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Gasonics Plasma Asher

The Gasonics Aura Asher is an automated upstream microwave plasma system used for stripping photoresist of clean 4 inch silicon wafers. The system generates a plasma of oxygen and nitrogen in a reaction chamber. This reactive mixture flows downstream to the process chamber where it reaches a state of “afterglow,” where it is highly reactive and no longer electrically active or damaging to the wafer surface. The dissociated oxygen chemically reacts with the photoresist effectively burning the resist off the wafer.

Picture and Location

 

 

 

Contact List and How to Become a User

Contact List

The following people make up the Tool Quality Circle:

  • Process Staff: Nancy Latta
  • Maintenance: Elmer Enriquez/Mike Dickey
  • Super-Users:

 

Training to Become a Tool User

The gasonics is an easy to use tool.  To get training contact a user of the tool and ask them to review the system with you.  This can be a staff member or other labmember.  You are responsible for reading and understanding the operating instructions and other related materials about the tool.

 

When you are comfortable with the opertaion of the gasonics contact the responsible staff member for qualification on the tool.  They may want to quiz you on the system to assure you have the knowledge necessary to run it.

 

 

Operating Procedures

 Safety Hazards

 WARNING: Proper use and safe operating of the equipment is the responsibility of the user of the system.  All users who work with, or are exposed to this equipment must take precautions to protect themselves against possible serious injury.  Do not be careless around this equipment.

 Electrical:  High RF voltages may be present at the output of this unit.  Use EXTREME CAUTION when working around any power supply areas.  High voltage exists throughout the system. Observe standard electrical safety precautions to avoid personal injury or damage to the equipment.

     Thermal:  Wafers can be very hot when the come out of the reaction chamber.  Allow the wafers time to cool prior to handling. 

       Covers:  DO NOT remove any covers or touch any lead wires to avoid electrical shock.

         Moving Parts:  Keep hands, hair, tools and loose clothing away from any moving parts to avoid personal injury or damage to the equipment.

           Emergency Shutdown Procedure

           Depressing the Emergency Off (EMO) located at the front and rear of the machine will instantly de-energize and remove all power to the system.

             General Information

            The Gasonics Aura Asher is an automated upstream microwave plasma system used for stripping photoresist of clean 4 inch silicon wafers.  The system generates a plasma of oxygen and nitrogen in a reaction chamber.  This reactive mixture flows downstream to the process chamber where it reaches a state of “afterglow,” where it is highly reactive and no longer electrically active or damaging to the wafer surface.  The dissociated oxygen chemically reacts with the photoresist effectively burning the resist off the wafer.

               System Features

               

                • Clean Equipment Group
                • Semi-Clean Equipment Group
                • Single Wafer Processing
                • In-Line Cassette to Cassette
                • Two Plumbed Process Gases (Oxygen and Nitrogen)
                • 4” Wafer Capability
                • Programmable Microprocessor
                • Automatic Wafer Handling
                • Infrared Heat Source to Elevate Wafer Temperature
                • 1kW Microwave Power Supply
                • Downstream Wafer Processing
                • Vacuum Quartz Reaction Chamber
                • Front and Backside Photoresist Removal
                • Automatic Photo Emission End Point Detection (not utilized)

               Status Check:

              Check Badger for reservations, problems notes, and to see if it is already enabled by another user.

              The system is available if the initial system and status checks are good. Enable the system on Badger.

                 Initial System Check List:

                  Display Screen: 

                  1.   SETUP:  IDLE or HIBERNATE is the normal state when the equipment is in a standby state.
                  2.   SETUP: STRIPPING indicates the system is currently in use.
                  3.   SETUP: PAUSED indicates he system is in an alarm state or the STOP pushbutton was depressed during processing.  See System Recovery Procedures below.
                  • Keyswitch Mode: AUTO
                  • Input Cassette (left cassette elevator): In the UP Position
                  • Output Cassette (right cassette elevator): In the Down Position

                     Running The Process:

                     

                    CAUTION:  The Gasonic’s uses lamp heating to enhance the photoresist strip rate.  Wafers can be heated to temperatures greater than 300ºC.  Please use caution if your devices are sensitive to temperatures in this range.

                     

                    PROCESS NOTE:  Ashing can leave behind non-volatile compounds.  It is recommended that a Spin-Rinse-Dry is done both before and after ashing.

                    • Login on Badger.  Failure to log in on Coral before pushing any buttons will result in the asher going into a fault state.
                    • If the display screen shows SETUP:  HIBERNATE, push START
                    • Load your wafers into Input Cassette.

                       

                      NOTE:  Your wafers MUST BE FLAT ALIGNED.  The wafer flats can either be aligned to the top or to the bottom of the Input Cassette.  Failure to align the flats can cause handling problems during processing.

                       

                      Verify Output Cassette is in place.

                        The Output Cassette is normally in the down position.

                        Display Screen:  SET UP: HIBERNATE

                          Press the  START button to go to the IDLE state.

                          Press RECIPE NO. button.

                          Press a three digit recipe sequence from the recipes below:

                            • Recipe 0, required- 5 second gas flow stabilization.
                            • Recipe 1, optional.  HiLamp Heating- 10 second wafer heating and ashing.
                            • Recipes 2 though 7, LoLamp Heating
                            • Variable ash time for specific photoresist thickness, see table below.
                            • Recipes A through D, No Heating
                            • Variable ash time for specific photoresist thickness, see table below.

                            Press ENTER.

                            Verify the three digit recipe sequence numbers are correct.

                              If the recipe sequence is not correct press CE and re-enter the three digit recipe sequence.

                              Press START button to begin processing.

                                All wafers in the Input Cassette will be ashed.

                                Press STOP to stop the flashing light.

                                Unload your wafers from the Output Cassette once all the wafers have been processed.

                                Replace the Output Cassette.

                                   Common Initial Recipe Table:

                                   

                                  Recipe Number

                                  Process

                                  0
                                  (Required)

                                  5 sec.
                                  Pressure and Gas Flow Stabilization

                                  1
                                  (Optional)

                                  10 sec.
                                  HiLamp Strip

                                   LoLamp Process Specific Recipe Table:

                                   

                                  Recipe Number

                                  LoLamp Strip Time (sec.)

                                  2

                                  30

                                  3

                                  45

                                  4

                                  60

                                  5

                                  75

                                  6

                                  90

                                  7

                                  100

                                   

                                   

                                   No Lamp Heating Process Specific Recipe Table:

                                  Recipe Number

                                  No Lamp Heating
                                  Strip Time (sec.)

                                  A

                                  25

                                  B

                                  50

                                  C

                                  75

                                  D

                                  100

                                   

                                   Process Recommendation Recipe Table:

                                   

                                  Photoresist and Processing
                                  Recipe Suggested

                                  1.0 or 1.6 Micron SPR 3612
                                  (As-Spun or Plasma Processed)

                                  3

                                  3 or 4 Micron SPR 220
                                  (As-Spun)

                                  4

                                  3 or 4 Micron SPR 220
                                  (Plasma Processed)

                                  4, twice

                                  7 Micron SPR 220
                                  (As-Spun)

                                  6

                                  7 Micron SPR 220
                                  (Plasma Processed)

                                  6, twice

                                  10 Micron SPR 220
                                  (As-Spun)

                                  4, twice

                                  10 Micron SPR 220
                                  (Plasma Processed)

                                  6, three times

                                   

                                   Shutdown

                                  1. Replace the Output Cassette once you have removed your wafers
                                  2. Wait until the Output Cassette has completed lowering.
                                  3. Disable Gasonics on Badger.

                                     System Recovery Procedures

                                    SETUP: PAUSED

                                      • If wafers are being processed and there is not wafer handling fault, press START.  They system should continue processing until all wafers have been processed.

                                      Broken Wafer:

                                        • Remove the protective plastic covering.
                                        • Make sure there are no obstructions in wafer handling and reaction chamber door pathwa
                                        • Carefully remove the Sender Cassette and set aside.
                                        • Carefully remove the Receiver Cassette and set aside.
                                        • Gently slide the Sender Wafer Handler to the left.
                                        • Gently slide the Receiver Wafer Handler to the right.
                                        • Gently slide the Wafer Tray / Reaction Chamber Door closed.
                                        • Replace the protective plastic covering.

                                        CAUTION:  MAKE SURE YOUR HANDS AND EVERYONE IS CLEAR OF THE WAFER ELEVATORS AND WAFER HANDLING PATHWAY

                                        • Press the START button.
                                        • The wafer handlers, wafer elevators and reaction chamber door should reset
                                        • If the system does not reset, repeat the above procedure to relocate the wafer handlers and reaction chamber doors.
                                        • If the system does not reset
                                        • Put the system down on Badger.

                                         

                                        Basic Troubleshooting

                                        Below are common error messages and the responses that labmembers may try to correct them.  If the suggested actions do not bring the system back to a usable state write the problem or shutdown on Badger to notify the appropriate staff members.

                                         

                                        Error: LOADING WAFER INPUT CASSETTE EMPTY

                                         

                                          • The wafer handler did not sense a wafer or no wafers are present in the Input Cassette.
                                          • Pressing START causes the system to go through the Warm-Up routine before attempting another loading of the wafer.
                                          • Pressing STOP clears the wafer path and returns the system to IDLE.

                                           

                                          Error: NO INPUT CASSETTE

                                            • The cassette elevator did not sense a cassette.  The cassette could be missing or not correctly positioned.
                                            • Reposition the Input Cassette and press START to resume processing.
                                            • Press STOP to abort processing.

                                             

                                            Error: NO OUTPUT CASSETTE

                                              • The cassette elevator did not sense a cassette.  The cassette could be missing or not correctly positioned.
                                              • Reposition the Output Cassette and press START to resume processing.
                                              • Press STOP to abort processing.

                                               

                                               


                                              APPENDIX: PROCESSING TID-BITS

                                               

                                              Wafer Heating:  Optical coupling of the quartz halogen lights with the substrate is resistivity and deposited film dependent.  Intrinsic silicon (high resistivity) will not reach as high of a peak temperature as heavily doped silicon (low resistivity).  Deposited layers will also affect the optical coupling and increase the peak temperature. 

                                               

                                              Aluminum Hillocks:  Hillocking in pure aluminum can initiate at temperatures as low as 90ºC.  Hillocking is pattern and thickness dependent and the severity of the hillocks increases with temperature.  Aluminum heats rapidly when exposed to quartz halogen heating sources.  If your samples are hillock sensitive, close scrutiny of this and all processes are required to identify your temperature limitations. 

                                               

                                              Non-Volatile Compounds:  Ashing works by carburization of the photoresist.  If there are components of the photoresist or contamination from prior processing that are not volatilized in the oxygen plasma will be left behind on the wafer.  A Spin-Rinse-Dry (SRD) is recommended both before and after ashing.

                                               

                                              Oxidation Potential: Ashing is done in an energetic oxygen plasma.  Oxidation of surface layers is highly likely.  If surface oxides are a concern for your samples a post ashing oxide removal step needs to be added to your process.  For example a short 50:1 HF dip can be used to remove any oxide that formed on aluminum.

                                              Process Monitoring and Machine Qualification

                                              Tool Qualification Run

                                               

                                              Frequency

                                               

                                              Procedure

                                               

                                              Responsibility

                                               

                                               

                                              Recommendation to users with critical processes

                                               

                                              Machine Status States

                                              Red:

                                              Yellow:

                                              Green:

                                               

                                              Process Monitoring Results

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