Plasma Cleaning

This procedure is used to clean surfaces and enhance attachment of PDMS to glass or PDMS to PDMS.

1. Clean all substrate surfaces with Scotch tape.

2. Place PDMS mold (feature side facing up) on a microscope slide. Transfer PDMS on slide into the plasma cleaner.

3. Put another microscope slide (to be attached to the feature face of PDMS mold) in the plasma cleaner.

4. Close the door to plasma cleaner, and close the valve (turn knob inward) on door to isolate inside from outside air. Set power level to medium.

5. Create vacuum by turning on pump. Watch needle on vacuum gage moving counterclockwise past the 200 mark.

6. Turn on power, slowly open valve (turn knob outward) until a purplish glow is observed.

7. Let the purplish glow persist for 25 seconds, then turn power off.

8. Open valve completely to let air in. Close valve to reestablish vacuum. Turn off pump when the needle on vacuum gage returns to its position around the 200 mark (this step is important in removing toxic gas generated in the plasma cleaner).

9. Open valve to let air in. Open door when atmospheric pressure is reached.

10. Remove PDMS mold on microscope slide and the other microscope slide.

11. Attach the empty microscope slide (the side facing up when placed in plasma cleaner) to the PDMS mold (feature, the side facing up) and squeeze for 30 seconds.

12. Remove the microscope slide lying underneath the PDMS mold (contacting the non-feature side). The PDMS mold should now be only attached to the originally empty microscope slide, with feature facing down to the slide.

From the manufacturer

http://www.harrickplasma.com/products_operation.php

PLASMA PRODUCTS:

Details of Operation

Note: A detailed User's Manual is provided with all Harrick Plasma's Plasma Cleaner models.

Principles of Operation

    • The sample is placed in the plasma vacuum chamber

    • Process gas(es) are admitted to the chamber at low flow rates (1-2 SCFH) using either a needle valve or the PlasmaFlo accessory and are kept at low pressure (~200-600 mTorr) through vacuum pumping

    • The gases are subject to induced RF magnetic and electric fields generated by a solenoidal coil current

    • Plasma is generated through the subsequent RF/collisional heating of the electrons in the gas

Details of Operation

    • The plasma vacuum chamber door has an o-ring quick disconnect seal for easy access to the chamber

    • The vacuum pump is connected to an outlet at the back of the reaction chamber

    • The needle valve is used to bleed in process gas and control the pressure during plasma processing

    • The RF power level can be adjusted by means of a three-way selector switch

    • The plasma will emit a characteristic glow, which visibly indicates the successful generation of the plasma state

    • The temperature change of a substrate during plasma treatment is minimal

    • The 3-way valve is used to quickly switch from bleeding in gas, isolating the chamber, and venting

Surface Cleaning / Modification

    • The interaction between the plasma and the surface is determined by:

      • The nature of the substrate and surface contaminant layers

      • The process gases used

      • The pressure and flow rate of the gases

      • The RF power level & length of sample exposure

    • For surface cleaning, a few seconds exposure, following pump down of the chamber and formation of plasma, is often adequate

    • Surface cleanliness can be tested most easily by observing the wettability of the sample: on a clean surface, water drops will not bead, but will spread out in a uniform film

Plasma Generation with Room Air as the Process Gas [+]