Date: 15/07/2012

Directed Self-Assembly is hot in semiconductor fab R&D, TEL partners with Imec

When the patterning on a silicon wafer is based on traditional photomask based lithography, the patterns are tough to draw below 20nm, the other method semiconductor industry is fast picking is Directed Self-Assembly (DSA). Directed Self-Assembly (DSA) is sublithographic patterning technique where cost is also not high. DSA lithography technique has just started in semiconductor device manufacturing. The recipe for commercializing this technology is hot pursuit by many semiconductor labs, much is happening in secrecy. However Imec is more open and announced some of its achievements.

Imec which is leading in Directed Self-Assembly (DSA) research explains: Directed Self-Assembly (DSA) is gaining momentum as a means for extending optical lithography beyond its current limits. DSA is an alternative patterning technology that enables frequency multiplication through the use of block copolymers. When used in conjunction with an appropriate pre-pattern that directs the orientation for patterning, DSA can reduce the pitch of the final printed structure. Moreover, DSA can be used to repair defects and repair uniformity in the original print. This repair feature is especially useful in combination with EUV lithography, which today is characterized by local variation in the CD (critical dimension), especially in case of small contacts.

Imec and Tokyo Electron (TEL) announce that they are accelerating research on Directed Self-Assembly (DSA) at imec’s recent 300mm fab-compatible DSA process line. After getting good results on imec’s 300mm DSA process line, imec and TEL now plans to expand their focus to explore DSA as a cost-effective and manufacturing viable patterning technique for 2x and beyond technologies.

Imec has said: it now has the complete toolset on-site including a dedicated and specially configured DSA coater/developer manufactured by TEL with installed DSA materials in gallon-size quantities, the metrology toolkit including DSA defect inspection, and in-house pattern transfer capabilities all in a representative 300mm cleanroom fab environment. With established 248nm, 193nm (dry and immersion) and EUV lithography tool sets on site, imec says it is uniquely positioned to study DSA defectivity aiming at increasing the pattern reliability of DSA for semiconductor fab standards. imec aims at further developing the possibilities of DSA repair in combination with EUV lithography, pushing imec’s ambition to bring EUV Lithography to production level.

Line features of size 12.5nm and 25nm contact holes are patterned on 300mm substrates at imec using pre-patterned lithography followed by DSA. In recent experiments using pre-patterned EUV holes, on wafers processed on TEL’s CLEAN TRACK LITHIUS Pro coater/developer interfaced to ASML’s NXE:3100, DSA repaired defective features, lowered line edge roughness (LER) and improved CD uniformity, claims Imec.

TEL’s configured DSA coater/developer and etch system supporting the DSA pattern transfer was used by imec along with its metrology, cleaning and pattern transfer toolsets. TEL to provide imec with new hardware as part of the joint work.

Next steps by Imec and TEL:

1. Imec and TEL are therefore investigating various integration scenarios for line and hole patterning.
2. Comprehensive evaluations to understand material and process interactions on critical dimension (CD) uniformity, line edge roughness (LER) and defect levels are planned. Imec and TEL aim at delivering electrical functional devices using DSA.

“With specially configured DSA coater/developer and etch systems at imec, we have the capability to explore DSA as a potential candidate for next-generation patterning technology”, commented Chung Gishi, Executive VP of Tokyo Electron Ltd. “We hope to understand the critical processes necessary to move early stage development into volume production to benefit our customers”.

“DSA continues to show much promise as part of the toolbox for advanced sub-20nm patterning. Our collaboration with Tokyo Electron has enabled us to rapidly implement DSA processing knowledge that has been developed in academia at the group of Prof Paul Nealey (University of Wisconsin at Madison) into a representative manufacturing environment. We are excited to extend this effort to dedicated newly developed DSA modules. Early access to this equipment allows us to identify and overcome the critical issues to make DSA ready for implementation into the manufacturing processes of our partners.” commented Kurt Ronse, Director Lithography Department at imec.

What is DSA/ self assembly? Self assembly is a learning from some of Nature's processes, To learn some basics of self assembly technology read this IEEE spectrum article at url, where the author has explained in detail with pictures.
http://spectrum.ieee.org/semiconductors/nanotechnology/selfassembly-takes-shape
This article is open to non-IEEE members too.