In the semiconductor manufacturing, the control of Chemical-Mechanical Planarization (CMP) process time for Shallow Trench Isolation (STI) is important. A wafer under-or over-polishing causes leakage and short-circuits making the chips defective. The CMP process control by interferometry is one of the most used systems to monitor the polishing time. In some cases, the interferometry process control is not possible because the wafer patterns cause some unwanted effects such as scattering, diffraction, and absorption. Consequently the signal is affected. In this paper, we apply a theoretical and experimental approach on the light reflected from different STI stacks in order to interpret the observed optical phenomenon. The experimental study is done to get close to the light measurement conditions within the manufacturing environment. With this experiment, we evidence that the trench pattern inside memory zones is responsible for the diffraction effect on the signal. In a production environment, this pattern results in a lower measured intensity when the size of memory area increases. Besides, numerical calculations are performed based on differential method in order to predict the diffracted intensity, which depends on the chip design parameters and the incident wavelengths tuning. By using STI models, this method helps to determine the wavelengths with the highest reflected intensity.
The challenge in the research is to develop a material thickness measurement method to monitor oxide polishing by Chemical-Mechanical Planarization (CMP) in the Shallow Trench Isolation (STI). The underlying aim is to build a statistical regulation model for the polishing time on one platen (the two others platens are monitored by an endpoint signal). In addition to the process parameters (head sweep, platen, and head rotation velocity), input and output polished material thicknesses data are essential to build a run-to-run model for CMP. Therefore, stack layer thickness, before and after polishing, needs to be measured fast enough to maintain the acceptable throughput and to control truthfully the polishing time wafer by wafer. In this paper, we describe how the spectroscopic reflectometry embedded in the polishing equipment, can meet the requirements of rapidity and capability of setting up a run-to-run control algorithm to maintain the thickness target for CMP STI.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.