Libor Vyklicky

Graded spin-on organic bottom antireflective coating for high NA lithography

Immersion lithography for the 32nm node and beyond requires advanced methods to control 193 nm radiation reflected at the resist/BARC interface, due to the high incident angles that are verified under high numerical aperture (NA) imaging conditions. Swing curve effects are exacerbated in the high NA regime, especially when highly reflective substrates are used, and lead to critical dimension (CD) control problems. BARC reflectivity control is also particularly critical when underlying surface topography is present in buried layers due to potential reflective notching problems. In this work, a graded spin-on organic BARC was developed to enable appropriate reflectivity control under those conditions. The graded BARC consists of two optically distinct polymers that are completely miscible in the casting solution. Upon film coating and post-apply baking, the two polymers vertically phase-separate to form an optically graded layer. Different characterization techniques have been applied to the study of the distribution of graded BARC components to reveal the internal and surface composition of the optically graded film, which includes Variable Angle Spectroscopic Ellipsometry (VASE) and Secondary Ion Mass Spectroscopy (SIMS). Also, optical constant optimization, substrate compatibility, patterning defectivity and etch feasibility for graded BARC layers are described. Superior 193 nm lithographic performance and reflectivity control of graded BARC beyond 1.20 NA compared to conventional BARCs is also demonstrated.

Developable BARC (DBARC) technology as a solution to today's implant lithography challenges

As patterning of implant layers becomes increasingly challenging it is clear that the standard resist/Top Antireflective Coating (TARC) process may be soon be limited in terms of its ability to meet implant targets at future nodes. A particularly attractive solution for patterning implant levels is the use of a Developable Bottom Anti-Reflective Coating (DBARC). Similar to a conventional BARC, a DBARC controls reflectivity from the underlying substrate by absorbing the incident radiation thereby minimizing detrimental effects of reflected light. However, unlike a conventional Bottom Anti-Reflective Coating (BARC) which requires a BARC open etch step, the DBARC is developed with the resist in a single step leaving the substrate ready for implantation. These properties make DBARC very attractive for implant layers. In this paper, we report on the development of KrF and ArF DBARCs for implant applications. Our primary interest is in developing solutions for patterning Post-Gate implant levels. We briefly describe our fundamental design concepts and demonstrate the concepts are robust as we develop ARTM602 DBARC to address the criteria for a production worthy DBARC. This includes data on EBR performance, drain line compatibility, sublimation and footing coverage over topography. In terms of lithographic performance, we demonstrate improved capability over the incumbent SLR/TARC process in many key areas. This includes through pitch performance, process window and profile integrity over topography for both KrF and ArF DBARC solutions. Several strategies to enhance profile by resist/DBARC matching are also demonstrated. From a platform robustness standpoint, we show that AR602 DBARC is ready for high volume manufacturing in terms of batch to batch control and shelf life.

Progress towards production worthy developable BARCs (DBARCs)

Developable bottom anti-reflective coating (DBARC) technology holds promise in two main areas of lithography. The first application of DBARC is in implant lithography where patterning implant levels would greatly benefit from improved reflection control such as provided by a conventional BARC. However, implant layers cannot withstand BARC open etch thereby making DBARC an attractive solution as the resist and DBARC are simultaneously dissolved during the development step leaving the underlying substrate ready for implantation. In comparison to current implant processes with top anti-reflective coatings (TARC), DBARCs are anticipated to offer improvements in reflection control which would translate to improved CDU and increased process window for both KrF and ArF implants. Indeed, this area has long been considered the ideal insertion point for DBARC technology. The second area where DBARC technology can make a significant impact is in non-implant lithography. In this large segment, the ability to replace a conventional BARC with a DBARC affords the device maker the ability to simplify both lithographic and integration processes. By replacing the BARC with a DBARC, the BARC open etch is negated. Furthermore, by applying this strategy on multilayer stacks it is possible to greatly simplify the process by avoiding both CVD steps and pattern transfer steps thereby easing integration. In this area, DBARC technology could have merit for low k1 KrF and ArF (dry) lithography as well as in immersion ArF processes. This paper describes our results in designing production worthy DBARCs for both implant and non-implant applications. A newly developed KrF DBARC platform is evaluated for logic implant applications and compared to a standard TARC implant process. Post develop residue and defectivity are checked for the new platform and the results compared to production worthy BARC and implant resists. A new ArF platform was also developed and initial lithographic results are reported for an implant application. Several non-implant applications were also investigated and results are reported for high resolution KrF and ArF (dry) lithography as well as an immersion ArF process.