JPH0488643A - Manufacture of polycrystalline silicon semiconductor device - Google Patents

Abstract

PURPOSE:To make it possible to form polycrystalline silicon films at desired positions by a method wherein a conductive amorphous silicon film and an intrinsic amorphous silicon film are annealed in a state that those silicon films come into contact to each other. CONSTITUTION:Respective metal films for dain electrode 2 use and source electrode 3 use and an N-type amorphous silicon film 4 are formed by superposing on a support substrate 1 and thereafter, the films are processed into a desired pattern form. Then, an intrinsic amorphous silicon film 5 is formed and is patterned. Thereby, a semiconductor thin film 6 consisting of places 5a having parts, at which the films 4 and 5 come into contact in parallel to their film surfaces, and a place 5b having not a part, at which the films 4 and 5 come into contact in parallel to their film surfaces, is formed. Then, an annealing treatment is performed. In this case, it is desirable to set an annealing temperature at 500 to 600 deg.C and an annealing time in 10 hours or thereabouts. Accrodingly, by annealing in such a range, parts 5A to correspond to the parts 5a are turned into polycrystalline silicon films and a part 5B to correspond to the part 5b is turned into an intrinsic amorphous silicon film or a fine crystal silicon film.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for manufacturing semiconductor devices such as thin film transistors.

(b) Prior Art In recent years, the development of thin film semiconductors such as amorphous silicon and polycrystalline silicon used in thin film solar cells and display elements for liquid crystal displays has progressed rapidly. Reasons for this include the fact that the thin film semiconductor can be formed over a large area and can be easily formed on a light-transmitting insulating substrate. For example, regarding semiconductor devices using thin film semiconductors, IEEE
ELECTRON DEVICE LETTER5,
VOL, EDL-8, NO, 9, SEPTEMBER1
987p, 425-427.

However, since the manufacturing methods for these thin film semiconductors are different, it has been difficult to manufacture a semiconductor device in which polycrystalline silicon and amorphous silicon are simultaneously formed on the same substrate.

Note that the amorphous silicon used in the present invention includes amorphous silicon and/or microcrystalline silicon.

(c) Problems to be Solved by the Invention Common methods for forming the aforementioned amorphous silicon include plasma gas decomposition method, CVD method, sputtering method, and
Examples include the CR (electron cyclotron resonance) method. In both cases, the substrate temperature is at most 500° C. or less, and is formed at a relatively low temperature.

On the other hand, typical conventional methods for forming polycrystalline silicon include a relatively old direct formation method and a recrystallization method in which an amorphous Sifucon is annealed to become polycrystalline.

The direct formation method is a method in which polycrystalline silicon is directly formed at high temperature from the initial stage by LPCVD or the like.

The recrystallization method can be subdivided into two types depending on the annealing method. One of these methods is called the in-phase growth method, in which amorphous silicon formed by plasma CVD or sputtering as a starting material is annealed at high temperatures. This is the way to do it. The other method is laser recrystallization, in which amorphous silicon formed as a starting material by plasma CVD, sputtering, or the like is recrystallized using light energy from a laser or the like.

In the direct formation method and the in-phase growth method, it is necessary to anneal at a higher temperature than the above-mentioned formation temperature of amorphous silicon, so amorphous silicon and polycrystalline silicon are formed together on the same substrate. is not possible. Furthermore, since the laser recrystallization method uses a laser to perform local annealing, it is possible to form a mixture of amorphous silicon and polycrystalline silicon, but current laser technology still has low stability in laser output. , it was not possible to manufacture semiconductor devices with good reproducibility.

As described above, since the manufacturing methods for amorphous silicon and polycrystalline silicon are completely different, conventionally, in order to form them on the same substrate, it was necessary to go through separate manufacturing steps.

Therefore, the purpose of the method for manufacturing a polycrystalline silicon semiconductor device of the present invention is to simultaneously form polycrystalline silicon and amorphous silicon on the same substrate, rather than through separate processes. be.

(d) Means for Solving the Problems The manufacturing method of the present invention is characterized in that in the manufacturing method of a semiconductor device made of a mixture of polycrystalline silicon and amorphous silicon, the polycrystalline silicon is conductive. It is formed by annealing amorphous silicon and intrinsic amorphous silicon in contact with each other.

(E) Function The polycrystalline silicon in the manufacturing method of the present invention is formed by annealing a semiconductor thin film in which conductive amorphous silicon and intrinsic amorphous silicon are brought into contact with each other on an insulating substrate.

In this case, the semiconductor thin film can transform into polycrystalline silicon at a lower temperature than when there is no contact.

Therefore, by bringing the conductive amorphous silicon into contact with the intrinsic amorphous silicon where polycrystalline silicon should be formed, polycrystalline silicon can be formed in a desired portion.

Further, at this time, in the portions which are not in contact with the conductive amorphous silicon, portions are produced that remain the amorphous silicon or become microcrystalline silicon even if not polycrystalline silicon.

(v) The embodiment diagram is a sectional view of a semiconductor device manufacturing process for explaining the manufacturing method of the present invention. The semiconductor device is a so-called thin film transistor, and its structural characteristics are that the thin film semiconductor in the channel portion is made of amorphous silicon, while the thin film semiconductors in contact with the source and drain electrodes are made of polycrystalline silicon. It's in the silicone part. This structure itself is the same as that described in the invention of Japanese Patent Application No. 1-183382.

Below, the manufacturing method of the present invention will be explained in detail with reference to the drawings.

In the first step shown in FIG.
) and n-type amorphous silicon (4), which is conductive amorphous silicon, are formed in an overlapping manner, and then processed into a desired pattern shape. Chromium, molybdenum, tantalum, etc. were used as the metal film. The n-type amorphous silicon (4) is similar to that conventionally formed by, for example, plasma CVD.

Specifically, the reaction gas is mainly composed of silane gas, to which a doping gas such as phosphine gas is added. The phosphorus concentration in the n-type amorphous silicon (4) is lXl0"c+n-"(XIO"cm-").

The substrate temperature is preferably 200-400°C and is 35°C in the embodiment.
The temperature was 0°C. The film thickness is 300 people.

In this step, n-type amorphous silicon (4) is formed in portions corresponding to the source and drain. The manufacturing method of the present invention is characterized by such a pattern. That is, in the case of the embodiment, in the amorphous silicon formed and annealed in a later process, only the amorphous silicon near the source and drain is transformed into polycrystalline silicon.

In the next second step shown in FIG. 5B, non-doped amorphous silicon, ie, intrinsic amorphous silicon (5), is formed and patterned. During this patterning, a portion of the n-type amorphous silicon (4) is also removed by etching to remove the drain and source electrodes.

As a result, the n-type amorphous silicon (4) and the intrinsic amorphous silicon (5) consist of a portion (5a) that has a portion in parallel contact with the film surface and a portion (5b) that does not have a portion where the n-type amorphous silicon (4) and the intrinsic amorphous silicon (5) contact in parallel A semiconductor thin film (6) is formed.

In this step, before forming the intrinsic amorphous silicon (5), it is preferable that the exposed surface of the n-type amorphous silicon be thinly etched. That is, this is to remove the natural oxide film during the process.

In the case of the plasma CVD method, the conditions for forming the intrinsic amorphous silicon (5) include decomposition and formation using the aforementioned silane gas or the like. The substrate temperature is preferably 200 to 400°C, and was set to 300°C in the example. Film thickness is approximately 2000-
There are 3000 people.

Next, in the third step shown in FIG. 2C, an annealing process is performed. In this case, the annealing temperature is 500-600℃,
The annealing time is preferably about 10 hours. In other words, if annealing is performed at a temperature above this temperature, all portions of the intrinsic amorphous silicon (5) will become polycrystalline. However, in this case, depending on the time of the annealing treatment, it is possible to convert the remaining amorphous silicon into microcrystalline silicon even if it does not transform into polycrystalline silicon.

Furthermore, below this temperature, the portions that should be made of polycrystalline silicon cannot be sufficiently polycrystallized.

Therefore, by annealing in this range, the above (
The portion (5A) corresponding to the portion 5a) becomes polycrystalline silicon, and the portion (5B) corresponding to the portion (5b) remains as intrinsic amorphous silicon or becomes microcrystalline silicon.

The polycrystallization step in the third step naturally occurs not only in the film thickness direction as shown, but also in the film plane direction, that is, in the lateral direction. However, the growth distance of polycrystalline in the lateral direction is at most about the thickness of the semiconductor thin film (6), and has almost no effect on the channel length of the semiconductor device of the embodiment.

Finally, in the fourth step shown in FIG. 3D, a gate insulating film (7) and a gate metal film (8) are formed and patterned. As the gate insulating film (7), a silicon nitride film, a silicon oxide film, tantalum oxide, or the like formed by a plasma CVD method, a thermal CVD method, or the like is used. The gate metal film is made of chromium, tantalum, molybdenum, aluminum, etc.

In this way, by processing conductive amorphous silicon into a desired pattern shape and bringing it into contact with intrinsic amorphous silicon, it is possible to form a mixture of polycrystalline silicon and amorphous silicon in a semiconductor device. becomes.

Furthermore, in the manufacturing method of the present invention, good polycrystalline silicon can be formed at a low temperature by using the annealing temperature. This also means that a good semiconductor device can be obtained without damaging the film quality of the remaining amorphous silicon due to annealing.

Further, in the embodiment, a case where polycrystalline silicon and amorphous SiFCON are mixed in one thin film transistor is described, but the manufacturing method of the present invention is not limited to this.

For example, in a semiconductor device formed by stacking a large number of thin film transistors on the same substrate, the semiconductor thin film may include thin film transistors made only of polycrystalline silicon and thin film transistors made only of amorphous silicon. It can be manufactured by the manufacturing method according to the present invention.

That is, for the portion of the semiconductor thin film in which a thin film transistor made only of polycrystalline silicon is to be formed, conductive amorphous silicon and intrinsic amorphous silicon should be laminated to form a thin film transistor made only of amorphous silicon. The portion of the semiconductor thin film can be obtained by forming only intrinsic amorphous silicon without forming the conductive amorphous silicon.

(G) Effects of the Invention According to the manufacturing method of the present invention, it is possible to form a semiconductor device in which polycrystalline silicon and amorphous silicon coexist in a desired pattern. Furthermore, since the annealing temperature for polycrystalline silicon can be kept low, good semiconductor device characteristics can be obtained without damaging the film quality of amorphous silicon.

[Brief explanation of the drawing]

The drawings are cross-sectional views of the semiconductor device manufacturing process for explaining the semiconductor device manufacturing method of the present invention.

Claims (1)

[Claims] (1) In a method for manufacturing a semiconductor device made of a mixture of polycrystalline silicon and amorphous silicon, the polycrystalline silicon is
A method for manufacturing a thin film transistor, characterized in that the thin film transistor is formed by annealing conductive amorphous silicon and intrinsic amorphous silicon in contact with each other.