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Matrix Plasma Asher, matrix

The Matrix plasma asher is used to strip photoresist from contaminated wafers using a combination of oxygen plasma, high power, higher pressure and a heated chuck (platen).

Picture and Location

Matrix 

Background

 

The Matrix is a resist asher that uses both an Oxygen plasma and heated chuck to strip hard to remove photoresist. Although it is particularly good for getting implanted or plasma damaged resist off samples, a combination of ashing and wet chemical stripping (sulfuric/peroxide or PRX127) may have to be employed to remove stubborn resist.

In general the tool uses high chamber pressure (3-4Torr) and RF power about 400-500Watts.  A heated chuck, 180-190C degrees also aids in the ashing of resist.

The tool is contaminated and receives 4 inch wafers only.  Users may attach smaller samples to carrier 4 inch wafers by using a variety of materials; kapton tape, photoresist, etc…

Process Capabilities

Cleanliness Standard

 The Matrix is a contaminated piece of equipment.

Performance of the Tool

What the Tool CAN do

The Matrix is a good tool for the removal of photoresist on contaminated wafers.  One should keep in mind, however, that when ashing PR off layers of some metals oxidation may occur.  To achieve good contact to those metals the oxide must be removed.

 

What the Tool CANNOT do

One question that comes up from time to time is whether or not the Matrix can be used to descum or partially etch photoresist.  It is not recommended due to the power, heated chuck and high pressure of the standard operation of the tool.  Control of such a mild etch is not possible on the matrix.

 

Process Monitoring

 Montioring is not done on a regular basis but will be performed in reaction to users concerns.

Contact List and How to Become a User

Contact List

 

The following people make up the Team Matrix:

  • Process and Training Staff: Nancy 
    To train on the matrix first view the training video and contact SNF training contact on the Equipment Summary page.
  • Maintenance: Elmer, Cesar and Mike Dickey
  • Super-Users: Jim Kruger

 

Training to Become a Tool User

 

The Matrix Plasma Asher is an easy to use machine.

 

Please follow the following procedure to become a qualified user of the Matrix plasma photoresist ashing system.

 

Read all material on the SNF website concerning the specific furnace, including Background, Process Capabilities, Operating Procedures and Process Monitoring.

 

View the Matrix Training Video.  After seeing the video contact the staff trainer with any questions you may have.

Once all questions have been answered and you feel confident in the use of the tool you will be qualified to use it anytime, 24/7.

Operating Procedures

 

When the screen is in the MAIN MENU option the following buttons show;

 

  • LOAD- Allows you to load a recipe.

 

  • RUN- Runs the recipe.
  • REPORT- Gives a slot-by-slot report of how many wafers in the cassette were processed, and notes any wafers were not processed and why they were not processed.

 

  • EDIT- Allows the user to edit the current recipe.

 

  • SAVE- Stores a recipe onto a magnetic card. It is used to record a new recipe. SAVE should not be used in normal stripping conditions. Do not overwrite any recipes on the magnetic card marked "STDO2Str". Please contact the equipment owners if you need to create a non-standard recipe.

 

Standby Check List

  • The STANDBY MODE menu is on the screen.
  • The RESET and SYSTEM lights are ON (look through the window on the lower half of the machine by the Emergency Power Off (EPO) button).
  • The green AC and RF lights are ON (behind the door on the bottom right side). If they are not on turn the RF Generator breaker switch off and on. If the lights still do not come on, the fuses may need replacement. Call the maintenance technician.
  • The temperature should be 180-190°C. This is especially important if you are running the "Pins Down" option which allows you to control the temperature of the wafers during the plasma etch.

NOTE: The door is interlocked, make sure the door is completely closed or the Matrix will not run.

Start-Up Procedures

  1. Push STANDBY EXIT to get out of STANDBY MODE. The "PRESSURIZING CHAMBER..." message will appear on the screen.
  2. When the chamber is vented the MAIN MENU will appear. This should take several minutes.
  3. The MAIN MENU will appear.

Load the Recipe

You will find magnetic cards that looks like a credit cards attached to the tool.  One card will have two strips.  The other card is used to give firmness to the cards for loading.  Do not be surprised if the second blank support card is missing; you may still load the recipe, just be careful not to force or bend the recipe card.

Push the LOAD button and the software will prompt you to load the first edge (1) of the two-sided magnetic card into the slot on the front of the machine.

 You will be asked to remove the card smoothly and told STEP #1 VALID.  Turn the card around and repeat to load the edge marked 2.  The recipe will be loaded once you get the STEP #2 VALID message.

Return to the MAIN MENU.

Editing the Recipe

First, a description of the recipe as it is loaded from the card.  The etch conditions are- 3.75Torr chamber pressure, 40% (of maximum) O2, 450Watts, EP (end point) set to timed (2 mins) and the pins are down (the wafer sits directly on the heated chuck).

There are two steps to the recipe, a set up step with no RF and the etch step.  Nothing should ever be changed in Step 1, the set up step.

Most users will change only the etch time, but be aware that anyone can change any parameter.  It is strongly suggested that you review the recipe before committing your wafer to etch.

The maximum time that can be set in the recipe is 4:59 minutes.  It is advised to consider running several short recipes rather than one long recipe.  The heated chuck may actually make the resist harder to strip by burning it.  This is particularly true for wafers bonded to carrier wafers using photoresist for deep RIE etching.

When in the MAIN MENU push the EDIT button.  The button choices you will see after getting into EDIT mode should be;

UP- this is a navigational button that moves the cursor up a line.

DOWN- moves the cursor down.

V— decreases the chosen parameter value by one.

V+- increases the value.

 

 

Check the Process

  1. Select RUN from the MAIN MENU. The RUN OPTIONS screen will appear.
  2. HOME the cassette.
  3. Load one wafer, flat down, in the marked cassette.
  4. Place the cassette on the loader plate.
  5. Press the SINGLE wafer option.
  6. The process steps will be displayed while the wafer is being processed.
  7. When the wafer is processed push ABORT. When the machine has halted, remove the cassette from the loader plate.
  8. Push EXIT, the MAIN MENU will appear.
  9. Put the dummy wafer back in the cassette. Secure the lid.

NOTE: If you must end the process before it finishes, push ABORT. The WAFER REPORT screen will appear. A report will automatically be displayed. Press CLEAR REPORT to get back to the MAIN MENU screen.

Run Your Wafers

  1. Select RUN from the MAIN MENU. The RUN OPTIONS screen will appear.
  2. HOME the cassette.
  3. Load the wafers, flat down, in the marked cassette.
  4. Place the cassette on the loader plate.
  5. Press the AUTO or SINGLE wafer option.
  6. The process steps will be displayed while the wafer is being processed.
  7. When all the wafers have been processed push ABORT. When the machine has halted, remove the cassette from the loader plate.
  8. Push EXIT, the MAIN MENU screen will appear.

Shutdown

  1. Select STANDBY.
  2. Disable the matrix and fill in the log.

 

Process Monitoring and Machine Qualification

 

Frequency

 As needed by user reports or after major repairs.

Procedure

 A resist coated wafer (3612, 1.0 um) is run using the standard O2 Strip program for 2 minutes.  Observe carefully the etch parameters; power, pressure and gas flow.  The resist should have cleared,  If not, contact responsible maintenance staff member

Responsibility

 Primarily the process staff member, but users are encouraged to run a qual if they feel the tool is not in good running order.  Staff should be informed of the results.

 

Machine Status States

Red: Shutdown- not available for use.

Yellow: Has an intermittent or 'work around' problem.  An example of this might be a loose casing that has to be in a correct position in order to satisfy an interlock.  A user may simply push the casing in the right spot for the tool to work.

Green: The tool is functioning properly.

 

ADDITIONAL PROCESS INFO

From labmember aintekofer:

lower chuck temperature (100C)
etch rate for 3612 photoresist ~70nm/min

 

 

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