Novel Polymeric Dissolution Inhibitor for the Design of Sensitive, Dry Etch Resistant, Base‐Developable Resist

Abstract

Polyphthalaldehyde (PPA) inhibits dissolution of novolac resins in aqueous base very efficiently. When an onium salt cationic photoinitiator such as triarylsulfonium or diaryliodonium metal halides is added lo the polymer mixture, PPA is completely reverted to the starting monomer by reaction with radiochemically generated acid and removed from the exposed area upon postbake, thereby recovering the intrinsic base solubility of the novolac resin. PPA as a polymeric dissolution inhibitor used in conjunction with onium salts provides aqueous-base-developable, high-contrast, positive resist systems very sensitive to deep UV radiation (full development at 2 mJ/cm2). The system offers stable development processes due to the induction effect and high contrast.Polyphthalaldehyde (PPA) derivatives depolymerize completely to starting monomers by reaction with radiochemically generated acids to provide extremely sensitive self-developing (1, 2) and thermally developable (3, 4) resist systems. The high sensitivity is a result of two stages of chemical amplification--acid-catalyzed acetal bond cleavage and subsequent depolymerization. Sensitive positive resist materials based on efficient main chain scission tend to suffer from poor plasma resistance which precludes their use in a device fabrication. One approach to practical utilization of these sensitive materials is to incorporate silicon in PPA which renders the highly sensitive material resistant to oxygen plasma so that the thermally imaged Sicontaining PPA serves as an etch mask for pattern transfer in the bilayer scheme (4). A similar approach has been taken to provide electron-beam-sensitive poly(olefin sulfones) with some practical utility other than mask making by incorporating Si into the structure (5).Another approach toward the design of sensitive positive resist systems with high dry etch resistance has been to mix poly(olefin sulfones) with novolac resins, thereby combining the high radiation sensitivity of the polymeric dissolution inhibitor with the high dry etch resistance of the base-soluble matrix resin (6-8). This concept of utilizing a polymeric dissolution inhibitor instead of diazonaphthoquinone has allowed extension of attractive features of diazonaphthoquinone/novolac photoresists --namely, high dry etch resistance and aqueous base development to provide high resolution, to electron beam lithography.As the circuit density in microelectronic devices becomes higher and higher, an increasing interest in lithography technologies based on short wavelength exposures has arisen because the resolution is directly proportional to the exposing wavelength. However, the diazonaphthoquinone novolac resists do not perform adequately as a single-layer resist when exposed to deep UV radiation (9) and poly(olefin sulfones) are not sensitive to UV radiations above 200 nm, though it has been reported that the charge transfer complex between polysulfone and a novolac resin renders such composite resists sensitive to deep UV radiation (i0).We have found that PPA inhibit...

Dissolution Kinetics and PAG Interaction of Phenolic Resins in Chemically Amplified Resists.

“…Furthermore, the acid-catalyzed imaging mechanism provides such high contrasts that it is more difficult to monitor the dissolution behavior of the deep UV positive resists. Thus, while the dissolution measurements of chemically-amplified resists by laser interferometry have been less successful, an alternative methodology employing a quartz crystal microbalance (QCM) has been extensively utilized at IBM Almaden Research Center in investigation of the dissolution kinetics of phenolic resists [1][2][3]. The QCM technique can be readily applied to measurements of extremely I. Photopolym.…”

Chemical amplification based on acid-catalyzed depolymerization.

“…The problem of exposure tool contamination associated with the polyphthalaldehyde (PPA) self developing resist [3][4][5] has been alleviated by devising thermally developable systems based on poly(4-chlorophthalaldehyde) (PCPA) [10,11]. Their poor dry etch resistance has been overcome by using PPA as a polymeric dissolution inhibitor for novolac resins [12,13] and by incorporating Si in the PPA structure to design a thermally developable 02 plasma etch barrier for an all-dry bilayer scheme [1 1,14]. A recent progress of the PPA-based resist systems is reported in this paper.…”

Negative resists for electron-beam lithography utilizing acid-catalyzed intramolecular dehydration of phenylcarbinol

“…The weight ratio of novolak resin to Diol-1 was kept constant at 100/20, while the DIT concentration was varied. The sensitivity increases with the DIT concentration, and the dissolution rate of the unexposed film decreases with the DIT concentration because DIT acts as a dissolution inhibitor of novolak resin [21]. The DIT concentration needs to be optimized to make the best use of the Diol-1 resist in terms of sensitivity and development time.…”