Photosensitive composition containing a cyclic dione polymer

The present invention provides a cyclic dione polymer, which is a homopolymer or a copolymer of a cyclic dione monomer selected from those represented by formulae (I) and (II) ##STR1## wherein PA1 A and B may be the same or different and are independently selected from the group consisting of halogen, hydrogen, C.sub.3-20 cyclic or pericyclic alkyl, C.sub.1-20 linear and branched alkyl, C.sub.6-20 aryl, C.sub.7-20 arylalkyl, C.sub.7-20 alkylaryl, silyl, alkylsilyl, germyl, alkylgermyl, alkoxycarbonyl, acyl, and a heterocylic group; or, A and B are linked together to form a C.sub.3-20 saturated or unsaturated cyclic hydrocarbon group or a substituted or unsubstituted heterocyclic group; PA1 C is selected from the group consisting of oxygen, sulfur, ##STR2## PA1 wherein each R.sup.1 is independently selected from C.sub.1-20 alkyl and phenyl.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a novel cyclic dione polymer, and more
 particularly relates to a novel cyclic dione polymer that is suitable for
 use in thin film coating and photoresist technology.
 2. Description of the Prior Art
 Nowadays, thin film coating and photoresist technology play very important
 roles in chemical engineering technology. A resin suitable for thin film
 coating should meet the requirements of not only having good film
 properties and good adherence to substrates, but also having good
 stability over a long storage time and low moisture absorbability.
 Therefore, a suitable resin should not have too many functional groups of
 high moisture absorbability. To be considered for application in IC
 photoresists, a suitable resin should further have other properties such
 as high etch and heat resistance, properties which are frequently achieved
 by molecular design.
 To date, the most frequently used resin for thin film coating is the
 copolymer of a maleic anhydride derivative and norbornene, which has been
 disclosed in U.S. Pat. No. 3,928,497. Such a resin is suitable for being
 applied in IC photoresists because it has a broad processing window and
 linear relationship. However, since maleic anhydride easily absorbs
 moisture to form acid molecules, it has an inferior shelf life. Moreover,
 when the humidity in the air varies greatly, the E.sub.0 (photo speed) and
 .gamma. (contrast) will be difficult to be controlled; therefore, a stable
 line width of good properties can not be obtained. Since the disadvantage
 of high absorbability of said resin is due to its chemical structure,
 incorporating a plastisizer of low moisture absorbability is the only way
 to date of decreasing the absorbability of the maleic anhydride
 derivative/norbornene copolymer. In addition, said copolymer has other
 disadvantages: the glass transition temperature is too high, the film
 properties are inferior, and the film will easily crack.
 SUMMARY OF THE INVENTION
 Therefore, an object of the present invention is to solve the
 above-mentioned problems and to provide a novel resin which has a lower
 moisture absorbability and transition temperature, good adherence and
 storage stability, and can be used in thin film coating and photoresist
 technology.
 To achieve the above object, the present invention uses specific monomers
 to prepare resins, so as to improve the properties of the resins. The
 present invention uses a cyclic dione monomer to replace the conventional
 maleic anhydride derivative, and further provides a resin system prepared
 from such a cyclic dione monomer. Since such a cyclic dione monomer has
 low moisture absorbability, the resin prepared from the monomer will have
 a decrease moisture absorbability.
 The novel resin system of the present invention is a cyclic dione polymer,
 which is a homopolymer or a copolymer of a cyclic dione monomer selected
 from those represented by formulae (I) and (II)
 ##STR3##
 wherein
 A and B may be the same or different and are independently selected from
 the group consisting of halogen, hydrogen, C.sub.3-20 cyclic or pericyclic
 alkyl, C.sub.1-20 linear and branched alkyl, C.sub.6-20 aryl, C.sub.7-20
 arylalkyl, C.sub.7-2, alkylaryl, silyl, alkylsilyl, germyl, alkylgermyl,
 alkoxycarbonyl, acyl, and a heterocylic group; or, A and B are linked
 together to form a C.sub.3-20 saturated or unsaturated cyclic hydrocarbon
 group or a substituted or unsubstituted heterocyclic group;
 C is selected from the group consisting of oxygen, sulfur,
 ##STR4##
 wherein each R.sup.1 is independently selected from C.sub.1-20 alkyl and
 phenyl.
 Representative examples of the cyclic dione monomers of formula (I) include
 ##STR5##
 Representative examples of the cyclic dione monomers of formula (II)
 include
 ##STR6##
 The cyclic dione polymer of the present invention can also be a copolymer
 including a cyclic olefin comonomer. That is, the cyclic dione polymer of
 the present invention can be a copolymer of at least one cyclic dione
 monomer of formula (I) or (II) and at least one comonomer of a cyclic
 olefin.
 The cyclic olefin suitable for use can be norbornene or a norbornene
 derivative.
 The norbornene derivative can be
 ##STR7##
 The norbornene derivative can also be a compound having the following
 formula:
 ##STR8##
 wherein m is an integer from 1 to 3; or a compound having the following
 formula:
 ##STR9##
 wherein q is an integer from 1 to 3, and X is selected from O, N, or S.
 A "chemically amplified resist" is a kind of photoresist in which the rate
 of dissolution in a developer can be changed by an acid produced by
 photoirradiation. Such a photoresist solution includes a protected resin,
 a photoacid generator, and a solvent. The so-called protected resin is a
 resin that is protected by an acid-labile protective group. The resin will
 be converted into alkali-soluble when the acid-labile protective group is
 decomposed. When the chemically amplified resist applied on a substrate is
 exposed to light, the photoacid generator will generate acid, and the acid
 will decompose the acid-labile protective group in the resin, thus making
 the resin soluble in an alkali developer.
 Therefore, if the cyclic dione polymer of the present invention is used for
 a chemically amplified resist, such a cyclic dione polymer preferably has
 an acid-labile protective group, which will be decomposed in the presence
 of an acid so that the cyclic dione polymer will be converted into an
 alkali-soluble polymer.
 Such an acid-labile protective group may be present in formula (I), formula
 (II), a cyclic olefin comonomer that can be copolymerized with formula (I)
 or (II), or present in any monomer that can be copolymerized with formula
 (I) or (II).
 For example, a cyclic olefin comonomer that can be copolymerized with
 formula (I) or (II) can be norbornene or a norbornene derivative. Such a
 norbornene derivative can have an acid-labile protective group D. Thus,
 when the cyclic dione polymer of the present invention is in the presence
 of an acid, the protective group D will be decomposed, such that the
 cyclic dione polymer will be converted to an alkali soluble polymer. Such
 norbornene derivatives include:
 ##STR10##
 wherein
 D is an acid-labile protective group, which is decomposed in the presence
 of an acid, so as to make the cyclic dione polymer alkali-soluble, and
 each R.sup.3 is independently selected from the group consisting of
 hydrogen, C.sub.1-20 linear and branched alkyl, C.sub.3-20 cyclic and
 pericyclic alkyl.
 Representative examples of D include:
 ##STR11##
 wherein R.sup.4 is selected from the group consisting of hydrogen,
 C.sub.1-20 linear and branched alkyl, C.sub.3-20 cyclic and pericyclic
 alkyl.
 As described above, the cyclic dione polymer of the present invention can
 be a copolymer of at least one cyclic dione monomer of formula (I) or (II)
 and at least one comonomer of a cyclic olefin. For example, formula (I)
 can be reacted with any above-mentioned norbornene derivative containing
 an acid-labile protective group via free radical polymerization. Also,
 formula (II) can be reacted with any above-mentioned norbornene derivative
 containing an acid-labile protective group via free radical
 polymerization. The obtained cyclic dione polymer can be represented by
 formula (III):
 ##STR12##
 wherein
 A, B, C, D, and R.sup.3 are defined as above,
 p, q, x, y, and z are the molar ratios of the corresponding monomers,
 p+q+x+y+z=1,
 p, q, x, y, and z are in the range of 0 to 0.5,
 p+q is larger than 0, and
 x+y+z is in the range of 0 to 0.8.
 Particularly, the obtained cyclic dione polymer can be represented by
 formula (IV):
 ##STR13##
 wherein
 A, B, C, D, and R.sup.3 are defined as above,
 p and y are the molar ratios of the corresponding monomers,
 p+y=1, and
 p and y are in the range of 0.1 to 0.9.
 The cyclic dione polymer of the present invention is not limited to those
 obtained via free radical polymerization. All homopolymers and copolymers
 obtained by using the cyclic dione monomer of formula (I) or (II) as the
 monomer are within the scope of the present invention, no matter what the
 polymerization is. The polymerization can be free radical polymerization,
 stepwise polymerization, anionic polymerization, or cationic
 polymerization.
 To make the cyclic dione polymer of the present invention suitable for thin
 film coating, the obtained cyclic dione polymer is preferably soluble in
 an organic solvent. A preferable cyclic dione polymer of the present
 invention has a glass transition temperature of 130.degree. C. to
 300.degree. C., a weight average molecular weight of 1000 to 50000, and a
 decomposition temperature (T.sub.d) higher than 130.degree. C. Such cyclic
 dione polymers that meet these requirements are very suitable for use as
 the resin for thin film coating. Thin film coating can be applied to the
 coating of photosensitive inks, printing inks, photoresists, and surface
 coating materials.
 When the cyclic dione polymer of the present invention is applied to a
 photoresist (photosensitive composition), a preferred wavelength range is
 from 150 nm to 600 nm, most preferably at a wavelength of 193 nm or 248
 nm. When the cyclic dione polymer of the present invention includes an
 acid-labile protective group, it is most suitable for use in chemically
 amplified photoresists.
 The cyclic dione polymer of the present invention can be blended with any
 other polymer to form a polymer blend. Thereby, the polymer blend can
 impart properties that the original cyclic dione polymer does not have,
 thus meeting various needs.
 The advantages of the present invention can be summarized as follows:
 1. The present invention uses a cyclic dione monomer to replace the maleic
 anhydride derivative as a monomer, such that the properties of the
 resulting resin can be improved by the improved monomer. Since the cyclic
 dione monomer has low moisture absorbability, the resulting novel resin
 containing such a cyclic dione will have low moisture absorbability, thus
 causing the resin to be more stable and have a long shelf life.
 2. The resin can impart good adherence to the substrate by the ketone group
 contained in the cyclic dione monomer.
 3. By means of the suitable alkyl group linked on the cyclic dione monomer,
 the freedom of the resin can be increased, thus lowering the glass
 transition temperature (Tg) of the resin to about 130.degree. C. to
 300.degree. C. Moreover, the cyclic dione polymer of the present invention
 has a weight average molecular weight of about 1000 to 50000; therefore,
 it has good film properties and will not crack.
 4. When the cyclic dione polymer of the present invention contains an
 acid-labile protective group, it can be applied in chemically amplified
 photoresists. Since exposure to light can cause the cyclic dione polymer
 of the present invention to undergo a distinguishing change in solubility,
 the E.sub.0 (photo speed) and .gamma. (contrast) are excellent for
 applications.

The following examples are intended to illustrate the process and the
 advantages of the present invention more fully without limiting its scope,
 since numerous modifications and variations will be apparent to those
 skilled in the art.
 EXAMPLE 1
 Synthesis of the Cyclic Dione Polymer (Resin)
 15.4 g of 2-methyl-2-ethyl-2H-pyran-3,6-dione, 9.81 g of
 t-butyl-2-carboxylate-5-[2,2,1.sup.1.4 ]heptene (a norbornene derivative),
 and 0.81 g of 2,2'-azobisisobutyronitrile (AIBN) were dissolved in 25 g of
 tetrahydrofuran (THF) and heated at 70.degree. C. for 8 hours. The
 reaction solution was dropped into a mixed solution of 100 ml of
 isopropanol and 100 ml of n-hexane to obtain 6.28 g of the resin (cyclic
 dione polymer) as a white solid. The resin has a Td of 192.degree. C.
 (analyzed by TGA), a Tg (analyzed by DSC) higher than Td, a weight average
 molecular weight of 3604 (analyzed by GPC), and a resin synthesis
 conversion ratio of 25.1%.
 EXAMPLE 2
 Test of Film Properties of the Resin
 1.5 g of the resin obtained from Example 1 was dissolved in 8.5 g of PGMEA
 (propylene glycol monomethyl ether acetate) and stirred for 8 hours. The
 mixture was filtered through a 0.2 .mu.m filter. 2 ml of the filtrate was
 applied to a 4 inch wafer by spin coating at 3000 rpm and soft baked at
 130.degree. C. The film thickness was measured at sixteen points by
 Nanospec as 5728.+-.32.ANG., indicating that the film properties are good.
 EXAMPLE 3
 Test of the Water Content of the Resin
 2.5 g of the resin obtained from Example 1 was dissolved in THF and stirred
 for 8 hours to obtain a 25% THF solution of resin. The resin solution was
 kept still at room temperature for 3 days. 4 to 5 g of the resin solution
 was titrated with Hydraual Composite 5 as a standard solution by using a
 Karl-Fischer instrument. The results showed that the resin has a water
 content of 0.589%.
 Comparative Example
 The same procedures as described in Example 1 were employed except that
 2-methyl-2-ethyl-2H-pyran-3,6-dione was replaced with maleic anhydride,
 thus, a copolymer of maleic anhydride was obtained. Then, a 25% maleic
 anhydride copolymer solution was prepared according to the method as
 described in Example 3. The water content of the resin (maleic anhydride
 copolymer) was measured to be 0.886%.
 The results show that the resin (cyclic dione polymer) of the present
 invention has a lower moisture absorbability than the conventional maleic
 anhydride copolymer resin; therefore, it has better stability and longer
 shelf life.