Computer-implemented reflectance system and method for non-destructive low dose ion implantation monitoring

• US 6,825,933 B2
• Filed: 06/07/2002
• Issued: 11/30/2004
• Est. Priority Date: 06/07/2002
• Status: Expired due to Term

• Current Assignee: N&K Technology Incorporated
• Original Assignee: N&K Technology Incorporated
• Inventors: Roberts, Jeff, Forouhi, Abdul Rahim
• Primary Examiner(s): STAFIRA, MICHAEL PATRICK
• Application Number:
  US10/165,771
• Publication Number:
  US 20030227630A1
• Time in Patent Office: 907 Days
• Field of Search: 356/445-448, 356/369, 356/364, 356/368, 356/381, 356/382, 356/367, 250/225
• US Class Current: 356/445
• CPC Class Codes: G01N 21/33 using ultraviolet light G01N21/39 takes precedence
• CPC Class Codes: G01N 21/55 Specular reflectivity
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10

Abstract

Embodied in a reflectance system capable of providing high resolution, repeatable, efficient, and accurate reflectance measurements of a silicon or silicon-oxide wafer at all wavelengths, the present invention, including an inventive and useful software tool with user interface, provides a solution to monitor non-destructively low dose ion implantation without potentially suffering from undesirable annealing effect. The computer-implemented method disclosed herein determines a reflectance change index that correlates to the ion dose. The reflectance change index is determined based on an absolute value of reflectance changes over the entire measured spectra. The reflectance changes are determined based on non-implanted and implanted reflectance measurements of the wafer respectively obtained at each of the wavelengths.

Claims

1. A computer-implemented reflectance method for non-destructive monitoring low dose ion implantation in a material, said method comprising the steps of:

a) providing illumination on a first sample of said material, wherein said material comprises silicon or silicon-oxide wafers and said first sample is a sample wafer thereof, and wherein said illumination spans a substantially broad range of wavelengths (wl);

b) obtaining non-implanted reflectance measurements (R_ref) of said first sample at each of said wavelengths (R_ref,wl);

c) implanting said first sample with said low dose of ions and obtaining implanted reflectance measurements (R_imp,wl) of said first sample at each of said wavelengths (R_imp,wl) wherein said non-implanted reflectance measurements are substantially simultaneously obtained at a location near center of said first sample and said implanted reflectance measurements are substantially simultaneously obtained at essentially same location of said first sample;

d) forming reflectance values over said wavelengths based on said non-implanted and implanted reflectance measurements;

e) comparing non-implanted and implanted reflectance values and determining reflectance changes; and

f) correlating an absolute value of said reflectance changes to said low dose including determining a reflectance change index value where said reflectance change index equals $\underset{\mathrm{wl}=190}{\overset{1000}{\sum <br><br>}}<br><br>\left|\left(\frac{\left(R_{\mathrm{ref},\mathrm{wl}}-R_{\mathrm{imp},\mathrm{wl}}\right)}{R_{\mathrm{ref},\mathrm{wl}}}\right)\right|$

such that said reflectance change index is directly related to said low dose.

5. The method of claim 1, wherein said location comprises at least three points arranged to be at equal distance from each other.

6. The method of claim 5, wherein said distance is about 1 mm.

7. The method of claim 1, wherein said location comprises a center point and eight points surrounding said center point at equal distance.

8. The method of claim 7, wherein said distance is about 1 mm.

17. The method of claim 1, wherein said ion implantation utilizing boron (B) ions.

18. The method of claim 1, wherein said illumination includes radiation frequencies in visible and invisible electromagnetic spectra.

19. The method of claim 1, wherein said range is about 190 nm to 1000 nm.

20. The method of claim 1, wherein said low dose is about 1.00E+11 to 1.00E+15.

29. A computer system programmed to perform the method steps of claim 1.

2. A non-destructive method of monitoring low dose ion implantation in a material, said method comprising the steps of:

a) providing illumination on a first sample of said material, wherein said material comprises silicon or silicon-oxide wafers and said first sample is a sample wafer thereof, and wherein said illumination spans a substantially broad range of wavelengths (wl);

b) obtaining non-implanted reflectance measurements (R_ref) of said first sample at each of said wavelengths (R_ref,wl);

c) implanting said first sample with said low dose of ions and obtaining implanted reflectance measurements (R_imp) of said first sample at each of said wavelengths (R_imp,wl), wherein said non-implanted reflectance measurements are substantially simultaneously obtained at a plurality of locations of said first sample and said implanted reflectance measurements are substantially simultaneously obtained at essentially same locations of said first sample;

d) forming reflectance values over said wavelengths based on said non-implanted and implanted reflectance measurements;

e) comparing non-implanted and implanted reflectance values and determining reflectance changes; and

f) determining a reflectance change index value where said reflectance change index equals $\underset{\mathrm{wl}=190}{\overset{1000}{\sum <br><br>}}<br><br>\left|\left(\frac{\left(R_{\mathrm{ref},\mathrm{wl}}-R_{\mathrm{imp},\mathrm{wl}}\right)}{R_{\mathrm{ref},\mathrm{wl}}}\right)\right|$

such that said reflectance change index is directly related to said low dose.

3. The method of claim 2, wherein each location comprises at least three points arranged to be at equal distance from each other.

4. The method of claim 3, wherein said distance is about 1 mm.

9. The method of claim 3, wherein each location comprises a center point and eight points surrounding said center point at equal distance.

10. A non-destructive method of monitoring low dose ion implantation in a material, said method comprising the steps of:

a) providing illumination on a first sample of said material, wherein said material comprises silicon or silicon-oxide wafers and said first sample is a sample wafer thereof, and wherein said illumination spans a substantially broad range of wavelengths (wl);

b) obtaining non-implanted reflectance measurements (R_ref) of said first sample at each of said wavelengths (R_ref,wl);

c) implanting said first sample with said low dose of ions and obtaining implanted reflectance measurements (R_imp) of said first sample at each of said wavelengths (R_imp,wl);

d) forming reflectance values over said wavelengths based on said non-implanted and implanted reflectance measurements, wherein said R_ref reflectance values are average reflectance values of said first sample before said low dose ion implantation and said R_imp reflectance values are average reflectance values of said first sample after said low dose ion implantation;

e) comparing non-implanted and implanted reflectance values and determining reflectance changes; and

f) determining a reflectance change index value where said reflectance change index equals $\underset{\mathrm{wl}=190}{\overset{1000}{\sum <br><br>}}<br><br>\left|\left(\frac{\left(R_{\mathrm{ref},\mathrm{wl}}-R_{\mathrm{imp},\mathrm{wl}}\right)}{R_{\mathrm{ref},\mathrm{wl}}}\right)\right|$

such that said reflectance change index is directly related to said low dose.

11. The method of claim 10, wherein said non-implanted reflectance measurements are substantially simultaneously obtained at one or more locations of said first sample and said implanted reflectance measurements are substantially simultaneously obtained at essentially same one or more locations of said first sample.

35. The method of claim 11, wherein each location comprises three or more points arranged to be at equal distance from each other.

12. A non-destructive method of monitoring low dose ion implantation in a material, said method comprising the steps of:

a) providing illumination on a first sample of said material, wherein said material comprises silicon or silicon-oxide wafers and said first sample is a sample wafer thereof, and wherein said illumination spans a substantially broad range of wavelengths (wl);

b) obtaining non-implanted reflectance measurements (R_ref) of said first sample at each of said wavelengths (R_ref,wl);

c) obtaining implanted reflectance measurements (R_imp) of a second sample of said material at each of said wavelengths (R_imp,wl), said second sample being implanted with said low dose of ions;

d) forming reflectance values over said wavelengths based on said non-implanted and implanted reflectance measurements, wherein said R_ref reflectance values are average reflectance values of said first sample and said R_imp reflectance values are average reflectance values of said second sample;

e) comparing non-implanted and implanted reflectance values and determining reflectance changes; and

f) determining a reflectance change index value where said reflectance change index equals $\underset{\mathrm{wl}=190}{\overset{1000}{\sum <br><br>}}<br><br>\left|\left(\frac{\left(R_{\mathrm{ref},\mathrm{wl}}-R_{\mathrm{imp},\mathrm{wl}}\right)}{R_{\mathrm{ref},\mathrm{wl}}}\right)\right|$

such that said reflectance change index is directly related to said low dose.

13. The method of claim 12, wherein said non-implanted reflectance measurements are obtained at a first location near center of said first sample and said implanted reflectance measurements are obtained at a second location near center of said second sample, and wherein said first location is essentially same as said second location.

14. The method of claim 13, wherein each of said first and second locations comprises at least three points arranged to be at equal distance of about 1 mm from each other.

15. The method of claim 13, wherein each of said first and second locations comprises a center point and eight points surrounding said center point at equal distance of about 1 mm.

16. The method of claim 12, wherein said non-implanted reflectance measurements are obtained at a plurality of locations of said first sample and said implanted reflectance measurements are obtained at a plurality of locations of said second sample.

21. A system for non-destructive monitoring low dose ion implantation in a material, comprising:

a light source means for providing illumination on a first sample of said material wherein said material comprises silicon or silicon-oxide wafers and wherein said illumination spans a substantially broad range of wavelengths (wl);

an optical sensing means optically coupled to said light source means for obtaining non-implanted reflectance measurements (R_ref) and implanted reflectance measurements (R_imp) of said sample at each of said wavelengths, (R_ref,wl) and (R_imp,wl), respectively, and transmitting reflectance measurements obtained thereof; and

a computing means operatively coupled to said optical sensing means for analyzing said transmitted reflectance measurements, comprising;

means for forming respective reflectance values over said wavelengths based on said non-implanted reflectance measurements and implanted reflectance measurements;

means for comparing said non-implanted and implanted reflectance values and determining reflectance changes;

means for determining a reflectance change index value, said reflectance change index correlating an absolute value of said reflectance changes to said low dose; and

means for providing said reflectance change index value to a user and receiving user input via a graphic user interface wherein said graphic user interface comprises an input area, an output area, and a result area, wherein said input area is configured to include placements for implant type, said non-implanted reflectance measurements, and said implanted reflectance measurements, wherein said output area is configured to include placements for said reflectance change index and said low dose, and wherein said result area is configured to display a graphical result showing a relationship between said reflectance change index and said low dose.

22. The system of claim 21, wherein said reflectance change index value equals $\sum _{}^{}$

wl=1901000

|((Rref,wl-Rimp,wl)Rref,wl)|.

23. The system of claim 21, wherein said light source means is capable of providing radiation frequencies in visible and invisible electromagnetic spectra.

24. The system of claim 21, wherein said range is about 190 nm to 1000 nm.

25. The system of claim 21, wherein said low dose is about 1.00E+11 to 1.00E+15.

26. The system of claim 21, wherein said implanted reflectance measurements are obtained from a second sample of said material wherein said computing means further comprising a storing means for storing said non-implanted reflectance measurements of said first sample.

27. The system of claim 21, wherein said computing means further comprising:

a storing means for storing said non-implanted reflectance measurements and said implanted reflectance measurements.

28. The system of claim 21, wherein said user input comprises ion implant types and ion implant doses.

30. A computer program product embodied in a reflectance system for implementing a method for non-destructive monitoring low dose ion implantation in a first wafer, the reflectance system comprises a light source means for providing visible and invisible light on said wafer at a substantially broad range of wavelengths (wl) and an optical sensing means for obtaining non-implanted and implanted reflectance measurements of said wafer at each of said wavelengths, (R_ref,wl) and (R_imp,wl), respectively, the computer program product comprising:

a computer-readable medium carrying computer-executable instructions for implementing the method wherein the computer-executable instructions comprise;

program code means for forming respective reflectance values over said wavelengths based on said non-implanted reflectance measurements and implanted reflectance measurements;

program code means for comparing said non-implanted and implanted reflectance values and determining reflectance changes;

program code means for determining a reflectance change index value, said reflectance change index correlating an absolute value of said reflectance changes to said low dose; and

program code means for providing a graphic user interface environment to display said reflectance change index value and receive user input;

wherein said graphic user interface environment comprises an input area, an output area, and a result area, wherein said input area is configured to include placements for implant type, said non-implanted reflectance measurements, and said implanted reflectance measurements, wherein said output area is configured to include placements for said reflectance change index and said low dose, and wherein said result area is configured to display a graphical result showing a relationship between said reflectance change index and said low dose.

31. The computer program product of claim 30, wherein said reflectance change index value equals $\sum _{}^{}$

wl=1901000

|((Rref,wl-Rimp,wl)Rref,wl)|.

32. The computer program product of claim 30, wherein said first wafer is a silicon or silicon-oxide wafer.

33. The computer program product of claim 30, wherein said implanted reflectance measurements are obtained from a second wafer made of same material of said first wafer.

34. The computer program product of claim 30, wherein said user input includes ion implant types and ion implant doses.

36. The computer program product of claim 30, wherein said graphic user interface environment further comprises a log/linear switch, a dose/text labels switch, a calculate button, a print button, and a close button.

37. The computer program product of claim 30, wherein said graphic user interface environment further comprises a calculate area, an add area, and a table area, wherein said calculate area is configured to calculate said reflectance change index, wherein said add area is configured to add said reflectance change index and said low dose to a table, and wherein said table area is configured to list said table.

38. The computer program product of claim 37, wherein said graphic user interface environment further comprises a dose/text labels switch, a calculate button, an add button, a remove button, a print button, and a close button.