ECECS 697 Compound Semiconductor Fabrication Laboratory

1
ECECS 697 Compound Semiconductor Fabrication
Laboratory

• Web-based service for support of classes.
• Enter at http//blackboard.uc.edu
• Login and select course
• Access
• Syllabus and related information at Course
  Information
• Slide presentations, homework, etc. at
  Course Documents
• Course announcements will be posted at
  Announcements

2
ECES 697 Compound Semiconductor Fabrication
Laboratory

• Goal To introduce the engineering and
  technology of III-V semiconductor device
  fabrication, fabrication process design and
  device and process characterization.
• Prerequisites undergraduate course in
  semiconductor materials and devices.
• Text None, handouts and copies of
  transparencies provided.
• Format
• Weekly lecture with handouts
• Weekly lab with GaAs MESFET fabrication project
• Assignments 15
• Lab notebook 20
• Final test 30
• Final project report 35

Source Gate Drain VS 0 VG
lt 0 VD gt 0
-





-
-




-
-
-
-
-
Semi-insulating GaAs substrate
3
Course Overview and Motivation

• Why interest in GaAs MESFETs?
• High speed microwave circuits.
• Simple fabrication process (no epitaxy).
• Low cost.
• Why study the fabrication of GaAs MESFET?
• Introduce device fabrication process
• Simple fab process
• Understand fab process capabilities and
  limitations
• Complete fab process for MESFET
• Evaluate results of process steps
• Characterize finished devices
• Acquire skills in device fabrication
• Experimental thesis or dissertation work
• Future job
• What are the commercial applications?

4
Submicron Channel GaAs MESFET
Source
Source
Drain
Gate
Gate
Channel width W
Drain
Source
Source
Channel length L
Source
Gate
5
GaAs MESFET Capabilities

• High electron mobility in GaAs channel
  gives high drain current ID and
  transconductance gm
• High electron mobility in GaAs channel
  gives short transit time and high speed
• Channel transit time
• Cutoff frequency fT

Lg
B. Turner, Ch 10 in GaAs Materials, Devices and
Circuits, Wiley, p. 361 (1985).
6
GaAs MESFET Performance
HEMT
C. W. Tu et al., Ch 4 in GaAs Technology, p. 107
(1985).
7
GaAs MESFET Commercial Applications

• Microwave integrated circuits
• Low noise preamplifiers
• Linear and power amplifiers
• Oscillators and mixers
• Applications
• Satellite communications
• Cellular phones
• Local area networks
• Optoelectronic Integrated Circuits
• Receivers
• Low noise preamplifiers
• Linear amplifiers
• Transmitters
• Laser driver amplifiers

8
Microwave Integrated Circuits
9
Optoelectronic Integrated Circuits
Compound Semiconductor vol. 6 (3), p. 55, April
2000.
10
Course Organization and Overview

• Lecture
• One to two hours weekly (Tuesday)
• Summarize process steps for next stage of device
  fab.
• What is to done. What is expected. What to be
  measured. What calculations and analysis.
• Present some theoretical background on processes
• Outline important measurements, calculations and
  analysis of results.
• Lab
• Four hour lab session weekly (Wednesday or
  Thursday)
• Initial demonstration of process and equipment
  use.
• Wafer processing
• Student groups of two or three
• Evaluation of results

• GaAs MESFET Fabrication
• Mask design
• Silicon nitride deposition
• Photolithography
• Mask alignment
• Optical exposure
• Resist development and processing
• Ion implantation
• SiN etching (wet and RIE)
• Metallization
• Ohmic contact
• Schottky contact
• Liftoff process
• Rapid thermal annealing
• MESFET characterization
• Test structure measurements

11
GaAs MESFET Fabrication Process
12
Course Schedule
13
Course Requirements and Grading

• Final Lab Report (35)
• Executive summary of device fab and results
  obtained
• Prepared by each student group (2 or 3)
• Typewritten, organized, well written
• Overview of fab process
• What was done, what achieved, what expected, what
  problems, what results, why
• Stand alone, inclusive of all results
• Process measurements and results
• Calculations, graphs and analysis
• Comparison with theoretical calculations and
  analysis of differences from measurements
• Summary of results, e.g. process successes or
  sources of problems, performance of device,
  analysis of test structure results.

• Lab Notebook (20)
• Keep notes from fab
• Key equipment settings and notes on operation
• Important observations, measurements,
  calculations and analysis
• Graded
• Lab Assignments (15)
• Weekly report on lab results
• Organized, neat
• Observations, measurements, example calculations
  and analysis of results.
• Final Test (30)
• Exam week
• Knowledge of fab process
• Theoretical calculations
• MESFET measurements
• Test structure operation and use