JPS588131B2 - Manufacturing method of semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for making a quinone diazo positive type photoresist negative by electron beam irradiation.

As is well known, there are two types of resists made of polymer materials: negative type and positive type. In both cases, the exposed area undergoes a chemical change. In the negative type, the exposed area remains, and in the positive type, the unexposed area remains, forming a mask. used as a pattern.

Of these two methods, a method has been proposed in which a quinone diazo positive type photoresist with excellent resolution is subjected to a series of treatments including electron beam exposure to leave the portion exposed to the electron beam, that is, a method of making the positive type photoresist negative. , has already been used for forming fine patterns, etc.

However, in the above series of processing, the ratio of the film thickness remaining after development processing to the film thickness of the photoresist applied at the beginning,
In other words, the higher the electron beam irradiation dose, the higher the residual film rate becomes.
Further, the longer the development time, the smaller the size.

For example, quinone diazo positive photoresist OFP
R (manufactured by Tokyo Ohka Kogyo Co., Ltd.) to the surface of a semiconductor substrate, etc.
m] thickness, and an electron beam was applied to this to a thickness of 3×10−5
[C/cm2], heat treated at 90°C for 20 to 30 minutes, and then developed with a tetramethylammonium hydroxide developer at 20%, resulting in a residual film thickness of approximately 6000 [C/cm2]. Å], that is, the remaining film rate is approximately 6
It becomes 0 [%].

In order to use the resist film thus formed as a mask for dry etching processing of a semiconductor substrate, etc., the resist film needs to have a thickness of at least about 1 [μm].

In order to form such a thick resist film using the conventional method described above, the coating film thickness and the amount of electron beam irradiation must be significantly increased compared to the above conditions.

However, when the thickness of the coating film is increased and the amount of electron beam irradiation is increased, the reflection of the electron beam on the surface of the semiconductor substrate causes fog on the resist film, resulting in poor pattern accuracy and a very long exposure time. There are problems such as the need for

For example, on a semiconductor substrate with a diameter of 75 [mm],
Approximately 1 [hour] to give a radiation dose of 5 [C/cm2]
Requires.

As described above, the conventional method of making a quinone diazo positive photoresist negative reduces the resolution and sensitivity of the photoresist, making it difficult to form a thick film.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a method for making a quinone diazo positive photoresist negative, which improves the sensitivity without impairing the resolution of the quinone diazo positive photoresist and prevents film thinning. It is in.

The method for manufacturing a semiconductor device of the present invention is characterized by coating the surface of a semiconductor substrate with a quinone diazo positive type photoresist and a negative type resist thereon, irradiating it with an electron beam according to a predetermined pattern, and performing heat treatment. , a resist film having a predetermined pattern is obtained by adding a step of removing unnecessary portions of the upper layer negative type resist film and a step of removing unnecessary portions of the lower layer quinone diazo positive type photoresist film using the remaining negative type resist film as a mask. The method includes the step of forming.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of essential parts showing an embodiment of the present invention in which a positive type photoresist is made negative.

As shown in Figure a, first, the above-mentioned OF
A positive type photoresist 2 such as PR is coated to a desired residual film thickness, for example, 1 [μm], and OB is applied on top of it.
For example, a negative type resist 3 for electron beam such as C (polyisoprene resist manufactured by Tokyo Ohka Kogyo Co., Ltd.) is
The coating is applied to a thickness of about 0.00 Å, and then the electron beam 4 is irradiated according to a predetermined pattern.

In the figure, 2' and 3' are the OFPR film 2 and OBC.
The portion of membrane 3 exposed to the electron beam is shown.

At this time, the irradiation amount of the electron beam is 1 × 10-5 [C/cm
2] is sufficient.

After that, heat treatment is performed at about 90 [° C.] for 20 to 30 [minutes].

Next, as shown in FIG. 5B, the entire surface of the resist film is irradiated with ultraviolet light 5.

The amount of ultraviolet rays irradiated may be slightly excessive so that the OFPR is sufficiently exposed.

Even if ultraviolet rays are irradiated in this manner, no change occurs because the upper OBC film 3 is not exposed to ultraviolet rays.

Therefore, by developing the upper OBC film 3 with xylene, only the portion 3' exposed to the electron beam remains as shown in FIG. 3C, and other unnecessary portions are removed.

At this time, the thickness of the OBC film 3' becomes slightly thinner than the initial thickness to about 2000 Å.

Next, using the remaining OBC film 3' as a mask, the underlying OFPR film 3 is treated with the aforementioned tetramethylammonium hydroxide developer for about 20 minutes, thereby removing the remaining OBC film as shown in FIG. The OFPR film 2' immediately below 3' remains, and other unnecessary parts are removed to form a desired pattern.

In the above-mentioned OFPR film development process, the portion 2' where the OFPR film is left is covered with the OBC film 3', so that the upper surface of the OFPR film 2' is not exposed to the developer, so that film thinning does not occur.

Therefore, in this embodiment, the amount of electron beam irradiation is approximately 1/1/1 compared to the amount of electron beam irradiation in the conventional example described above.
As a result, the electron beam irradiation time can be shortened to approximately 10 minutes, and work efficiency can be significantly increased.

In the above embodiment, it is necessary to select two types of developing solutions that react only with the target resist and do not react with the other resist at all.

The present invention is not limited to the one embodiment described above, but can be implemented with various modifications.

In addition, since the purpose of the upper layer of negative photoresist is to prevent film thinning of the lower layer of positive photoresist, it is sufficient to leave a coating thickness of 2000 mm as long as it remains thick enough to be effective as a protective film.
It is preferable to set the thickness to about 5000 [Å].

Further, the coating thickness of the lower positive type photoresist, the amount of electron beam irradiation, the development time, etc. may be appropriately selected depending on the purpose.

As explained above, according to the present invention, the amount of electron beam irradiation is required to make a positive photoresist negative, so that a resist film with a fine pattern having a film thickness required as a mask in dry etching processing etc. can be formed with high precision. In addition, it can be formed efficiently and greatly contributes to miniaturization and high integration of integrated circuits.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a main part showing the method of making a positive photoresist negative according to the present invention in order of steps. 1...Semiconductor substrate, 2...Positive type photoresist film, 3...Negative type resist film, 2,3'...Positive type and negative type resist The part of the film exposed to the electron beam, 4...
...electron beam, 5...ultraviolet light.

Claims (1)

[Claims] 1 Apply a quinone diazo positive type photoresist on the surface of the semiconductor substrate and a negative type resist on top of it,
irradiating the electron beam according to a predetermined pattern;
After that, a step of irradiating the entire surface with ultraviolet rays, a step of removing unnecessary parts of the upper layer negative type resist film, and a step of removing unnecessary parts of the lower layer positive type photoresist film using the upper layer negative type resist film as a mask are added. 1. A method for manufacturing a semiconductor device, the method comprising the step of forming a resist film having a pattern.