G.A. Soli

On-chip p-MOSFET dosimetry (CMOS ICs)

On-chip p-FETs were developed to monitor the radiation dose of n-well CMOS ICs by monitoring threshold voltage shifts due to radiation-induced oxide and interface charge. The design employs closed-geometry FETs and a zero-biased n-well to eliminate leakage currents. The FETs are operated using a constant current chosen to greatly reduce the FETs temperature sensitivity. The dose sensitivity of these p-FETs is about -2.6 mV/krad(Si) and the off-chip instrumentation resolves about 440 rad(Si)/b. When operated with a current at the temperature-independent point, it was discovered that the preirradiation output voltage is about -1.5 V, which depends only on design-independent silicon material parameters. The temperature sensitivity is less than 63 mu V/ degrees C over a 70 degrees C temperature range centered about the temperature-insensitive point. >

Total dose testing of a CMOS charged particle spectrometer

A first-generation CMOS Charged Particle Spectrometer chip was designed at JPL for flight on the STRV-2 spacecraft. These devices will collect electron and proton spectra in low Earth orbit as part of an experiment to demonstrate Active Pixel Sensor (APS) technology in space. This paper presents the results of total dose testing on these chips and, where possible, attempts to extend the results to other Active Pixel Sensors.

Active pixel sensors for mass spectrometry

Abstract Active pixel sensors (APS) are micro-fabricated CMOS amplifier arrays that are rapidly replacing CCD devices in many electronic imaging applications. Unlike the pixels of a CCD device, the sensing elements of the APS will respond to locally situated electrostatic charge, owing to the amplifier present in each pixel. We have built two small test arrays with microscopic aluminum electrodes integrated onto standard APS readout circuitry for the purpose of detecting low-energy gas-phase ions in mass spectrometers and other analytical instruments. The devices exhibit a near-linear dynamic range greater than four orders of magnitude, and a noise level of less than 100 electrons at room temperature. Data are presented for the response of the APS detectors to small ions in a miniature magnetic sector mass spectrometer and in an atmospheric pressure jet of helium. Data for individual highly-charged electrospray droplets are presented as well. Anticipated improvements suggest that in the near future APS ion detectors will posses noise levels approaching 10 electrons and will have a useful dynamic range over six orders of magnitude.

CRRES microelectronic test chip orbital data. II

Data from a MOSFET matrix on two JPL (CIT Jet Propulsion Laboratory) CRRES (Combined Release and Radiation Effects Satellite) chips, each behind different amounts of shielding, are presented. Space damage factors are nearly identical to ground test values for pMOSFETs. The results from neighboring rows of MOSFETs show similar radiation degradation. The SRD (Space Radiation Dosimeter) is used to measure the total dose accumulated by the JPL chips. A parameter extraction algorithm that does not underestimate threshold voltage shifts is used. Temperature effects are removed from the MOSFET data. >

Bench-level characterization of a CMOS standard-cell D-latch using alpha-particle sensitive test circuits

A methodology is described for predicting the SEU susceptibility of a standard-cell D-latch using an alpha-particle sensitive SRAM, SPICE critical charge simulation results, and alpha-particle interaction physics. Measurements were made on a 1.6- mu m n-well CMOS 4-kb test SRAM irradiated with an Am-241 alpha-particle source. A collection depth of 6.09 mu m was determined using these results and TRIM computer code. Using this collection depth and SPICE derived critical charge results on the latch design, an LET threshold of 34 MeV cm/sup 2//mg was predicted. Heavy ion tests were then performed on the latch and an LET threshold of 41 MeV cm/sup 2//mg was determined. >

Proton-sensitive custom SRAM detector

Because of the recently discovered importance of protons to the upset of spaceborne electronics, a custom 4-kB SRAM (static random-access memory) chip was tested with protons. The SRAM was developed to determine the single-event-upset hardness of CMOS latches using alpha particle measurements, by adjusting an offset voltage that reduces the charge required to upset a cell. The authors describe a calibration procedure for the SRAM detector. Source spectra were acquired with this chip by measuring the number of upset cells versus offset voltage. The SPICE assisted calibration utilizing 56 fC/V and the proton data identified a 4.32-pm silicon equivalent overlayer and a 6.64+or-0.31 mu m effective charge collection depth for protons and a 6.33- mu m collection depth for alpha particles. These collection depths can be used to predict the SRAM detector response to proton-produced ionization in space. The SRAM collects all of the charge from silicon recoils produced by Rutherford scattering; this charge is collected from very deep in the SRAM substrate.<<ETX>>

Test SRAMs for characterizing alpha particle tracks in CMOS/bulk memories

Describes a methodology for using alpha particles to provide an independent measure of the cross section of an upset sensitive region in test SRAMs (static random-access memories). In addition, the thickness of over-layers and the alpha-particle collection depth were determined. These parameters are necessary in order to make precise estimates of the upset rates of memories due to cosmic-ray strikes. Measurements were made on 1.6- mu m n-well CMOS 4-kb test SRAMs irradiated with an Am-241 alpha-particle source.<<ETX>>

Clementine RRELAX SRAM particle spectrometer

The Clementine RRELAX radiation monitor chip consists of a p-FET total dose monitor and a 4-Kbit SRAM particle spectrometer. Eight of these chips were included in the RRELAX and used to detect the passage of the Clementine (S/C) and the innerstage adapter (ISA) through the Earths radiation belts and the 21-Feb 1994 solar flare. This is the first space flight for this 1.2-/spl mu/m rad-soft custom CMOS radiation monitor. This paper emphasizes results from the SRAM particle detector which showed that it (a) has a detection range of five orders of magnitude relative to the 21-Feb solar flare, (b) is not affected by electrons, and (c) detected microflares occurring with a 26.5 day period. >

Depth measurements using alpha particles and upsetable SRAMs

A custom designed SRAM was used to measure the thickness of integrated circuit over layers and the epi-layer thickness using alpha particles and a test SRAM. The over layer consists of oxide, nitride, metal and junction regions.

Inverter matrix for the Clementine mission

An inverter matrix test circuit was designed for the Clementine space mission and is built into the RRELAX (Radiation and Reliability Assurance Experiment). The objective is to develop a circuit that will allow the evaluation of the CMOS FETs using a lean data set in the noisy spacecraft environment. As is shown, only nine data points are needed to acquire ten CMOS FET parameters.<<ETX>>