The industry is moving to the 45-nm process technology node. As with the 65-nm node, this migration will be pioneered by foundries partnering with first-tier movers such as large fabless companies and integrated device manufacturers (IDMs). The move to 45 nm, regardless of the application (e.g., FPGA or RF), poses a number of challenges.
Increased process complexity to boost device performance: Since traditional device scaling methods can no longer be applied due to the physical limitation of gate dielectrics material, many mobility enhancement techniques have to be introduced in this node, such as silicon germanium (SiGe), compressive and tensile nitride films, and stress memory effect for poly gates. To introduce these new techniques to boost device performance, new integration schemes, new materials, and new tools have dramatically increased the complexity of the 45-nm process.
Defect issues: New fabrication techniques often result in defect issues. As an example, consider how UMC's fabrication of working 45-nm SRAM identified potential defect issues associated with immersion lithography. Such issues include resist/topcoat selection and recipe optimization for each layer, compatible etch recipes to achieve the final resolution, and alignment limitations imposed by current scanners before immersion lithography's full maturity. Achieving a workable 45-nm yield requires ongoing identification of device optimization through various ultra-shallow junction techniques as well as back-end cleaning techniques to maintain the dielectric k integrity while also maintaining good defect control. Device adjustment, induced by the introduction of new materials such as SiGe into the PMOS source/drain area, may also be necessary.
Partnerships: Close collaboration between the manufacturer and tool/equipment partners is necessary to address the hardware limitations and issues that may arise during high-volume manufacturing. A close partnership with customers also is necessary to maximize process compatibility with their product needs.
As the chip world steps up its pace toward 45-nm adoption, overcoming these challenges while enhancing process margin and manufacturability will be critical to ensuring its success.
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