JPH04306549A - Microscopic laser mass spectrometer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 trace amounts of organic matter adhering to (contaminating) electronic components such as semiconductors, and more particularly to a mass spectrometer that performs ionization using a laser.

0002

[Prior art] The conventional mass spectrometer is JP-A-63-146
As described in Publication No. 339, the system was as shown in the system diagram of FIG. 1 is a mass spectrometry section, 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 condensing 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. Laser light generated from the laser light source 6 is focused onto the sample 2 by a condensing lens 22 and a light reflecting mirror 24 . Ions excited by this laser light pass through the ion passage hole 24 at the center of the light reflecting mirror 24 and are subjected to mass analysis by the mass spectrometer 1.

In this conventional apparatus, since there is a light reflecting mirror 24 between the condenser lens 22 and the sample 2, the numerical aperture (Nu
This method does not take into account the use of a lens with a large merical aperture, and has drawbacks such as the inability to observe the sample with a microscope or to focus a laser onto the sample.

0004

[Problems to be Solved by the Invention] In the conventional apparatus, since there is a light reflecting mirror between the sample and the condensing lens, N. A. It is necessary to use a lens with a small N.
A. Since it is virtually impossible to use a lens with a large .

Furthermore, in the conventional apparatus, a hole is made in the light reflecting mirror to allow the ions to pass through, and no consideration is given to efficiently sending the ions generated from the sample to the mass spectrometer.

Furthermore, the conventional apparatus described above does not take into account the irradiation of a sample with multiple types of laser beams, and therefore cannot ionize the sample under optimal conditions.

An object of the present invention is to use a lens with a large numerical aperture to focus a laser beam onto a sample. Another object of the present invention is to efficiently send ions generated from a sample to a mass spectrometer. Still another object of the present invention is to ionize the sample under optimal conditions by irradiating the sample with a plurality of types of laser beams.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a working distance of the objective lens by installing the objective lens at an angle between the electrode that accelerates or deflects ions and the sample stage. and increase the numerical aperture. In order to achieve another objective, an objective lens was installed outside of the path through which ions pass to efficiently send ions to the mass spectrometer. Moreover, in order to achieve the above-mentioned other object, two or more objective lenses are installed to irradiate the sample with two or more types of laser light.

[0009]

[Operation] The operation of the present invention will be explained with reference to FIG. 1 is a mass spectrometry section, 2 is a sample, 6a and 6b are laser light sources, 7a and 7b are laser beams, 8 is a light source for sample illumination, 9 is sample illumination light, 10
is a TV camera, 11 is a half mirror, 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 and 22b are objective lenses , 24c, 24d
26 is a light reflecting mirror, 26 is a sample stage, 28 is an ion extraction electrode, 30 is an ion reflector, and 34 is an ion detector.

[0010] When focusing the light using the objective lenses 22a and 22b, due to the wave nature of the light, the light is not focused on one exact point, but rather on a microscopic surface with a certain spread. This condensing diameter is determined by the numerical aperture of the lens and is given by the following formula.

(Focusing diameter) = 1.22 x (wavelength) / 2 (N.A.) In the conventional device, there was a light reflecting mirror between the objective lens and the sample, so the focal length of the objective lens was structurally limited. becomes long, making it impossible to increase the numerical aperture, and as can be seen from the above equation,
It was not possible to reduce the condensing diameter. However, in the present invention, there is no obstacle between the objective lenses 22a, 22b and the sample 2, and an objective lens with a small focal length and a large numerical aperture can be used. This allows the laser beam to be focused onto the sample.

0012

【Example】

(Embodiment 1) FIG. 1 shows a system diagram of an embodiment of the present invention. 1 is a mass spectrometer, 2 is a sample, 6a and 6b are laser light sources,
7a and 7b are laser beams, 8 is a sample illumination light source, 9 is a sample illumination light, 10 is a TV camera, 11 is a half mirror, 13
15 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, 2
1b is an ion beam, 22a and 22b are objective lenses, 2
4c is a light reflecting mirror, 24d is a rotating light reflecting mirror, 26
28 is an ion extraction electrode, 30 is an ion reflector, and 34 is an ion detector.

During mass spectrometry, two laser light sources 6a, 6
The laser beams 7a and 7b from b are each reflected by a light reflecting mirror 2.
4c and the rotating light reflecting mirror 24d,
The light is focused onto the sample 2 by objective lenses 22a and 22b. The ion beam 21 excited thereby enters the mass spectrometer 1. The ion beam 21 is connected to the ion reflector 3
0 and enters the ion detector 34. By measuring the time from when the laser beam 7 is irradiated until the ions reach the ion detector 34, the flight time of the ions can be determined. This allows the mass of the ion to be analyzed.

[0014] Also, when observing the sample, the rotating light reflecting mirror 2
4d is rotated in the direction of the broken line, and the light from the sample illumination light source 8 is reflected by the light reflecting mirror 24c and the rotating light reflecting mirror 24d, and is made to be incident on the sample by the objective lenses 22a and 22b. The resulting image of the sample is observed using the TV camera 10.

In this embodiment, although the objective lens is tilted, since two objective lenses 22a and 22b are used, images similar to those of a conventional microscope can be observed. Objective lens 2
An ion extraction electrode 28 is provided between 2a, 22b and the sample 2.
There are no obstacles other than the two objective lenses 22a and 22b.
It is possible to use a lens with a small focal length and a large numerical aperture. Therefore, it is possible to narrow the laser beam 7 onto the sample 2 by the objective lens 22b and irradiate the measurement position on the sample 2 with the laser beam.

Furthermore, since a gap is provided between the objective lenses 22a and 22b, the substance detached from the sample 2 by the laser beam can be sent to the mass spectrometer 1 without any obstruction.

Furthermore, two or more objective lenses 22a, 22
By providing b, the sample can be easily and efficiently irradiated with a plurality of types of laser beams 7a and 7b, and the ionization efficiency can be improved.

(Embodiment 2) FIGS. 2 and 3 are enlarged views of a laser irradiation part for a sample in Embodiment 2 of the present invention. FIG. 2 is a side view, and FIG. 3 is a plan view. In Example 2, the same light reflecting mirror 24e as 24c is used in place of the rotating light reflecting mirror 24d of Example 1, and rotating light reflecting mirrors 24f and 24g are used to switch between the laser beam and the sample illumination light.
has been established. Other than the above, this embodiment is the same as the first embodiment. With such a device, 193
The laser beams of 355 nm and 355 nm from the YAG laser are incident from 7a and 7b in the figure, respectively, to the light reflecting mirror 24c,
24e and objective lenses 22a and 22b. The same effects as in Example 1 were obtained with this device as well.

In the second embodiment, the rotating light reflecting mirrors 24f, 2
4g is provided outside the vacuum container, which has the advantage of being easy to manufacture and easy to handle.

(Embodiment 3) FIG. 4 shows a system diagram of Embodiment 3 of the present invention. In this example, the mass spectrometer 1 of Example 1 is installed horizontally, and the operation is the same as that of Example 1. The same effects as in Examples 1 and 2 were obtained.

[0021]

According to the present invention, there is no obstacle between the objective lens and the sample, and an objective lens with a small focal length and a large numerical aperture can be used. Furthermore, it is possible to observe the sample with a microscope and focus the laser beam onto a small area to be measured.

Furthermore, since the objective lens is mounted outside the ion path, the substances desorbed from the sample can be efficiently sent to the mass spectrometer, allowing highly sensitive mass spectrometry measurements of extremely small areas. , it is possible to obtain a mass spectrum with good S/N.

[Brief explanation of drawings]

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

FIG. 2 is a side view of a laser irradiation section for a sample in Example 2.

FIG. 3 is a plan view of a laser irradiation section for a sample in Example 2.

FIG. 4 is a system diagram of Example 3.

FIG. 5 is a system diagram of a conventional device.

[Explanation of symbols]

1. Mass spectrometry department 2‥‥‥Sample ８‥‥‥Light source for sample illumination １０‥‥‥TV camera １１‥‥‥Half mirror 13‥‥‥Switching mirror 15‥‥‥Camera lens 16‥‥‥Light reflecting mirror 19a, 19b‥‥‥Vacuum container 22‥‥‥Condensing lens 22a, 22b...Objective lens 24‥‥‥Light reflecting mirror

Claims (1)

[Claims] 1. A laser light source that excites a sample, a light source for illuminating the sample for observation, a light reflecting mirror that guides light from each of the light sources to the sample, a sample stage on which the sample is placed, and a light source for illuminating the sample. In a mass spectrometer equipped with an electrode that accelerates or deflects ions emitted from the sample and a detector that detects the flight time of the ions ejected from the electrode, an objective lens is installed at an angle between the electrode and the sample stage. A mass spectrometer characterized by: