Improved Drive Current in RF Vertical MOSFETS Using Hydrogen Anneal

This letter reports a study on the effect of a hydrogen anneal after silicon pillar etch of surround-gate vertical MOSFETs intended for RF applications. A hydrogen anneal at 800°C is shown to give a 30% improvement in the drive current of 120-nm n-channel transistors compared with transistors with out the hydrogen anneal. The value of drive current achieved is 250 μA/μm, which is a record for thick pillar vertical MOSFETs. This improved performance is obtained even though a sacrificial oxidation was performed prior to the hydrogen anneal to smooth the pillar sidewall. The values of subthreshold slope and DIBL are 79 mV/decade and 45 mV/V, respectively, which are significantly better than most values reported in the literature for comparable devices. The H₂ anneal is also shown to decrease the OFF-state leakage current by a factor of three.