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

• WAFER ALIGNMENT TO 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.

• 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.

Running a FOCUS and\or EXPOSURE matrix

The system is calibrated weekly on 4 inch Si wafers using resist SPR 955-0.9 and standard chuck (4”-500um). Your substrate type, thickness, and resist may require different focus and exposure setting than the standard calibration. A focus and\or exposure matrix should be done for each resist, to tweak your process relative to the calibration baseline. Once the process is optimized for a specific resist, the exposure time\focus will not change in future, since the lamp power is hold constant all the time.

The focus and\or exposure matrix (aka. "FEM" or "FEA") can be varied across this array to determine the optimum focus relative to the baseline. One focus step is equal to 0.1 um of focus depth. FOCUS OFFSET is an INTEGER!

• +1=0.1um of lens movement up from the wafer
• -1=0.1um of lens movement down toward the wafer

1. Before doing an EXPO job, LOG IN to [10,1] and type “CHUCK” – set the correct chuck size for the substrate (4” wafer-would be 100)
2. Use the command EXPO jobname\passname and hit enter
3. Enter starting row within array specified in the pass (for example : 1)
4. Enter ending row within the array specified in the pass (for example:6, depending how big is die size, and how many dies can fit in X direction)
5. Enter starting column within array specified in the pass (for example:1)
6. Enter ending column within the array specified in the pass(for example:6)
7. Enter either F=to vary the focus, E= to vary the exposure, or R for both (to increment focus for each row and exposure for each column within the array)
8. Enter the parameters as prompted by the computer. They will differ based on which option is chosen.
9. “Start AWH” process – press MANUAL when prompted
10. Press the MANUAL again
11. If you are doing an aligned test (like for exposure on top of a mesa) align the wafer now, press “EXPOSE”
12. If you are NOT doing an aligned test, just press “EXPOSE”
13. The command EXPO will shoot a specified serpentine array based on the parameters in your job\pass (first exposure - upper left corner)
14. When exposure is finished, follow the recipe (post exposure bake if needed) with development. Please take your time for inspection, and select best exposure time and focus.
15. The computer will ask you for the best row and column. Enter row and column number
16. The computer will then tell you the focus and exposure based on the row and column you input
17. Do not update system focus ! Input a focus offset into your own exposure job. (If you accidentally update system focus, you must change it back using the MODE command)
18. Unload the mask plate, and LOG OUT