Polyhydroxystyrene resists

Since the introduction of chemically amplified resist systems to DUV technology, the environmental stability and bake latitudes have been the major concern of this type of chemistry. Ketal resist systems have been very robust towards fiiese issues. The methoxypropene protected polyhydroxystyrene resist is our first initial work on ketal system. 

Fig. 28. Traditional duv-resist design using derivatives of polyhydroxystyrene. Monomer (a) contributes hydrophilic character to the polymer, and its acidic phenol group enhances aqueous base solubiUty monomer (b) provides acid-labile pendent groups.

Onium salts have been widely used as an acid generator for photo-, EB, and x-ray resist. In addition, aromatic polymers such as novolak and polyhydroxystyrene have been often used as a base polymer for EB and x-ray resist. The reaction mechanisms in a typical resist system have been investigated by pulse radiolysis [43,52,77-88], SR exposure [79,80,83-85], and product analysis [88]. Figure 6 shows the acid-generation mechanisms induced by ionizing radiation in triphenylsulfonium triflate solution in acetonitrile. The yields of products from electron beam and KrF excimer laser irradiation of 10 mM triphenylsulfonium triflate solution in acetonitrile are shown in Fig. 7 to clarify the... 

Ito, K. Schildknegt, and E.A. Mash, Negative chemical amplification resist systems based on polyhydroxystyrenes and N substituted imides or aldehydes, Proc. SPIE 1466, 408 (1991) H. Ito, Chemical amplification resists for microlithography, Adv. Polym. Sci. 172, 156 (2005). 

The main resist polymer platforms used in this form of chemical amplification comprise poly(hydroxy styrene), acrylate, alicyclic, and hybrid acrylate-alicyclic systems. Because of the great versatility of polyhydroxystyrene (PHOST) in... 

One of the most important ester-protected polyhydroxystyrene-based resist copolymers, ESCAP (environmentally stable chemically amplified photoresist), developed at IBM, is based on the random copolymerization of 4-hydroxystyrene with tert-butyl acrylate (XXX).On exposure, this resist copolymer is converted to a copolymer of 4-hydroxystyrene with acrylic acid through photoinduced acid-catalyzed deprotection of the tert-butyl group (see Scheme 7.34). Because this resist system can be annealed at temperatures near its Tg in a process that hlls up the free volumes (voids in the resist matrix), thus preventing the out-diffusion of photoacids from the matrix and in-diffusion of airborne bases into the resist, neutralization reactions between the photoacids and bases in the resist matrix (otherwise known as poisoning) are reduced, thus allowing... 

Polyhydroxystyrene (Figure 1.22) also contains a benzene ring. Polyhydroxystyrene can be applied to a basic polymer for KrF resist by using the absorption window at 250 nm. Chemical amplification is applied to polyhydroxystyrene. Details will be discussed in Chapter 2. 

Onium salts are decomposed by UV irradiation to produce acids. t-BCXZ (butoxycarbonyl) polyhydroxystyrene (t-BOCPHS) is decomposed by acid. t-BOCPHS added to oniiun salt is decomposed by acid produced from UV irradiation of the onium salt. Since acid is also produced by the photodecomposition reaction, heating the resist after irradiation (postbaking) gives further decomposition. Ito and Wilson reported a photochemical reaction, shown in... 

A chemically amplified, positive-working resist system based on silylated polyhydroxystyrene has shown its capability for application to quarter micron lithography. The present paper describes the recent improvement in the resist performance achieved through studies on polymer characteristics and process conditions. Possible measures to suppress a peculiar problem of positive-working chemical amplification systems, i.e., formation of T-shaped profile, is also presented. Although the development is still on the way, the silylated polyhydroxystyrene based resist tem shows excellent properties on resolution capability, sensitivity and process latitude. 

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