JPH04338650A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce a resistance of a source and drain region of a transistor and to connect electrically it with an electrode accurately. CONSTITUTION:A glass film 10 including diffusion impurities is formed on a thick semiconductor film 6, which is etched with the patterned glass film 10 as a mask and is left as a thin film to form a channel region 7, and thereafter the impurities are diffused from the glass film 10 onto the thick-left semiconductor film 6 under the glass film 10 by heat-treatment to form a source and drain region 9.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method for manufacturing the same, and more particularly to a bottom gate type thin film transistor with low resistance in the source and drain regions and a method for manufacturing the same.

0002

[Prior art] Thin film transistor (TFT)
For example, 20
This is a MOS transistor that uses a thin polycrystalline silicon film of about 0 angstroms as the transistor channel, and there is no need to create a channel in the silicon substrate like in a normal MOS transistor. Even after the region is formed and covered and insulated with an oxide film or the like, a MOS transistor can be formed again on that region. For this reason, research and development is progressing as an effective means for increasing the integration of transistors.

Thin film transistors can be divided into top gate types in which the gate electrode is formed above the channel and bottom gate types in which the gate electrode is formed below the channel. Which of the two is used depends on the manufacturing method of the semiconductor device to be manufactured.

FIG. 2 shows a main cross-sectional view of the manufacturing process of a conventional bottom gate type P-channel MOS transistor, and the manufacturing method will be explained below.

First, as shown in FIG. 2(a), an insulating film 2 is formed on a semiconductor substrate 1, and a gate electrode 3 is formed thereon. Thereon, a gate oxide film 4 and, for example, a polycrystalline silicon film 5 to which impurities are not added, which will become the source, drain, and channel regions, are deposited to a thickness of about 200 angstroms.

Next, as shown in FIG. 2(b), a photosensitive agent 8 is applied and patterned into a desired shape by photolithography, and then a large number of boron ions are implanted by ion implantation using the photosensitive agent 8 as a mask. Introduced into crystalline silicon film 5. The implantation energy at this time is set so that the ions remain within the polycrystalline silicon film 5.

Next, as shown in FIG. 2(c), the photosensitive agent 8 is removed, and boron is diffused and activated by heat treatment.
+ type source and drain regions 9 are formed.

Next, as shown in FIG. 2(d), an insulating film 11 is deposited over the entire surface, holes are made in the insulating film 11 for forming electrodes, and then source and drain electrodes 12 are formed.

[0009]

[Problems to be Solved by the Invention] The conventional method for manufacturing a semiconductor device is constructed as described above, and since the source, drain, and channel regions are all formed of a thin polycrystalline silicon film, the source, drain, and There has been a problem in that the resistance value of the region increases, and the voltage effectively applied to the channel portion decreases, causing performance deterioration of the MOS transistor.

In addition, in the step of forming holes for forming electrodes in FIG. 2(d), the removal rate of the insulating film (etching
Due to variations in the removal time (rate), it is necessary to increase the removal time (over-etching) than the removal time calculated from the film thickness.As a result, part of the polycrystalline silicon film that is the source and drain regions is also removed, and the thickness There have been problems in that the material becomes very thin or there are areas where it is completely removed, making it difficult to obtain a reliable electrical connection with low resistance between the electrodes.

The present invention was made in order to solve the above-mentioned problems, and provides a semiconductor device and a device that can reduce the resistance of the source and drain regions of a transistor and also enable reliable electrical connection with electrodes. The purpose of this study is to obtain a manufacturing method for the same.

0012

SUMMARY OF THE INVENTION In a semiconductor device according to the present invention, source and drain regions are formed of a thick semiconductor film.

Further, the method for manufacturing a semiconductor device according to the present invention includes forming a glass film containing a diffusion impurity on a thick semiconductor film, and etching the thick semiconductor film using the patterned glass film as a mask to leave a thin layer. After forming a channel portion using heat treatment, impurities are diffused from the glass film into the thick remaining semiconductor film under the glass film to form source and drain regions.

[0014]

In the semiconductor device according to the present invention, the source and drain regions are formed of a thick semiconductor film, so that the resistance of the source and drain regions of the transistor can be lowered and reliable electrical connection with the electrodes can be achieved.

[0015] The impurity-containing glass film in this invention is
It serves as a mask when selectively etching a thick semiconductor film thinner, and at the same time serves as a diffusion source for diffusing impurities into the remaining thick semiconductor film.

In addition, the thick semiconductor film that remains unetched in the present invention forms source and drain regions with low resistance, and at the same time prevents over-etching when forming holes for source and drain electrodes in the insulating film. , forming source and drain regions with sufficient film thickness to obtain reliable electrical connections with the source and drain electrodes.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a main cross-sectional view of the manufacturing process of a semiconductor device according to an embodiment of the present invention, and the manufacturing method will be described below.

First, as shown in FIG. 1A, an oxide film having a thickness of, for example, about 5,000 to 10,000 angstroms is deposited as an insulating film 2 on a semiconductor substrate 1 by the CVD method. For example, a polycrystalline silicon film of about 2000 angstroms is deposited on the insulating film 2 by the CVD method,
Gate electrode 3 is formed by anisotropic etching. Then, an oxide film of about 200 to 300 angstroms as a gate oxide film 4 and a thick polycrystalline silicon film 6 of about 2000 angstroms, for example, to which no impurities are added are deposited by CVD.

Next, as shown in FIG. 1B, a glass film 10 containing boron is deposited over the entire surface by CVD, and then a photosensitive material (not shown here) patterned by photolithography is applied as a mask. selectively removing the glass film 10 by anisotropic etching,
Furthermore, the photosensitizer is removed. Thereafter, using the glass film 10 as a mask, the polycrystalline silicon film 6 in the region that will become the channel portion is selectively removed by anisotropic etching so as to leave a thin layer, for example, about 200 angstroms, to form the channel region 7.

Next, as shown in FIG. 1(c), 900
Boron is diffused and activated from the glass film 10 into the thick polycrystalline silicon film 6 by heat treatment for about 10 minutes at a temperature of
After forming the source and drain regions 9 of approximately P+ type, the glass film 10 is removed.

Next, as shown in FIG. 1(d), an oxide film of, for example, about 5000 angstroms is deposited on the entire surface as an insulating film 11 by the CVD method, and holes for electrode formation are made in the insulating film 11. , source and drain electrodes 12
form.

As described above, according to this embodiment, the source and drain regions are thickened, so that the resistance of the source and drain regions of the transistor can be lowered, and reliable electrical connection with the electrodes can be achieved.

Furthermore, since the source and drain regions are formed of a thick semiconductor film, the source and drain regions can be formed with a low resistance value, and the film can be prevented from over-etching when making holes for the source and drain electrodes in the insulating film. Sufficient thickness remains to enable reliable electrical connection with the source and drain electrodes.

In the above embodiment, a boron-containing glass film was used to form a P-channel transistor, but when forming an N-channel transistor, a glass film containing arsenic or the like may be used. Effects similar to those of the embodiment can be obtained.

[0025]

As described above, according to the semiconductor device and the method for manufacturing the same according to the present invention, since the source and drain regions are formed of a thick semiconductor film, the resistance values of the source and drain regions can be lowered. In addition, it is possible to avoid electrical connection defects caused by over-etching when forming holes for source and drain electrodes in the insulating film, and it is possible to obtain reliable connections between the source and drain regions and the electrodes. be.

[Brief explanation of drawings]

FIG. 1 is a main cross-sectional view of the manufacturing process of a semiconductor device in an embodiment of the present invention.

FIG. 2 is a main cross-sectional view of a conventional semiconductor device manufacturing process.

[Explanation of symbols]

1 Semiconductor substrate 2 Insulating film 3 Gate electrode 4 Gate oxide film 5 Thin polycrystalline silicon film 6 Thick polycrystalline silicon film 7 Channel area 8. Photosensitizer 9 Source and drain region 10 Boron-containing glass membrane 11 Insulating film 12 Source and drain electrodes

Claims (2)

[Claims] 1. A semiconductor device, in a bottom gate type thin film transistor using a thin semiconductor film as a channel of the transistor, wherein the source and drain regions are each formed of a semiconductor film thicker than the channel made of the thin semiconductor film. 2. A step of forming an insulating film on a semiconductor substrate, a step of forming a gate electrode on the insulating film, and forming a gate oxide film over the entire surface of the insulating film including on the gate electrode. a step of sequentially depositing a thick semiconductor film and an impurity-containing glass film on the gate oxide film;
a step of selectively removing the glass film; a step of etching the thick semiconductor film to leave it thin using the glass film as a mask; and a step of removing impurities from the glass film to the thick semiconductor film below the glass film by thermal diffusion. A method of manufacturing a semiconductor device, comprising the step of forming source and drain regions by diffusion.