CN102456745A - 一种快闪存储器及其制备方法和操作方法 - Google Patents
一种快闪存储器及其制备方法和操作方法 Download PDFInfo
- Publication number
- CN102456745A CN102456745A CN2010105233211A CN201010523321A CN102456745A CN 102456745 A CN102456745 A CN 102456745A CN 2010105233211 A CN2010105233211 A CN 2010105233211A CN 201010523321 A CN201010523321 A CN 201010523321A CN 102456745 A CN102456745 A CN 102456745A
- Authority
- CN
- China
- Prior art keywords
- district
- silicon
- polysilicon
- oxide layer
- layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 230000015654 memory Effects 0.000 title claims abstract description 81
- 238000000034 method Methods 0.000 title claims abstract description 26
- 238000002360 preparation method Methods 0.000 title abstract description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 113
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 108
- 239000010703 silicon Substances 0.000 claims abstract description 108
- 238000007667 floating Methods 0.000 claims abstract description 56
- 239000000758 substrate Substances 0.000 claims abstract description 42
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 46
- 229920005591 polysilicon Polymers 0.000 claims description 46
- 239000013078 crystal Substances 0.000 claims description 35
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 17
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 13
- 230000004888 barrier function Effects 0.000 claims description 12
- 230000008569 process Effects 0.000 claims description 12
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 12
- 239000012190 activator Substances 0.000 claims description 7
- 238000005530 etching Methods 0.000 claims description 7
- 239000012535 impurity Substances 0.000 claims description 7
- 239000000377 silicon dioxide Substances 0.000 claims description 7
- 238000000137 annealing Methods 0.000 claims description 5
- 230000015572 biosynthetic process Effects 0.000 claims description 4
- 150000001875 compounds Chemical class 0.000 claims description 4
- 238000002347 injection Methods 0.000 claims description 4
- 239000007924 injection Substances 0.000 claims description 4
- 238000002955 isolation Methods 0.000 claims description 4
- 235000012239 silicon dioxide Nutrition 0.000 claims description 4
- 239000002019 doping agent Substances 0.000 claims description 3
- 238000001039 wet etching Methods 0.000 claims description 3
- 230000000694 effects Effects 0.000 abstract description 21
- 230000005641 tunneling Effects 0.000 abstract description 20
- 239000004065 semiconductor Substances 0.000 abstract description 8
- 238000005516 engineering process Methods 0.000 abstract description 3
- 229910044991 metal oxide Inorganic materials 0.000 abstract 2
- 150000004706 metal oxides Chemical class 0.000 abstract 2
- 230000000903 blocking effect Effects 0.000 abstract 1
- 230000000295 complement effect Effects 0.000 abstract 1
- 238000003860 storage Methods 0.000 description 10
- 230000005684 electric field Effects 0.000 description 9
- 238000004151 rapid thermal annealing Methods 0.000 description 5
- 229910004298 SiO 2 Inorganic materials 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000005669 field effect Effects 0.000 description 4
- 230000006870 function Effects 0.000 description 4
- 238000005036 potential barrier Methods 0.000 description 4
- 230000004069 differentiation Effects 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 230000014759 maintenance of location Effects 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 229910008065 Si-SiO Inorganic materials 0.000 description 2
- 229910006405 Si—SiO Inorganic materials 0.000 description 2
- 229910052785 arsenic Inorganic materials 0.000 description 2
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 206010021143 Hypoxia Diseases 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 208000018875 hypoxemia Diseases 0.000 description 1
- 210000003127 knee Anatomy 0.000 description 1
- 230000004807 localization Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000006386 memory function Effects 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/70—Bipolar devices
- H01L29/72—Transistor-type devices, i.e. able to continuously respond to applied control signals
- H01L29/739—Transistor-type devices, i.e. able to continuously respond to applied control signals controlled by field-effect, e.g. bipolar static induction transistors [BSIT]
- H01L29/7391—Gated diode structures
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/78—Field effect transistors with field effect produced by an insulated gate
- H01L29/788—Field effect transistors with field effect produced by an insulated gate with floating gate
- H01L29/7889—Vertical transistors, i.e. transistors having source and drain not in the same horizontal plane
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/86—Types of semiconductor device ; Multistep manufacturing processes therefor controllable only by variation of the electric current supplied, or only the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched
- H01L29/861—Diodes
- H01L29/8616—Charge trapping diodes
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B41/00—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates
- H10B41/20—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates characterised by three-dimensional arrangements, e.g. with cells on different height levels
- H10B41/23—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates characterised by three-dimensional arrangements, e.g. with cells on different height levels with source and drain on different levels, e.g. with sloping channels
- H10B41/27—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates characterised by three-dimensional arrangements, e.g. with cells on different height levels with source and drain on different levels, e.g. with sloping channels the channels comprising vertical portions, e.g. U-shaped channels
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Ceramic Engineering (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Computer Hardware Design (AREA)
- Non-Volatile Memory (AREA)
- Semiconductor Memories (AREA)
Abstract
Description
Claims (6)
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN2010105233211A CN102456745B (zh) | 2010-10-22 | 2010-10-22 | 一种快闪存储器及其制备方法和操作方法 |
US13/321,120 US8526242B2 (en) | 2010-10-22 | 2011-03-07 | Flash memory and fabrication method and operation method for the same |
PCT/CN2011/071550 WO2012051824A1 (zh) | 2010-10-22 | 2011-03-07 | 一种快闪存储器及其制备方法和操作方法 |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN2010105233211A CN102456745B (zh) | 2010-10-22 | 2010-10-22 | 一种快闪存储器及其制备方法和操作方法 |
Publications (2)
Publication Number | Publication Date |
---|---|
CN102456745A true CN102456745A (zh) | 2012-05-16 |
CN102456745B CN102456745B (zh) | 2013-09-04 |
Family
ID=45974647
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CN2010105233211A Active CN102456745B (zh) | 2010-10-22 | 2010-10-22 | 一种快闪存储器及其制备方法和操作方法 |
Country Status (3)
Country | Link |
---|---|
US (1) | US8526242B2 (zh) |
CN (1) | CN102456745B (zh) |
WO (1) | WO2012051824A1 (zh) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102769016A (zh) * | 2012-08-14 | 2012-11-07 | 北京大学 | 一种抗辐射的cmos器件及其制备方法 |
CN102986029A (zh) * | 2012-05-25 | 2013-03-20 | 华为技术有限公司 | 数据处理的方法、闪存及终端 |
WO2014177045A1 (zh) * | 2013-05-02 | 2014-11-06 | 复旦大学 | 一种半浮栅器件及其制造方法 |
CN104332502A (zh) * | 2014-11-07 | 2015-02-04 | 华为技术有限公司 | 一种互补隧穿场效应晶体管及其制作方法 |
WO2017079979A1 (zh) * | 2015-11-13 | 2017-05-18 | 华为技术有限公司 | 一种隧穿场效应晶体管及其制作方法 |
CN110770837A (zh) * | 2017-08-16 | 2020-02-07 | 桑迪士克科技有限责任公司 | 减少具有连接的源极端选择栅极的3d存储器设备中的热电子注入型读取干扰 |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102664192B (zh) | 2012-05-08 | 2015-03-11 | 北京大学 | 一种自适应复合机制隧穿场效应晶体管及其制备方法 |
US9159826B2 (en) * | 2013-01-18 | 2015-10-13 | Taiwan Semiconductor Manufacturing Company, Ltd. | Vertical tunneling field-effect transistor cell and fabricating the same |
CN103151391B (zh) * | 2013-03-18 | 2015-08-12 | 北京大学 | 垂直非均匀掺杂沟道的短栅隧穿场效应晶体管及制备方法 |
CN104716173B (zh) * | 2013-12-17 | 2018-03-20 | 中芯国际集成电路制造(上海)有限公司 | 一种半导体器件及其制造方法 |
US9343470B2 (en) * | 2014-08-13 | 2016-05-17 | Cypress Semiconductor Corporation | Integration of semiconductor memory cells and logic cells |
CN115019859B (zh) * | 2015-11-25 | 2023-10-31 | 日升存储公司 | 存储器结构 |
CN109075193A (zh) * | 2017-02-16 | 2018-12-21 | 华为技术有限公司 | 制作隧穿场效应晶体管的方法 |
US11456308B2 (en) * | 2020-10-05 | 2022-09-27 | International Business Machines Corporation | Low-voltage flash memory integrated with a vertical field effect transistor |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1997005655A1 (en) * | 1995-08-01 | 1997-02-13 | Advanced Micro Devices, Inc. | Three-dimensional non-volatile memory |
US6313487B1 (en) * | 2000-06-15 | 2001-11-06 | Board Of Regents, The University Of Texas System | Vertical channel floating gate transistor having silicon germanium channel layer |
CN1661784A (zh) * | 2004-02-04 | 2005-08-31 | 三星电子株式会社 | 自对准分裂栅非易失存储器结构及其制造方法 |
CN1805146A (zh) * | 2005-12-06 | 2006-07-19 | 北京大学 | 一种快闪存储器结构及其制备方法 |
Family Cites Families (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6248633B1 (en) * | 1999-10-25 | 2001-06-19 | Halo Lsi Design & Device Technology, Inc. | Process for making and programming and operating a dual-bit multi-level ballistic MONOS memory |
JP2002092674A (ja) * | 2000-09-20 | 2002-03-29 | Toshiba Corp | 切手検出装置、切手検出方法、書状処理装置および書状処理方法 |
US6951782B2 (en) * | 2003-07-30 | 2005-10-04 | Promos Technologies, Inc. | Nonvolatile memory cell with multiple floating gates formed after the select gate and having upward protrusions |
US6885044B2 (en) * | 2003-07-30 | 2005-04-26 | Promos Technologies, Inc. | Arrays of nonvolatile memory cells wherein each cell has two conductive floating gates |
US7148538B2 (en) * | 2003-12-17 | 2006-12-12 | Micron Technology, Inc. | Vertical NAND flash memory array |
US7241654B2 (en) * | 2003-12-17 | 2007-07-10 | Micron Technology, Inc. | Vertical NROM NAND flash memory array |
US7154779B2 (en) * | 2004-01-21 | 2006-12-26 | Sandisk Corporation | Non-volatile memory cell using high-k material inter-gate programming |
US7190616B2 (en) * | 2004-07-19 | 2007-03-13 | Micron Technology, Inc. | In-service reconfigurable DRAM and flash memory device |
US8288813B2 (en) * | 2004-08-13 | 2012-10-16 | Infineon Technologies Ag | Integrated memory device having columns having multiple bit lines |
US7158410B2 (en) * | 2004-08-27 | 2007-01-02 | Micron Technology, Inc. | Integrated DRAM-NVRAM multi-level memory |
US7378707B2 (en) * | 2005-05-26 | 2008-05-27 | Micron Technology, Inc. | Scalable high density non-volatile memory cells in a contactless memory array |
US7547599B2 (en) * | 2005-05-26 | 2009-06-16 | Micron Technology, Inc. | Multi-state memory cell |
US7829938B2 (en) * | 2005-07-14 | 2010-11-09 | Micron Technology, Inc. | High density NAND non-volatile memory device |
-
2010
- 2010-10-22 CN CN2010105233211A patent/CN102456745B/zh active Active
-
2011
- 2011-03-07 US US13/321,120 patent/US8526242B2/en active Active
- 2011-03-07 WO PCT/CN2011/071550 patent/WO2012051824A1/zh active Application Filing
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1997005655A1 (en) * | 1995-08-01 | 1997-02-13 | Advanced Micro Devices, Inc. | Three-dimensional non-volatile memory |
US6313487B1 (en) * | 2000-06-15 | 2001-11-06 | Board Of Regents, The University Of Texas System | Vertical channel floating gate transistor having silicon germanium channel layer |
CN1661784A (zh) * | 2004-02-04 | 2005-08-31 | 三星电子株式会社 | 自对准分裂栅非易失存储器结构及其制造方法 |
CN1805146A (zh) * | 2005-12-06 | 2006-07-19 | 北京大学 | 一种快闪存储器结构及其制备方法 |
Cited By (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102986029B (zh) * | 2012-05-25 | 2015-07-22 | 华为技术有限公司 | 数据处理的方法、闪存及终端 |
CN102986029A (zh) * | 2012-05-25 | 2013-03-20 | 华为技术有限公司 | 数据处理的方法、闪存及终端 |
US9281063B2 (en) | 2012-05-25 | 2016-03-08 | Huawei Technologies Co., Ltd. | Method for processing data, flash memory, and terminal |
CN102769016B (zh) * | 2012-08-14 | 2015-01-14 | 北京大学 | 一种抗辐射的cmos器件及其制备方法 |
CN102769016A (zh) * | 2012-08-14 | 2012-11-07 | 北京大学 | 一种抗辐射的cmos器件及其制备方法 |
WO2014177045A1 (zh) * | 2013-05-02 | 2014-11-06 | 复旦大学 | 一种半浮栅器件及其制造方法 |
US9508811B2 (en) | 2013-05-02 | 2016-11-29 | Fudan University | Semi-floating-gate device and its manufacturing method |
US9748406B2 (en) | 2013-05-02 | 2017-08-29 | Fudan University | Semi-floating-gate device and its manufacturing method |
CN104332502A (zh) * | 2014-11-07 | 2015-02-04 | 华为技术有限公司 | 一种互补隧穿场效应晶体管及其制作方法 |
US10141434B2 (en) | 2014-11-07 | 2018-11-27 | Huawei Technologies Co., Ltd. | Complementary tunneling field effect transistor and manufacturing method therefor |
WO2017079979A1 (zh) * | 2015-11-13 | 2017-05-18 | 华为技术有限公司 | 一种隧穿场效应晶体管及其制作方法 |
US10249744B2 (en) | 2015-11-13 | 2019-04-02 | Huawei Technologies Co., Ltd. | Tunnel field-effect transistor and method for manufacturing tunnel field-effect transistor |
CN110770837A (zh) * | 2017-08-16 | 2020-02-07 | 桑迪士克科技有限责任公司 | 减少具有连接的源极端选择栅极的3d存储器设备中的热电子注入型读取干扰 |
CN110770837B (zh) * | 2017-08-16 | 2023-10-31 | 桑迪士克科技有限责任公司 | 用于减少热电子注入型读取干扰的存储器设备和方法 |
Also Published As
Publication number | Publication date |
---|---|
WO2012051824A1 (zh) | 2012-04-26 |
CN102456745B (zh) | 2013-09-04 |
US20120113726A1 (en) | 2012-05-10 |
US8526242B2 (en) | 2013-09-03 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
CN102456745B (zh) | 一种快闪存储器及其制备方法和操作方法 | |
US6734063B2 (en) | Non-volatile memory cell and fabrication method | |
CN100527442C (zh) | 一种双鳍型沟道双栅多功能场效应晶体管及其制备方法 | |
US8076709B2 (en) | Nonvolatile semiconductor memory device | |
JP4282699B2 (ja) | 半導体装置 | |
CN100365819C (zh) | 一种快闪存储器结构及其制备方法 | |
CN100570898C (zh) | 用于多位存储的非挥发存储器件及其制作方法 | |
CN103887313B (zh) | 一种半浮栅器件及其制备方法 | |
CN101728394B (zh) | 用于多位存储的沟槽型非挥发存储器 | |
CN100490182C (zh) | 鳍型沟道双栅多功能场效应晶体管的制备方法 | |
CN1841783A (zh) | 分裂栅极存储单元及制造其阵列的方法 | |
CN103824860A (zh) | 制造存储器单元法、制造存储器单元装置法和存储器单元 | |
CN102738244B (zh) | 一种sonos快闪存储器及其制备方法和操作方法 | |
CN100468780C (zh) | 一种nrom闪存单元的制备方法 | |
US20130234223A1 (en) | Self-Aligned Stack Gate Structure For Use In A Non-volatile Memory Array And A Method Of Forming Such Structure | |
CN103165613A (zh) | 半导体存储器及其制造方法 | |
CN102760737A (zh) | 浮栅型eeprom器件及其制造方法 | |
CN102496629B (zh) | 一种电感应的可变浅结作为源漏区的浮栅型快闪存储器 | |
CN104124248A (zh) | 一种抬升共源区的nor型闪存单元及其制备方法 | |
CN102130132B (zh) | Eeprom器件及其制造方法 | |
CN206774545U (zh) | 一种nor型浮栅存储器 | |
CN106158613A (zh) | 一种提高浮栅器件电子保持性的方法及浮栅结构 | |
CN103594519A (zh) | 一种隧穿场效应浮栅晶体管及其制造方法 | |
CN104637885B (zh) | Flash器件源极多晶硅的形成方法 | |
CN1881615A (zh) | 电可擦除可编程只读存储器单元及其制造方法 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
C06 | Publication | ||
PB01 | Publication | ||
C10 | Entry into substantive examination | ||
SE01 | Entry into force of request for substantive examination | ||
C14 | Grant of patent or utility model | ||
GR01 | Patent grant | ||
ASS | Succession or assignment of patent right |
Owner name: SEMICONDUCTOR MANUFACTURING INTERNATIONAL (SHANGHA Free format text: FORMER OWNER: BEIJING UNIV. Effective date: 20150424 Owner name: BEIJING UNIV. Effective date: 20150424 |
|
C41 | Transfer of patent application or patent right or utility model | ||
COR | Change of bibliographic data |
Free format text: CORRECT: ADDRESS; FROM: 100871 HAIDIAN, BEIJING TO: 201203 PUDONG NEW AREA, SHANGHAI |
|
TR01 | Transfer of patent right |
Effective date of registration: 20150424 Address after: 201203 Shanghai City, Pudong New Area Zhangjiang Road No. 18 Patentee after: Semiconductor Manufacturing International (Shanghai) Corporation Patentee after: Peking University Address before: 100871 Beijing the Summer Palace Road, Haidian District, No. 5 Patentee before: Peking University |