Stepper 2 (AutoStep 200) Operating Procedures: Difference between revisions

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==Other Useful links for this system:==
{{WIP}}
== Cleaning the back-side of wafer ==
If the back side of wafer has some resist residue or particulates, this can cause errors in the interpreted best focus point since the wafer surface may be at a different height.
# Make sure all work surfaces/spin chucks/hot plates are cleaned! Don’t use wipes, instead use cleaned steel surfaces.
# Spin coat resist following the recipe for spinning/baking specific resist.
# Check back-side of wafer thoroughly for resist residue/particulates before loading into system!
# If you see particulates, try to blow off with high N2 flow first, you may need a razor blade to remove stubborn particles.
# If you see resist residue, do next:
## Place wafer upside down in POLOS spinner using non-contact chuck.
## Set spin speed to 2000rpm.
## Spin wafer, wait until at top speed.
## Squirt Acetone on sample back for 3 seconds. Followed by ISO for 3 sec.
## Spin Dry while blowing with N2.
# Load the wafer on chuck and then stage.


*[[Stepper 2 (Autostep 200) - Chuck Selection]] - Quick Summary
== Reticle Loading and Unloading ==
*[[Stepper 2 (Autostep 200) - Table of Chucks, Shims, Target Thicknesses]] - Detailed Info on the same
The alignment of the reticle (mask) to the system is critical for achieving reproducible alignment.  System alignment marks on the reticle are located near the right and left edges of the mask and are 103 mm apart so they do not get exposed within the 100 mm exposure area of the mask.  These marks are put on automatically by Photronix and the gds file can be obtained from Brian Thibeault if you use a different vendor. Use the following procedure to align the mask correctly to the system.
*[[Autostep 200 Mask Making Guidance|Stepper 2 (Autostep 200) - Mask Making Guidance]]


== Two Alignments: ==
'''Loading the reticle:'''


=== <small>1) Wafer alignment to the system ''/'' <u>Global (Manual Operation Only</u>)</small> ===
1)   Unlock spindle and swing lamp column to middle position so that the lens is exposed.
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:'''
2)   Place mask chrome side down so that wording appears correct ( as seen in L-edit file).


#Adjust the focus (Inc and Dec keys) to get a crisp image (you might have to change speed with the Fast/Slow key).
3)   Swing lamp column so that objective can be used to align mask, DO NOT tighten spindle lock at this time.
#Align the right mark using the numeric keys labeled with arrows.
#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.
#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.
#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:'''
4)   Using your hands and looking through microscope, shift and rotate mask so that the “crosses” are roughly aligned


#Adjust the focus (Inc and Dec keys) to get a crisp image (you might have to change speed).
5)   Tighten spindle lock. This releases a vacuum holder onto the top of the mask so that the mask may be precisely aligned.
#Align the right mark using the numeric keys labeled with arrows.
#Press "A" on the main keyboard to toggle to the left alignment mark.
#Use the Theta keys to rotate the left image into position. [Positive Theta= CW, Negative Theta=CCW rotation of chuck]
#If you run out of theta alignment, you will need to adjust your sample on the chuck.
#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.
#Press "A" again to move to the right alignment mark
#Again adjust the right alignment mark
#Repeat process until satisfied with the alignment.
#Once alignment is finished, you have two option for pieces (quarters): BR orientation, and BL orientation.
#'''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).
#After global alignment, press EXP on small keyboard and the job will be executed.
#Remove the sample from the stage when done.
#Develop resist and inspect in microscope for alignment.
#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.


=== <small>2) '''Wafer Alignment to mask ''/'' <u>Local Alignment (DFAS)</u>''' :</small> ===
6)    Looking through microscope, use alignment knobs (x,y) to translate and rotate(Θ) the mask into position.  First focus the objective by using the knob on top of the microscope.  Use the right alignment mark for the x-axis alignment and both alignment marks for the y-axis and rotation alignments.  '''NOTE:''' To get best and fastest results approach alignment from one direction, do not try to wiggle back and forth about the alignment position. Backlash in the mechanics can make this frustrating. You should see equal amounts of light in between all lines when the mask is aligned well (within 0.1 um).
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'''
7)   Once mask is aligned, pull the reticle vacuum button to the left of the lens column. The reticle is now vacuumed to the system.


#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.
8)   Use the stencil (usually L-shape mask cover), to cover part of the mask plate that you do NOT want to be exposed. If you have just one layer on your mask plate, you do not need to use the stencil. There are also blade apertures that could be used. The knobs on the lamp column  (X,Y) can be adjusted to 100,75,50 and 25% to be open. Fully open blade apertures would be at 100%
#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)

#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.
9)   You are now ready to proceed with a focus job, map job, or exposure job.

10) '''This part is important:''' If alignments are critical, do not just brush through this procedure.  The global alignment requires good, precise alignment of the reticle with the system in order to work correctly.  The local alignment system can adjust for local X and Y misalignment, but not rotational errors.

'''Unloading the reticle:'''

1)   Unlock spindle and swing lamp column to middle position so that the lens is exposed.

2)   Once mask is aligned, pull the reticle vacuum button to the left of the lens column. The reticle is now vacuumed to the system

Latest revision as of 23:24, 8 January 2024

Other Useful links for this system:

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.
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