JPH01169945A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain stable forms of electrodes and wirings without being affected by heat treating heat and atmosphere, and improve coating quality of the step-difference of an interlayer insulating film used between wirings, by controlling the shape of polycide structure. CONSTITUTION:A polycide multilayer is constituted by forming an insulating film 2, polysilicon 3 and tungusten silicide 4 on a semiconductor substrate 1. A pattern is formed by spreading photoresist 5 on the upper layer tungusten silicide 4, which is subjected to isotropic etching by using the pattern as a mask. Thereby, a shape having a taper angle at upper corners of the upper tungusten silicide 4 of polycide structure is obtained. Then, anisotropic etching is performed to form a superior polycide structure. Further heat treatment to deposite an insulating film 6 is performed.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing a semiconductor device, and in particular, the present invention relates to a method for manufacturing a semiconductor device, and in particular, the shape of a polycide electrode made of tungsten silicide formed on a substrate and the shape of its wiring are adjusted to the temperature and atmosphere of subsequent heat treatment. <Conventional technology> When forming electrodes and wiring having a polycide structure made of tungsten silicide on a semiconductor substrate, after forming an etching mask on the tungsten silicide film, in order to obtain a polycide structure, It is processed by reactive ion etching (RIE), and then heat treated in an oxygen atmosphere to cover the surfaces of the wiring and electrodes with an insulating film made of an oxide film.

At this time, if oxidation is performed immediately after etching by RIE with a polycide structure, a bulge 4a in which silicide has abnormally grown as shown in FIG. 2 will occur in a part of the upper corner of the tungsten silicide.

Note that this evaluation cannot be seen with SEM, but is confirmed for the first time with TEM.

In the figure, an insulating film 2. Polysilicon 3. Tungsten silicide 4 is sequentially laminated, and RI
After being processed into a desired shape by E, the surface is covered with an insulating film 6.

<Problems to be Solved by the Invention> The bulging 4a of tungsten silicide produced through the above steps can cause the shape to become unstable due to repeated heat treatments after polycide formation when a polycide structure is used as wiring and electrodes. This causes electrical leakage between the wiring.

The object of the present invention is to suppress the curling up at the upper corner of a polycide structure, maintain a good shape of the polycide structure even during subsequent heat treatment, and eliminate electrical leakage between interconnections.

A solution to the problem> In the etching process for forming electrodes and wiring from a polycide multilayer film deposited on a semiconductor substrate, tungsten silicide is etched using a resist as a mask material to form approximately 1/3 of the film thickness.
The resist is removed by somewhat isotropic etching, and then the resist is removed after forming a polycide structure by RIE, and the surface of the silicide processed into a desired shape is covered with an insulating layer.

Effect〉 A part of the upper corner of the polycide is scratched by isotropic etching, the environment in which it is exposed to oxygen during oxidation treatment is relaxed compared to the conventional one, and the splashing of tungsten silicide at a part of the corner is significantly suppressed. .

<Example> FIGS. 1(C) to (d) show an example of the etching process according to the present invention. In FIG. 1(a), an insulating film 2 made of an oxide film is formed on a semiconductor substrate 1 by, for example, dry oxidation. Polysilicon 3 is formed thereon by, for example, low-pressure CVD, and tungsten silicide 4 is further formed thereon by, for example, low-pressure CVD to form a polycide multilayer film.

Next, in order to form electrodes and wiring at desired positions on the polycide multilayer film, a photoresist 5 is applied onto the upper layer tungsten silicide 4, and a predetermined pattern is formed thereon. Using this resist 5 as a mask, as shown in FIG. 1(b), tungsten silicide 4 is isotropically coated with a film thickness of about 500 to 100 OA (initial thickness step) using, for example, 20 parts of nitric acid and 1 part of ammonium fluoride in fluoronitric acid. Perform etching. As a result, the upper tungsten silicide 4 having a polycide structure has a shape having a tapered angle at the upper corner. Next, as shown in FIG. 1C, tungsten silicide and polysilicon are anisotropically etched by RIE to form a good polycide structure. After removing the resist used as a mask material in an oxygen atmosphere, heat treatment is performed to deposit an insulating film 6 covering the polycide structure as shown in FIG. 1(d). In this state, the upper corner of the tungsten silicide has a taper angle, so the excess silicon in the tungsten silicide is uniformly diffused, and the outermost surface of the tungsten silicide has an even surface area that is directly exposed to oxygen, so an insulating film is deposited on the polycide structure. The film has a uniform thickness and good film quality. It has been confirmed that the polycide structure of the semiconductor device that has gone through the above process has almost no silicide splashing, and that the etching method has no effect on the actual device such as wiring resistance or damage.

Further, since the polycide structure has a taper angle in the above embodiment, the step coverage of the interlayer insulating film used between the wirings is improved, which also leads to a reduction in the number of subsequent steps.

<Effects of the Invention> As described above, according to the present invention, by controlling the shape of the polycide structure, the shapes of the electrodes and wiring can be made into stable shapes almost unaffected by the heat treatment temperature and atmosphere.
Furthermore, the yield can be improved by improving the step coverage of the interlayer insulating film used between the wirings.

[Brief Description of the Drawings] Figures 1(a) to (d) are cross-sectional views of a polycide structure when etched by the method of the present invention, and Figure 2 is a cross-sectional view of a polycide structure formed by a conventional etching method and then oxidized. FIG. 3 is a cross-sectional view when heat treatment is performed in an atmosphere. 1: Semiconductor substrate 2: Insulating film 3: Polysilicon 4: Tungsten silicide 5: Photoresist 6: Insulating film

Claims (1)

[Claims] 1. A method for forming polycide in a desired shape whose surface is covered with an insulating layer on a semiconductor substrate, comprising: depositing tungsten silicide on the top layer on the semiconductor substrate; and on the tungsten silicide. a step of isotropically etching the exposed tungsten silicide to the middle of the film thickness; a step of etching the tungsten silicide by performing anisotropic etching following the isotropic etching; A method for manufacturing a semiconductor device, comprising the step of forming an insulating layer covering the tungsten silicide.