The main contents of the chapter consist of the following: Introduction to semiconductor materials, summary of basic semiconductor devices, basics of IC processing.
COMSATS Institute of Information Technology Virtual campus Islamabad Dr. Nasim Zafar Electronics 1 EEE 231 Fall Semester – 2012 Summary 9/24/18 Dr Nasim Zafar Lecture No. 32 v Contents: Ø Introduction to Semiconductor Materials Ø Summary of Basic semiconductor devices Ø Basics of IC processing 9/24/18 Dr Nasim Zafar References Ø Microelectronic Circuits: Adel S. Sedra and Kenneth C. Smith. Ø Electronic Devices : Thomas L. Floyd ( Prentice Hall ). Ø Integrated Electronics Jacob Millman and Christos Halkias (McGrawHill) Ø 9/24/18 Electronic Devices and Circuit Theory: Robert Boylestad & Louis Nashelsky ( Prentice Hall ) Dr Nasim Zafar Introduction v Ø Ø From Discrete to Integrated! In 1954, Texas Instruments produced the first commercial silicon transistor. Before the invention of the integrated circuits, electronic equipment was composed of discrete components such as transistors, resistors, and capacitors. These components, often simply called “discrete”, were manufactured separately and were wired or soldered together onto circuit boards. 9/24/18 Dr Nasim Zafar Active Electronic Components v v An active electronic component either amplifies or switches – The most common active components are diodes and transistors – Both diodes and transistors are easy to make with semiconductors With semiconductor materials, it is possible to create complete circuits of active and/or passive components wired together. 9/24/18 Dr Nasim Zafar Integrated Circuits Ø Ø Ø Integrated circuits (ICs) are semiconductor devices that are complete circuits made up of transistors, diodes, capacitors, resistors and inductors. The complete circuit is made on a single piece of silicon called a chip Any circuit from a simple amplifier to a quad core microprocessor used in a PC can be made Dr Nasim Zafar Introduction to Semiconductor Materials v v Semiconductors are the materials with conductivity between conductor and insulator Its conductivity can be controlled by dopant concentration and applied voltage v Elemental Semiconductors: Silicon and Germanium v Compound Semiconductors: – SiGe, SiC – GaAs, InP, etc 9/24/18 Dr Nasim Zafar Introduction to Semiconductor Materials v v v v Boron doped semiconductor is ptype, majority carriers are holes P, As, or Sb doped semiconductor is ntype, the majority carriers are electrons Higher dopant concentration, lower resistivity At the same dopant concentration, ntype has lower resistivity than ptype 9/24/18 Dr Nasim Zafar Energy Band Structure of an Atom Valence shells Nuclei Conducting band, Ec Band gap, Eg Valence band, Ev 9/24/18 Dr Nasim Zafar 10 Characteristic Curves with DC Load Line Ø Ø Active Region: Qpoint, and current gain 9/24/18 Ø Point A corresponds to the positive peak. Ø Point B corresponds to the negative peak. Dr Nasim Zafar 51 Signals: Analog vs. Digital f(t) g(t) t t Analog: Analogous to some physical quantity 9/24/18 Dr Nasim Zafar Digital: can be represented using a finite number of digits 52 Transistor Biasing Circuits: Biasing Circuit Configurations: Ø 1. FixedBiased Transistor Circuits Ø 2. FixedBiased with Emitter Resistance Circuits Ø 3. VoltageDividerBiased Transistor Circuits 9/24/18 Dr Nasim Zafar 53 3. VoltageDividerBias Circuits: Ø Voltagedivider biasing circuit is the most widely used type of transistor biasing circuit Ø Ø Only one power supply is needed. and voltagedivider bias is more stable ( independent) than other bias types. 9/24/18 Dr Nasim Zafar 54 Summary of Semiconductor Devices MOSFETs D G B S 9/24/18 Dr Nasim Zafar 55 MOSFET Transistor Ø Metaloxidesemiconductor Ø Also called MOSFET (MOS Field Effect Transistor) Ø Simple, symmetric structure Ø Switch, good for digital, logic circuit Ø Most commonly used devices in the semiconductor industry 9/24/18 Dr Nasim Zafar 56 MOSFET Transistor v MOSFETs dominated IC industry since 1980s v Three kinds IC chips microprocessor, memory, and ASIC v Advantages of CMOS: low power, high temperature stability, high noise immunity, and clocking simplicity 9/24/18 Dr Nasim Zafar 57 MOSFETBasic Circuits 9/24/18 v NMOS v PMOS v CMOS Dr Nasim Zafar 58 MOSFETStructure Body B (bulk or substrate) Source S y Gate: metal or heavily doped polySi G Drain IG=0 D ID=IS IS Metal n+ oxide p n+ x W L 9/24/18 Dr Nasim Zafar 59 An Induced NChannel Figure 4.2: The EnhancementType NMOSFET Transistor A positive voltage applied to the gate. An n channel is induced at the top of the substrate beneath the gate 9/24/18 Dr Nasim Zafar 60 Summary: NMOS Operation VG > VT ; VDS 0 ID increases with VDS VG > VT; VDS small, > 0 ID increases with VDS , but rate of increase decreases VG > VT; VDS pinchoff ID reaches a saturation value, ID,sat The VDS value is called VDS,sat VG > VT; VDS > VDS,sat ID does not increase further, saturation region 9/24/18 Dr Nasim Zafar 61 NMOSFET Ø Faster than PMOS Ø Used for digital logic devices in 1970s and 1980s Ø Electronic watches and handhold calculators Ø Replaced by CMOS after the 1980s 9/24/18 Dr Nasim Zafar 62 CMOSFET Ø Most commonly used circuit in IC chip since 1980s Ø Low power consumption Ø High temperature stability Ø High noise immunity Ø Symmetric design 9/24/18 Dr Nasim Zafar 63 Summary Ø Ø Ø Ø As the microelectronics develops, more and more functions are fulfilled by IC chips The discrete devices and circuits, however, are still very important not only for practical applications, but also for better understanding and design of LSICs. Quantitative calculation is sometimes complicated but not difficult 9/24/18 Dr Nasim Zafar 64 As long as we know the parameter definitions clearly, results can Thank You 9/24/18 Dr Nasim Zafar 65 ... Dr Nasim Zafar 21 ForwardBiased Diode Circuit R R I F > 0A I F > 0A IF V IF V +V -V R R IF 9/24/18 Dr Nasim Zafar IF 22 ReverseBiased Diode Circuit R R 0A 0A IT IT V V +V -V R 9/24/18 R Dr Nasim. .. response, etc.). Dr Nasim Zafar 9/24/18 17 Ø Basic Devices: 9/24/18 v Diode: PN Junction v Bipolar Junction Transistor: BJT v MOS Transistor Dr Nasim Zafar 18 The Diode Anode 9/24/18 Dr Nasim Zafar Cathode...Summary 9/24/18 Dr Nasim Zafar Lecture No. 32 v Contents: Ø Introduction to Semiconductor Materials Ø Summary of Basic semiconductor devices Ø Basics of IC processing 9/24/18 Dr Nasim Zafar References