JPS6384117A - Etching of polyimide resin - Google Patents

Abstract

PURPOSE:To reduce the number of steps by superposing a polyimide region on a substrate at a predetermined film thickness ratio, and simultaneously etching together with a photoresist with gas containing CF4 at a predetermined ratio in O2. CONSTITUTION:A polyimide of thickness D and a photoresist of thickness (d) are superposed on a substrate, and d/D<1.5 is selected. A plasma etching is performed with gas containing 10-30% of CF4 in O2. In this case, since the etching ratio of the resist to the polyimide is specified by the mixture gas ratio, it is etched together with photoresist on the basis of the etching rate ratio so that there is no remaining polyimide when d/D is suitably selected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to dry etching of polyimide resin, and in particular, to etching the photoresist layer and polyimide layer of a pattern mask simultaneously to ensure that unnecessary portions of the polyimide resin are removed. Regarding how to remove.

[Conventional technology]

Polyimide resins have been used as glabellar insulating films in multilayer interconnections of semiconductor devices and the like. As refining technology and improvements in the resin materials themselves have progressed, it has become possible to obtain products of high quality, and they are now being used as interlayer insulating films and passivation films for multilayer wiring.

Next, a conventional polyimide resin pattern mask will be explained based on FIGS. 2(a) to 2(C). First, let's look at Figure 2 (
As shown in a), a polyimide resin 2 is provided on the surface of a substrate 1, and a photoresist 3 is further formed thereon. A photomask 4 with a required pattern drawn thereon is placed at a distance of 10 to 20 μm from the surface of the photoresist layer 30, and the mask pattern is exposed to the photoresist layer 3 by applying ultraviolet light.

Next, as shown in FIG. 2(b), the exposed photoresist layer 3 is developed with sodium silicate to remove the portion exposed to the ultraviolet light. And this photoresist layer 3
Using the pattern as a mask, unnecessary portions of the polyimide layer 3 are removed by etching with sodium silicate. Finally, as shown in Figure 2(C).

The photoresist layer is removed to obtain the required pattern of polyimide.

[Problem that the invention seeks to solve]

In the wet etching shown in FIGS. 2(a) to 2(C), there is a problem in that the unnecessary portions of the polyimide layer are not completely removed and remain very thinly on the surface of the substrate 1.

Conventionally, in order to remove this polyimide film, the substrate 1 is placed in a plasma etching device and etched in 02 plasma at about 1 Torr, or the substrate is immersed in a hydrazine solution and light etched is performed. The method has been done.

However, in the former method, the substrate that has been wet-etched with sodium silicate must be transported to a plasma etching device and set therein. In the latter case, after wet etching with sodium silicate, sufficient cleaning is required, and then an etching step with a hydrazine solution is required.

In either case, the number of steps will increase, but
This is not desirable at a production site because it leads to an increase in manufacturing costs.

[Means for solving problems]

The present invention is based on a polyimide resin layer (thickness D) provided on a substrate.
and a photoresist layer (thickness d) provided thereon are placed in a plasma etching apparatus.

The conventional problems were solved by simultaneously etching both layers in a plasma atmosphere consisting of a mixed gas of carbon tetrafluoride and oxygen. According to experiments conducted by the present inventor, an optimum embodiment can be obtained under the conditions that the film thickness ratio (d/l) of both layers is 1.5 or less and the proportion of carbon tetrafluoride in the mixed gas is 10% or more and 30% or less. It was done.

[For production]

FIG. 1 shows experimental data showing how the etching rate of polyimide resin and 7-photoresist changes when the flow rate of CF4 (carbon tetrafluoride) is changed. The discharge power at this time is 300
W and the etching pressure is 0.8 Torr. As you can see from this Figure 1.

The etching rate for the mixed gas ratio of polyimide resin and photoresist has been specified.

Given the thickness of the polyimide resin layer, the thickness of the photoresist can be determined based on the etching rate ratio to realize an etching method in which no residual polyimide is present.

For example, if the proportion of CF in the mixed gas is 25%,
The etching rate of polyimide resin is 3.800 jV
/min, that of 7 Otresist is 4,500^/
Assuming that the polyimide resin film thickness is 1 μm, it can be seen that the photoresist film thickness d should be 1.18 μm.

However, if the proportion of CF4 in the mixed gas is less than 10% or more than 35%, the etching rate for the polyimide resin will be low, resulting in a problem that productivity will decrease and this method is not practical.

Therefore, etching in which the mixing ratio of CF4 is in this state is not preferable.

For this reason, the ratio of CF4 to the mixed gas is 1
When the film thickness ratio d/D of both layers is 0 to 35% and 1.5 or less, the polyimide resin and the photoresist layer are plasma etched at the same time, and the photoresist layer is etched without any residual polyimide resin at the end of etching. A state is obtained in which the is completely removed.

〔Example〕

A polyimide resin was applied onto a glass substrate to a thickness of 1.4 μm by a spin cord method, and baked at 350° C. for 1 hour. The polyimide film thickness at this time was 1.0 μm.
Thereafter, a positive resist 0FPR800 manufactured by Tokyo Ohka Kogyo Co., Ltd., for example, was applied using a spin cord and prebaked at 90° C. for 5 minutes.

Next, in order to obtain a predetermined resist pattern, the mask pattern was exposed and developed to obtain a resist pattern. Then, post-baking was performed at 120° C. for 10 minutes. The film thickness of the resist at this time was 1.5 μm.

Next, this substrate was placed in a plasma etching apparatus, and the polyimide resin layer was dry etched under primary conditions.

What is the etching rate under these conditions?

Polyimide resin: Approximately 3,000^/min7: t
(L' cis): about 4500 A/InIn.

After etching for 3 minutes and 30 seconds, the photoresist was completely removed and a polyimide resin layer with a predetermined pattern was obtained. The thickness of the formed polyimide resin layer was 1.0 μm.

Note that the photoresists are not limited to the ones mentioned above.
Similar effects were obtained using other positive photoresists.

〔Effect of the invention〕

The present invention has the following effects.

(1) There is no need to perform a separate photoresist removal process.

(2) Unused portions of the polyimide resin are completely etched away.

(3) Good reproducibility of etching results.

(4) As a result of the above (1) to (3), the present invention makes it possible to simplify the process and reduce manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is experimental data showing the principle of the present invention. FIG. 2 shows a conventional etching method. 1... Board. 2...Polyimide resin layer. 3...Photoresist layer. 4...Photomask.

Claims (3)

[Claims] (1) A polyimide resin etching method characterized in that a polyimide resin layer and a photoresist layer thereon are simultaneously etched in a plasma atmosphere consisting of a mixed gas of carbon tetrafluoride and oxygen. (2) Etching of polyimide resin according to claim (1), characterized in that the ratio d/D of the film thickness D of the polyimide resin layer to the film thickness d of the photoresist layer is 1.5 or less. Method. (3) The proportion of carbon tetrafluoride in the mixed gas is 10% or more30
Claim No. (1) characterized in that it is less than %.
The method for etching polyimide resin according to item (2) or item (2).