Local patterning and metallization of semiconductor structures using a laser beam
Local patterning and metallization of semiconductor structures using a laser beam, e.g., micro-electronic devices, semiconductor substrates and/or solar cells, are described. For example, a method of fabricating a solar cell includes providing a substrate having an intervening layer thereon. The method also includes locating a metal foil over the intervening layer. The method also includes exposing the metal foil to a laser beam, wherein exposing the metal foil to the laser beam forms openings in the intervening layer and forms a plurality of conductive contact structures electrically connected to portions of the substrate exposed by the openings.
1. A method of fabricating a solar cell, the method comprising:
providing a substrate having a continuous intervening layer thereon;
locating a first metal foil over the continuous intervening layer;
exposing the first metal foil to a laser beam to form a conductive path through the continuous intervening layer and to form a conductive contact structure electrically connected to the substrate by the conductive path and to leave remaining unexposed first metal foil, wherein the conductive contact structure includes a metal portion of the first metal foil, the metal portion of the conductive contact structure connected to the remaining unexposed first metal foil by a weakened structure of the first metal foil, the weakened structure of the first metal foil including patterning; subsequent to exposing the first metal foil to the laser beam, separating and removing less than an entirety of the remaining unexposed first metal foil by separating a portion of the remaining unexposed first metal foil from the metal portion along the weakened structure and to leave remaining the weakened structure of the first metal foil including the patterning and to leave portions of the remaining unexposed first metal foil that overhang outermost edges of the substrate; and
bonding a second metal foil to the portions of the remaining unexposed first metal foil, wherein the second metal foil overhangs an outermost edge of the substrate.
2. The method of claim 1 , wherein bonding the second metal foil to the portions of the remaining unexposed first metal foil comprises welding the second metal foil to the portions of the remaining unexposed first metal foil.
3. The method of claim 1 , wherein exposing the first metal foil to the laser beam comprises using a pulse energy in the range of 200-350 microJoules.
4. The method of claim 1 , wherein exposing the first metal foil to the laser beam comprises using a pulse duration in the range of 10 picoseconds-200 nanoseconds.
5. The method of claim 1 , wherein locating the first metal foil over the substrate comprises locating a continuous sheet of the first metal foil over the substrate.
6. The method of claim 1 , wherein the substrate comprises a plurality of alternating N-type and P-type semiconductor regions.
7. The method of claim 1 , further comprising:
forming a plurality of semiconductor regions in or above the substrate.
8. The method of claim 1 , wherein:
the exposing the first metal foil to a laser beam forms the conductive contact structure by diffusing atoms of the first metal foil into the substrate.
9. The method of claim 8 , wherein exposing the first metal foil to the laser beam comprises using a pulse energy in the range of 200-300 microJoules.
10. The method of claim 8 , wherein exposing the first metal foil to the laser beam comprises using a pulse duration in the range of 1 nanosecond to 1 millisecond.
11. The method of claim 8 , wherein:
the continuous intervening layer includes an amorphous semiconductor layer, and
the exposing the first metal foil to the laser beam crystallizes a portion of the amorphous semiconductor layer.
12. The method of claim 11 , wherein exposing the first metal foil to the laser beam comprises using a pulse energy in the range of 200-300 microJoules.
13. The method of claim 10 , wherein exposing the first metal foil to the laser beam comprises using a pulse duration in the range of 10-200 nanoseconds.
14. The method of claim 1 , wherein the patterning includes perforation.