Scanning Ferromagnetic Resonance (FMR) for Wafer-Level Characterization of Magnetic Films and Multilayers

• US 20180267128A1
• Filed: 03/20/2017
• Published: 09/20/2018
• Est. Priority Date: 03/20/2017
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Headway Technologies Incorporated (TDK Corporation)
• Inventors: Guisan, Santiago Serrano, Thomas, Luc, Le, Son, Jan, Guenole
• Granted Patent: US 10,401,464 B2
• Time in Patent Office: Days
• CPC Class Codes: G01N 24/10 by using electron paramagnetic resonance G01N24/12 takes precedence
• CPC Class Codes: G01R 31/318511 Wafer Test
• CPC Class Codes: G01R 33/30 Sample handling arrangements, e.g. sample cells, spinning mechanisms
• CPC Class Codes: G01R 33/345 of waveguide type G01R33/343 takes precedence
• CPC Class Codes: G01R 33/60 using electron paramagnetic resonance G01R33/24, G01R33/62 take precedence
• CPC Class Codes: H01P 5/18 consisting of two coupled guides, e.g. directional couplers
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: H10N 50/85 Magnetic active materials

Abstract

A ferromagnetic resonance (FMR) measurement system is disclosed with a waveguide transmission line (WGTL) connected at both ends to a mounting plate having an opening through which the WGTL is suspended. While the WGTL bottom surface contacts a portion of magnetic film on a whole wafer, a plurality of microwave frequencies is sequentially transmitted through the WGTL. Simultaneously, a magnetic field is applied to the contacted region thereby causing a FMR condition in the magnetic film. After RF output is transmitted through or reflected from the WGTL to a RF detector and converted to a voltage signal, effective anisotropy field, linewidth, damping coefficient, and/or inhomogeneous broadening are determined based on magnetic field intensity, microwave frequency and voltage output. A plurality of measurements is performed by controllably moving the WGTL or wafer and repeating the simultaneous application of microwave frequencies and magnetic field at additional preprogrammed locations on the magnetic film.

Claims

1. A ferromagnetic resonance (FMR) measurement system for a wafer under test (WUT) on which one or a plurality of magnetic films are formed, comprising:

(a) a waveguide transmission line (WGTL) connected to a generator of microwaves;

(b) a magnet that provides a magnetic field which together with a simultaneous application of a microwave frequency is configured to induce a magnetic resonance condition in the one or plurality of magnetic films; and

(c) a system for detecting microwave absorbance by the one or plurality of magnetic films when a magnetic resonance condition is established wherein the WGTL and WUT are configured to move laterally and vertically relative to one another such that the WGTL contacts, or is placed proximate to the WUT at predetermined positions.

2. The FMR measurement system of claim 1 wherein the WGTL and WUT are installed in an electrical probe station.

3. The FMR measurement system of claim 1 wherein the WGTL is moved with respect to the WUT and the one or plurality of magnetic films, which are held stationary.

4. The FMR measurement system of claim 1 wherein the WUT and the one or plurality of magnetic films are moved with respect to the WGTL, which is held stationary.

5. The FMR measurement system of claim 1 wherein the WGTL is placed proximate to the WUT such that the vertical distance between the WGTL and WUT is less than 100 micrometers during a FMR measurement.

6. The FMR measurement system of claim 1 wherein the WGTL is a microstrip.

7. The FMR measurement system of claim 1 wherein the WGTL is a coplanar waveguide or a grounded coplanar waveguide.

8. The FMR measurement system of claim 1 wherein the WGTL is a stripline.

9. The FMR measurement system of claim 1 wherein the WGTL is a coaxial waveguide.

10. A scanning ferromagnetic resonance (FMR) measurement system, comprising:

(a) a controller with a first link to a RF generator, a second link to a power generator that is connected to a magnet, and a third link to one or both of a mounting plate on which a bent waveguide transmission line (WGTL) is mounted, and a wafer chuck configured to hold an overlying whole wafer under test (WUT) having a magnetic film with an exposed upper surface, the mounting plate and/or wafer chuck are programmed to move laterally and vertically in a step and repeat fashion;

(b) the RF generator that is configured to provide a sequence of RF input signals each comprising a different microwave frequency through a RF input cable to the bent WGTL;

(c) the bent WGTL that has a middle tip portion which is configured to contact a predetermined region of the exposed upper surface of the magnetic film during a FMR measurement to sequentially transmit the different microwave frequencies thereto; and

(d) the magnet having a magnetic pole piece aligned above the bent WGTL middle tip portion and providing a magnetic field through a mounting plate opening on the predetermined region of the magnetic film such that a FMR condition is established in the predetermined region thereby causing a unique microwave absorbance for each different microwave frequency (f_R) that results in a RF power loss for each combination of H_R and f_R and is detected from a RF output signal that passes from the WGTL to a RF detector, the RF detector is configured to send a voltage signal as an FMR measurement to the controller such that one or more magnetic properties are determined for the magnetic film.

11. The scanning FMR measurement system of claim 10 wherein the bent WGTL and mounting plate are installed in an electrical probe station.

12. The scanning FMR measurement system of claim 10 further comprised of a first RF connector that connects the RF input cable to the bent WGTL, and a second RF connector that connects the bent WGTL to the RF detector, and wherein the first and second RF connectors do not contact the exposed top surface of the magnetic film or extend beyond a plane of contact between the bent WGTL and the magnetic film.

13. The scanning FMR measurement system of claim 12 comprising a transmission mode for performing the FMR measurement wherein the RF input signal is transmitted through the first RF connector and the RF output signal is transmitted through the second RF connector.

14. The scanning FMR measurement system of claim 12 wherein the first and second RF connectors are end launch RF connectors.

15. The scanning FMR measurement system of claim 10 further comprised of a directional coupler, power divider, or bias tee that receives the RF input signal from the RF generator and then transmits the RF input signal through the RF input cable to the WGTL, the directional coupler, power divider, or bias tee also receives a reflected RF output signal from the WGTL and transmits the reflected RF output signal to the RF detector in a reflectance mode for performing the FMR measurement.

16. The scanning FMR measurement system of claim 10 wherein the bent WGTL has a substantially U-shape.

17. The scanning FMR measurement system of claim 10 wherein the mounting plate and bent WGTL are moved with respect to the WUT and magnetic film, which are held stationary.

18. The scanning FMR measurement system of claim 10 wherein the WUT and magnetic film are moved with respect to the WGTL and mounting plate, which are held stationary.

19. The scanning FMR measurement system of claim 10 wherein the bent WGTL and magnetic film are separated after the FMR measurement by a vertical movement to establish a gap therebetween before a lateral movement is performed to align the bent WGTL over another predetermined region in the magnetic film.

20. The scanning FMR measurement system of claim 10 wherein the FMR condition is established with each of the different microwave frequencies by sweeping the magnetic field from a minimum value to a maximum value.

21. The scanning FMR measurement system of claim 10 wherein the FMR condition is established by holding the magnetic field constant and sweeping with a plurality of different microwave frequencies applied in a sequential order.

22. A scanning ferromagnetic resonance (FMR) measurement system, comprising:

(a) a controller with a first link to a RF generator, a second link to power generator that is connected to a magnet, and a third link to one or both of a mounting plate to which a flat waveguide transmission line (WGTL) is attached, and a wafer chuck configured to hold an overlying whole wafer under test (WUT) having a magnetic film with an exposed upper surface, the mounting plate or wafer chuck are programmed to move laterally and vertically in a step and repeat fashion;

(b) the RF generator configured to provide a sequence of RF input signals each comprising a different microwave frequency through a RF input cable to the flat WGTL;

(c) the flat WGTL that is attached to the mounting plate through a first RF connector that is affixed to a top surface of the WGTL proximate to a first end thereof, and through a second RF connector affixed to a top surface of the WGTL proximate to a second end thereof, the flat WGTL has a bottom surface below a mounting plate opening and is configured to contact a predetermined region on the exposed upper surface of the magnetic film, and to sequentially transmit the plurality of microwave frequencies thereto; and

(d) the magnet having a magnetic pole piece aligned above the flat WGTL and providing a magnetic field through the mounting plate opening on the predetermined region of the magnetic film such that a FMR condition is established in the predetermined region thereby causing a unique microwave absorbance for each frequency (f_R) that results in a RF power loss for each combination of H_R and f_R and is detected from a RF output signal that passes from the WGTL to a RF power diode, the RF power diode is configured to convert the output signal to a voltage signal and to send the voltage signal to the controller such that one or more magnetic properties are determined for the magnetic film.

23. The scanning FMR measurement system of claim 22 wherein the flat WGTL and mounting plate are installed in an electrical probe station.

24. The scanning FMR measurement system of claim 22 wherein the vertical movement of the mounting plate or wafer chuck causes the bottom surface of the flat WGTL to contact the predetermined region of the exposed upper surface of the magnetic film.

25. The scanning FMR measurement system of claim 22 wherein the first and second RF connectors do not contact the exposed top surface of the magnetic film or extend below a plane of contact between the flat WGTL and exposed upper surface of the magnetic film.

26. The scanning FMR measurement system of claim 22 wherein the mounting plate and flat WGTL are moved with respect to the WUT and magnetic film, which are held stationary.

27. The scanning FMR measurement system of claim 22 wherein the WUT and magnetic film are moved with respect to the flat WGTL and mounting plate, which are held stationary.

28. The scanning FMR measurement system of claim 22 wherein the flat WGTL and magnetic film are separated after the FMR measurement by a vertical movement to establish a gap therebetween before a lateral movement is performed to align the flat WGTL over another predetermined region in the magnetic film.

29. The scanning FMR measurement system of claim 22 wherein the flat WGTL is comprised of a top conductor layer, a rigid substrate layer, a bottom ground plane layer including a signal layer, and a dielectric layer between the rigid substrate layer and bottom ground plane layer.

30. The scanning FMR measurement system of claim 22 wherein the FMR measurement is performed with a transmission mode wherein the RF input signal passes through the first RF connector, and the RF output signal passes through the second RF connector.

31. The scanning FMR measurement system of claim 22 further comprised of a directional coupler, power divider, or bias tee that receives the RF input signal from the RF generator and then transmits the RF input signal through the RF input cable to the WGTL, the directional coupler, power divider, or bias tee also receives a reflected RF output signal from the WGTL through the RF input cable, and transmits the reflected RF output signal to the RF detector in a reflectance mode for performing the FMR measurement.

32. The scanning FMR measurement system of claim 22 wherein the first and second RF connectors are end launch connectors.

33. A method of performing a scanning ferromagnetic resonance (FMR) measurement on a whole wafer under test (WUT) having an exposed magnetic film thereon, comprising:

(a) providing a wafer chuck on which the WUT is held, and having a first link to a controller;

(b) providing a waveguide transmission line (WGTL) that is configured to contact or be placed proximate to a first location on the exposed magnetic film;

(c) applying a sequence of RF input signals from a RF generator that has a second link to the controller, each RF input signal passes through the WGTL and comprises a different microwave frequency that is sequentially transmitted to the first location;

(d) applying a magnetic field from an overlying magnetic pole piece simultaneously with each different microwave frequency to establish a FMR condition thereby resulting in a RF output signal for each pair of an applied microwave frequency value and an applied magnetic field value; and

(e) transmitting a sequence of output RF signals from the WGTL to a RF detector that is configured to convert each output RF signal to a voltage signal and to send each voltage signal to the controller, the controller determines one or more properties in the exposed magnetic film.

34. The method of claim 33 wherein the WGTL and mounting plate are installed in an electrical probe station.

35. The method of claim 33 wherein contact between the WGTL and the exposed magnetic film is achieved by a vertical movement of the mounting plate or a vertical movement of the wafer chuck.

36. The method of claim 33 wherein the WGTL is affixed at two ends to a mounting plate, and is suspended through or below a mounting plate opening in order to contact or be placed proximate to the exposed magnetic film.

37. The method of claim 33 further comprised of performing a second FMR measurement at a second location on the exposed magnetic film after completing steps (a)-(e).

38. The method of claim 37 wherein performing the second FMR measurement comprises:

(a) separating the WGTL and exposed magnetic film using a vertical movement of the mounting plate or wafer chuck;

(b) performing a lateral movement of the mounting plate or wafer chuck such that the WGTL and magnetic pole piece are aligned above the second location; and

(c) performing a vertical movement of the mounting plate or wafer chuck such that the WGTL contacts or is moved proximate to the exposed magnetic film.

39. The method of claim 33 wherein the different microwave frequencies are between 1 and 100 GHz.

40. The method of claim 33 wherein the magnitude of the magnetic field is up to 3 Tesla.