JPS6012657A - Secondary ion mass spectrometer - Google Patents

Abstract

PURPOSE:To enable an insulating sample and a sample in which a molecular ion peak can be detected only with difficulty such as a macromolecular sample to be stably measured by neutralizing electric charges accumulated in the sample by means of low-energy secondary electrons without causing electrons to be directly incident upon the sample. CONSTITUTION:A secondary-beam-discharging plate 10 for example a plate made of a material such as Cu-Be alloy, is installed near a sample 3 and on a sample holder 4' for installing the sample 3. In analyzing secondary ions (Ip2) discharged from the surface of the insulating sample 3 by irradiating a primary ion beam (Ip1) on a spot (S) of the sample 3, a primary electron beam (Ie1) is irradiated upon the secondary-electron-discharging plate 10 in order to neutralize accumulated electric charges. As a result, secondary electrons (Ie2) are discharged from the secondary-electron-discharging plate 10 before becoming incident upon the sample surface to neutralize electric charges accumulated in the sample 3. The secondary electrons (Ie2) the energy of which is limited to 30 eV, can efficiently neutralize accumulated electric charges irrespective of the kind of the sample 3. In addition, since electrons with high speeds of not less than several hundreds eV do not become incident upon the sample surface, there is a decreased possibility that molecules of a high molecular compound or the like are severed by colliding with high- speed electrons, thereby facilitating the detection of a molecular ion peak.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a secondary ion mass spectrometer, and particularly relates to novel improvements that are useful for measuring insulators.

In general, a secondary ion mass spectrometer, as shown in FIG. do. The energy of secondary ions IP emitted from the sample 3 is selected by an electrostatic analyzer 5, subjected to mass analysis by a mass spectrometer 6, and detected by an ion detector 7. When the sample 3 is an insulator, the sample is conventionally irradiated with an electron beam 11 emitted by an electron gun 8. Figure 2 shows a detailed view of the vicinity of the sample. - The next ion beam P irradiates the sample 3 with a spot S, and the next ion beam Ip is emitted from the sample 3. On the other hand, the primary electron PME g1 irradiates the periphery of the spot S and is accumulated in the sample 3 made of an insulator: fL 7-
C charge is neutralized. In addition, in order to guide the secondary ions emitted from the surface of the sample 3 to the electrostatic analyzer 5, several 1006'
There is a potential gradient of V, and several 10,087 210-speed voltages are required for the middle electrons to reach the sample surface 3. Therefore, in the conventional method, when it is desired to detect a molecular ion beak in a polymer sample, molecules in the sample are cut off by collisions with these high-speed electrons, making it difficult to detect the molecular ion beak. Furthermore, since the sample is directly irradiated with electrons, the sample may be overheated and the conditions of the sample may change during measurement.

Next, when a substance is irradiated with electrons, all of the secondary electrons and backscattered electrons are emitted near the surface. The relationship between δ1, which is the ratio of the number of emitted electrons to the number of incident electrons, and Flto is as shown in FIG. 1! io and Eo are the points where the number of incident electrons and the number of re-emitted electrons are equal to 0, usually Eo
is several tens of gv. is about 1 to 10 Kev. Therefore E. When a sample is irradiated with electrons having energy below or above 80, the sample becomes negatively charged and the accumulated charge caused by the primary ion beam can be effectively neutralized. Now, when a layered insulator sample is directly irradiated with electrons, at the interface, depending on the material of the sample,
Because EAe''R changes, even if static electricity is prevented under the conditions of the first surface layer, the second and subsequent layers cannot be effectively prevented from charging.These are the drawbacks of the method in which electrons are directly incident on the sample.

The present invention eliminates the above-mentioned drawbacks and enables stable measurement of insulator samples, including samples such as polymer samples where molecular ion peaks are difficult to detect, and layered insulator samples. Be like n! This is what I did.

Below is the main part configuration 2 in the embodiment of the present invention! The sample 3 is placed on the sample holder 4+, which stores the sample 3, as shown in FIG.
A secondary electron emission plate 10, for example, 0u-
Set up an old-fashioned board like B. For such a configuration!
? When the spot S of the insulator sample 3 is irradiated with the primary ion beam P, and the secondary ions emitted from the sample surface 3 are analyzed, the -order electron beam is used to neutralize the accumulated charge. The secondary electron emission plate 10 is irradiated with the beam a. Therefore, the secondary electrons e are emitted from the secondary electron emission plate 10 and are incident on the sample surface to neutralize the accumulated charges.

(7) The energy of secondary electronics g11 is at most blade ev
Since the electron energy E0 in Fig. 3 is about the same as the electron energy E0 in Fig. 3, the accumulated charge can be efficiently neutralized regardless of the type of sample, if the energy is less than 7 mm. In addition, because high-speed electrons of several ioo e v or more are not incident on the sample surface, molecules such as polymers are not cut due to collision with high-speed electrons.
The probability that the molecular ion beak will be detected will decrease and the molecular ion beak will be detected sooner.

Examples in which similar effects were obtained will be shown below.

FIG. 5 shows an arrangement in which the secondary electron emission plate 10 is a flat plate, the distance from the sample surface 3 is minimized, and the plate is parallel to the sample surface.

In FIG. 6, the sample holder 41 itself is made of a secondary electron emitting material, such as Ow-B, and the sample holder 41 is made of a secondary electron emitting material such as Ow-B.
This is an example in which the sample holder 41 near the boundary between -41 and sample 13 is irradiated with primary electrons and one mue e8.

FIG. 7 shows an example in which the ring-shaped secondary electron emission plate 10 is irradiated with a primary electron beam, passing through the −th order ion beam P1 entirely in the middle of the secondary electron emission plate 10.

As described above, according to the present invention, since electrons are not directly incident on the sample, the sample is not heated and conditions do not change during measurement. In addition, nJC is accumulated in the sample by secondary electrons with low energy.
In order to neutralize the charge, it is easy to obtain a molecular ion peak with polymer samples, and insulator samples with a layered structure can be measured stably because the number of secondary electrons incident on the sample is constant. can. In addition, since the number of electrons incident on the sample is amplified by the secondary electron emission plate, it is possible to neutralize the sample with a smaller number of primary electron beams than in the past.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a conventional general secondary ion mass spectrometer 1. FIG. 2 shows a conventional charge neutralization method. FIG. 3 is a characteristic diagram showing the relationship between the incident energy of primary electrons and the ratio of the number of re-emitted electrons to the number of incident electrons. FIG. 4 is an explanatory diagram of main parts of an embodiment of the present invention. FIGS. 5 to 7 are explanatory diagrams of main parts showing other embodiments of the present invention. 1. Ion source 2. . -Next ion optical system 30. sample
40. Sample stand 41°. Sample holder 50. Electrostatic analyzer 60. Mass spectrometer 70. Ion detector 8
0. Electron gun 10. . Secondary electron emission plate work P80. -Next ion beam e11. - Next electron beam IP,. . Secondary ion e! ,. secondary electron day,
. - Above the next ion beam irradiation point Applicant Daini Seikosha Co., Ltd. Agent Mogami Patent Attorney Figure 4 Iρ1 Add 6UZJ 34'' Figure S Figure 7

Claims (1)

[Scope of Claims] A sample irradiated with a primary ion beam, a detector for detecting secondary ions emitted from the sample, and a primary electron beam irradiated near the primary ion beam irradiation spot of the sample. and an electron gun for irradiation,
By providing a secondary electron emitting member with a secondary electron emission rate larger than 1 in the vicinity of the irradiation spot with the -order ions, and irradiating the secondary electron emitting member with the -order electron beam of qJ, the A secondary ion mass spectrometer characterized in that the secondary ion mass spectrometer is configured such that secondary electrons emitted from a secondary electron emitting member are made to enter the vicinity of the secondary ion beam irradiation spot. amount