宇宙機用LSIの動作を阻害する放射線パルスノイズの解明とモデル化

JAXA宇宙科学研究所
小林大輔

財団法人 宇宙科学振興会平成２３年度宇宙科学奨励賞受賞記念講演 2012年3月6日

宇宙は過酷な放射線環境
A.H. -Siedle & L. Adams, “Hand book of radiation effects”, Oxford, 2001などを元に作成

銀河宇宙線

超新星爆発

87%陽子，1%重イオン
10GeV以下10個/cm2•s

放射線帯外帯

太陽99%電子
10MeV以下
1E6個/cm2•s
磁力線
地球

放射線帯内帯太陽高エネルギー粒子
96%陽子, 1GeV以下, 1E5個/cm2•s

99%陽子
数百MeV以下
1E5個/cm2•s2

宇宙に行くには放射線対策が必要

はやぶさ（スイングバイ）©池下章裕，JAXAデジタルアーカイブス3䊥䊮
宇宙機の頭脳「LSI」

ታ䉼䉾䊒䈱േ૞⏕⹺ 0..5/.00⚊ຠ䊌䉾䉬䊷䉳ᷣ䉂䈱?QGA䉼䉾䊒䈏⚊ຠ䈘䉏䈢䋮
?QGA䉼䉾䊒਄䈮ታⵝ䈚䈢䊥䊮䉫䉥䉲䊧䊷䉺䈏⊒ᝄ䈜䉎䈎䈬䈉䈎䉕⏕⹺䈚䈢䋮䊥䊮䉫䉥䉲䊧䊷䉺䈱೙ᓮ䊏䊮䈫㔚Ḯ䊶ELB䊏䊮䈱䉂䉕ធ⛯䈚䈩⏕⹺䉕ⴕ䈦䈢䋮••⚿ᨐ䋬ᱜᏱ䈮䊥䊮䉫䉥䉲䊧䊷േ૞ਛ䋬ᶖ⾌㔚ᵹ&/.k?એ
䊥䊮䉫Ბᢙ䋺䊋䉾䊐䉜800Ბ

4.00626MHz
提供柳川博士

電気信号の形で情報を処理
4

LSI: Large Scale Integration
LSI

トランジスタ〜1cm角~100nm

柳川博士提供

柴田直先生「半導体デバイス入門」昭晃堂

微細なスイッチ「トランジスタ」の集積体スイッチが高速にON/OFFして電気の流れを制御する
5

moothed waveform is superimposed onto the actual data in Fig. 3. For
nsient current waveforms were extracted from each charge distributions
1.8 V drain bias. The DSET pulse-width increases with the collectedbricated with Partially Depleted SOI process [15], thus we have assumedrom current pulses with the greatest collect charge is the worst-case0

放射線に弱い

放射線1発がスイッチに当たる
牧野博士 RASEDA 2010

0.6

Signal Observed

Current (mA)

0.5

Smoothed Waveform

0.4
0.3
0.2
0.1
0250

-0.1
-0.5

00.5

1.0
1.5
Time (ns)

2.0

2.5

3.0

制御されていない電気信号「ノイズパルス」が発生
ed charge
Fig. 3 The worst waveform of transient currents inV.

the case that the drain biased to 1.8 V. An example
誤動作を起こすof a smoothed line is superimposed.

6なぜ電気ノイズが発生するのか
放射線例α線 = 正の電気を帯びているクーロン力で自由に動けるノイズ電子

剥ぎ取る安西育郎先生「放射線と放射能」ナツメ社を元に作成発生するノイズ電子の量QDEPが重要
この量は放射線強度のパラメータLETで推定できる

7

urrent from Fig. 2. The extracted waveform shows a typicalf a fast rise time and an exponential decay tail. The charge
eform is superimposed onto the actual data in Fig. 3. Fort waveforms were extracted from each charge distributions
bias. The DSET pulse-width increases with the collected
Partially Depleted SOI process [15], thus we have assumed
pulses with theスイッチ素子1つ
greatest collect charge is the worst-case

対策にはパルスノイズの解明が必要

Signal Observed

Current (mA)

0.5PSmoothed Waveform

I0.4

≠

0.2
0.1
000.5

1.01.5Time (ns)

2.0

2.5

VPPN

0.3

-0.1
-0.5

NOR

牧野博士 RASEDA 2010

0.6

回路

PNtN

N
N

3.0Fig. 3 The worst waveform of transient currents inthe case that the drain biased to 1.8 V. An example
of a smoothed line is superimposed.

スイッチのノイズではなくて回路のノイズが必要
8

この研究の成果

回路における放射線ノイズパルスを解明しモデル化

1．測定法
2．推定法
3．理論

9

既存の測定方法
3576

IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 53, NO. 6, DECEMBER 2006

Yanagawa et al., IEEE TNS 53(6) 2006 p3575

Radiation SET

SNAPSHOT(Time-to-digital converter)
input
digitize & record

12 NOR gates

111100011111

read &decodeFig. 1. Overall test circuit for SET-pulse width measurement. SET pulse originated in a chain of cells under test propagates through the chain. The SET pulse is”.
then captured in Snapshot circuits. SET pulse is obtained as a bit sequence like “

Number ofobservations

40 Decoding
chain andradiation-hardened D-type FFs (D-FFs). Each30 60 accuracy
isnot guareven-numbered inverter’s
output was fed into the next stage
20
anteed.
inverter and one
D-FF, as shown in the figure. The clock portsof D-FFs
10were all connected to the output of the 110th inverter(node X in Fig. 1). All D-FFs were triggered simultaneously
when the0leading edge (positive edge) of the SET pulse arrived
0.2 D-FFs
0.4stored0.6
at node X, 0and thereby,
the SET0.8
pulse as1.0
a bit 1.2,” where (ns)the string of ‘1’
sequence like “SET widthFig. 2. Calibration circuits using built-in pulse generator. Circuit configuration

0.2μm FDSOI NOR
256 MeV Ni

corresponded to the SET pulse. We extended the FF chain
beyond the node X (right side of the node X) to capture the SET
pulse correctly, because the SET pulse might propagate beyond
the node X due to a delay time for triggering the D-FFs.
can be calculated by
The SET-pulse width

I was used to calibrate Snapshot circuits, and configuration II was used to confirm that SET-pulse width did not vary depending on the length of the cell chain.

自動測定回路を設計．幅を観測できる．
(1)

I was used to determine the values of T and , by inputtingreference pulses coming from the pulse generator circuit. In configuration II, a 6-cell or 12-cell NOR chain was inserted between
the pulse generator and the Snapshot circuit. This configuration

10

:LGWK QV:LGWK QV

観測値（最頻値）

既存技術の成果：幅と放射線強度の関係
1.00.8
1.0
0.6
0.8
0.4
0.6
0.2
0.4
0.0
0.2 00.000

牧野博士提供0.2μm FDSOI NOT

20406020H9FP PJ80

1000.2200.40.60.8
1.04060801002(pCѥPPJ0H9FPLinear Energy Transfer: LET

少00.2
0.4
0.6
0.8
1.0 多(pCѥP
FDSOI技術の場合発生ノイズ電荷量
QDEP = LET × tSOI
Linear Energy Transfer: LET

幅以外はどうなんだろう？
11

成果1：全波形観測法
Kobayashi et al., IEEE TNS 55(6) 2008 p2872

チップ

オシロスコープVO

バイアスティTime

IDp

Radiation
IDp
IDnTime

IDnTime12

結果

OBAYASHI et al.: WAVEFORM OBSERVATION OF DSETS EMPLOYING MONITORING TRANSISTOR TECHNIQUE

放射線をpsレーザで代用
パルス成長の様子の実測に成功
パルスが底を打つ様子や急峻な電圧低下とゆっくりとした回復などの特徴を確認（デバイスシミュレーションでの予想と一致）

g. 10. DSET waveforms obtained when the target inverter was irradiated withrious laser PEs.

ereinafter, for simplicity, we would like to explain them taking
n -type MT for example.

131．測定法
簡単な回路で波形を明らかにできる
しかし，他の回路ではどうなるか予想できない

2．推定法

14

FD-SOI NMOS

Krypton .

既存の推定方法

3. Experimental Results

Fig. 2 shows a histogram of a collected charge distribution with the drain biased to 1.8 V. The collectedcharges were computed by integrating the current signals. These results are reasonable, since the struck locationsof ions are completely random during the irradiation, and transient current response varies depending on thelocation of ion strikes in the transistor (such as gate hit or drain hit [14]). In here, to estimate the DSET
pulse-width by the table-based estimation, we have to obtain the current waveform with same ion strike
condition like the ion strike location for each bias condition. Thus, we extracted waveforms from the collectedcharge distribution with the greatest collect charge as typical waveforms in each drain bias condition.
Fig. 3 shows an extracted waveform of transient current from Fig. 2. The extracted waveform shows a typical
ion-induced drain current waveform, i.e., consisting of a fast rise time and an exponential decay tail. The chargeof the extracted waveform is 230 fC. Smoothed waveform is superimposed onto the actual data in Fig. 3. For
every drain bias condition, smoothed transient current waveforms were extracted from each charge distributionsin the same manner as the case of the 1.8 V drain bias. The DSET pulse-width increases with the collectedcharge in theNOR
case of the inverter cell fabricated with Partially Depleted SOI process [15], thus we have assumed
that the DSET pulse-width obtained from current pulses with the greatest collect charge is the worst-casescenarios.
スイッチ素子1つで発生したノイズ
P

デバイスシミュレーション→計算量が膨大回路で発生するノイズ（これを知りたい）

PPCounts1510N0050

Signal Observed

0.5PtNN

50.6

V

Current (mA)

20

N

100
150
200
Corrected Charge (fC)

固定V

Smoothed Waveform

0.4
0.3

I0.2

N

0.1
0250

-0.1
-0.5

00.5

1.0
1.5
Time (ns)

2.0

2.5

3.0

スイッチ素子1つ
Fig. 2 An example of a collected charge
distribution with the drain biased at 1.8 V.

Fig. 3 The worst waveform of transient currents inthe case that the drain biased to 1.8 V. An example
of a smoothed line is superimposed.

異常波形を出力することがあった
15

1040

Fig. 5. Simulation results for the single nMOSFET under 40-MeV
成果2：テーブル参照法による推定
vs.
curves for estimation from 0 to 9 ps. (c) From 10 ps to 1 ns. We
Kobayashi et al., IEEE TNS 54(4) 2007 p1037

IEEE TRANSACTIONS ON NUCLE

電圧を変えた応答

各時刻での電流・電圧を表にして保存
読みとりながら回路方程式を解く

16
Fig. 5. Simulation results for the single nMOSFET under 40-MeV/mg heavy ion impact. (a)vs. charactevs.
curves for estimation from 0 to 9 ps. (c) From 10 ps to 1 ns. We plottedvs.
curves in these two figures

Inverter's Output Voltage: VO (V)結果
Laser PE: 82 pJ

2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0
Time: t (ns)線：推定点：実測

172．推定法
単体スイッチの応答があれば回路の応答を推定できる

放射線衝突の結果であって原因でない原因である放射線とパルスの関係を答えるには？

3．理論
18

理論：物理モデル（FDSOI想定）

Fig. 5. Simulation results for the single nMOSFET under 40-MeV/mg heavy ion impact. (a)vs. characteristics under various
vs.
curves for estimation from 0 to 9 ps. (c) From 10 ps to 1 ns. We plottedvs.
curves in these two figures merely to show theInverter's Output Voltage: VO (V)3376

IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 53, NO. 6, DECEMBER 2006

Laser PE: 82 pJ

2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0
Time: t (ns)Fig. 7. [2-D simulation results] Time evolution of the stored charges on thepC/ m. These gate charges aregate electrode in the case thatcounter-charges to the holes biasing the body region positively via gate-bodycapacitance.

irradiation.
was obtained by reading out the amount of thecounter-charges on the gate electrode at 7.4 ps from Fig. 7. We
conclude that our theoretical descriptions for the discharge components are acceptable.
B. 3-D Device Verification (3-D Simulation Results)

底を打ってゆっくり回復

t = τ0 ln∗

各要素のバランスで決まる

�From the 2-D simulation study, we revealed that theheavy-ion-induced transient currents in the FD-SOI MOSFETs have three current components: (1) prompt current (1stdischarge component), (2) parasitic bipolar current, and (3)stored-carrier discharge current (2nd discharge component).
Because the ion track model is not realistic in the 2-D simulations, however, our findings in the 2-D study must be examinedin 3-D devices.
Fig. 8 shows the 3-D simulation results, and clearly demonstrates that the heavy-ion-induced transient current has three
is dicomponents as we revealed in the 2-D study.
vided into two parts and the 2nd part is identical to the holecurrent.
We would like to discuss here the avalanche generation effects in these 3-D simulations because the drift-diffusion model
generally overestimates the avalanche generation rate.
were kept intact whether the avalanche generation module
was activated or not as shown in Fig. 9. This indicates that theavalanche generation effect was negligibly small andrepresented the discharge flow of deposited electrons. Note that
we used the 0.1-pC/ m LET for the confirmation because thecalculation did not converge when the LET was 0.4 pC/ m andthe avalanche generation module was deactivated. We considered that the confirmation result is valid for the higher LET cases
because the avalanche generation effect becomes negligible as
the LET value increases [10].
ofWhen the LET was 0.4 pC/ m (Fig. 8), we obtained. It is difficult to theoretically0.44 fC by integratingfrombecause the deposited carriers
estimateare localized around the ion track. By approximating the value
by the total space charges in the entire body region before irradibecomes 0.24 fC roughly equal to theation, the estimatedof 0.44 fC. We thus conclude that our findings
measuredin the 2-D study are applicable to real 3-D devices.

QDEPIp(ON) τ0�Fig. 8. [3-D simulation results] Time evolution of currents induced by apC/ m (top figure) and difference inheavy-ion strike withelectron currents (bottom figure). Plotted values are doubled data observed in
the simulated half device. Points indicated by a single letter are discussed inFig. 10.

放電過程が重要Fig. 7. SET voltage pulse estimation result: mixed(dashed line) is superimposed for reference, represvoltage pulse.

CL |VT p |+ τ1 +
Finally, we would like to comment on issu
Ip(ON)
Fig. 9. [3-D simulation results] Difference in electron currents when theavalanche generation module was activated and deactivated. Note that the0.1-pC/ m LET was used.

perimental values. Even if constant LET ions
are used,vs. curve shapes will vary mFig. 10 shows impacts of the stored-carrier discharge currenton transientpulse heights(a) and width (b). As
the LETvaluelocation
fluctuations[5],[7],[9]. Also, curve
increases, its impacts become more serious. The peak value,occur
duetomA,
signalof mefor example,
is raisedby 0.4and thetransfer
pulse width islimitations
expanded by 8.8 ps when the LET value is 0.4 pC/ m. Pulse width,
andis test
fixtures.
narrowin particular,
enormously
widened The
by this 1stcurrent
compo- peaks in Fig
QDEP = LET × tSOI よりt*は放射線強度LETの対数関数と書ける
nent. Since the pulse width is an important factor characterizing
will be lost in measurement data because of t
single event transients, we must pay careful attention to this discharge component.
tations of the present measurement apparatu
Kobayashi et al., IEEE TNS 56(6) 2009 p3043D. Perspectives
on Device Downscaling
Effects test, and lower thanresolution
for the laser
19
We would like to discuss the device downscaling impact onion test).
We
needwith them proper
the stored-carrierdischarge
current.
Whentothe deal
ideal constant-

底C. Impact of the Stored-Carrier Discharge Current (3-DSimulation Results)

回復

1.0
地上中性子

1.0 地上中性子0.80.8
1.00.6理論がある今0.80.4?
0.60.20.36 ns0.4
直線0.0203050 70
0.2 1020H9FP PJ

1.00.6

理論がなかった昔

0.80.40.60.20.4
0.00.20.0

宇宙重イオン（指標） （指標） （限界）

宇宙重イオン（限界）（指標） （指標）:LGWK QV:LGWK QV:LGWK QV:LGWK QV考察できるようになった

放射線が弱いと0 パルスが伸びる?
20406020H9FP PJ
00080

1000.2
200.0

0.4
0.6
0.8
1.04060801002(pCѥP
PJ0H9FP
Linear Energy Transfer: LET
対数プロット
0.20.40.60.81.0(pCѥP
Linear Energy Transfer: LET

10000.1100.20.3
2030 0.4 0.5
50 0.770 1.01002(pCѥP
PJ0H9FP
Linear Energy Transfer: LET
00.2 0.3
0.5 0.7 1.0(pCѥP
Linear Energy Transfer: LET•LET 0.4 pC/μmで大きくなるのは疑わしい．測定結果の検討が必要

データを見直して解析に誤りがあることがわかった．
•地上中性子環境における平均SET幅は0.36nsより短いと見積ってよいであろう

20

この研究の成果
回路における放射線ノイズパルスを解明しモデル化

1．測定法
2．推定法
3．理論
1と2は製造技術に依らない．
3はFDSOI製造技術に注目．ただし，バルク製造技術
でも同様の対数関数的な振舞を確認できている．
21

謝辞
本研究は多くの方々に支えによって実施できました．特に下記の方々には実験や議論の際にお力添えをいただきました．お名前を挙げて感謝の意を表します．
Dr. V. Ferlet-Cavrois (ESA) Dr. D. McMorrow (NRL)あDr. P. Paillet (CEA)
新井康夫先生（KEK）大野守史様（産総研）
柴田直先生（東大）三田吉郎先生（東大）
柳川善光博士（日立）牧野高紘博士（原子力機構）
齋藤宏文先生（宇宙研）池田博一先生（宇宙研）
廣瀬和之先生（宇宙研）
本研究にあたり下記の助成をいただきました．関係各位に謹んで御礼申し上げます．
文部科学省科学研究費補助金（若手研究B）
日本学術振興会科学研究費補助金（基盤研究C）
宇宙科学振興会国際学会出席旅費支援
最後に宇宙科学振興会の皆様
並びに本賞選考委員会の皆様に心からの感謝を申し上げます．
22