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Product Briefing Outline: KLA-Tencor has released the WaferSight 2 that measures bare wafer flatness, shape, edge roll-off and nano-topography in a single system. Designed for 45nm wafer requirements and below, the new tool enables a higher degree of precision and tool matching capability compared to previous systems for wafer suppliers and incoming wafer quality control for IC makers. WaferSight 2 has been accepted for silicon and SOI production applications.

Problem: Studies by leading lithography system suppliers have shown that slight variations in wafer flatness can consume as much as 50% of the critical lithography depth of focus budget at 45nm. Geometric consistency at the near-edge region of a wafer (defined as occurring within a distance of 1mm to 5mm from the edge) is a new challenge in manufacturing due to various processing variations near the edge, as compared to the center of a wafer. The resulting shape or thickness variation is described as edge roll-off (ERO). It can significantly affect lithography focus control at the outermost fields and CMP consistency in the area. The ITRS roadmap notes that since nano-topography may be only nanometers from peak to valley, nano-topography accuracy can be affected by chuck effects on the measurement system. WaferSight 2 eliminates chuck effects by using a full edge-grip wafer handing system, capturing artifact-free nano-topography data from the front and backsides of the wafer in the same scan as it acquires flatness and edge-roll off data.

Solution: Nanotopography control has become critical at the 45nm node because it is a cause of reduced process margin in CMP and can cause CD variation in lithography. The new WaferSight 2 provides nano-topgraphy measurement performance with improvements in precision.  It is claimed to be the first tool to measure both frontside and backside nano-topography in a single, non-destructive measurement. By combining flatness and nano-topography in one system, shorter cycle times, reduced WIP queuing and move times, smaller footprint, and more efficient facilities usage are features claimed by the company, compared to multiple tool solutions. The system can be certified for 45nm production because of its sub-nm flatness gauge precision and has demonstrated a 200 percent tool-to-tool matching improvement over the WaferSight 1. WaferSight 2’s ERO measurement provides the accurate data needed to help control the effects of edge roll-off on die yield at the margins of the wafer. Angular ERO variation can be quantified using WaferSight 2; variations between wafer suppliers, between wafers and within-wafer are evident in ERO data. The new system also eliminates chuck effects by using a full edge-grip wafer handing system, capturing artifact-free nano-topography data from the front and backsides of the wafer in the same scan as it acquires flatness and edge-roll off data. WaferSight 2 can also be seamlessly combined with KLA-Tencor’s fab data management system FabVision, creating a package that enables offline analysis of archived or current metrology data, with fully customized charts and reports.


Applications: SOI and bare silicon wafer measurement for 45nm-and-below production.

Platform: WaferSight 2 combines the technology from NanoMapper and WaferSight 1 into a single fully-integrated platform combining improved precision for 45nm-and-below process requirements. Other developments include cleaner wafer handling with PEEK grippers and fingers. An improved gauge mechanical design and the use of KLA-Tencor’s proprietary standard platform wafer handing system improves reliability and reduces PM cycles.

Availability: December 2007 onwards.