Through substrate VIAS
View Patent ↗Through substrate vias (TSVs) are provided after substantially all high temperature operations needed to form a device region of a first thickness proximate the front surface of a substrate wafer by: (i) from the front surface, forming comparatively shallow vias of a first aspect ratio containing first conductors extending preferably through the first thickness but not through the initial wafer thickness, (ii) removing material from the rear surface to form a modified wafer of smaller final thickness with a new rear surface, and (iii) forming from the new rear surface, much deeper vias of second aspect ratios beneath the device region with second conductors therein contacting the first conductors, thereby providing front-to-back interconnections without substantially impacting wafer robustness during manufacturing and device region area. Both aspect ratios are desirably about ≦40, usefully ≦10 and preferably ≦5.
1. A method for forming through substrate via (TSV) connections, comprising:
providing a substrate wafer of first thickness, having a front surface and an opposed rear surface, and in which front surface semiconductor devices have already been formed in a device region of a first thickness proximate the front surface;
forming first vias containing first conductors and extending from the front surface into or through the device regions but not through the substrate wafer;
removing material from the rear surface of the substrate wafer to form a thinned substrate wafer of a reduced thickness and having a newly exposed rear surface;
forming a second via extending inward from the newly exposed rear surface to intercept multiple ones of the first conductors while leaving intact the portion of the device region in which the first vias are formed located between the front surface of the substrate wafer and the bottom of the second via;
depositing a conductive lining in the second via making electrical contact with the first conductors, wherein a cavity remains in the second via after depositing the conductive lining, thereby providing electrical or thermal continuity or both from the front surface to the newly exposed rear surface; and
filling the cavity with a dielectric material.
2. The method of claim 1 , further comprising providing electrical interconnections between one or more contacts in the device region and one or more of the first conductors in the first vias thereby electrically coupling at least one of the contacts to the conductive lining of the second via.
3. The method of claim 1 , wherein the first vias have a first width and a first depth and the second via has a second width and a second depth, such that the second depth is larger than the first depth and the second width is larger than the first width.
4. The method of claim 1 , wherein the first vias and the second via both have aspect ratios in the range of about 1 to 40.
5. The method of claim 1 , wherein the first depth is larger than the thickness of the device region.
6. The method of claim 1 , wherein the first depth is less than or equal about 50 percent of the reduced thickness.
7. The method of claim 1 , wherein the reduced thickness is about 5 to 50 percent of the first thickness.
8. The method of claim 7 , wherein the first depth is about 1 to 30 micrometers.
9. The method of claim 8 , wherein the first width is about 0.1 to 10 micrometers.
10. An electronic device, comprising:
a substrate having a front surface and rear surface, with a device region of a first thickness proximate the front surface;
multiple first via cavities with first conductors therein, extending to a first depth from the front surface and into the device region; and
a second via cavity with a second conductor therein, extending to intersect the multiple first via cavities at a second depth from the rear surface, wherein the second depth is greater than the first depth and has a foot-print overlapping the multiple first via cavities, wherein the first and second conductors are electrically coupled to form at least one electrically-conductive path extending across the device region, the second conductor partially fills the second via cavity, and a dielectric material fills a remainder of the second via cavity.
11. The device of claim 10 , wherein the first depth exceeds the first thickness.
12. The device of claim 10 , wherein the first via cavities and the second via cavity have dielectric liners.
13. A method for forming through substrate via (TSV) connections, comprising:
providing a substrate wafer having a front surface and an opposed rear surface, and in which front surface semiconductor devices have already been formed in a device region proximate the front surface;
forming first vias containing first conductors and extending from the front surface into or through the device regions but not through the substrate wafer;
forming a second via extending inward from the rear surface to intercept multiple ones of the first conductors while leaving intact the portion of the device region in which the first vias are formed located between the front surface of the substrate wafer and the bottom of the second via; and
depositing a second conductor in the second via making electrical contact with the first conductors, thereby providing electrical or thermal continuity or both from the front surface to the rear surface.
14. The method of claim 13 , wherein a cavity remains in the second via after depositing the second conductor, and wherein the method further comprises:
filling the cavity with a dielectric material.
15. The method of claim 13 , wherein forming the first vias comprises:
forming a dielectric liner on sidewalls of the first vias; and filling the first vias with the first conductors.
16. The method of claim 13 , further comprising: forming a dielectric liner on sidewalls of the second via prior to depositing the second conductor in the second via.
17. The method of claim 13 , further comprising the step, performed after forming the first vias and before forming the second via, of:
removing material from the rear surface of the substrate wafer to thin the substrate wafer.