|Optical measurement of narrow holes
By: Roei Yiftah, Industrial Product Manager; Moshe Danziger, Application Engineer, and Shmulik Barzilay, International Sales Manager, Optimet
|Measurement range (mm)||6|
- Lateral resolution [X*Y]: 5μm X 10μm
- Scanning axis: X axis
- Measurement frequency: 3000Hz
- Laser power: Max
- Auto exposure: on
- Laboratory Conoscan3000
- As can be seen in the pictures above, the impression gves very clear data and can be measured up to an angle of 85°, above that angle there is no data. The diameter of the impression at 85° is 0.554mm and the height from th wafer’s surface to that minimum diameter is 3.636mm
A scan was done on the same hole as the impression above was taken. 2 holes were scanned in order to do a correct alignment when combining the scans:
After combining the scans and tilting them to 0°:
- The slight difference between the impression scan and the wafer’s scan might be due to the difference in the angles measured since by combining the 2 scans of the wafer we were able to reach ±90° (impression only ±85°)
- The difference between nominal diameter from customer (0.5mm) and actual diameter measured might be due to inaccuracies in alignment of the 2 scans.
- As can be seen from the pictures above, the hole’s dimensions are the same as measured before: 0.552mm diameter
- The 2nd hole has a diameter of 0.563mm, but I didn’t take an impression of it so I can’t compare. (The neck might be deeper than the first hole and is either out of WR or I didn’t tilt the wafer to a steep enough angle to reach the 90° wall)
- Measure height from top surface to where the hole reaches minimum diameter of 0.5mm – Accomplished. Diameter measured: ~0.55mm.
- Measure up to ±90° of hole’s walls - Accomplished.
- As seen from the pictures above, the CP-10 with optical filter and 50mm lens is fully capable of measuring the requested diameter even if it’s >3.5mm deep. That gives an aspect ratio of 1:7 – the largest in the market by far!
- Suggestion for this application :
Use 2 ConoPoint-10 sensors at which each sensor is tilted 5°-7° compared to the sample’s top surface as shown in the illustration below (need to ad optical filters):
Each sensor will cover the steep angles of the other wall, so one wall will always be deeper than the second. Then the profiles need to be tilted to align the top surface to 0°, and then correlate both scans to find where the neck reaches 0.5mm.
Optimet is the only company which can get these results, no other technology can reach our abilities and doesn’t match us in this application.
Download Optical measurement of narrow holes (pdf)