MEMS device trench plating process and apparatus for through hole vias
View Patent ↗A method for forming through hole vias in a substrate uses a partially exposed seed layer to plate the bottom of a blind trench formed in the front side of a substrate. Thereafter, the plating proceeds substantially uniformly from the bottom of the blind hole to the top. To form the through hole, the rear face of the substrate is ground or etched away to remove material up to and including the dead-end wall of the blind hole.
1. A method for forming a via for a MEMS device, comprising:
forming at least one trench with a dead-end wall in a front side of a substrate;
forming a partially exposed seed layer in the trench;
depositing a conductive material in the trench;
coupling the conductive material electrically to the MEMS device; and
removing material from a backside of the substrate to a point at which the dead-end wall of the trench has been removed.
2. The method of claim 1 , wherein forming the partially exposed seed layer comprises depositing an inhibition layer over a portion of a seed layer down to a level within at least about 100 μm of the dead-end wall of the trench.
3. The method of claim 2 , wherein the inhibition layer is at least one of silicon dioxide, alumina, tantalum oxide and chromium oxide.
4. The method of claim 1 , wherein the conductive material is deposited by electroplating.
5. The method of claim 4 , wherein the conductive material is at least one of copper, gold, and nickel.
6. The method of claim 2 , wherein forming the inhibition layer covering a portion of the seed layer down to a level just above the dead-end wall of the blind trench comprises at least one of tilting the substrate with respect to a sputtering target and disposing the sputtering target at an angle with respect to a line normal to a surface of the substrate.
7. The method of claim 6 , wherein tilting the substrate with respect to the target comprises tilting the substrate to produce a deposition angle of between about 45 degrees and 90 degrees with respect to the wafer.
8. The method of claim 6 , wherein forming the inhibition layer covering a portion of the seed layer down to a level just above the dead-end wall of the blind trench further comprises at least one of rotating the tilted substrate and rotating the target about the line normal to the surface of the substrate.
9. The method of claim 8 , wherein the rotating of the tilted substrate results in the deposition of the inhibition layer that ends within about 100 μm or less of the dead-end wall of the blind trench.
10. The method of claim 1 , wherein the partially exposed seed layer includes at least one of chromium, copper, gold, and nickel.
11. A substrate for the formation of a MEMS device, comprising:
at least one opening formed in a substrate;
a partially exposed seed layer in the opening; and
a conductive material plated into the opening, providing an electrical connection to the MEMS device.
12. The substrate of claim 11 , wherein the partially exposed seed layer comprises an inhibition layer covering a portion of the seed layer down to a level within at least about 100 μm or less of an end of the opening.
13. The substrate of claim 12 , wherein the inhibition layer comprises at least one of silicon dioxide, alumina, tantalum oxide and chromium oxide.
14. The substrate of claim 11 , further comprising:
a sacrificial layer deposited on the substrate; and
a device layer secured to the sacrificial layer, from which features of the MEMS device are formed.
15. The substrate of claim 14 , further comprising:
a cap wafer with a relieved area providing clearance for the device, hermetically sealed to at least one of the substrate, sacrificial layer and device layer.
16. The substrate of claim 11 , wherein the conductive material comprises at least one of gold, copper or nickel.
17. The substrate of claim 11 , wherein the partially exposed seed layer comprises at least one of titanium, chromium, copper, gold and nickel.
18. The substrate of claim 11 , wherein the at least one opening has a ratio of depth to width of at least about one-to-one.
19. A configuration for forming a via for a MEMS device, comprising:
means for forming at least one trench with a dead-end wall in a front side of a substrate;
means for forming a seed layer in the trench;
means for depositing a conductive material within the trench;
the MEMS device formed over the substrate;
means for coupling the conductive material electrically to the MEMS device; and
means for removing material from a backside of the substrate to a point at which the dead-end wall of the trench has been removed.