Device Design for a 12.3-Megapixel, Fully Depleted, Back-Illuminated, High-Voltage Compatible Charge-Coupled Device

A 12.3-megapixel charge-coupled device (CCD) that can be operated at high substrate-bias voltages has been developed in support of a proposal to study dark energy. The pixel size is 10.5 mum, and the format is 3512 rows by 3508 columns. The CCD is nominally 200 mum thick and is fabricated on high-resistivity n-type silicon that allows for fully depleted operation with the application of a substrate-bias voltage. The CCD is required to have high quantum efficiency (QE) at near-infrared wavelengths, low noise and dark current, and an rms spatial resolution of less than 4 mum. In order to optimize the spatial resolution and QE, requirements that have conflicting dependences on the substrate thickness, it is necessary to operate the CCD at large substrate-bias voltages. In this paper, we describe the features of the CCD, summarize the performance, and discuss in detail the device-design techniques used to realize 200-mum-thick CCDs that can be operated at substrate-bias voltages in excess of 100 V.

I. Introduction

We have developed fully depleted back-illuminated charge-coupled devices (CCDs) that address the tradeoff of the fully depleted CCD technology in terms of quantum efficiency (QE) and spatial resolution. This paper was motivated by a proposal for a space-based telescope to study dark energy [1], [2].