Aaron Thean

CMOS Vertical Multiple Independent Gate Field Effect Transistor (MIGFET)

Perfectly self aligned vertical multiple independent gate field effect transistor (MIGFET) CMOS devices have been fabricated. The unique process used to fabricate these devices allow them to be integrated with FinFET devices. Device and circuit simulations have been used to explain the device and explore new applications using this device. A novel application of the MIGFET as a signal mixer has been demonstrated. The undoped channel, very thin body, perfectly matched gates allows charge coupling of the two signals and provide a new family of applications using the MIGFET mixer. Since the process allows integration of regular CMOS double gate devices and MIGFET devices this technology has potential for various digital and analog mixed-signal applications.

A cost effective 32nm high-K/ metal gate CMOS technology for low power applications with single-metal/gate-first process

For the first time, we have demonstrated a 32 nm high-k/metal gate (HK-MG) low power CMOS platform technology with low standby leakage transistors and functional high-density SRAM with a cell size of 0.157 mum2. Record NMOS/PMOS drive currents of 1000/575 muA/mum, respectively, have been achieved at 1 nA/mum off-current and 1.1 V Vdd with a low cost process. With this high performance transistor, Vdd can be further scaled to 1.0 V for active power reduction. Through aggressive EOT scaling and band-edge work-function metal gate stacks, appropriate Vts and superior short channel control has been achieved for both NMOS and PMOS at Lgate = 30 nm. Compared to SiON-Poly, 30% RO delay reduction has been demonstrated with HK-MG devices. 40% Vt mismatch reduction has been shown with the Tinv scaling. Furthermore, it has been shown that the 1/f noise and transistor reliability exceed the technology requirements.

Heteroepitaxy of InP on Si(001) by selective-area metal organic vapor-phase epitaxy in sub-50 nm width trenches: The role of the nucleation layer and the recess engineering

This study relates to the heteroepitaxy of InP on patterned Si substrates using the defect trapping technique. We carefully investigated the growth mechanism in shallow trench isolation trenches to optimize the nucleation layer. By comparing different recess engineering options: rounded-Ge versus V-grooved, we could show a strong enhancement of the crystalline quality and growth uniformity of the InP semiconductor. The demonstration of III-V heteroepitaxy at scaled dimensions opens the possibility for new applications integrated on Silicon.

Vertical GAAFETs for the Ultimate CMOS Scaling

In this paper, we compare the performances of FinFETs, lateral gate-all-around (GAA) FETs, and vertical GAAFETs (VFETs) at 7-nm node dimensions and beyond. Comparison is done at ring oscillator level accounting not only for front-end of line devices but also for interconnects. It is demonstrated that FinFETs fail to maintain the performance at scaled dimensions, while VFETs demonstrate good scalability and eventually outperform lateral devices both in speed and power consumption. Lateral GAAFETs show better scalability with respect to FinFETs but still consume 35% more energy per switch than VFETs if made under 5-nm node design rules.

InGaAs Gate-All-Around Nanowire Devices on 300mm Si Substrates

In this letter, we present the first InGaAs gate-all-around (GAA) nanowire devices fabricated on 300mm Si substrates. For an L_G of 60 nm an extrinsic g_m of 1030 μS/μm at V_ds = 0.5 V is achieved which is a 1.75× increase compared with the replacement fin FinFet process. This improvement is attributed to the elimination of Mg counterdoping in the GAA flow. Ultrascaled nanowires with diameters of 6 nm were demonstrated to show immunity to D_it resulting in an SS_SAT of 66 mV/decade and negligible drain-induced barrier lowering for 85-nm L_G devices.

A new complementary hetero-junction vertical Tunnel-FET integration scheme

This paper presents a new integration scheme for complementary hetero-junction vertical Tunnel FETs (VTFETs), whereby a sacrificial source layer is used during the device fabrication and replaced by the final hetero-source materials, respectively for n- or p-TFETs, thereby minimizing the thermal budget applied to the source junctions. With the demonstration of this source-replacement-last module for a vertical Ge hetero-junction n-TFET, we show that it is possible to grow highly doped hetero-junctions on a Si channel with steep doping profiles and without damaging the high-κ gate-dielectric interface. This scheme allows for the integration of complementary low-bandgap materials on a Si platform providing high on-currents combined with the Si channel based low off-currents.

Impact of the channel thickness on the performance of ultrathin InGaAs channel MOSFET devices

InGaAs channel MOSFET devices with a channel thickness down to 3nm were fabricated and systematically characterized. Thinner channels result in improved electrostatics, however, the mobility rapidly drops to 110 cm2/Vs for the 3nm thick channel which results in significant loss of the drive current. 10 nm was found to be the optimum channel thickness with 77 mV/dec sub-threshold swing (SS). To account for the band-mixing and nonparabolicity of the III-V systems, 8-bands k.p simulations were conducted to gain an accurate insight into the device operation. As also verified experimentally, simulations suggest that the accumulation capacitance value increases as the channel thickness decreases due to the variations in the inversion charge profile. Simulations suggest that the InP buffer response affects the effective mass of the carriers and reduces the mobility as the channel becomes thinner. Based on this work, InGaAs channel thicknesses of 5nm and below hit severe performance issues.

Scaling of 32nm low power SRAM with high-K metal gate

This paper describes SRAM scaling for 32 nm low power bulk technology, enabled by high-K metal gate process, down to 0.149 mum2 and 0.124 mum2. SRAM access stability and write margin are significantly improved through a 50% Vt mismatch reduction, thanks to HK-MG Tinv scaling. Cell read current is increased by 70% over Poly-SiON process. Ultra dense cell process window is expanded with optimized contact process. A dual-ground write assist option can additionally enable ultra dense 0.124 mum2 cell to meet low power application requirements.

Embedded SiGe S/D PMOS on thin body SOI substrate with drive current enhancement

We report for the first time PMOS drive current enhancement with in-situ boron doped SiGe incorporation in recessed S/D regions for devices built on thin body SOI substrate. For P-channel PD-SOI devices with 450 A silicon on insulator and 38nm gate length, 35% linear drain current enhancement and 20% saturation drain current improvement have been achieved with this approach. Device integration and performance improvement are discussed below.

Selective area growth of InP in shallow trench isolation on large scale Si(001) wafer using defect confinement technique

Heterogeneous integration of III–V semiconductors on Si substrate has been attracting much attention as building blocks for next-generation electronics, optoelectronics, and photonics. In the present paper, we studied the selective area epitaxial studies of InP grown on 300 mm on-axis Si (001) substrates patterned with Shallow Trench Isolation (STI) using the necking effect technique to trap crystalline defects on the sidewalls. We make use of a thin Ge buffer in the bottom of the trench to reduce interfacial strain at the interface and to promote InP nucleation. We could show here, by systematic analysis, the strong impact of the growth temperatures and pressures of the InP layer on the growth uniformity along the trench and crystalline quality that we correlated with resistance changes and interdiffusion measured in the III–V layer. The key challenge remains in the ultimate control of crystalline quality during InP selective growth in order to reduce defect density to enable device-quality III–V virtual...