Engineering topics

Mccaldin, J. O.

Publications and source records attributed to Mccaldin, J. O..

5 records

NASA NTRS1976

Solid-state growth of Si to produce planar surfaces

Paralleling the sophisticated control of Si and GaAs growth from fluid media, we demonstrate control of Si growth using a solid growth medium. Faceted dissolution pits were first produced in a Si substrate using standard photolithographic techniques and Al metallization. Si was then evaporated onto the cold structure, depositing as amorphous material. Upon heating, the amorphous Si migrated through the solid Al and grew rapidly in the faceted pits, typically refilling them flush with the surrounding substrate. Evidence that the rapid growth occurs only while the amorphous Si is dissolving into the Al is presented.

Boatright, R. L.↗

NASA NTRS1975

Interfacial impurities and the reaction between Si and evaporated Al

As commonly formed, the interface between substrate Si and evaporated Al is laden with impurities. Subsequent heating causes modest dissolution of Si into solid Al, the dissolution morphology being influenced by the interface impurities. In the present experiments, the amount of Si dissolving was considerably enhanced, causing sufficient interface movement to carry most interfaces clear of the original impurities. Under these conditions, the Si/Al interface assumes, during brief heat treatment, a simple shape composed of a few 111 plane-type facets. Such Si/Al interfaces produced in situ should be useful for low-temperature solid-state growth of Si.

Best, J. S.↗

NASA NTRS1975

Interface effects in the dissolution of silicon into thin gold films

The dissolution of crystalline Si and amorphous Si substrates into thin films of evaporated Au was studied with an electron microprobe and scanning electron microscopy. The dissolution pattern was found to be nonuniform along the plane of the surface and dependent on the crystalline orientation of the Si substrate. The dissolution is greatly facilitated when a very thin layer of Pd is evaporated between the Si substrate and the Au film.

Sankur, H.↗

NASA NTRS1974

Atom movements occurring at solid metal-semiconductor interfaces

Solid metal-semiconductor interfaces often undergo chemical reaction at rather low temperatures, in some cases not much above room temperature. After some general discussion of these reactions, more detailed consideration is given to simple noncompound-forming systems, and, in particular, to the Si-Al, Ge-Al, and Si-Au systems. Diffusive transport of Si or Ge in these solid metallizations is very rapid, though the converse process, diffusion of metal in solid Si or Ge, is usually so slow as to be negligible. The interface reaction itself is less well understood but is becoming controllable in intrinsically favorable cases like Ge-Al and in other cases by more sophisticated means.

Mccaldin, J. O.↗

NASA NTRS1973

Solid-phase epitaxial growth of Si mesas from Al metallization.

Using scanning electron microscopy, Si epitaxial growth from solution in solid Al onto crystal Si substrates was studied. Growth in reentrant corners of the substrate was found to be favored over growth onto a flat surface. These preferred locations for growth appear to be the result of a force not present in conventional crystal growth from fluid media, namely, the nonuniform stress field present in solids.

Sankur, H.↗