JPH06124683A - Secondary ion mass spectrometer - Google Patents

Abstract

PURPOSE:To increase the accuracy and the efficiency of mass spectrometry by optically and directly measuring the shape and the depth of the surface of a sample during the impact of the primary ions of an SIMS and accurately limiting a detecting region within a flat and wide region and also accurately measuring the depth thereof. CONSTITUTION:This mass spectrometer is provided with an electrostatic sector 5 for directing to the outside of an optical axis secondary ions 3 extracted from the surface of a sample S in a vertical direction and an interference microscope 10 in which a luminous flux is introduced prependicularly into a region for the primary ions 2 of the sample S to be applied to and then a reflected luminous flux is made to interfere with a reference luminous flux and the shape of the surface of the region for ions to be applied to is measured from the interference fringe thereof to accurately measure the shape of the flat part of the bottom of a crater formed by the impact of the primary ions and then adjust the opening of a slit 7 for limiting a visual field so that a region under mass spectrometry accords with or suits the flat region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary ion mass spectrometer, and more particularly, to a secondary ion mass spectrometer capable of optically detecting the shape and depth of a sample surface for precise analysis.

[0002]

2. Description of the Related Art Secondary ion mass spectrometry (SIMS) is an elemental analysis in the depth direction of a sample surface by sputtering the sample surface by ion bombardment and mass analyzing secondary ions emitted from the sample surface. Is to do.

In SIMS, primary ions are dug in the depth direction while scanning a predetermined area on the surface of the sample to perform elemental analysis at the depth. The cross-sectional shape of the crater of the sample excavated by impact is, for example, as shown in FIG. In order to improve the detection sensitivity of depth direction analysis, FIG.
The secondary ions are detected only from the flat area A in the center of. The setting of the area A is empirically set by the correlation between the scanning area of the primary ion beam and the beam diameter. Also,
The depth D from the sample surface is also indirectly obtained from the sputtering time.

[0004]

As described above, conventionally, the range for analyzing secondary ions is empirically set without considering the strength of interaction between the primary ion beam and the actual sample. However, the flat region is not always used sufficiently, and the actually flat portion is not effectively used to increase the number of detected secondary ions. In addition, the depth was only indirectly obtained, and the accuracy in the depth direction was not necessarily high.

The present invention has been made in view of such a situation, and an object thereof is to optically directly measure the shape and depth of the sample surface during the impact of the primary ions and detect the secondary ions. By accurately limiting the area to be flat to the widest area possible and measuring its depth accurately, SI
It is to improve the accuracy of MS and improve the analysis efficiency.

[0006]

A secondary ion mass spectrometer of the present invention that achieves the above object irradiates a sample surface with primary ions, and emits secondary ions emitted from the irradiation region in a direction perpendicular to the sample surface. In the secondary ion mass spectrometer that can extract and extract the extracted secondary ions on the variable field limiting slit and adjustably limit the analysis region, the secondary ions extracted in the vertical direction from the sample surface A means for directing it off-axis and a means for introducing a light beam perpendicularly to the primary ion irradiation region of the sample, causing the reflected light beam and the reference light beam to interfere, and measuring the surface shape of the ion irradiation region from the interference fringes. It is characterized by having.

[0007]

In the present invention, the means for directing the secondary ions extracted in the vertical direction from the sample surface to the outside of the optical axis and the sample 1
Since a light beam is introduced perpendicularly to the secondary ion irradiation region, the reflected light beam and the reference light beam are caused to interfere with each other, and means for measuring the surface shape of the ion irradiation region from the interference fringes is provided.
The shape of the flat part at the bottom of the crater part formed by secondary ion bombardment can be accurately measured, and it is optimal by adjusting the aperture of the field limiting slit so that the analysis region matches or matches the calculated flat region. It is possible to perform secondary ion mass spectrometry efficiently and with high precision by determining a specific analysis area, and moreover, since the depth of the area can be accurately obtained, perform accurate secondary ion mass spectrometry in the depth direction. You can

[0008]

EXAMPLE An example of the secondary ion mass spectrometer of the present invention will be described below. The basic principle of the present invention is that the sample surface is measured in real time during secondary ion mass spectrometry using an interference microscope. Simultaneously observe and observe the surface shape and depth of the crater dug by sputtering, set a flat and optimum analysis range, and directly and accurately measure the depth to improve the accuracy of SIMS. , To improve analysis efficiency.

FIG. 1 is a sectional view showing the main part of this SIMS device. The surface of a sample S is sputtered by primary ions 2 which are incident while scanning from a primary ion irradiation system 1. The secondary ions 3 emitted from the sample surface are captured by the extraction lens 4, bent by the electrostatic sector 5, pass through the energy dispersion limiting slit 6, and form an image on the field limiting slit 7. Therefore, the secondary ion analysis range on the surface of the sample S can be adjusted by the opening diameter of the field limiting slit 7. The secondary ions passing through the field limiting slit 7 are subjected to elemental analysis by the mass spectrometer 8.

By the way, in the present invention, a hole 9 is formed in a part of the electrostatic sector 5 for bending the secondary ion 3 off-axis so that the analysis region of the sample S can be observed from directly above by the interference microscope 10. The illumination light from the interference microscope 10 and the reflected light from the sample S can pass through the hole 9 coaxially with the extraction lens 4. Therefore, one parallel light emitted from the laser 11 and split by the half mirror 12 enters the analysis region of the sample S from directly above through the hole 9 and is reflected in the opposite direction and again passes through the hole 9 and is reflected by the half mirror. Return to 12. The other parallel light split by the half mirror 12 returns in the opposite direction at the fixed mirror 13, is combined with the light returned from the sample S at the half mirror 12, is condensed by the lens 14, and forms an interference fringe on a predetermined surface. To do. This interference fringe is magnified and observed through the eyepiece lens 15.

In the above-described structure, a predetermined region of the sample S is irradiated with the primary ions 2 from the primary ion irradiation system 1 while scanning, and the secondary ions 3 emitted from the irradiation region.
Can be captured by the extraction lens 4, bent by the electrostatic sector 5 to the outside of the optical axis of the lens 4 and guided to the mass spectrometer 8, and mass analysis of secondary ions at that sample position and at that depth can be performed. At the same time, the parallel light of one optical path of the interference microscope 10 is introduced perpendicularly to the sample S from the hole 9 of the electrostatic sector 5, and the reflected light from the vicinity of the analysis region is guided directly through this hole 9 to a fixed mirror. By interfering with the parallel light of the other optical path reflected by 13, and observing the interference fringes in an enlarged manner through the eyepiece lens 15, the surface shape and depth near the analysis region can be directly measured. That is, this interference fringe shows the difference in the depth of the crater formed by sputtering the sample S with the primary ion beam, and the resolution is 0.
It is about 1 nm, and the number of interference fringes is measured to find the variation in depth, and the flat portion of the crater is found.
By adjusting the opening of the field limiting slit 7 so that the analysis region matches or conforms to the obtained flat region, the optimum analysis region is determined, and secondary ion mass spectrometry is performed efficiently and highly accurately. be able to. Moreover, the depth of the analysis region can be accurately determined from the number of interference fringes in that region,
Accurate depth direction secondary ion mass spectrometry can be performed.

The secondary ion mass spectrometer of the present invention has been described above based on the embodiment, but the present invention is not limited to this embodiment and various modifications can be made. For example, in FIG. 1, the interference fringes are observed by the eye for measurement, but instead, the interference fringes are photoelectrically converted, and the flat region, depth, etc. are obtained based on the data. You can also Further, the interferometer of the interference microscope is not limited to the Michelson type, and other types may be used.

[0013]

As is apparent from the above description, according to the secondary ion mass spectrometer of the present invention, means for directing secondary ions extracted in the vertical direction from the sample surface to the outside of the optical axis,
Since a light beam is introduced perpendicularly to the primary ion irradiation region of the sample, the reflected light beam and the reference light beam are caused to interfere with each other, and a means for measuring the surface shape of the ion irradiation region from the interference fringes is provided. The shape of the flat part of the bottom of the crater part formed by ion bombardment can be accurately measured, and the optimum viewing area can be adjusted by adjusting the aperture of the field limiting slit so that the analysis area matches or matches the obtained flat area. Since the analysis region is determined, secondary ion mass analysis can be performed efficiently and with high accuracy, and the depth of the region can be accurately determined. Therefore, accurate depth direction secondary ion mass analysis can be performed. it can.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main part of a secondary ion mass spectrometer according to the present invention.

FIG. 2 is a diagram showing a cross-sectional shape of a crater of a sample dug by impact of primary ions.

[Explanation of symbols]

 S ... Sample 1 ... Primary ion irradiation system 2 ... Primary ion 3 ... Secondary ion 4 ... Extraction lens 5 ... Electrostatic sector 6 ... Energy dispersion limiting slit 7 ... Field-of-view limiting slit 8 ... Mass spectrometer 9 ... Hole 10 ... Interference microscope 11 ... Laser 12 ... Half mirror 13 ... Fixed mirror 14 ... Lens 15 ... Eyepiece

Claims (1)

[Claims] 1. A sample surface is irradiated with primary ions, secondary ions emitted from the irradiation region are extracted in a direction perpendicular to the sample surface, and the extracted secondary ions are imaged on a variable field limiting slit. In a secondary ion mass spectrometer that can limit the analysis region to be adjustable, a means for directing secondary ions extracted in the vertical direction from the sample surface to the outside of the optical axis and 1
And a means for causing a reflected light beam to interfere with the reference light beam and measuring the surface shape of the ion irradiation region from the interference fringes. Ion mass spectrometer.