Photon Factory Activity Report 2005 #23 Part B (2006)
Materials Science

7C,10B,12C,13C/2005G242

Grazing incidence X-ray reflectivity of HfO2/Si film
Jiangwei FAN1, Nobuyuki MATSUBAYASHI1, Isao KOJIMA*1 and Shiqiang WEI2
1
NMIJ/AIST, Tsukuba, Ibaraki 305-8565, Japan2
NSRL/USTC, Hefei, 230029, China
Introduction
Total reflection X-ray has been considered as a
powerful tool for the study of surface and interface
phenomena since the last several decade. [1] In this report,grazing incidence X-ray reflectivity spectra for 200nm
thick HfO2/Si film synthesized by RF magnetron
sputtering were obtained when the X-ray incident angles
were below and beyond the critical angle.
Experimental
Film deposition was carried out in an ultrahigh vacuum(7×10-8 Pa) radio-frequency (r.f) magnetron sputteringsystem.[2] A 3 in. metallic Hf (99.9% purity) disc wasused as the sputtering target with argon as the plasmagenerating gas.
The angle resolved sample stage with an angle
resolution of 0.006° was designed and employed in themeasurement. A receiving slit with a same size as thefront one after sample is used to eliminate the scattering
effect. Halfcut procedure alignment was done to setup theinitial position of the sample before every measurement.
At last, the incident angle was calibrated by compared tothe theoretical XRR spectrum.[3] The refection spectra
were recorded as log(I0/I), in the same way as theabsorption one.
Also XPS spectra have been taken at BL-13C for thesame samples and the results will be presented elsewhere.
Results and Discussion
Figure1 shows the gracing incidence X-ray reflectivity
spectra for 200nm thick HfO2/Si film at different incident
angle. The spectra could be categorized into three parts
according to the different incident angles. i) When theincident angles αi are below the critical angle (αi=0.144°,0.194°, 0.244°, and 0.294°), the reflectivity spectrapresent a similar appearance to the conventionaltransmission mode X-ray absorption spectroscopy (fig. 2).
This could be understood that under this condition, only
the imaginary part β(E)of the complex refractive index
n(E)=1-δ(E)-iβ(E) contribute to the reflectivity spectra asa function of energy, which is in the same case of theconventional transmission mode. ii) When the incident
angles are large than the critical angle, as shown in figure
1 (αi=0.344°, 0.394°), the shape of the spectra becomemuch different: the intensity increase dramatically with
the increase of the incident energy. This phenomenon isdue to the contribution of the real part of the complex
refractive index of HfO2. iii) When the incident angle
increase to 0.444°, a periodic oscillation can be observed
obviously before the absorption edge. This is because the152

Users' ReportX-ray penetration depth is up to 200 nm at this angle,
reaching the Si substrate, interference occurring at
interface to form the oscillation.

Fig 1 X-ray reflectivity spectra for 200nm thick HfO2/Si
film at different incident angle.

Fig 2 Normalized spectra below critical angle comparedto the conventional transmission mode X-ray absorptionfor HfO2 powder
References[1] P. Borthen et al., Phys. Rev. B 52 3017 (1995).
[2] T. Fujimoto et al., Rev. Sci. Instrum. 70 4362 (1999).
[3] http://www-cxro.lbl.gov/optical_constants/layer2.html*i.kojima@aist.go.jp