We present Single Event Effect (SEE) and Total Ionizing Dose (TID) data for 1 Gbit DDR SDRAMs (90 nm CMOS technology) as well as comparing this data with earlier technology nodes from the same manufacturer

Berg, M. D.

Crain, S.

Friendlich, M.

George, J.

Gorelick, Jerry L.

Kim, H.

Koga, R.

LaBel, K.

Ladbury, Raymond L.

Reed, R. A.

Yu, P.

NASA Technical Reports Server

IEEE NSREC 2006 PI-1 - To be presented by R. Ladbury, Ponte Vedra Beach, Florida, July 17-21,2006. 
Radiation Performance of 1 Gbit DDR 
SDRAMs Fabricated in the 90 nm CMOS 
Technology Node 
R. Ladbury, Member, IEEE, M. D Berg, Member, IEEE, H. Kim, Member, IEEE, K. LaBel, Member, 
IEEE, M. Friendlich, Member, IEEE, R. Koga, Member, IEEE, J. George, Member, IEEE, S. Crain, 
Member, IEEE, P. Yu, Member, IEEE, R. A. Reed, Member, IEEE 
Abstract- We present Single Event Effect (SEE) and Total 
Ionizing Dose (TID) data for 1 Gbit DDR SDRAMs (90 nm 
CMOS technology) as well as comparing this data with earlier 
technology nodes from the same manufacturer. 
Index Terms-radiation effects, reliability estimation, statistics, 
quality assurance, probability. 
I. INTRODUCTION 
Synchronous Dynamic Random Access Memories 
(SDRAMs) are both a cutting edge CMOS technology and a 
enabling technology for space flight. As such, radiation test 
results are of interest to both technologists and designers. 
Single event latchup (SEL) response is a major concern, since 
it has made recent commercial memory generations difficult 
and expensive to qualify. This is because even for parts that 
remain functional after SEL, reliability may be compromised 
by latent damage.[l] Despite such challenges and others 
relating to obsolescence and supply, lot-to-lot variability, and 
qualification expense, the advantages conferred by DRAMS 
over other memory solutions usually dictate their use for mass 
storage applications. In this poster, we present data on the 
Single-Event Effects (SEE) and Total Ionizing Dose (TID) 
susceptibility of Samsung 1 Gbit Double Data Rate (DDR) 
SDRAMs (K4HlG0438).[2] 
Devices Tested: Sarnsung K4HlG0438 
256M x 4 configuration 
66-pin Thin Shrink Small Outline Package (TSSOP) 
Internal speeds up to 266 MHz 
Vdd: 2.5 V 
Die Revisions (Revs): 
NASA GSFC: Rev A (90 nm CMOS) 
The Aerospace Corporation: Rev M (100 nm CMOS) 
Test Systems: 
Manuscript received July 8, 2006. This work was supported in part the 
NASA James Webb Space Telescope (JWST) Program and the NEPP 
Electronic Radiation Characterization (ERC) Project. 
R. Ladbury is with Muniz Engineering, Inc (MEI), Greenbelt, MD 20771, 
USA (phone: 301-286-1030; fax: 301-286-4699; e-mail: 
Rayrnond.L.Ladbury. 1 @gsfc.nasa.gov). 
J. L. Gorelick is with Boeing Space and Intelligent Systems (BSIS), Los 
Angeles, CA USA, (jeny.l.gorelick@boeing.com ). 
NASA GSFC's Low-Cost Digital Tester (LCDT) and Aerospace's 
test system have been described previously.[3,4] 
Test Facilities - Heavy Ion 
NASA GSFC performed tests at: 
SEE Test Facility (SEETF) at Michigan State 
University (high Linear Energy Transfer-LET) .[5] 
-Texas A&M University Cyclotron Center (TAMU - 
The 40 MeVIamu tune was used to ensure penetration 
to the sensitive volume from the front-side for low 
LET ions.) 
The Aerospace Corporation used the Lawrence Berkeley 
National Laboratory's (LBNL) 88-inch Cyclotron. 
TABLE I: EFFECTIVE LET OF TEST 
IONS 
Test Facilities - Proton 
The Aerospace Corporation used LBNL as well as the 
Indiana University Cyclotron Facility (IUCF). Proton energies 
at LBNL were 20, 30 and 50 Mev, while those at NCF were 
98 and 200 MeV. All proton testing was done at normal 
incidence.H~~vy-ION SEE TESTING 
NASA GSFC 
Initial SEE testing was carried out at the SEETF on 
packaged devices. Due to temporal and economical 
constraints, testing was conducted with a single ion incident at 
0°, 45", and 60" to the DUT normal to give 3 effective LETS. 
https://ntrs.nasa.gov/search.jsp?R=20080039559 2019-08-30T05:24:51+00:00Z
IEEE NSREC 2006 PI- 1 - To be presented by R. Ladbury, Ponte Vedra Beach, Florida, July 17-2 1,2006. 2 
be determined unambiguously, only data for normal incidence 
ions are reported here. LET for the tests at TAMU was 
estimated using the same method as was used for the SEETF. 
The Aerospace Corporation 
Heavy-ion testing at the LBNL facility used a 10 MeVIamu 
tune, so the the DUTs be thinned to a thickness of 3 mils 
(about 120 pm) and mounted face down so they could be 
irradiated from the backside. All ions were incident normal to 
the device. 
Test Methods 
Similar testing methods were used by both NASA GSFC 
and The Aerospace Corporation. The test flow was as follows: 
Write DUT with a fixed test pattern 
Read back test pattern and verify. 
Begin Irradiation and read DUTs repeatedly 
If a reading differs from the programmed pattern, 
tally a single-event upset (SEU). Aerospace 
corrected the error before continuing reading, 
while GSFC did not. 
If a large number of errors occur simultaneously, 
and errors continue after the beam was stopped, we 
stop the run and tally a single-event functional 
interrupt (SEFI). If errors do not continue with no 
beam, the large error is tallied as a burst, block or 
colurnn erorr. 
A SEFI causing a significant power supply current 
jump and not recovering after stopping the beam 
and refreshing device mode registers was called an 
SEL. 
Because of the complexity of SEE data for SDRAMs, the 
addresses, values and times of all errors were recorded for post 
processing to extract multi-bit upsets, different SEFI modes, 
stuck bits, etc. The Aerospace Corporation conducted all 
irradiations at room temperature. GSFC looked for SEL 
susceptibility at both ambient temperature and at 85 "C. 
Internal DUT frequencies were 100 MHz. 
The Aerospace Corporation performed proton tests at 
LBNL and IUCF with a primary emphasis on SEE (similar 
method to heavy ion testing). TID data was taken noting only 
functional performance and supply current variances. No 
additional parametric measurements were made during testing. 
Fig. 1. X-Ray Photo of the DUT. Determining effective LET 
as a function of angle requires correcting for the energy lost by 
the ion as it traverses overburden to the sensitive volume, as 
well the usual llcosq dependence. 
111. DATA ANALYSIS 
In terms of error types and complexity, an SDRAM is more 
like a rnicrocontroller with a large memory array than a simple 
memory array. Effects of SEFIs are particularly important for 
most space applications.[4,7] 
The two organizations independently performed data 
analysis. Though similar methodologies were utilized, SEFI 
defmition and data parsing may have been differed. 
Additionally, the fact that there were two die revisions tested 
may skew results. No attempt was made to coordinate the 
analyses. 
GSFC SEE Data Analysis 
During postprocessing, based on the time stamps, addresses 
and memory contents, data were classified into: 
Single-bit Upsets (SBUs) 
Multi-bit upsets (MBUs) 
Burst errors (temporary strings of errors - self- 
recovering) 
Burst errors (persistent - non-recovering) classified 
as SEFI 
Address errors (multiple errors in same row, block, 
or column) 
SEL 
Because statistics for the burst error modes and address 
errors was limited, and because they often have comparable 
operational consequences, these three modes are combined and 
reported here as "SEFI" in the results section. Because it can 
be difficult to determine all the effects of such large errors, 
SBUs and MBUs were determined using only the portion of 
each run before such a "SEFI" was observed. 
The Aerospace Corporation Data Analysis 
The Aerospace Heavy ion and proton data were analyzed in 
a manner similar to GSFC's. Based on the totals for each error 
type and the fluence accumulated up to the occurrence of the 
first SEFI or other large error, average cross sections were 
calculated for all the runs at each effective LET value. 
Aerospace observed no multi-bit errors and only one run at the 
highest LET showed a SEFI. Aerospace did additional work to 
characterize SEFI consequences beyond having bursts of 
IEEE NSREC 2006 PI-1 - To be presented by R. Ladbury, Ponte Vedra Beach, Florida, July 17-2 1,2006. 3 
errors and what actions were necessary to correct the error 
condition. 
TID data concerned only functionality and consisted of 
observing that parts remained functional with no gross changes 
in error rates at the highest test operating speed as dose 
accumulated during proton testing. 
IV. HEAVY-ION AND PROTON SEE RESULTS 
GSFC Results - SEL at NSCL SEETF 
SEL was observed only at the highest LET tested (108 
Me~*cm2/m~)  and at elevated temperature (85 OC). Figure 3 
shows the measured SEL cross section and the upper limit for 
the cross section at the next highest LET tested (47 Mev*cm2 
Img). Although we cannot definitely rule out the possibility of 
SEL between these two LET values, the low SEL cross section 
at 108 Mev*cm2 lmg suggests that the threshold is probably 
closer to this value rather than the lower limit of the range. 
1 W5 
1 0" 
0 40 80 120 
Effective LET (MeV*cm2/mg) 
Fig. 2. 3 SEL cross section and upper limits thereof as a function of 
effective LET. 
GSFC SEE Results 
Figure 4 shows cross sections for SBU, MBU and SEFIs 
(determined in post processing) as a function of effective LET. 
It is interesting to note that the MBU cross section (for >1 bit 
upset) is nearly a constant proportion of the SEU cross section 
over the high-LET range carried out at the MSU SEETF. Both 
the SEU and MBU cross section continue to increase up to the 
highest effective LET tested, while the SEFI cross section 
appears to saturate over this range. MBUs and "SEFIs" were 
only observed in the SEETF data (LET> 27 Me~cm21m~).  
Aerospace Results 
Figure 5 shows The Aerospace Corporation heavy-ion SEU 
data from LBNL. The bit-error cross section is approximately 
20x higher than the cross section for single-bit errors for the 
GSFC data on the rev. A die.. No MBUs were noted in this 
data. Seven SEFIs were recorded-but only at the highest LET 
tested (59.9 ~evcrn21rn~) yielding an average cross section of 
4.75'10-6 cm2 per device. At least two "SEFI" modes were 
observed. One mode would be better characterized as a burst 
error, in which a large number of errors are seen, but recovery 
can be achieved by simply rewriting the data into the memory. 
The other mode is properly a SEFI, as power cycling was 
necessary to recover normal device functionality. 
No SEL was seen at room temperature. The upper bound of 
the 95% confidence level (CL) for SEL cross section is 10-6 
cm2. 
Effective LET (MeVwm2/mg) 
Fig. 3. SEU, MBU and SEFI cross sections as a function of effective 
LET for GSFC data (statistical error bars shown if they are not 
negligible). 
A 
10. 1 + v 
0 10 20 30 40 50 60 70 
LET (MeV.cm2/mg) 
Fig. 4 Cross section vs. LET for heavy ions from data taken by the 
Aerospace Corporation. 
Multiple potential explanations exist on the differences 
between the GSFC and The Aerospace Corporation's results. 
They include: 
Different die revisions (A versus M) 
Different test ion energylparticle ranges (NSCL 
SEETF and TAMU versus LBNL) 
Thinned die versus unmodified 
Angular effects versus normal incidence 
Figure 6 shows The Aerospace Corporation's proton SEU 
data for both the 1 Gbit DDR and the preceding generation 
512 Mbit DDR from the same vendor. As expected due to 
geometric cell size issues, the per bit cross sections for the 1 
Gbit device are somewhat lower than for the 512 Mbit DDR. 
All errors observed were isolated single-bit errors-which is 
not unexpected since all runs were performed with the proton 
beam incident normal to the device. 
IEEE NSREC 2006 PI-1 - To be presented by R. Ladbury, Ponte Vedra Beach, Florida, July 17-21,2006. 4 
3 
W 
UY 4 A 1 Gbit DDR I 
1 0"O I I I I 
1 0" SEE testing, high-energy ions (e.g. at MSU's SEETF and at 
Proton Energy (MeV) 
TAMU) can be used to obtain a thorough characterization of 
the device. In carrying out such a strategy, it is helpful to 
capitalize on the greater LET selectability at T N ,  making 
use of the SEETF primarily for high-LET ions that cannot be 
delivered by lower energy facilities. It is also helpful to have a 
detailed understanding of the overburden the beam must 
penetrate above the sensitive volume. 
- 3 
u N' 
10.8 - 
- 
C 
ti 
UY 
V) 
lvg 
0 
TABLE 111: SEL ONSET LETS SDRAM GENERATIONS. 
Fig. 5. SEU cross section vs proton energy. Statistical error bars are 
shown if they are not negligible.TID DEGRADATION 
TID degradation is generally thought to improve as CMOS 
feature sue shrinks. However, the very stringent requirements 
on leakage currents in DRAM access FETs make this more 
uncertain for DRAMS. While detailed studies of TID induced 
parametric degradation remain to be done, the parts tested with 
protons by Aerospace functioned with no apparent degradation 
to > 100 krads(Si). 
A 
. .. . .. .. ... . . . .. .. .' -- -- --- 
A 
VI. FUTURE WORK 
While the test results to date are encouraging for use of 
these memories in space missions, several hurdles remain to be 
traversed. Full parametric TID testing is scheduled to be 
performed once additional test parts are received in August. 
Proton testing over angles is also anticipated to better 
characterize susceptibility to multi-bit SEU and other proton- 
induced effects. We also plan to extend our study of volatile 
memory devices as parts from other vendors and new 
generations of technology become available. 
Reference Part # 
and Size 
VII. DISCUSSION 
Data for the current 1 Gbit 90 nrn feature size DDR 
SDRAMs demonstrate that reduced feature sue does not 
necessarily correlate to worse radiation performance. SEU 
cross sections on a per bit basis are lower than those of the 
previous 512 Mbit devices. SEL performance of the 1 Gbit 
devices is significantly better than for previous generations 
(see Table 11), and SEU, MBU and SEFI rates remain 
manageable with mitigation techniques used with previous 
generations (error correction codes, error scrubbing, creative 
memory organization and so on.). For example, a conservative 
fit to the GSFC datas yields rates for Geostationary orbit of 
10-11-10-10 upsets per bit per day for the revision A die, 
while the Aerospace data yield a rate roughly 10 times higher 
for the revision M die. SEFIs and other block errors can be 
expected to occur at a rate of roughly 10-4 per device-day. 
Multibit upsets could occur at a rate of once in 10-100 days. 
Protons should not cause either SEFIs or MBUs. 
The current work also demonstrates that even if a device is 
not amenable to repackaging or other package modification for 
SEL LETth 
MeV%rn2/rng 
VIII. CONCLUSION 
64 Mbit 
128 Mbit 
256 Mbit 
512 Mbit 
1 Gbit 
The radiation performance (SEE and TID) of the Samsung 
1-Gbit DDR SDRAMS makes them excellent candidates for 
space flight applications. SEL susceptibility is low, especially 
at low temperatures. SEFI susceptibility appears to be 
comparable to that of previous generations. MBUs were seen 
at high LET in SEE testing of the rev. A version of the die, but 
not the rev. M version. The Rev. M version also yielded a 
higher per bit cross section than the rev. A die. Finally, we 
note that in the past SDRAMs have shown lot-to-lot variation 
in TID and SEE susceptibility. Additional testing is strongly 
advised to ensure adequate radiation performance in future 
appli~ati0ns.R~~EREN~ES 
[I] R. Pease, "Microelechonic Piece Part Radiation Hardness Assurance for 
Space Systems", 2004 NSREC Short Course. 
[2] MIL-HDBK-814, "Ionizing Dose and Neutron Hardness Assurance 
Guidelines for Microcircuits and Semiconductor Devices." 
[3] A. Johnston and C. Lancaster, "A Total Dose Homogeneity Study of the 
108A Operational Amplifier," IEEE Trans. Nucl. Sci., NS-26, No. 6, Dec. 
1979. 
[4] J. Krieg et al., "Hardness assurance implications of bimodal total dose 
response in a bipolar linear 
[5] M. Shaneyfelt et al., "Impact of passivation layers on enhanced lowdose- 
rate sensitivity and pre-irradiation elevated-temperature stress effects in 
bipolar linear ICs," IEEE Trans. Nucl Sci., 49, No. 6, Dec. 2002. 
[6] A. Namenson, "Lot Uniformity and Small Sample Sizes in Hardness 
Assurance", IEEE Trans. Nucl. Sci. 35, No. 6, Dec. 1988. 
[7] Resources for distributions, likelihood methods and inference include 
NISTISEMATECH e-Handbook of Statistical Methods, 
www.itl.nist.govldiv898/handbooW, 2005, mathworld.wolfram.com, 
www.Weibull.com, and www.resacorp.com 
Not observed 
4 . 4 ~  LETth <I5 
28c LETth c35  
30< LETth c47.6 
46.5< LETth 4 0 7 . 6  (85'C) 
8 
8 
8 
9 
This Work 


Radiation Performance of 1 Gbit DDR SDRAMs Fabricated in the 90 nm CMOS Technology Node

Radiation Performance of 1 Gbit DDR SDRAMs Fabricated in the 90 nm CMOS Technology Node

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