Design Considerations for a Two-Phase, Buried-Channel, Charge-Coupled Device

Design Considerations for a Two-Phase, Buried-Channel, ChargeCoupled Device By J. McKENNA, N. L. SCHRYER, and R. H. WALDEN (Manuscript received March 29, 1974) The design of a two-phase, buried-channel (or bulk-channel) chargecoupled device is presented. Directionality is obtained by using a steppedoxide structure. The basic operation of the device is explained, and the effect that changes in various design parameters have o?i its operation is examined in some detail. A set of roughly optimal parameters are found that yield an extremely fast and efficient device. We estimate a chargetransfer time of 1.8 ns and a charge capacity of 4-1 X 10u (electrons/cm"1). Only existing technology is necessary for its fabrication. This paper presents some design considerations for a two-phase, buried-channel (or bulk-channel) charge-coupled device ( B C C D ) . T h e concept of the B C C D has been presented previously, 1 - 2 and operation of three-phase B C C D ' s has been demonstrated. 3 - 6 Two-phase surface charge-coupled devices (CCD's) have advantages over three-phase surface C C D ' s in m a n y applications, and several designs have been discussed. 7 - 1 2 Therefore, it seems important and timely to consider the design of two-phase B C C D ' s . We present here a brief review of the basic n-channel B C C D structure. Figure 1 shows the C C D electrode configuration originally proposed for the buried-channel device. 1 Beneath the charge-transfer electrodes are successively a layer of silicon dioxide about 1200 A thick, a layer of n-type single-crystal silicon, and finally the substrate of lightly doped p-type silicon.