V02 Process Technologies WS 23.pdf

V2 V02 Process Technologies for Microfluidic Chips Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 1 Contents V2 Contents 3.1 Introduction 3.2 SU-8 Processing 3.3 Soft-Lithography with PD...

V2 V02 Process Technologies for Microfluidic Chips Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 1 Contents V2 Contents 3.1 Introduction 3.2 SU-8 Processing 3.3 Soft-Lithography with PDMS 3.4 Bonding Technologies 3.4.1 PDMS - PDMS 3.4.2 Substrate Bonder 3.4.3 Feedthroughs Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 2 Learning target V2 Learning target  To know and to explain the major technologies for fabrication of microfluidic chips Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3 V2 3.1 Introduction Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 4 3.1 Introduction V2 Process Technologies for Microfluidic Chips Lithography Molding technology Etching using thick photoresists using soft silicone of glass SU-8 PDMS (HF* solution, Laser) Poly(dimethylsiloxane) HF*.. Hydrofluoric acid Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 5 3.1 Introduction V2 6 Etching of Glass Wet etching Laser (HF solution) Mask Glass HF solution Glass Polymer http://www.industrial-lasers.com/articles/ https://lightfab.de (in Aachen) Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3.2 Lithography with SU-8 3.2 Lithography with EPON SU-8 Negative Photoresist* * US Patent No. 4882245 (1989) by IBM Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 V2 7 3.2 Lithography with SU-8 V2 8 Lithography Process with SU-8 Wafer 1. Cleaning 2. Prebake UV light 6. Exposure 7. Post-Exposure Bake PEB (Hotplate) Photo resist SU-8 3. Coating 4. Softbake (Hotplate) 8. Development* 9. Postbake (Hotplate) 10. Process control Mask 5. Alignment * Developer: PGMEA (propylene-glycol-methyl-ether-acetate) Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3.2 Lithography with SU-8 https://www.youtube.com/watch?v=WAFE6pZBT9c&t=60s C.J. Lawrence: Phys. Fluids 31 2786-2795 (1988) D.B. Hall et al.: Polymer Eng. Sci. 38 (12) 2039-2045 (1998) Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 V2 9 3.2 Lithography with SU-8 V2 10 Photo Resist  Negative Positive (e.g. SU-8) (e.g. AZ - Novolack) Exposed areas are cross-linked in  PEB  Polymer structures in exposed areas will cracked under UV exposure In the development step the non-  No PEB is needed exposed areas will be dissolved  In the development step the exposed areas will be dissolved  Higher resolution Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3.2 Lithography with SU-8 V2 EPON™ SU-8 Available in Different Viscosities Type Viscosity Layer Thickness (max.) Selection 10-5 m2/s µm SU-8 2 4.5 5 SU-8 5 29 15 SU-8 10 105 30 SU-8 25 250 40 SU-8 50 1225 100 SU-8 100 5150 200 SU-8 2100 4500 250 SU-8 2150 8000 650 http://www.microchem.com Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 11 3.2 Lithography with SU-8 V2 How to Spin Coat a Thick Layer of Photo Resist - Principle of Gyrset RC8 from Suss Microtech RC8 from Suss Microtech www.suss.com Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 12 V2 13 Süss Video Spin-Coater 3.2 Lithography with SU-8 Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3.2 Lithography with SU-8 www.microchem.com Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 V2 14 3.2 Lithography with SU-8 V2 15 Basic Components of a Negative Photo Resist Resist Matrix (RM) Photo Acid Generator (PAG) Solvent Defines physical properties Defines photochemical properties Defines solvent power of RM and PAG in solvent  Solubility in developer  Wavelength of exposure  Stability in alkaline solutions  Light absorbing capacity  Stability in electroplating  Sensitivity  Temperature stability  Resolution  Resistance to etching  Viscosity  Layer formation Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23  Solubility 3.2 Lithography with SU-8 V2 16 SU-8 Resist matrix PAG Solvent EPON™ SU-8 Epoxy Triaryl-sulfonium- γ-Butyrolactone (Ts = 150 °C) resin hexafluorantimonate Cyclopentanon (Ts = 131 °C) 1,3 Dioxolan (Ts = 75 °C) Ts … Boiling point Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3.2 Lithography with SU-8 V2 17 Resist Matrix RM  EPON™ SU-8 Epoxy resin (Shell Chemical)  Consists of a glycidylether-derivate of bisphenol A  8 epoxy groups in one molecule (therefore the “8” at “SU-8”) formula according to N. LaBianca, J.D. Gelorme, Proc. SPIE 2438, 1995 Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3.2 Lithography with SU-8 V2 1. Cleaning 18 2. Prebake Wafer Photo Acid Generator PAG  During exposure, the activator PAG Photo resist SU-8 is generated in negative photo resists  Activator is responsible for cross-linking 3. Coating 4. Softbake (Hotplate) Mask of resist in PEB step 5. Alignment  Cross-linking proportional to exposure doses of light  Activator has influence on  Chemical and thermal stability of resist 6. Exposure 7. PEB  Shape of resist side walls 8. Development* 9. Post bake 10. Process control Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3.2 Lithography with SU-8 V2 PAG in SU-8  Triaryl-sulfonium hexafluorantimonate (around 10 wt.%)  UV exposure at 365 nm (I-line) results in release of fluor antimony acid (HSbF6)  HSbF6 acts as catalyzer  Provokes cross-linking of epoxy groups during PEB H+ Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 19 3.2 Lithography with SU-8 https://dr.ntu.edu.sg/handle/10356/5524 Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 V2 20 3.2 Lithography with SU-8 V2 21 + HA PAG in SU-8  During cross-linking  Reorientation of epoxy-groups Epoxy group  Generation of 3D network  Shrinking of film  Mechanical tensile stress  Cross-linking  Above glass temperature TgSU-8 in PEB step  TgSU-8 = 55 °C Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3.2 Lithography with SU-8 www.microchem.com V2 Spectral Distribution of Mercury Lamp Filter for λ < 350 nm necessary to prevent over-exposure at resist surface → negative side walls, T-topping Intensity (a.u) I-line (365)  I-line 22 G-line (436) H-line (405) Deep UV ( 10 µm were not possible (they were Advantages of SU-8  Processing with standard UV-lithography  Layer thicknesses > 500 µm possible  Aspect ratio > 100 possible  Transparent  Biocompatible Drawbacks of SU-8  Resist removal  Mechanical stress SSLS' strategic partner CAMD, Baton Rouge, Louisiana only optimized for high-resolution semiconductor structures) Microstructures in 1000-µm SU-8. The bridges intersecting the cylindrical structures are 10 µm wide yielding an aspect ratio of 100. The inside lamellae are only 5 µm wide yielding an aspect ratio of 200. Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3.2 Lithography with SU-8 V2 Exp. SU-8 SiO2 Si wafer Micro Channel Fabrication with SU-8 Exp. SU-8 Glass wafer Unexp. SU-8 Exp. SU-8 S. Tuomikoski et al.: Sensors and Actuators A 120 (2) 408-415 (2005) Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 26 3.2 Lithography with SU-8 Other Properties of SU-8  High resistance to chemicals   Good mechanical properties   High thermal stability   High optical transparency   Biocompatible   Auto fluorescence  Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 V2 27 3.2 Lithography with SU-8 http://www.microchem.com Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 V2 28 3.3 Soft-Lithography with PDMS V2 29 chem8.org 3.3 Soft-Lithography Transfer of micro and nano structures by printing using soft stamps Developed to transfer structured surface assembled G.M. Whitesides (1939*) http://gmwgroup.harvard.edu/ monolayers (SAM) to planar surfaces Introduced by A. Kumar, G.M. Whitesides: Appl. Phys. Lett. 63 2002-2004 (1993) Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3.3 Soft-Lithography with PDMS V2 Soft-Lithography =  Manufacturing of elastic PDMS* stamps +  Transfer of stamp structures to surfaces by printing * PDMS: Poly(dimethylsiloxane) Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 30 3.3 Soft-Lithography with PDMS Soft-Lithography  Manufacturing of elastic PDMS stamps with micro/nano structures * PDMS: Poly(dimethylsiloxane) R.S. Kane et al.: Biomaterials 20 (22-24) 2363-2376 (1999) Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 V2 31 3.3 Soft-Lithography with PDMS V2 www.eulitha.com PDMS Stamp Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 32 3.3 Soft-Lithography with PDMS V2 33 Soft-Lithography  Transfer of stamp structures to surfaces by printing SAM … surface assembled monolayer e.g. alkanethiol, is carrier for chemical/biological functionality G.M. Whitesides et al.: Annu. Rev. Biomed. Eng. 3 335-373 (2001) Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3.3 Soft-Lithography with PDMS Poly(dimethylsiloxane) en.wikipedia.org PDMS V2 Silicone (H3C)3Si [SiO(CH3)2]n Si(CH3)3  Colorless  Chemically inert  Transparent  Known in cosmetic products  Non-toxic  Biocompatible Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 34 3.3 Soft-Lithography with PDMS V2 PDMS Poly(dimethylsiloxane) Sylgard 184 Elastosil RT 601 A/B Dow Corning Wacker Chemie AG Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 35 3.3 Soft-Lithography with PDMS V2 PDMS 2 Components A B Pre-polymer with Pt catalyst Cross-linking agent Mixing* Typical mix ratio A:B = 10:1 @ RT under vacuum Cross-linking / Vulcanization* @ (480‘ / RT) or (45’ / 100°C) or (20’ / 125°C) or (10’ / 150°C) * for Sylgard 184, similar recommendations for Elastosil RT 601 Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 36 3.3 Soft-Lithography with PDMS Cross-linking Mechanism Prepolymer Cross-linking agent J. Roth: Funktionaliserung von Silikonoberflächen, Dissertation TU Dresden (2009) Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 V2 37 3.3 Soft-Lithography with PDMS V2 38 Properties of PDMS (Sylgard 184)  Young’s modulus around 1 MPa  Optically transparent for λ » 300 nm  Thermal conductivity 0.2 W/mK  Shore A hardness 50  Coefficient of expansion 310 ppm 1/°C  Disruptive strength 540 V/mm  Temperature stability - 45°C … 200 °C  Hydrophobic surface Contact angle H2O » 110° http://www.elveflow.com  Viscoelastic material  Surface can be made hydrophilic with O2 plasma treatment (contact angle H2O » 10°)  Relatively permeable for non-polar gases (e.g. O2, N2, CO2)* * G. Firpo et al.: J. Membrane Sci. 481 1-8 (2015) Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3.3 Soft-Lithography with PDMS V2 Soft-Lithography RM µCP MIMIC μTM TM Replica Molding MIcroMolding In Capillaries µ Contact Printing µ Transfer Molding Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 39 3.3 Soft-Lithography with PDMS V2 Most important 40 molding Master mold Master mold wmin = 30 nm wmin = 30 nm wmin = 1000 nm wmin = 250 nm N.C. Lindquist et al.: Rep. Prog. Phys. 75 036501 (2012) wmin … Smallest structure width published Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3.3 Soft-Lithography with PDMS Replica Molding for Fabrication of Microfluidic Channels A. Sengupta et al.: Liquid Crystals Reviews 2 (2) 73–110 (2014) Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 V2 41 3.3 Soft-Lithography with PDMS V2 42 http://www.youtube.com/watch?v=Acm_bH413wk L. Bulut et al.: Comustion and Flame 154 206-216 (2008) Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 physics.arizona.edu Microcontact Printing - µCP 3.3 Soft-Lithography with PDMS V2 43 Soft-Lithography Pros Cons  Cheap  No clean room processing needed  Simple processing  Small portion of waste (additive process)  Suitable for rapid prototyping  Large freedom in designs hydrophilic/hydrophobic behavior in  Printing on curved surfaces possible micro channels  When contact pressure is to high, deformations of small structures occur (micro contact printing)  PDMS needs more effort to control  Partly incompatible to organic solvent Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3.4 Bonding Technologies 3.4 Bonding Technologies Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 V2 44 3.4.1 PDMS-PDMS or PDMS-Glass Bonding V2 45 3.4.1 Bonding of PDMS-PDMS or PDMS-Glass  Gluing  Heating over glass temperature Tg  Thermal compression  Ultrasonic PDMS  Laser welding !  Plasma (surface modification) Glass / PDMS Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 3.4.1 PDMS-PDMS or PDMS-Glass Bonding Bonding  Reversible PDMS-Glass Bonding PDMS layer adhere to SiO2 surfaces up to a pressure of 0.35 bar without glue  Irreversible 1. Oxygen plasma (mostly used) reactive OH-groups are formed at the surface 2. Concentration gradient (only for PDMS-PDMS bonding) Variation of components A and B Cross-linking at interface through temperature treatment Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 V2 46 3.4.1 PDMS-PDMS or PDMS-Glass Bonding ims.ut.ee Oxygen Plasma Treatment of PDMS Surface  Methyl groups (Si-CH3) replaced by silanol groups (Si-OH)  Hydrophobic surface is replaced by hydrophilic surface  Plasma-treated surfaces are only 10 min stable in air Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 V2 47 3.4.1 PDMS-PDMS or PDMS-Glass Bonding ims.ut.ee Bonding of O2 Plasma-treated PDMS Surfaces  Covalent bonding  Works also for SiO2 surfaces - PDMS Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 V2 48 3.4.2 Substrate Bonder V2 3.4.2 Substrate Bonder In some cases an aligned bonding is necessary Substrate Electrode Substrate bonder Side wall channel Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 49 3.4.2 Substrate Bonder Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 V2 50 3.4.2 Substrate Bonder Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 V2 51 V2 blogs.rsc.org PDMS Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 sybbure.org blogs.rsc.org 3.4.3 Feedthroughs in PDMS-based Channels 52 blogs.rsc.org 3.4.3 Feedthroughs Conclusion V2 Conclusion V3  Two technologies to realize polymer-based microfluidic channels  Photo lithography with SU-8  Molding / Soft lithography with PDMS  Both materials are biocompatible  Structure dimensions down to nm-range possible  Can be combined with thin-film processing Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 53 V2 One Minute Paper 1. What was the most important topic you understood? 2. What was the topic you didn‘t catch? Lecture „Microfluidic Systems - Bio-MEMS“ – V02 Process Technologies Prof. Dr.-Ing. Uwe Schnakenberg | Institute of Materials in Electrical Engineering1 | WS 23 54