Fabrication of through-silicon vias on silicon wafers
A through-silicon via fabrication method comprises forming a substrate by bonding the front surface of a silicon plate to a carrier using an adhesive layer therebetween to expose the back surface of the silicon plate. A silicon nitride passivation layer is deposited on the exposed back surface of the silicon plate of the substrate. A plurality of through holes are etched in the silicon plate, the through holes comprising sidewalls and bottom walls. A metallic conductor is deposited in the through holes to form a plurality of through-silicon vias.
1. A through-silicon via fabrication method comprising:
(a) forming a silicon plate having a front surface, one or more features therein, and a back surface;
(b) providing a carrier for supporting the silicon plate;
(c) forming a substrate by bonding the front surface of the silicon plate to the carrier using an adhesive layer therebetween to expose the back surface of the silicon plate;
(d) depositing a silicon nitride passivation layer on the exposed back surface of the silicon plate of the substrate;
(e) etching a plurality of through holes in the silicon plate, the through holes comprising sidewalls and a bottom wall;
(f) depositing in each of the through holes:
(i) an oxide liner on the sidewalls and bottom wall of the through holes;
(ii) a sealing layer over the oxide liner, the sealing layer comprising silicon nitride; and
(iii) a metallic conductor over the sealing layer to form a plurality of through-silicon vias;
(g) after (f), chemical mechanical polishing the back surface of the silicon plate to expose the to portions of the metallic conductor deposited into the through holes of the silicon plate;
(h) removing a native oxide film formed on the exposed portions of the metallic conductor in the through holes by (1) maintaining the substrate at a first temperature of from about 100° C. to about 220° C. in a process zone comprising a pair of process electrodes, (2) introducing into the process zone, a reducing gas comprising ammonia or hydrogen, and (3) applying a first power to the process electrodes; and
(i) after (h), performing a silane soaking step comprising (1) maintaining the substrate at a second temperature of from about 100° C. to about 220° C. in the process zone comprising the pair of process electrodes, (2) introducing into the process zone, a soaking gas comprising silane, and (3) applying a second power to the process electrodes.
2. A method according to claim 1 wherein (d) comprises depositing the silicon nitride passivation layer by:
(i) placing the substrate comprising the silicon plate in a process zone comprising process electrodes and a gas distributor;
(ii) introducing into the process zone, a deposition gas comprising a silicon-containing gas and a nitrogen-containing gas; and
(iii) energizing the deposition gas to form a plasma to deposit the silicon nitride passivation layer.
3. A method according to claim 2 wherein the silicon-containing gas comprises silane and the nitrogen-containing gas comprises ammonia.
4. A method according to claim 3 wherein the deposition gas further comprises a diluent gas comprising nitrogen (N 2 ), helium (He), or argon (Ar).
5. A method according to claim 3 wherein the deposition gas comprises silane at a flow rate of from about 50 to about 1000 sccm; ammonia at a flow rate of from about 100 sccm to about 1000 sccm; and nitrogen at a flow rate of from about 500 to about 25,000 sccm.
6. A method according to claim 2 wherein the deposition gas is maintained at a pressure of from about 2 Torr to about 5.5 Torr.
7. A method according to claim 2 wherein the substrate is maintained at a temperature of from about 100° C. to about 220° C.
8. A method according to claim 2 comprising energizing the deposition gas by applying power at a primary frequency to the process electrodes about the process zone at a power level of from about 100 Watts to about 1600 Watts.
9. A method according to claim 2 wherein the deposition gas further comprises an oxygen-containing gas to dope oxygen into the deposited silicon nitride passivation layer.
10. A method according to claim 9 wherein the oxygen-containing gas comprises nitrous oxide or carbon dioxide.
11. A method according to claim 9 wherein the oxygen-containing gas is provided at a flow rate of from about 500 sccm to about 10,000 sccm.
12. A method according to claim 1 wherein (e) comprises etching the through holes to have an aspect ratio of at least about 10:1.
13. A method according to claim 1 further comprising, after (f), flipping the substrate over.
14. A method according to claim 1 wherein the reducing gas is provided in a volumetric flow rate of from about 100 to about 3000 sccm; and wherein the first power is applied to the process electrodes at a primary frequency of about 13.6 MHz, and at a first power level of from about 150 to about 1200 watts.
15. A method according to claim 1 wherein the reducing gas further comprises nitrogen in a volumetric flow rate of from about 1000 to about 20,000 sccm.
16. A method according to claim 1 comprising applying the first power for a time period of from about 5 to about 40 seconds.
17. A method according to claim 1 wherein the soaking gas comprises silane in a volumetric flow rate of from about 100 to about 1000 sccm; and wherein the second power is applied the process electrodes at a primary frequency of about 13.6 MHz, and at a second power level of from about 150 to about 1200 watts.
18. A method according to claim 1 wherein the soaking gas comprises nitrogen at a flow rate of from about 1000 to about 25,000 sccm.
19. A method according to claim 1 further comprising, after the silane soaking, depositing a protective coating on top of the metallic conductor deposited in the through holes.
20. A method according to claim 19 wherein the protective coating comprises:
(1) a lower layer comprising a silicon nitride layer in a thickness of from about 200 Å to about 1500 Å;
(2) a middle layer composed of silicon oxide in a thickness of from about 0.5 microns to about 3 microns; and
(3) an upper layer comprising silicon nitride in a thickness of from about 0.5 microns to about 3 microns.
21. A method according to claim 19 wherein the protective coating comprises a single layer of silicon oxide or silicon nitride, the single layer provided in a thickness of from about 0.5 microns to about 6 microns.
22. A method according to claim 19 wherein the protective coating comprises a silicon nitride layer and a silicon oxide layer.
23. A method according to claim 1 comprising depositing an oxide liner on the surface of the silicon plate.
24. A method according to claim 1 wherein the sealing layer comprises a density that is at least 50% higher than the density of the oxide liner.
25. A through-silicon via fabrication method comprising:
(a) forming a silicon plate having a front surface, one or more features therein, and a back surface;
(b) providing a carrier for supporting the silicon plate;
(c) forming a substrate by bonding the front surface of the silicon plate to the carrier using an adhesive layer therebetween to expose the back surface of the silicon plate;
(d) depositing a silicon nitride passivation layer on the exposed back surface of the silicon plate of the substrate;
(e) etching a plurality of through holes in the silicon plate, the through holes comprising sidewalls and a bottom wall;
(f) depositing in each of the through holes:
(1) an oxide liner on the sidewalls and bottom wall of the through holes;
(2) a sealing layer over the oxide liner, the sealing layer comprising silicon nitride; and
(3) a metallic conductor over the sealing layer to form a plurality of through-silicon vias;
(g) removing a native oxide film formed on the exposed portions of the metallic conductor in the through holes by (1) maintaining the substrate at a first temperature of from about 100° C. to about 220° C. in a process zone comprising a pair of process electrodes, (2) introducing into the process zone, a reducing gas comprising ammonia or hydrogen, and (3) applying a first power to the process electrodes; and
(h) after (g), performing a silane soaking step comprising (1) maintaining the substrate at a second temperature of from about 100° C. to about 220° C. in the process zone comprising the pair of process electrodes, (2) introducing into the process zone, a soaking gas comprising silane, and (3) applying a second power to the process electrodes.
26. A method according to claim 25 further comprising, after (f), depositing a protective coating on top of the metallic conductor deposited in the through holes.
27. A method according to claim 26 wherein depositing a protective coating comprises depositing:
(1) a lower layer comprising a silicon nitride layer;
(2) a middle layer composed of silicon oxide; and
(3) an upper layer comprising silicon nitride.
28. A through-silicon via fabrication method comprising:
(a) forming a silicon plate having a front surface, one or more features therein, and a back surface;
(b) providing a carrier for supporting the silicon plate;
(c) forming a substrate by bonding the front surface of the silicon plate to the carrier using an adhesive layer therebetween to expose the back surface of the silicon plate;
(d) depositing a silicon nitride passivation layer on the exposed back surface of the silicon plate of the substrate;
(e) etching a plurality of through holes in the silicon plate, the through holes comprising sidewalls and bottom walls;
(f) depositing a metallic conductor in each of the through holes to form a plurality of through-silicon vias;
(g) removing a native oxide film formed on the exposed portions of the metallic conductor in the through holes; and
(h) after (g), soaking the silicon plate in silane; and
(i) after (g), depositing a protective coating on top of the metallic conductor in the through holes, the protective coating comprising:
(1) a lower layer comprising a silicon nitride layer;
(2) a middle layer composed of silicon oxide; and
(3) an upper layer comprising silicon nitride.
29. A method according to claim 28 wherein (d) comprises depositing the silicon nitride passivation layer by:
(i) placing the substrate comprising the silicon plate in a process zone comprising process electrodes and a gas distributor;
(ii) introducing into the process zone, a deposition gas comprising a silicon-containing gas and a nitrogen-containing gas; and
(iii) energizing the deposition gas to form a plasma to deposit the silicon nitride passivation layer.
30. A method according to claim 28 wherein the silicon-containing gas comprises silane and the nitrogen-containing gas comprises ammonia.
31. A method according to claim 30 wherein the deposition gas further comprises a diluent gas comprising nitrogen (N 2 ), helium (He), or argon (Ar).
32. A method according to claim 30 wherein the deposition gas comprises silane at a flow rate of from about 50 to about 1000 sccm; ammonia at a flow rate of from about 100 sccm to about 1000 sccm; and nitrogen at a flow rate of from about 500 to about 25,000 sccm.
33. A method according to claim 29 wherein the substrate is maintained at a temperature of from about 100° C. to about 220° C.
34. A method according to claim 28 wherein (e) comprises etching the through holes to have an aspect ratio of at least about 10:1.