CONFIDENTIAL
Minimum Undercut for UBM Etch
John Taddei
Director of Process Engineering Development
April, 2019
Rev Nov 18
Who is Veeco Precision Surface Processing (PSP)?
Advanced
Packaging
50 Years of Leadership
in Wet Processing Technology and Innovation
>3,000 System Shipments
Extensive Global Presence
MEMS
Solvent
3 Product Platforms
Wireless (RF)
WaferStorm® / WaferEtch® / Brush Cleaner
Standard and Tailored Solutions
Customer Oriented Focus
Etch
Power
Electronics
Seasoned and Accomplished Team
LED
114 employees
Data Storage
Equipment Assembly & Test
In Horsham, PA
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Confidential
Clean
World Class Applications Expertise
Horsham, PA Lab
 Full Process Capability
 Solvent
 Etch
 Clean
Team of Highly Experienced
Scientists
Complete Metrology Suite
 Ability to quantify results
immediately
 Qualify performance relative to
customer requirements
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UBM and RDL Etch
Process Metrics
 Complete seed layer etch
 Complete barrier layer etch
 Minimum Undercut (bump integrity)
 Etch Uniformity
 Low COO
 Throughput
 Chemical Costs
 Waste Costs
UBM
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RDL
Advanced Packaging Process Flow
Deposit
passivation
layer
Clean,
deposit barrier
and seed layers
Define
passivation
layer
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Lithography:
resist applied,
exposed, and
developed
PR Strip
UBM Etch
Bumps
plated
Reflow
(Solder)
Resist stripped,
barrier and
seed layers
etched
Under Bump Metal Etch (UBM)
Undercut Minimization Tools1-Arm scan hyperbolic motion for uniform clearing
2-Process Monitor to stop immediately
3-Selective chemistry
4- Chemistry Management (COO)
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WaferChek® Process Control for Endpoint Detection
Process Monitor Benefits
 Uniform Minimum Undercut
 Higher Throughput
 Longer Chemical Life
 Less Waste Generation
 Immediate Process Feedback
 Actionable
 Chemical Management
 Alarms
 Messages
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UBM Etch – Cu and TI\TIW
Goal: Etch Depth Equal to Undercut
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Comparison of Wet Process Tool Results
Immersion
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Low End Single Wafer
PSP Wafer Etch
Poor Uniformity
Poor Etch Rate Control
No Endpoint
Modest Uniformity
Modest Etch Rate Control
No Endpoint
Best Uniformity
Best Etch Rate Control
Endpoint
100+% Over etch
Highest Undercut
High Chemical Usage
75% Over etch
Large Undercut
Moderate Chemical Usage
Minimum Over etch
Minimum Undercut
Low Chemical Usage
Confidential
Increased density for Bumps
Current Products
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Future
UBM Etch - Smaller bumps & higher density
20µm
Pitch
Before Cu Etch
After Cu Seed Layer Etch
10µm
Pitch
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Confidential
Degradational Fluid Mixing Arm
Peroxide Properties
 H2O2 degradation, especially when heated. Short
chemical life whether tool is in operation or standby
 400 A\min etch rate limited by 40C temperature
Veeco Solution
 Mix 80+\- .2C DI Water and 20+\- .2C H2O2 at
dispense point in arm in 5:1 ratio (DIW:H2O2)
70C 1:5
mixture
etches wafer
80C DI
Water
 Resultant mixture is at 70C with temperature control
 Resultant mixture etches wafer at 3x etch rate of
40C H2O2 (1,250 A\min)
 Etchant is sent to drain and NOT recycled to tankeliminates standby peroxide use and recycle
degradation risk
20C
H2O2
WaferEtch: Key Features and Benefits
Features:
 Chemical reclamation
and reuse
 Collection ring
 Hyperbolic arm
motion
 Uniform cross-wafer
dispense
 Adaptive spiking
 Consistent chemical
concentration
 Automatic endpoint
detection
 Etch termination using
in-situ wafer monitoring
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Confidential
Benefits:
 > 99% reduction of
chemical waste
 Versus single-pass approach
 < 1% etch non-uniformity
 By means of optimized, nonlinear motion profile
 Enhanced wafer-to-wafer
etch uniformity
 Chemical spiking based on
measured concentration
 Markedly reduced undercut
and up to 40% lower CoO
 Relative to alternative UBM
etch technologies
Target Markets
• Advanced Packaging
• MEMs
• Wireless/RF
• Power Electronics
• Solid-State Lighting/LED
• Photonics
Primary Application Suite
• UBM Etch
• Wafer Thinning
• TSV Reveal
CONFIDENTIAL
Thank You
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Confidential