Micro Displacement Measurement System using Self-coupling Effect of Semiconductor Laser

Abstract

Recently, a line width of integrated circuit has been reduced to tens of nm and a demand for compact micro displacement measurement sensors in the manufacturing process increases. A laser interferometer is used as a conventional method of detecting a micro displacement, but some disadvantages; a weakness for external vibration, difficulties with optical alignment and so on. Then we proposed a compact micro displacement measurement system, which is proof against an external vibration and can detect a micro displacement without an external interferometer, by making use of the self coupling effect of the semiconductor laser. In this sensor system, the sensor head is movable, and continuously vibrates with small amplitude. The sensor head is controlled so that the vibration signal has a maximum. The displacement of target is measured from that of sensor head. It is confirmed that this system can be measured with a resolution of tens of nanometers to several micrometers.