JPH0777232B2 - Semiconductor device - Google Patents

Description

The present invention relates to a semiconductor device, and more particularly to a radiation-resistant semiconductor device suitable for use in an environment where it is exposed to strong radiation such as for mounting on an artificial satellite.

[Conventional technology]

A semiconductor device that receives strong radiation changes its operating state due to generation of electron-hole pairs.

To minimize the change, CVD (chemi
Insulating film using cal vapor deposition), especially BPSG
It is effective to use a (boro-phospho-silicate glass) film, and the insulation isolation film of the conventional radiation resistant semiconductor device is formed by forming a thermal oxide film 42 on a semiconductor substrate 41 and then using a CVD film as shown in FIG. The BPSG film 43 has a structure formed by removing unnecessary parts of the BPSG film 43 by etching and reflowing the BPSG film 43 at a high temperature.

Further, in order to facilitate the control of the etching of the BPSG film 43 in FIG. 3, the structure as shown in FIG. 4 was also used. To make this structure, a thermal oxide film 52 is formed on a semiconductor substrate 51, a polycrystalline silicon film 53 is laminated, and then BPSG is added.
The film 54 is formed. Next, the unnecessary portion of the BPSG film 54 is etched until the polycrystalline silicon film 53 is exposed. At this time, since the polycrystalline silicon film 53 acts as an etching stopper, etching removal residue and damage to the semiconductor substrate surface are prevented. It becomes possible to do. After etching the BPSG film 54,
The polycrystalline silicon film 53 is isotropically removed by etching to remove the BPSG film.
54 is reflowed at a high temperature to obtain an insulating separation film.

[Problems to be solved by the invention]

In the conventional semiconductor device described above, the structure of the insulating separation film is such that, instead of thinning the thermal oxide film on the semiconductor substrate, the effect of radiation is minimized by using a superior BPSG film with special radiation resistance. Therefore, it is necessary to make the thermal oxide film on the semiconductor substrate as thin as possible.
It is not possible to suppress the diffusion of impurities such as phosphorus and boron from the BPSG film, and these impurities diffuse into the semiconductor substrate,
There is a defect that the effect as an insulating separation film is lost and the threshold voltage of the MOS transistor changes.

In contrast to the conventional semiconductor device described above, the present invention reduces the influence of radiation on the semiconductor device by thinning the thermal oxide film on the semiconductor substrate, and the radiation resistance characteristics on the thermal oxide film are better than those of the BPSG film. Is inferior, but better than thermal oxide film
It has an original content that it is possible to prevent the impurity diffusion into the semiconductor substrate which occurs during the high temperature reflow of the insulating BPSG film by stacking the CVD oxide films.

[Means for solving problems]

The semiconductor device of the present invention is a semiconductor device in which a field insulating separation film is formed on a semiconductor substrate, and an N-type or P-type diffusion layer is formed in a region other than the region where the field insulating separation film is formed. Separation membrane thickness 30
A thermal oxide film of 0 Å or less, a CVD oxide film, and a BPSG film are formed of three layers, and these three layers are patterned into the same shape.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 (a) is a longitudinal sectional view of the first embodiment of the present invention. In the figure, 1 is a semiconductor substrate, 2 is a silicon oxide film formed by a thermal oxidation method (hereinafter referred to as a thermal oxide film), 3
Is a silicon oxide film formed by a CVD method (hereinafter referred to as a CVD oxide film), 4 is a BPSG film formed by a CVD method, 6 is a polycrystalline silicon film for a gate, and 7 and 8 are P-type or N-type.
Source and drain regions formed by diffusing a type impurity, 9 is an insulating film such as a silicon oxide film,
Reference numeral 10 is a metal film for electrodes formed on the contact portions of the source / drain / gate, and 11 is a protective film formed on the surface of the semiconductor device, such as a PSG film.

Next, the embodiment shown in FIG. 1 (a) will be described in detail by a manufacturing method with reference to FIGS. 1 (b) to (g).

In FIG. 1 (b), a thermal oxide film 2 is formed on one surface of a semiconductor substrate 1 by a thermal oxidation method to a thickness of 50 to 300 Å, then by a CVD method
The CVD oxide film 3 is formed to a thickness of 500 to 1500Å, and the BPSG film 4 is formed.
It shows a process in which the photosensitive resin 5 is applied by a spinner method or the like after being laminated to a thickness of 3000 to 6000Å by the CVD method.

Next, FIG. 1 (c) shows a step of etching away the BPSG film 4 and the CVD oxide film 3 using the photosensitive resin 5 that leaves a portion corresponding to the insulating isolation region as a mask. At this time, etching of the CVD oxide film 3 is performed so that the film thickness of the CVD oxide film 3 remaining after the etching is sufficient to prevent impurity diffusion that occurs during high temperature reflow of the BPSG film 4 together with the thermal oxide film 2. Adjust the amount.

In FIG. 1 (d), after removing the photosensitive resin 5 for the mask, the BPSG film 4 is reflowed by a high temperature heat treatment, and the patterned BPSG film 4 is used as a mask to form the CVD oxide film 3 and the thermal oxide film. A step of etching and removing 2 until the surface of the semiconductor substrate 1 is exposed is shown.

Next, after forming a silicon oxide film to be a gate oxide film by a thermal oxidation method, a polycrystalline silicon film 6 for a gate is formed. (FIG. 1 (e)).

In FIG. 1 (f), after removing an unnecessary portion of the gate polycrystalline silicon film 6 by etching using a photosensitive resin, P
A process of forming the source region 7 and the drain region 8 by diffusing a type or N type impurity is shown.

Next, an insulating film 9 such as a silicon oxide film is formed by the CVD method, and the contact portions of the source, drain and gate are removed by etching using a mask of photosensitive resin (FIG. 1 (g)).

Then, the metal film 10 for electrodes is formed and patterned by a known method, and the protective film 11 is formed on the surface to obtain the embodiment shown in FIG. 1 (a).

FIG. 2 (a) is a vertical sectional view of the second embodiment of the present invention. In the figure, 21 is a semiconductor substrate, 22 is a thermal oxide film, and 23 is
CVD oxide film, 24 is a polycrystalline silicon film used as a stopper during etching of the BPSG film, 25 is a BPSG film formed by a CVD method, 27 is a polycrystalline silicon film for a gate, 28.
Reference numeral 29 is a source region and drain region, 30 is an insulating film such as a silicon oxide film, 31 is an electrode metal film formed at the source / drain / gate contact portions, and 32 is a surface protective film.

Next, the embodiment shown in FIG. 2A will be described in detail with reference to FIGS. 2B to 2E by the manufacturing method.

FIG. 2B shows the thermal oxide film 22 and the CVD oxide film 2 on the semiconductor substrate 21 as in the embodiment shown in FIG.
After forming 3, the polycrystalline silicon film 24 is formed to a thickness of 500 to 2000Å, the BPSG film 25 is further laminated, and then the photosensitive resin 26 is applied.

FIG. 2C shows a process of etching the BPSG film 25 until the polycrystalline silicon film 24 is exposed, using the photosensitive resin 26 that leaves a portion corresponding to the insulation isolation region as a mask. At this time, since the polycrystalline silicon film 24 to serve as an etching stopper is present under the BPSG film 25, the BPSG film 25 can be easily etched without causing damage to the underlying substrate, which is a problem in the above-described embodiment. Can be done

Next, FIG. 2D shows a step of removing the photosensitive resin 26 after the polycrystalline silicon film 24 is removed by isotropic etching.

In FIG. 2 (e), after the BPSG film 25 is reflowed by a high temperature heat treatment, the patterned BPSG film 25 is used as a mask.
A process of etching and removing the CVD oxide film 23 and the thermal oxide film 22 until the surface of the semiconductor substrate 21 appears.

Then, in the same manner as in the embodiment shown in FIG. 1A, the polycrystalline silicon film 27 for the gate and the metal film for the electrode are formed.
By forming 31 etc., the embodiment shown in FIG. 2 (a) is obtained.

〔The invention's effect〕

As described above, the present invention maintains the radiation resistance of the semiconductor device by forming a CVD oxide film after forming a thin thermal oxide film on the semiconductor substrate in the isolation region and further stacking a BPSG film. As it is, there is an effect that it is possible to prevent the impurity diffusion generated during the high temperature reflow of the BPSG film for insulation separation from reaching the substrate.

[Brief description of drawings]

FIG. 1 (a) is a longitudinal sectional view of the first embodiment of the present invention,
FIGS. 2 (b) to 2 (g) are sectional views showing the manufacturing process of the embodiment shown in FIG. 1 (a), and FIG. 2 (a) is a longitudinal sectional view of the second embodiment of the present invention. 2B to 2E are cross-sectional views showing the manufacturing process of the embodiment shown in FIG. 2A, and FIGS. 3 and 4 are cross-sectional views of two conventional semiconductor devices. 1.21 ... Semiconductor substrate, 2.22 ... thermal oxide film, 3.23 ...
... CVD oxide film, 4.25 ... BPSG film, 6.24.27 ... Polycrystalline silicon film, 7.28 ... Source region, 8.29 ... Drain region, 9.30 ... Insulating film, 10・ 31 …… Metallic film for electrodes.

Claims (1)

[Claims] 1. A semiconductor device in which a field insulating separation film is formed on a semiconductor substrate, and an N-type or P-type diffusion layer is formed in a region other than the region in which the field insulating separation film is formed. A semiconductor device in which a thermal oxide film having a thickness of 300 Å or less, a CVD oxide film, and a BPSG film are formed in three layers, and these three layers are patterned into the same shape.