Microscale Tensile Tester Update 3 ChengChieh Chao Maryam

Micro-scale Tensile Tester Update # 3 Cheng-Chieh Chao Maryam Ziaei-Moayyed Ranadeep Bhowmick Sujay Bangalore Ramachandra ME 342 Spring 2006 Prof. Beth Pruitt

SU-8 dogbones SU-8 5 ( 5 µm) SU-8 2 ( 2 µm) • Mask for the dog-bone structure (with the correct polarity/alignment) in hand • Processing: Substrate Pretreat Coat Soft bake [ 65 o. C 1 min; 95 o. C larger time to ensure that wafer does not stick to mask] Expose using Karlsuss Si substrate SU-8 2 ( 2 µm) 8 s; using 4 exposures of 2 sec duration SU-8 5 ( 5 µm) 25 s; using 10 exposures of 2. 5 sec duration Al substrate SU-8 2 ( 2 µm) 7. 2 s; using 3 exposures of 2. 4 sec duration SU-8 5 ( 5 µm) 22. 5 s; using 9 exposures of 2. 5 sec duration Post exposure bake Develop

Images of the Su-8 dog-bones Characterization: 200 µm Thickness Exposure time Stiction 20 µm

Dog-bone Release 1. Omnicoat Release Steps: Coat release layer (~ 30 nm thickness) Bake @ 200 o. C Coat, expose, post expose bake, develop SU-8 structures Strip SU-8 Immerse in Remover PG (NMP) at 80 o. C Disadvantage: Su-8 peels off but cannot retain its structural integrity and forms a gel like substance

Dog-bone Release 2. Schematic of the set-up for Al dissolution Electrolytic Release cathode anode electrolytic solution Pt foil sacrificial Al layer Steps Si wafer SU-8 dog-bone • Al layer of 500 nm thickness deposited on Si wafer • SU-8 is deposited/exposed/developed on top of the Al layer • Place another Si/glass wafer on top of the wafer with the dogbone structure to help prevent disintegration of Su 8 since its hydrophobic • The sacrificial layer of Al removed by anodic dissolution ( 2 M Na. Cl in H 20; 0. 5 V) • Waiting for the results !!

Actuator : Revised Process flow

Actuator Characterization:

Cell phone camera Image of the Actuator

Good exposure(1. 6 µm PR) Bad exposure(7 µm PR)

Sensing Circuit

Things to be done 1. Testing to be done with AD 7746 Evaluation Board 2. Start on the SOI wafers Pad-etch still needs to be characterized 3. Training required on : wire- bonding wafer saw nano-vac 4. Back up plan for CPD for releasing comb drive from the oxide layer

Thank You