2.3 Test results
2.3.3 SEU
Table 17 presents the SEU results for two ACMOS devices (54AC174 and 54AC374) tested with four heavy ions (Ho, Xe, Kr, and Ar).
Figure 9, and Figure 10 below show the SEU Weibull cross section curves for the 54AC174 and 54AC374 devices.
Figure 9. SEU Weibull cross section for the 54AC174 device Table 17. SEU results for two ACMOS devices tested with four heavy ions
Device 54AC174 54AC374
Ion Xe, Kr, Ar, Ho Xe, Kr, Ar
Fluence
(ions/cm2) ≤ 1 x 108 ≤ 1 x 107
LET max.
(MeV-cm2/mg) 71 56
Effective LET max.
(MeV-cm2/mg) 120 112
Saturated cross section 8.70E-07 2.94E-06
Threshold LET 8.5 10.1
Temperature
(°C) 25
Supply voltage VCC = VCC max = 2
Figure 10. SEU Weibull cross section for the 54AC374 device
Table 18 and Table 19 present the worst SEU for the 54AC174 and 54AC374 devices.
Table 18. Worst SEU for the 54AC174 device, S/N = 5
Run Ion LET
102.5 9.99E+06 139 8.70E-07
65 6
83 99.8
1.00E+07 136 8.50E-07
82 70.2 79 4.94E-07
102
Ar 8.5
33.3 2.69E+07 41 8.66E-08
103 28.5 1.94E+07 21 6.77E-08
104 25.8 5.66E+07 3 3.31E-09
101 24.9 1.02E+08 1 6.13E-10
100 21.0 1.09E+08 2 1.15E-09
Table 19. Worst SEU for the 54AC374 device, S/N = 2
Run Ion LET
2 Xe 55.9 111.8 1.00E+07 235 2.94E-06
60 3
1 55.9 5.67E+06 50 1.10E-06
4 Kr 32.4 32.4
1.00E+07 56 7.00E-07
7 Ar 10.1 20.2 7 8.75E-08
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3 Glossary of terms
Cross section: The number of events per unit fluence, expressed in units of cm²/device or cm²/bit. In the event of the device being tilted at an angle θ, the fluence must be corrected by multiplying it by cosine θ.
DUT: Device under test
Effective LET: The equivalent LET obtained by tilting the device under test with respect to the axis beam, hence increasing the path length of the ion and the total energy deposited.
Effective LET = Incident LET x 1/cosine θ where θ is the tilt angle of the device. Effective LET may also be used in referring to the actual LET in a sensitive volume after taking into account the energy loss in “dead layers” such as metalization and passivation.
Energy: The energy imparted to the ion by the accelerator. This may be in units of total energy (MeV) or energy per nucleon (MeV/n).
Fluence: The total amount of particle radiant energy incident on a surface in a given period of time, divided by the area of the dimensions (in cm2/bit). Fluence also includes the flux integrated over time. Units are ions/cm2.
Flux: The number of ions passing through a unit area perpendicular to the beam in one second, expressed in ions/cm²/s.
Ion species: Type of ion being used for irradiation (e.g. oxygen, neon)
Level of interest: A cross section, energy, LET, or fluence having some particular significance for a program or project.
Linear energy transfer (LET): The amount of energy deposited per unit length along the path of the incident ion. It is expressed in units of MeV-cm2/mg which is the energy per unit length divided by the density of the irradiated medium.
Range: The distance traveled, without straggling, in the target material by the specified ion of a given charge state and energy.
Saturated cross section - also known as asymptotic cross section: The cross section for which an increase in LET does not result in an increased number of events.
Serial number (S/N): Unique code and consecutive number assigned to all devices Single event burnout (SEB): Triggering of the parasitic bipolar structure in a power transistor, accompanied by regenerative feedback, avalanche, and high current condition. A SEB is potentially destructive unless suitably protected.
Single event effect (SEE): Any measurable or observable change in the state or performance of a microelectronic device, component, subsystem, or system (digital or analog) resulting from a single energetic particle strike.
Single event functional interrupt (SEFI): A soft error that causes the component to reset, lock-up, or otherwise malfunction. SEFIs typically occur in complex devices with built-in state/control sections like modern memories (SDRAM, DRAM, NOR-and NAND-Flash) and all types of processors, FPGA, or ASICS. Two main types of SEFIs are distinguished depending on the action required to restore functionality: reset by software or by power cycling. The stored data may or may not be lost.
Single event gate rapture or dielectric rupture (SEGR): Destructive rupture of a gate oxide or any dielectric layer by a single ion strike. This leads to gate leakage currents under bias and can be observed in power MOSFETs, linear integrated circuits (with internal capacitors), or as stuck bits in digital devices.
Single event latchup (SEL): A permanent and potentially destructive state of the device under test whereby a parasitic thyristor structure is triggered by an ion strike and creates a low impedance, high current path.
Single event transient (SET): A temporary voltage excursion (voltage spike) at a node in a logic or linear integrated circuit caused by a single energetic particle strike.
Single event upset (SEU) - also known as a soft error: The change of state of a latched logic cell from one to zero or vice-versa. A single event upset is non-destructive and the logic element can be rewritten or reset.
Threshold LET: The lowest LET at which a SEE occurs.
Weibull fit: F(x) = A (1-exp{-[(x-x0)/W]s}), with X = effective LET in MeV-cm2/mg
F(x) = the SEE cross section in cm² A = limiting or plateau cross section
x0 = onset parameter, such that F(x) = 0 for x < x0 W = width parameter
s = a dimensionless exponential
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Appendix A General test setup (UCL)
The test board required the following apparatus (Table 20) and setup (Figure 11) to operate properly.
Figure 11. Test setup Table 20. Test apparatus
Equipment Function Test conditions
MI-03 Power supply VDD1 and VDD2
ME-44, ME-48 Oscilloscope
-ME-53 Guard system VDD1: Gamme 3, Ith = 80 mA
GND VCC VCC1 VCC2 VCC3 VCC4
CLK1CLK1
Appendix B SEL test method (UCL)
For SEL test detection, runs up to a fluence of 1.107 ions/cm² for SEL monitoring only were performed. This configuration allowed the latchup sensitivity of the device to be verified with cocktail number 1 (see Table 5: Ions used in UCL (cocktail number 1)). The test stopped when the maximum fluence was reached or when a hundred events were detected.
Appendix C SEL test principle (UCL)
A power supply was applied to the device under test (DUT) through the guard system. To obtain 6 V on the DUT, a voltage of 6.3 V was applied. The threshold current of the guard system was set to 80 mA. When an event occurred, the guard system sent a trigger command to the oscilloscope. The power supply was held ‘on’ for 1 ms and cut ‘off’ for 7 ms.
It was then restarted with nominal current consumption.
At the end of each run, the test program read the “local scope counter” of the oscilloscope which represented the total event count. The recorded current waveforms were downloaded and stored.
Event description
During the test, the guard system controlled the device’s current. If the value exceeded 80 mA, the delatcher was triggered and the event was counted as a SEL.Figure 12 shows a common SEL characteristic.
Figure 12. Common SEL characteristic
1. Legend: Tm = hold time for 1 ms; Tc = cut off time for 7 ms
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Appendix D SET test method (UCL)
For SET test detection, runs up to a fluence of 1x106 ions/cm² were performed. Latchup monitoring was also performed during these tests. This configuration allowed the SET and the SEL sensitivity of the device to be verified with cocktail number 2 (see Table 6: Ions used in UCL (cocktail number 2)). The test stopped when the maximum fluence was reached or when four hundred events were detected.
Appendix E SET test principle (UCL)
The guard system was used on the power supply of the component to detect SEL and to prevent the destruction of the DUT. An oscilloscope was connected to OUT*(DUT pin 22) and OUT/(DUT pin 23) to perform the SET test. This oscilloscope was configured to monitor pulse width on the output signals. The shape of the OUT* and OUT/ signals are shown in Figure 13.
Figure 13. Shape of OUT* and OUT/ signals
Pulse width modifications of both signals were detected. When such a modification occurred, it was due to SET. The oscilloscope internal counter was then incremented and the trace was stored.
At the end of each run, the test program read the “local scope counter” of the oscilloscope which represented the total event count. The recorded current waveforms were downloaded and stored.
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Appendix F SET block diagram (TAMU)
The DUT was irradiated to a maximum total ion fluence of 1x108 ion/cm². During the course of the test, five different serial numbers of the DUT (101, 102, 103, 104, 105) were irradiated with a minimum effective LET of 33.3 MeV-cm²/mg and a maximum effective LET of 82.9 MeV-cm²/mg. Except for the test where serial number 101 was irradiated to 1E8 ions/cm², the tests used a maximum fluence of 1E7 ions/cm². At TAMU, the lids were removed from the DUT to give full exposure to the top surface of the die using the 15 MeV/n beam.
The output was monitored with both a data acquisition system to allow transients from all six outputs (1Y, 2Y, 3Y, 4Y, 5Y and 6Y) to be captured, and a pair of high-resolution
oscilloscopes to capture detailed images of the transient behavior on a sub-set of the transients. Output 1Y was monitored with the oscilloscope to capture both positive and negative going transients. The actual trigger setting was recorded in the run logs. The data acquisition system and the oscilloscopes were located in the control room while the power supplies, meters, and switch matrix were located in the exposure room. The outputs were brought to the control room using shielded SMA and BNC cables.
Figure 14. SET block diagram (TAMU)
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Appendix G SEU test method (TAMU)
The devices under test were irradiated to a maximum total ion fluence of 1x108 ions/cm² at a maximum effective LET of 120 MeV-cm²/mg using the worst-case voltage (3 V) and temperature (25 °C). The lids were removed from the devices prior to testing to give full exposure to the top surface of the die.
To achieve an effective linear energy transfer (LET) of 120 MeV-cm²/mg the devices were irradiated with Ho at an angle of approximately 54 degrees. The effective LET is the normal LET divided by the cosine of the angle of irradiation. The use of effective LET is accepted in test standards. The Ho range to the Bragg peak using a 15 MeV/n beam is 112 μm.
A variety of LETs and angles were used to obtain LET values from 8.5 to 120 MeV-cm²/mg.
Prior to and immediately following the heavy ion exposure, the devices underwent a “health check”. This test verified that the device met the datasheet specifications and did not suffer any degradation that would confound the SEU data.
The test platform also monitored for clear errors (all bits were set to “0”) and clock errors (all bits switched states simultaneously). Note that the inputs were held in the opposite state from the outputs so that if a clock transient occurred, all bits would flip simultaneously.
of SEL runs 70 to 75 for the 54AC14 device
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Appendix H Summary of SEL runs 70 to 75 for the 54AC14 device