JPH01235352A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To uniformly deposit a passivating film to be formed on a metal electrode film upper layer by a method wherein a conductive film is etched by an isotropic etching method in a first process and by an anisotropic etching method in a second process so that it can be etched continuously. CONSTITUTION:A silicon oxide film 2, a gate silicon oxide film 4 and a polysilicon film 3 are formed on a P-type silicon substrate 1. After that, an N-type conductive film 5 is formed by an ion implantation method; after that, a BPSG film 6 is deposited. In succession, a polysilicon film 14 is deposited on a substrate where a contact hole has been opened selectively; an Al film 8 is applied; a conductive film of a two-layer structure is formed. A resist mask 13 is patterned. After that, the Al film 8 is etched isotropically. Then, the Al film 8 and the conductive film composed of the polysilicon film are etched down to an end in the thickness direction by an anisotropic etching method. By this setup, a passivating film to be formed on a metal electrode film upper layer can be deposited uniformly; a crack or the like is not produced in the passivating film due to a temperature stress or the like when a semiconductor device is mold-packaged; the moistureproofness can be enhanced furthermore.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for forming electrode wiring by etching a metal film.

[Conventional technology]

Conventionally, in the manufacturing method of this type of semiconductor device, the fourth
As shown in the figure, after an aluminum film 8 is deposited by sputtering or the like, etching is performed using a photoresist using a dry etching method with constant etching gas pressure and etching power to form electrode wiring. In other conventional examples, electrode wiring was formed by wet etching a metal film such as the aluminum film 8 using photoresist, for example, with a phosphoric acid solution at about 40 to 60°C.

[Problem to be solved by the invention]

In the conventional semiconductor device manufacturing method described above, the side surface of the metal electrode film of the electrode wiring becomes perpendicular or inversely tapered to the underlying boron-doped phosphosilicate glass film, that is, the BPSG film 6, and as a result, the metal electrode film When the low concentration PSG film 9 and the plasma nitride film 10 are deposited on the upper layer by the atmospheric pressure CVD method, the step coverage of the low concentration PSG film 9 and the plasma nitride film 10 is extremely deteriorated, as shown in FIG. The thickness of the plasma nitride film 10 may become extremely thin at some corners of the metal electrode film or the aluminum film 8), or it may become impossible for the plasma nitride film 10 to completely cover the aluminum film 8). As a result, plasma nitride film cracks and low PSG film cracks occur in thin areas of the plasma nitride film 10 due to temperature stress during mold packaging of semiconductor devices. This has a major drawback in that the moisture resistance of the semiconductor device is extremely reduced and the reliability of the product is impaired. In addition, in conventional semiconductor device manufacturing methods,
As mentioned above, as a result of the etching surface of the metal electrode film (8) becoming perpendicular or inversely tapered with respect to the underlying BPSG film 6, in a semiconductor device having a two-layer electrode wiring structure, the glabellar insulating film on the lower electrode wiring is Because step coverage deteriorates extremely,
This method has a major drawback in that the film thickness of the upper layer electrode wire may become extremely thin or the wire may be disconnected in the region where the upper layer electrode wire and the lower layer electrode wire intersect.

[Means to solve the problem]

The method of manufacturing a semiconductor device of the present invention includes an etching step of selectively removing a conductive film deposited on a substrate to form an electrode wiring, wherein the etching step removes the conductive film from the substrate. The method consists of a first step in which the initial film thickness is removed by isotropic etching up to the middle, and a second step in which the film is removed by anisotropic etching up to the end.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(a) to 1(f) are cross-sectional views of semiconductor chips arranged in the order of steps for explaining the first embodiment of the present invention.

First, as shown in FIG. 1(a), a P-type silicon substrate 1
A silicon oxide film 2 is selectively formed thereon by photolithography.

Subsequently, as shown in FIG. 1(b), a gate oxide silicon film 4 is formed to a thickness of 50 nm by thermal oxidation, a polysilicon film is further deposited by CVD, and phosphorus is diffused to increase the conductivity of the polysilicon. After increasing the temperature, a polysilicon film 3 is formed by selectively etching using photoresist.

Thereafter, an N-type conductive layer 5 was formed by ion implantation, and then a BPSG film 6 was formed to a thickness of 11,000 by atmospheric pressure CVD.
About n is deposited.

Subsequently, as shown in FIG. 1(c), the BPSG film 6 is
Heat treated at 00° C., reflowed the BPSG film 6, and then selectively opened contact holes using a dry etching method. Using the substrate as a substrate, a polysilicon film 14 was deposited to a thickness of about 200 nm using the CVD method. Subsequently, an aluminum film 8 is formed to a thickness of 1l10 by sputtering.
A conductive film having a two-layer structure of polysilicon film/aluminum film is formed. Thereafter, as shown in FIG. 1(d), a resist mask 13 for forming electrode wiring is patterned using photoresist.

After that, by dry etching method, CCe4-CF4
, BCJ? Maintain the pressure of the mixed gas in step 3 at 17 Pa,
At an etching power of 400 W, the aluminum film is dry-etched to a thickness of about 500 nm in the thickness direction.

Under these conditions, isotropic etching is difficult (first step).

Further, as shown in FIG. 1(e), the pressure of the above-mentioned mixed gas was maintained at about 7 Pa, and the etching power was increased to 100 OW to etch a conductive film consisting of an aluminum film and a polysilicon film in the thickness direction. Etching until the end. Under these conditions, anisotropic etching is performed (second
process).

Next, as shown in FIG. 1(f), the resist mask 13 is removed by low-temperature ashing, and after washing with water, a low concentration PSG film 9 is formed to a thickness of 11,000 nm by normal pressure CVD.
Then, a plasma nitride film 10 is deposited to a thickness of about 300 nm by plasma CVD to complete the semiconductor chip. FIG. 2 shows a partially enlarged sectional view.

In addition, in the case of the above-mentioned mixed gas, isotropic etching is performed at a pressure of 15 to 18 Pa and an etching power of 400 to 500 W, and the thickness of the conductive film removed in the first step is 3 times the initial film thickness.
A suitable range is 0 to 70%, and anisotropic etching is achieved at a pressure of 8 to 10 Pa and an etching power of 800 to iooow. It is convenient because it is possible to switch between isotropic and anisotropic etching simply by changing the pressure of the scrap and the etching power.

Compared to conventional etching of a conductive film using only isotropic etching, the cross-sectional shape of the electrode wiring becomes gentler, so that step coverage of the low concentration PSG film and plasma nitride film is improved, and moisture resistance is improved.

FIG. 3 is a sectional view of a semiconductor chip for explaining a second embodiment of the present invention.

This example is a method for manufacturing a semiconductor device using two layers of aluminum electrode films, and in the same manner as the first example,
After depositing an aluminum film 8 and forming a lower layer electrode wiring by two-step etching of isotropic etching and anisotropic etching, the photoresist mask was removed, and after washing with water, a plasma nitride film 11 was formed by plasma CVD. Deposit to a thickness of 11,000 nm.

Subsequently, through holes are selectively opened in the plasma nitride film 11 using photoresist, and then another aluminum film 12 is deposited, and this aluminum film 12 is selectively formed using photoresist in the same manner as described above. By means of isotropic etching and anisotropic etching, patterning is performed to form upper layer electrode wiring. Next, low concentration PSG13 was deposited to a thickness of 11,000 nm using the normal pressure CVD method.
After that, a plasma nitride film 14 is deposited.

In this embodiment, even when the lower aluminum film 8 is formed relatively thick, the upper aluminum film 12 does not break at the intersection with the lower aluminum film, resulting in a highly reliable semiconductor. A device is obtained.

In the above embodiments, when etching the conductive film, the first
Although the isotropic etching step is carried out by a dry etching method, it goes without saying that a similar effect can be obtained if a wet etching method is used.

〔Effect of the invention〕

As explained above, the present invention uses isotropic etching in the first step to etch the conductive film, and anisotropic etching in the second step, thereby etching the metal electrode continuously. As the shape of the etched surface of the film (electrode wiring) becomes more uniform, the step coverage of the passivation film formed on the metal electrode film is improved, and the passivation film is deposited uniformly, making it easier to mold package semiconductor devices. This has the effect of further improving moisture resistance and increasing the reliability of the product, since cracks in the passivation film do not occur due to temperature stress, etc. during the process.

In addition, in a semiconductor device with a structure using two layers of metal electrode films, the step coverage of the glabella insulating film is improved, so that the upper layer electrode wire is not disconnected in the area where the upper layer electrode wire and the lower layer electrode wire intersect. In addition, since the film thickness of the lower electrode wiring can be formed thicker, it is possible to correct disconnections at the contact portion between the lower electrode wiring and the silicon substrate therebelow, which is a great effect.

As explained above, by using the method of manufacturing a semiconductor device using the present invention, it is possible to improve the temperature stress and moisture resistance of the semiconductor device, and also to form a thick passivation film, so that the mold resin filler generated during mold packaging can be reduced. This also serves as a countermeasure against damage caused by damage, and highly reliable semiconductor devices can be provided at low cost.

[Brief explanation of the drawing]

1(a) to 1(f) are cross-sectional views of semiconductor chips arranged in the order of steps for explaining the first embodiment of the present invention;
The figure is a partially enlarged sectional view of FIG. 1(f), FIG. 3 is a sectional view of the semiconductor chip for explaining the second embodiment, and FIG. 4 is a sectional view of the semiconductor chip for explaining the conventional example. It is. 1... P-type silicon substrate, 2... silicon oxide film,
3... Polysilicon film, 4... Gate silicon oxide film, 5... N-type conductive layer, 6... BPSG film, 8...
Aluminum film, 9...Low concentration PSG film, 10.11
...Plasma nitride (arsenic film, 12...aluminum film,
13...Low concentration PSG film, 14...Plasma nitride film, 15...N type well, 16...P type conductive layer. Agent Patent Attorney Oto Uchihara Figure 1

Claims (1)

[Claims] In a method for manufacturing a semiconductor device, the method includes an etching step of selectively removing a conductive film deposited on a substrate to form an electrode wiring, wherein the etching step includes isotropically etching the conductive film to the middle of its initial film thickness. 1. A method for manufacturing a semiconductor device, comprising a first step of removing the semiconductor device by a method, and a second step of removing the device by an anisotropic etching method.