Semiconductor device manufacturing: process – Formation of semiconductive active region on any substrate – Amorphous semiconductor
Reexamination Certificate
2001-04-09
2003-11-25
Coleman, W. David (Department: 2823)
Semiconductor device manufacturing: process
Formation of semiconductive active region on any substrate
Amorphous semiconductor
C438S788000, C438S903000, C118S7230VE, C118S724000
Reexamination Certificate
active
06653212
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a thin film forming apparatus and a thin film forming method and to a method for producing a thin film semiconductor device, more particularly relates to a thin film forming apparatus and a thin film forming method and to a method for producing a thin film semiconductor device capable of producing a high quality thin film and capable of producing a thin film semiconductor device able to be applied to a large-sized display device.
Note that, in the present invention, “single crystalline semiconductor” is a concept including not only a single crystalline silicon, but also a single crystalline compound semiconductor, for example single As) and a single crystalline silicon-germanium (Si—Ge). Further, in the present invention, “single crystal” is a concept including this even for a single crystal containing sub grain boundaries and dislocation.
BACKGROUND ART
In a thin film transistor (hereinafter referred to as a TFT) drive type liquid crystal display device, an amorphous silicon TFT has been used, but a polycrystalline silicon TFT has an electron field effect mobility of a high
100
or so in comparison with an amorphous silicon TFT and can be given higher performance, so an integral drive circuit type TFT has mainly been employed.
Conventionally, the technique of forming an amorphous silicon layer by plasma CVD or the like and crystallizing the polycrystalline silicon layer and improving the crystallinity by activation annealing by irradiation by a pulse-like excimer laser beam has been studied and developed.
However, the process of production of the semiconductor as described above has the following problems. Namely, in a method of producing a thin film transistor having a high mobility as a polycrystalline silicon film by melting an amorphous silicon film by irradiation of a laser such as an excimer laser or an argon laser to the amorphous silicon film and recrystallizing the same, since a laser such as an excimer laser or argon laser is used, there is the problem in that it is difficult to form a thin film in a large area and therefore the desired yield and quality can hardly ever be obtained.
Note that the technique of improving the excimer laser device so as to stabilize the excimer laser output and therefore enable formation of a thin film over a large area can be considered, but there was the problem that improvement of an excimer laser device is high in cost. In this way, in the prior art, there was a problem in improvement of the performance and quality and reduction of costs along with enlargement of the size of the substrate.
In order to solve the problems, recently, catalytic CVD enabling fabrication of a polycrystalline silicon film and a silicon nitride film on an insulating substrate such as a glass substrate at a low temperature has been developed and practical application studied.
Even by the technique using catalytic CVD, however, in the same way as with plasma CVD, there was the problem that a transition layer of the initial stage amorphous silicon (5 to 10 nm) was apt to be formed according to the substrate or film forming conditions if forming a polycrystalline silicon film on a glass substrate. In the case of a bottom gate type TFT, there was the problem that the desired electron mobility could hardly ever be obtained. A bottom gate type TFT is generally easily produced in terms of yield and productivity, so development of a technique for producing a high quality bottom gate type TFT has been demanded.
Further, there was the problem that when employing catalytic CVD, if the total film formation rate is small, the temperature of the substrate would rise or unevenness would occurred in the temperature of the substrate due to the radiant heat from a thermal catalyst and that variations would occur in the film thickness and the film quality.
DISCLOSURE OF THE INVENTION
The present invention was made in consideration with such a circumstance and has as its first object to provide a thin film forming apparatus and a thin film forming method for forming a high quality thin film on a substrate.
A second object of the present invention is to provide a thin film forming apparatus and a thin film forming method and a method for producing a thin film semiconductor device for forming a thin film having a high quality and able to be applied to also a large sized display device.
A third object of the present invention is to provide a thin film forming apparatus and a thin film forming method and a method for producing a thin film semiconductor device capable of forming a high quality thin film at a high speed.
A fourth object of the present invention is to provide a thin film forming apparatus and a thin film forming method and a method for producing a thin film semiconductor device making it possible to form a high quality thin film and produce a thin film semiconductor device and capable of preventing deterioration of a thermal catalyst.
The thin film forming apparatus of the present invention is a thin film forming apparatus comprising a vacuum chamber, a substrate, a thermal catalyst, and a heating means for heating the thermal catalyst, wherein a gas introduction system for introducing a gas is connected to the vacuum chamber and wherein the gas is fed from the gas introduction system into the vacuum chamber to form a thin film on a surface of the substrate by utilizing a thermal decomposition reaction and a catalytic reaction by the thermal catalyst, the gas introduction system introduces a carrier gas containing hydrogen and a material gas for forming a thin film on the substrate, and the carrier gas is fed into the vacuum chamber during at least the formation of the thin film.
In this way, when a thin film is formed on the substrate, the carrier gas containing hydrogen is constantly fed, so activated hydrogen H* generated in the carrier gas cleans the substrate surface and a high quality thin film can be formed on the substrate. Further, carrier gas containing hydrogen is constantly introduced during the film formation of the substrate, therefore the thermal catalyst is protected from influence of another gas, so it becomes possible to prevent the deterioration of the thermal catalyst.
Alternatively, the thin film forming apparatus of the present invention is a thin film forming apparatus comprising a vacuum chamber, a substrate, a thermal catalyst, and a heating means for heating the thermal catalyst, wherein a gas introduction system for introducing a gas is connected to the vacuum chamber and wherein the gas is fed from the gas introduction system into the vacuum chamber to form a thin film on a surface of the substrate by utilizing a thermal decomposition reaction and a catalytic reaction by the thermal catalyst, the gas introduction system introduces a carrier gas containing hydrogen and a material gas for forming the thin film on the substrate, and the apparatus comprises a means for raising a concentration of the material gas in the vacuum chamber in the middle of the formation of the thin film on the substrate.
The means for raising the concentration of the material gas is provided with a carrier gas controlling means for reducing or stopping the feed of for example the carrier gas.
In this way, when forming a thin film on the substrate, since a carrier gas containing hydrogen is used, the activated hydrogen H* generated in the carrier gas cleans the substrate surface, and a high quality thin film can be formed on the substrate. Further, since provision is made of a means for reducing or stopping the introduction of for example the carrier gas after an elapse of a predetermined time after the start of the film formation when forming various films, it is possible to form a thin film on the substrate at a high speed by raising a ratio of the material gas in the vacuum chamber and it becomes possible to improve workability.
At least a first material gas for forming a first thin film on the substrate and a second material gas for forming a second thin film on the substrate are fed from the gas introduction syst
Yamanaka Hideo
Yamoto Hisayoshi
Coleman W. David
Kananen Ronald P.
Rader & Fishman & Grauer, PLLC
Sony Corporation
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