RECENT DEVELOPMENTS IN NUCLEAR METHODS IN SUPPORT OF SEMICONDUCTOR CHARACTERIZATION

摘要

The semiconductor industry heads towards shrinking device dimensions and new materials, there is a need for accurate and reliable physical characterization of very thin films. Most of the physical characterization of semiconductor devices are performed by Secondary Ion Mass Spectrometry (SIMS) and Rutherford Backscattering Spectrometry (RBS). The great sensitivity and the good reproducibility of SIMS and the quantitative compositional analysis of RBS are the strong characteristics in favor for this choice. Less well known are the applications of nuclear techniques for the analysis of ultra thin layers related to semiconductor materials. In this article, we will demonstrate by means of many examples and by selecting the appropriate nuclear techniques, these techniques lead to a better insight in material characterization In a first example we demonstrate the increased sensitivity by the study of the growth high-K materials based on ALCVD and MOCVD. In this example Rutherford Backscattering Spectrometry (RBS) and Nuclear Reaction Analysis (NRA) are used for the absolute quantification while High Resolution RBS (HRBS) and High Energy Elastic Recoil Analysis (H-ERD) are used for extreme depth resolutions down to 1nm. In a second example, we demonstrate the use of NRA in combination with Secondary Ion Mass Spectroscopy (SIMS). Combining the details of the SIMS profiles with the integral measurements of NRA provides then an excellent way to certify the SIMS profiles and to study effects such as self-sputtering during ion implantation, dose loss during annealing etc.. In a third example, the sub-nm depth resolution capabilities of HERD are demonstrated for the detection of Boron at the SiO_2/Si interface. Substantial differences with SIMS profiles in the near surface region could be demonstrated and provided insight in the fundamental mechanisms leading to the SIMS distortions. In a last example, the sub-nm depth resolution capabilities of Medium Energy Ion Scattering (MEIS) will be demonstrated in the characterization of the damage and annealing behavior of ultra shallow As implants in Si. An important issue in this area is the accurate determination of the near-Surface distribution of shallow implants and at interfaces. We conclude that for many problems in material characterization, a combined use of conventional techniques such as SIMS together with dedicated nuclear techniques provide good insight in the material behavior in shallow layers.