MICROFABRICATED INDUCTORS WITH THROUGH-WAFER VIAS
The present invention relates to microfabricated inductors with through-wafer vias. In one embodiment, the present invention is an inductor including a first wafer, a first plurality of metal fillings located within the first wafer, and a first plurality of metal conductors connecting the first plurality of metal fillings together to form a first spiral with a first plurality of windings. In another embodiment, the present invention is a method for producing an inductor including the steps of forming a first plurality of vias in a first substrate, filling the first plurality of vias in the first substrate with a first plurality of metal fillings, forming a first plurality of metal conductors, and connecting pairs of the first plurality of metal fillings together using the first plurality of metal conductors to form a spiral.
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1. Field
The present invention relates to microfabricated inductors with through-wafer vias.
2. Related Art
RF systems often use inductors. However, conventional inductors with an air center require a large amount of physical space and may also have a relatively low Q factor. This can place a limit or hamper the ability of reducing the size of RF systems. Furthermore, the relatively low Q factor can reduce the performance of RF systems at high frequencies.
Thus, there is a need for inductors which occupy a reduced amount of space and possess an improved Q factor.
SUMMARYIn one embodiment, the present invention is an inductor including a first wafer, a first plurality of metal fillings located within the first wafer, and a first plurality of metal conductors connecting the first plurality of metal fillings together to form a first spiral with a first plurality of windings.
In another embodiment, the present invention is an inductor including a first wafer, a first plurality of metal fillings located within the first wafer, a first plurality of metal conductors connecting pairs of the first plurality of metal fillings together to form a first portion of a first spiral. The present invention also includes a second wafer, a second plurality of metal fillings located within the second wafer, and a second plurality of metal conductors connecting pairs of the second plurality of metal fillings together to form a second portion of the first spiral. The first portion of the first spiral and the second portion of the first spiral can be bonded together to form the first spiral.
In yet another embodiment, the present invention is a method for producing an inductor including the steps of forming a first plurality of vias in a first substrate, filling the first plurality of vias in the first substrate with a first plurality of metal fillings, forming a first plurality of metal conductors, and connecting pairs of the first plurality of metal fillings together using the first plurality of metal conductors to form a spiral.
The features, objects, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, wherein:
Methods and systems that implement the embodiments of the various features of the present invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the present invention and not to limit the scope of the present invention. Reference in the specification to “one embodiment” or “an embodiment” is intended to indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least an embodiment of the present invention. The appearances of the phrase “in one embodiment” or “an embodiment” in various places in the specification are not necessarily all referring to the same embodiment. Throughout the drawings, reference numbers are re-used to indicate correspondence between referenced elements.
Inductor 2 includes a plurality of vias 6 which can be filled with metal fillings 8. The metal fillings 8 can be connected by conductors 10. Metal fillings 8 and conductors 10 can form windings and/or loops within substrate 4. The metal fillings 8 can be, for example, copper (Cu), copper alloys, silver (Ag), silver alloys, or any other types of conductive metal. Conductor 10 can also be copper (Cu), copper alloys, silver (Ag), silver alloys, or any other types of conductive metal. In one embodiment, metal fillings 8 and conductor 10 are formed from the same type of conductive metal. In another embodiment, metal fillings 8 and conductor 10 are formed from different types of conductive metal. The conductors 10 can be formed on a surface of the substrate 4.
A current can flow, for example, into metal filling 8a, from metal filling 8a to conductor 10a, from conductor 10a to metal filling 8b, from metal filling 8b to conductor 10b, from conductor 10b to metal filling 8c, and so on such that the metal current traverses the loops formed by metal fillings 8 and conductors 10 within substrate 4.
Since inductor 2 is formed within substrate 4, inductor 2 can utilize less space. Inductor 2 can be 10 times smaller in each of three dimensions, thickness, width, and length when compared with a conventional inductor with an air center. Thus, inductor 2 can be approximately 1,000 times smaller than conventional inductors formed with wires, such as conventional inductors with air centers.
where R is the inductor's internal electrical resistance and ωL is the inductor's capacitive or inductive reactance at resonance.
As seen in
In
In
In
In
In
In
In
In
In both the embodiment depicted in
where R is the inductor's internal electrical resistance and ωL is the inductor's capacitive or inductive reactance at resonance, any decrease in the amount of resistance results in an overall increase in the Q factor.
Furthermore, as shown in
Claims
1. An inductor comprising:
- a first wafer;
- a first plurality of metal fillings located within the first wafer; and
- a first plurality of metal conductors connecting the first plurality of metal fillings together to form a first spiral with a first plurality of windings.
2. The inductor of claim 1 wherein the first wafer includes a first plurality of vias coated with an insulation material, the first plurality of vias containing the first plurality of metal fillings.
3. The inductor of claim 1 wherein the first wafer includes a first plurality of trenches coated with an insulation material, the first plurality of trenches containing the first plurality of metal conductors.
4. The inductor of claim 3 wherein each of the first plurality of trenches have a depth to spacing aspect ratio equal to or greater than 2:1.
5. The inductor of claim 1 wherein the first plurality of metal fillings is rectangular shaped in cross section.
6. The inductor of claim 1 wherein the first plurality of metal fillings is oval shaped in cross section.
7. The inductor of claim 1 further comprising:
- a second plurality of metal fillings located within the first wafer, each of the second plurality of metal fillings connected to one of the first plurality of metal fillings to form a metal fillings group conducting in parallel.
8. The inductor of claim 1 further comprising:
- a second plurality of metal fillings located within the first wafer; and
- a second plurality of metal conductors connecting the second plurality of metal fillings together to form a second spiral including a second plurality of windings, the first spiral connected to the second spiral to form a spiral group conducting in parallel.
9. An inductor comprising:
- a first wafer;
- a first plurality of metal fillings located within the first wafer;
- a first plurality of metal conductors connecting pairs of the first plurality of metal fillings together to form a first portion of a first spiral;
- a second wafer;
- a second plurality of metal fillings located within the second wafer; and
- a second plurality of metal conductors connecting pairs of the second plurality of metal fillings together to form a second portion of the first spiral, the first portion of the first spiral and the second portion of the first spiral bonded together to form the first spiral.
10. The inductor of claim 9 wherein the first plurality of metal fillings are substantially aligned with the second plurality of metal fillings.
11. The inductor of claim 10 wherein the first plurality of metal filings and the second plurality of metal fillings are bonded through a ductile metal bump.
12. The inductor of claim 11 wherein the ductile metal bump is a gold bump.
13. The inductor of claim 9 wherein
- the first wafer includes a first plurality of vias coated with an insulation material, the first plurality of vias containing the first plurality of metal fillings, and
- the second wafer includes a second plurality of vias coated with the insulation material, the second plurality of vias containing the second plurality of metal fillings.
14. The inductor of claim 9 wherein
- the first wafer includes a first plurality of trenches coated with an insulation material, the first plurality of trenches containing the first plurality of metal conductors, and
- the second wafer includes a second plurality of trenches coated with the insulation material, the second plurality of trenches containing the second plurality of metal conductors.
15. The inductor of claim 14 wherein the first plurality of trenches and the second plurality of trenches each have a depth to spacing aspect ratio equal to or greater than 2:1.
16. The inductor of claim 9 wherein the first plurality of metal fillings is rectangular shaped in cross section.
17. The inductor of claim 9 wherein the first plurality of metal fillings is oval shaped in cross section.
18. The inductor of claim 9 further comprising:
- a third plurality of metal fillings located within the first wafer, each of the third plurality of metal fillings connected to one of the first plurality of metal fillings to form a first metal fillings group conducting in parallel; and
- a fourth plurality of metal fillings located within the second wafer, each of the fourth plurality of metal fillings connected to one of the second plurality of metal fillings to form a second metal fillings group conducting in parallel.
19. The inductor of claim 9 further comprising:
- a third plurality of metal fillings located within the first wafer;
- a third plurality of metal conductors connecting pairs of the third plurality of metal fillings together to form a first portion of a second spiral;
- a fourth plurality of metal fillings located within the second wafer; and
- a fourth plurality of metal conductors connecting pairs of the fourth plurality of metal fillings together, to form a second portion of the second spiral, the first portion of the first spiral and the second portion of the second spiral bonded to form the second spiral, wherein the first spiral and the second spiral are connected to form a spiral group conducting in parallel.
20. A method for producing an inductor comprising the steps of:
- forming a first plurality of vias in a first substrate;
- filling the first plurality of vias in the first substrate with a first plurality of metal fillings;
- forming a first plurality of metal conductors; and
- connecting pairs of the first plurality of metal fillings together using the first plurality of metal conductors to form a spiral.
21. The method of claim 20 further comprising the step of:
- forming an insulating layer within the first plurality of vias.
22. The method of claim 20 further comprising the steps of:
- forming a first plurality of trenches within the first substrate;
- forming a first insulating layer within the first plurality of trenches; and
- forming the first plurality of metal conductors on top of the first insulating layer within the first plurality of trenches.
23. The method of claim 22 further comprising the step of:
- increasing a winding density of the spiral by forming each of the first plurality of trenches with a depth to spacing aspect ratio equal to or greater than 2:1.
24. The method of claim 23 further comprising the step of forming the first plurality of trenches with deep reactive ion etching using a time sequenced etch and passivation process.
25. The method of claim 20 further comprising the step of
- plating metal into photoresist molds to form the first plurality of metal conductors.
26. The method of claim 20 wherein the first plurality of metal fillings are formed in a rectangular cross section shape to reduce resistance within the first plurality of metal fillings.
27. The method of claim 20 wherein the first plurality of metal fillings are formed in an oval cross section shape to reduce resistance within the first plurality of metal fillings.
28. The method of claim 20 further comprising the steps of:
- forming a second plurality of vias in a second substrate;
- filling the second plurality of vias in the second substrate with a second plurality of metal fillings;
- forming a second plurality of metal conductors;
- connecting pairs of the second plurality of metal fillings together using the second plurality of metal conductors; and
- connecting the first plurality of metal fillings to the second plurality of metal fillings to form the spiral.
29. The method of claim 28 further comprising the step of bonding the first plurality of metal fillings to the second plurality of metal fillings using gold thermocompression bonding.
30. The method of claim 28 further comprising the step of plating metal into photoresist molds to form the first plurality of metal conductors and the second plurality of metal conductors.
31. The method of claim 28 further comprising the steps of:
- forming a first plurality of trenches within the first substrate;
- forming a first insulating layer within the first plurality of trenches;
- forming the first plurality of metal conductors on top of the first insulating layer within the first plurality of trenches;
- forming a second plurality of trenches within the second substrate;
- forming a second insulating layer within the second plurality of trenches; and
- forming the second plurality of metal conductors on top of the second insulating layer within the second plurality of trenches.
32. The method of claim 31 further comprising the step of
- increasing a winding density of the spiral by forming each of the first plurality of trenches and each of the second plurality of trenches with a depth to spacing aspect ratio equal to or greater than 2:1.
33. The method of claim 32 further comprising the step of forming the first plurality of trenches and the second plurality of trenches with deep reactive ion etching using a time sequenced etch and passivation process.
34. The method of claim 28 wherein the first plurality of metal fillings and the second plurality of metal fillings are formed in a rectangular cross section shape to reduce resistance within the first plurality of metal fillings and the second plurality of metal fillings.
35. The method of claim 28 wherein the first plurality of metal fillings and the second plurality of metal fillings are formed in an oval cross section shape to reduce resistance within the first plurality of metal fillings and the second plurality of metal fillings.
Type: Application
Filed: Mar 5, 2009
Publication Date: Sep 9, 2010
Applicant: TELEDYNE SCIENTIFIC & IMAGING, LLC (Thousand Oaks, CA)
Inventors: Alexandros Papavasiliou (Thousand Oaks, CA), Jeffrey F. DeNatale (Thousand Oaks, CA), Philip A. Stupar (Oxnard, CA), Robert L. Borwick, III (Thousand Oaks, CA)
Application Number: 12/398,942
International Classification: H01F 5/00 (20060101); H01F 7/06 (20060101);