MultiMEMS MPW Design Introduction Course Part 2

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MultiMEMS MPW Design Introduction CoursePart 2

• Process Description - Part I

Prototype micro rate gyro from SensoNor
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Contents

• Process Description, Part I
• Cross section overview
• Key process features
• MPW process step-by-step
• Process Description, Part II
• Absolute limitations
• Process monitors
• Test data

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Cross section overview
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Feature 1 Buried Piezo-resistors

• Buried under epi-layer
• Used for long-term stability
• Sheet resistivity ca. 500 W/
• Cannot be used in epi-thick membrane

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Feature 2 Surface Piezo-resistors

• Diffused into epi-layer surface
• Offers highest sensitivity
• Sheet resistivity ca. 800 W/
• Particularly suited on springs

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Feature 3.1 Buried conductors

• Under epi-layer
• Contact to buried resistor
• Used for crossing anodic bonding area (top glass
  will not bond directly onto surface features)

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Feature 3.2 Surface conductors

• Implanted in epi-layer surface
• used to contact surface resistors and buried
  conductors or as ordinary interconnects

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Feature 4Wet Backside etch

• Electro-chemical etch-stop allows 3 different
  thicknesses
• full-wafer thickness (400 mm)
• e.g. heavy seismic masses
• epi-layer thickness (3 mm)
• thin membrane, springs
• n-well thickness (23 mm)
• thick membranes, masses, bosses,

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Feature 5Dry Release Etch

• Allows moving structures
• Gas/fluid flow through wafer
• Through epi-thick membranes only
• cuts through 6 mm thick Si

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Feature 5 Dry Release Etch

• Recesses/channels
• allowed design rule violation, 10 mm depth, not
  guaranteed

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Feature 6.1 Top Glass

• Single-sided structuring of top glass for
• Reference cavity formation
• Bond-pad area
• Allow movement of structures
• Gas/fluid channels

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Feature 6.2 Bottom Glass

• Double-sided structuring (through-wafer wet etch)
  of bottom glass
• Used e.g. as pressure inlet
• Single side cavity possible

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Feature 6.3 Glass bonding

• Triple-stack anodic bonding offers
• added functionality
• Reference cavity pressure
• Damping
• Overforce protection
• micro-encapsulation
• Media protection of front-side
• More robust handling
• Less package-stress sensitive

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Overview of process
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MPW Process (1)

• NOWEL
• n impl. diff.
• BUCON
• p impl. diff.

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MPW Process (2)

• BURES
• p impl. diff.
• n epi

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MPW Process (3)

• TIKOX
• 2 oxidations
• SUCON
• p impl. diff.

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MPW Process (4)

• SURES
• p impl.
• NOSUR
• n impl. diff

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MPW Process (5)

• COHOL
• oxide etch
• MCOND
• Al sputter pattern

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MPW Process (6)

• BETCH
• TMAH etch
• NOBOA
• oxide etch
• RETCH
• dry etch

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MPW Process (7)

• TOGE BOGEF BOGEB
• wet etching of glass anodic bonding
• Dicing

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Process Description

• End of this Chapter
• Questions or Comments?