JPS6383721A - Radiation sensitive positive type resist and its production - Google Patents

Abstract

PURPOSE:To improve dry etching resistance and sensitivity by incorporating specific ratios of phenyl alpha-chloroacrylate and 2,2,3,3-tetrafluoropropyl alpha- chloroacrylate into a titled resist. CONSTITUTION:This radiation sensitive positive type resist consists of a copolymer contg. phenyl alpha-chloroacrylate and 2,2,3,3-tetrafluoropropyl alpha-chloroacrylate at 50:50-80:20wt. Radical polymn. is executed under the conditions of 50-65% polymn. rate at the time of producing said copolymer by mixing phenyl alpha- chloroacrylate and 2,2,3,3-tetrafluoropropyl alpha-chloroacrylate and subjecting the same to the radical polymn. The preferable limiting viscosity of the copolymer is 0.5-2.0 limiting viscosity measured at 25 deg.C in methyl ethyl ketone. The radiation sensitive positive type resist provided with both of good dry etching resistance and high sensitivity is thereby obtd.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a radiation-sensitive positive resist used for manufacturing ICs, LSIs, etc. and their ultrafine processing, and a method for manufacturing the same. More specifically, the present invention relates to a radiation-sensitive positive resist that is suitably used when performing microfabrication using a dry etching method, and a method for manufacturing the same.

[Conventional technology]

As a radiation-sensitive positive resist, PBS (poly 1-
butenesulfone) and “EBR-9” (poly 2,2.2-
Trifluoroethyl α-chloroacrylate (manufactured by Toshiku Co., Ltd.), PMMA (polymethyl methacrylate), and the like are used.

Furthermore, as a copolymer of "E B R-9" monomer and other aromatic monomers, a copolymer of 2,2,2-trifluoroethyl α-chloroacrylate and phenyl α-chloroacrylate has been proposed. (Unexamined Japanese Patent Publication No. 57-11)
8243).

[Problem that the invention attempts to solve]

It has been known for a long time that PMM△ is used as a positive-type electric conductor, but it has low sensitivity and has problems with productivity when used for IC, LSI assembly, etc. using electron beam exposure equipment. was there.

PBS has been widely used in the past for the production of photomasks, but its sensitivity varies greatly depending on various conditions during development, as well as temperature and humidity, making it difficult to produce photomasks with good reproducibility and yield. It was difficult.

Recently, in the manufacture of LSIs and the like, as higher integration has progressed, patterns 11] have entered the submicron range. In this case, it is necessary to use dry etching instead of the conventional wet etching method to transfer the resist pattern with good reproducibility.

Generally, in positive type electron beams, sensitivity and dry etching resistance are in a contradictory relationship, and the higher the sensitivity, the worse the dry etching resistance becomes. That is, P
BS has extremely high sensitivity but poor dry etching resistance, while PMMA has some degree of dry etching resistance but 1
The intensity is low.

The above-mentioned phenyl α-chloroacrylate and 2.2.
A copolymer with 2-trifluoroethyl α-chloroaqualer-1 has been proposed, but it is not sufficiently sensitive and has insufficient adhesion to silicon wafers, resulting in cracks in the resist film and the formation of fine patterns after development. This causes problems such as peeling.

The present invention was devised in view of the various drawbacks of the prior art, and its object is to provide a radiation-sensitive positive-working film which has good dry etching resistance and high sensitivity at the same time.

[Means for solving problems]

The object of the present invention is to combine phenyl α-chloroacrylate and 2,2,3,3-tetrafluoropropyl α-chloroaquala-1 in an ω ratio of 50:50 to 80:2.
Radiation-sensitive positive resist made of 0○mu copolymer and phenyl α-chloroacura-1 to 2.2, 3.3
-Tetrafluoropropyl α-taloloaclara-1~ to produce a copolymer by radical polymerization. This is achieved through manufacturing methods.

That is, in the present invention, as a component to be copolymerized with phenyl α-chloroacrylate, 2, 2.3.3
It is important to use -Te1-rafluoropropyl α-chloroacrylate.

In order to achieve higher sensitivity than PMMA, the proportion of phenyl α-chloroacura-1 to 8 in the copolymerization component must be
It is preferable to set it to 0 weight ω% or less, more preferably 70 hands rM% or less.

91 or 50 Iff of phenyl α-chloroacrylate
If it is less than i%, the adhesion to silicon wafers and dry etching resistance will deteriorate. More preferably, the maximum weight is 55% or more.

Therefore, the proportion of phenyl α-taloloaclara-1 to 91 in the total Ide composition is preferably 80% by weight or less, and 50% by weight or more.

The intrinsic viscosity, which is related to the molecular weight of the copolymer, is an important factor in the performance of Regis 1~.

The intrinsic viscosity of the copolymer in the present invention is 0.5-2.
It is preferably after 0, more preferably from 0.9 to 1.6. Generally, the higher the molecular weight, the higher the sensitivity; however, the filterability and coating properties deteriorate, making it difficult to form a good resist film.

The regimen of the present invention] is preferably M as described below.
It is dissolved in a solvent containing CA (methyl cellosolve acetate) as a main component and used as a resist solution, that is, a resist composition. It's impossible. If the solution viscosity is too high, the filtration properties and coating properties will deteriorate (as mentioned above).

The copolymers of the present invention preferably have a solution viscosity in the range of 20 to 70 c.p., more preferably 25 to 45 c.p., when dissolved in MCA at a temperature of 5%.

The solvent for dissolving the polymer of the present invention is not particularly limited, but MCA alone or a mixed solvent mainly composed of MCA is preferably used. As a mixed solvent, especially MC
Those containing 70% or more of A are preferably used.

As the solvent mixed with MCA, known ester-based, ketone-based, etc. solvents can be used.

2 lower alcohols, preferably methanol, in MCA
When it is mixed in an amount of 0 weight or less, the solution viscosity becomes lower at the same polymer temperature, and a better coating film without coating unevenness can be formed. The amount of methanol is more preferably 3 to 10% by weight of the total solvent. If it is less than 3%, the effect will be small, and if it exceeds 10%, the solution viscosity will increase.

As mentioned above, the resist of the present invention is used as a resist solution, but in order to preserve the resist solution using the copolymer of the present invention for a long period of time without changing over time, it is necessary to . It is preferred to add a radical inhibitor into a copolymer containing 3-tetrafluoropropyl α-chloroacrylate and a solvent based on MCA.

In the present invention, when a radical inhibitor is added to a resist solution made of a specific copolymer containing 2,2,3,3-tetrafluoropropyl α-chloroacrylate, the resist solution can be used without causing a change in viscosity. It can be stably stored for a long period of time, for example, for one year or more at room temperature, or for two months or more at 50°C.

The radical inhibitor used in the present invention may be any radical inhibitor as long as it is stable at room temperature, but it is preferably one with a molecular weight of 600 or less. That is, the resist solution is spin-coded onto the substrate and prebaked at 160°C to 210'C, but it is preferable that it evaporate and be lost during prebaking. If the radical inhibitor remains in the resist film after pre-beta, it will precipitate into the resist film and become a compound, causing undesirable effects such as adversely affecting the sensitivity of the resist.

The radical inhibitors used in the present invention include stable radicals such as tri-p-nitrophenylmethyl, diphenylvicrylhydrazyl, and galpinoxyl, benzoquinone, chlorobenzoquinone, 2,5-dichlorobenzoquinone, 2,3-dimethylbenzoquinone, 2. Quinones such as 5-dimethylbenzoquinone, methoxybenzoquinone, methylbenzoquinone, tetrapro[benzoquinone, tetrachlorobenzoquinone, tetrachlorobenzoquinone, trichlorobenzoquinone, 1-rimedylbenzoquinone, α-naph 1--, 2-nitro-1- Naphthols such as naphthol, β-naphthol, 1-nitro-2-naphthol,
Hydroquinone, catechol, resorcinol, o-t-butylphenol, p-methoxyphenol, p-ethoxyphenol, 2,6-di-t-butyl-p-cresol,
2,6-di-1-butylphenol, 2,4-di-t-
Phenols such as butylphenol, 3,5-di-t-butylphenol, 3,5-di-t-butylcatecholoxybenzoic acid, 2,2°-medylenebis (6-t-butylene cresol), 2,4- Examples include nitrophenols such as dinitrophenol, O-nitrophenol, m-nitrophenol, and nitrophenol, but the above-mentioned phenols are particularly preferred in terms of stability and safety.

Of course, oxygen also has an inhibiting effect, but pressurizing an organic solvent with oxygen is not a preferred method because it is extremely dangerous and the amount that can be dissolved in the solvent is limited.

The base of the radical inhibitor used in the present invention is 0.01 to 5%, preferably 0.01 to 5%, based on the weight of the polymer. It is 1-2%.

Next, the manufacturing method of the present invention will be explained.

Phenyl α-chloroacrylate of the present invention and 2.

Copolymers with 2,3,3-tetrafluoropropyl α-chloroacrylate are preferably prepared by bulk or solution polymerization with radical initiators.

Although bulk polymerization without using a solvent is also possible, solution polymerization is more preferable from the viewpoint of polymerization control.

In the case of precipitation polymerization, in which the produced polymer begins to precipitate as soon as the process starts, a resist with good resolution cannot be obtained.

The polymerization solvent used in the present invention may be any solvent as long as it dissolves the monomer and the produced polymer.

Usually, ketones such as acetone and methyl ethyl ketone, ethers such as dioxane and tetrahydrofuran, esters such as ethyl acetate and propyl acetate, and aprotic polar solvents such as dimethylformamide and dimethyl sulfoxide are used.

The amount of solvent used in the procedure is usually 0.3 to the monomer.
~5.0 times the amount, preferably 0.5 to 1.5 times the amount used. If the amount of solvent is small, the polymerization time will be shortened, but the generation of polymerization heat will be significant and control will be difficult. Conversely, if the amount of solvent is large, the polymerization time will be longer, but the polymerization will be easier to control.

The polymerization temperature naturally varies depending on the type of initiator and solvent used, but is usually 30 to 90°C, preferably 40 to 70'C.

The reaction time naturally varies depending on other reaction conditions, such as the polymerization temperature, the type and amount of initiator, the type and amount of solvent, and the ratio of monomers used, but it is usually 2 to 30 hours.
Preferably it is 5 to 20 hours.

In preparing the copolymers of the present invention, the degree of polymerization is important in that it does not significantly affect the performance of the resulting polymer.

Since the reactivity ratios of Amejo Tsuma and Nanatsuma are not equal, the copolymer produced in the early stage of polymerization is richer in phenyl α-chloroacrylate than the charging ratio, and the copolymer produced in the late stage of polymerization is richer in phenyl α-chloroacrylate than the charging ratio. 3. Rich in 3-tetrafluoropropyl α-chloroacrylate.

A polymer obtained at a polymerization rate of 70% or more has a large difference in composition between molecules, causing phase separation when a resist film is formed. It goes without saying that polymers that undergo phase separation cannot be used as the resist 1 to form fine patterns.

We investigated a polymerization method that can form a fine pattern without causing phase separation, and found that the polymerization rate is 65% or less, more preferably 65% or less.
It has been found that polymerization can be carried out at 0% or less. However, from the viewpoint of productivity, it is preferable that the polymerization rate is 50% or more.

The radical initiator used for polymerization is not particularly limited as long as it is used in ordinary radical chassis, but diacyl peroxides such as diacetyl peroxide, dipropionyl peroxide, dibutyryl peroxide, dibenzoyl peroxide, etc. ,2
-azobis(propionitrile), 2,2°-azobis(butyronitrile), 2,2'-azobis(valeronitrile), 2,2-azobis(3-methylbutyronitrile), 2.2' Azobis such as -azobis(2-methylpropionitrile), 2,2-azobis(methyl-2-methyl-propionate), 1,1'-azobis(1-phenylethane), and azohisdiphenylmethane are preferred.

After the combination reaction, it is once dissolved in a solvent, reprecipitated in a non-solvent, washed, and then dried.

The resists 1 to 1 of the present invention are prepared by dissolving the polymer obtained by the above method in a desired solvent together with a radical inhibitor at a predetermined concentration, microfiltering it with a membrane filter of 0.2 to 0.45μ, and using it. It will be done.

The radiation-sensitive positive resist of the present invention thus obtained is suitably used for forming fine patterns on various substrates using an electron beam exposure apparatus, as well as for fine processing using various dry etching methods. Of course, since it has sufficient adhesion to the substrate, it can also be used for wet etching.

Also far ultraviolet light, soft X$3;! Since it is also sensitive to electromagnetic waves, it can also be used for batch transfer using the electromagnetic waves mentioned above.

Method for measuring properties and evaluating effectiveness ■ Method for measuring sensitivity of radiation-sensitive positive resist First, dissolve the polymer in a suitable solvent such as methyl cellosolve azetate and apply it to a 0.2-0.45μ membrane filter. and filter to prepare a resist solution. This resist solution is applied onto a substrate using a spinner to form a uniform resist solution with a thickness of 0.4 to 1.0 .mu.m.

Next, remove the solvent! Perform pre-bake treatment to improve adhesion to J plate. In the case of the radiation-sensitive positive resist of the present invention, it is preferable to prebake at 160'C to 210C for 15 minutes to 1 hour.

Using an electron beam exposure device, a fixed area on the substrate is exposed at 10 to 20 locations with a fixed amount of current, while changing the exposure time geometrically. For the exposed portion, the amount of electricity per unit area (μC/cnf) is calculated from the area, amount of current, and exposure time.

Next, the substrate is immersed in a suitable developer at a constant temperature for a certain period of time, and then immersed in a non-solvent for rinsing. After drying, post-bake the substrate. Generally, it is preferable to set the temperature at which the boss 1 to plate is lower than the glass transition temperature of the polymer.

Measure the film thickness of exposed and unexposed areas on the substrate using a surface roughness meter or the like. A sensitivity curve is created by plotting the amount of electricity (exposure amount) on the horizontal axis and the film thickness of the exposed portion on the vertical axis. Sensitivity is defined as the point where this sensitivity curve intersects with the horizontal axis.

The film thickness before exposure is also measured and compared with the film thickness of the unexposed area after development, and the decrease is taken as film reduction.

Generally, in a radiation-sensitive positive resist, the polymer in the exposed portion undergoes main chain scission, resulting in a decrease in molecular weight. When this is developed, the polymer in the exposed areas dissolves at a faster rate than the polymer in the unexposed areas, thus forming a resist pattern. In this manner, during development, the film thickness of the unexposed portion is always reduced compared to before development.

The sensitivity of radiation-sensitive positive resists varies depending on the type of developer, temperature, development time, and resist film thickness, and data on sensitivity alone is meaningless unless these are described. That is, when a long development time and a high development temperature are used, the sensitivity apparently increases, but the film loss also increases.

(2) Method for evaluating the adhesion of a positive resist to a semiconductor substrate such as a silicon wafer The formation of a resist film is the same as in the method for measuring sensitivity described above. A line and space or lattice pattern of 0.5 to 5 μm is exposed and developed by electron beam exposure.

In general, positive pear-shaped wires 1 to 1 are coated on a substrate and then prebaked at a temperature above the glass transition point.

Since the resist is considered to be in a liquid state during pre-beta, there is no strain between it and the substrate. When this is cooled to air temperature, resist film thickness distortion stress occurs because the polymer forming the resists 1 to 1 generally has a larger coefficient of thermal expansion than the substrate.

If the adhesive strength between the substrate and the resist is not sufficient, cracks will occur in the resist film during development due to this strain.

In addition, if the adhesive strength between the substrate and resist is not sufficient, 1μ
The following patterns may peel off during development.

The above is evaluated by observing vA using an optical microscope with a magnification of 100 to 1000 times.

(Example) Example 1 Phenyl α-chloroacrylate 5.5C1,2°2.
3.3-te1-lafluoroprobil α-chloroacrylate 4.5 g, azobisisobutyronitrile 35 ma,
Acetone8. ○q was placed in a 200 ml eggplant flask and stirred to dissolve. After purging the inside of the flask with nitrogen, polymerization was carried out in a water bath at 50'C for 9 hours.

The obtained polymer was dissolved in 70ml of methyl ethyl ketone and mixed with a mixture of methanol and water (2:1)10. The polymer was poured into the container and re-precipitated. The precipitated polymer was separated and dried in a vacuum dryer. A copolymer of 5.91C] was obtained. Polymerization conditions, intrinsic viscosity at 25°C in methyl ethyl ketone, 5
% MCA solution solution viscosity and elemental analysis values are shown in Table 1. The composition of the copolymer calculated from the elemental analysis values is phenyl α-
Chloroacrylate: 2,2,3,3-tetrafluoropropyl α-chloroacrylate-1 ~ 63:37 (ff
1 amount ratio).

5.0CI of polymer powder obtained by the above method, 2.6-di-t-butyl-p-cresol (BHT>50mg)
．． It was dissolved in a mixed solvent of 3 g of MCA:methanol at a ratio of 95:5 and filtered under nitrogen pressure using a 0.2μ membrane filter.

Spin the resist solution onto the silicon wafer at 1000 revolutions! ~ and prebaked at 200'C for 30 minutes.

The resist film thickness was 5530.

The resist film was transparent and no clouding due to phase separation was observed.

Using an electron beam exposure device (Elionix ERE-301), 7JO speed voltage 20 kV, current Q 2 rl A 0
．． An area of 45 x 0.60 mm was scanned and exposed while sequentially changing the exposure time. At the same time, lines and spaces of 1μ were exposed.

Substrate with methyl isopropanol 8
3 minutes under stirring at 25°C in a developer of 2:18 (weight ratio)>
The sample was soaked in H and then in isopropanol for 30 seconds.

It was post-baked at U100'C for 30 minutes, and the resist film thicknesses of the unexposed and exposed areas were sequentially measured to create a sensitivity curve.

Sensitivity is 12μChart, film loss in unexposed areas is 100
It was a person.

When the line and space areas and unexposed areas were inspected using an optical microscope, no peeling of the pattern or cracks in the resist film were observed.Next, a PMMA film was coated using a parallel plate reactive ion etching device. Dry etching was performed together with the wafer, and the film reduction speeds of both were compared.

Etching gas is carbon tetrafluoride:oxygen 96:4, pressure 4
．． Etching was performed at OPa, 25° C., 0.64 w/− for 3 minutes. After the edge leg, the film thickness was measured and the film thinning rate was calculated. The film reduction rate of PMMA is 660 people/min, and the resist of the present invention has a film reduction rate of 430 people/min (PMMA ratio 0.65
times).

Examples 2 and 3.4 The same method as in Example 1 was used to prepare a copolymer of 10 by changing the ratio of monomers charged. The conditions and results are shown in Table 2. The solubility of the polymer of the present invention decreases as the content of phenyl α-chloroacrylate increases. In this example, known polymers (phenyl α-chloroacrylate and 2.2.2-
In order to strictly compare the sensitivity with the copolymer (copolymer with 1-trifluoroethyl α-chloroacrylate), a developer was used that gave the same film loss under the same development conditions.

As the content of phenyl α-taloloacrylate 1 increases, the culm sensitization becomes lower, but the dry etching resistance 111 increases. The composition of the copolymer is determined depending on the purpose of use. The sensitivity to d3 P M M under the same conditions is 50 μC/
car, it can be seen that the uninvented polymer is superior in both sensitivity and dry etching resistance.

Comparative Examples 1 and 2 Using the same seven polymers as in Example 1, 1 d of copolymer was produced under the polymerization conditions shown in Table 1.

Prepare a resist solution, coat it on a silicon wafer, and look at the 08 field of view of the optical box microscope at 11! l! Upon inspection, white turbidity was observed due to phase separation of the polymer.

Further, when a 1 μm line-and-space resist pattern was formed in the same manner as in Example 1, the edge roughness was inferior to that in Example.

Comparative Example 3 + 415 A copolymer consisting of phenyl α-chloroacryla-1~ and 2.2.2-trifluoroedyl α-chloroacryla-1~ was prepared by the same method as in Example 1 into 1-I! ′:′,.

These copolymers were prepared using methyl isobutylene at 25°C.
In this case, the film loss is approximately half that of the copolymer of the present invention with a corresponding copolymer composition. is approximately the same as the polymer of the present invention, which has a corresponding 21 polymer composition.

A solution was prepared, coated on a silicon wafer, and evaluated in the same manner as in Example 1 (cracks J3 and peeling of fine patterns were observed in one area from Regime 1 to the elbow).

Comparative Example 6 In the same method as Example 1, the phenyl α -ri [Loa Clila -1) to 2.2.2-1 to Lefluo Exit α -Lolo Cryla -1 ~

In this case, the Φ combined pressure ratio was as low as 58.1%, so no phase separation was observed in the coating film 1; The pattern of (j, he still observed.

(Effects of the Invention) Since the present invention is configured as shown in Fig.
It is now possible to transfer the resulting positive-type wire-sensitive film and its manufacturing method.

Claims (4)

[Claims] (1) Phenyl α-chloroacrylate and 2,2,3,
A radiation-sensitive positive resist made of a copolymer containing 3-tetrafluoropropyl α-chloroacrylate in a weight ratio of 50:50 to 80:20. (2) The radiation-sensitive positive resist according to claim (1), which has an intrinsic viscosity of 0.5 to 2.0 as measured at 25°C in methyl ethyl ketone. (3) Solution viscosity at 25°C when dissolved in methyl cellosolve acetate at 5% temperature is 20-70c. p. A radiation-sensitive positive resist according to claim (1). (4) Phenyl α-chloroacrylate and 2,2,3,
3-Tetrafluoropropyl α-chloroacrylate is mixed with 3-tetrafluoropropyl α-chloroacrylate to produce a copolymer by radical polymerization, and the radical polymerization is carried out at a polymerization rate of 50 to 65%. Law.