Characterization of ultra thin layers by Rutherford backscattering spectrometry

Rutherford Backscattering Spectrometry (RBS) is well known for the quantitative compositional analysis of thin films. As the semiconductor industry heads towards shrinking device dimensions and new materials, there is a need for accurate and reliable characterization of very thin films. With a careful selection of RBS analysis conditions and instrumentation, a depth resolution down to 1 nm can be obtained. Mainly the reduction in analysis energy and improved detector resolution contribute to this enhancement. At the same time it is demonstrated that the sensitivity of RBS improves to below the 1% level. The effect of reduction in analysis energy will be illustrated in the study on the segregation process of Cu on a Al(Cu) surface. Furthermore, it will be demonstrated that the use of dedicated spectrometers to improve detector resolution leads to extreme depth resolutions allowing the analysis of SiGe layers less than 10 nm thick and the analysis of thin oxynitrydes which are only 2.5 nm thick.