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Int. J. Metrol. Qual. Eng. 4, 8186 (2013) c
EDP Sciences 2013
DOI: http://dx.doi.org/10.1051/ijmqe/2013040
Web End =10.1051/ijmqe/2013040
Determination of multilayer thicknesses of GaAs/AlAs superlattice by grazing incidence X-ray reectivity
L.L. Ren , H.F. Gao, S.T. Gao, J.J. Liu, and W. Zhang
National Institute of Metrology of China, Beijing 100013, P.R. China
Received: 19 November 2012 / Accepted: 11 July 2013
Abstract. The grazing incidence X-ray reectivity is used to determine the multilayer thickness of GaAs/AlAs supperlattice. The measurement process includes the tting model and the measurement conditions (dierent powers of 45 kV 40 mA, 40 kV 40 mA and 35 kV 40 mA, dierent step sizes
of 0.005, 0.008 and 0.010, and dierent times per step of 1 s, 2 s, 3 s). In order to obtain the valid measurement process, the combined standard deviation is used as the normal of the tting results selection. As a result, the measurement condition of 0.008 step size and 2 s time per step with the power 40 kV
40 mA is selectable with the operation stability of facilities and smaller error.
Keywords: Multilayer thickness; grazing incidence X-ray reectivity; GaAs/AlAs supperlattice; combined standard deviation; valid measurement process
1 Introduction
Thin and multilayer lms with thickness of a few nanometer are widely used in the solid state electronic and optoelectronic devices [1, 2]. Many techniques are used to characterize the thin lm thickness. Sputter techniques like secondary ion mass spectrometry (SIMS) and sputter-assisted Auger electron spectroscopy (AES) allow the layer thickness and composition to be estimated, but they provide an absolute thickness only with reference to a standard. Optical methods like photoluminescence (PL) and atomic force microscopy (AFM) [3] give further information, but they impose restrictions on the structure to be investigated. Finally, transmission electron microscopy (TEM) allows the determination of the layer thickness; however, sample preparation is complicated and destructive [4]. Grazing incidence X-ray reectivity (GIXRR) is a powerful and eective method for characterizing lm thickness, surface/interface roughness and density for ultra layers without any damage of the materials [57]. Moreover, GIXRR is an absolute method to give the structure parameters without any reference to the standard. We have studied the traceability of the angle and wavelength of the GIXRR instrument in our institute [8, 9]. Single...