Through substrate vias
Through substrate vias (TSVs) are provided after substantially all high temperature operations needed to form a device region ( 26 ) of a first thickness ( 27 ) proximate the front surface ( 23 ) of a substrate wafer ( 20, 20′ ) by: (i) from the front surface ( 23 ), forming comparatively shallow vias ( 30, 30′ ) of a first aspect ratio containing first conductors ( 36, 36′ ) extending preferably through the first thickness ( 27 ) but not through the initial wafer ( 20 ) thickness ( 21 ), (ii) removing material ( 22 ″) from the rear surface ( 22 ) to form a modified wafer ( 20′ ) of smaller final thickness ( 21′ ) with a new rear surface ( 22′ ), and (iii) forming from the new rear surface ( 22′ ), much deeper vias ( 40, 40′ ) of second aspect ratios beneath the device region ( 26 ) with second conductors ( 56, 56′ ) therein contacting the first conductors ( 36, 36′ ), 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 providing through substrate vias (TSVs), comprising:
providing a substrate having an initial thickness between an initial back side and a front side thereof;
forming an electronic device region in or on the substrate proximate the front-side and of a first depth;
etching one or more front-side cavities of a first width and a second depth, and having substantially vertical first sidewalls;
filling the front-side cavities with a first conductor so that the first conductor is in direct contact with the first sidewalls;
removing material from the initial back side of the substrate to form a modified substrate having a modified thickness less than the initial thickness and expose a new back side thereof;
etching one or more back-side cavities of a second width and a third depth, and having substantially vertical second sidewalls, thereby exposing one or more of the conductors in one or more of the front-side cavities;
forming dielectric portions on the second sidewalls; and
depositing a second conductor in the one or more back-side cavities electrically coupled to one or more of the first conductors of the front-side cavities.
2. The method of claim 1 , wherein the first depth is less than the second depth.
3. The method of claim 1 , wherein the second depth is less than the third depth.
4. The method of claim 1 , further comprising, providing a dielectric liner in one or more of the first or second vias or both to substantially insulate a conductor therein from the modified substrate.
5. The method of claim 1 , wherein the modified thickness is in the range of about 5 to 50 percent of the initial thickness.
6. The method of claim 5 , wherein the modified thickness is in the range of about 5 to 35 percent of the initial thickness.
7. The method of claim 1 , wherein the front-side cavities have an aspect ratio (AR 30 ) in the range of about 1≦AR 30 ≦40.
8. The method of claim 7 , wherein the front-side cavities have an aspect ratio (AR 30 ) in the range of about 1≦AR 30 ≦10.