Process Sequence: Pressure-Actuated ValveOutlineWafer 1: Process Sequence Silicon Substrate SU-8 Bottom Fluid LayerWafer 1: Process Sequence PDMS Gas LayerWafer 1: Process Sequence PDMS Thin Flex LayerWafer 1: Layer IntegrationWafer 2: Process Sequence Pyrex Substrate SU-8 Cover LayerWafer 2: Process Sequence Adding SU-8 Top Fluid LayerIntegration of Wafer 1 and Wafer 2PDMS Layer Removal and Attachment *Theresa ValentineAlternate SequenceProcess Sequence: Pressure-Actuated ValveENMA490October 14, 2003Outline•Wafer 1 Fabrication–Silicon Substrate–SU-8 Bottom Fluid Layer–PDMS Gas Layer–PDMS Thin Flex Layer–Wafer 1 Layer Integration•Wafer 2 Fabrication–Pyrex Substrate–SU-8 Cover Layer–SU-8 Top Fluid Layer•Integration of Wafer 1 and Wafer 2•PDMS Layer Removal and AttachmentPyrex SubstrateSU-8 Cover LayerPDMS Thin Flex Layer PDMS Gas LayerSU-8 Bottom Fluid LayerSubstrate (Si)FINAL RESULTWafer 1Wafer 2SU-8 Top Fluid LayerWafer 1: Process SequenceSilicon SubstrateSU-8 Bottom Fluid Layer• Start with a 4” diameter Silicon Wafer.• Spin on SU-8 photoresist (orange).• Pre-bake at 95°C.Silicon• Align wafer with Mask 1 –Bottom Fluid Layer Mask.• Expose SU-8 to UV light.• Post-bake at 95°C.STEP 1STEP 3STEP 2SU-8 Photoresist• Develop SU-8 in SU-8 developer. STEP 4Wafer 1: Process SequencePDMS Gas LayerSTEP 1STEP 2STEP 3SU-8 Photoresist• Spin on SU-8 photoresist (orange).• Pre-bake at 95°C.• Align wafer with Mask 2 –Gas Layer Mask.• Expose SU-8 to UV light.• Post-bake at 95°C.STEP 4• Develop SU-8 in SU-8 developer.• Dip wafer in 0.1 M sodium dodecyl sulfate (SDS) adhesion barrier and let dry naturally.STEP 5• Mix PDMS (Sylgard 184, Dow-Corning) 10:1 with curing agent.• Spin on PDMS (purple).• Bake in box furnace for 2 h at 70°C. PDMSSilicon• Start with a 4” diameter Silicon Wafer.Wafer 1: Process SequencePDMS Thin Flex LayerSTEP 1STEP 2STEP 3SU-8 Photoresist• Spin on SU-8 photoresist (orange).• Pre-bake at 95°C.• Align wafer with Mask 3 –Thin Flex Layer Mask.• Expose SU-8 to UV light.• Post-bake at 95°C.STEP 4• Develop SU-8 in SU-8 developer.• Dip wafer in 0.1 M sodium dodecyl sulfate (SDS) adhesion barrier and let dry naturally.STEP 5• Mix PDMS (Sylgard 184, Dow-Corning) 10:1 with curing agent.• Spin on PDMS (purple).• Bake in box furnace for 2 h at 70°C. PDMSSilicon• Start with a 4” diameter Silicon Wafer.Wafer 1: Layer IntegrationSilicon SU-8 Photoresist PDMS• Take the Silicon substrate and SU-8 Bottom Fluid Layer.STEP 1STEP 2• Align the PDMS Gas Layer on top of the SU-8 Bottom Fluid Layer.• See Theresa’s Assembly Slide for PDMS layer removal and attachmentSTEP 3• Align the PDMS Thin Flex Layer on top of the PDMS Gas Layer.• See Theresa’s Assembly Slide for PDMS layer removal and attachmentPDMS Thin Flex Layer PDMS Gas LayerSU-8 Bottom Fluid LayerSubstrate (Si)WAFER 1: COMPLETEWafer 2: Process SequencePyrex SubstrateSU-8 Cover Layer• Start with a 4” Pyrex Wafer and drill the required throughput holes in the wafer (use a barrier such as tape (on the bottom) to avoid problems in subsequent steps).STEP 2• Spin on SU-8 photoresist (orange).• Pre-bake at 95°C.STEP 1STEP 3• Align wafer with Mask 4–SU-8 Cover Layer Mask.• Expose SU-8 to UV light.• Post-bake at 95°C.Silicon SU-8 Photoresist Not exposed to UV-light (will be developed away).Wafer 2: Process SequenceAdding SU-8 Top Fluid LayerSilicon SU-8 PhotoresistSTEP 1• Start with the wafer from the Pyrex Substrate and SU-8 Cover Layer Not exposed to UV-light (will be developed away).STEP 2• Spin on another layer of SU-8 photoresist (orange).• Pre-bake at 95°C.STEP 3 Not exposed to UV-light (will be developed away).• Align wafer with Mask 5–SU-8 Top Fluid Layer Mask.• Expose SU-8 to UV light.• Post-bake at 95°C.STEP 4• Develop SU-8 in SU-8 developer.Pyrex SubstrateWAFER 2: COMPLETEIntegration of Wafer 1 and Wafer 2 PDMS Thin Flex Layer PDMS Gas LayerSU-8 Bottom Fluid LayerWAFER 1Pyrex SubstrateSU-8 Top Fluid Layer SU-8 Cover LayerWAFER 2 InvertedPyrex SubstrateSU-8 Top Fluid Layer SU-8 Cover LayerPDMS Thin Flex Layer PDMS Gas LayerSU-8 Bottom Fluid LayerSubstrate (Si)FINAL RESULTWafer 1Wafer 2Substrate (Si)PDMS Layer Removal and Attachment*Theresa Valentine•Gently loosen edges of cured PDMS with razor blade•Submerge PDMS wafer in dish of methanol•Hold one edge of PDMS with tweezers and gently pull from wafer (keeping in methanol as much as possible)•Remove wafer from dish and allow PDMS to float•Slide (electrode) wafer to be assembled under PDMS layer in dish•Coarse align PDMS to wafer while in dish•Remove wafer and PDMS from dish and align carefully by hand or under microscope, dropping methanol on if sticking occurs, then let dry.•Materials:–Methanol•Equipment:–Razor blade–TweezersAlternate Sequence•In addition to the Process sequence described above, another mask set is being created to create the same design with all PDMS layers.•The procedure is very similar, except the current SU-8 layers will not be patterned on the device itself, but will rather be used as a mold to create PDMS layers, which will then be removed and layered to create the device.•Wafer 1 Fabrication–Silicon Substrate–PDMS Bottom Fluid Layer–PDMS Gas Layer–PDMS Thin Flex Layer•Wafer 2 Fabrication–Pyrex Substrate–PDMS Cover Layer–PDMS Top Fluid
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