JPH0691066B2 - Method for forming photosensitive organic resin film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a technique for forming a multilayer wiring board using a photosensitive organic resin as an insulating film material.

[Conventional technology]

FIG. 2 is a process drawing of an insulating film forming method using a liquid organic resin as a material in a conventional multilayer wiring board.
In FIG. 2, reference numeral 1 is a substrate, 2 is a lower layer wiring conductor, 3
Is a photosensitive organic resin after coating, 4 is an insulating film after heat treatment, 5
Means an upper layer wiring conductor. (A) A liquid organic resin 3 is applied on the substrate 1 on which the lower layer wiring conductor 2 is formed by a spin coating method. Since organic resin has fluidity,
As shown in (b), the surface of the organic resin after coating is flat even on the substrate 1 having surface irregularities due to the formation of the lower layer wiring conductor 2. Then, heat treatment is performed, so that the liquid organic resin 3 becomes the insulating film 4. During this heat treatment, volume contraction occurs due to evaporation of the solvent contained in the organic resin,
A step that reflects the shape of the lower layer wiring conductor 2 is formed on the surface of the insulating film 4 (Takaki and Tsuneji, Proc. If the upper-layer wiring conductor 5 is formed on the surface of the insulating film having a step, the covering of the conductor with respect to the step shape is deteriorated, which eventually causes disconnection, which hinders the formation of the multilayer wiring. As a method of reducing the unevenness of the surface of the insulating film, a method of mechanically polishing with an abrasive has been proposed (RC Landice (R.
C. Landis), May 1985, 35th ECC Conference Bulletin (P.
roc. 35 th ECC Conf.) Page 384], fine processing is difficult, and the insulating film surface may be damaged or contaminated by an abrasive or the like.

[Problems to be Solved by the Invention]

An object of the present invention is to use an organic resin having photosensitivity as an insulating film material and to flatten the insulating film surface by partially controlling the film thickness of the insulating film after exposure / development using photolithography technology. The purpose is to provide a method of

[Means for Solving the Problems]

Briefly describing the present invention, the present invention is an invention relating to a method for forming an insulating film using a photosensitive polyimide resin, wherein in a step of forming an insulating film using a photosensitive polyimide resin, a photosensitive polyimide is formed on a substrate having convex portions. The step of applying resin,
And a step of partially forcing the film thickness of the insulating film by irradiating the periphery of the convex portion with exposure light of which intensity is changed.

Taking the negative photosensitive organic resin as an example, the principle of the present invention will be described with reference to FIG. In FIG. 1, reference numeral 6 denotes an intensity distribution of exposure light, 101 denotes a substrate, 201 denotes a lower layer wiring conductor, 301 denotes a photosensitive organic resin after coating, and 401 denotes an insulating film after heat treatment. The photosensitive organic resin 301 having a step formed subsequent to the lower layer wiring conductor 201 on the substrate 101 as shown in (b) is exposed by light having the intensity distribution 6 of (a). afterwards,
When the development is performed, the amount of the photosensitive organic resin dissolved during the development depends on the exposure intensity, so that the insulating film 401 having a flattened surface is formed as shown in (c).

As a method for obtaining the exposure light with the intensity changed, in each of the examples described later, a method of providing a minute rectangular pattern in the light shielding portion and controlling the aperture ratio by changing the length of one side or the interval between the patterns has been described. The same effect can be obtained by providing a circular pattern and changing the diameter or the pattern interval.
Moreover, the same effect can be obtained by arranging a pattern having an arbitrary shape. That is, generally, the same effect can be obtained as long as the pattern dimension in the direction in which the exposure intensity distribution has a gradient is a fine pattern having an exposure wavelength or less.

Although the negative photosensitive organic resin is used in the embodiment of FIG. 1, the exposure intensity distribution shown in FIG. Can flatten the insulating film surface by using the reverse exposure intensity distribution.

In the examples described below, the case where the photosensitive organic resin is exposed using the photomask has been described, but as a method of irradiating the exposure light with a predetermined intensity changed, a laser or an electron beam is used, Irradiation may be performed while controlling the exposure beam to a predetermined intensity.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to these examples.

Example 1 FIG. 3 is a diagram for explaining an example of a method for obtaining the intensity distribution of the exposure light shown in FIG. In FIG. 3, reference numeral 6 is an intensity distribution of exposure light, 7 is an exposure photomask,
Reference numeral 8 indicates a minute square pattern formed on the exposure photomask. By providing a minute rectangular pattern 8 on the light-shielding portion of the exposure photomask 7, the length of one side or the pattern interval is changed to control the aperture ratio (ratio of the area of the rectangular pattern per unit area). The intensity distribution 6 of the exposure light is realized. If the length of one side is equal to or less than the exposure wavelength of the photosensitive organic resin, due to diffraction of light passing through the rectangular pattern or irregular reflection at the edge of the rectangular pattern,
The light intensity distribution on the surface of the photosensitive organic resin can be regarded as smooth in practice.

FIG. 4 shows the exposure intensity (arbitrary unit, abscissa) and the film weight reduction (arbitrary unit, lengthwise) when using a photomask based on the principle of FIG. 3 and using a photosensitive polyimide resin as the negative photosensitive organic resin. It is a graph showing an example of the relationship with (axis). In the photosensitive polyimide resin, the energy of the irradiated light is absorbed by the photosensitive group to cause a photocrosslinking reaction, which makes it difficult to dissolve in the developing solution. Therefore, the higher the exposure intensity, the smaller the amount of dissolution in the developer and the smaller the amount of film loss.

Example 2 FIG. 5 shows a process chart of an example of a wiring board forming method using a photosensitive polyimide resin as an insulating film material as an example. In FIG. 5, reference numeral 102 is a substrate, 202 is a lower layer wiring conductor, 302 is a photosensitive organic resin after coating, 402 is an insulating film after heat treatment, and 501 is an upper layer wiring conductor. A photosensitive polyimide resin 302 is applied on the substrate 102 on which the lower layer wiring conductor 202 is formed (a) [see (b)]. When heat treatment is performed to evaporate the solvent or the like contained in the organic resin, a step reflecting the shape of the lower layer wiring conductor 202 is generated as shown in (c). After this,
By performing exposure and development using the exposure photomask 7 shown in FIG. 3 and heat treatment, an insulating film 402 having a flat surface can be obtained as shown in (d). Therefore, (e)
As shown in FIG. 5, the upper layer wiring conductor 501 free from disconnection can be formed, and the wiring can be easily multilayered.

Example 3 In Example 2, the case where the step formed on the surface of the insulating film was flattened was taken as an example. However, as shown in FIG. 6 as an explanatory view, a film was formed from a photosensitive organic resin having a flat surface. It can also be applied to the case of forming an insulating film whose thickness is partially controlled. Sixth
In the drawing, reference numeral 103 is a substrate, 303 is a photosensitive organic resin after coating, 403 is an insulating film after heat treatment, 601 is an intensity distribution of exposure light, and 701 is an exposure photomask. When the exposure intensity distribution 601 of (b) is realized by the photomask 701 having the pattern of the shape shown in (a), and the substrate 103 coated with the photosensitive organic resin 303 of (c) is exposed and developed, The insulating film 403 having a film thickness distribution as shown in (d) can be formed.

〔The invention's effect〕

As described above, according to the present invention, it is possible to partially control the film thickness of the insulating film after the photosensitive organic resin is exposed and developed. When forming a plate, using a photomask that realizes an exposure intensity distribution that corresponds to the stepped shape that occurs on the photosensitive polyimide resin surface makes it possible to flatten the insulating film surface by exposure and development, thus making the wiring finer. ,
Multilayering becomes easy.

[Brief description of drawings]

FIG. 1 is a process diagram illustrating the principle of the present invention using a negative photosensitive organic resin as an example, FIG. 2 is a process diagram of a conventional method for forming a multilayer wiring board, and FIG. 3 is an implementation of FIG. FIG. 4 is an explanatory view of an example of a method for obtaining the intensity distribution of exposure light, FIG. 4 is a graph showing the relationship between exposure intensity and film weight loss for a photosensitive polyimide resin based on the principle of FIG. 1, and FIG. FIG. 6 is a process diagram showing an example of a method for forming a multilayer wiring board according to the present invention, and FIG. 6 is an explanatory diagram of an example in the case of partially controlling the film thickness of an insulating film according to the present invention. 1,101,102,103 …… Substrate, 2,201,202 …… Lower layer wiring conductor,
3,301,302,303 …… Photosensitive organic resin after coating, 4,401,40
2,403 …… Insulation film after heat treatment, 5,501 …… Upper layer wiring conductor,
6,601 …… Exposure light intensity distribution, 7,701 …… Exposure photo mask, 8 …… Small square pattern formed on exposure photo mask

Claims (3)

[Claims] 1. A step of applying a photosensitive polyimide resin to a substrate having a convex portion in an insulating film forming step using a photosensitive polyimide resin, and exposing light having a different intensity around the convex portion. A method of forming an insulating film using a photosensitive polyimide resin, which comprises a step of partially forcing the film thickness of the insulating film by irradiation. 2. A method for obtaining exposure light with varying intensity according to claim 1, wherein a plurality of fine patterns are provided on a photomask and one or both of the dimensions of the fine patterns and the intervals between the fine patterns are changed. A method of forming an insulating film using a photosensitive polyimide resin, comprising: 3. A method of irradiating the exposure light with the intensity changed according to claim 1, wherein the focused exposure beam is irradiated while controlling the intensity thereof to a predetermined intensity to partially change the film thickness of the insulating film. A method for forming an insulating film using a photosensitive polyimide resin, which is characterized in that