Dendritic polymers and making method

Details Dendritic polymers and making method Dendritic polymers and making method

2000-03-24

2002-07-02

Teskin, Fred (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S087000, C526S173000, C526S293000, C526S326000, C526S332000, C526S333000, C525S242000, C525S292000, C525S308000, C525S312000

Reexamination Certificate

active

06414101

ABSTRACT:

This invention relates to novel dendritic or hyperbranched polymers of phenol derivatives and a method for preparing the same. More particularly, it relates to novel dendritic or hyperbranched polymers of polyhydroxystyrene derivatives and a method for preparing the same. The novel dendritic or hyperbranched polymers are useful as a base resin for resist material in forming ultrafine patterns during the microfabrication of VLSI.
BACKGROUND OF THE INVENTION
While a number of recent efforts that are being made to achieve a finer pattern rule in the drive for higher integration and operating speeds in LSI devices, lithography is thought to hold particular promise as the next generation in microfabrication technology. Deep-UV, EB and x-ray lithography is capable of achieving a minimum feature size of 0.2 &mgr;m or less.
Recently developed acid-catalyzed chemically amplified positive resists, such as those described in JP-B 2-27660, JP-A 63-27829, U.S. Pat. No. 4,491,628 and U.S. Pat. No. 5,310,619, utilize a high-intensity KrF excimer laser as the deep-UV light source. These resists are especially promising for deep-UV lithography due to their excellent properties including sensitivity, resolution, and dry etching resistance.
For example, JP-A 62-115440 discloses a resist material comprising poly-4-tert-butoxystyrene and a photoacid generator. Similarly, JP-A 3-223858 discloses a two-component resist material comprising a resin bearing tert-butoxy groups within the molecule, in combination with a photoacid generator. JP-A 4-211258 discloses a two-component resist material which is comprised of polyhydroxystyrene bearing methyl, isopropyl, tert-butyl, tetrahydropyranyl, and trimethylsilyl groups, together with a photoacid generator.
In the state-of-the-art, the base polymers which have been developed for resists are synthesized by conventional techniques, typically addition polymerization such as radical polymerization, anion polymerization and cation polymerization as described in JP-A 4-279608, JP-A 57-44608, and JP-B 63-36602. The polymers synthesized by such conventional techniques basically have linear structures.
These linear polymer resins for resist material, however, suffer from several problems. If they are required to be processed to such a finer pattern that the size of polymer molecules may become approximate to the size of fine lines, then a desired pattern of fine lines cannot be formed. Their heat resistance, sensitivity and resolution are unsatisfactory. A further improvement is thus needed.
An object of the invention is to provide a novel and improved dendritic or hyperbranched polymer which can be used as the base resin to formulate a resist composition which is superior to prior-art resists in sensitivity, resolution, exposure latitude, process flexibility and reproducibility, and which forms a resist pattern having excellent plasma etching resistance and outstanding thermal stability. Another object of the invention is to provide a method for preparing the dendritic or hyperbranched polymer.
SUMMARY OF THE INVENTION
We have found a novel dendritic or hyperbranched polymer of a phenol derivative that can be produced by the method to be described later. A resist composition formulated using this dendritic or hyperbranched polymer as the base resin is superior in resolution, exposure latitude, process flexibility, and practical utility and is advantageously used for precise microfabrication. Namely, the dendritic or hyperbranched polymer is quite useful as the base resin in resist material for VLSI microfabrication.
In a first aspect, the invention provides a polymer in the form of a dendritic or hyperbranched polymer of a phenol derivative having a weight average molecular weight of 500 to 10,000,000.
In one preferred embodiment, the polymer includes recurring units (I) and/or recurring units (II) and recurring units (III) as shown below. The number of units (III) is 1 to 1,000.
Herein R
1
is hydrogen or methyl, R
2
is independently a straight, branched or cyclic alkyl group of 1 to 30 carbon atoms or aryl group of 6 to 30 carbon atoms, R
3
is a hydroxyl or OR
4
group, R
4
is an acid labile group or acid stable group, x is 0 or a positive integer, y is a positive integer, and the sum of x and y is up to 5.
Herein R
1
is as defined above, and R
5
is a straight, branched or cyclic alkylene group of 1 to 30 carbon atoms or arylene group of 6 to 30 carbon atoms, or a mixture thereof, which may contain an ether or ester bond.
The units (III) are preferably of the following formula (3a):
wherein X is a valence bond or a straight or branched alkylene group of 1 to 10 carbon atoms which may contain a hydroxyl or carbonyl group.
In a more preferred embodiment, the dendritic or hyperbranched polymer comprises recurring units of at least one of the following formulae (4) to (8):
wherein broken lines represent polymer chains of the recurring units (I) and/or (II), and A represents the units (III)
In a second aspect, the invention provides a method for preparing the dendritic polymer defined above, comprising the steps of polymerizing a hydroxystyrene derivative monomer into an intermediate and finally into a polymer, adding a branching monomer midway in the polymerization step to introduce branch chains into the intermediate, and repeating the polymerizing and branching steps until the desired polymer is obtained.
In one preferred embodiment of the method, the hydroxystyrene derivative monomer is represented by at least one of the following general formula (i) and (ii), and the branching monomer is presented by the following formula (iii).
Herein R
1
, R
2
, R
3
, x, and y are as defined in claim
2
, R is a protective group for a hydroxyl group, R
0
is a valence bond or an alkylene group of 1 to 20 carbon atoms, and X is a halogen atom, aldehyde group or alkoxycarbonyl group.
Preferably, the polymerization step entails living polymerization, typically living anion polymerization.
The novel polymers or macromolecules of the invention are dendritic or hyperbranched polymers of phenol derivatives. When these polymers are used as the base resin, the resulting resist compositions are improved in performance due to the increased branches and increased free volume of the polymers, as compared with the prior art linear structure base resins. For example, the dendritic or hyperbranched polymers have a smaller molecular size than corresponding linear polymers, which leads to an improved resolution. When it is desired to improve heat resistance by increasing the molecular weight of the polymer, this can be accomplished without increasing the viscosity considerably, which leads to an improved process stability. The dendritic polymers have an increased number of terminuses, which is effective for improving adhesion to substrates. The polymers can be designed as desired since the number of branches and terminuses can be freely controlled.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The polymer or high molecular weight compound of the invention is a dendritic or hyperbranched polymer of a phenol derivative having a weight average molecular weight of 500 to 10,000,000.
Preferably the polymer is comprised of recurring units (I) and/or recurring units (II) and recurring units (III) as shown below. The number of units (III) is 1 to 1,000, more preferably 1 to 500, and most preferably 1 to 200.
Herein R
1
is hydrogen or methyl, R
2
, which may be the same or different, is a straight, branched or cyclic alkyl group of 1 to 30 carbon atoms or aryl group of 6 to 30 carbon atoms, R
3
is a hydroxyl or OR
4
group, R
4
is an acid labile group or acid stable group, x is 0 or a positive integer, y is a positive integer, satisfying x+y≦5. Preferably, R
3
is OR
4
.
Herein R
1
is as defined above, and R
5
is a straight, branched or cyclic alkylene group of 1 to 30 carbon atoms or arylene group of 6 to 30 carbon atoms, or a mixture thereof, which may contain an ether or ester bond.
More preferably, the units (III) are of the following formula (3a):
wherein X is a valence bond or

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