Multilayer electronic structures with vias having different dimensions

1. A multilayer electronic interconnect support structure for coupling to a chip, comprising at least two feature layers extending in an X-Y plane and separated by a via layer comprising a dielectric material comprising a polymer matrix that is sandwiched between two adjacent feature layers, the via layer comprising a plurality of via posts that couple adjacent feature layers in a Z direction perpendicular to the X-Y plane, wherein a first via post in the via layer has different dimensions in the X-Y plane from a second via post in the via layer.

2. The multilayer electronic support structure of claim 1 , wherein one of said first via post and second via post is not substantially cylindrical in shape.

3. The multilayer electronic support structure of claim 1 , wherein the at least one via comprises a seed layer and a metal layer electroplated over the seed layer.

4. The multilayer electronic support structure of claim 3 , wherein the seed layer comprises copper.

5. The multilayer electronic support structure of claim 4 , wherein the seed layer further comprises an underlying adhesive metal layer comprising at least one of the group consisting of titanium, chromium, tantalum and tungsten.

6. The multilayer electronic support structure of claim 3 , wherein the metal layer comprises copper.

7. The multilayer electronic support structure of claim 1 , wherein the smallest dimension in the X-Y plane of a first via post is at least 20% larger than the smallest dimension in the X-Y plane of a second via post in the same via layer.

8. The multilayer electronic support structure of claim 7 , wherein a smallest dimension in the X-Y plane of a third via post is at least 20% larger than the smallest dimension in the X-Y plane of the first via post.

9. The multilayer electronic support structure of claim 1 , wherein at least one via post has a substantially circular cross section.

10. The multilayer electronic support structure of claim 1 , wherein at least one via post has a square cross-section.

11. The multilayer electronic support structure of claim 1 , wherein at least one via post is asymmetrical in the X-Y plane, having a linear shape.

12. The multilayer electronic support structure of claim 1 , wherein at least one via post is asymmetrical in the X-Y plane, extending in a first direction in the X-Y plane, at least three times the extension in a second direction in the X-Y plane that is perpendicular to the first direction.

13. The multilayer electronic support structure of claim 1 , wherein at least one via post has a diameter of less than 50 microns.

14. The multilayer electronic support structure of claim 1 wherein, at least one via post has a diameter of less than 40 microns.

15. The multilayer electronic support structure of claim 1 wherein at least one via post has a diameter of 30 microns or less.

16. The multilayer electronic support structure of claim 1 , wherein a feature layer and the at least one via layer are fabricated by a process comprising the steps of:

(a) obtaining a substrate including an underlying via layer that is treated to expose the copper thereof;

(b) depositing a seed layer over the underlying via layer;

(c) applying a first layer of photoresist over the seed layer;

(d) exposing and developing the first layer of photoresist to form a negative pattern;

(e) depositing a metal layer into the negative pattern;

(f) stripping away the first layer of photoresist leaving the feature layer upstanding;

(g) laying down a second layer of photoresist;

(h) exposing and developing the second layer of photoresist to create a negative pattern including a via layer comprising at least two vias posts of different in-plane dimensions;

(i) depositing a metal layer into the pattern in the second layer of photoresist;

(j) stripping away the second layer of photoresist;

(k) removing the exposed seed layer, and

(l) laminating a dielectric material over the at least two vias posts of different in-plane dimensions.

17. The multilayer electronic support structure of claim 16 , wherein the process further comprises: (m) thinning the dielectric to expose the metal.

18. The multilayer electronic support structure of claim 17 , wherein the process further comprises: (n) depositing a metal seed layer over the thinned surface.

19. The multilayer electronic support structure of claim 1 , wherein the at least one via layer is fabricated by a process including the steps of:

(i) obtaining a substrate including an underlying feature layer that is treated to expose the copper thereof;

(ii) covering the underlying feature layer with a seed layer;

(iii) depositing a metal layer over the seed layer;

(iv) applying a layer of photoresist over the metal layer;

(v) exposing a positive pattern of vias;

(vi) etching away the exposed metal layer and seed layer;

(vii) stripping away the photoresist, leaving at least two components in the via layer having different in plane dimensions, and

(viii) laminating a dielectric material over the at least two components in the via layer.

20. The multilayer electronic interconnect support structure for coupling to a chip of claim 1 , selected from the group consisting of IC substrates and IC interposers.