Hiroshi Goto

On the accuracy and efficiency of substrate current calculations for sub-μm n-MOSFET's

The accuracy and efficiency of the self-consistent (regarding the electric field) Monte Carlo model, nonself-consistent Monte Carlo model, and the soft-threshold lucky electron model (LEM) for the calculation of substrate currents in deep sub-/spl mu/m n-MOSFETs are investigated. While the two Monte Carlo models are in good agreement with the experiment, the simpler LEM model still gives reasonable results even for a 0.16 /spl mu/m n-MOSFET. On the other hand, huge differences in the CPU time consumption are found and the LEM is about four orders of magnitude faster than the self-consistent Monte Carlo simulations. The nonself-consistent calculations are only one order of magnitude slower than the LEM. The good agreement with the experiment is obtained without considering the so-called surface impact ionization or any fitting of parameters on the device level.

Analysis of highly doped collector transistors by using two-dimensional process/device simulation and its application of ECL circuits

A report is presented of the results of an investigation of device parameters and collector-to-emitter breakdown voltages of double polysilicon self-aligned transistors with highly doped collectors using a two-dimensional process/device simulation system. Favourable phosphorous-ion implanting condition for a highly doped pedestal collector was found to achieve a high cutoff frequency as well as low AC base resistance and small base-collector capacitance, thereby keeping the minimum collector-to-emitter breakdown voltage of 3 V. The authors also report ECL circuit performance improvements achieved in experiments that realized a minimum ECL gate delay time of 26.3 ps/gate at switching current of 1.64 mA as a result of process optimization. Moreover, a 1/8 static frequency divider T-F/F has been observed to operate up to a maximum frequency of 15.8 GHz. >

High-speed Si hetero-bipolar transistor with a SiC wide-gap emitter and an ultrathin heavily doped photoepitaxially grown base

The authors describe the AC performance of a Si-heterojunction bipolar transistor using a SiC wide-gap emitter with a photoepitaxially grown heavily doped ultrathin base (SiC-EBT). A 30-GHz cutoff frequency and low base resistance were achieved, while retaining an acceptable current gain and preventing tunneling current. The DC characteristics of the SiC-EBT were good enough to use in high-performance LSIs.<<ETX>>

Trench Isolation Schemes for Bipolar Devices --- Benefits and Limiting Aspects

This paper gives a review of benefits and limiting aspects in trench isolation techniques for bipolar deviices. The most sophisticated trench isolation techniques have realized not only higher packing densities but reduced collector-substrate, wiring-substrate and base-collector parasitic capacitances. By using these techniques, high performance bipolar devices have been fabricated while crystal defects caused by trench structures are the serious problem. Trench isolaltion techniques are still in progress, and it seems now that there is no apparent limiting aspect until the trench width reaches the filler material width to sustain enough breakdown voltage.

SiC Growth and Its Application to High-Speed Si-HBTs

This paper discusses the limitations of a conventional poly-Si emitter for sub 0.5μm bipolar transistors and presents a breakthrough using a heterojunction at the emitter-base junction with an SiCx widegap emitter. Both SiCx widegap emitter HBTs and poly-Si emitter transistors with comparable device structures are examined. Low base resistance was achieved using a 1x1019/cm3 base dopant concentration, while retaining an acceptable current gain and suppressing forward-bias tunneling current using the SiCx emitter. A very thin , highly doped base was combined with the SiCx emitter to demonstrate high-speed capability.

Inverse modeling-a promising approach to know what is made and what should be made

Inverse modeling is a promising approach to know device structures made in experiments. We show our inverse modeling approach and its efficiency by demonstrating accurate extraction of deep submicron MOSFET structures. We also show that our approach can predict device performance to optimize its structure for required specification.

SiCχ:F Hetero-Emitter and Epitaxial-Base Bipolar Transistors

This paper discusses the technology issues on an emitter and base for sub 0.5 µm bipolar transistors. The new opportunities offered by heterojunction structures and a low-temperature-grown epitaxial base increase the freedom of device design. The SiCx wide-gap emitter with thin, highly doped epitaxial base shows superior characteristics for LSI application owing to the freedom. Low base sheet resistance was achieved using 1×1019 /cm3 concentration base, while retaining an acceptable current gain and suppressing forward-bias tunneling current. We obtained a 30 GHz cutoff frequency for a 35-nm base width.