by Debra Vogler, senior technical editor, Solid State Technology

Sept. 16, 2008 – KLA-Tencor Corporation recently introduced the Surfscan SP2^XP, a new monitor-wafer inspection system for the IC market that builds upon its sister tool with the same name, introduced last year for the wafer manufacturing market. The latest version features improved sensitivity to defects on silicon, poly and metal films, and enhanced ability to sort defects by type and size, compared with its predecessor, the Surfscan SP2. The new system also introduces an ultra-high sensitivity operating mode to accelerate fabs’ development of devices at 32nm and beyond.

Key to the product’s opto-mechanical innovation is the use of custom polarizers, according to Rahul Bammi, senior director of marketing for KLA-Tencor’s Surfscan/ADE division. Most defect detection systems work by detecting the scatter off a laser-illuminated wafer surface and measuring the signal-to-noise (S/N) ratio. With larger grain size films, there is more scattering that limits the ability to detect defects. “We’ve developed polarizers that optimize the S/N ratio and are customized for each type of film (poly-Si, W, etc.), which leads to greater sensitivity,” Bammi told SST. The company would not release the exact percentage improvement achieved with the new technology, except to say that it is “significant.”

The ultra-high sensitivity mode is enabled by smaller pixels that can detect defects in the mid-20nm range, a capability needed by R&D groups working on 32nm and beyond, noted Bammi.

An improved defect class engine, multi-channel capability, and improved dynamic range together enable better defect sizing, which improves binning accuracy. In particular, obtaining the correct size of some larger defects is now possible. Previously, larger size defects had been merely classified as “large” and not actually assigned a size. Knowing a defect’s size enables better root cause analysis.

Another feature — differential interference contrast (DIC) channel — is a well-known technology used by microscope manufacturers that enables capture of shallow, flat, and faint defects of interest, such as residues or bumps. These types of defects, which occur more often in 45nm/32nm processes (and are not easily captured by darkfield scattering at these nodes) are becoming more problematic because of the growing need for wet clean processes that can leave residues, bumps left behind after CMP, and watermarks or other residues after immersion lithography.

Surfscan SP2^XP‘s Differential Interference Contrast (DIC) channel enables capture of shallow, flat and faint defects-of-interest, such as residues or bumps. (Source: KLA-Tencor)

Bammi told SST that a beta site evaluation was recently completed at a leading chipmaker, and the company has several orders from fab equipment manufacturers as well as leading logic and memory fabs in Asia, the US, and Europe, and has already started shipping systems. The edge-handling version of the Surfscan SP2^XP for the wafer manufacturing market has installations of multiple systems at every leading wafer manufacturer. — D.V.