Semiconductor Modelling

1. Semiconductor Modelling Eli Drew Shazz

2. Semiconductor History • 1600 to 1800 – research in electrical and magnetic phenomena • 1876 – Telephone invented • 1880 – Light Bulb • 1897 – Radio, electron was identified. • Early Vacuum tube era (WWII), audio systems and radio • Vacuum tubes today – TV picture tubes, monitors, high frequency transmitters, microwave power tubes.

3. History Contd. Semiconductor Era • First transistor 1947 • First single Crystal Germanium 1952 • First single crystal Silicon 1954 • First IC device, TI, 1958 • First IC Product, Fairchild Camera 1961

4. Why Semiconductors? • Why not? • Although many electronic devices can be made using vacuum tube technology, the developments in the semiconductor field in the past 50 years has made electronics, smaller, faster and more reliable. • Microwave oven • electronic balance • Video Games • Radio • Television • VCR • Watch • CD Player • Stereo • Computer • Lights • Air Conditioner • calculator

5. Understanding Silicon • A very commonly used element. • Main element in sand and quartz. • In the periodic table it sits next to aluminum, below carbon and above germanium.

6. Understanding Silicon • Carbon, silicon and germanium each have four electron in their outer orbital which allows them to form nice crystals. • A pure silicon crystal is nearly an insulator. • Doping silicon or introducing impurities • N type : phosphorus or arsenic ( 5 outer electrons) • P type : boron or gallium ( 3 outer electrons)

7. Creating a Diode A diode is the most simplest possible semi conductor. A device that blocks current in one direction while letting current flow in another direction is called a diode.

8. Creating a transistor • It takes three layers rather than two. • It can be either PNP or NPN sandwich. • It can act as a switch or an amplifier. • It looks like two diodes back to back. • First transistor invented at Bell Labs on December 16, 1947 by William Shockley, John Bardeen & Walter Brattain.

9. Advantages of transistor • Compared to vacuum tubes • Smaller • Lighter • Less Power Consumption • More Rugged • Lower Voltages • Less Heat • Greater Reliability

10. Semiconductor Crystals • Regular ordered arrangement of atoms over a large scale. • Lattice and a basis • Lattice : ordered arrangement or points in space • Basis : simplest arrangement of the atoms which is repeated at every point in the lattice.

11. Use of semi-conductors • Automotive Industry • TPM – Tire pressure monitoring (since 2004) • The loud in your alarm clock. • Data zooms through a bunch in your cell phone when you get a call. • An Mp3’s menu system, also responsible for turning your digital music into sound in your ear bud.

12. Semiconductors in Space • Electronics are required to operate in high-radiation environment resulting from particles trapped in planetary magnetic fields, galactic cosmic rays, or high energy protons. • Military equipment needs to withstand any bursts of hostile nuclear explosions.

13. Semiconductor failures • Primary effects include : • TID (Total Ionizing Dose) creates bulk-oxide and an interface trap charge that reduces the operating properties. • SEE (Single Event Effects) happens when a cosmic ray or a very high energy particle impinges on a device. • Results in radiation-hardened technology – special steps in materials, process and design.

14. Gallium Arsenide Semiconductors • GaAs • made up of Gallium and Arsenic • Conducts electricity faster than silicon • Ability to emit light and make less noise over most other semi-conductors. • Slow production times and high cost

15. Basic Trend • Smaller transistors (Up to 100M per chip now, over 1 billion before 2010) • More complex circuit chips. • Complete system on a chip. • Continuous declining cost of transistors. ($1 – 1968, .01 – 1976, .00001 – 1992) • Higher frequency operation • Higher switching speeds 3 GHZ now, 10 GHZ by 2010)

16. Got Crystal? Scientists trying to develop semiconductor “alloy crystals” propose growing in space. • They possess highly desirable thermoelectric and electro-optic properties. • Impossible to grown on earth. • Germanium is 3 times heavier than silicon and sinks to the bottom of the melt in the crucible, destroying desired homogeneous concentration in the crystal.

17. Is gravity at home? • These crystals take up to 14 days to grow. • In the absence, the ingredients don’t separate readily and the molten material tends to pull away from the container shortly. • Not sure about how commercial this will get, but John Walker and his colleagues would like to show that growing crystals in space can yield better crystals consistently.

18. Major technological breakthrough(1997 – 2000) • From 2009 onwards, circuits will be created by exposure to extreme ultraviolet rays (EUV). • Today processors are fabricated using 90-nanometer technology. • EUV lithography uses radiation with wavelength of only 13.5 nano.

19. Challenges • This huge leap also brings challenges with it such as developing completely new light sources, optical components and photoresist finishes. • Entire lithographical process has to be performed in a vacuum since EUV is absorbed by all materials including air. • Multi layer mirrors have to be used. • The crux of this lithography is to have an efficient and economic EUV source available.

20. References • http://britneyspears.ac/lasers.htm • http://www.theautochannel.com/news/2005/03/29/022963.html • http://www.destinationdigital.org/node/3 • http://www.ieee.org/organizations/pubs/newsletters/npss/june2000/semi.htm • http://electronics.howstuffworks.com/diode4.htm • http://www2.austin.cc.tx.us/HongXiao/overview/history-semi/ • http://www.sciencedaily.com/releases/2000/06/000602074630.htm • http://www.azom.com/news.asp?newsID=2265 • http://pchem1.rice.edu/~arb/research.htm#alum