VLSI Technology

VLSI Technology :VLSI Technology Scaling Moore’s Law 3D VLSI


The beginning :The beginning


Transistor Size Scaling :Transistor Size Scaling MOSFET performance improves as size is decreased: shorter switching time, lower power consumption. 2 orders of magnitude reduction in transistor size in 30 years.


Significant Breakthroughs :Significant Breakthroughs Transistor size: Intel’s research labs have recently shown the world’s smallest transistor, with a gate length of 15nm. We continue to build smaller and smaller transistors that are faster and faster. We've reduced the size from 70 nanometer to 30 nanometer to 20 nanometer, and now to 15 nanometer gates. Manufacturing process: A new manufacturing process called 130 nanometer process technology (a nanometer is a billionth of a meter) allows Intel today to manufacture chips with circuitry so small it would take almost 1,000 of these "wires" placed side-by-side to equal the width of a human hair. This new 130-nanometer process has 60nm gate-length transistors and six layers of copper interconnect. This process is producing microprocessors today with millions of transistors and running at multi-gigahertz clock speeds. Wafer size: Wafers, which are round polished disks made of silicon, provide the base on which chips are manufactured. Use a bigger wafer and you can reduce manufacturing costs. Intel has begun using a 300 millimeter (about 12 inches) diameter silicon wafer size, up from the previous wafer size of 200mm (about 8 inches).


Major Design Challenges :Major Design Challenges Microscopic issues ultra-high speeds power dissipation and supply rail drop growing importance of interconnect noise, crosstalk reliability, manufacturability clock distribution Macroscopic issues time-to-market design complexity (millions of gates) high levels of abstractions design for test reuse and IP, portability systems on a chip (SoC) tool interoperability


Integrated Circuits :Integrated Circuits Digital logic is implemented using transistors in integrated circuits containing many gates. small-scale integrated circuits (SSI) contain 10 gates or less medium-scale integrated circuits (MSI) contain 10-100 gates large-scale integrated circuits (LSI) contain up to 104 gates very large-scale integrated circuits (VLSI) contain >104 gates Improvements in manufacturing lead to ever smaller transistors allowing more per chip. >107 gates/chip now possible; doubles every 18 months or so Variety of logic families TTL - transistor-transistor logic CMOS - complementary metal-oxide semiconductor ECL - emitter-coupled logic GaAs - gallium arsenide


Slide 7 :What are shown on previous diagrams cover only the so called front‑end processing ‑ fabrication steps that go towards forming the devices and inter‑connections between these devices to produce the functioning IC's. The end result are wafers each containing a regular array of the same IC chip or die. The wafer then has to be tested and the chips diced up and the good chips mounted and wire‑bonded in different types of IC package and tested again before being shipped out.


Moore’s Law :Moore’s Law Gordon E. Moore - Chairman Emeritus of Intel Corporation 1965 - observed trends in industry - # of transistors on ICs vs. release dates: Noticed number of transistors doubling with release of each new IC generation release dates (separate generations) were all 18-24 months apart Moore’s Law: The number of transistors on an integrated circuit will double every 18 months The level of integration of silicon technology as measured in terms of number of devices per IC This comes about in two ways – size reduction of the individual devices and increase in the chip or dice size As an indication of size reduction, it is interesting to note that feature size was measured in mils (1/1000 inch, 1 mil = 25 mm) up to early 1970’s, whereas now all features are measured in mm’s (1 mm = 10-6 m or 10-4 cm) Semiconductor industry has followed this prediction with surprising accuracy


Slide 9 :In 1965, Gordon Moore predicted that the number of transistors that can be integrated on a die would double every 18 to 14 months i.e., grow exponentially with time Amazing visionary – million transistor/chip barrier was crossed in the 1980’s. 2300 transistors, 1 MHz clock (Intel 4004) - 1971 42 Million, 2 GHz clock (Intel P4) - 2001 140 Million transistor (HP PA-8500) Moore’s Law Source: Intel web page (www.intel.com)


Moore’s Law :Moore’s Law From Intel’s 4040 (2300 transistors) to Pentium II (7,500,000 transistors) and beyond Relative sizes of ICs in graph


Ever since the invention of integrated circuit, the smallest feature size has been reducing every year. Currently (2002) the smallest feature size is about 0.13 micron. At the same time the number transistors per chip is increasing due to feature size reduction and increase in chip area. Classic example is the case of memory chips: Gordon Moore of Intel in early 1970s found that: “density” (bits per chip) growing at the rate of four times in 3 to 4 years - often referred to as Moore’s Law. In subsequent years, the pace slowed down a bit, data density has doubled approximately every 18 months – current definition of Moore’s Law. :Ever since the invention of integrated circuit, the smallest feature size has been reducing every year. Currently (2002) the smallest feature size is about 0.13 micron. At the same time the number transistors per chip is increasing due to feature size reduction and increase in chip area. Classic example is the case of memory chips: Gordon Moore of Intel in early 1970s found that: “density” (bits per chip) growing at the rate of four times in 3 to 4 years - often referred to as Moore’s Law. In subsequent years, the pace slowed down a bit, data density has doubled approximately every 18 months – current definition of Moore’s Law.


Limits of Moore’s Law? :Limits of Moore’s Law? Growth expected until 30 nm gate length (currently: 180 nm) size halved every 18 mos. - reached in 2001 + 1.5 log2((180/30)2) = 2009 what then? Paradigm shift needed in fabrication process


Technological Background of the Moore’s Law :Technological Background of the Moore’s Law To accommodate this change, the size of the silicon wafers on which the integrated circuits are fabricated have also increased by a very significant factor – from the 2 and 3 in diameter wafers to the 8 in (200 mm) and 12 in (300 mm) diameter wafers The latest catch phrase in semiconductor technology (as well as in other material science) is nanotechnology – usually referring to GaAs devices based on quantum mechanical phenomena These devices have feature size (such as film thickness, line width etc) measured in nanometres or 10-9 metres


Recurring Costs :Recurring Costs cost of die + cost of die test + cost of packaging variable cost = ---------------------------------------------------------------- final test yield cost of wafer cost of die = ----------------------------------- dies per wafer × die yield  × (wafer diameter/2)2  × wafer diameter dies per wafer = ----------------------------------  --------------------------- die area  2 × die area


Yield Example :Yield Example Example wafer size of 12 inches, die size of 2.5 cm2, 1 defects/cm2,  = 3 (measure of manufacturing process complexity) 252 dies/wafer (remember, wafers round & dies square) die yield of 16% 252 x 16% = only 40 dies/wafer die yield ! Die cost is strong function of die area proportional to the third or fourth power of the die area


Intel 4004 Microprocessor :Intel 4004 Microprocessor


Intel Pentium (IV) Microprocessor :Intel Pentium (IV) Microprocessor


Die Size Growth :Die Size Growth Die size grows by 14% to satisfy Moore’s Law Courtesy, Intel


Clock Frequency :Clock Frequency Lead microprocessors frequency doubles every 2 years P6 Pentium ® proc 486 386 286 8086 8085 8080 8008 4004 0.1 1 10 100 1000 10000 1970 1980 1990 2000 2010 Year Frequency (Mhz) 2X every 2 years Courtesy, Intel


Examples of Cost Metrics (1994) :Examples of Cost Metrics (1994)


VLSI :VLSI Very Large Scale Integration design/manufacturing of extremely small, complex circuitry using modified semiconductor material integrated circuit (IC) may contain millions of transistors, each a few mm in size applications wide ranging: most electronic logic devices


Origins of VLSI :Origins of VLSI Much development motivated by WWII need for improved electronics, especially for radar 1940 - Russell Ohl (Bell Laboratories) - first pn junction 1948 - Shockley, Bardeen, Brattain (Bell Laboratories) - first transistor 1956 Nobel Physics Prize Late 1950s - purification of Si advances to acceptable levels for use in electronics 1958 - Seymour Cray (Control Data Corporation) - first transistorized computer - CDC 1604


Origins of VLSI (Cont.) :Origins of VLSI (Cont.) 1959 - Jack St. Claire Kilby (Texas Instruments) - first integrated circuit - 10 components on 9 mm2 1959 - Robert Norton Noyce (founder, Fairchild Semiconductor) - improved integrated circuit 1968 - Noyce, Gordon E. Moore found Intel 1971 - Ted Hoff (Intel) - first microprocessor (4004) - 2300 transistors on 9 mm2 Since then - continued improvement in technology has allowed for increased performance as predicted by Moore’s Law


Three Dimensional VLSI :Three Dimensional VLSI The fabrication of a single integrated circuit whose functional parts (transistors, etc) extend in three dimensions The vertical orientation of several bare integrated circuits in a single package


Advantages of 3D VLSI :Advantages of 3D VLSI Speed - the time required for a signal to travel between the functional circuit blocks in a system (delay) reduced. Delay depends on resistance/capacitance of interconnections resistance proportional to interconnection length


Advantages of 3D VLSI :Advantages of 3D VLSI Noise - unwanted disturbances on a useful signal reflection noise (varying impedance along interconnect) crosstalk noise (interference between interconnects) electromagnetic interference (EMI) (caused by current in pins) 3D chips fewer, shorter interconnects fewer pins


Advantages of 3D VLSI :Advantages of 3D VLSI Power consumption power used charging an interconnect capacitance P = fCV2 power dissipated through resistive material P = V2/R capacitance/resistance proportional to length reduced interconnect lengths will reduce power


Advantages of 3D VLSI :Advantages of 3D VLSI Interconnect capacity (connectivity) more connections between chips increased functionality, ease of design


Advantages of 3D VLSI :Advantages of 3D VLSI Printed circuit board size/weight planar size of PCB reduced with negligible IC height increase weight reduction due to more circuitry per package/smaller PCBs estimated 40-50 times reduction in size/weight


3D VLSI - Challenges and Solutions :3D VLSI - Challenges and Solutions Challenge: Thermal management smaller packages increased circuit density increased power density Solutions: circuit layout (design stage) high power sections uniformly distributed advancement in cooling techniques (heat pipes)


Influential Participants - Industry :Influential Participants - Industry Mitsubishi, TI, Intel, CTS Microelectronics, Hitachi, Irvine Sensors, others... high density memories AT&T high density “multiprocessor” Many other applications/participants


Three Dimensional VLSI :Three Dimensional VLSI Moore’s Law approaching physical limit Increased performance expected by market Paradigm shift needed - 3D VLSI many advantages over 2D VLSI economic limitations of fabrication overhaul will be overcome by market demand Three Dimensional VLSI may be the savior of Moore’s Law