JPH0786305A - Semiconductor device producing method - Google Patents

Abstract

PURPOSE:To efficiently introduce H groups into a polysilicon film covered with an interlayer insulation film. CONSTITUTION:After thermally diffusing impurities into a polysilicon film by a heat treating step, interlayer insulation films 21 and 23 are formed on the film 3, H groups are fed into the film 3 from an H supply film formed on the top faces of the films 21 and 22 by a heat treating step, whereby the films 21 and 23 are made dense to prevent the pass of H groups to be fed to the film 3 from being blocked before the second heat treating step. Thus, the film 3 is efficiently hydrogenized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and is suitable for application to, for example, a method for manufacturing a thin film transistor used for adjusting the light amount of each pixel constituting a liquid crystal display.

[0002]

2. Description of the Related Art Conventionally, various driving methods have been known as a driving method for a liquid crystal display, but an active matrix method is drawing attention because of its excellent display performance. In the active matrix system, each pixel electrode is driven by switching using thin film transistors. This thin film transistor 1 is formed in the following order of steps.

First, a polysilicon film 3 to be a channel layer is formed on an insulating substrate 2 made of glass or quartz glass by low pressure CVD.
After deposition by (chemical vapor deposition),
A gate oxide film 4 is deposited on the upper surface thereof. Subsequently, a polysilicon electrode 5 is formed on the upper surface of the gate oxide film 4, and then,
An interlayer insulating film 6 is deposited on the entire surface of the insulating substrate 2. Next, heat treatment (950 to 1000 [° C.]) activates and diffuses the impurities doped in the polysilicon film 3 (FIG. 2).
(A)).

After this heat treatment, the interlayer insulating film 6 is etched to form an opening reaching the end of the polysilicon film 3,
The aluminum electrode 7 is formed. Next, the interlayer insulating film 8 laminated on the upper surface of the aluminum electrode 7 is etched to form an opening reaching the end of the polysilicon film 3 on the side opposite to the previously formed aluminum electrode 7. The electrode 9 is formed.

After that, a plasma silicon nitride film (P-SiN: H) 10 containing a hydrogen group is formed on the upper surface of the interlayer insulating film 8 excluding the transparent electrode 9, and a second heat treatment (3
50 to 400 [° C.]) to supply hydrogen groups from the hydrogen-containing layer into the polysilicon film 3 (FIG. 2 (B)). This hydrogen radical injection eliminates dangling bonds from the polysilicon film 3 to increase electron mobility.

[0006]

However, when a thin film transistor is formed in this order of steps, the first heat treatment causes the quality of the inter-layer insulation film 6 to be finely changed, which impedes the passage of hydrogen groups into the polysilicon film 3. However, dangling bonds could not be sufficiently reduced.

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose a semiconductor device manufacturing method capable of efficiently injecting hydrogen groups into a polysilicon film covered with an interlayer insulating film. To do.

[0008]

In order to solve such a problem, in the present invention, the polysilicon film 3 is formed on the base substrate 2.
, A first heat treatment step of thermally diffusing the impurities implanted in the polysilicon film 3, a step of forming interlayer insulating films 21 and 23 on the polysilicon film 3, and an interlayer insulating film 21. , 23 and a second heat treatment step of supplying a hydrogen group from the hydrogen supply film 25 to the polysilicon film 3 are included in the semiconductor device manufacturing method.

[0009]

The interlayer insulating films 21 and 23 are formed on the upper surface of the polysilicon film 3 after the impurities in the polysilicon film 3 are thermally diffused by the first heat treatment step.
It is possible to effectively avoid the possibility that the film quality of the interlayer insulating films 21 and 23 becomes dense before the second heat treatment step. As a result, hydrogen groups can be efficiently supplied to the polysilicon film 3 in the second heat treatment step.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1 in which parts corresponding to those in FIG. 2 are designated by the same reference numerals, 20 indicates a thin film transistor as a whole. In the case of this embodiment, the main step is to form the thin film transistor 20 by providing the first heat treatment step after forming the polysilicon electrode and before forming the interlayer insulating film. The manufacturing process will be described below in order. First, as in the conventional case, a polysilicon film 3 to be a channel layer is formed on the insulating substrate 2 by low pressure CVD (chemical vapor deposition).
), And the gate oxide film 4 is deposited on the upper surface thereof.

Subsequently, a polysilicon electrode 5 is formed on the upper surface of the gate oxide film 4. After this process, the process proceeds to the impurity thermal diffusion process (FIG. 1A). After that, phosphorus silicate
Low pressure CVD of the interlayer insulating film 21 made of glass (PSG)
Are deposited on the surface of the insulating substrate 2. Thus, in the case of this embodiment, the first heat treatment is performed on the interlayer insulating film 21.
Since the interlayer insulating film 21 is formed before the formation of the above, the conventional thermal curing of the interlayer insulating film 21 does not occur at this point.

After this step, the step of forming the aluminum electrode 22 is performed as in the conventional case. That is, the interlayer insulating film 21 is etched to form an opening reaching the end of the polysilicon film 3, and aluminum is vapor-deposited in the opening by a sputtering method. Subsequently, a second interlayer insulating film 23 is laminated so as to cover the patterned aluminum electrode 22 and the first interlayer insulating film 21. Next, the interlayer insulating films 21 and 23 on the opposite side of the aluminum electrode 22 with the polysilicon electrode 5 sandwiched therebetween are etched to form an opening reaching the polysilicon film 3, and a transparent electrode 24 is formed.

After completion of the series of treatments, a plasma silicon nitride film (P-SiN: H) 25 containing hydrogen groups is formed on the upper surface of the interlayer insulating film 23 except the transparent electrode 24, and after the completion of the second treatment. Move to the heat treatment process (Fig. 1)
(B)). By this heat treatment, supply of hydrogen radicals from the plasma silicon nitride film 25 to the polysilicon film 3 is started.

Only by the second heat treatment, heat is applied to the two interlayer insulating films 21 and 23.
Therefore, the film quality of the two interlayer insulating films 21 and 23 is in a relatively rough state, which is a stage before the quality is changed to a dense state.
Therefore, the hydrogen radicals diffused from the plasma silicon nitride film 25 easily pass through the interlayer insulating films 21 and 23 and reach the polysilicon film 3. As a result, the dangling bonds of the polysilicon film 3 can be efficiently eliminated, and the electron mobility can be improved as compared with the conventional one.

The on-current of the thin film transistor 20 formed by the above process is about 100 [μA],
The on-state current of the thin film transistor 1 formed by the conventional process can be doubled as compared with the value of 50 [μA]. Further, the value of the leak current flowing when the thin film transistor 20 is turned off is also a fraction (1 [pA] or less) of the leak current (5 [pA]) when formed in the conventional process order. ) Can be done.

According to the above steps, hydrogen groups can be injected into the polysilicon film 3 before the interlayer insulating film 21 is hardened by heat and the film quality becomes dense. It can be further enhanced. As a result, the field electron mobility in the thin film transistor can be further improved as compared with the conventional one. Further, since the hydrogenation efficiency can be increased, the second heating time required for hydrogenation can be further shortened compared to the conventional case.

In the above-described embodiments, the case where the plasma silicon nitride film 25 is used as the hydrogen group supply film has been described, but the present invention is not limited to this, and any other compound film can be used as long as it contains hydrogen. May be used. For example, P-SiCH or plasma amorphous Si (a-Si
H) may be used.

In the above embodiment, the case where the interlayer insulating films 21 and 23 are formed of phosphorus silicate glass (PSG) has been described, but the present invention is not limited to this, and non-doped silicate glass (NSP) is used. ) Or boron-phosphorus-silicate glass (BPSG) or the like.

Further, in the above-mentioned embodiment, the case where the thin film transistor is formed on the insulating substrate made of glass or quartz glass has been described, but the present invention is not limited to this.
It can also be applied to the case of forming on another insulating substrate or a semiconductor substrate.

Further, in the above-mentioned embodiment, the case where the gate electrode is formed of polysilicon has been described, but the present invention is not limited to this, and may be formed of a metal material.

Further, in the above-mentioned embodiment, the case where the pixel electrode of the liquid crystal display is switched by the thin film transistor has been described, but the present invention is not limited to this, and the line sensor or SRAM (static random access) is used.
It can also be applied to a thin film transistor for driving a memory).

Further, in the above-mentioned embodiments, the method of manufacturing the thin film transistor has been described, but the present invention is not limited to this, and includes a hydrogenation step of injecting hydrogen groups into the polysilicon film via the interlayer insulating film. It can also be applied to the method of manufacturing a semiconductor device.

[0024]

As described above, according to the present invention, after the impurities in the polysilicon film are thermally diffused by the first heat treatment step, the interlayer insulating film is formed on the polysilicon film and then the first insulating film is formed. Hydrogen radicals are supplied into the polysilicon film by the heat treatment step of 2. Accordingly, it is possible to effectively avoid the possibility that the quality of the interlayer insulating film becomes dense before the second heat treatment step and the passage of hydrogen groups is hindered. As a result, the supply efficiency of hydrogen radicals to the polysilicon film in the second heat treatment step can be further improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of a semiconductor device manufacturing method according to the present invention.

FIG. 2 is a schematic cross-sectional view for explaining a conventional manufacturing method.

[Explanation of symbols]

1, 20 ... Thin film transistor, 2 ... Insulating substrate, 3 ...
... polysilicon film, 4 ... gate oxide film, 5 ... polysilicon electrode, 6,8,21,23 ... interlayer insulating film, 7,
22 ... Aluminum electrode, 9, 24 ... Transparent electrode, 1
0,25 ... Plasma silicon nitride film.

Claims (2)

[Claims] 1. A step of forming a polysilicon film on a base substrate, a first heat treatment step of thermally diffusing impurities implanted in the polysilicon film, and an interlayer insulating film on the polysilicon film. A semiconductor device comprising: a forming step; a step of forming a hydrogen supply film on the interlayer insulating film; and a second heat treatment step of supplying a hydrogen group from the hydrogen supply film to the polysilicon film. Production method. 2. The method of manufacturing a semiconductor device according to claim 1, further comprising a step of forming a channel layer and a step of forming a gate electrode before the first heat treatment step.