RECENT SUCCESSES IN THE USE OF SECONDARY-ION MASS-SPECTROMETRY IN MICROELECTRONICS MATERIALS AND PROCESSING

Secondary ion mass spectrometry (SIMS) has been used for over 20 years by the microelectronics industry to determine in-depth distributions of dopants and impurities which become incorporated into semiconductor materials. SIMS not only has extremely high sensitivity (sub-part per million for almost all elements), but inherent in the secondary ion f ormation process is the ability to determine in-depth elemental distri butions. While SIMS appears to be an ideal depth profiling technique, in reality, it has had many drawbacks in the past. Three of them are t he following. (1) Sentitivities can vary from element to element, and from one matrix to another. (2) Reliable profiles within the top 100 A ngstrom of the sample are difficult to obtain due to changing ion yiel ds within this region. (3) Atomic mixing in the sample lattice due to energetic ion bombardment can distort sharply falling in-depth element al distributions. The aim of this paper is to show how SIMS has recent ly overcome these problems to allow us to obtain accurate depth profil es within the top 100 Angstrom of a sample with minimal matrix effects on sensitivities. We show examples from three areas: (1) analysis of shallow dopants and junctions in semiconductors; (2) analysis of 100 A ngstrom thick SiO2 gate dielectric films; (3) analysis of surface cont amination on Si wafer surfaces. All of these problems are of intense c urrent interest and are at the forefront of SEMATECH's perceived need for Si semiconductor characterization efforts into the next century.