JP2989369B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for easily flattening an interlayer insulating film in a multilayer wiring.

[0002]

2. Description of the Related Art Higher integration of semiconductor devices in accordance with recent technological advances has necessitated a demand for multilayer metal wiring. Here, as a problem in the multi-layer wiring, when the underlying interlayer insulating film is not flattened, stress is applied to the metal wiring and disconnection is easily caused. In particular, in a semiconductor device having a thick oxide film layer as a field oxide film due to LOCOS, the level difference of the interlayer insulating film is inevitably increased based on the field oxide film, and the metal wiring film is easily broken.

[0003] Therefore, research and development of such flattening of the interlayer insulating film has been promoted, and as a conventionally known flattening technique of the interlayer insulating film, after forming the interlayer insulating film,
After a photoresist film, a polyimide film, a SOG film, etc. are entirely formed, the surface of this insulating film is flattened, and then these films are sacrificed as well as the entire surface is etched at a uniform rate together with the protrusions of the interlayer insulating film. Has been done (etchback method).

[0004]

The above-mentioned conventional planarization technique requires a thick sacrificial layer for filling the step of the interlayer insulating film, so that there is a problem that the cost is increased accordingly. In order to etch the sacrificial layer and the interlayer insulating film at a constant rate, it takes time to optimize the etching rate. In the case of resist etch-back, it is particularly difficult to control and the desired flattening is sufficient. Some were unable to achieve this.

[0005] The present invention advantageously solves the above-mentioned problem, and achieves a simple and sufficient planarization of an interlayer insulating film, thereby reducing product costs and stabilizing product characteristics. It is an object to propose a method of manufacturing a semiconductor device.

[0006]

According to the present invention, an oxidation-resistant film is selectively formed on a main surface of a semiconductor substrate by a photolithographic method using a mask, and then oxidized to locally form a field oxide film. After forming an interlayer insulating film covering the semiconductor substrate and the coating formed on the surface of the substrate, an etching-resistant film is selected by a photolithographic method using the mask used for forming the oxidation-resistant film. And then etching the interlayer insulating film on the field oxide film through the opening of the anti-etching film until it is almost the same height as other regions. is there.

In the present invention, isotropic etching is advantageous for the etching, and it is advantageous to reflow the interlayer insulating film after the etching.

[0008]

According to the method of the present invention described above, after forming an interlayer insulating film, an etching resistant film is selectively formed on the interlayer insulating film by using a mask once used, and the opening of the etching resistant film is formed. The feature is that the interlayer insulating film on the field oxide film is etched through, and thus the flattening without increasing the number of masks can be achieved by forming a thick sacrificial film as conventionally performed, Since the etch back after that can be performed unnecessarily, not only the cost can be advantageously reduced, but also the adjustment of the etching rate (condition setting) between the sacrificial film and the interlayer insulating film is not required, so that stable etching can be performed. Flattening can be performed easily.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. 1 to 5 show a method of manufacturing a semiconductor device using the present invention in a cross-sectional manner in time series.

First, as shown in FIG. 1, an oxidation-resistant film 2 (specifically, a silicon nitride film) is formed on a main surface of a semiconductor substrate (typically a silicon substrate) 1 by photolithography using a mask 3. It is selectively formed by a method.

Next, oxidation, especially thermal oxidation, is performed to form a field oxide film 4 on the surface of the semiconductor substrate facing the opening of the oxidation resistant film 2 (so-called LOCOS). The thickness of the field oxide film 4 is about the same as that of the conventional LOCOS, and is usually about 3000 ° with respect to the surface of the semiconductor substrate. Thereafter, a semiconductor element (not shown in the figure) is formed in the active region surrounded by the field oxide film 4 through various conventionally known processes, and a gate electrode (for example, polysilicon) 5 is formed on the active. An interlayer insulating film 6 is formed by CVD or the like so as to cover the surface of the semiconductor substrate 1 and the film 4 formed thereon (FIG. 2).
reference). The thickness of the interlayer insulating film 6 is about the same as that of the related art, and is about 6000 ° on the semiconductor substrate 1, the gate electrode 5, and the field oxide film 4. The steps so far are the same as the conventional method.

Next, as shown in FIG.
An etching resistant film 7 is selectively formed thereon by using the mask 3 shown in FIG. 1 so that an opening is formed on the field oxide film 4. It is advantageous that the etching resistant film 7 is a photoresist film because it does not increase the number of steps. Further, the thickness of the etching resistant film 7 is not necessarily required to be equal to the thickness for flattening the underlying interlayer insulating film, and is sufficient to be at least enough to form an opening on the field oxide film 4. This is an advantage in comparison with.

Next, as shown in FIG. 4, the interlayer insulating film 6 formed on the field oxide film is etched through the opening of the etching resistant film 7 so as to have almost the same height as other regions. . If the etching amount is about 3000 ° in the depth direction in the case of the current LOCOS film thickness, it can be made almost the same height as other regions. This etching also
The isotropic etching is advantageous in flattening the interlayer insulating film 6 because an undercut occurs under the etching resistant film 7. Examples of such isotropic etching include chemical dry etching (CDE) and wet etching. For example, as an example of CDE, C
F ₄ / O ₂ = 106/48 SCCM may be performed at 15 Pa and a microwave output of 700 W.

Next, as shown in FIG. 5, after the etching resistant film is removed by a conventionally known method, for example, by an asher, the interlayer insulating film 6 is reflowed to further promote the flattening. Thus, the interlayer insulating film 6
The material to be reflowed is suitable, for example, PSG, B
PSG and the like are preferred.

In FIGS. 1 and 3, the mask 3 is conceptually shown as a photomask of the same size, but the present invention is not limited to this drawing, and a commonly used reticle may be used. Needless to say.

[0016]

According to the method of manufacturing a semiconductor device of the present invention, an interlayer insulating film is formed so as to cover a film formed on the surface of a semiconductor substrate, and then a mask used for forming an oxidation resistant film is reused. An etching-resistant film is selectively formed by a photolithographic method, and then the interlayer insulating film on the field oxide film is etched through the opening of the etching-resistant film until it is almost at the same height as other regions. In addition, flattening without increasing the number of masks can be performed stably and simply while reducing costs.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one step of the method of the present invention.

FIG. 2 is a cross-sectional view showing one step of the method of the present invention.

FIG. 3 is a sectional view showing one step of the method of the present invention.

FIG. 4 is a cross-sectional view showing one step of the method of the present invention.

FIG. 5 is a sectional view showing one step of the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor base 2 Oxidation resistant film 3 Mask 4 Field oxide film 5 Gate electrode 6 Interlayer insulating film 7 Etch resistant film

Claims (1)

(57) [Claims] An oxidation-resistant film is selectively formed on a main surface of a semiconductor substrate by a photolithographic method using a mask, and then oxidized to form a field oxide film locally, and then an interlayer insulating film is formed. Is formed covering the semiconductor substrate and the film formed on the surface of the substrate, and then an etching-resistant film is selectively formed by a photolithographic method using the mask used for forming the oxidation-resistant film. A method of manufacturing a semiconductor device, comprising: etching an interlayer insulating film on a field oxide film through an opening in an etching film until the interlayer insulating film has substantially the same height as another region.