Specific Process Knowledge/Lithography/Coaters/Spin Coater: RCD8 processing: Difference between revisions
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=Spin coating= | =Spin coating= | ||
Spin coating on Spin Coater: RCD8 consists of a selection of the following steps: | Spin coating on Spin Coater: RCD8 consists of a selection of the following steps: | ||
#Resist dispense | #Resist dispense | ||
#(Recipe start) | |||
#Optional: Closing the Gyrset (if used) | #Optional: Closing the Gyrset (if used) | ||
#Optional: Resist spreading at low spin speed | #Optional: Resist spreading at low spin speed | ||
#Spin-off | #Spin-off | ||
#Deceleration | #Deceleration | ||
#Opening Gyrset | #Opening Gyrset (if used) | ||
The wafer is first centered on the chuck and held in place by vacuum (or pins in the case of the non-vacuum chuck). | The wafer is first centered on the chuck and held in place by vacuum (or pins in the case of the non-vacuum chuck). After the resist has been dispensed, the recipe is started. A short spin at low spin speed may be used as the first step of the recipe, in order to spread the resist over the wafer surface before spin-off. | ||
The spin-off cycle determines the thickness of the resist coating. The thickness is primarily a function of the spin-off speed and the spin-off time, both following an inverse power-law. | The spin-off cycle determines the thickness of the resist coating. The thickness is primarily a function of the spin-off speed and the spin-off time, both following an inverse power-law. | ||
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=Dispense= | =Dispense= | ||
The dispensed | Resist dispense on the Spin Coater: RCD8 can only be done manually, as the motorized media arm was decommissioned in 2024. Manual dispense is done by administering the resist directly onto the substrate, after it has been loaded into the machine but before the recipe has been started. In most cases, it is done by pushing the resist out of a prefilled syringe (dispense cartridge). Thin resists can be dispensed by pouring the resist directly from a bottle, but that is more difficult to control. | ||
The volume dispensed from a syringe may be estimated by measuring the distance the resist level is displaced during a dispense, and calculating the corresponding volume using the diameter of the syringe (23 mm). A displacement of 10 mm corresponds to a dispensed volume of 4 ml. This calculation can also be used to mark the syringe with appropriately spaced guide lines in order to dispense a specific volume. 4-5 ml is an appropriate volume for a 100 mm wafer. | |||
==Tips and tricks for dispensing thick resist== | |||
High viscosity resists, such as the SU-8 formulations for coating thicknesses 50µm and above, are difficult to dispense. To have any kind of control, they require use of a dispense syringe. | |||
'''Filling the syringe:'''<br> | |||
Syringes should be filled the day before spin coating, especially for thick resists like SU-8 3035 or XFT 75. They should be stored vertical in order to allow bubbles to settle at the top. | |||
A syringe consists of an end cap, the syringe barrel, and a piston that seals off the syringe after filling. To fill a syringe, bring all the necessary parts to a fume hood, along with the resist bottle. It is recommended to clean all parts with a nitrogen gun (these parts are standard labware and therefore not supplied particle-free). Put the end cap on the syringe barrel and open the resist bottle. Hold the syringe at a slight angle and slowly start pouring the resist from the bottle. Start gently and be patient; the flow of resist can quickly become too fast and too wide for the syringe. Allow the resist to flow down along the inner wall of the syringe to minimize bubble formation, taking care to avoid the top few cm of the syringe. You'll need some free space at the top for the piston; so, please stop pouring the resist before it's too late, as the viscous resist will continue to flow once you have lowered the bottle. If the resist drips on the outside of the bottle, wipe it off, but avoid wiping the opening of the bottle (due to risk of contaminating the remaining resist). When you have put down the resist bottle, insert the piston and push it all the way down to the surface of the resist in the syringe. Wipe any resist from the end of the syringe. Finally, label your syringe and store it in the chemical cabinet (in E-4). | |||
'''Dispensing from the syringe:'''<br> | |||
Start by removing the end cap from the syringe. For the first dispense, remove any air in the tip of the syringe by dispensing the first drop somewhere outside the substrate. Start the dispense in the center of the wafer, keeping the tip of the syringe as close to the substrate as possible (so the dispensed resist forms a continuous puddle, rather than strings that bunch up and trap air). Make sure the dispensed resist puddle is in the center of the substrate; otherwise, some of the substrate may not be covered during spinning, even though a lot of resist was dispensed. During dispensing, the position of the puddle can be controlled by moving the syringe tip while continuing the dispensing process. Towards the end of the dispense, move the tip to the edge of the puddle. Stop the dispense, but keep the tip at the last spot to allow the last resist to finish flowing. Now, lift the tip a couple of cm up, then down again and up again, in order to break the thin string of resist that forms between the tip and the puddle. | |||
'''Bubbles in the resist film after coating:'''<br> | |||
Bubbles in the resist after coating can successfully be popped (using e.g. an Eppendorf pipette tip), either while still on the chuck or after moving to the hotplate. Sometimes bubbles appear in the film during the first stage of softbaking. These can also be popped. | |||
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Text below was in the original section "Automatic dispense" TARAN 27-08-2025 | |||
Automatic dispense on the Spin Coater: RCD8 is done using a Nordson EFD Performus VII pressurised cartridge dispense system. The syringe containing the resist is mounted on the media arm, and the resist is dispensed using a nitrogen pressure supplied by the control box. The dispense rate is controlled by the nitrogen pressure, while the dispense time, and thus the volume, is set in the recipe. The dispensed volume may be estimated by measuring the distance the resist level is displaced during a dispense, and calculating the corresponding volume using the diameter of the syringe (23 mm). A displacement of 10 mm corresponds to a dispensed volume of 4 mL. | Automatic dispense on the Spin Coater: RCD8 is done using a Nordson EFD Performus VII pressurised cartridge dispense system. The syringe containing the resist is mounted on the media arm, and the resist is dispensed using a nitrogen pressure supplied by the control box. The dispense rate is controlled by the nitrogen pressure, while the dispense time, and thus the volume, is set in the recipe. The dispensed volume may be estimated by measuring the distance the resist level is displaced during a dispense, and calculating the corresponding volume using the diameter of the syringe (23 mm). A displacement of 10 mm corresponds to a dispensed volume of 4 mL. | ||
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*'''1 DCH Gyrset cleaning''' | *'''1 DCH Gyrset cleaning''' | ||
Gyrset down; 10s @ 100rpm; 1s @ 0rpm; 10s @ -30rpm; 20s @ 1500rpm; Gyrset up. | Gyrset down; 10s @ 100rpm; 1s @ 0rpm; 10s @ -30rpm; 20s @ 1500rpm; Gyrset up. | ||
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*'''1 DCH predispense''' | *'''1 DCH predispense''' | ||
0.2s dispense at cup (arm position 0mm). | 0.2s dispense at cup (arm position 0mm). | ||
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==Manual dispense templates== | ==Manual dispense templates== | ||
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*'''1 TMPLT man disp Gyrset sprd''' | *'''1 TMPLT man disp Gyrset sprd''' | ||
Gyrset down; spread step; spin-off; deceleration; Gyrset up. | Gyrset down; spread step; spin-off; deceleration; Gyrset up. | ||
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==Automatic dispense templates== | ==Automatic dispense templates== | ||
*'''1 TMPLT aut disp SU8''' | *'''1 TMPLT aut disp SU8''' | ||
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*'''1 TMPLT aut disp Gyrset sprd''' | *'''1 TMPLT aut disp Gyrset sprd''' | ||
Dispense; Gyrset down; spread step; spin-off; deceleration; Gyrset up. | Dispense; Gyrset down; spread step; spin-off; deceleration; Gyrset up. | ||
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=Processing results= | =Processing results= | ||