Back-illuminated large area frame transfer CCDs for space-based hyper-spectral imaging applications

Abstract

Standard offerings of large area, back-illuminated full frame CCD sensors are available from multiple suppliers and they continue to be commonly deployed in ground- and space-based applications. By comparison the availability of large area frame transfers CCDs is sparse, with the accompanying ~2x increase in die area no doubt being a contributing factor. Modern back-illuminated CCDs yield very high quantum efficiency in the 290 to 400 nm band, a wavelength region of great interest in space-based instruments studying atmospheric phenomenon. In fast framing (e.g. 10 – 20 Hz), space-based applications such as hyper-spectral imaging, the use of a mechanical shutter to block incident photons during readout can prove costly and lower instrument reliability. The emergence of large area, all-digital visible CMOS sensors, with integrate while read functionality, are an alternative solution to CCDs; but, even after factoring in reduced complexity and cost of support electronics, the present cost to implement such novel sensors is prohibitive to cost constrained missions. Hence, there continues to be a niche set of applications where large area, back-illuminated frame transfer CCDs with high UV quantum efficiency, high frame rate, high full well, and low noise provide an advantageous solution. To address this need a family of large area frame transfer CCDs has been developed that includes 2048 (columns) x 256 (rows) (FT4), 2048 x 512 (FT5), and 2048 x 1024 (FT6) full frame transfer CCDs; and a 2048 x 1024 (FT7) split-frame transfer CCD. Each wafer contains 4 FT4, 2 FT5, 2 FT6, and 2 FT7 die. The designs have undergone radiation and accelerated life qualification and the electro-optical performance of these CCDs over the wavelength range of 290 to 900 nm is discussed.