From: EEE Links, July 1996
HITACHI EEPROMS
by Dr. Kusum Sahu
Radiation Effects and Testing Group
Goddard Space Flight Center
301-731-8954
kusum.sahu.1@gsfc.nasa.govHigh-density EEPROMs are being increasingly needed by NASA spaceflight projects. Previously, a number of NASA projects were using the 28C256 EEPROM, manufactured by Seeq. Total dose radiation testing of this part showed that failures could be expected in the range of 2.5 - 20 krads(Si). This part, however, has recently become unavailable, due to the manufacturer going out of business.
A 128K x 8 EEPROM has recently become available from Hitachi (Hitachi part number HN58C1001).The part can be purchased as a packaged part (32-pin plastic DIP and 32 lead Plastic SOP and TSOP packages) as well as in die form from Hitachi. Two packaging houses, Space Electronics Inc. (SEI) and Austin Semiconductor have packaged the die from Hitachi in their proprietary "Radiation Hard packages" . GSFC has performed total dose radiation characterization tests on these parts (SEI part number 28C010 and Austin part number AS58C1001). The radiation testing was performed using a Co-60 gamma-ray source. It should be noted that since gamma rays very effectively penetrate any parts package unlike the electrons and protons in the space environment , the test results presented below provide the radiation characteristics of the Hitachi die and not the shielding effectiveness of the radiation hard packaging by either SEI or Austin Semiconductor.
The dose rate during gamma ray testing was approximately 100 rads(Si)/hour. The radiation steps were 2.5, 5, 10, 15, 20, 25, 30, 50, 75 and 100 krads(Si). After the 100 krads(Si) exposure, parts were annealed for 384 hours at 25 °C , after which the parts were annealed for 168 hours at 100 °C. Initially and after each irradiation and annealing step, parts were tested according to the manufacturer’s specifications. The parts were kept under static bias during irradiation and annealing.
Electrical parametric tests included power supply current, leakage current and output level, as well as AC timing measurements. The electrical measurements included nine initial (pre-rad) functional tests at 1.0 MHz: These functional tests were WRITE/READ ZEROES, WRITE/READ ONES and WRITE/READ CHECKERBOARD with Vcc = 4.75 V, Vil = 0.0 V and Vih = 4.75 V, the same three tests with Vcc = 5.00 V, Vil = 0.0 V and Vih = 5.00 V, and the same three tests with Vcc = 5.25 V, Vil = 0.0 V and Vih = 5.25 V. After the first (2.5 krad) irradiation, three additional functional tests were added. These were READ CHECKERBOARD tests, for the purpose of determining if the checkerboard pattern read into the parts before irradiation could still be read after irradiation. These
tests were performed with Vcc = 4.75 V, Vil = 0.0 V and Vih = 4.75 V, with Vcc = 5.00 V, Vil = 0.0 V and Vih = 5.00 V and with Vcc = 5.25 V, Vil = 0.0 V and Vih = 5.25 V.All irradiated parts ( four from SEI and three from Austin ) passed all functional and electrical parametric tests up to and including the 50 krad(Si) level.
The SEI parts passed functional tests up to 100 krads(Si), however, the Austin parts failed functionally at 75 and 100 krads(Si). After annealing for 384 hours at 25°C, two of the three Austin parts passed all functional tests, while one part continued to fail functionally.
Both Austin and SEI parts passed all parametric tests up to 20 krads(Si) and were within the specification limits provided by the manufacturers. However, at 30 krads(Si) and above, some degradation in both ICC and IIL was observed in the Austin parts, while the SEI parts showed degradation only in IIL. The ICC readings for the SEI parts ranged from about 22 to 30 mA, against a specification limit of 20 mA. The IIL readings for both SEI and Austin parts ranged from 8 to 50 mA at the 100 krads(Si) level, against a specification limit of 2 mA.
On annealing the parts at 25°C up to 384 hours, some recovery was observed for both parameters. No rebound effects were observed on annealing the parts for 240 hours at 100°C.
Details of the radiation test data can be obtained by calling the GSFC Office of Mission Assurance Information Center, John Bollman, 301-286-7240 and citing the report numbers, PPM-95-182 and PPM-96-003 for the SEI and Austin parts, respectively.
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