Variable capacitor tuned using laser micromachining

• US 20090002914A1
• Filed: 06/27/2008
• Published: 01/01/2009
• Est. Priority Date: 06/29/2007
• Status: Active Grant

• Current Assignee: Corporation for National Research Initiatives
• Original Assignee: Corporation for National Research Initiatives
• Inventors: Ozgur, Mehmet, Huff, Michael A.
• Granted Patent: US 9,099,248 B2
• Time in Patent Office: Days
• US Class Current: 361/281
• CPC Class Codes: H01G 5/145 with profiled electrodes
• CPC Class Codes: H01L 28/60 Electrodes

Abstract

A variable capacitor device is disclosed in which the capacitive tuning ratio and quality factor are increased to very high levels, and in which the capacitance value of the device is tuned and held to a desired value with a high level of accuracy and precision using a laser micromachining tuning process on suitably designed and fabricated capacitor devices. The tuning of the variable capacitor devices can be performed open-loop or closed-loop, depending on the precision of the eventual capacitor value needed or desired. Furthermore, the tuning to a pre-determined value can be performed before the variable capacitor device is connected to a circuit, or alternatively, the tuning to a desired value can be performed after the variable capacitor device has been connected into a circuit.

Claims

1. A variable capacitor fabricated on substrate, the capacitor comprising:

a first plate fabricated on the substrate,

a dielectric fabricated on the first plate,

a second plate fabricated on the dielectric so that the dielectric is located between the first and second plates,

the second plate including a plurality of subparts that are connected together by a plurality of trimmable connections,

each of the subparts having predefined dimensions so as to provide a tuning range for the capacitor'"'"'s capacitance value, the capacitor'"'"'s capacitance value being tuned to a predetermined value by at least one of the trimmable connections being trimmed from the capacitor.

2. The capacitor of claim 1, wherein each of subparts has predefined dimensions that are comparable each of the other subparts'"'"' dimensions so that the capacitive value of the capacitor will be changed by a single predefined amount for each subsection that is trimmed from the capacitor.

3. The capacitor of claim 1, wherein each of subparts has predefined dimensions that are comparable to at least some of the other subparts'"'"' dimensions and that varying from at least others of the other subparts'"'"' dimensions so that the capacitive value of the capacitor will be changed by a variable amount, depending on the particular subsections trimmed and the number of subsections trimmed from the capacitor.

4. The capacitor of claim 2, wherein each of the subparts changes the capacitive value of the capacitor by a predetermined amount, depending on whether the subpart is trimmed or not trimmed from the second plate, and wherein the number of subparts is such that the capacitor device is tunable over a range of capacitive values with a tuning ratio of at least 10.

5. The capacitor of claim 4, wherein the predetermined amount by which each of the subparts changes the capacitive value of the capacitor and the number of subparts are such that the tuning ratio is at least 100.

6. The capacitor of claim 4, wherein the predetermined amount by which each of the subparts changes the capacitive value of the capacitor and the number of subparts are such that the tuning ratio is at least 10.

7. The capacitor of claim 1, wherein the first and second plates and the dielectric are made from thin film depositions using photolithographic processes, and wherein the second plate has a shape that facilitates trimming of at least the second plate by a laser micromachining tool to tune the capacitance value of the capacitor to a predefined amount.

8. The capacitor of claim 1, wherein the substrate is made from a material that is either a solid bulk substrate material or comprised of a stack of layers of substrate material.

9. The capacitor of claim 8, wherein the substrate is made from an insulating material selected from the group consisting of ceramics, low-temperature co-fired ceramic, alumina, sapphire, glass, polystyrene, polycarbonate, and PMMA plastics and polytetrafluoroethylene.

10. The capacitor of claim 8, wherein the substrate is made from a semi-insulating material selected from the group consisting of GaAs, high-resistivity silicon, polysilicon, SiC, GaN, and diamond-like Carbon.

11. The capacitor of claim 8, wherein the substrate is made from a material selected from the group consisting of polyflon, beryllia, sapphire, aluminum nitride, lithium niobate (LiNbO₃), random and woven fiber reinforced glass substrates, polymers, and laminates.

12. The capacitor of claim 1, wherein the capacitor further comprises first and second electrodes connected, respectively, to the first and second plates.

13. The capacitor of claim 11, wherein the first and second electrodes are made from a highly conductive metal deposited onto the substrate by sputtering or evaporation.

14. The capacitor of claim 13, wherein the first and second electrodes are made from a material selected from the group consisting of gold, copper and silver.

15. The capacitor of claim 1, wherein the dielectric is made from an insulator material selected from the group consisting of silicon dioxide, silicon nitride, hafnium oxide, alumina and zirconium oxide, strontium oxide, titanium oxide , barium titanate, Barium strontium titanium oxide (“

BSTO”

), PZT, dielectric forms of carbon nanotubes.

16. The capacitor of claim 1, wherein the dielectric is made from an insulator material deposited on the substrate using a deposition process selected from the group consisting of chemical vapor deposition and atomic layer deposition.

17. A method of tuning capacitor devices fabricated on a wafer substrate, each capacitor device comprising:

a first plate fabricated on the substrate,

a dielectric fabricated on the first plate,

a second plate fabricated on the dielectric so that the dielectric is located between the first and second plates,

the second plate including a plurality of subparts connected together by a plurality of trimming connections, each of the subparts having predefined dimensions so as to provide a tuning range for the capacitor'"'"'s capacitance value,

the method comprising the steps of;

providing a laser device that emits a laser beam for cutting and thereby trimming subparts of the second plate;

registering the laser beam to the capacitor device on the wafer substrate to be tuned,

moving the laser beam along the capacitor device on an open-loop basis and thereby cutting at least one trimming connection,

whereby the capacitor'"'"'s capacitance value is tuned to a predetermined value by the at least one of the trimming connections being cut by the laser beam.

22. The method of claim 17, wherein each of subparts has predefined dimensions that are comparable to at least some of the other subparts'"'"' dimensions and that varying from at least others of the other subparts'"'"' dimensions so that the capacitive value of the capacitor will be changed by a variable amount, depending on the particular subsections trimmed and the number of subsections trimmed from the capacitor.

18. A method of tuning capacitor devices fabricated on a wafer substrate, each capacitor device comprising:

a first plate fabricated on the substrate,

a dielectric fabricated on the first plate,

a second plate fabricated on the dielectric so that the dielectric is located between the first and second plates,

the second plate including a plurality of subparts connected together by a plurality of trimming connections, each of the subparts having predefined dimensions so as to provide a tuning range for the capacitor'"'"'s capacitance value,

the method comprising the steps of;

providing a laser device that emits a laser beam for cutting and thereby trimming subparts of the second plate,

registering the laser beam to the capacitor device on the wafer substrate to be tuned,

moving the laser beam along the capacitor device and thereby cutting at least one trimming connection,

obtaining a measurement of the capacitance value of the capacitor,

determining, on the basis of the measurement of the capacitance value of the capacitor to either continue moving the laser beam along the capacitor device and thereby cutting at least one additional trimming connection, or stop moving the laser beam along the capacitor device, whereby the capacitor'"'"'s capacitance value is tuned to a predetermined value by the at least one of the trimming connections being cut by the laser beam.

19. The method of claim 18 further comprising the steps of:

providing a computer for controlling the operation of the laser device,

providing an automated wafer probe station with at least one probe for providing a real-time capacitance measurement of the capacitor device while the laser is cutting and thereby trimming the capacitor device, and

providing a metrology tool connected to the at least one probe to provide feedback to the computer to control the movement of the laser over the capacitor device on the wafer.

20. The method of claim 19, wherein the computer includes a software program that interprets the feedback received from the at least one probe through metrology tool, and then uses the feedback to control the position of the laser, and thus the laser beam on the capacitor device to thereby trim the capacitor to the predetermined value of capacitance.

21. The method of claim 18, wherein each of subparts has predefined dimensions that are comparable each of the other subparts'"'"' dimensions so that the capacitive value of the capacitor will be changed by a single predefined amount for each subsection that is trimmed from the capacitor.

23. The method of claim 18, wherein the first and second plates and the dielectric are made from thin film depositions using photolithographic processes.

24. The method of claim 18, wherein the dielectric is made from an insulator material deposited on the substrate using a deposition process selected from the group consisting of chemical vapor deposition and atomic layer deposition.

25. A method of tuning capacitor devices fabricated on a wafer substrate, each capacitor device comprising:

a first plate fabricated on the substrate,

a dielectric fabricated on the first plate,

a second plate fabricated on the dielectric so that the dielectric is located between the first and second plates,

the second plate including a plurality of subparts connected together by a plurality of trimming connections, each of the subparts having predefined dimensions so as to provide a tuning range for the capacitor'"'"'s capacitance value,

the method comprising the steps of;

providing a laser device that emits a laser beam for cutting and thereby trimming subparts of the second plate,

registering the laser beam to the capacitor device on the wafer substrate to be tuned,

moving the laser beam along the capacitor device and thereby cutting at least one trimming connection,

obtaining a measurement of the dimensions of the capacitor and thereby estimating the capacitance value,

determining, on the basis of the measurement of the capacitance value of the capacitor to either continue moving the laser beam along the capacitor device and thereby cutting at least one additional trimming connection, or stop moving the laser beam along the capacitor device, whereby the capacitor'"'"'s dimensions and resultant capacitance value is tuned to a predetermined value by the at least one of the trimming connections being cut by the laser beam.

26. The method of claim 25 further comprising the steps of:

providing a computer for controlling the operation of the laser device,

providing an automated wafer probe station and optical system for providing a real-time dimensional measurement of the capacitor device dimensions while the laser is cutting and thereby trimming the capacitor device, and

providing a metrology tool connected to the at least one probe to provide feedback to the computer to control the movement of the laser over the capacitor device on the wafer.

27. The method of claim 26, wherein the computer includes a software program that interprets the feedback received from the at least one probe through metrology tool, and then uses the feedback to control the position of the laser, and thus the laser beam on the capacitor device to thereby trim the capacitor to the predetermined value of capacitance.

28. The method of claim 25, wherein each of subparts has predefined dimensions that are comparable each of the other subparts'"'"' dimensions so that the capacitive value of the capacitor will be changed by a single predefined amount for each subsection that is trimmed from the capacitor.

29. The method of claim 25, wherein each of subparts has predefined dimensions that are comparable to at least some of the other subparts'"'"' dimensions and that varying from at least others of the other subparts'"'"' dimensions so that the capacitive value of the capacitor will be changed by a variable amount, depending on the particular subsections trimmed and the number of subsections trimmed from the capacitor.

30. The method of claim 25, wherein the first and second plates and the dielectric are made from thin film depositions using photolithographic processes.

31. The method of claim 25, wherein the dielectric is made from an insulator material deposited on the substrate using a deposition process selected from the group consisting of chemical vapor and atomic layer deposition.

32. A method of tuning variable capacitor devices fabricated on a wafer substrate, each capacitor device comprising:

a first plate fabricated on the substrate,

a dielectric fabricated on the first plate,

a second plate fabricated on the dielectric so that the dielectric is located between the first and second plates,

the second plate including a plurality of subparts connected together by a plurality of trimming connections, each of the subparts having predefined dimensions so as to provide a tuning range for the capacitor'"'"'s capacitance value,

wherein the capacitor device has been mounted in an untrimmed state onto a Printed Circuit Board or ceramic substrate and then trimmed using the method comprising the steps of;

providing a laser device that emits a laser beam for cutting and thereby trimming subparts of the second plate,

registering the laser beam to the capacitor device on the wafer substrate to be tuned,

moving the laser beam along the capacitor device and thereby cutting at least one trimming connection,

obtaining a measurement of the capacitance value of the capacitor,

determining, on the basis of the measurement of the capacitance value of the capacitor to either continue moving the laser beam along the capacitor device and thereby cutting at least one additional trimming connection, or stop moving the laser beam along the capacitor device, whereby the capacitor'"'"'s capacitance value is tuned to a predetermined value by the at least one of the trimming connections being cut by the laser beam.

33. The method of claim 32 further comprising the steps of:

providing a computer for controlling the operation of the laser device,

providing an automated wafer probe station with at least one probe for providing a real-time capacitance measurement of the capacitor device dimensions while the laser is cutting and thereby trimming the capacitor device, and

providing a metrology tool connected to the at least one probe to provide feedback to the computer to control the movement of the laser over the capacitor device on the wafer.

34. The method of claim 33, wherein the computer includes a software program that interprets the feedback received from the at least one probe through metrology tool, and then uses the feedback to control the position of the laser, and thus the laser beam on the capacitor device to thereby trim the capacitor to the predetermined value of capacitance.

35. The method of claim 33, wherein each of subparts has predefined dimensions that are comparable each of the other subparts'"'"' dimensions so that the capacitive value of the capacitor will be changed by a single predefined amount for each subsection that is trimmed from the capacitor.

36. The method of claim 33, wherein each of subparts has predefined dimensions that are comparable to at least some of the other subparts'"'"' dimensions and that varying from at least others of the other subparts'"'"' dimensions so that the capacitive value of the capacitor will be changed by a variable amount, depending on the particular subsections trimmed and the number of subsections trimmed from the capacitor.

37. The method of claim 33, wherein the first and second plates and the dielectric are made from thin film depositions using photolithographic processes.

38. The method of claim 33, wherein the dielectric is made from an insulator material deposited on the substrate using a deposition process selected from the group consisting of chemical vapor and atomic layer deposition.