JPS61231545A - Photoresist composition and formation of resist pattern - Google Patents

Abstract

PURPOSE:To improve the resistance of a photoresist composition to oxygen plasma while maintaining the sensitivity to far ultraviolet rays and the resolving power by using the silyl ether of the naphthoquinonediazidosulfonic ester of novolak. CONSTITUTION:A photoresist layer made of the silyl ether of the naphthoquinonediazidosulfonic ester of novolak is formed as the 2nd layer of a resist having a two-layered structure. The photoresist layer has improved resistance to oxygen plasma as well as high sensitivity and resolving power. When the photoresist layer is used, a fine and sharp pattern having high resolving power and a high aspect ratio can be formed. The photoresist can be easily removed with sulfuric acid or an ordinary org. solvent.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a photoresist composition used in a two-layer resist for forming a fine resist pattern on the order of submicrons, and a method using this photoresist. The present invention relates to a method of forming a fine resist pattern using a two-layer resist.

(Prior Art) In recent years, demands for higher integration of semiconductor devices and the like have been increasing, and along with this, technical demands regarding the formation of fine patterns have also become increasingly strict. As a microfabrication technology that meets these demands, a resist pattern is formed using ionizing radiation such as electron beams, X-rays, and short wavelength ultraviolet rays, and then the resist pattern is precisely formed by dry etching using ions, plasma, etc. There is a need for a method for transferring to an underlying layer such as a substrate.

By the way, as characteristics of the resist used in such microfabrication, high resolution, high sensitivity, and high dry etching resistance are naturally required. However, in the case of large-scale integrated circuits (LSI), etc., the surfaces of wafers including substrates are often uneven, and patterning of a resist layer on such an uneven surface is difficult to avoid. As a result, the resolution is lowered due to the influence of diffused reflection and interference of light, and as a result, pattern dimensions are susceptible to changes.

It was difficult to form the resist pattern to the designed dimensions.

Further, in the case of electron beam exposure, it is easily affected by backscattering of electrons from the underlayer side and also easily affected by the proximity effect.

The disadvantage is that the pattern deteriorates and a beautiful and sharp resist pattern cannot be obtained.

A resist with a multilayer structure has been proposed for the purpose of preventing the influence of light reflection from the unevenness of the substrate.

A three-layer resist has been proposed as a resist with this multilayer structure, and this three-layer resist is formed by, for example, forming the first layer as a photoresist layer, the second layer as an Si02 layer, and the third layer as a thin photoresist layer. This method solved problems such as light reflection due to the unevenness of the substrate during resist patterning, and made it possible to form fine and sharp patterns, but the process was extremely long and complicated, so it was difficult to shorten the process. was desired.

In response to this demand, a two-layer resist was proposed. By forming the resist into a two-layer structure, it is possible to shorten the formation process and realize a resist pattern with high resolution.

However, the upper layer of this two-layer structure, that is, the second resist layer, has the characteristics of both the 5i02 and photoresist layers used for the second and third layers of the three-layer structure, respectively. required. That is, the photoresist is required to have high sensitivity, high resolution, and high resistance to oxygen plasma.

In recent years, research has been conducted to improve materials used for photoresist layers in multilayer structures, and photoresists such as those described below have been proposed (Reference: ``Silicone-based negative resist MS
NR427th Semiconductor/Integrated Circuit Technology Symposium (11
December 384, 2.48-53)).

According to this document, the first layer (lower layer) is placed on the base layer and the
After forming a resist layer of Z-1350 (a product name of a positive photoresist manufactured by Shipplay) and prebaking, a silicone-based negative resist SIR (Silicone-basad Nega) was formed as a second layer (upper layer).
tiveResist) or MSNR (Methacrylated 5
ilicone BasedNegative Re5
A silicon-containing resist layer (abbreviation of IST) is formed, and this two-layer structure resist is used to realize 0.71 LvI in line and space.

The reason why research on photoresists used for the upper layer is conducted on silicone-based photoresists is because the silicon contained in the photoresist reacts with oxygen due to the reactive ions of oxygen gas, forming a silicon oxide layer on the upper layer. It is thought that this is because this layer acts as a barrier layer and resists oxygen gas reactive ion etching.

(Problems to be Solved by the Invention) However, the photoresist used as the upper layer as disclosed in this document is a photoresist that is highly sensitive in the ultraviolet wavelength region, so it does not have sufficient resolution. do not have.

In the light exposure method, the shorter the wavelength of the light, the better the resolution of the pattern and the higher the throughput, so a photoresist that can be exposed in the deep ultraviolet region is desired.

In addition, when forming each photoresist layer, the time for pre-bake etc. is as short as possible, and if possible, the photoresist is such that it does not require pre-bake, and it is easy to peel off when pattern formation of semiconductor elements is completed. A photoresist with excellent properties is desired. If a resist pattern is formed using such a photoresist, it can be expected that the formation process will be simple and easy.

Therefore, the first object of the invention of this application is to provide a photoresist composition for use in a two-layer resist, which has excellent dry etching resistance, can be exposed in the deep ultraviolet region, and has high sensitivity. It is an object of the present invention to provide such photoresist compositions with high resolution, such as 0.5 IL.

A second object of the invention of this application is to provide a method for forming a resist pattern by which a two-layer resist pattern can be simply and easily formed using such a photoresist composition.

(Means for Solving the Problems) In order to achieve the first object of the present invention, in a photoresist composition used for a two-layer resist, this composition is a silyl ester of naphthoquinonediazide sulfonic acid ester of novolak. It is characterized by being an ether.

In order to achieve the second object of the present invention, according to the resist pattern formation of the present invention, when forming a resist pattern with a two-layer structure of a photoresist layer and a polymer layer, a polymer layer is formed on the base layer. forming a photoresist layer comprising a silyl ether of a naphthoquinonediazide sulfonic acid ester of novolak over the polymer layer;

A process of selectively irradiating this photoresist layer with 200 to 300 nm of deep ultraviolet rays and developing the exposed photoresist layer to form a pattern of the photoresist layer, and using the pattern of the photoresist layer as a mask. The present invention is characterized by a method for forming a resist pattern, comprising a step of selectively removing the above-described polymer layer using a photoresist.

(Function) As described above, according to the first invention of this application, the second layer of the two-layer resist is formed using silyl ether of naphthoquinonediazide sulfonic acid ester of novolak (5i-LN
This photoresist layer has high sensitivity and high resolution, as well as
It has the property of improving oxygen plasma resistance. Further, when a resist pattern is formed using this photoresist layer, a fine and sharp resist pattern with high resolution and a large 7-spectrum ratio can be formed. Moreover, this photoresist can be easily peeled off using sulfuric acid or a commonly used organic solvent.

Furthermore, according to the second invention of this application, Si-LMR is soluble in benzene, xylene and other less polar solvents, so Si-LMR is dissolved in novolac naphthoquinonediazide sulfonic acid ester (hereinafter also referred to as LNR), AZ-
1350J (trade name of 5hipley) or other novolaks by continuous coating without baking the base, the process can be simplified.

(Example) Examples of the present invention will be described below.

It should be noted that the embodiments described below are merely examples, and the numerical values, shapes, materials, and other aspects of the conditions described herein may vary depending on, for example, the dimensional accuracy of the intended final pattern. However, it is not limited to the following examples.

(a) Trimethylsilyl ether (S
i-LMR) synthesis method.

First, the photoresist composition of the present invention, Si-
The method for synthesizing LMR will be explained.

In order to silylate the OH group of naphthoquinonediazide sulfonic acid ester (LMR) of novolac resin, triethylamine was used as a catalyst, and this LM was silylated in tetrahydrofuran.
Against R and this LMR! , and 5 to 2.0 gram equivalents of trimethylchlorosilane were reacted at room temperature.

Purification was carried out by dissolving the isolated crude product in benzene, toluene or other organic solvents, and pouring it into methanol or hexane for crystallization. Solid Si-LMR was obtained by this crystallization.

(b) Si-LMR film formation method A method for forming a photoresist layer film using the Si-LMR obtained by the method will be explained.

Si-LMR has high solubility in polar solvents such as acetate esters and alkyl ketones, as well as chlorobenzene, toluene, benzene, xylene, and other non-polar solvents. Therefore, Si-LMR can be dissolved in these solvents and spin coated. When a film was formed on a substrate such as St using the method, a good film was formed.

(c) Method for Forming a Resist Pattern An example of a method for forming a resist pattern with a two-layer structure using this Si-LMR will be described.

@1 Figures (A) to (C) are process diagrams for explaining the method of forming a resist pattern according to the present invention, and schematically show the state of the resist in the main steps.

First, apply LMR as the first layer on the base layer 10! form 12. For this reason, LMR is converted into methylcellosolve acetate.
Dissolved at a ratio of 0% by weight, filtered through a 0.21m filter, and then spin-coated onto a Si substrate to form a 1.51%
Next, as a second layer on this LMRfi 12, Si-LMR, which is a photoresist composition of the present invention, is dissolved in xylene at a ratio of 10% by weight, and spin coating is applied. 0.2 by law
#L intestine thickness 5i-L) IR layer 14 was formed (first
Figure (A)).

Next, LNRN five layers and Si-LMRM! After baking the substrate 10 on which 14 was formed at 70°C for 30 minutes,
80sJ by contact method with ~300n intestinal far ultraviolet rays
Exposure was carried out at a dose of "/am". After that, the temperature was 100°C.
After baking for 30 minutes, a 5i-LNH pattern was formed by developing at 23°C for 10 seconds in a solution of 2 parts of cyclohexane to 1 part of chlorobenzene (Figure 1C).
B)), 5i-LNRji) 1 remaining after this development
4 is indicated by 14a.

Next, using the Si-LMH pattern 14a as a mask, the sample was etched in a parallel plate type etching device using 02 plasma, the gas flow rate was 5O3CG)I, the power density was 0.081/c2, and the gas pressure was Etching was carried out for 20 minutes under the condition of 5 Pa, and the lower layer LMR calendar 12
was selectively removed (Fig. 1(C)).

The portion of LMRyI112 remaining by this etching is shown as 12a, and this portion 12a and the above-mentioned 5i-LNR
The remaining portion 14a forms a two-layer resist pattern.

When the pattern thus formed was observed using a scanning electron microscope (SEW'), it was observed that a line and space pattern of 0.51 L■ was formed with a thickness of 1.8 JL-. Ta. In addition, the 5i-LNR was only etched by the oxygen plasma.

In addition, instead of LMH used for the first layer in the above-mentioned example, AZ-1350 (positive photoresist manufactured by Shipley) was formed on the substrate to a thickness of 1.51 L by a spin code method. After that, the resist pattern obtained by forming the same process as in the above-mentioned example was subjected to SEX.
As a result of observation, it was found that a line and space pattern of 0.5 JL intestine was formed.

In the above examples, the trimethylsilyl ether of novolac naphthoquinonediazide sulfonic acid ester (LMR) was explained, but other LMR silyl ethers other than LMH trimethylsilyl ether, such as LMR dimethylsilyl ether and LMR T- A similar effect can be expected with butyldimethylsilyl ether.

(Effects of the Invention) As can be seen from the examples described above, according to the resist layer of the present invention, by silylating the OH group of LMR,
Oxygen plasma resistance can be improved while maintaining the physical properties of LMR, such as sensitivity to far ultraviolet rays and resolution. For example, according to the data in the example, S
It can be seen that the film thickness reduction of i-LMH in oxygen plasma is 1/25 or less.

Furthermore, since Si-LMR can be dissolved in solvents with low polarity such as benzene and xylene, a solvent with low polarity is used as the solvent for Si-LMH and used for the first layer. L
Dissolution of MR, AZ-1350, other novolacs, etc. can be avoided.

This eliminates the need for a pre-bake step, which is normally carried out after the formation of the first layer, to prevent this layer from being attacked by a solvent such as a photoresist used subsequently.

Therefore, according to the resist pattern forming method of the present invention, a film can be formed by continuous coating without baking the underlying layer, and the process can be shortened because the photoresist layer can be easily peeled off.

Furthermore, since the first layer is formed flat on the base layer, the second layer is not adversely affected by diffused reflection or interference of light due to unevenness on the base layer.

For the above reasons, a fine photoresist pattern with a high spectral ratio of 7 can be formed in a high throughput, making it possible to provide a semiconductor device that is inexpensive and has high reliability.

[Brief explanation of the drawing]

FIGS. 1A to 1C are process diagrams for explaining the resist pattern forming method according to the present invention. 10... Lower J: #i layer, lOa...
Irregularities of base layer 12... Naphthoquinonediazide sulfonic acid ester of Novolak (LMR) 14... Trimethylsilyl ether of naphthoquinonediazide sulfonic acid ester of Nopolar 2 (Si-L
MR) 12a...L) Remaining portions of the IR layer 14a...5
Remaining portion of the i-LMR layer. Patent applicant: Oki Electric Industry Co., Ltd. (above) Fuji Pharmaceutical Co., Ltd. IO = (a) below M t
oa: VZ layer irregularities 12: Noho 2 Tsuku's 1-futoquinone diazine 1-sul friend ester CLMR) 12;
i: LMR) 14P min 141: Si-LMR
4niP procedural amendment April 4, 1986

Claims (2)

[Claims] (1) A photoresist composition for forming a resist pattern, characterized in that the composition is a silyl ether of novolac naphthoquinonediazide sulfonic acid ester. (2) In forming a resist pattern with a two-layer structure of a photoresist layer and a polymer layer, a step of forming a polymer layer on the base layer, and a step of forming a silyl ether of novolac naphthoquinonediazide sulfonic acid ester on the polymer layer. forming a photoresist layer comprising:
a step of selectively irradiating and exposing the photoresist layer with deep ultraviolet light of 00 to 300 nm, and then developing the photoresist layer to form a pattern of the photoresist layer; using the pattern of the photoresist layer as a mask, forming the polymer layer; A method for forming a resist pattern, comprising the step of selectively removing the resist pattern.