Process Sequence: Pressure-Actuated Valve ENMA490 October 14, 2003

Outline 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 Attachment Pyrex Substrate SU-8 Cover Layer PDMS Thin Flex Layer PDMS Gas Layer SU-8 Bottom Fluid Layer Substrate (Si) FINAL RESULT Wafer 1 Wafer 2 SU-8 Top Fluid Layer

Wafer 1: Process Sequence Silicon Substrate SU-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 1 STEP 3 STEP 2 SU-8 Photoresist Develop SU-8 in SU-8 developer. STEP 4

Wafer 1: Process Sequence PDMS Gas Layer STEP 1 STEP 2 STEP 3 SU-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. PDMS Silicon Start with a 4” diameter Silicon Wafer.

Wafer 1: Process Sequence PDMS Thin Flex Layer STEP 1 STEP 2 STEP 3 SU-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. PDMS Silicon Start with a 4” diameter Silicon Wafer.

Wafer 1: Layer Integration SiliconSU-8 Photoresist PDMS Take the Silicon substrate and SU-8 Bottom Fluid Layer. STEP 1 STEP 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 attachment STEP 3 Align the PDMS Thin Flex Layer on top of the PDMS Gas Layer. See Theresa’s Assembly Slide for PDMS layer removal and attachment PDMS Thin Flex Layer PDMS Gas Layer SU-8 Bottom Fluid Layer Substrate (Si) WAFER 1: COMPLETE

Wafer 2: Process Sequence Pyrex Substrate SU-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 1 STEP 3 Align wafer with Mask 4–SU-8 Cover Layer Mask. Expose SU-8 to UV light. Post-bake at 95°C. SiliconSU-8 Photoresist Not exposed to UV-light (will be developed away).

Wafer 2: Process Sequence Adding SU-8 Top Fluid Layer SiliconSU-8 Photoresist STEP 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 Substrate WAFER 2: COMPLETE

Integration of Wafer 1 and Wafer 2 PDMS Thin Flex Layer PDMS Gas Layer SU-8 Bottom Fluid Layer WAFER 1 Pyrex Substrate SU-8 Top Fluid Layer SU-8 Cover Layer WAFER 2 Inverted Pyrex Substrate SU-8 Top Fluid Layer SU-8 Cover Layer PDMS Thin Flex Layer PDMS Gas Layer SU-8 Bottom Fluid Layer Substrate (Si) FINAL RESULT Wafer 1 Wafer 2 Substrate (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 –Tweezers

Alternate 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 Layer