Papers by Keyword: Stiction

Abstract: Recently, a surface energy reduction process (SERP) for stiction-free drying is used for a high aspect pattern structure like shallow trench isolation (STI). The key technology of SERP is trimethylsilyl (TMS) groups termination of the device surface. To explain the electrical influence of TMS groups was found acceptable by measuring the planar capacitor flat-band voltage shift, and the threshold voltage characteristics of 1x-nm node MOS transistors.

Abstract: As semiconductor devices continue to scale down to smaller sizes, high aspect ratio (HAR) structures are required to achieve the desired device performance. As such, wet processing becomes a very challenging process step due to the capillary forces that are generated during drying. The strength of the capillary force is dependent on the surface tension and contact angle of the fluid that is being dried, as well as the feature spacing and AR. If the drying forces are too high (Figure 1), then the features may break or collapse onto each other resulting in poor device yield. Other factors affecting a structure’s susceptibility to collapse include pattern geometry and material composition [1].

Abstract: Valve stiction is one of the main reasons which lead to control loop oscillation.However, there is not a mature method to diagnose the stiction.Under the premise of unknown the control system model,this paper put forward a new method based on the process output signal processing to realize control valve stiction of fault diagnosis.The results of the experiment and simulation to show that the method is effective.

Abstract: Aiming to explain phenomena of “stiction” and “snap-back”, a ball-surface adhesion is simulated with molecular dynamics (MD) based on multi-body EAM potential function. Surface atoms “summon up” and migrate, which lead to the phenomenon of “stiction”. The migration velocity of interface atom is not consistent. Some atoms migrate too fast, which lead to the phenomenon of “snap-back”. The “Snap-back” phenomenon appears twice during the adhesion process. A “neck-separation” phenomenon is found. The adhesive force in the separation process obviously lagged the adhesive force in the contact process, which shows there is energy loss during the adhesion process. The curve of adhesion deformation is simulated finally, and compared with relevant results.

Abstract: Pattern collapse has long been known in photoresist patterning where the resist patterns merge or collapse during rinsing and drying steps [. The forces responsible for this collapse were identified as capillary forces during the drying process. Structures such as titanium nitride DRAM cylinders [ and silicon Flash shallow trench isolation (STI) lines have also been observed to be pattern collapse sensitive due to increase in aspect ratio of the features. Micro-electromechanical systems (MEMS) devices also show a similar phenomenon, but on a larger length scale, and is referred to as stiction [. For the technology nodes <14 nm, back-end-of-line (BEOL) low-k structures are also on the verge to show pattern collapse behavior. Whether a structure is sensitive to pattern collapse or not depends on several parameters, which will be analyzed in this paper.

Abstract: A variational method using the principle of virtual work (PVW) is presented to formulate the problem of the microcantilever stiction. Compared with the Rayleigh–Ritz method using the arc-shaped or S-shaped deflection, which prescribes the boundary conditions and thus the deflection shape of a stuck cantilever beam, the new method uses the matching conditions and constraint condition derived from PVW and minimization of the system free energy to describe the boundary conditions at the contact separation point. The transition of the beam deflection from an arc-shape-like one to an S-shape-like one with the increase of the beam length is shown by the new model. The (real) beam deflection given by this new model deviates more or less from either an arc-shape or an S-shape, which has significant impact on the interpretation of experimental data. The arc-shaped or S-shaped deflection assumption ignores the beam bending energy inside the contact area and the elastic energy due to the beam/substrate contact, which is inappropriate as shown by this study. Furthermore, the arc-shaped or S-shaped deflection only approximately describes the deflection shape of a stuck beam with zero external load and obviously, the external load changes the beam deflection. The Rayleigh–Ritz method using the arc-shaped or S-shaped deflection assumption in essence can only be used to tell approximately whether stiction occurs or not. Rather than assuming a certain deflection shape and by incorporating the external load, the new method offers a more general and accurate study not only on the microcantilever beam stiction but also on its de-adherence.

Abstract: In this paper, we studied stiction behavior of HAR pattern (line and space pattern) dependence on adhesion force with surface tension of drying liquid and surface contact angle. Surface tension effect was evaluated with various drying liquids such as IPA, ethanol and HFE (hydrofluoroether) chemical. Patterns treated by dHF, APM and surface modifier were introduced to investigate dependence of pattern collapse on contact angle. The high temperature D.I. water rinse followed by high temperatures drying using liquid with low surface tension was a most effective. Furthermore, surface modification method using HMDS (hexamethyldisilazane) chemical was also effective.

Abstract: Stiction is a common problem in spring-diaphragm type valves, which are widely used in the process industry. A non-invasive method for detecting and quantifying stiction in control valve has been presented in this paper. Although there have been many attempts to understand and detect stiction in control valves, none of the current methods can simultaneously detect and quantify stiction. The method first detects nonlinearity in a control loop by the use of the sensitivity of the normalized bispectrum or bicoherence to the nonlinear interactions that may be present in the control error signal.If nonlinearity is detected, then controlled variable(pv) and controller output(op) signals are filtered using frequency domain wiener filter to obtain filtered pv and op signals.This work describes a model free method that can detect and quantify stiction that may be present in control valves using routine operating data obtained from the process. No additional excitation or experimentation of the plant is required.

Abstract: We report our efforts towards designing and fabricating capacitive microaccelerometers with flat bottom surfaces free from the notching effects of Deep Reactive Ion Etching (DRIE) based on SOI process. The substrate layer under the device structure is etched and a metal film is deposited to the backside of moving structure for protecting the bottom surfaces so that the stiction problem and notching effects are avoided. The test results demonstrate that SOI accelerometers have been released successfully. The measured sensitivity is 169.1mV/g and the linearity of output is within 0.202%.

Abstract: The stiction of control valve is one of main causes which make control loop instable in the process industry. Now a number of studies on the diagnosis of control valves are based on stiction. It needs developing a proper method which can detect, quantify, and compensate stiction. A non-invasive method has been used into the fault diagnosis for stiction of pneumatic control valve. Firstly, a two-parameter data-driven model about stiction has been established, and on the basis of separable least squares method, combined with the global search algorithm to deduce the model identification method. Secondly, ellipse fitting method has been adopt to confirm whether the stiction existed, thus the stiction could be quantified, and on this basis, the stiction was compensated. So it improved the performance of control system. Thirdly, the validity of the method was confirmed by simulation.