Commercial EUV mask blank readiness for 32 nm HP manufacturing

摘要

Successful commercialization of extreme ultraviolet lithography (EUVL) requires high quality EUV mask blanks for patterned masks that are essentially defect-free and very flat with high performance reflective multilayers. For 32 nm half-pitch (HP) integrated circuit manufacturing, such blanks require zero defects down to 25 nm diameter sizes while simultaneously meeting other specifications. At least three critical specifications that need continued improvements (total defects, defect size inspection, and substrate flatness control) are challenging to attain individually; meeting all requirements simultaneously will be especially challenging. Since early 2003, SEMATECH has been engaged with the mask blank materials and mask tool supplier community to drive the readiness of alpha, beta, and production mask blanks to support EUV lithography introduction. SEMATECH uses its commercial mask blank development roadmap together with neutral metrology evaluations of commercial suppliers' materials to monitor progress against needed production requirements. Commercial blank capability has improved significantly over the past two years; however, beta-level performance has still not been attained for all requirements. Attaining integrated blank specifications is more difficult than meeting individual specifications. Significant improvements including defectivity, flatness, coefficient of thermal expansion (CTE), reflectivity, wavelength control, and buffer/absorber stack performances are needed. Several orders of magnitude improvement is needed in defectivity levels alone coupled with increased detection sensitivity to 25 nm diameter defects. This paper will illustrate the recent rate of improvements along with an updated SEMATECH commercial roadmap, highlighting individual specification performances and total blank integrated performance levels currently better than 0.2 def/cm~2 at ≥ 80 nm polystyrene latex (PSL), peak reflectivity ≥ 64.0%, substrate flatnesses ≤ 175 nm peak-to-valley (P-V), with other key requirements. EUV blank cost of ownership studies will highlight the cost to manufacture these materials and show potential issues if yields are marginal.