Solar cell with silicon oxynitride dielectric layer

1. An emitter region of a solar cell, the emitter region comprising:

a portion of a substrate having a back surface opposite a front surface;

a silicon oxynitride (SiO x N y , 0<x, y) dielectric layer disposed on the back surface of the portion of the substrate, wherein the silicon oxynitride dielectric layer has a non-homogeneous distribution of nitrogen, wherein the silicon oxynitride dielectric layer has a thickness approximately in the range of 10-20 Angstroms, and wherein the silicon oxynitride dielectric layer has a first nitrogen-rich region having a thickness approximately in the range of 4-5 Angstroms, a nitrogen-poor region disposed above the first nitrogen-rich region and having a thickness approximately in the range of 5-6 Angstroms, and a second nitrogen-rich region disposed above the nitrogen-poor region and having a thickness approximately in the range of 4-5 Angstroms; and

a semiconductor layer disposed on the silicon oxynitride dielectric layer.

2. The emitter region of claim 1 , wherein the front surface is a light receiving surface of the solar cell.

3. The emitter region of claim 1 , wherein the semiconductor layer disposed on the silicon oxynitride dielectric layer is a boron-doped silicon layer.

4. The emitter region of claim 3 , wherein the silicon oxynitride dielectric layer comprises boron atoms.

5. The emitter region of claim 1 , wherein the silicon oxynitride dielectric layer is for inhibiting dopant penetration from the semiconductor layer to the portion of the substrate.

6. The emitter region of claim 1 , wherein the silicon oxynitride dielectric layer is a silicon oxynitride tunnel dielectric layer for the emitter region.

7. The emitter region of claim 1 , further comprising:

a metal contact disposed on the semiconductor layer.

8. A solar cell, comprising:

a first emitter region, comprising:

a first portion of a substrate having a back surface opposite a light receiving surface;

a silicon oxynitride (SiO x N y , 0<x, y) dielectric layer disposed on the back surface of the first portion of the substrate, wherein the silicon oxynitride dielectric layer has a non-homogeneous distribution of nitrogen, wherein the silicon oxynitride dielectric layer has a thickness approximately in the range of 10-20 Angstroms, and wherein the silicon oxynitride dielectric layer has a first nitrogen-rich region having a thickness approximately in the range of 4-5 Angstroms, a nitrogen-poor region disposed above the first nitrogen-rich region and having a thickness approximately in the range of 5-6 Angstroms, and a second nitrogen-rich region disposed above the nitrogen-poor region and having a thickness approximately in the range of 4-5 Angstroms; and

a P-type semiconductor layer disposed on the silicon oxynitride dielectric layer; and

a second emitter region, comprising:

a second portion of the substrate;

the silicon oxynitride dielectric layer disposed on the back surface of the second portion of the substrate; and

an N-type semiconductor layer disposed on the silicon oxynitride dielectric layer.

9. The solar cell of claim 8 , wherein the silicon oxynitride dielectric layer is for inhibiting dopant penetration from the P-type semiconductor layer to the first portion of the substrate, and wherein the silicon oxynitride dielectric layer is a silicon oxynitride tunnel dielectric layer for the first and second emitter regions.

10. The solar cell of claim 8 , wherein the first and second emitter regions are separated by a trench formed in the substrate, between the first and second portions of the substrate.

11. An emitter region of a solar cell, the emitter region comprising:

a portion of an N-type bulk silicon substrate having a back surface opposite a light receiving surface;

a silicon oxynitride (SiO x N y , 0<x, y) dielectric layer disposed on the back surface of the portion of the N-type bulk silicon substrate, wherein the silicon oxynitride dielectric layer has a non-homogeneous distribution of nitrogen, wherein the silicon oxynitride dielectric layer has a thickness approximately in the range of 10-20 Angstroms, and wherein the silicon oxynitride dielectric layer has a first nitrogen-rich region having a thickness approximately in the range of 4-5 Angstroms, a nitrogen-poor region disposed above the first nitrogen-rich region and having a thickness approximately in the range of 5-6 Angstroms, and a second nitrogen-rich region disposed above the nitrogen-poor region and having a thickness approximately in the range of 4-5 Angstroms;

a boron-doped polycrystalline silicon layer disposed on the silicon oxynitride dielectric layer; and

a metal contact disposed on the boron-doped polycrystalline silicon layer.

12. The emitter region of claim 11 , wherein the silicon oxynitride dielectric layer is for inhibiting dopant penetration from the boron-doped polycrystalline silicon layer to the portion of the N-type bulk silicon substrate, and wherein the silicon oxynitride dielectric layer is a silicon oxynitride tunnel dielectric layer for the emitter region.