Delivers world-class device patterning and productivity for 7 nm node applications and beyond
For advanced processes, the number of layer stacks is increasing at a rapid rate, and wafers are experiencing additional stresses. Greater wafer warpage due to film stress and planarization processes drive problematic grid error as well as alignment mark shape error. The simplest solution is to measure the grid errors after they’ve been induced by process steps. Historically though, that has not been possible due to the extra time required for such measurements.

The newly developed inline Alignment Station (iAS) is a high speed, extremely accurate wafer pre-measurement module that provides feed forward alignment results for all shots on every wafer without any impact to scanner throughput. iAS can be integrated with the NSR-S631E immersion scanner, and also can be retrofit to a number of existing scanner models, with minimal effect on the fab footprint. Pre-measurement, dense sampling, and high order grid correction are performed by iAS, then traditional EGA is performed on the scanner wafer stage using sparse sampling and final linear correction. This innovative system optimizes on-product overlay using all-shot alignment with no impact on scanner throughput, delivering world-class patterning and productivity for 7 nm node applications and beyond.

iAS enables all shot alignment with sophisticated shot shape modes and high order correction capabilities
Various alignment modes are possible with the iAS such as Standard, Plus Edge Dense (increased edge sites), Scrambled, and Plus Intra-shot (increased sites within-shot). This enables adaptability for a variety of types of wafer grid error. In addition, there are a number of correction modes including Linear, High-order Global, Local Area, and Die-by-Die correction methods that compensate for different types of deformation.

Minimizes edge placement errors for advanced multiple patterning
iAS has demonstrated excellent capabilities on distorted grid wafers, using high order correction capabilities and dense sampling to dramatically reduce overlay error. One evaluation using ten wafers having five different error types showed overlay results improved from 4.5 nm 3σ using 16-point EGA with linear correction only, to < 2 nm using 84-point EGA and 7th order correction with iAS.

Marked performance improvements have also been achieved using the advanced iAS die-by-die corrections. iAS collects and analyzes shot-by-shot data to dramatically improve on-product overlay performance without an impact to scanner productivity. A comparison of 16-point linear correction, vs. 40-point high order correction, compared with all shot iAS alignment and high order compensation, showed that on-product overlay was reduced by more than 60% from x =9.2 nm and y=9.7 nm, down to x and y = 2.6 nm.

Optimizes affordability with ultra-high throughput up to 270 wafers per hour
With iAS, the NSR-S631E can process 270 wafers per hour (WPH) while performing all shot alignment with four sophisticated shot shape modes, and providing global high order correction and shot linear correction. Data intensive, feed forward lithography solutions such as iAS will enable customers to simultaneously achieve next-generation performance and productivity objectives.

Enhances On-Product Overlay with Various Alignment Modes and Correction Methods

iAS enhances on-product overlay by adapting to various types of wafer grid error and correcting for different grid signatures.