Abstract: A method and apparatus for the measurement of wafer thickness, flatness and the trench depth of any trenches etched thereon using the back surface of the wafer to accurately measure the back side of a trench, rendering the trench an effective bump, capable of being measured on the top surface and the bottom surface through a non-contact optical instrument that simultaneously measures the wavelength of the top surface and bottom surface of the wafer, converting the distance between wavelengths to a thickness measurement, using a light source that renders the material of which the wafer is composed transparent in that wavelength range, i.e., using the near infrared region for measuring the thickness and trench depth measurement of wafers made of silicon, which is opaque in the visible region and transparent in the near infrared region. Thickness and flatness, as well as localized shape, can also be measured using a calibration method that utilizes a pair of optical styli.

Abstract: A system for the measurement of high aspect ratio trenches. The preferred embodiment consists of three elements: a) an integrated microscope and optical height sensor, b) an axially dispersive, afocal lens system, which is included in the optical height sensor, and c) an algorithm for processing the optical height sensor data to produce the depth of the high aspect ratio trench. The present invention combines a traditional imaging microscope with a chromatic confocal, single point, height sensor. This combination instantaneously provides an image of the object and the height value at one point in the image. No mechanical movement is necessary anywhere in the system to achieve that result. The chromatic confocal height sensor is integrated with a traditional microscope through the use of separate wavelength bands such as a wavelength band in the visible part of the spectrum, and a wavelength band in the infrared or ultraviolet part of the spectrum.