PiezoMEMS Foundry to Support Research Projects Naomi Montross, Joe Evans, Gerald Salazar, Spencer Smith, Bob Howard, Radiant Technologies, Inc. 2019 International Workshop on Acoustic Transduction Materials and Devices May 7, 2018

Radiant Technologies has completed the first test wafer of its I-Beam piezoMEMS process. Radiant will accept capacitor or piezoMEMS foundry projects from universities and organizations to run on this process.

Introduction Objective of the I-Beam Process Description of the Process Example Devices Project Flow Contact Info

Objective of the Foundry Service Shift the focus from the complexity of piezoMEMS fabrication to more important issues associated with device design and performance . Reduce the time and cost to complete the fabrication of piezoMEMS or integrated capacitor designs. Generate higher yield to increase the population of functional devices available in a project. Provide a path to physically plug piezoMEMS and integrated capacitor circuits directly into analog or digital control circuits.

Overview of Process Flow The three fundamental steps of the process flow: Fabricate the solid state capacitors atop the wafer. Deposit the metallic I-Beams above the capacitors and pattern them into the geometry of the final mechanical structures. Execute a single through-wafer DRIE step to remove all silicon from beneath the I-Beams. The process utilizes thick metal layers above the actuator and sensor capacitors to create robust structures.

Process Flow Simple Repeatable Robust Affordable Fast High Yield Start with thin PZT Capacitors Execute backside DRIE etch Deposit I-Beam Simple Repeatable Robust Affordable Fast High Yield

From Layout…to Device… Through-wafer hole Cantilever

Calibrated. Error = 1.13m/V x 0.1Vpp = 0.11m …to Test… Etched backside well seen through transparent PZT/SiO2 layers. Electrodes PZT Thirty second loop of 1m 4/20/80 PNbZT measured with AFM. Calibrated. Error = 1.13m/V x 0.1Vpp = 0.11m

…to Package If the die is 1.7 millimeters on a side or smaller, it will fit in a TO-18 transistor can. If the die is larger than 1.7mm, Chrome/Copper/Gold solder pads on the die allow soldering directly to printed circuit boards. Radiant uses an SOIC format on a 3.4mm x 3.4mm die floor plan

Thermal Silicon Dioxide Solid State Module Exploded view of a Radiant integrated PZT capacitor. FE TE VIA ILD M1 BE VIA PZT Passivation Substrate Thermal Silicon Dioxide MIRROR Electrodes Patterned BE FE overlap of BE Edge Combine PZT/Glass passivation for reliability.

Advantages of Radiant’s Capacitor Stack FE ILD M1 Silicon substrate Mirror, I-Beam, Sensor Patterned Bottom Electrode provides more flexible device design. Ferroelectric material overlap of BE edge prevents TDDB arising from etch damage at the ferroelectric boundary. ILD Passivation improves reliability and capacitor survivability in post processing. ILD allows non-circuit metal layers to be positioned above the capacitor.

Uniformity & Yield No shorts out of 64 capacitors across two wafers. 1m-thick - 100,000m2 - 4/20/80 PNbZT - Platinum electrodes

Example Device Membrane with Center Mass Backside

Example Device Dual Strings Backside

Example Device Tuning Fork

Example Devices

Project Flow Radiant provides a GDS II file of the STARTW project. STARTW includes the wafer boundaries, alignment marks, and an assortment of design-rule-compliant cells such as vias, capacitors, solder pads, etc. that are building blocks for larger structures. Customer executes design. Radiant conducts a final design review of the project, acquires masks and fabricates the wafers. Finished dice are be submitted to the researcher. Radiant advises on testing.

StartW Wafer 4” Wafer Boundary Alignment Marks Cell Library

Contact Please contact Naomi Montross or Joe Evans at Radiant Technologies in Albuquerque. +1-505-842-8007 radiant@ferrodevices.com *** Put “Foundry” in the Subject Line to route it to Radiant’s clean room. This PowerPoint file will be on-line at www.FerroFoundry.com