課程名稱 ：微製造技術 Microfabrication Technology

授課教師 ：王東安 Lecture 1

Lecture 1 1 Course Overview

•Lecture 1 Introduction to microfabrication •Lectures 2-4 Lithographic techniques •Lectures 5-6 Vacuum science and etching •Lectures 7-10 Thin film processes •Lectures 11-12 Micromachining processes •Lecture 13 MEMS devices Textbook: Stephen A. Campbell, The Science and Engineering of Microelectronic Fabrication, Oxford University Press, 2001 Reference: M. J. Madou, Fundamentals of Microfabrication, CRC, 2002

Lecture 1 2 Goals of this course

•Introduce microfabrication techniques •Perspective on MEMS research and devices

Lecture 1 3 Related Courses at IPE

•Thin film engineering 薄膜工程 •Nano fabrication technology 奈米加工技術 •Epitaxy engineering 磊晶工程

Lecture 1 4 Course Mechanics

•Lectures: Monday 9:10-noon M106 精密館 •Homework: Due the following Monday at 9:10am •Exam: Two midterms and Final exam •Oral Report: Select one research paper related to microfabrication, approved by the instructor. Present the paper at the end of the term.

Lecture 1 5 Course Mechanics (Cont.)

•Office hours: R358 電機大樓 Mondays 2-3pm •Credit breakdown (approximate) 20% homework 20% midterm I 20% midterm II 20% final exam 20% oral report

Lecture 1 6 Lecture Outline

•Reading Campbell: Chapter 1 •Today’s lecture –Definition of MicroFabrication –Historical tour of microfabrication –Fabrication process of microelectronics –Substrate material •Phase diagram •Crystal structure •Czochralski growth •Wafer specifications

Lecture 1 7 Definition of MicroFabrication

•Fabrication of devices with at least some of their dimensions in the micrometer range. •Techniques: –IC methods –Micromolding –Wire electrodischarge machining –Laser machining –Ion- and electron-beam machining –CNC milling

Lecture 1 8 History of Batch Fabrication Technology

•Planar integrated circuit technology 1958 – •Thin film deposition and etching •A few m on top of the substrate •CMOS integrated circuits technology enables the development of MEMS by 1980

Lecture 1 9 Progress of Silicon Microelectronics

• Density increase by increments of 4X every 3 years. • Most fundamental changes in the fabrication process: Minimum feature size can be printed in the chip. • Shorter distances that electrons and holes travel improve transistor speed. • Pack transistors together, decrease the parasitic capacitance. • ICs progressed from 10 um to under 1 um.

Lecture 1 10 Example-A Resistor Voltage Divider

•A re

Lecture 1 11 Example-Fabrication Process

•Substrate: Silicon wafer •Grow a thermal oxide of Silicon to prevent leakage between resistors •Deposit a conducting layer for resistors

Lecture 1 12 Photolithography

•Transfer pattern from photomask to wafer •Optical lithography: spread photoresist on wafer, expose photoresist, develop, Etch the film without significantly attack the resist. •After etching, rinse wafer, remove resist.

Lecture 1 13 Unit Processes for Thin Film Deposition •Sputtering: using charged articles of ions to bombard a target containing the deposition material. The target erodes and falls onto the wafer. •Evaporation: Heating material to be deposited to create a vapor stream, coating wafer placed in the stream. •Chemical vapor deposition: Gasses are flown into a chamber containing heated wafer. A chemical reaction occurs that leaves the desired film on wafer.

Lecture 1 14 Doping –n-channel MOSFET

•A blanket insulator •A patterned metal layer •Selectively dope source and drain regions. •Dopants are donors (n-type) or acceptors (p-type)

Lecture 1 15 Doping Techniques

•Diffusion: introduce impurities by exposing heated wafer to a dopant containing gas. •Ion implantation: Accelerate a beam of ionized atoms/molecules toward the wafer.

Lecture 1 16 Epitaxial Growth

•Grow thin layers of semiconductor on top of the wafer.

Lecture 1 17 Roadmap of the Course

Lecture 1 18 Why Substrate Matters?

•Diffusion depends on crystalline perfection in wafer, which in tern depends on process temperature. •Solid solubility and the doping of semiconductors crystals •Crystal structures and defects in crystalline materials •Three classes of materials: single crystal, amorphous materials, polycrystalline

Lecture 1 19 Phase Diagram

•Most materials are mixtures of materials. •Phase diagram: a way to present properties of mixtures of materials

Lecture 1 20 Ex. 2.1 Calculate fraction of 50% charge that is molten at 1150oC •x: fraction of the charge that is molten •1-x: fraction of the charge that is solid •0.5=0.22*x+0.58*(1- x) •x=0.22 •22% of the charge is molten, 78% is solid

Lecture 1 21 Phase diagram for GaAs

•Intermetallics: two solid phases that melt to form a single liquid phase •Compound GaAs

Lecture 1 22 Phase diagram for As-Si

•Solid solubility: Maximum concentration of an impurity that can be dissolved in another material under equilibrium conditions •Solvus curve •Solid solubility of As in Si is comparatively large->As can be used to form very heavily doped and low resistance regions such as source and drain contacts for MOS transistors

Lecture 1 23 Solid solubility of Si impurities •Doping concentration exceed solid solubility by quenching.

Lecture 1 24 Three types of cubic crystals

•Direction: [xyz] •Plane: (xyz) •Equivalent planes: {xyz}

Lecture 1 25 Three types of cubic crystals

•Cubic symmetry: with each edge of the unit cell being the same length. •In a crystal with cubic symmetry, (100) (010) (001) planes have the same properties, the only difference is an arbitrary choice of coordinate system.

Lecture 1 26 Diamond structure: Si, Ge

•Group IV elements: need 4 more valence electrons to complete their valence shell. In crystal, this is done by forming covalent bonds with 4 nearest neighbor atoms.

Lecture 1 27 Semiconductor defects

•Four types of defects –Point •Vacancy •Interstitial •Substitution impurity •Dislocation: sign of stress –Line –Area –Volume

Lecture 1 28 Movement of edge dislocation •Result of shear stress

Lecture 1 29 Area defect

•Stacking fault

Lecture 1 30 Lecture 1 31 Czochralski growth

•The technique to produce most of the crystals from which wafers are cut –Solidification of a crystal from a melt

Lecture 1 32 Lecture 1 33 Bridgman growth of GaAs

Lecture 1 34 Lecture 1 35 Lecture 1 36 Lecture 1 37 Wafer specification •Primary flat: perpendicular to <110> direction •Minor flat:

Lecture 1 38 Lecture 1 39