EE412: EVG Spraycoater Characterization Project Owner: Mahnaz Mansourpour Project Mentor: Jason Parker Student Investigator: Ehsan Sadeghipour 1/12/2011

Target: The target is the conformal coverage of wafers with 30 um and 50 um deep features. Conformal coverage will be defined as 3 um thick +/- 0.5 um. The features on half of the wafers will be based on a mask provided by Mahnaz Mansourpour, and the other half will be based on a mask provided by Ehsan Sadeghipour. Machines: 1. stsetch for features – Qualified 2. spraycoater for coating – Qualified 3. Wafer saw for dicing – Qualified 4. Hummer for conductive layer deposition – Need Training Characterization tools (qualified on all already): 1. Optical Microscope – A “first look” at conformality of coverage 2. Nanospec – A “first look” at thickness of resist 3. SEM – A detailed look at coverage conformality, resist thickness, and pull-back 4. Contact Angle Measurement – Measure hydrophobicity of different pretreatments Spraycoater Characterization Experimental Plan

Thicknesses to try: um um Features to try: 1. Mahnaz Mansourpour’s test features 2. Ehsan Sadeghipour’s device features Resist: Start with SPR220-7:MEK:EL (11.4:60.6:28 & 8:57:35) in week 3 and narrow choice further from there Variables Studied: 1. Resist Mix 2. Nozzle Pressure 3. Number of Passes 4. Velocity Profile Spraycoater Characterization Experimental Plan

Assumptions: 1. With ventilation improvements temperature and humidity in lab will remain constant. 2. Any variation in temperature and humidity will have negligible effects on the process. 3. Nozzle pressure, resist mix, and nozzle speed will be reproducible over project length. Success Criteria: 1. Keeping up with the agreed upon schedule of throughput 2. Adjusting experimental plan on weekly basis to account for previous week’s learning 3. Goal is to reach 3 um thick +/- 0.5 um by the end of the quarter. Measurement tool: SEM tool in SNF 1. Measure minimum point of coverage and maximum point of coverage 2. Goal: Minimum of 2.5 um and maximum of 3.5 um 3. Resolution: 0.1 um 4. Anticipated data points: 6 thickness measurements per sample (location on next slide) 5. Qualitative notes: i. Resist pooling at corners, ii. Pullback at edges, iii. Wall coverage 6. Anticipated errors: i. Parallax, ii. Charging (reduced by cleaving & metalization) Spraycoater Characterization Experimental Plan

Wafer Setup: Resist Measurement: Spraycoater Characterization Experimental Plan MM – 30 um 2.ES – 30 um 3.MM – 50 um 4.ES – 50 um 2. Pullback 6. Outside Corner Thickness 4. Inside Corner Thickness 1. Top Thickness 3. Bottom Thickness 5. Wall Thickness

Schedule: Week 1: Logistics Week 2: STS Etch 8 Wafers Week 3: Mix two resists. Spraycoat six wafers using two resists and three pressures. Week 4: Characterize Week 3 wafers. Spraycoat three wafers using 3, 5, and 10 passes using best resist mix of week 3. Week 5: Characterize Week 4 wafers. Try four velocity profiles to find best option. Week 6: STS etch 8-20 new wafers with patterns as needed. Week 7: Characterize wafers with new resist formulations. Week 8: Characterize wafers with wider range of nozzle pressures. Week 9: Characterize number of passes or velocity profile. Week 10: Data analysis and writing report. Spraycoater Characterization Experimental Plan