Helmut Puchner

STI stress-induced increase in reverse bias junction capacitance

A new contribution to reverse-biased junction capacitance is reported. This component arises from trench isolation stress-induced bandgap narrowing that changes the built-in potential. Experimental junction capacitance measurements show good correlation to simulated oxidation stresses. The reported data agrees well with the predicted values from basic device equations. Stress induced capacitance increase of 12% (7.5%) at 3.3 V reverse bias for p/sup +//n (n/sup +// p) junctions, respectively is observed. In addition, well-understood reverse junction leakage relation to stress is also reported. This phenomenon will become increasingly important as trenches become shallower and more tightly spaced.

N-Well Engineering to Improve Soft-Error-Rate Immunity for P-Type Substrate SRAM Technologies

We present experimental as well as simulation data which emphasizes the impact of the well and substrate architecture for the charge collection efficiency during an alpha particle hit. Several different SRAM cores with implanted buried layer, epitaxial grown and standard CZ substrates are subjected to alpha-particle events and the soft error rate is recorded. The best SER immunity was achieved with the standard CZ substrate. This findings are contradictive to earlier reports for DRAM memory cores and will be explained in detail within this paper. Resulting from this analysis we optimize the substrate to improve the SER immunity of SRAM cores.

OPTIMIZED SUBAMORPHIZING SILICON IMPLANTS TO MODIFY DIFFUSION AND ACTIVATION OF ARSENIC, BORON, AND PHOSPHORUS IMPLANTS FOR SHALLOW JUNCTION CREATION

Subamorphizing silicon preimplants were combined with relatively high dose drain (1014atoms/cm2) arsenic, boron, and phosphorus implants. The studies included as-implanted distributions. Extensive secondary ion mass spectrometry and spreading resistance profiling (SRP) analyses were carried out. It was found that the SRP analyses could be used to optimize the silicon implant energy. The resulting dopant profiles showed that not only was channeling suppressed and dopant diffusion reduced but activation also could be controlled. Equivalent medium doped drain regions of 150 nm were created using conventional furnace anneals. It was concluded that subamorphizing silicon preimplants could be used to create very shallow junctions in the medium dose drain regions of silicon-based devices.

Impact of Shallow Trench Liner Oxidation Scheme on Junction Leakage

Shallow trench liner oxidation scheme is shown to have direct bearing on the reverse biased junction leakage. Experiments reducing liner oxide thickness and nitride undercut while increasing effective active area actually reduced the leakage currents by 40%. Silicided and unsilicided area, corner and perimeter intensive diodes all exhibited this behaviour. The perimeter component of leakage was most affected by liner oxidation scheme. Simulations of the oxidation process indicate a correlation between stress induced during the liner options and junction leakage.

Deactivation Phenomenon for 0.18um Technology Indium Channel NMOS Devices

We present experimental as well as simulation data which ehibits a deactivation phenomenon of Indium in the low dose regime. We used Indium to fabricate super-steep retrograde channel profiles for a state-ofthe-art CMOS technology. By introduction of a specific combination of dopants Indium exhibits an unexpected deactivation phenomenon which could be verified experimentally as well as by using quantumchemical simulation tools. It was found that the combination of Indium, Boron and Nitrogen in the channel region causes severe deactivation and an increase in channel dose was ineffective to raise the threshold voltage.

Integrated simulation of the plasma-assisted gate oxide nitridation

Quantum chemical calculations were employed to get insight into the mechanisms involved in plasma-induced nitridation of gate oxide that will suppress boron penetration. The roles played by the nitrogen cations and atoms were explored. It was shown that B interaction with siloxane rings that contain incorporated nitrogen yielded a larger energy gain than rings without nitrogen. This explains the chemical nature of the nitrogen-induced barrier effect. Monte Carlo simulations were used to simulate the necessary energy of incident N2 cations to produce the bond cleavage down to a particular depth in the amorphous SiO2 layer. A combination of the HPEM and PCMC codes were used to simulate nitrogen atomic and cation fluxes and their energy distributions at the wafer surface. Combining simulated cation fluxes and their energy distributions at the wafer surface. Combining simulated cation energies with PROMIS Monte Carlo simulation results make it possible to derive the plasma process parameters that will permit a desired level of nitridation to be reached.

Fabrication of Shallow Junctions with Conventional Furnace Equipment by Using Silicon Preimplants

The global scaling down of device dimensions requires process technologies which are able to create ultra-shallow junctions. Besides using ultra-low implant energies for shallow junction creation we present an alternative approach for the creation of MDD (Medium Doped Drain) junctions by using moderately low implant energies. Our approach employs the dopant/point-defect interaction mechanism to retard dopant diffusion as well as dopant de-activation in the tail of the diffusion profiles to achieve suitable shallow junctions. The silicon preimplant allows fabrication of 90nm arsenic, 150nm phosphorus, and 140nm boron metallurgical junctions for a 40keV arsenic, 20keV phosphorus, and 8keV boron implant.

Plasma-induced nitridation of gate oxide dielectrics: Linked equipment-feature atomic scale simulations

Quantum chemical calculations were employed to get insight into the mechanisms involved in plasma-induced nitridation of gate oxide that will suppress boron penetration. The roles played by the nitrogen cations and atoms were explored. It was shown that B interaction with siloxane rings that contain incorporated nitrogen yielded a larger energy gain than rings without nitrogen. This explains the chemical nature of the nitrogen-induced barrier effect. Monte Carlo simulations were used to simulate the necessary energy of incident N2 cations to produce the bond cleavage down to a particular depth in the amorphous SiO2 layer. A combination of the hybrid plasma equipment model and plasma chemistry Monte Carlo codes was used to simulate nitrogen atomic and cation fluxes and their angular and energy distributions at the water surface. Combining simulated cation energies with PROMIS Monte Carlo simulation results makes it possible to derive plasma process parameters that will permit a desired level of nitridation...

The Role of Technology CAD in Early Process Development

A methodology for optimizing the benefits of simulation tools in the early stages of process development is presented. Especially, when optical printing tools are not yet available for manufacturing the next technology node, TCAD tools are used to estimate future nodes. To be able to predict the detailed device behavior of future technologies TCAD tools have to be carefully calibrated and validated. The performance of a device technology is predicted and optimized. The future success of TCAD will depend on the availability and reliability of 3D TCAD tools. An outlook is presented at most critical problems requiring a full 3D simulation suite.

Simulation of ultra-low energy ion implantation from a remote plasma source using Monte Carlo techniques

We present simulation as well as experimental data for ultra-low energy nitrogen ion implants from a remote nitrogen plasma source. Nitrogen plasma ion implantation is used to create highly effective diffusion barriers for dopants. We used a commercially available plasma etch tool to create a diffusion barrier for boron in a p-channel CMOS device to avoid boron penetration as well as to decrease the electrical thickness of the gate oxide. We employ a Monte Carlo ion implantation tool to simulate the penetration depth as well as doping levels for the nitrogen plasma doping.