Laser-imaging patterned wafer inspection

05/01/1998

Laser-imaging patterned wafer inspection

The ILM-2230 laser-imaging darkfield patterned wafer inspection system combines oblique angle darkfield illumination with small-pixel, high data rate image processing. This combination provides superior capture rate of a wide range of yield-critical defect types on =0.25-?m devices, at high throughput and with a low nuisance defect rate. The system is optimized for advanced interconnect process-inspection applications, such as CMP. The CMP process introduces many new defect types and noise sources, including color from oxide thickness variation, underlying and top surface pattern variations, and grain noise from metal and polysilicon. The ILM-2230 suppresses these noise sources to provide a high capture rate on these new classes of defects, while delivering a throughput up to 20 wafers/hour at the sensitivities required for sub-0.25-?m devices. The digital image processing system uses a low-noise, high-speed sensor that provides the sensitivity needed to detect such defect types as microscratches, pattern deformations, residual metal tungsten, and microbridging. Two advanced optical filtering techniques facilitate collection of the nonrepetitive defect signal and block noise from horizontal and vertical lines. KLA-Tencor Corp., San Jose, CA; ph 408/875-4200, www.kla-tencor.com