Non-contact measurement of thickness uniformity of chemically etched Si membranes by fiber-optic low-coherence interferometry

In this paper we present a contactless technique for thickness measurement of chemically etched Si membranes. This technique is based on low-coherence interferometry performed by single-mode fiber-optic sensing configuration. We are able to measure the thickness of Si membranes with accuracy of about 40 nm. We used the proposed technique for the fast measurement of thickness uniformity of central position of Si membranes with overall dimensions of 2times2 mm² all around one 3 inch {100} Si wafer with starting thickness of 380 mum. Additionally, we measured the thickness uniformity of several membranes with central boss by scanning. The accuracy of the technique is about 100 nm.