Thickness uniformity of gas-phase coatings in narrow channels: I. Long channels

Abstract

The process of thin film deposition from a gas phase in long narrow channels has been theoretically described. The analytical expressions have been derived for the function of coating thickness distribution along the channel for an arbitrary deposition mechanism. Universal quantitative criteria have been obtained which characterize the degree of coating thickness uniformity or conformal ability of the film-forming substance. The coating thickness distribution in any channel is shown to be described in relative coordinate system by universal distribution curve dependent on the process parameters only, but not on the shape and dimensions of a channel. The prospects of using the simulation results in different processes of coating deposition are discussed. The results obtained can be quantitatively applied to deposition processes of one-component coating such as poly-p-xylylene one. A method is proposed to improve the coating thickness uniformity applicable to various gas-phase deposition processes including deposition of poly-p-xylylenes with high limiting temperature of polymerization, such as PPX-C and PPX-D. The methods are also proposed to evaluate the main characteristics of the deposition process using film thickness distribution in narrow channels. The model is verified by experimental results.

Chemical vapor deposition of poly-p-xylylene in narrow tubes

“…In such cases, the layer thickness tends to be reduced along the length of the capillary in a manner that is approximately exponential but actually far more complicated. 12, 13 Beach and Ganguli have demonstrated that the surface polymerization of PPX requires successful docking of isolated MPX at the terminal positions of the growing polymeric chain. 7,8 To reduce adsorption and subsequent condensation of the vaporized monomer, the temperature of the substrate must be raised to the socalled "ceiling temperature", the highest temperature at which adsorption is still possible.…”

“…or, by combining equations (11) and (13) and considering the kinetic gas theory term for the mean squared velocity <v 2 >= 3 RT M , this leads eventually to…”

A Fluoropolymer Coating on Carbon Fibers Improves Their Adhesive Interaction with PTFE Matrix

“…The difficulty of plasma-chemical treatment of internal surfaces of capillary-porous systems, including clothes, accounts for the fact that coating of carbon fibers as parts of yarns and clothes is so far scarcely investigated. In Refs [48,49], a method for calculation of the active plasma particles' penetration depth into the capillaries has been proposed. Calculations by this method estimate the depth of the treated surface of a capillary as 10 capillary diameters.…”

Vapor‐Assisted Micropatterning in Replica Structures: A Solventless Approach towards Topologically and Chemically Designable Surfaces

“…S1, Supporting Information). [56,57] that at the open surface, and x/b is the ratio of depth over width of the feature -reveals a uniform behavior. As indicated in Figure S1, the dimensionless thicknesses measured for feature sizes ranging from 25 lm to 200 lm, are falling onto a single trend line.…”

“…This behavior is in accordance with the theoretical studies by Tolstopyatov et al, who found universal thickness distributions for the deposition of unfunctionalized poly-p-xylylene in microchannels. [56,57] While the results obtained by imaging ellipsometry suggest a lower feature size of about 25 lm, a more functional evaluation is needed in order to ensure that these coatings can still support effective immobilization. To address this question, we conducted immobilization studies with a model ligand, hydrazide-derived biotin, on the microstructures surfaces (experiments were conducted for 150 lm, 100 lm, 50 lm, 25 lm).…”