JP2000155413A - Formation of organic insulating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a thick organic insulating film on a semiconductor substrate without causing pattern collapse. SOLUTION: A negative type photosensitive resin applied on a semiconductor substrate 1 is prebaked to form a 1st photosensitive resin layer 10. A 2nd photosensitive resin layer 11 is formed on the 1st photosensitive resin layer 10 and only the 2nd photosensitive resin layer 11 is exposed through a photomask 3. After this exposure for a short exposure time, the 1st and 2nd photosensitive resin layers 10, 11 are simultaneously etched and then heat-cured. The objective thick organic insulating film is formed without causing pattern collapse.

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, a resilient organic insulating film 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 an organic insulating film will be described. First, a conventional method of forming an organic insulating film using an organic resin containing a photosensitive group, that is, a photosensitive resin will be described with reference to FIG. 2A to 2D are process cross-sectional views for explaining a conventional method of forming an organic insulating film, wherein 1 is a semiconductor substrate made of silicon or the like, and 2 is a photosensitive resin layer (an organic insulating film described later). 8, a photomask, 4 a light-transmitting portion of the photomask 3, 5 a photosensitive portion of the photosensitive resin 2, 6 a non-photosensitive portion of the photosensitive resin 2, 7 an opening, and 8 an organic portion. The insulating film 9 is an opening of the organic insulating film 8.

Hereinafter, the manufacturing process will be described in order. First, a photosensitive resin layer 2 is applied on a semiconductor substrate 1 made of silicon or the like (see FIG. 2A).

Thereafter, light is applied to the photosensitive resin layer 2 through the light transmitting portion 4 of the photomask 3, and a predetermined region corresponding to the light transmitting portion 4 is exposed to become a photosensitive portion 5. In addition, since light is shielded below the image portion of the photomask 3, the unexposed portion 6 is formed (see FIG. 2B).

Next, a developing process is performed in which the unexposed portion 6 of the photosensitive resin layer 2 is etched with a developing solution to leave the photosensitive portion 5 and form the opening 7. At this stage, the edge portion of the opening 7 is formed to be upright (see FIG. 2C).

After that, a heat treatment is performed to form the photosensitive resin layer 2.
The solvent contained therein is volatilized, and the photosensitive portion 5 of the photosensitive resin layer 2 is cured to form an organic insulating film 8. In the process of volatilizing and thermally curing the solvent, the photosensitive resin layer 2 contracts. When a polyimide precursor is used as the photosensitive resin, the thickness of the organic insulating film 8 after curing becomes about 50 to 60% of the thickness before curing. Shrinkage of the photosensitive resin also occurs in the lateral direction, and although the shrinkage is small near the interface with the semiconductor substrate 1, the shrinkage is large in the upper layer, and the opening 9 of the cured organic insulating film 8 is formed as shown in FIG. It becomes somewhat tapered as shown in d).

[0008]

As described above, when a pattern of a thick organic insulating film is formed, the photosensitive layer is formed by a conventional forming method so that the organic insulating film 8 after heat curing has a desired thickness. Since the resin layer 2 is thickly applied, it takes more than two minutes to expose the thick photosensitive resin layer 2, and there is a problem that the exposure time becomes longer. From this, the surface temperature of the photosensitive resin layer 2 is increased by the long-time exposure, nitrogen is desorbed from the photosensitive resin layer 2, bubbles are generated at the photosensitive portion 5, and the pattern of the organic insulating film 8 is formed. Cause collapse.

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 the steps of: first prebaking a negative photosensitive resin applied on a semiconductor substrate;
A first step of forming a second photosensitive resin layer, and a second step of prebaking a negative photosensitive resin applied on the first photosensitive resin layer to form a second photosensitive resin layer And thereafter, a third step of exposing only the second photosensitive resin layer via a photomask, and thereafter, the unexposed portion of the second photosensitive resin layer and the first exposed portion immediately below the unexposed portion. A fourth step of etching the photosensitive resin layers together, and a fifth step of performing a heat treatment at a temperature higher than the pre-bake temperature to simultaneously cure the first and second photosensitive resin layers.
And the step of

[0011] With this configuration, the first and the first are placed on the semiconductor substrate.
After the formation of the second photosensitive resin layer, only the second photosensitive resin layer is exposed, and then the two layers are etched together. Therefore, the exposure state of the first photosensitive resin layer is incomplete. However, the first photosensitive resin can be etched using the exposed portion of the second photosensitive resin layer as a mask. Further, the first photosensitive resin layer does not need to perform mask alignment,
It is only necessary to align the mask by exposing the photosensitive resin layer, and the mask alignment process can be simplified. Furthermore, there is no need to match the patterns of the first photosensitive resin layer and the second photosensitive resin layer, and a thick organic insulating film can be formed in a pattern by a simple number of steps.

[0012]

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. Here, a description will be given by taking, as an example, a photosensitive resin in which a precursor (polyamide) that becomes a polyimide after heat curing contains a negative photosensitive group. However, a negative photosensitive group is used as a precursor of a polybenzoxazole-based resin. It may be contained.

In FIG. 1, components corresponding to those of the conventional example are denoted by the same reference numerals. Reference numeral 1 denotes a semiconductor substrate made of silicon or the like, 3 denotes a photomask, 4 denotes a light-transmitting portion of the photomask 3, 10 and 11 denote a photosensitive resin layer containing a negative photosensitive group in polyamide, and 12 denotes a photosensitive resin layer 11 Photosensitive section,
Reference numeral 13 denotes an unexposed portion of the photosensitive resin layer 11, reference numeral 16 denotes an opening formed by development, reference numeral 17 denotes a final organic insulating film subjected to heat treatment, and reference numeral 18 denotes an opening formed in the organic insulating film 17.

The method of forming an organic insulating film having a thickness of about 30 μm will be described below in the order of the manufacturing steps. First, a negative photosensitive resin is applied on the semiconductor substrate 1 for about 30 minutes.
After coating with a film thickness of μm, it is prebaked in a temperature range of 80 to 120 ° C. and dried to form a photosensitive resin layer 10 (see FIG. 1A).

Next, a negative photosensitive resin whose heat curing temperature is lower than that of the negative photosensitive resin used in the previous step by using a different amount of solvent is used. Is applied on the photosensitive resin layer 10 at 70 to 110 ° C.
Prebaked and dried in the temperature range of
The photosensitive resin layer 11 is formed on the substrate. Photosensitive resin layer 10
And 11 have substantially the same thickness (thickness of about 30 μm) (see FIG. 1B).

Next, the photomask 3 is exposed to light in the direction of the arrow. Then, the light transmitting portion 4 of the photomask 3
A predetermined portion of the photosensitive resin layer 11 corresponding to the portion becomes the photosensitive portion 12, and a portion corresponding to the image portion of the photomask 3 is blocked from light and becomes the non-photosensitive portion 13 (see FIG. 1C).

When the resin is thermally cured to form an organic insulating film, the thickness of the organic insulating film is 5 times the thickness of the applied organic resin.
In consideration of shrinkage to about 60%, the film is formed thick so that the total film thickness of the photosensitive resin layer 10 and the photosensitive resin layer 11 becomes about 60 μm.

When the pre-bake temperature of the photosensitive resin layer 10 and the photosensitive resin layer 11 is increased, the photosensitive resin layer 1
0, the adhesiveness between the photosensitive resin layer 11 is deteriorated, and the photosensitive resin layer 11 peels off during development in a later step, and the sensitivity of the photosensitive resin is lowered, so that a problem arises in that opening is not possible. Conversely, the photosensitive resin layer 10 and the photosensitive resin layer 1
When the pre-bake temperature of both is lowered, the layers of the photosensitive resin layer 10 and the photosensitive resin layer 11 are broken and mixed when the photosensitive resin layer 11 is applied, so that exposure and development in the subsequent steps can be performed well. There is a problem that is not. Therefore, a pre-bake temperature at which the adhesion can be ensured is experimentally determined, the pre-bake temperature of the photosensitive resin layer 10 is set to a temperature range of 80 to 120 ° C., and the pre-bake temperature of the photosensitive resin layer 11 formed on 5 to 5 from the pre-bake temperature of the conductive resin layer 10
It has been found that when the temperature is set to be as low as about 30 ° C., the progress of curing of the photosensitive resin layer 10 can be suppressed, and the adhesion between the lower layer and the upper layer can be secured.

Thereafter, the semiconductor substrate 1 is immersed in a developing solution so that the unexposed portion 13 of the photosensitive resin layer 11 and the photosensitive resin layer 1
An etching process with 0 is performed. At this time, first, the unexposed portion 1
3 is etched and the photosensitive resin layer 10 is exposed,
The photosensitive section 12 functions as an etching mask. Therefore, the photosensitive resin layer 10 located immediately below the unexposed portion 13 is etched, and the photosensitive resin layer 10 immediately below the exposed portion 12 remains. Then, since the etching with the developing solution is isotropic etching, the opening 16 becomes overhanging (see FIG. 1D).

Next, a heat treatment at 300 to 400 ° C. is performed to thermally cure the photosensitive resin layer 10 and the photosensitive portion 12 which have been partially left together, to obtain a polyimide precursor used as the photosensitive resin ( (Polyamide) is changed to a polyimide integrated by polycondensation. This polyimide film is finally used as the organic insulating film 17 (see FIG. 1E). Since the resin shrinks during the heat treatment, the resin layer having a thickness of 60 μm before the thermosetting becomes an organic insulating film 17 having a thickness of about 30 μm.

In this embodiment, after laminating the photosensitive resin layer 10 and the photosensitive resin layer 11 on the semiconductor substrate, only the photosensitive resin layer 11 is exposed to form a pattern, so that the exposure time per layer is short. Thus, bubbles which are easily generated at the time of exposure can be prevented, and the thickness of the organic insulating film can be increased without causing pattern collapse. In addition, since a resin of the same quality has a multi-layer structure, the upper layer and the lower layer are well compatible with each other, and a good organic insulating film from which the photosensitive resin in the upper layer does not peel can be formed in a pattern.

Although it has been described that only the photosensitive resin layer 11 is exposed, the lower photosensitive resin layer 10 does not have to be exposed to the lower level, and the photosensitive resin layer 10 is not exposed. The vicinity of the interface with the layer 11 may be exposed, or even the vicinity of the interface with the photosensitive resin layer 10 in the upper photosensitive resin layer 11 may be exposed. If the surface layer is exposed, there is no hindrance to development.

In the above embodiment, the precursor of the polyimide resin is used as the organic resin. However, the same effect can be obtained by using the precursor of the polybenzoxazole resin. However, in the case of a polybenzoxazole-based resin, shrinkage during thermosetting is smaller than that of polyimide, and the film is finished to a thickness of about 70%. (Resin) may be applied by about 20 μm.

[0025]

As described above, according to the present invention, after the first and second photosensitive resin layers are formed on a semiconductor substrate in an overlapping manner, only the second photosensitive resin layer is exposed, Are etched together, even if the exposure state of the first photosensitive resin layer is incomplete, the first photosensitive resin can be etched using the exposed portion of the second photosensitive resin layer as a mask. Also,
It is not necessary to perform mask alignment in the first photosensitive resin layer, and it is sufficient to perform mask alignment by exposing the second photosensitive resin layer, and the mask alignment process can be simplified. Furthermore, there is no need to match the patterns of the first photosensitive resin layer and the second photosensitive resin layer, and a thick organic insulating film can be formed by a simple number of steps.

[Brief description of the drawings]

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

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

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 3 photomask 4 light-transmitting portion of photomask 3 10, 11 photosensitive resin layer 12 photosensitive portion of photosensitive resin layer 11 13 unexposed portion of photosensitive resin layer 11 16 opening of photosensitive resin layer 17 organic Insulating film 18 Opening of organic insulating film 17

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H01L 21/312 H01L 21/30 573 // C08L 79:04 79:08 F term (reference) 2H025 AA00 AA13 AA20 AB16 AB20 AC01 AD01 BC13 BC69 DA12 FA12 FA29 FA39 4F073 AA06 BA31 BB08 BB11 CA41 CA45 EA71 GA01 HA07 HA10 5F046 NA03 NA09 NA14 NA18 5F058 AA10 AB10 AD01 AD04 AD08 AD09 AF04 AG01 AG02 AG03 AG09 AH01

Claims (4)

[Claims] A first photosensitive resin layer formed by pre-baking a negative photosensitive resin applied on a semiconductor substrate;
And b) prebaking the negative photosensitive resin applied on the first photosensitive resin layer to form a second photosensitive resin layer.
And thereafter, a third step of exposing only the second photosensitive resin layer via a photomask, and thereafter, the unexposed portion of the second photosensitive resin layer and the portion immediately below the unexposed portion A fourth step of etching the first photosensitive resin layer together; and a fifth step of heating at a temperature higher than the pre-bake temperature to simultaneously cure the first and second photosensitive resin layers. A method for forming an organic insulating film having: 2. The method according to claim 1, wherein a negative photosensitive resin that is thermally cured at a temperature lower than a curing temperature of the negative photosensitive resin used in the first step is used in the second step, A method for forming an organic insulating film, wherein the pre-bake temperature in the step is set lower than the pre-bake temperature in the first step. 3. The pre-bake temperature in the second step is 5 ° C. to 30 ° C. lower than the pre-bake temperature in the first step.
A method for forming an organic insulating film, wherein the temperature is set as low as about ° C. 4. The method according to claim 1, wherein the first photosensitive resin and the second photosensitive resin are obtained by adding a negative photosensitive group to a polyimide resin or a polybenzoxazole resin. A method for forming an organic insulating film.