JPH02184076A - Manufacturing method of thin film transistor - Google Patents

Abstract

PURPOSE:To make it possible to achieve the formation of a polycrystalline silicon film from an amorphous silicon film in a very short time in comparison with a solid-phase growing method by annealing by adopting steps by which the amorphous silicon film is formed on an insulating substrate, thereafter thermal oxidation is performed, and the polycrystalline silicon film is formed from the amorphous silicon film. CONSTITUTION:AN amorphous silicon film 2 is deposited on the surface of a quartz substrate 1. Then patterning is performed into a specified shape. Thereafter, thermal oxidation is performed for two hours in a dry oxygen gas atmosphere at, e.g. a flow speed of 10slm and at 1,000 deg.C. Then the formation of a polycrystalline silicon film from the amorphous silicon film 2 is made to progress. A polycrystalline silicon film 3 is formed. At the same time, an SiO2 layer 4 is formed on the surface of the polycrystalline silicon film 3. Then, a polycrystalline silicon film 5 for forming a gate electrode is formed on the SiO2 layer 4. Thereafter, selective etching is sequentially performed for the polycrystalline silicon film 5 and the SiO2 layer 4, and a gate oxide film 6 and a gate electrode 7 are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a thin film transistor used in a 1:1 image sensor, a liquid crystal device, etc.

[Prior Art] When manufacturing a thin film transistor using an insulating substrate, for example, a quartz substrate, an amorphous silicon film is deposited on the quartz substrate, and then this amorphous silicon film is made into a polycrystalline silicon film. will be held.

Here, conventional methods for converting an amorphous silicon film into a polycrystalline silicon film include a melt recrystallization method, that is, a method in which an amorphous silicon film is heated and melted to recrystallize it, and an annealing solid phase growth method. That is, a method of solid phase growth using annealing has been used.

[Problems to be Solved by the Invention] However, although it is possible to make the grain size of silicon relatively large using the melt recrystallization method, it is difficult to uniformly process a large area, and it is difficult to uniformly treat a large area. There was a problem in that it was not possible to manufacture a thin film transistor having a .

Furthermore, when using the annealing solid-phase growth method, it is possible to uniformly process a large area, but there is a problem that the process requires a long time. In particular, for example, in the case of a thin film transistor for driving a 1x image sensor, it is sufficient to form a polycrystalline silicon film with a silicon grain size of 3.0 OOA, but when using this annealing solid phase growth method, is 4 to make the silicon grain size 3,0OOA.
This took 0 hours, which was a factor in reducing throughput.

In view of this, an object of the present invention is to enable thin film transistors using polycrystalline silicon films as semiconductor materials to be manufactured with good throughput.

[Means for Solving the Problems] The method for manufacturing a thin film transistor according to the present invention will be described with reference to the drawings of the embodiments.
The method includes a step of forming an amorphous silicon film 2 thereon and then performing thermal oxidation to form the amorphous silicon film 2 into a polycrystalline silicon film 3.

[Operation] Solid-phase growth can be advanced by thermally oxidizing the amorphous silicon film 2, but when forming the amorphous silicon JII 2 into the polycrystalline silicon film 3 by solid-phase growth by thermal oxidation, In this method, the amorphous silicon film 2 can be turned into a polycrystalline silicon film in a much shorter time than when using the annealing solid phase growth method.

Further, during thermal oxidation, a thermal oxide film 4 is formed on the surface of the polycrystalline silicon 1113, and this thermal oxide film 4 can be used to form the gate oxide film 6.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

First, as shown in FIG. 1A, a quartz substrate 1 is prepared, and low pressure CVD is performed under the conditions shown in Table 1 to form amorphous silicon If! on the surface of the quartz substrate 1. Deposit 2.

Table 1 Next, after patterning the amorphous silicon film 2 into a predetermined shape, thermal oxidation is performed for 2 hours in a dry oxygen gas atmosphere at 1000° C. at a flow rate of 1051 m. In this way, the conversion of the amorphous silicon film 2 into a polycrystalline silicon film progresses, and as shown in FIG. 1B, a polycrystalline silicon film 3 is formed and 5i02 Layer 4 is formed. Here, the grain size of silicon in the polycrystalline silicon film 3 is about 1,000 to 3,000 A, depending on the film formation temperature of the amorphous silicon film 2, as shown in FIG.

By the way, when trying to obtain a similar grain size by annealing solid phase growth method, the amorphous silicon film 2 is grown at 600°C.
for 30 hours in a nitrogen gas atmosphere, and then further continued.
Annealing for 10 hours must be performed in a nitrogen gas atmosphere at 1000°C.

Next, as shown in FIG. 1C, after forming a polycrystalline silicon film 5 for forming a gate electrode on the 5i02 layer 4, this polycrystalline silicon film 5 is doped with n-type impurities to lower its resistance. Thereafter, polycrystalline silicon film 5 and 5i02 layer 4 are sequentially selectively etched to form gate oxide film 6 and gate electrode 7.

Next, as shown in the first diagram, a boron glass (BSG) film 8 is formed over the entire surface and heated at 950° C. for 30 minutes to thermally diffuse boron B into the polycrystalline silicon film 3, forming the source and drain regions. Diffusion layers 9 and 10 are formed.

Next, as shown in FIG. 1E, BSGII! After removing 8, heating is performed for 25 minutes in an oxygen atmosphere at 925° C. to form a 5i02 film 11 by thermal oxidation, and then an interlayer insulating film 12 is formed over the entire surface.

Next, as shown in FIG. 1F, from the interlayer insulation film 12 to 5i
After forming contact holes 13 and 14 in the 02 film 11 and forming aluminum electrode layers 15 and 16 through these contact holes 13 and 14, a sintering process is performed, followed by a temperature of 300°C and 5 pressures. Crab 0.
Plasma hydrogen treatment is performed under the conditions of 5 torr, IKIII, and time: 40 minutes.

Here, a P-channel thin film transistor can be obtained.

Table 2 shows the characteristics of the thin film transistor manufactured according to this example together with a comparative example.

Table 2 In this comparative example, the amorphous silicon film 2 was heated in a nitrogen gas atmosphere at 600°C for 30 hours, and then further heated for 1000 hours.
This is a thin film transistor manufactured through the same process as this example after performing annealing for 10 hours in a nitrogen gas atmosphere at .degree. In Table 2, ros is the drain-source voltage VOg of -5 [V] and the gate voltage ■.

I OFF is the drain-source current when the voltage is -17 [V], and I OFF is the train-source voltage ■
This is the drain-source current when Ds is -5 [V] and the gate voltage VG is 0 [■].

As is clear from Table 2, also in this example,
A polycrystalline silicon film is formed by an annealing solid phase growth method, and a thin film transistor having substantially the same characteristics as a thin film transistor manufactured using this polycrystalline silicon film as a semiconductor material can be obtained. According to this embodiment, in order to convert the amorphous silicon WA2 into a polycrystalline silicon film,
Two hours of thermal oxidation is sufficient.

Further, according to this embodiment, the gate oxide film 6 is a 5i film formed by thermal oxidation when forming the polycrystalline silicon film 3.
Since it can be formed using the 02 layer 4, the number of manufacturing steps can be reduced accordingly.

Therefore, according to this embodiment, it is possible to improve the throughput and reduce the cost.

[Effects of the Invention] According to the present invention, by employing a step of forming an amorphous silicon film on an insulating substrate and then performing thermal oxidation to form the amorphous silicon film into a polycrystalline silicon film, Compared to the solid phase growth method using annealing, polycrystalline silicon removal from an amorphous silicon film can be achieved in a much shorter time, and thermal oxidation that is formed when forming a polycrystalline silicon film Since the gate oxide film can be formed using a film, throughput can be improved and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the method for manufacturing a thin film transistor according to the present invention, and FIG. 2 is a diagram showing the relationship between the deposition temperature of an amorphous silicon film and the grain size of silicon in a polycrystalline silicon film. It is. 1...Quartz substrate 2...Amorphous silicon film 3...Polycrystalline silicon film Fig. 1

Claims (1)

[Claims] A method for manufacturing a thin film transistor comprising the steps of forming an amorphous silicon film on an insulating substrate and then performing thermal oxidation to form the amorphous silicon film into a polycrystalline silicon film.