Secondary ion mass spectrometry characterization of indium-implanted silicon wafers

Abstract

Indium is a key element in the formation of well, channel, and halo profiles in semiconductor fabrication. Indium has the advantage of being a large atom with a small projected range, creating a steeper implant profile than the boron implant used in the past [Proceedings of the 14th International Conference on Ion Implantation Technology, ITT, 2002]. Typically, secondary ion mass spectrometry (SIMS) is used to provide implant profiles; however, when a set of indium-implanted samples were analyzed on the Cameca IMS-6F, non-repeatability of the implant profile was observed in the samples that had not received an oxide spacer prior to implantation. This non-repeatability was not observed when the same samples were analyzed on the Perkin-Elmer 6300 quadrupole secondary ion mass spectrometer. Several reasons for this were hypothesized: (1) an amorphous layer was being created due to the large size of the indium atom; (2) increased damage and surface roughening occurred on the samples that did not receive an oxide layer prior to implantation; (3) Gibbsian segregation similar to that of Cu in SiO 2 was being observed [Secondary Ion Mass Spectrometry, Wiley, New York, 1989, p. 2.2-1]; and (4) sample heating was changing the thermodynamic properties of the samples. To explore these possibilities, two sets of indium-implanted samples—with and without spacer oxide—were analyzed with atomic force microscopy (AFM) for surface roughness and with transmission electron microscopy (TEM) for differences in amorphization. SIMS analysis was also conducted on both types of dynamic SIMS instruments to develop an analytical protocol for determining the indium implant profile. Repeatable results, consistent with analysis on the quadrupole SIMS, were obtained by utilizing the cold finger on the Cameca 6F.