METHOD OF FABRICATING AN ULTRA-SMALL CONDENSER MICROPHONE

• US 20090130783A1
• Filed: 11/05/2008
• Published: 05/21/2009
• Est. Priority Date: 11/16/2007
• Status: Active Grant

• Current Assignee: TDK Corporation
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: IMAI, Tadao, DOI, Kazumoto, IWASEKI, Hiroaki, MIYASHITA, Yoshiyuki
• Granted Patent: US 7,855,095 B2
• Time in Patent Office: Days
• US Class Current: 438/10
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: Y10T 29/49005 Acoustic transducer

Abstract

In the present invention, a semiconductor substrate wherein a plurality of MEMS microphones is formed is disposed opposed to a discharge electrode in a state of being stuck on a sheet. Electretization of a dielectric film provided in the MEMS microphone is performed by irradiating the dielectric film between a fixed electrode and a vibration film provided in the MEMS microphone with ions resulting from a corona discharge of the discharge electrode in a state that a predetermined potential difference is applied to the fixed electrode and the vibration film and fixing charges based on the ions to the dielectric film. The electretization is successively performed to each MEMS microphone on the semiconductor substrate by relatively moving the semiconductor substrate and the discharge electrode. Therefore, electretization of the dielectric film in the MEMS microphone chip is realized using a low-cost and simple fabricating equipment and productivity can be enhanced.

Claims

1. A method of fabricating an ultra-small condenser microphone including a vibration film of which an outer edge is supported by a base formed of a semiconductor substrate, a dielectric film formed on the vibration film and a fixed electrode arranged above the dielectric film via a space, the method comprising the steps of:

sticking a sheet on an opposite surface of a surface whereon the vibration film is formed in the semiconductor substrate wherein a plurality of the ultra-small condenser microphones is formed;

disposing the semiconductor substrate stuck on the sheet opposed to a discharge electrode;

performing electretization for fixing charges in the dielectric film by irradiating the dielectric film placed between the fixed electrode and the vibration film provided in an ultra-small condenser microphone on the disposed semiconductor substrate with ions resulting from a corona discharge of the discharge electrode in a state that a predetermined potential difference is given between the fixed electrode and the vibration film; and

wherein the electretization for the dielectric film provided in the plurality of the ultra-small condenser microphones on the semiconductor substrate is successively performed by relatively moving the semiconductor substrate and the discharge electrode.

3. A method according to claim 1, wherein the semiconductor substrate and the discharge electrode move relatively in a time interval of that an amount of charges deposited in the dielectric film reaches a predetermined amount, and the electretization for the dielectric film provided in the plurality of the ultra-small condenser microphones on the semiconductor substrate is performed continuously.

11. A method according to claim 1, wherein the discharge electrode is a needle electrode.

15. A method according to claims 1, wherein the ultra-small condenser microphone to be electretized is selected by giving the potential difference between the fixed electrode and the vibration film and a time to electretize is adjusted with a time to give the potential difference.

19. A method according to claim 1, wherein static electricity is removed by giving a ground potential to the fixed electrode and the vibration film before giving the potential difference between the fixed electrode and the vibration film.

23. A method according to claim 1, wherein the predetermined potential difference is given between the fixed electrode and the vibration film through probe pins.

28. A method according to claim 23, wherein irradiation with the ions on the dielectric film provided in an ultra-small condenser microphone except for an ultra-small condenser microphone to be electretized is avoided by using a cover having conductivity provided in a probe card supporting the probe pins and connected to a ground potential through a high resistance.

29. A method according to claim 28, wherein frosted black coating is applied to a surface of the cover opposed to the semiconductor substrate.

30. A method according to claim 23, wherein the probe pins are set through portions except for above the fixed electrode provided in the ultra-small condenser microphone to be electretized.

31. A method according to claim 23, an ion-shielding shutter having conductivity connected to a ground potential opens/closes a path of ions resulting from the discharge electrode to the semiconductor substrate.

35. A method according to claim 1, further comprising the step of:

separating the semiconductor substrate stuck on the sheet into pieces on the sheet; and

wherein the electretization is performed in a state that the separated semiconductor substrates are held together by the sheet.

39. A method according to claim 1, wherein the discharge electrode is arranged in a wafer prober, and the semiconductor substrate wherein the plurality of the ultra-small condenser microphone is formed is disposed on a stage provided in the wafer prober.

43. A method according to claim 1, wherein a distance between the disposed semiconductor substrate and the discharge electrode is adjustable.

47. A method according to claim 43, wherein the distance between the disposed semiconductor substrate and the discharge electrode is adjusted based on a scale which specifies a position of the discharge electrode.

2. A method of fabricating an ultra-small condenser microphone including a vibration film of which an outer edge is supported by a base formed of a semiconductor substrate, a dielectric film formed on the vibration film and a fixed electrode arranged above the dielectric film via a space, the method comprising the steps of:

sticking a sheet on an opposite surface of a surface whereon the vibration film is formed in the semiconductor substrate wherein a plurality of the ultra-small condenser microphones is formed;

disposing the semiconductor substrate stuck on the sheet opposed to a discharge electrode;

performing electretization for fixing charges in the dielectric film by irradiating the dielectric film placed between the fixed electrode and the vibration film provided in an ultra-small condenser microphone on the disposed semiconductor substrate with ions resulting from a corona discharge of the discharge electrode in a state that a predetermined potential difference is given between the fixed electrode and the vibration film;

inspecting an amount of charges deposited in the dielectric film provided in an ultra-small condenser microphone completed the electretization on the semiconductor substrate in parallel with the electretization; and

wherein the electretization for the dielectric film provided in the plurality of the ultra-small condenser microphones on the semiconductor substrate and the inspection of an amount of deposited charges in the dielectric film completed the electretization on the semiconductor substrate are successively performed by relatively moving the semiconductor substrate and the discharge electrode.

4. A method according to claim 2, wherein the semiconductor substrate and the discharge electrode move relatively in a time interval required for the inspection of the amount of deposited charges, and the electretization for the dielectric film provided in the plurality of the ultra-small condenser microphones on the semiconductor substrate and the inspection of the amount of deposited charges in the dielectric completed the electretization on the semiconductor substrate is performed continuously.

5. A method according to claim 2, wherein the inspecting step comprises the steps of:

changing the potential difference given between the fixed electrode and the vibration film in one direction within a predetermined range; and

measuring a capacitance of a condenser composed of the fixed electrode and the vibration film in every potential difference.

6. A method according to claim 5, wherein a potential difference of which a decreasing rate of the capacitance relative to the increase in the potential difference is maximum and a potential difference of which an increasing rate of the capacitance relative to the increase in the potential difference is maximum are obtained based on the measured capacitance, and the amount of deposited charges is inspected based on an intermediate value of the obtained respective potential differences.

7. A method according to claim 6, wherein the capacitance is measured by reducing a variation of the potential difference given between the fixed electrode and the vibration film around the potential difference of which the decreasing rate of the capacitance relative to the increase in the potential difference is maximum and the potential difference of which the increasing rate of the capacitance relative to the increase in the potential difference is maximum.

8. A method according to claim 6, wherein, in finishing giving the potential difference to measure the capacitance, giving the potential difference to measure the capacitance is finished after a potential difference corresponding to the intermediate value is given to the fixed electrode and the vibration film.

9. A method according to claims 5, wherein, in giving the potential difference to measure the capacitance, the same potential given to the fixed electrode is applied to the base supporting the outer edge of the vibration film.

10. A method according to claim 2, wherein at least one or more chips are interposed between an ultra-small condenser microphone to be electretized and an ultra-small condenser microphone to be inspected the amount of deposited charges in parallel with the electretization on the semiconductor substrate.

12. A method according to claim 2, wherein the discharge electrode is a needle electrode.

16. A method according to claim 2, wherein the ultra-small condenser microphone to be electretized is selected by giving the potential difference between the fixed electrode and the vibration film and a time to electretize is adjusted with a time to give the potential difference.

20. A method according to claim 2, wherein static electricity is removed by giving a ground potential to the fixed electrode and the vibration film before giving the potential difference between the fixed electrode and the vibration film.

24. A method according to claim 2, wherein the predetermined potential difference is given between the fixed electrode and the vibration film through probe pins.

27. A method according to claim 2, wherein the inspection of the amount of deposited charges is performed through probe pins.

36. A method according to claim 2, further comprising the step of:

separating the semiconductor substrate stuck on the sheet into pieces on the sheet; and

wherein the electretization is performed in a state that the separated semiconductor substrates are held together by the sheet.

40. A method according to claim 2, wherein the discharge electrode is arranged in a wafer prober, and the semiconductor substrate wherein the plurality of the ultra-small condenser microphone is formed is disposed on a stage provided in the wafer prober.

44. A method according to claim 2, wherein a distance between the disposed semiconductor substrate and the discharge electrode is adjustable.

13. A method of fabricating an ultra-small condenser microphone including a vibration film of which an outer edge is supported by a base formed of a semiconductor substrate, a dielectric film formed on the vibration film and a fixed electrode arranged above the dielectric film via a space, the method comprising the steps of:

sticking a sheet on an opposite surface of a surface whereon the vibration film is formed in the semiconductor substrate wherein a plurality of the ultra-small condenser microphones is formed;

disposing the semiconductor substrate stuck on the sheet opposed to a tip of a needle discharge electrode; and

performing electretization for fixing charges in the dielectric film by irradiating each dielectric film between each fixed electrode and each vibration film with ions resulting from a corona discharge of the discharge electrode in a state that a predetermined potential difference is given between each fixed electrode and each vibration film provided in a plurality of the ultra-small condenser microphones, all of the plurality of the ultra-small condenser microphones being contained in an area on the semiconductor substrate to be irradiated with the ions.

17. A method according to claim 13, wherein the ultra-small condenser microphone to be electretized is selected by giving the potential difference between the fixed electrode and the vibration film and a time to electretize is adjusted with a time to give the potential difference.

21. A method according to claim 13, wherein static electricity is removed by giving a ground potential to the fixed electrode and the vibration film before giving the potential difference between the fixed electrode and the vibration film.

25. A method according to claim 13, wherein the predetermined potential difference is given between the fixed electrode and the vibration film through probe pins.

32. A method according to claim 13, wherein, using a unit for switching a conducting state and a non-conducting state interposed in each electrical path to apply a voltage in order to give the predetermined potential difference to the fixed electrode and the vibration film provided in each of the ultra-small condenser microphones to be simultaneously electretized, a part of the electrical paths is to be the non-conducting state in order to stop giving the potential difference selectively.

34. A method according to claim 32, wherein the unit for switching the conducting state and the non-conducting state is arranged on a probe card or on a board to which the probe card is connected.

37. A method according to claim 13, further comprising the step of:

separating the semiconductor substrate stuck on the sheet into pieces on the sheet; and

wherein the electretization is performed in a state that the separated semiconductor substrates are held together by the sheet.

41. A method according to claim 13, wherein the discharge electrode is arranged in a wafer prober, and the semiconductor substrate wherein the plurality of the ultra-small condenser microphone is formed is disposed on a stage provided in the wafer prober.

45. A method according to claim 13, wherein a distance between the disposed semiconductor substrate and the discharge electrode is adjustable.

14. A method of fabricating an ultra-small condenser microphone including a vibration film of which an outer edge is supported by a base formed of a semiconductor substrate, a dielectric film formed on the vibration film and a fixed electrode arranged above the dielectric film via a space, the method comprising the steps of:

sticking a sheet on an opposite surface of a surface whereon the vibration film is formed in the semiconductor substrate wherein a plurality of the ultra-small condenser microphones is formed;

disposing the semiconductor substrate stuck on the sheet opposed to a linear discharge electrode; and

performing electretization for fixing charges in the dielectric film by irradiating each dielectric film between each fixed electrode and each vibration film with ions resulting from a corona discharge of the discharge electrode in a state that a predetermined potential difference is given between each fixed electrode and each vibration film provided in a plurality of the ultra-small condenser microphones, all of the plurality of the ultra-small condenser microphones being contained in an area on the semiconductor substrate to be irradiated with the ions.

18. A method according to claim 14, wherein the ultra-small condenser microphone to be electretized is selected by giving the potential difference between the fixed electrode and the vibration film and a time to electretize is adjusted with a time to give the potential difference.

22. A method according to claim 14, wherein static electricity is removed by giving a ground potential to the fixed electrode and the vibration film before giving the potential difference between the fixed electrode and the vibration film.

26. A method according to claim 14, wherein the predetermined potential difference is given between the fixed electrode and the vibration film through probe pins.

33. A method according to claim 14, wherein, using a unit for switching a conducting state and a non-conducting state interposed in each electrical path to apply a voltage in order to give the predetermined potential difference to the fixed electrode and the vibration film provided in each of the ultra-small condenser microphones to be simultaneously electretized, a part of the electrical paths is to be the non-conducting state in order to stop giving the potential difference selectively.

38. A method according to claim 14, further comprising the step of:

separating the semiconductor substrate stuck on the sheet into pieces on the sheet; and

wherein the electretization is performed in a state that the separated semiconductor substrates are held together by the sheet.

42. A method according to claim 14, wherein the discharge electrode is arranged in a wafer prober, and the semiconductor substrate wherein the plurality of the ultra-small condenser microphone is formed is disposed on a stage provided in the wafer prober.

46. A method according to claim 14, wherein a distance between the disposed semiconductor substrate and the discharge electrode is adjustable.