1. Development of Low Noise, Back-side Illuminated Silicon Photodiode Arrays S.E. Holland, W.W. Moses (LBNL, UC Berkeley) This document presented by DongHa Kah in KNU IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 44, NO. 3, JUNE 1997

2. Contents 1. Abstract 2. Introduction 3. Background 4. Device Design 5. ITO (skip) 6. Noise Performance and Conclusion http://wsc.lbl.gov/Science-Articles/Research- Review/Highlights/2000/stories/astrophysics/silicon2.html

3. Cover page ✓ P-I-N diode arrays(3x4), one pindiode size : 3 mm x 3 mm, thickness : 300 μm ✓ ohmic(n + ) depth 10 nm made by poly-silicon ✓ ARC 57 nm-thick from ITO, low series resistance and good transmittance ✓ Q.E.>70% at 400~1000 nm ✓ bulk capacitance : 3.2 pF/ch, leakage current : 20~50 pA ✓ Equivalent input noise charge : 140 e - @ 4 μs-shaping ✓ Energy resolution 12% (FWHM) by coupled to a CsI(Tl) with 141 keV gamma

4. Introduction ✓ PET(Positron emission tomography) 양전자방출단층촬영장치는 양전자방출 방사성동위원소에서 양전자방출 후 소멸반응에 의해 180 도 방향으로 방출된 511 keV 에너지를 갖는 두 개의 감마선을 검출하여 영상을 구성하는 장치이다. 핵의학 영상 기기의 최근 진보 http://dhkah.files.wordpress.com/2010/09/jung_nucl-med-mol-imaging_2008.pdf PET@WIKI http://en.wikipedia.org/wiki/Positron_emission_tomography

5. PET@WIKI http://en.wikipedia.org/wiki/Positron_emission_tomography

6. Introduction GOAL : High resolution PET To develop photodiode arrays for use in PET Conjunction with PMT for determination of both the crystal of interaction and the DOI within an individual crystal for the 511 keV photons [1] [1] http://dhkah.files.wordpress.com/2010/08/moses_nuclear-science-ieee-transactions-on_1994.pdfhttp://dhkah.files.wordpress.com/2010/08/moses_nuclear-science-ieee-transactions-on_1994.pdf DESIGN STUDIES FOR A PET DETECTOR MODULE USING A PIN PHOTODIODE TO MEASURE DEPTH OF INTERACTION http://breast.lbl.gov/~wwwinstr/projects/PET_Modules/

7. Introduction 반응깊이 측정 (Depth of Interaction, DOI) PET 검출기에 얇고 긴 섬광결정을 사용함으로써 고분해능, 고민감도 영상을 획득할 수 있다. 그러나 이로 인해 원형 PET 의 시야 외곽에 위치한 선원으로부터 방출된 감마선이 검출기면에 비스듬히 입사하여 인접한 2 개 이상의 섬광결정 픽셀을 투과하는 비율이 높아지게 되고, 그 결과 시야 외곽 부분의 공간분해능이 저하된다. 공간분해능의 저하를 개선하기 위해서 감마선이 섬광결정과 반응한 깊이를 측정하는 다양한 방법이 연구되고 있다. 그 중 두층 섬광결정을 사용하는 것이 효율적으로 정확하게 반응깊이를 측정하는 방법으로 제 안되고 있으며, 현재 LYSO/LuYAP 과 LYSO/GSO 두층섬광결정을 적용한 PET 이 상품화되어 판매되고 있다. 이러한 PET 시스템에서 감마선 반응 깊이는 두 섬광결정의 감쇠시간 차이로 인해 발생하는 펄스형태의 변화를 측정하여 구별한다.

8. Introduction

9. Background - photodiode ✓ To use the Gettering techniques - minimization of the leakage current by impurities in the silicon band-gap - 400 nA/cm 2 ➔ 1 nA/cm 2 with MOSFET ✓ No problem about MOSPET process(900 ℃ 3h) ✓ 3% FWHM at 60 keV gamma (8h) FABRICATION OF DETECTORS AND TRANSISTORS ON HIGH-RESISTIVITY SILICON http://dhkah.files.wordpress.com/2010/08/holland_nuclear-instruments-and-methods-in-physics-research-section-a_1989.pdf

10. Background Goal : Good blue/UV response Scintillation crystalBGOLSOCsI(Tl) emission peak480 nm415 nm550 nm absorption depth in Si400 nm130 nm1000 nm

11. Device Design ✓ 8 kΩ ⋅ cm n-type, -oriented 300 μm-thick wafer ✓ Etching thick polysilicon gettering layer - 10 nm - simple process - twice as absorbing as lightly-doped and single-crystal silicon - But, it can be thin minimizes ✓ Quantum efficiency v.s. wavelength for varying polysilicon thicknesses

12. Device Design ✓ Quantum efficiency v.s. wavelength for 10 nm polysilicon + 57 nm ITO-ARC Scintillation crystalBGOLSOCsI(Tl) emission peak480 nm415 nm550 nm absorption depth in Si400 nm130 nm1000 nm Q.E. with ITO-ARC90%75%-

13. Noise Performance &Conclusion ✓ Leakage current : 0.3 nA/cm2@100V ✓ Capacitance : 40~60 pF/cm2 ✓ Full-depletion voltage : 30 V ✓ Equivalent input noise charge : 140 e - @ 4 μs-shaping - capacitance - series resistance ( ❈ ITO have good properties both resistivity and transmittance) - leakage current ✓ Energy resolution 12% (FWHM) by coupled to a CsI(Tl) with 141 keV gamma