Advanced patterning solutions based on double exposure: double patterning and beyond

Abstract

The CD control of the first lithography (L1) patterns is a important issue in the single-etch double patterning (SEDP) process. In this process, L1 patterns are cured either chemically or thermally and then subjected to the second lithography (L2). A chemical curing process using a surface curing agent (SCA) often results in the CD growth due to the "positive" interaction between the first and second resists. A thermal curing process using a thermal cure resist (TCR) often results in the CD loss due to the volumetric shrinkage of the L1 patterns during the L2 process. By combining SCA and TCR concepts, we developed a simple "hybrid" curing system which offers precise control of the L1 CD after double patterning. This hybrid curing system involves thermal curing followed by a liquid rinse process using a double patterning primer (DPP). DPP is an aqueous solution formulated with SCA components and enhances "positive" interaction between L1 and L2 patterns. While CD loss of 5~6nm is observed without DPP treatment, ~11nm CD growth was observed with TCR after DPP treatment. The L1 CD after double patterning was precisely controllable by post-priming bake process with the rate of -0.3nm/°C in the temperature ranging from 120 ~ 150°C. Taking advantage of the CD growth with DPP treatment, we further developed three different advanced patterning schemes: 1. "Shrink Process Assisted by Double Exposure" (SPADE I), 2. "Space Patterning Assisted by Double Exposure" (SPADE II), and 3. "Sidewall Patterning Assisted by Double Exposure" (SPADE III). Using SPADE I, contact hole CD was reduced by 10~30nm and excellent through pitch performance was observed. SPADE I can also improve LER/LWR when used in the formation of smaller trenches. SPADE II was developed for self-aligned pitch splitting of contact holes and SPADE III was developed for self-aligned pitch splitting of lines. In this paper, the use of DPP in various SPADE technologies is described and its potential in the advanced patterning schemes is discussed.