Optical wafer level mapping for MMIC processing

Abstract

There is a growing need for rapid non-destructive mapping of defects and polishing damage in semi-insulating GaAs wafers used in the efficient manufacture of microwave and millimeter wave monolithic integrated circuits (MMICs). Optical mapping by spatially resolved photoluminescence (SRPL) of whole wafers with high spatial resolution has been demonstrated. Video rate SRPL scans reveal dislocations, arsenic precipitates, and scratch-like defects in GaAs wafers. Considerable variations in defect densities are seen in material from different sources. This paper studies the relationship between wafer level optical maps and device parameters in order to determine the impact of the various defects.

Non-Destructive Optical Techniques for Characterizing Semiconductor Materials and Devices

“…Asthe beamis scanned overa wafer, the SRPL systemsearchesfor changesin PLintensity, which indicate the presence ofdefects. 3 The pumping beamis scanned in and out ofthe plane ofFigure 1 by an acousto-optic deflector, and within the plane by a scanning mirror. The beamis then focused to a 1-to 2-micron scanning spoton the sample.…”

“…5 These cellscan assemble intoso-called lineage boundaries, which are sheets of defective material extending along the growth axisofa crystal. 3 Figure 3a shows a SRPL scancontaining two discontinuous lineage boundaries and two continuous arcs ofresidual polishing damage. The wafer map shown in Figure3b contains 5620 scans.…”