Sputtered then evaporated back metal process for increased throughput
A method is described that includes sputtering multiple layers on a back surface of the photovoltaic structure, the photovoltaic structure being made of at least one group III-V semiconductor material, and evaporating, over the multiple layers, one or more additional layers including a metal layer, the back metal structure being formed by the multiple layers and the additional layers. A photovoltaic device is also described that includes a back metal structure disposed over a back surface of a photovoltaic structure made of a group III-V semiconductor material, the back metal structure including one or more evaporated layers disposed over multiple sputtered layers, the one or more evaporated layers including a metal layer. By allowing evaporation along with sputtering, tool size and costs can be reduced, including minimizing a number of vacuum breaks. Moreover, good yield and reliability, such as reducing dark line defects (DLDs), can also be achieved.
1. A method of forming a back metal structure on a photovoltaic structure, the method comprising:
sputtering multiple layers on a back surface of the photovoltaic structure, the photovoltaic structure being made of at least one group III-V semiconductor material;
evaporating, over the multiple layers, one or more additional layers including a metal layer; and
performing an air break between the sputtering and the evaporating,
wherein the back metal structure is formed by the multiple layers and the one or more additional layers.
2. The method of claim 1 , wherein a deposition rate from the evaporating of the one or more additional layers is greater than a deposition rate from the sputtering of the multiple layers.
3. The method of claim 1 , wherein a duration of the evaporating of the one or more additional layers is shorter than a duration of the sputtering of the multiple layers.
4. The method of claim 1 , wherein the sputtering of the multiple layers includes sputtering a layer closest to the back surface of the photovoltaic structure, the layer being configured to adhere remaining layers of the multiple layers to the back surface of the photovoltaic structure.
5. The method of claim 1 , wherein the sputtering of the multiple layers includes sputtering a layer made of a reflecting material.
6. The method of claim 1 , wherein the sputtering of the multiple layers includes sputtering a layer that is closest to the one or more additional layers, the layer being configured to provide a migration barrier from the metal layer to the photovoltaic structure.
7. The method of claim 6 , wherein the layer from the multiple layers that is closest to the one or more additional layers has a thickness greater than 100 nanometers.
8. The method of claim 1 , wherein the sputtering of the multiple layers is a low-pressure sputtering process.
9. The method of claim 1 , wherein the sputtering of the multiple layers includes sputtering one or more of the multiple layers at a target power of 1 Watt/cm 2 or higher.
10. The method of claim 1 , wherein the sputtering and the evaporating are both performed within a single manufacturing tool in consecutive process operations.
11. The method of claim 1 , wherein the sputtering of the multiple layers includes applying multiple sputtering targets within a single manufacturing tool.
12. The method of claim 1 , wherein:
the sputtering of the multiple layers is concurrently performed on a plurality of photovoltaic structures that include the photovoltaic structure, and
the evaporating of the one or more additional layers over the multiple layers is concurrently performed on the plurality of photovoltaic structures.
13. A method of forming a back metal structure on a photovoltaic structure, the method comprising:
sputtering multiple layers on a back surface of the photovoltaic structure that is made of a group III-V semiconductor material;
disposing one or more evaporated layers including a metal layer and over the multiple sputtered layers; and
forming a back metal structure from the multiple sputtered layers and the one or more evaporated layers,
wherein the multiple sputtered layers include a layer closest to the back surface of the photovoltaic structure, the layer being configured to adhere remaining layers of the multiple sputtered layers to the back surface of the photovoltaic structure.
14. The method of claim 13 , further comprising forming the multiple sputtered layers to include a layer made of a reflecting material.
15. The method of claim 13 , further comprising forming the multiple sputtered layers to include a layer that is closest to the one or more evaporated layers, the layer being configured to provide a migration barrier from the metal layer to the photovoltaic structure.
16. The method of claim 13 , wherein the layer from the multiple sputtered layers that is closest to the one or more evaporated layers has a thickness greater than 100 nanometers.
17. The method of claim 13 , further comprising forming a thickness of the one or more evaporated layers to be greater than a thickness of the multiple sputtered layers.
18. The method of claim 13 , further comprising providing one or more of an encapsulant layer, a glass or plastic layer, or an anti-reflective coating (ARC) on a front side of the photovoltaic structure and at least partially over a front surface of the photovoltaic structure.
19. The method of claim 13 , further comprising providing one or more of a dielectric layer, a glass or plastic layer, or an ARC disposed on a back side of the photovoltaic structure and at least partially over the back surface of the photovoltaic structure.
20. A method of forming a back metal structure on a photovoltaic structure, the method comprising:
sputtering multiple layers on a back surface of the photovoltaic structure, the photovoltaic structure being made of at least one group III-V semiconductor material; and
evaporating, over the multiple layers, one or more additional layers including a metal layer,
wherein the back metal structure is formed by the multiple layers and the one or more additional layers, and
wherein the sputtering of the multiple layers includes sputtering one or more of the multiple layers at a target power of 1 Watt/cm 2 or higher.