Control of dielectric chemical mechanical polishing (CMP) using an interferometry based endpoint sensor

We report on the application of an optical endpoint sensor to various dielectric CMP processes. First, we demonstrate that this endpoint sensor can be used as an in-situ rate monitor. Since this sensor is based on interferometric measurements, the removal rate determined from the endpoint trace agrees well with that calculated from ex-situ measurements (less than 3% error on average). Secondly, we show that this endpoint technique provides excellent control on both shallow trench isolation (STI) and low level interlayer dielectrics (ILD). Although this technique is difficult for high level ILDs, it is the first CMP endpoint technology in the literature that is able to cover a wide variety of dielectric CMP processes.