JP2002365803A - Resist composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resist composition for ArF excimer laser having such radiation resistance as to ensure a small dimensional change under observation with a scanning electron microscope(SEM), as a resist composition containing a methacrylate resin and a photo-acid generator. SOLUTION: The resist composition contains (A) a copolymer containing methyladamantyl methacrylate and norbornene carbolactone methacrylate as constitutional units, (B) a photo-acid generator and (C) a cholic acid derivative of formula (1) (where R1 -R3 are each H, hydroxyl or tert-butyl and R4 is H or tert-butyl).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a resist composition, and more particularly to a chemically amplified resist composition having excellent radiation resistance.

[0002]

2. Description of the Related Art In a conventional photolithography technique, g-line (436 nm) and i-line (365 n)
m), and as the resist, a dissolution-suppressing positive resist using a novolak resin as a base resin and naphthoquinonediazide as a photosensitive agent was mainly used. However, lithography using excimer laser light (248 nm, 193 nm, etc.), which is far ultraviolet light that is advantageous for miniaturization, is required, and a conventional g-line or i-line resist has too large light absorption as a resist. A good resist pattern could not be obtained, and the sensitivity was greatly increased.

A resist for an ArF excimer laser lithography having an exposure wavelength of 193 nm has a particularly large problem of light absorption, and the components of the resist are greatly restricted. Such a resist composition suitable for irradiation with an excimer laser includes a component having an acid dissociable functional group and an acid catalyst generated from a component that generates an acid upon irradiation with light (hereinafter, referred to as a “photoacid generator”). Many chemically amplified resists utilizing an amplification reaction have been proposed. For example, the carboxylic acid tert
A composition containing a polymer having a -butyl ester group or a tert-butyl carbonate group of phenol and a photoacid generator has been proposed (see Japanese Patent Publication No. 2-27660). Also, in order to improve the shape of the resist pattern by increasing the light transmittance of the resist film, a (meth) acrylate resin represented by polymethyl methacrylate, which is highly transparent to far ultraviolet rays and excellent in light transmittance, is used. There has been proposed a chemically amplified resist composition using the same.
-226461). Furthermore, in order to improve dry etching resistance and appropriately control acid diffusion to improve pattern shape, sensitivity, resolution, etc., a high molecular weight or low molecular weight additive is blended to form a multi-component composition of three or more components. Many proposals have been made (for example, see JP-A-11-2024).
No. 91).

[0004]

However, after exposure and development using these resins, a scanning electron microscope (SEM) observation is performed to confirm the resist pattern, and the volume of the resist is reduced by electron beam irradiation. I do. SE
M observation is an essential step after exposure and development regardless of prototypes and products in order to confirm whether exposure and development have been performed properly. Also, in order to check the uniformity of the exposed and developed states in the wafer, some chips on the wafer were extracted and SEM
Since the observation is performed, not all chips are performed. For this reason, in the chip subjected to SEM observation, the resist is reduced and the pattern size is reduced.
The pattern dimension of the chip not subjected to SEM observation does not change. As a result, the in-plane uniformity of the pattern dimensions is adversely affected, and it is necessary to minimize the dimensional fluctuation due to SEM observation.

For example, a resist comprising a copolymer resin containing 2-methyl-2-adamantyl methacrylate and 2,6-norbornene carboractone methacrylate in a weight ratio of 50:50 and a photoacid generator are prepared, and an antireflection film is prepared. It was coated on a substrate and exposed and developed to resolve a 140 nm line and space. FIG. 1 shows the time variation of the dimensional variation of the resist pattern when the resist pattern was observed for 45 seconds with an electron microscope (SEM) at 4 pA and 800 V. It is thought that the size changes due to SEM observation occur because the ester bond of the methacrylate resin is cut by electron beam irradiation and the structure is destroyed. However, as shown in FIG. After 5 seconds, the size of the resist pattern becomes 10 nm
It is also difficult to accurately determine conditions such as exposure and focus because of fluctuation (reduction). In addition, it is not possible to reconfirm the location once observed by SEM, and there is a problem in that dimensional uniformity is deteriorated by observing the pattern by SEM.

Accordingly, the present invention provides a resist composition comprising a methacrylate resin and a photoacid generator.
An object of the present invention is to provide a chemically amplified resist composition for ArF excimer laser, which has a small amount of dimensional variation of a resist pattern during SEM observation and has radiation resistance.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above problems, and is directed to (A) a copolymer containing methyl adamantyl methacrylate and norbornene carboractone methacrylate as constituent units, and (B) a photoacid. Provided is a resist composition comprising a generator and (C) a cholic acid derivative represented by the general formula (1). (1) (In the general formula (1), R ₁ , R ₂ and R ₃ are each independently a hydrogen atom, a hydroxyl group or a tert-butyl group;
₄ is a hydrogen atom or a tert-butyl group. )

In a preferred embodiment, the component (A) further comprises γ-butyrolactone methacrylate as a constituent unit.

In a further preferred embodiment, the copolymer (A) contains methyl adamantyl methacrylate in an amount of 30 to 80% by weight in the copolymer.

[0010] In another preferred embodiment, the component (C) is cholic acid, lithocholic acid, deoxylithocholic acid,
tert-butylcholic acid, tert-butyllithocholic acid and te
It is characterized in that it is at least one compound selected from rt-butyldeoxycholic acid.

In a further preferred embodiment, the resist composition of the present invention is characterized in that it contains 1 to 15% of the cholic acid derivative represented by the above general formula (1).

The reason that the resist composition having such a composition can provide radiation resistance is that even if an ester bond is decomposed by irradiation to form a free volume, tert-butylcholate or the like added as the component (C) is not used. It is presumed that the high carbon density has the effect of suppressing the structural relaxation of the resist.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Component (A) The component (A) in the present invention has an alkali-soluble group protected by a dissolution inhibiting group, and the dissolution inhibiting group is dissociated by the action of an acid generated by the photoacid generator to have a carboxyl group. A resin that becomes an alkali-soluble resin is used. Preferably, it is a copolymer (hereinafter, referred to as “polymer (A)”) made of a methacrylate resin containing methyl adamantyl methacrylate and norbornene carboractone methacrylate as essential constituent units. In the present invention, by using the polymer (A) comprising such a methacrylate resin in the main chain, it is possible to obtain, as a resist, a resist composition having particularly excellent transparency to radiation and resistance to dry etching.

The polymer (A) may contain the above essential constituent unit as a main component. In addition, the polymer (A) dissociates in the presence of an arbitrary constituent unit, preferably an acid, to generate an acidic functional group. One or more other structural units can be contained. Specific examples of these include γ-butyrolactone methacrylate.

The ratio of each component in the polymer (A) can be used in any ratio. In particular, methyl adamantyl methacrylate is used in the polymer (A) in an amount of 30%.
Preferably, it is contained at a ratio of about 80% by weight. The weight average molecular weight of the polymer (A) is usually from 5,000 to 15,
000, preferably 8,000 to 12,000.
In this case, the weight average molecular weight of the polymer (A) is 5,000.
If it is less than 15,000 or more than 15,000, the resolution as a resist tends to decrease. The polymer (A) in the present invention is preferably as low as possible in impurities such as halogens and metals, whereby the sensitivity, resolution, process stability, pattern shape and the like as a photosensitive resist are further improved. As a method for purifying the polymer (A), for example,
Examples include chemical purification methods such as washing with water and liquid-liquid extraction, and combinations of these chemical purification methods with physical purification methods such as ultrafiltration and centrifugation.

Component (B) The component (B) of the present invention comprises a photoacid generator which generates an acid upon irradiation with radiation (hereinafter referred to as "exposure"). The photoacid generator (B) dissociates the carboxyl group in the polymer (A) by the action of the acid generated by the exposure, and as a result, the exposed portion of the resist film becomes easily soluble in an alkali developing solution, so that the positive type It has the function of forming a resist pattern. Examples of such a photoacid generator (B) include an onium salt, a halogen-containing compound, a diazoketone compound, a sulfone compound, and a sulfonic acid compound.

Specific examples of these photoacid generators (B) include diphenyliodonium trifluoromethanesulfonate, bis (4-tert-butylphenyl) iodonium trifluoromethanesulfonate, and bis (4-tert-butylphenyl) iodonium nonafluoro. n-butanesulfonate, triphenylsulfonium trifluoromethanesulfonate, triphenylsulfonium nonafluorobutanesulfonate, cyclohexyl (2-oxocyclohexyl) sulfonium trifluoromethanesulfonate, dimethylphenylsulfonium trifluoromethanesulfonate, dimethylphenylsulfonium nonafluorobutanesulfonate, and the like. Can be

In the present invention, the photoacid generator (B) can be used alone or in combination of two or more. The amount of the photoacid generator (B) used depends on the sensitivity as a resist and the development. From the viewpoint of ensuring the properties, it is usually 0.1 to 10 parts by weight, preferably 0.5 to 7 parts by weight, based on 100 parts by weight of the polymer (A). In this case, the photoacid generator (B)
If the amount used is less than 0.1 part by weight, the sensitivity and developability of the resist tend to decrease, while if it exceeds 10 parts by weight, the transparency to radiation decreases as the resist and a rectangular resist pattern is obtained. Tends to be difficult to be performed.

Component (C) Next, the component (C) in the present invention is represented by the general formula (1):
And a cholic acid derivative represented by In the present invention,
R _{4 in the} general formula (1) is characterized by being a hydrogen atom or a tert-butyl group, and it is considered that a similar effect can be obtained when the compound has a substituent such as a methyl adamantyl group. Can be Since the component (C) of the present invention has a high carbon density and a high bulk, even if the ester bond in the resist resin is decomposed by radiation irradiation to generate a free volume, the volume reduction due to this is reduced and the structure of the resist film is reduced Is considered to be stable. In the present invention,
The component (C) can be used alone or in combination of two or more. The amount of the component (C) used is the amount of the polymer (A) 1
The amount is usually 20 parts by weight or less, preferably 1 to 15 parts by weight with respect to 00 parts by weight. In this case, if the amount of the component (C) is less than 1 part by weight, the effect of radiation resistance is small, and if it exceeds 20 parts by weight, the lithography performance tends to be significantly reduced.

[Various Additives] Furthermore, the resist composition of the present invention suppresses the diffusion phenomenon of the acid generated from the photoacid generator (B) in the resist film upon exposure, and prevents an undesired chemical reaction in the unexposed area. An acid diffusion controller having an inhibitory action can be blended. When the acid diffusion controller is added, the storage stability of the obtained resist composition is further improved, the resolution as a resist is further improved, and a change in the time from exposure to development (PED) of a resist pattern is caused. It is possible to suppress a change in line width and to obtain a composition having extremely excellent process stability. As the acid diffusion controller, a nitrogen-containing organic compound whose basicity does not change by exposure or heat treatment during the resist pattern forming step is preferable. Examples of such nitrogen-containing organic compounds include monoamino compounds, diamino compounds, polymers having three or more nitrogen atoms, amide group-containing compounds, urea compounds, and nitrogen-containing heterocyclic compounds.

The resist composition of the present invention may optionally contain a surfactant having an effect of improving coating properties and developability. Examples of such a surfactant include nonionic surfactants such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether. These surfactants can be used alone or in combination of two or more. The amount of the surfactant is usually 2 parts by weight or less based on 100 parts by weight of the total of the polymer (A), the photoacid generator (B) and the cholic acid derivative (C). In addition, examples of the additives other than the above include an antihalation agent, an adhesion aid, a storage stabilizer, and an antifoaming agent.

[Preparation of Composition Solution] The chemically amplified resist composition of the present invention usually has a total solid content of, for example, 5 to 50% by weight, preferably 10 to 20%, when used.
By dissolving in a solvent so that the weight% becomes, for example, by filtering through a filter having a pore size of about 0.2 μm,
It is prepared as a composition solution. Examples of the solvent used for preparing the composition solution include 2-butanone and 2-butanone.
Linear ketones such as pentanone, 2-heptanone, 3-methyl-2-butanone, 2-hexane, 4-methyl-2-pentanone; cyclic ketones such as cyclopentanone; propylene glycol monomethyl ether acetate, propylene glycol mono Propylene glycol monoalkyl ether acetates such as ethyl ether acetate; alkyl 2-hydroxypropionates such as methyl 2-hydroxypropionate and ethyl 2-hydroxypropionate; and ethyl lactate.

[Method of Forming Resist Pattern] The resist composition of the present invention is particularly useful as a chemically amplified positive resist. When forming a resist pattern, the resist composition of the present invention, by appropriate coating means such as spin coating, casting coating, roll coating, for example, on a substrate such as a silicon wafer, a wafer coated with aluminum After coating, a resist film is formed, and if necessary, a heat treatment is performed, and then the resist film is exposed so as to form a predetermined resist pattern. The radiation used at this time is preferably an ArF excimer laser (wavelength 193 nm) or a KrF excimer laser (wavelength 248 nm). In the present invention, it is preferable to perform a heat treatment (hereinafter, referred to as “PEB”) after the exposure. By this PEB treatment, the dissociation reaction of the acid-dissociable organic group proceeds smoothly. The heating conditions for PEB vary depending on the composition of the resist composition, but are usually 30 to 2 times.
00 ° C, preferably 50 to 170 ° C.

[Observation by Electron Microscope (SEM) and Measurement of Dimensional Variation] When a sample surface is irradiated with a finely focused electron beam, secondary electrons, reflected electrons, Auger electrons, X
Lines, fluorescence, etc. are generated. The amount of emitted secondary electrons changes due to minute irregularities on the sample surface. If the incident electron beam is two-dimensionally scanned on the sample surface and the generated secondary electrons are detected as an image signal, a contrast image corresponding to the unevenness of the surface shape can be obtained. This is the principle of a scanning electron microscope. Super LS
In order to perform the process control of I with high accuracy, it is necessary to measure dimensions of a photoresist, a film after etching, and the like in-line. These measurements are made fully automatically and quickly,
In addition, it is necessary to return the wafer to the manufacturing process after the measurement, and the pattern measurement requires accuracy, speed, reproducibility and nondestructive properties. Therefore, a dedicated apparatus based on a scanning electron microscope has been developed. Since this is a nondestructive inspection, it is preferable to perform observation and measurement at a low energy of 1 keV or less in order to avoid occurrence of damage due to electron beam irradiation. Nevertheless, in the prior art, as described above (shown in FIG. 1), a significant dimensional change has been a problem with the passage of SEM observation time, but the resist composition of the present invention has
It was found that the radiation resistance during EM observation was extremely large. FIG. 2 shows that 2-methyl-2-adamantyl methacrylate, 2,6-norbornene carboractone methacrylate, and γ-butyrolactone methacrylate were mixed at 50: 3 as described in detail in Examples described later.
To the polymer (A) containing a ratio of 0:20, a photoacid generator and te
0, 5, 10, 15% of rt-butyl cholate respectively
The resist pattern containing the prepared resist composition was coated on an anti-reflective coating substrate, exposed and developed, and a 130 nm liner-and-space resolved resist pattern was observed for 5 seconds with a 4 pA, 800 V electron microscope (SEM). This shows the amount of dimensional variation of the resist pattern. From the results in FIG.
The dimensional variation (5 nm) when 10% of tert-butyl cholate was added was 7 times greater than that without (12 nm).
It can be seen that the radiation resistance was improved by decreasing the particle diameter by nm.

[0025]

EXAMPLES Hereinafter, the resist composition according to the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples.

Example 1 100 parts by weight of a methacrylate resin represented by the formula (2) as a component (A) (molar ratios represented by x, y and z in the formula are specifically shown in Table 1). When,
2.0 parts by weight of triphenylsulfonium nonafluorobutanesulfonate as the component (B) and tert-butylcholate, tert-butyllithocholate or
Any one of tert-butyl deoxycholate 5
15.0 parts by weight and 0.2 parts by weight of triethanolamine as other components were mixed in the amounts shown in Table 1, and these were dissolved in 700 parts by weight of propylene glycol monomethyl ether acetate to form a positive resist solution. I got (2)

Next, this resist solution is applied on an anti-reflection film using a spinner, and is applied on a hot plate.
By drying at 0 ° C. (pre bake) for 60 seconds, a resist layer having a thickness of 400 nm was formed. Then
After selectively irradiating an ArF excimer laser (193 nm) with an ArF exposure apparatus (manufactured by Nikon),
PEB treatment at 30 ° C. for 60 seconds, then 2.38% by weight
Paddle development with an aqueous solution of tetramethylammonium hydroxide for 60 seconds, washing with water for 30 seconds and drying.

With the limiting resolution of the resist pattern formed by such an operation, a 120 nm line and space pattern was formed at a ratio of 1: 1. As a result of measurement that time the exposure time (sensitivity) mJ / cm @ 2 (energy amount) in units were 16.0mJ / cm ^2. Also, 1
A 30 nm line-and-space 1: 1 pattern shape was a good resist pattern with high perpendicularity.

Further, no peeling of the resist pattern was observed and the adhesion was good. Using the pattern obtained above, as an evaluation of line slimming for the evaluation of radiation resistance, a 140 nm isolated pattern was measured using a lateral SEM trade name "S-8820" (manufactured by Hitachi, Ltd.) under measurement conditions of 4 p.
A, the resist pattern width was measured at 800 V (the time affected by the electron beam was about 5 seconds).
The resist pattern having a width of 40 nm hardly changed.

[0030]

[Table 1]

Example 2 In Example 1, each unit in the component (A) was replaced with (x = 50 mol%, y = 30 mol%,
z = 20 mol%) and a positive resist solution was prepared in the same manner as in Example 1 except that the component (C) was changed to cholic acid (3%), and then a resist pattern was formed under the same conditions as in Example 1. Formed.

The critical resolution of the resist pattern formed by such an operation was a line-and-space pattern of 130 nm having a ratio of 1: 1. As a result of measurement that time the exposure time (sensitivity) mJ / cm @ 2 (energy amount) in units were 14.0mJ / cm ^2. Also, 1
A 30 nm line-and-space 1: 1 pattern was a good resist pattern with high perpendicularity. Further, as a result of evaluating the line slimming of the resist pattern, a dimensional change of 6.8 nm was confirmed.

Comparative Example 1 In Example 1, each unit in the component (A) was replaced with (x = 50 mol%, y = 30 mol%,
z = 20 mol%), a positive resist solution was prepared in the same manner as in Example 1 except that the component (C) was not added (0%), and then the resist pattern was prepared under the same conditions as in Example 1. Was formed.

With the limiting resolution of the resist pattern formed by the above operation, a 130 nm line and space pattern was formed at a ratio of 1: 1. As a result of measurement that time the exposure time (sensitivity) mJ / cm @ 2 (energy amount) in units were 14.0mJ / cm ^2. Also, 1
A 30 nm line-and-space 1: 1 pattern was a good resist pattern with high perpendicularity. Further, as a result of evaluating the line slimming of the resist pattern, a dimensional change of 12 nm was confirmed.

Comparative Example 2 In Example 1, each unit in the component (A) was replaced with (x = 50 mol%, y = 50 mol%,
z = 0 mol%) to 100 parts by weight of the copolymer,
A positive resist solution was prepared in the same manner as in Example 1 except that the component (C) was not added (0%), and a resist pattern was formed under the same conditions as in Example 1. With the critical resolution of the resist pattern formed by such an operation, a 130 nm line and space pattern was formed at a ratio of 1: 1.

The exposure time (sensitivity) at that time is set to mJ /
When measured in cm 2 (energy amount), 14.
It was 0 mJ / cm ² . In the case of a pattern shape having a line and space of 1: 1 of 130 nm, the resist pattern had high perpendicularity and was a good resist pattern. Further, as a result of evaluating the line slimming of the resist pattern, a dimensional change of 14 nm was confirmed.

Comparative Example 3 In Example 1, each unit in the component (A) was replaced with (x = 50 mol%, y = 0 mol%, z
= 50 mol%) to 100 parts by weight of the copolymer
A positive resist solution was prepared in the same manner as in Example 1 except that the component (C) was not added (0%), and a resist pattern was formed under the same conditions as in Example 1.

The critical resolution of the resist pattern formed by such an operation was a line-and-space pattern of 130 nm having a ratio of 1: 1. As a result of measurement that time the exposure time (sensitivity) mJ / cm @ 2 (energy amount) in units were 14.0mJ / cm ^2. Also, 1
A 30 nm line-and-space 1: 1 pattern was a good resist pattern with high perpendicularity. Further, as a result of evaluating the line slimming of the resist pattern, a dimensional change of 16 nm was confirmed.

[0039]

Since the resist composition of the present invention is excellent in SEM resistance, a semiconductor device such as an VLSI manufactured by using the resist composition can measure the film size after photoresist etching by, for example, in-line by SEM. Measurement can be performed quickly and accurately. This makes it possible to control the process of the VLSI or the like with high accuracy, which greatly contributes to stable product quality.

[Brief description of the drawings]

FIG. 1 shows a dimensional variation amount when a resist pattern exposed and developed using a conventional resist is observed for 45 seconds by SEM.

FIG. 2 shows a resist pattern obtained by exposing and developing the resist composition according to the present invention by changing the amount of component (C) added.
The dimensional variation when observed at M for 5 seconds is shown.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hideo Haneda 150 Nakamaruko Nakahara-ku Kawasaki City Kanagawa Prefecture Inside Tokyo Ohka Kogyo Co., Ltd. F term (for reference) 2H025 AA03 AB16 AC04 AC08 AD03 BE00 BE10 BG00 CB08 CB14 CB41 CC20 FA17 4J100 AL08P AL08Q AL08R BC09P BC27Q BC53Q BC53R CA04 CA05 DA01 JA38

Claims (5)

[Claims] 1. A copolymer containing (A) methyl adamantyl methacrylate and norbornene carboractone methacrylate as constituent units, (B) a photoacid generator,
(C) a cholic acid derivative represented by the following general formula (1):
A resist composition comprising: (1) (In the general formula (1), R ₁ , R ₂ and R ₃ are each independently a hydrogen atom, a hydroxyl group or a tert-butyl group, and R ₄ is a hydrogen atom or a tert-butyl group.) 2. The resist composition according to claim 1, wherein the component (A) further contains γ-butyrolactone methacrylate as a constituent unit. 3. The resist composition according to claim 1, wherein the component (A) contains methyl adamantyl methacrylate in a proportion of 30 to 80% by weight in the copolymer. 4. The component (C) is at least one compound selected from cholic acid, lithocholic acid, deoxycholic acid, tert-butylcholic acid, tert-butyllithocholic acid and tert-butyldeoxycholic acid. The resist composition according to claim 1, wherein: 5. The resist composition according to claim 1, wherein the composition contains 1 to 15% of a cholic acid derivative represented by the general formula (1).