Film thickness uniformity

The film thickness uniformity and film composition depend, in part, on the molecular or atomic flux variation across a substrate. This flux variation is a function of the directionality of the evaporation source (i.e., the molecular-beam distribution) and the orientation of the substrate relative to the source (7). In this section, the fundamental equations that describe the distribution of the incident flux will be introduced, along with the solution of these equations for the evaporation of group II-VI compound-semiconductor materials. 

Chemical vapor deposition (CVD) of thin solid films from gaseous reactants is reviewed. General process considerations such as film thickness, uniformity, and structure are discussed, along with chemical vapor deposition reactor systems. Fundamental issues related to nucleation, thermodynamics, gas-phase chemistry, and surface chemistry are reviewed. Transport phenomena in low-pressure and atmospheric-pressure chemical vapor deposition systems are described and compared with those in other chemically reacting systems. Finally, modeling approaches to the different types of chemical vapor deposition reactors are outlined and illustrated with examples. 

In practice, the recirculation cells are often eliminated by increasing the inlet flow rate, a procedure that also improves film thickness uniformity. However, because of nonlinear interactions among buoyancy, viscosity, and inertia terms, the transitions between the flow patterns may be abrupt, and multiple stable-flow fields may exist for the same parameter values (24,195,... 

Of importance to the mechanical design of the calendering system and to the prediction of the film thickness uniformity is the force separating the two rolls, F. This is computed by integrating the pressure over the area of interest on the surface of the roll... 

The only disadvantage of this instrument is the requirement that the index of refraction be known. Particularly for plasma-enhanced films, the index of refraction can vary considerably, depending on deposition conditions. However, for a production process where the index of refraction is well known, and the primary issue is film thickness uniformity, the Nano Spec can provide information very quickly. 

Aluminum, copper, titanium Sputtering targets Rolling, forging Atom emission trajectory, sputtered film thickness uniformity (higher uniformity leads to higher reliability in electronic devices)... 

It plays the same role as the effectiveness factor in heterogeneous catalysis and is a measure of the film thickness uniformity. It represents the ratio of the total reaction rate on each pair of wafers to that we would obtain if the concentration in the cell formed by the two wafers were equal to the bulk concentration everywhere. Thus, if the surface reaction is the rate controlling step, n = 1, whereas if the diffusion between the wafers controls, n < 1. In the limit of strong diffusion resistance the deposition is confined to a narrow outer band of the wafers and a strongly nonuniform film results. 

Thin solid films of polymeric materials used in various microelectronic applications are usually commercially produced the spin coating deposition (SCD) process. This paper reports on a comprehensive theoretical study of the fundamental physical mechanisms of polymer thin film formation onto substrates by the SCD process. A mathematical model was used to predict the film thickness and film thickness uniformity as well as the effects of rheological properties, solvent evaporation, substrate surface topography and planarization phenomena. A theoretical expression is shown to provide a universal dimensionless correlation of dry film thickness data in terms of initial viscosity, angular speed, initial volume dispensed, time and two solvent evaporation parameters. 

To properly understand CMP film thickness control, the CMP engineer should understand the sources of thickness variation and how they impact the total film thickness uniformity. Nonuniformity can be grouped in two categories—random variation and systematic variation. Examples of random variation include wafer-to-wafer (WTW), run-to-run (RTR), and some elements of within-wafer (WIW) variations. Elements of random variation add to the total thickness variation by their root mean square [19]... 

Fj, is negligible for bubbles of diameter smaller than 300 jam. Then the forces due to x and 11 counterbalance each other. Hence, at equilibrium the role of the repulsive disjoining pressure is to keep the film thickness uniform, whereas the role of the attractive transversal tension is to keep the bubble (droplet) attached to the surface. In other words, the particle sticks to the surface at its contact line where the long-range attraction prevails (see Figure 5.13), whereas the repulsion predominates inside the film, where Ft = > 0. Note that this conclusion is valid not only for... 

A considerable difference in composition between the evaporated and deposited materials. Therefore, many compounds and alloy compositions, due to stoichiometry problem, can only be deposited with difficulty. The same problems take place for materials that have high melting temperature and low saturated vapor pressure Line-of-sight trajectories and hmited-area sources result in poor film-thickness uniformity and in poor surface coverage on complex surfaces Possible contamination from the evaporator The need to periodically load the evaporator... 

Luna-Moreno D, Monzon-Hemandez D (2007) Effect of the Pd-Au thin film thickness uniformity on the performance of an optical fiber hydrogen sensor. Rev Appl Surf Sci 253 8615-8619 Luna-Moreno D, Monzon-Hemandez D, VUlatoro J, Badenes G (2007) Optical fiber hydrogen sensor based on core diameter mismatch and annealed Pd-Au thin films. Sens Actuators B 125 66-71 Lundstrom 1, Shivaraman MS, Svensson C, Lundkvist L (1975) A hydrogen-sensitive MOS field-effect transistor. J Appl Phys Lett 26 55-57... 

For polycrystalline films, the film grain structure resulting from sputter deposition typically has many crystallographic orientations without preferred texture. However, evaporative deposition leads to highly textured films for which the grain size is typically greater than that of the sputtered films. Sputter deposition offers better control in maintaining stoichiometry and film thickness uniformity than evaporative deposition, and has the flexibility to deposit essentially any crystalline and amorphous materials. These issues are discussed in more detail in Section 1.8. 

An alternative chemical synthesis mefliod to eonventional solution-based CP deposition is the so-called vapour phase polymerization (VPP) teehnique (Mohammadi et al. 1986 Kim et al. 2003 Wintiier-Jensen and West 2004 Winther-Jensen et al. 2005 Fabretto et al. 2008). There is much interest in this method because it provides high eontrol over CP film thickness, uniformity, and density. Typically, the formation of conjugated polymers is carried out directly on the surface of the substrate in a two-step process. First, fire oxidant such as iron tosylate in n-butanol is applied on the substrate using solvent coating processes and then the coated surface is exposed to a reactive CP monomer vapour. PEDOT films have been reported to have with conductivities as high as approximately 3400 S.cm or S cm for a thickness of 60 mn, which is equivalent to commercially available indium tin oxide (ITO) (Fabretto et al. 2012). 

The film-thickness uniformity has been more difflcult to optimize when UNCD films are grown using MPCVD systems powered by microwaves of 2.45 GHz. 

However, a new MPCVD system installed in the Center for Nanoscale Materials at Argonne, which features 915 MHz microwave power, has already demonstrated that film-thickness uniformity with < 5% is achievable, which is needed for commercial implementation of the UNCD hermetic coatings. 

Fig. 3 Optimization of UNCD film-thickness uniformity via position on the substrate holder in the MPCVD system...

G.R. Haupt, C.E. Wichersham, Drift in film thickness uniformity arising from sputtering target recrystallization, J. Vac. Sci. Technol. A7 (3) (1990) 2355. 

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