Flash Memory Overview: Technology & Market Trends. Allen Yu Phison Electronics Corp.

Transcription

1 Flash Memory Overview: Technology & Market Trends Allen Yu Phison Electronics Corp.

2 25,000 20,000 15,000 The NAND Market 40% CAGR 10,000 5,000 ($Million) The fastest growth rate among all memories (NOR, DRAM, SRAM), 2001 to 2010 Surpassed NOR in 2005, catching up DRAM $20B in 2010, looking at $30B in coming years New applications consume more and more NAND flash Source: ForwardInsights

3 Applications 40,000 35,000 30,000 25,000 20,000 15,000 10,000 5,000 0 Petabytes >150% growth rate ~100% growth rate Digital Camera Music Player USB Drive Camcorder Mobile Phone Gaming Media Tablets Computing Automotive Other Source: Gartner, Phison Marketing

4 Accelerator Light weight Low power consumption No acoustic noise Anti-shock Small form factor High IOPS The SSD Hype Inhibitor Cost, cost, cost Users hesitation; lack of understanding Lack of standards, metrics and consensus SSD market is ramping up, cost remains the major gating item. Not restricted to form factor and interface, the definition is broadening, or blurring Check out JEDEC JC64.8 for SSD Endurance and Data Retention Verification Test

5 Embedded NAND Solutions Bandwidth & Functionality JC-64.1 Flash Memory Module, Electrical Specifications UFS1.0 3Gbps UFS2.0 6Gbps emmc4.3 52MHz Boot Sleep emmc4.4 emmc4.41 DDR Multiple partition Trim HPI emmc4.5 Extend partition RTC Discard

6 More Embedded Solutions EZ-NAND: a standard protocol that allows the lithography specific issues and other low-level NAND management to be abstracted from a host controller PATA-NAND: a PATA controller with high capacity NAND flash memory in a BGA package, error correction, flash management and FTL are invisible to a host controller SATA-NAND: a SATA controller with high capacity NAND flash memory in a BGA package, error correction, flash management and FTL are invisible to a host controller Host Controller Host I/F Flash Controller NAND I/F NAND Flash

7 Market Trend by Technology Percentage of Megabyte 100% 80% 60% 40% 20% 0% 1Q09 2Q09 3Q09 4Q09 1Q10 2Q10 3Q10 4Q10 1Q11 2Q11 3Q11 4Q11 SLC NAND MLC NAND 8LC NAND 16LC NAND Others 8LC is like MLC in 2006, fast penetration rate The coexist of SLC, MLC and 8LC Although 8LC enjoys cost advantage, it requires higher ECC Market segmentation by technology Source: Gartner

8 Market Segments Removable Content storage, backup, transfer Performance and reliability are concerned, but cost is everything Cost driven Computing Major storage, data processing Ask for high throughput, high random IOPS, high endurance cycle Performance, reliability and cost are all considerable

9 The beauty of the imperfect NAND

10 The imperfection of NAND As a memory, NAND flash is Slow, hundreds of μs for read, a few ms for write Not random accessible A defect memory, with bit errors and bad blocks Hard to use, a controller to manage raw NAND As a storage, NAND flash is Still a few dollars per GB, not as cost competitive as traditional magnetic or optical Not rewritable, block erase before write Controller to manage NAND flash technology dependent issues, and to boost performance and reliability So, why are we using NAND? And the market is growing

11 Throughput (logarithm ) The Beauty of NAND Cache memory - speed is everything SRAM Storage - cost driven Tape HDD Performance NAND gap DRAM A new tier in the system memory hierarchy Fill the gap between processor and hard drive A storage class memory No moving parts, low power, slim, light weight, etc Cost (logarithm )

12 Technology Migration Process migration faster than Moore s Law, literally the technology driver in semi NAND flash is challenging the limitation of litho Less electrons in FGs, lead to increasing RBER, need powerful ECC engine Finer geometry results sever FG interference, data integrity is a concern due to program/read disturbance Increasing block size and page size: save the die size, good for sequential write, but bad for random performance

13 Floating Gate Simple floating gate technology, CMOS process Well studied, hundreds of research papers As SLC MLC 8LC, voltage window is narrowing

14 Issue of Data Loss As silicon process continue to shrink Thinner tunnel oxide Fewer electrons in FG Easy path for electron to escape Less charge loss tolerance Increasing error bits! Source: IEDM, IRPS

15 Issue of FG Interference FG-FG coupling results program and read disturbance Voltage shift that narrows read windows Read fail! Source: ISSCC, SSDM

16 Emerging Flash Technologies 3D matrix flash Stacked floating gate NAND Bit-cost scalable technology (BiCS) Charge trap flash (CTF) Vertical gate NAND flash (VG-NAND) Terabit cell array transistor (TCAT) Bandgap engineered SONOS (BE-SONOS) Nanocrystal memory Phase change memory (PCM) Resistive RAM (RRAM) Memristor Magnetic racetrack memory Source: IEDM, VLSI

17 Controller Technology As NAND flash continue to shrink through technology migration, the cost of controller is actually surging up Powerful ECC engine to fix the ever increasing UBER Global wear leveling to cover the degrading endurance Dynamic sensing to offset severe read/write disturbance More buffers to accommodate the larger page size Multi-channel for high throughput

18 ECC R-S, Hamming, BCH, turbo, LDPC, the Shannon's limit The correction power is a probability of failure, which is dominated by correctable bits, regardless the size of codeword ECC engine is taking a significant real estate on the die 12bit/512B 15bit/512B 24bit/1KB 48bit/2KB

19 Wear Leveling Evenly spread program/erase cycles over all NAND blocks to best use every block and prolong NAND lifetime Total Erase Count: MAX Erase Count:181 AVG:135.4 STD: Without Wear-Leveling Total Erase Count: MAX Erase Count:147 AVG:137.6 STD: With Wear-Leveling

20 The Trends NAND flash market continues to grow and prosper in the coming years, thanks to the emerge of new devices like Smartphone, media tablets and other handhelds. These devices use more MCPs than SSDs, the boundary between the two is diminishing. Silicon technology migration leads to lower cost at the expense of performance and reliability. SLC, MLC and 8LC will coexist to serve different needs; on the other hand, the industry never stops looking for universal memories. Controller technology that enables NAND flash applications continues to evolve. NAND flash characteristics are deteriorating for every generation, innovative controller technology is in need to serve the demand of IOPS, reliability, throughput and power for nowadays mobile systems.

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