JPH06310092A - Laser ionized neutral particle mass spectrograph - Google Patents

Abstract

PURPOSE:To prevent a laser beam from being irradiated to a surface of a sample while bringing a laser passing position to the surface of the sample as close as possible in a mass spectrograph to measure a mass spectrum of the photoexcited ions by ionizing a neutral particle sputtered from the surface of the sample by the laser beam. CONSTITUTION:A mass spectrograph is constituted in such a way that an ion beam B is irradiated to a surface of a solid sample by an ion beam generating device 12, an electrostatic lens 13 and a scanning electrode 14, and a neutral particle C is sputtered, and is ionized by an ultraviolet laser beam L to generate a light exciting ion Ic, and an abrasion ion is removed by an extraction electrode 16 and an energy analyzer 17. In this mass spectrograph, the ultraviolet laser beam L is made incident in the oblique rear direction of the surface of the solid sample 11, and a side surface of the solid sample 11 intercepts the lower part of the ultraviolet laser beam L, so that the ultraviolet laser beam L is prevented from being irradiated to an analyzing surface of the solid sample 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to photoexcited ions obtained by ionizing a neutral particle having no electric charge by a laser among particles sputtered by applying an ion beam to a solid sample as an analyte. The present invention relates to a laser ionization neutral particle mass spectrometer that performs mass analysis of a sample by measuring a mass spectrum.

[0002]

2. Description of the Related Art In this type of laser ionization neutral particle mass spectrometer, in order to efficiently ionize neutral particles sputtered from the surface of a solid sample with laser light,
It is desirable that the laser beam passage position be as close to the solid sample surface as possible. However, in this case, there is a problem that a part of the laser is irradiated onto the sample surface and new ions (laser ablation ions) are generated.

Therefore, the inventors of the present invention have disclosed in Japanese Unexamined Patent Publication No. 3-291.
In the inventions of 559 and JP-A-4-58447, an apparatus for effectively separating ions such as laser ablation ions and secondary ions and detecting only photoexcited ions was devised. FIG. 4 shows an overall view of the laser ionization neutral particle mass spectrometer invented by the present inventors.

In FIG. 4, an ion beam generator 32 is shown.
The ion beam B is further generated. Next, after the ion beam B is converged by the electrostatic lens 33, the scanning electrode 3
The surface of the solid sample 31 is oscillated by 4 to scan the surface of the solid sample 31, and is impacted on the surface. The impact of the ion beam B sputters the neutral particles C and the secondary ions I ₂ . Neutral particles C
Are photoexcited ions I which are ionized by the ultraviolet laser light L.
_c . The photoexcited ions I _c are extracted from the ionization region by the extraction electrode 36, and the energy analyzer 37
After passing through, the mass is separated by a mass analyzer 38 using a magnetic field or an electric field, and then pulsed by an ion detector 39,
It is counted by the pulse counter 40.

In such an apparatus, the generation position of the photoexcited ion I _c is different from that of the laser ablation ion or secondary ion I ₂ generation apparatus. Therefore, since the electric potential applied by the extraction electrode 36 is different, the energy can be easily separated by the energy analyzer 37. Therefore, the photoexcited ion I _c is effectively separated from the laser ablation ion or the secondary ion and detected. It is possible. Therefore, the laser passage position can be brought close to the sample surface, and the neutral particles can be efficiently photoionized.

[0006]

However, in addition to the generation of laser ablation ions by irradiating the sample surface with part of the laser, a chemical reaction occurs, for example, because the sample surface is heated by the laser. Problems such as the inability to analyze arise. Therefore, it is necessary to provide a method of irradiating the sample surface with the laser and bringing the laser as close to the sample surface as possible.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to make a laser passing position as close to the sample surface as possible so as to enhance the ionization efficiency of neutral particles sputtered from the sample surface. Can get closer,
Moreover, it is another object of the present invention to provide a laser ionization neutral particle mass spectrometer which does not irradiate the sample surface with a laser.

[0008]

In order to achieve the above object, the present invention has the following constitution. That is, means for irradiating the surface of a solid sample, which is an analyte, in a vacuum with an ion beam to sputter neutral particles from the surface of the solid sample (ion beam generator, electrostatic lens, scanning electrode, etc.); A pulse laser that ionizes neutral particles to generate photoexcited ions, a mass analyzer that mass-separates the photoexcited ions, and an ion detector that detects the ions mass-separated by the mass analyzer, and further In the laser ionization neutral particle mass spectrometer having a means (extraction electrode, energy analyzer, etc.) for removing ablation ions generated by direct irradiation of the solid sample by the pulse laser, the pulse laser Incident on the surface of the solid sample obliquely from the rear side, and the side surface of the solid sample is set to the pulse laser. Pulse laser by blocking some of the positions the laser device so as not to irradiate the analytical surface of the solid sample surface.

[0009]

In the above structure, the laser light passes obliquely from the rear to the front with respect to the sample surface to be analyzed, with the lower portion of the laser light shielded by the side surface of the sample.
The lower portion of the laser beam, which has hitherto been irradiated on the sample surface, is blocked by the side surface of the sample and is not irradiated on the sample surface. As a result, the problem that the sample surface is not heated by the laser and a chemical reaction occurs to make analysis impossible can be solved. Further, the laser passage position is almost the same as in the conventional case, and can be brought close to the sample surface. Although the lower part of the laser light irradiates the side surface of the sample, if there is a distance from the analysis position, there is no fear of thermal influence.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an illustrated embodiment. 1 and 2 are an overall schematic view showing a laser ionization neutral particle mass spectrometer of the present invention, and an enlarged view near a solid sample. As shown in FIG. 1, solid sample 1
An ion beam generator 12, an electrostatic lens 13, and a scanning electrode 14 are arranged diagonally above 1 in the same manner as in the conventional case, and an extraction electrode 16 and an energy analyzer 17 are provided on the solid sample 11. A mass analyzer 18, an ion detector 19, and a pulse counter 20 are connected to the energy analyzer 17.

The ion beam B generated by the ion beam generator 12 is converged by the electrostatic lens 13 and then
The scanning electrode 14 vibrates and impacts while scanning the surface of the solid sample 11. Neutral particles C and secondary ions I ₂ are sputtered from the solid sample 11 by the impact of the ion beam B. The neutral particles C are ionized by the ultraviolet laser light L from the pulse laser 15 and become photoexcited ions I _c .
This photoexcited ion I _c is extracted from the ionization region by the extraction electrode 16, energy-separated from laser ablation and secondary ions by the energy analyzer 17, and then mass-separated by the mass analyzer 18 using a magnetic field or an electric field. It is converted into electric pulses by the ion detector 19 and counted by the pulse counter 20.

In the above-mentioned structure, the laser device 1
5, the ultraviolet laser light L is directed to the upper side surface of the solid sample 11 so that part of the ultraviolet laser light L is solid sample 11
The ultraviolet laser light L passes through the surface of the solid sample 11 from obliquely rearward to obliquely forward while being blocked by the upper end of the side surface of the solid sample 11.

In such a structure, as shown in FIG. 2, the lower portion a of the ultraviolet laser light L, which is conventionally irradiated on the surface 11a of the solid sample 11, is the side surface 1 of the solid sample 11.
The surface 11 of the solid sample 11 blocked by the upper end of 1b
a will never be illuminated. The lower part a of the ultraviolet laser light L irradiates the side surface 11b of the sample, but it does not exert a thermal influence by setting an appropriate distance from the analysis position.

The lower part a of the ultraviolet laser beam L is the solid sample 1
By not irradiating the surface portion of No. 1, the solid sample 11
The surface of is not heated by the laser light L and does not cause a chemical reaction. FIG. 3 is a graph showing the photoexcited ion intensity with respect to the sample surface when such an apparatus is applied to the Si oxide film, and it can be seen that there is no thermal influence by the laser.

[0015]

As described above, according to the present invention, a pulsed laser for ionizing neutral particles sputtered from the surface of a solid is made incident obliquely behind the solid sample, and the side surface of the solid sample is the pulse laser. Since the pulsed laser is prevented from irradiating the analysis surface of the solid sample by blocking a part of it, it is possible to prevent the laser from irradiating the sample surface with the passing position of the laser as close to the sample surface as possible. It enables surface analysis that is not affected by.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the entire laser ionization neutral particle mass spectrometer of the present invention.

FIG. 2 is an enlarged view of the vicinity of a solid sample in the apparatus of FIG.

FIG. 3 is a graph showing an example of depth direction analysis of a Si oxide film according to the present invention.

FIG. 4 is a schematic diagram showing a conventional laser ionization neutral particle mass spectrometer.

[Explanation of symbols]

B ion beam C neutral particles I _c photoexcitation ion I ₂ secondary ions 11 solid sample 12 ion beam generator 13 electrostatic lens 14 scan electrodes 15 pulse laser 16 lead electrode 17 energy analyzer 18 mass analyzer 19 ion detector 20 Pulse counter

Claims (1)

[Claims] 1. A means for irradiating the surface of a solid sample, which is an analyte, in a vacuum with an ion beam to sputter neutral particles from the surface of the solid sample, and ionizing the neutral particles to generate photoexcited ions. A pulse laser, a mass analyzer for mass-separating the photoexcited ions, and an ion detector for detecting ions mass-separated by the mass analyzer, and the pulse laser directly irradiates the solid sample. In a laser ionization neutral particle mass spectrometer having a means for removing ablation ions generated by the mass spectrometer, the pulse laser is made incident from obliquely behind the surface of the solid sample, and the side surface of the solid sample is the pulse. By blocking a part of the laser, the pulsed laser is prevented from irradiating the analysis surface of the solid sample surface. Laser ionization neutral mass spectrometer, characterized in that a device.