Trench process and structure for backside contact solar cells with polysilicon doped regions
View Patent ↗A solar cell includes polysilicon P-type and N-type doped regions on a backside of a substrate, such as a silicon wafer. A trench structure separates the P-type doped region from the N-type doped region. Each of the P-type and N-type doped regions may be formed over a thin dielectric layer. The trench structure may include a textured surface for increased solar radiation collection. Among other advantages, the resulting structure increases efficiency by providing isolation between adjacent P-type and N-type doped regions, thereby preventing recombination in a space charge region where the doped regions would have touched.
1. A solar cell, comprising:
a solar cell substrate having a front side configured to face the sun during normal operation and a backside opposite the front side;
a P-type doped region and an N-type doped region of the solar cell over the solar cell substrate;
a first dielectric between the solar cell substrate and the P-type and N-type doped regions;
a trench separating the P-type doped region and the N-type doped region and at least partially dividing the first dielectric, wherein a surface of the trench is textured; and
a second dielectric formed over the surface of the trench.
2. The solar cell of claim 1 , further comprising a third dielectric formed in the trench over the second dielectric.
3. The solar cell of claim 2 , wherein the third dielectric comprises silicon nitride.
4. The solar cell of claim 1 , wherein the second dielectric comprises thermal oxide.
5. The solar cell of claim 1 , wherein the P-type and N-type doped regions comprise polysilicon.
6. The solar cell of claim 1 , wherein the solar cell substrate comprises silicon.
7. The solar cell of claim 6 , wherein the silicon is N-type.
8. The solar cell of claim 1 , wherein the first dielectric comprises silicon dioxide.
9. The solar cell of claim 1 , wherein the second dielectric comprises silicon dioxide.
10. The solar cell of claim 1 , further comprising interdigitated metal contact fingers electrically coupled to the P-type and N-type doped regions.
11. A semiconductor device, comprising:
a P-type doped region and an N-type doped region formed on a backside of a solar cell substrate, wherein the P-type and N-type doped regions are formed over a first dielectric;
a trench structure separating the P-type doped region and the N-type doped region and at least partially dividing the first dielectric, wherein a surface of the trench structure is textured; and
a second dielectric formed on the surface of the trench structure.
12. The semiconductor device of claim 11 , further comprising a third dielectric formed on the second dielectric in the trench structure.
13. The semiconductor device of claim 12 , further comprising metal contacts electrically coupled to the P-type and N-type doped regions through the third dielectric.
14. The semiconductor device of claim 11 , wherein the solar cell substrate comprises silicon.
15. The semiconductor device of claim 14 , wherein the silicon is N-type.
16. The semiconductor device of claim 11 , wherein the P-type doped region and the N-type doped region comprise polysilicon.
17. A method of fabricating a solar cell, the method comprising:
forming a first dielectric on a silicon substrate;
forming a P-type doped region and an N-type doped region over the first dielectric;
forming a trench separating the P-type doped region from the N-type doped region and at least partially separating the first dielectric;
texturing a surface of the trench; and
forming a second dielectric over the surface of the trench.
18. The method of claim 17 , further comprising:
forming a third dielectric over the second dielectric in the trench.
19. The method of claim 17 , wherein said forming the trench includes laser trenching to separate the P-type doped region from the N-type doped region.
20. The method of claim 17 , wherein the second dielectric comprises thermal oxide.