MEMS Stiction Testing Apparatus and Method

• US 20090320557A1
• Filed: 06/24/2009
• Published: 12/31/2009
• Est. Priority Date: 06/26/2008
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Sawyer, William, Sammoura, Firas N., Yang, Kuang L.
• Granted Patent: US 8,215,151 B2
• Time in Patent Office: Days
• US Class Current: 73/9
• CPC Class Codes: B81C 99/0045 End test of the packaged device

Abstract

A MEMS stiction testing method applies a first electrical signal to a MEMS device having two opposing surfaces to cause the two opposing surfaces to make physical contact. The two opposing surfaces produce a second electrical signal when in physical contact. The method then substantially mitigates the first electrical signal after detecting that the second electrical signal has reached a prescribed maximum value.

Claims

1. A MEMS stiction testing method comprising:

applying a first electrical signal to a MEMS device having two opposing surfaces, the first electrical signal causing the two opposing surfaces to make physical contact, the two opposing surfaces producing a second electrical signal when in physical contact; and

substantially mitigating the first electrical signal after detecting that the second electrical signal has reached a prescribed maximum value.

2. The method as defined by claim 1 wherein applying the first electrical signal to the MEMS devices comprises applying the first electrical signal to the MEMS device in a stepped manner.

3. The method as defined by claim 1 wherein substantially mitigating comprises one of:

completely turning off the first electrical signal; and

reducing the first electrical signal in a stepped manner.

4. The method as defined by claim 1 wherein the opposed surfaces separate at a given signal level while mitigating the first electrical signal, the method further comprising at least one of:

monitoring the second electrical signal to detect when the second electrical signal has reached a prescribed value indicative of surface separation; and

recording the given signal level.

5. The method as defined by claim 1 wherein the first electrical signal is a voltage, and the second electrical signal is a current.

6. The method as defined by claim 1 wherein the prescribed maximum value is between about 300 and 700 pico-amps.

7. The method as defined by claim 1 wherein the two opposing surfaces form a variable capacitor.

8. The method as defined by claim 1 further comprising:

measuring the capacitance between the two opposing surfaces after substantially mitigating the first electrical signal.

9. The method as defined by claim 8 further comprising:

measuring the capacitance between the two opposing surfaces prior to applying the first electrical signal; and

comparing the capacitance measurement from after substantially mitigating the first electrical signal with the capacitance measurement from prior to applying the first electrical signal.

10. The method as defined by claim 1 wherein the MEMS device includes at least one of:

a high-G MEMS inertial sensor;

a low-G MEMS inertial sensor; and

a MEMS microphone.

11. A MEMS stiction testing apparatus comprising:

a signal generator configured to provide a first electrical signal that when applied to a MEMS device having two opposing surfaces causes the two opposing surfaces to make physical contact, the two opposing surfaces producing a second electrical signal when in physical contact;

a signal monitor configured to substantially mitigate the first electrical signal after detecting that the second electrical signal has reached a prescribed maximum value.

12. The apparatus as defined by claim 11 wherein the signal generator is configured to provide the first electrical signal in a stepped manner.

13. The apparatus as defined by claim 11 wherein the signal monitor is configured to substantially mitigate the first electrical signal by one of:

completely turning off the first electrical signal; and

reducing the first electrical signal in a stepped manner.

14. The apparatus as defined by claim 11 wherein the opposed surfaces separate at a given signal level while mitigating the first electrical signal, and wherein the signal monitor is further configured to at least one of:

monitor the second electrical signal to detect when the second electrical signal has reached a prescribed value indicative of surface separation; and

record the given signal level.

15. The apparatus as defined by claim 11 wherein the first electrical signal is a voltage, and the second electrical signal is a current.

16. The apparatus as defined by claim 11 wherein the prescribed maximum value is between about 300 and 700 pico-amps.

17. The apparatus as defined by claim 11 wherein the two opposing surfaces form a variable capacitor.

18. The apparatus as defined by claim 11 wherein the signal monitor is further configured to measure the capacitance between the two opposing surfaces after substantially mitigating the first electrical signal.

19. The apparatus as defined by claim 18 wherein the signal monitor is further configured to measure the capacitance between the two opposing surfaces prior to applying the first electrical signal and compare the capacitance measurement from after substantially mitigating the first electrical signal with the capacitance measurement from prior to applying the first electrical signal.

20. The apparatus as defined by claim 11 wherein the apparatus is a parametric analyzer.

21. The apparatus as defined by claim 11 wherein the MEMS device includes at least one of:

a high-G MEMS inertial sensor;

a low-G MEMS inertial sensor; and

a MEMS microphone.

22. A computer program product for use on a computer system for MEMS stiction testing, the computer program product comprising a computer usable medium having computer readable program code thereon, the computer readable program code comprising:

program code for applying a first electrical signal to a MEMS device having two opposing surfaces, the electrical signal causing the two opposing surfaces to make physical contact, the two opposing surfaces producing a second electrical signal when in physical contact; and

program code for substantially mitigating the first electrical signal after detecting that the second electrical signal has reached a prescribed maximum value.