Patterning of silicon oxide layers using pulsed laser ablation
A method for making an ablated electrically insulating layer on a semiconductor substrate. A first relatively thin layer of at least an undoped glass or undoped oxide is deposited on a surface of a semiconductor substrate having n-type doping. A first relatively thin semiconductor layer having at least one substance chosen from amorphous semiconductor, nanocrystalline semiconductor, microcrystalline semiconductor, or polycrystalline semiconductor is deposited on the relatively thin layer of at least an undoped glass or undoped oxide. At least a layer of borosilicate glass or borosilicate/undoped glass stack is deposited on the relatively thin semiconductor layer. The at least borosilicate glass or borosilicate/undoped glass stack is selectively ablated with a pulsed laser, and the relatively thin semiconductor layer substantially protects the semiconductor substrate from the pulsed laser.
1. A method for making an ablated electrically insulating layer on a semiconductor substrate, said method comprising:
depositing a first relatively thin layer of at least an undoped glass or undoped oxide on a surface of a semiconductor substrate having n-type doping;
depositing a first relatively thin semiconductor layer having at least one substance chosen from amorphous semiconductor, nanocrystalline semiconductor, microcrystalline semiconductor, or polycrystalline semiconductor on said relatively thin layer of at least an undoped glass or undoped oxide;
depositing at least a layer of borosilicate glass or borosilicate/undoped glass stack on said relatively thin semiconductor layer; and
selectively ablating said layer of at least borosilicate glass or borosilicate/undoped glass stack with a pulsed laser, said relatively thin semiconductor layer substantially protecting said semiconductor substrate from said pulsed laser.
2. The method of claim 1 , further comprising a subsequent thermal oxidation process to oxidize said relatively thin semiconductor layer.
3. The method of claim 1 , wherein said semiconductor substrate comprises silicon.
4. The method of claim 1 , wherein said first relatively thin layer of undoped glass or undoped oxide has a thickness approximately in the range of 3 to 100 nanometers.
5. The method of claim 1 , wherein said first relatively thin semiconductor layer has a thickness approximately in the range of 3 to 30 nanometers.
6. The method of claim 1 , wherein said laser has a pulse length of approximately 200 picoseconds or less and a wavelength of approximately 1064 nanometers or less.
7. The method of claim 1 , further comprising process flow steps for making a thin monocrystalline semiconductor solar cell.
8. The method of claim 7 , wherein said thin monocrystalline semiconductor solar cell comprises a thin monocrystalline silicon layer in the thickness range of 10 to 100microns.
9. The method of claim 7 , wherein said thin monocrystalline semiconductor solar cell comprises a back-contact/back-junction solar cell.
10. The method of claim 1 , further comprising process flow steps for making a crystalline semiconductor based photovoltaic solar cell comprising an all-back-contact back-junction solar cell.
11. The method of claim 1 , wherein said ablations are used to make openings to delineate base and emitter regions of an all back contact, back junction solar cell.
12. The method of claim 10 , wherein said crystalline semiconductor based photovoltaic solar cell comprises an epitaxial silicon thin film solar substrate.
13. The method of claim 12 , wherein said epitaxial thin film solar substrate has a thickness in the range of approximately 10 to 100 microns.
14. The method of claim 12 , wherein said epitaxial thin film comprises a substantially planar epitaxial film formed via an epitaxial silicon liftoff process.
15. The method of claim 12 , wherein a front surface of said epitaxial thin film comprises three-dimensional pyramids or prisms formed via a textured template liftoff process.
16. The method of claim 1 , wherein said relatively thin semiconductor layer is a relatively thin silicon layer.
17. The method of claim 1 , wherein said relatively thin semiconductor layer is a relatively thin amorphous semiconductor layer.
18. The method of claim 1 , wherein said relatively thin semiconductor layer is a relatively thin amorphous silicon layer.