Vialess integration for dual thin films—thin film resistor and heater
View Patent ↗A process is described for integrating two closely spaced thin films without deposition of the films through deep vias. The films may be integrated on a wafer and patterned to form a microscale heat-trimmable resistor. A thin-film heating element may be formed proximal to a thin-film resistive element, and heat generated by the thin-film heater can be used to permanently trim a resistance value of the thin-film resistive element. Deposition of the thin films over steep or abrupt topography is minimized by using a process in which the thin films are deposited in a sequence that falls between depositions of thick metal contacts to the thin films.
1. A heat-trimmable thin-film resistor comprising:
a thin-film resistive element configured as a resistor that is electrically connected to a first conductive interconnect formed at a first level located in the direction of a first facing side of the thin-film resistive element;
a thin-film heating element proximal at least a portion of the thin-film resistive element, wherein a first facing side of the thin-film heating element is located proximal a second facing side of the thin-film resistive element; and
a second conductive interconnect formed at a second facing side of the thin-film heating element.
2. The heat-trimmable resistor of claim 1 , wherein the first conductive interconnect is formed prior to the formation of the thin-film resistive element.
3. The heat-trimmable resistor of claim 1 , wherein the second conductive interconnect is formed after formation of the thin-film heating element.
4. The heat-trimmable resistor of claim 3 , wherein a portion of the second conductive interconnect covers substantially all of at least one non-active region of the heat-trimmable resistor.
5. The heat-trimmable resistor of claim 1 , further comprising a thermally conductive layer located between the first facing side of the thin-film heating element and second facing side of the thin-film resistive element.
6. The heat-trimmable resistor of claim 5 , wherein the thermally conductive layer comprises Si 3 N 4 or SiC.
7. The heat-trimmable resistor of claim 5 , wherein the thickness of the thermally conductive layer is between about 50 nm and about 400 nm.
8. The heat-trimmable resistor of claim 1 , wherein the thin-film heating element is patterned to include a plurality of elongate legs.
9. The heat-trimmable resistor of claim 8 , wherein the elongate legs have lengths between about 10 microns and about 300 microns and widths between about 250 nm and about 10 microns and thicknesses between about 5 nm and about 100 nm.
10. The heat-trimmable resistor of claim 1 , wherein the thin-film heating element comprises TaAl.
11. The heat-trimmable resistor of claim 1 , wherein the thin-film resistive element comprises CrSi.
12. The heat-trimmable resistor of claim 11 , wherein the thickness of the thin-film resistive element is between about 3 nm and about 20 nm.
13. The heat-trimmable resistor of claim 1 , further comprising at least one contact pad for an external probe, the at least one contact pad electrically connected to the thin-film resistive element or the thin-film heating element.
14. The heat-trimmable resistor of claim 1 incorporated in an integrated circuit.
15. A process for forming an integrated heat-trimmable resistor comprising:
depositing on a substrate a thin-film heating material proximal a thin-film resistive element, wherein the thin-film resistive element connects to a conductive interconnect formed on a side of the thin-film resistive element that is opposite a side facing the thin-film heating material;
patterning the thin-film heating material to form a thin-film heating element; and
depositing, after the depositing of the thin-film heating material, a first conductive interconnect material to be electrically connected to the thin-film heating element.
16. The process of claim 15 , further comprising:
depositing on the substrate a thin-film resistive material to be electrically connected to a second conductive interconnect;
patterning the thin-film resistive material to form the thin-film resistive element.
17. The process of claim 15 , wherein a portion of the first conductive interconnect covers substantially all of at least one non-active region of the heat-trimmable resistor.
18. The process of claim 15 , further comprising depositing a layer of thermally conductive material prior to deposition of the thin-film heating material.
19. The process of claim 18 , wherein the thermally conductive material is disposed between the thin-film resistive element and the thin-film heating material.
20. The process of claim 18 , wherein the thermally conductive material comprises Si 3 N 4 or SiC.
21. The process of claim 18 , wherein the thermally conductive material has a thickness between about 50 nm and about 400 nm.
22. The process of claim 15 , wherein the thin-film heating material comprises TaAl.
23. The process of claim 15 , wherein the thickness of the thin-film heating material is between about 10 nm and about 100 nm.
24. The process of claim 15 , wherein the patterning of the thin-film heating material comprises forming elongate heating members in the thin-film heating element.
25. The process of claim 15 , further comprising patterning the first conductive interconnect material.
26. The process of claim 25 , wherein the patterned first conductive interconnect material forms at least one heater connector extending across non-active regions of the heater.
27. The process of claim 15 , wherein the first conductive material comprises AlSiCu.
28. A process for forming electrical contacts to two integrated thin-film layers comprising:
depositing on a substrate a first thin-film layer to be electrically connected to an underlying conductive interconnect;
depositing proximal the first thin-film layer a second thin-film layer to be electrically connected to a second conductive interconnect; and
depositing on the substrate subsequent the deposition of the second thin-film layer the second conductive interconnect.
29. The process of claim 28 , wherein the first thin-film layer is separated from the second thin-film layer by a distance between about 50 nm and about 400 nm.
30. The process of claim 28 , further comprising patterning the first thin film layer to form a thin-film resistive element or thin-film heating element.
31. The process of claim 28 , further comprising patterning the second thin film layer to form a thin-film resistive element or thin-film heating element.
32. A dual thin-film device comprising:
a first thin-film element electrically connected to a first conductive interconnect that is located in a direction of a first facing side of the first thin-film element; and
a second thin-film element having a first facing side that is proximal a second facing side of the first thin-film element and is electrically connected to a second conductive interconnect that is located in a direction of a second facing side of the second thin-film element.
33. The dual thin-film device of claim 32 , wherein the first thin-film element comprises a thin-film resistive element.
34. The dual thin-film device of claim 32 , wherein the second thin-film element comprises a thin-film heating element.
35. The dual thin-film device of claim 32 , wherein the first thin-film element is separated from the second thin-film element by a distance between about 50 nm and about 400 nm.