JP3286010B2 - X-ray fluorescence analyzer and X-ray irradiation angle setting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of irradiating a test object such as a semiconductor wafer with excitation X-rays, and converting the fluorescent X-rays generated from the test object into an energy dispersion system (EDX, Energy D).
The present invention relates to an X-ray fluorescence analyzer for analyzing with an ispersive X-ray spectrometer) and an X-setting irradiation angle setting method for setting an X-ray irradiation angle for a test object.

[0002]

2. Description of the Related Art Conventionally, by irradiating an X-ray to a test object such as a semiconductor wafer having an optically smooth flat surface at a low incident angle, fluorescence X from a sample attached to the surface of the test object is detected. Total reflection X-ray fluorescence spectrometer (To
tal Reflection X-ray Fluorescence) is known, and information only in the vicinity of the surface of the test object can be obtained at a high S / N ratio by totally reflecting the excited X-rays on the surface of the test object.

Further, the characteristic X-rays generated from the opposite cathode of the X-ray generation source are separated into single characteristic X-rays by a spectral means comprising a dispersive crystal and a slit or the like, and then the monochromatic light is irradiated onto a test object. Reflection X-ray fluorescence analyzer (Japanese Patent Application No. 1-27)
No. 2124), the background noise is reduced by monochromatic excitation X-rays, and the detection limit of trace elements is improved. Widespread.

FIG. 4 is a schematic diagram showing an example of a conventional X-ray fluorescence analyzer. The X-ray fluorescence analyzer includes an X-ray tube 61 for generating an X-ray beam B1 and a spectral crystal 62 for separating an X-ray beam B2 composed of a single characteristic X-ray from the X-ray beam B1. A collimator 63 for blocking other characteristic X-rays, and a test object 60 such as a semiconductor wafer.
Table 64 for supporting the moving table 6 and the moving table 6
4, a table controller 65 for setting the three-dimensional position and the angle with respect to the X-ray beam B2, a detector 66 for detecting the fluorescent X-ray B3 generated from the test object 60, and a signal output from the detector 66. And a distance sensor 68 for measuring the distance to both ends of the test object 60 on both sides of the detector 66. 69 are provided. The X-ray beam B2 is incident on the surface of the test object 60 at an angle at which the X-ray beam is totally reflected, for example, at an angle of about 0.06 degrees. Component information can be obtained.

Each of the distance sensors 68 and 69 emits a laser beam toward the test object 60, and detects a change in the position reflected by the test object 60. By interpolating between the reflection positions by a straight line, it is possible to estimate the vertical position and inclination of the test object 60 immediately below the detector 66.

FIG. 5 is a block diagram showing another example of a conventional X-ray fluorescence analyzer. The X-ray fluorescence analyzer includes an X-ray tube 71 for generating an X-ray beam B1, and an X-ray beam B
1, a separating crystal 72 for separating an X-ray beam B2 composed of a single characteristic X-ray, a collimator 73a for blocking other characteristic X-rays, and a test object 70 such as a semiconductor wafer.
Table 74 for supporting the X-ray beam B2
A collimator 73b for blocking scattered X-rays other than the above, and an X-ray counter 8 for measuring the X-ray intensity of the X-ray beam B2
1 and a table control unit 75 for setting a three-dimensional position of the moving table 74 and an angle with respect to the X-ray beam B2.
A detector 76 for detecting the fluorescent X-rays B3 generated from the test object 70; and a pre-converter for converting the time integrated value of the charge pulse output from the detector 76 into a step-like voltage pulse having a wave height. An amplifier 77; a proportional amplifier 78 for shaping the waveform into a pulse having a wave height proportional to the rising width of the voltage pulse output from the preamplifier 77;
A peak height analyzer 79 for measuring the count rate of each peak value output from the controller 8, and data for processing data measured by the peak height analyzer 79 and the X-ray counter 81 and issuing a command to the table controller 75. It is composed of a processor 80 and the like. X
The line beam B2 is incident on the surface of the test object 70 at an angle of total reflection, for example, at an angle of about 0.06 degrees, as in FIG. It is possible to obtain the component information of the minute amount of deposit.

[0007] In the X-ray fluorescence spectrometer shown in FIG. 5, a method for setting the irradiation angle of the energy beam to the test object 70 is proposed in Japanese Patent Application No. 2-400231.

FIG. 6 is a process chart showing this irradiation angle setting method. First, in FIG. 6A, the X-ray tube 71 or X
An X-ray beam B2 emitted from an X-ray source 82 composed of a ray tube 71 and a spectral crystal 72 directly enters an X-ray counter 81 to measure the X-ray intensity of the X-ray beam B2. The intensity value is stored in a memory or the like in the data processor 80. At this time, the test object 70 is set at a position that does not block the X-ray beam B2, and is slightly tilted toward the X-ray source 82.

Next, in FIG. 6B, the data processor 8
The table controller 75 drives the moving table 74 based on the command from 0, and measures the X-ray intensity by the X-ray counter 81 while gradually raising the test object 70. When the test object 70 interrupts the X-ray beam B2 little by little and the X-ray intensity output from the X-ray counter 81 reaches a reference value, for example, half of the initial intensity value, the rise of the test object 70 is stopped. .

Next, in FIG. 6 (c), based on a command from the data processor 80, the X-ray intensity is measured while gradually tilting the inclination of the test object 70 in a direction approaching horizontal. When the intensity value output from the X-ray counter 81 reaches a maximum, the angular displacement of the test object 70 is stopped. If the maximum value of the X-ray intensity at this time is larger than the reference value, the test object 7
0 is determined not to be parallel to the X-ray beam B2, and in the next FIG. 6 (d), as in FIG.
Is gradually increased to control the vertical position of the test object 70 so that the X-ray intensity becomes a reference value.

Next, in FIG. 6 (e), similarly to FIG. 6 (c), the test object 70 is gradually angularly displaced so that the X-ray intensity is controlled to a maximum value.

In this way, the rising and angular displacement of the test object 70 are repeated, and when the reference value by the raising operation and the maximum value by the angular displacement operation become equal, the traveling direction of the X-ray beam B2 and the test object 70 Is set in parallel with the inspection surface of. Thereafter, the table controller 75 sets the moving table 7 so that the incident angle with respect to the X-ray beam B2 becomes a predetermined total reflection angle.
4 to complete the setting of the irradiation angle of the X-ray beam on the test object 70.

As described above, since the excitation X-ray beam itself is used for adjustment, accurate position and angle adjustment can be performed. Therefore, even if the X-ray beam axis fluctuates with time, the fluctuation error is reduced by the adjustment. Can be absorbed. Also,
Even if the periphery of the test object 70 is curved and lowered by its own weight, the vicinity of the center where the fluorescent X-rays are generated is properly adjusted. Furthermore, when measuring a semiconductor wafer on which a pattern has been formed as a test object, it is possible to set a desired incident angle with respect to the uppermost surface of the semiconductor wafer.

[0014]

The X-ray fluorescence analyzer shown in FIG. 4 uses an optical device independent of the incident position and direction of the X-ray beam B2.
Even if the position and angle adjustment by 69 is perfect, the relative position between the X-ray beam B2 and the test object 60 is not always set accurately. In particular, when the main axis of the X-ray beam B2 changes due to replacement or repair work of the X-ray tube 61 or the spectral crystal 62, the X-ray beam B2 and the distance sensor 6 are changed.
It is necessary to readjust the relative position with respect to 8,69. Also,
This relative position may fluctuate greatly due to a temperature change in the apparatus.

In order to detect as many fluorescent X-rays as possible to increase the sensitivity, it is necessary to dispose the detector 66 very close to the test object 60.
It is difficult to arrange the measurement area No. 9 and the fluorescent X-ray generation area so as to coincide with each other. Therefore, the distance sensor 68,
69 measures the position of another area of the test object 60 different from the X-ray generation area, and interpolates and calculates the position and inclination of the fluorescent X-ray generation area using these measured values. Therefore, when the surface of the test object 60 is curved, there is a problem that an accurate position and inclination cannot be obtained.

Further, since the light emitted from the distance sensors 68 and 69 is incident on the surface of the test object 60 almost perpendicularly,
If the material of the test object is affected by light absorption or transmission or light scattering due to the surface state, the intensity of the reflected light is insufficient, and the distance sensors 68 and 69 may malfunction.
In particular, when measuring a semiconductor wafer on which a pattern has been formed as the test object 60, there is a problem in that scattering or diffraction of light occurs, resulting in measurement failure.

On the other hand, in the fluorescent X-ray analyzer shown in FIG. 5, the X-ray intensity is measured using the X-ray counter 81 while the height adjustment and the angle adjustment of the moving table 74 are performed alternately. It takes time.

An object of the present invention is to provide a fluorescent X-ray analyzer and an X-ray irradiation angle setting method which can quickly and accurately adjust the position and angle of a test object in order to solve the above-mentioned problems. It is to be.

[0019]

According to the present invention, there is provided an X-ray beam irradiating means for irradiating an X-ray beam at a predetermined angle to an inspection surface of an object to be inspected, and an X-ray beam generated from a sample attached to the inspection surface. X-ray fluorescence detection means for detecting X-ray fluorescence, X-ray beam detection means for detecting the intensity of an X-ray beam passing near the inspection surface, supporting the object, and performing the inspection An X-ray fluorescence spectrometer comprising: a subject support means for controlling a three-dimensional position of a surface and an angle with respect to the X-ray beam; irradiating a light beam near an inspection area of the inspection surface to which the X-ray beam is applied And a light beam position detecting means for detecting a position of the light beam reflected from the inspection surface.

Further, according to the present invention, X
In the X-ray irradiation angle setting method of setting the irradiation angle of a X-ray beam, the X-ray beam is blocked by the X-ray beam while moving the X-ray beam in a direction substantially perpendicular to the traveling direction of the X-ray beam. Detecting a change in intensity and setting the height of the test object; and irradiating the inspection surface of the test object with a light beam that forms a predetermined angle with the X-ray beam traveling direction. And setting the angle of the test object by detecting the position of the light beam reflected by the X-ray irradiation angle setting method.

[0021]

According to the present invention, the height of the test object is detected by using the X-ray beam detecting means for detecting the intensity of the X-ray beam passing near the surface of the test object, and the height of the test surface is measured. The angle of the test object can be detected by irradiating a light beam near the inspection area and using a light beam position detecting means for detecting the position of the light beam reflected from the inspection surface. Therefore, since the detection time of the light beam position is short, the angle adjustment of the test object is speeded up. In addition, since the inspection region that generates the fluorescent X-rays and the region irradiated with the adjustment light beam can be matched, the height and angle of the inspection region can be detected with high accuracy.

Further, according to the present invention, a change in the intensity of the X-ray beam obstructed by the object is detected while moving the object in a direction substantially perpendicular to the traveling direction of the X-ray beam. Detecting the position of the light beam by irradiating the inspection surface of the test object with a light beam and detecting the position of the light beam reflected on the inspection surface. Since the time is short, the angle of the test object can be quickly adjusted, and the height and angle of the inspection region that generates the fluorescent X-ray can be set with high accuracy.

[0023]

FIG. 1 is a block diagram showing an X-ray fluorescence analyzer 1a according to one embodiment of the present invention. The X-ray fluorescence analyzer 1a includes an X-ray tube 11 for generating an X-ray beam B1.
And an X-ray comprising a single characteristic X-ray from the X-ray beam B1.
A spectral crystal 12 for separating the line beam B2, a collimator 13a for blocking other characteristic X-rays, and a moving table 14 for supporting the object 10 such as a semiconductor wafer.
A collimator 13b for blocking scattered X-rays other than the X-ray beam B2, and an X-ray counter 2 such as a scintillation counter for detecting the X-ray intensity of the X-ray beam B2.
1 and a table controller 15 for setting a three-dimensional position of the moving table 14 and an angle with respect to the X-ray beam B2.
And a detector 16 such as a lithium drift type Si detector for detecting fluorescent X-rays B3 generated from the test object 10.
A proportional amplifier 18 for shaping the waveform into a pulse having a wave height proportional to the rising width of the charge pulse output from the detector 16; and a wave height analysis for measuring the count rate of each wave height value output from the proportional amplifier 18. Device 19 and wave height analyzer 1
9 and a data processor 20 for processing data measured by the X-ray counter 21 and issuing a command to the table control unit 15, and the like.
Is irradiated near the inspection area of the test object 10 to be irradiated with the light beam L1.
And a light sensor array 31 such as a one-dimensional CCD (charge-coupled device) for detecting the position of the light beam L1 reflected on the surface of the test object 10.

The X-ray beam B2 is incident on the surface of the test object 10 at an angle at which it is totally reflected, for example, at an angle of about 0.06 degrees, thereby providing information on the vicinity of the surface of the test object 10, for example, a trace amount. Information on the components of the kimono can be obtained.

FIG. 2 is a process chart showing an X-ray irradiation angle setting method according to one embodiment of the present invention. First, according to the procedure shown in FIG. 6, the three-dimensional positions and angles of the test object 10 and the moving table 14 are adjusted using only the X-ray beam B2, and as shown in FIG. The state where the traveling direction of the line beam B2 is parallel to the surface of the test object 10 is set. Next, in this state, the surface of the test object 10 is irradiated with the light beam L1 emitted from the laser light source 30, and the light beam L1 reflected on the surface of the test object 10 is received by the optical sensor array 31. Then, the pixel array number N at the position where the received light intensity distribution becomes maximum is stored in the memory in the data processor 30. In this way, the light receiving position of the light beam L1 when the first test object 10 is at the reference position from the start of the analysis is determined in advance, and the second and subsequent test objects 10 are adjusted in the following procedure.

First, in FIG. 2A, a new specimen 1
0 on the moving table 14, the X-ray tube 1
1 or an X-ray beam B2 emitted from an X-ray source 22 composed of an X-ray tube 11,
The X-ray intensity of the X-ray beam B <b> 2 is measured by direct incidence on the X-ray beam 1, and the initial intensity value is stored in a memory in the data processor 20. At this time, the test object 10 is set at a position that does not block the X-ray beam B2.

Next, in FIG. 2B, the table controller 15 drives the moving table 14 based on a command from the data processor 20 to gradually raise the test object 10 and To measure the X-ray intensity. When the test object 10 interrupts the X-ray beam B2 little by little and the X-ray intensity output from the X-ray counter 21 reaches a reference value, for example, half of the initial intensity value, the rise of the test object 10 is stopped. .

Next, referring to FIG.
The light beam L1 emitted from 0 is incident on the surface of the test object 10, the light beam L1 reflected on the surface of the test object 10 is received by the optical sensor array 31, and the light intensity distribution of the received light at this time is obtained. The pixel array number M at the maximum position is measured.
At this time, if the measured pixel array number M is different from the pixel array number N stored as a reference, the following relational expression (1) is used.
Is used to calculate the angle error Δθ of the surface of the test object 10 with respect to the horizontal direction.

D × sinΔθ = P × (M−N) (1) where D is the distance between the reflection position on the test object 10 and the optical sensor array 31, and P is the pixel of the optical sensor array 31 Pitch. Accordingly, the light receiving position of the light beam L1 can be quickly matched with the initial reference position by angularly displacing the test object 10 by the angle Δθ.

If the X-ray intensity at this time is larger than the reference value, it is determined that the test object 10 is not parallel to the X-ray beam B2, and in FIG. Next, the test object 10 is gradually raised, and the vertical position of the test object 10 is controlled so that the X-ray intensity becomes the reference value again.

Next, in FIG. 2E, similarly to FIG. 2C, the difference between the light receiving position of the light beam L1 reflected by the test object 10 and the initial reference position is measured, and the following equation is obtained. The angle error Δθ of the test object 10 is calculated using 1).

In this manner, when the test object 10 is repeatedly raised and angularly displaced, the X-ray intensity is set to the reference value and the light receiving position of the light beam L1 is set to the initial reference position. The object 10 is set in a parallel position, that is, the traveling direction of the X-ray beam B2 and the inspection surface are set in parallel. Thereafter, the table controller 15 drives the moving table 14 so that the incident angle with respect to the X-ray beam B2 becomes a predetermined total reflection angle, and the setting of the irradiation angle of the X-ray beam with respect to the test object 10 is quickly completed. can do.

In this way, the angle can be adjusted quickly and with high accuracy. Further, the light beam L1 is
By launching at a low angle to the zero surface,
Since total reflection is realized on the surface of the test object, adjustment is possible even for a transparent test object such as a glass plate. Also,
When the surface of the test object 10 is rough and scatters the light beam L1, it is possible to switch to the conventional method shown in FIG.

FIG. 3 shows another embodiment of the present invention.
It is a block diagram which shows the line analyzer 1b. In the present embodiment, the X-ray fluorescence spectrometer 1b is the same as that shown in FIG. 1, except that another set of a laser light source 32 and an optical sensor array 33 for measuring the angle of the test object 10 is added. Are different. Thus, the two light beams L1 and L2
By measuring the angular error of the test object 10 by using, the measurement range and the measurement accuracy can be further improved.

In each of the above embodiments, the test object 1
Although an example has been described in which the light beams L1 and L2 reflected at 0 are directly received by the light sensor arrays 31 and 33, when the resolution of the light sensor arrays 31 and 33 is insufficient, the light beams L1 and L2 are provided before the light sensor arrays 31 and 33. A concave lens is arranged to light beam L1,
By expanding the angular displacement of L2, the measurement accuracy of the angle error Δθ can be further improved. Also, an example in which a one-dimensional CCD is used as the optical sensor arrays 31 and 33 has been described. However, a one-dimensional PSD (optical position detecting element) may be used, and measurement is similarly performed using a two-dimensional optical sensor array. It is possible.

[0036]

As described in detail above, according to the present invention, the work of adjusting the angle of the test object is speeded up, and the position and angle of the inspection area can be directly measured. Becomes possible.

[Brief description of the drawings]

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

FIG. 2 is a process chart showing an X-ray irradiation angle setting method according to one embodiment of the present invention.

FIG. 3 is a fluorescent X-ray analyzer 1 according to another embodiment of the present invention.
It is a block diagram showing b.

FIG. 4 is a schematic configuration diagram showing an example of a conventional X-ray fluorescence analyzer.

FIG. 5 is a configuration diagram showing another example of a conventional X-ray fluorescence analyzer.

FIG. 6 shows X used in the X-ray fluorescence analyzer of FIG.
FIG. 4 is a process chart showing a line irradiation angle setting method.

[Explanation of symbols]

 1a, 1b X-ray fluorescence analyzer 10 Test object 11 X-ray tube 12 Dispersion crystal 13a, 13b Collimator 14 Moving table 15 Table controller 16 Detector 17 Preamplifier 18 Proportional amplifier 19 Wave height analyzer 20 Data processor 21 X Line counter 30, 32 Laser light source 31, 33 Optical sensor array

Continuation of front page (56) References JP-A-4-208900 (JP, A) JP-A-3-148056 (JP, A) JP-A-4-1433643 (JP, A) JP-A-5-2057 (JP) , U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 23/223

Claims (2)

(57) [Claims] 1. An X-ray beam irradiating means for irradiating an X-ray beam at a predetermined angle to an inspection surface of a test object, and an X-ray beam irradiating means for detecting fluorescent X-rays generated from a sample attached to the inspection surface. X-ray fluorescence detection means, X-ray beam detection means for detecting the intensity of an X-ray beam passing near the inspection surface, the three-dimensional position of the inspection surface, and the X-ray beam, An X-ray fluorescence analyzer comprising: an object support unit configured to control an angle with respect to a line beam; a light beam irradiation unit configured to irradiate a light beam near an inspection area of the inspection surface on which the X-ray beam is irradiated; An X-ray fluorescence analyzer, comprising: a light beam position detector for detecting a position of a light beam reflected from the inspection surface. 2. An X-ray irradiation angle setting method for setting an irradiation angle of an X-ray beam on an inspection surface of a test object, wherein the test object is moved in a direction substantially perpendicular to a traveling direction of the X-ray beam. Detecting a change in the intensity of the X-ray beam blocked by the test object and setting the height of the test object; and setting the X-ray beam traveling direction and a predetermined direction on the inspection surface of the test object. Setting an angle of the test object by irradiating an angled light beam and detecting a position of the light beam reflected on the inspection surface. Method.