Schubert S. Chu

The first GeSn FinFET on a novel GeSnOI substrate achieving lowest S of 79 mV/decade and record high Gm, int of 807 μS/μm for GeSn P-FETs

The worlds first GeSn p-FinFETs formed on a novel GeSn-on-insulator (GeSnOI) substrate is reported, with channel lengths L<inf>ch</inf> down to 50 nm and fin width W<inf>Fin</inf> down to 20 nm. In comparison with other reported GeSn p-FETs, record low S of 79 mV/decade, record high G<inf>m, int</inf>, of 807 μS/um (VDs of −0.5 V), and the highest G<inf>m, int</inf>/S<inf>sat</inf>, were achieved. The highest high-field hole mobility of 208 cm2/Vs (at inversion carrier density of 8×10⁻² cm⁻²) for GeSn p-FETs with CVD grown GeSn channel was also obtained.

Atomic Layer Deposition (ALD) Processes for ULSI Manufacturing

Atomic layer deposition (ALD) is a technique where precursors are introduced alternatively, and a monolayer (or fraction thereof) is deposited on the surface at a time [1–4]. The sequential introduction of all precursors, separated by purge steps, completes an ALD cycle. Figure 14.1 illustrates the steps that comprise an ALD cycle.

Integrating Selective Epitaxy in Advanced Logic & Memory Devices

INTRODUCTION Selective epitaxy has gained increasing momentum in advanced high-performance logic as well as volatile and nonvolatile memory device fabrication. The advantages of this technique range from the well documented application of strained SiGe epitaxial films used to increase hole mobility and performance in pFET devices to intrinsic Si epitaxial layers used to prevent short channel effects in memory devices (DRAM). Other applications call upon the time tested strengths of epitaxy in ensuring abrupt, activated doped layers or junctions without the defectivity associated with implanted profiles.

Record high mobility (428cm 2 /V-s) of CVD-grown Ge/strained Ge 0.91 Sn 0.09 /Ge quantum well p-MOSFETs

It is the first time that CVD-grown GeSn channels with low thermal budget of 400°C significantly outperforms the Ge channel processed at high thermal budget of 550°C. Low thermal budget is necessary to prevent the Sn loss during the process. Note that only MBE-grown GeSn had large mobility reportedly in the past. Even with high Sn content (9%), the strong photoluminescence is observed from GeSn layers on Ge buffer on 300mm Si (001), indicating the high crystalline quality by CVD epitaxy. Ge cap with significant Δ Ev at Ge/GeSn interface can ensure the gate stack quality, and reduce the scattering of holes in the GeSn quantum wells by oxide/interface charges and surface roughness. However, the mobility is degraded by thick cap due to low hole population in the GeSn wells. The ∼7% mobility enhancement on <110> channel direction is observed using external transverse uniaxial tensile strain of ∼0.11% due to the reduction of effective mass. The mobility of GeSn QW p-MOSFETs increases with decreasing temperature at both high and low inversion carrier density, indicating that the mobility is dominated by phonon scattering. On the contrary, Ge channels are dominated by Coulomb scattering at low inversion carrier density, which has decreasing mobility with decreasing temperature. The normalized noise power density of GeSn p-MOSFETs decreases with increasing Ge cap thickness, reportedly for the first time, indicating that the carrier number fluctuation and correlated mobility fluctuation can be reduced when the carriers are away from interface.

Strained Ge 0.91 Sn 0.09 Quantum Well p-MOSFETs

Pseudomorphic Ge_0.91Sn_0.09 on Ge on Si with strong photoluminescence and low defect density is used for p-MOSFET channels. The mobility of Ge_0.91Sn_0.09 Quantum Well p-MOSFETs are higher than control Ge p-MOSFETs due to hole population in the GeSn wells. The 7.5% mobility enhancement on <;110> channel direction is observed using external transverse uniaxial tensile strain (~0.11%). The highest [Sn] of 9% in the channels grown by CVD, Pt SB S/D, high I_on/I_off ratio, and strain-enhanced mobility are obtained in this work.

Thermal chemical vapor deposition of epitaxial germanium tin alloys

A pseudomorphic growth of GeSn epitaxial films with [Sn] up to 16 at.% on relaxed Ge underlayer was demonstrated in a reduced pressure thermal chemical vapor deposition chamber. GeSn film resistivity can be as low as 0.3 mOhm-cm by in-situ boron doping of GeSn. Also, a GeSiSn film growth containing [Si]~24 at.% and [Sn]~4 at.% was achieved by flowing SiH4 during GeSn growth.