X-ray of High Order Planes, Pathway for HBT Control

E.M. Rehder, S. Iyer, C.r. Lutz, K.S. Stevens, T.L. Wolfsdorf-Brenner, R.E. Welser

Kopin Corp., 695 Miles Standish Blvd., Taunton, MA  02780, erehder@kopin.com


Keywords: HBT, X-ray, Characterization



High volume HBT (Heterojunction Bipolar Transistor) production benefits from non-destructive measurement techniques to verify the quality of every product wafer.  X-ray diffraction is non-destructive and sensitive to layer thicknesses and compositions.  The thin layers typical of HBT designs yield week diffraction intensity, which are overwhelmed by the signal from the substrate in the conventional (004) orientation.  We have found that be diffracting from the (117) planes, much more information can be obtained.  As the HBT layer peaks move away from the substrate signal this enables the in-line measurement of B+HBT product wafer characteristics, such as base dopint1.  In this paper, we develop a new curve fitting methodology, and demonstrate the precise measurement of the base doping of HBT wafers in the production line for the first time.  This technique is demonstrated to measure base doping changes i9n production as small as 1.8%


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