JPH047095B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device, and particularly to a taper etching method thereof.

The semiconductor device of the present invention refers to a single semiconductor device,
It refers to semiconductor devices in a broad sense, including semiconductor integrated circuit devices, hybrid integrated circuit devices formed by combining these with thin film integrated circuit devices, thick film integrated circuit devices, etc., and large-scale integrated circuit devices of each of the above devices.

When etching the object to be etched using the photo-etching method,
In most cases, the etching is isotropic. In isotropic etching, the etching step has an inclination that is close to perpendicular to the substrate, so if metal wiring is formed on top of the etching step, there is a risk of lower yield and reliability due to disconnection at the step. be. Therefore, various taper etching methods have been proposed, and some have been successfully implemented. However, conventional taper etching methods, such as methods using a phosphor glass layer, methods using ion implantation, and methods using a silica film, all have extremely poor dimensional accuracy compared to isotropic etching. If it was required, it would be difficult to apply, or even if it were applied, it would be necessary to strictly control the working methods and working conditions at the manufacturing site.

Here, conventional isotropic etching and taper etching will be explained using FIGS. 1 and 2. First, a case will be described in which a silicon oxide film on a silicon substrate is isotropically etched using 1:6 buffered hydrofluoric acid. First, a silicon oxide film 2 is formed on a silicon substrate 1, and then a predetermined pattern is formed using a photoresist 3 (FIG. 1a). After post-baking, when the silicon oxide film 2 is etched down to the silicon substrate 1 with buffered hydrofluoric acid, the lateral direction is as shown in FIG.
Edges of photoresist 3 and silicon oxide film 2
An etched shape is obtained by etching the radius from the point of contact with the silicon oxide film 2 by an amount equal to the thickness of the silicon oxide film 2 (FIG. 1b). However, usually, taking into account variations, over-etching is performed for about 1 minute to ensure that no silicon oxide film remains (FIG. 2c).
After that, when the photoresist 3 is removed and aluminum 5 is deposited, the aluminum 5 tends to adhere discontinuously at the upper edge of the silicon oxide film 2, sometimes causing disconnection (Fig. 1 d). ).

Next, conventional taper etching will be explained. First, a silicon oxide film 2 is placed on a silicon substrate 1.
After forming, for example, a thin phosphorous glass layer 4 is formed on the surface of the silicate film 2, and then a predetermined pattern is formed using a photoresist 3 (FIG. 2a). After post-baking, the silicon oxide film 2 is etched down to the silicon substrate 1 using buffered hydrofluoric acid, resulting in a tapered etched shape having an inclination of 90° or less with respect to the silicon substrate 1 in the lateral direction (second Figure b). However, as with isotropic etching, if you over-etch for about 1 minute,
The amount of dimensional change with respect to the pattern dimension of the photoresist is greater than that in the case of isotropic etching (FIG. 2a). Thereafter, when the photoresist 3 is removed and aluminum 5 is deposited, the cross section of the aluminum 5 to which it is deposited is continuous in all regions (FIG. 2d). As described above, conventional taper etching is very effective in preventing wire breakage in aluminum, but on the other hand, it has the disadvantage of impairing dimensional accuracy.

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, an object of the present invention is to provide a method for manufacturing a semiconductor device that can easily and reproducibly obtain taper etching with extremely high dimensional accuracy.

In the process of taper etching an object to be etched on a substrate, the method for manufacturing a semiconductor device of the present invention includes performing a process on the surface of the object to cause a first taper etch that proceeds in a direction transverse to the substrate surface. , forming a predetermined pattern using photoresist,
After using the photoresist as a mask to increase the etching rate of only the exposed area of the etching target to cause a second taper etch that proceeds in the vertical direction with respect to the substrate surface, the photoresist is removed as a mask. The method is characterized in that the object to be etched is etched, and the first and second taper etches are performed simultaneously.

Next, one embodiment of the present invention will be described using FIG. 3. First, a silicon oxide film 2 is formed on a silicon substrate 1, a thin phosphorous glass layer 4 is formed on the surface of the silicon oxide film 2, and then a photoresist 3 is formed.
A predetermined pattern is formed using (FIG. 3a).
After post-baking, ions are implanted using the photoresist 3 as a mask to form a region of the silicon oxide film 2' having a high etching rate (FIG. 3b). After this, when etching is performed with buffered hydrofluoric acid, taper etching proceeds in the vertical direction using the same principle as conventional taper etching (lateral taper etching) (Fig. 3c). When the etching reaches the silicon substrate 1, the shape of the etching becomes a two-stage taper in which a horizontally tapered surface and a vertically tapered surface are overlapped (FIG. 3d). When over-etching is further carried out for about 1 minute, the amount of dimensional change with respect to the pattern dimension of the photoresist is as follows:
The amount of dimensional change is very small compared to the case of isotropic etching and conventional tapered etching (FIG. 3e).
Thereafter, when the photoresist 3 is removed and aluminum 5 is deposited, the aluminum 5 can provide good step coverage in any region (FIG. 3f), similar to the conventional taper etching.

As described above, by using the present invention, dimensional accuracy can be improved over conventional etching, and a good taper can be obtained.

In the above embodiments, the case where a silicon oxide film is etched with buffered hydrofluoric acid is described, but the technical scope of the present invention is not limited to the above embodiments. This applies to all etchants including liquids, gases, and plasmas, and the method of accelerating the etching rate of the object to be etched is not limited to ion implantation, but also applies to all other methods.

[Brief explanation of drawings]

Figures 1a to 1d are cross-sectional views showing etching cross-sections in conventional isotropic etching, and Figures 2a to 2d are cross-sectional views showing etching cross-sections in conventional taper etching. 3a to 3f are cross-sectional views showing etched cross-sections according to embodiments of the present invention. In the figure, 1...silicon substrate, 2...
Silicon oxide film, 2'...Silicon oxide film with high etching speed, 3...Photoresist, 4...
Thin phosphorus glass, 5...Aluminum.

Claims (1)

[Claims] 1. In the step of taper etching an object to be etched on a substrate, a process is performed to cause a first taper etch to proceed in a direction transverse to the surface of the substrate on the surface of the object to be etched, and then a predetermined pattern is etched using a photoresist. after forming a second taper etch extending vertically relative to the substrate surface by increasing the etching rate of the exposed areas of the etching material using the photoresist as a mask; A method for manufacturing a semiconductor device, characterized in that the object to be etched is etched using the photoresist as a mask, and the first and second taper etches are performed simultaneously.