Paper AS-FrM10
Acquisition of Quantitative Implant Coverage Maps of Semiconductor Devices with ToF-SIMS

Friday, November 13, 2009, 11:20 am, Room C2

Secondary Ion Mass Spectrometry (SIMS) is commonly used to acquire quantitative implant profiles in Si-based semiconductors. While dynamic SIMS is the preferred technique due to its sensitivity, Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) can also be used. The benefit of ToF-SIMS is that the full spectrum is acquired instead of a few selected species. Thus, unexpected species can be retrospectively included in the analysis in post-processing. Typically when measuring implant profiles, SIMS is used to verify a dose and depth distribution as quality control on single wafers from a single fab implant tool. Data from large areas are required to ensure that signal-to-noise levels are reasonable. Occasionally, it is important to measure implant doses on completed or near-completed devices. When this is the case, one no longer has large uniform areas from which to acquire high signal-to-noise data. Instead, the actual implant information is spatially patterned and may be vertically distinct, therefore containing multiple vertical layers. 3D measurements can be performed to determine the spatial distribution of major device constituents, such as metallization lines and insulating paths, but it is very difficult to determine quantitative implant information while measuring the full 3D distribution. This difficulty arises from the inherently low signal-to-noise measurement that cannot be helped by the use of spatial binning. To some extent, these issues can be overcome in ToF-SIMS as the user has independent control over sputter rate and acquisition times. Methods for preparing samples and acquiring data have been developed along with processing protocols to quantify the implant coverage and 3D distribution of implants in semiconductor devices using ToF-SIMS. These procedures, examples and limitations of the technique will be discussed.

^†Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.