JPH07226184A - Mass spectrometer - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to significantly shorten the distance between a sample and an accelerating electrode and to enhance the efficiency of collecting molecules generated from the sample. A mass spectrometer equipped with an ion acceleration electrode 40 having a lens 22 for condensing a laser beam, or a Fresnel lens having a mesh electrode at the center.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for analyzing minute organic substances adhering (contaminating) to electronic parts such as semiconductors, and more particularly to a mass spectrometer for performing ionization using a laser.

[0002]

2. Description of the Related Art A conventional mass spectrometer is disclosed in JP-A-4-1540.
As described in Japanese Patent Laid-Open No. 39, the structure shown in FIG. 1 is a mass spectroscope, 2 is a sample, 6 is a laser light source, 8 is a light source for observation illumination, 18 is a vacuum chamber, 21b is an ion beam, 22 is a condenser lens, 24 is a light reflection mirror, 2
4a is an ion transmission hole, 26 is a sample stage, 30 is an ion reflector, 34 is an ion detector, and 40 is an ion acceleration electrode. The laser light generated from the laser light source 6 is condensed on the sample 2 by the condenser lens 22 and the light reflection mirror 24. Ions excited by this laser light are reflected by the light reflection mirror 2
4 Passes through the ion passage hole 24a at the center, and is mass analyzed by the mass spectrometric section 1.

In the conventional apparatus shown in FIG. 4, since the condenser lens 22 is provided between the sample 2 and the ion accelerating electrode 40, the distance between the sample and the ion accelerating electrode is too wide, and the molecules desorbed from the sample are removed. Is extremely difficult to collect efficiently.

[0004]

In the above-mentioned conventional apparatus, since the condenser lens exists between the sample and the accelerating electrode, it is necessary to open the space between the sample and the accelerating electrode. Good to send to mass spectrometer is extremely difficult. An object of the present invention is to significantly shorten the distance between the sample and the accelerating electrode and increase the collection efficiency of molecules generated from the sample.

When the accelerating electrode is brought close to the sample, the condenser lens and the accelerating electrode come very close to each other, and the electric field in the ion accelerating region is greatly disturbed. As a result, mass resolution and ion collection efficiency are greatly reduced. In the present invention, this problem is solved by completely integrating the ion acceleration electrode and the condenser lens.

[0006]

In order to solve the above object, an accelerating electrode and a laser focusing lens are integrated. The integration was performed by the following two methods.

1. As shown in FIG. 2, the condenser lens was completely embedded in the acceleration electrode. This made it possible to shorten the distance between the sample and the electrode. Therefore, the efficiency of collecting molecules generated from the sample can be increased. Also, the objective lens was tilted and installed so as to be removed from the passage through which the ions pass so that the ions could be efficiently sent to the mass spectrometer.

Further, by completely embedding the lens in the electrode, the influence on the electric field of the lens is minimized and the deterioration of the resolution is prevented.

2. In order to achieve the same object, a Fresnel lens having an accelerating electrode as shown in FIG. 3 is used so that the distance between the accelerating electrode and the sample can be shortened. Further, a reticulated accelerating electrode is arranged in the central portion so that the ions can be efficiently sent to the mass spectrometer.

In this case, the lens and the electrode have a plate shape, the electric field in the acceleration region is not disturbed at all, and the resolution is not deteriorated at all.

[0011]

Function The molecular beam generated from the extremely small area (about 1 μmφ) of the sample by the focused laser irradiation advances with divergence. Therefore, when the distance between the accelerating electrode and the sample becomes long, this spread greatly reduces the number of molecules entering the accelerating region by the electrode. In the conventional apparatus, since the objective lens is provided between the accelerating electrode and the sample, the distance between the accelerating electrode and the sample becomes long due to the structure. However, in the present invention, since the accelerating electrode in which the objective lens is embedded or the Fresnel lens having the accelerating electrode is used, the distance between the sample and the accelerating electrode can be brought close to the working distance of the lens. , It becomes possible to guide the molecule to the acceleration region.

Further, since the condenser lens is embedded in the electrode, the disturbance of the electric field in the acceleration region due to the lens is small, and the deterioration of resolution can be avoided.

When a Fresnel lens is used, an electric field that is substantially parallel to the traveling direction of ions is formed, so that a spectrum with higher resolution can be obtained.

[0014]

【Example】

[Embodiment 1] FIGS. 1 and 2 are block diagrams showing an embodiment of the present invention. 1 is an overall view, and FIG. 2 is an enlarged view of an electrode portion.
1 is a mass spectrometer, 2 is a sample, 6a and 6b are laser light sources,
7a and 7b are laser lights, 8 is a sample illumination light source, 9 is sample illumination light, 10 is a TV camera, 11 is a half mirror, and 15
Is a camera lens, 16a and 16b are light reflecting mirrors, 17
Is an optical path, 18 is a vacuum chamber, 19 is a vacuum container, 21a is a molecular beam, 21b is an ion beam, 24 is a light reflection mirror,
26 is a sample stage, 30 is an ion reflector, and 34 is an ion detector. Reference numeral 40 is an accelerating electrode, and 22 is a condenser lens embedded in the accelerating electrode.

At the time of mass analysis, the laser light 7a from the laser light source 6a is condensed on the sample 2 by the condenser lens 22. The molecular beam 21 a thus excited enters the mass spectrometric unit 1. Here, the molecular beam is ionized by the laser beam 7b from the laser light source 6b, and the ion beam 21
b. The ion beam 21b is reflected by the ion reflector 30 and enters the ion detector 34. The ion flight time can be known by measuring the time from the irradiation of the laser beam 7b to the arrival of the ions at the ion detector 34. This enables mass spectrometry of ions.

At the time of observing the sample, the light from the light source 8 for illuminating the sample is made incident on the sample from the condenser lens 22. The resulting image of the sample is observed by the TV camera 10.

In this embodiment, as shown in FIG. 2, the electrode in which the condenser lens 22 is embedded is used as the acceleration electrode 40. In this case, the distance between the acceleration electrode 40 and the sample 2 can be made extremely short.
Therefore, the molecules desorbed from the sample can be efficiently sent to the mass spectrometric section, and the sensitivity can be improved.

Further, since the condenser lens 22 is embedded in the electrode, the disturbance of the electric field is small and a spectrum with high resolution can be obtained.

[Embodiment 2] FIG. 3 shows an enlarged view of an electrode portion in Embodiment 2 of the present invention. In the present embodiment, a Fresnel lens 42 having a hole in the center and a mesh electrode 41 is
The acceleration electrode was used. In this case, by using a thin Fresnel lens, the distance between the accelerating electrode 47 and the sample 2 is further shortened, and the desorbed molecules can be efficiently sent to the mass spectrometric section, and the sensitivity can be improved.

Further, since the electric field formed between the Fresnel lens 42 and the sample 2 is an electric field substantially parallel to the traveling direction of the ions, there is almost no disturbance of the electric field, and a spectrum with extremely high resolution can be obtained.

[0021]

According to the present invention, the distance between the electrode and the sample can be brought close to the working distance of the condenser lens, and the molecules desorbed from the sample can be efficiently sent to the mass spectrometer, and the sensitivity is high. Analysis is possible.

Further, by integrating the electrode and the condenser lens, influence on the electric field in the acceleration region of the condenser lens is reduced, and a spectrum with high mass resolution can be obtained.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention.

FIG. 2 is an enlarged view of an accelerating electrode unit according to the first embodiment.

FIG. 3 is an enlarged view of an accelerating electrode portion according to a second embodiment.

FIG. 4 is a system diagram of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Mass spectrometry part, 2 ... Sample, 6 ... Laser light source, 7 ... Laser light, 8 ... Sample illumination light source, 9 ... Sample illumination light, 10 ... TV camera, 11 ... Half mirror, 13 ... Switching mirror, 15 ... Camera lens, 16 ... Light reflecting mirror, 17 ... Optical path, 18 ... Vacuum chamber, 19 ... Vacuum container, 21a ... Molecular beam, 21b ... Ion beam, 22 ... Condensing lens, 24 ... Light reflecting mirror, 30 ... Ion reflector, 34 ... Ion detector, 34a ... Ion passage hole, 40 ... Accelerating electrode, 41 ... Reticulated electrode, 42 ... Fresnel lens.

Front page continued (72) Inventor Masayoshi Ezawa 3300 Hayano, Mobara-shi, Chiba Hitachi Ltd. Electronic Devices Division

Claims (5)

[Claims] 1. A laser light source for exciting a sample, a light source for observing and illuminating the sample, a light reflection mirror for guiding light from each of the light sources to the sample, a sample stage on which the sample is arranged, and a light emitted from the sample. In a mass spectrometer equipped with an accelerating electrode for accelerating ions, an ion reflector for reflecting the accelerated ions, and an ion detector for detecting the ions reflected by the ion reflector, a lens for laser focusing and the accelerating electrode A mass spectrometer characterized by being integrated. 2. A mass spectrometer according to claim 1, further comprising an accelerating electrode in which a condenser lens is embedded. 3. A mass spectrometer according to claim 1, further comprising a Fresnel lens having an accelerating electrode. 4. The mass spectrometer according to claim 3, further comprising a Fresnel lens having a reticulated acceleration electrode. 5. The mass spectrometer according to claim 4, further comprising a Fresnel lens having a mesh electrode in the central portion.