Optimization of fully-implanted NPNs for high-frequency operation

Abstract

Abstract-With a very straightforward (low-cost) process flow as basis, fully-implanted washed-emitter-base (WEB) NPN's have been optimized for operation in the 10-30 GHz range. Above 20 GHz the best overall performance is achieved by heavy doping of the epi. A low-stress silicon rich nitride layer is proven effective as surface isolation before contact window dip-etch.

Surface-passivated high-resistivity silicon as a true microwave substrate

“…GHz was derived from the former DIMES-03 process GHz [15] and has been used here for the fabrication of the microwave passive components and the TWA. HF and high-voltage (HV) transistors are available (Table I).…”

“…Since the very high silicon resistivity results in excessively wide space-charge regions (in the 20-m range) of the collector-substrate junctions and low integral p-type doping between neighboring n-type regions placed in the substrate, a special p-well isolation structure has been developed for dense integration of the transistors. A 3-m-deep boron-doped p-well with a peak doping concentration of 2 10 cm is created by implantation and thermal annealing prior to the implantation of the n sub-collector regions and blanket deposition of the n-type layer, in which the active devices are built [15]. Outside the silicon device regions, this n silicon layer is removed by trench etching so that the passive components can be placed directly on the HRS substrate where substrate losses are the lowest.…”

“…This, however, brings several technological issues in focus that may form bottlenecks, in particular the considerable losses in the conventional silicon substrates [6]. Currently, resistivities of at most [10][11][12][13][14][15][16][17][18][19][20] cm [low-resistivitysilicon(LRS)]arebeingused.Thiscorrespondsto conductivities that lead to considerable substrate losses and, thus, to excessive attenuation of integrated transmission lines [7] and reduced quality factors of on-chip inductors [8]. III-V-based processes have ideal substrates in that respect, but these lack other important properties such as high thermal conductivity and high and frequency-independent permittivity that qualify silicon as a true microwave substrate [7].…”

Varying Characteristics of Bipolar Transistors with Emitter Contact Window Width

“…In order to improve the accuracy of process simulation, the fully coupled point defect model was selected to predict post-implant dopant diffusions during some of the critical process steps and the corresponding model parameters (e.g., dopant diffusivity, equilibrium concentration and diffusivity of silicon interstitials, and so on, see reference [2] (Fu et al 2001)) were calibrated by using Inverse modelling driver PROFILE. It is worth noting that such a calibration procedure was based on comparisons of simulated dopant profiles given by TSUPREM-4 with the corresponding SIMS data detected from the accompanying wafers of the WEB bipolar process published in reference [6] (Nanver et al 1996). On the other hand, Phillips unified mobility model and field dependent mobility model, which are thought to be suitable for bipolar transistor simulation, were chosen to perform the subsequent MEDICI device simulation.…”

“…Fully-implanted washed-emitter-base (WEB) NPN bipolar transistors were optimized for operation in the 10-30 GHz range with low-stress silicon nitride film as surface isolation layer [6] (Nanver et a]. 1996).…”