Methods of forming a TSV wafer with improved fracture strength

1. A method comprising:

forming through-substrate vias through a thickness of a substrate and forming semiconductor devices on a front side of the substrate, the thickness of the substrate being measured from the front side of the substrate to a back side of the substrate;

removing a first portion of the substrate to form an opening that extends a predetermined depth into the back side of the substrate and that defines a second portion of the substrate, the second portion remaining in direct contact with and laterally surrounding a vertical sidewall of one of the through-substrate vias;

filling the opening with an alternate material having a lower modulus of elasticity than the substrate such that the alternate material extends laterally between adjacent second portions that laterally surround adjacent through-substrate vias, the alternate material being at least as thermally conductive as the substrate; and

polishing the back side of the substrate so that an exposed surface of the alternate material is essentially co-planar with the back side of the substrate.

2. The method of claim 1 , the filling of the opening with the alternate material being carried out at a process temperature less than or equal to 400° C.

3. The method of claim 1 , the alternate material comprising silicon or germanium and being polycrystalline or amorphous.

4. The method of claim 1 , the second portion extending laterally from the vertical sidewall of the one of the through-substrate vias to the alternate material by a distance greater than or equal to a diameter or a width of the through-substrate via.

5. The method of claim 1 , the removing of the first portion of the substrate to form the opening in the back side of the substrate being performed such that the opening has a depth that is less than or equal to approximately 50% of the thickness of the substrate.

6. The method of claim 1 , further comprising: forming metal contacts on the back side of the substrate in direct contact with the through-substrate vias.

7. A method comprising:

forming an array of through-substrate vias through a thickness of a single crystal silicon substrate and forming semiconductor devices on a front side of the single crystal silicon substrate, the through-substrate vias extending vertically from the front side of the substrate to a back side of the substrate;

removing a first portion of the substrate to form an opening that extends a predetermined depth into the back side of the substrate and that defines a second portion of the substrate, the second portion containing the array and remaining in direct contact with and laterally surrounding vertical sidewalls of the through-substrate vias;

filling the opening with an alternate material to improve a durability of the single crystal silicon substrate and reduce a potential for cracking during fabrication, the alternate material having a lower modulus of elasticity than the single crystal silicon substrate; and

polishing the back side of the substrate so that an exposed surface of the alternate material is essentially co-planar with the back side of the substrate.

8. The method of claim 7 , the filling of the opening with the alternate material being carried out at a process temperature less than or equal to 400° C.

9. The method of claim 7 , the alternate material comprising silicon or germanium and being polycrystalline or amorphous.

10. The method of claim 7 , the alternate material being at least as thermally conductive as the single crystal silicon substrate.

11. The method of claim 7 , the alternate material being physically separated from any of the through-substrate vias by a distance greater than or equal to a diameter or a width of the through-substrate vias.

12. The method of claim 7 , further comprising:

forming metal contacts on the back side of the substrate in direct contact with the through-substrate vias.

13. A method comprising:

forming through-substrate vias through a thickness of a substrate and forming semiconductor devices on a front side of the substrate, the thickness of the substrate being measured from the front side of the substrate to a back side of the substrate;

removing a first portion of the substrate to form an opening that extends a predetermined depth into the back side of the substrate and that defines a second portion of the substrate,

the second portion remaining in direct contact with and laterally surrounding a vertical sidewall of one of the through-substrate vias such that the vertical sidewall is physically separated from the opening by a distance that is at least equal to a width of the through-substrate via, and

the predetermined depth being approximately one-half the thickness of the substrate;

filling the opening with an alternate material having a lower modulus of elasticity than the substrate such that the alternate material extends laterally between adjacent second portions that laterally surround adjacent through-substrate vias, the alternate material being at least as thermally conductive as the substrate; and

polishing the back side of the substrate so that an exposed surface of the alternate material is essentially co-planar with the back side of the substrate.

14. The method of claim 13 , the filling of the opening with the alternate material being carried out at a process temperature less than or equal to 400° C.

15. The method of claim 13 , the alternate material comprising silicon and being polycrystalline or amorphous.

16. The method of claim 13 , the alternate material comprising aerogel.

17. The method of claim 13 , the alternate material comprising a metal.

18. The method of claim 13 , further comprising: forming metal contacts on the back side of the substrate in direct contact with the through-substrate vias and physically separated from the alternate material.