0.18 μm low voltage/low power RF CMOS with zero Vth analog MOSFETs made by undoped epitaxial channel technique

Abstract

We introduce 0.18 /spl mu/m CMOS with multi-V/sub th/'s for mixed high-speed digital and RF-analog applications. The V/sub th/'s of MOSFETs for digital circuits are 0.4 V for NMOS and -0.4 V for PMOS, respectively. In addition, there are n-MOSFETs with zero-volt-Vth for RF analog circuits. The zero-volt-Vth MOSFETs were made by using undoped epitaxial layer for the channel regions. Though the epitaxial film was grown by reduced pressure chemical vapor deposition (RP-CVD), the film quality is good because higher pre-heating temperature (940/spl deg/C for 30 seconds) is used in H/sub 2/ atmosphere before epitaxial growth. The epitaxial channel MOSFET shows higher peak g/sub m/ and f/sub T/ than those of bulk cases. Furthermore, the g/sub m/ and f/sub T/ values show significantly improved performances under the low supply voltage, which is important for 0.18 /spl mu/m CMOS with low power/low supply voltage operation. Additionally, in our experiment no significant difference was observed between the reliability of gate oxide grown on bulk and the reliability of that grown on epitaxial layers. The undoped-epitaxial-channel MOSFETs with zero-V/sub th/ will be effective to realize high performance and low power CMOS devices for mixed digital and RF-analog applications.