Pattern formation resist and pattern formation method

Disclosed is a pattern formation resist which can be exposed with deep UV, has a high dry etching resistance, has a large allowance in a development manipulation using an aqueous alkali solution, and can form a fine pattern having a good sectional shape. The resist comprises an alkali-soluble polymer and a compound represented by the following formula (I) and simultaneously containing, in a single molecule, a substituent which decomposes with an acid and a group which produces an acid with deep UV: ##STR1## wherein the substituent which decomposes with an acid is present in at least one of R.sub.1 to R.sub.4, and when R.sub.1 to R.sub.4 have a group except for the substituent which decomposes with an acid, R.sub.1 represents a nonsubstituted or substituted aliphatic hydrocarbon group, each of R.sub.2 and R.sub.3 independently represents a hydrogen atom or a non-substituted or substituted aliphatic hydrocarbon group, and R.sub.4 represents a nonsubstituted or substituted aliphatic hydrocarbon group.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a pattern formation resist and a pattern 
formation method using the same and, more particularly, to a pattern 
formation resist exposed with deep UV and a pattern formation method using 
the same. 
2. Description of the Related Art 
Pattern formation resists are widely used in the field of electronic parts, 
such as semiconductor integrated circuits, which require various 
microprocessing techniques. In particular, it is required to form fine 
patterns using the resists of this type because users desire multiple 
functions and high packing densities in electronic equipment. As an 
exposure apparatus for use in this pattern formation, a step-and-repeat 
type reduction-projecting mask aligner is known. Examples of a radiation 
used in this exposure apparatus are g line (wavelength 436 nm), h line 
(wavelength=405 nm), and i line (wavelength=365 nm) of a mercury lamp, and 
XeF (wavelength=351 nm), XeCl (wavelength=308 nm), KrF (wavelength=248 
nm), KrCl (wavelength=222 nm), ArF (wavelength=193 nm), and F2 
(wavelength=157 nm) as an excimer laser. In order to form fine patterns, 
the wavelength of a radiation is preferably as short as possible. For this 
reason, a demand has arisen for a resist which is exposed with deep UV 
such as an excimer laser. 
Conventionally known examples of the resist for an excimer laser are a 
resist consisting of an acryl polymer, such as polymethylmethacrylate 
(PMMA) or polyglutarmaleimide (PGMI); and a resist consisting of a 
polymer, in which phenol is bonded in a molecule, and an azide 
photosensitive agent. However, the former resist is low in sensitivity 
with respect to an excimer laser and poor in dry etching resistance. 
Although the latter resist has a high sensitivity and a high dry etching 
resistance, the shape of a pattern formed by this resist is a reversed 
triangle. Therefore, it is difficult to control exposure and development 
steps. 
Recently, U.S. Pat. Nos. 4,491,628 and 460,310, for example, disclose 
resists each consisting of a polymer, in which a group unstable against 
acids is substituted on the side chain of a resin having a dry etching 
resistance, and a compound which produces an acid when irradiated with an 
ionizing radiation. However, since the group unstable against acids is 
substituted on the side chain of the polymer in these resists, no stable 
sensitivity nor stable resolution can be obtained. 
From this point of view, Published Unexamined Japanese Patent Application 
No. 64-35433 describes a resist containing a binder consisting of an 
alkali-soluble polymer, and an organic compound having a group which forms 
a strong acid by a radiation effect together with a group which decomposes 
into an acid. An onium salt is exemplified as the organic compound in 
Published Unexamined Japanese Patent Application No. 64-35433, and an 
iodonium salt and a sulfonium salt are disclosed as practical examples of 
the onium salt. However, since the onium salt decomposes during storage, 
sensitivity stability upon exposure is hindered. In addition, the onium 
salt largely absorbs light having a wavelength of 248 nm. Therefore, if a 
large amount of the onium salt is used, resolution is lowered. 
Consequently, it is impossible to add a sufficient amount of the onium 
salt, in consideration of the above relationship between the onium salt 
and the resolution. For this reason, the solubility of unexposed portions 
cannot be satisfactorily suppressed in a development step subsequent to 
exposure, and this makes it difficult to form fine patterns. 
On the other hand, other problems arise in various exposure methods along 
with reduction in minimum dimensions. For example, in exposure using 
light, an interference occurs by reflected light components due to steps 
formed on a substrate (e.g., a semiconductor substrate) and largely 
influences dimensional precision. In electron beam exposure, on the other 
hand, when a resist is micropatterned, it is impossible to increase the 
ratio of the height to width of the pattern due to a proximity effect 
caused by backscattering of electrons. 
As a method of solving the above problems, a multilayered resist process 
has been developed, and a summary of this process is described in "Solid 
State Technology," 74. 1981. In addition, many studies concerning this 
multilayered resist process have been reported. A method which is 
presently, most generally attempted is a three-layered structure resist 
process. More specifically, this three-layered structure includes a lowest 
layer which has functions of flattening steps on a semiconductor substrate 
and preventing reflection from the substrate, an interlayer which serves 
as an etching mask of the lowest layer, and an uppermost layer as a 
photosensitive layer. 
The above three-layered resist process has an advantage that finer 
patterning can be performed than in the case of a single-layered resist 
process. However, according to this three-layered resist process, the 
number of process steps before pattern formation is undesirably increased. 
That is, no resist can satisfy both photosensitivity with respect to a 
radiation, such as deep UV, and resistance against reactive ion etching 
using an oxygen plasma. Therefore, these functions must be separately 
imparted to different layers to result in a three-layered structure. As a 
result, the number of process steps is increased by those required for the 
layer formation. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a pattern formation 
resist which is exposed well with a radiation having a short wavelength, 
such as deep UV or an ionizing radiation, has a high dry etching 
resistance, can be easily controlled in an exposure step and a development 
step using an aqueous alkali solution, and can form a fine pattern having 
a good sectional shape. 
It is another object of the present invention to provide a pattern 
formation resist having high storage stability. 
It is still another object of the present invention to provide a pattern 
formation resist which is exposed well with a radiation having a short 
wavelength, such as deep UV or an ionizing radiation, has a high oxygen 
reactive ion etching resistance (oxygen RIE resistance), can be developed 
with an aqueous alkali solution, and is useful in a two-layered resist 
process. 
It is still another object of the present invention to provide a method 
capable of forming a fine pattern having a good sectional shape. 
According to the present invention, there is provided a pattern formation 
resist comprising: 
an alkali-soluble polymer; and 
a compound represented by the following formula (I) and simultaneously 
containing, in a single molecule, a substituent which decomposes with an 
acid and a group which produces an acid with a radiation. 
##STR2## 
It should be noted that the substituent which decomposes with an acid is 
present in at least one of R.sub.1 to R.sub.4. When R.sub.1 to R.sub.4 
have a group except for the substituent which decomposes with an acid, 
R.sub.1 represents a nonsubstituted or substituted aliphatic hydrocarbon 
group, a nonsubstituted or substituted alicyclic hydrocarbon group, a 
nonsubstituted or substituted aromatic hydrocarbon group, or a 
nonsubstituted or substituted heterocyclic group, each of R.sub.2 and 
R.sub.3 independently represents a hydrogen atom, a nonsubstituted or 
substituted aliphatic hydrocarbon group, a nonsubstituted or substituted 
alicyclic hydrocarbon group, a nonsubstituted or substituted aromatic 
hydrocarbon group, or a nonsubstituted or substituted heterocyclic group, 
and R.sub.4 represents a nonsubstituted or substituted aliphatic 
hydrocarbon group, a nonsubstituted or substituted alicyclic hydrocarbon 
group, a nonsubstituted or substituted aromatic hydrocarbon group, a 
nonsubstituted or substituted heterocyclic group, or an alkoxyl group. 
Note that R.sub.2 and R.sub.3 may form a cyclic hydrocarbon group or a 
heterocyclic group. 
Examples of the alkali-soluble polymer are a acrylic acid polymer; a 
copolymer of acrylic acid and styrene; a methacrylic acid polymer; a 
copolymer of methacrylic acid and styrene; a copolymer of maleic acid and 
styrene; a copolymer of maleic acid monomethylester and styrene; a phenol 
novolak resin; a cresol novolak resin; a xylenol novolak resin; a 
vinylphenol resin; an isopropenylphenol resin; a copolymer of vinylphenol 
and, e.g., acrylic acid, a methacrylic acid derivative, acrylonitrile, or 
a styrene derivative; a copolymer of isopropenylphenol and, e.g., acrylic 
acid, a methacrylic acid derivative, acrylonitrile, or a styrene 
derivative; a copolymer of acrylic acid or methacrylic acid and 
acrylonitrile or a styrene derivative; an acrylic resin; a methacrylic 
resin; and a copolymer of malonic acid and vinylether. More practical 
examples are poly (p-vinylphenol), a copolymer (copolymerization ratio=1 : 
1) of p-isopropenylphenol and acrylonitrile, a copolymer (copolymerization 
ratio=1 : 1) of p-isopropenylphenol and styrene, a copolymer 
(copolymerization ratio=1 : 1) of p-vinylphenol and methylmethacrylate, 
and a copolymer (copolymerization ratio=1 : 1) of p-vinylphenol and 
styrene. 
As the above alkali-soluble polymer, one in which silicon is bonded on its 
main or side chain can be used. Examples of the alkali-soluble polymer are 
(a) polysiloxane having phenol on its side chain, (b) polysilane having 
phenol on its side chain, and (c) a novolak resin synthesized from phenol 
having silicon on its side chain. Practical examples of the polysiloxane 
of item (a) above are shown in Table 1 (to be presented later), and those 
of the polysilane of item (b) above are shown in Table 2 (to be presented 
later). Practical examples of the novolak resin of item (c) above are 
those which are obtained by condensing a silicon-bonded phenol monomer 
shown in Table 3 (to be presented later) and phenol with formalin or 
aldehyde. Examples of the phenol are phenol, o-chlorophenol, 
m-chlorophenol, p-chlorophenol, m-cresol, p-cresol, xylenol, bisphenol A, 
4-chloro-3-cresol, dihydroxybenzene, and trihydroxybenzene. 
Examples of the alkali-soluble copolymer having silicon bonded on its main 
or side chain are those obtained by introducing silicon into, e.g., an 
acrylic resin, a methacrylic resin, a copolymer of acrylic acid or 
methacrylic acid and acrylonitrile or a styrene derivative, and a 
copolymer of malonic acid and vinylether. Practical examples of such an 
alkali-soluble polymer are shown in Table 4 (to be presented later). 
Examples of the substituent, which is introduced into at least one of 
R.sub.1 to R.sub.4 and decomposes with an acid, are ester derivatives such 
as methylester, ethylester, t-butylester, p-methoxybenzylester, 
2,4,6-trimethylbenzylester, pentamethylbenzylester, 
9-anthranylmethylester, benzohydrylester, triphenylenemethylester, 
phthalimidomethylester, tetrahydropyranylester, and trimethylsilylester; 
carbonate derivatives such as t-butoxycarbonyloxy and 
eenzyloxycarbonyloxy; ether derivatives such as methylether, 
isopropylether, t-butylether, benzylether, allylether, methoxymethylether, 
tetrahydropyranylether, and trimethylsilylether; and heterocyclic 
compounds such as a 1,3-dioxolane-4-one derivative, a 1,3-oxazoline 
derivative, and a 1,3-oxazine derivative. 
The substituent which decomposes with an acid is preferably introduced into 
R.sub.4 of formula (I). This substituent is preferably an ester 
derivative, and most preferably t-butylester. 
Examples of the nonsubstituted aliphatic hydrocarbon group to be introduced 
to R.sub.1 to R.sub.4 of formula (I) are those enumerated below. Examples 
of the substituted aliphatic hydrocarbon group are those obtained by 
substituting the nonsubstituted aliphatic hydrocarbon groups enumerated in 
item (1) below with substituents enumerated in item (2) below. 
(1) Nonsubstituted Aliphatic Hydrocarbon Groups 
A methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl 
group, an isobutyl group, a sec-butyl group, a t-butyl group, a pentyl 
group, a t-pentyl group, an isopentyl group, a neopentyl group, a hexyl 
group, an isohexyl group, a heptyl group, an octyl group, a nonyl group, a 
decyl group, a vinyl group, an allyl group, an isopropenyl group, a 
propenyl group, a methallyl group, a crotyl group, an ethynyl group, a 
propynyl group, a pentenyl group, a benzyl group, a trityl group, a 
phemotyl group, a styryl group, a cinnamyl group, and a benzhydryl group. 
(2) Substituents 
Di-substituted amino groups (e.g., a dimethylamino group, a diethylamino 
group, a dibutylamino group, a methylethylamino group, a methylbutylamino 
group, a diamylamino group, a dibenzylamino group, a diphenethylamino 
group, a diphenylamino group, a ditolylamino group, and a dixylylamino 
group), mono-substituted amino groups (e.g., a methylamino group, an 
ethylamino group, a propylamino group, an isopropylamino group, a 
t-butylamino group, an aninorine group, an anisidino group, a phenetidino 
group, a toluidino group, a xylidino group, a pyridylamino group, and a 
benzylideneamino group), acylamino groups (e.g., a formylamino group, an 
acetylamino group, a benzoylamino group, a cinnamoylamino group, a 
pyridinecarbonylamino group, and a trifluoroacetylamino group), tertiary 
amino groups (e.g., a trimethylamino group, an ethyldimethylamino group, 
and a dimethylphenylamino group), an amino group, a hydroxyamino group, an 
urido group, a semicarbazido group, di-substituted hydrazino groups (e.g., 
a dimethylhydrazino group, a diphenylhydrazino group, and a 
methylphenylhydrazino group), mono-substituted hydrazino groups (e.g., a 
methylhydrazino group, a phenylhydrazino group, a pyridylhydrazino group, 
and a benzylidenehydrazino group), a hydrazino group, azo groups (e.g., a 
phenylazo group, a pyridylazo group, and a thiazolylazo group), an azoxy 
group, an amidino group, amoyl groups (e.g., a carbamoyl group, an oxamoyl 
group, and a succinamoyl group), a cyano group, a cyanato group, a 
thiocyanato group, a nitro group, a nitroso group, oxy groups (e.g., a 
methoxy group, an ethoxy group, a propoxy group, a butoxy group, a 
hydroxyethoxy group, a phenoxy group, a naphthoxy group, a pyridyloxy 
group, a thiazolyloxy group, and a neacetoxy group), a hydroxy group, thio 
groups (e.g., a methylthio group, an ethylthio group, a phenylthio group, 
a pyridylthio group, and a thiazolinethio group), a mercapto group, 
halogen groups (e.g., a fluoro group, a bromo group, and an iodide group), 
a carboxy group, ester groups (e.g., a methylester group, an ethylester 
group, a phenylester group, and a pyridylester group), a thiocarboxy 
group, a dithiocarboxy group, thioester groups (e.g., a methoxycarbonyl 
group, a methylthiocarbonyl group, and a methylthiothiocarbonyl group), 
acyl groups (e.g., a formyl group, an acetyl group, a propiolnyl group, an 
acryloyl group, a benzoyl group, a cinnamoyl group, a pyridinecarbonyl 
group, and a thiazolecarbonyl group), thioacyl groups (e.g., a thioformyl 
group, a thioacetyl group, a thiobenzoyl group, and a thiopyridinecarbonyl 
group), a sulfinic acid group, sulfinyl groups (e.g., a methylsulfinyl 
group, an ethylsulfinyl group, and a phenylsulfinyl group), sulfonyl 
groups (e.g., a mesyl group, an ethylsulfonyl group, a phenylsulfonyl 
group, a pyridylsulfonyl group, a tosyl group, a tauryl group, a 
trimethylsulfonyl group, and an aminosulfonyl group), hydrocarbon groups 
(e.g., an alkyl group, an aryl group, an alkenyl group, and an alkinyl 
group), a heterocyclic group, and hydrogen silicide groups (e.g., a silyl 
group, a disilanyl group, and a trimethylsilyl group). 
Examples of the nonsubstituted alicyclic hydrocarbon groups to be 
introduced to R.sub.1 to R.sub.4 of formula (I) are those enumerated in 
item (3) below. Examples of the substituted alicyclic hydrocarbon group 
are those obtained by substituting the nonsubstituted alicyclic 
hydrocarbon groups enumerated in item (3) below with the substituents 
enumerated in item (2) above. 
(3) Nonsubstituted Alicyolic Hydrocarbon Groups 
A cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl 
group, a cycloheptyl group, a cyclooctyl group, a cyclopentenyl group, a 
cyclohexenyl group, a cycloheptenyl group, a cyclooctenyl group, a 
cyclopentadienyl group, and a cyclohexadienyl group. 
Examples of the nonsubstituted aromatic hydrocarbon group to be introduced 
to R.sub.1 to R.sub.4 of formula (I) are those enumerated in item (4) 
below. Examples of the substituted aromatic hydrocarbon group are those 
obtained by substituting the nonsubstituted aromatic hydrocarbon groups 
enumerated in item (4) below with the substituents enumerated in item (2) 
above. 
(4) Nonsubstituted Aromatic Hydrocarbon Groups 
A phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a 
tetralinyl group, an azulenyl group, a biphenylenyl group, an 
acetonaphthylenyl group, an acetonaphthenyl group, a fluorenyl group, a 
triphenylenyl group, a pyrenyl group, a chrysenyl group, a picenyl group, 
a perylenyl group, a benzopyrenyl group, a rubicenyl group, an ovalenyl 
group, an indenyl group, a pentalenyl group, a heptalenyl group, an 
indacenyl group, a phenalenyl group, a fluoranthenyl group, an 
acephenantolylenyl group, an aceantolylenyl group, a naphthacenyl group, a 
pleiadenyl group, a pentaphenyl group, a pentacenyl group, a 
tetraphenylenyl group, a hexaphenyl group, a hexacenyl group, a 
trinaphelenyl group, a heptaphenyl group, a heptacenyl group, and a 
pyranthrenyl group. 
Examples of the nonsubstituted heterocyclic group to be introduced to 
R.sub.1 to R.sub.4 of formula (I) are those enumerated in item (5) below. 
Examples of the substituted heterocyclic group are those obtained by 
substituting the nonsubstituted heterocyclic groups enumerated in item (5) 
below with the substituents in item (2) above. 
(5) Nonsubstituted Heterocyclic Groups 
A pyrrole ring group, a pyrroline ring group, a pyrrolidine ring group, an 
indole ring group, an isoindole ring group, an indoline group, an 
isoindoline ring group, an indolizine ring group, a carbazole ring group, 
a carboline ring group, a furan ring group, an oxolane ring group, a 
chroman ring group, a coumaran ring group, an isozenzofuran ring group, a 
phthalan ring group, a dibenzofuran ring group, a thiophene ring group, a 
thiolane ring group, a benzothiophene ring group, a dibenzothiophene ring 
group, a pyrazole ring group, a pyrazoline ring group, an indazole ring 
group, an imidazole ring group, an imidazoline ring group, a 
benzoimidazole ring group, a naphthoimidazole ring group, an oxazole ring 
group, an oxazoline ring group, an oxazolidine ring group, a benzoxazole 
ring group, a benzoxazolidine ring group, a naphthoxazole ring group, an 
isoxazole ring group, a benzoxazole ring group, a thiazole ring group, a 
thioazoline ring group, a thiazolidine ring group, a benzothiazoline ring 
group, a naphthothiazole ring group, an isothiazole ring group, a 
benzoisothiazole ring group, a triazole ring group, a benzotriazole ring 
group, an oxadiazole ring group, a thiadiazole ring group, a 
benzoxadiazole ring group, a benzothiadizole ring group, a tetrazole ring 
group, a purine ring group, a pyridine ring group, a pyperidine ring 
group, a quinoline ring group, an isoquinoline ring group, an acridine 
ring group, a phenanthridine ring group, a benzoquinoline ring group, a 
naphthoquinoline ring group, a naphthyridine ring group, a phenanthroline 
ring group, a pyridazine ring group, a pyrimidine ring group, a pyrazine 
ring group, a phthalazine ring group, a quinoxaline ring group, a 
quinazoline ring group, a cinnoline ring group, a phenazine ring group, a 
perimidine ring group, a triazine ring group, a tetrazine ring group, a 
pterindine ring group, an oxazine ring group, a benzoxazine ring group, a 
phenoxazine ring group, a thiazine ring group, a benzothiazine ring group, 
a phenothiazine ring group, an oxadiazine ring group, a thiadiazine ring 
group, a dioxolan ring group, a benzoioxole ring group, a dioxane ring 
group, a benzodioxane ring group, a dithiosolan ring group, a 
benzodithiosollur ring group, a dithiane ring group, a benzodithiane ring 
group, a pyrane ring group, a chromene ring group, a xanthene ring group, 
an oxane ring group, a chromane ring group, an isochromane ring group, a 
trioxane ring group, a thiolane ring group, a thian ring group, a trithian 
ring group, a morpholine ring group, a quinuclidine ring group, a 
selenazole ring group, a benzoselenazole ring group, a naphthoselenazole 
ring group, a tellurazole ring group, and a benzotellurazole ring group. 
Practical examples of a compound represented by formula (I) will be shown 
in Table 5 (to be presented later). 
A compound represented by formula (I) is added in an amount of preferably 1 
to 300 parts by weight, and more preferably 5 to 100 parts by weight with 
respect to 100 parts by weight of the alkali-soluble polymer. The mixing 
ratio of the compound is defined for the reasons to be explained below. 
That is, if the mixing ratio of the compound is less than one part by 
weight, it is difficult to obtain a sufficient dissolution suppressing 
effect with respect to an aqueous alkali solution (developer), and 
consequently pattern formation may become difficult to perform. If, on the 
other hand, the mixing ratio of the compound exceeds 300 parts by weight, 
film properties may be degraded to make it difficult to form a resist 
layer having a uniform thickness. 
The resist according to the present invention further contains, in addition 
to the alkali-soluble polymer and a compound represented by formula (I), 
an organic solvent for dissolving the above components. Examples of the 
organic solvent are ketone solvents such as cyclohexanone, acetone, 
methylethylketone, and methylisobutylketone; cellosolve solvents such as 
methylcellosolve, methylcellosolveacetate, ethylcellosolveacetate, and 
butylcellosolveacetate; and ester solvents such as ethyl acetate, butyl 
acetate, and isoamyl acetate. These solvents can be used singly or in the 
form of a mixture of two or more. 
The resist according to the present invention can contain a surfactant as a 
film modifier and a dye as an antireflection agent, in addition to the 
alkali-soluble polymer and a compound represented by formula (I). 
(1) A method of forming a pattern by a single-layered process and (2) a 
method of forming a pattern by a two-layered process, each using the 
pattern formation resist according to the present invention, will be 
described below. 
(1) Pattern Formation Method by Single-Layered Process 
First, a resist containing the alkali-soluble polymer, a compound 
represented by formula (I), and the organic solvent is coated on a 
substrate by, e.g., a spin coating method or a dipping method, and dried 
to form a resist layer. As the alkali-soluble polymer in the resist, one 
in which no silicon is bonded on its main or side chain is used. Examples 
of the substrate are a silicon wafer, a silicon wafer on which various 
insulating films, electrodes, or interconnections are formed, a blank 
mask, and a semiconductor wafer consisting of a Group III-V compound such 
as GaAs or AlGaAs. 
Subsequently, deep UV or an ionizing radiation is selectively radiated on 
the resist layer through a mask having a desired pattern, thereby 
performing pattern exposure. Examples of deep UV are excimer lasers such 
as XeF (wavelength=351 nm), XeCl (wavelength=308 nm), KrF (wavelength=248 
nm), KrCl (wavelength=222 nm), ArF (wavelength=193 nm), and F.sub.2 
(wavelength=157 nm); g line (wavelength=436 nm), h line (wavelength=405 
nm), and i line (wavelength=365 nm) of a mercury lamp. Examples of the 
ionizing radiation are an electron beam, and X-rays. Note that when an 
electron beam is used, the pattern exposure is performed by scanning the 
beam. Subsequently, by developing the pattern-exposed resist layer by, 
e.g., a dipping method or a spraying method using an aqueous alkali 
solution, a desired pattern is formed. As the aqueous alkali solution, it 
is possible to use, for example, an aqueous organic alkali solution such 
as an aqueous tetramethylammoniumhydroxide solution, or an aqueous 
inorganic alkali solution such as potassium hydroxide or sodium hydroxide. 
These aqueous alkali solutions are normally used at a concentration of 15 
wt. % or less. In addition, rinsing may be performed using water or the 
like after the development. 
(2) Pattern Formation Method by Two-Layered Resist Process 
First, after a polymeric material is coated on a substrate like that used 
in the single-layered process described above, baking is performed at 
100.degree. C. to 250.degree. C. for 30 to 150 minutes to form a polymeric 
material layer (flattening layer) having a desired height. As the above 
polymeric material, any polymeric material can be used so long as it has 
purity with which no troubles are caused in the fabrication of 
semiconductor devices. Practical examples of the polymeric material are a 
positive resist consisting of substituted o-quinonediazide and a novolak 
resin, polystyrene, polymethylmethacrylate, polyvinylphenol, a novolak 
resin, polyester, polyvinylalcohol, polyethylene, polypropylene, 
polyimide, polybutadiene, polyvinyl acetate, and polyvinylbutyral. These 
resins are used singly or in the form of a mixture of two or more. 
Subsequently, a resist containing the alkali-soluble polymer, a compound 
represented by formula (I), and the organic solvent is coated on the 
polymeric material layer by, e.g., a spin coating method using a spinner, 
a dipping method, a spraying method, or a printing method, and dried to 
form a resist layer. As the alkali-soluble polymer in the resist, one in 
which silicon is bonded on its main or side chain is used. 
Next, pattern exposure is performed by selectively radiating deep UV or an 
ionizing radiation from the above-mentioned light source on the resist 
layer through a mask having a desired mask. In this exposure step, a 
solubility of exposed portions in an aqueous alkali solution becomes lower 
than that of unexposed portions. Upon exposure, either a contact exposure 
scheme or a projecting exposure scheme may be adopted. Subsequently, the 
aqueous alkali solution is used to perform development by, e.g., the 
dipping method or the spraying method, thus forming a desired pattern. 
This pattern is used as a mask to etch away exposed portions of the 
flattening layer by an oxygen reactive ion etching method (oxygen RIE 
method). At this time, the resist which constitutes the pattern contains 
an alkali-soluble polymer having silicon bonded on its main or side chain. 
For this reason, when the pattern is exposed to the oxygen RIE, a silicon 
dioxide (SiO.sub.2) layer or an analogous layer is formed on the surface 
layer of the pattern, and the result is that the pattern has a oxygen RIE 
resistance 10 to 100 times that of the exposed portions of the flattening 
layer. Consequently, since the pattern serves as a good mask in the oxygen 
RIE, the portions of the flattening layer exposed from the pattern are 
selectively removed by the oxygen RIE, and an optimal pattern profile 
results. 
The single-layered pattern and the two-layered pattern thus obtained by the 
above steps of formation are used as a mask to etch the substrate or the 
like. As an etching means, a wet etching method or a dry etching method is 
employed. In order to form a fine pattern of 3 .mu.m or less on a 
substrate or the like, the dry etching method is preferably adopted. When 
a silicon oxide film is an object to be etched, an aqueous hydrofluoric 
acid solution or an aqueous ammonium fluoride solution, for example, is 
used as a wet etchant. When aluminum is an object to be etched, it is 
possible to use, e.g., an aqueous phosphoric acid, an aqueous acetic acid 
solution, or an aqueous silver nitrate solution. When a chromium film is 
an object to be etched, an example of the etchant is an aqueous ammonium 
cerium nitrate solution. Examples of a dry etching gas are CF.sub.4, 
C.sub.2 F.sub.6, CCl.sub.4, BCl.sub.3, Cl.sub.2, HCl, and H.sub.2, and 
these gases can be combined together as needed. The etching conditions, 
e.g., the concentration of the etchant (or the concentration of the dry 
etching gas) in a reaction chamber, the reaction temperature, and the 
reaction time are determined on the basis of a combination of the type of 
a material, on which a fine pattern is to be formed, and the resist, but 
are not particularly limited by the etching method. 
After the etching step, the pattern consisting of the resist, or the 
pattern consisting of the polymeric material and the resist, which remains 
on the substrate, is removed by, e.g., a stripper such as J-100 
(tradename) available from NAGASE KASEI K.K., or an oxygen plasma. 
In addition to the above steps, it is possible to add further steps in 
correspondence with an application. Examples of the additional step are a 
rinsing step (normally using water) for washing away a developer after 
development, a pretreatment step performed before coating of solutions in 
order to improve adhesion properties between the resist layer and the 
flattening layer or between the flattening layer and the substrate, a 
baking step performed before or after development, and an ultraviolet ray 
reradiation step performed before dry etching. 
According to the pattern formation resist of the present invention as 
described above, in the selective radiation (exposure) step using deep UV 
or an ionizing radiation, a compound represented by formula (I) as one 
component of the resist produces an acid, and this acid decomposes the 
substituent, which decomposes with an acid, in a compound of formula (I). 
A mechanism of producing the acid is assumed that C.dbd.O in the above 
formula is excited with light, a bond of R.sub.1 SO.sub.3 --C is ruptured 
by a dislocation reaction, and the isolated R.sub.1 SO.sub.3 produces an 
acid as R.sub.1 SO.sub.3 H. 
A compound represented by formula (I) initially has an effect of 
suppressing dissolution. However, this dissolution suppressing effect 
vanishes upon decomposition of the substituent which decomposes with an 
acid, and a pattern latent image forms. This latent image is 
preferentially removed by dissolution in development performed after the 
exposure, thus forming a pattern (positive pattern). 
In addition, since the alkali-soluble polymer is mixed in the resist, it is 
possible to perform development using an aqueous alkali solution after the 
exposure. Therefore, a swell of the pattern is suppressed compared with 
the case of development using an organic solvent. 
It is, therefore, possible to form a fine positive pattern which is exposed 
well with deep UV or an ionizing radiation, can be easily controlled in 
the exposure and development steps, has a high dry etching resistance, and 
has a made rectangular sectional shape. 
In addition, a compound represented by formula (I), which is contained in 
the resist, has both the portion which produces an acid and the 
substituent which decomposes with an acid. Therefore, the number of types 
of components constituting the resist can be decreased. This facilitates 
mixing control of the respective components for preparing the resist, 
improves the reproducibility of resolution, and further improves storage 
stability. 
Furthermore, a polymer having silicon bonded on its main or side chain is 
used as the alkali-soluble polymer constituting the resist, and this makes 
it possible to form a fine pattern having a high oxygen RIE resistance by 
the exposure and the development using an aqueous alkali solution. 
Therefore, by forming the pattern on a polymeric material layer 
(flattening layer) and dryetching the flattening layer with an oxygen 
plasma using the pattern as an oxygen RIE-resistant mask, a fine 
two-layered pattern having a high aspect ratio and a good sectional shape 
can be formed. 
Additional objects and advantages of the invention will be set forth in the 
description which follows, and in part will be obvious from the 
description, or may be learned by practice of the invention. The objects 
and advantages of the invention may be realized and obtained by means of 
the instrumentalities and combinations particularly pointed out in the 
appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will be described in detail below by way of its 
examples. 
EXAMPLE 1 
70 g of poly(p-vinylphenol) and 30 g of a compound represented by formula 
(I), both shown in Table 6 (to be presented later), were dissolved in 250 
g of ethylcellosolveacetate, and the resultant solution was filtered using 
a fluorine resin membrane filter having a pore size of 0.2 .mu.m, thus 
preparing a resist. 
The prepared resist was coated on a silicon wafer, and the wafer was dried 
on a hot plate at 90.degree. C. for five minutes, thereby forming a 
1.0-.mu.m thick resist layer. The formed resist layer was subjected to 
pattern exposure (100 mJ/cm.sup.2) by a reduction projecting exposure 
machine using a KrF (wavelength=248 nm) excimer laser beam. The resulting 
material was heated on the hot plate at 120.degree. C. for one minute. 
Thereafter, the resultant material was developed by dipping in a 1.8-wt. % 
aqueous tetramethylammoniumhydroxide solution (to be abbreviated an 
aqueous TMAH solution hereinafter) for one minute, thus forming a positive 
pattern. 
EXAMPLES 2-6 
Pairs of alkali-soluble polymers and compounds represented by formula (I), 
mixing amounts of which are listed in Table 6 (to be presented later), 
were dissolved each in 250 g of ethylcellosolveacetate. The resultant 
solutions were filtered by a fluorine resin membrane filter having a pore 
size of 0.2 .mu.m, thereby preparing five types of resists. 
Subsequently, following the same procedures as in Example 1, these resists 
were subjected to coating drying, pattern exposure, and baking on silicon 
wafers. Thereafter, development was performed with a 2.38-wt. % aqueous 
TMAH solution, thus forming five types of positive patterns. 
The shapes of the positive patterns of Examples 1 to 6 were examined. The 
result is also shown in Table 6 (to be presented later). 
As is apparent from Table 6, fine positive patterns with a rectangular 
profile could be formed with high precision according to Examples 1 to 6. 
In addition, a period in which a sensitivity change falls within a range of 
.+-.10% at room temperature (25.degree. C.) was checked for each of the 
resists used in Examples 1 to 6. As a result, the periods of these 
resists were 12 months or more. That is, it was confirmed that each resist 
had high storage stability. 
EXAMPLE 7 
An aluminum film was coated on a silicon wafer, and a resist like that in 
Example 1 was coated on the aluminum film. Following the same procedures 
as in Example 1, exposure and development were performed to form a pattern 
0.35 .mu.m in width. Subsequently, portions of the aluminum film exposed 
from the pattern as a mask were subjected to dry etching using CBrCl.sub.3 
gas. Consequently, the above 0.35-.mu.m pattern could be faithfully 
transferred onto the aluminum film. 
EXAMPLES 8-12 
Pairs of alkali-soluble polymers and compounds represented by formula (I), 
mixing amounts of which are shown in Table 7 (to be presented later), were 
dissolved each in 250 g of ethylcellosolveacetate. The resultant solutions 
were filtered by a fluorine resin membrane filter having a pore size of 
0.2 .mu.m, thus preparing five types of resists. 
Subsequently, following the same procedures as in Example 1, these resists 
were subjected to coating, drying, pattern exposure, and baking on silicon 
wafers. Thereafter, development was performed with a 2.38-wt. % aqueous 
TMAH solution, thereby forming five types of positive patterns. 
Controls 1 & 2 
Pairs of alkali-soluble polymers and compounds each having, in a single 
molecule, a substituent which decomposes with an acid and a group which 
produces an acid with light, in mixing amounts shown in Table 8 (to be 
presented later), were dissolved each in 250 g of ethylcellosolveacetate. 
The resulting solutions were filtered by a fluorine resin membrane filter 
having a pore size of 0.2 .mu.m, thus preparing two types of resists. 
Subsequently, following the same procedures as in Example 1, these resists 
were subjected to coating, drying, pattern exposure, and baking on silicon 
wafers. Thereafter, development was performed with a 2.38-wt. % aqueous 
TMAH solution, thereby forming two types of positive patterns. 
A period in which a sensitivity change falls within a range of .+-.10% at 
room temperature (25.degree. C.) was examined for each of the resists of 
Examples 8 to 12 and Controls 1 and 2. In addition, the shapes of the 
positive patterns formed by Examples 8 to 12 and Controls 1 and 2 were 
checked. The results of Examples 8 to 12 are shown in Table 7 (to be 
presented later), and those of Controls 1 and 2 are shown in Table 8 (to 
be presented later). 
As is apparent from Tables 7 and 8, according to Examples 8 to 2, fine 
positive patterns with a rectangular profile could be formed with high 
precision, and the storage stability of each resist was good. Conversely, 
Controls 1 and 2 were poor in both pattern resolution and storage 
stability. 
EXAMPLE 13 
A silicon-bonded alkali-soluble polymer and compound represented by formula 
(I), mixing amounts of which are shown in Table 9 (to be presented later), 
was dissolved in 400 g of ethylcellosolveacetate. Thereafter, the 
resultant solution was filtered by a fluorine resin membrane filter having 
a pore size of 0.2 .mu.m, thereby preparing resist. 
Subsequently, a polymeric material solution containing a commercially 
available novolak resin was coated on a silicon substrate to have a 
thickness of 2.0 .mu.m. Thereafter, the resultant material was heated at 
220.degree. C. for 30 minutes to form a polymeric material layer 
(flattening layer). The above resist was coated on the flattening layer to 
have a thickness of 0.6 .mu.m, and the resultant material was dried on a 
hot plate at 90.degree. C. for five minutes. Pattern exposure (100 
mJ/cm.sup.2) was then performed using a KrF excimer laser beam 248 nm in 
wavelength. The resulting material was heated on the hot plate at 
100.degree. C. for five minutes. After the heating, the resultant material 
was developed by dipping in a 1.0-wt. % aqueous TMAH solution for one 
minute to form a positive pattern (upper pattern). 
The silicon substrate having the upper pattern was placed in a dry etching 
apparatus (HIRRIE (tradename): available from TOKUDA SEISAKUSHO K.K.). 
Reactive ion etching (RIE) was performed using an oxygen plasma at a power 
of 0.8 W/cm.sup.2, an oxygen gas pressure of 4 Pa, and a flow rate of 50 
sccm for two minutes, thereby selectively etching the lower flattening 
layer by using the upper pattern as a mask. At this time, a flattening 
pattern was formed on the silicon substrate. 
EXAMPLES 14-18 
Pairs of silicon-bonded alkali-soluble polymers and compounds represented 
by formula (I), mixing amounts of which are shown in Table 9 (to be 
presented later), were dissolved each in 400 g of ethylcellosolveacetate. 
Thereafter, the resultant solutions were filtered by a fluorine resin 
membrane filter having a pore size of 0.2 .mu.m, thereby preparing five 
types of resists. 
Subsequently, five types of flattening patterns were formed using these 
resists, respectively, in the same method as Example 13. 
The shapes of the flattening patterns of Examples 13 to 18 were observed by 
a scanning electron microscope. The result is also shown in Table 9 (to be 
presented later). 
As is apparent from Table 9, it was possible to form two-layered patterns 
each having a fine and sharp pattern profile 0.3 .mu.m in both line width 
and line interval. 
In addition, a period in which a sensitivity change falls within a range of 
.+-.10% at room temperature (25.degree. C.) was checked for each of the 
resists used in Examples 13 to 18. As a result, these resists had periods 
of 12 months or more. That is, it was confirmed that each resist had high 
storage stability. 
As has been described above, the pattern formation resist according to the 
present invention is exposed well with deep UV or an ionizing radiation, 
has a high dry etching resistance, and can suppress swell or the like 
because it can be developed with an aqueous alkali solution after 
exposure. The result is that a fine pattern having a rectangular sectional 
shape is formed with high precision through simple steps and control. In 
addition, the pattern formation resist according to the present invention 
has a high storage stability. This makes it possible to use the resist as 
a mask in a dry etching step for semiconductor devices. 
Furthermore, the pattern formation resist according to the present 
invention, which contains as one component an alkali-soluble polymer in 
which silicon is bonded on its main or side chain, makes it possible to 
form a fine pattern having an oxygen RIE resistance by exposure using deep 
UV or a ionizing radiation and development using an aqueous alkali 
solution. Therefore, this pattern formation resist can be applied to a 
two-layered resist process which can be micropatterned more finely than a 
single-layered resist process. 
Additional advantages and modifications will readily occur to those skilled 
in the art. Therefore, the invention in its broader aspects is not limited 
to the specific details, and illustrated examples shown and described 
herein. Accordingly, various modifications may be made without departing 
from the spirit or scope of the general inventive concept as defined by 
the appended claims and their equivalents. 
TABLE 1 
______________________________________ 
##STR3## 
##STR4## 
##STR5## 
##STR6## 
##STR7## 
##STR8## 
##STR9## 
##STR10## 
##STR11## 
##STR12## 
______________________________________ 
TABLE 2 
______________________________________ 
##STR13## 
##STR14## 
##STR15## 
______________________________________ 
TABLE 3 
______________________________________ 
##STR16## 
##STR17## 
##STR18## 
##STR19## 
##STR20## 
##STR21## 
##STR22## 
##STR23## 
##STR24## 
##STR25## 
##STR26## 
##STR27## 
##STR28## 
##STR29## 
##STR30## 
##STR31## 
##STR32## 
##STR33## 
##STR34## 
##STR35## 
##STR36## 
##STR37## 
##STR38## 
##STR39## 
##STR40## 
##STR41## 
##STR42## 
##STR43## 
##STR44## 
______________________________________ 
TABLE 4 
______________________________________ 
##STR45## 
##STR46## 
##STR47## 
##STR48## 
##STR49## 
##STR50## 
______________________________________ 
TABLE 5 
__________________________________________________________________________ 
##STR51## 
##STR52## 
##STR53## 
##STR54## 
##STR55## 
##STR56## 
##STR57## 
##STR58## 
##STR59## 
##STR60## 
##STR61## 
##STR62## 
##STR63## 
##STR64## 
##STR65## 
##STR66## 
##STR67## 
##STR68## 
##STR69## 
##STR70## 
##STR71## 
##STR72## 
##STR73## 
##STR74## 
##STR75## 
##STR76## 
##STR77## 
##STR78## 
__________________________________________________________________________ 
TABLE 6 
__________________________________________________________________________ 
Alkali-soluble polymer 
Compound represented by formula (I) 
(numerals in parentheses 
(numerals in parentheses represent 
Example 
represent mixing amount) 
mixing amount) Pattern 
__________________________________________________________________________ 
shape 
1 Poly(p-vinylphenol) (70 g) 
##STR79## Sharp pattern profile of 
0.35 .mu.m 
2 1:1 copolymer of poly(p-vinylphenol- methy methacrylate) (70 
##STR80## Sharp pattern profile of 
0.35 .mu.m 
3 1:1 copolymer of poly(styrene-maleic acid) (70 g) 
##STR81## Sharp pattern profile of 
0.35 .mu.m 
4 Novolak resin (m-cresol:p-cresol = 1:1) (70 g) 
##STR82## Sharp pattern profile of 
0.35 .mu.m 
5 Poly(p-vinylphenol) (70 g) 
##STR83## Sharp pattern profile of 
0.35 .mu.m 
6 Poly(p-vinylphenol) (70 g) 
##STR84## Sharp pattern profile of 
0.35 .mu.m 
__________________________________________________________________________ 
TABLE 7 
__________________________________________________________________________ 
Alkali-soluble 
polymer 
(numerals in Period 
parentheses 
Compound represented by formula (I) of sensi- 
Ex- represent 
(numerals in parentheses represent tivity 
Pattern 
ample 
mixing amount) 
mixing amount) 10% shape 
__________________________________________________________________________ 
8 Poly(p-vinyl- phenol) (50 g) 
##STR85## &gt;12 months 
Sharp pattern 
of 0.35 .mu.m 
9 1:1 copolymer of (styrene- maleic acid methylester) (40 
##STR86## &gt;12 months 
Sharp pattern 
of 0.35 .mu.m 
10 Novolak resin (m-cresol: p-cresol = 1:1) (60 g) 
##STR87## &gt;12 months 
Sharp pattern 
of 0.35 .mu.m 
11 Poly(p-vinyl- phenol) (50 g) 
##STR88## &gt;12 months 
Sharp pattern 
of 0.35 .mu.m 
12 1:1 copolymer of poly(.alpha.- methylstyrene- maleic 
acid methylester) (90 g) 
##STR89## &gt;12 months 
Sharp pattern 
of 0.35 
__________________________________________________________________________ 
.mu.m 
TABLE 8 
__________________________________________________________________________ 
Compound having in one molecule both substituent 
Alkali-soluble polymer 
which decomposes with acid and group which produces 
(numerals in parentheses 
acid with light (numerals in parentheses 
Period of 
Control 
represent mixing amount) 
mixing amount) sensitivity 
Pattern 
__________________________________________________________________________ 
shape 
1 Poly(p-vinylphenol) (70 g) 
##STR90## 3 months Tapered pattern 
of 0.40 .mu.m 
2 Cresol novolak resin (90 g) 
##STR91## 4 months Sharp pattern of 
0.40 
__________________________________________________________________________ 
.mu.m 
TABLE 9 
__________________________________________________________________________ 
Silicon-bonded alkali-soluble polymer 
Compound represented by formula (I) 
(numerals in parenthesis represent 
(numerals in parentheses represent 
Example 
mixing amount) mixing amount) Pattern 
__________________________________________________________________________ 
shape 
13 
##STR92## 
##STR93## Sharp pattern of 
0.35 .mu.m 
(70 g) (30 g) 
14 
##STR94## 
##STR95## Sharp pattern 0f 
0.35 .mu.m 
(50 g) (50 g) 
15 
##STR96## 
##STR97## Sharp pattern of 
0.35 .mu.m 
(70 g) (30 g) 
16 
##STR98## 
##STR99## Sharp pattern of 
0.35 .mu.m 
(60 g) (40 g) 
17 
##STR100## 
##STR101## Sharp pattern of 
0.35 .mu.m 
(80 g) (20 g) 
18 
##STR102## 
##STR103## Sharp pattern of 
0.35 .mu.m 
(70 g) (30 g) 
__________________________________________________________________________