University of California, Santa Barbara ME/ECE 141 B LAB 3 (FINAL LAB): In this lab, you will fabricate an entire device from beginning to end using all the steps you learned this quarter using the mask that you designed. The most important part of this lab report is the careful and thorough reporting of everything that you did, so that we can inspect the chips afterwards, recreate your steps, and assign you the proper grade. Please keep track and write down everything that you did, every step along the way, and finally document with as many figures as possible. Process Overview: Step 1: Hard mask deposition, lithography, metal etch, microchannel etch, and hard mask removal 1. Use&E‐Beam&evaporator&to&deposit&500&Å& of&Chromium&and&500&Å&of&Gold&following&the&detailed&procedure&below.&&Bob$will$help$you$with$the$E‐beam$eva porator$–$Make$s ure$you$are$properly $trained .&2. Sol vent&clean&your&s amples&and&spin& positive& tone&photoresist,&following&the&procedure&describ ed&b elow.&&Expose&photor esist&with&the&microchannel&pattern&and&develop.&3. Use&Gold&et chant&to&etch&the&Gold&then&C hrome&etcha nt&to&etch&the&Chrome.&&&a. From&Etch&Rates&for&Micromachining &Processing‐&Part& II&(Williams,&Gup ta,&Wasil ik&2003)&i. Gold&Etch:&AU‐5&etches&gold& at&~660n m/min&ii. Chrome&Etc h:&CR‐7&etches&chrom e&at& ~170nm/min&iii. Chrome&Etch:&CR‐14&etches&chrome&at&~93nm/min&Ask$Bob&for &further&detailed& instructions&and&safety&precautions.&4. Inspect &wafer&(and&t ake&pictures)&to&ensure&that&you&have&etched&a ll&the&way&throug h&the&metal.&&5. Leaving&the&photoresist&on&the&sample,&etch&your&sample&approximately&10 &microns&in&Buffered&HF&(BHF).&The&etch&rate&of&BHF&for&glass&slides&is&~1.13&µm/min.&&Immerse&the&chip&in&DI&for&1&minute &before&you&place&it&in&HF.&Thi s&prevents&bubble&formation&and&ensures&uniform&etch ing&i n&HF.&PLE ASE& READ&SAFETY&INFORMATI ON&REGARDING&HF&ETCHING&(on&web)&PRIOR&T O&THIS&S TEP.&6. Strip&off&Au&using&th e&Gold&etch&and&Cr&using&Chrome&etch.&&Step 2: Lithography using the metal mask pattern, metallization and lift-off 1. Sol vent&clean&samples&and&spin&positive&tone&photore sist&(See &below&for&process&details).&2. Align&the&metal&mas k&pattern&(darkfield)&to&transfer&the&electrode&pattern&to&the&sample s.&See&Bel ow&for&the&detailed&p rocess&st eps.&Remember&that&there&is&an&additi onal&toluene&soak&step&involve d&he re.&Also&the&exposure&and &develop&times&required&are&longe r. 3. Pre pare&the&evaporator&to&ev aporate&500&Å&of&Titanium&and&500&Å&of&Gold.&Bob$will$help$you$wit h$the$E‐beam$evaporator.&4. Lift‐off&the&undesired&metal&by&placing&the&sa mples&in &Acetone.&Be&extr eme ly&gentle &or&a ll&the&me tal&may&come&off.&5. Strip&off&the&photoresist&in&acetone&and&then&rinse&the&samples&in&isopropy l&alcohol&and&DI&H2O.& Step 3: PDMS preparation and channel sealing1. Pre pare&a&10:1&mixture&of&PD MS&base &to&curing‐ag ent&in&a&disposable&metal &tray.&&Prepare&enough&to&cover&a&glass&slide&by&3‐5mm.&2. Place&a&blank&glass&s lide& in&anoth er&disposable&tray&and&po ur&PDMS&ont o&it.&3. Put&into&vacuum&chamber&to&remove&bubbles.&4. Place&a&cover&to&reduce&evap oration&and&cure&on&the&hot&plate&or&o ven&at&&80C&for&10&minutes&5. Allow&it&to&cool& to&room&temperature.&6. Use&a&razor&blade&to&cut&out&a&rectangular&piece&larger&than&the&fluidic&pattern.&7. Use&the&biopsy&punch&to &cut&access&holes&in&the&PDMS &above&each&of&the&micro channel&reservo irs.&8. Descum&with&O2&plasma,&align&access&holes&to&the&reservo irs&and&bond.& Step 4: Experiments within channels and efficient reporting See below for details. Detailed processing steps: Chip handling 1. Use&gloves&while&handling&the&chip.&2. Using&the&diamond&tipped&scribe,&make&a&small&‘G’&scratch&at&the&edge&on&the&back&side&of&the&chip.&This&is&done&becau se&the&chips&are&trans parent&and&a &mark&he lps&in&disting uish ing&t he&top&side&du ring& processing.&3. &Avoid&scrat chin g&the&front&surface&of&the&chip&‐&al ways&place&the&chip&on&a&clean&wipe.&&4. It&might&take&some&t ime& in&getting&used&to&holding&the&chips.&&Chip Cleaning 1. Place&the&chips&to&be&cle aned&in&a&chip&holder&and&the n&immer se&in&a&beaker&containing&Acetone(&ACE&).&Keep&the& beaker&in&the&ultrasonic&cleaner&for&3&minutes.&2. Repeat&for&3&minutes&in&beaker&of&Isopropyl&a lcoh ol&(&ISO&)&in&the&ultrasonic&cleaner.&3. Rinse&the&chip&in&deionized&(DI)&water.&&4. Blow&dry&with&N 2&.&5. Dehydr ate&i n&125&de g&C&oven&if&going&directly&to&lithography.&&Note: 1. The&cleaning&solutions&c an&b e&reused &several&time s.&All&the&groups&will&share&the&same&set&of&cleaning&solvents,&so&be& careful&not&to&contaminate&the&so lutions.& &2. In&case&the&existing&cleaning&solv ents&need&to&be&repla ced,&dispose&them&in&the&appropriate&container‐&Do$n ot$pour$solvents$ down$th e$drain.&&3. All&beakers&in&the& lab&must&be&labeled&correctly.&Beakers&are&color&coded&to&prevent&cross‐contamination,&please&do&not&us e&for&oth er&purposes.$ Optical lithographyThe following detailed procedures given here are for optical lithography using AZ 4110, which is a positive photoresist. Spin on Photoresist 1. Place&cleaned&chips& on&the&aluminum&tray,&place&the&tray&on&the&aluminum&block&in &the& furn ace.&&Dehydr ation&bake&for&3&minutes&at&120&°C .&2. Place&chips& under&the&HMDS &vapor&deposition&hood&for&1‐3&minutes.&3. Place&a&dummy& chip &on&the&spinner&and&set&the&sp inner&speed&at&4000&RPM.&This&is&to&check&if&the&spinner&vacuum &is&on&and&other&t hing s&are&working&as&expe cted .&4. Place&the&actual&sample&on&the&spinner&and&p ut&on&a&f ew&drops&of&the&r esist&till&all&o f&the&chip&is&covered.&5. Spi n&the&chip&at &4000&RPM.&6. Pre ‐bake&for&1&minute&at &85&°C&on&the&hot&plate.&Exposure using MJB-3 mask aligner 1. Turn&on&<POWER>&2. Slide&out&m ask&holder&and&put&the&correc t&mask&in&wit h&the&chrome&sid e&facing&the&chip.&3. Put&your&chip&on&the&chuck&a nd&slide& tray& under&m ask&4. Rotate&lever&to&raise&chuck.&Make&sur e&you&actually&are&in&<CONTACT>.&5. Put&chip&in&<SEPERA TION>an d&align&mask&to&your&pattern,&(if&needed)&6. Set &exposur e&<TIMER>&(UV=7.5&mW/cm2)&recommended&for&resist&in&use&(17‐25&seconds).&F or&AZ&4110,&this&time&is &20&s econds.&7. Bring&chip&and&mask&in&contact&a nd&press&<EXPOSE>&8. Lower&chuck&and&remove&your&chip.&Developing (AZ 400K ) 1.