10 October 2014 Interface and facet control during Czochralski growth of (111) InSb crystals for cost reduction and yield improvement of IR focal plane array substrates
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Abstract
Focal plane arrays (FPAs) made on InSb wafers are the key cost-driving component in IR imaging systems. The electronic and crystallographic properties of the wafer directly determine the imaging device performance. The “facet effect” describes the non-uniform electronic properties of crystals resulting from anisotropic dopant segregation during bulk growth. When the segregation coefficient of dopant impurities changes notably across the melt/solid interface of a growing crystal the result is non-uniform electronic properties across wafers made from these crystals. The effect is more pronounced in InSb crystals grown on the (111) axis compared with other orientations and crystal systems. FPA devices made on these wafers suffer costly yield hits due to inconsistent device response and performance. Historically, InSb crystal growers have grown approximately 9-19 degree off-axis from the (111) to avoid the facet effect and produced wafers with improved uniformity of electronic properties. It has been shown by researchers in the 1960s that control of the facet effect can produce uniform small diameter crystals. In this paper, we share results employing a process that controls the facet effect when growing large diameter crystals from which 4, 5, and 6” wafers can be manufactured. The process change resulted in an increase in wafers yielded per crystal by several times, all with high crystal quality and uniform electronic properties. Since the crystals are grown on the (111) axis, manufacturing (111) oriented wafers is straightforward with standard semiconductor equipment and processes common to the high-volume silicon wafer industry. These benefits result in significant manufacturing cost savings and increased value to our customers.
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Nathan W. Gray, Nathan W. Gray, Victor Perez-Rubio, Victor Perez-Rubio, Joseph G. Bolke, Joseph G. Bolke, W. Brock Alexander, W. Brock Alexander, } "Interface and facet control during Czochralski growth of (111) InSb crystals for cost reduction and yield improvement of IR focal plane array substrates", Proc. SPIE 9220, Infrared Sensors, Devices, and Applications IV, 922003 (10 October 2014); doi: 10.1117/12.2061973; https://doi.org/10.1117/12.2061973
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