JP4469465B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a semiconductor device, a semiconductor layer of a thin film transistor for constituting the image display application equipment in conjunction with such liquid crystal display device (hereinafter referred to as TFT), to manufacture how the thin film to be the insulating film layer Related.
[0002]
[Prior art]
A conventional method for producing a thin film will be described below.
[0003]
FIG. 9 shows a cross-sectional view of the main part of the TFT. A gate electrode 2 is formed on a glass substrate 1, an amorphous silicon semiconductor layer 4 is formed through a gate insulating film 3, and source and drain electrodes 6a and 6b are connected through n + amorphous silicon semiconductor layers 5a and 5b. Is formed.
[0004]
Conventionally, the above-described gate insulating film 3 (3000 非晶 質), amorphous silicon semiconductor layer 4 (500Å), channel stopper insulating film 7 (2000Å) n + amorphous silicon semiconductor layers 5a and 5b are formed of material gases as shown in FIG. The plasma chemical vapor deposition apparatus using glow discharge of SiH4, NH3, and PH3 is used. The plasma chemical vapor deposition apparatus shown in FIG. 10 is a capacitive coupling type in which the discharge electrode 14 and the counter discharge electrode 12 are installed in parallel, and the substrate is installed on the counter discharge electrode 12.
[0005]
In this plasma chemical vapor deposition apparatus, after the thin film is deposited, NF ₃ , SF _{6 is} used to prevent generation of dust due to peeling of the film attached to the counter electrode 14 other than the substrate, the deposition chamber 11 and the like. Gas cleaning such as introducing a gas such as CF ₄ and removing the film by glow discharge is performed periodically. Further, in order to stabilize the quality of the film to be manufactured, a film deposition operation is performed immediately after periodic cleaning without installing the substrate, and then a thin film is deposited on the substrate for manufacturing the TFT.
[0006]
[Problems to be solved by the invention]
However, in the conventional method, as shown in FIG. 5, a change in film quality was observed along with a change in TFT characteristics over time, which seems to be due to a change in film quality along with the number of depositions immediately after cleaning. This is because fluorine, which is a gas component used during gas cleaning, remains in the deposition chamber and is mixed as an impurity in the TFT formation film. In order to counter these problems, if the deposited film thickness is increased to a film thickness equivalent to 3 sheets (12000 mm) without installing the substrate immediately after cleaning, the change in TFT characteristics over time shown in FIG. 5 is improved. However, there is a problem that the generation of dust increases as shown in FIG.
[0007]
[Means for Solving the Problems]
In the method of manufacturing a semiconductor device according to the present invention, in a plasma chemical vapor deposition apparatus using a fluorine-based gas as a cleaning gas, immediately after gas cleaning, a substrate is not installed in the plasma chemical vapor deposition apparatus. a glow discharge in the SiH ₄ gas atmosphere diluted with glow discharge and hydrogen gas in a hydrogen gas atmosphere was continuously processed only by switching the gas without stopping the glow discharge, SiH ₄ gas diluted with the hydrogen gas The hydrogen gas / SiH ₄ gas ratio in the atmosphere is 4 or more .
[0010]
Further, in the plasma chemical vapor deposition apparatus using a fluorine-based gas as a cleaning gas, the method for manufacturing a semiconductor device according to the present invention is performed immediately after gas cleaning without placing a substrate in the plasma chemical vapor deposition apparatus. % of hydrogen and glow discharge in the SiH ₄ gas atmosphere diluted with glow discharge and hydrogen gas in the gas atmosphere was continuously processed only by switching the gas without stopping the glow discharge, before Symbol 100% hydrogen gas atmosphere The continuous treatment of the glow discharge in the above and the glow discharge in an SiH ₄ gas atmosphere diluted with hydrogen gas is repeated at least a plurality of times.
[0012]
Producing how the semiconductor device of the present invention, depositing a film by glow discharge at regular deposition chamber residual components of the cleaning gas adhering to the material constituting the exposed device after cleaning and 100% hydrogen gas atmosphere It is vaporized and excited without being absorbed, and is taken into the deposited film by glow discharge in a SiH ₄ gas atmosphere diluted to 80% or more with hydrogen gas. That is, the residual component of the cleaning gas is effectively fixed in the film with a low deposited film thickness of amorphous silicon with a low deposition rate.
[0013]
That is, after cleaning the deposition chamber, a glow discharge in a 100% hydrogen gas atmosphere and a glow discharge in a SiH ₄ atmosphere diluted with hydrogen gas with a H ₂ / SiH ₄ gas ratio of 4 or more are continuously performed. The effect of the cleaning gas residue can be suppressed efficiently. Accordingly, unnecessary impurities can be prevented from being mixed into a thin film such as a gate insulating film or an amorphous silicon semiconductor layer to be manufactured, and as a result, film quality can be stabilized and TFT characteristics can be improved.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the present invention will be described below.
[0017]
A gate insulating film and an amorphous silicon semiconductor layer are manufactured by introducing SiH ₄ , NH ₃ , and H ₂ gas using a chemical vapor deposition apparatus using a 13.56 MHz glow discharge as shown in FIG. A TFT was formed as shown in FIG. FIG. 1 shows the state of the apparatus from NF ₃ gas cleaning to continuous discharge of H 2 glow discharge and SiH ₄ glow discharge diluted with H 2.
[0018]
Immediately after cleaning, a glow discharge in a 100% H ₂ gas atmosphere is continued without a substrate being placed in the deposition apparatus, and a continuous transition to a glow discharge in a SiH ₄ gas atmosphere by H2 dilution with addition of SiH ₄ gas is performed without stopping the discharge. Process. In the glow discharge of SiH ₄ gas by this H 2 dilution, the process shown in FIG. 1 is performed in which the H ₂ / SiH ₄ gas ratio is changed and this continuous process is repeated a plurality of times.
[0019]
When the content of impurities in the deposited film immediately after cleaning is compared with the change in the H ₂ / SiH ₄ gas ratio during glow discharge, the result shown in FIG. 2 is obtained.
When the H ₂ / SiH ₄ gas ratio is 4 or more, the content of impurities incorporated in the TFT formation film increases linearly.
[0020]
The dependence of the impurity content in the TFT formation film on the number of processed substrates is shown in FIG. 3, and it is the continuous glow discharge in the H ₂ gas 100% atmosphere and the glow discharge in the SiH ₄ gas atmosphere diluted with H ₂ gas. By repeating the treatment a plurality of times, the content of impurities in the TFT formation film decreases. Further, FIG. 4 shows that a large amount of the cleaning gas component is taken in during the formation of the amorphous silicon in the TFT formation film.
[0021]
Further, FIG. 5 shows the mobility of the TFT when the H ₂ glow discharge and the H ₂ diluted SiH ₄ glow discharge are processed in different numbers. FIG. 7 shows that the TFT characteristics can be improved with a thin deposited film thickness after cleaning by continuously performing a combination of H ₂ glow discharge and SiH ₄ glow discharge by H ₂ dilution. Further, FIGS. 5 and 6 show TFT mobility and dust generation after the H ₂ glow discharge / H ₂ diluted SiH ₄ glow discharge continuous treatment is performed three times without stopping the discharge. Further, FIG. 8 shows a change in mobility in the first TFT substrate after cleaning by changing the number of repetitions of H ₂ / SiH ₄ glow discharge. The H ₂ / SiH ₄ gas ratio is set to 4, and a stable film quality can be obtained by repeating twice or more times.
[0022]
As described above, the contamination of the glow discharge and the H ₂ gas diluted with the SiH ₄ of impurities by performing glow discharge and continuous discharge by the gas atmosphere TFT formed film with H ₂ gas atmosphere of 100% after cleaning It is possible to realize a stable film formation with no dependency on TFT characteristics. Furthermore, since the deposited film thickness immediately after cleaning can be reduced, the cleaning removal time of the deposited film can be shortened, and the generation of dust due to film peeling can be suppressed.
[0023]
In the example, NF ₃ was used as the cleaning gas.
A fluorine-based gas such as CF ₄ or SF ₆ may be used. Similar effects can be expected with a mixed gas of H ₂ gas and other active gas, such as H ₂ + SiH ₂ Cl ₂ .
[0024]
Although the above description has focused on examples of gate insulating films and amorphous silicon semiconductor thin films used for TFTs, it goes without saying that other semiconductor devices using amorphous silicon are plasma chemical vapor deposition. The present invention is also effective for a method of manufacturing a semiconductor device and a semiconductor manufacturing apparatus having a step of depositing a thin film other than amorphous silicon using the method.
[0025]
【The invention's effect】
Above, the present invention, SiH ₄ diluted with glow discharge and H ₂ gas subsequently with H ₂ gas atmosphere of 100% without installing a substrate in a deposition apparatus after the cleaning of chemical vapor deposition apparatus for manufacturing a semiconductor thin film By performing continuous discharge by glow discharge in a gas atmosphere at least a plurality of times, impurities in the TFT forming film are reduced, and a TFT having sufficient characteristics can be obtained immediately after cleaning, which is of great industrial value.
[Brief description of the drawings]
FIG. 1 is a time chart in a deposition chamber at the time of cleaning in an embodiment of the present invention. FIG. 2 contains impurities in the first film of the substrate prepared by installing the substrate in the apparatus after cleaning in the embodiment of the present invention. FIG. 3 shows the amount of H ₂ gas / SiH ₄ gas ratio. FIG. 3 shows the TFT content after cleaning the impurity content in the TFT film prepared by installing the substrate in the apparatus after cleaning in the embodiment of the present invention. FIG. 4 is a diagram showing the number of times of deposition on a substrate. FIG. 4 is a diagram showing the content of impurities in a TFT formation film for each film when a substrate is installed in the apparatus after cleaning in an embodiment of the present invention. FIG. 5 is a diagram showing a change over time in TFT characteristics created by installing a substrate in the apparatus after cleaning in the embodiment of the present invention. FIG. 6 shows that the substrate is installed in the apparatus after cleaning in the embodiment of the present invention. FIG. 7 is a diagram showing the number of dust attached to the TFT substrate prepared by placing the substrate. FIG. 7 is a diagram showing the deposited film thickness immediately after cleaning with respect to the H ₂ / SiH ₄ gas ratio in the embodiment of the present invention. FIG. 9 is a diagram showing the mobility of the first TFT substrate prepared by placing the substrate in the apparatus after cleaning in the embodiment of the invention with respect to the number of repetitions of H ₂ / SiH ₄ glow discharge. Sectional cross-sectional view [Fig. 10] Schematic diagram of chemical vapor deposition system [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Gate electrode 3 Gate insulating film 4 Amorphous silicon semiconductor film 5a, 5b n + amorphous silicon semiconductor film 6a, 6b Source / drain electrode 7 Channel stopper insulating film 11 Deposition chamber 12 Counter discharge electrode 13 Substrate 14 Discharge electrode 15 Gas 16 Discharge power supply

Claims (4)

In a plasma chemical vapor deposition apparatus that uses a fluorine-based gas as a cleaning gas, immediately after gas cleaning, a glow discharge and hydrogen gas in a 100% hydrogen gas atmosphere without a substrate installed in the plasma chemical vapor deposition apparatus. in continuously processed only by switching the gas without stopping the glow discharge and glow discharge in SiH ₄ gas atmosphere diluted,
A method of manufacturing a semiconductor device, wherein a hydrogen gas / SiH ₄ gas ratio in a SiH ₄ gas atmosphere diluted with hydrogen gas is 4 or more . In a plasma chemical vapor deposition apparatus that uses a fluorine-based gas as a cleaning gas, immediately after gas cleaning, a glow discharge and hydrogen gas in a 100% hydrogen gas atmosphere without a substrate installed in the plasma chemical vapor deposition apparatus. The glow discharge in the SiH ₄ gas atmosphere diluted with the above is continuously processed only by switching the gas without stopping the glow discharge,
And glow discharge in a hydrogen gas atmosphere in the 100%, the continuous process of the glow discharge in the SiH ₄ gas atmosphere diluted with the hydrogen gas, the manufacturing method of this a semi-conductor device you wherein repeated at least several times . The method of manufacturing a semiconductor device according to either of claims 1 or claim 2 wherein the fluorine-based gas, characterized in that NF _3, or SF _6, the or at either of CF _4. Hydrogen gas / SiH ₄ gas ratio in the SiH ₄ gas atmosphere diluted with the hydrogen gas, a method of manufacturing a semiconductor device according to claim 2, wherein the this is 4 or more.

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