Photoresists with Reduced Environmental Impact:  Water-Soluble Resists Based on Photo-Cross-Linking of a Sugar-Containing Polymethacrylate

Abstract

A family of water-soluble, negative-tone, high-resolution, chemically amplified photoresists based on partially or fully deprotected poly(1,2:5,6-di-O-isopropylidene-3-O-methacryloyl-α-d-glucofuranose) is described. Both the molecular weight of the parent ketal-protected polymer and the extent of its deprotection to a water-soluble polymer containing 3-O-methacryloyl-d-glucopyranose repeat units must be carefully controlled to provide good coating and imaging properties. The two ketal protecting groups of the poly(1,2:5,6-di-O-isopropylidene-α-d-glucofuranose) have different reactivity, and their complete removal requires long reaction times under hydrolytic conditions. The detailed deprotection chemistry of the polymer is readily understood through model studies with the fully and partially protected analogues of the polymer pendant groups: 1,2:5,6-di-O-isopropylidene-α-d-glucofuranose and 1,2-isopropylidene-α-d-glucopyranose. When combined with a water-soluble photochemical precursor of acid such as (4-methoxyphenyl)dimethylsulfonium trifluoromethanesulfonate, films of the deprotected or partially deprotected poly(1,2:5,6-di-O-isopropylidene-3-O-methacryloyl-α-d-glucofuranose) undergo acid-catalyzed cross-linking. The enhanced performance of the partially deprotected polymers over that of poly(3-O-methacryloyl-d-glucopyranose) suggests that the presence of remaining hydrophobic groups that afford water dispersibility rather than full solubility may be key to their performance. Imaged negative-tone features as small as 0.2 μm are obtained with these materials that have sensitivities of ca. 30 mJ/cm2 with wholly aqueous casting and processing.

A water‐developable negative photoresist based on the photocrosslinking of N‐phenylamide groups with reduced environmental impact

“…Adhesion of the copolymer films on the silicon wafer was greatly improved by treating the silicon wafer with a H 2 SO 4 -H 2 O 2 solution. 2 The photosensitivity of copolymer B-2 was higher than that of copolymer A-2. The crosslinked areas of the film seemed not to take up water during development.…”

“…The copolymer solution was filtered with a Millipore filter and spincoated on a silicon wafer which was pretreated with the 7 : 3 mixture (v/v) of concentrated H 2 SO 4 and 30% H 2 O 2 at 120°C for 10 min, followed by boiling in water for 5 min. 2 The film on the silicon wafer was covered with a mask after drying at 120°C for 20 min. The copolymer A-2 film was irradiated with the UV light of 254 nm for 2 h (26.6 J/cm 2 ) and B-2 for 30 min (6.8 J/cm 2 ).…”

“…Recently, there has been an increasing interest in developing a new type of photoresist with environmentally friendly, water-castable, or water-developable photoresist materials. [1][2][3][4] Such a water-soluble photoresist would be important for its use in the production of the black matrix of color-cathode ray tubes, 5 in the manufacturing of screen printing plates, and in the immobilization of enzymes. 6 Water-soluble photoresists are prepared by utilizing the photochemical reaction of rearrangement, [7][8] deprotection, 9 -10 or crosslinking.…”

“…Hult et al 20 -21 and Willson et al 1 reported a water-soluble chemically amplified negative-tone photoresist. Recently, Fréchet et al [2][3][4] reported waterdevelopable chemically amplified photoresists based on the crosslinking of PVA matrix resin, 4 and those containing sugar 2 or oxazoline groups. 3 Other watersoluble photoresists such as that containing polymeric azide groups, 5 or acrolein-modified PVA-sodium dichromate system, 22 were also reported.…”

Polymers from aryl cyclic sulfonium zwitterions—photosensitive materials cast from and developed in water

“…7 The irradiated film was developed with water. Other polymers used for water-soluble resists include poly(vinyl alcohol), 8 a sugar-containing polymethacrylate, 9 styrene copolymers bearing pendant ammonium sulfonate groups and vicinal diol functionalities, 10 and poly(methyl acrylamidoglycolate methyl ether).…”