JPS61245534A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain through holes with the same diameters when a resin is applied to a substrate having a difference in level on the surface of the substrate while the surface of the resin being flattened and the through holes are formed in the projected and recessed portions of the substrate by rotating a mask with opaque and transparent portions on the surface of the resin, exposing the resin to light in opposition to the through holes, and, after the resin exposed to light is removed by development, perform etching the substrate anew. CONSTITUTION:A negative type photoresist mask 12 with a prescribed configuration is provided on and Si substrate 11 and etched to form a recessed portion 17 having a level difference 16 on the exposed portion. Then, through holes are desired to be formed in a projected portion and the recessed portion 17, and therefore fist a resin 18, such as polyimide or the like, is applied to the whole surface while the surface of the resin is being flatted. Thereafter, another mask 19 for covering the holes is provided on the resin 18 and the resin exposed in windows is removed by exposure to light followed by development. A photoresist 22 is applied to the whole surface as the windows are filled with the photoresist 22 and the surface thereof is covered by still another mask with opaque and transparent portions 13 and 15, respectively. The lastsaid mask is rotated and the through holes 20 and 21 positioned in the projected portion and recessed portion 17, respectively, are formed in the resin 18. A smaller diameter portion is equalized to a larger diameter portion in diameter by etching.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a technique for microfabrication of polyimide resin films.

[Background technology]

In semiconductor devices such as ICJP LSI, as the number of elements per chip increases by the order of ten thousand, wiring made of aluminum or the like that connects electrodes of elements tends to have a multilayer structure of two or three layers.

In this multilayer wiring structure, a silicon oxide-based inorganic insulating film has traditionally been used as an interlayer insulating film between upper and lower wirings, but when a film with a thickness of 1 μm or more is formed with this film, it can be strained during heat treatment. In addition, if there is a step on the underlying substrate, the step becomes even more severe on the surface of the multi-layered insulating film, causing problems such as disconnection in the wiring provided above. there were.

Instead of such inorganic insulating films, organic insulating films that can be processed at relatively low temperatures and can ensure surface flatness have come to be used. In particular, a wiring structure using a highly heat-resistant polyimide polymer resin developed by the present inventor as a glabellar insulating film is employed. (Industrial Research Council Electronic Materials 198
(See page 30, July 2007) This polyamide resin is produced by applying a prepolymer solution of a polyimide resin, which is a polymer obtained by reacting an aromatic diamine and an aromatic tetracarboxylic dianhydride, to the surface of a substrate. After coating with a spinner, the solvent component is evaporated,
It is polymerized and hardened by heat treatment at 200 to 300°C.

When making a through hole to connect the upper and lower 8β (aluminum) wiring in an interlayer insulating film using polyimide resin, if there is a step in the underlying substrate, the following will occur. There's a problem.

In FIG. 7, reference numeral 1 indicates a base substrate, and reference numeral 2 indicates a stepped portion, which is formed by, for example, an oxide film (Sins) used as a diffusion mask, or β wiring in the lower layer.

Reference numeral 3 denotes a coating made of polyimide resin or the like, which is formed sufficiently thick so that the surface becomes the same flat surface regardless of the level difference in the base.

4 and 5 are through holes, and 6 is a resist mask used to open the through holes.

Even if the window holes corresponding to the through holes in the resist mask 6 have the same diameter at"at, if the polyimide is isotropically etched through them, the thickness of the polyimide film will be different in the areas where the underlying depth is different. In addition, the thickness of the hole differs at the bottom, >b.For this reason, the resistance of the wiring in the through-hole section changes, and the resistance value varies widely in the thick part of the polyimide film. This is not preferable, especially as the through-hole size becomes finer.

[Purpose of the invention]

The present invention has been made to overcome the above-mentioned problems, and its purpose is to provide a through-hole etching technique that eliminates the variation in the dimensions of through-holes in interlayer films using polyimide resin and enables microfabrication. It is in.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, when making a through hole in a polyimide resin film on a substrate base having a step, after the first etching for the through hole, the mask used to form the step by etching is used. By blocking the through holes in the high part of the base due to the step with resist, and additionally etching the through holes in the low part of the base in this state, through holes with the same diameter are obtained without involving the step in the base, and the fineness of the through hole is This enables processing and eliminates variations in through-hole resistance.

〔Example〕

FIGS. 1 to 5 show an embodiment of the present invention, and are cross-sectional views of a process for forming through holes in a resin film on a substrate having steps.

Each step will be explained below.

(1) For example, a base substrate 11 having an oxide film (Sift) formed on the surface of a Si (silicon) substrate is prepared. A photoresist process is performed to form the surface portion of this base substrate, for example, as a mask for diffusion. That is, a photoresist material (negative type) 12 is applied to the entire surface,
A photomask 14 having a partially opaque portion 13 thereon
are overlapped and exposed through the °C transparent portion 15. (FIG. 1) (2) The exposed portions are polymerized and hardened by developing the resist material, and the uncut portions are selectively dissolved and removed to obtain a photoresist mask. By etching the C substrate using this photoresist mask, a recess 17 having a step 16 is bored out. (Figure 2) (31) Apply polyimide resin to the entire surface to form an insulating film with a thickness of about 1.5 to 2.0 μm. This film is made by applying a prepolymer solution of polyimide resin or a medium-sized compound solution. After coating the substrate surface with a spinner, the solvent component is vapor-deposited and further heated at 200 to 300°C.
A polyimide resin film 18 with a flat surface is formed by heat treatment and curing.

(Figure 3) (4) After this, photoresist is formed on the entire surface, exposed and developed using a photomask with a specific through-hole pattern, and using the completed mask 19, polyimide resin is coated with hydrazine solution. By etching, as shown in FIG. 1, through holes 20 and 21 are made. This through hole has a bottom diameter of a on the high side of the base surface.
is large, and the bottom diameter is small on the lower side of the base surface.

After opening such through holes, photoresist 22 is applied to fill these through holes. On this photoresist, the photomask 1 used in the step (1) is
Repeat step 4 and expose at ℃. (Fig. 4) (5) After this, if development is carried out, the photoresist 22 in the part exposed to °C through the transparent part 15 of the photomask 14 will remain, the other part will be removed, and the through hole on the lower side of the underlying surface will remain. 21 is exposed.

Here, the polyimide resin is etched again using a hydrazine solution, etc., and by controlling the amount of etching, the through holes 20 on the side of the base covered with the resist are etched.
A through-hole 21 on the lower underground side is machined having the same bottom diameter b' as the bottom diameter a. (Fig. 5) (61 Finally, by removing the photoresist 22. mask 19, a through hole 20.21 with the same bottom diameter (a = b') is created despite the difference in height of the underlying surface due to the step. You can get it.

FIG. 8 is a sectional view showing an embodiment of the present invention in a semiconductor device.

23 is a semiconductor (silicon) substrate on which semiconductor elements such as transistors are formed, and 24 is a surface oxide film having steps. 25 and 26 are Aμ wiring (electrodes) of the first layer. 27
is an interlayer film made of polyimide resin. 28.29
30.31 is a through hole, and 30.31 is an AJ wiring in the second layer. In this case, the depths of the -p''C through holes 28 and 29 differ due to the step difference in the surface oxide film 240, but the diameters of the bottoms of the holes are made equal by additional etching of the deeper through holes 29.

〔Effect of the invention〕

According to the present invention described above in the examples, the following effects can be obtained.

+11 When a through hole is made using an insulating film made of polyimide resin or the like formed on a substrate with a step difference, the flattening of the surface of the polyimide film creates a difference in the thickness of the polyimide film between the top and bottom of the step difference, which results in isotropy. When a through hole is formed by etching, the dimensions of the through hole will be different, but by additionally etching the through hole below the step, it can be made to match the diameter of the through hole above.

(When performing additional etching for the 21 through-holes, using the same mask used for the initial step processing to close the through-holes that are not additionally etched is a convenient and accurate way to create a resist pattern without creating a new mask.) Mask format is available.

(3) With the above 111 and 121, it is possible to miniaturize the through hole dimensions and reduce the through hole resistance,
As a result, the size of the IC chip can be reduced.

Although the invention made by the present inventor has been specifically explained above based on examples, the present invention is not limited to the above-mentioned examples (although it is possible to make various changes without departing from the gist of the invention). Not even.

For example, in place of wet etching using hydrazine or the like for through-hole etching of polyimide resin and additional etching, similar effects can be expected to be produced when dry etching is used in combination.

[Application field]

The present invention can be applied to all multilayer wiring structures of linear ICs that use organic resin as an interlayer insulating film.

[Brief explanation of drawings]

1 to 6 are cross-sectional views of a semiconductor device process showing an embodiment of the present invention. FIG. 7 is a cross-sectional view showing the form of through holes in the polyimide layer on the base step. FIG. 8 is a sectional view of a semiconductor device showing a specific example of the present invention. 11... Substrate, 12... Photoresist material, 13...
- Opaque part, 14... Photomask, 15... Transparent part, 16... Step part, 17... Concave part, 18... Polyimide resin, 19... Mask, 20, 21...・
Through hole, 22...photoresist. fart \

Claims (1)

[Claims] 1. A part of the surface of the substrate is etched to form a height difference, a film with a flat surface is formed by applying an organic resin thereon, and a part of this film is etched to form a through hole. After opening, the mask used for the step etching is used to cover the through holes in the film in the high part of the base due to the step with a resist film, and in this state, the through holes in the low part of the base are etched. A method for manufacturing semiconductor devices. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the organic resin is a polyimide resin.