Controlling dopant diffusion in a semiconductor region
View Patent ↗Dopant diffusion into semiconductor material is controlled during fabrication of a semiconductor structure by depositing a nucleation layer over a first layer of the semiconductor structure and depositing a device layer containing the dopant over the nucleation layer. The nucleation layer serves as a diffusion barrier by limiting in depth the diffusion of the dopant into the first layer. The dopant can include arsenic (As).
1. A method for controlling the diffusion of a first dopant into a first region of a semiconductor substrate during the fabrication of a multi-layer semiconductor structure, comprising:
(a) depositing a nucleation layer over and directly in contact with the substrate of the semiconductor structure; and
(b) depositing a second layer containing the first dopant over the nucleation layer, wherein the first dopant includes arsenic (As) and the nucleation layer serves as a diffusion barrier to the arsenic dopant to suppress diffusion of the first dopant into the first region, and
wherein material contained in the nucleation layer serves as a source of a second dopant that forms an n-p junction in the first region.
2. The method as recited in claim 1 , wherein the nucleation layer is a material that has a similar lattice parameter as the first region.
3. The method as recited in claim 1 , wherein the first region comprises germanium (Ge) and the nucleation layer comprises InGaP.
4. The method as recited in claim 1 , wherein the nucleation layer has a thickness equal to 350 angstroms or less.
5. The method as recited in claim 1 , wherein a two-step diffusion profile is formed in the first region that results in a shallow n-p junction in the first region.
6. The method as recited in claim 1 , wherein diffusion of the first dopant into the first region primarily involves solid state diffusion.
7. The method as recited in claim 1 , wherein the nucleation layer, the second layer and the substrate form part of a solar cell.
8. A method for controlling the diffusion of a first dopant into a first region of a semiconductor substrate, comprising:
(a) depositing a nucleation layer on a surface of the substrate, wherein material contained in the nucleation layer serves as a source of a second dopant that diffuses into the first region; and
(b) depositing a second layer containing the first dopant over the nucleation layer, wherein the nucleation layer serves as a diffusion barrier to the first dopant to suppress diffusion of the first dopant into the first region.
9. The method of claim 8 wherein the nucleation layer, the second layer and the substrate form part of a solar cell.
10. The method of claim 8 , wherein a diffusion depth of the first dopant into the first region is greater than a diffusion depth of the second dopant into the first region.
11. The method of claim 8 , wherein diffusion of both the first and second dopant forms a two-step diffusion profile in the first region.
12. The method of claim 8 , wherein diffusion of both the first and second dopant primarily involves solid state diffusion.
13. The method of claim 8 , wherein diffusion of both the first and second dopant occurs during metal organic chemical vapor deposition.
14. The method of claim 8 , wherein depositing a second layer comprises depositing a GaAs buffer layer on a surface of the nucleation layer.
15. The method of claim 14 , wherein depositing a second layer further comprises depositing a dual junction solar cell on the GaAs buffer layer.