JPS6161424A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a taper on a polycrystaline silicon layer and to obtain a highly reliable multilayer wiring structure by a method wherein a plasma treatment is applied to the photosensitive resin film and after the photosensitive resin film is made to deform by heat in a trapezoidal form, an etching is performed on the polycrystalline silicon layer using the photosensitive resin film as a mask. CONSTITUTION:A photosensitive resin film 1 is formed on a polycrystalline silicon layer 2 on an insulating film, such as an oxide film 3, formed on a semiconductor substrate 4 in the desired pattern, and after that, a plasma treatment of N2 is performed at temperatures of 140-180 deg.C and the photosensitive resin film is made to deform by heat and is formed in a pattern in a trapezoidal configuration. An etching is performed on the polycrystalline silicon layer in a taper form in an etching condition within an extent that the ratio of the etching rate (ratio of selectivity) of the polycrystalline silicon layer to the photosensitive resin film is desirably an extent of 2.0 to 5.0 using the photosensitive resin film formed in a trapezoidal form as a mask according to a reactive ion etching method, wherein chlorine gas or fluorine gas is used, or a parallel plate plasma etching method, wherein chlorine gas or fluorine gas is used.

Description

[Detailed Description of the Invention] The present invention is a semiconductor device! Regarding the manufacturing method, in particular, in the step of forming a conductive layer such as aluminum for wiring on a polysilicon layer via an insulating film, by forming the polysilicon layer in a tapered shape, the aluminum for wiring, etc. The present invention relates to a semiconductor device manufacturing method that prevents step breakage.

Conventionally, a photosensitive resin film on a polysilicon layer is masked by reactive ion etching using chlorine-based gas or fluorine-based gas as an etching gas, or parallel plate plasma etching using chlorine-based or fluorine-based gas as an etching gas. In the method of taper etching the polysilicon layer, for example, when the polysilicon layer is undercut by reactive ion etching using 8F, and the photosensitive resin film is used as a mask, the polysilicon layer is undercut. There is a method of etching the silicon layer into a tapered shape as shown in FIG. 1(a).

In the same figure, 13 is a photosensitive resin film, 23 is a polysilicon layer,
3 is an oxide film, and 4 is a semiconductor substrate. At this time, the pressure inside the reaction chamber during etching is about 1oPa. However, in the conventional method, the so-called isotropic etching property in which the lateral etching speed of the polysilicon layer 23 is approximately equal to the vertical etching speed of the polysilicon layer 23 is used to form the taper of the polysilicon layer 23. 1. When the desired pattern width of the photosensitive resin on the polysilicon layer is approximately twice the thickness of the polysilicon layer or less, the shape of the polysilicon layer after etching becomes It does not become trapezoidal as shown in figure (a);
There was a drawback that it became triangular as shown in XrJ1 diagram (b). In this figure, 14 is a photosensitive resin film, and 24 is a polysilicon layer.

Furthermore, in the taper etching of the polysilicon layer by the conventional method, the pattern width of the polysilicon layer changes drastically depending on the amount of overetching of the polysilicon layer. The disadvantage is that it is extremely difficult to perform etching with good reproducibility to a desired pattern width.

The present invention provides reactive ion etching using the above-mentioned conventional chlorine-based gas or fluorine-based gas as an etching gas;
Alternatively, the polysilicon layer can be etched by parallel plate plasma etching using chlorine gas or fluorine gas, thereby eliminating the drawbacks of the method of chipping the polysilicon layer and obtaining an extremely reliable multilayer wiring structure. The present invention provides a taper etching method.

In the method according to the present invention, a photosensitive resin film is formed in a desired pattern on a polysilicon layer on an insulating film such as an oxide film formed on a semiconductor substrate, and then the cross section of the photosensitive resin film is changed from a rectangular shape to a trapezoidal shape. Preferably 140 to change the shape
Perform N2 plasma treatment at a temperature of ℃~180℃,
The photosensitive resin film is thermally deformed to form a trapezoidal pattern as shown in FIG. The etch rate ratio (selectivity) between the polysilicon and the photosensitive resin film is preferably 2.0 to 5.0 by using the parallel plate plasma etching process using the trapezoidal photosensitive resin film as a mask. In this method, the polysilicon layer is etched into a tapered shape under etching conditions within a range of 0.0.

Next, an embodiment of the etching method according to the present invention will be described with reference to the drawings.

After forming, for example, an oxide film as an insulating film 3 on the surface of a semiconductor 4, for example, an N-type silicon wafer used in FIG. Approximately 600 oA is formed. Thereafter, a positive type photosensitive resin lftX1, for example, 0FPR-800 (product name of Tokyo Ohka Co., Ltd.) is formed in a desired pattern on this polysilicon layer, and post-baked for 30 minutes in an N2 atmosphere. The temperature at this time is approximately 1
The temperature is set within the range from 00'O to 130°0, and the temperature is controlled with an accuracy of ±5°C.

Next, the semiconductor wafer with the photosensitive resin film patterned by the method described above is placed in a barrel-type plasma etching cap using N2 gas at a 140° angle, as shown in FIG. 2(a).
N2 bubble treatment at any temperature from 0 to 180℃ for 30 minutes.
The photosensitive resin film 1 (FIG. 1(a)) is thermally deformed into a trapezoidal cross-sectional shape as indicated by 11 in FIG. 2(b). The N2 plasma processing conditions at this time are, for example, an excitation frequency of 13.56 MHz.

The pressure during plasma treatment in the reaction chamber is 0.4 to 0.6 Torr.
r.

Rin, F, power is 200W.

Here, the higher the temperature of the N2 plasma treatment, the more acute the contact angle between the photosensitive resin film and the polysilicon layer.

Next, chlorine-based gas or fluorine-based gas such as CCt2F,
The photosensitive resin film 11 is etched by reactive ion etching using a gas containing N2 added to the etching gas as an etching gas.
The polysilicon layer 2 is etched using the mask as a mask. The etching conditions at this time are, for example, an excitation frequency of 13.56.
MHz, 几, F, power is 600W, CC2, F2 stream view is 60CC/min.

The N2 flow rate was 15 CC/min, and the pressure inside the reaction chamber during etching was 16 Pa.

When the etching progresses and the photosensitive resin film 11 remains at the interface point A with the polysilicon film 21, there is no undercut in the polysilicon film 2' (FIG. 2C).
).

As the etching progresses further, the photosensitive resin film 12 is worn away during etching and retreats inward from point A, as shown in FIG.
It will look like d) 12. At this time, as the photosensitive resin film 12 retreats due to etching, the polysilicon film 21 begins to be etched into a tapered shape, and when the etching is completed, the polysilicon layer 22 becomes tapered as shown in FIG. 2(d). It becomes like this. Therefore, the sharper the contact angle of the photosensitive resin film with the polysilicon layer, the sharper the taper angle of the polysilicon layer. Further, since the speed at which the photosensitive resin film 11 (FIG. 2(C)) retreats inward from point A increases as the selectivity ratio decreases, the taper angle of the polysilicon layer is determined by the selectivity ratio. However, in the present invention, taper etching is performed by changing the taper angle of the polysilicon layer arbitrarily by changing the temperature conditions of the N2 plasma treatment under etching conditions that keep the selectivity constant. Let's do it.

As described above, according to the present invention, reactive ion etching using chlorine-based gas or fluorine-based gas or parallel plate plasma etching using chlorine-based gas or fluorine-based gas is performed to oxidize a semiconductor substrate. In a method of taper etching the polysilicon layer using a photosensitive resin film formed in a desired pattern on a polysilicon layer on an insulating film such as a film as a mask, the pattern of the polysilicon layer is Pattern with fine width (1,
It has become clear that taper etching is possible up to a thickness of about 5 μm) and that the taper angle of the polysilicon layer can be controlled arbitrarily.

Therefore, it is clear that the taper etching method according to the present invention is a highly controllable taper etching method that can obtain an extremely reliable multilayer wiring structure.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are cross-sectional views showing the tapered shape of the polysilicon layer after the polysilicon layer has been tapered by a conventional etching method. Figure 1(a) shows that the pattern width of the photosensitive resin film used as a mask is 2 times the film thickness of the polysilicon layer to be etched.
Figure 1 (b) shows a cross section when the pattern width of the photosensitive resin film used as a mask is about twice the thickness of the polysilicon layer to be etched. Show the diagram. FIGS. 2(a) to 2(d) are cross-sectional views for explaining each process of an embodiment of the present invention. In the figure, 1.11, 12, 13, 14... photosensitive resin film, 2.21, 22, 23.24... polysilicon layer, 3...・Insulating film, e.g. oxide film, 4...
・Semiconductor substrate e.g. N-type silicon wafer, broken ma.
...Photosensitive at oil film 1 before N2 plasma treatment
Breaking the mold! ′! i! b... This is the mold before the photosensitive resin lrJ recedes during etching.

Claims (3)

[Claims] (1) A polysilicon layer formed on a semiconductor substrate is formed on the polysilicon layer by reactive ion etching using chlorine-based gas or fluorine-based gas, or parallel plate plasma etching using the above gas. In the method of taper etching the polysilicon layer using a photosensitive resin film formed as a pattern as a mask, plasma treatment is applied to the photosensitive resin film having a rectangular cross section, and the photosensitive resin film is heated into a trapezoidal shape. A method for manufacturing a semiconductor device, comprising forming a taper in the polysilicon layer by deforming the polysilicon layer and etching the polysilicon layer using the trapezoidal photosensitive resin film as a mask. (2) The conditions for applying plasma treatment to the photosensitive resin film are 14
The method for manufacturing a semiconductor device according to claim 1, wherein the temperature is from 0° C. to 180° C. and the plasma treatment is nitrogen (N_2) plasma treatment. (3) When etching the polysilicon layer, the etching rate ratio between the polysilicon and the photosensitive resin film is 2.0 to 5.
．． 2. The method of manufacturing a semiconductor device according to claim 1, wherein the etching is performed under etching conditions within a range of 0.