Deposition uniformity

CVD reactors can have one of several configurations. Each has particular advantages and disadvantages. Reactors that support wafers horizontally have difficulty controlling the deposition uniformity over all the exposed wafers. Reactors having vertical wafer support produce uniform deposition, but are mechanically complex. Barrel reactors are not suited for extended operation at temperatures greater than 1200°C. 

Some electroplating solutions produce more uniform deposits than others, and the ability of a solution to deposit uniform coatings is measured by its throwing power (see Section 12.1). 

Paints are specially formulated for one of two processes. In the first, anodic electrodeposition, the article to be painted is made the anode in a d.c. circuit. Cathodic electrodeposition is the reverse operation. The process takes place under carefully controlled conditions in a tank. Current passes through the paint causing it to deposit uniformly over the article in a uniform film whose thickness can be accurately controlled. The paint film is insoluble in water and exhibits remarkable adhesion after stoving. Electrodeposition is widely used to apply primers, e.g. by car manufacturers, and one coat finishes. 

Deposit uniformity The uniformity of a deposit is an important factor in its overall corrosion resistance and is a function of geometrical factors and the throwing power of the plating solution. A distinction is made here between macro-throwing power, which refers to distribution over relatively large-scale profiles, and micro-throwing power, which relates to smaller irregularities... 

As lithium does not deposit uniformly for the reason mentioned above, mechanical stress is created in the lithium electrode under the protective film. 

Figure 2.10. Control of deposition uniformity in a tubular reactor (a) susceptor parallel to gas flow, (b) titled susceptor.

Reactor wall thermal boundary conditions can have a strong effect on the gas flow and thus the deposition. Here, for example, we indicate how cooling the reactor walls can enhance deposition uniformity. We consider the results of three simulations comparing the effects of two different wall boundary conditions. Figure 4 shows how the ratio of the computed susceptor heat flux to the onedimensional heat flux varies with the disk radius for the different conditions (the Nusselt number Nu is a dimensionless surface heat flux). In two cases the reactor walls are held at 300 K (0 = 0), and in one case the walls are insulated ( 0/ r —... 

Solution Composition Effect on Solution Stability, Deposition Kinetics, and Deposit Uniformity... 

Although electroless deposition seems to offer greater prospects for deposit thickness and composition uniformity than electrodeposition, the achievement of such uniformity is a challenge. An understanding of catalysis and deposition mechanisms, as in Section 3, is inadequate to describe the operation of a practical electroless solution. Solution factors, such as the presence of stabilizers, dissolved O2 gas, and partially-diffusion-controlled, metal ion reduction reactions, often can strongly influence deposit uniformity. In the field of microelectronics, backend-of-line (BEOL) linewidths are approaching 0.1 pm, which is much less than the diffusion layer thickness for a... 

The growth rate is quite sensitive to the axial temperature profile. An axial temperature profile that increases along the reactor because it improves the deposition uniformity is commonly used in industry. The temperature of each successive zone in the furnace (defined by the furnace elements in Figure E14.5a) can be adjusted by voltage applied to variac heaters. The zone temperatures are assumed constant within each zone, T-,j = 1,..., ntv where ntz is the number of temperature zones to be used,... 

Equations (11.1)-(11.3) respectively express conservation of mass, momentum, and energy. To nondimensionalize these equations, the initial diameter do, the initial centreline velocity Uq, and a characteristic temperature difference To are used as scales. If the heat is deposited uniformly over a unit volume at a constant rate J, for a total time th into the flow. To may be defined as the resultant net temperature change that would result if this heat was deposited To = Jth/ P p ... 

To a good approximation, we believe that all of the supported catalysts behave as Pt or Rh metal surfaces. The loadings are sufficient to deposit uniform... 

From the species profiles, determine the mass flux to the chemically active surface. Plot and discuss the species mass flux to the surface as a function of position along the surface. Based on these profiles, discuss the deposition uniformity on the wafer. How would wafer-rotation affect the result ... 

There are some good chemical-vapor-deposition reactors that deliberately starve the rotating disk. However, the similarity is broken by the recirculation, and the one-dimensional analysis techniques described herein lose their validity. If the chemical reaction on the surface is sufficiently slow, compared to mass transfer through the boundary layer, then the deposition uniformity will not be much affected by the boundary-layer similarity. In these... 

D.I. Fotiadis, A.M. Kremer, DP. McKenna, and K.F. Jensen. Complex Flow Phenomena in Vertical MOCVD Reactors Effects on Deposition Uniformity and Interface Abruptness. J. Cryst. Growth, 85 154—164,1987. 

Nevertheless, these methods all result in a filter that captures the atmospheric particles. The mass loading can be large, the deposit uniform, and the filter reasonably stable under transport to a central analytical laboratory. Numerous papers have treated analysis of such filters, so this information is not repeated. This chapter focuses on the problems of chemical analyses of impactor substrates, for which the problems are more serious and the solutions elusive. 

The utilization of nickel level on catalyst as an age marker is based on previous evidence that nickel deposits uniformly on the circulating catalyst inventory, independent of catalyst activity (1.2). In contrast to the case for nickel, vanadium... 

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