JP2003186190A - Resist material and exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable an ultra-microfabrication superior to the conventional techniques by using a polymeric material having low absorption in the wavelength region of vacuum ultraviolet radiation (VUV). <P>SOLUTION: In an exposure method in which a resist layer is selectively exposed with UV and patterned in a prescribed shape, a polymeric material having an introduced cyclopentane group in which one or more of hydrogen atoms combining to each of adjacent two carbon atoms have been replaced with fluorine atoms is used as a polymeric material forming the resist layer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resist material and an exposure method for performing fine processing in, for example, the field of semiconductors.

[0002]

2. Description of the Related Art In the field of semiconductors, for example, with the high integration of semiconductor elements, there is an urgent need to establish a new process technology capable of processing an ultrafine pattern of, for example, 0.1 μm or less.

A so-called lithographic technique is indispensable for processing a fine pattern, and in order to improve optical resolution and cope with ultra-fine processing by shortening an exposure wavelength.
Conventional mercury lamp g-line, i-line and KrF (Krypton
Fluorine: a wavelength of 248 nm) and ArF (argon / fluorine: a wavelength of 193 nm) excimer laser ultraviolet ray lithography technology has been industrially applied. These techniques are applied to the fabrication of devices having a design rule of 0.13 μm or more due to the limitation of resolution due to the wavelength.

On the other hand, there is an urgent need to develop a new lithography technique that enables the fabrication of devices having a design rule of 0.1 μm or less. Therefore, vacuum ultraviolet rays (VUV: VUV: 170 nm or less) obtained by further shortening the wavelength of the exposure light source used in the conventional lithography technique.
The development of new exposure technology using vacuum ultraviolet rays is being actively pursued. As a specific light source, F ₂
Development of a lithography technique using a (fluorine dimer) excimer laser (wavelength: 157 nm) is proceeding as a successor to the existing lithography technique, ArF lithography. Moreover, as a successor to F ₂ lithography,
Ar ₂ (Argon dimer) excimer laser (wavelength 126
nm) has been proposed.

[0005]

However, in the above-mentioned vacuum ultraviolet (VUV) wavelength region, ordinary organic materials that have hitherto been used as resist materials have large optical absorption, and the irradiated light is resist. There is a problem that a rectangular resist pattern having a good shape cannot be formed without reaching the lower part of the layer, and the resist pattern deteriorates. That is, for example, a novolac resin (for i-line lithography), a polyhydroxystyrene resin (Kr) that serves as a main skeleton of a polymer that constitutes an existing resist material.
Resins such as F lithography) and acrylic resins (ArF lithography) have large optical absorption in the vacuum ultraviolet region, and cannot be used as resist materials for VUV lithography.

Therefore, as a measure against resist pattern deterioration, the resist film thickness is reduced to about 70 nm or less to improve the transmittance of the resist layer as a whole, but the resist film thickness is thin. Therefore, there are problems that sufficient etching resistance cannot be obtained and that the number of defects in the resist layer increases due to thinning.

As another countermeasure for resist pattern deterioration, a surface imaging method involving a silylation reaction or the like that enables patterning even with low transmittance has been applied.
The surface imaging method has problems that the edge portion of the resist pattern is significantly roughened and that the dimensional controllability is not sufficient.

Therefore, the present invention has been proposed in view of such conventional circumstances, and it is an object of the present invention to provide a resist material using a polymer material having low light absorption in the wavelength range of vacuum ultraviolet (VUV). To aim. Another object of the present invention is to provide an exposure method using the above resist material, which enables finer processing than ever before.

[0009]

DISCLOSURE OF THE INVENTION The present invention is directed to a vacuum ultraviolet region of an alicyclic group which tends to be more transparent among aromatic rings and alicyclic groups which are groups for maintaining etching resistance. The present invention relates to a method for more efficiently reducing the light absorption of. Particularly, the present invention relates to an efficient method of reducing light absorption when a cyclopentane group is used as an alicyclic group.

That is, the resist material according to the present invention is
A polymer material containing a cyclopentane group as an alicyclic group, characterized in that one or more hydrogen atoms bonded to two adjacent carbon atoms of the cyclopentane group are each substituted by a fluorine atom. And

Further, the exposure method according to the present invention is an exposure method in which a resist layer is selectively exposed to ultraviolet rays to be patterned into a predetermined shape, and two carbons adjacent to each other are used as the polymer material forming the resist layer. It is characterized in that a polymer material in which a cyclopentane group in which one or more hydrogen atoms bonded to atoms are substituted with fluorine atoms is introduced is used.

In the present invention, by using a specific polymer material having a cyclopentane group in which one or more of hydrogen atoms bonded to two adjacent carbon atoms are each substituted with a fluorine atom, a sufficiently transparent alicyclic ring can be obtained. A group group can be obtained, and it becomes possible to obtain a resist material having small light absorption in the vacuum ultraviolet region while suppressing deterioration of adhesion and etching resistance. A good rectangular resist pattern can be obtained by exposing and patterning into a predetermined shape using such a resist material.

The reason for this will be described below. Usually, an aromatic ring or alicyclic group is introduced into the polymer material constituting the resist material in order to maintain etching resistance. That is, the novolak resin which is a resin for i-line lithography and the polyhydroxystyrene resin which is a resin for KrF lithography are both resins having an aromatic ring, and the acrylic resin for ArF lithography is Since the aromatic ring has large absorption at 193 nm which is the exposure wavelength of ArF lithography, an alicyclic group is introduced instead of the aromatic ring. However, these aromatic rings and alicyclic groups have large light absorption in the vacuum ultraviolet region and cannot be contained in the polymer material that constitutes the resist material for VUV lithography as they are.

On the other hand, when the hydrogen atom contained in the aromatic ring and the alicyclic group is replaced with a fluorine atom, the substituted aromatic ring and the alicyclic group are exposed to more vacuum ultraviolet rays than those in the unsubstituted case. It is known that light absorption in the area is reduced. Considering only from the viewpoint of reducing the light absorption in the vacuum ultraviolet region, it is most desirable to replace all hydrogen atoms contained in the aromatic ring and alicyclic groups with fluorine atoms. The converted organic material is not suitable for use as a resist material because its adhesiveness with a silicon oxide film, an organic or inorganic antireflection film, which is a base of a resist layer, is significantly deteriorated. That is, from the viewpoint of avoiding a decrease in adhesiveness, it is desirable to suppress the ratio of substituting the hydrogen atoms contained in the aromatic ring and the alicyclic group with fluorine atoms as much as possible. Further, the organic material tends to deteriorate in etching resistance as the ratio of the hydrogen atom contained in the organic material to be replaced by the fluorine atom increases. It is desirable to suppress the ratio of replacing contained hydrogen atoms with fluorine atoms as much as possible.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a resist material and an exposure method to which the present invention is applied will be described in detail with reference to the drawings.

The exposure method of the present invention is applied, for example, to the processing of an ultrafine pattern in a semiconductor device,
Specifically, a step of forming a resist layer by applying a resist material having a photosensitizing effect on a substrate, a step of selectively exposing the resist layer to vacuum ultraviolet rays to be exposed, and a step of developing the resist layer by a predetermined process. And a step of forming a pattern.

As the vacuum ultraviolet ray for sensitization, a vacuum ultraviolet ray having an arbitrary wavelength can be used. In particular, by using the vacuum ultraviolet ray having a specific wavelength (110 nm to 170 nm), resolution higher than ever can be obtained. Performance is obtained. More desirably, the exposure wavelength is more preferably in the range of 120 nm to 165 nm. Specifically, a wavelength of 157 nm using an F ₂ (fluorine dimer) excimer laser as a light source,
Vacuum ultraviolet light having a wavelength of 126 nm using an Ar ₂ (argon dimer) excimer laser as a light source can be used.

The polymeric material used for the resist layer is
A polymer material containing a cyclopentane group, for example, a novolak resin containing a cyclopentane group, a polyhydroxystyrene resin containing a cyclopentane group, an acrylic resin containing a cyclopentane group, a siloxane resin containing a cyclopentane group, and a cyclopentane group. The basic skeleton is a silsesquioxane resin containing a polycycloolefin resin containing a cyclopentane group. Further, polynorbornane also has a saturated hydrocarbon five-membered ring in a part of the norbornane structure, and is therefore within the scope of the present invention.

In the present invention, one or more of each hydrogen atom bonded to two adjacent carbon atoms of the cyclopentane group contained in the polymer material as described above is substituted with a fluorine atom.

The remaining hydrogen atoms of the cyclopentane group are other than other groups such as an alkyl group and a fluorine atom as long as the absorption coefficient at the wavelength of vacuum ultraviolet rays for exposure of the entire resist layer is 5 μm ⁻¹ or less. May be substituted with a halogen atom, an amino group, a nitro group, a methylene group and derivatives thereof. In addition, when two or more of the remaining hydrogen atoms of the cyclopentane group are substituted with a substituent other than a fluorine atom, these substituents may be different or the same, or they may be bonded to each other. Good. further,
These substituents may be bonded to each other.

As the polymer used in the resist layer, a polymer material containing these cyclopentane groups may be used alone, and in some cases, a photo-acid generator for improving exposure sensitivity and a developing property may be used. Any or all of a dissolution inhibitor for this purpose and a crosslinking agent for resolution characteristics may be added. These additives may be contained in any proportion as long as the absorption coefficient of the entire resist layer at the wavelength of vacuum ultraviolet rays for exposure is 5 μm ⁻¹ or less. However, the weight ratio with respect to the polymer material used for the resist layer is preferably 25% or less. If it is contained more than this, the resolution performance of the resist material as a whole may deteriorate.

Polymer materials containing cyclopentane groups include
An ester group, a phenol group, an alcohol group, a carboxyl group, a fluorinated ester group, a fluorinated phenol group, a fluorinated alcohol group, a fluorinated carboxyl group, or the like, which causes a chemical reaction by light irradiation and thus brings about resolution performance, or A group consisting of a derivative of these groups may be contained, and when these groups are not contained, a chemical reaction of the cyclopentane group itself by light irradiation, or in the main skeleton of the polymer material Resolution performance may be obtained by utilizing a chemical reaction by light irradiation.

In the present invention, even if an organic or inorganic antireflection film or a film such as a hard mask made of a material other than silicon or silicon oxide is provided between the resist layer and the substrate made of silicon or the like. Good.

The thickness of the resist layer is 70 nm or more,
It is preferably 100 nm or more. As a result, the etching resistance is surely secured, and a high-quality resist layer with few defects is obtained. Even if the film thickness of the resist layer is 70 nm or less, it is of course possible to pattern the resist layer by using the material according to the present invention. However, in the etching process which is a post process of patterning the resist layer, the film of the resist layer is formed. Since the thickness is too thin, good etching may not be possible.

The reason why the fluorinated cyclopentane group according to the present invention is more transparent than the cyclopentane group which is not so is explained below. Examples of fluorinated cyclopentane groups according to the invention are 1,1,2,2-tetrafluorocyclopentane, examples of other cyclopentane groups are 1,1,3,3-tetrafluorocyclopentane. To adopt.

The energies of the above two kinds of molecules were derived by theoretical calculation. The calculation was performed by first optimizing the structure of each molecule by applying the ab initio molecular orbital method. This gave an optimized structure for each molecule. The Hartree-Fock method is used as the ab initio molecular orbital method, and the 6-31G * basis function (reference document:
P. C. Hariharan, J .; A. Pople,
Theoret. Chim. Acta, 28, 197
3, 213, and M.M. M. Francl, W.F. J. Pe
tro, W. J. Herhre, J .; S. Binkle
y, M. S. Gordon, D.M. J. DeFree,
J. A. People, J.P. Phys. Chem. , 7
7, 1982, 3654).

Using the optimized structure thus obtained, a
A theoretical calculation of absorption spectra of various molecules was performed by applying a density functional theory method, which is a kind of b initio molecular orbital method. In the calculation of the density functional theory, Vosko-Wilk
-Nusair's correlation potential (reference: S.
H. Vosko, L .; Wilk, M .; Nusair, C
an. J. Phys. , 58, 1980, 1200). Further, the basis functions used are DZ basis functions (reference: TH Dunning Jr., J. Ch.
em. Phys. , 53, 1970, 2823).
dberg basis function (reference: TH Dunnin
g Jr. , P .; J. Harrison, In Mod
ern Theoretical Chemistr
y, Vol. 2, Ed. : H. F. Schaefer
III, Plenum Press, New Yor
k, 1977). In calculating the absorption spectrum, the time-dependent density functional theory (reference: R. Bauernschmitt, R. Ahl
richs, Chem. Phys. Lett. , 25
6, 1996, 454, and M.M. E. Casida,
C. Jamorski, K .; C. Casida, D.M.
R. Salahub, J .; Chem. Phys. 10,
8, 1998, 4439).

Note that the program Gauss is used for both the Hartree-Fock method calculation and the density functional calculation.
ian 98 (Gaussian 98, Revisi
onA. 7, M.I. J. Frisch, G.F. W. Truc
ks, H.K. B. Schlegel, G .; E. Scuse
ria, M .; A. Robb, J .; R. Cheesema
n, V. G. Zakrzewski, J. et al. A. Mont
ogomery Jr. R.K. E. Stratman
n, J. C. Burant, S.M. Dappich, J .;
M. Millam, A .; D. Daniels, K .; N.
Kudin, M .; C. Strain, O.M. Farka
S.J. Tomasi, V .; Barone, M .; Cos
si, R.A. Cammi, B.I. Mennucci, C.I. P
omelli, C.I. Adamo, S.M. Cliffor
d, J. Ochterski, G.M. A. Peterss
on, P.I. Y. Ayala, Q.A. Cui, K .; Moro
kuma, D.I. K. Malick, A .; D. Rabuc
k, K. Raghavachari, J. et al. B. Fore
sman, J .; Ciolowski, J .; V. Ort
iz, A. G. Baboul, B.I. B. Stefano
v. G. Liu, A .; Liashenko, P. et al. Pis
korz, I. Komaromi, R .; Gompert
S.R. L. Martin, D.M. J. Fox, T .; Ke
ith, M.I. A. Al-Laham, C.I. Y. Pen
g, A. Nanaakkara, C.I. Gonzale
z, M. Challacombe, P .; M. W. Gil
1, B.I. Johnson, W.W. Chen, M .; W. Wo
ng, J. L. Andres, C.I. Gonzalez,
M. Head-Gordon, E.I. S. Replogl
e, J. A. People, Gaussian, In
c. , Pittsburgh PA, 1988). The computer used is a workstation (COMTEC Octane workstation) manufactured by Daikin Industries, Ltd.

Using the density functional method, 1, 1, 2,
2-tetrafluorocyclopentane and 1,1,3,3-
FIG. 1 shows the result of calculation of the absorption spectrum of tetrafluorocyclopentane in the vacuum ultraviolet region. The applied calculation method is the same as the derivation of the charge density and energy by the density functional theory, but in the absorption spectrum,
In addition to the method of the density functional method described above, the time-dependent density functional theory (reference: R. Bauernschmit
t, R.A. Ahlrichs, Chem. Phys. Le
tt. 256, 1996, 454, and M.P. E. Ca
sida, C.I. Jamorski, K .; C. Casid
a, D. R. Salahub, J .; Chem. Phy
s. , 108, 1998, 4439) was applied.

As can be seen from FIG. 1, 1, 1, 3, 3
-Compared to tetrafluorocyclopentane 1,1,2,2
The absorption peak of tetrafluorocyclopentane showed a smaller value in the vacuum ultraviolet region, particularly in the wavelength range of 150 nm to 160 nm. From these results, it is understood that the present invention can significantly reduce the light absorption of cyclopentane in the vacuum ultraviolet region.

[0031]

EXAMPLES Specific examples to which the present invention is applied will be described below based on experimental results.

The absorption spectra of 1,1,2,2-tetrafluorocyclopentane and 1,1,3,3-tetrafluorocyclopentane in the vacuum ultraviolet region were measured. The absorption spectrum measuring device was a homemade device, the light source was a deuterium lamp (30 W), and a MgF ₂ lens was used for the light source optical system. As the spectroscope unit, a concave diffraction grating having 1200 lines / mm (MgF ₂ coating) was used. The inverse line number is about 4 nm, and the wavelength measurement range is 125 nm to 300 nm. Semi-double beam measurement is possible in the sample chamber kept in vacuum.
A gas cell with a window of MgF ₂ is installed. The measurement was carried out by introducing a gas of sample molecules whose temperature and pressure were controlled into this gas cell. The condenser mirror is a toroidal mirror. The pressure in the vacuum part of the sample chamber is 4 × 10 ⁻⁵ Tor.
It is about r. As the detector, 6199 type Photomul manufactured by JASCO Corporation was used.

As a result of the measurement, 1,1,2,2-tetrafluorocyclopentane and 1,1,2 at a wavelength of 157 nm were obtained.
Table 1 shows the relative values of the absorbance of 1,3,3-tetrafluorocyclopentane. In Table 1, 1, 1, 3, 3-
The absorbance of tetrafluorocyclopentane was normalized and shown as 1.

[0034]

[Table 1] As is clear from Table 1, 1,1,2,2 according to the present invention
It can be seen that the absorbance of tetrafluorocyclopentane is indeed lower than that of 1,1,3,3-tetrafluorocyclopentane not according to the invention.

That is, according to the present invention, it is possible to efficiently reduce the light absorption in the region of alicyclic vacuum ultraviolet rays, and a new process that enables the processing of ultrafine patterns of 0.1 μm or less, for example. It is possible to provide a resist material for the technology.

Although cyclopentane has been described as an alicyclic group in the above embodiments, the present invention is not limited to this, and for example, an alicyclic group containing another cyclopentane group moiety. (For example, norbornane, tricyclodecane) and the like are also applicable. That is, the present invention is not limited to the above description,
Modifications can be made as appropriate without departing from the scope of the present invention.

[0037]

According to the present invention, the absorption of light in the alicyclic vacuum ultraviolet region can be efficiently reduced, and a resist pattern having a good shape can be obtained. It is possible to perform ultrafine processing more than ever, such as realizing an ultrafine pattern of 1 μm or less.

[Brief description of drawings]

FIG. 1 is a result of calculating absorption spectra of 1,1,2,2-tetrafluorocyclopentane and 1,1,3,3-tetrafluorocyclopentane in a vacuum ultraviolet region using a density functional theory method. FIG.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H025 AA03 AA09 AB16 AC04 AC08                       AD01 AD03 BE00 CB08 CB14                       CB17 CB29 CB32 CB41 CC17                 4J002 BB001 BC121 BG031 BK001                       CD021 CP031 FD146 FD206                       GP03

Claims (23)

[Claims] 1. A polymer material containing a cyclopentane group as an alicyclic group, wherein at least one hydrogen atom bonded to two adjacent carbon atoms of the cyclopentane group is substituted with a fluorine atom. A resist material characterized in that 2. The resist material according to claim 1, wherein at least one hydrogen atom of the remaining hydrogen atoms of the cyclopentane group is substituted with a substituent other than a fluorine atom. 3. The resist material according to claim 2, wherein two or more hydrogen atoms of the remaining hydrogen atoms of the cyclopentane group are substituted with a substituent other than a fluorine atom. 4. The resist material according to claim 3, wherein the substituents are the same. 5. The resist material according to claim 3, wherein the substituent is a methylene group or a derivative thereof. 6. The resist material according to claim 3, wherein the substituents are different substituents. 7. The resist material according to claim 3, wherein the substituents are bonded to each other. 8. The polymeric material contains at least one selected from a novolac resin, a polyhydroxystyrene resin, an acrylic resin, a siloxane resin, a silsesquioxane resin, and a polycycloolefin resin as a basic skeleton. The resist material according to claim 1. 9. The resist material according to claim 1, wherein the polymer material contains a group that causes a chemical reaction when irradiated with light. 10. The resist material according to claim 1, which contains at least one selected from a photo-acid generator, a dissolution inhibitor, and a crosslinking agent as an additive. 11. The resist material according to claim 10, wherein the content of the additive is 25% by weight or less. 12. The vacuum ultraviolet wavelength of the polymer material
Absorption coefficient is 5 μm ^-1Characterized by
The resist material according to claim 1. 13. The absorption coefficient at a VUV wavelength is 5
The resist material according to claim 1, wherein the resist material has a thickness of μm ⁻¹ or less. 14. An exposure method in which a resist layer is selectively exposed to ultraviolet rays to be patterned into a predetermined shape, and adjacent two adjacent polymer materials are used as the polymer material forming the resist layer.
An exposure method comprising using a polymer material in which a cyclopentane group in which one or more hydrogen atoms bonded to one carbon atom are substituted with fluorine atoms is used. 15. The polymer material is a novolac resin,
The exposure method according to claim 14, which comprises at least one selected from a polyhydroxystyrene resin, an acrylic resin, a siloxane resin, a silsesquioxane resin, and a polycycloolefin resin as a basic skeleton. 16. The polymer material according to claim 14, wherein the polymer material contains a group that causes a chemical reaction when irradiated with light.
The exposure method described. 17. The exposure method according to claim 14, wherein the resist layer contains at least one selected from a photo-acid generator, a dissolution inhibitor and a crosslinking agent as an additive. 18. The exposure method according to claim 17, wherein the content of the additive is 25% by weight or less. 19. The vacuum ultraviolet wavelength of the polymer material
Absorption coefficient is 5 μm ^-1Characterized by
The exposure method according to claim 14. 20. The vacuum ultraviolet wavelength of the resist layer
Absorption coefficient is 5 μm ^-1Characterized by
The exposure method according to claim 14. 21. The exposure method according to claim 14, wherein vacuum ultraviolet rays are used as the ultraviolet rays. 22. The vacuum ultraviolet ray having a wavelength of 110 nm to
22. The exposure method according to claim 21, which is 170 nm. 23. The exposure method according to claim 21, wherein a fluorine dimer excimer laser is used as a light source for the vacuum ultraviolet rays.