Branson Asher

Owned by Wirth, Justin C
Last updated: Feb 03, 2022 by Hosler, Richard S
9 min read


Refer to the Material and Process Compatibility page for information on materials compatible with this tool.
Equipment Status: Set as UP, PROBLEM, or DOWN, and report the issue date (MM/DD) and a brief description. Italicized fields will be filled in by BNC Staff in response to issues. See Problem Reporting Guide for more info.

StatusUP
Issue Date and Description


Estimated Fix Date and Comment

Responding StaffFrancis

Error rendering macro 'excerpt-include' : User 'null' does not have permission to view the page 'eLog - General Etching'.


iLab Name:  Branson
iLab Kiosk:  BRK Etch Core
FIC: Shared
Owner:  Francis Manfred
Location: Cleanroom - K Bay
Maximum Wafer Size: 6"/150 mm

Overview

TypeMaterialsRestricted MaterialsAvailable GasesMax RF PowerWafer Size
Barrel AsherSi, Oxides, Nitrides, Polymers, Organics
O2, Ar?4 inch (100 mm) SEMI Specification

General Description

The Branson Asher plasma system generates a low pressure, low temperature gaseous plasma.  Plasma reactions such as ashing, etching, and polymer surface modification can be performed.  Typical applications include cleaning substrates, curing PDMS, and stripping photo resist or other organics using Ar/O2 plasma.

Technology Overview 


Equipment Overview

Branson Asher Cabinet/Enclosure

  1. Process Programmer front panel controls and indicators
  2. Convectin gauge for chamber pressure readout
  3. Process chamber
  4. Plasma controller
  5. RF Generator

Branson Asher Component Descriptions

Process programmer PM906T/Temperature Controller PM921

Overview

The upper half of this assembly is labeled, Temperature Controller PM921 and is not used.  The majority of controls located on the lower half, labeled Process Programmer PM906T, are also not used in normal operation of the Branson Asher.  There are only three switches used on this controller, see below for more details.

Configuration

  1. Manual/Auto toggle switch - This switch will remain in the manual position and should never be switched to auto.
  2. Vacuum toggle switch - This switch will open or close the pump isolation valve.  When the switch is in the up position and the amber light is on, the isolation valve is open and the pump is evacuating the chamber.
  3. Purge toggle switch - This switch will open or close the purge gas valve.  When the switch is in the up position and the amber light is on, the purge gas is flowing into the chamber.


275 Convectron Gauge

Overview

The convection parini gauge is used to display the current chamber pressure.  The gauge will operate under the full range of the Branson Asher's capability (~100 mTorr to Atmosphere).  This gauge is also interlocked via iLab and will not display current pressure if not activated in the iLab kiosk.

Configuration

  1. The gauge has an indicator light to distinguish between readings output in Torr and those output in mTorr.  Please pay attention to this indicator when reading pressure data from this gauge.


Branson Asher Process Chamber

Overview

The process chamber is made from quartz and has a hinged access door through which samples are inserted or removed.  The door is sealed with a silicone bell jar gasket.  The etch tunnel is made from metal and sits inside the chamber but is not mounted down.  Caution must be excersized when placing or removing the sample boat so the etch tunnel is not moved causing breakage of the quartz tubes located at the top and bottom of the chamber (around the etch tunnel).

Configuration

  1. Chamber door latch in the closed position
  2.  Chamber door latch in the open position
  3. Process gas inlet and Pumping line outlet (Fragile made of quartz)
  4. Etch tunnel assembly
  5. Sample boat

Opening the chamber door

The chamber is made from quartz and is fragile. Do not pull on the chamber door handle. Once the handle is in the unlatch position, shown in figure 2 to the left, only pressure differences are holding the door closed.


  1. Make sure the Vacuum switch toggle on the Process Programmer PM906T is in the off position.
  2. Pull the chamber door latch 90 degrees into the unlatched position as shown in image 1 to the left.
  3. Twist the chamber door latch 90 degrees clockwise as shown in image 2 to the left.
  4. Change the Purge toggle switch on the process programmer PM906T to the on position, wait for atmospheric pressure to be reach and the door should swing open easily.  

Closing the chamber door

  1. Make sure the Purge toggle switch on the Process Programmer PM906T in in the off position.
  2. Swing the door closed and rotate the latch 90 degrees counterclockwise.  The door should now stay shut on its own.
  3. Push the door latch 90 degrees into the latched position as shown in image 1 to the left.  You should feel the latch pulling the door tight against the bell jar.
  4. Change the Vacuum toggle switch on the process programmer PM906T to the on position, the system should reach ~150 mTorr within a few minutes.  If it does not, there may be a sealing issue at the door.  Try Opening the chamber door per instructions above, and then repeat the Closing the chamber door instructions again.

If the system does not reach <200 mTorr within a few minutes, there may be a sealing issue at the door.  Try Opening the chamber door per instructions above, and then repeat the Closing the chamber door instructions again. If the problem persists, contact the staff.


Plasma Controller PM325

Overview

The plasma controller pm325 provides gas control for Ar and O2 process gases.  This unit also provides control and power readout of the RF system.

Configuration

  1. Gas rotameter used to control the flow of Argon in the Branson Asher.  The rotomater provides a device for measuring the flow rate of gas, as well as a needle valve for adjusting the flow rate.  It is important to note that the current installed rotameter is not calibrated for Ar, so the readout is not precise and should be treated as a relative reference to your previous process.
  2. Gas rotameter used to control the flow of Oxygen in the Branson Asher.  The rotomater provides a device for measuring the flow rate of gas, as well as a needle valve for adjusting the flow rate.  It is important to note that the current installed rotameter is not calibrated for O2, so the readout is not precise and should be treated as a relative reference to your previous process.  Additionally there are two indicating balls in the rotameter, you should note which ball you are taking your reading from, top or bottom and be consistent in future runs.
  3. Toggle switch providing ON/OFF control of the Argon gas supplied to the system.
  4. Toggle switch providing ON/OFF control of the Oxygen gas supplied to the system.
  5. RF power ON/OFF toggle switch.
  6. RF power level adjustment knob. (must be turned fully counter clockwise before turning the RF power toggle [5] to the on position)
  7. Gauge for RF power readout selection (forward / reverse power)
  8. RF power level gauge (displays both forward and reverse power depending on selection of readout toggle switch [7])


RF Generator PM1

Overview

The RF generator provides dynamically regulated RF power to maintain constant level into a normal load, or to limit power if the load is removed.  

Configuration

  1. The Ready indicator should be lit green indicating the AC power is on, warmed up and ready to provide RF power.


Standard Operating Procedure

Training / SOP Video

Written SOP

The following instructions are meant to be a guide, but some process parameters may change based on your samples and experience. Please note that the chamber components are delicate; do not bump the etch tunnel assembly or drop the sample boat. If the RF generator is powered off, do not attempt to turn it back on unless specifically instructed by a lab staff member.

Initial tool state inspection

  1. Log into iLab, navigate to the BRK Etch Kiosk, and activate your Branson Asher Session to power on the control PC monitor.
  2. After successfully starting your kiosk session you should see the 275 Convectron Gauge turn ON and show approximately atmospheric pressure (~760 Torr).
  3. The switches for the Process Programmer PM906T should be in the following state.
    1. Switch 1, up position for Manual operation.
    2. Switch 2, down position for Vacuum OFF indicator light is OFF.
    3. Switch 3, down position for Purge OFF indicator light is OFF.

  4. The controls for the Plasma Controller PM325 should be in the following state.

    1. Knob 1 should be rotated fully clockwise to the OFF position


    2. Knob 2 should be rotated fully clockwise to the OFF position
    3. Switch 3 should be in the down position for Ar flow OFF
    4. Switch 4 should be in the down position for O2 flow OFF
    5. Switch 5 should be in the down position for RF power OFF
    6. Knob 6 should be rotated fully counterclockwise to the OFF position
    7. Switch 7 should be in the up position indicating FWD power
    8. Gauge 8 should currently read 0 or full left postion

  5. The Ready indicator of the RF Generator PM1 should be lit green indicating the AC power is on, warmed up and ready to provide RF power.


Processing a wafer

  1. Open the door to the etch chamber
  2. Remove the quartz boat from the chamber.
  3. Place your samples in the quartz boat.
  4. Return the boat to the etch chamber.
  5. Close the chamber door.

  6. Turn the vacuum switch to the ON position. The indicator should illuminate and pressure will begin falling indicated by the 275 Convectron Gauge.

  7. After chamber pressure reaches < 200 mTorr, turn the Argon and/or O2 Gas flow switches to the ON position.

  8.  Adjust the Ar and O2 flow valves to achieve the desired pressure in the etch chamber. 

    The process must operate between 1 Torr and 2 Torr chamber pressure to achieve desired results. Do not operate the system outside this pressure band.

    2. Typical values for Ar flow, indicated by the ball inside the rotameter, range from 120 - 140 (These values are relative as the gauge is not calibrated to the gas)

    3. Typical values for the O2 flow, indicated by the two balls inside the rotameter, range from 12-14 for the upper ball, and 6-7 for the lower ball (These values are relative as the gauge is not calibrated to the gas)

  9. Make sure the RF power adjustment knob (2) is turned fully counter clockwise, switch the RF Power toggle (1) to the Up or ON position.

  10. Make sure the FWD / REFL switch (3) is in the Up or FWD position and adjust the RF power adjustment knob (2) clockwise until the desired power level is reached. 

    2. Processing power capability ranges from about 10 - 500 Watts, with 100-200 Watts typical.

  11. Begin timing.

  12. You can verify proper plasma ignition two ways while running the process.

    1. Turn off the lights in the cleanroom bay, and observe the purple glow visible inside the chamber.  It is difficult to see without turning the lights off.

    2. Flip the FWD / REFL switch on the Plasma Controller PM325 to the down position indicating reflected power.  REFL or reflected power should indicate at or near zero when plasma has properly ignited.

  13. When etch is done, turn the RF POWER switch OFF,then turn the RF LEVEL control to zero. 

  14. Turn the Argon and/or O2 Gas flow switches OFF and let pump to < 200 mTorr. 

  15. Turn the VACUUM switch OFF. 

  16. Flip up the handle on the door and rotate to the right - BUT DO NOT PULL ON THE HANDLE! 

  17. Turn the PURGE switch ON. 

  18. Wait for the door to open, then flip the PURGE switch to the OFF position. 

  19. Remove your sample(s). 

  20. Return quartz boat to the chamber.

  21. Close and latch the chamber door.

  22. Sign out of the coral system.

 

Questions & Troubleshooting



Process Library

References