Zinc oxide film method and structure for CIGS cell
View Patent ↗A method for fabricating a thin film photovoltaic device. The method includes providing a substrate comprising an absorber layer and an overlying window layer. The substrate is loaded into a chamber and subjected to a vacuum environment. The vacuum environment is at a pressure ranging from 0.1 Torr to about 0.02 Torr. In a specific embodiment, a mixture of reactant species derived from diethylzinc species, water species and a carrier gas is introduced into the chamber. The method further introduces a diborane species using a selected flow rate into the mixture of reactant species. A zinc oxide film is formed overlying the window layer to define a transparent conductive oxide using the selected flow rate to provide a resistivity of about 2.5 milliohm-cm and less and an average grain size of about 3000 to 5000 Angstroms.
1. A method of forming a zinc oxide film for a photovoltaic device, the method comprising:
providing a substrate in a deposition chamber, wherein the substrate comprises an absorber layer and an overlying window layer; and
flowing a zinc-containing precursor, an oxygen-containing precursor, and a boron-containing precursor together into the deposition chamber to form a zinc oxide film over the window layer.
2. The method of claim 1 , wherein the zinc-containing precursor is diethylzinc vapor.
3. The method of claim 1 , wherein the oxygen-containing precursor is water vapor.
4. The method of claim 1 , wherein the oxygen-containing precursor to zinc-containing precursor ratio is greater than about 1 to about 4.
5. The method of claim 1 , wherein the oxygen-containing precursor to zinc-containing precursor ratio is about 1.
6. The method of claim 1 , wherein the boron-containing precursor to zinc-containing precursor ratio ranges from about zero to about five percent.
7. The method of claim 1 , wherein the boron-containing precursor to zinc-containing precursor ratio is one percent.
8. The method of claim 1 , wherein the substrate is maintained at a temperature of about 130 Degrees Celsius to about 190 Degrees Celsius.
9. The method of claim 1 , wherein the substrate is maintained at a temperature greater than about 200 Degrees Celsius.
10. The method of claim 1 , wherein the zinc oxide film has a transmission rate of 80 percent and greater for electromagnetic radiation having a wavelength of about 800 nanometers to about 1200 nanometers.
11. The method of claim 1 , wherein the flowing the precursors increases a pressure of the deposition chamber to about 0.5 to about 1 Torr.
12. A method for forming a thin film photovoltaic device, the method comprising:
providing a substrate having a first electrode layer, an absorber material overlying the first electrode layer, and a window layer overlying the absorber layer; and
forming a zinc oxide layer characterized by grain size ranging from about 3000 Å to about 5000 Å overlying the window layer using at least two precursor gases including a zinc-containing precursor and an boron-containing precursor flowed together, as well as a carrier gas comprising a nitrogen species.
13. The method of claim 12 , further comprising an oxygen-containing precursor, wherein the oxygen-containing precursor is derived from water vapor.
14. The method of claim 12 , wherein the zinc-containing precursor is derived from diethylzinc.
15. The method of claim 12 , wherein the zinc oxide layer is characterized by an optical transmission rate of 99% and greater.
16. The method of claim 12 , wherein the substrate is maintained at a temperature of about 130 Degrees Celsius to about 190 Degrees Celsius.
17. The method of claim 12 , wherein the substrate is maintained at a temperature greater than about 200 Degrees Celsius.
18. The method of claim 12 , wherein the boron-containing precursor to zinc-containing precursor ratio ranges from about zero to about five percent.