Ceramic films thickness

Equally important as tape casting in the fabrication of multilayer ceramics is thick film processing. Thick film technology is widely used in microelectronics for resistor networks, hybrid integrated circuitry, and discrete components, such as capacitors and inductors along with metallization of MLC capacitors and packages as mentioned above. 

The trend which arises from a consideration of Eq. (17.2) is that the lower the value of the Hamaker constant, A, the higher the equilibrium film thickness (Clarke, 1987). Striking confirmation experimentally of such a trend has come from work in which the local Hamaker constants in silicon nitride ceramics have been determined from spatially resolved-valence electron energy-loss spectroscopy (French et al 1998). Conversely, if A is too large, then there will be no thickness Z for which Eq. (17.2) is satisfied. 

For a suitably high critical value of A, this theoretical model predicts a lower limit on the equilibrium thickness that can be observed. This lower limit on Z, Z n, is defined by the conditions F= 0 and <1F/<1L = 0 since for a stable film F= 0 and dF/dL > 0 (Clarke, 1987). Various solutions to these conditions have been examined by Knowles and Turan (2000). In the absence of capillary pressure and external pressure, Zmin = 2.58. Using reasonable estimates for Knowles and Turan estimate Zmin to be >6.50 A. That in practice the observed intergranular film thicknesses are typically of the order of 1-2 nm in non-oxide engineering ceramics indicates that the relevant Hamaker constants for ceramics are significantly lower than the critical value. 

HRTEM observations of three differently misoriented interphase boundaries between hexagonal boron nitride (h-BN) and 3C silicon carbide (3C SiC) grains showing an orientation dependence on equilibrium film thickness. In (a) and (b) the (0001) of the highly anisotropic b-BN are parallel to the interface, whereas in (c) they make an angle of 68° with the interphase boundary (reprinted from Ultramicroscopy, Knowles KM and Turan S, The dependence of equilibrium film thickness on grain orientation at interphase boundaries in ceramic-ceramic composites, 83(3/4) 245-259 (2000) with kind permission of Elsevier Science). 

Knowles, K.M. and Turan, S., (2000), The dependence of equilibrium film thickness on grain orientation at interphase boundaries in ceramic-ceramic composites , Ultramicroscopy, 83 (3/4), 245-259. 

The story gets better. C. H. Anderson and E. S. Sabisky, "The absence of a solid layer of helium on alkaline earth fluoride substrates," J. Low Temp. Phys., 3, 235-8 (1970), reported the thickness of helium liquid condensed from vapor onto ceramic substrates. Van der Waals attraction nicely explains film thickness vs. the chemical potential of helium in the vapor. 

Abstract. Liquid phase deposition methods are a useful way to create mineral oxide films from aqueous solution under near-ambient conditions. These approaches have been applied to the creation of ceramic coatings on polymers and on polymer-matrix composites. Control has been achieved over the adherence and crystallinity of the solution-deposited thin films based on controlling the composition of both the deposition solution and the substrate surface. The challenge of depositing such films from water, while minimizing film cracking has also been addressed. Crack-free ceramic films of up to 200 nm thickness have been achieved on a variety of polymer substrates. 

In thick-film technology (layer thickness > 1 pm), roll or tampon printing methods well known in the porcelain industry are suitable for applying layers of defined geometry on the green ceramic. The thickness is controlled by precise adjustment of the paste viscosity and solid content. To provide an adequate three-phase boundary, zirconia is added to the platinum to form a cermet (ceramic-metal compound). 

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