OAI Model 200 Tabletop Mask Aligner Portland State University WARNING: This machine exposes users to ultraviolet radiation. Do not touch the lens underneath the lamp hood as it may damage the machine and cause sever burns. Exposure to pressurized gas, high voltage electricity and mercury vapor may result from improper use of this equipment. Recommended Apparel: Eyewear rated to 400nm, clean room suits and nitrile gloves are required in this lab environment. For additional safety and emergency information please reference the last page of this manual and the appropriate manufacturer documentation.
Preliminary Set Up: Image of pressure buttons Image of exhaust fan 1) Check that the primary systems are connected to a wall outlet and that any power strips or surge protectors in their path are activated. 2) Verify that the vacuum and compressed gas feeds are turned on. If either of these are not working then check that the vacuum pump is on, its valve is open and that the nitrogen gas pressure is at 60 psig. 3) Move the microscope platform to the back of the tabletop and mask aligner platform completely to the right by using the black pressure buttons. 4) Make sure that the ozone exhaust fan in the lamp hood is now on and that the vent tube is securely in place before continuing to the lamp warmup. 5) Set the timer to 1 second and turn it on to enable use of the mask assembly. The shutter will open momentarily. Keep the timer switch on throughout this tutorial. Warmup Procedure: 1) Power on the constant intensity controller, using the large switch. 2) Set Current-Voltage (CV) selector to VOLTS, Intensity-Power (IP) selector to WATTS and the mode to Constant Intensity (CI). 3) Briefly depress the Start switch to turn the lamp on, you will hear a clicking sound. 4) Allow the lamp to warm up for about 10 minutes before moving on with this section of the manual. Please take this time to work through the mask, substrate and alignment procedures. Cooling Diagnostic: 1) After 10 minutes have elapsed the lamp power indicator will probably read between somewhere between 375W-625W. 2) To check if the lamp is operating properly adjust the power knob to set the machine to 500W (rated wattage), flip the CV switch to measure VOLTS and verify that it reads
Rated Voltage: Check this out to make sure. 340V± 2.0V. This diagnostic indicates if the lamp is overcooled (<338V ) or undercooled (>342V). 3) In the unlikely event that a cooling problem is found then ask a professor or look in the OAI manuals for directions on adjusting the airflow damper. Open or close this damper to manipulate the voltage back into the proper 4V range before continuing with any experiments. 4) Set the power draw to 450W (idle rating) until ready to preform an exposure, at which point one should readjust this setting to meet experimental parameters. Mask Placement: *Nitrile gloves are mandatory for this section.* 1) Make sure that the mask is cleaned of particulates before installing. 2) Loosen the six placement screws on top of the mask assembly and remove any placeholder material. 3) Place the mask underneath the clamps with the emulsion side down and push it flush against all three alignment pins. 4) A square cutout slid between the mask and the placement brackets may be used to help keep the mask level, secure and limit the exposure area. 5) When the mask is in place, tighten the placement screws enough to mitigate movement but not so much that they bend the surface. 6) If the mask is set at an angle to the front of the module then loosen the thumbscrews on either side of the frame to rotate it until it is parallel to the front of the machine. 7) Push in the Mask Vacuum button to affix the mask to the frame. Intensity Reading: *All recommended apparel should be used in section.* 1) Flip the IP switch to mw/cm^2 and verify the reading of 0.0. 2) Set a UV probe in the center of the exposure plane (on top of the mask assembly). 3) Set exposure timer to 5-10 seconds and check that the CIC is on constant intensity mode.
4) Move the assembly and probe under the lamp to activate the shutter and get a baseline reading. 5) If the system has not been calibrated recently then continue with the steps 6-9, otherwise skip to step 10. 6) Set the CIC to CP mode and channel A. 7) Open the shutter and adjust corresponding CAL knob until that the intensity reading on the probe and CIC are approximately equal. 8) Switch back to CI mode and turn the SET knob both clockwise and counter clockwise (higher and lower intensity) to verify that the power supply is accurately tracking the changes seen on the probe. If the tracking is faulty then reattempt the previous step to obtain a better equivalency setting. 9) Switch to channel B and repeat steps 6 and 7 to finish calibrating the device. 10) Check that the readings are within experimental parameters and use the SET control to readjust the desired intensity as need. Both channels A and B can be preconfigured to different values if so desired. Substrate Placement: *Nitrile gloves mandatory for this section.* 1) Move the microscope arm to the far back corner of the bench and then the mask assembly to the far right. The microscope has two movement handles so be sure to use the one closest to the surface of the table top. The mask frame will not open if the microscope is near it. 2) Flip the Mask Frame switch to the Open position and it should automatically rise about 40º. If the frame does not open immediately then recheck that the timer switch is on and that the microscope/mask assemblies are in their proper storage positions. 3) Once the frame is open, place the substrate chip in the middle of the vacuum chuck completely covering the + sign in its center. 4) The chip, like the mask, should be set parallel to the front of the aligner. Any patterning from previous exposures should be oriented to match the current the mask.
5) Use the Sub. Vac switch to secure the substrate to the mask aligner. 6) Close the mask frame. Mask Alignment: 1) Rotate the lens selector on the microscope to the empty slot so that it has ample clearance when passing over the placement screws on the mask holder. 2) The microscope should not hit the mask frame when it is in use so adjust the height accordingly. 3) Move the mask assembly slightly to the left so that it is lines up with the microscope. 4) Using the lower movement handle on the microscope arm to pull it forward above the mask. 5) Flip the Ball Vac switch to the unlock position to allow for raising of the substrate. 6) Thee Chuck Z Adjust has a D.C. ammeter read out and is controlled by the belt equipped knob on the front of the alignment module. 7) Turn the Chuck Z Adjust knob clockwise until a reading of 15-25 ma is had. 8) Select the lowest magnification on the microscope and set the light source to about 50% power. 9) Use the control handle on the upper arm of the microscope assembly to orient the microscope more precisely. The top and bottom buttons allow for small modifications in the Y and X direction respectively. Be careful when using these controls because the light and power sources may get damaged or disconnected if this piece too quickly or far from their initial position. 10) Adjust the microscope till the mask can be seen with both eyes and then focus the optics as needed. The lowest magnification is good for setup and to finding alignment features because it has the best field depth and view. Once the microscope is in focus it will remain that way regardless of magnification changes. 11) Turn the black knob on front of the alignment module (not the Chuck Z Adjust) and view the substrate raising and leveling through the microscope. 12) Once the substrate reaches the mask a significant resistance will be felt in the knob, the belt will stop moving and the chuck should become level. 13) Lock the Ball Vac into position and prepare for final alignment.
14) Use the three long stemmed adjustment bars around the outside of the assembly to lower and then precisely align the substrate and mask. The middle bar controls the Y- Axis, the right controls the X and the far left controls rotation, theta. The movements are on the scale of micrometers so it is most beneficial when the microscope is in focus during these adjustments. 15) Raise the substrate with the previously used black knob until contact is made. This is known as making soft contact. The hard contact switch can be thrown to increase resolution but it will cause a residue to form on the mask after exposure. 16) Turn on the Contact Vac to lock in the final changes and prepare for exposure. 17) Rotate microscope lens to the empty compartment and carefully return the arm to its storage position, this can probably be done without changing the elevation of the arm. 18) Turn off the alignment optic power unit. Exposure: *All recommended apparel should be used in this section.* 1) Set the timer to the desired exposure time. 2) Double check power and intensity settings. 3) Move the assembly completely underneath the hood to activate the lamp. To avoid severe burns, do not touch the lamp or hood while in operation or shortly thereafter. 4) Wait for the lamp to finish its exposure and then move the assembly back to its alignment position. Substrate Removal: *Nitrile gloves are mandatory for this section.* 1) Turn off the Hard Contact switch if it was used during the exposure. 2) Turn off the Contact Vac. Adjust switch. 3) Close the contact vacuum by fully rotating the Contact Vac. Adjust valve clockwise. 4) If the substrate is sticking to the mask then turn on the Nitrogen Purge switch and open the Nitrogen Purge Flow Valve for 5-10 seconds to break the adhesion.
5) Lower the substrate from the mask using the black knob to avoid accidental contact in later trials. 6) Check that the alignment optics are in storage position. 7) Open the mask frame and turn off the Sub. Vac. 8) Carefully remove the substrate and then close the mask frame. 9) Turn the timer off. Mask Removal: *Nitrile gloves are mandatory for this section.* 1) Loosen the six thumbscrews on top of the mask assembly. 2) Turn off the mask vacuum and remove the mask. Shutdown: 1) If the lamp is going to be use again with the hour then set its power the idle amount of 450W. 2) If the lamp is no longer needed then turn off the power switch on the constant intensity controller. 3) Close the vacuum valve and turn off the vacuum pump. 4) Turn off the compressed gas source. 5) Turn off the external power strip or surge protecter connecting to the main apparatus. Emergency Procedure: 1) The lab should be evacuated immediately whenever an explosion occurs, the lamp malfunctions or smoke can be detected. 2) Shut down electric and gas connections at their external source. 3) Notify an instructor or any other relevant authority of the situation and make mention of a possible mercury vapor leak. 4) If a clean up is to be attempted then use a chemical respirator, full body clean suit, proper lab goggles, double layered nitrile gloves and a syringe capable of picking up liquid mercury. Safety Measures: 1) Protective eyewear should be rated to 400nm (most sunglasses meet this specification).
2) Full body clean suits are both required in most cleanroom environments and ideal in use of this machine. In lieu of a ʻbunny suitʼ, lab coats and long pants can provide sufficient UV protection but may contaminate nearby experiments. 3) Nitrile gloves are appropriate at this work station and may be double layered for additional protection. 4) Cosmetics are strictly prohibited in the cleanroom but certain sunscreens may be permitted at instructor discretion. Please reference OAI manuals for more information pertaining to setup, experimental, safety and emergency procedures.