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CdZnTe Substrate Screening

Description:

TECHNOLOGY AREA(S): Electronics

OBJECTIVE: This topic seeks the development of a non-destructive technique to unambiguously identify those subsurface defects within the CdZnTe substrate which cause large defects in the epitaxial HgCdTe film. This non-destructive technique shall be able to be scaled up to a manufacturing capability for rapid low cost screening of large CdZnTe substrates before HgCdTe epitaxial film growth is initiated.

DESCRIPTION: HgCdTe infrared detector array technology has improved significantly over the last decade. Single element mm sized detectors made from bulk HgCdTe crystals in the 1960s have been transformed today through research into arrays having more than one million elements with each element measuring below 20 micrometers. This has resulted in DoD infrared systems having much greater sensitivity at a much larger field of view. One major drawback to such large arrays, however, is the yield of such arrays is dramatically reduced by large defects in the HgCdTe film which cause many adjacent HgCdTe detectors to be defective with high noise and lower signal. Recent research has identified the cause of some of these large defects as arising from an imperfect CdZnTe substrate surface. Even after addressing this issue, however, large HgCdTe epitaxial film defects are still driving down the yield of large arrays making their costs rise to prohibitive levels for some applications. New non-destructive technologies are sought which will identify defects below the surface of the single crystal CdZnTe substrate which cause large, yield limiting defects in the HgCdTe films. This technique should be able to be rapidly applied to 7cm × 7.5cm and larger substrates in a manufacturing setting.

PHASE I: Demonstrate correlation between defects identified in the subsurface region of the CdZnTe substrate and large defects in the epitaxial HgCdTe film grown on the same substrate. This correlation shall be shown for a minimum of six defects on at least two different substrates. The HgCdTe films shall be at least five micrometers thick. The composition of the HgCdTe films shall be chosen to represent that composition typically grown which requires large format focal plane arrays. The films shall be grown by a state-of-the-art HgCdTe foundry producing state-of-the-art large HgCdTe arrays.

PHASE II: Modify the subsurface CdZnTe defect detection system to allow for non-destructive rapid inspection of substrates at least 7cm × 7.5 cm in size within the two year period of performance. Demonstrate prototype system on several 7cm × 7.5 cm films with large defects in the films. The prototype system shall demonstrate good correlation between the defects found in the CdZnTe subsurface and large defects seen on the HgCdTe film on the same substrate.

PHASE III: Transition operation of a single wafer non-destructive system to HgCdTe foundry operators.Provide supporting documentation for its operation and maintenance.Correlation of subsurface CdZnTe defects with large HgCdTe defects shall be greater than 90%. Time to non-destructively screen a 7cm × 7.5 cm CdZnTe substrate shall be less than 1 hour. Yield of large HgCdTe arrays shall be demonstrated to increase at least 25% after using this non-destructive inspection system in the HgCdTe foundry. Deliver a lot of substrates and large arrays for verification testing to demonstrate quality, consistency and reproducibility of this inspection method.

KEYWORDS: Infrared detectors, CdZnTe substrates, HgCdTe epitaxy

References:

J. D. Benson, L. O. Bubulac, M. Jaime-Vasquez, J. M. Arias, P. J. Smith, R. N. Jacobs, J. K. Markunas, L. A. Almeida, A. Stoltz, P. S. Wijewarnasuriya, J. Peterson, M. Reddy, K. Jones, S. M. Johnson, and D. D. Lofgreen, J. Electron. Mater. 46, (2017).; J. D. Benson, L. O. Bubulac, A. Wang, R. N. Jacobs, J. M. Arias, M. Jaime-Vasquez, P. J. Smith, L. A. Almeida, A. Stoltz, P. S. Wijewarnasuriya, A. Yulius, M. Carmody, M.Reddy, J. Peterson, S. M. Johnson, J. Bangs, and D. D. Lofgreen, J. Electron. Mater. 47, 5671 (2018).; J. D. Benson, L. O. Bubulac, M. Jaime-Vasquez, C. M. Lennon, P. J. Smith, R. N. Jacobs, J. K. Markunas, L. A. Almeida, A. Stoltz, J. M. Arias, P. S. Wijewarnasuriya, J. Peterson, M. Reddy, M. F. Vilela, S. M. Johnson, D. D. Lofgreen, A. Yulius, M. Carmody, R. Hirsch, J. Fiala, and S. Motakef, J. Electron. Mater. 44, 3082 (2015).; J. D. Benson, L. O. Bubulac, M. Jaime-Vasquez, C. M. Lennon, J. M. Arias, P. J. Smith, R. N. Jacobs, J. K. Markunas, L. A. Almeida, A. Stoltz, P. S. Wijewarnasuriya, J. Peterson, M. Reddy, K. Jones, S. M. Johnson, and D. D. Lofgreen, J. Electron. Mater. 45, 4502 (2016).

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