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Title: Radiation-induced gain degradation in lateral PNP BJTs with lightly and heavily doped emitters

Abstract

Ionizing radiation may cause failures in ICs due to gain degradation of individual devices. The base current of irradiated bipolar devices increases with total dose, while the collector current remains relatively constant. This results in a decrease in the current gain. Lateral PNP (LPNP) transistors typically exhibit more degradation than vertical PNP devices at the same total dose, and have been blamed as the cause of early IC failures at low dose rates. It is important to understand the differences in total-dose response between devices with heavily- and lightly-doped emitters in order to compare different technologies and evaluate the applicability of proposed low-dose-rate hardness-assurance methods. This paper addresses these differences by comparing two different LPNP devices from the same process: one with a heavily-doped emitter and one with a lightly-doped emitter. Experimental results demonstrate that the lightly-doped devices are more sensitive to ionizing radiation and simulations illustrate that increased recombination on the emitter side of the junction is responsible for the higher sensitivity.

Authors:
 [1];  [2];  [3];  [4];  [5]
  1. Univ. of Arizona, Tucson, AZ (United States)
  2. Vanderbilt Univ., Nashville, TN (United States)
  3. RLP Research, Inc., Albuquerque, NM (United States)
  4. Sandia National Labs., Albuquerque, NM (United States)
  5. VTC Inc., Bloomington, MN (United States)
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
491557
Report Number(s):
SAND-97-0425C; CONF-970711-15
ON: DE97003203; TRN: 97:012450
DOE Contract Number:
AC04-94AL85000
Resource Type:
Technical Report
Resource Relation:
Conference: 34. IEEE nuclear and space radiation effects conference, Snowmass, CO (United States), 21-25 Jul 1997; Other Information: PBD: [1997]
Country of Publication:
United States
Language:
English
Subject:
44 INSTRUMENTATION, INCLUDING NUCLEAR AND PARTICLE DETECTORS; JUNCTION TRANSISTORS; PHYSICAL RADIATION EFFECTS; IONIZING RADIATIONS; FAILURES; EXPERIMENTAL DATA; RADIATION DOSES

Citation Formats

Wu, A., Schrimpf, R.D., Pease, R.L., Fleetwood, D.M., and Kosier, S.L.. Radiation-induced gain degradation in lateral PNP BJTs with lightly and heavily doped emitters. United States: N. p., 1997. Web. doi:10.2172/491557.
Wu, A., Schrimpf, R.D., Pease, R.L., Fleetwood, D.M., & Kosier, S.L.. Radiation-induced gain degradation in lateral PNP BJTs with lightly and heavily doped emitters. United States. doi:10.2172/491557.
Wu, A., Schrimpf, R.D., Pease, R.L., Fleetwood, D.M., and Kosier, S.L.. Sun . "Radiation-induced gain degradation in lateral PNP BJTs with lightly and heavily doped emitters". United States. doi:10.2172/491557. https://www.osti.gov/servlets/purl/491557.
@article{osti_491557,
title = {Radiation-induced gain degradation in lateral PNP BJTs with lightly and heavily doped emitters},
author = {Wu, A. and Schrimpf, R.D. and Pease, R.L. and Fleetwood, D.M. and Kosier, S.L.},
abstractNote = {Ionizing radiation may cause failures in ICs due to gain degradation of individual devices. The base current of irradiated bipolar devices increases with total dose, while the collector current remains relatively constant. This results in a decrease in the current gain. Lateral PNP (LPNP) transistors typically exhibit more degradation than vertical PNP devices at the same total dose, and have been blamed as the cause of early IC failures at low dose rates. It is important to understand the differences in total-dose response between devices with heavily- and lightly-doped emitters in order to compare different technologies and evaluate the applicability of proposed low-dose-rate hardness-assurance methods. This paper addresses these differences by comparing two different LPNP devices from the same process: one with a heavily-doped emitter and one with a lightly-doped emitter. Experimental results demonstrate that the lightly-doped devices are more sensitive to ionizing radiation and simulations illustrate that increased recombination on the emitter side of the junction is responsible for the higher sensitivity.},
doi = {10.2172/491557},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jun 01 00:00:00 EDT 1997},
month = {Sun Jun 01 00:00:00 EDT 1997}
}

Technical Report:

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  • A comparison is presented of ionizing-radiation-induced gain degradation in lateral, substrate, and vertical PNPs. The dose-rate dependent of current gain degradation in lateral PNP BJTs is even stronger than the dependence previously reported for NPN BJTs. Various mechanisms are presented and their relative significance for gain degradation in the lateral, substrate, and vertical PNPs is discussed. A detailed comparison of the lateral and substrate PNP devices is given. The specific lateral and substrate devices considered here are fabricated in the same process and possess identical emitters. Even though these devices have identical emitters and undergo the same processing steps, themore » lateral devices degrade significantly more than the substrate devices.« less
  • The physical mechanisms for gain degradation in laterals PNP bipolar transistors are examined experimentally and through simulation. The effect of increased surface recombination velocity at the base surface is moderated by positive oxide charge.
  • Ionizing-radiation-induced gain degradation in lateral PNP bipolar junction transistors is due to an increase in base current as a result of recombination at the surface of the device. A qualitative model is presented which identifies the physical mechanism responsible for excess base current. The increase in surface recombination velocity due to interface traps results in an increase in excess base current and the positive oxide charge moderates the increase in excess base current and changes the slope of the current-voltage characteristics. Analytical and empirical models have been developed to quantitatively describe the excess base current response to ionizing radiation. Itmore » is shown that the surface recombination velocity dominates the excess base current response to total dose.« less