PolyMUMPs process
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Transcript of PolyMUMPs process
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Introduction to MEMS Design &
Micromachining
Chapter 1(Three Layer PolySi Surface Micromachining Process)
Reference:PolyMUMPs Design Book Version 11.0
Dr Shafaat Ahmed
HEC Foreign Professor
Center for Advanced Studies in Engineering,
Islamabad, Pakistan
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1 Basic Micromachining Steps
Wafer
Deposition/
Growth Lithography Etch
MEMS
Chips
Steps in fabrication cycle
Basic steps: Deposition/Growth, Lithography, Etch
Other steps: doping, bonding, annealing,
Integrated Circuits and MEMS steps Identical
Process complexity/yield related to central loop
Reference: Chapter 8 from Hsus book
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2 Micromachining Classifications
Bulk Micromachining
Surface MicromachiningLIGA (X-ray lithography, electro-deposition, and molding)
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2.1 Bulk Micromachining
Bulk micromachining is a process based on etchingwells in the silicon, glass or any other substrate,leaving suspended structures by anisotropic andselective etching.
Deposit thin films on substrate and pattern themlithographically, Selectively etch away a portion ofthe substrate to form a free standing 3-Dmicrostructures bound by a cavity
Typically wet etching and relatively less expensiveequipment
Anisotropic etchants: KOH, EDP (Ethylene-Diamine-Pyrocatechol), TMAH (Tetra-Methyl AmmoniumHydroxide)
Isotropic Etchants:
HF (nitric and acetic acids, difficult to work with),
XeF2, BrF3(gas phase, gentle)
Echants demonstrate different etch rates in differentcrystal directions
etch rate is slowest, and fastest
Fastest:slowest can be more than 400:1
Etch stops: p+ silicon, p-n junction
Etch mask: SiO2, Si3N4
Issues with IC compatibility
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2.1 Bulk Micromachining
CMOS compatible Bulk Micromachining Supported CAN-MEMS post-process from 1997-1999 MITEL1.5, Supported since 1995. Last Run in August 2001
Presently some universities have the post-processing capability
Deposition of Pt and Si3N4layer on Bonding pads of CMOS Mitel1.5
Back side etching maskWafer Front Side Opening
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2.1 ProtolyneTM Technology from
Micralyne
Low cost proto-typing technology on glass
substrate for microfluidic applications. Design of Microchannels Courtesy ofRichard Oleschuck,
Queens University
Glass
Substrate
Bottom Plate
Etch
Holes=1.5 mmDeposit Mask
Pattern Mask
Litghography
Etch Channels in
Glass Substrate
Remove
Mask Layer
Etch Holes on
Top Plate= 2 mm
Etch Holes on Top
Glass Plate= 2 mm
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2.1 Bulk Micromachining- Examples
SEM photo of an etched cavity plus
an oxide arrow: (rectangulargeometry in (100) plane of Si wafer
Piezo resistive flow sensor fabricated by
anisotropic wet chemical etc. Slantedetched side walls (111) plane orientation
CMOS compatible bulk micromachining
suspended inductor
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Deposit thin films on substrate and pattern them lithographically, Selectivelyetch away one or more intermediate thin films to release a free standing 3-D onthe top of the substrate.
This leaves the wafer untouched, but add/remove layers above the wafersurface
2.2 Surface Micromachining
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2.2 Surface Micromachining Issues
Gear Train, Courtesy of Ash Parameswaran, Simon Fraser
University
CMOS compatible release etchant (HF) which does not attack Si
High temperature annealing to remove residual stresses from PolySi. DamageIC metalization
Release layer provides electrical isolation between electrostatic device elements
Typically Plasma etched and relatively expensive equipment
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2.2 Surface Micromachining Materials
Structural Sacrificial Etchant
PolySilicon Silicon Dioxide HF
Silicon Dioxide PolySilicon XeF2
Aluminium Photoresist O2Plasma
Photoresist Aluminium Al etch
Aluminium Single Crystal
Silicon
EDP, TMAH, XeF2
Poly-SiGe Poly-SiGe DI water
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3. Poly-Multi User MEMS Processes (Poly-MUMPs)
MUMPs: A Surface
Micromachining Process
3 Poly silicon layers
1 metal layer
2 Oxide Layers
1 Silicon Nitride layer
Multi ProjectWafer
More information on MUMPS:
http://www.memscap.com/
Ref: PolyMUMPs Design Book
http://www.memscap.com/http://www.memscap.com/ -
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3.1 PolyMUMPs Process Overview
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3.1 Step-by-step development of PolyMUMPs Process Layers
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3.1 Step-by-step development of PolyMUMPs Process Layers
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3.1 Step-by-step development of PolyMUMPs Process Layers
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3.1 Step-by-step development of PolyMUMPs Process Layers
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3.1 Step-by-step development of PolyMUMPs Process Layers
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3.1 Step-by-step development of PolyMUMPs Process Layers
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3.1 Step-by-step development of PolyMUMPs Process Layers
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4.1 MEMS Development in PolyMUMPs
Provides access to standard and reliable technology
to develop MEMS structures at reasonable cost
Process has fixed set of rules: material. Layer
thickness, gaps.
Designer has to converge his design to PolyMUMPs.
Keep in mind, dont expect PolyMUMPs to fulfill your
design requirements
Multi Project
Wafer
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5.1 Some design developed in PolyMUMPs Process
Heat ctuator based microgrippers
Poly1 is used as structural layer for gripper and heat actuators Poly2 and Metal is used for interconnections Pads are used for electrical probing the heat actuators during testing Not necessary to use all layers
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5.1 Some design developed in PolyMUMPs Process
ccelerometer
Si Nitride is used to isolate the device from substratePoly0 is used as base electrodePoly1 is used as structural layer to make the proof mass and springsPoly2 combined with Poly1 to increase the thicknessEtch holes on Poly2 layer ensure fast removal of sacrificial layer
Pads are used for electrical probing during testing
4 1
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4.1 PolyMUMPs in L-Edit
Menu bar Standard toolbar
Locator
Status bar
Drawing toolbar
Layer
palette
Mouse
button bar
MEMS Pro toolbar
Place & route
toolbar
Verificationtoolbar
Editing
toolbar
3D model
toolbar
Layout Area
4 1 L P l tt
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4.1 Layer Palette
Layer Name
Layer Palette
Scrollbar
3 Parts: names, icons, scrollbar
Used to display & select activelayer.
Mouse button functions on
icons:
Left: select layer
Middle: hide/show layer
Right: hide/show/lock/unlock
individual or all layers.
Each step (deposit, etch,
mask) of PolyMUMPs processhere is represented by a
LAYER NAME with specific
color
4 2 S t T h l Fil
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4.2 Setup Technology File
L-Edit uses a 256-color palette.
Each file has its own colorpalette.
These are colors that can beused to represent objects in that
file. Click on the color/code on the
left to select the color to edit.
Color: displayed color
Code: a 4-bit binary code to
represent the color. Composition: RGB (red, green,
and blue) component of the color(0-255).
Setup> Palette L-Edit command)
color code composition
4 2 Set p Design Technolog
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4.2 Setup DesignTechnology
Specify Technology name.
Specify Technology units Microns
Millimeters
Centimeters
Mils
Inches Other
Specify relationshipbetween L-Edit internalunit(used for calculation)and Technology unit.
Rescaling options:
Maintain physical size ofobjects
Rescale the design
Technology Unit
4 2 Setup Layers
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4.2 SetupLayers
Setup > Layers (L-edit command)
Setup Layers Layers List
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Setup LayersLayers List
First 7 layers (Layout Gridthrough
Error Layer) are Special LayersforL-Edit system objects.
The rest are custom layout layers.
To edit a layer: select a layer from
the list box.
To add a layer: click Add layer.
To remove a layer: click Delete layer.
To rearrange layers: click
or
buttons.
Name of the highlighted layer can
be specified in the Layer namebox: