JPH0589823A - Mass-spectrometer - Google Patents

Abstract

PURPOSE:To converge a laser beam onto a specimen and send ions generated thereby effectively to a mass-spectrometric part by installing one or two objective lenses inclined between the specimen and an electrode to accelerate or deflect the ions. CONSTITUTION:When mass-spectrometry is executed, a laser beam 7a emitted by a laser beam source 6a is reflected by a mirror 24c and converged onto a specimen by an objective lens 22a installed aslant. Laser beam 7b from another laser beam source 6b is converged on the central part of the specimen 2 by another lens 22b installed aslant, and an ion beam 21b excited is put incident to a mass-spectrometric part 1, reflected by an ion reflector 30, and cast onto an ion sensor 34. The ion flying time can be determined by measuring the time from irradiation with the laser beam 7 till the ion attaining the sensor 34. Thereby the mass of the ion can be analyzed. When the specimen is to be observed, the beam from a light source 8 for illuminating the specimen, is cast onto the specimen using an illumination lens 23, and the image of the specimen is observed using a TV camera 10.

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 a trace amount of organic substances adhering (contaminating) to electronic parts such as semiconductors, and more particularly to a mass spectrometer for ionizing using a laser.

[0002]

2. Description of the Related Art A conventional mass spectrometer is disclosed in JP-A-63-146.
As described in Japanese Unexamined Patent Publication No. 339, it was as shown in the system diagram of FIG. 1 is a mass spectrometric unit, 2 is a sample, 6 is a laser light source, 8 is a light source for observation illumination, 12 is a light introducing means, 18 is a vacuum chamber, 22 is a condenser lens, 24 is a light reflecting mirror, 24
a is an ion passage hole, 26 is a sample stage, 28 is an ion extraction electrode, 30 is an ion reflector, 34 is an ion detector, 3
4a is an ion passage hole. 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. The ions excited by the laser light pass through the ion passage hole 24a in the center of the light reflection mirror 24, and are mass analyzed by the mass analysis unit 1.

In this conventional apparatus, since the light reflecting mirror 24 is provided between the condenser lens 22 and the sample 2, it is not considered to use a lens having a large numerical aperture, and the sample can be observed with a microscope. There is a defect that the laser cannot be narrowed down on the sample.

[0004]

In the conventional apparatus, since there is a light reflecting mirror between the sample and the condenser lens, it is necessary to use a lens having a small numerical aperture and a long focal length, and a lens having a large numerical aperture is used. Is virtually impossible,
The sample cannot be observed under a microscope and the laser cannot be narrowed to that location.

Further, in the conventional apparatus, the light reflecting mirror is perforated to allow the ions to pass therethrough, and it is not considered to efficiently send the ions generated from the sample to the mass spectrometric section.

Further, in the above-mentioned conventional apparatus, the irradiation of the sample with plural kinds of laser light is not taken into consideration, and the ionization of the sample cannot be performed under the optimum conditions.

It is an object of the present invention to use a lens having a large numerical aperture so that a laser can be narrowed down on a sample.

Another object of the present invention is to efficiently send the ions generated from the sample to the mass spectrometer.

Still another object of the present invention is to irradiate a sample with a plurality of types of laser light to ionize the sample under optimum conditions.

[0010]

In order to achieve the above object, the present invention sets the working distance of the objective lens by tilting the objective lens between it and a plurality of electrodes for accelerating or deflecting the ions. Shorten and increase numerical aperture. In order to achieve other purposes, the objective lens is installed outside the passage through which the ions pass so that the ions can be efficiently sent to the mass spectrometer. Further, in order to achieve still another object, two or more objective lenses are installed and two or more kinds of laser beams are irradiated on the sample.

[0011]

The operation of the present invention will be described with reference to FIG. 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, 13 is a switching mirror, 15 is a camera lens, 16 is a light reflecting mirror, 17a is an optical path, 18 is a vacuum chamber, 19 is a vacuum container, 21b is an ion beam, 22a,
22b is an objective lens, 23 is an illuminating lens, 24c is a light reflecting mirror, 26 is a sample stage, 28a and 28b are ion extraction electrodes, 30 is an ion reflector, and 34 is an ion detector.

Here, when the light is focused by the objective lenses 22a and 22b, due to the wave nature of the light, the light is not focused at one exact point, and the surface becomes a minute surface having a certain spread. This condensing diameter is determined by the numerical aperture of the lens and is given by the following equation.
(Condensing diameter) = 1.22 × (wavelength) / 2 (numerical aperture) In the conventional device, since the light reflecting mirror is provided between the objective lens and the sample, the focal length of the objective lens becomes long due to the structure, and the aperture is increased. The number could not be increased, and as can be seen from the above equation, the focused diameter could not be reduced. However, in the present invention, there is no obstacle between the objective lenses 22a and 22b and the sample 2,
An objective lens having a small focal length and a large numerical aperture can be used. As a result, the laser light can be narrowed down on the sample.

Further, the two pairs of electrodes provided above and below the objective lens can efficiently guide the ion particles desorbed from the sample by the laser light to the time-of-flight mass spectrometer. Further, since the conical trumpet tube with the gas introduction tube attached to the lower part can generate the molecular flow in the direction of the time-of-flight mass spectrometer, mass analysis can be performed efficiently and with high sensitivity.

[0014]

【Example】

(Embodiment 1) FIGS. 1 and 2 show system diagrams of one embodiment of the present invention. FIG. 2 is an enlarged view of the laser irradiation part on the sample.
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, 13 is a switching mirror, 15 is a camera lens, 16 is a light reflecting mirror, 17a is an optical path, 1
8 is a vacuum chamber, 19 is a vacuum container, 21b is an ion beam,
22a and 22b are objective lenses, 23 is an illumination lens, 2
4c is a light reflection mirror, 26 is a sample stage, 28a and 28b are ion extraction electrodes, 30 is an ion reflector, and 34 is an ion detector.

At the time of mass analysis, the laser light 7a from the laser light source 6a is reflected by the light reflecting mirror 24c and then focused on the sample 2 by the objective lens 22a. The laser light 7b from the laser light source 6b is focused on the central portion by the objective lens 22b. The ion beam 21b thus excited enters the mass spectrometric unit 1. The ion beam 21b is reflected by the ion reflector 30 and enters the ion detector 34. The flight time of the ions can be known by measuring the time from the irradiation of the laser beam 7 until the ions reach the ion detector 34. This allows the mass of the ions to be analyzed.

Further, at the time of observing the sample, light from the sample illuminating light source 8 is made incident on the sample by the illuminating lens 23.
The resulting image of the sample is observed by the TV camera 10.

In this embodiment, since the objective lens 22a is inclined, an image similar to that of a conventional microscope cannot be observed. However, since the depth of focus is at 30 μm,
× It is possible to observe the measurement location with a visual field of width 500 μm.
There is no obstacle other than the ion extracting electrode 28b between the objective lenses 22a and 22b and the sample 2, and two objective lenses 22a and 22b having a small focal length and a large numerical aperture can be used. Therefore, the laser light 7a can be narrowed down on the sample 2 by the objective lens 22a, and the laser light can be irradiated to the measurement position on the sample 2.

Further, two ion extraction electrodes 28a and 28b are provided above and below the objective lenses 22a and 22b, and a voltage is applied between these electrodes to efficiently remove the substance desorbed from the sample 2 by the laser beam 7. It can be sent to the mass spectrometric unit 1.

Also, two or more objective lenses 22a, 22
By providing b, it is possible to easily and efficiently irradiate the sample with a plurality of types of laser beams 7a and 7b, and it is possible to improve the ionization efficiency.

(Embodiment 2) FIG. 3 shows an enlarged view of a laser irradiation portion for a sample in Embodiment 2 of the present invention. In the second embodiment, a conical sample introducing tube 44 having a gas introducing tube 43 is provided instead of the ion extracting electrode 28 of the first embodiment. The substance desorbed from the sample 2 by the laser beam 7a by the gas flow from the gas introduction tube 43 can be efficiently sent to the mass spectrometric unit 1. The laser light 7b is focused on the central portion by the objective lens 22b and ionizes the neutral particles. In addition, the degree of vacuum in the sample chamber is 1 × 10 ￣ 3 Pa, and the degree of vacuum on the detector side is 1 × 10 ￣
The material desorbed from the sample 2 by the laser light 7a can be sent to the mass spectrometric section 1 at 4 Pa or more by the differential pumping. In such an apparatus, at the time of mass analysis, laser light of 355 nm from a YAG laser and 193 nm from an excimer laser are respectively incident from 7a and 7b in FIG.
Was irradiated. The same effects as in Example 1 were obtained with this device.

In the second embodiment, the gas flow from the gas introduction pipe 43 and the method of introducing the substance desorbed from the two samples 2 by differential evacuation are used together.

[0022]

According to the present invention, there is no obstacle between the objective lens and the sample, and the objective lens having a small focal length and a large numerical aperture can be used. Further, it is possible to observe the sample with a microscope and to narrow down the laser light to the measurement location.

Further, by attaching the objective lens so as to be removed from the path of the ions and further installing the flow of molecular particles and the extraction electrode, the substance desorbed from the sample can be efficiently sent to the mass spectrometer, and it is very small. The location can be measured with high sensitivity and S
A mass spectrum with a good / N 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 a laser irradiation part on the sample of FIG.

FIG. 3 is an enlarged view of a laser irradiation part for a sample of the second embodiment,

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Mass spectrometry part, 2 ... Sample, 8 ... Sample illumination light source, 10 ... TV camera, 13 ... Switching mirror, 15 ... Camera lens, 16 ... Light reflection mirror, 19a, 19b ... Vacuum container, 22 ... Condensing lens , 22a, 22b ... Objective lens, 24 ... Light reflection mirror.

Claims (2)

[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 the sample In a mass spectrometer equipped with a plurality of electrodes for accelerating or deflecting the ions emitted from the detector and a detector for detecting the flight time of ions ejected from the mass spectrometer, an inclined objective lens having two electrodes arranged before and after is installed. A mass spectrometer characterized in that 2. The mass spectrometer according to claim 1, wherein a conical sample introducing trumpet tube having a gas introducing tube attached to the lower part is installed.