Process monitoring using advanced inspection methodologies - a study with CVD

Defect free film deposition is one of the most challenging steps in CMOS manufacturing for 28nm process node and beyond. For precise control over surface, excellent uniformity and accurate material characteristics are required. IC manufacturers find it critical to monitor the film deposition process in terms of layer uniformity and other signatures/defects induced on the surface during the deposition process. In this work, an oxide layer deposited using flowable chemical vapor deposition (FCVD) process on a 300mm bare silicon wafer has been studied. Different process conditions with varying amount of precursor and reactant gases have been employed for the deposition of the oxide. The so called “haze” signatures and statistics found during inspection on the post-deposition surfaces are used to measure variation in surface quality, serving as a means to qualify the FCVD process. For this study, an FCVD tool fitted with two chambers with two sides each has been employed for the deposition of oxide. The integrated SURFmonitor feature of KLA-Tencor´s SP3 - a blanket wafer defect inspection tool set - was successfully utilized to highlight the variation of the CVD tool´s performance. Firstly, the overall study clearly demonstrates the capability of SURFmonitor to differentiate the process conditions between Process - 1 and Process -2. Also, for a given process, it showcases the capability of differentiating between different deposition chambers. In addition, for a given process and specific chamber, grid analysis feature of SURFmonitor has been applied to highlight the within-spec and the out-of-spec areas for each of the wafers. The methodology described in this paper has already proven to be quite effective in monitoring the CVD process.