B. Polsky

Investigation of the Statistical Variability of Static Noise Margins of SRAM Cells Using the Statistical Impedance Field Method

The statistical variability of the static noise margin of a six-transistor bulk complementary metal-oxide-semiconductor static random access memory (SRAM) cell due to random doping fluctuations (RDFs) is investigated via 3-D technology computer-aided design simulations. The SRAM cell is created through 3-D process simulations of the entire cell as a single structure. The process flow is based on a typical 32-nm technology. The effects of RDFs on the cell performance are investigated using the highly efficient statistical impedance field method.

Simulations of ultrathin, ultrashort double-gated MOSFETs with the density gradient transport model

We report the results of numerical simulation of nanoscale SOI structures under highly non-equilibrium conditions with the Density Gradient model. The simulations have been carried out with the general purpose device simulator DESSIS. We show that 2D quantum mechanical effects are important for the structures under investigation. We demonstrate that our implementation of the DG model is robust and enables efficient simulation far from equilibrium, for both the drift-diffusion and hydrodynamic transport model.

On negative differential resistance in hydrodynamic simulation of partially depleted SOI transistors

We show that the negative differential resistance in the I/sub d/-V/sub ds/ characteristics observed in hydrodynamic transport simulations of partially depleted silicon-on-insulator MOSFETs disappears if the nonlocality of tunneling effects are properly accounted for in the recombination-generation process.

Investigation of Proximity Effects in a 6T SRAM Cell Using Three-Dimensional TCAD Simulations

In this paper, we study the impacts of proximity effects on the electrical characteristics Id-Vg and the static noise margin of a six-transistor (6T) bulk complementary metal-oxide-semiconductor (MOS) static random access memory (SRAM) cell using 3-D process and device technology computer-aided design (TCAD) simulations. We show that when a 6T SRAM cell is simulated as a single continuous 3-D structure, effective stresses in channels are reduced due to close proximity of n-channel and p-channel MOS transistors in the cell with respect to simulations of transistors as discrete 3-D structures. Furthermore, we find that doping in channels of SRAM transistors is reduced by well proximity and implant shadowing. Stress and doping proximity effects have opposite contributions to device performance. We estimate the influence of proximity effects for typical 32-nm technology to be more than 10% for certain electrical cell characteristics. We thus conclude that, to accurately predict electrical cell behavior via TCAD simulations, the 6T SRAM cell should be a single continuous 3-D structure, instead of a set of six discrete transistors, which are simulated as individual 3-D devices and connected via a netlist.

Simulations of quantum transport in HEMT using density gradient model

In this paper, quantum transport simulations for AlGaAs/InGaAs HEMT devices based on the density gradient model are presented. It is shows that size quantization effects have a pronounced influence on the electrical characteristics.

Three-dimensional TCAD Process and Device Simulations

Shrinking feature sizes, novel device designs as well as stress engineering increase the need for three- dimensional process and device simulations. We present several application examples for full 3D process and device simulations using Sentaurus TCAD, including a 3D NMOSFET with shallow trench isolations (STI), a PMOSFET device with SiGe pockets for stress engineering (similar to the structure presented in Ref. [1]) and a Omega-FinFET (similar to structures presented in Refs. [2,3]). TCAD simulations of the full process flow as well as of the electrical device characteristics are performed. We also show examples of 3D oxidation simulations with Sentaurus Process.

Simulations of ultrathin SOI with quantum transport models

In this report we investigate quantum effects in ultrathin SOIs in the framework of the density gradient model. It is demonstrated that this approach can correctly predict not only threshold voltage shifts but also spatial carrier distributions. The simulation results are in excellent agreement with the rigorous but computationally expensive solution of the Schrodinger equation coupled to the drift-diffusion transport equations.

Simulation of electron tunneling in HEMT devices

We report results of 2D simulations of the electron tunneling through hetero-interfaces and gate Schottky contact in AlGaAs/InGaAs HEMT. For the first time the rigorous non-local tunneling models have been applied for heterostructure device simulations. The simulations have been performed within hydrodynamic transport model to account for hot electrons. The tunneling through hetero-interfaces fully controls the drain current. The tunneling through the Schottky barrier is responsible for the gate leakage and can significantly affect the transfer characteristics. Further, we have found that the breakdown characteristics of a HEMT are strongly affected by the gate leakage due to tunneling through the Schottky barrier. This effect may lead to a considerable underestimation of the HEMT breakdown voltage, when non-destructive measurement methods are applied.