JPH01231353A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form multilayer electrode structure, in which short circuit failure and deterioration of dimensional accuracy are not generated, easily by forming a deposite film composed of an insulating material having the selectivity of etching to both of an Nth layer electrode material and an interlayer insulating oxide film material, removing the deposit film through anisotropic etching and forming a N+1th layer electrode. CONSTITUTION:A gate oxide film 102 and a field oxide film 103 are formed onto an silicon substrate 101, and first layer electrodes 104a, 104b are shaped in a polycrystalline silicon film deposited onto the oxide films 102 and 103. Interlayer insulating oxide films 107a, 107b are formed onto the surfaces of the electrodes 104a, 104b. An undercut section in the field oxide film 103 under the polycrystalline silicon electrode 104b is not buried only with the oxide film 107b and left. An silicon nitride film 109 is deposited onto the whole surface, and gotten rid of through anisotropic dry etching. Consequently, the silicon nitride film also intrudes into the undercut section, and the undercut section is buried with silicon nitride 110a, 110b because the intruding silicon nitride cannot be taken off through subsequent anisotropic dry etching. Second layer electrodes 113a, 113b are shaped. Accordingly, polycrystalline silicon is not penetrated into the undercut section, and is not left as etching residue.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor integrated circuit device having a multilayer electrode structure.

[Conventional technology] In recent years, as semiconductor devices have become smaller and more highly integrated.

Semiconductor integrated circuits having a multilayer electrode structure are widely used.

FIG. 2 is a cross-sectional view of an active region and a field region showing a method of forming a two-layer electrode according to a conventional manufacturing method in the order of steps. First, a gate oxide film 202 is formed on the silicon substrate 2.
Then, a field oxide film 203 is formed, and the polycrystalline silicon film deposited thereon is subjected to lithography and etching to form first layer electrodes 204a and 204b (FIG. 2(a)).

Next, the oxide film 202 on the gate 1 exposed on the silicon substrate 201 is removed using a hydrofluoric acid-based etching solution.
)), the silicon substrate 20 is newly processed through a thermal oxidation process.
At the same time, an interlayer insulating oxide film 207 is formed on the surfaces of the first layer electrodes 204a and 204b.
a, 207b (FIG. 2(C); refresh step). Thereafter, after depositing polycrystalline silicon II 209 (FIG. 2(d)), second layer electrodes 210a and 210b are formed by photolithography and etching (FIG. 2(e)).

[Problems to be Solved by the Invention] During the above process, in FIG. 2(b), the semiconductor substrate 201
In order to completely remove the exposed gate oxide film 202, etching is normally performed for an additional period of time compared to etching the thickness of the gate oxide film 202. Therefore,
The gate oxide film 202 under the first layer electrode 204a and the field oxide film 203 under the first layer electrode 204b made of polycrystalline silicon are undercut. In the active region, the undercut portion is filled with an oxide film formed by thermal oxidation of the silicon substrate 201 and the polycrystalline silicon electrode 207a, as shown in FIG. 2(C).

On the other hand, in the field region, since the field oxide film 203 is thick, the silicon substrate 201 is hardly oxidized, and the field oxide film 203 under the polycrystalline silicon electrode 204b
The undercut portion is the polycrystalline silicon electrode 204b.
The oxide film 207b formed by thermal oxidation remains unfilled, and when the polycrystalline silicon film 209 is deposited in the next step,
The deposited polycrystalline silicon enters into this undercut portion as shown in FIG. 2(d). Normally, patterning of a polycrystalline silicon film is performed by anisotropic dry etching, so the polycrystalline silicon that has entered the undercut portion remains without being removed as polycrystalline silicon residue 212, as shown in FIG. 2(e). do.

FIG. 3 is a perspective view showing an example of a two-layer electrode structure on a field region formed by a conventional manufacturing method. As shown in the figure, first layer electrodes 303a, 303b and second layer electrode 30
7a and 307b, the etching residues 309a to 309d of the polycrystalline silicon of the second layer electrodes that have entered the undercut portions along the first layer electrodes 303a and 303b due to the above-mentioned cause may cause the second A short circuit failure occurs between the layer electrodes 307a and 307b.

Further, if, for example, isotropic dry etching is performed to remove the multi-node silicon that has entered the undercut portion, a problem arises in that the dimensions of the second layer electrode are significantly reduced from the designed values.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device having a multilayer electrode structure that eliminates the above-mentioned drawbacks and does not cause short circuit failures or deterioration of dimensional accuracy.

[Means for Solving the Problems 1] The present invention provides an M layer (where M is an integer of 2 or more) having an active region on a semiconductor substrate and a field region in which a field oxide film is formed by oxidation of the semiconductor substrate.
In the method for manufacturing a semiconductor device having a multilayer electrode, following the formation of an Nth layer electrode (where N represents an integer of 1≦N≦M−1) and the formation of an interlayer insulating oxide film, the Nth layer electrode A deposited film made of an insulating material that has etching selectivity to both the material and the interlayer insulating oxide film material is formed, and then the deposited film is removed by anisotropic etching, and then the N+1 layer electrode (where N is (having the same meaning as above) is formed.

[Function] In the present invention, after forming the interlayer insulation oxidation model, the upper layer electrode is not immediately formed, but an insulating material having etching selectivity with respect to the electrode and the oxide film is buried in the undercut portion of the field oxide film. will be established.

Thereafter, the electrode material is deposited so that it does not enter the undercut portion.

Therefore, it is possible to eliminate inconveniences such as poor contact between electrodes and a significant reduction in electrode dimensions from the old values.

[Example] Next, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of an active region and a field region showing a method of forming a two-layer electrode according to an embodiment of the present invention in the order of steps. First, a gate oxide film 102 is placed on a silicon substrate 1.
Then, a field oxide film 103 is formed, and the polycrystalline silicon film deposited thereon is subjected to photolithography and etching to form first layer electrodes 104a and 104b (FIG. 1(a)).

Next, the goo 1 to oxide film 102 exposed on the silicon substrate 101 are removed using a hydrofluoric acid-based etching solution.
)), the silicon substrate 10 is newly processed through a thermal oxidation process.
At the same time, an interlayer insulating oxide film 107 is formed on the surfaces of the first layer electrodes 104a and 104b.
a, 107b (Fig. 1(C); refreshment stage). The process up to this point is exactly the same as the conventional technology shown in FIGS. 2(a) to 2(C), and as shown in FIG. 1(b), the gate oxide film 1 under the first layer electrode 104a made of polycrystalline silicon
02 and the field oxide film 1 under the first layer electrode 104b
03 is undercut. In the active region, Figure 1 (
As shown in C), the undercut portion is filled with an oxide film formed by thermal oxidation of the silicon substrate 101 and the polycrystalline silicon electrode 104a, but in the field region, because the field oxide film 103 is thick, the silicon substrate 101 is hardly oxidized and the polycrystalline silicon electrode 104a is not oxidized. The undercut portion of the field oxide film 103 under the crystalline silicon electrode 104b remains unfilled with only the oxide film 107b formed by thermal oxidation of the polycrystalline silicon electrode 104b. Next, silicon nitride v1
After depositing 09 on the entire surface (FIG. 1(d)), it is removed by anisotropic dry etching (FIG. 1(e)).
). In these steps, the silicon nitride film also penetrates into the undercuts 1 to 1, and the silicon nitride that has entered cannot be removed by the next anisotropic dry etching, so the undercuts are as shown in FIG. 1(e). It will be filled with silicon nitride 1ioa and 110b as shown. Thereafter, a polycrystalline silicon film 112 is deposited (FIG. 1(f)), and second layer electrodes 113a and 113b are formed by photolithography and etching (FIG. 1(g)).

As mentioned above, in this example, silicon nitride is buried in the undercut portion of the field oxide film that occurs during etching of the Goo 1-M film, so polycrystalline silicon is buried in the undercut portion during subsequent electrode formation. It will not get into the water and become etching residue. Therefore, it is possible to eliminate the inconveniences that occur in the conventional example, such as short-circuit failures occurring between the second layer electrodes and the finished dimensions of the electrodes being significantly reduced from the design values.

In this embodiment, silicon is used as the semiconductor, but it is obvious that the present invention can be applied to other semiconductors as well. In addition, in this example, silicon nitride is etched into the undercut part of the field oxide film, but it has etching selectivity with respect to the electrode material and the oxide film, and improves oxidation resistance in the hot oxidation process. If you have it,
Other materials may also be used. Generally speaking, although this embodiment shows an example of a two-layer electrode, the present invention can also be applied to an electrode structure having three or more layers.

[Effects of the Invention] As mentioned above, according to the present invention, it is easy to form a multilayer electrode structure that does not cause short circuit failures or deterioration of dimensional accuracy.
In particular, it will greatly contribute to the realization of high-density semiconductor integrated circuits.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an active region and a field region showing an embodiment of the present invention in the order of steps, and FIG. 2 is a sectional view of an active region and a field region showing a method of forming a two-layer electrode structure in the order of steps according to the prior art. FIG. 3 is a perspective view of a field region of a two-layer double pole groove structure formed by the prior art. 101, 201, 301... silicon substrate 102
, 106.202.206...gate oxide film 103,
203.302...Field oxide film 104a, 1
04b, 204a, 204b, 303a, 30
3b ... 1st layer electric (Gaga 107a, 107b, 2
07a, 207b, 305a, 305b...Interlayer insulating oxide film 109...Silicon nitride film 110a, 110b...Embedded silicon nitride 1
12.209...Polycrystalline silicon film 113a, 113
b, 210a, 210b, 307a, 307b...
Second layer weight (212.309a, 309b, 309c,
309d...Polycrystalline silicon residue

Claims (1)

[Claims] (1) Manufacture of a semiconductor device equipped with a multilayer electrode of M layers (where M is an integer of 2 or more) having an active region on a semiconductor substrate and a field region in which a field oxide film is formed by oxidation of the semiconductor substrate In the method, following the formation of the Nth layer electrode (where N represents an integer of 1≦N≦M−1) and the formation of the interlayer insulating oxide film, either of the Nth layer electrode material and the interlayer insulating oxide film material is added. A deposited film made of an insulating material with etching selectivity is formed, and then the deposited film is removed by anisotropic etching, and then the N+1
1. A method of manufacturing a semiconductor device, comprising forming layer electrodes (N has the same meaning as above).