JP2001083112A - Photoelectron spectroscopic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photoelectron spectroscopic device which can set the incident angle of X-rays at the critical total reflection angle in a short time. SOLUTION: The operator of a photoelectron spectroscopic device inputs the wavelength λ (nm) of exciting X-rays and the density ρ(kg/m3) of a sample to be measured by using an inputting means 18. These input signals λ and ρare sent to a central control means 17 which sends the signals λ and ρ to a piezoelectric element control means 14. The control means 14 finds the critical total reflection angle θc from the expression: θc=0.51λ√ρ. Upon finding the critical angle θc, the control means 14 elongates the body 12 of a piezoelectric element in the direction A and, at the same time, contracts the body 13 of another piezoelectric element 13 in the direction -A so that the angle between the center axis of a multi-capillary 15 and the surface of the sample may become θc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photoelectron spectroscopy device.

[0002]

2. Description of the Related Art A photoelectron spectroscopy device is known as a surface analysis device. This photoelectron spectroscopy device irradiates an X-ray (characteristic X-ray such as MgKα ray or AlKα ray) onto a sample surface, and is emitted from the sample by the irradiation. This device measures the kinetic energy of photoelectrons and performs qualitative and quantitative analysis of surface elements from the measurement results, as well as analysis of the state of chemical bonding.

The kinetic energy of photoelectrons detected by a photoelectron spectrometer is as low as about 0 to 3 keV, and the escape depth of these electrons is at most several nm. For this reason, if a photoelectron spectroscopy device is used, it is possible to obtain information only on the sample pole surface, which is several nm from the sample surface.

Recently, in order to improve the detection sensitivity in a photoelectron spectrometer, excited X-rays are incident on a sample at a critical angle of total reflection or less determined by the wavelength and the sample material to maximize the photoelectron intensity. Total reflection photoelectron spectroscopy, which increases the P / B ratio, is often used.

As described above, when the incident angle of X-rays on the sample is less than the critical angle for total reflection, the penetration depth of the excited X-rays into the sample becomes very small, and the photoelectron generation region is limited to the vicinity of the sample surface layer. Can be As a result, the distance traveled by the generated photoelectrons in the sample, that is, the distance from the point where the photoelectrons are generated to the sample surface is shortened, the background signal amount due to inelastic scattered electrons is considerably reduced, and contaminant elements existing on the sample surface are reduced. And measurement with high sensitivity to the chemical state thereof can be performed.

[0006] Such total reflection photoelectron spectroscopy is effective for a sample having a mirror-like sample surface, and is particularly useful for analyzing surface contaminants such as semiconductor wafers.

At the time of analysis by this total reflection photoelectron spectroscopy, the operator tilts the sample tilt stage while observing the detected spectrum so that the P / B ratio where the photoelectron peak appears becomes the best. Line incident angle is set.

[0008]

However, it takes a long time to set the X-ray incident angle to the critical angle of total reflection from the detected spectrum, and the burden on the operator becomes considerably large. Also, it is difficult to set the X-ray incident angle to the total reflection critical angle with good reproducibility.

The present invention has been made in view of the above points, and an object of the present invention is to provide a photoelectron spectroscopy apparatus capable of setting an X-ray incident angle to a critical angle for total reflection in a short time. .

[0010]

Means for Solving the Problems A photoelectron spectroscopy apparatus according to the present invention that achieves this object includes an X-ray source, a sample stage,
A tilting means attached to the sample stage; and a multi-capillary attached to the tilting means and configured by bundling a plurality of capillaries in substantially the same direction. And irradiating the sample via the.

[0011]

Embodiments of the present invention will be described below.

FIG. 1 is a diagram showing an example of the photoelectron spectroscopy apparatus of the present invention. First, the configuration of the apparatus shown in FIG. 1 will be described.

In FIG. 1, reference numeral 1 denotes a chamber. 2
Is an X-ray source arranged in the chamber 1;
Includes a filament 3, a focus adjustment electrode 4, and a target 5. The target 5 is made of Al.

Reference numeral 6 denotes an X-ray monochromator spectral crystal curved in a double focusing type.
Is disposed in the chamber so as to face the X-ray source 2. The X-ray monochromator spectral crystal 6 is formed of a crystal [α-SiO 2].
The rays are split by the dispersive crystal 6 and monochromated into Alkα rays. When the sample is irradiated with such monochromatic X-rays, continuous X-rays due to bremsstrahlung are removed, and the background signal due to inelastic scattered electrons is reduced.

Reference numeral 7 denotes a semiconductor wafer as a sample to be measured. The semiconductor wafer 7 is held by a sample holder 8.
The sample holder 8 is placed on a sample stage 9 placed in a chamber. The sample stage 9 is centered on an XY stage 10 and an axis (not shown) parallel to the Y axis shown in FIG. It is composed of a tilt stage 11 that tilts.

On the tilt stage 11, a piezoelectric element body 12,
The piezoelectric element bodies 12 and 13 are arranged on the tilt stage 11 along the direction connecting the spectral crystal 6 and the sample stage 9. These piezoelectric element bodies 1
Reference numerals 2 and 13 are configured to expand and contract in a direction (A-(-A) direction) perpendicular to the reference plane B of the tilt stage 11 under the control of the piezoelectric element control means 14.

A multi-capillary 15 is mounted on the piezoelectric elements 12 and 13. Multicapillary 1
Numeral 5 is located between the spectral crystal 6 and the sample holder 8, and is configured by bundling a plurality of glass capillaries in substantially the same direction. The X-ray entrance 15a of the multi-capillary 15 is directed toward the spectral crystal 6, while the X-ray exit 15b of the multi-capillary 15 is directed toward the sample 7.

FIG. 2 is a cross-sectional view when the multi-capillary 15 is cut along its longitudinal direction. FIG. 3 is a view of the multi-capillary 15 as viewed from the side of the spectral crystal 6.
As is apparent from FIG. 3, the cross-sectional shape of the multi-capillary 15 is quadrangular, and the cross-sectional shape of each capillary is circular.

The inner surface of each capillary is formed so that incident X-rays travel while being totally reflected.
Each capillary includes an X-ray focusing unit and an X-ray parallelizing unit as shown in FIG. The X-ray focusing unit
It is formed in a tapered shape to condense the lines. On the other hand, the inside diameter of the X-ray parallelizing portion is almost the same in any portion in order to irradiate the sample with a parallel X-ray flux.

In FIG. 1, reference numeral 16 denotes a beam stopper. The beam stopper 16 is mounted on the X-ray incidence side of the multi-capillary 15. The beam stopper 16 is attached to the multi-capillary so as not to block the X-ray entrance of the multi-capillary 15,
It serves to prevent X-rays that have not entered the multicapillary from irradiating the sample.

Reference numeral 17 denotes central control means. The central control means 17 is connected to the piezoelectric element control means 14, the input means 18, and the stage control means 19, respectively. In addition,
The stage control means 19 controls the sample stage 9.

Reference numeral 20 denotes an exhaust device, and the inside of the chamber 1 is evacuated to an ultrahigh vacuum by the exhaust device 20.

An electron spectroscope for detecting photoelectrons emitted from the sample is disposed above the sample 7, and the electron spectrometer is composed of an input lens (deceleration lens) 21 composed of a plurality of electrostatic lenses. And the hemispherical analyzer 22
And a detector 23. The input lens 21 is arranged so that its optical axis is substantially perpendicular to the sample surface.

The configuration of the apparatus shown in FIG. 1 has been described above. The operation of this apparatus will be described below.

First, prior to sample analysis, the operator inputs the wavelength λ (nm) of the excited X-rays and the density ρ (kg / m ³ ) of the sample to be measured by the input means 18. In this case, the operator inputs the wavelength λ of the Alkα ray as the excitation X-ray and the density ρ of the Si wafer as the sample to be measured. These input signals λ, ρ are sent to the central control means 17, which sends the signals λ, ρ to the piezoelectric element control means 14.

The piezoelectric element control means 14 receiving these signals λ and ρ obtains a critical angle for total reflection θc from the following equation (1).

Θc = 0.51λ√ρ (1) When the piezoelectric element control means 14 determines the critical angle for total reflection θc, the angle formed between the central axis O of the multi-capillary 15 and the sample surface becomes θc. So that the piezoelectric element 12
Is extended in the A direction, and the piezoelectric element body 13 is contracted in the −A direction. That is, the piezoelectric element control means 14 calculates the multi-capillary 1 from the obtained θc and the distance L between the piezoelectric element bodies.
The amount of displacement of the piezoelectric elements 12 and 13 is calculated so that the angle formed between the central axis O of 5 and the sample surface becomes θc, and a voltage corresponding to this is supplied to the piezoelectric elements 12 and 13.

When the multi-capillary 15 is tilted in this manner, the X-ray source 2 generates X-rays.

X-rays generated by the X-ray source 2 are separated by the X-ray monochromator crystal 6. The Alkα ray separated by the X-ray monochromator crystal 6 is a multi-capillary 15
And is first totally reflected and collected by the inner surface of each capillary of the X-ray collector. And the collected X
The rays are totally reflected and parallelized on the inner surfaces of the capillaries of the X-ray parallelizing section, and all X-rays are incident on the sample 7 at the critical angle for total reflection θc. As a result, the background signal amount due to the inelastic scattered electrons is considerably reduced for the above-described reason, so that a contaminant element existing on the semiconductor wafer surface can be specified and a measurement with high sensitivity to the chemical state can be performed.

The operation of the apparatus shown in FIG. 1 has been described above. In this apparatus, the piezoelectric element for tilting the multi-capillary is automatically set so that the angle formed between the multi-capillary and the sample surface becomes a critical angle for total reflection. Is displaced to
The X-ray incident angle on the sample can be set to the critical angle for total reflection in a short time, and the burden on the operator is greatly reduced as compared with the conventional case. Also, the X-ray incident angle can be set to the critical angle for total reflection with good reproducibility.

In addition, when the tapered multi-capillary is used as described above, the total reflection of X-rays and the X-ray condensing on the inner surface of each of the capillaries can be applied to the surface of the sample in comparison with the method using a parallel plate solar slit. The brightness of the irradiated X-ray flux is improved.

Although the embodiment of the present invention has been described using the photoelectron spectroscopy apparatus of FIG. 1, the present invention is not limited to this example.

For example, in the apparatus shown in FIG. 1, the cross-section of the multi-capillary is rectangular, but the cross-section of the multi-capillary may be circular or elliptical. If the inner surface of each capillary is coated with gold or the like, the reflectivity of X-rays can be increased.

In an environment where only one fixed sample (for example, a Si wafer) is repeatedly measured, the piezoelectric element is controlled so that the inclination angle of the multi-capillary with respect to the sample surface is determined in advance by the total reflection criticality of the substance to be measured. It may be fixed at an angle.

In the above example, the multi-capillary is placed on the sample stage. However, the multi-capillary is not placed on the sample stage, but placed near the X-ray monochromator or the non-monochromatic X-ray tube. It is also possible.
In addition, even when the X-rays from the non-monochromatic X-ray tube are directly received by the multi-capillary without using the X-ray monochromator, continuous X-rays due to bremsstrahlung are removed to some extent by the multi-capillary.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a photoelectron spectroscopy device of the present invention.

FIG. 2 is a cross-sectional view of the multi-capillary taken along its longitudinal direction.

FIG. 3 is a view of the multi-capillary as viewed from the side of the spectral crystal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Chamber, 2 ... X-ray source, 3 ... Filament, 4 ... Focus adjustment electrode, 5 ... Target, 6 ... X-ray monochromator spectral crystal, 7 ... Sample to be measured, 8 ... Sample holder, 9
... sample stage, 10 ... XY stage, 11 ... tilt stage, 12 ... piezoelectric element body, 13 ... piezoelectric element body, 14 ... piezoelectric element control means, 15 ... multicapillary, 15a ... X
Line entrance, 15b X-ray exit, 16 beam stopper, 17 central control unit, 18 input unit, 19 stage control unit, 20 exhaust unit, 21 input lens, 22 hemispherical analyzer, 23 Detector

Claims (8)

[Claims] 1. An X-ray source, a sample stage, a tilting means mounted on the sample stage, and a multi-capillary mounted on the tilting means and configured by bundling a plurality of capillaries in substantially the same direction. A photoelectron spectrometer, wherein the sample is irradiated with X-rays from the X-ray source via a multi-capillary. 2. The photoelectron spectroscopy apparatus according to claim 1, further comprising means for controlling said tilting means based on the wavelength of the excited X-rays and the density of the sample. 3. The photoelectron spectroscopy device according to claim 1, wherein the tilting unit is formed of a piezoelectric element. 4. Each of the capillaries is composed of an X-ray focusing section and an X-ray parallelizing section, and the X-ray focusing section is formed in a tapered shape, while the X-ray parallelizing section is The photoelectron spectroscopy device according to any one of claims 1 to 3, wherein the inner diameter is substantially the same in any part. 5. An X-ray monochromator for monochromaticizing X-rays generated from an X-ray source is arranged between the X-ray source and the multi-capillary. A photoelectron spectroscopy apparatus according to any one of the above. 6. A photoelectron spectrometer comprising an X-ray source, a sample stage, and a multi-capillary arranged between the sample stage and the X-ray source, the plurality of capillaries being bundled in substantially the same direction. An X-ray source from the X-ray source.
A photoelectron spectrometer characterized in that a sample is irradiated with a line through a multi-capillary. 7. Each of the capillaries is composed of an X-ray focusing section and an X-ray parallelizing section, and the X-ray focusing section is formed in a tapered shape, while the X-ray parallelizing section is 7. The photoelectron spectroscopy device according to claim 6, wherein the inner diameter is substantially the same in any part. 8. An X-ray monochromator for monochromaticizing X-rays generated from the X-ray source is arranged between the X-ray source and the multi-capillary. Photoelectron spectrometer.