Patent ID: 6671059
Filing Date: 2003-12-30
Classification: H01L

Abstract:
A system for determining a thickness of at least one layer on at least one semiconductor wafer, comprising:a first laser for projecting a first laser pulse on a surface of the at least one layer, thereby generating an acoustical wave due to beating of the surface of the at least one layer, the acoustic wave propagating through the at least one layer and returning a partial echo wave to the surface in response to the acoustic wave reaching an interface of the at least one layer, wherein the echo wave returning to the surface changes a surface reflection property of the surface; a second laser for projecting a series of second laser pulses on the surface of the at least one layer, the second laser pulses adapted for use in measuring the surface reflection property changes of the surface; a detector for measuring laser pulses of the second laser pulses reflected from the surface of the at least one layer, thereby sensing the reflection property changes of the surface of the at least one layer over a period of time; and a processor for determining the thickness of the at least one layer by analyzing the reflection property changes over the period of time.