AVS 46th International Symposium
    Plasma Science and Technology Division Monday Sessions
       Session PS-MoM

Paper PS-MoM10
Effect of Surface Oxide Loss on Surface Potential Measurement (SPM) Accuracy for Plasma Charging Damage Characterization

Monday, October 25, 1999, 11:20 am, Room 609

Session: Plasma Damage
Presenter: S. Ma, Hewlett-Packard Company
Authors: S. Ma, Hewlett-Packard Company
K. Nauka, Hewlett-Packard Company
R. Kavari, Hewlett-Packard Company
Correspondent: Click to Email
It is well recognized that the surface potential measurement (SPM) technique can be used as a process diagnostic tool for evaluating plasma-induced charging damage in MOS devices. To date, it is the simplest and cheapest non-invasive method using blank oxide wafers to monitor cumulative wafer charging after plasma exposure. Despite of its convenience, SPM's results do not always correlate well with MOS device charging damage data, especially in sputter clean, metal etch and oxide etch processes. There is limited understanding currently available to explain why the weak correlation sometimes exists. This paper examines the reason why surface potential measurement (SPM) results after plasma exposure do not always correlate to the results of plasma induced charging damage measurement on devices. One very important explanation has been found to be non-uniform surface oxide loss during plasma exposure on test wafers. From biased oxygen plasma exposure experiments in a M0RI source high density plasma etcher, the SPM results lost their correlation to antenna capacitor device damage when the substrate bias was sufficient to etch the surface oxide. As the amount of surface oxide loss increases, deposited surface charge distribution correlates better to surface oxide loss than to the damaged antenna capacitor data. Longer plasma exposure time with more oxide loss also shifts the SPM results to a higher averaged value. Compared to the device damage data, the critical surface oxide loss causing misleading SPM results is estimated to be around 70Å. Therefore, this characterization method is applicable to plasma induced charging damage for limited processes that do not cause severe surface oxide loss such as resist ashing, high oxide selectivity poly etch, etc.