Tetrahydrofuran compounds having alicyclic structure

Details Tetrahydrofuran compounds having alicyclic structure Tetrahydrofuran compounds having alicyclic structure

2002-04-08

2003-01-21

Owens, Amelia (Department: 1625)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C549S429000

Reexamination Certificate

active

06509481

ABSTRACT:

This invention relates to novel tetrahydrofuran compounds useful as monomers to form base resins for use in chemically amplified resist compositions adapted for micropatterning lithography.
BACKGROUND OF THE INVENTION
While a number of recent efforts are being made to achieve a finer pattern rule in the drive for higher integration and operating speeds in LSI devices, deep-ultraviolet lithography is thought to hold particular promise as the next generation in microfabrication technology. In particular, photolithography using a KrF or ArF excimer laser as the light source is strongly desired to reach the practical level as the micropatterning technique capable of achieving a feature size of 0.3 &mgr;m or less.
The resist materials for use in photolithography using light of an excimer laser, especially ArF excimer laser having a wavelength of 193 nm, are, of course, required to have a high transmittance to light of that wavelength. In addition, they are required to have an etching resistance sufficient to allow for film thickness reduction, a high sensitivity sufficient to eliminate any extra burden on the expensive optical material, and especially, a high resolution sufficient to form a precise micropattern. To meet these requirements, it is crucial to develop a base resin having a high transparency, rigidity and reactivity. None of the currently available polymers satisfy all of these requirements. Practically acceptable resist materials are not yet available.
Known high transparency resins include copolymers of acrylic or methacrylic acid derivatives and polymers containing in the backbone an alicyclic compound derived from a norbornene derivative. All these resins are unsatisfactory. For example, copolymers of acrylic or methacrylic acid derivatives are relatively easy to increase reactivity in that highly reactive monomers can be introduced and acid labile units can be increased as desired, but difficult to increase rigidity because of their backbone structure. On the other hand, the polymers containing an alicyclic compound in the backbone have rigidity within the acceptable range, but are less reactive with acid than poly(meth)acrylate because of their backbone structure, and difficult to increase reactivity because of the low freedom of polymerization. Additionally, since the backbone is highly hydrophobic, these polymers are less adherent when applied to substrates. Therefore, some resist compositions which are formulated using these polymers as the base resin fail to withstand etching although they have satisfactory sensitivity and resolution. Some other resist compositions are highly resistant to etching, but have low sensitivity and low resolution below the practically acceptable level.
SUMMARY OF THE INVENTION
An object of the invention is to provide a novel tetrahydrofuran compound useful as a monomer to form a polymer for use in the formulation of a photoresist composition which exhibits firm adhesion and high transparency when processed by photolithography using light with a wavelength of less than 300 nm, especially ArF excimer laser light as the light source.
We have found that a tetrahydrofuran compound of formula (1), (2), (3) or (4) can be prepared in high yields by a simple method to be described later, that a polymer obtained from this tetrahydrofuran compound has high transparency at the exposure wavelength of an excimer laser, and that a resist composition comprising the polymer as a base resin is improved in adhesion to substrates.
The present invention provides a tetrahydrofuran compound of the following general formula (1).
Herein the broken line represents a single bond, a divalent organic group, or a structure in which the alicyclic structure in the form of norbornene or tetracyclo[4.4.0.1
2,5
.1
7,10
]dodecene and the tetrahydrofuran cyclic structure share one or two constituent carbon atoms, and k is 0 or 1.
In one embodiment, the invention provides a tetrahydrofuran compound having the following general formula (2).
Herein X is a single bond or a group —(CH
2
)
m
— in which one or more methylene groups may be replaced by one or more oxygen atoms, m is an integer of 1 to 8, and k is 0 or 1.
Another embodiment is a tetrahydrofuran compound having the following general formula (3).
Herein one of two Y's is an oxygen atom and the other is a methylene group, and k is 0 or 1.
A further embodiment is a tetrahydrofuran compound having the following general formula (4):
Herein one of two Z's is an oxygen atom and the other is a methylene group, and k is 0 or 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The tetrahydrofuran compounds of the present invention have the general formula (1).
Herein, the broken line represents a single bond, a divalent organic group, or a structure in which the alicyclic structure in the form of norbornene or tetracyclo[4.4.0.1
2,5
.1
7,10
]dodecene and the tetrahydrofuran cyclic structure share one or two constituent carbon atoms, and k is 0 or 1.
The divalent organic group is preferably a group —(CH
2
)
m
— in which one or more methylene groups may be replaced by one or more oxygen atoms, wherein m is an integer of 1 to 8. Therefore, the preferred tetrahydrofuran compounds are those of the general formula (2).
Herein X is a single bond or a group —(CH
2
)
m
— in which one or more methylene groups may be replaced by one or more oxygen atoms, m is an integer of 1 to 8, and k is 0 or 1.
Those tetrahydrofuran compounds of the general formulae (3) and (4) are also preferred.
Herein one of two Y's is an oxygen atom and the other is a methylene group, and k is 0 or 1.
Herein one of two Z's is an oxygen atom and the other is a methylene group, and k is 0 or 1.
Illustrative examples of the inventive tetrahydrofuran compound are given below.
It is believed that resist polymers obtained using these tetrahydrofuran compounds as the monomer exhibit good adhesion to substrates because the tetrahydrofuran moiety regarded as a polar group that brings out adhesion is positioned at a site separated apart from the polymer backbone by a linker such as an alkylene group. By selecting a tetrahydrofuran compound having a linker of optimum length and type as the monomer to form a polymer, the polymer as a whole can be adjusted to an appropriate lipophilicity and controlled in dissolution properties.
The tetrahydrofuran compounds of the invention can be produced by the following three methods, for example, but the invention is not limited to these methods.
The first method is synthesis by intramolecular dehydration/cyclization reaction of a corresponding diol compound (5).
Herein the broken line and k are as defined above.
Better results are obtained from intramolecular dehydration reaction when an acid or a salt thereof, or a phosphorus reagent is used.
Examples of the acid used herein include inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, perchloric acid, and phosphoric acid and organic acids such as formic acid, acetic acid, benzoic acid, p-toluenesulfonic acid, and benzenesulfonic acid, and salts thereof as well as cation-exchange resins. Examples of the phosphorus reagent include hexamethylphosphoric triamide (HMPA), dialkyl azodicarboxylate-triphenylphosphine, triethylphosphine, and potassium carbonate-triphenylphosphine.
The second method involves the steps of converting a diol compound (5) to a compound (6) having a leaving group such as a halogen atom, alkylsulfonyloxy group or arylsulfonyloxy group, and treating the compound (6) with a base for cyclization into a tetrahydrofuran compound (1).
Herein, X is a halogen atom, alkylsulfonyloxy group or arylsulfonyloxy group, and the broken line and k are as defined above.
The first step is to synthesize the compound (6) having a leaving group. Since the compound (5) has two primary hydroxyl groups in the molecule, only one of which should be converted to a leaving group X, the amounts of reagents and reaction conditions must be carefully determined.
In the case of the compound (6) having a leaving group X w

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