Apparatus and method for detecting an endpoint of an etching process by transmitting infrared light signals through a semiconductor wafer

Abstract

An apparatus for etching a first side of a semiconductor wafer down to a desired level. The apparatus includes an etching chamber. The apparatus also includes a wafer chuck configured to engage the wafer by a second side of the wafer, and position the wafer in the etching chamber. The apparatus also includes a light source unit positioned such that light signals generated by the light source unit are directed into the wafer. Moreover, the apparatus includes a light receiving unit positioned such that the light signals generated by the light source unit emanate out of the wafer and are received with the light receiving unit. The light receiving unit includes a first optical material and a second optical material having an interface therebetween. The first optical material has a linear index of refraction, whereas the second optical material has a nonlinear index of refraction which is dependent on an intensity level of the light signals received with the light receiving unit. The light signals are refracted at the interface if the linear index of refraction of the first optical material does not match the nonlinear index of refraction of the second optical material. A method of etching a first side of a semiconductor down to a desired level is also disclosed.