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Product Briefing Outline: Tokyo Ohka Kogyo Co., Ltd. (TOK) and Dow Corning Electronics have jointly developed bilayer photoresist used for DRAM production applications. The new bilayer photoresist uses a Dow Corning silicon polymer in the imaging layer to provide better etch selectivity than other products on the market today, the company claims. Dow Corning and TOK have had a joint development agreement since 2002 to develop advanced silicon-based photolithography materials.  Problem: Photoresist is a light-sensitive material that becomes either soluble or insoluble after exposure to light, allowing portions to be selectively removed during subsequent etching processes. Adding Dow Corning's silicon polymer to TOK's photosensitive materials enables the use of thinner photoresist layers, which is claimed to improve pattern resolution and allows smaller circuit patterns to be transferred onto target wafers without pattern collapse issues.

Solution: The new photoresist is intended to provide a more cost-effective lithography solution by eliminating the hardmask layer and accompanying process steps required by multilayer photoresist processes. It can be used for both dry and immersion lithography, an advanced imaging technology that is gaining market acceptance for the 45nm node and beyond. TOK has said that it has already demonstrated the use of the photoresist under immersion lithography conditions to produce 35nm line/space patterns.

Applications: DRAM using both dry and immersion lithography for the 45nm node and beyond.

Platform: Customized silsesquioxane resins.

Availability: December 2007 onwards.