Radiation Hardness Test Chip Matthias Harter, Peter Fischer Uni Mannheim.
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Transcript of Radiation Hardness Test Chip Matthias Harter, Peter Fischer Uni Mannheim.
SchaltungstechnikSimulationund
SchaltungstechnikSimulationund
Radiation Hardness Test Chip
Matthias Harter, Peter Fischer
Uni Mannheim
CBM Meeting Dresden Rad. Hard. TestChip 2LS Schaltungstechnik & Simulation
SchaltungstechnikSimulationund
Overview
1. Reminder: Radiation Damage & Remedies 2. Chip description3. First results
Note: Not yet clear how much rad. hardness we need for CBM... This little work is just a contribution to discussions...
CBM Meeting Dresden Rad. Hard. TestChip 3LS Schaltungstechnik & Simulation
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Radiation Damage – very superficial
Ionizing radiation leads to positive charges in thick oxides Threshold voltage shift – decreasing for NMOS leakage ‘around’ NMOS creation of parasitic NMOS (field oxide)• PMOS remains unaffected.
Large local charge deposition can lead to• SET: single event transient = spike on signal• SEU: single event upset = bit flip• SEGR: single event gate rupture (really?)
CBM Meeting Dresden Rad. Hard. TestChip 4LS Schaltungstechnik & Simulation
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Remedies
Enclosed NMOS (other shapes are possible!) Guard rings between NMOS with drains on
different potential Special FF design / redundancy / voting
/ hamming... for SEU / SET
Consequences:• need special extraction files• larger area (x4 for digital designs)• larger caps -> often more power in digital (x4)• Hard to make good NMOS current source
(large L no possible)• Hard to make good NMOS switches
(very asymmetric & large caps)
CBM Meeting Dresden Rad. Hard. TestChip 5LS Schaltungstechnik & Simulation
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Example: radhard MUX2->1
Our ‘mixed mode’ lib uses separate nets for digital wells (nwell, pwell)
Digital PMOS: vddd!
Digital NMOS:gndd!
PWELL NMOS:gndb!
NWELL PMOS: vddb!
Guard rings
EnclosedNMOS
CBM Meeting Dresden Rad. Hard. TestChip 6LS Schaltungstechnik & Simulation
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Radhard vs. Normal Layout
We want to compare both types.Therefore made cells with equal transistor / layout size:
Hard
Normal
CBM Meeting Dresden Rad. Hard. TestChip 7LS Schaltungstechnik & Simulation
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Test Chip Goals:
• Verify models (speed)• Measure SEU during irradiation• Measure leakage after irradiation for ‘hard’ and ‘non-hard’ layouts• Keep chip very simple for easy testing with minimal equipment
Circuits:• 1 ring oscillator with 101 inverters & enable. Sim. frequency: 176 MHz• 8 normal shift registers, 16 Bit, common data input, one output via 8-1
MUX• 16 linear feedback shift registers (LFSR) producing pseudo random bit
sequences, 16 bit long. Test equality of all 16 LFSRs to detect SEU.• Rad hard output drivers.• All pads have ESD protection diodes
CBM Meeting Dresden Rad. Hard. TestChip 8LS Schaltungstechnik & Simulation
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Radhard vs. Normal Layout
Chip is implemented twice:1. radhard with round NMOS + guard rings
2. Normal Layout. Widths of MOS are same as for round devices
Identical pinout! 17 pins per side (just one side of a JLCC68) Switch between the two versions by rotating carrier in socket!
radhard version(pads at inner side)
normal Version(edge of die)
1 2 3 ... 17
123...17
CBM Meeting Dresden Rad. Hard. TestChip 9LS Schaltungstechnik & Simulation
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Test Chip Layout
could cut here
Another project..
This chip
CBM Meeting Dresden Rad. Hard. TestChip 10
LS Schaltungstechnik & Simulation
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Detail of pinout…D
outS
Rm
ux
Osc
Out
LFSR
eq
DoutL
FSR
<1
>
SR
sel<
0>
SR
sel<
1>
SR
sel<
2>
gndd!
vddd!
vddb!
gndb!
clk
Din
SR
rese
tN
Osc
En
gndd!
gndd!
1.8 V
optionalSRsel<2..0>
selects shift registerto send toDoutSRmux
3
176 MHzOscEn
SRsel<2..0>
16x16x
8x
16x
16x
clk
DinSRresetN 16x16x16x
16x
16x
=?LFSReq
resetNclk
DinSRis the inputof all shiftregisters
LFSReqshows that allLFSRs have sameoutput
1 2 4 14 15
5 6 7 8 9 10 11 17
CBM Meeting Dresden Rad. Hard. TestChip 11
LS Schaltungstechnik & Simulation
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Measurements: Ring Oscillator
Works as expected. Simulated speed:
176MHz Measured:
• Supply [V] Speed [MHz]
• 1.8 150• 1.7 140• 1.6 130• 1.5 117• 1.2 78• 1.0 51
1.8V
1.0V
CBM Meeting Dresden Rad. Hard. TestChip 12
LS Schaltungstechnik & Simulation
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Measurements: LFSR
Works as expected Produces nice spectrum on Analyzer...
after resetoutput
reset
clocked @ 120MHz
CBM Meeting Dresden Rad. Hard. TestChip 13
LS Schaltungstechnik & Simulation
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Problems & Summary
Shift registers also work as expected Problem: Large supply current. May be setup but more likely
wrong type of substrate connection somewhere...
Good agreement in speed. Must check voltage dependence.
Next steps:• Decide if irradiation of this is interesting• May resubmit in 3 weeks if there is a bug. May increase register
length.