JPS60193335A - Production of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain an electrode wiring free of interruption in steps, by utilizing the features a P type photoresist for forming films of Si3N4, SiO2 and the like in a stepped shape with the use of resist once formed as a mask and for subsequently providing an electrode metal in self-alignment again with the use of this resist. CONSTITUTION:An SiO2 film 2 and an Si3N4 film 3 are layered and adhered on a semiconductor substrate 1, which is wholly covered with a P type photoresist film 6. The film 6 is first formed with an aperture (a). Anisotropic etching is performed with the use of the residual film 6 as a mask to remove the film 3 exposed in the aperture and then the film 2. The side walls of the aperture (a) thus produced are trimmed to be vertical. After that, the substrate 1 is dipped in a resist developing solution to overdevelop the resist film 6, whereby the resist film 6 is retreated to be a film 6'. The exposed end of the film 3 is removed by dry etching to form a stepped shape in the ends of the films 3 and 2 within the aperture (a). An electrode metal is then vapor deposited with the sue of the film 6' as a mask so as to obtain an electrode having a stepped end within the aperture (a).

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method for manufacturing a semiconductor device in which an electrode metal is formed by forming an opening in two types of insulating films having different cutting rates formed on a semiconductor substrate. It depends.

(Prior Art) In recent years, silicon nitride films have come to be widely used as surface protection films of semiconductor devices as a means to improve the reliability of semiconductor devices.

However, silicon nitride film is more difficult to process than silicon oxide film.
The extremely slow rate of conversion caused several difficulties in the manufacturing process of semiconductor devices.

For example, as shown in FIG. 1, a silicon oxide film 2 and a silicon/nitride film 3t each have a thickness of 2000 A on a VC semiconductor substrate 1.
A photoresist 4 is formed on the surface of the photoresist 4 to form an opening a. Next, using the photoresist 4 as a mask, the silicon nitride film 3 and the silicon oxide film 2 are etched using, for example, 1:6 buffered hydrofluoric acid. Because of the high speed, an overhang portion as shown in FIG. 2 occurs. Therefore, if the electric rod metal 5 is formed in this state, a step break 7 will occur in the electrode metal at the overhang portion, as shown in FIG.

Therefore, in order to solve this problem, the opening in the insulating film is separated into two parts, and in the first etching, only the silicon nitride film 3 is etched to a larger area than the desired opening, using a dry etching method, for example. Then, in the second etching process, only the silicon oxide film 2 is etched using the photoresist 4' shown in FIG. 4 as a mask. There is a method of removing the / and finally forming the electrode gold [5]. This state is shown in FIG. 5. In this method, the ends of the silicon nitride film 3 and the silicon oxide film 2 are formed in a step-like manner, so that the step break 7 of the electrode metal 5 described above does not occur.

However, when using this method, the photoetching process must not be performed more than three times, twice for opening holes in the insulating film and once for electrode formation, and the relative positioning in each photoetching process must be Considering the degree of III, this method has the disadvantage that it cannot be used in the case of minute patterns such as microwave transistors.

(Objective of the Invention) An object of the present invention is to utilize the characteristics of a positive photoresist to form a silicon nitride film and a silicon oxide film using the once-formed photoresist as a mask, in order to eliminate such defects. The present invention provides a method for manufacturing a semiconductor device with high relative positioning accuracy, which does not cause step breakage by forming the semiconductor device in a stepwise manner and also forming the electrode metal in a self-aligned manner using the photoresist.

(Embodiments) Next, preferred embodiments of the present invention will be described in more detail with reference to the drawings.

FIG. 6 shows a silicon nitride film 3 on a silicon oxide film 2 on a semiconductor substrate l, after a positive photoresist 6 is formed on this surface and an opening a is provided.

A state in which openings a are sequentially formed in the silicon nitride [3 silicon oxide film 2] using a parallel plate type dryer and etching device is shown. Since this is anisotropic etching using a parallel plate type dryer and etching device, etching is performed vertically without proceeding in the lateral direction.

Next, the semiconductor substrate treated in this way is immersed again in a positive photoresist developer and over-developed.
As shown in FIG. 7, the edge of the positive photoresist 6 is recessed to form a pattern 6' and the edge of the silicon nitride film 3 is exposed. Further, when the semiconductor substrate is subjected to dry etching and etching, the exposed end portions of the silicon nitride film 3 are removed, and the silicon nitride film 3 and the silicon oxide film 2 are formed in a stepped shape, as shown in FIG. Next, the surface of the semiconductor substrate is stained with other metals (e.g. Ti-P
FIG. 9 shows a state in which electrode metal 5 is formed by depositing L-AU) and using the lift-aqua method.

As is clear from FIG. 9, when the method for manufacturing a semiconductor device according to the embodiment is used, there is no overhang part, so there is no breakage of the electrode metal, and the silicon nitride film 2 and the silicon nitride film 3 Since the relative positioning of the opening and the electrode metal 5 is self-aligned, there is no possibility that the positional relationship will shift. Furthermore, since it is an alpha line, this method is particularly effective in the manufacturing process of microwave transistors and microwave ICs having fine patterns with openings of several microns.

Although this embodiment has been described using a silicon oxide film and a silicon nitride film as the insulating films, this is not particularly limited, and any other insulating film with different etching rates may be used. It's okay even if it is. Further, although '@electrode metal Ti-pt-Atr is shown as an example, its type is not limited at all.

[Brief explanation of drawings]

1 to 5 are cross-sectional views for explaining a conventional method of manufacturing a semiconductor device. 6 to 9 are cross-sectional views for explaining a method of manufacturing a semiconductor device according to an embodiment of the present invention. 1... Semiconductor substrate, 2... Silicon oxide film, 3... Silicon "A (tJs 4,4'
...Photoregis), 5. 5'・・・・・・
Electrode metal, 6. 6'・・・Positive photoresist. Section 1, Figure 2, Section 4, Figure 8b, Figure 7, Figure 6.

Claims (1)

[Claims] A first insulating film is provided on a semiconductor substrate, and a second insulating film having a lower processing rate than the first insulating film is disposed on the first insulating film.
When forming an electrode metal by forming an opening in a semiconductor substrate having an insulating film, a step of covering the second insulating film with a positive photoresist and sequentially etching away the insulating film; a step of performing a development process on the semiconductor substrate to expose an end portion of the second insulating film; a step of subsequently performing an etching process again to remove the end portion of the second insulating film; 1. A method of manufacturing a semiconductor device, comprising the steps of depositing an electrode metal on a semiconductor substrate and forming an electrode by a lift-away method using the photoresist.