Makoto Miyamura

Polymer Solid-Electrolyte Switch Embedded on CMOS for Nonvolatile Crossbar Switch

A polymer solid-electrolyte (PSE) switch has been embedded in a 90-nm-node CMOS featuring a forming-less programming and extremely high on/off ratio of 105. A fast programming of 10 ns is also demonstrated for 50-nmΦ 1 k-b array by introducing the PSE switches integrated with a fully logic compatible process below 350°C. A high free volume in the PSE is supposed to result in the smooth formation of the Cu bridge without destroying the electrolyte, thereby also resulting in forming-less programming and high breakdown voltage. High disturbance reliability (T50; 50% fail) is extracted to be over 10 years at operation condition. The improved switching characteristics enable us to accurately program the crossbar circuit in a practical scale (32 × 32) without cell transistors. The developed switch is a strong candidate for realizing a low-power and low-cost nonvolatile programmable logic.

High mobility MISFET with low trapped charge in HfSiO films

MISFETs with HfSiO (EOT:1.8 nm) gate insulator have been reached high Ion (95%) and low gate leakage current (1/100) against SiO/sub 2/ gate film. This was achieved by the suppression of the remote Coulomb scattering, caused by the electron traps in the HfSiO gate stack. It was experimentally confirmed that less than 3/spl times/10/sup 12/ C/cm/sup 2/ electron trap level is required to get high mobility.

Programmable cell array using rewritable solid-electrolyte switch integrated in 90nm CMOS

Programmable devices such as SRAM-based FPGAs have the major challenges of power consumption and circuit area due to the excessive standby leakage current and the threshold voltage variation in highly scaled SRAM. Back-end-of-line (BEOL) device, which is integrated in the interconnect layers, is attractive for reducing the performance gap between FPGA and cell-based ASIC [1–4]. In this paper, we demonstrate the fundamental operations of a programmable cell array and a 32×32 crossbar switch using a nonvolatile and rewritable solid-electrolyte switch (nanobridge or NB). A 72% reduction in chip-area compared with that of a standard-cell-based design is achieved on a 90nm CMOS platform.

A highly manufacturable low power and high speed HfSiO CMOS FET with dual poly-Si gate electrodes

For 90 nm node poly-Si gated MISFETs with HfSiO (1.8 nm) insulator, a nearly symmetrical set of Vths for NFET and PFET: (0.38 V and -0.46 V, respectively) have been realized for low power device operation. The key technology is the suppression of Vth instability in PFETs arising from oxidation of the poly-Si/HfSiO interface, combined with channel engineering for the PFET. Our poly-Si/HfSiO gate-stacked CMOSFETs realize low I/sub off/ (N/PFET: 4.8/3.6 pA//spl mu/m) and high I/sub on/ (N/PFET: 469/140 /spl mu/A//spl mu/m) at V/sub DD/=1.2 V. Further, for SRAM cell using this CMOS, normal operation has been achieved.

First demonstration of logic mapping on nonvolatile programmable cell using complementary atom switch

Reconfigurable nonvolatile programmable logic using complementary atom switch (CAS) is successfully demonstrated on a 65-nm-node test chip. Various logics are realized by synthesizing RTL codes and mapping the configurations into CAS-based programmable cell array. Each cell includes the two 4-input LUTs, 19×16 crossbar switch, and 368-b CAS. The CAS integrated over CMOS reduces the cell area by 78% compared to a conventional SRAM-based design.

Electron energy-loss spectroscopy analysis of the electronic structure of nitrided Hf silicate films

We have shown, using electron energy-loss spectroscopy, that incorporating N into a Hf silicate film reduces the band gap. We also experimentally clarified that the Hf atoms in the film are coordinated by N atoms, and we used ab initio electronic structure calculations to show that the Hf–N coordination can be a cause of the decrease in the band gap. Therefore, when a Hf silicate film is used as a gate dielectric in a metal-oxide-semiconductor field-effect transistor, N incorporation can affect the gate leakage current because the decrease in the band gap lowers the band offsets of the dielectric on Si.

Improved Off-State Reliability of Nonvolatile Resistive Switch With Low Programming Voltage

A complementary atom switch (CAS) is proposed to realize low programming voltage and high off-state reliability for crossbar switch application. Two atom switches with bipolar operation are connected in series with opposite direction, in which the two atom switches work as a single element. The two off-state atom switches in the CAS complementarily divide voltage stress, greatly enlarging the off-state lifetime. The CAS is embedded in Cu BEOL on a 65-nm-node CMOS platform without degrading the CMOS and interconnect performances. The CAS using two atom switches is one of the candidates for realizing energy-efficient nonvolatile programmable switches.

Highly reliable, complementary atom switch (CAS) with low programming voltage embedded in Cu BEOL for Nonvolatile Programmable Logic

A novel complementary atom switch (CAS) embedded in Cu BEOL has been developed to realize low programming voltage of 2V and extremely high disturbance reliability of OFF-state (T0.1>10 years at 1V, 125°C). The decrement of solid-electrolyte density successfully reduces the programming voltage down to 2V. Two bipolar resistive-change elements such as atom switches are connected in series with opposite direction, in which the two OFF-state elements complementarily divide the voltage stress, greatly enlarging the OFF-state lifetime. The highly reliable, complementary atom switch is a promising device for energy efficient, Nonvolatile Programmable Logic (NPL).

SRAM critical yield evaluation based on comprehensive physical / statistical modeling, considering anomalous non-Gaussian intrinsic transistor fluctuations

Critical SRAM yield evaluation/analysis for more robust design optimizations against variation is presented based on comprehensive physical modeling and statistical analysis of transistor intrinsic fluctuations for 65 nm-node and beyond MOSFETs. Predictive atomistic-3D-TCAD simulations reveal the origins of the non-Gaussian Vth-distribution that causes large sigmaVth deviation from the Pelgrom-relationship for specific small gate length devices. By using realistic statistical compact-modeling and fast Monte Carlo circuit simulations, it was demonstrated that the appropriate cell-design recognizing the anomalous sigmaVth enables to rescue significant possible yield loss caused by the particular behaviors of the intrinsic transistor fluctuations.

The influence of incorporated nitrogen on the thermal stability of amorphous HfO2 and Hf silicate

We investigated the thermal stability of a N-incorporated amorphous Hf silicate film in terms of Hf diffusion in the film using high-angle annular-dark-field scanning transmission electron microscopy. We first examined HfxSi1−xO2 (x=0.5,1.0) films with and without N incorporation. Our analysis showed that N incorporation (15at.% of N) into the Hf0.5Si0.5O2 film significantly suppressed chemical component separation during annealing at 1000°C. In contrast, clear separation of Hf-rich and Hf-poor (SiO2-rich) regions occurred in the Hf0.5Si0.5O2 film without N incorporation. In addition, HfO2 crystalline particle formation was observed in the HfO2 films with and without N incorporation (25at.% of N). These results strongly suggest that Si–N bonding in the N-incorporated Hf0.5Si0.5O2 film, rather than Hf–N chemical bonding, is the main cause of the suppression of the chemical component separation and HfO2 crystallization. Second, we examined Hf diffusion in a SiO2 film with and without N incorporation and fou...