Thin film thickness measuring system

Abstract

A set of optical lens elements coupled with a diode array spectrophotometer employed to measure thickness of thin films especially on semiconductor substrates is disclosed. The system comprises an optical sample compartment and deep ultraviolet diode array spectrophotometer manufactured by Hewlett-Packard. The sample compartment consists of a pair of prisms coupled with a pair of convex lenses. Prisms and convex lenses are used in a reflective mode instead of their usual transmissive mode, and therefore act like mirrors. This enables the ultraviolet beam to converge at the surface of semiconductor wafer sample at a single point with an almost normal incident angle, thereby introducing a large depth of focus with a small spot size. Also a condensing lens in front of the Deuterium lamp slowly reduces the beam diameter. Diode array spectrophotometer employs a sealed spectrophotometer that includes an entrance slit, a holographic grating, and a diode array detector. An A/D converter and an interface data acquisition board follows the detectors. The objective is to measure reflectance from semiconductor material and then measure film thicknesses based on the data. The deep UV spectrum enables the algorithms to yield ultra thin film measurements and also includes information regarding refractive indices of material under test.

Dependencies are inferred from the claim text.