Scalability of dry-etch processing for small unit-cell HgCdTe focal-plane arrays

A combination of mechanical experiments and fabrication of very-long-wavelength infrared (VLWIR) HgCdTe-infrared detectors has been used to investigate the interaction between various unit-cell design and dry-etch process variables on final unit-cell dimensions and detector performance. Etch rate, which determines the process time required to achieve a specified etch depth, was found to be a function of both the trench width opening used to delineate an individual detector element in a focal-plane array (FPA) and the mesa profile observed during etching. Current-voltage (I-V) probe data at 78 K demonstrated the successful fabrication of 30 µm unit-cell, VLWIR-HgCdTe diodes with mesa delineation performed by dry etching. The breakdown performance of these diodes is sensitive to trench width and dry-etch process time.

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