JPS5923419B2 - mass spectrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ion, micro, or probe type mass spectrometer.

Conventionally, in this type of device, the primary ion beam derived from the ion source is mass-separated using a three-dimensional focusing type mass separator, and a first spot is created at the connection port with the measurement chamber in front of the primary ion beam. is reduced in a reduced system in the measurement chamber to produce a final spot on the surface of the sample in front of it, and the secondary ions generated on the surface are guided to the mass spectrometer in front of it, thus According to the analysis, a formula was proposed that allowed the element concentration distribution in the sample to be known;
In this case, the first spot tends to expand into an oval shape depending on the energy spread of the ions departing from the ion source, the aberration of the mass separator, etc., and thus the final spot is shaped into a predetermined small circular shape. Further, in the case of a reduced system, it is necessary to increase the length considerably in order to increase the reduction rate.

Furthermore, in this case, since there is no means to detect the actual position of the first spot, it is troublesome to adjust the first spot so that it is accurately located at the connection port between the mass separator and the measurement chamber. It comes with certain inconveniences. The purpose of the present invention is to obtain an apparatus free from such inconveniences, and the primary ion beam derived from the ion source is mass-separated using a three-dimensional focusing type mass separator and then connected to a measurement chamber in front of the primary ion beam. After creating a first spot at the mouth, this is then reduced by a reduction system in the measuring chamber to create a final spot on the surface of the sample in front of it, thereby reducing the secondary ions generated on the surface. A slit plate is provided at the connection port, and a circular slit with a smaller diameter than the first spot is provided at the location where the first spot is formed. , a beam sensor is arranged around the outer periphery of the slit,
The present invention is characterized in that the excitation current of an electromagnet for beam deflection provided in the mass separator is controlled by the output of the beam sensor. An example of implementing the present invention will be explained with reference to the attached drawings.

In the drawing, reference numeral 1 indicates an ion source such as a duoplasmatron, and a primary ion beam 2 such as argon ions derived from the ion source 1 is mass-separated by a three-dimensional focusing type mass separator 3 in front of the ion source. After producing a first spot 6 at the connection port 5 with the measurement chamber 4, this is then reduced by a reduction system 7 in the measurement chamber 4 to produce a final spot 9 on the surface of the sample 8 in front of it. As a result, secondary ions 10 generated on the surface are guided to a mass spectrometer 11 in front of the secondary ions 10. The reduced system 7 includes, for example, the first
It is composed of a reduction lens 7a, a second reduction lens 7b, and a slit 7c in between. The inside of the separator 3 is evacuated by, for example, a turbo molecular type pump 12, and the inside of the measurement chamber 4 is evacuated by, for example, a sputter ion type pump 13. Although the above is not particularly different from the conventional one, according to the present invention, a slit plate 14 is provided at the connection port 5 described above.
A circular slit 15 having a smaller diameter than the first spot 6 is provided at the location where the first spot 6 is formed.

The diameter of the slit 15 is, for example, 300 microns, and the first spot 6 is corrected as a circular spot with a diameter of 300 microns according to the slit 15. Next, the first spot 6 is corrected as a circular spot with a diameter of 300 microns by the reduction system 7, for example. /300, so that the final spot 9 is obtained as a circular spot with a diameter of 1 micron. Furthermore, since the slit 15 has a conductance of, for example, about 5α/Sec with respect to argon gas, by maintaining the ion source 1 side at, for example, 10 −5 Torr, it becomes possible to maintain the measurement chamber 4 side at, for example, 10 −0 Torr. In this way, the sample 8 is kept in an ultra-high vacuum to eliminate contamination with hydrocarbons and the like, making it possible to analyze trace amounts of carbon, hydrogen, and the like. The first spot 6 should always be formed on the slit 15, and in order to do this, four beam sensors 16 are arranged around the outer circumference of the slit 15, as shown in FIGS. 2 and 3, for example. Set up Thus, for example, when the first spot 6 deviates to the left or right, the left and right sensors 16
, 16, the difference in current is detected and the excitation current of the beam deflecting electromagnet 17 is controlled by a servo motor or the like to correct this. The same applies to the case where is shifted back and forth. In the drawing, reference numeral 18 indicates the upper sub-dresser of the sensor 16. As described above, according to the present invention, a slit plate is provided at the connection port between the mass separator and the measurement chamber, and this plate is provided with a circular slit located at the location where the first spot is formed and having a smaller diameter than the spot. Even if the first spot is an oval with a somewhat large diameter, it can be corrected with the slit to obtain a predetermined small circle, and this can be reduced using the reduction system to form the final spot. The slit can be easily formed into a predetermined size and shape, eliminating the inconvenience of making the reduced system long, and furthermore, the slit prevents the inflow of argon gas and other gases from the ion source side. It is possible to achieve a relatively high degree of vacuum in the measurement chamber, that is, an ultra-high vacuum, with large restrictions, and this has the effect of making it possible to analyze hydrogen, carbon, etc., which was previously impossible.

Furthermore, according to the present invention, a beam sensor is disposed around the slit, and the output of the beam sensor controls the excitation current of the beam deflection electromagnet provided in the mass separator. A spot can be automatically and accurately generated at the connection port between the mass separator and the measurement chamber, and there is no trouble in adjusting the position of the first spot unlike in the conventional device.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an example of the apparatus of the present invention, FIG. 2 is an enlarged cross-sectional side view of the main part thereof, and FIG. 3 is a partially cut-away plan view thereof. 1...Ion source, 2...Primary ion beam, 3...
・Mass separator, 4...Measurement chamber, 5...Connection port, 6.
...1st spot, 7...reduced system, 8...sample, 9
...Final spot, 10...Secondary ion beam, 1
1...Mass spectrometer, 14...Slit plate, 15...
- Slit, 16...beam sensor, 17...electromagnet.

Claims (1)

[Claims] 1. After mass-separating the primary ion beam derived from the ion source using a three-dimensional focusing type mass separator and creating a first spot at the connection port with the vacuum atmosphere measurement chamber in front of it,
Next, this is reduced in a reduction system in the measurement chamber to create a final spot on the surface of the sample in front of it, and the secondary ions generated on the surface are guided to the mass spectrometer in front of it. A slit plate is provided at the connection port, a circular slit is located at the location where the first spot is formed and has a smaller diameter than the first spot, and a beam sensor is arranged around the outer periphery of the slit. A mass spectrometer characterized in that the excitation current of a beam deflection electromagnet provided in the mass separator is controlled by the output of the beam sensor.