Microelectronics Research Center

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STS ICP
Instructions by: Pezhman Monajemi

IMPORANT: You must submit a process flow online prior to getting checked off to use this tool. An example of a sample process flow can be found here. If you have any questions regarding process flows, contact Janet Cobb-Sullivan.

I. Introduction

The STS ICP is a CMOS-Compatible tool used for integrated MEMS-CMOS processes, and is meant for narrow (<10 micron in width) high aspect-ratio trench etching in Silicon and SOI wafers. Non-CMOS-compatible materials and masks are NOT allowed in this tool.

II. Machine Specifications

At the MiRC, this system is used only for etching high aspect-ratio trenches in Silicon and SOI wafers.

This system has the following gases available for processing:

  • SF6
  • C4F8
  • AR
  • O2

This system uses the following gases for cleaning:

  • O2

The following substrate(s) and materials are allowed in the system:

  • Silicon, polysilicon
  • SiOX, SiXNY, SiOXNY

The following types of photoresists are allowed:

  • SC1800 series and SPR220 from Shipley
  • AZ4000 series from Clariant
  • NPR from Futurex.

IF YOU WANT TO PROCESS ANY OTHER MATERIAL, YOU MUST GET APPROVAL FIRST.

Note:

  1. SU8, ANY TYPE OF POLYMER, POLYIMIDE, RESIN and ANY TYPE OF METAL are ABSOLUTELY FORBIDDEN to be used as a mask.
  2. THROUGH-WAFER ETCH IS NOT ALLOWED in this system.
  3. If you want to etch more than 200 microns, you must mount your wafer on top of another 4" wafer.
  4. Your photoresist must be baked for at least 10 minutes at 90°C-100°C before loading into the machine.
  5. Silicon Nitride can be used as a mask but it has a poor selectivity.

III. System Components

This system consists of the following:

  1. Double carousel loadlock
  2. One process chamber
  3. Mechanical Pumps
  4. RF stack
  5. Prime Power Distribution cabinet
  6. De-ionized heater/chiller
  7. Gases
    1. Non-toxic with no specific effects, but will not support life: AR
    2. Semi-toxic and non-flammable/liquefiable: C4F8
    3. Semi-Toxic and non-flammable: SF6
    4. Flammable/explosive: O2

IV. Personal Safety:

  1. To prevent risk of personnel injury, all maintenance and repair procedures must be undertaken by technically qualified person(s) who are fully aware of all relevant safety precaution associated with processing, operating and maintaining the equipment.
  2. If you detect any chemical fume from the process chamber, please STOP your process and contact MiRC staff immediately.
  3. Potentially lethal voltages (in excess of 30 volts AC and 50 volts DC) are present on the equipment. If you see any open and broken wire or exposure electrical parts, DO NOT try to fix it. You have to contact MiRC staff right away.
  4. To prevent an uncontrolled hazardous gas flow to the process chamber, which could result in personal injury, DO NOT open the by-pass valve in the gas box when flowing a process gas.

V. Operating Instructions

  1. Loading a sample
    1. Login to the machine.
    2. Make sure there is no wafer already in the chamber, if there is any, you have to unload it using the Unload button in the Transfer window located at the bottom right of the screen.
    3. Click on Vent and wait until the loadlock is completely vented.
    4. Load the wafer with the flat facing the white line marked on the carousel.
    5. The wafer can be loaded to any one of the wafer handlers (each handler is marked with a number on the upper right hand corner).
    6. After loading the wafer, close the loadlock lid and close the handle (make sure you hear click sound when the handle is snapped into closed position).
    7. Press Pump + Map button. This option pumps down the loadlock and maps the carousel to check if a wafer has been placed in either one of the wafer handler. Once the program has finished the mapping of the wafer, the wafer with the handler number will be displayed in the Wafer Diagram or Slot box (either number 1 or 2).
    8. Click on Load to load the wafer into the chamber.

    Note:

    • Make sure that the wafer handler number displayed in the Slot box next to the Load button in the Transfer window is correct.
    • If it is not correct then left click on the Slot box and type in the correct number of the wafer handler and then press Enter on the keyboard.
    • Press the Load button in the Transfer window to load the wafer into the chamber.
  2. Operating
    1. Selecting a recipe
    2. Execute a process recipe:
    3. If a recipe is available for the process, press the Select button in the Process window.
    4. A new window will pop up displaying various recipes that are available. Highlight the desired recipe.
    5. If the wafer has been loaded into the chamber, then one can go ahead and press Process to start processing.
    6. Usually before the process, a helium leak up test will be performed with a loaded wafer. If the reading is not below the set value (10mT/min) then there may be a leak. You should check on the back of your wafer to make sure it’s clean and free of scratches. If the problem persists, then contact the MiRC staff.
    7. Writing or modifying a recipe
      1. If you need to write or modify a recipe, then press the Recipe button in the Process window.
      2. A new window will pop up showing the recipe for the current process. Press Open a recipe button on the top of the new window.
      3. Each recipe contains 2 parts: A standard process and the recipe. The standard process is built in processes that the machine goes through whenever a recipe is run. One should only modify the recipe.
      4. Click on the name of the recipe that you have selected. The following options are displayed that are set in the company for standard recipes:
        1. General: Description of the process, type of process and the process times can be modified. Process times are specified by the number of total cycles. Switching parameters will enable the passivation/etching process. Discrete and continuous option is used when 2 or more process recipes are used one after the other. By choosing the discrete option, the RF and the gases are stopped before continuing with the next process. The continuous option enables for the processes to run right after the other. The default setting is discrete.
        2. Pressure:: Pressure is controlled either by setting the automatic pressure control (APC) to open up at certain percentage or adjust so that a constant pressure is kept.
        3. Gases: Gas flow is set here.
        4. RF: Power for the coil and the platen, as well as the matching capacitor values are set here. Even 1W of change in RF power will have a large effect on the profile.
        5. HBC: Helium Back Cooling parameters (pressure, flow, and tolerance) are set here.
        6. He LUR: Before each process the helium leak up rate is checked with a loaded wafer. The value with a clean wafer should not exceed 10mT/min. One minute is the default time for checking the helium leak up rate. If the leak up rate is more than the set point, then the process will hold until further notice.
      5. Save and exit the window after modifying the recipe.
        1. During the process, check if the parameters are within the specs.
        2. All windows with light blue letters (e.g. Process times) can be modified during the process; it will be rounded to the next process cycle. This will not change the recipe.
      6. If one needs to abort the process, then press Abort and confirm it.

        7. Note:

        1. DO NOT change the settings of Pressure, Gases, HBC and He LUR. If you need to do so, contact the trainer.

        2. DO NOT increase the platen power above 20W.

  3. Unloading a Sample
    1. At the end of the process, the Unload button will be highlighted.
    2. Unload the wafer and then vent the chamber to retrieve the wafer.

      3. Warning: If one of the following conditions occurs, immediately stop operating the ICP and place a "machine down" sign on the system. Contact MiRC technical staff immediately.

    3. If you find that your wafer is broken or chipped when you remove it from the ICP.
    4. If your wafer does not return to the loadlock when the ICP tries to unload it.

VII. Troubleshooting

  1. If the wafer is not detected by the software then from the Edit option, one can Create a wafer or Delete a wafer from the chamber.
  2. If the Load button is not active, there is either a wafer inside the chamber, or that the system is not in the active mode. In this case contact one of the staff.
  3. If there is any active alarm shown in the main screen, click on Accept and wait until the alarm is cleared, then call one of MiRC staff.

VIII. DO’s and DON’Ts

  • DO NOT attempt to open the loadlock while a process is running.
  • DO NOT proceed with processing in the face of an unknown error. Contact the trainer and/or maintenance staff first.
  • DO NOT use the machine if another user has placed a ‘machine down’ sign on it; ask the technical staff to verify that it is working.
  • DO ask the trainer, cleanroom / technical staff, and other users questions about anything that is not clear or that you do not understand.

  • Caveat:
    The trainer can answer most questions regarding materials, but will provide the contact information for someone who can in the event that he/she does not know. Ask other users of the equipment that work with that material for advice on specific processing issues. To do this, email the list of users for this equipment:
    icp_3-users@grover.mirc.gatech.edu

IX. Check-off requirements

To be checked off, you must be able to do, to demonstrate, and to know the following items if asked:

  • Know the materials that can be etched
  • Know what materials are allowed in the system
  • Know the specific materials and processes you will be using the system for
  • Vent the loadlock
  • Load a sample
  • Load a process
  • Edit a process and save it as yours.
  • Run a sample
  • Unload a sample
  • Run a clean process