A micro-ellipsometry method based on polarization shifting interferometry for determining complex reflective index

In hard disk drive (HDD) industry, the flying height measurement is one of the key processes for validating the recording head production. In order to assure the reliability of the HDD, the flying performance of recording heads has to be measured and compared with the original design. However, as the capacity of HDD increases exponentially, the design of the flying height of a recording head has to be as low as about 10 nanometer. Thus, the precision of flying height measurement is of critical importance. One important input parameter of the flying height measurement is the complex refractive index of the surface of recording heads. In this paper, we present a novel technique for measuring complex reflective index of a relatively small spot size (0.1 micron) using a combined micro-ellipsometry and phase shifting interferometer. This paper shows that the measurement of the complex reflective index can be done for each recording head and that improved precision of the flying height measurement can be obtained.