From Wafers to Atoms in Minutes

Fabs today are searching for anything that will improve time to data. That is, anything that will aid in the fast and accurate identification of yield-limiting defects and rapid tool qualification. This is all aimed at statistical analysis leading to the correlation of defect and process signatures to wafer yield. Typically, this data has been obtained by getting one or two cross-sections per wafer; however, five to 10 cross-sections are better for the purpose of creating Pareto analysis and getting a wider view of what goes on in the process. Historically, this has required the wafer to be taken out of the fab line and sent for study in failure analysis (FA) labs. Thus, the need has increased for more in-fab defect analyzing tools that will be capable of keeping wafers in the fab. Returning 300 mm wafers to the line to maintain yield, getting necessary and timely data, and minimizing scrap have been major drivers for in-fab analysis.

FEI Co., (Hillsboro, Ore.) has introduced its DA 300HP defect analyzer tool, which it expects will be an option for filling this need. Developed in partnership with logic and foundry customers, the platform is aimed at semiconductor development and production. Working with electron and ion beams in its defect review mode, it provides fully automated defect redetection and cross-section capabilities.

In its automated process, the platform looks at a reference image and a defect image, and also creates an outline image — an accurate rendition of the defect's physical size and shape. This assists in the decision of how to automatically do the necessary cross-section. Once the defect is outlined, the platform automatically zooms in on the defect and cuts the cross-section (Figure ). The tool exhibits versatility in terms of its interface with other inspection systems, and with respect to physical defects at gate and other areas, other <0.10 µm defects.

The system is designed to provide high SEM resolution on cross-section features, and to minimize beam damage to the sample. (Source: FEI Co.)

The system is optimized for rapid, accurate analysis of systematic as well as yield-limiting defects, and boasts >90% success rate on voltage contrast defects; something of particular utility for manufacturers who have been stymied by the inability to analyze defects from the e-beam inspectors. The platform's automated slice-and-view capability also provides the defect's profile. Web functional, the system can be operated remotely, and data can be viewed as it is being acquired.

To perform defect review with both the electron and ion beams at the 90 and 65 nm nodes, changes were made to the electron and ion columns. SEM voltage varies from 400 V to 30 KeV, and the best resolution possible on cross-section features is claimed as a result of its tilted dual beam system. The ion column provides >2× milling throughput relative to the previous generation, and its performance has been extended to the low voltage end — from 5 to 30 KeV — to minimize sample damage, especially for copper and low-k, and optimize cross-section quality.

The system's TEM sample preparation capability, which allows the extraction of small chunks from the wafer that are then brought out through a small loadlock in front of the tool, is advantageous for processing time, because the fab can continue doing defect analysis on the wafer while the sample itself is headed to the lab for TEM analysis. The process goes from wafer chunks to TEM results in less than an hour.

By working with a suite of platforms, the new tool offers higher throughput and a link between the fab and the lab for defect analysis, process monitoring, and development.

For additional information on inspection, measurement and test, go to www.semiconductor.net/imt