Advanced lithography is transitioning to the high-NA EUV era with highly valuable technological advancements. We explored the limits of hexagonal contact hole and pillar patterning for memory device by utilizing holistic patterning technology of materials and process optimization, pattern rectification by directed self-assembly of block copolymer, and phase shift mask with low-n that can maximize patterning resolution in 29nm pitch design, which is the inflection point of high-NA EUV patterning. Focusing on pattern transfer, we were able to secure contact hole patterning, contact hole DSA rectification and pillar patterning in the 0.33NA process. It was also confirmed that phase shift mask can improve local CD uniformity by more than 23% compared to binary mask. In addition, we demonstrated dose and local CD uniformity in 0.55NA EUV resulting from changes in stochastic impact following the imaging contrast improvement of 0.55NA. This paper presents our latest patterning experience for 29nm pitch hexagonal contact hole and pillar array patterning and outlook for the future transition to the high-NA EUV process.
Improving local critical dimension uniformity (LCDU) as well as productivity in the extreme pitch of EUV layers is the most important challenge in DRAM device. In general, automated source optimization (SO) process is limited to investigate all possible candidates for the best LCDU performance, like fixing the amount of mirror in specific sigma and generating uncommon pole shapes. In this paper, we present LCDU improvement method in hexagonal contact array patterns based on controlling the center sigma position in the EUV pupil. We demonstrated that the LCDU was improved when the source points were located on the outer edge side of pupils regardless of normalized image log slope (NILS). This indicated the mirror location in the source is significant for LCDU in the similar NILS conditions. Moreover, it was confirmed that the CD along the critical direction increased as source points moved toward the center of the 3-beam imaging area, thus the changed CD ellipticity could further improve LCDU or cut down ACI defect source. The results showed a similar tendency in both the binary mask (BIN) and phase shift mask (PSM) even to differ type of resist. Overall, we verified the correlation of LCDU and ADI CD ellipticity through the sigma center position control, and we believe this approach will contribute to future research on improving LCDU.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.