JPH04282831A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a fine contact hole having an excellent dimensional accuracy at a resin film covering a semiconductor substrate. CONSTITUTION:A step of forming a resin film 2 on a semiconductor substrate 1 and an insulating film, a step of forming an inorganic film 3 in close contact with the film 2, a step of processing the film 3 with a mask 4a patterned on the film 3 by anisotropic dry etching to form a hole 3 for exposing the film 2, and a step of processing the film 2 from the hole 3a by anisotropic dry etching to form a contact hole 2a for exposing the substrate 1 are provided. The film 2 is a polyimide film, and the film 3 is an SOG film.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of microfabrication of a resin film. Organic resins such as polyimide are used as interlayer insulating films and cover protective films of semiconductor devices. In recent years, as semiconductor devices have become more highly integrated and packages have become thinner, there has been a demand for increasingly finer processes.

0002

2. Description of the Related Art FIGS. 2(a) to 2(d) are cross-sectional views showing the process of a conventional example, and the conventional example will be explained below with reference to these figures.

Reference 1 in FIG. 2A is, for example, a Si substrate on which elements are formed, and a polyimide film 2 is formed by coating polyimide thereon. A resist film 4 is formed by applying a resist onto the polyimide film 2, and heating is performed to scatter the solvent. However, annealing to polymerize and solidify the polyimide is not performed.

Referring to FIG. 2(b), the resist film 4 is developed with an organic alkali or hydrazine using a normal lithography technique to form a resist mask 4a having openings 4b.

FIG. 2(c) The polyimide film 2 is removed by wet etching from the reference hole 4b.
is etched to form a contact hole 2b that exposes the surface of the Si substrate 1. At this time, the organic alkali or hydrazine used for developing the resist film 4 can be used as is as the etching solution.

FIG. 2(d) shows a state in which the resist mask 4a has been peeled off and removed using a reference organic solvent or the like. Thereafter, the polyimide is polymerized and solidified by final annealing at approximately 300 to 400°C, and processing is completed.

Thereafter, a bonding pad is formed in the contact hole 2b by, for example, gold plating. However, this conventional method has the following drawbacks.

(2) Since the molecular structures and components of the resist and polyimide are similar, it is difficult to obtain a high selectivity for etching with organic alkali or hydrazine. ■Side etching occurs and dimensional accuracy decreases.

For bonding pads with dimensions of several tens of micrometers or more, the drawbacks of the conventional method do not pose much of a problem in practice, but as the degree of integration of semiconductor devices increases, the required contact hole dimensions become smaller than 10 micrometers. When this happens, it becomes difficult to control the dimensions using conventional methods. In other words, it is difficult to achieve dimensional accuracy no matter how severely the polyimide etching conditions are controlled.

Although there have been attempts to improve dimensional accuracy by using photosensitive polyimide, this has not yet been put to practical use.

[0011]

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a method for finely processing a resin film such as a polyimide film with high dimensional accuracy.

0012

[Means for solving the problem] Figures 1(a) to (e)
FIG. 2 is a cross-sectional view showing the process of the example. The above issues are
a step of forming a resin film 2 on the semiconductor substrate 1 or an insulating film; a step of forming an inorganic film 3 in close contact with the resin film 2;
processing the inorganic film 3 by anisotropic dry etching using a mask 4a patterned on the surface of the inorganic film 3 to form an opening 3a exposing the resin film 2;
The problem is solved by a method of manufacturing a semiconductor device which includes the steps of processing the resin film 2 through the opening 3a by anisotropic dry etching to form a contact hole 2a exposing the semiconductor substrate 1.

The present invention is also solved by a method of manufacturing a semiconductor device in which the resin film 2 is a polyimide film and the inorganic film 3 is an SOG film.

[0014]

[Operation] If the inorganic film 3 is formed in close contact with the resin film 2,
The selectivity to the inorganic film 3 when etching the resin film 2 can be increased. Therefore, if the resin film 2 is processed by anisotropic dry etching using the inorganic film 3 as a mask, the dimensional accuracy can be increased, and the contact hole 2a can be formed with high dimensional accuracy without side etching. Can be done.

Adopting a polyimide film as the resin film 2 and an SOG film as the inorganic film 3 has a great practical effect.

[0016]

Embodiment FIGS. 1(a) to 1(e) are diagrams showing the process of the embodiment. Examples will be described below with reference to these figures.

FIG. 1(a) After polyimide is coated to a thickness of several μm on the Si substrate 1 on which the reference element has been formed, the polyimide is polymerized and solidified by annealing at about 300 to 400° C., and the polyimide film 2 is formed. Form.

An SOG film 3 is formed by coating SOG on the polyimide film 2 to a thickness of several thousand Å. Furthermore, the SOG film 3
A resist film 4 having a thickness of several μm is formed thereon. Figure 1(b)
The reference resist film 4 is patterned to form a resist mask 4a having an opening 4b of, for example, 3 μm square.

FIG. 1(c) The SOG film 3 is etched anisotropically through the reference hole 4b by reactive ion etching (RIE) to form the polyimide film 2.
An opening 3a is formed to expose the. As the etching gas, for example, a compound gas containing C and F, such as CF4, to which a small amount of O2 is added is used.

FIG. 1(d) The polyimide film 2 is etched anisotropically through the reference opening 3a by RIE to form a contact hole 2a exposing the Si substrate 1. As shown in FIG. As an etching gas, for example, O2
A small amount of compound gas containing C and F, such as CF4, is added to the mixture. At this time, the resist mask 4a is also etched to some extent, but it is completely removed by ashing after etching. The resist mask 4a may be removed by ashing before etching.

FIG. 1(e) The reference SOG film 3 is removed by etching using an etching gas prepared by adding a small amount of O2 to a compound gas containing C and F, such as CF4. By selecting the type of etching gas, mixing ratio, pressure and flow rate, polyimide film 2
The selectivity ratio of the SOG film 3 to the SOG film 3 can be made sufficiently large.

In this way, a contact hole 2a of 3 μm square is formed in the polyimide film 2 formed on the semiconductor substrate 1.
was formed. After this, the Si in the contact hole 2a
Gold plating was performed on the substrate 1 to form bonding pads.

According to the method of the present invention, it is also possible to form contact holes with dimensions of 1 μm or less. In the embodiments of the present invention described above, the steps in which the polyimide film is deposited directly on the surface of the semiconductor substrate have been described with reference to FIG. 1, assuming that the polyimide film functions as an interlayer insulating film. However, the field of application of the present invention is not limited to the case where a polyimide film is directly formed on the surface of a semiconductor substrate, and many modifications are possible. For example, a polyimide film may be further formed on a passivation film such as a PSG (phosphorus glass) film. Normally, it has been pointed out that when a relatively brittle material such as a PSG film is formed uniformly over a pick-up area like a passivation film, chips and cracks may occur due to subsequent thermal expansion and contraction history. In order to solve this problem, it may be possible to form a polyimide film overlying the passivation film to reinforce the passivation film. The present invention is also applicable to the case where a polyimide film is layered on the surface of such a passivation film.

Furthermore, in the embodiment, an SOG film was used as the inorganic film 2 that served as a mask when etching the polyimide film 2, but other methods such as Si using the CVD method were also used.
It is also possible to use an O2 film, a PSG film, etc.

[0025]

[Effect of the invention] As explained above, according to the present invention,
Fine pores on the order of μm can be stably formed with high dimensional accuracy in a resin film such as a polyimide film.

The present invention contributes to miniaturization of semiconductor devices.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(e) are diagrams showing the process of an example.

FIGS. 2(a) to 2(d) are diagrams showing a conventional process.

[Explanation of symbols]

1 is a semiconductor substrate, which is a Si substrate 2 is a resin film and is a polyimide film. 2a and 2b are contact holes 3 is an inorganic film, which is an SOG film. 3a is open hole 4 is resist film 4a is a mask and is a resist mask

Claims (2)

[Claims] 1. A step of forming a resin film (2) on a semiconductor substrate (1) or an insulating film, a step of forming an inorganic film (3) in close contact with the resin film (2), and a step of forming an inorganic film (3) on the semiconductor substrate (1) or an insulating film. 3) Processing the inorganic film (3) by anisotropic dry etching using a mask (4a) patterned on the surface to form openings (3a) exposing the resin film (2); The resin film (2) is processed through the opening (3a) by anisotropic dry etching, and the semiconductor substrate (
1) forming a contact hole (2a) exposing the contact hole (2a); 2. The method of manufacturing a semiconductor device according to claim 1, wherein the resin film (2) is a polyimide film, and the inorganic film (3) is an SOG film.