JP2002122557A - Method and apparatus for fluorescent x-ray analysis - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus, for a fluorescent X-ray analysis, wherein the shape of a specimen can be decided precisely by a method wherein W-L β rays or the like are used as a primary X-ray source, the surface of a silicon substrate is irradiated with primary X-rays at a prescribed very small angle of incidence, the kind of a contaminant is decided on the basis of the energy of fluorescent X-rays from the specimen and the existence amount of the contaminant is decided on the basis of the intensity of the fluorescent X-rays. SOLUTION: An angle of irradiation ϕa and an angle of irradiation ϕb are decided in such a way that a value in which the intensity Ia2 of fluorescent X-rays from a standard sample 2 is multiplied by the ratio PF1/PF2 of the particle size factor of a standard sample 1 to that of the standard sample 2 becomes close to the value of the intensity Ia1 of fluorescent X-rays from the standard sample 1. On the basis of the intensity Ia3 of fluorescent X-rays and the intensity Ib3 of fluorescent X-rays regarding a sample to be measured at the decided angles of irradiation ϕa, ϕb, the shape of the specimen is decided. Therefore, the shape of the specimen regarding the sample to be measured can be decided precisely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray fluorescence analysis method and apparatus for measuring an X-ray fluorescence of an object, such as a silicon substrate, on a sample surface of a sample.

[0002]

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

[0003]

Incidentally, it is generally known that, in the total reflection X-ray fluorescence analysis, the incident angle dependence of the intensity of the X-ray fluorescence changes depending on the adhesion form of the object to be measured (contaminant). . For example, as shown in FIG. 4, the fluorescent X-ray 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 SiO ₂ as shown in FIG. To do so, as shown in FIG.
FIG. 5B shows a case where the particles exist in a granular form as shown in FIG.
As shown in FIG. 5C, or in the case of being present in the oxide film SiO ₂ or at the interface between the oxide film SiO ₂ and silicon Si as shown in FIG. Show. Conversely, the attachment form of the object can be determined from the incident angle dependence of the fluorescent X-ray intensity.

[0004] As described above, if the form of attachment of the object to be measured becomes clear, the source of the object to be measured (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, the contaminant is considered to be 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. ,
From the result, if the attachment form of the object is determined visually (qualitatively), the determination of the attachment form of the object becomes inaccurate because it may depend on the subjectivity of the analyst. There was a problem.

An object of the present invention is to provide a method and an apparatus for X-ray fluorescence analysis capable of solving the above problems and accurately determining the form of an object to be measured.

[0007]

In order to achieve the above object, a method of X-ray fluorescence analysis according to claim 1 of the present invention irradiates a sample surface with primary X-rays and applies a primary X-ray to the sample surface. This is a method for measuring fluorescent X-rays generated from an object, wherein the standard X-rays of the standard samples 1 and 2 having the same abundance of the object but different in the form of the object are different from each other. And the intensity of fluorescent X-rays is measured. For any two irradiation angles φa, φb (φa <φb) among the plurality of irradiation angles φ1 to φn, the ratio of the fluorescent X-ray intensities Ia1, Ib1 of the standard sample 1 is obtained as the particle size coefficient PF1 of the standard sample 1, 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. In the present invention, the fluorescent X-ray intensity ratio at two irradiation angles is defined as a particle size coefficient PF. And Ia2 · PF1 / PF
The irradiation angles φa and φb are set so that the value of 2 approaches the value of Ia1.
Is determined, and from the fluorescence X-ray intensities Ia3 and Ib3 of the sample to be measured at the determined irradiation angles φa and φb,
This determines the form of the device under test.

According to a fifth aspect of the present invention, there is provided an X-ray fluorescence spectrometer for irradiating a sample surface with primary X-rays and measuring X-ray fluorescence generated from an object to be measured existing 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. Measuring means for measuring the intensity of X-rays; and arbitrary two irradiation angles φa among the plurality of measured irradiation angles.
, Φb (φa <φb), the fluorescence X of the standard sample 1
The ratio between the line intensities Ia1 and Ib1 is determined as the particle size coefficient PF1 of the standard sample 1, and the ratio between the fluorescent X-ray intensities Ia2 and Ib2 of the standard sample 2 is determined as the particle size coefficient PF2 of the standard sample 2.
The irradiation angle φ is adjusted so that the value of 1 / PF2 approaches the value of Ia1.
a calculating means for determining a and φb; and a form determining means for determining the form of the object to be measured from the intensities Ia3 and Ib3 of the fluorescent X-rays of the sample to be measured at the determined irradiation angles φa and φb. .

According to the present invention, the ratio PF1 of the particle size coefficient between the standard sample 1 and the standard sample 2 is added to the fluorescent X-ray intensity Ia2 of the standard sample 2.
The value multiplied by / PF2 is the fluorescent X-ray intensity Ia1 of the standard sample 1.
The irradiation angles φa and φb are determined so as to approach the value of, and the form of the object to be measured is determined from the fluorescent X-ray intensities Ia3 and Ib3 of the sample to be measured at the determined irradiation angles φa and φb. The form of the measured object of the sample to be measured can be accurately determined.

In the present invention, the case where the value of Ia2 · PF1 / PF2 approaches the value of Ia1 is defined as (Ia2 / Ia1) · (P
This means that the coefficient A approaches 1 when F1 / 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 0.3 to
3 is preferable, 0.4 to 2.5 is more preferable, and 0.5
To 2, more preferably 0.7 to 1.5, most preferably 0.8 to 1.2.

Preferably, the determined irradiation angle φa,
The form of the measured object is determined from the intensity ratio or the intensity difference of the fluorescent X-rays for the sample to be measured at φb. Also,
For example, the form of the object to be measured is also determined by first-order differentiation of the measured fluorescent X-ray intensity curve for a plurality of irradiation angles. 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 the form of a film, a grain, 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.

[0012]

Embodiments of the present invention will be described below 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 present apparatus includes an X-ray source 2 for generating X-rays, and diffracts X-rays from the X-ray source 2 to monochromatic by diffracting the X-rays.
A small predetermined incident angle (for example, 0.05 ° to 0.2 °) toward the surface of the sample 50 such as a silicon substrate on
°) and the fluorescent X-rays B3 from the sample 50 that has received the primary X-rays B1 facing the surface of the sample 50
And a detector 4 for detecting 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 means constitute a measuring means 5,
This measuring means 5 is provided for 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 be measured.
The primary X-rays are irradiated with a plurality of different irradiation angles φ1 to φ1.
Irradiate with φn and measure the intensity of fluorescent X-ray B3.

The calculating means 6 of the present apparatus is capable of arbitrarily setting two irradiation angles φa and φb among the plurality of measured irradiation angles.
(Φa <φb), the fluorescent X-ray intensity I of the standard sample 1
The ratio between a1 and Ib1 is obtained as the particle size coefficient PF1 of the standard sample 1, and the ratio between 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 irradiation angles φa, φa are set so that the value of F2 approaches the value of Ia1.
Determine b. Further, the morphology determining means 8 determines the intensity Ia3, Ib3 of the fluorescent X-rays for the sample to be measured at the determined irradiation angles φa, φb, for example, the intensity ratio Pa of Ia3 and Ib3.
From F3, the form of the measured object is determined.

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, total reflection X-ray fluorescence analysis (measurement at an irradiation angle φc to be described later) is performed on a standard sample having a known contamination amount in advance, The relationship between the amount of contamination and the fluorescent X-ray intensity will be clarified. That is, a calibration curve indicating the relationship between the amount of contamination and the fluorescent X-ray intensity is created. Next, a total reflection X-ray fluorescence measurement is performed on the sample to be measured whose contamination amount is unknown,
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 this embodiment,
The adhered form of the measured object in the standard sample 1 is a film form, and the adhered form of the measured object in the standard sample 2 is a granular form.

In this embodiment, a film-like standard sample 1
Is left in a hydrogen fluoride atmosphere for 30 minutes,
Dissolve the silicon oxide film on the sample surface in hydrogen fluoride, then leave the sample in the air, dry the solution on the silicon substrate, and change the adhesion form of the object to be measured on the silicon substrate from film to granular. To obtain a granular standard sample 2. In this case, the abundance of the measured object does not change.

As described above, a comparison between the case where the object to be measured in FIG. 5A is present on the substrate in the form of a film and the case where the object to be measured is present in the form of particles in FIG. Are equal, the relationship between the intensity of the fluorescent X-ray B3 and the incident angle of the primary X-ray B1 is greatly 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 is also greatly different.

In the present apparatus, first, 1
Next, the standard 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 to obtain fluorescent X-rays.
Measure the intensity of line B3.

Next, the operation of the calculating means 6 will be described for two cases in which two different irradiation angles φa and φb are selected from the data of a plurality of measured irradiation angles.

Case 1: Irradiation angle φa = 0.05 °, φ
When b = 0.15 ° is selected In this case, Ni-K for the film-form standard sample 1 is used.
The α-ray intensity is 20.65 cps at 0.05 °
It is 335.65 cps at 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 = 2
0.65 / 335.65 = 0.06. The intensity of the Ni—Kα ray of the granular standard sample 2 was 158.79 cps at 0.05 ° and 444.05 at 0.15 °.
cps. Therefore, the particle size coefficient P of the standard sample 2, which is the ratio of the fluorescent X-ray intensities Ia2 and Ib2 of the standard sample 2,
When F2 is obtained, PF2 = 158.79 / 444.05
= 0.36. Thereby, the particle size coefficients PF1 and PF
The ratio of 2 is PF1 / PF2 = 0.06 / 0.36 = 1 /
It becomes 6.

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

Here, PF1 / PF2 = 1/6 determined as described above so that the coefficient A becomes a standard approaching 1;
The ratio of the fluorescent X-ray intensity Ia2 of the granular standard sample 2 to the irradiation angle of the primary X-ray B1 as shown in FIG. 2A and the fluorescent X-ray intensity Ia1 of the film-shaped standard sample 1, that is, Ia2 / I.
Using A1, A = (Ia2 / Ia1) · (1/6), and the coefficient A for the irradiation angle of the primary X-ray B1 shown in FIG.
Plot the relationship. In this case, as shown in FIG. 2C, A = 1 near the irradiation angle of 0.07 °. That is, when preparing a calibration curve used in the quantitative analysis, it is preferable to perform total reflection X-ray fluorescence analysis at an irradiation angle φc = 0.07 ° where the coefficient A is close to 1 under this condition.

Case 2: Irradiation angle φa = 0.09 °, φ
When b = 0.17 ° is selected Also in this case, the same calculation as in Case 1 is performed, and FIG.
The relationship between the coefficient A and the irradiation angle of the primary X-ray B1 shown in FIG. As shown in FIG. 2B, the irradiation angle is 0.09.
In the vicinity of °, A = 1. That is, when preparing a calibration curve used in the quantitative analysis, it is preferable to perform the fluorescent X-ray analysis at an irradiation angle φc = 0.09 ° at which the coefficient A is close to 1 under this condition.

When, for example, the irradiation angles φa = 0.09 ° and φb = 0.17 ° determined by the arithmetic means 6, the total reflection X-ray fluorescence measurement of the film-like standard sample 1 was performed. At an intensity of 0.09 °.
It is 419.58 cps at 60 cps and 0.17 °. Therefore, the fluorescent X-ray intensity I for the standard sample 1
The particle size coefficient PF1 of the standard sample 1, which is the ratio of a1 and Ib1, is P
F1 = 103.60 / 419.58 = 0.25.
When the intensity of the Ni-Kα ray is converted into the amount of nickel contamination using the above-mentioned calibration curve at the irradiation angle φc = 0.09 °, it becomes about 1.5 × 10 ¹² atoms / cm ² . For the granular standard sample 2, the intensity of the Ni-Kα ray was 0.09 °.
404.91 cps at 0.17 ° and 415.
30 cps. Therefore, 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 PF2 = 404.91 / 415.30 =
0.97. Thereby, the particle size coefficients PF1 and P
The ratio of F2 is PF1 / PF2 = 0.25 / 0.97 ≒ 1
/ 4.

At this time, the coefficient A is A = (Ia2 / Ia1)
(PF1 / PF2) = (404.91 / 103.6)
0) ・ (0.25 / 0.97) ≒ 1.

Next, for the sample to be measured whose adhesion form is unknown, the determined irradiation angle φa = 0.0
The total reflection fluorescent X-ray is measured at 9 ° and φb = 0.17 °. In the case of a granular sample to be measured, as in 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 at 0.17 °.
cps. Therefore, the particle size coefficient PF3 of the sample to be measured, which is the ratio of the fluorescent X-ray intensities Ia3 and Ib3 of the sample to be measured, is PF3 = 404.91 / 415.30 =
0.97.

The form determining means 8 calculates, for example, the particle size coefficient PF based on the value of the particle size coefficient PF3 for the sample to be measured.
Using PF = 0.5 as a criterion, it is determined that the film shape is obtained when PF ≦ 0.5, and the particle shape is obtained when PF> 0.5. Of course, the standard of 0.5 changes depending on analysis conditions and necessary information. In the present embodiment, PF3 = 0.97
Since PF> 0.5, the adhesion form of the measured object is determined to be granular.

Thus, according to the present invention, Ia2 · PF1 / PF
2 is closer to the value of Ia1, that is, the coefficient A is 1
The irradiation angles φa and φb are determined so as to approach the above. From the ratio PF3 of the fluorescent X-ray intensities Ia3 and Ib3 of the sample to be measured at the determined irradiation angles φa and φb, the adhesion form of the object to be measured is accurately determined. Can be determined.

In this embodiment, the attachment form of the object to be measured is determined from the intensity ratio of the fluorescent X-rays with respect to the sample to be measured. Thus, the attachment form of the object to be measured may be determined.

As shown in FIG. 5, even if the adhesion form of the object to be measured is determined by the curve of FIG. 3 obtained by first-order differentiation of the fluorescent X-ray intensity curve for a plurality of measured irradiation angles. Good. That is, the fluorescent X-ray intensity curve of the granular sample to be measured in FIG. 5B has a peak position ahead of the fluorescent X-ray intensity curve of the film-shaped standard sample in FIG. From the curves of FIGS. 3A and 3B obtained by first-order differentiation of the fluorescent X-ray intensity curves of FIGS. 5A and 5B, respectively, the peak position P2 of FIG. Based on the fact that the sample is located ahead of the peak position P1 in FIG. 3 (A), it is possible to determine that the adhesion form of the measurement target sample to the measured object is granular.

[0031]

As described above, according to the present invention,
The irradiation angle φa is set so that the value obtained by multiplying the fluorescent 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. , Φb, and the determined irradiation angles φa, φb
X-ray intensity Ia3,
Since the form of the measured object is determined from Ib3, the form of the measured object of the sample to be measured can be accurately determined.

[Brief description of the drawings]

FIG. 1 is a side view showing an X-ray fluorescence analyzer according to one embodiment of the present invention.

FIGS. 2A to 2C are characteristic diagrams showing a relationship between a coefficient A and an irradiation angle.

FIGS. 3A and 3B are characteristic diagrams showing the relationship between the first-order differentiated fluorescent X-ray intensity and the irradiation angle of the primary X-ray.

FIGS. 4A to 4C are side views showing a form of an object to be measured.

FIGS. 5A to 5C are characteristic diagrams showing a relationship between fluorescent X-ray intensity and primary X-ray irradiation angle.

[Explanation of symbols]

5 measuring means, 6 arithmetic means, 8 form determining means, 50
... sample, B1 ... primary X-ray, B3 ... fluorescent X-ray.

Claims (5)

[Claims] 1. A fluorescent X-ray analysis method for irradiating a sample surface with primary X-rays and measuring fluorescent X-rays generated from an object to be measured existing on the surface of the sample, wherein the amount of the object to be measured is The primary X-rays are irradiated at different irradiation angles φ1 to φn, respectively, on the standard samples 1 and 2 which are equal but have different forms of the object to be measured, and the intensity of the fluorescent X-rays is measured. Irradiation angles φa,
For φb (φa <φb), the ratio of the fluorescent X-ray intensities Ia1 and Ib1 of the standard sample 1 is determined as the particle size coefficient PF1 of the standard sample 1, and the ratio of the fluorescent X-ray intensities Ia2 and Ib2 of the standard sample 2 is determined. Calculated as the particle size coefficient PF2, Ia2 · PF1 /
The irradiation angles φa and φa are set so that the value of PF2 approaches the value of Ia1.
An X-ray fluorescence analysis method for determining φb and determining the form of the object from the X-ray fluorescence intensity Ia3, Ib3 of the sample to be measured at the determined irradiation angles φa, φb. 2. The X-ray fluorescence analysis method according to claim 1, wherein a form of the object is determined from an intensity ratio or an intensity difference of X-ray fluorescence with respect to the sample to be measured at the determined irradiation angles φa and φb. 3. The X-ray fluorescence analysis method according to claim 1, wherein the form of the object to be determined is an attachment form of the object. 4. The X-ray fluorescence analysis method according to claim 1, wherein the form of the object to be determined is the size of the object. 5. An X-ray fluorescence analyzer for irradiating a sample surface with primary X-rays and measuring fluorescent X-rays generated from an object to be measured existing on the surface of the sample, wherein the amount of the object to be measured is Measuring means for measuring the intensity of fluorescent X-rays by irradiating the primary X-rays at a plurality of different irradiation angles φ1 to φn, respectively, on the standard samples 1 and 2 which are equal but have different forms of the object to be measured; For any two irradiation angles φa, φb (φa <φb) of the plurality of measured irradiation angles, the ratio of the fluorescent X-ray intensities Ia1, Ib1 of the standard sample 1 is determined by the particle size coefficient P of the standard sample 1.
F1 and the fluorescent X-ray intensity Ia2, Ib2 of the standard sample 2
Is determined as the particle size coefficient PF2 of the standard sample 2, and Ia2
Calculation means for determining the irradiation angles φa and φb so that the value of PF1 / PF2 approaches the value of Ia1; and X-ray fluorescence analyzer comprising: a morphological determining means for determining a morphology of an object to be measured.