JPH02206115A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enhance a step coverage of a wiring electrode and a protective film on its upper layer by a method wherein a first insulating film, a second insulating film and a third insulating film whose etching rate is higher than that of the second insulating film are formed as an interlayer insulating film, the third insulating film is etched anisotropically and a through-hole is formed on a conductive layer of a semiconductor substrate. CONSTITUTION:A first insulating film 3 whose stress is low with reference to a semiconductor substrate 1, a second insulating film 4 and a third insulating film 5 whose etching rate with reference to an isotropic etching operation is higher than that of the second insulating film are piled up, as an interlayer insulating film 7, one after another on the semiconductor substrate 1; the third insulating film 5 is etched isotropically by making use of a photoresist pattern 6 as a mask. After that, the second insulating film and the first insulating film 4, 3 are etched anisotropically by a reactive ion etching operation; a through-hole 8 reaching the surface of a conductive layer 2 is formed. Accordingly, an edge part of the through-hole at the third insulating film 5 is formed so as to be inclined. Thereby, when a protective film 10 is formed on the surface of the semiconductor substrate 1, a step coverage of a wiring electrode 9 and the protective film 10 on its upper layer is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing semiconductor devices such as semiconductor integrated circuits.

[Conventional technology]

In recent years, as semiconductor integrated circuits have become more integrated, through holes formed in semiconductor devices have come to be formed anisotropically by reactive ion etching.

A conventional method of manufacturing a semiconductor device of this type will be explained with reference to FIG.

In the manufacturing process of this semiconductor device, first a silicon substrate
A diffusion layer 2' is formed on the silicon substrate 1' on which the diffusion layer 2' is formed, and an interlayer insulating film 7' is deposited on the silicon substrate 1', as shown in FIG. 2(a). A photoresist pattern 6 serving as a mask pattern is formed thereon.

Next, as shown in FIG. 2 Φ), the interlayer insulating film 7' is anisotropically etched by reactive ion etching using the photoresist pattern 6 as a mask to form a through hole 8'. At this time, the glabellar insulating film 7' is etched anisotropically, so that a through hole 8' is vertically etched along the edge of the photoresist pattern 6. Then, as shown in FIG. 2(C), an aluminum wiring electrode 9' is formed in the through hole 8' by selective etching using a photoresist (not shown) as a mask, and this aluminum wiring electrode 9' is then formed in the through hole 8'. A protective film 10 is formed on the surface of the formed silicon substrate 1'.

[Problem to be solved by the invention] However, in this conventional method for manufacturing a semiconductor device,
Since the through hole 8' is formed by anisotropic etching, the step coverage of the aluminum wiring electrode 9' formed in the through hole 8' and the overlying protective film 10 deteriorates, resulting in an increase in wiring resistance. , there was a problem of decreased reliability.

Therefore, an object of the present invention is to improve the step coverage of the wiring electrode formed in the through hole and the protective film formed on the upper layer of the wiring electrode, thereby reducing the wiring resistance and improving the reliability of a semiconductor device. An object of the present invention is to provide a method for manufacturing.

[Means for Solving the Problems] A method for manufacturing a semiconductor device according to the present invention includes forming a first insulating film with low stress on the semiconductor substrate on the surface of the semiconductor substrate on which a conductive layer is formed in a part of the surface. A second insulating film is formed on the surface of the first insulating film, and a second insulating film is etched on the surface of the second insulating film at a higher etching rate than the second insulating film for isotropic etching. A step of forming an interlayer insulating film by forming the third insulating film, a step of forming a photoresist pattern on the third insulating film, and a step of forming the third insulating film on the conductive layer using the photoresist pattern as a mask. etching the second and first insulating films anisotropically by reactive ion etching to expose the surface of the conductive layer and form a through hole;
The method includes a step of forming a wiring electrode in the through hole, and a step of forming a protective film on the surface of the semiconductor substrate on which the wiring electrode is formed.

[For production]

According to the method of the present invention, a first insulating film that has low stress on a semiconductor substrate, a second insulating film, and a second insulating film that has a higher etching rate than the second insulating film for isotropic etching. The third insulating film is formed as an interlayer insulating film on the surface of the semiconductor substrate, and the third insulating film is isotropically etched using the photoresist pattern as a mask. is etched equally horizontally and vertically from the edge of the photoresist pattern on the third insulating film side, and the opening in the third insulating film formed by etching is the same as the opening for etching formed in the photoresist pattern. It is formed to be larger than the width and to be inclined so as to become smaller from the photoresist pattern side toward the second insulating film side. At this time, the second insulating film, which is the lower layer of the third insulating film, is hardly etched because its etching rate is lower than that of the third insulating film with respect to isotropic etching. Then, the second and first insulating films are etched anisotropically by reactive ion etching, so that the second and first insulating films are vertically etched along the edges of the photoresist pattern, making them conductive. Through holes are formed that reach the surface of the layer. Therefore, since the edge of the through hole in the third insulating film is formed at an angle, when a wiring electrode is formed in the through hole and a protective film is formed on the surface of the semiconductor substrate on which the wiring electrode is formed, the wiring electrode And the step coverage of the overlying protective film is improved.

〔Example〕

An embodiment of the method for manufacturing a semiconductor device according to the present invention will be described with reference to FIG.

In the manufacturing process of this semiconductor device, first, a diffusion layer 2, which becomes a conductive layer, is formed in a part of the surface of a silicon substrate 1, which becomes a semiconductor substrate. Next, as shown in FIG. 1(a), on the surface of the silicon substrate 1 on which the diffusion layer 2 has been formed, a silicon dioxide film 3, which becomes a first insulating film with low stress on the silicon substrate 1, is formed. A silicon nitride film 4, which becomes a second insulating film, is formed on the surface of this silicon dioxide film 3. Furthermore, a phosphosilicate glass film 5 (hereinafter referred to as PSG film 5), which serves as a third insulating film with a higher etching rate than the silicon nitride film 4 for isotropic etching, is formed on the surface of the silicon nitride film 4. and silicon dioxide film 3. Silicon nitride film 4 and glabella insulating film 7 made of PSGSbO2
form. Next, a photoresist pattern 6 is formed on the PSG film 5.

Then, as shown in FIG. 1(b), using the photoresist pattern 6 as a mask, etching is performed in the PSGSbO2 direction by wet etching using buffered butic acid. At this time, since PSGSbO2 isotropically etched from the edge of the photoresist pattern 6 on the PSG film 5 side in both the horizontal and vertical directions, the PSGSbO2 opening formed by etching is not formed in the photoresist pattern 6. The opening width is larger than the width of the opening, and the opening width is inclined so as to become smaller from the photoresist pattern 6 side toward the silicon nitride film 4 side. Further, the silicon nitride film 4 which becomes the PSGSbO2 layer is hardly etched because PSGSbO2 also has a low etching rate compared to isotropic etching. Then, as shown in FIG. 1(C), the silicon nitride film 4 and the silicon dioxide film 3 are anisotropically etched by reactive ion etching using a batch type dry etching device or the like, to thereby remove the surface of the diffusion layer 2. is exposed to form a through hole 8. At this time, since the silicon nitride film 4 and the silicon dioxide film 3 are etched anisotropically, they are etched vertically along the edge of the photoresist pattern 6, forming a through hole 8 that reaches the surface of the diffusion layer 2. be done. In this case, the pressure should be 30 to 100 mT.
Reactive ion etching was performed with an output of 1000 to 1350 W and a reaction gas of CHF310□.

Next, as shown in FIG. 1(d), a wiring electrode 9 made of aluminum or the like was formed in the through hole 8 by selective etching using a photoresist (not shown) as a mask. A protective film 10 is formed on the surface of a silicon substrate l. At this time, since the edge of the PSGSbO2 through hole is formed with an inclination, when the wiring electrode 9 is formed in the through hole 8 and the protective film 10 is formed on the surface of the silicon substrate 1 on which the wiring electrode 9 is formed, the wiring Step coverage of the electrode 9 and the protective film 10 can be improved, wiring resistance can be reduced, and reliability can be improved.

Furthermore, in this embodiment, the silicon nitride film 4, which is hardly etched by wet etching, was used as the second insulating film that forms the middle layer of the glabella insulating film 7.
By over-etching using PSGSbO2 jet etching, it is possible to easily form the PSGSbO2 opening at an angle.

In this embodiment, the diffusion layer 2 has been described as a conductive layer, but a conductive layer made of polycrystalline silicon gate wiring or the like may be used.

〔Effect of the invention〕

According to the method of manufacturing a semiconductor device of the present invention, the first insulating film and the second insulating film, which have low stress on the semiconductor substrate, and the second insulating film are etched more isotropically than the second insulating film. A third insulating film with a high etching rate is sequentially formed as an interlayer insulating film on the surface of the semiconductor substrate, and the third insulating film is isotropically etched using the photoresist pattern as a mask. Since the first insulating film was etched anisotropically by reactive ion etching to form a through hole on the conductive layer formed on the semiconductor substrate, the edge of the through hole in the third insulating film was inclined. It is possible to improve the step coverage of the wiring electrode formed in the through hole and the overlying protective film, thereby reducing wiring resistance and improving reliability.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(d) are cross-sectional views showing the steps of an embodiment of the present invention, and FIGS. 2(a) to (C) are cross-sectional views showing the conventional manufacturing steps of a semiconductor device. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate (silicon substrate), 2... Conductive layer (diffusion layer), 3... First insulating film (silicon dioxide film), 4... Second insulating film (silicon nitride film) ), 5...
・Third insulating film (phosphosilicate glass (PSG)
) film), 6... photoresist pattern, 7...
・Interlayer insulating film, 8... Through hole, 9... Wiring electrode, 10... Protective film

Claims (1)

[Claims] A first insulating film having low stress with respect to the semiconductor substrate is formed on the surface of a semiconductor substrate having a conductive layer formed on a part of the surface, and a second insulating film is formed on the surface of the first insulating film. forming an interlayer insulating film by forming a third insulating film having a higher etching rate than the second insulating film with respect to isotropic etching on the surface of the second insulating film; , forming a photoresist pattern on the third insulating film; isotropically etching the third insulating film on the conductive layer using the photoresist pattern as a mask; etching the first insulating film anisotropically by reactive ion etching to expose the surface of the conductive layer and forming a through hole; forming a wiring electrode in the through hole; and forming a wiring electrode in the through hole. A method for manufacturing a semiconductor device, comprising the step of forming a protective film on the surface of the formed semiconductor substrate.