Self-aligned subchannel implant complementary metal–oxide semiconductor devices fabrication

Abstract

High-speed and low-power complementary metal–oxide semiconductor devices with subchannel implants have been proposed and demonstrated recently. In subchannel implant devices, the alignment of the gate and the buried implant region is a critical issue. In this article, a fully self-aligned gate and subchannel implant fabrication method is proposed using either focused-ion-beam or conventional ion implantation. This method defines the gate and produces the subchannel implant in the same step. By doing this, the buried implant region and gate are automatically aligned. By exposing the resist with a B+ ion beam, we verified that the dose needed to produce the subchannel implant matches the dose needed to expose the resist (1013 ion/cm2). We have simulated the implant profile and the expected device performance. The subthreshold current was found to be decreased by 1–2 orders of magnitude. Since the process requires implantation through the gate oxide, capacitors were built over the gate oxide for C–V measurement and implanted over a range of doses. Proper postimplantation treatment has been developed to prevent increasing of the interface state density.