JPH11219949A - Formation of pattern of organic insulating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a thick organic insulating film in the form of a pattern without causing pattern collapse. SOLUTION: A non-photosensitive resin layer 11 is formed on a semiconductor substrate 1, a photosensitive resin layer 12 is formed on the resin layer 11 and pre-baked, subjected to a light exposure through a photomask 3 and to a continuous process of developing the resin layer 12 with use of an alkali developing solution and of etching the resin layer 11, and then the layers 12 and 11 are both subjected to a thermosetting process. As a result, even when the resin layer 11 has a small thickness, a pattern of good organic insulating film can be made thick.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for forming a pattern of a thick organic insulating film on a semiconductor substrate.

[0002]

2. Description of the Related Art In recent years, an organic insulating film having elasticity has been formed on the surface of a semiconductor chip in order to reduce the stress of a mold resin applied to the semiconductor chip.

Hereinafter, a conventional method for forming a pattern of an organic insulating film will be described. First, an organic resin containing a photosensitive group,
That is, a first method of a conventional pattern forming method for forming an organic insulating film using a photosensitive resin will be described with reference to FIG. 2A to 2C are cross-sectional views for explaining a conventional method for forming a pattern of an organic insulating film, wherein 1 is a semiconductor substrate made of silicon or the like, 2 is a photosensitive resin, 3 is a photomask, Denotes a light transmitting portion of the photomask 3, 5 denotes a photosensitive portion of a photosensitive resin, and 6 denotes an opening.

Hereinafter, the manufacturing process will be described in order. First, a photosensitive resin 2 is placed on a semiconductor substrate 1 made of silicon or the like.
Is applied. Thereafter, a predetermined area of the photosensitive resin 2 is exposed using the photomask 3 to form a photosensitive portion 5 (FIG. 2).
(A)). Next, the photosensitive portion 5 is etched with an alkali developer to perform a developing process for forming an opening 6 in the photosensitive resin 2. At this stage, the edge of the opening 6 is formed to be upright (see FIG. 2B). Thereafter, the photosensitive resin 2 is cured by performing a heat treatment. At this time, the solvent contained in the photosensitive resin 2 volatilizes, and the photosensitive resin 2 shrinks. And the cured photosensitive resin 2
Has a thickness of about 70 to 80% before curing. Photosensitive resin 2
Shrinkage occurs not only in the thickness direction but also in the lateral direction, and there occurs a phenomenon in which the shrinkage is small near the interface with the semiconductor substrate 1 but large in the upper layer portion. And the photosensitive resin 2
The opening 6 of the organic insulating film formed by thermally curing
It becomes tapered as shown in (c).

Next, a second conventional method for forming a pattern of an organic insulating film will be described with reference to FIG.
As a second conventional method, there is a method using a photoresist, and FIGS. 3A to 3E are cross-sectional views showing a conventional manufacturing process for forming an organic insulating film. In FIG. 3, 1 is a semiconductor substrate made of silicon or the like, 7 is a non-photosensitive resin (ordinary organic resin containing no photosensitive group), 3 is a photomask, 8 is a photoresist, 9 is a photosensitive portion of the photoresist 8, Reference numeral 10 denotes an opening.

Hereinafter, a specific example will be described in the order of the manufacturing process. For example, a non-photosensitive resin 7 of about 20 μm is applied on a semiconductor substrate 1 made of silicon or the like (see FIG. 3A). Next, after applying a photoresist 8 of about 2 μm on the non-photosensitive resin 7, the photoresist 8 is exposed using the photomask 3. Then, a photosensitive portion 9 is provided at a predetermined position of the photoresist 8 corresponding to the light transmitting portion 4 of the photomask 3.
Is formed, the photoresist 8 is developed with an alkali developing solution. At the same time, the non-photosensitive resin 7 is etched (see FIG. 3B). At this time, the photoresist 8
Although only the photosensitive portion 9 is removed, the non-photosensitive resin 7 is isotropically etched, and the opening 10 of the non-photosensitive resin 7 formed by etching has a tapered edge portion (FIG. 3C). See). Then, only the photoresist 8 is removed using n-butyl acetate to expose the surface of the non-photosensitive resin 7 (see FIG. 3D). Thereafter, when the non-photosensitive resin 7 is heated and cured, the non-photosensitive resin 7 shrinks in the same manner as in the first method, and the thickness of the thermosetting organic insulating film is reduced to 14 to 16 μm. Decrease (Fig. 3
(E). In the second method, when the non-photosensitive resin 7 is etched with an alkaline developer, the edge of the opening 10 becomes tapered. In addition, since the upper layer of the non-photosensitive resin 7 contracts when the non-photosensitive resin 7 is thermally cured, the edge portion of the opening 10 formed by the second method is smaller than that of the first method. The angle of the taper increases.

[0007]

As described above, when a pattern of a thick organic insulating film is formed, the conventional first forming method employs such a method that the organic insulating film after thermosetting has a desired thickness. The photosensitive resin 2 is thickly applied, and the photosensitive resin 2 is directly exposed without using a photoresist. Therefore, it takes 2 to 10 minutes to expose the thick photosensitive resin 2, and there is a problem that the processing time of the exposure process becomes longer. Therefore, the surface of the photosensitive resin 2 is heated by the long-time exposure, the solvent contained in the resin is volatilized, and bubbles are generated in the photosensitive portion 5 to cause a pattern collapse. Problems arise.

On the other hand, in the second conventional forming method, after applying the non-photosensitive resin 7 thickly, a photoresist 8 having a thickness of about 2 μm is applied, and after exposure, etching with an alkali developing solution is performed. In this method, when the photoresist 8 is developed with an alkali developing solution and the thick non-photosensitive resin 7 is etched with the same alkali developing solution, the side etching of the opening 10 becomes large. Hangs down, and in some cases, the photoresist 8 is released. As a result, there is a drawback that pattern collapse occurs.

The present invention solves such a conventional problem and provides a method for forming a pattern of a thick organic insulating film without causing pattern collapse.

[0010]

In order to achieve this object, a method for forming a pattern of an organic insulating film according to the present invention comprises applying a non-photosensitive resin onto a semiconductor substrate and pre-baking the non-photosensitive resin to obtain a first pattern. A first step of forming a second resin layer, a second step of applying a photosensitive resin on the first resin layer and pre-baking the photosensitive resin to form a second resin layer;
Thereafter, a third step of exposing the second resin layer through a photomask, and thereafter, the photosensitive portion of the second resin layer and the first resin layer are continuously performed using an alkali developing solution. The method includes a fourth step of performing etching, and a fifth step of performing heat treatment at a temperature higher than the pre-bake and then curing the first and second resin layers together.

According to this configuration, after a non-photosensitive resin and a photosensitive resin are sequentially applied to the semiconductor substrate and prebaked,
Expose the photosensitive resin and etch with an alkali developer,
Since the non-photosensitive resin and the photosensitive resin are thermally cured together to form a pattern of the organic insulating film, a thick organic insulating film can be formed even if the thickness of the non-photosensitive resin is reduced. Also, since the upper layer (photosensitive resin) pattern formed for etching is utilized without removing it, and the non-photosensitive resin and photosensitive resin are heat-cured together for final use, no photoresist is used. A pattern can be formed, and the manufacturing process can be simplified.

[0012] The second invention is a multilayer structure in which the photosensitive resin is a polyimide resin or a polybenzoxazole resin containing a photosensitive group, and the non-photosensitive resin is a polyimide resin or a polybenzoxazole resin containing no photosensitive group. Therefore, a good organic insulating film can be formed in which the non-photosensitive resin and the photosensitive resin are well compatible and the upper layer pattern for etching is not peeled off.

In a third aspect of the present invention, the non-photosensitive resin and the photosensitive resin are prebaked in a temperature range of 100 ° C. to 140 ° C.,
Since the pattern is formed by etching and then thermally cured together, the adhesion between the lower layer (non-photosensitive resin) and the upper layer (photosensitive resin) of the organic insulating film is good, and a good organic insulating film can be formed.

In the fourth invention, the thickness of the photosensitive resin is made substantially equal to the thickness of the non-photosensitive resin, so that the thickness of the non-photosensitive resin can be reduced to about half, and the edge portion of the opening has a tapered shape. And the pattern of the organic insulating film can be accurately formed.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for forming a pattern of an organic insulating film according to the present invention will be described with reference to the drawings.

FIG. 1 is a process sectional view for explaining a method for forming a pattern of an organic insulating film according to an embodiment of the present invention. In FIG. 1, components corresponding to those of the conventional example are denoted by the same reference numerals. 1 is a semiconductor substrate made of silicon or the like, 3 is a photomask, 4 is a light transmitting portion of the photomask 3,
11 is a non-photosensitive resin made of a polyimide or polybenzoxazole-based resin containing no photosensitive group, 12 is a photosensitive resin made of a polyimide or polybenzoxazole-based resin containing a photosensitive group, and 13 is a photosensitive resin 12 exposed to light. The portion 14 is an opening formed by etching.

Hereinafter, a method of forming an organic insulating film having a thickness of about 30 μm will be described as an example in the order of manufacturing steps. First, a non-photosensitive resin 11 is applied on the semiconductor substrate 1 to a thickness of about 20 μm, and prebaked in a temperature range of 100 to 140 ° C. to slightly cure the non-photosensitive resin 11 (FIG. 1A). reference). The photosensitive resin 12 is coated on the non-photosensitive resin 11 with a thickness substantially equal to the thickness of the non-photosensitive resin 11 (about 20 μm).
And prebaked in a temperature range of 100 to 140 ° C. to slightly cure the photosensitive resin 12. Considering that the thickness of the organic insulating film shrinks to 70 to 80% of the thickness of the applied resin when the resin is heat-cured to finish the organic insulating film, the non-photosensitive resin 11 and the photosensitive resin are considered. Twelve film thicknesses are formed to a total thickness of about 40 μm.

If the pre-bake temperature of the non-photosensitive resin 11 and the photosensitive resin 12 is increased, the non-photosensitive resin 11
The adhesion between the resin and the photosensitive resin 12 deteriorates, and the photosensitive resin 12 peels off during development in a later step. Conversely, when the pre-bake temperature is lowered, the photosensitive resin 1
2 is applied, the non-photosensitive resin 11 and the photosensitive resin 12
Layers were broken and mixed, and the problem that exposure and development in the subsequent steps were not performed well was found, and a pre-bake temperature capable of ensuring adhesion was experimentally determined. The result was obtained.

After the photosensitive resin 12 is formed on the non-photosensitive resin 11 on the semiconductor substrate 1, the photomask 3 is exposed by irradiating light from the direction of the arrow, and the light transmitting portion 4 of the photomask 3 is exposed.
The photosensitive portion 13 is formed at a predetermined position of the photosensitive resin 12 corresponding to the above (see FIG. 1B).

Next, the semiconductor substrate 1 on which the non-photosensitive resin 11 and the photosensitive resin 12 are formed is immersed in an alkali developing solution, and the photosensitive resin 12 is developed and the non-photosensitive resin 11 is etched. Initially, the photosensitive portion 13 of the photosensitive resin 12 is etched with an alkali developing solution, and the photosensitive portion 1 is etched.
3 is removed. Even if the development process of the photosensitive resin 12 is completed, the semiconductor substrate 1 is continuously immersed in the alkali developing solution,
The non-photosensitive resin 11 is etched using the photosensitive resin 12 as a mask. Thus, the openings 14 are formed in the photosensitive resin 12 and the non-photosensitive resin 11 (see FIG. 1C). At this time, the photosensitive portion 13 of the photosensitive resin 12 is sharply etched, but the etching of the non-photosensitive resin 11 by the alkali developing solution is performed by isotropic etching, and the opening of the non-photosensitive resin 11 is It is over-etched further outward and is opened in a tapered shape. However, the film thickness of the non-photosensitive resin 11 in the present embodiment is
Since the width of the opening is reduced to に as compared with the method described above, the degree of opening in the tapered shape can be reduced to １ ／.

Next, a heat treatment at 300 to 400 ° C. is performed to thermally cure the non-photosensitive resin 11 and the photosensitive resin 12 together, thereby forming the non-photosensitive resin 11 and the photosensitive resin 12 as an integral organic insulating film. Last use (see FIG. 1 (d)).
During the heat treatment, the solvent in the resin volatilizes, and both the non-photosensitive resin 11 and the photosensitive resin 12 shrink, so that the organic insulating film after thermosetting becomes 70 to 80% of the thickness before hardening, The resin layer having a thickness of 40 μm including the non-photosensitive resin 11 and the photosensitive resin 12 becomes an organic insulating film having a thickness of about 30 μm. In addition, the portion of the upper photosensitive resin 12 that protrudes inside the opening 14 is also reduced, and the opening 14 is formed in a shape as shown in FIG.

As described above, in the embodiment of the present invention, a non-photosensitive resin and a photosensitive resin are sequentially applied to a semiconductor substrate and prebaked, and then the photosensitive resin is exposed to light and exposed to an alkaline developer. Etching and heat curing of the non-photosensitive resin and photosensitive resin together to form a pattern of the organic insulating film.Thus, even if the non-photosensitive resin is formed thinner than before, a thick organic insulating film is formed. can do. Also, since the upper layer (photosensitive resin) pattern formed for etching is utilized without removing it, and the non-photosensitive resin and photosensitive resin are heat-cured together for final use, no photoresist is used. A pattern can be formed, and the manufacturing process can be simplified.

The photosensitive resin may be a polyimide resin or a polybenzoxazole resin containing a photosensitive group, and the non-photosensitive resin may be a polyimide resin or a polybenzoxazole resin containing no photosensitive group. Because of the structure, the non-photosensitive resin and the photosensitive resin are well compatible with each other, and a good organic insulating film that does not peel off the upper layer pattern for etching can be formed.

Further, since the thickness of the photosensitive resin is made substantially equal to the thickness of the non-photosensitive resin and the thickness of the non-photosensitive resin is reduced to about half, the tapered edge portion of the opening can be reduced. In addition, the pattern of the organic insulating film can be accurately formed.

In this embodiment, the upper limit for forming the organic insulating film thick is about 50 μm, but the lower limit is not limited. It is possible to form an organic insulating film having a thickness of 10 μm or less by a conventional method. However, by employing this embodiment, a pattern with higher accuracy can be formed as compared with a pattern of the conventional method having the same film thickness.

[0026]

As described above, according to the present invention, the non-photosensitive resin and the photosensitive resin are pre-baked and slightly cured, and after the pattern is formed by etching, the non-photosensitive resin and the photosensitive resin are heated together. Since the pattern is formed by curing, a thick organic insulating film can be formed even when the thickness of the non-photosensitive resin is reduced. Also, since the upper layer (photosensitive resin) pattern to be formed for etching is not removed and heat cured together with the non-photosensitive resin for final use, the pattern can be formed without using a photoresist, simplifying the manufacturing process. It has a special effect that it can be converted.

[Brief description of the drawings]

FIG. 1 is a process sectional view of a method for forming a pattern of an organic insulating film according to an embodiment of the present invention.

FIG. 2 is a process sectional view of a conventional organic insulating film pattern forming method.

FIG. 3 is a process cross-sectional view of another conventional method for forming a pattern of an organic insulating film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 3 Photomask 4 Transparent part of photomask 3 11 Non-photosensitive resin 12 Photosensitive resin 13 Photosensitive part of photosensitive resin 12 14 Opening

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/30 573

Claims (4)

[Claims] A first step of applying a non-photosensitive resin on a semiconductor substrate and pre-baking the non-photosensitive resin to form a first resin layer; and a photo-sensitive layer on the first resin layer. A second step of applying a resin and pre-baking the photosensitive resin to form a second resin layer; a third step of exposing the second resin layer through a photomask; and A fourth step of continuously etching the photosensitive portion of the second resin layer and the first resin layer using an alkali developing solution; and thereafter, performing a heat treatment at a temperature higher than the pre-bake. And a fifth step of curing the second resin layer together. 2. The photosensitive resin according to claim 1, wherein the photosensitive resin is a polyimide resin containing a photosensitive group or a polybenzoxazole resin containing a photosensitive group, and the non-photosensitive resin is a polyimide resin containing no photosensitive group or polybenzoxazole. A method for forming a pattern of an organic insulating film, which is an oxazole-based resin. 3. The method according to claim 1, wherein the pre-baking of the non-photosensitive resin and the photosensitive resin is performed in a temperature range of 100 ° C. to 140 ° C. 4. The method according to claim 1, wherein the thickness of the photosensitive resin is made substantially equal to the thickness of the non-photosensitive resin.