JPH06196701A - Thin film transistor and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a TFT which is suitable for mass-production at a low price by providing a semiconductor film with a silicon film including the conductivity of a specific micro-crystal phase in the part distant from an i-type insulating film by within a limited value. CONSTITUTION:Plasma 9 is generated by a high-frequency power supply 8 between an anode electrode 6 and a cathode electrode 7, and while raw material gas and hydrogen gas are introduced in a reaction chamber, the raw material gas and the hydrogen gas are dissolved in the plasma 9 to form an a-Si film in a substrate 10. While only hydrogen gas is introduced therein, a dark conductivity of 1X10<-3>S/cm or more is obtained by applying hydrogen plasma treatment to the a-Si film formed on the substrate for about 50 seconds per one cycle. Therefor, a silicon film including the micro-crystal phase having conductivity of 50X10<-9>S/cm or more can be formed in the part of within 500Angstrom from the beginning of film formation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor (hereinafter referred to as a TFT) used in a liquid crystal display device, a method for manufacturing the thin film transistor, a liquid crystal display device, and a device used for manufacturing the TFT.

[0002]

2. Description of the Related Art In a liquid crystal display device, an active element such as a TFT is provided for each pixel in order to display a high resolution image. A large number of this TFT can be formed over a large area, and a very large number of pixels can be controlled.

Conventionally, as a semiconductor film of this TFT, an amorphous silicon (a-Si) film formed by a reactive plasma chemical vapor deposition method (RF-PCVD method) using a radio frequency (RF) discharge, A polycrystalline silicon (poly-Si) film or the like obtained by recrystallizing an a-Si film formed by a thermochemical vapor deposition method (thermal CVD method) or the like by a solid phase growth method or a laser annealing method has been used. .

On the other hand, a silicon (μc (microcrystal) -Si) film containing a microcrystalline phase is produced by the RF-PCVD method under high RF power and high hydrogen dilution conditions. It is known that by using this μc-Si film for an amorphous solar cell having a pin structure, the open circuit voltage of the amorphous solar cell is increased and the photoelectric conversion efficiency is improved. Further, it is known that the higher the RF power and the higher the hydrogen dilution ratio, the easier the formation of the μc-Si film.

When a silicon film containing a microcrystalline phase is produced under high RF power and high hydrogen dilution conditions, the crystallization of silicon depends on the type and thickness of the substrate. For example, B ₂ H ₅
20% of SiH ₄ containing 0.7% of H2 and 800 of H ₂
sccm, substrate temperature 260 ° C., RF power density 0.
The relationship between the film thickness and the dark conductivity of the p-type silicon film produced under the film forming conditions of 04 W / cm ² and the pressure of 100 Pa is shown in Table 1 below.

[0006]

[Table 1]

From Table 1 above, when the film thickness of the p-type silicon film formed under the above conditions is 1000 angstroms or more, the film thickness is 500 angstroms or less.
It can be seen that it has a dark conductivity that is on the order of ** orders of magnitude. From this, the p-type silicon film formed under the above conditions becomes a-Si when the film thickness is 500 angstroms or less, and 50 when it is 1000 angstroms or more.
It is considered that μc-Si is formed on the a-Si having a film thickness of 0 angstrom or more.

Further, SiH ₄ containing 0.5% of PH ₃ is added to 2
0 sccm, H ₂ 1400 sccm, substrate temperature 260
℃, RF power density 0.05W / cm ² , pressure 110P
The relationship between the film thickness and the dark conductivity of the n-type silicon film produced under the film forming condition a is shown in Table 2 below.

[0009]

[Table 2]

From Table 2, this n-type silicon film becomes a-Si when the film thickness is 200 angstroms or less, and when it is more than 200 angstroms, a-Si having a film thickness of approximately 200 angstroms is formed. And on top of that, μc-S
It is considered that i is formed.

As described above, when continuous film formation is performed using a normal P-CVD apparatus even under conditions of high RF power and high hydrogen dilution, which are conditions under which μc-Si is easily formed, the film formation is started from the start. Within 500 Å, it was difficult to microcrystallize a-Si to obtain μc-Si.

Generally, in a TFT, a field-effect mobility (field-ef) in a very thin semiconductor film in contact with an insulating film.
fect mobility) determines the magnitude of the on-current of the TFT. The thickness of this semiconductor film is 10 in a normal TFT.
00 angstroms or less, preferably about 200
~ 600 Angstroms. Therefore, when the semiconductor film of the TFT is formed under the conditions of high RF power and high hydrogen dilution as described above, this semiconductor film becomes a-Si, so that the ON current of the TFT cannot be increased. Conceivable.

Further, in the following document (1), a normal RF
It is shown that a μc-Si film can be formed by repeating the formation of a silicon film and the hydrogen plasma treatment using a -PCVD apparatus.

(1) K. Nomoto, Y. Urano, JL Guizo
t, G. Ganguly and A. Matsuda: Japanese Journal of A
pplied Physics Vol. 29, No. 8, August, 1990, pp. L1
372-L1375. "Role of Hydrogen Atoms in the Formation
Process of Hydrogenated Microcrystalline Silicon "In the method described in the literature (1), an a-Si film is formed using only SiH ₄ , hydrogen plasma treatment is performed on the a-Si film, and a certain period of time is elapsed from the hydrogen plasma treatment. After that, the next a-Si film is formed, but no example of using this method for a TFT has been reported.

[0015]

By the way, in order to produce a large-sized and high-definition liquid crystal display, it is necessary to charge the capacity consisting of the liquid crystal layer and the storage capacitor in a short gate switching time. However, a-
In a TFT using a Si film, the on-current cannot be increased because the field effect mobility of the semiconductor film is low.
In such a TFT, it is necessary to increase the size of the TFT in order to increase the on-current, but this leads to a reduction in the aperture ratio of the liquid crystal display device.

On the other hand, in a TFT using a poly-Si film as a semiconductor film, the on-current of the TFT can be increased because the field effect mobility of the semiconductor film is large. However, if the a-Si film is crystallized by the solid phase growth method and the po
In order to obtain a ly-Si film, it is necessary to perform heat treatment at 600 ° C. or higher for about 10 hours. For this reason, it is difficult to use an ordinary glass substrate, and a large-area TFT cannot be obtained. Further, in the case of recrystallizing the a-Si film by the laser annealing method to obtain the poly-Si film, it is necessary to use an expensive laser annealing device having a low processing speed, which is not suitable for mass production.

The present invention has been made in view of the above circumstances, and its purpose is to improve the on-current and to provide a TFT that is inexpensive and suitable for mass production, a manufacturing method thereof, and a large-sized TFT including the TFT. It is an object of the present invention to provide a method for manufacturing a high-definition liquid crystal display device and a device used for manufacturing the TFT.

[0018]

A thin film transistor of the present invention comprises a substrate, a gate electrode formed on the substrate, an insulating film formed on the substrate to cover the gate electrode, and an insulating film on the insulating film. A thin film transistor comprising: a semiconductor film formed on a semiconductor film; and a source electrode and a drain electrode formed on the semiconductor film, wherein the semiconductor film is i-type and is located within 500 angstroms from the insulating film. Further, it has a silicon film containing a microcrystalline phase having an electric conductivity of 5 × 10 ⁻⁹ S / cm or more, and thereby the above object is achieved.

Another thin film transistor of the present invention comprises a substrate, a gate electrode formed on the substrate, an insulating film formed on the substrate so as to cover the gate electrode, and formed on the insulating film. A thin film transistor comprising a semiconductor film and a source electrode and a drain electrode formed on the semiconductor film, wherein the semiconductor film is a p-type or an n-type and is within 500 angstroms from the insulating film, It has a silicon film containing a microcrystalline phase having an electric conductivity of 1 × 10 ⁻³ S / cm or more, and thereby the above object is achieved.

Another thin film transistor of the present invention is a substrate, a gate electrode formed on the substrate, an insulating film formed on the substrate so as to cover the gate electrode, and formed on the insulating film. A thin film transistor comprising a semiconductor film and a source electrode and a drain electrode formed on the semiconductor film, wherein the semiconductor film has a bonded hydrogen amount of 10 atomic% or less in a portion within 500 angstroms from the insulating film. Has a silicon film containing the microcrystalline phase of, thereby achieving the above object.

Another thin film transistor of the present invention comprises a substrate, a gate electrode formed on the substrate, an insulating film formed on the substrate so as to cover the gate electrode, and formed on the insulating film. A thin film transistor including a semiconductor film and a source electrode and a drain electrode formed on the semiconductor film, wherein the semiconductor film has a crystal volume fraction of 10% or more in a portion within 500 angstroms from the insulating film. Has a silicon film containing the microcrystalline phase of, thereby achieving the above object.

In the method for producing a semiconductor film of the present invention, the source gas containing a silicon element and the hydrogen gas introduced into the reaction chamber of the plasma chemical vapor deposition apparatus are decomposed by plasma to form an amorphous silicon layer on the insulating film. A silicon layer containing a microcrystalline phase by repeating the step of forming hydrogen gas into the reaction chamber, performing hydrogen plasma treatment on the amorphous silicon layer, and microcrystallizing the amorphous silicon layer. A method of manufacturing a semiconductor film, the method including the step of forming a semiconductor film having:

Before forming the semiconductor film on the insulating film, a step of subjecting the upper surface of the insulating film to hydrogen plasma treatment may be further included.

In the step of forming the amorphous silicon layer on the insulating film, the amorphous silicon layer may be formed to a thickness within the range of 1 angstrom to 1000 angstrom.

Another method of manufacturing a semiconductor film according to the present invention comprises: a first film forming step of forming a silicon layer containing a microcrystalline phase having a hydrogen dilution ratio of 200 or more and a thickness of 100 angstroms or less; Hydrogen dilution ratio of 2 to 10 on the silicon layer
And a second film forming step of forming a silicon layer having a microcrystalline phase at 0, whereby the above object is achieved.

A method of manufacturing a semiconductor film, comprising:

A method of manufacturing a liquid crystal display device according to the present invention is a method of manufacturing a liquid crystal display device having a thin film transistor, wherein the step of forming a semiconductor film for the thin film transistor is a reaction of a plasma chemical vapor deposition apparatus. A step of decomposing a source gas containing a silicon element introduced into the chamber by plasma and forming an amorphous silicon layer on the substrate;
It includes a step of forming a semiconductor film made of a silicon layer containing a microcrystalline phase by repeating a step of introducing hydrogen gas into the reaction chamber and performing a hydrogen plasma treatment on the amorphous silicon layer. The above object is achieved.

The plasma chemical vapor deposition apparatus of the present invention comprises:
A reaction chamber for forming a semiconductor thin film and subjecting the semiconductor thin film to hydrogen plasma treatment, a first line connected to the reaction chamber for introducing hydrogen gas into the reaction chamber, and the reaction chamber For introducing a source gas used for forming the semiconductor thin film into the reaction chamber.
And a third line connected to the second line for discharging the raw material gas from the second line, and introducing the raw material gas into the reaction chamber and the third line. And means for switching the discharge to the line.

Another plasma-enhanced chemical vapor deposition apparatus of the present invention is a reaction chamber for forming a semiconductor thin film and subjecting the semiconductor thin film to hydrogen plasma treatment, and a reaction chamber connected to the reaction chamber for supplying hydrogen gas. A first line for introducing into the reaction chamber, a second line connected to the reaction chamber for introducing a source gas used for forming the semiconductor thin film into the reaction chamber, Is connected to the second line,
A third line for discharging the raw material gas from the second line, a connecting portion between the second line and the third line, and the second line between the reaction chamber First provided
Apparatus, a second valve provided in the third line, and a control means for controlling opening / closing of the first valve and the second valve. The control means introduces the source gas into the reaction chamber by opening the first valve and closing the second valve when forming the semiconductor thin film. When the semiconductor thin film is subjected to the hydrogen plasma treatment, the second valve is opened and the first valve is closed to shut off the introduction of the source gas into the reaction chamber. Therefore, the above object is achieved.

[0030]

In the TFT of the present invention, a silicon film having a microcrystalline phase is formed very thin and used as a semiconductor film. A silicon film having this microcrystalline phase, that is, μc-Si
The film is formed by repeating the formation of the a-Si film and the hydrogen plasma treatment on the a-Si film. Further, it can be also formed by first forming a silicon film under the condition that the hydrogen dilution ratio is 200 or more, changing the hydrogen dilution ratio to 2 to 100, and continuing the normal film on the previously formed silicon film. .

The μc-Si film formed in this way is
When used as a semiconductor film of FT, the field effect mobility is larger than that of a semiconductor film made of an a-Si film, and therefore, the TFT
The control current is improved. Further, since the RF-CVD apparatus is used for film formation, the μc-Si film is formed at low temperature. Therefore, it is possible to use a glass substrate,
An FT can be formed.

[0032]

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

Example 1 First, the step of forming the μc-Si film will be described below.

In this step, the usual RF-PCV is used.
An RF-PCVD film forming apparatus as shown in FIG. 1 is used instead of the D apparatus. This film forming apparatus is a standard RF-PCVD
In addition to the configuration of the apparatus, it is provided with two gas introduction lines, a hydrogen gas introduction line 1 and a source gas introduction line 2.

In this apparatus, when the compressed air valve 3 of the raw material gas introduction line 2 is open and the compressed air valve 4 is closed, the raw material gas is introduced into the reaction chamber 30 together with the hydrogen gas. On the contrary, when the compressed air valve 3 is closed and the compressed air valve 4 is open, the source gas is directly discharged by the exhaust pump 5 and only hydrogen gas is introduced into the reaction chamber 30. The pneumatic valves 3 and 4 are controlled by a control device 32 connected to a timer 31. By the control, the pneumatic valves 3 and 4 allow both the raw material gas and the hydrogen gas to be introduced into the reaction chamber 30 for a set time, and following the introduction,
It is opened and closed for a certain set time so that only hydrogen gas is introduced into the reaction chamber 30.

In the RF-PCVD film forming apparatus shown in FIG. 1, a high frequency power source 8 supplies power between the anode electrode 6 and the cathode electrode 7 to generate plasma 9. While the source gas and the hydrogen gas are being introduced into the reaction chamber 30, both the source gas and the hydrogen gas are decomposed in the plasma 9 and an a-Si film is formed on the substrate 10. Further, while only hydrogen gas is being introduced, the a-Si film formed on the substrate 10 is subjected to hydrogen plasma treatment. By repeating the formation of such an a-Si film and the hydrogen plasma treatment, a μc-Si film having a desired thickness can be obtained.

The formation of the μc-Si film in this embodiment is
The details will be described below. First, RF- shown in FIG.
From the raw material introduction line 2 of the PCVD apparatus, monosilane (SiH ₄ ) 1 sccm as a raw material gas and diborane (B ₂ H ₆ ) with a gas doping ratio of 1% as a doping gas.
Was introduced into the reaction chamber 30. At the same time, 100 sccm of hydrogen (H ₂ ) was introduced into the reaction chamber 30 from the hydrogen gas introduction line 1, the substrate temperature was 300 ° C., and the RF power density was 1 W / cm.
² , 1 on the substrate 10 under the condition that the pressure is 100 Pa
A Si film of 0 angstrom was formed. Subsequently, the compressed air valve 3 is closed and the compressed air valve 4 is switched to the open state to stop the introduction of the raw material gas, introduce only H ₂ 100 sccm, and perform the hydrogen plasma treatment on the previously formed Si film. It was The cycle of the formation of the Si film and the hydrogen plasma treatment was repeated to finally form a Si film having a film thickness of 500 angstrom.

FIG. 2 shows the relationship between the time for which the hydrogen plasma treatment is performed in one cycle and the dark conductivity of the silicon film formed as described above. Here, 200
W power was supplied. From this figure, by performing the hydrogen plasma treatment for about 50 seconds per cycle, the dark conductivity of the silicon film sharply increases by about 7 digits, and 1 × 10 ⁻³ S
It can be seen that a dark conductivity of not less than / cm is obtained. This means that in a very thin film, the crystal structure is changed by hydrogen plasma treatment for about 50 seconds, and even in a region within 500 angstroms from the start of film formation, which was difficult to microcrystallize by conventional continuous film formation. , Shows that the silicon film is microcrystallized.

In this embodiment, the Si film is formed to have a thickness of 10 Å per cycle, but when the crystal structure of the film is changed by the hydrogen plasma treatment as described above, the film thickness is 1 to 1000 Å, preferably 5 Å. 1
It may be 00 angstrom.

When the amount of bound hydrogen in the μc-Si film formed by repeating the above-mentioned cycle was quantified by the infrared absorption spectroscopy, the amount of bound hydrogen in the ordinary a-Si film was 13 to 20 atomic%. However, the content was 4 to 10 atomic%. This is because, of a-Si and crystalline Si mixed in the μc-Si film, the amount of bound hydrogen in crystalline Si is approximately 0%.

Further, the composition of the film formed as described above was analyzed, and the film was analyzed by backscattered electron diffraction and Raman spectroscopy. As a result, it was confirmed that the film formed as described above was a silicon film containing a microcrystalline phase.

The Raman spectrum of this μc-Si film is
And peak unique broad to a-Si in the vicinity of 480 cm ^-1, a peak of the crystal Si of 520 cm ^-1, i.e. Si-
It was divided into a sharp peak of Si bond and a crystal volume fraction representing the ratio of crystalline Si in this μc-Si film was measured from these integrated intensity ratios. As a result, normal CV
A formed by the D method under normal a-Si film forming conditions
The crystal volume fraction is 0% in the -Si film and the silicon film formed by the P-CVD method to a thickness of 500 μm or less without performing the hydrogen plasma treatment as described above. High RF power, high hydrogen dilution rate aS
In the μc-Si film formed by repeating the formation of the i film and the hydrogen plasma treatment, the crystal volume fraction was 10% or more, and the maximum μc-Si film was obtained.

[0043] In the above method, when forming the a-Si film has formed the p-type [mu] c-Si film by using diborane (B ₂ H ₆₎ as the doping gas, diborane (B ₂ H ₆ By using a phosphine (PH ₃ ) gas in place of), an n-type μc-Si film can be formed. If no doping gas is used, i-type μc
-Si film is obtained. The conductivity of this i-type μc-Si film is 5 × 10 ⁻⁹ S / cm or more.

In the above-mentioned document (1), in order to analyze the influence of H ₂ on the microcrystallization of the silicon film, the next silicon film is formed after a certain time has passed after the hydrogen plasma treatment. It has started. For this reason, the method of Document (1) reduces the throughput. On the other hand, according to the method of the present embodiment, since the a-Si film formation and the hydrogen plasma treatment are performed without time, the throughput does not decrease.

Further, in the above-mentioned document (1), introduction of SiH ₄ and H ₂ is switched, and SiH ₄ is formed at the time of forming the a-Si film.
However, since only H ₂ is introduced into the reaction chamber during the hydrogen plasma treatment, there is a problem that the pressure fluctuation in the reaction chamber becomes large. However, in this embodiment, a normal R
A hydrogen gas introduction line 1 and a raw material gas introduction line 2 are provided in the F-PCVD apparatus, and a valve 3 of the raw material gas introduction line 2 is provided.
Since the opening / closing of No. 4 is controlled by the control device 32 connected to the timer 31, it is possible to stop only the introduction of the raw material gas. As a result, the total flow rate of the raw material gas and the hydrogen gas introduced into the reaction chamber 30 changes only about 1% between the time of forming the a-Si film and the time of the hydrogen plasma treatment, and suppresses the pressure fluctuation in the reaction chamber 30. be able to.

Example 2 Another method of forming a silicon film containing a microcrystalline phase from the start of film formation will be described below.

First, Si is placed in the reaction chamber of the RF-PCVD apparatus.
A raw material gas containing H ₄ and hydrogen gas are introduced, the hydrogen dilution ratio (SiH ₄ / H ₂ ratio) is 200 or more, and the power density is 0.03 to
1.5 W / cm ² (preferably 0.1 to 0.3 W / c
The silicon film is formed to a thickness of about 100 Å under the condition of m ² ). After that, the hydrogen gas flow rate is changed so that the hydrogen dilution ratio becomes 2 to 100, and the power density is 0.03 to 1.
A silicon film is formed on the previously formed silicon film under the condition of 5 W / cm ² .

In this embodiment, first, the flow rate of SiH ₄ is 1 sccm, the flow rate of H ₂ is 1000 sccm, the power density is 1 W / cm ² , the substrate temperature is 300 ° C., and the pressure is 100 P.
A silicon film having a thickness of about 100 Å was formed under the condition a. Then, change the flow rate of H ₂ to 70 sccm,
A silicon film is formed on the previously formed silicon film,
Finally, a silicon film having a film thickness of 100 angstrom was formed.

The silicon film formed as described above is
When analyzed by infrared absorption spectroscopy, backscattered electron diffraction, Raman spectroscopy and the like as in Example 1, it was confirmed that this silicon film was a μc-Si film. The amount of bound hydrogen in this μc-Si film was 0 atomic%, and the crystal volume fraction was 30% or more. Further, the i-type [mu] c-Si film dark conductivity to be 2 × 10 ^{over 8} S / cm or more was measured, and a very good dark conductivity obtained by the method described above.

In this embodiment, first, the hydrogen dilution ratio is set to 200.
Since the silicon film is formed at an extremely high value as described above, the film formation rate is very slow at 0.05 angstrom / sec or less, but a μc-Si film is obtained from about 100 angstrom or less from the start of film formation. be able to. Thus, first, with a very high hydrogen dilution ratio, μc-Si is formed from the film formation start to about 100 angstroms.
Since the film is formed, the subsequently formed silicon film also contains a microcrystalline phase under the influence of the previously formed μc-Si film. In addition, the μc-Si film is about 1
Since the hydrogen dilution ratio is changed to 2 to 100 after the formation of 00 angstrom, the film forming rate is also 0.2 to 0.3.
Can be increased to Angstrom / sec. In this way, a silicon film finely crystallized from 100 angstroms or less from the start of film formation can be formed to a desired thickness.

FIG. 3 shows a main part of a liquid crystal display device provided with a TFT having a semiconductor film formed by the method shown in the first embodiment.

In this liquid crystal display device, a gate electrode 12 is formed on a glass substrate 11, and an anodized film 13 is formed on the surface of the gate electrode 12. The gate insulating film 14 is formed so as to cover the entire surface of the substrate 11 in such a state. A p-type μc-Si semiconductor layer 15 is formed on the gate insulating film 14 so as to overlap the gate electrode 12. An etching stopper 16 is formed in the central portion on the semiconductor layer 15, and the source thin film 17a and the source thin film 17a are formed in a state where the etching stopper 16 covers an end portion of the etching stopper 16 and a part of the semiconductor layer 15 and is divided on the etching stopper 16. The drain thin film 17b is formed.

A source electrode 18a is formed on the source thin film 17a.
And the drain electrode 1 is formed on the drain thin film 17b.
8b is formed. A protective film 20 is formed on the source electrode.
a is formed, and the pixel electrode 2 is formed on the drain electrode 18b.
0b is formed, and a protective film 21 is further formed as the uppermost layer so as to cover the entire surface of the substrate 11.

The liquid crystal display device as described above is manufactured as follows.

First, a tantalum (Ta) thin film having a thickness of about 300 nm is formed on the glass substrate 11 by sputtering, and the thin film is patterned by photolithography and etching to form the gate electrode 12. Then, the substrate 11 in that state is immersed in an ammonium tartrate solution, and an electric current is applied from the outside to anodize. Thus, the anodic oxide insulating film 13 having a thickness of 300 nm is formed on the gate electrode 12.

Next, as shown in FIG. 4, an in-line type C
Using a VD device, a silicon nitride (Si ₃ N ₄ ) film 14,
Si for the μc-Si film 15 and the etching stopper 16
_{A 3} N ₄ film is formed. First, the glass substrate 11 is carried into the SiN ₄ film forming chamber 23 from the load chamber 22, the SiN ₄ film forming chamber, monosilane (SiH _4), ammonia (NH ₃₎ and introduced to the plasma discharge hydrogen (H ₂₎ To do. As a result, the Si ₃ N ₄ gate insulating film 14 having a thickness of 300 nm is formed.

Next, the glass substrate 11 is loaded into the μc-Si film forming chamber 24, and μc is formed on the gate insulating film 14 formed previously.
-Si film 15 is formed. The formation conditions are as follows: monosilane (SiH ₄ ) 1 sccm as a source gas, diborane (B ₂ H ₆ ) with a gas doping ratio of 1% as a doping gas, the flow rate of hydrogen (H ₂ ) is 100 sccm, and the power density is 0.7 W. / Cm ² , the substrate temperature was 300 ° C., and the pressure was 100 Pa. Under such conditions, first, an a-Si film having a thickness of 20 Å per cycle is grown. Subsequently, electric power having a power density of 0.7 W / cm ² is applied and hydrogen plasma treatment is performed for about 50 seconds. The formation of such an a-Si film and the hydrogen plasma treatment are repeated to obtain a p-type μc-Si film 1 having a film thickness of 300 Å.
5 is formed.

Then, the glass substrate 11 is loaded into the Si ₃ N ₄ film forming chamber 25, and monosilane (SiH ₄ ) is introduced into the film forming chamber 25.
Ammonia (NH ₃ ) and hydrogen (H ₂ ) were introduced, and a Si ₃ N ₄ film having a thickness of 300 nm was formed by μc-S.
It is formed on the i film 15. When the formation of the Si ₃ N ₄ film is completed, the glass substrate 11 is unloaded from the unload chamber 26, and S
The etching stopper 16 is formed by patterning the i ₃ N ₄ film.
And Then, n ⁺ -doped Si is formed by a CVD method or the like.
A film is formed and patterned to form a source thin film 17a and a drain thin film 17b.

Next, titanium (Ti) is laminated to a thickness of about 300 nm by a sputtering method and patterned to form a source electrode 18a and a drain electrode 18b. Here, the channel length is 10 μm and the channel width is 4
It was formed as 0 μm.

Then, using a target of indium oxide containing 5% of tin (Sn), sputtering was performed in an oxygen atmosphere to form indium oxide with a thickness of about 70 nm.
By patterning, the protective film 20a is formed on the source electrode 18a, and the pixel electrode 2 is formed on the drain electrode 18b.
0b was formed. Then, a Si ₃ N ₄ film having a thickness of 330 nm was formed and patterned to form a protective film 21.

As described above, one substrate 11 of the liquid crystal display device having the TFT as shown in FIG. 3 is formed.

In this state, when the characteristics of the TFT formed by the above-mentioned method are measured, the on-current when a gate voltage of 10 V is applied is 1.5 × 10 ⁻⁶ A or more, which means that the semiconductor film a The value could be 1.5 times as large as when the -Si film was used.

After that, a glass plate which is the other substrate of the liquid crystal display device on which a color filter, a black matrix, and an ITO electrode are formed is bonded to the glass substrate 11 which is the above-mentioned one substrate with a gap, and the gap is formed. Inject liquid crystal into. Then, a polarizing plate is attached to these substrates and a backlight is attached to manufacture a liquid crystal display device.

As described above, according to the above method, T
Since the ON current of the FT can be improved, it becomes possible to manufacture a liquid crystal display device for an engineering workstation having 16-inch 1280 × 3 × 1024 picture elements, which has been difficult in the past.

Since the semiconductor film of the TFT can be formed at a low temperature, an inexpensive glass substrate can be used as the substrate.

In the above embodiment, an example in which a p-type μc-Si film is used as a semiconductor film of a TFT has been described, but the present invention is not limited to this, and an i-type or n-type μc-Si film is used.
A Si film can also be used.

Further, although the μc-Si film serving as the semiconductor film of the TFT is formed here by the method shown in the first embodiment, it may be formed by the method shown in the second embodiment.

In the above-mentioned embodiment, the TFT having the reverse stagger structure is used for explanation, but the same effect can be obtained also with the stagger structure TFT.

[0069]

As is apparent from the above description, according to the present invention, a silicon film containing a microcrystalline phase can be formed within 500 Å from the start of film formation. Therefore, by using such a silicon film as a semiconductor film of a TFT, a T film having excellent field effect mobility can be obtained.
It is possible to form a large number of FTs on a large-sized substrate at low cost. Therefore, a large-sized and high-definition liquid crystal display device used for an engineering workstation can be realized.

In addition, a line for introducing hydrogen gas into the reaction chamber and a line for introducing raw material gas are independently provided in a normal RF-PCVD apparatus, and a valve provided in the raw material gas introducing line is opened and closed. Since it is possible to stop only the introduction of the raw material gas by controlling the above, it is possible to suppress the pressure fluctuation in the reaction chamber as much as possible.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an RF-PCVD apparatus capable of hydrogen plasma treatment used in the present invention.

FIG. 2 is a diagram showing a change in dark conductivity of a silicon film with respect to a hydrogen plasma treatment time.

FIG. 3 is a cross-sectional view of essential parts of a liquid crystal display device that is an embodiment of the present invention.

FIG. 4 is a diagram of an in-line CVD apparatus used in the present invention.

[Explanation of symbols]

 1 Hydrogen Gas Line 2 Raw Material Gas Line 3, 4 Pneumatic Valve 5 Exhaust Pump 8 High Frequency Power Supply 9 Plasma 10 Substrate 11 Glass Substrate 12 Gate Electrode 14 Gate Insulating Film 15 μc-Si Semiconductor Film 18a Source Electrode 18b Drain Electrode 31 Timer 32 Control Device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H01L 21/336

Claims (11)

[Claims] 1. A substrate, a gate electrode formed on the substrate, an insulating film formed on the substrate to cover the gate electrode, a semiconductor film formed on the insulating film, and the semiconductor. A thin film transistor having a source electrode and a drain electrode formed on a film, wherein the semiconductor film is i-type and has a conductivity of 5 × 10 ⁻⁹ S in a portion within 500 Å from the insulating film. / Cm
A thin film transistor having a silicon film containing the above microcrystalline phase. 2. A substrate, a gate electrode formed on the substrate, an insulating film formed on the substrate to cover the gate electrode, a semiconductor film formed on the insulating film, and the semiconductor. A thin film transistor comprising a source electrode and a drain electrode formed on a film, wherein the semiconductor film is a p-type or an n-type,
Conductivity is 1 x 10 within the range of 00 angstrom
^-3 A thin film transistor having a silicon film containing a microcrystalline phase of ³ S / cm or more. 3. A substrate, a gate electrode formed on the substrate, an insulating film formed on the substrate to cover the gate electrode, a semiconductor film formed on the insulating film, and the semiconductor. A thin film transistor having a source electrode and a drain electrode formed on a film, wherein the semiconductor film includes a microcrystalline phase having a bonded hydrogen amount of 10 atomic% or less in a portion within 500 angstroms of the insulating film. A thin film transistor having a silicon film. 4. A substrate, a gate electrode formed on the substrate, an insulating film formed on the substrate so as to cover the gate electrode, a semiconductor film formed on the insulating film, and the semiconductor. A thin film transistor having a source electrode and a drain electrode formed on a film, wherein the semiconductor film includes a microcrystalline phase having a crystal volume fraction of 10% or more in a portion within 500 angstroms from the insulating film. A thin film transistor having a silicon film. 5. A step of decomposing a source gas containing a silicon element and a hydrogen gas, which are introduced into a reaction chamber of a plasma enhanced chemical vapor deposition apparatus, by plasma to form an amorphous silicon layer on an insulating film, and the reaction. A step of forming a semiconductor film having a silicon layer containing a microcrystalline phase by repeating a step of introducing hydrogen gas into a chamber, performing hydrogen plasma treatment on the amorphous silicon layer, and microcrystallizing the amorphous silicon layer. A method for manufacturing a semiconductor film, including: 6. The method of manufacturing a semiconductor film according to claim 5, further comprising a step of subjecting an upper surface of the insulating film to a hydrogen plasma treatment before forming the semiconductor film on the insulating film. 7. The method of manufacturing a thin film transistor according to claim 5, wherein, in the step of forming the amorphous silicon layer on the insulating film, the amorphous silicon layer is formed to a thickness in the range of 1 Å to 1000 Å. Method. 8. A first film forming step of forming a silicon layer containing a microcrystalline phase having a hydrogen dilution ratio of 200 or more and a thickness of 100 angstroms or less, and a hydrogen dilution ratio of 2 to 2 on the formed silicon layer. And a second film forming step of forming a silicon layer having a microcrystalline phase at 100. 9. A method for manufacturing a liquid crystal display device having a thin film transistor, wherein the step of forming a semiconductor film for the thin film transistor comprises a raw material containing a silicon element introduced into a reaction chamber of a plasma enhanced chemical vapor deposition apparatus. By including a step of decomposing gas by plasma to form an amorphous silicon layer on a substrate and a step of introducing hydrogen gas into the reaction chamber and performing hydrogen plasma treatment on the amorphous silicon layer, a microcrystalline phase is contained. A method of manufacturing a liquid crystal display device, which includes the step of forming a semiconductor film made of a silicon layer. 10. A reaction chamber for forming a semiconductor thin film and performing hydrogen plasma treatment on the semiconductor thin film, and a first line connected to the reaction chamber for introducing hydrogen gas into the reaction chamber. A second line connected to the reaction chamber for introducing a source gas used for forming the semiconductor thin film into the reaction chamber, and a second line connected to the second line, The source gas is the second
Plasma chemical vapor deposition apparatus provided with a third line for discharging from the above line and means for switching between introducing the source gas into the reaction chamber and discharging to the third line. 11. A reaction chamber for forming a semiconductor thin film and subjecting the semiconductor thin film to a hydrogen plasma treatment, and a first line connected to the reaction chamber for introducing hydrogen gas into the reaction chamber. A second line connected to the reaction chamber for introducing a source gas used for forming the semiconductor thin film into the reaction chamber, and a second line connected to the second line, The source gas is the second
Third line for discharging from the line, a connecting portion between the second line and the third line, and a first valve provided in the second line between the reaction chamber. And a second valve provided in the third line, and a control means for controlling opening / closing of the first valve and the second valve. When the semiconductor thin film is formed, the control means controls the first
The second valve is opened and the second valve is closed to introduce the source gas into the reaction chamber, and when the semiconductor thin film is subjected to the hydrogen plasma treatment, the second valve is opened. And a device for shutting off the introduction of the source gas into the reaction chamber by closing the first valve and closing the first valve.