Stepper 2 (AutoStep 200) Operating Procedures

Other Useful links for this system:

• Stepper 2 (Autostep 200) - Chuck Selection - Quick Summary
• Stepper 2 (Autostep 200) - Table of Chucks, Shims, Target Thicknesses - Detailed Info on the same
• Stepper 2 (Autostep 200) - Mask Making Guidance

Two Alignments:

1) Wafer alignment to the system / Global (Manual Operation Only)

The keyboard alone is used in this part of the exposure sequence to align the wafer to the system.  The sequence of operations you do will depend on whether or not you used standard alignment keys or not.  If you placed the sample close to the position you did during the first exposure, you should see an alignment mark in the right side of the screen.  If not, you will need to find this mark using the position joystick by following a spiraling outward from the initial position. Pressing “F” repeatedly on the keyboard will do this spiral finding for you automatically. The red arrows on the number keys indicate the direction of movement for each keystroke.  There are also + and -theta (angle) keys for rotation.   Inc and Dec are used for microscope focus.  The enter key on the numeric keypad changes from fast to slow movement.   To change the joystick speed hit O on the main keyboard.  Once the alignment mark is found follow one of the following procedures. Most of the time we use Non-Standard Alignment keys:

Standard Alignment Keys:

1. Adjust the focus (Inc and Dec keys) to get a crisp image (you might have to change speed with the Fast/Slow key).
2. Align the right mark using the numeric keys labeled with arrows.
3. Use the Theta keys to rotate the left image into position. Positive Theta = clockwise rotation of chuck.  If you run out of theta alignment, you will need to adjust your sample on the chuck.
4. The left image(left side of monitor) is used for theta only. The right image(right side of monitor) is used for x, and y alignment. Use the right image (right side of monitor) to do your best alignment. This step is important.
5. Repeat process until satisfied with the alignment. You can obtain better than 0.2 um alignment consistently if you are careful.

Non-Standard Alignment Keys:

1. Adjust the focus (Inc and Dec keys) to get a crisp image (you might have to change speed).
2. Align the right mark using the numeric keys labeled with arrows.
3. Press "A" on the main keyboard to toggle to the left alignment mark.
4. Use the Theta keys to rotate the left image into position. [Positive Theta= CW, Negative Theta=CCW rotation of chuck]
5. If you run out of theta alignment, you will need to adjust your sample on the chuck.
6. The left image(left side of monitor) is used for theta only. The right image(right side of monitor) is used for x, and y alignment. Use the right image (right side of monitor) to do your best alignment. This step is important.
7. Press "A" again to move to the right alignment mark
8. Again adjust the right alignment mark
9. Repeat process until satisfied with the alignment.
10. Once alignment is finished, you have two option for pieces (quarters): BR orientation, and BL orientation.
11. BR orientation - make sure you are on the right alignment mark before pressing "EXP", BL orientation - make sure you are on the left alignment mark before pressing "EXP". In both cases do your best alignment, but verify final alignment looking at the right image (right side of monitor).
12. After global alignment, press EXP on small keyboard and the job will be executed.
13. Remove the sample from the stage when done.
14. Develop resist and inspect in microscope for alignment.
15. Computer may ask for next wafer.  To escape out of this press CTRL C followed by A and the enter key to abort out of the loop. If you have another wafer with the same job\pass, you can do it now without aborting.

2) Wafer Alignment to mask / Local Alignment (DFAS) :

The best way to use this is to use a mapping routine followed by a shoot using the corrections given by the map.  A mapping routine should be set-up in your mapping pass. Usually we do not map all dies, just selected ones. You could selected in each row few dies. The mapping pass should have a name different then any other pass. It could be named mapxx or some other name (for example: local). Make sure you specify die x die is to be used and that you have the correct key offsets for the global and local alignment marks.  The command you will use is:

• MAP jobname\mapxx, passname

1. Proceed as normal. Find a global alignment mark and do your best alignment. The first pass (mapxx) is the mapping pass. The system will do mapping, using dies that are selected in mapping pass. It will look for DFAS alignment mark in each die, and make corrections. When asked to make corrections, say yes. After corrections are applied, the exposure job will be performed shooting the pass named " passname". Follow instructions on screen when using this function.
2. Remove the sample from the stage when done. (If Match was enabled, you will have to wait until the match is done again.  It will do this before asking you for the next wafer). Develop resist and inspect in microscope for alignment (if needed)
3. Computer will ask for next wafer.  To escape out of this press CTRL C followed by A and the enter key to abort out of the loop.  If you have another wafer with the same job\pass, you can do it now without aborting by placing it on the chuck and hitting MANUAL.