Two-dimensional low-coherence interferometry for the characterization of nanometer-wafer-topographies

Within this work a scan-free, low-coherence interferometry approach for surface pro fi lometry with n m-precision is presented. The basic setup consist of a M i c h e l s o n-type interferometer which is powered by a supercontinuum light-source (Delta lambda = 400 - 1700 n m). The introduction of an element with known dispersion delivers a controlled phase variation which can be detected in the spectral domain and used to reconstruct height di ff erences on a sample. In order to enable scan-free measurements, the interference signal is spectrally decomposed with a grating and imaged onto a two-dimensional detector. One dimension of this detector records spectral, and therefore height information, while the other dimension stores the spatial position of the corresponding height values. In experiments on a height standard, it could be shown that the setup is capable of recording multiple height steps of 101 n m over a range of 500 mu m with an accuracy of about 11.5 nm. Further experiments on conductive paths of a micro-electro-mechanical systems (MEMS) pressure sensor demonstrated that the approach is also suitable to precisely characterize nanometer-sized structures on production-relevant components. The main advantage of the proposed measurement approach is the possibility to collect precise height information over a line on a surface without the need for scanning. This feature makes it interesting for a production-accompanying metrology.