JPS60149119A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a thin film field effect transistor having better ON-OFF characteristics, by forming a recession in the underside of a holder in which an insulating substrate is arranged so that both the under faces are aligned, and by plasma-processing the substrate with the holder grounded, where the substrate is mounted in the underside of the conducting holder for the substrate and an amorphous Si thin film is deposited on the substrate surface with plasma to make an optoelectric transducer. CONSTITUTION:A substrate holder 10 and an insulating substrate 1 to be grown are arranged in a plasma CVD apparatus. That is, the holder 10 which is made of Al and has larger area than the insulating substrate 1 is grounded and forms a recession of depth d1 in the underside of the holder 10. The glass insulating substrate 1 of thickness d2 is housed in the recession and is secured firmly by holding members 11 and screws 12 positioned a the circumference. On that occasion, the depth d1 and thickness d2 are equalized so that the under face 10a of the holder 10 is aligned with the under face of the substrate. Thereafter, an amorphous Si thin film is deposited over the under face with plasma-processing and the substrate 1 is then removed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a semiconductor device, particularly a thin film field effect transistor ( From now on T
FT).

Structure of the conventional example and its problems Amorphous silicon (including microcrystalline silicon) deposited by plasma chemical vapor deposition method is used for thin film solar cells.
It is expected that the insensor photoelectric conversion device will be put to practical use as a two-image display device. These devices are made by laminating multiple thin films with different properties, and for the purpose of industrially depositing these laminated films over a large area and in large quantities, a plasma chemical vapor deposition device having multiple plasma deposition chambers is used. Here, as an example of such an apparatus that has been developed, an apparatus having two plasma deposition chambers will be explained. As shown in FIG. 1, the substrates 1a and 1b are held by a substrate holder 2 and placed in a first vacuum chamber 3 facing downward, and a first thin film is deposited on the main surfaces of the substrates 1a and Ib. Thereafter, the substrate 1 is moved together with the substrate holder 2 by the transport mechanisms 4a and 4b via the opening/closing plate 5 to a second vacuum chamber 6 in a vacuum state, where a second thin film is deposited. 7a and 7b are plasma electrodes, 8 is a substrate holding stand, and 9 is a back plate.

Normally, when a thin film is deposited, the substrate holder 2 also serves as an electrode facing the plasma electrodes 7a and 7b, and the substrate holder 2 itself is fixed at a ground potential.

Next, FIG. 2 shows a cross-sectional view of a portion of a conventionally used substrate holder 2 where a substrate is held. The metal substrate holder 8 has an aperture 8a that is slightly smaller in area than the main surface of the substrate 1 on one side of the metal substrate holder 8, and a hole 8a for the substrate 1 on the other side of the metal substrate holder 8. A hole 8b slightly larger than the main surface area is formed.

In this way, the board 1 is dropped from the side of the large hole 8b, and then the metal back plate 9 is dropped into the back side of the board, and the end 1 of the board 1 is
A was held by a stand 8 and a plate 9. In this structure, the electrical contact between the substrate holding table 8 and the back plate 9 during plasma discharge depends only on mechanical contact.
Even if the holding base 8 is grounded, the back plate 9, that is, the substrate 1, cannot be brought to a sufficient ground potential.

Using the conventional substrate holder 2 shown in FIGS. 1 and 2, silane and ammonia are used as source gases and argon is used as a diluent gas on a metallic silicon substrate 1 doped with phosphorus at a high concentration by plasma chemical vapor deposition.

A first thin film of silicon nitride using nitrogen, hydrogen, etc.
The second thin film, amorphous silicon, is made of 400
A large number of thin film field effect transistors (TPTs) with a channel length of 10 μm and a channel width of 1 μm were formed by depositing and selectively etching. One of the drain current-gate voltage characteristics of the TPT is shown in the curve U in Figure 3, and as shown in Figure 3 ■, the TPT
T switch-on state (in this explanation, the gate voltage value is 1)
6V) and off state (in this explanation, when the gate voltage value is 1,
oV), the drain current ratio (ON-OFF ratio) is 6
It was more than digit (1o5).

On the other hand, in response to the demand for low-cost substrates and when applying TPT to switching matrix arrays such as liquid crystal displays, it is necessary to use a transparent insulating substrate instead of a silicon substrate. Formation is important.

However, as in the case described above, silicon nitride and amorphous metal are deposited on a glass substrate 1 on which a gate metal is selectively deposited using the conventional substrate holder 2 using a similar plasma chemical vapor deposition apparatus. It is shown in curve 1 in Figure 3.

As shown in the figure, the 0N-OFF ratio of the TPT is two digits (
102), which was too small to withstand practical use.The inventors investigated this problem and assumed that it was because the back plate 9 of the substrate 1 was not sufficiently maintained at the ground potential.The present invention solves this problem. By solving the problem, it is possible to create a good thin film transistor.0 Purpose of the Invention That is, the present invention was made in view of the above-mentioned problem, and it is possible to fabricate a thin film transistor of good quality on an insulating substrate such as glass. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can obtain desired characteristics even when a conductor device is formed.

Structure of the Invention The present invention provides a substrate holder used in a plasma chemical vapor deposition apparatus used for forming a thin film on an insulating substrate, in which the area where the substrate is closely held is larger than the area of the substrate, and the area is grounded. The present invention provides a method for manufacturing semiconductor devices, particularly TPTs, by forming a thin film while directly connected to an electric potential.

Description of examples Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 4 shows a substrate holding section used in one embodiment of the present invention.

A conductive substrate holding stand 1° made of aluminum or the like is formed with a recess slightly larger than the insulating substrate 1 made of glass or the like and having a depth dl, and the substrate 1 is held in this recess by a holding part 11 and screws 12. It is stored closely on the stand 1o. In this case, by matching the thickness d2 of the substrate and the depth dl of the recess to a mechanical precision level, the back surface of the substrate 1 can be brought into close contact with the substrate holding table 1o, and the film forming surface (front surface) of the substrate 1 can be kept in close contact with the substrate holder 1o. It is preferable that the main surface 10a of the holding table 10 is flush with the main surface 10a exposed to plasma.

Using the above-mentioned substrate holding table 10 and the apparatus shown in FIG. 1, silane and ammonia are deposited as raw material gases onto the surface of the downward glass substrate 1 on which gate metal (not shown) is selectively formed by plasma chemical vapor deposition. .

Using argon, nitrogen, hydrogen, etc. as a diluent gas, silicon nitride and amorphous silicon were deposited 4,000 times each to form a channel with a channel length of 10 μm and a channel width of 10 m.
When a TPT of m was formed, the drain current-gate voltage characteristic of the TPT was the same as that shown in curve 1 of FIG. 3. That is, a TPT exhibiting an extremely excellent ON-OFF ratio of 5 digits (106) or more could be formed on the glass substrate 1.

Another embodiment of the invention is shown in FIG. It has an opening 13 on one side with an inner diameter 11 smaller than the size of the substrate 1,
and an inner diameter 1 larger than the size L of the substrate 1 from the other surface side.
Aluminum substrate support member 1 having two openings 14
After placing the glass substrate 1 on the end 15a of the glass substrate 1 with the surface on which TPT is formed facing downward, a substrate holder having a convex portion 16 having an outer diameter 13 smaller than the inner diameter 122 of the aperture 14 described above is placed. 17. Then, the holding base 17 and the support member 16 are brought into close contact with each other.

A glass substrate 1 on which gate metal is selectively deposited using the substrate holder 17 and support member 16 as described above.
Even when a TPT made of silicon nitride or amorphous silicon with a channel length of 10 μm and a channel width of 10 m is formed on the top, the drain/current-gate voltage characteristics of the TPT are as shown in curve 11 in Figure 3, and as shown in Figure 5. A substrate holding mechanism with a structure like this was also effective in forming TPT on a glass substrate. Note that the structure shown in FIG. 6 is easy to work with because the substrate 1 can always be held facing downward when it is held on the substrate holder, and dust does not adhere to the substrate 1. It has advantages such as being difficult to use.

In the above embodiments of the present invention, silicon nitride is used.

Although the method for manufacturing a TPT made of amorphous silicon has been mainly described, the present invention is also effective for manufacturing methods for other semiconductor devices having an interface between an insulator such as silicon nitride and a semiconductor such as amorphous silicon. This is supported by the following. For example, a device having a metal-silicon nitride-amorphous silicon-metal structure was formed on a glass substrate using a conventional substrate holder and the substrate holding mechanism of the present invention, and the capacitance-voltage characteristics were measured. The case was as shown in FIG. Curve 1 in FIG. 6 is the case when the conventional substrate holder is used, and curve U is the case when the substrate holding mechanism of the present invention is used. As is clear from this figure, the use of the substrate holding mechanism of the present invention is more stable with fewer defect levels and the like at the silicon nitride-amorphous silicon interface.

It has been described above that the present invention is effective in manufacturing the present conductor device by the plasma chemical vapor phase method, and the reasons for this are thought to be as follows.

That is, in the conventional substrate holder, an insulating substrate such as glass is used instead of a conductive substrate such as silicon doped with high concentration of phosphorus, so that the back plate 9 located on the back side of the substrate is replaced by the holder 8. There is no sufficient electrical connection with the substrate 1, and the plasma electric field around the substrate 1 is disturbed.
Affects the decomposition of raw material gases such as silane and changes the quality of the deposited film.

However, as in the present invention, the existence of a conductive holder directly connected to the ground potential on the back surface of the substrate makes it possible to prevent disturbances in the plasma electric field and to form a semiconductor film with uniform film quality over the entire surface of the substrate 1. Can be created. This is presumed to be the reason why a good multilayer thin film can be formed on an insulating substrate using the plasma deposition method.

Effects of the Invention As described above, the present invention provides semiconductor devices, particularly silicon nitride, amorphous silicon, etc., by plasma chemical vapor deposition on an insulating substrate such as glass using an apparatus having several vacuum chambers. When manufacturing TFTs, the substrate is held on a substrate holder that is larger than the area of the substrate and is directly connected to the ground, making it possible to manufacture TPTs with excellent ON and OFF characteristics with good reproducibility. It shows excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a semiconductor device manufacturing apparatus, FIG. 2 is a structural sectional view of a conventional substrate holder, and FIG. A diagram showing the current-voltage characteristics of the TPT with a noodle formed thereon.
The figure shows the capacitance-voltage characteristics of devices having a metal-silicon nitride-amorphous silicon-metal structure formed on a glass substrate using the conventional and present substrate holders. 1...Substrate, 10.17...Substrate holding stand, 3゜6...Deposition chamber, 4a, 4b...
・Transportation mechanism, 5... mark ・Opening/closing plate, 7a, 7b...
・Plasma electrode, 11... Presser foot removal, 12...
...Screw, 13.14...Opening part, 15...
...Supporting member, 16. Old...Convex part. Name of agent: Patent attorney Toshio Nakao and one other name
1 Figure 3 Gate voltage Figure 4 O

Claims (4)

[Claims] (1) The back side of an insulating substrate is held in close contact with a conductive substrate holder having a larger area than the substrate via a holding mechanism, and the front surface of the substrate is turned downward in a first vacuum chamber. is arranged to face a discharge electrode, and a first thin film is formed on the surface of the substrate using a plasma chemical vapor deposition method with the substrate holder itself directly connected to ground potential;
The substrate holder holding the substrate is moved to a second vacuum chamber communicating with the first vacuum chamber, and the substrate holder itself is placed on the first thin film in the second vacuum chamber. 1. A method of manufacturing a semiconductor device, comprising forming a second thin film using a plasma chemical vapor deposition method while directly connected to a ground potential. (2) The method for manufacturing a semiconductor device according to claim 1, characterized in that the end portion of the surface of the insulating substrate is pressed by a metal body attached to the substrate holder. (3) The substrate holder and the insulating substrate are held in close contact by bringing the back side of the insulating substrate into contact with the convex portion of the substrate holder and placing the end of the front surface of the insulating substrate on a holding member. A method for manufacturing a semiconductor device according to claim 1, characterized in that: (4) The method for manufacturing a semiconductor device according to claim 1, wherein the first or second thin film is a non-single crystal silicon film.