Surface imaging resist systems

Polymers bearing pendant 1,2,3,4-tetrahydro-l-naphthylideneamino p-sty-renesulfonate (NISS) units were synthesized and they were utilized in the surface imaging resist system using CVD method (12, 13). The NISS imits in the polymers can form p-styrenesulfonic add units upon UV irradiation as shown in Scheme I (14). This paper describes the polymer synthesis, the photochemistry of NISS units in polymers, the water sorption to the irradiated polymer films, the formation of silicon oxide networks at the irradiated polymer surface, and the etdiing resistance to ojygen plasma of the polymer fflms which are irradiated and subsequently erqmsed to the vapor of alkoxysUanes. 

Besides using the resists to etch copper boards, metal parts, or silicon surfaces, new applications have been disclosed. Spatial images have been holographically recorded in resists.— The resist systems of siloxanes can be converted after imaging by oxidation into passivated glass for direct formation of insulated circuits.— The resist can be filled with glass 9 or metals— and fired to form circuits directly. In one application, the resists are filled with electroless plating sensitizer for deposition of... 

The three main approaches to multilayer resist imaging systems (see Chapter 16 for details) include (i) hard mask (HM) processes, (ii) top surface imaging (TSI) processes requiring latent image formation only near the surface of the resist, thus circumventing any transparency requirements, and (iii) bilayer resist (BLR)... 

As with all chemically amplified resists, a major concern is, however, the latent image stabflity and the susceptibility to environmental conditions. With t-BOC deprotecdon systems, the influence of airborne nudeophilic contaminants has been recently demonstrated (23) the observadon of surface residues in a number of such materials (23, 24) may be traced back to the presence of ppb amounts of volatile bases. In the case of the acetal systems (19-21), the influence of trace bases is less pronounced, as even amine hydrochlorides are sdll sufficiendy addic to have some catatydc activity. Linewidth dianges with the interval between exposure and post exposure bake have been observed for both the t-BOC and the acetal systems. In the case of the t-BOC tystems, long intervals (several hoius) between exposure and post-e]q)osure bake will lead to a decrease of apparent sensidvity, which manifests itself as a linewidth inCTease, or, in extreme cases, as faUure to open the imaged areas. These effects are normally due to contaminadon by base traces, or, in cases where the presence of even ppb amounts of bases can be excluded, may be assumed to be the result of the same, unspecified chain terminadon (add annihilation) mechanism which is responsible for the containment of the calalytic reacdon to the immediate vicinity of the imaged resist. 

A second approach modifies the CA resist chemistry. Eor example, researchers have introduced basic additives into the resist formulation to minimize the impact of surface contamination of the resist film (82,83). A resist that already contains added base (and consequendy requites a larger imaging dose) should be less affected by the absorption of small amounts of basic contaminants. Systems of this type have been claimed to have improved resolution as well. The rationalization here is that the acid that diffuses into the unexposed regions of the resist film is neutralized and does not contribute to image degradation (84,85). 

---