JPS62297840A - Negative type electron ray resist material and formation of resist pattern - Google Patents

Abstract

PURPOSE:To obtain substantial sensitivity adequate for application to a two layer resist method by using a 2,3-epoxypropyl dimethylsilyl ether which is a phenolic resin as a negative type electron ray resist material. CONSTITUTION:The 2,3-epoxypropyl dimethylsilyl ether which is the phenolic resin is used as the negative type electron ray resist material. The negative type resist material is formed by protecting the hydroxyl group of the phenolic resin with the 2,3-epoxypropyl dimethylsilyl group. This phenolic resin may be any one kind selected from the group consisting preferably of a paracresol novolak resin, metacresol novolak resin, 4-ternary butyl phenol novolak resin, and polyvinyl phenol or may be a combination of >=2 kinds thereof. The epoxy group introduced into the resist material has high polymn. reactivity with electron rays and contributes to the improvement of the sensitivity; therefore, the above-mentioned resist material has the excellent sensitivity to the electron rays.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Field of Industrial Application) This invention provides an electron beam resist for microfabrication that is suitable for use in manufacturing semiconductor devices, wiring circuits, or other microstructures. The present invention relates to a material and a resist pattern forming method using this material.

(Prior Art) In recent years, with the increasing integration of semiconductor devices, technical requirements regarding fine pattern formation have become stricter. for example,
Resists are also required to have high sensitivity and submicron resolution. In particular, when manufacturing large-scale integrated circuits, resist patterns may often be formed on substrates or other bases that have steps, such as those caused by multilayering of wiring, during the process. In such a case, when attempting to form a pattern using a single layer resist, it is difficult to form a pattern with the designed dimensions.

In order to solve this problem, a two-layer resist method has been proposed, and the development of resist materials suitable for this method is also progressing. Proceedings J (198
5) p. 98-105).

According to the two-layer resist method disclosed in this document, oxygen plasma etching (02-RI) is used as the upper resist layer.
E) Resistant silicon-containing electron beam resist (SNR:
5ilicon-based NegativeRe
sist), and this resist has an acceleration voltage of 20
For an electron beam of kV, TeDn = 5, OJAC/c
It is reported to have a sensitivity of m2.

(Problems to be Solved by the Invention) As is well known, electron beam phosphorography has a low throughput, so a highly sensitive resist is required for patterning with electron beam phosphorography.

However, the sensitivity of the conventional SNH mentioned above is 5 JL
C/cm2, and with this level of sensitivity, there was a problem that the throughput in electron beam phosphorography could not be increased because exposure took time.

In view of the conventional problems as described above, the first object of the invention of this application is to provide a negative electron beam resist material having sufficient sensitivity suitable for application to a two-layer resist method.

A second object of the invention of this application is to provide a method for forming a negative resist pattern using this negative resist material.

(Means for Solving the Problems) In order to achieve the object of the first invention, according to the invention, a negative electron beam resist material is made of a phenolic resin.
, 3-epoxypropyldimethylsilyl ether. The negative resist material is one in which the hydroxyl group of a phenol resin is protected with a 2,3-dipoxypropyldimethylsilyl group represented by the following formula (I).

In carrying out the present invention, this phenolic resin is preferably para-cresol novolac resin (■), meta-cresol novolak resin (][), ]4- Tertiary butylphenol novolac resin V) and polyvinylphenol (V)
It may be one type selected from the group of , or a combination of two or more types.

In this case, the weight average molecular weight of the phenolic resin is approximately 600.
A weight average molecular weight of from about 600 to about 10,000 can be used, but preferably from about 600 to about 8,000. If the weight average molecular weight is outside the range of about 600 to about 10,000, a resist film cannot be formed. be.

Furthermore, in a preferred embodiment of the present invention, the silyl group introduction rate of 2,3-epoxypropyldimethylsilyl ether of the phenol resin is set to 70 to 1 of the total phenolic hydroxyl groups.
It is preferable to set it to 00 mol%.

Further, in order to achieve the object of the second invention, according to the invention, first, a resist film of 2,3-epoxypropyldimethylsilyl ether of phenolic resin is formed as an upper resist on a lower resist.

Thereafter, this upper resist layer is exposed by drawing with an electron beam.

After this drawing, the upper layer resist is developed with a mixed solvent containing a saturated hydrocarbon and a lower alcohol to form a 0-layer resist pattern.

After that, reactive ion etching is performed on the lower resist using the obtained upper resist pattern as a mask.
forming a layered resist pattern;

In this case, the lower layer resist is preferably a photoresist or a polymer.

In addition, the saturated hydrocarbon contained in the mixed solvent for developing the upper layer resist is cyclohexane, n-hexane, n-pentane, or n-heptane, and the lower alcohol contained in this mixed solvent is impropatol, n-heptane, etc. Preference is given to propanol or n-butanol.

Furthermore, the etching of the lower resist using the upper resist pattern as a mask is preferably oxygen plasma etching.

(Function) Thus, the resist material of the present invention is 2,3-epoxypropyldimethylsilyl ether. According to this resist material, the epoxy group introduced by etherifying the hydroxyl group of the phenol resin with a 2,3-epoxypropyldimethylsilyl group has high polymerization reactivity with electron beams, contributing to high sensitivity. Therefore, the sensitivity to electron beams is excellent, and the exposure time required for electron beam irradiation with the same dose under the same conditions is shortened, thereby improving throughput.

Furthermore, as a result of this etherification, the resist material contains a silyl group, so it has excellent reactive ion etching resistance.

Therefore, this resist material is particularly useful for use in electron beam lithography.

In this case, it is not necessary to make the introduction rate of 2゜3-epoxypropyldimethylsilyl groups in the above-mentioned phenol resin 100% by mole based on the total hydroxyl groups, but it is approximately 70 to 100% by mole based on the total hydroxyl groups.
When the introduction rate is set within the range of mol %, sufficient resistance to oxygen reactive ion etching (02-RIE) can be ensured.

Also, within this introduction rate, as will be explained later,
The sensitivity of the resist material of the present invention to electron beams is also more satisfactory than that of the conventional resist material, which is preferable.

In addition, these negative electron beam resists are sufficiently sensitive to electron beams, so they can be used for electron beam phosphorography at 2
It can be used in a layered resist method to improve throughput.

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

The present invention will be described below with reference to preferred embodiments, but even if preferred specific materials, numerical conditions, shapes, arrangement relationships, and other conditions within the scope of the present invention are described in these embodiments, these are merely mere examples. It should be understood that the description is illustrative and is not intended to limit the invention in any way unless specifically limited.

[I] Manufacturing example of the negative electron beam resist material of the present invention.

Production Example 1> Synthesis of 2°3-epoxypropyldimethylsilyl ether (Vl) of balacresol novolak resin (I[).

First, 12 g of Baracresol novolak resin (weight average molecular weight 650) and 26 g of allyldimethylchlorosilane.
9 g was dissolved in 200 m of THF (tetrahydrofuran).

Next, add 24.2 g of triethylamine to this solution for about 1 hour.
The resulting mixture was heated under reflux for about 6 hours, cooled to room temperature, and then filtered to remove triethylamine hydrochloride. At this time, when the filtrate was subjected to aWra, a small amount of triethylamine hydrochloride precipitated, so it was diluted with 100 m of bencef and filtered.

Then, after distilling off the benzene, the residue was vacuum dried overnight to obtain allyldimethylsilyl ether 2 of Nopolar 2 resin.
0.6g was obtained.

When the infrared (IR) absorption of a sample of allyldimethylsilyl ether of the novolac resin obtained in this way was examined, no absorption of hydroxyl groups was observed, and it was confirmed that the silyl group introduction rate was almost 100%. .

Next, after dissolving 20 g of this sample in 250 mL of dichloromethane, 18.7 g of metachloroperbenzoic acid (effective amount 85%) was added little by little to this solution. Stir for hours. Thereafter, this solution was heated under reflux for about 4 hours, and then cooled to room temperature.

After this cooling, dichloromethane is distilled off under reduced pressure at a suitable pressure below atmospheric pressure, and then cyclohexane and n-
The product was diluted with 500 mL of a mixed solvent with hexane at a volume ratio of 1:1, and after thorough stirring, insoluble metachlorobenzoic acid was filtered off.

After that, the filtrate was diluted with 100 ml of NaHCO3 saturated aqueous solution.
Washed twice, then washed twice with 100 mJl of water, and once with 100 mJl of phase saline.

After that, the solvent was distilled off, and the residue was vacuum-dried overnight.
9.8g of Balacresol Novolak Resin (It) 2
．． 3-Epoxypropyldimethylsilyl ether (VI
) was obtained.

Production Example 2> Synthesis of 2,3-epoxypropyldimethylsilyl ether (■) of polyvinylphenol (V).

In this case as well, it was produced in the same manner as in Production Example 1, and will be explained below.

First, polyvinylphenol resin (weight average molecular weight 50
00) 12g and allyldimethylchlorosilane 27.0
g was dissolved in 200 mfL of THF (tetrahydrofuran).

Next, add 24.2 g of triethylamine to this solution for about 1 hour.
The resulting mixture was heated under reflux for about 4 hours, cooled to room temperature, and then filtered to remove triethylamine hydrochloride. After concentrating the filtrate, the product was diluted with 100 ml of benzene and filtered repeatedly. After concentrating this filtrate under reduced pressure, the resulting residue was vacuum dried overnight to obtain 20.0 g of allyldimethylsilyl ether of polyvinylphenol.

The sample of allyldimethylsilyl ether of polyvinylphenol thus obtained was described in Production Example 1.
When we investigated infrared (IR) absorption in the same way as in the case of
No absorption of hydroxyl groups was observed, and the silyl group introduction rate was approximately 100.
It was confirmed that %.

Next, after dissolving 20 g of this sample in 250 mL of dichloromethane, 18.0 g of metachloroperbenzoic acid (effective rate 85%) was added little by little to this solution. Stir for hours. Thereafter, this solution was heated and concentrated for about 3 hours, and then cooled to room temperature.

After this cooling, dichloromethane was distilled off under reduced pressure, and then the product was diluted with 500 m of a mixed solvent of cyclohexane and n-hexane at a volume ratio of 1:1, and after thorough stirring, Insoluble metachlorobenzoic acid was filtered off.

After that, the filtrate was diluted with 100ml of NaHCO3 saturated aqueous solution for 4 hours.
Washed twice, then twice with 100 mjL of water, and once with 100 m1 of saturated saline.

Thereafter, the organic layer of the cyclohexane/n-hexane solvent and the final product was dried with MgSO4, the solvent was distilled off, and the residue was vacuum-dried overnight to give 18.6 g of polyvinylphenol (V) at 2°C. 3-epoxypropyldimethylsilyl ether (■) was obtained.

Production Example 3> 2,3-epoxypropyldimethylsilyl ether of polyvinylphenol (V) (silyl group introduction rate 80%) (
■) Synthesis of.

In this case, the process was carried out in substantially the same manner as in Production Example 2, but with the following conditions changed.

That is, polyvinylphenol (weight average molecule Ji5
000) Allyldimethylchlorosilane 14 for 12g
Dissolve in THF 200m using g, and in this solution,
12 g of triethylamine was added dropwise. Further, the amount of metachloroperbenzoic acid added in the subsequent step was 14.5 g. Other conditions were substantially the same as in Production Example 2>. As a result, the substance (■) above was obtained.

[II] Sensitivity to electron beam and 02-RIE resistance <Example 1> Sensitivity to electron beam 2° of para-cresol novolak resin (IF) 2° of 3-epoxypropyl dimethylsilyl ether (Vl), polyvinylphenol (V) 3-epoxypropyldimethylsilyl ether (■) and 2,3-epoxypropyldimethylsilyl ether of polyvinylphenol (
Each sample (silyl group introduction rate: 80%) (■) was individually dissolved in xylene to prepare a resist solution.

These resist solutions were applied onto a silicon substrate, and each sample 2, 3-
Epoxypropyldimethylsilyl ether (VI), (
The resist layers (2) and (2) were formed separately.

Next, these resist layers were soft baked at a temperature of 60° C. for 30 minutes.

Next, a line pattern of 2 g of Igm was formed on these resist layers using a 20 kV electron beam with the dose as a parameter.
It was drawn through a space of m.

Next, the resist layer after drawing was developed with a mixed developer of cyclohexane and Improper Tool, and then rinsed with Improper Tool for 15 seconds, and the remaining film thickness of the resulting negative pattern was measured. The measurement results are shown in FIG.

Figure 1 shows the dose amount on the horizontal axis and the normalized residual film rate on the vertical axis. The curve shown is data for the resist layer of the sample (■).

Table 1 shows the developer, the development time, and the dose that gives a residual film rate of 50%, obtained from the experimental results.

Table 1 0,t Resist Developer Development time Remaining film rate Dn (volume ratio) (sec) (JLC/cm2) (VI)
! /19 15 4.0 (■) 1
/19 35 2.0 (■) 3/17
23 3.5 (However, the volume ratio of the developer is cyclohexane/isopropanol.) As can be understood from this residual film rate Dn, these resist materials have a higher resistance to electron beams than conventional ones, for example, 2 gC/c.
It can be seen that the sensitivity is m2. Therefore, it can be seen that the exposure time to obtain the same dose under the same conditions can be reduced compared to the conventional method. For example, in the case of sample (■), the dose is 2 gC/cm2, so the exposure time is is approximately 1/2 that of the conventional method, and as a result, throughput is improved.

<Example 2> Baracresol novolac resin (It
), 2,3-epoxypropyldimethylsilyl ether (■) of polyvinylphenol (V), 2,3-epoxypropyldimethylsilyl ether of polyvinylphenol (■), and 2,3-epoxypropyldimethylsilyl ether of polyvinylphenol (silyl group introduced Sample resist layers of 80%) (■) were individually formed to have a thickness of 0.57 zm, and soft baked at a temperature of 60° C. for 30 minutes.

In addition, a resist layer of AZ-2400 (resist material manufactured by Shipley) was coated on the substrate with a thickness of 2 gm.
Comparative samples were prepared by hard baking at a temperature of .degree. C. for 1 hour.

Next, using a parallel plate type dry etching device, the radio frequency (RF) power density was set to 0.08 W/Cm2, the oxygen (02) gas flow rate was set to 203 CCM, and the oxygen gas pressure was set to 5.
02-RIE was performed as Pa.

Figure 2 shows the results of this experiment. Figure 2 shows the horizontal axis of time (
In the figure, 0 is the sample (■) and Δ is the sample (■).
■), The opening shows the 02-RIE curvature curves of the sample (■) and × comparative sample, respectively.

As can be understood from the experimental results, the electron beam resist material of the present invention has superior oxygen dry etching resistance to the conventional AZ-2400 resist.

<Example 3> 02-RIE resistance For example, para-cresol novolak resin (II) 2,
3-epoxypropyldimethylsilyl ether (incorporation rate: 100%) was hard-baked into a 2 gm thick lower layer resist (AZ-2400: resist manufactured by Silapray).
An upper layer resist is formed by coating to a thickness of 0.35 gm, and this upper layer resist is selectively irradiated with, for example, a 20 kV electron beam at a dose of 10 gC/cm'', and then, The upper resist was developed using a mixed solvent of cyclohexane and isopropanol in a volume ratio of 1:19 to form an upper resist pattern.

When the obtained pattern was observed with a scanning electron microscope (SEM), it was found that 0.5 lmL/S (line and space) was resolved. The film thickness of the upper resist layer at this time was 0.3 gm.

Next, using this upper layer resist pattern as an etching mask, the lower layer AZ-2400 resist was subjected to oxygen plasma etching (02-RIE), and the pattern was exposed to SEM.
When observed, it was found that the lower resist pattern was formed with a L/S of 0.5 μm and an aspect ratio of 4. The thickness of the upper resist film at this time is 0.1 gm.
Therefore, it was found that it fully plays its role as an etching mask.

<Example 4> Sensitivity to electron beams 2,3-epoxypropyldimethylsilyl ether (incorporation rate 100%
) It was coated on a silicon substrate to a thickness of 0.4 μm, irradiated with a 20 kV electron beam using the dose as a parameter, and then developed for 15 seconds with a mixed solvent of cyclohexane and inpropyl alcohol at a volume ratio of 1:19. The film thickness of the pattern was measured. Remaining film rate of this pattern is 50% (Dn)
The dose amount to give was about 4 gC/Cm2.

<Example 5> Sensitivity to electron beam 2. of polyvinylphenol (■) "The sensitivity of 3-epoxypropyldimethylsilyl ether (introduction rate lOO%) was determined in the same manner as in Example 4, and the residual film rate was 50.
% dose was 2.0 gC/cm2.

Thus, it can be seen that this negative electron beam resist material has higher sensitivity to electron beams than conventional electron beam resists, and also has higher 02-RIEM properties. Furthermore, by forming a two-layer resist pattern using this negative type electron beam resist material, it is possible to improve the throughput in electron beam phosphorography.

[Method for forming a 112-layer resist pattern Example 1] A resist material such as AZ-2400 is spin-neated at 300 Orpm on a base 10 such as a silicon (St) substrate, and then this is coated at a temperature of about 200°C for about 1 Baked for an hour. Repeat this process once again and
A lower resist layer 12 of AZ-2400 having a total thickness of 2 JLm was formed on the i-substrate 10 (FIG. 3(A)).

Next, a resist film made of the negative electron beam resist material of the present invention is applied to the upper resist layer 14 on the lower resist layer 12.
(Fig. 3 (A)), in this case, the resist material was 2 of Baracresol Nopola 7 resin (I[).
,3-epoxypropyldimethylsilyl ether (■)
was used. This sample (Vl) was dissolved in a xylene solution to prepare a coating solution, and this coating solution was applied by spin coating onto the lower resist layer 12 to a thickness of 0.35 gm, and then at a temperature of about 60 degrees for about 30 minutes. Baking was performed to form an upper resist layer 14.

Next, this upper layer resist [4 was irradiated with an electron beam 16 to draw a 0.5 μm line and space (L/S) pattern (FIG. 3 CB)), in this case,
The accelerating voltage of the electron beam was set to about 20 kV, and the dose was set to about 10 kV.
It was set as gC/cm2.

In the figure, the irradiated portion of the upper resist 14 by this electron beam irradiation is indicated by 14a, and the unirradiated portion is indicated by 14b.

After that, the upper resist 14 is developed and the irradiated area 14a is
An upper resist pattern 18 was obtained (see Fig. 3 (C)).
)) As this developing solution, a mixed solvent in which cyclohexane and Improper Tool were mixed at a volume ratio of 1 part to 19 parts was used. In this case 1, the development time is about 15 seconds, and after development, the sample is rinsed for about 15 seconds with an inproper tool, and then the sample is post-baked at a temperature of about 100°C for about 15 minutes. A resist pattern 18 as schematically shown in ) was obtained.

A sample for observation with a scanning electron microscope (SEM) was prepared from the sample of the upper resist pattern 18 obtained in this way, and when the cross section was observed, it was found that the L/S was 0.5 gm as designed. It was confirmed that the resolution was obtained. Further, the film thickness of the upper resist pattern 18 at that time was 0.3 gm.

Next, using this upper layer resist pattern 18 as an etching mask, lower layer resist pattern 18 (AZ-2400)
02-RIE was performed on 02-RIE to form a lower resist pattern 20 (FIG. 3(D)).
RIE was carried out using the above-mentioned 02-RIE resistance test <Example 2>
The test was carried out under almost the same conditions as in the above case.

The two-layer resist pattern of the upper and lower resist patterns 18 and 12a obtained in this way (FIG. 3(D)
) was observed using SEM, it was found that 0.5 gmL/
It was confirmed that the image was resolved with S. It was also confirmed that the thickness of the lower resist pattern 20 at that time was approximately 2 gm, and that the upper resist pattern remained with a thickness of approximately 0.1 JLm.

Method Example 2 In this example, 2,3-epoxypropyl dimethylsilyl ether (■) of polyvinylphenol (V) is used as the negative electron beam resist material of the upper layer resist. A two-layer resist pattern was formed in substantially the same manner.

The difference between Method Example 2 and Method Example 1 is that the dose of the electron beam is 6 μC/cm 2
The development was performed once for 35 seconds with a mixed solvent of cyclohexane and impropatur at a volume ratio of 1:19.

The lower resist material, the resist thicknesses of the upper layer and the lower layer, and the like are the same as those in Example 1.

When the resulting two-layer resist pattern was observed with an SEM, it was confirmed that a resolution of 0.5 pmL/S was obtained.

It is clear that the invention is not limited only to the embodiments described above, but that many modifications can be made without departing from the scope of the invention.

For example, in the above examples, the phenolic resins include para-cresol novolak resin (II) and 2,3-epoxypropyl dimethylsilyl ether of polyvinylphenol (V) (samples (VI), (■) and (■)). However, other meta-cresol novolak resins (
II) and 4-tert-butylphenol novolak resin (
In the case of 2.3-epoxypropyldimethylsilyl ether (No. 117), as well, as in the case of samples (Vl), (■), and (■) of the example, compared to conventional electron beam resist materials, High sensitivity to electron beams, and high 0
It has 2-RIEIilPt properties, and therefore can be expected to be used for forming a two-layer resist pattern to improve throughput.

Moreover, as already explained, 2.
When the introduction rate of 3-dipoxypropyldimethylsilyl group is set within the range of about 70 to 100 mol% based on the total hydroxyl groups, reactive ion etching against oxygen (0
Although it is preferable to ensure sufficient resistance against RIE (2-RIE) and to improve sensitivity, the introduction rate may be set to be lower than 70% if a slight decrease in effectiveness is acceptable.

Further, in the above embodiments, cyclohexane is used as the saturated hydrocarbon, but n-hexane, n-pentane, n-heptane or any other suitable saturated hydrocarbon can be used.

Furthermore, although Impropatool is used as the lower alcohol, n-propanol, n-phthanol, or any other suitable lower alcohol can be used.

(Effects of the Invention) As is clear from the above description, the negative electron beam resist material of the present invention has a phenol resin containing a 2,3-epoxypropyldimethysilyl group that has high polymerization reactivity to electron beams. 2 JA for electron beams due to the introduction of
It has a high sensitivity of C,/cm2, and
High dry etching resistance.

Therefore, this resist material can be used in electron beam lithography to improve throughput.

[Brief explanation of drawings]

FIG. 1 is a curve diagram showing the electron beam sensitivity characteristics of a resist used to explain this invention, FIG. 2 is a curve diagram showing dry etching resistance characteristics of a resist used to explain this invention, and FIGS. I])
1A and 1B are process diagrams for explaining the resist pattern forming method of the present invention. 1O... Underlayer, 12... Lower layer resist 14... Upper layer resist, 14a... Unirradiated area 14b... Irradiated area, 16... Electron beam'
18... Upper layer resist pattern 20... Lower layer resist pattern. Patent Applicant: Oki Electric Industry Co., Ltd. Same as above Fuji Pharmaceutical Co., Ltd.

Claims (8)

[Claims] (1) A negative electron beam resist material characterized by being 2,3-epoxypropyldimethylsilyl ether of phenolic resin. (2) The scope of claims characterized in that the phenolic resin is one or more selected from the group of para-cresol novolak resin, metacresol novolac resin, 4-tert-butylphenol novolak resin, and polyvinylphenol. Negative electron beam resist material according to item 1. (3) Claim 1 or 2 characterized in that the silyl group introduction rate of 2,3-epoxypropyldimethylsilyl ether of the phenol resin is 70 to 100 mol% of the total phenolic hydroxyl groups. Negative electron beam resist material described above. (4) A step of forming a resist film of 2,3-epoxypropyldimethylsilyl ether of phenolic resin as an upper layer resist on the lower layer resist, a step of writing this upper layer resist with an electron beam, and a step of saturating the upper layer resist after writing. A step of developing with a mixed solvent of hydrocarbons and lower alcohols, and a step of performing reactive ion etching on the lower resist using the obtained upper resist pattern as a mask to form a two-layer resist pattern. A resist pattern forming method characterized by: (5) The resist pattern forming method according to claim 4, wherein the lower resist layer is a photoresist or a polymer. (6) Saturated hydrocarbons such as cyclohexane, n-hexane,
5. The resist pattern forming method according to claim 4, wherein n-pentane or n-heptane is used. (7) The resist pattern forming method according to claim 4, wherein the lower alcohol is isopropanol, n-propanol, or n-butanol. (8) The resist pattern forming method according to claim 4, wherein the reactive ion etching is oxygen plasma etching.