Conductive-bridge Memory (CBRAM®) with Excellent High-temperature Retention and Tolerance to High Levels of Gamma Radiation
Dr. Venkatesh P. Gopinath, V.P. of CBRAM Technology Adesto Technologies Outline/Contents
• Introduction to Adesto Technologies
• Introduction to CBRAM
• CBRAM from Adesto® – General characteristics – High-T retention – Radiation tolerance
• Conclusions
2 Adesto Technologies Corporate Overview
Overview: Private company founded in 2007 by semiconductor industry veterans Locations: Headquarters in Silicon Valley, California / Offices in Asia, Europe Employees: 100 (Engineering=70, Sales/Marketing=20, Other=10) Status: $50M+ profitable business, supporting over 100 tier 1 customers Business Model: Discrete product manufacturing and technology licensing Technologies: Serial Flash / DataFlash® / CBRAM® Solid Intellectual Property Position: Over 100 patents granted or filed
3 Outline/Contents
• Introduction to Adesto Technologies
• Introduction to CBRAM
• CBRAM from Adesto – General characteristics – High-T retention – Radiation tolerance
• Conclusions
4
Moore’s Law
Device Dimension (nm) Dimension Device S Inoue, T Kono, S Itoh, T Higashiki, LithoVision 2008
5 Candidates for Next Generation NVM
• Ferroelectric RAM (FeRAM)
• Magnetic RAM (MRAM)
• Phase Change Memory (PCM)
• Resistance Change RAM (RRAM) (metal oxides)
6 Resistance Change Memory Taxonomy
Conductive Bridging RAM (CBRAM)
R. Waser, R. Dittmann, G. Staikov, and K. Szot., “Redox-Based Resistive Switching Memories – Nanoionic Mechanisms, Prospects, and Challenges”, Adv. Mater., vol. 21, 2632–2663 (2009).
7 Example of Electrochemical Memory Implementations
8 What is it Made Of?
Anode CBRAM uses 25%
1 of all the elements 2 H He 1.0079 Electrolyte 4.0026 3 4 5 6 7 8 9 10 Li Be B C N O F Ne 6.941 9.0122 Cathode CBRAM / CMOS Build uses 10.811 12.011 14.007 15.999 18.998 20.180 11 12 ~75% of all the elements ! 13 14 15 16 17 18 Na Mg Al Si P S Cl Ar 22.990 24.305 More than Moore in action. 26.982 28.086 30.974 32.065 35.453 39.948
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 39.098 40.078 44.956 47.867 50.942 51.996 54.938 55.845 58.933 58.693 63.546 65.39 69.723 72.61 74.922 78.96 79.904 83.80
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 85.468 87.62 88.906 91.224 92.906 95.94 98 101.07 102.91 106.42 107.87 112.41 114.82 118.71 121.76 127.60 126.90 131.29
55 56 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 132.91 137.33 174.97 178.49 180.95 183.84 186.21 190.23 192.22 195.08 196.97 200.59 204.38 207.2 208.98 209 210 222
57 58 59 60 61 62 63 64 65 66 67 68 69 70 La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb 138.91 140.12 140.91 144.24 145 150.36 151.96 157.25 158.93 162.50 164.93 167.26 168.93 173.04
89 90 91 92 93 94 95 96 97 98 99 100 101 102 Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No 227 232.04 231.04 238.03 237 244 243 247 247 251 252 257 258 259
9 Operating Principle of a CBRAM Cell
R > 10MW Program RON ~ kW Erase
10 ROFF ~ 10 Ω 4 RON ~ 10 Ω
10 CBRAM cells as quantum point contacts (QPCs)
Physical picture is atomic: Ag/GeS /W 2 1 atom1G0 2 atoms2G0
2 G0 = 2e /h = (13kW)-1 Not continuum:
Jameson et al., EDL 33, 257 (2012) r APL 99, 063506 (2011)
Summary of QPC-related device behavior: “Conductive bridge random access memory (CBRAM) technology”, Jameson & Van Buskirk Similar observations in other systems: - in - Gap: Terabe et al., Nature 433, 48 (2005) Advances in nonvolatile memory and storage Non-gap: See paper for 8 refs from 2012/13 technology, ed. Y. Nishi, Woodhead Pub.
11 Outline/Contents
• Introduction to Adesto Technologies
• Introduction to CBRAM
• CBRAM from Adesto – General characteristics – High-T retention – Radiation tolerance
• Conclusions
12 CMOS Integration
• Adesto has successfully completed baseline integration flow in a standard CMOS Logic fab
• Adesto’s process integration enables the introduction of CBRAM memory stack into CMOS BEOL without affecting the line
• Over 8000 wafers processed so far without any issue on background CMOS process
13 1Mb Array Architecture and Diagram
BL (0) 8-BLs BL(7) BL(0) BL(7) Zone 0 VAN (0) VAN (127)
127 Sectors WL(0) ......
WL(255) ......
: : BL(0) BL(7) BL(0) BL(7) VAN (0) VAN (127) Zone 3 ... WL(j) ......
14 Importance of the Fermi wavelength in QPCs
To open first conductance RON Metal Semi channel (R~1/G0), need d~lF 1 MW 1 atom
Width 100 kW d 1 atom N atoms
1/G0=13 kW Ins. Ins. QPC 13/2 kW To reach a given 13/3 kW 3 atoms Metals: RON, a semi
lF ~ 1 Å 1 atom ~ 1 G0 (13kW) QPC must be wider than a Semiconductors: metal QPC lF >> 1 Å 1 atom << 1 G0 13/N kW
15 CBRAM: Cell Structure and Architecture
• 128kb–1Mb EEPROM-compatible products Amorphous • I2C interface alloy containing a semiconductor • 1T1R
BL Anode • 130nm Cu BEOL
WL Oxide
Metal cathode
16 Outline/Contents
• Introduction to Adesto Technologies
• Introduction to CBRAM
• CBRAM from Adesto – General characteristics – High-T retention – Radiation tolerance
• Conclusions
17 CBRAM: Forming
• In general, first write is slower than subsequent writes • But, high yield still achievable with forming pulse of 10ms/3V
18 CBRAM: Write Speed
BL Anode BL discharge BL WL 100ns
Low-R ON state
BL 3V
WL Write time <10ns 2V WL
• Write speed depends “exponentially” on voltage • At a write voltage of 3V, sub-10ns writes are possible • Typical program uses ~2V/100ns-1us
19 CBRAM: Erase Speed
BL Anode
BL precharge 10ns WL
BL 2V WL High-R OFF state Erase time ~10ns BL
• Above a voltage of ~2V, sub-10ns erases are also possible • Typical erase uses ~1.5V/100ns-1us
20 CBRAM: Immunity to Read Disturbs
RON<33kW R>133kW ROFF>400kW R<133kW
100ns 100ns
• The exponential dependence of speed on voltage allows read disturbs to be avoided • Typical read uses ~0.2V/100ns
21 Outline/Contents
• Introduction to Adesto Technologies
• Introduction to CBRAM
• CBRAM from Adesto – General characteristics – High-T retention – Radiation tolerance
• Conclusions
22 The Need for High-T Retention in Emerging Memories
• Operational requirement for some applications (e.g., automotive) • Other applications (e.g., code storage) utilize wafer-level or package-level programming, followed by solder reflow for board mount • Low-density demonstrations to prove out new technology
TP = 260ºC, tP = 30s
Worst case: Surface mount of a thin Reflow package using Pb-free T profile solder
IPC/JEDEC J-STD-020D.1, Fig. 5-1
23 CBRAM: Example of Long-term High-T Retention
• Cells are stable at 10x greater R than that of a 1-atom point contact of a
typical metal (i.e., ~1/G0)
• High-T retention of a given R state is insensitive to the operation used to obtain that state
RON = 1/G0 = 13kW
• Ongoing product-level retention tests at 110ºC have shown no fails after more than 8 months
~900 hours
24 CBRAM: Retention through Simulated Solder Reflow
Anneal profile simulating high-T portion Retention yields following of multiple Pb-free solder reflows simulated reflow
6x spec @ 260ºC Each dot is a different algorithm 3x spec @ 217ºC
• Excellent retention is achievable at reflow-like times and temperatures • Algorithm design is important, even with suitable materials system
25 Outline/Contents
• Introduction to Adesto Technologies
• Introduction to CBRAM
• CBRAM from Adesto – General characteristics – High-T retention – Radiation tolerance
• Conclusions
26 CBRAM – Robust in Extreme Environments
Recent News ―
Collaboration with Adesto Technologies and Nordion Confirms Gamma Irradiation Tolerance of CBRAM® Non-Volatile Memory
Wednesday, October 16, 2013
Capability Opens New Market Opportunities to Ultra-Low Power Memory Products
Sunnyvale, CA, October 16, 2013 -- Adesto Technologies, a memory solutions provider delivering innovative products for code and data storage applications, and Nordion, with global expertise in the design and construction of commercial gamma irradiation systems, today announced the successful completion of gamma irradiation testing of Adesto’s CBRAM non-volatile memory products. The results demonstrated CBRAM’s tolerance for gamma testing with device function and data storage surviving gamma radiation exposure…
“Gamma irradiation is a proven technique for the sterilization of single use medical devices and other consumer products that require strict microbial decontamination.” ― Emily Craven, Manager of Sterilization Science at Nordion
27 CBRAM® Gamma Tolerance Study
Study 1: (vs. Conventional Flash) Study 2: (High Dose Gamma)
Conventional Flash Memory Devices
CBRAM Devices
• Tests performed by ASU
• Tests performed by Nordion – Leading provider of isotopes and radiation therapy services to the medical and health care industry • Results : CBRAM PASSED Data Retention Test CBRAM had no failure even at twice the normal dose used for Gamma Sterilization
28 CBRAM Cell Tolerance to Gamma Radiation – Resistance Distribution
Program State (LRS) Erase State (HRS)
50kGy Dose
29 Summary and Outlook for CBRAM
• Field of emerging memory is diverse and vibrant
• CBRAM has been a leading candidate, and has recently made significant new advancements
• CBRAM has achieved high-T retention by using a combination of materials engineering & a properly designed algorithm Opportunities for apps w/ high-T operation or requiring solder reflow
• Tolerance to gamma radiation has also been achieved Opportunities for medical or aerospace applications
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