Under construction on 12/24/2014
Requirement on Alignment Marks (Targets)
1. Assisted Top Side Alignment (TSA)
2. Assisted Top Side Alignment (TSA) for Large Gaps
3. Assisted Back Side Alignment (BSA)
3.3.8.1. Overview Process Flow
STEP 1
• Move microscopes until the mask targets appear in the center of the field of view (FOV).
• Press Focuspos. Up -> Down to focus the microscope onto the mask targets.
• Select a mask target. The pattern recognition memorizes their position.
• Adjust focus and illumination.
STEP 2
• Set the focus button to Focuspos. Down -> Up to set focus and illumination on the wafer.
• The operator moves the wafer to find the wafer targets and the pattern recognition memorizes their position.
STEP 3
• The operator aligns the targets.
• The wafer stage is moved so that the wafer targets are positioned under the mask targets.
• During alignment the assisted alignment pad displays the current alignment status of mask to wafer.
• When mask and wafer are aligned to each other:
• The assisted alignment pad displays a single cross hair with rectangle.
• All displacement data are zero.
STEP 6
• The wafer is moved into the exposure gap and exposure starts.
3.3.8.2. Target Position Training
Preliminary Steps • Create and save a MA-Recipe,
• The alignment mode must be Assisted Alignment.
• Load mask and substrate
• As soon as the wafer has reached its alignment position the functional area Alignment Assistant pops up.
• Press the button AL Training to get access to the AL Training Pad.
TSA Target Training Mask
• Adjust the microscope until the mask targets are in focus and in the field of view. Low magnification can be used for this purpose. Fine adjustment should be performed with high magnification.
• Set focus and illumination on mask
• Press Target Mask Left
• Press Define Search Area
• A dialog window appears and prompts you to adjust the search window.
• A pink frame defines the target search area.
• Grab the pink frame and change the size of the target search area according to your needs. Define the search area as large as necessray.
• Confirm with OK.
• Press Define Target
• A dialog window appears and prompts you to adjust the target window.
• A pink frame defines the area for target definition.
• Grab the pink frame and position it around the selected target. Define the frame with 5 to 10 pixels surrounding the target (about 2mm wide).
• Confirm with OK.
• Press Save Actual Target Parameters to save the target position..
The info Selected Target saved pops up.
• The trained target is displayed in the viewing window at the bottom of the alignment assistant.
• Repeat Define Search Area and Define Target for the right mask target.
• Press Alignment to return to the live image and start with alignment of the wafer targets.
• Set the focus button to Focuspos. Down -> Up.
• Move the wafer target to a clearfield area (see 3.4.1) .
• Make sure that the mask targets do not interfere with the wafer targets. Use a clear field area of the mask for wafer target definition.
• Make sure that the targets stay within the search area.
• Press the button AL Training to get access to the AL Training Pad.
• Press Target Wafer Left
• Press Define Search Area
• A dialog window appears and prompts you to adjust the search window.
• A pink frame defines the target search area.
• Grab the pink frame and change the size of the target search area according to your needs. Define the search area as large as necessary.
• Confirm with OK.
• Press Define Target
• A dialog window appears and prompts you to adjust the target window. A pink frame defines the area for target definition.
• Grab the pink frame and position it around the selected target. Define the frame with 5 to 10 pixels surrounding the target (about 2mm wide).
• Confirm with OK.
• Press Save Actual Target Parameters to save the wafer position.
The info Selected Target saved pops up.
• The trained target is displayed in the viewing window at the bottom of the alignment assistant.
• Repeat Define Target for the right wafer target.
• Press Alignment to return to the live image and start aligning wafer and mask target to each other.
The target training is completed now.
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3.3.8.3. Start Assisted Alignment
• The Assisted Alignment Window is active.
• The system calculates the displacement from the trained and/or stored mask and wafer target positions and displays it into the Assisted Alignment Display
• Align the wafer in X, Y and Theta while the alignment status is displayed simultaneously at the Assisted Alignment Display.
• The square means the displacement in X and Y.
• The colored circle means the displacement in Theta
Green - displacement clockwise (starboard)
Orange - displacement counterclockwise (portside)
The background color of the displacement data changes depending on the calculated values:
• Grey - target found (live view), displacement > 4-times allowed value,
• Light Grey - target position grabbed,
• Yellow - target found, displacement < 4-times allowed value,
• Green - displacement < allowed displacement,
• Red - target not found.
RO = Runout
dT = Delta Theta
• As soon as the alignment meets the specification, the circle disappears and the small cross overlays the cross hair. All boxes for displacement data are green.
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OR:
,
• Press BACK if you wish to grab the mask targets again.
• Press AL CHECK to review the alignment accuracy.
The system moves from the alignment into the exposure gap, simulating the exposure situation
At Vacuum Contact or Hard Contact mode press
AL CHECK a second time to create a vacuum chamber or apply a nitrogen purge below the wafer.
• If the accuracy is not sufficient press BACK to return to alignment gap.
• If the accuracy is sufficient, press EXPOSURE to expose.