Ellipsometry is a method for determining the refractive index and extinction coefficients of a sample by measuring the change in polarization state of surface reflected light. Film thickness and optical constants of an adsorption layer or oxide film on a substrate surface can be determined with exceptional sensitivity. Conventional interference spectroscopy utilizes light passed through separate optical paths, while ellipsometry is a form of interferometry that uses two vibrational components with the same optical path, providing measurements with excellent accuracy and sensitivity.
JASCO's ellipsometer employs a proprietary polarization modulation technique (a PEM dual lock-in system) utilizing a photoelastic modulator, instead of the rotational drive mechanism of conventional ellipsometers. The PEM dual lockin system provides a stable measurement with additional capabilities including highspeed data sampling and wavelength scanning.
- Automated wavelength scanning
The PEM dual lock-in system (JP Pat. # 2064627) automatically controls the PEM drive voltage for the current wavelength with an optical servo (JP Pat. #2081599) to increase ordinate accuracy during high speed scanning.
- High-speed data sampling
Using high-speed electrical modulation, the PEM dual lock-in system enables high-speed data sampling in as little as 1 millisecond (optional 20 microseconds), far faster than systems that mechanically rotate a polarizer/analyzer combination.
- High stability and reliability
The PEM dual lock-in system offers a static measurement free from mechanical error with high stability by using the optical servo and an optical reference.
- Highly sensitive thin film analysis
The PEM dual lock-in system employs a proprietary polarizing configuration offering maximum sensitivity for extremely thin dielectric and semiconductor films.