J. Kuss

A 0.063 µm 2 FinFET SRAM cell demonstration with conventional lithography using a novel integration scheme with aggressively scaled fin and gate pitch

We demonstrate the smallest FinFET SRAM cell size of 0.063 µm2 reported to date using optical lithography. The cell is fabricated with contacted gate pitch (CPP) scaled to 80 nm and fin pitch scaled to 40 nm for the first time using a state-of-the-art 300 mm tool set. A unique patterning scheme featuring double-expose, double-etch (DE2) sidewall image transfer (SIT) process is used for fin formation. This scheme also forms differential fin pitch in the SRAM cells, where epitaxial films are used to merge only the tight pitch devices. The epitaxial films are also used for conformal doping of the devices, which reduces the external resistance significantly. Other features include gate-first metal gate stacks and transistors with 25 nm gate lengths with excellent short channel control.

High performance extremely thin SOI (ETSOI) hybrid CMOS with Si channel NFET and strained SiGe channel PFET

For the first time, we report high performance hybrid channel ETSOI CMOS by integrating strained SiGe-channel (cSiGe) PFET with Si-channel NFET at 22nm groundrules. We demonstrate a record high speed ring oscillator (fan-out = 3) with delay of 8.5 ps/stage and 11.2 ps/stage at VDD = 0.9V and VDD = 0.7V, respectively, outperforming state-of-the-art finFET results. A novel “STI-last” integration scheme is developed to improve cSiGe uniformity and enable ultra high performance PFET with narrow widths. Furthermore, cSiGe modulates device Vt, thus providing an additional knob to enable multi-Vt while maintaining undoped channels for all devices.

UTBB FDSOI transistors with dual STI for a multi-V t strategy at 20nm node and below

We introduce an innovative dual-depth shallow trench isolation (dual STI) scheme for Ultra Thin Body and BOX (UTBB) FDSOI architecture. Since in the dual STI configuration wells are isolated from one another by the deepest trenches, this architecture enables a full use of the back bias while staying compatible with both standard bulk design and conventional SOI substrates. We demonstrate in 20nm ground rules that we are able to tune Vt by more than 400mV, that transistor performance can be boosted by up to 30% and that Ioff can be controlled over 3 decades by allowing more than VDD/2 to be applied on the back gate.

Ultra-thin-body and BOX (UTBB) fully depleted (FD) device integration for 22nm node and beyond

We present UTBB devices with a gate length (L<inf>G</inf>) of 25nm and competitive drive currents. The process flow features conventional gate-first high-k/metal and raised source/drains (RSD). Back bias (V<inf>bb</inf>) enables V<inf>t</inf> modulation of more than 125mV with a V<inf>bb</inf> of 0.9V and BOX thickness of 12nm. This demonstrates the importance and viability of the UTBB structure for multi-V<inf>t</inf> and power management applications. We explore the impact of GP, BOX thickness and V<inf>bb</inf> on local V<inf>t</inf> variability for the first time. Excellent A<inf>Vt</inf> of 1.27 mV·µm is achieved. We also present simulations results that suggest UTBB has improved scalability, reduced gate leakage (I<inf>g</inf>) and lower external resistance (R<inf>ext</inf>), thanks to a thicker inversion gate dielectric (T<inf>inv</inf>) and body (T<inf>si</inf>) thickness.

Scalability of Extremely Thin SOI (ETSOI) MOSFETs to Sub-20-nm Gate Length

We report high-performance extremely thin SOI MOSFETs fabricated with a channel thickness down to 3.5 nm, sub-20-nm gate length, and contacted gate pitch of 100 nm. At an effective channel length of 18 nm, a drain-induced barrier lowering of 100 mV is achieved by either thinning the channel to 3.5 nm or by applying a reverse back-gate bias to 6-nm channel MOSFETs. Moreover, minimal increase in series resistance is seen when the channel is scaled to 3.5 nm, resulting in no performance degradation with SOI thickness scaling.

Extremely thin SOI (ETSOI) technology: Past, present, and future

As the mainstream bulk devices face formidable challenges to scale beyond 20nm node, there is an increasingly renewed interest in fully depleted devices for continued CMOS scaling. In this paper, we provide an overview of extremely thin SOI (ETSOI), a viable fully depleted device architecture for future technology. Barriers that prevented ETSOI becoming a mainstream technology in the past are specified and solutions to overcome those barriers are provided.

High performance UTBB FDSOI devices featuring 20nm gate length for 14nm node and beyond

We report, for the first time, high performance Ultra-thin Body and Box (UTBB) FDSOI devices with a gate length (L_G) of 20nm and BOX thickness (T_BOX) of 25nm, featuring dual channel FETs (Si channel NFET and compressively strained SiGe channel PFET). Competitive effective current (I_eff) reaches 630μA/μm and 670μA/μm for NFET and PFET, respectively, at off current (I_off) of 100nA/μm and V_dd of 0.9V. Excellent electrostatics is obtained, demonstrating the scalability of these devices to14nm and beyond. Very low A_Vt (1.3mV·μm) of channel SiGe (cSiGe) PFET devices is reported for the first time. BTI was improved >20% vs a comparable bulk device and evidence of continued scalability beyond 14nm is provided.

Strain engineered extremely thin SOI (ETSOI) for high-performance CMOS

High-performance strain-engineered ETSOI devices are reported. Three methods to boost the performance, namely contact strain, strained SOI (SSDOI) for NFET, and SiGe-on-insulator (SGOI) for PFET are examined. Significant performance boost is demonstrated with competitive drive currents of 1.65mA/μm and 1.25mA/μm, and I_eff of 0.95mA/μm and 0.70mA/μm at I_off =100nA/μm and V_DD of 1V, for NFET and PFET, respectively.

Challenges and opportunities of extremely thin SOI (ETSOI) CMOS technology for future low power and general purpose system-on-chip applications

Extremely thin SOI (ETSOI) MOSFET is a viable option for future CMOS scaling owing to superior short-channel control and immunity to random dopant fluctuation. However, challenges of ETSOI integration have so far hindered its adoption for mainstream CMOS. This is especially true for low-power applications, where SOI wafer cost is deemed to significantly add to the total cost. We have recently reported a novel integration scheme to overcome some of the major ETSOI manufacturing issues such as difficulty in doping thin silicon layer, process induced silicon loss, and the dilemma of reduction of external resistance and the increase of parasitic capacitance [1, 2]. The proposed integration flow significantly simplifies device processing and leads to considerable reduction in the number of critical masks [2].

FDSOI CMOS devices featuring dual strained channel and thin BOX extendable to the 10nm node

We report FDSOI devices with a 20nm gate length (L_G) and 5nm spacer, featuring a 20% tensile strained Silicon-on-Insulator (sSOI) channel NFET and 35% [Ge] partially compressive strained SiGe-on-Insulator (SGOI) channel PFET. This work represents the first demonstration of strain reversal of sSOI by SiGe in short channel devices. At V_dd of 0.75V, competitive effective current (I_eff) reaches 550/340 μA/μm for NFET, at I_off of 100/1 nA/μm, respectively. With a fully strained 30% SGOI channel on thin BOX (20nm) substrate and V_dd of 0.75V, PFET I_eff reaches 495/260 μA/μm, at I_off of 100/1 nA/μm, respectively. Competitive sub-threshold slope and DIBL are reported. With the demonstrated advanced strain techniques and short channel performance, FDSOI devices can be extended for both high performance and low power applications to the 10nm node.