JP2000131446A - X-ray detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact X-ray detector to measure the intensity of X-rays only in a wavelength band useful for an X-ray source. SOLUTION: A slit 2 for regulating the amount of capturing of X-rays 30a is arranged in the front surface of an X-ray detector 10. In a detector case 1, only a band of an X-ray wavelength to be measured is reflected by both a metal thin film filter 3 for extracting only X-rays 30a by cutting light rays except the X-ray region of plasma 20a and a multilayer film mirror 4 to reflect an X-ray wavelength to be measured to make it incident onto the light receiving surface of a photodiode 6 for X-rays, and the dose of the incident X-rays is achieved by a measuring device 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray detector for measuring an X-ray dose.

[0002]

2. Description of the Related Art In recent years, X-ray lithography, X-ray microscopes,
X-ray sources such as a small synchrotron radiation beam used for an X-ray analyzer and a laser plasma X-ray source are being developed. To use such an X-ray source, it is necessary to monitor the X-ray intensity in the used wavelength band.

Conventionally, as described in Japanese Patent Application Laid-Open No. 5-341051, X-rays transmitted through a plurality of filter films having different X-ray transmission wavelength ranges are detected by separate X-ray detection elements, and those X-rays are detected. Some devices detect an X-ray dose based on the output of an X-ray detection element.

[0004]

However, the above-mentioned prior art requires a plurality of detecting sections each including a filter film and an X-ray detecting element for measuring the X-ray intensity in the wavelength band to be measured. Since the X-ray intensity is measured based on the difference in the transmittance of the film, the detection process is complicated, and the measurement accuracy is reduced when the X-ray intensity is different at the positions of the plurality of detection units. An object of the present invention is to provide a small-sized X-ray detector for accurately measuring the X-ray intensity in the wavelength band used by an X-ray source.

[0005]

An object of the present invention is to provide a mirror for reflecting an X-ray wavelength to be measured, an X-ray detecting element for detecting X-rays reflected from the mirror, and an output from the X-ray detecting element. Measurement means for measuring the X-ray dose based on the X-ray detector.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION
Focusing on the fact that a mirror having a specific reflection wavelength band such as a multilayer mirror is used as a mirror for guiding X-rays to an X-ray irradiator in a device requiring an X-ray source, a mirror having such characteristics is used. As a filter, X-ray intensity of only the wavelength to be measured can be accurately monitored. In addition, the inventors pay attention to the fact that the plasma formation position changes due to a change in the state of the target or a change in the energy of the laser beam applied to the target, such as a laser plasma X-ray, and rotate the detector. By finding the rotation angle at the position where the X-ray intensity is the strongest, it was possible to confirm the plasma formation position. Below,
An embodiment of an X-ray detector using a mirror that reflects an X-ray wavelength to be measured will be described.

FIG. 1 shows an X-ray detector according to a first embodiment of the present invention. When a converged laser beam is irradiated on a target such as a metal, the target is optically broken down and ionized by a strong electric field of the laser beam.

The electrons generated by the ionization of the metal element are heated by absorbing the energy of the laser beam by a process such as reverse braking radiation, and a high-temperature, high-density laser plasma 20 is formed in a range where the target laser beam penetrates. You.

At this time, the X-ray 30
Occurs. An X-ray detector 10 is provided for monitoring the intensity of the generated X-ray 30.

The X-ray detector 10 has a slit 2 for adjusting the amount of X-rays taken in front of the X-ray detector 10.
A metal thin film filter 3 of Al or the like is mounted inside the detector case 1 in order to cut out light beams other than the X-ray region of the plasma and extract only X-rays.

The extracted X-rays are reflected by the multilayer mirror 4 that reflects the X-ray wavelength of the object to be measured only in the wavelength band desired to be measured by the apparatus, and are incident on the light receiving surface of the photodiode 6 for X-rays. You.

The multilayer mirror 4 is held by a mirror holder 5. The X-ray photodiode 6 generates a signal current based on the incident optical power, and the preamplifier 7
Converts the signal current into an output voltage. The waveform of the output voltage is recorded and processed by the measuring device 8.

At this time, an equation for obtaining the X-ray intensity P (W) from the voltage v (V) obtained by the measurement is represented by the following equation.

P = K · v (Equation 1) K = 1 / (α · Tx · RT · R · R _F ) (Equation 2) Here, the X-ray capture rate at the slit 2 is α (% ), The X-ray transmittance of the metal thin film filter 3 is Tx (%), the X-ray reflectivity of the multilayer mirror 4 is RT (%), the response coefficient of the X-ray photodiode 6 is R (A / W), the preamplifier. 7 is R _F (Ω), and the X-ray intensity coefficient is K (W / V).

At this time, in order to guide the X-rays 30 generated from the laser plasma 20 onto the light receiving surface of the X-ray photodiode 6, the positional relationship between the slit 2 and the multilayer mirror 4 is arranged according to the following equation.

Θ = tan ⁻¹ (R1 / D1) = tan ⁻¹ (R2 / D2) = tan ⁻¹ (R3 / D3) (Equation 3) W1> 0 (Equation 4) W2> 0 (Equation 4) 5) Here, the distance from the laser plasma 20 to the slit 2 is R1, the distance from the optical axis of the X-ray 30 used as the light source of the apparatus to the center of the slit 2 is D1, and the distance from the laser plasma 20 to the multilayer mirror 4 is D1. The distance is R2, the distance from the optical axis of the X-ray 30 to the center of the multilayer mirror 4 is D2, the incident angle of X-rays on the multilayer mirror 4 is θ, and the distance from the multilayer mirror 4 to the photodiode 6 for X-rays. L, the distance from the center of the multilayer mirror 4 to the center of the X-ray photodiode 6 is D3, the gap between the end of the case 1 and the optical axis of the X-ray 30 is W1, the X-ray 30a for monitoring and the end of the preamplifier 7 The gap between the portions is W2.

Next, the X-ray detection range of the X-ray detector 10 will be described with reference to FIG. As a mirror used in the apparatus, there is a Mo / Si multilayer mirror or the like. As shown in the figure, the reflectance has two peaks in the vicinity of 13 nm and in a visible light region of 500 to 600 nm.

In order to detect only the X-ray intensity at a wavelength of 13 nm to be monitored, an Al thin film filter or the like that cuts the visible light region and transmits only the X-ray region may be used. At this time, the range of the arrow shown in the figure is the X-ray detection range.

As described above, the X-ray detector 10 is
Since it can be composed of only the metal thin film filter 3, the multilayer mirror 4, the photodiode 6 for X-rays and the preamplifier 7, the size and weight can be reduced. When the X-ray generated, such as a laser plasma X-ray source, has an angular distribution characteristic, the values of Expressions 4 and 5 are made closer to 0, so that the intensity of the X-rays 30 used as the light source of the apparatus is reduced. Since the direction of the monitor X-ray 30a approaches, the error between the X-ray intensity used for the light source of the apparatus and the X-ray intensity measured for the monitor can be further reduced.

A second embodiment of the present invention will be described with reference to FIG. This embodiment is different from the X-ray detector 10 in the first embodiment.
In addition, a swing mechanism 40 is added to the configuration of FIG.

In the laser plasma 20, the position where the plasma is formed changes due to a change in the state of the target or a change in the energy of the laser beam.

As shown in the upper part of FIG. 3, when the plasma formation position changes from 20a to 20b, the X-ray detector 10 is adjusted so that the X-ray 30a generated from the laser plasma 20a impinges on the multilayer mirror 4. When the position of the laser plasma is changed and the X-rays 30b are generated at 20b, the X-rays 30b come off the multilayer mirror 4, so that the X-rays cannot be detected.

Therefore, as shown in the lower diagram of FIG.
The rotation amount β of the position where the X-ray intensity becomes the highest is obtained by rotating the swinging mechanism 40 by the control device 9 that controls the direction of the plasma, thereby calculating the change amount S of the plasma formation position.

As described above, according to the present embodiment, it is possible to confirm a change in the plasma formation position due to a change in the state of the target or a change in the energy of the laser beam applied to the target, such as a laser plasma X-ray. is there.

[0025]

According to the present invention, since the X-ray detector can be composed of a small number of components, the X-ray detector can be miniaturized, and the X-ray intensity at only the wavelength used by the X-ray source can be measured accurately.

[Brief description of the drawings]

FIG. 1 is a diagram showing an X-ray detector according to a first embodiment of the present invention.

FIG. 2 is a graph showing an X-ray detection range according to the embodiment of the present invention.

FIG. 3 is a diagram showing an X-ray detector according to a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Detector case, 2 ... Slit, 3 ... Metal thin film filter, 4 ... Multilayer mirror, 6 ... X-ray photodiode, 7 ... Preamplifier, 8 ... Measuring instrument, 9 ... Control device, 10
... X-ray detector, 20 ... laser plasma, 30 ... X-ray, 4
0: Swing mechanism.

Claims (4)

[Claims] A mirror for reflecting an X-ray wavelength to be measured;
An X-ray detector comprising: an X-ray detection element that detects X-rays reflected from the mirror; and a measuring unit that measures an X-ray dose based on an output from the X-ray detection element. 2. An X-ray detector according to claim 1, further comprising a metal thin-film filter at a stage preceding the X-ray detection element to cut off a light beam outside the X-ray region of the light source. 3. An X-ray detector according to claim 1, further comprising a slit for adjusting the amount of X-rays at a stage preceding the X-ray detection element. 4. The control means according to claim 1, 2 or 3, wherein said control means controls the direction of said detector based on the measured value of said measuring means, and the direction of said detector is controlled by a command from said control means. An X-ray detector including a swing mechanism for changing.