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Automated wafer inspection enables high-brightness LED production monitoring

Following its acquisition of Candela Instruments, KLA-Tencor has introduced the Candela CS20, an automated wafer inspection system designed to address the defect management requirements of high-brightness light-emitting diodes (HB-LEDs). The system, which is based on proprietary, multichannel detection architecture, can non-destructively inspect transparent wafers and epi layers for micro-pits and other defects at throughputs of up to 25 wafers per-hour, thus enabling production-line monitoring for wafers used to produce HB-LED devices.

During HB-LED production, contaminants such as particles and stains can alter film characteristics or cause adhesion problems for subsequent layers, according to Jeff Donnelly, vice president and general manager of KLA-Tencor's Growth and Emerging Markets (GEM) division. He added that surface and sub-surface defects, crystal dislocations and excessive roughness can impact subsequent processes and substantially degrade device performance and yield.

Donnelly said the CS20 combines optical profilometry, scatterometry, phase shift and reflectometry profile methods to inspect wafers on the surface and within the substrate or epi layers. The system can inspect transparent wafers such as sapphire, gallium nitride (GaN) and silicon carbide (SiC), as well as epi layers like GaN and SiC, and it can detect defects such as micro-pits, crystal defects, lattice mismatch, stains and particles.

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