Process and hardware for deposition of complex thin-film alloys over large areas
Systems and methods for depositing complex thin-film alloys on substrates are provided. In particular, systems and methods for the deposition of thin-film Cd 1-x M x Te ternary alloys on substrates using a stacked-source sublimation system are provided, where M is a metal such as Mg, Zn, Mn, and Cu.
1. A stacked-source sublimation system for the deposition of a complex thin-film alloy on a substrate, the system comprising:
a first crucible containing a first source material, wherein the first crucible is operatively connected to a first heating element and defines a first heated pocket opening upward at a pocket opening;
a second crucible containing a second source material, wherein the second crucible is operatively connected to a second heating element and defines a second heated pocket opening upward into a manifold comprising a plurality of conduits, and wherein the plurality of conduits connects the second heated pocket to the first heated pocket; and
the substrate operatively connected to a third heating element situated vertically above the pocket opening;
wherein the plurality of conduits is distributed uniformly over a bottom wall of the first heated pocket and each of the plurality of conduits extends vertically upward to connect the second heated pocket to the first heated pocket through the bottom wall.
2. The system of claim 1 , wherein the second crucible is situated vertically below the first crucible.
3. The system of claim 1 , wherein:
the first heating element maintains the first heated pocket at a first temperature ranging from about 100° C. to about 1000° C., wherein the first temperature is above the sublimation temperature of the first source material;
the second heating element maintains the second heated pocket at a second temperature ranging from about 100° C. to about 1000° C.,
wherein the second temperature is above the sublimation temperature of the second source material; and
the third heating element maintains the substrate at a third temperature ranging from about 100° C. to about 1000° C., wherein the third temperature is less than the first temperature.
4. The system of claim 3 , wherein:
the first source material is a compound chosen from telluride compounds, sulfide compounds, chloride compounds, and selenide compounds; and
the second source material is a metal or a compound chosen from telluride compounds, sulfide compounds, chloride compounds, and selenide compounds.
5. The system of claim 4 , wherein:
the metal is chosen from Mg, Zn, Mn, Cu, Hg, Bi, Pb, and Cd;
the telluride compounds are chosen from CdTe;
the sulfide compounds are chosen from CdS; and
the chloride compounds are chosen from CdCl.sub.2, CuCl.sub.2, and MgCl.sub.2.
6. The system of claim 5 , wherein:
the first source material consists of CdTe and the second source material consists of Mg;
the first temperature ranges from about 540° C. to about 620° C.;
the second temperature ranges from about 350° C. to about 520° C.; and
the third temperature ranges from about 300° C. to about 550° C.
7. The system of claim 3 , wherein a first flux of vaporized first source material from the first heated pocket is controlled by manipulating the first temperature of the first heated pocket.
8. The system of claim 3 , wherein a second flux of vaporized second source material from the plurality of conduits is controlled by manipulating the second temperature of the second heated pocket.
9. The system of claim 8 , wherein:
the second flux is controlled by a flux control element operatively connected to the manifold; and
the flux control element is chosen from:
an adjustable shutter plate situated across each conduit cross section of the plurality of conduits, wherein the shutter plate occludes the plurality of conduits when adjusted to a closed shutter position and the shutter plate opens the plurality of conduits when adjusted to an open shutter position; and
a plurality of adjustable valves operatively connected to the plurality of conduits of the manifold, wherein the plurality of valves occludes the plurality of conduits when adjusted to a closed valve position and the plurality of valves opens the plurality of conduits when adjusted to an open valve position.
10. The system of claim 1 , wherein the substrate is situated above the pocket opening at a vertical separation distance of at least 1 μm.
11. The system of claim 1 , wherein the system is situated within a vacuum device to maintain the system within an operational atmosphere at a pressure ranging from about 0.1 mTorr to about 100 mTorr.