Measurement of different mobile ion concentrations in the oxide layer of a semiconductor wafer

• US 6,569,691 B1
• Filed: 11/15/2000
• Issued: 05/27/2003
• Est. Priority Date: 03/29/2000
• Status: Expired due to Fees

• Current Assignee: Semiconductor Diagnostics, Inc. (SEMILAB Félvezeto Fizikai Laboratórium Zrt.)
• Original Assignee: Semiconductor Diagnostics, Inc. (SEMILAB Félvezeto Fizikai Laboratórium Zrt.)
• Inventors: Wilson, Marshall D., Jastrzebski, Lubomir L., Savtchouk, Alexander
• Primary Examiner(s): Smith, Matthew
• Assistant Examiner(s): Lee, Calvin
• Application Number:
  US09/713,617
• Time in Patent Office: 923 Days
• Field of Search: 438/510-569, 438/70-75, 438/17, 438/14-16
• US Class Current: 438/14
• CPC Class Codes: G01N 33/0095 Semiconductive materials
• CPC Class Codes: H01L 22/14 for electrical parameters, e.g. resistance, deep-levels, CV, diffusions by electrical means
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

A method and apparatus for measuring the concentration of different mobile ions in the oxide layer of a semiconductor wafer from the contact potential shift caused by different ions drifting across the oxide that includes depositing charge (e.g., using a corona discharge device) on the surface of the oxide and heating the wafer to allow different mobile ions in the oxide to drift. The difference in the contact potential measured before and after heating provides an indication of the different mobile ion concentration in the oxide layer.

Claims

1. A method of measuring at least two different ion concentrations within an oxide layer of a semiconductor, the method comprising:

applying a first predetermined bias temperature stress (BTS)-conditioning to the semiconductor wafer including the oxide layer disposed thereon to cause ions of a first type to migrate within the oxide layer; and

applying a second predetermined BTS-conditioning to the semiconductor wafer to cause ions of a second type to migrate within the oxide layer, wherein the first predetermined BTS-conditioning does not substantially cause the ions of the second type to migrate within the oxide layer.

2. The method of claim 1 further including measuring the first contact potential after the ions of the first type migrate within the oxide layer.

3. The method of claim 2 wherein the first contact potential is also measured before the ions of the first type migrate within the oxide layer.

4. The method of claim 2 further including measuring the second contact potential after the ions of the second type migrate within the oxide layer.

5. The method of claim 4, wherein the second contact potential is also measured before the ions of the second type migrate within the oxide layer.

6. The method of claim 4 including measuring the oxide leakage current at the first and the second predetermined BTS-conditionings, correcting the first contact potential with the oxide leakage current measured at the first predetermined BTS-conditioning, and correcting the second contact potential with the oxide leakage current measured at the second predetermined BTS-conditioning.

7. The method of claim 1 further including measuring the second contact potential after the ions of the second type migrate within the oxide layer.

8. The method of claim 7 the second contact potential is also measured before the ions of the second type migrate within the oxide layer.

9. The method of claim 1, wherein the first predetermined BTS-conditioning includes biasing the semiconductor wafer with a predetermined first charge and heating the semiconductor wafer to a predetermined first temperature for a predetermined first time period.

10. The method of claim 1, wherein the second predetermined BTS-conditioning includes biasing the semiconductor with a predetermined second charge and heating the semiconductor wafer to a predetermined second temperature for a predetermined second time period.

11. The method of claim 1 further including a pre-BTS conditioning to cause a random distribution of ions of the first and second types to redistribute into a non-random distribution.

12. The method of claim 11, wherein the ions of the first and second types are caused to migrate to the surface of the oxide layer.

13. The method of claim 11, wherein the ions of the first and second types are caused to migrate to an interface between the oxide layer and the semiconductor.

14. The method of claim 1, wherein the ions of the first type have an ion mobility that is larger than the ion mobility of the ions of the second type at a constant temperature.

15. The method of claim 1, wherein the ions of the first type are Na₊.

16. The method of claim 15, wherein the ions of the second type are Cu⁺.

17. The method of claim 1, wherein the semiconductor wafer further includes a metal layer periodically patterned on a top surface of the oxide layer.

18. The method of claim 17, wherein the metal layer is copper.

19. The method of claim 1, wherein the first predetermined BTS-conditioning includes biasing the semiconductor with a predetermined first charge and heating the semiconductor wafer to a predetermined first temperature for a predetermined first time period, and the second predetermined BTS-conditioning includes biasing the semiconductor with a predetermined second charge and heating the semiconductor wafer to a predetermined second temperature for a predetermined second time period.

20. The method of claim 19, wherein the first charge and the second charge are equal.

21. The method of claim 20, wherein the first temperature and the second temperature are equal.

22. The method of claim 20, wherein the first time period and a second time period are equal.

23. The method of claim 19, wherein the first temperature and the second temperature are equal.

24. The method of claim 23, wherein the first time period and a second time period are equal.

25. The method of claim 19, wherein the first time period and a second time period are equal.

26. The method of claim 19, wherein the first and the second temperatures are between about 150°

C. and about 300°

C.

27. The method of claim 19, wherein the first and the second charges are between about 0.1 to about 6 MV/cm.

28. The method of claim 19, wherein the first and the second time periods are between 30 sec and 3600 sec.

29. The method of claim 19, wherein the second predetermined BTS-conditioning includes biasing the semiconductor with a charge of about 1.5 MV/cm and heating the semiconductor to about 170°

C. for a time period of at least about 20 minutes for a 1000 Å

oxide thickness.

30. The method of claim 29, wherein first predetermined BTS-conditioning includes biasing the semiconductor with a charge of about 0.5 MV/cm and heating the semiconductor to about 170°

C. for a time period of at least about 2 minutes for a 1000 Å

oxide thickness.

31. The method of claim 19, wherein the second predetermined BTS-conditioning includes biasing the semiconductor with a charge of about 1.5 MV/cm and heating the semiconductor to about 2250°

C. for a time period of at least about 3.5 minutes for a 1000 Å

oxide thickness.

32. The method of claim 19, wherein the biasing charges applied to the surface of the oxide layer are produced from a corona charging element.

33. A method for determining different mobile ion concentrations within an oxide layer disposed on a surface of a semiconductor wafer, comprising:

depositing a first charge on at least a portion of the surface of the oxide layer at a low temperature at which a first mobile ion does not substantially move,

measuring the contact potential on the surface of the oxide layer,

heating the semiconductor wafer and oxide layer to a first temperature sufficient to force substantially all of the first mobile ions to migrate across the oxide layer from the surface to an interface between the oxide layer and semiconductor wafer,

measuring a first shift in contact potential after said heating to the first temperature,

determining the first mobile ion concentration within the oxide layer on the basis of the first shift;

depositing a second charge on at least a portion of the surface of the oxide layer at a low temperature at which a second mobile ion does not substantially move,

measuring the contact potential on the surface of the oxide layer,

heating the semiconductor wafer and oxide layer to a second temperature sufficient to force substantially all of the second mobile ions to migrate within the oxide layer from the surface to an interface between the oxide layer and semiconductor wafer,

measuring a second shift in contact potential after said heating to the second temperature,

determining the second mobile ion concentration within the oxide layer on the basis of the second shift.

34. The method of claim 33 further including determining the oxide leakage at the first charge and the second charge and using the oxide leakage at the first charge and the second charge in determining the first and second ion concentrations.

35. A system for the measurement of mobile contaminant ion concentration in an oxide layer of a semiconductor wafer, comprising:

a charge deposition device configured to deposit charge on the oxide layer of the wafer;

a temperature stress device including a element for heating the wafer to a temperature sufficient to allow mobile ions to drift;

a measurement device configured to measure the contact potential; and

a semiconductor wafer holder including at least one semiconducting wafer having an oxide layer disposed on a surface of a semiconductor wafer, wherein a metal layer is patterned onto a surface of the oxide layer.