Trion Sirius-T2 RIE Etcher

Author: Roger Robbins
10/3/2017

Sirius-T2 RIE Etcher Operation Manual

Purpose

This operation manual presents the operation instructions for Automatic Single Operation and Manual Operation for the Trion Sirus-T2 RIE (Reactive ion Etcher) Etcher.  The Automatic Operation runs pre-programmed process instructions and the Manual Operation allows real time adjustments to optimize process parameters in order to set up a new process or adjust an established process.

Startup and Login

If the system is totally shut down, this is the procedure to revive it and set up the etch process software.  But be practical here; if the system is off for a reason, don’t start it up – there should be a sign denoting that there is a problem.  (Startup is normally a staff operation.) STEP 1.  Power up the system by pressing the MAIN power switch (button) behind the keyboard front panel.  This switches on the power to the system, including the computer and screen.

STEP 2.  Double press the etcher control program icon:

This will open the control software and the screen will look like Figure 3. Log on to the tool with your username and password. If you are not able to log on, please see Roger Robbins for training.

Automatic Single Process

STEP 1.  Click the button on the home screen (Figure 3) that says “LOAD/EDIT RECIPE”. This will bring up the screen that looks like this:

STEP 2.  Press the “Recipe from Disc” icon in lower left button group to find a canned recipe. STEP 3.  Press the button labeled with your selected etch program and review process parameter values in case someone has modified them. You can change the parameters to suit your process requirements from this window by tapping the parameter box and typing in new numbers.  Leave the “Refl. Tol (W)” and “RF Stable Time (s)” values alone.

Record in your lab notebook the values for your particular process so you can reestablish your process if someone changes the numbers.  If you change parameters, press the EXIT button and your numbers will be used but not saved.  This would preserve the original parameters for the process buttons on the select parameter icon screen. NOTE: If someone has edited the parameters in a canned program, but not “saved” the changes onto the hard drive, the modified parameter set is retained in the “Active” memory.  If you want to run the reference program with the original values, you must click “Download/Edit Recipe” and then click the “Recipe from Disk” buttons and then select the canned recipe button.  This should provide the ref values – unless the someone has saved new values.  Please check the canned values in Appendix D with the saved values to be sure. STEP 4.  Vent Chamber.  When you select the EXIT button from the parameter review panel, the program brings up the following screen, from which you can load your sample by pressing the “Vent Reactor” button.

STEP 5.  Load Sample.  In general, if you have a small sample (<1 inch in size) it will stay in the location you put it at, but if you have a wafer-sized substrate, the vacuum will create a thin sheet of expanding air struggling to get out from under the wafer.  This will cause the wafer to slide to the edge of the RF electrode platen.  This may cause a bit of non-uniform etching near the edge of the wafer closest to the rim of the RF platen.  The “industry standard” solution to this is to use a tiny amount of Kapton tape to keep your wafer from sliding around.

STEP 6.  Close the chamber lid and start process by pressing the “Automatic Single Process” button on the same screen as the “Vent Reactor” button. This will bring up an overlay window asking for “Lot No.” and “Comment” input.  If you fill out these blanks, the system will record highly detailed data on the process performance.  This will help you if your process fails so you can know exactly what happened (i.e. did you use an improper value in the process instruction data, or perhaps a tool failure…).

STEP 7.  Remove Sample at completion of process.  When the process times out, the screen will show an overlay window declaring the process finished.

STEP 8.  Pump the chamber down again by clicking on the “Manual Process Control” button in the center of the above screen.  You will see the screen below.  Press the grey “Vacuum Closed” and “Press Iso Closed” buttons to pump down to 50 mTorr.  When the pressure is at target, press the green “Vacuum Open” and “Press Iso Open” buttons again to close off the vacuum gauge and seal the chamber.  This action is imperative to prevent the chamber from absorbing water vapor form the air, which results in a long pump-down time for the next user, which may be you…HOWEVER:  We now have a dry pump on the system and you can use the “Standby” button to establish a vacuum between uses.  So when you finish your process and logout, just push the ”Stand By Mode” button and leave.

Manual Process Control

This category allows the user to create process parameters to etch a new material.  In this segment of the program you have the freedom to adjust process parameter set points in real time during an active run.  However the time parameter set point is ignored in case you decide to lengthen it in real time – meaning that you have to turn off the process manually to stop it. STEP 1.  Activate the Manual Mode. From the front page of the control software, open the “Recipe Parameters” page by clicking on the “Load/Edit Recipe” button or “Download Recipe” button.  On the Recipe parameters” page, you can “Create New Recipe” or load a “Recipe from Disk” to bring up the “Select Recipe” page for modifying parameters in a standard recipe.

STEP 2.  From this page you have the ability to select parameter choices and values as well as actually manually run the process with the buttons at the bottom of the page.  Note that depending on what is running, the window presents new buttons when necessary and makes them vanish if they cannot be used in the current state of operation.

Also, there are two buttons that enable you to download values from a standard pattern or save the current recipe.  The “EXIT” button brings back the front page

Typical Manual Process Sequence

This process sequence is copied almost verbatim from the Sirius T2 Plus “Operation and Maintenance Manual”

1. Once you have loaded your sample, the Manual Process mode can be called up from the main Control Panel.
2. In the Manual Process mode you can edit parameters and manually run the process. HOWEVER, the listed process time will not stop the process and the parameter tolerance fault settings will not be used to fault process.
3. To run in manual process mode, first press the “Vacuum” button.
4. Then Press the “Press Iso” button and this will pump the chamber down.
5. Once the chamber is pumped down to the desired vacuum pressure, then press the “Gas” button. This will turn the chosen gases on and adjust the throttle valve to achieve the requested pressure.
6. After the gases are flowing and the pressure is adjusting, wait until the pressure set point is achieved.
7. After the pressure has stabilized at the set point, press the “RF” button to turn on the RF power to strike a plasma..
8. Once the “RF” is on the tool will tune the reflective power to the process conditions.
9. The process will run and count up the process time, but will not shut off the process even if the “Process Time” is met.
10. To turn off the process, press the “RF” button.
11. Then press the “Gases” button. This will turn off all the gases, open the throttle valve to 100% and pump down the chamber.
12. At this point, you can press the “EXIT” button to return to the Main Control Panel.
13. When you retrieve your sample and have no more to process, pump down the chamber so it will remain under vacuum until the next user needs it – i.e Press the “Standby” button (only if we have a dry pump connected to the system).

Appendix A: Data Logs

If you need to view the process history data from a saved log sheet, you would exit the process control software by pressing the “EXIT” button at the lower right of the main panel.  This will bring up the standard Windows icon page.

Click on the “My Documents” icon to see the files, and click on the “Process Data” line in the Local Disc (C: ) list to bring up a list of Logs.  Click on your log of interest and you will find data as shown in the next image below.

Please don’t store this data unless you really have a need for it.  Otherwise our hard drive will fill up quickly.

Appendix B: Trion Plasma Gas Applications

Notes

1.  The Trion Sirus-T2 tool is an Reactive Ion Etcher (RIE) which enhances anisotropic etching (mostly vertical etching not horizontal etching) by creating a plasma voltage gradient above the surface of the substrate, causing ion acceleration and thus bombardment of the sample surface which physically breaks chemical bonds and makes the surface more reactive to the active chemical etchants.  This means the etch process will proceed faster in a vertical direction and create more vertical oriented sidewalls.
2. Another chemical phenomenon sometimes appears in some etch chemistries that ion bombardment from the RIE etch mechanisms can resolve.  That is, in some chemistries, the etch by-products can polymerize on the etching surface and inhibit the chemical removal of the surface.  In this scenario, ion bombardment will physically remove the deposits and allow the etch chemistry to continue etching the horizontal surface (vertical etching) and the sidewalls profit from the deposition by inhibiting sidewall etching via the polymer deposition – thus producing straight sidewalls.
3.  I have discovered that the calibration resist-etch-rate determined by the one minute etch, measure, and repeat procedure produces an etch rate faster than if the etch went to total time completion in one step.  The current conclusion is that the longer etch-to-completion time compared to the multi-step and measure process creates a tougher resist during the process (i.e. vulcanization-like chemistry) which bonds the long polymer chains by crosslinking them in many places; thus progressively inhibiting rapid molecular chain-cutting and extraction by the plasma.   This may also be an RF Power related effect as well. Thus, data for the charts has been revamped by etching to the full time for each data point from a fresh resist coat.  This should match the etch processes used in normal etching.
4. We have switched out the gas mix of CF₄ + %8 O₂ and replaced it with Argon. You can open both CF₄ and O₂ to obtain the original mix.
5. Mechanical stylus (DekTac) method of tracing the etch rate of an underlying material with the DekTak profilometer, given the etch rate of top layer:

There is a limit to the process vacuum pressure that the vacuum pump can achieve that you need to know about to be able to set a process gas flow rate that the tool can achieve. The graph below shows the base pressure that the vacuum pump can achieve for a given process gas flow.  There is an example shown of what happens to the process pressure if you exceed the pumping capacity of the pump when too much gas flow (Red graph line set at 100 mTorr) runs into the pump limit and follows the pumping boundary beyond the crossover point.

Consider the layer geometry:  Resist on top, depth of resist lost in etch, substrate to be etched at bottom

Appendix C: S1813 Etch Calculator (SF6)

NOTE:  This calculator was contrived by parametric equations determined by actual etch data taken by measuring each etch depth data point (as an average of 49 points) on an individual wafer run through the entire process to reflect how the tool will be used.  Also, because of the complexity of the interactions between the four contributing parameters and the resulting calibration data scatter, the tested calculation accuracy can be as accurate as 1% or in error by as much as 7%.  Thus we claim that this is an “estimation” of the process results, with the idea that this calculation gives the user a reasonable starting point for developing individual processes. ATTENTION UTD tool users:  ACCESSING THE CALCULATOR ON THE TRION ETCHER:

1. Exit Trion control software – (see pg. 15 for Windows icons)
2. Double tap the computer icon on the Windows page
3. Tap the Local Disc C:
4. Double tap the program “TrionRIEOperationManual2.docx”
5. Tap the “Welcome Back box”
   1. Or if it disappears before you can tap the box, tap the

blue hollow arrow with an “X” inside to make the box reappear so you can tap it.

6. The Calculator should show up on the screen.
7. Double tap the calculator box to activate it.
8. Type in parameters & find the resulting S1813 resist amount removed.
9. Type outside the calculator box to deactivate it.
10. Tap File & Close ( or “X” in upper right corner of screen)
11. Again tap “X” in upper right corner of screen
12. Restart Trion control software with a double tap of the icon “PLC_3.02_Bld2”

NOTE:  If you don’t follow directions exactly you could end up lost in the software cold dark woods!

Appendix D: Etch Rate Data

Etch rate data has been collected on a few standard processes (4 in dia wafers) to enable a customer to estimate the etch time to clear a common film from the substrate.

Appendix E: List of Canned Processes

Appendix F: Staff Instructions for Changing Process Gas Scale Factors

The Trion Sirus T2 RIE Plasma Etcher chassis that we have has mass Flow Controllers for 4 gasses.  There is no room to add more.   So if the process flows that use this tool require a different gas for processing, then one of the current gases will have to be terminated and replaced by the new gas.  This will necessitate changing the gas scale factor in the mass flow controller.  The following are the instruction steps to change the scale factors STEP 1.  Log on to the Trion and click on the “Hardware Setup” button. STEP 2.  Click on “Configure Hardware” STEP 3.  Click on the name of the gas to change:

• Erase the old gas name and type in the new gas name

STEP 4.  Exit STEP 5.  Click on “Scale Factors” STEP 6.  Change the scale factor to match the new gas. Example:  Old gas:  CF4 + 8% O2 = 93 New Gas:  Argon = 282 STEP 7.  Exit and change gas cylinder to new gas. Pump out the gas line and open the valve to the new gas.