MULTI-JUNCTION SOLAR CELLS WITH RECESSED THROUGH-SUBSTRATE VIAS

1 . A multi junction solar cell device, comprising:

a substrate comprising a front side surface and a backside surface;

an epitaxial region overlying the substrate, wherein the epitaxial region comprises at least one multi junction solar cell;

a plurality of cap regions overlying the epitaxial region;

a metal region overlying each of the plurality of cap regions;

a plurality of recesses within the backside surface of the substrate, wherein each of the plurality of recesses corresponds to one of the metal regions;

a through-substrate via extending through the epitaxial region and the substrate from the metal region to the corresponding recess;

an electrically insulating liner disposed on the sidewalls of each of the through-substrate vias and within the corresponding recess;

a via metal contact corresponding to each of the through-substrate vias;

a backside metal on the backside substrate surface;

an insulating region between each of the via metal contacts and the backside metal;

an electrically conductive metal within each of the through-substrate vias electrically connecting each of the plurality of cap regions with the corresponding via metal contact;

wherein the via metal contacts and the backside metal layer form a substantially planar surface.

2 . The multi junction solar cell device of claim 1 , wherein the electrically insulating liner is characterized by a liner thickness and each of the plurality of recesses is characterized by a recess depth, wherein the liner thickness is about the same as the recess depth.

3 . The multi junction solar cell device of claim 1 , wherein the electrically insulating liner comprises a photosensitive polymer.

4 . The multi junction solar cell device of claim 1 , wherein the electrically insulating liner is electroplated.

5 . The multi junction solar cell device of claim 1 , wherein the substrate is an electrically conductive semiconductor.

6 . The multi junction solar cell device of claim 1 , wherein the substrate is a semi-insulating semiconductor.

7 . The multi junction solar cell device of claim 1 , comprising an optical cover material overlying the plurality of cap regions and the epitaxial region.

8 . The multi junction solar cell device of claim 3 , wherein at least some of the via metal contacts are interconnected.

9 . The multi junction solar cell device of claim 1 , comprising metal gridlines along cap regions that extend from exposed metal of the through-via region on the top side of the device.

10 . The multi junction solar cell device of claim 1 , wherein the via metal contacts and the backside metal are separated by an insulator.

11 . The multi junction solar cell device of claim 1 , comprising a seed layer overlying the insulating liner.

12 . The multi junction solar cell device of claim 1 , comprising a dielectric material overlying at least a portion of the metal regions, the cap regions, the front side substrate surface, or a combination of any of the foregoing.

13 . A method of forming a multi junction solar cell device, comprising:

providing an electrically conductive semiconductor substrate comprising:

a topside surface and a backside surface;

an epitaxial region overlying the substrate, wherein the epitaxial region comprises at least one multi junction solar cell;

a plurality of cap regions overlying the epitaxial region; and

a metal region overlying each of the cap regions;

providing a plurality of recesses in the backside surface of the substrate, wherein each of the plurality of recesses corresponds to one of the plurality of cap regions;

etching through-substrate vias extending from each of the plurality of recesses to the corresponding cap region;

providing an insulating liner within the sidewalls of each of the plurality of through-substrate vias and within each of the recesses;

providing an electrically conductive metal within each of the through-substrate vias; and

providing via metal contacts and a backside metal to provide a metallized backside surface;

wherein the metallized backside surface is substantially planar.

14 . The method of claim 13 , comprising, before providing a plurality of recesses:

bonding a cover glass on the front side surface of the device; and

thinning the substrate.

15 . The method of claim 13 , wherein bonding comprises:

applying a planarization adhesive over the front side surface of the device; and

bonding a cover glass to the adhesive.

16 . The method of claim 13 , comprising, after providing an insulating liner, providing a seed layer on the insulating liner and on the backside surface of the substrate.