Locating defects on wafers for analysis by SEM/EDX, AFM, and other microanalysis techniques

Small-probe analytical tools (SEM/EDX, AFM, AES, TOF-SIMMS, XPS, among others) are essential for failure analysis in the semiconductor industry. One of the major challenges in this area is in locating the defect within the analytical tool so the defect can be analyzed. The problem is especially difficult for analysis of particles/defects on unpatterned wafers. We have eliminated this problem by developing a new technique called Mark-Assisted Defect Analysis (MADA). The instrument we developed to perform MADA has a robust defect locating capability, and the ability to place micron-sized laser marks in the vicinity of the defect. The marks serve as in-situ landmarks that direct subsequent analysis efforts to the defects location. MADA has enabled numerous analytical techniques to be employed which were previously not possible due to the difficulty in locating the defect within the analytical tool. Examples include the use of multiple analytical techniques for analysis of the same defect, AFM analysis of sub-half-micron particles on bare wafers, SEM/EDX analysis on defects that provide optical contrast but are nearly imperceptible by the SEM, and particle/defect analysis on unpatterned wafers using analytical tools that cannot accept full-wafer samples. In this paper we present an overview of the MADA technique and provide several examples of how the technique was employed to solve challenging defect analysis problems on unpatterned wafers.