JPS5928344A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form the pattern surface into a gentle taper and eliminate the disconnection of a wiring provided thereon, by a method wherein when a polycrystalline Si film, which is formed on an insulating film provided on a semiconductor substrate, is patterned, diffusion or ion implantation is effected to an intermediate part of the thickness of the Si film, and the etching rate at the surface layer of the Si film is set to be high. CONSTITUTION:An insulating film 2 is provided on a semiconductor substrate 1, and a polycrystalline Si film 3 is deposited on the film 2. Diffusion or ion implantation is effected to an intermediate part of the thickness of the film 3 to form a polycrystalline Si film 5 different in film quality, i.e., high in etching rate. Then, a thin oxide film 6 is formed by oxidation on the surface of the film 5, and a photoresist film 7 is provided on the oxide film 6 in a predetermined pattern. Etching is effected to remove the exposed part of the film 6. With the remaining film 6 used as a mask, the different-quality film 5 and the film 3 thereunder are etched to obtain under the film 6 a laminate of the films 5 and 3 in which the film 5 on the film 3 is smaller in width than the film 3. The film 6 is removed, and an Al wiring 9 is deposited on the whole surface including the laminate through an insulating film 8.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a pattern on a polycrystalline silicon film.

Conventionally, a method for forming a pattern of a polycrystalline silicon film grown on an insulating film on a semiconductor substrate is
An oxide film pattern is formed on the surface of the polycrystalline silicon film through a -a treatment and a photoetching process, and the oxide film pattern is used as a protective film.

In both cases, the polycrystalline silicon film is etched isotropically using etching solution or etching gas. The polycrystalline silicon film pattern is also etched from the side surface covered with the protective film, and the polycrystalline silicon film pattern after etching progresses in the side face direction by the same film thickness. The shape was a very steep step. For this reason, when forming, for example, a contact hole in a later process, the photoresist that should serve as a protective film is formed thinly at the edges of the polycrystalline silicon film pattern, and cannot withstand the etching process, resulting in pinholes. , when forming aluminum wiring to connect each transistor to obtain a desired transistor circuit,
When an aluminum wiring crosses a steeply stepped portion of the polycrystalline silicon film pattern, a disconnection occurs, resulting in a decrease in the yield of semiconductor devices.

An object of the present invention is to provide a polycrystalline silicon film pattern forming method that solves the above-mentioned problems and does not cause a decrease in the yield of semiconductor devices.

The feature of this invention is, for example, that a polycrystalline silicon film grown on an insulating film on a semiconductor substrate is selectively processed using a photoresist film or an oxide film as a protective film to form a desired polycrystalline silicon film pattern. In a method for manufacturing a device, a process of performing a diffusion or implantation process halfway through the thickness of a polycrystalline silicon film grown on an insulating film on a semiconductor substrate to form a polycrystalline silicon film with different film quality (compared to the lower layer) After that, the surface of the polycrystalline silicon film is oxidized to form a thin oxide film, and through a photoetching process, the surface of the polycrystalline silicon film is oxidized. It consists of a process of forming a film pattern and a process of etching the upper layer film preferentially compared to the entire lower layer film of polycrystalline silicon film of different film quality using the oxide film as a protective film. Due to the combination, the shape of the polycrystalline silicon film pattern is formed into a gently tapered shape.

Next, one embodiment of the present invention will be explained using the drawings.

1 to 5 are cross-sectional views of a semiconductor device for sequentially explaining one embodiment of the present invention. The method of forming a pattern of a polycrystalline silicon film in this embodiment involves performing a diffusion process or an implantation process 4 halfway through the thickness of a polycrystalline silicon film 3 grown on an insulating film 2 on a semiconductor substrate 1. Steps of forming a crystalline silicon film 5 (FIG. 1) and thereafter, oxidizing the surface of the polycrystalline silicon film 5 to form a thin oxidized film 6, and coating the surface of the oxide film 6 with a photoresist film 7. (FIG. 2) After a photo-etching process, an oxide film 6 to serve as a protective film is patterned on the polycrystalline silicon film 5 (FIG. 3). Next, the entire oxide film 6 is etched as a protective film, but at this time, in the previous step, diffusion treatment or implantation treatment 4 is performed, so that the upper polycrystalline silicon film 5 is different from the lower polycrystalline silicon film 3. Since the film quality is such that the etching rate is high, the upper film 5 is etched more dominantly than the lower film 3 (FIG. 4).

That is, an insulating film 2. is formed on the surface of a semiconductor substrate 1. A polycrystalline silicon film 3 is deposited in this order. Next, polycrystalline silicon film 3
In order to form a polycrystalline silicon film 5 of different film quality on the surface, diffusion treatment or implantation treatment 4 is all performed, and further protection is applied to the surface of the polycrystalline silicon film 3.5 when the polycrystalline silicon film 3.5 is selectively etched. An oxide film 6 and a photoresist film 7, which are to become a film, are sequentially formed, and a photo-etching process is performed to pattern the oxide film 6 on the surface of the polycrystalline silicon film 5. After that, when etching the polycrystalline silicon films 3 and 5 using the oxide film 6 as a protective film, the upper polycrystalline silicon film 5 has a film quality that has a higher etching rate than the lower polycrystalline silicon film 3. Because of this, the etching process is predominant, and the pattern shape of the resulting polycrystalline silicon film 3.5 is etched so as to produce a gentle taper.

According to this embodiment, the pattern of the polycrystalline silicon film 3.5 attached to the insulating film 2 on the semiconductor substrate 1 forms steps that produce a gentle taper sound. When the L contact hole is completely opened, the photoresist film that is to serve as a protective film does not become thinner due to the thickness of the polycrystalline silicon film pattern, so there is a problem that it cannot withstand the etching process and pinholes occur. It becomes difficult. Further, after this, in order to connect each transistor to obtain a desired transistor, an aluminum thin film 9 is formed, and when the aluminum wiring 9 is patterned through a photoetching process (FIG. 5), a polycrystalline silicon film is formed. The problem of disconnection of the aluminum wiring 9 that crosses over 3 and 5 is also less likely to occur, and this can greatly contribute to improving the yield and quality of semiconductor devices.

[Brief explanation of drawings]

1 to 5 are cross-sectional views showing an embodiment of the present invention in the order of steps. In the figure, 1... semiconductor substrate, 2... oxide film, 3
...Polycrystalline silicon film, 4... Implantation or diffusion treatment, 5... Phosphorus-doped polycrystalline silicon film (having a film quality with a faster etching rate than 3) ), 6... Oxide film, 7... Photoresist film, 8... Insulating film, 9... Aluminum thin film (wiring). Salary 1 Ward Figure 4 Figure 5

Claims (1)

[Claims] In order to make the etching rate of the upper layer of the polycrystalline silicon film grown on the insulating film on the semiconductor substrate faster than that of the lower layer, impurities are ion-implanted or diffused to the middle of the film thickness to separate the upper and lower layers. A process of forming polycrystalline silicon films with different film qualities in different parts, then oxidizing the surface of the polycrystalline silicon film to form a thin oxide film, and forming an oxide film pattern on the polycrystalline silicon film through a photo-etching process. and a step in which the upper layer of the polycrystalline silicon film of different film quality is processed and etched more quickly than the lower layer using the oxide film as a protective film. A method for manufacturing a semiconductor device, characterized in that a polycrystalline silicon film pattern is formed with gentle steps.