EE412 Project: Corrosion resistant ALD coatings Alex Haemmerli and Joey Doll Mentor: J Provine

Corrosion in MEMS/NEMS Devices Chemical corrosion Electrochemical corrosion M. Hon et al. Sens. and Act. A (2008)

Common Passivation Options From “Corrosion behavior of parylene-metal-parylene thin films in saline”, W. Li et al, ECS Transactions (2008) Thermal oxidation LPCVD dielectrics PECVD dielectrics LPCVD polymers (parylene) 5um thick parylene C 90C saline Failure via moisture diffusion Considerations – Conformality/thickness (NEMS) – Moisture permeability – Electrical properties (breakdown, leakage) – Mechanics (modulus, residual stress) – Deposition temperature

Proposed Project Characterize the corrosion resistance of ALD oxide films (Al 2 O 3, HfO 2, ZrO 2 ) in ionic solution – Film composition, thickness, and laminates Experiment variables – Solution (focus on saline) – pH, time, temperature, voltage Performance metrics – C-V stability – Leakage current – Impedance stability

Project Scope Equipment to be used – Savannah (trained) – Oxidation (thermco/tylan) – Metal dep (gryphon) and ALD film thickness (woolam) – Patterning (ASML, karlsuss1/2, wetbenches, p5000) – Dicing (wafersaw) – Probe station and electronics (Pruitt lab) SNL equipment desired – SEM and/or FIB (trained) – Maybe XPS (trained) Materials required – 5-10 wafers Budget – Transparency mask (<$20 or free) – AgCl reference electrode (<$100 if required, probably not)

Project Timeline Week 0: This document Week 1: Plan process flow and masks, perform design of experiments, finish training Weeks 2-3: Process and dice test wafers, deposit initial ALD films Weeks 4-5: Develop measurement setup, perform initial measurements Weeks 6-10: More test wafers, ALD and experiments

Process Flow Oxidize wafer Deposit 250nm Al (gryphon) Litho (karlsuss) Etch (wbmetal/p5000) – (optional) Undercut and roughen (pad etch) Frontside protect, wafer saw, strip resist ALD deposition

Measurement Setup -Reference electrode (e.g. AgCl) required? -Not shown: impedance analyzer and C-V connections -Test structure size effects (defects) – big, medium, small? -Keep resistor impedance > 1kOhm

Experiments and Data Reduction Variables – Single layer film composition (HfO, ZrO, AlO) – Film thickness (start with 10nm) – Solution pH (start with pH 7) – Temperature (start with room temp) – Bias potential (start with 1V) – Bias time (1 hour, 24 hours) Data reduction – Impedance/leakage vs. time – % change in impedance/leakage from start to end