JP2004354392A5 - - Google Patents

Description

X-ray fluorescence analysis method and apparatus

  The present invention relates to an X-ray fluorescence analysis method and apparatus for X-ray fluorescence measurement of an object to be measured existing on the surface of a sample such as a silicon substrate.

  2. Description of the Related Art Conventionally, it has been known to perform total reflection X-ray fluorescence analysis in order to determine, for example, the type and abundance of a contaminant that is an object to be measured attached to a silicon substrate surface. In order to analyze contaminants existing in the vicinity of the silicon substrate surface as the object to be measured, mainly transition metals such as iron, nickel, copper, and zinc, for example, using a W-Lβ ray or the like as a primary X-ray source, Primary X-rays are irradiated on the surface of the silicon substrate at a predetermined small incident angle, and the type is determined from the energy of the fluorescent X-rays from the object to be measured, and the amount is determined from the intensity of the fluorescent X-rays.

By the way, it is generally known that, in the total reflection X-ray fluorescence analysis, the incident angle dependence of the intensity of the fluorescent X-ray changes depending on the attachment form of the object to be measured (contaminant). As shown in FIG. 3 , for example, the X-ray fluorescence intensity is such that an object to be measured attached to the surface of a silicon substrate having an oxide film is dispersed in a film form on the oxide film SiO2 as shown in FIG. In this case, as shown in FIG. 4 (A) , when it exists in a granular form as shown in FIG. 3 (B) , as shown in FIG. 4 (B) , or as shown in FIG. When it exists at the interface between the oxide film SiO2 and the silicon Si, the incident angle dependency is shown as shown in FIG. 4C . Conversely, the attachment form of the object can be determined from the incident angle dependence of the fluorescent X-ray intensity.

  As described above, if the form of attachment of the object is clarified, the source of the object (contaminant) can be known. For example, if the silicon substrate is contaminated during the wet cleaning process, the contaminant adheres in the form of a film, and if the contamination occurs during the mechanical transport of the silicon substrate, the contaminant adheres in the form of particles. Further, if the contamination occurs during the film formation process of the silicon substrate, it is considered that the contaminant is present in the film.

  However, as in the prior art, the intensity of the fluorescent X-ray was measured by changing the incident angle of the primary X-ray from the relationship between the incident angle dependence of the intensity of the fluorescent X-ray and the form of attachment of the object to be measured. Therefore, if the form of attachment of the object to be measured is determined visually (qualitatively), the determination of the form of attachment of the object to be measured may be inaccurate because it may depend on the subjectivity of the analyst. was there.

  SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a method and an apparatus for X-ray fluorescence analysis that can accurately determine the form of an object to be measured.

In order to achieve the above object, an X-ray fluorescence analysis method according to the present invention provides a method for irradiating a sample surface with primary X-rays and measuring X-ray fluorescence generated from an object to be measured present on the sample surface. X- ray analysis method, wherein the primary X-rays are irradiated at a plurality of different irradiation angles φ1 to φn to measure the intensity of the fluorescent X-rays, and the fluorescent X-rays obtained at arbitrary two irradiation angles are measured. The form of the object to be measured is determined based on the magnitude relationship between the intensities .
According to this configuration, from the magnitude relationship of the fluorescent X-ray intensities obtained at any two different irradiation angles, the form of the measured object is determined based on the incident angle dependence that changes depending on the form of attachment of the measured object. Therefore, the form of the device under test can be accurately determined.

Preferably, the magnitude relationship between the fluorescent X-ray intensities at the two irradiation angles is an intensity ratio or an intensity difference between the fluorescent X-rays , and the form of the object to be measured is determined from this. Further, the form of the object to be measured is also determined by, for example, first-order differentiation of the measured fluorescent X-ray intensity curve with respect to a plurality of irradiation angles.

Preferably, in the X-ray fluorescence analysis method, a plurality of irradiation angles φ1 to φ1 different from each other are applied to the primary X-rays for the standard samples 1 and 2 having the same amount of the object to be measured, but having different forms of the object to be measured. Irradiate with φn and measure the intensity of fluorescent X-rays.
Any two irradiation angles .phi.a among a plurality of irradiation angles φ1~φn, φb (φa <φb) for a plurality of sets of each particle size coefficient of the standard sample 1 the ratio of the fluorescent X-ray intensity of the standard sample 1 Ia1, Ib1 PF1 is obtained, and the ratio of the fluorescent X-ray intensities Ia2 and Ib2 of the standard sample 2 is obtained as the particle size coefficient PF2 of the standard sample 2. In the present invention, the fluorescent X-ray intensity ratio at two irradiation angles is defined as a particle size coefficient PF.
Then, based on the obtained fluorescent X-ray intensities Ia1 and Ia2 and the particle size coefficients PF1 and PF2 , the set of the irradiation angles φa and φb is set so that the value of Ia2 · PF1 / PF2 is closest to the value of Ia1. selected, the selected irradiation angle .phi.a, from the intensity Ia3, Ib3 of X-ray fluorescence for the sample to be measured in .phi.b, it is what determines the form of the object to be measured.

An X-ray fluorescence analyzer corresponding to the preferred X-ray fluorescence analysis method described above irradiates a sample surface with primary X-rays and measures X-ray fluorescence generated from an object to be measured present on the surface of the sample. And irradiating the primary X-rays at a plurality of different irradiation angles φ1 to φn with respect to the standard samples 1 and 2 having the same amount of the object to be measured, but having different adhesion forms of the object to fluoresce. X-ray fluorescence intensity of the standard sample 1 for each of a plurality of sets of arbitrary two irradiation angles φa and φb (φa <φb) among the measurement means for measuring the X-ray intensity and the measured plural irradiation angles. ia1, obtains the ratio of Ib1 as particle size coefficient PF1 of the standard sample 1, seeking fluorescent X-ray intensity Ia2, Ib2 ratio of the standard sample 2 as particle size coefficient PF2 of the standard sample 2, fluorescence for those obtained each set X-ray intensity Ia1, Ia2 and particle size From PF1, PF2, as the value of Ia2 · PF1 / PF2 approaches most to the value of Ia1, irradiation angle .phi.a, a calculating means for selecting a set of .phi.b, the selected irradiation angle .phi.a, for the measurement target sample in .phi.b A morphology determining means for determining the morphology of the object to be measured based on the intensity of the fluorescent X-rays Ia3 and Ib3.

According to this configuration , the value obtained by multiplying the fluorescent sample X-ray intensity Ia2 of the standard sample 2 by the ratio PF1 / PF2 of the particle size coefficients of the standard sample 1 and the standard sample 2 approaches the value of the fluorescent X-ray intensity Ia1 of the standard sample 1. As described above, the irradiation angles φa and φb are selected , and the form of the object to be measured is determined from the intensity Xa3 and Ib3 of the fluorescent X-rays of the sample to be measured at the selected irradiation angles φa and φb. The morphology of the sample under test can be determined.

  In the present invention, the case where the value of Ia2 · PF1 / PF2 approaches the value of Ia1 means that the coefficient A approaches 1 when (Ia2 / Ia1) · (PF1 / PF2) = A. As the coefficient A approaches 1, the form of the DUT can be determined with high accuracy. The range of the coefficient A is preferably from 0.3 to 3, more preferably from 0.4 to 2.5, still more preferably from 0.5 to 2, particularly preferably from 0.7 to 1.5, and from 0.8 to 1. 2 is most preferred.

The form of the measured object to be determined is, for example, the attached form or size of the measured object. The attached form of the measured object refers to a case where the measured object exists on the surface of the silicon substrate in a film shape, a granular shape, or the like. The size of the object to be measured refers to the size of the particle size in the case of a granular shape, and the size of the length, width, and height in the case of a film or other cases.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic side view of a total reflection X-ray fluorescence spectrometer according to an embodiment of the present invention. The apparatus includes an X-ray source 2 for generating X-rays, and diffracts the X-rays from the X-ray source 2 into a single color, and converts the primary X-rays B1 into a sample 50 such as a silicon substrate on a sample stage 70. The spectroscopic crystal 3 which is incident at a small predetermined incident angle (for example, 0.05 ° to 0.2 °) toward the surface of the sample 50 and the sample 50 which has received the primary X-ray B1 facing the surface of the sample 50 And a detector 4 for detecting the fluorescent X-rays B3 from the apparatus, and analyzes the fluorescent X-rays B3 generated from the measured object existing on the sample surface of the sample 50. The sample stage 70 on which the sample 50 is placed is driven by driving means (not shown), and the sample 50 is irradiated with the primary X-ray B1 at an arbitrary irradiation (incident) angle and position.

  The X-ray source 2, the spectral crystal 3, the detector 4, the sample stage 70, and the driving unit constitute a measuring unit 5. The measuring unit 5 has the same amount of the object to be measured, Are irradiated with the primary X-rays at a plurality of different irradiation angles φ1 to φn to measure the intensity of the fluorescent X-rays B3.

  The calculating means 6 of the present apparatus determines the ratio of the fluorescent X-ray intensities Ia1 and Ib1 of the standard sample 1 for any two of the measured irradiation angles φa and φb (φa <φb) to the standard sample. 1 and the ratio of the fluorescent X-ray intensities Ia2 and Ib2 of the standard sample 2 is obtained as the particle size coefficient PF2 of the standard sample 2. The angles φa and φb are determined. Further, the form determining means 8 determines the form of the measured object from the intensity Xa of fluorescent X-rays Ia3 and Ib3, for example, the intensity ratio PF3 of Ia3 and Ib3 for the sample to be measured at the determined irradiation angles φa and φb.

Hereinafter, the operation of the present apparatus will be described.
For example, when performing quantitative analysis of nickel of a contaminant which is an object to be measured on a silicon substrate, a total reflection X-ray fluorescence analysis ( irradiation angle φc (for example, 0.09 °)) to clarify the relationship between the amount of contamination and the fluorescent X-ray intensity. That is, a calibration curve indicating the relationship between the amount of contamination and the fluorescent X-ray intensity is created. Next, total reflection X-ray fluorescence measurement is performed on the sample to be measured whose contamination amount is unknown, and the fluorescent X-ray intensity of the sample to be measured is measured. The intensity is converted to the amount of contamination using the calibration curve. In the present embodiment, the adhered form of the measured object on the standard sample 1 is a film form, and the adhered form of the measured object on the standard sample 2 is a granular form.

  In this embodiment, the silicon oxide film on the surface of the sample is dissolved in hydrogen fluoride by leaving the film-shaped standard sample 1 in a hydrogen fluoride atmosphere for 30 minutes, and then the sample is left in the atmosphere. The solution was dried on the silicon substrate, and the adhesion form of the object to be measured on the silicon substrate was changed from a film shape to a granular shape to obtain a granular standard sample 2. In this case, the abundance of the measured object does not change.

As described above, in the case where the object to be measured shown in FIG. 4 (A) is present in the film form on the substrate, when compared with the case where there granulated in FIG. 4 (B), with equal abundance of the workpiece However, the relationship between the intensity of the fluorescent X-ray B3 and the incident angle of the primary X-ray B1 is significantly different between the film-shaped standard sample 1 and the granular standard sample 2. Therefore, the abundance of the measured object calculated using the calibration curve also differs greatly.

  In this apparatus, first, the primary X-ray B1 is irradiated on the standard sample 1 and the standard sample 2 at a plurality of different irradiation angles φ1 to φn by the measuring unit 5 to measure the intensity of the fluorescent X-ray B3.

Next, the operation of the calculating means 6 will be described for, for example, two cases out of various cases (plural sets) in which two different irradiation angles φa and φb are selected from the plurality of measured irradiation angle data. .

Case 1: When the irradiation angles φa = 0.05 ° and φb = 0.15 ° are selected. In this case, the Ni-Kα ray intensity of the film-form standard sample 1 is 20.65 cps when the intensity is 0.05 °. It is 335.65 cps at 0.15 °. Therefore, when the particle size coefficient PF1 of the standard sample 1, which is the ratio of the fluorescent X-ray intensities Ia1 and Ib1 for the standard sample 1, is obtained, PF1 = 20.65 / 335.65 = 0.06.
The intensity of the Ni—Kα ray of the granular standard sample 2 is 158.79 cps at 0.05 ° and 444.05 cps at 0.15 °. Therefore, when the particle size coefficient PF2 of the standard sample 2, which is the ratio of the fluorescent X-ray intensities Ia2 and Ib2 of the standard sample 2, is obtained, PF2 = 158.79 / 444.05 = 0.36. Thus, the ratio between the particle size coefficients PF1 and PF2 is PF1 / PF2 = 0.06 / 0.36 = 1/6.

  At this time, the coefficient A is A = (Ia2 / Ia1) · (PF1 / PF2) = (158.79 / 20.65) · (0.06 / 0.36) ≒ 1.3.

Case 2: When the irradiation angle φa = 0.09 ° and φb = 0.17 ° are selected
In this case, as a result of total reflection X-ray fluorescence measurement of the film-shaped standard sample 1, the intensity of the Ni-Kα ray is 103.60 cps at 0.09 ° and 419.58 cps at 0.17 °. Therefore, the particle size coefficient PF1 of the standard sample 1, which is the ratio of the fluorescent X-ray intensities Ia1 and Ib1 for the standard sample 1, is PF1 = 103.60 / 419.58 = 0.25. When the intensity of the Ni-Kα ray was converted into the amount of nickel contamination using the calibration curve at the irradiation angle φc = 0.09 ° for the quantitative analysis , it was about 1.5 × 10 ¹² atoms / cm ² . Become.
Regarding the granular standard sample 2, the intensity of the Ni-Kα ray is 404.91 cps at 0.09 ° and 415.30 cps at 0.17 °. Therefore, the particle size coefficient PF2 of the standard sample 2, which is the ratio of the fluorescent X-ray intensities Ia2 and Ib2 for the standard sample 2, is PF2 = 404.91 / 415.30 = 0.97. Thus, the ratio between the particle size coefficients PF1 and PF2 is PF1 / PF2 = 0.25 / 0.97 ≒ 1/4.

At this time, the coefficient A is A = (Ia2 / Ia1) · (PF1 / PF2) = (404.91 / 103.60) · (0.25 / 0.97) ≒ 1. Therefore, among the various cases including Case 1, the coefficient A of Case 2 is close to 1, so that the irradiation angles φa = 0.09 ° and φb = 0.17 ° of Case 2 are determined.

  Next, the total reflection fluorescent X-ray measurement is performed at the determined irradiation angles φa = 0.09 ° and φb = 0.17 ° with respect to the sample to be measured whose adhesion form is unknown. In the case of the granular sample to be measured, similarly to the case of the standard sample 2, the intensity Ia3, Ib3 of the Ni-Kα ray is 404.91 cps at 0.09 ° and 415.30 cps at 0.17 °. . Therefore, the particle size coefficient PF3 of the measurement target sample, which is the ratio of the fluorescent X-ray intensities Ia3 and Ib3 of the measurement target sample, is PF3 = 404.91 / 415.30 = 0.97.

  Based on the value of the particle size coefficient PF3 for the sample to be measured, the morphological determination means 8 determines the particle size coefficient PF, for example, PF = 0.5 as a criterion. Is determined to be granular. Of course, the standard of 0.5 changes depending on analysis conditions and necessary information. In this embodiment, since PF3 = 0.97 and PF> 0.5, the adhesion form of the measured object is determined to be granular.

  Thus, the present invention determines the irradiation angles φa and φb so that the value of Ia2 · PF1 / PF2 approaches the value of Ia1, that is, the coefficient A approaches 1, and determines the determined irradiation angles φa and φb. From the ratio PF3 of the fluorescence X-ray intensities Ia3 and Ib3 of the sample to be measured in the above, the adhesion form of the measurement object can be accurately determined.

  In the present embodiment, the attachment form of the object is determined from the intensity ratio of the fluorescent X-rays for the sample to be measured. The attachment form of the measurement object may be determined.

As shown in FIG. 4 , the attachment form of the measurement object may be determined based on the curve of FIG. 2 obtained by first-order differentiating the fluorescent X-ray intensity curve with respect to a plurality of measured irradiation angles. In other words, the fluorescent X-ray intensity curve of the measured sample of particulate in FIG. 4 (B), there compared to the forward peak position to the fluorescent X-ray intensity curve of the standard sample film-like in FIG. 4 (A), the these fluorescent X-ray intensity curve obtained respectively by first derivative to FIG. 2 (a), the a curve of the (B), the peak position P2 shown in FIG. 2 (B) diagram of Fig. 4 (a), (B) Based on the fact that the sample is located ahead of the peak position P1 of 2 (A) , it is possible to determine that the attachment form of the measurement target sample to the measurement target is granular.

FIG. 1 is a side view showing an X-ray fluorescence analyzer according to one embodiment of the present invention. (A), (B) is a characteristic diagram showing the relationship between the primary differentiated fluorescent X-ray intensity and the primary X-ray irradiation angle. (A)-(C) is a side view which shows the form of an object to be measured. (A)-(C) are characteristic diagrams showing the relationship between the fluorescent X-ray intensity and the primary X-ray irradiation angle.

Explanation of reference numerals

  5: measuring means, 6: calculating means, 8: morphological determining means, 50: sample, B1: primary X-ray, B3: fluorescent X-ray.

Claims (6)

A fluorescent X-ray analysis method of irradiating a sample surface with primary X-rays and measuring fluorescent X-rays generated from an object to be measured existing on a sample surface portion,
The primary X-rays are irradiated at a plurality of different irradiation angles φ1 to φn, and the intensity of the fluorescent X-rays is measured, and the intensity of the fluorescent X-rays obtained at any two irradiation angles is determined based on the magnitude relation of the fluorescent X-ray intensities. An X-ray fluorescence analysis method for determining the form of a measurement object. 2. The fluorescent X-ray analysis method according to claim 1, wherein the magnitude relationship between the fluorescent X-ray intensities at the two irradiation angles is an intensity ratio or an intensity difference between the fluorescent X-rays. In claim 2,
The primary X-rays are radiated at a plurality of different irradiation angles φ1 to φn for the standard samples 1 and 2 having the same abundance of the DUT, but having different forms of the DUT, to reduce the intensity of the fluorescent X-rays. The ratio of the fluorescent X-ray intensities Ia1 and Ib1 of the standard sample 1 was determined as the particle size coefficient PF1 of the standard sample 1 for each of a plurality of arbitrary two irradiation angles φa and φb (φa <φb). The ratio between the fluorescent X-ray intensities Ia2 and Ib2 of the sample 2 is determined as the particle size coefficient PF2 of the standard sample 2, and from the obtained fluorescent X-ray intensities Ia1 and Ia2 and the particle size coefficients PF1 and PF2, Ia2 · PF1 A pair of irradiation angles φa and φb is selected such that the value of / PF2 is closest to the value of Ia1,
An X-ray fluorescence analysis method for determining a form of an object to be measured based on X-ray fluorescence intensities Ia3 and Ib3 of a sample to be measured at the selected irradiation angles φa and φb. The X-ray fluorescence analysis method according to any one of claims 1 to 3, wherein the form of the measured object to be determined is an attached form of the measured object. The X-ray fluorescence analysis method according to any one of claims 1 to 3, wherein the form of the object to be determined is the size of the object. An X-ray fluorescence analyzer for irradiating a sample surface with primary X-rays and measuring X-ray fluorescence generated from an object to be measured present on a sample surface portion,
The primary X-rays are irradiated at different irradiation angles φ1 to φn on the standard samples 1 and 2 which have the same amount of the object to be measured, but have different forms of the object to be measured, so that the intensity of the fluorescent X-rays is increased. Measuring means for measuring;
The measured plurality of arbitrary two irradiation angles .phi.a of irradiation angle, φb (φa <φb) a plurality of sets for each X-ray fluorescence intensity Ia1, particle size ratio of the standard sample 1 of Ib1 of the standard sample 1 The ratio of the fluorescent X-ray intensities Ia2, Ib2 of the standard sample 2 is determined as the particle size coefficient PF2 of the standard sample 2, and the fluorescent X-ray intensity Ia1, Ia2 and the particle size coefficient PF1, Calculating means for selecting a pair of irradiation angles φa and φb from PF2 such that the value of Ia2 · PF1 / PF2 is closest to the value of Ia1;
A fluorescent X-ray analyzer comprising: a form determining means for determining the form of the measured object from the fluorescent X-ray intensities Ia3 and Ib3 of the sample to be measured at the selected irradiation angles φa and φb.

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