Question & Answer
Q1. How to make sure that the tool is fully functional?
Answer: –
– Load FSM certified 20 M radius 100mm curve mirror
– Perform First Scan using any Laser (780 or 650) and expect the measured radius to be 20+/-0.4M.
Q2. How to automatically calculate Film-Stress using FSM128 system?
Answer: –
a. Generate “Pre” file:
– Before the film deposition, perform the first scan or the first map and the save the data file.
– Set Stress Constant: Set Stress constant for your substrate material at “Setup->System->Preset->” then Click OK. Example, for Si <100>, this value is 180.55 GPa.
– Save Recipe File: Save recipe file at “Setup->Recipe->Save”
b. Generate Post File:
– Load film deposited wafer.
– Load the Pre file.
– Load Recipe file.
– Perform Second Scan or Second Map to generate Stress profile along with other data.
Q3. Does it require separate stages for different wafer sizes?
Answer: –
No. The wafer stage has multiple pin potions to accommodate wafers of different sizes.
Q4. Can the system measure transparent glass wafers?
Answer: – Yes.
Q5. Can the system measure patterned wafers?
Answer: – Yes.
Q6. What is a Periodic Maintenance Service?
Answer: –
Recommended to be performed by FSM trained technicians every year. This includes changing consumable parts and tuning other parts. This ensures that the system provides accurate data for a very longer period of time (20Y).
Q7. What is the automatic laser switching feature?
FSM Stress tools come equipped with dual lasers, typically chosen from 780 nm, 650 nm, or 810 nm. Each system includes two of these three options. If a laser exhibits poor reflection during measurement, the system automatically switches to the other laser to ensure accurate readings.
Q8. How can this feature be verified?
1. Automatic Verification:
- Ensure that the “Auto Laser Switch” option is enabled (Setup → …).
- Use a SiN-coated wafer (~100 nm thickness). Start a scan with the 780 nm laser. Since 780 nm reflects less on SiN, the system should automatically switch to 650 nm.
2.Manual Method (FSM Technician Only, Not Recommended for Users):
- Start a scan with the 780 nm laser.
- After the system determines the baseline laser value (minimum after adjustment) but before scanning begins, manually block the detector.
- The detector will register a significantly lower reflected value, triggering an automatic switch to 650 nm.
- The switching event will be recorded in the log file and the output file (under the profile picture).
Q9. FSM_MultiScan Overview:
FSM_MultiScan is an executable tool that allows users to download multiple scans simultaneously into a CSV file.
How to Use:
- Download exe (or the .zip file, then unzip it).
- Copy the exe file into the C:\Program Files\FSM folder.
- Right-click the file → Properties → Compatibility → Check “Run this program as an administrator” → Click Apply, then OK.
- Create a shortcut and place it on the desktop.
- The new shortcut will replace the previous one on your desktop.
Q10. Could you please share some details on how the detector works?
The detector is a small circular photodetector (less than 2 cm in diameter) divided into two sections (A on the top and B on the bottom), separated by a horizontal line. The detector is mounted in a mechanical assembly that moves vertically (up and down), but not horizontally.
At the start of measurement, the laser is fired from above and its reflection is scanned by the detector. The detector then fine-tunes its vertical position so the beam is centered.
When scanning begins, the reflected beam position shifts according to the wafer’s surface profile. The detector captures these shifts, and the software calculates both the wafer profile and the bow.
Q11. What is the Z limit, and what happens if the laser spot is not centered while measuring?
The Z-stage has a limited travel range, typically sufficient to capture up to ~1 mm bow on a 300 mm wafer scan. If the reflected beam moves outside this vertical range (above or below the detector’s travel), the detector cannot track it, and the system will fail to produce a valid measurement. On that case, we recommend using smaller scan length (such as: 260mm or less for a 300mm wafer).
Q12. Can we change the threshold of the intensity optimization value Q = (A–B) / (A+B)?
Yes, it is possible to change this threshold. However, this is considered a system-level setup parameter, and adjustments are only made if there is a strong technical justification.