XRF measurement apparatus for detecting contaminations on the bevel of a wafer

• US 9,541,511 B2
• Filed: 01/21/2014
• Issued: 01/10/2017
• Est. Priority Date: 01/30/2013
• Status: Active Grant

• Current Assignee: Bruker Axs GMBH (Bruker Corporation)
• Original Assignee: Bruker Axs GMBH (Bruker Corporation)
• Inventors: Vigliante, Assunta
• Primary Examiner(s): LOGIE, MICHAEL J
• Application Number:
  US14/159,469
• Publication Number:
  US 20140211914A1
• Time in Patent Office: 1,085 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G01N 21/9503 Wafer edge inspection
• CPC Class Codes: G01N 2223/076 X-ray fluorescence
• CPC Class Codes: G01N 2223/6116 semiconductor wafer
• CPC Class Codes: G01N 2223/652 impurities, foreign matter, trace amounts
• CPC Class Codes: G01N 23/20025 Sample holders or supports therefor
• CPC Class Codes: G01N 23/223 by irradiating the sample with X-rays or gamma-rays and by measuring X-ray fluorescence

Abstract

An XRF (XRF=x-ray fluorescence) measurement apparatus (1) has an x-ray source (2) for generating x-rays (4), x-ray optics (3) for directing x-rays (4) from the x-ray source (2) to a sample (5) and an EDS (EDS=energy dispersive spectroscopy) detector (7) for detecting fluorescent x-rays (14) from the sample (5). The apparatus is characterized in that the sample (5) is a wafer (6), in particular a Si wafer, wherein the x-ray optics (3) is positioned to direct the x-rays (4) onto the bevel (12) of the wafer (6). The x-ray source (2) plus the x-ray optics (3) has a brilliance of at least 5*10⁷ counts/sec mm², preferably at least 1*10⁸counts/sec mm². The apparatus allows an improved contamination control of wafers, in particular silicon wafers.

Claims

1. An XRF (XRF=x-ray fluorescence) measurement apparatus comprising:

a sample, wherein said sample is a wafer or an Si wafer having a bevel;

an x-ray source for generating x-rays;

x-ray optics elements, said x-ray optics elements being disposed, structured and dimensioned to direct x-rays from the x-ray source onto said bevel of said wafer, wherein a combination of said x-ray source and said x-ray optics elements drive generated x-rays to a brilliance of at least 5*10⁷ counts/sec mm²;

an EDS (EDS=energy dispersive spectroscopy) detector for detecting fluorescent x-rays from said wafer;

auxiliary x-ray optics elements for directing x-rays from said x-ray source onto said wafer; and

a switching element for switching the apparatus between a first operation mode and a second operation mode, wherein, in said first operation mode, said x-ray optics elements are positioned to direct x-rays from said x-ray source onto said bevel of said wafer and, in said second operation mode, said auxiliary x-ray optics elements are positioned to direct x-rays from said x-ray source onto a flat side of said wafer, wherein said switching element comprises a first moving stage for exchanging said x-ray optics elements with said auxiliary x-ray optics elements by displacing said x-ray optics elements and said auxiliary x-ray optics elements substantially transverse to a direction of travel of the x-rays, said switching element also comprising a second moving stage for pivoting and shifting said wafer relative to a path of the x-rays when switching from said first to said second operation mode.

2. The apparatus of claim 1, wherein said brilliance is at least 1*10⁸ counts/sec mm².

3. The apparatus of claim 1, wherein said x-ray optics elements and said wafer are positioned such that the x-rays strike a surface of said bevel at an angle of between 0.05°

and 6°

.

4. The apparatus of claim 1, wherein said x-ray optics elements and said wafer are positioned such that the x-rays directed onto said wafer propagate substantially in an x-z plane parallel to a flat side of said wafer.

5. The apparatus of claim 1, wherein a surface normal of a flat side of said wafer is oriented horizontally.

6. The apparatus of claim 1, wherein the x-rays directed onto said wafer propagate in a substantially horizontal x-direction.

7. The apparatus of claim 1, wherein said x-ray source is of a metal jet target type.

8. The apparatus of claim 1, wherein said x-ray optics elements include a Montel mirror, a Goebel mirror or a double curved multilayer mirror.

9. The apparatus of claim 1, wherein said bevel of said wafer is located in a focus of said x-ray optics elements.

10. The apparatus of claim 1, wherein, at a position on a surface of said wafer, the x-rays directed onto said wafer have a width that matches a width of said wafer.

11. The apparatus of claim 1, the apparatus further comprising:

a further EDS detector for detecting fluorescent x-rays from said wafer; and

a handling stage for shifting said wafer relative to a path of the x-rays directed onto said wafer in two independent directions transverse to the x-rays directed onto the sample and for rotating said wafer with respect to a rotation axis perpendicular to a flat side of said wafer.

12. The apparatus of claim 11, wherein said two independent directions are mutually orthogonal directions.

13. The apparatus of claim 11, wherein said EDS detector and said further EDS detector view said wafer at substantially right angles with respect to the x-rays directed onto said wafer and at a substantially right angle with respect to each other.

14. A method for examining a wafer using the apparatus of claim 1, the method comprising the steps of:

a) detecting fluorescent x-rays from the wafer; and

b) determining contaminations on said bevel of said wafer or said silicon wafer by means of XRF.

15. The method of claim 14, wherein a gallium L line is utilized for x-ray generation in said x-ray source.