AVS 46th International Symposium
    Applied Surface Science Division Tuesday Sessions
       Session AS-TuM

Paper AS-TuM3
Quantitative Determination of Oxide Layer Thickness and Nitrogen Profiles for Si Gate Oxides

Tuesday, October 26, 1999, 9:00 am, Room 6A

Session: Ion Beam Analysis and Depth Profiling
Presenter: O. Brox, Universität Münster, Germany
Authors: O. Brox, Universität Münster, Germany
K. Iltgen, AMD Saxony Manufacturing GmbH, Germany
E. Niehuis, ION-TOF GmbH, Germany
A. Benninghoven, Universität Münster, Germany
Correspondent: Click to Email
Accurate characterization of ultra-thin nitrided gate oxides is crucial for future semiconductor device scaling. We have investigated the capabilities of TOF-SIMS to control oxide thicknesses down to 2-3 nm and to quantify the nitrogen depth distribution. For all experiments we used the TOF III instrument, equipped with a flexible gas ion source and a cesium source (0.6 - 10 keV) for crater formation. An additional gas ion source (Ar@super@+, 11 keV) was applied for the analysis of the crater bottom. SiO@sub 2@ layer thicknesses can be determined by measuring exactly the position of the SiO@sub 2@/Si interface during depth profiling. This interface is indicated by drastic changes in the yield of the characteristic secondary ion species Si@sub x@O@sub y@@super -@. We found that the maximum in the Si- emission describes the position of the SiO@sub 2@/Si interface very exactly and that down to less than 3 nm oxide thickness a linear relationship exists between the position of this maximum and the oxide thickness as determined by TEM. We determined the nitrogen concentration in the oxide layers by following the nitrogen specific secondary ion SiN@super -@ and at the same time the SiO@sub n@@super -@ (n=0,1,2,3) intensities, which allow to calculate the corresponding lattice valency [1]. Relative sensitivity factors for nitrogen as a function of lattice valence were determined by using a nitrogen implant sample with a known nitrogen concentration. This allows to correct the measured SiN@super -@ profiles. We will report on these depth profiling results, the strong influence of the sputter ion energy on the width of the transient regime, changing between 1 nm for 0.4 keV and about 8 nm for 5 keV, on the influence of sample temperature during sputtering and on possible improvements by applying sputter ion energies @<=@ 0.4 keV combined with simultaneous Cs and noble gas sputtering. . @FootnoteText@ [1] C. Plog, L. Wiedmann, A. Benninghoven, Surf. Sci. 67 (1977) 565.