JPH08172201A - Manufacture of thin film and thin film transistor - Google Patents

Abstract

PURPOSE: To manufacture a TFT having small characteristic change by crystallizing an amorphous silicon thin film containing fluorine and forming a crystalline silicon thin film of a nonsingle crystal containing the fluorine of a specific range. CONSTITUTION: An amorphous silicon fluoride film 2 is formed on a transparent glass board 1 as the precursor of an active semiconductor layer 4, and processed in an island state by a photolithography and etching. Then, it is crystallized to an active semiconductor layer 4 to form a single crystalline silicon fluoride containing fluorine of 0.01 to 20 atomic %. In the TFT formed in this manner, the unbonded hand of the silicon of the defect of the semiconductor layer is terminated by the fluorine having strong bonding force with the silicon, and hence the fluorine is scarcely isolated. Accordingly, the thin film transistor in which characteristic change scarcely occurs can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film manufacturing method applied to a semiconductor device and the like, and a thin film transistor applied to a liquid crystal display device, an image sensor and the like using this manufacturing method.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been installed in viewfinders of home video cameras and notebook computers. Among these liquid crystal display devices, active matrix type liquid crystal display devices capable of high image quality display. Is especially attracting attention. In this active matrix type liquid crystal display device, as a switching element of the pixel electrode,
Thin Film Transistor (TFT)
Abbreviated) is often used.

An example of such a TFT is Active Matrix Liquid Crystal Displays'.
Page 2 to 5 of the 93 symposium proceedings (ACTIVE MATRIX LIQUID CRYSTAL DISPLAYS '93 SY
MPOSIUM PROCEEDINGS, p.2-5). As an example thereof, a method of manufacturing the TFT shown in FIG. 3 will be described below. First, a silicon dioxide film 13 is formed on the crystalline silicon substrate 12. An amorphous silicon film is formed thereon by a low pressure CVD method, and then crystallized by thermal annealing at 600 ° C. to form an active semiconductor layer 4 of polycrystalline silicon, which is processed into an island shape. A gate insulating layer 5 is formed thereon. Next, after forming the gate electrode 6, the gate electrode 6
The impurities are introduced by ion implantation using the mask as a mask
The drain region 7 and the drain region 8 are formed. Then, after forming the interlayer insulating layer 9, a contact hole, a source electrode 10 and a drain electrode 11 are formed to complete the TFT.

[0004]

In the conventional manufacturing method,
In order to reduce defects in the active semiconductor layer, a method of terminating dangling bonds of silicon by adding hydrogen has been used. However, due to the heat stress caused by the manufacturing process of the TFT, the heat generation due to the operation of the TFT, the applied electric field, and the like, hydrogen desorption occurs in the active semiconductor layer, and defects may increase and characteristics may change. Therefore,
There has been a demand for a method of manufacturing a TFT that has a small characteristic change due to heat stress, electric field stress, and the like.

An object of the present invention is to provide a thin film transistor in which a non-single-crystal crystalline silicon thin film which hardly changes its characteristics is formed and which is used as an active semiconductor layer and which hardly changes its characteristics.

[0006]

A non-single crystalline crystalline silicon thin film is formed by crystallizing an amorphous silicon thin film containing fluorine, and a thin film transistor is manufactured by using it as an active semiconductor layer.

[0007]

The following effects are obtained by crystallizing the amorphous silicon thin film containing fluorine to form a non-single crystal crystalline silicon thin film. That is, since the bond between silicon and fluorine is strong, fluorine is less likely to be released due to thermal stress, and the non-single-crystal crystalline silicon thin film thus manufactured is less likely to change in characteristics.
Therefore, by crystallizing an amorphous silicon thin film containing fluorine to form a non-single-crystal crystalline silicon thin film and using it as an active semiconductor layer, it is possible to provide a thin film transistor in which characteristic changes do not easily occur.

[0008]

EXAMPLES Examples of the present invention will be described below.

(Embodiment 1) FIGS. 1A to 1D are sectional views showing an example of a manufacturing process of a top gate type TFT according to the present invention. The first embodiment will be described below with reference to this drawing. First, as a precursor of the active semiconductor layer 4, a film thickness of 10 is formed on the translucent glass substrate 1 by, for example, a plasma CVD method.
A film of 0 nm of fluorinated amorphous silicon 2 is formed (Fig. (A)),
It is processed into islands by using photolithography and etching. Next, for example, XeCl laser having a wavelength of 308 nm is irradiated and crystallized to form, for example, polycrystalline silicon fluoride as the active semiconductor layer 4 (FIG. 1B). Silicon dioxide having a film thickness of 100 nm is formed thereon as the gate insulating layer 5 by, for example, the atmospheric pressure CVD method. further,
Chromium having a film thickness of 200 nm is formed as the gate electrode 6 by a sputtering method and processed by using photolithography and etching. Next, using the gate electrode 6 as a mask, phosphorus serving as a donor is introduced as an impurity by, for example, an ion implantation method to form a source region 7 and a drain region 8 (FIG. 1C). After that, silicon dioxide having a film thickness of 300 nm is formed as the interlayer insulating layer 9 by, for example, an atmospheric pressure CVD method, and then a contact hole is formed by photolithography and etching. Further, the source electrode 10 and the drain electrode 11 are formed with a film thickness of 70, for example.
A 0 nm titanium film is formed and processed to complete a TFT (FIG. 1D).

The top gate type TFT manufactured according to the first embodiment has the following effects. This is because the dangling bond of silicon, which is a defect of the active semiconductor layer, is terminated by fluorine having a strong bonding force with silicon, so that it is difficult for fluorine to be released and a characteristic change is unlikely to occur.

(Embodiment 2) FIGS. 2A to 2E are sectional views showing an example of a manufacturing process of a top gate type TFT according to the present invention. The first embodiment will be described below with reference to this drawing. First, as a precursor of the active semiconductor layer 4, a film thickness of 10 is formed on the translucent glass substrate 1 by, for example, a plasma CVD method.
A film of 0 nm of fluorinated polycrystalline silicon 3 is formed (FIG. 2).
(A)). Then, after silicon and fluorine are introduced into the fluorinated polycrystalline silicon 3 by an ion implantation method to make it amorphous (FIG. 2B), it is processed into an island shape by using photolithography and etching. Next, for example, the wavelength 308
XeCl laser of nm (FIG. 2C) is irradiated and crystallized to form, for example, polycrystalline silicon fluoride as the active semiconductor layer 4. Silicon dioxide having a film thickness of 100 nm is formed thereon as the gate insulating layer 5 by, for example, the atmospheric pressure CVD method. Further, the gate electrode 6 has a film thickness of 200 nm.
Chromium is formed into a film by the sputtering method and processed by using photolithography and etching. Next, using the gate electrode 6 as a mask, phosphorus serving as a donor is introduced as an impurity by, for example, an ion implantation method to form a source region 7 and a drain region 8 (FIG. 2D). in addition,
As the interlayer insulating layer 9, for example, a film thickness of 30 is formed by the atmospheric pressure CVD method.
After forming 0 nm silicon dioxide, contact holes are formed by photolithography and etching. Furthermore, the source electrode 10 and the drain electrode 1
Titanium having a film thickness of 700 nm, for example, is formed and processed to complete the TFT (FIG. 2E).

The top gate type TFT manufactured according to the second embodiment has the following effects. This is because the dangling bond of silicon, which is a defect of the active semiconductor layer, is terminated by fluorine having a strong bonding force with silicon, so that it is difficult for fluorine to be released and a characteristic change is unlikely to occur.

In the second embodiment, fluorinated polycrystalline silicon was used as the precursor of the active semiconductor layer, but this may be fluorinated amorphous silicon, fluorinated microcrystalline silicon, or fluorine-free amorphous. Quality silicon, microcrystalline silicon, polycrystalline silicon, etc. may be used.

In the second embodiment, silicon and fluorine are introduced by an ion implantation method in order to amorphize the precursor of the active semiconductor layer. This is because the ions containing silicon and fluorine decomposed and produced by high frequency discharge are introduced. A method of accelerating and introducing without mass separation may be used. When the precursor of the active semiconductor layer contains fluorine, at least silicon may be introduced to make the precursor amorphous.

In the first and second embodiments, the plasma CVD method is used as the method for forming the precursor of the active semiconductor layer, but the low pressure CVD method, the sputtering method, the vacuum deposition method and the photo CVD method are used.
Any method such as a method that can form a predetermined precursor may be used.

In the first and second embodiments, the XeCl laser was irradiated to crystallize the precursor of the active semiconductor layer. However, any method that can crystallize the precursor may be applied by Ar ion laser irradiation or a furnace. Thermal annealing or the like may be used.

In the first and second embodiments, polycrystalline silicon fluoride is used as the active semiconductor layer. However, any non-single crystalline crystalline silicon containing fluorine may be used, and microcrystalline silicon fluoride or the like may be used. .

In the first and second embodiments, polycrystalline silicon is used as the active semiconductor layer. However, after crystallizing, irradiation of plasma containing fluorine or irradiation of plasma containing fluorine in order to further lower the energy barrier of grain boundaries of polycrystalline silicon. It is even better to inject fluorine.

In the first and second embodiments, silicon dioxide formed by the atmospheric pressure CVD method at 420 ° C. is used as the gate insulating layer, but any material may be used as long as it functions as the gate insulating layer, for example, low pressure CVD method, Plasma CVD
Alternatively, silicon nitride, tantalum oxide, or the like formed by a film formation method such as a sputtering method, a sputtering method, or an ECR-CVD method may be used.

In the first and second embodiments, chromium is used as the gate electrode, but any material that acts as an electrode may be used, such as titanium, tantalum, molybdenum,
A transparent conductive layer such as polycrystalline silicon or ITO doped with a large amount of metal such as aluminum or impurities may be used.

In the first and second embodiments, titanium is used as the source electrode and the drain electrode, but any material that works as an electrode may be used. For example, a large amount of metal or impurities such as chromium, tantalum, molybdenum and aluminum. A transparent conductive layer such as doped polycrystalline silicon or ITO may be used.

In the first and second embodiments, silicon dioxide formed by the atmospheric pressure CVD method is used as the interlayer insulating layer, but any material may be used as long as it functions as an insulating layer, for example, low pressure CVD method, plasma CVD method, Alternatively, silicon nitride, tantalum oxide, or the like formed by a film formation method such as a sputtering method or an ECR-CVD method may be used.

In the first and second embodiments, phosphorus is used as an impurity for forming the source / drain regions. However, in the case of manufacturing an n-channel TFT, any substance such as arsenic that acts as a donor may be used. Channel TFT
In the case of manufacturing, any material that works as an acceptor such as aluminum or boron may be used.

In the first and second embodiments, the ion implantation method is used as a method for adding impurities, but any method can be used as long as the impurities can be added. A method of accelerating and introducing without separation or a plasma doping method may be used.

In the first and second embodiments, the translucent glass substrate is used, but any material having an insulating surface may be used, and a crystalline silicon substrate having a surface formed with silicon dioxide or a metal plate may be used. Good.

In the first and second embodiments, an example of the manufacturing process of the top gate type TFT is shown, but a bottom gate type or vertical type TFT may be used.

[0027]

As described above, according to the present invention, the following effects can be obtained by crystallizing an amorphous silicon thin film containing fluorine to form a non-single crystalline crystalline silicon thin film. Since the bond between silicon and fluorine is strong, fluorine is less likely to be released due to heat stress, and the non-single-crystal crystalline silicon thin film thus manufactured is less likely to change in characteristics. Further, by using it for the active semiconductor layer, it is possible to provide a thin film transistor in which the characteristic change hardly occurs.

[Brief description of drawings]

1A to 1D are cross-sectional views of a manufacturing process of a top gate type TFT according to the present invention.

2A to 2E are cross-sectional views of a manufacturing process of a top gate type TFT according to the present invention.

FIG. 3 is a cross-sectional view of a conventional thin film transistor.

[Explanation of symbols]

 1 Transparent Glass Substrate 2 Amorphous Silicon Fluoride 3 Polycrystalline Silicon Fluoride 4 Active Semiconductor Layer 5 Gate Insulating Layer 6 Gate Electrode 7 Source Region 8 Drain Region 9 Interlayer Insulating Layer 10 Source Electrode 11 Drain Electrode 12 Crystalline Silicon Substrate 13 Silicon dioxide

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H01L 27/12 R (72) Inventor Yutaka Miyata 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. Within

Claims (14)

[Claims] 1. An amorphous silicon thin film containing at least fluorine is formed and then the amorphous silicon thin film is crystallized to obtain 0.01 atomic% or more and 20 at.
A method for producing a thin film, which comprises forming a non-single-crystal crystalline silicon thin film containing ommic% or less of fluorine. 2. An amorphous silicon thin film is formed by plasma CVD.
The method for producing a thin film according to claim 1, wherein the thin film is directly deposited by a vacuum method, a low pressure CVD method, or a sputtering method. 3. An amorphous silicon thin film is amorphous by introducing a fluorine-containing polycrystalline silicon thin film, a microcrystalline silicon thin film, or an amorphous silicon thin film by accelerating ions containing at least silicon by an electric field. The thin film manufacturing method according to claim 1, wherein the thin film is formed by qualification. 4. An amorphous silicon thin film is made amorphous by introducing a polycrystalline silicon thin film, a microcrystalline silicon thin film, or an amorphous silicon thin film by accelerating ions containing at least silicon and fluorine by an electric field. The thin film manufacturing method according to claim 1, wherein the thin film is formed by: 5. Amorphization of the thin film generates ions containing at least an element to be introduced by high frequency discharge plasma,
The thin film manufacturing method according to claim 3 or 4, wherein the ions are accelerated by an electric field and introduced into the thin film without mass separation. 6. The method for producing a thin film according to claim 1, wherein the crystallization is performed by laser beam irradiation or thermal annealing. 7. The method for producing a thin film according to claim 1, wherein the non-single-crystal crystalline silicon thin film is a polycrystalline silicon thin film or a microcrystalline silicon thin film. 8. An amorphous silicon thin film containing at least fluorine is formed, and then the amorphous silicon thin film is crystallized to form 0.01 atomic% or more 20.
A thin film transistor comprising a non-single crystalline crystalline silicon thin film containing atomic% or less of fluorine as an active semiconductor layer. 9. An amorphous silicon thin film is formed by plasma CVD.
9. The thin film transistor according to claim 8, wherein the thin film transistor is directly deposited by a sputtering method, a low pressure CVD method, or a sputtering method. 10. The amorphous silicon thin film is amorphous by introducing a fluorine-containing polycrystalline silicon thin film, a microcrystalline silicon thin film, or an amorphous silicon thin film by accelerating ions containing at least silicon by an electric field. The thin film transistor according to claim 8, wherein the thin film transistor is formed by qualification. 11. An amorphous silicon thin film is made amorphous by introducing a polycrystalline silicon thin film, a microcrystalline silicon thin film, or an amorphous silicon thin film by accelerating ions containing at least silicon and fluorine by an electric field. The thin film transistor according to claim 8, wherein the thin film transistor is formed by: 12. Amorphization of a thin film is performed by generating ions containing at least an element to be introduced by high frequency discharge plasma, and accelerating the ions by an electric field without mass separation to introduce them into the thin film. The thin film transistor according to claim 10 or 11, which is made. 13. The thin film transistor according to claim 8, wherein the crystallization is performed by laser beam irradiation or thermal annealing. 14. The thin film transistor according to claim 8, wherein the non-single-crystal crystalline silicon thin film is a polycrystalline silicon thin film or a microcrystalline silicon thin film.