Non-Destructive Cryogenic Wafer Mapper for Infrared Detector Material Screening

Quality control tools for compound semiconductor operations are desired to provide cost and time savings. 8D Photonics (www.8Dphotonics.com) has been providing the infrared community with the capability to perform cryogenic wafer mapping of minority carrier lifetime and photoluminescence spectra since its inception in 2016. The 8D IR Pioneer wafer mapping system has already demonstrated cooling and lifetime/photoluminescence mapping of 150 mm wafers down to a temperature of 26 K with a temperature uniformity better than 1 K from center to edge of the wafer. Our second-generation 8D IR Explorer software was designed with throughput and usability in mind and includes autotuning features that allow non-experts access to what would otherwise be complicated measurements and analysis. In the first 12 months of the proposed effort, we will install the 8D IR Pioneer wafer mapping system at two different growth foundries for testing and evaluation. Focal plane arrays (FPA) based on dual-color detectors are useful for a variety of applications such as providing enhanced contrast in imaging systems for aircraft. Characterization of dual-color wafers is very challenging using existing techniques as the longer wavelength absorber layer is typically grown on top of the shorter wavelength absorber layer such that the longer wavelength layer blocks optical access to the shorter wavelength layer. The key innovation in this proposal is the development of a novel dynamic charge detection approach to characterize the otherwise-obscured shorter wavelength region of dual-color wafers. When a dual-color wafer is integrated with a read-out circuit, the wafer is typically flipped over, presenting the shorter wavelength absorber layer on the FPA surface. After substrate removal, proper optical access is obtained for both the short and long wavelength layers, however, this is only achieved after a significant amount of fabrication and integration. Our proposed approach to characterizing the as-grown dual-color wafers will result in substantial time and cost savings at all stages of the manufacturing effort from wafer growth to FPA hybridization. Approved for Public Release | 23-MDA-11401 (14 Mar 23)