Process control and monitoring with laser interferometry based endpoint detection in chemical mechanical planarization

First, a brief presentation of the principles behind laser interferometry based in-situ endpoint detection is made, including the underlying theory of operation, system architecture and filtering methodology. This is followed by experimental data taken with various process wafers, including tungsten, copper, blanket oxide, silicon-on-oxide, shallow trench isolation (STI), and interlayer dielectric (ILD) wafers. Pre- and post-processing thickness data and removal rates are compared with ex-situ measurements for accuracy and repeatability. Finally, specific examples are discussed to show the benefits of in-situ removal rate monitoring and endpoint detection in chemical mechanical planarization for improved line monitoring and process control.