Stroboscopic scanning white light interferometry at 2.7 MHz with 1.6 µm coherence length using a non-phosphor LED...

Area of Science:

• Optics and Photonics
• Metrology
• Microelectromechanical Systems (MEMS)

Background:

• Stroboscopic scanning white light interferometry (SSWLI) is crucial for 3D measurements of oscillating samples.
• Existing commercial SSWLI systems have limitations in pulsing frequency, hindering high-speed measurements.
• There is a need for improved light sources to overcome these limitations.

Purpose of the Study:

• To develop a high-frequency, high-performance light source for SSWLI.
• To enhance the precision and applicability of SSWLI for dynamic micro-scale measurements.
• To enable 3D profiling of high-frequency oscillating MEMS devices.

Main Methods:

• Designed and constructed a 400-620 nm wideband 150 mW light source by combining non-phosphor white and cyan LEDs.
• The light source produces an interferogram with a 1.6 µm width and no side peaks.
• Integrated the new light source into an SSWLI system for dynamic measurements.

Main Results:

• Achieved 10 nm precision when measuring a calibration artifact.
• Demonstrated 40 nm precision in the 3D profile measurement of a 2.72 MHz capacitive micromachined ultrasonic transducer (CMUT) membrane.
• The developed light source is compatible with solid-state technology.

Conclusions:

• The novel wideband light source significantly improves SSWLI capabilities for dynamic measurements.
• The system offers high precision for characterizing high-frequency MEMS devices.
• This advancement paves the way for more sophisticated metrology in micro-systems engineering.