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Operating Instructions- Ox-RIE

Thanks to Yunhan Chen and Monica Hew for the operating instructions. Oxford-rie is a capacitively coupled plasma (ccp) etch equipment with fluorine based etch gases and oxygen. It belongs to the "Flexible" group.

Picture and Location

 The tool is located at D section of the lab, right across the non-metal wet bench. Lab Map.

Pic1_OX-RIE photo

Pic2_Location

Background

 The OX-RIE Oxford etcher is a reactive ion etcher (RIE), designed for etching various materials as shown in the performance of the tool section. The OX-RIE is currently approved to etch [Materials] only. Please contact Jim McVittie (mcvittie@stanford.edu) for approval to etch other substrates. The system is gold contaminated.


There are several important points regarding usage of this etcher:

  1. Only 4” wafers can be etched using this machine. Any smaller chips must be mounted on a carrier wafer for etching. Any carrier wafers that are not etched by the chemistry can be used; Si and SiO2-on-Si wafers are acceptable with most chemistries.

  2. 5mm EBR (edge-bead removal) is required on all wafers due to the wafer clamp. The backside of the wafer must also be clean.

  3. Never run the etcher without a wafer in the chamber. The plasma will damage the wafer clamp if it is exposed.

  4. Never place a wafer back into the etch chamber after running a process without physically resetting it! The wafer may shift, leading to breakage.

  5. The measured bias voltage may drift significantly if an oxide carrier wafer is used, but this is not indicative of actual process variations.

Process Capabilities

Cleanliness Standard

  • Oxford-RIE belongs to the gold contaminated group.  See Material section of our website for details.

 

Performance of the Tool

What the Tool CAN do

    1. Types of materials to be etched
      • Dielectric materials (SiO2, SiNx, etc.)
      • Silicon-based materials (Si, a-Si, poly-Si)
      • Polyimide, Diamond-like carbon (DLC), other carbon based materials
    2. List of Available Gasses

        • CHF3
        • SF6
        • N2
        • CF4
        • Ar
        • O2

     

      What the Tool CANNOT do

      • Item A.

       

      Process Monitoring
      • Si Etch rate 
      • PR Etch rate 
      • Thermal oxide etch rate

       

      Contact List and How to Become a User

      Contact List

      The following people make up the Tool Quality Circle:

      • Process Staff:  Usha Raghuram
      • Maintenance:  Elmer Enriquez
      • Super-Users:

       

      Training to Become a Tool User

       

      Operating Procedures

      1. Check for tool status and configuration in Badger and make sure the tool is available for processing.

      2. Enable the tool on Badger.

      3. Log in: System→Password

        1. Log in with the username and password for PC2000NT: Username = “OPT”, password = “OPT”
        2. If needed the log in for Windows is: Username = “OPT”, password = “OPTOPT”
      4. Vent the load lock: System→Pumping

        1. Press the “Stop” button under the loadlock on the diagram. (stops pumping the loadlock)
        2. A window will show saying “Loadlock is empty, OK to stop pumping down loadlock?” Press “OK”
        3. Press the “Vent” button under the load lock on the diagram (vents load lock). You will not be able to vent if the tool is not enabled.

           Pic3_Pumping
      5. Wait for load lock to vent. If the pressure of the load lock doesn’t go up after a while, press “Stop” followed by “Evacuate→Cancel”, then repeat step 4.

      6. Open the loadlock and load your wafer. Wafer flat much face the two screw on the platter.

      7. Evacuate the load lock: System→Pumping

        1. Press the “Stop” button under the load lock on the diagram. (stops venting the load lock)
        2. Press the “Evacuate” button under the load lock on the diagram (pumps down the load lock)
        3. When prompted by the system, enter the wafer name.
      8. Wait for loadlock to pump

      9. Load recipe: Process→Recipe

        1. Make sure the system is in “automatic” mode. If it is in manual mode, change it to automatic.
        2. Press “Load”, click “Yes” when asked whether to overwrite, and choose the desired recipe.
        3. Review steps and ensure recipe is correct.
        4. You can edit the recipe steps in the panel on the left-hand side. These settings will only change temporarily unless you manually save the recipe. Before pressing “Save” button, change the recipe name to avoid overwriting the original recipe.
          Pic3_Pumping 
      10. Run the recipe: in Process→Recipe, press the “Run” button. The system will automatically load the wafer to the chamber, run the recipe, and unload the wafer back to the load lock.

      11. Vent the load lock: Process→Recipe

        1. Press “Stop“ button (stops venting the load lock) 
        2. Press “Yes” to confirm “ready to remove the wafer”
        3. Press “Vent” button (pumps down the vents load lock)
      12. Unload wafer: Open the load lock and retrieve the wafer. NEVER place the wafer back into the etch chamber without physically resetting it! The wafer may shift, leading to breakage.

      13. Evacuate the load lock: System→Pumping

        1. Press “Stop “ button (stops venting the loadlock)
        2. Press “Evacuate” button (pumps down the loadlock)
        3. Press “Cancel” (No Wafer)
      14. Log out: System→Password, then press “verify” without entering a username. The program will then enter the “View Only” mode.

      Recipe management

      Recipe management screen can be accessed by pressing ProcessRecipe located at the top left of the screen. The left side of the screen shows the recipe that is currently loaded to the program. The panel on the right side is the Step Library.

                       Pic5_Recipe2

      Step Library

      Step Library stores process steps that can be used to compose a recipe. Several standard steps are stored here.
      • Press “New” or choose an existing step and press “Edit” to open the Process Step Editor.
      • After editing the step parameters and name, click “OK” to save or “Cancel” to discard the changes.
      • Choose an existing step and press “Copy” to duplicate this step, or press “Delete” to delete this step from the Step Library. DO NOT delete existing standard steps in the step library.
      • When creating a new recipe or edit an existing recipe, steps can be directly copied from the Step Library. However, please note that once a step is copied to a recipe from the Step Library, any edit on this step in the Step Library will not affect the step in the recipe, and vice versa.
                      Pic6_Recipe3

      Create a New Recipe

      • Press “New” in the Current Recipe panel, click “Yes” to clear current recipe. A blank recipe is then created.
      • Click on the empty step in the recipe box, click “Edit Step” to open the Process Step Editor. Edit the name and parameters of this step and press “OK” to save.
      • You can also drag a step in the Step Library, to the recipe box. This step will then be copied to the currently recipe. Click on this step in the current recipe box and press “Edit Step” to edit this step. Any changes will not affect the step that is saved in the Step Library.
      • Create a repeating loop
        1. Click on an empty step and press “Repeat Step”.
        2. Enter the number of times that the loop will repeat.
        3. Close the loop by insert a loop step by pressing “Loop Step”.
        4. Any steps between Repeat Step and Loop Step will be repeated the number of times that has been set in the Repeat Step.
          Pic7_Recipe4 
      • Delete a step by click on the step and press “Delete Step”. Press “Yes” to confirm.
      • Edit the Recipe Name and press “Save” to save the current recipe.
       

      Edit an Existing Recipe

      • Press “Load”, click “Yes” when asked whether to overwrite, and choose the desired recipe.
                      Pic8_Recipe5
      • This recipe is now loaded to the currently recipe panel.
      • Click on the step you want to edit. And choose from the Step Commands as needed. If press “Edit Step”, the Process Step Editor will be open. The step parameters can then be changed.
      • You can drag a step from the Step Library and release on top of the step you want to replace in the current recipe window. Click “Yes” to confirm replacing steps.
                      Pic9_Recipe6
      • Before pressing “Save” button, change the Recipe Name to avoid overwriting the original recipe.
       

      Process Monitoring and Machine Qualification

       

      Frequency

      The Ox-RIE qual runs two wafers through the CHF3/CH4/Ar etch process. We use the Oxide ER test recipe in the library. One wafer with a 1.6um 3612 Photoresist pattern and one wafer with a 10,000A SiO2 coating are etched separately for 10 minutes and 2 minutes respectively. Nanospec measurements are taken before and after etching to calculate the PR and SiO2 etch rate respectively. To calculate the PR:Si selectivity, the two wafers coated in photoresist are then stripped of resist so that the Silicon step height may be measured via Alphastep.

      Procedure

      SUMO Wafer #
      (all Si 4" wafers)
      Coating Pattern
      (using SUMO mask)
      -  10,000A SiO2 gold
       -  1.6um 3612 PR pattern, 1min bake @ 110C  gold

       


      Pre-Etch Wafer Measurements

      All pre-etch measurements are taken on Nanospec. Reference the SUMO Characterization How-To's for Nanospec operating procedure.

      For the SiO2 wafer, use the Oxide on Silicon Recipe (#1). For Wafer 88, use the Positive Resist on Silicon Recipe (#10). Use 10x magnification for all measurements (Objective 1 on Nanospec).

      1.  Use the reference wafer to calibrate before measuring.
      2. Take readings for the Center, Top, Flat, Right and Left positions of the wafer. Readings should be taken about 15mm from the wafer edge.
            a.  For PR wafer, measure the PR thickness, which is darker in color than the Si. Accidentally measuring the Si will result in a <100A reading.
      3. Calculate the averages.
      4. Record results on the SUMO Qualification Log Sheet. 

        

      Etch Process

      Before loading the wafers,  season the chamber so that the chamber surface chemistry is brought to equilibrium with the process being run. This enables the actual process to stabilize quickly after the plasma is turned on. This seasoning also leads to more repeatable etching result.

      1. Season the chamber for 15 minutes using the Oxide etch CF4 / CHF3. Follow the standard operating procedure as outlined above, or on the procedure print-out at the tool. Be sure to check the program parameters while seasoning and adjust the resistor/capacitor settings as necessary.
      2. Run a separate etch for each of the two wafers. Each etch is 10 minutes for the PR wafer and 2 minutes for the SiO2 wafer.

      Recipe = Oxide_ER_Test : Oxide etch CF4 / CHF3

        • CHF3 (40.0 sccm)
        • CH4 (20 sccm)
        • Ar (30 sccm)
        • Power : 500W (Fwd)
        • Pressure: 100 mT
       

      Post-Etch Wafer Measurements

      1. Measure post-etch thickness for all wafers using the same Nanospec as before and the same respective Nanospec analysis recipes.
      2. Take readings for the Center, Top, Flat, Right and Left positions of the wafer. Readings should be taken about 15mm from the wafer edge.
      3. Calculate the etch-rate for PR and SiO2 by subtracting the post-etch thickness from the pre-etch thickness and then dividing by etch time.
      4. To calculate selectivity, measure the Silicon step height of PR wafer.
      5.              a.   Strip the wafers of PR using the Strip.rcp recipe on Matrix.
                     b.   Measure the step height at each of the 5 points via Alphastep. Readings should be taken about 15mm from the wafer edge.
                     c.   Calculate the average step height.
                     d.   Calculate the amount of Si lost and divide by etch time to determine the Si etch rate.
      6.  Calculate the selectivity by dividing the PR etch rate by the Si etch rate.

       

      Reported Data

      Qual data may also be found on the Badger comment log. The following data is reported for the Ox-RIE qual:

      • PR Etch Rate (3612)
      • Si Etch Rate
      • PR:Si Selectivity
      • SiO2 Etch Rate
      • SiO2:PR Selectivity

      Machine Status States

      • Red: A major sub-system of the tool (RF power supply, mass flow controller, vacuum pump, etc.) is not functioning up to standard.
      • Yellow: A sub-system of the tool not common to all recipes is not up to standard. For example, a specific gas is being replaced.
      • Green: System is up to standard.

       

      Process Monitoring Results

       

       

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