Body Potential Measurement Methods and Pocket Implant Effect on PD-SOI Devices

• Main Authors: Yu-Sheng Lai, 賴祐生
• Other Authors: Mao-Chieh Chen
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/70080239789085105932

碩士 === 國立交通大學 === 電子工程系所 === 94 === This thesis studies device properties of partially depleted (PD) SOI nMOSFETs. The first part of the study contains the discussion and development of body potential measurement methods for the floating body (FB) PD-SOI devices, while the second part contains the investigation of the effect of pocket implant on the device properties. The FB PD-SOI devices feature small area and high speed, but their unfixed body potential results in some operational uncertainty. By employing the commonly used null-body-current method to measure the body potential (VB), we found that inaccurate data of VB are easily obtained whenever there is a large value of differential body potential with respect to the change of drain voltage (dVB/dVD). Accurate body potential can be obtained by prolonging the measurement time or with the aid of interpolation to the monitored small positive/negative small body current. Pocket implant will affect many device characteristics, including threshold voltage and drain-to-body and body-to-source junction properties. To reduce floating body effect by reducing body potential, it is helpful to increase the forward junction current at the source-to-body junction. To achieve the goal of reducing body potential without affecting all other device characteristics, we propose the pocket implant scheme as follows, based on the results of our experimental study. In the first place, we may somewhat reduce the implantation dose for the conventional well and the tilt-angle pocket implant. Then, an additional zero-degree pocket implant with appropriate implantation conditions is performed only at the source-to-body junction to enhance its forward junction current, while another additional zero-degree pocket implant with a lower dose (than the previous one at the source-to-body junction) is performed only at the drain-to-body junction so as to restrain its reverse junction current and junction capacitance.