In-situ plasma etch process endpoint control in integrated circuit manufacturing

In-situ noninvasive etch process endpoint control with repeatable accuracy is essential for producing the kinds of yields, product quality, and throughput necessary for IC manufacturers to remain competitive. A unique in-situ endpoint detection system with the capability to accept different, multiple sensors based on various optical analytical techniques is described here. When combined in the same touchscreen instrument platform, these different techniques increase instrument flexibility in handling a larger variety of applications, directly enhancing the ability to increase process yields. Weak optical emission spectroscopy (OES) wavelength intensities resulting from either weak transitions or low emitting species concentrations from low exposed area and/or low vapor pressure species, requires a highly sensitive endpoint detection system containing highly sensitive and efficient sensors, transducers, signal conditioning components and software, and flexible algorithms to call process endpoint. These same requirements are necessary in other optical analytical techniques such as optical reflectometry or optical interferometry using single or multiple wavelength static or scanning transmission and detection. The paper describes how the optical sensor signal is subsequently processed into an electronic signal upon which proprietary window triggering software endpoint algorithms are applied to call an end to the process condition. This endpoint system is more than a process control tool, as it also offers data analysis capability, making it an in-situ diagnostic instrument for process troubleshooting and process development.