JP2002368010A - Manufacturing method of thin-film transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a thin oxide film on the surface, and to prevent contaminants from adhering to a silicon film by carrying out annealing in oxidation atmosphere in a hydrogenation process after amorphous silicon is deposited. SOLUTION: In the manufacturing method of a thin-film transistor where an amorphous silicon film 21 is formed on a glass substrate 11, hydrogen in the amorphous silicon film is separated, the amorphous silicon film is machined to a polycrystalline silicon film 13, island-like polycrystalline silicon films 13a, 13b, and 13c are formed, a gate electrode 15 is formed, impurities are injected to the island-like polycrystalline silicon film, and the impurities are activated, the amorphous silicon film 21 is deposited to form a silicon oxide film 22 when the hydrogen contained in the amorphous silicon film 21 is separated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thin film transistor (TF) provided on an insulating film formed on a glass substrate.
T) or a method of manufacturing a thin film integrated circuit using the same, particularly a thin film integrated circuit for an active liquid crystal display device (liquid crystal display).

[0002]

2. Description of the Related Art In recent years, 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. In general, a thin film silicon semiconductor is used for a thin film transistor used in these devices. Among thin-film silicon semiconductors, there is a thin-film silicon semiconductor that is made of polycrystalline silicon having crystallinity. The polycrystalline silicon thin-film transistor has an electron mobility that is at least two orders of magnitude higher than that of an amorphous silicon thin-film transistor. It has an advantage that the driving circuit can be integrated on the same substrate. In recent years, in the field of liquid crystal display devices, technology for manufacturing a thin film transistor array with a built-in drive circuit using a polycrystalline silicon thin film transistor on a glass substrate that is inexpensive and easy to increase in area has been actively developed, and practical use has begun.

A method for 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. 5A, a silicon oxide film serving as a buffer layer 12 is formed on a glass substrate 11 by a plasma CVD method. Thereafter, amorphous silicon (a-Si) 21 is deposited by a plasma CVD method without taking the glass substrate on which the silicon oxide thin film is formed into the atmosphere. Then, after performing a heat treatment of about 400 to 450 ° C. for about 60 minutes in a nitrogen atmosphere to reduce hydrogen in the a-Si film,
The a-Si film is polycrystallized by annealing using an excimer laser to form a polycrystalline silicon (poly-Si) film 13. At this time, an XeCl excimer laser having a wavelength of 308 nm is used as the excimer laser. Next, as shown in FIG.
After processing the i-film into a desired shape, a mask for impurity implantation is formed with the photoresist 22, and impurities (phosphorous ions) are implanted into the source and drain regions 13c. Next, a silicon oxide film to be the gate insulating film 14 is formed. Thereafter, an impurity (phosphorus ion) is implanted to form the gate electrode 15 and to form the low concentration impurity implantation (LDD) region 13b in the thin film transistor. Region 1 in which impurities are not implanted
Reference numeral 3a denotes intrinsic polycrystalline silicon, which becomes a channel region. Next, as shown in FIG. 5C, after forming a silicon oxide film 16 serving as an interlayer insulating film, annealing of the implanted impurities is performed at a temperature of 500 to 600 ° C. in a reduced-pressure nitrogen atmosphere. It is done by doing. Next, a contact hole is opened in the insulating film on the source and drain regions, and a wiring 1 is formed.
7 and 18 are formed. Finally, a protective insulating film 19 made of silicon nitride is formed, and annealing is performed in a hydrogen atmosphere, whereby dangling bonds in the polycrystalline silicon thin film are compensated with hydrogen to improve characteristics and a thin film transistor is completed.

[0004]

In the above-mentioned conventional method, after the amorphous silicon film is deposited or dehydrogenated, the film surface is contaminated with organic substances, boron, alkali metals and the like by being exposed to an atmosphere in a clean room. Could be done. If crystallization is performed while the film surface is still contaminated, contaminants will be taken into the poly-Si film. This causes deterioration of transistor characteristics and reliability.

According to the present invention, a thin oxide film is formed on a surface by annealing in an oxidizing atmosphere in a dehydrogenation step after deposition of amorphous silicon to solve the above-mentioned conventional problem. Provided is a method for manufacturing a thin film transistor which prevents the thin film from being attached to a film.

[0006]

In order to achieve the above object, a method for manufacturing a thin film transistor according to the present invention comprises forming an amorphous silicon film on a glass substrate, releasing hydrogen in the amorphous silicon film, Processing an amorphous silicon film into a polycrystalline silicon film, forming an island-shaped polycrystalline silicon film, forming a gate electrode, implanting impurities into the island-shaped polycrystalline silicon film, and activating the impurities In the manufacturing method, after depositing an amorphous silicon film on the glass substrate, when desorbing hydrogen contained in the amorphous silicon film, annealing is performed in an oxidizing atmosphere to form a silicon oxide film. Is formed.

According to the present invention, in the dehydrogenation step after the deposition of amorphous silicon, annealing is performed in an oxidizing atmosphere to form a thin oxide film on the surface and prevent contaminants from adhering to the silicon film. I do. Further, even if a contaminant adheres to the surface of the oxide film, the contaminant is also removed by removing the oxide film immediately before performing the laser crystallization.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the annealing condition for desorbing hydrogen is a temperature of 400 ° C. or more and 600 ° C. or less, so that hydrogen in the amorphous silicon film is desorbed and amorphous. It is preferable to form a thin silicon oxide film on the surface of the silicon film.

Further, it is preferable to perform plasma discharge when the hydrogen is desorbed.

It is preferable that the desorption of hydrogen is performed by irradiating strong light having a wavelength in the range from the ultraviolet region to the near infrared region. In the above, the intense light refers to, for example, light of 5 kW or more emitted by a Xe arc lamp.

Preferably, the silicon oxide film is removed before or after processing the amorphous silicon film into a polycrystalline silicon film.

Hereinafter, embodiments of the present invention will be described 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 plasma CV was removed without taking out the glass substrate on which the silicon oxide thin film was formed into the atmosphere.
An amorphous silicon (a-Si) film 21 is deposited on a glass substrate by the method D. Next, to reduce hydrogen in the a-Si film,
In order to form a thin thermal oxide film 22 on the film surface, 400 mm
A heat treatment of about 600 ° C. for about 60 minutes is performed. Next, the a-Si film was polycrystallized by excimer laser annealing immediately after the thermal oxide film 22 was removed by wet etching with diluted hydrofluoric acid.
A poly-Si film 13 is formed. At this time, an XeCl excimer laser having 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 by a photoresist 23, and impurities (phosphor ions) are implanted into the source and drain regions 13c. inject. Next, a silicon oxide film to be the gate insulating film 14 is formed. Thereafter, an impurity (phosphorus ion) is implanted to form the gate electrode 15 and to form the LDD region 13b in the thin film transistor. The region 13a into which impurities are not implanted is intrinsic polycrystalline silicon, and serves as a channel region. Next, as shown in FIG. 1C, after a silicon oxide film 16 serving as an interlayer insulating film is formed, the implanted impurities are activated by annealing at a temperature of 500 to 600 ° C. in a reduced-pressure nitrogen atmosphere. It is done by doing. Next, contact holes are opened in the insulating film on the source and drain regions, and wirings 17 and 18 are formed. Finally, a protective insulating film 19 made of silicon nitride is formed, and annealing is performed in a hydrogen atmosphere, whereby dangling bonds in the polycrystalline silicon thin film are compensated with hydrogen to improve characteristics and a thin film transistor is completed.

Embodiment 2 First, as shown in FIG. 2A, a silicon oxide film serving as a buffer layer 12 is formed on a glass substrate 11. Thereafter, the plasma CV was removed without taking out the glass substrate on which the silicon oxide thin film was formed into the atmosphere.
An amorphous silicon (a-Si) film 21 is deposited on a glass substrate by the method D. Next, to reduce hydrogen in the a-Si film,
400-450 under oxidizing atmosphere (oxygen, ozone, mixed gas of oxygen and nitrogen, etc.) to form a thin oxide film on the film surface
Plasma discharge is performed while maintaining the substrate temperature at ° C. Next, wet etching is performed with dilute hydrofluoric acid, and immediately after the thermal oxide film 22 is removed, the a-Si film is polycrystallized by excimer laser annealing to form a poly-Si film 13. At this time,
As the excimer laser, a XeCl excimer laser having a wavelength of 308 nm is used. Next, as shown in FIG. 2B, after processing the poly-Si film into a desired shape, a mask for impurity implantation is formed by a photoresist 23, and the source and drain regions 1 are formed.
Impurities (phosphorus ions) are implanted into 3c. Next, a silicon oxide film to be the gate insulating film 14 is formed. Thereafter, a gate electrode 15 is formed, and the LDD region 13b is formed on the thin film transistor.
Is implanted to form (). The region 13a into which impurities are not implanted is intrinsic polycrystalline silicon, and serves as a channel region. Next, as shown in FIG. 2C, after a silicon oxide film 16 serving as an interlayer insulating film is formed, the activation of the implanted impurities is performed under a reduced-pressure nitrogen atmosphere.
This is performed by annealing at a temperature of 0 to 600 ° C. Next, contact holes are opened in the insulating film on the source and drain regions, and wirings 17 and 18 are formed. Finally, a protective insulating film 19 made of silicon nitride is formed, and annealing is performed in a hydrogen atmosphere, whereby dangling bonds in the polycrystalline silicon thin film are compensated with hydrogen to improve characteristics and a thin film transistor is completed.

Embodiment 3 First, as shown in FIG. 3A, a silicon oxide film serving as a buffer layer 12 is formed on a glass substrate 11. Thereafter, the plasma CV was removed without taking out the glass substrate on which the silicon oxide thin film was formed into the atmosphere.
An amorphous silicon (a-Si) film 21 is deposited on a glass substrate by the method D. Next, to reduce the hydrogen in the a-Si film,
In order to form a thin thermal oxide film 22 on the surface of the film, an output (20 kW) and a substrate feed speed such that the substrate temperature becomes 400 to 600 ° C. under an oxidizing atmosphere (oxygen, ozone, a mixed gas of oxygen and nitrogen, etc.) Anneal by Xe arc lamp at (20 mm / s). Next, the a-Si film is polycrystallized by excimer laser annealing immediately after the thermal oxide film 22 is removed by wet etching with dilute hydrofluoric acid.
Form 3 As the excimer laser, a XeCl excimer laser having a wavelength of 308 nm is used. Next, as shown in FIG. 3B, after processing the poly-Si film into a desired shape, a mask for impurity implantation is formed with a photoresist 23 and impurities (phosphorus ions) are implanted into the source and drain regions. I do. Next, a silicon oxide film to be the gate insulating film 14 is formed. Thereafter, a gate electrode 15 is formed to form a thin film transistor.
Impurities (phosphorus ions) are implanted to form LDD regions. The region 13a into which impurities are not implanted is intrinsic polycrystalline silicon, and serves as a channel region. Next, FIG.
As shown in (c), after the silicon oxide film 16 serving as an interlayer insulating film is formed, the activation of the implanted impurities is performed by an output (40
kW) and a feed speed (20 mm / s) to perform lamp annealing. Next, contact holes are opened in the insulating film on the source and drain regions, and wirings 17 and 18 are formed. Finally, a protective insulating film 19 made of silicon nitride is formed, and annealing is performed in a hydrogen atmosphere, whereby dangling bonds in the polycrystalline silicon thin film are compensated with hydrogen to improve characteristics and a thin film transistor is completed.

Embodiment 4 First, as shown in FIG. 4A, a silicon oxide film serving as a buffer layer 12 is formed on a glass substrate 11. Thereafter, the plasma CV was removed without taking out the glass substrate on which the silicon oxide thin film was formed into the atmosphere.
An amorphous silicon (a-Si) film 21 is deposited on a glass substrate by the method D. Next, to reduce the hydrogen in the a-Si film,
In order to form a thin thermal oxide film 22 on the film surface, 400 mm
A heat treatment of about 600 ° C. for about 60 minutes is performed. Subsequently, the a-Si film is polycrystallized by excimer laser annealing to form a poly-Si film 1.
Form 3 At this time, the wavelength of the excimer laser is 308n
An XeCl excimer laser of m is used.

Next, as shown in FIG. 4B, after processing the poly-Si film into a desired shape, a mask for impurity implantation is formed with a photoresist 23 and impurities (phosphorus) are formed in the source and drain regions 13c. Ions). After performing wet etching with dilute hydrofluoric acid to remove the thermal oxide film 22,
A silicon oxide film to be the gate insulating film 14 is formed. Thereafter, an impurity (phosphorus ion) is implanted to form the gate electrode 15 and to form the LDD region 13b in the thin film transistor. The region 13a into which impurities are not implanted is intrinsic polycrystalline silicon, and serves as a channel region. Next, FIG.
As shown in (c), after the silicon oxide film 16 to be the interlayer insulating film is formed, the implanted impurities are activated by annealing at a temperature of 500 to 600 ° C. in a reduced-pressure nitrogen atmosphere. Next, contact holes are opened in the insulating film on the source and drain regions, and wirings 17 and 18 are formed. Finally, a protective insulating film 19 made of silicon nitride is formed, and annealing is performed in a hydrogen atmosphere, whereby dangling bonds in the polycrystalline silicon thin film are compensated with hydrogen to improve characteristics and a thin film transistor is completed.

[0018]

As described above, according to the method of the present invention, a thin oxide film is formed on the surface by performing the dehydrogenation treatment in an oxidizing atmosphere, and contaminants are prevented from adhering to the silicon film. Even if contaminants adhere to the surface of the oxide film, removing the oxide film immediately before performing laser crystallization also removes the contaminants at the same time. A film is obtained.

[Brief description of the drawings]

FIGS. 1A to 1C are explanatory sectional views showing manufacturing steps of an n-type TFT according to a first embodiment of the present invention.

FIGS. 2A to 2C are n-type TFTs according to a second embodiment of the present invention;
Explanatory sectional view showing the manufacturing process of

FIGS. 3A to 3C are n-type TFTs according to a third embodiment of the present invention;
Explanatory sectional view showing the manufacturing process of

FIGS. 4A to 4C are n-type TFTs according to a fourth embodiment of the present invention;
Explanatory sectional view showing the manufacturing process of

5 (a) to 5 (c) are explanatory sectional views showing a conventional n-type TFT manufacturing process.

[Explanation of symbols]

 Reference Signs List 11 glass substrate 12 buffer layer (silicon oxide) 13 polycrystalline silicon 13a intrinsic polycrystalline silicon (channel region) 13b low concentration impurity implantation region (LDD region) 13c high concentration impurity implantation region (SD region) 14 gate insulating film (silicon oxide 15) Gate electrode (MoW alloy) 16 Interlayer insulating film (silicon oxide) 17, 18 SD wiring (Al / Ti) 19 Protective insulating film (silicon nitride) 21 Amorphous silicon film 22 Thermal oxide film 23 Photoresist

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference)

Claims (5)

[Claims] An amorphous silicon film is formed on a glass substrate, hydrogen in the amorphous silicon film is released, and the amorphous silicon film is processed into a polycrystalline silicon film. Forming a gate electrode, implanting an impurity into the island-shaped polycrystalline silicon film, and activating the impurity. A method of manufacturing a thin film transistor, comprising: depositing an amorphous silicon film on the glass substrate; ,
A method for manufacturing a thin film transistor, comprising: annealing in an oxidizing atmosphere to form a silicon oxide film when desorbing hydrogen contained in the amorphous silicon film. 2. An annealing condition for releasing hydrogen is a temperature of 400 ° C. or more and 600 ° C. or less, wherein hydrogen in the amorphous silicon film is released and a thin silicon oxide film is formed on the surface of the amorphous silicon film. The method for manufacturing a thin film transistor according to claim 1, wherein a film is formed. 3. The method of manufacturing a thin film transistor according to claim 1, wherein plasma is discharged when said hydrogen is desorbed. 4. The method of manufacturing a thin film transistor according to claim 1, wherein the desorption of hydrogen is performed by irradiating strong light having a wavelength in a range from ultraviolet to near infrared. 5. The method according to claim 1, wherein the silicon oxide film is removed before or after processing the amorphous silicon film into a polycrystalline silicon film.