Stepper 2 (AutoStep 200) Operating Procedures

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Work In Progress

This article is still under construction. It may contain factual errors. Content is subject to change.


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.

  1. Make sure all work surfaces/spin chucks/hot plates are cleaned! Don’t use wipes, instead use cleaned steel surfaces.
  2. Spin coat resist following the recipe for spinning/baking specific resist.
  3. Check back-side of wafer thoroughly for resist residue/particulates before loading into system!
  4. If you see particulates, try to blow off with high N2 flow first, you may need a razor blade to remove stubborn particles.
  5. If you see resist residue, do next:
    1. Place wafer upside down in POLOS spinner using non-contact chuck.
    2. Set spin speed to 2000rpm.
    3. Spin wafer, wait until at top speed.
    4. Squirt Acetone on sample back for 3 seconds. Followed by ISO for 3 sec.
    5. Spin Dry while blowing with N2.
  6. Load the wafer on chuck and then stage.

Logging into computer and checking the system

The system administrator will set up a directory for you to LOG IN and use the stepper at the time of training.

  1. At the colon log into the system using LOG IN [10,xxx] where xxx is your account number.
  2. Type CHUCK
  3. You need to select C-change chuck size. Use 2 for 2” diameter wafers, 3 for 3” diameter wafers, 100 for 4” diameter wafers, and 142 smaller substrates ( ¼ of 2” or smaller parts). This number is used for telling the system where the chuck center is and for wafer auto leveling.
  4. After select proper chuck, use Q- quit when done.
  5. FOR STAFF AND EXPERIENCED USERS ONLY: Type SETUP and hit enter. Align the target and press “expose”. We use it as a method to verify all sub systems are operating properly and to reset system focus before an exposure job is performed.

Reticle Loading and Unloading

Loading the reticle:

 Mask Alignment on this system is automatic. You need to have the square marks on the top and bottom of the mask. These are put on automatically by Photronix and the gds file can be obtained from Brian Thibeault if you use a different vendor. There are 10 reticle box positions on the elevator. Slot 1 is dedicated for a calibration mask. Slots 2-10 are available for your use. Slots will NOT be dedicated for any users.

  1. Load the reticle into a box with chrome side down (insert photo shown in the figure 1.)
  2. Type RMSL on the main computer at the colon prompt.
  3. Swing the reticle forks 90 degrees away from the reticle elevator.
  4. Pull out knob, insert box in one of the slots (2-10), release knob to hold   box.
  5. Make sure the box is sitting properly in place.
  6. Hit Enter on the computer and the system will map the reticles.
  7. On them main monitor you will get information about the reticle name and the slot# it is loaded (if the reticle does not have a name it will say just NONE)

Unloading the reticle:

 At the end of each job you need to unload the mask

  1. Type RMSR on the main computer at the colon prompt.
  2. Wait for the reticle to be loaded back in the reticle box.
  3. Type RMSL on the main computer at the colon prompt.
  4. Get your reticle from  the reticle box
  5. NOTE: NEVER try to manually unload the reticle (as you would in GCA 6300 Stepper #1). Always use commands.

Loading a wafer into the system

  1. Attach the appropriate chuck to the system. ( insert link "How to select proper chuck")
  2. Make sure you know your substrate thickness and wafer diameter.
  3. TARGET thickness is : 12.150mm +/- 0.1mm (TARGET= Chuck thickness+ Substrate thickness)
  4. Each chuck has two numbers on top side (for example 100mm/500um) showing wafer diameter, and substrate thickness. ( insert link with TARGET thickness )
  5. Place a wafer centered on the chuck, noting the orientation (major flat always touching two front screws, minor flat touching the screw either on left or right side)
  6. If you are doing an alignment step, make sure to place the wafer in the same orientation as it was in the first exposure.
  7. The set screws in the chuck can help to get reproducible placement of the wafer.
  8. When the wafer is in place, flip the chuck vacuum switch upwards to hold the sample.
  9. Place the sample chuck onto the stage, again trying to be repeatable, and flip the stage vacuum switch upwards to hold the chuck.
  10. If your sample is thin (150um thinner than the number on top side of chuck), then you need to use SHIM ( we have 130,180, 230, 260um metal shims)
  11. If you need a shim with different thickness you can try cutting some shim stock (stored in drawer next to Autostep200).
  12. Be careful when placing the chuck on to the system. Do not set the chuck onto the built-in reticle on the left side of the stage.
  13. Make sure the chuck vacuum is properly holding the chuck in place (it can tip forwards before the vacuum holds it in place).
  14. At this stage type AWLT Jobname\Passname. This will test the auto-leveling of your wafer ( auto-leveling cannot be done on pieces smaller then ¼ of 2”, so when writing the program make sure that you at the LEVELER batch size input value -1( TURN off leveling).
  15. At "START AWH" (automatic wafer handling) prompt, press MANUAL button.
  16. Press MANUAL again.
  17. Choose “N” to answer to all questions ( if not sure, use what is default value (*)).
  18. If you have an auto focus error or leveling error, the system will tell you.

Running a JOB - Normal Operation

  1. At the colon sign type LOG IN [10, xxx], and hit enter ( xxx- your account)
  2. Make sure you have loaded the reticle as described above.
  3. Make sure you have loaded the wafer as described above.
  4. Type EXEC jobname\passname and hit enter. (See “Wafer alignment to mask / Local Alignment (DFAS)” below for local alignment job syntax)
  5. Type in the desired exposure time if different
  6. Type in desired focus offset.
  7. Reticle T: 0
  8. Reticle Bar Code: Enter a bar code name if you have one on the mask, otherwise, hit Enter.
  9. Floor#:  Enter the elevator slot number where you put your reticle ( it could be any # (2-9), #1- only for SETUP mask).
  10. If MATCH was enabled, the system loads the reticle and you will see the left screen perform the InSitu-Match routine on your mask.
  11. Press MANUAL key when “Start AWH” prompt is seen.
  12. Press MANUAL again as prompted
  13. Sample will move to alignment position/do global alignment.
  • 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 is used for theta only.
  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 is used for theta only.
  7. Press "A" again to move to the right alignment mark
  8. Again adjust the right alignment mark
  9. Repeat process until position and Theta are acceptable.
  10. Always use your RIGHT alignment mark (right side of monitor) for alignment. 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"
  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 (if needed)
  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 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

JOB Programing - FULL

This section describes how to set up a job to do a step and repeat exposure of your patterns. A more detailed description is given in section 8 of the Autostep 200 Advanced Operation and Utilization (White binder\Biljana's desk).  Jobs are created using the SPEC command.  First information about the array steps, alignment offsets, and general job is asked for. Passes are attached to each job to apply parameters unique to each pass specified. You can have up to 6 passes in one job. In this way all exposure information for a complete mask set can be specified all in one job.  Following is the procedure for setting up a job and passes.

Notes: If at any point you wish to stop and start over with the job description hit CTRL C followed by A and ENTER on the keyboard to abort the SPEC command.  An abort of this type will result in no saved information.  Also when a * is displayed, this indicates the default value if you hit enter for a reply to a question asked by the computer in setting up or editing any job.  If a numeric value is asked for hitting enter will leave the value previously specified, if that exists.  Also, if you put in an incorrect value and wish to go back a step type “?” and ENTER.

  1. At the colon sign type SPEC “jobname” and hit enter.  The "jobname" can be 1-9 alphanumeric characters long.
  2. Select M (metric units)
  3. Input a job comment such as “HBT-1 process”
  4. Set tolerance to 1
  5. Hit Enter for scale
  6. Hit enter for orthogonality
  7. Leveler Batch Size- input 1 to use wafer leveling, and -1 to turn leveling off.
  8. Enter the wafer diameter in mm.  This defines the maximum area in which exposure can occur.  If you have a square or non-circular piece, you will need to specify a diameter that includes the entire square, not the length of a square.
  9. Enter the step size in X in mm at the wafer plane
  10. Use “C” for specifying the number of columns to expose and "A" to fill in all area in X direction to the edge of a circular wafer. For square pieces you will always use “C”.  For quarter wafers, you will most likely use “C” and make the job array look square. You will then use dropouts in each pass to specify more complicated array shapes.
  11. When “C” is entered, you will then be able to enter the number of columns desired.
  12. Repeat 9 through 11 for the Y step. The final array is centered on the wafer.
  13. Translate Origin is generally used only if the wafer is off-center.
  14. If you wish to see an “*” cartoon of the exposure array hit Y for display, otherwise hit Enter.
  15. Layout will give you a display of the number of rows and columns and the distance from die (1,1) to the array center, taking origin translation into account. Usually this is not looked at. Hit enter to pass this up.
  16. If you wish to adjust the numbers of rows and columns you can do this at the Adjust prompt.  Usually, you can hit enter to skip this.
  17. Standard Keys: If you choose "Y", then the die used for right and left alignment is chosen automatically by the system.  This is good if you have a wafer larger than 63.5 mm in the X direction and both alignment marks are exactly 63.5 mm apart. If you do not meet these conditions (most jobs do not), you will need to choose "N".
  18. If “N” is chosen you will need to enter the row and column of the right alignment die.
  19. For wafers: We usually select right and left alignment die bellow the center of wafer, and on the same row. Most practical is selecting left and right alignment die to be in last row. This also helps to quickly find alignment die, and do alignment.
  20. For pieces: We usually select right and left alignment die to be in the last row.

Right\Left Key Offset:

The key offset is distance from the die (mask) center to the alignment mark center on the first layer (or the layer you will be aligning to).  Enter the number in (mm) at the wafer plane.  See picture below for sign convention of an alignment mark placed in quadrant 1 on the mask. The picture assumes normal Cartesian coordinates with the center-lines crossing at (0,0) and the mask is chrome-side down and oriented as it would be on the stepper. (This is the same orientation that you will have when viewing your L Edit file).

Sign Convention for Alignment key offset on Mask (main cell)- insert the photo

  1. If Non-standard alignment keys are selected (most of the time they are, step 18), you will need to select the left and right alignment die. For example if we have 10X10 exposures, this could be for right alignment die (R=10,C=10) and for the left alignment die (R=10,C=1).
  2. Left Key Offset and Right Key Offset are always same. Only for user who have one single exposure (one die), they would need to have left and right key offset different!
  3. Skip through epi shift.
  1. Now you are ready to enter information specific to passes.
  2. Enter the name of the first pass.  When you expose a job, you will specify it as jobname\passname.  The name of a pass can be 1 to 9 alphanumeric characters long.  (i.e. emitter)
  3. Next enter a pass comment
  4. Enter "Y" or "N" for local alignment. 
  5. If this is a first pass (there is no any pattern on your wafer), you need to select in here "N". Follow instructions to finish writing this pass, and saving.
  6. If this is a second pass or any other pass with critical alignment you should select "N". Follow instructions to finish writing this pass, and saving.
  7. Aligning a second layer to the first layer (crirtical alignment and you need to use local alignment mark) would require writing a pass ( usually called "mapping pass". In this case you need to select "Y" for local alignment. Local alignment mark (DFAS) needs to to be on the layer that is being used for aligning.
  8. Expose Mapping Pass:  Yes for (die x die) alignment and exposure.
  9. Use two point alignment:  Yes will check your local alignment marks on your global alignment die and correct for rotation error prior to shooting.
  10. Set Rotation Tolerance to 2microRadians
  11. Continue with Mapping:  Yes if mapping should continue after 2-point alignment.
  12. Number of alignments per die:  Enter 1

Local Alignment Mark Offset:

The local alignment mark offset is distance from the die (mask) center to the local alignment mark center(DFAS) on the first layer (or the layer you will be aligning to).  Enter the alignment mark position in X, and Y in (mm) at the wafer plane.  See picture above for sign convention of the global alignment mark being placed next to global alignment mark in quadrant 1 on the mask. The picture assumes normal Cartesian coordinates with the center-lines crossing at (0,0) and the mask is chrome-side down and oriented as it would be on the stepper. (This is the same orientation that you will have when viewing your L Edit file).

  1. Monitor Mapping Corrections:  Choose "Y" if you want to see data before exposure to make a judgment on whether to continue.
  2. Map Every Nth Wafer:  Enter 1 to map every wafer you shoot.
  3. Next, input an exposure time between 0 and 128 sec. The calibrations are done at 0.38 sec. for 0.9um SPR 955-CM resist on silicon.  This time should be optimized for your substrate and process before doing the real devices to ensure optimum resolution.  Dose is calibrated for the system each lamp change.
  4. 33) Expose Calib Factor: 1
  5. 34) Focus Offset:  Based on a focus calibration that you do, you will have a focus offset from the baseline calibration job.  This calibration is done daily with a mark built-in to the system.  Focus offset is an integer.  +1 = 0.1 microns of lens movement up from the wafer.  -1 = 0.1 microns towards the wafer.
  6. 35) Microscope focus offset:  Same units as above.  Used so that your wafer will be in focus right away.  You will find out this number the first time you expose.
  7. 36) Enable Match:  Can use marks on your mask to make sure reticle is exactly aligned.  If you have the marks (standard on Photronix masks), and say yes:
  8. a.     Match Template Name:  MATCH
  9. b.     Match every Nth Wafer:  Enter 1.
  10. c.     Reticle Rotation Offset:  Enter 0.
  11. d.     Reticle T: 0
  12. 37) AWA Parameter File Name:  just press Enter
  13. 38) Use pass shift to shift all exposures in this pass by a set amount.  Usually this option is passed over, but may be used if you have multiple levels on a single mask and are aperturing all layers but the one of interest and this pattern is off-center.  You would enter the correct offset to ensure pattern alignment. See picture below for sign convention for X and Y for pass shifts to place pattern into center of wafer. Enter the number in mm at the wafer plane.  See picture below for sign convention of pass shift for a pattern placed in quadrant 1. The picture assumes normal Cartesian coordinates with the center lines crossing at 0,0 and the mask is chrome-side down and oriented as it would be on the stepper.

39) Reticle Bar Code:  If you have a bar code on your reticle, enter the value here, otherwise hit enter.

40) Masking Aperture Setting:  You can set the aperture blades independently, entering values between 0 and 97 for the blade movement, in millimeters.  0 is completely open for all blades.  The smallest square you can aperture to is 5mm x 5mm (that means 1mm x 1mm at the wafer plane)

41) Reticle Alignment Offset:  Enter 0 for all these values.

42) Reticle Alignment Phase:  Enter N for negative (clear squares)

43) Reticle Transmission:  Hit Enter.

44) Array or Plug.  When P is entered, only those row and column sites that the user enters will be exposed.  When A is entered all sites previously specified will be exposed except dropouts specified later.

45) When P is entered, enter the row and column numbers of die you wish to be exposed.  Enter D at the R prompt to display the currently selected die. Press return with a blank entry at the R prompt when finished.

46) In the dropout section, sites or entire rows or columns can be removed from the exposure.  Enter the row.  Then enter at the C prompt: nothing to remove the whole row, the first and last column number with a dash in between (i.e.3-6) to remove several sits, or a single number to remove a single site.  Enter D at the R prompt to view the die that will be exposed.  Enter V at the R prompt to see a list of dropouts. Enter ? at the R prompt to put back in the last die that was dropped out.  Again hit return with no entry at the R prompt to exit.

47) Answer Y to save pass.

48) If no other passes are desired, hit enter with no entry at the name prompt.

49) Enter another pass name if desired and hit enter.

50) If the pass information is mostly the same as a previous pass, hit Y at the Copy prompt and enter the name of the pass to be copied, then change any needed parameters after the job is saved using the EDIT command.

51) Say Y to Write to Disk or all information will be lost.

52) You are ready.

Editing an existing job: 

To edit an existing job, use the EDIT command followed by the file name.  You can then scroll through job and all passes and change any desired parameters.

Don’t forget to save the changes.  If you just wanted to look at the program you can use the EDIT command and then use CTRL C followed by A and a carriage return to abort the command and not save any changes.

You can also edit a job by using the JOB command.  You can play with this.  It is menu driven and lets you easily change parameters without having to scroll through an entire program.

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