Undergraduate Research Spring Semester Summary

1
Undergraduate Research Spring Semester Summary

• Evan Lintz
• Dr. Xing
• May 2008

2
Spring Semester Project

• ICP System
• Fundamental etching principles
• ICP etching of GaN
• Diodes made on etched GaN

3
Plasma Etching Overview

• Plasma Based Dry Etching RF power to drive
  chemical reactions

Tianhong Cui Dr. Bruce Gale (University of
Utah)
4
Plasma Etching Overview

• Advantages
• No handling of dangerous chemicals
• Isotropic or anisotropic etch profiles
• High resolution and cleanliness
• Better process control
• Ease of automation
• Less undercutting
• Smoother etches

Tianhong Cui Dr. Bruce Gale (University of
Utah)
5
Plasma Etching Overview

• Plasma
• Partially ionized gas consisting of equal number
  of ions and electrons and a different number of
  neutral molecules
• Formation
• RF energy applied to a pair of electrodes in
  evacuated chamber with gas
• Electrons collide with neutral molecules form
  ions and more electrons until steady state
  reached
• Plasma ionization recombination

Tianhong Cui Dr. Bruce Gale (University of
Utah)
6
Plasma Etching Overview

• Reactive Ion Etching (RIE)
• Chemical etching is accompanied by ionic
  bombardment (combination of physical and chemical
  etching)
• Increases etch rate
• Structural degradation
• Lower selectivity
• Only one control point

Tianhong Cui Dr. Bruce Gale (University of
Utah)
7
Plasma Etching Overview

• RIE Disadvantages
• Tradeoff between etching rate and anisotropic
  profile
• Tradeoff between damage of high etching rate and
  anisotropic profile
• Solution Inductively Coupled Plasma (ICP)

Tianhong Cui Dr. Bruce Gale (University of
Utah)
8
Plasma Etching Overview

• ICP Overview
• Uses electron cyclotron resonance source to
  supplement RIE system
• Magnetic field used to enhance transfer of energy
• Two RF power generators to control ion kinetic
  energy and ion density separately
• Thus can use lower or higher energy ions
• Less Damage than RIE
• Unconstrained Geometry (90 Sidewall)
• Higher Selectivity than RIE High aspect ratio

Magnetic Field
Tianhong Cui Dr. Bruce Gale (University of
Utah)
9
ICP Etching of GaN

• Test designed to calibrate new ICP system

Apply PR Alpha-Step
Etch in ICP Alpha-Step
Remove PR Alpha-Step
PR
PR
PR
GaN
GaN
10
ICP Etching of GaN

• ICP Etch
• BCl3 (16sccm) 1min 5/250W (RIE/ICP) to etch
  oxide
• Cl2 (32sccm) 4 sec (8/400W) to strike the
  plasma
• Cl2 etch all using ganetch program 5/250W
• 5mT, 25C GaN Cl2 GaCl3 NH3
• John Simon ran tests for 1,2,3,6,12 Minutes
• I ran test for etches of 5,10,15,20 Minutes

PR
PR
GaN
John Simon (University of Notre Dame)
11
ICP Etching of GaN
John Simon (University of Notre Dame)
12
ICP Etching of GaN

• 1 Minute

• 6 Minute

• 3 Minute

John Simon (University of Notre Dame)
13
ICP Etching of GaN
John Simon (University of Notre Dame)
14
Diodes Made on Etched GaN

• Diodes Made
• Same structures on 0,5,10,15,20 Minute Etches

15
ICP Etching of GaN (my results)

• SEM- 20 Minute Etch

John Simon (University of Notre Dame)
16
ICP Etching of GaN (my results)

• SEM of 20 Minute Etch

John Simon Kevin Goodman (University of Notre
Dame)
17
Diodes Made on Etched GaN
18
Diodes Made on Etched GaN

• No Pattern
• Ideality Factor 1.1

19
Diodes Made on Etched GaN

• Significant Leakage on Diode

Chuanxin Lian (University of Notre Dame)
20
Diodes Made on Etched GaN

• Reasons for Leakage
• Contaminated Nickel Source
• Thermal Evaporator Instead of E-Beam
• No Schottky Barrier
• Leaks
• Diodes may be too close together

21
Conclusions

• Research this Year
• LPCVD SiN
• ICP
• Fundamental etching principles
• ICP etching of GaN
• Diodes made on etched GaN
• Thank you to everyone for your help!

22
Comments?