Micro-scale Tensile Tester Update # 3 Cheng-Chieh Chao Maryam Ziaei-Moayyed Ranadeep Bhowmick Sujay Bangalore Ramachandra ME342 Spring 2006 Prof. Beth Pruitt

SU-8 dogbones SU-8 2 ( 2 µm) SU-8 5 ( 5 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 4exposures 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 3exposures 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 200 µm 20 µm Characterization: Thickness Exposure time Stiction

Dog-bone Release 1.Omnicoat Release Steps: Coat release layer (~ 30 nm thickness) 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.Electrolytic Release anode cathode sacrificial Al layer Si wafer SU-8 dog-bone Pt foil Schematic of the set-up for Al dissolution Steps 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 Su8 since its hydrophobic The sacrificial layer of Al removed by anodic dissolution ( 2 M NaCl in H 2 0; 0.5 V) Waiting for the results !! electrolytic solution

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 AD7746 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