Woodpile Structure Fabrication

1
Woodpile Structure Fabrication

• Chris McGuinness
• July 8, 2009
• Workshop on Novel Concepts for Linear
  Accelerators and Colliders
• Working Group 2 Dielectric Laser Accelerators

2
Outline

• Motivation
• Fabrication Process
• Fabrication Parameters
• Layer Adhesion
• Future Plans

3
Motivations
Sources
Gradient
Fabrication
4
Fabrication Process

• Step 1 SiO2 Deposition - LPCVD
• Uniformity 1-2
• Controllability 7
• Step 2 Resist Coat
• Step 3 Optical Lithography
• Minimum feature size 450nm
• Alignment 3s60nm
• Step 4 Plasma etch SiO2
• Step 5 Poly-si Deposition

5
Fabrication Process

• Step 6 Chemical Mechanical Polish
• Step 7 Repeat process for remaining layers
• Final Step HF Vapor Etch

6
Four Layer Test Structure
7
Fabrication Deviations
Parameter Summary
Target Measured
Rod Width 500nm 498nm 74nm
Tapper Angle 0o 10.4o 0.6o
Layer Thickness 632nm 611nm 73nm
Alignment Offset lt80nm 138nm
8
Tapper Angle
AMT 8100 - Hexode Plasma Etcher
CHF3 50 sccm O2 30 sccm
CHF3 85 sccm O2 6 sccm
5.1o
6.6o
P5000 -Magnetically Enhanced RIE
CF4 50 sccm CH3F 20 sccm Ar 100 sccm
CF4 50 sccm CH3F 25 sccm Ar 120 sccm
0o
3.4o
9
Rod Width
Measurement Resolution 25nm
10
Layer Thickness
Deposition LPCVD TEOS

• Uniformity 1-2
• Controllability 7

11
Layer Adhesion
12
Stress
13
(No Transcript)
14
Annealed WaferHF Vapor Etch
Not Annealed, Buffered HF Etch
Annealed, Buffered HF Etch
Annealed, Vapor HF Etch
Not Annealed, Vapor HF Etched
15
Measure Adhesion Strength
......
16
Future Direction

• Complete 15 layer structure
• Optical measurements
• Spectroscopy
• Coupling
• Mode excitation
• Beam measurements
• Wakefield modes
• Simulations
• Consider fabrication variations
• Couplers

17
THE END
18
FTIR Spectroscopy Measurements
19
Finite Thickness SimulationReflection/Transmissi
on(averaged over SP polarizations, and polar
angle ?, f0)
20
SimulationReflection/Transmission(averaged
over SP polarizations, and polar angle ?, f0)
21
Simulation vs. Measurement