Improvement of high resistivity substrate for future mixed analog-digital applications

Fully oxygen precipitated (FOP) wafers can suppress slip generation during the STI process and maintain high substrate resistivity. Additional boron implantation can suppress the leakage current between the adjacent wells due to shallow Xj. No effect on MOSFET characteristics by this implantation was observed. The high resistivity substrate (HRS) can provide good ESD performance and suppress the passage of high frequency signals through the substrate in resistors. Thus, HRS with FOP & additional implantation is effective for future mixed signal CMOS with RF circuits.

Introduction

Recently, high resistivity substrate (HRS) requirements have increased for high Q inductor and suppression of substrate noise from digital to analog circuits [1], [2]. However, the HRS wafer has some problems, that is slip generation during STI process due to low residual oxygen, and higher leakage current between adjacent nwells due to extremely lower impurity concentration in the substrate. In this paper, it is shown to resolve these problems and obtain not only suppression substrate noise but also good characteristics of ESD and resistor on HRS.