JP2000183339A - Semiconductor device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device where a semiconductor substrate is prevented from being etched, due to overetching at patterning a gate electrode and the desired characteristics can be obtained, and to provide a manufacture method thereof. SOLUTION: A gate insulating film 2 is formed on a silicon substrate 1, and the polycrystalline silicon layer 3 of structure containing an oxygen leak layer 5 is formed on the gate insulating film 2. The polycrystalline silicon layer 3 is formed of a lower polycrystalline silicon layer 4, an oxygen leakage layer 5 and an upper polycrystalline silicon layer 6. The upper polycrystalline silicon layer 6, except for a gate electrode pattern on the upper side from the oxygen leakage layer 5, is removed through reactive ion etching. An oxide silicon film is formed by oxidizing the surfaces of the lower polycrystalline silicon layer 4 and the upper polycrystalline silicon layer 6, which lie above the gate insulating film 2. Then, the oxide silicon film is removed through isotropic etching, and the gate insulating film 2 is exposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly, to a semiconductor device having a thin gate insulating film and a method of manufacturing the same.

[0002]

2. Description of the Related Art For example, in the case of an N-type MOSFET,
An N-type region serving as a source and a drain is formed at a predetermined distance in the vicinity of the surface of a P-type silicon substrate, a gate insulating film is provided on the substrate surface between the source and the drain, and a gate electrode is formed on the gate insulating film. It is provided and configured. M
In the OSFET, in order to increase the saturation current and improve the subthreshold characteristics, it is necessary to reduce the gate length and increase the capacitance of the gate insulating film.
Therefore, as a means for improving the performance of MOSFET,
Conventionally, the thickness of a gate insulating film has been reduced.

[0003] A polycrystalline silicon film is provided on the gate insulating film.
That is, a gate electrode pattern is formed by the steps of photoresist coating → pattern exposure → etching → photoresist stripping. In this etching in photolithography, a gate insulating film is used as a film for stopping the etching.

[0004]

However, according to the conventional method of manufacturing a semiconductor device, if the thickness of the gate insulating film is small, if over-etching occurs, a part or all of the gate insulating film is removed. Therefore, the possibility that the silicon substrate is etched is increased. When the silicon substrate is etched, the parasitic resistance of the MOSFET increases, and it becomes impossible to produce a MOSFET having desired characteristics.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a semiconductor device and a method of manufacturing the same, in which a semiconductor substrate is prevented from being etched by overetching when patterning a gate electrode, and desired characteristics can be obtained.

[0006]

According to a first aspect of the present invention, a gate electrode pattern is formed on a semiconductor substrate via a thinned gate insulating film. In the semiconductor device, there is provided the semiconductor device, wherein the gate electrode pattern is divided into an upper pattern and a lower pattern by an insulating thin film layer.

According to this structure, the gate electrode pattern is divided into an upper pattern and a lower pattern via the insulating thin film layer. Thus, when patterning the gate electrode, the etching stops at the insulating thin film layer, so that the semiconductor substrate can be prevented from being etched by over-etching. As a result, a semiconductor device having desired characteristics can be obtained.

[0008] To achieve the above object, the present invention provides:
As a second feature, a gate insulating film is formed on a silicon substrate, a polycrystalline silicon layer having a structure including an oxygen leak layer is formed on the gate insulating film, and the oxygen leak layer of the polycrystalline silicon layer is formed. A portion other than the upper gate electrode pattern is removed by reactive ion etching from above, and the surface of the polycrystalline silicon layer remaining on the gate insulating film is oxidized to form an oxide film. Provided is a method for manufacturing a semiconductor device, which is removed by etching.

According to this method, a polycrystalline silicon layer including an oxygen leak layer is formed on the gate insulating film, and the polycrystalline silicon layer other than the upper gate electrode pattern is removed from the oxygen leak layer by etching. Therefore, when patterning the gate electrode, the etching stops at the oxygen leak layer, and the semiconductor substrate can be prevented from being etched by over-etching. As a result of preventing the semiconductor substrate from being etched, a semiconductor device having desired characteristics can be obtained.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 show a method of manufacturing a semiconductor device according to the present invention. The manufacturing method shown in FIG.
, The process proceeds in the order of the figure numbers.

First, as shown in FIG.
A gate insulating film 2 made of SiO2 is formed on the silicon substrate 1 by thermal oxidation of the substrate. Then, as shown in FIG.
The polycrystalline silicon layer 3 is formed by CVD (Chemical Vapor Deposition: Chemi
A film is formed on the gate insulating film 2 by cal vapor deposition. This polycrystalline silicon layer 3 has a lower polycrystalline silicon layer 4 in the lower part, an oxygen leak layer 5 made of SiO2 in the middle part, and an upper polycrystalline silicon layer 6 in the upper part.
It has a layer structure. The oxygen leak layer 5 can be formed by temporarily supplying oxygen into a CVD reactor when forming a polycrystalline silicon layer. A gate electrode is patterned on the polycrystalline silicon layer 3 by photolithography. In this photolithography, a resist pattern 7 according to the pattern of the gate electrode is formed. In the photolithography step, the polycrystalline silicon layer 3 is formed by reactive ion etching.
Is etched. At the time of this etching, the oxygen leak layer 4 is detected by the end point detector, and as shown in FIG. 3, only the upper polysilicon layer 6 is etched, and the lower polysilicon layer 4 is not etched. 2 above.

Next, an oxidation treatment is performed in an oxygen atmosphere. By this oxidation treatment, upper polycrystalline silicon layer 6 is oxidized, and lower polycrystalline silicon layer 4 on gate insulating film 2 is converted to silicon oxide film 8, as shown in FIG. The surface (upper surface and both sides) of upper polycrystalline silicon layer 6 is oxidized simultaneously with oxidation of lower polycrystalline silicon layer 4. Further, isotropic etching is performed on the silicon oxide film 8 to remove the silicon oxide film 8 as shown in FIG. 5, exposing the gate insulating film 2 and the upper polycrystalline silicon layer 6.

In the above embodiment, a silicon nitride layer or a silicon oxide layer containing nitrogen can be used as gate insulating film 2. In this case, when oxidizing lower polycrystalline silicon layer 4 described with reference to FIG. 4, it is possible to prevent the oxidizing species from diffusing to the lower portion of the gate electrode.
Therefore, even when the thickness of lower polycrystalline silicon layer 4 is larger than that in the above-described embodiment, it is possible to prevent the thickness of the gate insulating film below the gate electrode from increasing.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the semiconductor device shown in FIGS. 1 to 5, the best results are obtained when the thickness of the oxygen leak layer 5 is 2 mm or less and the thickness of the lower polycrystalline silicon layer 4 is 5 mm to 50 mm. Was done.

[0015]

As is apparent from the above description, according to the semiconductor device of the present invention, the gate electrode pattern is divided into an upper pattern and a lower pattern by the insulating thin film layer. Thus, the gate electrode can be formed without causing the etching of the semiconductor substrate, and a semiconductor device having desired characteristics can be obtained.

According to the method of manufacturing a semiconductor of the present invention, a polycrystalline silicon layer including an oxygen leak layer is formed on a gate insulating film, and the polycrystalline silicon layer other than the gate electrode pattern above the oxygen leak layer is formed. Is removed by etching, so that even when the thickness of the gate insulating film is small, the gate electrode can be formed without etching the semiconductor substrate, and a semiconductor device having desired characteristics can be formed. Obtainable.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first step of a method for manufacturing a semiconductor device according to the present invention.

FIG. 2 is a sectional view showing a second step following the step in FIG. 1;

FIG. 3 is a sectional view showing a third step following the step in FIG. 2;

FIG. 4 is a sectional view showing a fourth step following the step in FIG. 3;

FIG. 5 is a sectional view showing a fifth step following the step in FIG. 4;

[Explanation of symbols]

 Reference Signs List 1 silicon substrate 2 gate insulating film 3 polycrystalline silicon layer 4 lower polycrystalline silicon layer 5 oxygen leak layer 6 upper polycrystalline silicon layer 7 resist pattern 8 silicon oxide film

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4M104 BB01 BB36 CC05 DD65 DD74 FF13 HH11 5F033 HH04 MM08 MM15 QQ10 QQ13 QQ25 QQ68 QQ76 QQ89 VV06 XX00 5F040 DC01 EC02 EC04 EC05 EC07 FC00 FC22

Claims (7)

[Claims] 1. A semiconductor device having a gate electrode pattern formed on a semiconductor substrate via a thinned gate insulating film, wherein the gate electrode pattern is divided into an upper pattern and a lower pattern by an insulating thin film layer. A semiconductor device characterized in that: 2. The semiconductor device according to claim 1, wherein said upper and lower patterns are formed by a polycrystalline silicon layer, and said insulating thin film layer is formed by a silicon oxide layer. 3. A gate insulating film is formed on a silicon substrate, a polycrystalline silicon layer including an oxygen leak layer is formed on the gate insulating film, and the polycrystalline silicon layer is left except for a gate electrode pattern portion. Removing the upper portion of the oxygen leak layer by etching, and oxidizing the surface of the lower portion of the oxygen leak layer and the surface of the gate electrode pattern portion of the polycrystalline silicon layer remaining on the gate insulating film. Forming an oxide film by etching, and removing the oxide film by etching to leave a portion of the gate electrode pattern on the gate insulating film. 4. The polycrystalline silicon layer, wherein a lower polycrystalline silicon layer is formed on the gate insulating film, the oxygen leak layer is formed thereon, and an upper polycrystalline silicon layer is formed on the oxygen leak layer. 4. The method for manufacturing a semiconductor device according to claim 3, wherein the semiconductor device is formed by forming. 5. The oxygen leak layer is formed by temporarily supplying oxygen in a CVD reaction atmosphere when forming the polycrystalline silicon layer.
The manufacturing method of the semiconductor device described in the above. 6. The method according to claim 3, wherein the gate insulating film is a silicon nitride film or a silicon oxide film containing nitrogen. 7. The etching for removing a portion of the polycrystalline silicon layer above the oxygen leak layer is performed by reactive ion etching, and the etching for removing the oxide film is performed by isotropic etching. The method for manufacturing a semiconductor device according to claim 3.