Modeling and experimental simulation of the low-frequency transfer inefficiency in bucket-brigade devices

Abstract

The work presented in this paper extends the available theory and it also presents a model for the low-frequency charge transfer in MOS bucket-brigade devices (BBD's). Our new theory which characterizes the low-frequency component of transfer inefficiency in terms of the subthreshold current is frequency independent and it incorporates both channel-length and barrier-height modulations. This model was verified experimentally on simulated BBD's. After proving both theoretically and experimentally that the low-frequency transfer inefficiency of BBD devices is due to subthreshold current, we successfully used this knowledge to design an improved BBD device. This improved device includes only one extra ion-implantation step relative to the original BBD device. An ion implant is used in part of the BBD channel.