Organic underlayer materials with exceptionally high thermal stability

Abstract

Multilayer hardmask (MLHM) schemes have been implemented as an indispensable process for ArF lithography which continues to demand thinner photoresist films. There are many variations of MLHM and semiconductor manufacturers choose to adopt their own designs, depending on their specific needs and technical advances. The quad-layer stack consisting of photoresist, organic ARC, CVD Si hardmask, and spin-on carbon underlayer is one of them. Despite the need for wafer transporting between the spin track and CVD equipment, this scheme is attractive because it can avoid laborious elaboration of sophisticated etching chemistries for spin-on Si-ARC and carbon underlayer. One of the issues arising from the mixed film forming process is the thermal stability of carbon underlayer at high temperatures during the CVD process of the Si hardmask. Organic underlayer which shows high thermal stability is crucial for this mixed hardmask process. These types of thermally stable organic film can also be used for other applications such as the spacer patterning technique for pitch size shrinkage. In this paper, we discuss the development of organic resins with high thermal stability, their physical properties, and their lithographic behaviors in the MLHM schemes.

Progress in Spin-on Hard Mask Materials for Advanced Lithography

“…SOC carbon content and hard mask performance Table 1 shows the carbon content of the optimized PGMEA soluble SOC baked at 230°C/60s (90% C) and 400°C/120s (81% C). In trilayer process, resist patterns are transferred on Si BARC by fluorocarbon plasma etching such as CF 4 , CHF 3 or C 4 F 8 . Oxygen plasma is used to transfer patterns from Si BARC to SOC layer, and then fluorocarbon plasma is used to transfer patterns into substrates.…”

“…The etch condition of 10mT/Power 450W/Bias 100V/100sccm/60deg Temp was used for both CF 4 and BCl 3 gases. The AZ ® Spin-on TiOx and ZrOx films show comparable and better etch resistance respectively comparing to Silicon Oxide against CF 4 gas (table 3).…”

“…Compared to the amorphous carbon layers (ACL) obtained using chemical vapor deposition (CVD) process, a spin-on process provides lower cost of ownership, less defectivity and better alignment accuracy [1][2][3][4]. In addition, SOC can provide good gap filling and planarization performance for severe topography depending on the SOC morphology and viscosity.…”