Seed layer

Chemical Inhomogenities or Compositional Separation. Compositional separation at the grain boundaries influences the magnetic interactions of the individual grains. Deposition parameters such as temperature, substrate material, and the use of a seed layer play an important role. 

Then a very thin barrier layer and a copper seed layer are formed (Figs. 21 (b) and 21 (c)>). In order to conduct the electric current, good conductive material, e.g., copper, will be coated on the surface of the copper seed layer which forms a rough surface as shown in Fig. 21(d). Since multilayer s introduction into IC production, the surface coated with copper must be very smooth, clean, and bare of dielectric stacks... 

Hoffmann, M. Hofer, C. Schneller, T. Bottger, U. Waser, R. 2002. Preparation and aging behavior of chemical-solution-deposited (Pb(Mg1/3Nb2/3)03)i x-(PbTi03)x thin films without seeding layers. J. Am. Ceram. Soc. 85 1867-1869. 

A SILAR-grown ZnO thin film has also been used as a seed layer for CBD-grown nanostructures.28 The seed layer was grown from an ammine-com-... 

Figure 14.12. SEM images of the ZnO materials formed under various conditions (a, b) at a zinc nitrate/HMTA concentration of 0.005 M (c, d) at a zinc nitrate/HMTA concentration of 0.005 M and (e, f) at a zinc nitrate/HMTA concentration of 0.02M. All are on an indium tin oxide seed layer. The seed layer used for (c, d) was different from the seed layer used for (a, b, e, and f). [Reproduced with permission from Ref. 64. Copyright 2006 American Chemical Society.]64... 

Figure 17.11. Process steps for forming Cu interconnects using the single damascene process (dielectric patterning) (a) planarized substrate (b) dielectric deposition (c) dielectric RIE through photoresist mask (d) etched insulator (e) deposition of diffusion barrier (Ta) and Cu seed layer (/) electrodeposition of Cu into a via (vertical interconnection) ( ) CMP of Cu excess Qi) patterning and deposition of Cu line (wire).

The selective Cu deposition process was suggested by Ting and Paunovic (13) as an alternative means of fabricating multilevel Cu interconnections (Fig. 19.4). The first step in this through-mask deposition process (14) is the deposition of a Cu seed layer on a Si wafer, and then a resist mask is deposited and patterned to expose the underlying seed layers in vias and trenches. In the next step, Cu is deposited to fill the pattern. After the Cu deposition mask is removed, the surrounding seed layer is etched and dielectric is deposited. Electroless Cu deposition has been suggested for the blanket and selective deposition processes (15). 

Figure 19.4. Through-mask deposition process (a) Si substrate (b) Cu seed layer deposition (c) photoresist deposition and patterning (d) through-mask electroless deposition of Cu (e) stripping of photoresist and etching of Cu seed layer outside line (f) dielectric deposition.

It is seen from the discussion above that Cu is electrodeposited in vias and trenches on a bilayer a barrier metaVCu seed layer. When the barrier layer is composed of two layers (e.g., TiN/Ti), Cu is electrodeposited as a trilayer a barrier bilayer/Cu seed layer. This type of underlayer for electrodeposition of Cu raises a series of interesting theoretical and practical questions of considerable significance regarding the reliability of interconnects on chips. In Section 19.1 we have noted that interconnect reliability depends on the microstructural attributes of electrodeposited Cu (for Cu-based interconnects). These microstractural attributes, such as grain size, grain size distribution, and texture, determine the mechanical and physical properties of the thin films. Thus, one basic question in the foregoing series of questions is the problem of the influence of the underlayer barrier metal on the microstructure of the Cu seed layer. The second question is the influence of the microstructure of the Cu seed layer on the structure... 

The first apparent report in the open literature of CD PbSe for photoconductive detectors was in 1949 [53], The PbSe was deposited from a solution of PbAci and selenourea onto a predeposited (from PbAci and thiourea) layer of PbS. The PbS layer acted as a seed layer, presumably to obtain faster deposition (it was noted that the PbSe deposition was much slower than that of PbS). The photoconductivity of this film exhibited a broad maximum between 3 and 4 p,m, giving a reasonable response out to beyond 4.5 p,m (PbS drops off at 3 iJim). 

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