50 nm vertical replacement-gate (VRG) nMOSFETs with ALD HfO/sub 2/ and Al/sub 2/O/sub 3/ gate dielectrics

Abstract

We have integrated HfO/sub 2/ and Al/sub 2/O/sub 3/ gate dielectrics grown by atomic layer chemical vapor deposition (ALD) with poly-Si gate electrodes in the vertical replacement-gate (VRG) MOSFET geometry. These transistors are among the first reported with ALD HfO/sub 2/ gate dielectrics, and have HfO/sub 2/ target equivalent oxide thicknesses (tEOT's) down to 13 /spl Aring/. The poly-crystalline HfO/sub 2/ films in these VRG nMOSFETs exhibit extremely low gate leakage (GL) current densities of J/sub G/ /spl sim/ 10/sup -7/ A/cm/sup 2/ at V/sub G/-V/sub T,Long/ = 0.6 V for 15 /spl Aring/ tEOT devices. This indicates that amorphous gate dielectrics may not be necessary to meet GL requirements. HfO/sub 2/ devices with 50 nm gate length L/sub G/ exhibit drive currents [normalized by the coded width W/sub C/] of 490 /spl mu/A//spl mu/m for 1 V operation (overdrive V/sub GS/-V/sub T/ = 0.6 V) with good short-channel performance. These results demonstrate that ALD is compatible with the demanding VRG geometry, thereby illustrating that it should be well-suited to essentially any novel device structure built with Si-compatible materials.