Thickness Calculation of Silicon Dioxide Nano-Film Based on GIXRR Reflectivity Curve.

To obtain nanometer thin film thickness fastly and accurately, a formula of linear fitting method based on the periodic Kiessig fringes for thickness determination is applied, and a series of SiO2 nanometer films on Si substrate with the film thickness ranging from 10 to 120 nm have been calculated with the formula. These samples are prepared with thermal atomic layer deposition (T-ALD) process and film thickness is measured with grazing incidence X-ray reflection (GIXRR) technique, in addition, the linear fitting procedure and several influencing factors among it are studied, all of the work is based on the reflectivity curve from GIXRR experiment. While at the same time, another fitting method based on a soft named Global Fit2.0 is brought into this study to compare the two obtained thicknesses from two kinds of analysis methods. In the end a novel method for film thickness determination-empirical curve is presented. The results show that: during the linear fitting process, the peak position series have a main effect on thickness determination, thickness will increase when the peak position adds up; Besides, any peak's corresponding reflection angle also has a significant effect on the thickness determination, it is expressed in the form of interference fringe period, thickness will decrease while the interference fringe period increases, however, the errors from either peak series or fringe period can be further weakened with trial and error method, calibration procedure of critical angle and interference fringe period individually. Choosing the same sample with random thickness, no matter using the linear fitting and soft fitting method, the two gained film thicknesses are consistent and the thickness deviation is less than 0.1 nm, which illustrates the accuracy of linear fitting method for thickness determination. An empirical relationship between film thickness and interference fringe period is then put forward on the foundation of the accurate thickness determination, according this curve, the target film thickness is directly got by putting an interference fringe period in the empirical curve. This novel method not only avoids the messy procedure of choosing peak position series or their corresponding angles during linear fitting process, but also avoids the complex task of building a correct structure for soft fitting process; it is of great significance in confirming thin film thickness with quick speed and high accuracy.

Spectral analysis of irregular roughness artifacts measured by atomic force microscopy and laser scanning microscopy.

Atomic force microscopy (AFM) and laser scanning microscopy (LSM) measurements on a series of specially designed roughness artifacts were performed and the results characterized by spectral analysis. As demonstrated by comparisons, both AFM and LSM can image the complex structures with high resolution and fidelity. When the surface autocorrelation length increases from 200 to 500 nm, the cumulative power spectral density spectra of the design, AFM and LSM data reach a better agreement with each other. The critical wavelength of AFM characterization is smaller than that of LSM, and the gap between the measured and designed critical wavelengths is reduced with an increase in the surface autocorrelation length. Topography measurements of surfaces with a near zero or negatively skewed height distribution were determined to be accurate. However, obvious discrepancies were found for surfaces with a positive skewness owing to more severe dilations of either the solid tip of the AFM or the laser tip of the LSM. Further surface parameter evaluation and template matching analysis verified that the main distortions in AFM measurements are tip dilations while those in LSM are generally larger and more complex.

Dual-Probe Atomic Force Microscopy based on tuning fork probes for critical dimension metrology.

Atomic force microscopy (AFM) is widely used for nano-dimensional metrology in semiconductor manufacturing and metrological system. However, the conventional AFM can't provide accurate CD characterization of nanostructures, due to its top-down configuration and probe-size effect. In this paper, we develop a dual-probe atomic force microscopy (DPAFM). Compared to conventional optical-lever based AFM, the DPAFM exploits two tuning fork probes that simplifies significantly the setup and can be controlled based on frequency-modulation (FM) mode. The developed DPFAM is implemented that builds a zero-reference point by dual-probe alignment firstly, following which, characterizes nanostructures from two sides independently with the two probes. The final CD feature is determined by matching profiles from the two probes based on the zero-reference point. The capability of the DPAFM is validated by experiments on a CD-standard structure, that achieves the true CD assessment with good accuracy and repeatability.

Traceable nano geometric structure measurement and international comparison.

The accuracy of geometric structure plays a key role to guarantee high quality of the nano function device and electronic device. In June 1998, the Consultative Committee for Length (CCL) of International Committee for Weights and Measures decided to carry out international comparisons of five different types of artifacts: Step height standards, 1D-gratings, line scales, 2D-gratings and line width standards. The paper described the activity of NIM in the international comparison measurement of first three items, include the characters of artifacts, the working principle of instruments, the measuring procedures, the calculation methods, the comparison results and the measurement uncertainty.

Atomic force microscope scanning head with 3-dimensional orthogonal scanning to eliminate the curved coupling.

An atomic force microscopy (AFM) scanning head is designed with the probe orthogonal scanning mode for metrological AFM to eliminate the curvature distortion. The AFM probe is driven by piezostage and the scanning trajectory of the probe in 3 directions are orthogonal to reduce the cross coupling. A new optical lever amplification optical path is developed to eliminate the coupling error. The tracing lens and probe tip are moved as an integrated part. The AFM is operated at contacting mode. The step approach process of the probe tip is tested to the sample surface and the noise of the AFM head is analyzed. The response of the probe demonstrates a 0.5 nm resolution of the probe head in the z direction. Finally, the planar scanning performance of the scanning head is demonstrated compared with tube scanning AFM.