Simulation of silicon dry etching through a mask in low pressure fluorine-based plasma (original) (raw)
Related papers
Deep trench etching in silicon with fluorine containing plasmas
Applied Surface Science, 1996
Single crystal silicon was etched with mixtures of SF,. CBrF,, Ar and O,, using different electrode materials to obtain deep trenches. The etch rates. both vertically and horizontally increase when the relative flow of SF, increases. When using aluminium or stainless steel electrodes, the amount of SF, has to be limited to 10% of the total flow of fluorine containing gases to obtain wall profiles with an angle of over 80". However, in all these cases considerable surface roughness is observed. A solution to this problem is the use of a graphite electrode, which permits the use of SF, as the sole halogen containing gas to obtain vertical walls. Depending on the Ar addition, processes with good anisotropy and without surface roughness can be obtained.
Simulation of fluorocarbon plasma etching of SiO2 structures
Microelectronic Engineering, 2001
A surface model for open area etching of SiO is coupled with a model to calculate the local values of etching rate on 2 each elementary surface of the structure being etched. The surface model includes the surface chemistry for ion-enhanced etching or deposition. The local etching model (essentially a local flux calculation model) includes shadowing effects of ions / neutrals and re-emission, while charging effects are simulated only by an increased ion angular spread. Aspect ratio dependent and independent etching as well as transition from etching to deposition are predicted and studied as a function of plasma phase composition. Variations of etching yield versus aspect ratio can be graphically depicted as paths on the two dimensional plot of equal yield contours versus the normalised fluorine and carbonaceous radicals flux. Operation regimes of the plasma allowing minimisation of aspect ratio dependent phenomena can be easily identified by such graphical representation.
Analytical modeling of silicon etch process in high density plasma
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 1999
Plasma etching of silicon is one of the important etching processes used in modern integrated circuit manufacturing and micro-electro-mechanical systems fabrication. A good understanding of this process leads to better models which are the key to easier and less costly plasma etching process design. The main focus of this paper is on the simulation of the ion reflection from feature sidewalls and the resulting microtrenches. Pure Cl 2 plasma was used for experiments because of the simple chemistry. SPEEDIE ͑Stanford etching and deposition profile simulator͒ was used in this work. Langmuir adsorption model was used for etching kinetics. Self-consistent calculations were done for fluxes using surface coverage dependent sticking probabilities. For ion reflection, it was assumed that the reflected ions come off with a distribution about the specular reflection angle. This distribution is modeled as cos n ͑ is the deviation from the specular angle͒ and is important in getting the correct shape for microtrenches in simulations. A three-dimensional ͑3D͒ calculation of the reflection flux was done taking into account the 3D angular distribution of the incoming ions. The ion reflection efficiency was deducted from the silicon ion enhanced etching yield versus ion angle of incidence data. The simulation results match the experimental profiles fairly well.
Journal of Applied Physics, 2000
A surface model is presented for the etching of silicon ͑Si͒ and silicon dioxide (SiO 2 ) in fluorocarbon plasmas. Etching and deposition are accounted for using a generalized concept for the ''polymer surface coverage,'' which is found to be equivalent to a normalized fluorocarbon film thickness covering the etched surfaces. The model coefficients are obtained from fits to available beam experimental data, while the model results are successfully compared with high-density plasma etching data.
2002
This paper presents guidelines for the deep reactive ion etching (DRIE) of silicon MEMS structures, employing SF 6 O 2-based high-density plasmas at cryogenic temperatures. Procedures of how to tune the equipment for optimal results with respect to etch rate and profile control are described. Profile control is a delicate balance between the respective etching and deposition rates of a SiO F passivation layer on the sidewalls and bottom of an etched structure in relation to the silicon removal rate from unpassivated areas. Any parameter that affects the relative rates of these processes has an effect on profile control. The deposition of the SiO F layer is mainly determined by the oxygen content in the SF 6 gas flow and the electrode temperature. Removal of the SiO F layer is mainly determined by the kinetic energy (self-bias) of ions in the SF 6 O 2 plasma. Diagrams for profile control are given as a function of parameter settings, employing the previously published "black silicon method". Parameter settings for high rate silicon bulk etching, and the etching of micro needles and micro moulds are discussed, which demonstrate the usefulness of the diagrams for optimal design of etched features. Furthermore it is demonstrated that in order to use the oxygen flow as a control parameter for cryogenic DRIE, it is necessary to avoid or at least restrict the presence of fused silica as a dome material, because this material may release oxygen due to corrosion during operation of the plasma source. When inert dome materials like alumina are used, etching recipes can be defined for a broad variety of microstructures in the cryogenic temperature regime. Recipes with relatively low oxygen content (1-10% of the total gas volume) and ions with low kinetic energy can now be applied to observe a low lateral etch rate beneath the mask, and a high selectivity (more than 500) of silicon etching with respect to polymers and oxide mask materials is obtained. Crystallographic preference etching of silicon is observed at low wafer temperature (120 C). This effect is enhanced by increasing the process pressure above 10 mtorr or for low ion energies (below 20 eV). [720] Index Terms-Cryogenic etching, profile control, reactive ion etching (RIE).
Microelectronic Engineering, 1999
A surface model for Si and SiO2 etching in fluorocarbon plasmas has been developed as a part of a complete plasma simulator including plasma physics, plasma chemistry, surface chemistry and a topography profile evolution simulator. It can predict the transition from etching to deposition region, which depends on F and CFx radical concentration, ion flux to the surface and ion energy. The coupling of the surface model with the profile simulator can predict the RIE lag during etching of features with different aspect ratios.
Simulation of cryogenic silicon etching under SF6/O2/Ar plasma discharge
Journal of vacuum science & technology, 2016
An etching simulator is developed to study the two-dimensional (2D) silicon etch profile evolution under SF 6 /O 2 inductively coupled plasma discharge. The simulator is composed of three modules: plasma kinetic module, sheath module, and etching module. With this approach, the authors can predict the 2D etch profile evolution versus reactor parameters. Simulation results from the sheath model show that the shape of the bimodal ion energy distribution function for each incident angle depends on the ion mass. It is all the larger that the ion mass is low. As shown in the experiment, the simulation results reveal that the atomic oxygen plays an important role in the passivation process along the side-wall. Indeed, the simulation results show the decrease of the undercut when the %O 2 increases. This improves the etching anisotropy. However, the decrease in the etch rate is observed for a high %O 2. Moreover, for a moderate direct current (DC) bias (some 10 V), a low variation of the silicon etch profile versus DC bias is observed. The moderate ion energy only allows removing of the passivation layer on the surface bottom. The etching process is mainly controlled by the chemical etching under fluorine flux. V
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2003
As the microelectronics industry continues to shrink feature size and increase feature density in the back-end of integrated circuits, the traditional empirical approach to plasma etch process development is becoming prohibitively expensive and time consuming. Fundamental physics based models can prove useful in driving down process development time and cost. In this article, an integrated equipment-feature scale modeling infrastructure for SiO 2 and photoresist ͑PR͒ etching in fluorocarbon based plasma discharges is described. The model correlates process conditions with plasma properties, surface interactions, and etch results. A validated plasma chemistry for Ar/c-C 4 F 8 /CF 4 and detailed plasma-surface reaction mechanisms for SiO 2 /PR etching have been incorporated in the model. Major surface reactions for SiO 2 etching include neutral surface passivation, fluorocarbon radical polymerization, and ion assisted etching of volatile products. The mechanism for PR erosion includes energy/angle dependent ion sputtering, ion activation, F atom etching with ion assistance, and fluorocarbon radical deposition. Computed SiO 2 and PR etch profiles and rates have been validated by comparing with experimental results in a commercial inductively coupled plasma ͑ICP͒ etch tool. The validated model is used for a detailed investigation of SiO 2 /PR etching in a representative 300 mm wafer ICP tool. It is found that SiO 2 etch rate is a nonlinear function of Ar/c-C 4 F 8 ratio, where the highest etch rate is obtained when sufficient neutral passivation takes place while polymer deposition is still small. Deviating from this condition reduces SiO 2 etch rate by either excessive polymerization or insufficient passivation. PR etch rate and facet size, however, increase monotonically with Ar/c-C 4 F 8 ratio due to reduced polymer deposition. The effect of CF 4 ratio in the Ar/c-C 4 F 8 /CF 4 source gas on SiO 2 etching depends on the Ar fraction. When Ar fraction is large, replacing cC 4 F 8 with CF 4 reduces surface passivation and thereby decreases SiO 2 etch rate. However, at small Ar fractions, CF 4 addition reduces polymer formation and increases the SiO 2 etch rate. For the range of conditions explored, SiO 2 etch characteristics are insensitive to bias frequency as the ion energies are well above the threshold energy for etching. The plasma zone height ͑PZH͒ impacts the fluxes of etchants to the wafer and consequently the SiO 2 /PR etch rates. PZH, however, does not influence etch uniformity noticeably as diffusion is dominant at low gas pressures.
Modeling of Aspect Ratio Dependent Etching in an Inductively Coupled Plasma
MRS Online Proceedings Library (OPL) , 1995
ABSTRACT - SPEEDIE is used to simulate aspect ratio dependent etching of silicon dioxide in an inductively coupled plasma. Overhang test structures and standard via/trench structures are etched in the system under standard processing conditions. Results from the overhang test structure yield information about the ion angular distribution and aid in the development of the model. The simultaneous etching and deposition model includes such effects as ion enhanced polymer deposition, angle dependent polymer sputtering, Langmuir adsorption saturation model, and surface dependent sticking probability. The model is able to capture all the lag trends, defined as the difference in etch rate for different aspect ratios, and profiles accurately.
Nanomaterials, 2020
In this paper, we study the plasma-less etching of crystalline silicon (c-Si) by F2/N2 gas mixture at moderately elevated temperatures. The etching is performed in an inline etching tool, which is specifically developed to lower costs for products needing a high volume manufacturing etching platform such as silicon photovoltaics. Specifically, the current study focuses on developing an effective front-side texturing process on Si(100) wafers. Statistical variation of the tool parameters is performed to achieve high etching rates and low surface reflection of the textured silicon surface. It is observed that the rate and anisotropy of the etching process are strongly defined by the interaction effects between process parameters such as substrate temperature, F2 concentration, and process duration. The etching forms features of sub-micron dimensions on c-Si surface. By maintaining the anisotropic nature of etching, weighted surface reflection (Rw) as low as Rw < 2% in Si(100) is ac...