Vertical processing of 0.05-µm-class SiO2 holes with an aspect ratio around 20 was realized using a dipole-ring-type magnetron reactive-ion-etching system in a mixture of C4F8/O2/Ar gas. Secondary ion mass spectrometric study of the F and C concentration profiles of the polymer deposited inside the holes in the depth direction revealed that a very small amount of polymer deposition occurred in this system. This indicates that energetic species reached the hole bottoms with excellent verticality, even in an extremely fine feature. In contrast, the CHF3/CO process (tapered shape) resulted in an extremely thick polymer and carbonized region on the sidewalls, suggesting the presence of energetic species sticking to the sidewalls. The effects of energetic species impinging onto the sidewalls and the protection resulting from polymer deposition have been discussed in terms of the etched shape and F/C depth profile. Vertical incidence of the energetic species into the holes is concluded to be a significant factor in realizing a vertical profile.

Single-mask, three-dimensional microfabrication of high-aspect-ratio structures in bulk silicon using reactive ion etching lag and sacrificial oxidation Appl. Phys. Lett. 85, 6281 (2004); 10.1063/1.1834720Surface analysis by secondary-ion mass spectroscopy during etching with gas-cluster ion beam Characterization of fluorocarbon films deposited on sidewall and bottom surfaces during high-aspect-ratio contact hole etching has been investigated by secondary ion mass spectrometry ͑SIMS͒. Very high-aspect-ratio contacts, with hole diameters ranging from 0.06 to 0.18 m, were etched in 1 m thick SiO 2 films with polycrystalline Si hard masks by high density CHF 3 /CO or C 4 F 8 /O 2 /Ar plasma generated by a dipole ring-type magnetron reactive ion etching reactor. A series of SIMS studies for test element group chips with high density contact holes first reveal that the SIMS profiles obtained from the etched samples qualitatively exhibit a good measure of fluorocarbon profiles on the inner surfaces of the high-aspect-ratio contact holes. Quantitative evaluation is also discussed further. Fluorocarbon films on the sidewalls polymerized from CHF 3 /CO plasma show a great accumulation of C-rich films at an aspect ratio of around 4. With an increasing aspect ratio of more than approximately 8, the polymers are found to change from C-rich to F-rich films. On the other hand, fluorocarbon films on the sidewalls polymerized from C 4 F 8 /O 2 /Ar plasma are more uniform, much more fluorinated, and much thinner than those of the CHF 3 /CO plasma. Both polymers show a clear C pileup on the Si substrates at the bottom of the contact holes even for sub-0.1 m contacts. This work successfully demonstrates the usefulness of the SIMS measurement for characterizing high-aspect-ratio contacts down to sub-0.1 m diameters.

Phase Unwrapping (PU) is the key step in the image processing for Interferometric Synthetic Aperture Radar (InSAR). In the Extended Kalman Filter (EKF) model of PU, due to the state space model is not taken into account the terrain factors, it is often resulted in unwrapping error delivery as the pixel to the next when the state changes rapidly in steep terrain. The observation equation is nonlinear and usually applied in PU through linear processing, requiring the system model and noise statistics known. But in fact the mathematical model or statistical noise is completely or partially unknown; the results have been inevitably lead to the declining of valuation accuracy and filter divergence. If directly applied in phase unwrapping, it is made impossible to retrieve surface deformation. In order to solve this problem and fully consider the terrain effect and model error, an adaptive EKF PU algorithm (AEKFPU) for InSAR is presented. On the one hand, it is achieved local adaptive estimation of image fringe frequency through 2D FFT and Chirp-Z Transform (CZT) joint method, by considering the impact of terrain factors on unwrapping results; On the one hand, the fading factor is calculated by innovation covariance and adaptively adjusted with the error covariance so as to suppress the memory length of the filter, compensating the effect of incomplete information on unwrapping. The experimental results are proved the proposed method is effective, it can be dealt with phase unwrapping and filtering simultaneously, and can be adaptively considered terrain factors in state space model and compensated for model error in observation equation model, ultimately improving the accuracy of phase unwrapping.