Characteristics of an improved chemically amplified deep-ultraviolet positive resist

Abstract

Chemically amplified positive resist formulations have been shown to exhibit high photospeed, excellent resolution, and tolerance to process parameters such as softbake, exposure, postexposure bake, developer concentration, and temperature. Many chemically amplified positive resists, however, adhered poorly to some substrates (e.g., Si3N4), required considerable optimization of the etch process to achieve desired etch selectivities and were sensitive to airborne basic contaminants. Many chemically amplified negative resists while not as sensitive to contaminants in the clean room air, show retrograde wall angles especially on antireflection coatings, demonstrate poor latitude in defining contact holes and are difficult to strip after pattern transfer steps. In this article we discuss our efforts toward designing new deep-ultraviolet (UV) matrix resins and resist formulations as well as efforts toward defining an optimized process. The optimized resist process demonstrates 0.25 μm line and space (L/S) and 0.30 μm contact hole resolution in 0.8 μm thick resist films with a GCA deep-UV exposure tool. The resist also exhibits excellent adhesion on most semiconductor substrates (e.g., Si, polysilicon, SiO2, Si3N4), thermal stability to at least 140 °C, an order of improvement in postexposure delay latitude over that of CAMP1 (poly t-butoxycarbonyloxystyrene-sulfone formulated with photoacid generators) and etch selectivity comparable to that of novolac based resists. In addition, the polymers developed were designed for ease of manufacture with regard to reproducibility, low metal concentration, and cost.