Etching of SiO[sub 2] and Si in fluorocarbon plasmas: A detailed surface model accounting for etching and deposition (original) (raw)
Related papers
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 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.
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.
Simulation of silicon dry etching through a mask in low pressure fluorine-based plasma
Vacuum, 1996
The ion beam assisted etching of silicon through a mask in a low pressure fluorocarbon plasma is considered. The two-dimensional profiles of etched grooves are calculated using a proposed model involving a function of mask size, the fluxes of incident chemically active and non-active species from the plasma and bombarding ions. The model a/so includes the processes of adsorption, heterogeneous reactions, desorption, physical sputtering, activation of surface atoms and stochastic mixing between monolayers. Special attention is given to the etching anisotropy, lateral etching and elemental composition at the surface of a groove. It is shown, that formation of an inhibiting film on the sidewall of groove increases the etching anisotropy, however, the process of stochastic mixing leads to the formation of the altered layer in the near surface region. The thickness of altered layer and elemental composition at different surface regions of etched groove is considered.
Journal of Applied Physics, 2002
A model to calculate etching rates in SiO 2 features in fluorocarbon plasmas is presented. The model can predict several aspect ratio dependent phenomena such as reactive ion etching ͑RIE͒ lag, etch stop, inverse RIE lag, and aspect ratio independent etching ͑ARIE͒ at least for a limited range of aspect ratio values. The model includes three components: ͑a͒ a surface model for open area etching of SiO 2 ͑and Si͒ ͓Gogolides et al., J. Appl. Phys. 88, 5570 ͑2000͔͒; ͑b͒ a flux calculator, which calculates local fluxes on each elementary surface of the feature being etched; and ͑c͒ a coupling of the two models ͑a͒ and ͑b͒, the focal point of coupling being the simultaneous calculation of the neutral species fluxes and the corresponding effective sticking coefficients. The model is applied for trench etching and the gas phase conditions considered correspond to a generic fluorocarbon gas. A different approach is presented by which the gas phase composition is divided ͑i.e., mapped͒ into regions leading to ͑a͒ deposition, ͑b͒ RIE lag with no etch stop, ͑c͒ intense RIE lag and etch stop, ͑d͒ inverse RIE lag, and ͑e͒ ARIE. Based on the proposed model an explanation of the aspect ratio dependent phenomena and ARIE is attempted, and a comparison with experimental data is done. Two parameters were found to be important in this explanation: the polymer surface coverage at the bottom of the etched feature and the effective sticking coefficients of the neutral species on the sidewalls of the etched feature.
2001
As part of a project with SEMATECH, detailed chemical reaction mechanisms have been developed that describe the gas-phase and surface chemistry occurring during the fluorocarbon plasma etching of silicon dioxide and related materials. The fluorocarbons examined are C 2 F 6 , CHF 3 and C 4 F 8 , while the materials studied are silicon dioxide, silicon, photoresist, and silicabased low-k dielectrics. These systems were examined at different levels, ranging from in-depth treatment of C 2 F 6 plasma etch of oxide, to a fairly cursory examination of C 4 F 8 etch of the low-k dielectric. Simulations using these reaction mechanisms and AURORA, a zero-dimensional model, compare favorably with etch rates measured in three different experimental reactors, plus extensive diagnostic absolute density measurements of electron and negative ions, relative density measurements of CF, CF 2 , SiF and SiF 2 radicals, ion current densities, and mass spectrometric measurements of relative ion densities. University, plus all their coworkers, for early access to their experimental data.
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2004
The etching of Si, SiO 2 , Si 3 N 4 , and SiCH in fluorocarbon plasmas is accompanied by the formation of a thin steady-state fluorocarbon film at the substrate surface. The thickness of this film and the substrate etch rate have often been related. In the present work, this film has been characterized for a wide range of processing conditions in a high-density plasma reactor. It was found that the thickness of this fluorocarbon film is not necessarily the main parameter controlling the substrate etch rate. When varying the self-bias voltage, for example, we found a weak correlation between the etch rate of the substrate and the fluorocarbon film thickness. Instead, for a wide range of processing conditions, it was found that ion-induced defluorination of the fluorocarbon film plays a major role in the etching process. We therefore suggest that the fluorocarbon film can be an important source of fluorine and is not necessarily an etch-inhibiting film.
Modelling of fluorine based high density plasma for the etching of silica glasses
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2011
Etching simulator has been developed to study the etching of silica glass (Pyrex ® , D263 ® , AF45 ® , and Vycor ® ) in SF 6 /Ar plasma. The etching model is based on the development of the plasma kinetic model coupled to 2D Monte Carlo surface model to predict the etched surface morphology as a function of the operating condition. The results obtained by the model are compared with experimental results: etching rate and roughness. A satisfactory agreements between experimental results and the model concerning the etching rate and the etched surface morphology have been obtained for different glasses.
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.