Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2002-04-24
2004-03-30
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S907000, C430S910000, C430S905000, C525S242000, C525S245000, C525S247000, C525S268000, C549S386000
Reexamination Certificate
active
06713228
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polymer and a resist composition that can be used as an electronic industrial material such as photoresist, and more particularly, to monomers having multi-ring structure, and a photosensitive polymer and a resist composition obtained from the same.
2. Description of the Related Art
As the manufacture of semiconductor devices becomes complicated and the integration density of semiconductor devices highly increases, there is a need to form a fine pattern. Furthermore, with regard to 1-Gigabit or more semiconductor devices, a pattern size having a design rule of 0.15 &mgr;m or less is needed. However, when a conventional photoresist material is exposed with KrF excimer laser (248 nm), there is a limitation in forming such a fine pattern. For this reason, development of a lithography technique using a new exposure light source, ArF excimer laser (193 nm), is under way to be commercially available in the near future. Also, for adoption to the manufacture of semiconductor devices in which formation of patterns of 0.15 &mgr;m or less is needed, research into another next-generation technique using F
2
excimer laser (157 mn) as a new exposure light source is being extensively conducted.
Whereas research into ArF and F
2
excimer laser techniques is being vigorously carried out, existing resist compositions suitable for use in those techniques cause many problems in practical use, compared to conventional KrF resist compositions. Almost all well-known ArF resist compositions contain (meth)acryl-based polymers. Among these polymers, a methacrylate copolymer having an alicyclic protecting group, which is expressed by the formula below:
This polymer has an adamantyl group, which contributes to enhancing resistance to dry etching, and a lactone group, which improves adhesiveness, in its methacrylate backbone. As a result, the resolution of the resist and the depth of focus has improved. However, resistance to dry etching is still weak, and serious line edge roughness is observed after line patterns are formed from the resist layer.
Another drawback of the polymer having the formula above is that the raw material used to synthesis the polymer is expensive.
As another conventional resist composition, a cycloolefin-maleic anhydride (COMA) alternating polymer having the following formula has been suggested:
In the production of copolymer, such as a COMA alternating polymer having the formula above, resistance to dry etching is improved and the production cost of raw material is cheap, whereas resolution of the polymer sharply decreases. Also, the copolymer has a glass transition temperature (Tg) of 200° C. or higher due to the structural strength of norbornene contained in the backbone, resulting in processing difficulty. In addition, the synthetic polymers have in their backbone the alicyclic group, which shows prominent hydrophobicity, and thus the adhesiveness to neighboring material layers is very poor.
To overcome the-described problems, in recent years, polymers having various structures have been proposed, the polymers exemplified by a copolymer of a COMA system and a monomer units having a (meth)acylate-based backbone:
Since the copolymer having the above structure has a glass transition temperature (Tg) lower than that of the COMA system, the processing can be easily carried out. Also, since a polarity change occurs to (meth)acrylate monomer units, increased resolution can be achieved. However, according to reports hitherto made, resistance to dry etching has not been enhanced very much. To increase the resistance to dry etching, a bulky protecting group such as an adamantly group, rather than a t-butyl group, is introduced to the above structure. However, the resulting resist still exhibits weak resistance to dry etching or poor patterns.
As the pattern rule becomes finer in the manufacture of semiconductor devices, the aspect ratio is considerably increased, resulting in the collapse of patterns. To avoid this, a lithography technique using ArF excimer lasers may be used. However, in the case of using the lithography technique using ArF excimer lasers, patterns must be formed such that a resist layer is coated on a wafer to a thickness of 4000 A or less. As the thickness of the resist layer is reduced as above, it is necessary to enhance resistance to dry etching.
Another conventional resist composition proposed for enhancing resistance to dry etching includes a polymer having only a norbornene structure in its backbone, represented by the following formula:
However, in order to obtain the above structure, a catalyst made from a heavy metal such as platinum or nickel is necessary. The heavy metal used as a catalyst during polymerization cannot be completely removed. Thus, the resist composition obtained from the polymer may cause serious contamination due to the heavy metal, making practical use difficult.
SUMMARY OF THE INVENTION
To solve the above problems, it is a first object of the present invention to provide monomers used as raw materials for polymers that can be adopted to various light sources including KrF excimer lasers, ArF excimer lasers or F
2
excimer lasers in a photolithography process.
It is a second object of the present invention to provide a photosensitive polymer which can be obtained by a simple synthesis method and can provide enhanced resistance to dry etching without contamination due to a heavy metal catalyst.
It is a third object of the present invention to provide a resist composition having enhanced resistance to dry etching and good transmittance, can adopt various light sources including KrF excimer lasers, ArF excimer lasers or F
2
excimer lasers in a photolithography process and can provide a good lithographic property of high resolution.
The first object of the present invention can be accormplished by providing a monomer having a structure represented by the following formula:
wherein R
1
is -H or -CH
3
, R
2
and R
3
are -H, -OH or an alkyl group having 1-20 carbon atoms. In the monomer according to the present invention, R
2
and R
3
are preferably selected from a group consisting of alkyl, hydroxyalkyl, alkyloxy, carboxyl, carbonyl, ester, and fluorinated alkyloxy.
Preferably, the monomer has a structure represented by the following formula:
Also, the monomer preferably has a structure represented by the following formula:
The monomer may have a structure represented by the following formula:
Also, the monomer may have a structure represented by the following formula:
Further, the monomer may have a structure represented by the following formula:
To achieve the second object, there is provided a photosensitive polymer comprising a monomer unit represented by the following formula:
wherein R4 and R
5
are -H or -CH
3
, and R
6
and R
7
are -H1 -OH or an alkyl group containing 1-20 carbon atoms.
In a preferred photosensitive polymer, at least one of R
6
and R
7
is selected from a group consisting of alkyl, hydroxyalkyl, alkyloxy, carboxyl, carbonyl, ester and fluorinated alkyloxy.
Preferably, the photosensitive polymer has a structure represented by the following formula:
wherein R
8
is an alkyl group having 4-12 carbon atoms, and s is an integer from 0 to 2, preferably 1 to 2.
More preferably, R
8
is one of t-butyl, tetrahydropyranyl or a substituted or unsubstituted alicyclic group. Examples of R
8
is selected from a group consisting of 1 -methyl-1-cyclohexyl, 1-ethyl-1-cyclohexyl, 2-methyl-2-norbomyl, 2-ethyl-2-norbornyl, 2-methyl-2-isobomyl, 2-ethyl-2-isobomyl, 8-methyl-8-tricyclo[5.2.1.0
2,6
]decanyl, 8-ethyl-8-tricyclo [5.2.1.0
2,6
]decanyl, 2-methyl-2-adamantyl, 2-ethyl-2-adamantyl, 1 -adamantyl-1-methylethyl, 2-methyl-2-fenchyl and 2-ethyl-2-fenchyl.
Also, the photosensitive polymer preferably has a structure represented by the following formula:
wherein R
9
is a C
1
~C
20
hydrocarbon group.
In the above formula, R
9
is selected from a group consisting of methyl, ethyl, a t-butyl and cyclohexyl.
Prefera
Kim Hyun-Woo
Lee Sung-Ho
Woo Sang-Gyun
Baxter Janet
Marger & Johnson & McCollom, P.C.
Samsung Electronics Co,. Ltd.
Thornton Yvette C.
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