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Cleanroom Facilities: Experience from an User Cleanroom Facilities: Experience from an user Mark Ming-Cheng Cheng Electrical and Computer Engineering Wayne State University Detroit MI USA [email protected] WAYNE STATE UNIVERSITY Cheng Cleanroom 8/2 Thin Micro/NanoFilm Deposition Fabrication Microfabrication is the term that describes processes of fabrication of miniature structures, of mironmeter sizes and smaller. Historically the earliest microfabrication processes were used for integrated circuit fabrication, also known as “ semiconductor manufacturing ”, ” microelectronic fabrication ”, ” VLSI technology ”. 65nm 2 cores; Introduced 2006 291 millions transistors 1.8 ~3GHz Die size 111mm 2; 65W WAYNE STATE UNIVERSITY Cheng Cleanroom Thin Micro/NanoFilm Deposition Fabrication In the last two decades, microfabrication has been used in many research fields, including * Micro Electromechanical System (MEMS) * RF MEMS (resonators, filters, switches, phase shifters) * Microfluidics/ Lab-on-Chip * Bio MEMS * Solar cells * Flat panel display * NEMS WAYNE STATE UNIVERSITY Cheng Cleanroom EnablingThin Film Deposition Technology in iPhone Microphone Accelerometer GPU (graphic processor) 45nm WAYNE STATE UNIVERSITY Cheng Cleanroom ThinHow Film Deposition to Make Sandwiches? Add bread Cut bread Cut vegetables Place vegetables … METHOD AND APPARATUS FOR MAKING A SANDWICH International Publication Number WO 2006/068865 AW Section (54) WAYNE STATE UNIVERSITY Cheng Cleanroom How to Make Devices? /etching pMOS Deposition Module Photolightography Module (Pattern Transfer) Etching Module WAYNE STATE UNIVERSITY Cheng Cleanroom Materials Semiconductor Insulator Metal (Si, C, SiC, GaAs ) (SiO 2, Si 3N4,glass, (Au, Pt, Al, Cr, Ti, Ni..) polymer, ceramics) WAYNE STATE UNIVERSITY Cheng Cleanroom Thin Film Deposition (overview) 0 I. Furnace (Few hundred~1100 C, atmosphere): SiO 2, P++ II. Low Pressure Chemical Vapor Deposition System (LPCVD): polycrystalline Si, amorphous SiO 2 III. Plasma Enhanced Chemical Vapor Deposition System (PECVD): amorphous Si, nitride, SiO 2 IV. E-beam Evaporator : metals (Al, Cr, Cu, Au, Ni, Pt, Ti, Mo),Si, Ge V. Sputtering: Target Ti, Al, Al with 1%Si, 1%Cu), Mo, Au, Pt, Ta, Ni, Co, Cr, Si, Pyrex, ITO Gas Ar, N 2, O 2 WAYNE STATE UNIVERSITY Cheng Cleanroom Furnace Few hundred~1100 0C, atmosphere Thermal oxide (dry): excellent electrical property, 10nm~300nm S i + O 2 → S i O 2 Thermal oxide (wet): 100nm~1-2µm Boron diffusion (BN source):boron doping, P++ etching stop Metal annealing (N 2 gas) WAYNE STATE UNIVERSITY Cheng Cleanroom Low Pressure Chemical Vapor Deposition I . Polysilicon 600 o C SiH 4 → Si + 2H2 Pressure 50-150Pa Deposition rate 100~200 0A/min, 600~650 0C Polycrystalline Si ~2µm Polysilicon is widely used as metal gate in CMOS as well as structural layers in MEMS . II. Low temperature oxide (LTO) 400 o C SiH 4 + O2 →SiO 2 + 2H2 WAYNE STATE UNIVERSITY Cheng Cleanroom Plasma Enhanced Chemical Vapor Deposition Reaction Gas SiH 4, NH 3, N 2O Power max 400W Temperature 25~300 0C Deposited Materials α-Si : gas SiH 4 Si xNy: gas SiH 4, NH 3 Si xOy: gas SiH 4, N 2O SiO xNy: gas SiH 4, NH 3, N 2O Typically used for depositing passivation layers Deposition rate 400 0A/min (deepening on power and temp) WAYNE STATE UNIVERSITY Cheng Cleanroom E-beam evaporator x2 wafers Two evaporators: BJD, FC Available sources: metals (Al, Cr, Cu, Au, Dual Guns with 4 pockets Ni, Pt, Ti, Mo),Si, Ge Substrate heating ~250 0C * There will be additional material fee for Au and Pt WAYNE STATE UNIVERSITY Cheng Cleanroom Photographic Process WAYNE STATE UNIVERSITY Cheng Cleanroom Photolithography “ Print with the light” Cr mask in contact with wafers Light sensitive film Contact Aligner Provide alignment in x,y,z directions Exposure resolution ~0.8µm WAYNE STATE UNIVERSITY Cheng Cleanroom Photolithography (steps) I. Spin-coating PR II. Soft Bake III. Alignment/ Exposure IV. Developer (Selectively remove PR) WAYNE STATE UNIVERSITY Cheng Cleanroom SU-8 SU-8 ( from Microchem) A viscos polymer that can be spin- coated and produce microstructures Negative Photoresist Thickness 1~300µm Microstructures with high aspect ratio 20 WAYNE STATE UNIVERSITY Cheng Cleanroom Thin Film Etching (Overview) I. Wet etching, isotropic etching: Au etch, Al etch, Cr etch, Ni etch II. Wet etching, anisotropic etching (bulk micromachining): TMAH etch III. Metal Lift-off VI. RCA clean: wafer cleaning V. Dry etching, anisotropic etching LAM etcher ( polysilicon, nitride, SiO 2) DRIE (silicon); high aspect ratio silicon microstructures. VI . Dry etching, isotropic etching Drytech (PR, PDMS) XeF 2 (silicon) WAYNE STATE UNIVERSITY Cheng Cleanroom Wet etching I. Isotropic Si HNO 3:HF:CH 3COOH Substrate orientation II. Anisotropic (110) Si TMAH, KOH Crystal Plane Orientation (111) Si WAYNE STATE UNIVERSITY Cheng Cleanroom DRIE (Deep Reactive Ion Etching) Bosch Process Silicon etch rate 0.6-0.7µm/loop; 3-4 µm/min Mask: PR, SiO 2, Al WAYNE STATE UNIVERSITY Cheng Cleanroom Drytech Dry Isotropic etching of polymers (Oxygen plasma, Asher) Reaction gas: O 2, Ar, CF 4 Power Max 300W Oxygen plasma is widely used for (1)Substrate cleaning (2)Removal of PR (3)Removal of polymer/organic materials (4)PDMS bonding WAYNE STATE UNIVERSITY Cheng Cleanroom XeF 2 Xenon Difluoride (XeF2) Etching • Home-made equipment (Cheng, Xu) • Dry, Isotropic etching of Si 2XeF 2 + Si →2Xe + SiF 4 • High selectivity for Al, SiO 2, Si 3N4,PR,PSG • Typical etch rates of 1 to 3 µm/min • XeF 2 reacts with water (or vapor) to form HF WAYNE STATE UNIVERSITY Cheng Cleanroom Other Capabilities Packaging Wafer Bonder Dicing Saw Wire Bonder Characterization Surface Profiler Interferometer WAYNE STATE UNIVERSITY Cheng Cleanroom On-Going Projects Dr Yong Xu (Joined Wayne State 2002) NSF ECCS A novel 3-dimensional neural probe technology combining electrical and chemical interfaces (PI) NSF CMMI Collaborative Research: Fish-Inspired Ultra-Sensitive Infrasound Sensor for Critical Infrastructure Monitoring and Geo-Hazards Early Warning (PI) NSF ECCS CAREER : Wearable accelerometers for continuous respiratory sound monitoring (PI) NIH R21 Development of a neurotransmitter based epiretinal prosthesis (co-PI) NSF CBET Neurophysiologically-based computational platform for the characterization and optimization of retinal prosthetic stimulation (Co-PI) Dr Amar Basu (Joined Wayne State 2008) NSF CBET Microfrationation in Droplets (FD) - Linking Proteomic Separations to High Throughput Functional Screening (PI) Dr Mark Ming-Cheng Cheng (Joined Wayne State 2008) NSF CBET CAREER : A Robust, Chronic Neural Prosthesis Using High-Capacity Graphene Electrodes and Biodegradable Silicon Support (PI) WAYNE STATE UNIVERSITY Cheng Cleanroom Resources Related Courses ECE 5575 Introduction to Micro and Nano Mechanical Systems ECE 6570 Smart Sensor Technology I: Design ECE 7570 Smart Sensor Technology II: Characterization and Fabrication Schedule https://my.ilabsolutions.com/service_center/show_external/2964/nan o-fabrication-core-facility WAYNE STATE UNIVERSITY Cheng Cleanroom Nanotechnology Nanotechnology deals with structures sized between 1 to 100 nanometers in at least one dimension, and involves developing materials or devices possessing at least one dimension within that size. WAYNE STATE UNIVERSITY Cheng Cleanroom.
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