JP4514785B2 - Total reflection X-ray fluorescence analyzer - Google Patents

Description

  The present invention relates to a total reflection X-ray fluorescence analyzer that measures a peripheral portion in the vicinity of an edge of a disk-shaped sample.

  The total reflection X-ray fluorescence analyzer is used for analyzing wafers, glass substrates and the like in quality control analysis of semiconductor manufacturing processes. Since the peripheral part near the edge of the wafer is easily contaminated in the semiconductor manufacturing process, it was not used for manufacturing the chip, but the wafer was enlarged in diameter, while an ultra-small microchip was manufactured. If the peripheral portion in the vicinity of the edge of the wafer is available, thousands of microchips can be manufactured only in that region. Therefore, in order to use the peripheral part near the edge of the wafer as effectively as possible, the total reflection fluorescent X that can measure the area up to several millimeters before the edge of the wafer and check the contamination near the edge of the wafer. There is a line analyzer (see Patent Document 1).

Also, when the wafer is placed on a table with the wafer diameter increasing, the peripheral part near the edge protruding from the table is bent slightly downward, so that the primary to the surface of the wafer There is a total reflection fluorescent X-ray analyzer that corrects the incident angle of X-rays according to the measurement position of the wafer (see Patent Document 2). In this apparatus, the measurement intensity of fluorescent X-rays at each measurement position is used for correction (referred to as center intensity correction), and when the measurement position is in the vicinity near the edge of the wafer, the periphery near the edge Measurement strength at is required.
Japanese Patent Laid-Open No. 2002-5858 JP 2006-214868 A

  However, these conventional techniques cannot accurately analyze an arbitrary measurement site in the vicinity of the edge of a disk-shaped sample such as a wafer. When the edge of the sample is moved into the field of view of the detector on the stage, as shown in FIG. 4B, the sample S occupies only a part of the field of view F of the detector. This is because it can only be measured and does not match the measurement intensity for the measurement site occupying the entire field of view F of the detector as shown in FIG. 4A.

  The present invention has been made in view of the above-described conventional problems, and provides a total reflection X-ray fluorescence analyzer capable of performing an accurate analysis on an arbitrary measurement site in the peripheral portion near the edge of a disk-shaped sample such as a wafer. For the purpose.

In order to achieve the above object, the total reflection X-ray fluorescence analyzer of the present invention detects the intensity of generated X-rays by making primary X-rays incident on the surface of a disk-shaped sample at a minute incident angle. A total reflection X-ray fluorescence analyzer for measuring with a measuring instrument, wherein an initial position detecting means for detecting an initial position of the sample with respect to the detector, and an arbitrary measurement on the surface of the sample by moving the sample from the initial position Based on the stage for moving the part within the visual field of the detector, the initial position detected by the initial position detecting means, and the direction and amount of movement by the stage , the position after movement of the sample with respect to the detector is calculated. , the position after the movement of the sample to the calculated detector, based on a predetermined size and shape of the field of view of the detector in height of a predetermined geometry and the sample surface of the sample, you within the field of view of the detector Calculating the area of the measurement site is the area of that surface of the sample, and a calculation means based on the measurement strength measured by the area and the detector of the measurement site was the calculated, to calculate the measured intensity per unit area ing.

  According to the total reflection X-ray fluorescence spectrometer of the present invention, the area of the measurement site in the field of view of the detector is calculated, and based on the calculated area of the measurement site and the measured intensity measured by the detector, per unit area Therefore, it is possible to accurately analyze an arbitrary measurement site in the vicinity of the edge of a disk-shaped sample such as a wafer.

  In the total reflection X-ray fluorescence analyzer of the present invention, the stage has an incident angle adjusting means for changing the incident angle by changing the inclination of the sample, and the reference X-rays generated uniformly from the sample surface The control means for changing the incident angle at the arbitrary measurement site in the incident angle adjusting unit so that the measurement intensity at the arbitrary measurement site matches the measurement intensity at the reference site serving as a reference on the surface of the sample. Preferably, the control means uses the measured intensity per unit area calculated by the calculating means as the two measured intensities to be matched.

  According to this preferable configuration, an accurate measurement intensity can be obtained for an arbitrary measurement site in the peripheral portion near the edge of the sample, and the incident angle of the primary X-ray can be appropriately corrected.

  Hereinafter, a total reflection X-ray fluorescence analyzer which is an embodiment of the present invention will be described. As shown in FIG. 1, the total reflection X-ray fluorescence spectrometer 1 uses a spectroscopic element 13 to monochromatize X-rays 12 from an X-ray tube 11 on a surface Sa of a disk-like sample such as a silicon wafer. The X-ray source 6 that irradiates the next X-ray 14 at a minute incident angle θ, for example, 0.05 °, the XYθ stage 22 that rotates and moves the placed sample S, and the swivel stage 23 that adjusts the inclination of the sample S. , A detector 16 such as an SSD for measuring the intensity of the fluorescent X-ray 15 generated from the sample S, and a beam sensor constituting an initial position detecting means 20 for detecting the initial position of the sample S relative to the detector 16. 24, based on the initial position detected by the initial position detecting means 20 and the direction and amount of movement by the stage 21, the area of the measurement site in the field of view of the detector 16 is calculated and calculated. Based on the area of the fixed part and the measured intensity measured by the detector 16, the calculating means 31 for calculating the measured intensity per unit area and the control means 30 for controlling the swivel stage 23 as the incident angle adjusting means are provided. Prepare.

  As shown in FIG. 2, the beam sensor 24 includes an irradiation unit 24a that irradiates a band-shaped line beam L, and a light receiving unit 24b that is arranged at a position facing the irradiation unit 24a and receives the line beam L in a linear shape. The peripheral portion in the vicinity of the edge of the sample S is arranged at a position where a part of the line beam L is shielded. In the illustrated beam sensor 24, the irradiating unit 24a and the light receiving unit 24b are shown as one body, but may be separate. The stage 21 uses a known positioning device (refer to Japanese Patent Laid-Open No. 8-161049), and the XYθ stage 22 includes a sample stage 22a on which the sample S is placed and a drive unit 22b that drives the sample stage 22a. It is configured.

  As shown in FIG. 3, the field of view F of the detector 16 is circular at the height of the surface Sa of the sample and has a predetermined field of view. In the initial state of the stage 21, the center 25 of the field of view F of the detector 16 and the sample It coincides with the center of the table 22a. The sample stage 22a can move in the XY directions without changing the orientation of the sample S in the XY coordinates fixed in the space with the center 25 of the field of view F of the detector 16 as the origin (0, 0), and the center (rotation) of itself. (Axis) can be rotated in the φ direction. The sample S is arranged so that the center 51 of the sample S coincides with the center of the sample stage 22a in the initial state, and in a predetermined direction of the sample stage 22a in the initial state, for example, the notch N direction of the sample S (the direction of the sample S). The sample is placed on the sample stage 22a by a robot hand (not shown) so that the direction from the center 51 to the notch N matches. However, they usually do not match perfectly and are slightly off. The initial position with respect to the detector 16 is detected using the beam sensor 24 for the sample S placed in such a manner as follows.

  When the stage 21 is controlled by the control means 30 and the sample stage 22a on which the sample S is placed is rotated 360 degrees, according to the rotation angle, that is, the deviation between the center of the sample stage 22a and the center 51 of the sample S and the notch The amount of light received by the beam sensor 24 (the length of Lb (FIG. 2)) changes according to the notch of N. Since the dimensional shape of the sample S is known, the position of the center 51 of the sample S and the position of the notch N with respect to the center of the sample stage 22a in the initial state, that is, the center 25 of the visual field of the detector 16 from the change in the amount of received light according to the rotation angle. Is obtained by the control means 30. This is the initial position of the sample S with respect to the detector 16, and the beam sensor 24, the stage 21 and the control means 30 constitute the initial position detection means 20.

The stage 21 receives a command from the control means 30, and moves the placed sample S from the initial position in the XY direction without changing the orientation of the sample S, thereby detecting an arbitrary measurement site on the surface of the sample S. Move into 16 fields of view F. The calculation means 31 included in the control means 30 is based on the initial position of the sample S detected by the initial position detection means 20 and the direction and amount of movement of the sample S by the stage 21 after the movement of the sample S relative to the detector 16. The position of is calculated. Based on the calculated position of the sample S relative to the detector 16, the predetermined dimension shape of the sample S, and the predetermined dimension shape of the field of view F of the detector 16 at the height of the sample surface, The area of the sample surface in the field of view F, that is, the area of the measurement site is calculated. For example, when the measurement site occupies the entire field of view F of the detector 16 at the center of the sample S, the area of the field of view is equal to the area of the measurement site, but the measurement site is the peripheral portion near the edge of the sample S. In the case where only a part of the visual field F is occupied, the area of the measurement site is smaller than the visual field area. The calculation means 31 further calculates a measurement intensity per unit area based on the calculated area of the measurement site and the measurement intensity measured by the detector 16. Here, the unit area may be a visual field area or a value irrelevant to the visual field area, for example, 1 cm ² .

  The stage 21 has a swivel stage 23 as incident angle adjusting means, and changes the incident angle θ by changing the tilt of the sample. Then, the control means 30 performs the measurement intensity at any measurement site in addition to the measurement intensity at the reference site serving as the reference on the surface of the sample for the reference X-rays generated uniformly from the sample surface in order to perform the above-described center intensity correction. So that the incident angle adjustment means changes the incident angle at the arbitrary measurement site. Here, the control means 30 uses the measurement intensity of the reference X-ray per unit area calculated by the calculation means 31 as the two measurement intensities to be matched.

The operation of the total reflection X-ray fluorescence spectrometer 1 of this embodiment will be described. First, correction of the incident angle of the primary X-ray will be described. When the sample S is placed on the sample table 22a, the initial position of the sample S is obtained by the initial position detecting means 20 as described above. That is, as shown in FIG. 3, for example, if the center 25 of the field of view F of the detector 16 is the origin (0, 0) of the XY coordinates, the coordinates (x ₀₎ of the center 51 of the sample S, which is the initial position of the sample S. , Y ₀ ). A portion centered on the center 25 of the field of view F, that is, a sample portion centered on the center of the sample stage 22a at the initial position, is a reference on the surface Sa of the sample with respect to the reference X-ray 5 generated uniformly from the surface Sa of the sample. The reference X-ray 5 is uniformly generated from the surface Sa of the sample by adjusting the stage angle by the swivel stage 23 so that the incident angle θ of the primary X-ray 14 is appropriate to the reference site 50. For example, the reference intensity I ₀ of the Si-Kα line is measured. In this case, since the reference part 50 is a part near the center 51 of the sample S, the measurement area is the same as the area M ₀ of the field of view F of the detector 16. This visual field area M0 is _defined as a unit area. The stage angle is adjusted by a method already known from Japanese Patent Laid-Open No. 8-161049.

Next, the drive unit 23 of the stage 21 by a command from the control means 30 as shown in FIG. 4A, the sample S on the sample stage 22 without changing the orientation of the sample S x _1, Y-direction in the X-direction By moving the distance y ₁ , for example, a desired measurement site 53 that is a site near the center of the sample S is arranged in the field of view F of the detector 16. At this time, the center 51 of the sample S after the movement is in the position of the XY coordinates (x ₀ + x ₁ , y ₀ + y ₁ ). By the calculation means 31, the coordinates (x ₀ + x ₁ , y ₀ + y ₁ ) of the center 51 of the sample S, the sample size and shape, for example, the radius of the silicon wafer and the field size of the detector, for example, the radius of the circular field F are obtained. Based on this, the measurement area of the measurement site 53 that is a site near the center of the sample S is calculated. In this case, since the measurement site 53 is near the center of the sample S, the measurement area is the same as the area M ₀ of the field of view F of the detector 16.

The measurement site 53, which is near the center of the sample S, is irradiated with the primary X-ray 14, and the incident angle θ is changed to the swivel stage 23 while measuring the measurement intensity I ₁ of the Si-Kα ray. units measured intensity I ₁ of the area M Si-K [alpha line per _0, is matched to the measured intensity I ₀ of the Si-K [alpha line per unit area M ₀ obtained in the reference part 50, a stage angle at that time with θ ₁ is stored in the control means 30.

Next, as shown in FIG. 4B, the stage 21 moves a distance of x _{2 in} the X direction and y _{2 in} the Y direction without changing the orientation of the sample S from the initial position of the sample S by a command from the control means 30. Then, a desired measurement site 52 that is a peripheral portion in the vicinity of the edge of the sample S is arranged in the visual field F of the detector 16. At this time, the sample S occupies only a part of the field of view F of the detector and is smaller than the field of view M _{0 of the} detector 16, but the coordinates (x ₀ + x ₂ , y ₀ + y ₂ ) of the center 51 of the sample S are calculated by the calculation means 31. in the same manner as above using a measuring area M ₁ of the measurement site 52 shown by oblique lines are calculated. This was irradiated to the measuring site 52 primary X-ray 14, by changing the incident angle θ to the swivel stage 23 while measuring the measured intensity I ₂ of the Si-K [alpha line, per unit area M ₀ at the measurement site 52 The measured intensity I ₂ × (M ₀ / M ₁ ) of the Si-Kα line is matched with the measured intensity I ₀ of the Si-Kα line per unit area M ₀ obtained in the reference region 50, and the stage at that time storing an angle theta ₂ to the control unit 30.

According to the total reflection X-ray fluorescence analysis apparatus 1 of the present embodiment, the measurement site 52 in the peripheral portion in the vicinity of the edge where only a part of the field of view F of the detector occupies the accurate unit area M ₀ . By obtaining the measured intensity I ₂ × (M ₀ / M ₁ ) of the reference X-ray 5, the incident angle θ of the primary X-ray can be appropriately corrected.

Next, a case where the analysis target element of the disk-shaped sample S is measured will be described. In the same manner as described above, the sample S is moved on the stage 21 to place a desired measurement site in the field of view F of the detector 16. In the case of the measurement site 53 occupying the entire field of view F of the detector 16, the measurement area calculated by the calculation means 31 is the same as the area M ₀ of the field of view F of the detector 16. Next, the measurement site 53 is irradiated with the primary X-ray 14, the stage angle is set to the stored stage angle θ _1, and the intensity of the fluorescent X-ray 15 generated from the sample S is measured. Since the measurement site 53 occupies the entire visual field F of the detector 16, the measurement area calculated by the calculation means 31 is the same as the area M ₀ of the visual field F of the detector 16, and the analysis target generated from the sample S the intensity K ₀ per unit area M ₀ of the fluorescent X-ray 15 of the element is measured by the detector 16, obtains a quantitative analysis using the measured intensities K _0.

In the case of the detector 16 measuring sites 52 occupies only part of the field of view F of the measurement area is calculated by the calculating means 31 becomes the M _1. Next, the measurement site 52 that occupies only a part of the visual field F of the detector 16 is irradiated with primary X-rays, and the stage angle is set to the stored stage angle θ ₂ , and the analysis target element generated from the sample S is detected. The intensity K ₁ of the fluorescent X-ray 15 is measured, and the calculation means 31 calculates the measured intensity K ₁ × (M ₀ / M ₁ ) of the fluorescent X-ray 15 per unit area M ₀ . A quantitative analysis value is obtained using the measured intensity K ₁ × (M ₀ / M ₁ ) of the fluorescent X-ray 15 per unit area M ₀ .

According to the total reflection X-ray fluorescence spectrometer 1 of the present embodiment, the areas of the measurement parts 52 and 53 in the visual field F of the detector 16 are calculated, and the calculated areas of the measurement parts 52 and 53 and the detector 16 are calculated. Since the measured intensity of the fluorescent X-ray 15 per unit area M ₀ is calculated based on the measured intensity of the fluorescent X-ray 15, the detector in the vicinity of the edge of the disk-shaped sample S such as a silicon wafer is detected. Accurate analysis can be performed for any measurement site that occupies only a part of the 16 fields of view F. The peripheral part near the edge where the disk-shaped sample S is likely to be contaminated, for example, an area of several millimeters along the edge of the disk-shaped sample S can be measured to identify the contaminated part.

In the present embodiment, the intensity of the Si-Kα ray that is the reference X-ray 5 is set to the incident angle θ of the primary X-ray 14 at the sample site centered on the center of the sample stage 22a at the initial position that is the reference site 50 (see FIG. The reference angle I ₀ is measured by adjusting the stage angle so that 1) is appropriate, but the reference portion is another position of the surface Sa of the sample where the deflection of the disk-shaped sample S does not occur. Also good. Although the Si-Kα ray generated from the silicon wafer that is the sample S is used as the reference X-ray 5, the element is not limited to the main component that is uniformly distributed in the sample S, but is also uniformly distributed in the film formed in the sample S X-ray fluorescence may be used.

In addition, about correction | amendment of the incident angle of a primary X-ray, the area of a measurement site | part can also be made into a unit area as follows. The reference intensity I ₀ of the Si—Kα line of the reference region 50 is measured in the same manner as when the visual field area M ₀ is the unit area. Area of the reference site 50 is the same as the field area M _0.

In the same manner as described above, the measurement area M ₀ is calculated for the measurement site 53 shown in FIG. 4A. While measuring the measurement intensity I ₁ of the Si—Kα ray at the measurement site 53, the incident angle θ is changed to the swivel stage 23, and the measurement intensity I ₁ of the Si—Kα ray per unit area M ₀ at the measurement site 53 is obtained. The measured intensity I ₀ of the Si-Kα ray per unit area M ₀ obtained at the reference region 50 is matched.

In the same manner as above, the measurement area M ₁ of the measurement site 52 shown by hatching shown in Figure 4B is calculated. The calculation means 31 calculates the measured intensity I ₀ × (M ₁ / M ₀ ) of the Si-Kα line per unit area M ₁ of the reference region 50. While measuring the measurement intensity I ₂ of the Si—Kα ray at the measurement site 52, the incident angle θ is changed to the swivel stage 23, and the measurement intensity I ₂ of the Si—Kα ray per unit area M ₁ at the measurement site 52 is obtained. And the calculated intensity I ₀ × (M ₁ / M ₀ ) of the Si-Kα line per unit area M ₁ of the reference region 50.

According to this example, the measured unit area of the reference portion 50 calculated from the measured intensity I ₂ of the Si—Kα ray of the measurement portion 52 in the vicinity of the edge where the sample S occupies only a part of the field of view F of the detector is calculated. Since it matches the intensity I ₀ × (M ₁ / M ₀ ) of the Si-Kα ray per M _1, the incident angle θ of the primary X-ray can be corrected appropriately.

1 is a schematic view of a total reflection X-ray fluorescence spectrometer that is an embodiment of the present invention. It is the arrangement | positioning figure which showed the relationship between the beam sensor of the same apparatus, and the sample position on a sample stand. It is a figure which shows the initial position of the sample of the apparatus. It is a figure which shows the measurement area of the center vicinity site | part of the sample of the apparatus. It is a figure which shows the measurement area of the measurement site | part of the peripheral part of the edge vicinity of the sample of the apparatus.

Explanation of symbols

1 Total reflection X-ray fluorescence analyzer 5 Reference X-ray (Si-Kα ray)
14 Primary X-ray 15 Fluorescent X-ray 16 Detector (SSD)
20 Initial position detection means 21 Stage 23 Incident angle adjustment means (swivel stage)
24 Beam sensor 30 Control means 31 Calculation means 50 Reference part S Sample

Claims (2)

A total reflection X-ray fluorescence analyzer that makes primary X-rays incident on a surface of a disk-shaped sample at a minute incident angle and measures the intensity of the generated fluorescent X-rays with a detector,
An initial position detecting means for detecting an initial position of the sample with respect to the detector;
A stage for moving any measurement site on the surface of the sample into the field of view of the detector by moving the sample from the initial position;
Based on the initial position detected by the initial position detector and the direction and amount of movement by the stage , the position after movement of the sample with respect to the detector is calculated, and the position after movement of the sample with respect to the calculated detector, Based on the predetermined size and shape of the sample and the predetermined size and shape of the field of view of the detector at the height of the sample surface, the area of the measurement site, which is the area of the sample surface within the field of view of the detector, was calculated and calculated A total reflection X-ray fluorescence spectrometer comprising: a calculation means for calculating a measurement intensity per unit area based on an area of a measurement site and a measurement intensity measured by the detector. In claim 1,
The stage has incident angle adjusting means for changing the incident angle by changing the tilt of the sample,
With respect to the reference X-rays generated uniformly from the sample surface, the arbitrary measurement is performed on the incident angle adjusting means so that the measurement intensity at the arbitrary measurement site matches the measurement intensity at the reference site serving as the reference on the surface of the sample. Comprising control means for changing the incident angle at the site;
The total reflection fluorescent X-ray analyzer using the measurement intensity per unit area calculated by the calculation means as the measurement intensity to be matched by the control means.

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