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Product Briefing Outline: KLA-Tencor has launched the Surfscan SP2^XP, a new unpatterned wafer inspection system designed to meet 45nm IC manufacturing requirements for all types of bare wafers, including prime wafers, SOI (silicon-on-insulator), epitaxial and engineered substrates. Employing a proprietary five-channel inspection technology, the Surfscan SP2^XP is claimed to enable the detection of all major types of defects of interest.  The tool can then quickly group wafers into defect-free, re-workable and scrap categories based on type and number of defects. Improved detection enables wafer manufacturers to re-work many wafers that were previously scrapped, elevating yield and increasing profitability, according to the company. The new system has been extensively tested through beta partnerships with leading wafer suppliers, including Soitec, the largest supplier of SOI wafers in all sizes.
 
Problem: As feature sizes continue to shrink a reliable way of detecting yield-killing intrinsic or ‘crystallographic' defects on 45nm-generation prime, epi and SOI wafers have become challenging. With continued need to improve defect levels on bare wafers of all types to prevent yield loss in chip manufacturing, wafer manufacturers need better inspection tools to enable and re-work of polished wafers to improve yield loss.

Solution: Enhanced with dual-incidence darkfield channels, plus the addition of a new brightfield channel, the Surfscan SP2^XP system captures the full spectrum of defect types, then utilizes multi-channel comparison algorithms to reliably separate unacceptable "intrinsic" defects from re-workable ones, in a single inspection step.  Even with its added detection capabilities, the new system delivers 20% to 50% higher throughput, depending on the operating mode, compared with the Surfscan SP2.
The new system can perform oblique and normal incidence scans in one step.  With both narrow and wide collection channels, the Surfscan SP2^XP can generate data from five different optical configurations: oblique-narrow, oblique-wide normal-narrow, normal-wide, and brightfield.  This unique, comprehensive optical design enables detection of all defect types. The system's UV wavelength confines the laser beam to the wafer surface, minimizing false counts from buried defects. The 30nm sensitivity on polished wafers is claimed to be the industry's highest production sensitivity level.

Applications: The Surfscan SP2^XP system can capture shallow CMP scratches —defects that affect yield for Flash memory applications. The system also identifies previously unnoticed defect types such as orange peel, watermarks, slurry residue, and surface roughness changes that have low scattering intensity and a high correlation to process tool issues. The SP2^XP detects and separates LLPD faceted pits (also called air pockets or air bubbles) from other defects such as micro-scratches, chatter marks, and particles. Controlling these defect types is critical to gate performance. In epitaxial silicon wafers, the most common crystallographic defect is the epi stacking fault (ESF). The new system enables improved separation of stacking faults from other common epi defects, such as particles and flakes, which may pass IC manufacturers' requirements for 45nm. SOI wafers, like prime wafers, can contain yield-killing void defects at the surface of the SOI wafer.  The technology can separate voids from the relatively innocuous particles and other fall-on defects, which may be re-workable. With this capability, wafers having large particles only need not be scrapped along with wafers having voids.
 
Platform: The new system incorporates a brightfield channel that provides another means of detecting challenging defect types. This brightfield channel, operating simultaneously with the darkfield channels, provides Differential Interference Contrast (DIC) capability, which uses the phase of the laser beam to distinguish large and shallow defects, providing additional defect classification.

Availability: February 2007 onwards.