JPH0430176B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a method for manufacturing a semiconductor device in which polycrystalline silicon is oxidized to form an interlayer insulating layer between two electrode layers.

[Prior art]

Hereinafter, a method for manufacturing a semiconductor device with a two-layer gate electrode structure will be described as an example.

FIG. 1 is a cross-sectional view of the main parts of a double-layer gate electrode structure semiconductor device manufactured by a conventional method. 1st
In the figure, 1 is a semiconductor substrate, 2 is a semiconductor substrate 1
3 is a field oxide film formed on the surface of the field oxide film 2 to provide insulation between adjacent elements; 3 is a first gate oxide film (continuing to the field oxide film 2 in a direction perpendicular to the plane of the paper) from above the field oxide film 2; (not shown in the figure.) The remaining portion of the first polycrystalline silicon layer that was not oxidized when a second gate oxide film (described later) was formed by thermal oxidation. a first layer gate electrode 4 consisting of a second gate oxide film formed by oxidizing the first polycrystalline silicon layer;
is a second gate electrode made of a second polycrystalline silicon layer formed on the second gate oxide film 4.

In manufacturing the above-described two-layer gate electrode structure semiconductor device, a first polycrystalline silicon layer is formed over the field oxide film 2 and the first gate oxide film by vapor phase growth. Phosphorus is diffused into the next first polycrystalline silicon layer to lower the specific resistance. Next, a second gate oxide film 4 is formed by thermally oxidizing the surface side of the first polycrystalline silicon layer. At this time, the remaining portion of the first polycrystalline silicon layer becomes the first layer gate electrode 3. Furthermore, the main part of the manufacturing process is completed by forming a second layer gate electrode 5 made of a second polycrystalline silicon layer on this second gate oxide film 4.

The second gate oxide film 4 is formed by thermally oxidizing the surface side of the first polycrystalline silicon layer in which phosphorus is diffused. The surface shape of the first layer gate electrode 3, which is the remaining portion of the first polycrystalline silicon layer, becomes very different, and the breakdown voltage between the first layer gate electrode 3 and the second layer gate electrode 5 is also affected. .

That is, the conventional second gate oxide film 4 is
However, since the first polycrystalline silicon layer undergoes phosphorus diffusion, when thermally oxidized, the first layer gate electrode 3 under the second gate oxide film 4 In this case, recrystallization of polycrystalline silicon occurs due to the effects of phosphorus and heat, creating unevenness on the surface and concentration of electric field, which causes the first layer gate electrode 3
The breakdown voltage between the gate electrode 5 and the second layer gate electrode 5 decreases.

[Summary of the invention]

The present invention has been made for the purpose of eliminating the above-mentioned drawbacks of the conventional devices, and is intended to provide a method for manufacturing a semiconductor device having a two-layer electrode structure, by forming a layer on an underlying electrode layer formed on a semiconductor substrate with or without an insulating film. The upper surface side of the oxygen-doped polycrystalline silicon layer formed in the above is oxidized to form an interlayer insulating layer, and the composite layer of the portion of the oxygen-doped polycrystalline silicon layer that remains unoxidized and the underlying electrode layer is used as the first layer electrode. By doing so, there is provided a method for manufacturing a semiconductor device in which unevenness on the upper surface of the first layer electrode is eliminated and the withstand voltage between the first layer electrode and the second layer electrode is improved.

[Embodiments of the invention]

The present invention will be described below based on an example in which the present invention is applied to the manufacture of a semiconductor device with a double-layered gate electrode structure.

FIG. 2 is a cross-sectional view of the main parts of a double-layer gate electrode structure semiconductor device manufactured by the method of the example. In FIG. 2, the same reference numerals as in FIG. 1 represent the same components as shown in FIG. 3a is a lint-doped polycrystalline silicon layer formed over the field oxide film 2 and over the first gate oxide film (not shown) and constitutes a part of the first layer gate electrode; 3b;
is a remaining portion of the oxygen-doped polycrystalline silicon layer formed on the phosphorus-doped polycrystalline silicon layer 3a that was not oxidized when a second gate oxide film, which will be described later, was formed by thermal oxidation. The phosphorus-doped polycrystalline silicon layer 3a and the remaining portion 3b of the oxygen-doped polycrystalline silicon layer constitute the first layer gate electrode 3.
4a is a second gate oxide film formed by oxidizing the upper surface side of the oxygen-doped polycrystalline silicon layer.

Next, the method of the example will be explained.

Phosphorus-doped polycrystalline silicon, which becomes a part of the first layer gate electrode, is produced by vapor phase growth using a reduced pressure method, and the resistivity is lowered by diffusing phosphorus. Next, the oxygen-doped polycrystalline silicon layer is heated to
A film with a thickness of 1000 Å is produced by low pressure vapor phase epitaxy at 630° C. under the conditions of silane gas (SiH ₄ ), nitrous oxide gas (N ₂ O), and helium gas (He). The oxygen concentration at this time is 30 atomic percent.

A second gate oxide film 4a is formed by thermally oxidizing the upper surface side of 700 Å out of 1000 Å of this oxygen-doped polycrystalline silicon. Second gate oxide film 4a
When formed of oxygen-doped polycrystalline silicon, there are many traps in the oxygen-doped polycrystalline silicon that remains unoxidized under the second gate oxide film 4a, which prevents phosphorus from entering. Therefore, recrystallization of polycrystalline silicon due to heat hardly occurs. As a result of this effect, the surface of the first layer gate electrode 3 is free from irregularities and electric field concentration is reduced, so that the withstand voltage between the first layer gate electrode 3 and the second layer gate electrode 5 is increased.

In the above explanation, the case where phosphorus is diffused into a polycrystalline silicon layer to which phosphorus is not added to form a phosphorus-doped polycrystalline silicon layer is explained, but instead of diffusion, phosphorus may be ion-implanted.
Alternatively, a polycrystalline silicon layer may be formed in a phosphorus atmosphere to form a phosphorus-doped polycrystalline silicon layer.

Further, in the above embodiment, a case was described in which the present invention was applied to manufacturing a semiconductor device with a two-layer gate structure. It can be widely applied to manufacturing.

Furthermore, in the above embodiment, the case where the first layer electrode is a phosphorus-doped polycrystalline silicon layer interposed below an oxygen-doped polycrystalline silicon layer is described;
The present invention can also be applied to a case where another electrode layer, for example, a molybdenum silicide layer, is interposed below the oxygen-doped polycrystal.

〔Effect of the invention〕

In the method of manufacturing a semiconductor device of the present invention,
Since no unevenness occurs on the upper surface of the oxygen-doped polycrystalline silicon layer constituting the upper surface side of the first layer electrode, the withstand voltage between the first layer electrode and the second layer electrode is improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the main parts of a semiconductor device with a two-layer gate electrode structure manufactured by a conventional method, and FIG. FIG. In the figure, 1 is a semiconductor substrate, 2 is a field oxide film (insulating film), and 3 is a first layer gate electrode (first layer gate electrode).
3a is a phosphorus-doped polycrystalline silicon layer (underlying electrode layer), 3b is a remaining portion of the oxygen-doped polycrystalline silicon layer that has not been oxidized, 4 and 4a are second
A gate oxide film (interlayer insulating layer), 5 is a second layer gate electrode (second layer electrode). Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A step of forming an underlying electrode layer on a semiconductor substrate with or without an insulating film, a step of forming an oxygen-doped polycrystalline silicon layer on the underlying electrode layer,
The upper surface side of the oxygen-doped polycrystalline silicon layer is oxidized to form an interlayer insulating layer, and a first layer electrode is formed using the portion of the oxygen-doped polycrystalline silicon layer that remains unoxidized and the underlying electrode layer. A method for manufacturing a semiconductor device, comprising a step of configuring the interlayer insulating layer, and a step of forming a second layer electrode on the interlayer insulating layer. 2 The oxygen concentration of the oxygen-doped polycrystalline silicon layer is 1
2. The method of manufacturing a semiconductor device according to claim 1, wherein the atomic percentage is greater than or equal to atomic percent. 3. The method of manufacturing a semiconductor device according to claim 1 or 2, wherein the underlying electrode layer is a polycrystalline silicon layer to which phosphorus is added by diffusion or ion implantation. 4. The method of manufacturing a semiconductor device according to claim 1 or 2, wherein the underlying electrode layer is a polycrystalline silicon layer to which phosphorus is attached, which is formed in an atmosphere containing phosphorus. 5. Claim 1 or 2, wherein the underlying electrode layer is made of molybdenum silicide.
A method for manufacturing a semiconductor device according to section 1.