The One-Transistor, One-Capacitor (1T1C) Dynamic Random Access Memory (DRAM), and its Impact on Society R. Jacob Baker Department of Electrical and Computer Engineering Boise State University 1910 University Dr., ET 201 Boise, ID 83725 [email protected] Abstract – Memory technology development, in particular dynamic random access memory (DRAM), has been the greatest driving force in the advancement of solid-state technology for integrated circuit development over the last 40 years. The origin of DRAM circuits and technology can be traced to Dr. Dennard’s Patent (Number 3,387,286) granted on June 4, 1968. This truly visionary work, using a single transistor and capacitor (the 1T1C), is one of the most manufactured devices in the history of mankind. This talk will review the impact of his invention and discuss the brilliance of Dr. Dennard for conceiving the invention of the 1T1C cell prior to the maturity of metal oxide semiconductor (MOS) technology and in the face of critics that may have likely asked “why in the world would we want a memory, DRAM, that forgets its’ contents!?” Baker 1 Let’s Step Back in Time What are the following (hint: they were found in your local supermarket in the 50s, 60s, and early 70s) Photos taken from ebay.com Baker 2 Semiconductor-based Electronics were still new during this period of time Does anyone remember the birth of the transistor radio? Below is seen the 2-transistor Furtura transistor radio (ca. 1955) 9 Note the output is via an earphone 9 Also note the schematic (not many, if any, consumer electronics products today come with a schematic) Photos taken from ebay.com Baker 3 Evolution of the Transistor Radio These were a big deal both because they were portable (something not practically possible with vacuum tube radios) and because they used a new technology (solid-state devices that didn’t wear out) Photos taken from ebay.com Baker 4 Growing Complexity Note the use of bipolar junction technology to replace vacuum tubes Photo taken from ebay.com Baker 5 What was going on with memory storage during this time? Dominated by the magnetic core memory seen below During the 1960s solid-state memory was developed based on the BJT 9 Ultimately wasn’t successful (compared to MOS-based memory) 1 mm Image from wikipedia.org Baker 6 So why is Dr. Dennard’s invention such a big deal? During the excitement of bipolar technology replacing vacuum tubes in most electronic devices he filed an invention disclosure on July 14, 1967 that 9 Used metal-oxide-semiconductor (MOS) technology 9 Proposed a memory, the one-transistor, one-capacitor (1T1C cell), that forgets its contents! Why is using MOS technology such a big deal over bipolar? 9 MOS technology is scalable! 9 Another significant contribution from Dr. Dennard’s is scaling theory. Why is a memory that forgets its contents such a big deal? 9 It’s small! 9 It’s fast! Baker 7 Dennard’s Scaling Theory* Predicted that MOS devices would continue to shrink in size (scale) over time 9 Higher density 9 Faster 9 Low power Also discussed how interconnect would scale 9 RC times of the lines don’t scale but as distances shrink delays drop * Dennard, R.H.; Gaensslen, F.H.; Rideout, V.L.; Bassous, E., and LeBlanc, A.R., “Design of ion-implanted MOSFET's with very small physical dimensions,” IEEE Journal of Solid-State Circuits, Volume 9, Issue 5, Oct 1974, pp. 256 - 268 Baker 8 Scaling Theory Scaling from Dennard’s paper 9 Device and Circuit Scaling 9 Interconnect Scaling 9 Scale parameter is about 1.4 (1/κ = 0.7) Baker 9 The One-Transistor, One-Capacitor (1T1C) Dynamic Random Access Memory (DRAM) cell The array is formed with word (row) and column (bit) lines Baker 10 Folded and Open Arrays The open array Baker 11 Folded and Open Arrays The folded array Baker 12 The Folded Array Baker 13 Further Reduction in Cell Size Sharing the bitline contact Baker 14 Mbit Pair: Folded Array Baker 15 Folded Array Cell Size Baker 16 Open Array: 6F2 Baker 17 Array Block Baker 18 The 1T1C DRAM Cell ACT Row 1 1-transistor, 1-capacitor (1T1C) DRAM Cell Row 2 EQ VDD/2 NLAT Col 1 I/O I/O Baker 19 SEM Photo of a Modern DRAM Array Baker 20 How is DRAM used today? Workstations Personal Digital Assistants Units - 1.69M Units – 8.9M DRAM – 5,741MB/unit average DRAM - 65MB average DRAM Revenue - $1,164M DRAM Revenue - $698M Source: iSuppli Source: iSuppli PC Servers, Enterprise Units – 0.91M DRAM – 24,581MB Notebook DRAM Revenue - $2,684M Computers Source: iSuppli Units - 51M Desktop Computers DRAM – 510MB Units – 150M DRAM Revenue - $3,105M DRAM – 560MB Source: iSuppli DRAM Revenue - $10,048M Source: iSuppli Memory Upgrades Printers Units – 87M Units - 112M DRAM – 295MB DRAM – 35MB DRAM Revenue - $3,060M DRAM Revenue - $156M Source: iSuppli Source: iSuppli Baker 21 Communications and Networking Market Cellular Phones Set­Top Boxes Cable Modems Units - 740M Units – 62M Units – 15.7M DRAM – 5MB DRAM – 56MB DRAM – 8MB Flash – 87MB Flash – 2MB DSL Modems Cellular Base Stations Units – 55M Units - 0.35M DRAM – 8MB DRAM - 256MB Flash –2MB Flash – 5112MB LAN Switches Low­End to Mid­Range Routers Units – 113.5M Units – 1.5M DRAM – 15MB DRAM – 406MB Sources: iSuppli, Gartner, Portelligent, Instat Baker 22 DRAM Demand by End-Use Application 100% Industrial Automotive Consumer Mobile Communications PC Graphics 80% Wired Other Data Communications Processing* 60% Upgrade Modules Entry­ Level Servers (x86) Mobile/Notebooks 40% Percent of Total Megabits of Total Percent 20% Desktop PC 0% 2004 2005 2006 2007 2008 2009 *Other Data Processing includes mainframe servers, enterprise servers, workstations, handheld PCs, storage cards, printers, and internet appliances Baker 23 2Gb DDR3 1Gb Worldwide DRAM Shipments by TypeDDR2 1Gb DDR3 51 2 Mb D DR 512Mb DDR3 100% 512 Mb DDR2 90% 80% 128Mb 256Mb DDR 70% RDRAM 60% 256 Mb SD 50% 128 Mb DDR 40% 128 Mb SDR 64Mb DDR 64M b SDRAM 30% 64Mb EDO 006 2007 2008 2009 24 20% 16Mb SDRAM Percent of Total Megabytes Produced Megabytes Total of Percent 10% FP/EDO 0% 2002 2003 2004 2005 2 Baker DRAM Technology Trends 100% 90% 80% 70% 60% DDR3 DDR2 50% Units DDR 40% SDRAM 30% 20% 10% 0% 2002 2003 2004 2005 2006 2007 2008 2009 2010 Baker 25 DRAM Density Trends 100% 90% 80% 4 Gb 70% 2 Gb 60% 1 Gb 512 Mb 50% Units 256 Mb 40% 128 Mb 64 Mb 30% 16 Mb 20% 10% 0% 2002 2003 2004 2005 2006 2007 2008 2009 2010 Source: IDC, Isuppli, Gartner, IC Insights Q106 Baker 26 Baker Units in Millions 10,000,000 20,000,000 30,000,000 40,000,000 50,000,000 60,000,000 0 1Q95 3Q95 1Q96 Historical PCMarket Growth 3Q96 1Q97 Grand Total 3Q97 1Q98 3Q98 1Q99 3Q99 1Q00 3Q00 1Q01 Grand Total 3Q01 1Q02 3Q02 1Q03 3Q03 1Q04 3Q04 1Q05 3Q05E -15% -10% -5% 0% 5% 10% 15% 20% 25% 30% 35% Year over Year Growth 27 Price per Bit Cycles 100,000.00 1975 Historically Price per Bit has 1977 declined by an average of 9% 10,000.00 1974 every quarter 1979 1976 (1974-2005) 1981 1978 1983 1,000.00 1980 1985 1982 1987 1984 1989 100.00 1991 1993 1986 1988 1995 1990 1994 10.00 1992 1997 1996 1999 1.00 Price per Bit (Milicents) per Price 1998 2001 2000 2003 2005 0.10 2002 2004 0.01 1 100 10,000 12 Cumulative Bit Volume (10 ) 1,000,000 100,000,000 Source: Gartner, 05/05 Baker 28 Americas DRAM Unit Shipments by Density 2,000.0 1,800.0 1,600.0 1Gb 1,400.0 1,200.0 512Mb 1,000.0 64Mb Millions of Units 800.0 256Mb 600.0 128Mb 400.0 200.0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 1Mbit 4Mbit 16Mbit 64Mbit 128Mbit 256Mbit 512Mbit 1Gbit 2Gbit 4Gbit 8Gbit Baker 29 Baker 100,000 200,000 300,000 400,000 500,000 600,000 700,000 0 Apr-98 Jul-98 256Mb EquivalentUnit DRAMShipments Oct-98 Jan-99 Apr-99 Jul-99 Oct-99 Jan-00 Apr-00 256Mb EquivalentUnitsShipped Jul-00 Oct-00 Jan-01 Apr-01 (K Units) Jul-01 Oct-01 Jan-02 Apr-02 12/12 Growth Total 256MbEU Jul-02 Oct-02 Jan-03 Apr-03 Jul-03 Oct-03 Jan-04 Apr-04 Jul-04 Oct-04 Jan-05 Apr-05 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 30 DRAM Applications with the Highest Unit Growth Rates (CAGR 2004 – 2008) Entry-Level PC Servers Internet Appliances Mobile PCs Wireless LAN Client Access Wireless LAN Access Point/Bridge SAN Switches MP3 player Flash Storage Cards Digital TVs DVD Video Recorder 0% 10% 20% 30% 40% 50% 60% Baker 31 Fastest Growing DRAM Consumption (CAGR 2004 – 2009) Enterprise Servers Upgrade Module Handheld Computers Mobile PCs Deskbound PCs Entry-Level PC Servers Workstations Internet Appliances Remote Access RAC & RAS Mobile Handsets 0% 20% 40% 60% 80% 100% Baker 32 Summary Overview DRAM chips are found in virtually every computer in use today. Looking at the simplicity of the 1T1C cell one might wonder about the significance of this invention by modern day standards. However, if it is remembered that this idea was conceived back in the 1960s before MOS technology had matured enough for production or the idea that circuits could be “dynamic” (only operating correctly for a short period of time) the significance of the invention becomes clear.