manufacturing a thin film transistor according to claim 1, wherein a silicon oxide film is formed on the surface of the amorphous silicon film by plasma discharge in an oxidizing atmosphere. 6. The method of manufacturing a thin film transistor according to claim 1, wherein the silicon oxide film is formed on the surface of the amorphous silicon film by irradiating strong light in the ultraviolet region in an oxidizing atmosphere. 7. A method of manufacturing a display device, comprising the method of manufacturing a thin film transistor according to claim 1.