KLA-Tencor says backside wafer inspection finds lurking defects
SAN JOSE --KLA-Tencor Corp. today said it is the first company to supply a fully automated system for inspection of wafer backsides during the production of 0.13-micron ICs on 300-mm silicon substrates.
The new Backside Inspection Module (BSIM) enables non-destructive inspection on the backside of patterned wafers with the sensitivity to detect particles as small as 50 nm (0.05 micron), said San Jose-based KLA-Tencor.
The metrology supplier said its field trials in the past year have indicated that backside defects can account for as much as 10% of a wafer fab's baseline yield loss. This is enough to result in millions of dollars lost in annual revenues, according to KLA-Tencor.
"Automated, non-destructive wafer backside inspection must be incorporated as a routine step into every process module in order to recover these yield losses," said Rick Wallace, executive vice president of the Wafer Inspection Group at KLA-Tencor. "With so much of a chip manufacturer's investment riding on a 300-mm wafer, backside defects can no longer be tolerated."
According to KLA-Tencor, backside defects can have a significant impact on wafer and process uniformity. The company said its field trials show wafer backsides can become contaminated or damaged at nearly every process step, including deposition, etch, and chemical mechanical planarization (CMP).
An emerging challenge in 300-mm fabs is dealing with double-sided polished wafers for advanced process applications. Polishing steps can bring backside defects to the surface, according to KLA-Tencor. These defects can then cause distortion on the front wafer surfaces during exposure steps in lithography processes, the company said. Backside defects have also migrated between processes, creasing gate dielectric failures.
Typically, backside wafer inspection has been labor intensive. To analyze the potential for backside defects, fab engineers often must manually inspect wafers decreasing tool productivity and risk damaging the patterned front side of substrates, noted KLA-Tencor. Consequentially, many fabs do not use backside inspection at all. |
