SOI Detector R&D: Past & Future

KEK
SOI技術による光、放射線
ピクセル検出器
Dec. 18, 2010
二重ベータ崩壊研究懇談会
@モンタナリゾート岩沼
KEK 新井康夫
[email protected]
http://rd.kek.jp/project/soi/
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OUTLINE
1.
2.
3.
4.
5.
Introduction
SOI Pixel Process
Developed Pixel Detectors
Process Improvements
Summary
詳しくは
Silicon-On-Insulator (SOI) Wafer
SmartCut (1991)
Michel. Bruel
Leti(仏）)
Layer Transfer
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SOI Pixel検出器
Charged Particle
KEK 測定器開発プロジェクト
• 高比抵抗Si基板と低比抵抗Si基板を絶縁層を介して張合わせ。
• 高比抵抗部に不純物implant、p-n junctionを生成。
• 絶縁層(BOX: Buried Oxide)に穴を開けセンサーと回路を接続。
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Metal contact & p+ implant
1st Al
Handle Wafer
Copyright 2007 Oki Electric Industry Co.,Ltd
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SOI Pixel検出器の特徴
• 余分な物質が少なく、多重散乱をおさえられる。
• 電極容量が小さく、少ない電荷(薄いセンサー）で大きなS/Nが得
られる。
• 複雑な信号処理回路を各ピクセルに持たせられる。
• 高レート、高速読み出し、ローカルメモリー等が可能。
• 機械的接合がなく、高分解能化、低価格化が望める。
• 産業界の標準
プロセスを基本に
開発。
Possible Radiation Detection Schemes
X−ray, Visible Light,
Near Infra Red, ...
Thin detector(~50um).
Low mass Multi layer
by adding
conversion layer
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OKI 0.2 mm FD-SOI Pixel Process
Process
0.2mm Low-Leakage Fully-Depleted SOI CMOS (OKI)
1 Poly, 4 (5) Metal layers, MIM Capacitor, DMOS option
Core (I/O) Voltage = 1.8 (3.3) V
SOI wafer
Diameter: 200 mm,
Top Si : Cz, ~18 -cm, p-type, ~40 nm thick
Buried Oxide: 200 nm thick
Handle wafer: Cz ~700 or FZ~10k-cm , 720 mm thick
Backside
Thinned and deposited with Al (200 nm).
An example of a
SOI Pixel cross
section
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Integration Type Pixel (INTPIX)
Vsense 
Q 0.6 fC

 70mV
C
8 fF
b-ray

Size : 14 mm x 14 mm
with CDS circuit
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Integration Type Pixel (INTPIX4)
Largest Chip so far.
15 mm
10 mm
17x17 mm, 512x832 (~430k）
pixels、13 Analog Out、CDS
circuit in each pixel.
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Counting
Type Pixel
(CNTPIX5)
Energy selection and
counting hit in each pixel
5 x15.4 mm2
72 x 272 pixels
64um x 64 um pixel
3 side buttable
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CNTPIX5
Pixel Layout
64x64 um2
ピクセル内
にすべての
エレクトロニ
クスを内蔵
~600 Tr/pix
x 72 x 212
= 10 M Trs
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X-ray Measurementｓ with SOI pixel
5mm
高分解能
ピクセル内でエネルギー
分離が可能
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Buried p-Well to suppress back gate effect
One of the major issues in realizing SOI pixel sensor is
Back Gate Effect. To deplete the sensor Si, we have to
apply high voltage (~100V) from back. This back voltage
affect the characteristics of the transistor.
MOS Tr
Vback
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Buried p-Well (BPW)
BPW Implantation
Substrate Implantation
Buried
Oxide
(BOX)
SOI Si
Pixel
P+
Peripheral
BPW
• Cut Top Si and BOX
• High Dose
• Keep Top Si not affected
• Low Dose
• Suppress the back gate effect.
• Shrink pixel size without loosing sensitive area.
• Increase break down voltage with low dose region.
• Less electric field in the BOX which promote recombination
of electron and hole, thus improves radiation hardness.
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Vback Effect to Id-Vg
w/o BPW
with BPW=0V
NMOS
back channel open
shift
Back gate effect is completely suppressed by the BPW.
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Nested BNW/BPW Structure
implant
• Signal is collected with
the deep Buried P-well.
• Back gate and Cross
Talk are shielded with
the Buried N-well.
• Test chip is under
process.
こういった複雑な構造も可能に
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MPW (Multi Project Wafer) runs
We are operating our
own MPW runs Twice
per Year by including
many designs from
other laboratory.
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KEK SOI Pixel MPW run Users/Collaborations
KEK, Tsukuba Univ., Tohoku Univ., Kyoto Univ.,
Kyoto U. of Education, Osaka Univ., JAXA/ISAS,
RIKEN, AIST (Japan)
LBNL, FNAL, Univ. of Hawaii (U.S.A.)
INP Krakow, INFN Padova, Louvain-la-Neuve Univ.,
Universität Heidelberg (Europe)
IHEP China, Budker Institute of Nucl. Phys. (Asia)
Supporting Companies
OKI Semiconductor Co. Ltd. ,
OKI Semiconductor Miyagi Co. Ltd. ,
T-Micro Co. Ltd. (ZyCube),
Rigaku Co. Ltd.
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Summary
• SOI ピクセルは理想的な構造を
持ったモノリシック放射線検出器。
• Multi Project Wafer runを定期的に行う事で、様々な
応用に向けた検出器の設計が進んでいる。
• より複雑なセンサー構造、高比抵抗化、薄型化、極低
温応用、３次元実装等多くのR&Dが進んでいる。
• 興味のある方はぜひご参加下さい。
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Supplement
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Total Ionization Dose effect can be compensated by back bias
Leak Current and VTh resumes to nearly original value by biasing
back side even after 100Mrad.
Vback= 0 -10 -20 -30V
1015 p/cm2
(~100 Mrad)
before
irradiation
1015 p/cm2
(~100 Mrad)
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e. Double SOI Layer wafer
Increase radiation hardness by compensating
Oxide/Interface Trap charge with middle layer bias.
circuit
sensor
additional
conduction layer
Shield sensors
from circuit
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Concentration Profile of Implanted Dopant
By adjusting Implant Energy and Flux, we can create p-layer
under the BOX without changing the active density.
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FZ-SOI Wafer Process
Resistivity is increased
10 times high!
During the conventional SOI process, many
slips were generated in the 8’’ FZ-SOI wafer.
Before Oxidation
Conventional SOI
Process
Improved SOI
Process
Slips
We optimized the process parameters, and succeeded to
perform the process without creating many slips.
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FZ-SOI Wafer Depletion
FZ-SOI wafer of 260um width is fully depleted @22V while
CZ-SOI wafer requires more than 250V.
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SOI Pixel Process Flow
SOI (40 nm)
Box (Buried
Oxide)
(200 nm)
650um
Handle Wafer
p+
n+
Handle Wafer
n+
Handle Wafer
p+
50~650um
Al
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