JPH04192249A - Mass spectrometry method for secondary ion - Google Patents

Abstract

PURPOSE:To take in secondary ions within the incident angle of a maximum transfer lens, and thereby enhance resolving power in the direction of depth by allowing both applied voltage to a sample and voltage to be applied to a secondary pull-out lens to be variable. CONSTITUTION:Primary ion beams (I) are radiated onto a sample 1. When the suitable level of positive voltage 18 applied to the sample 1 from a sample applying voltage source 2, and when the suitable level of negative voltage is applied to an electrode 3 from a pull-out voltage source 4, secondary ions are focused in a main slit 6 by means of a transfer lens 5, the energy and the mass of the secondary ions passing through the hole of the main slit 6 are separated by means of a mass spectrometry unit 7, so that they are thereby detected by a secondary ion detector 9 via a slit 8. The detected signal is processed by a signal processing means 10, so that the mass spectrum of the processed one is indicated on a display means 11. The voltage sources 2 and 4 are regulated by an operator while being closely watched in such a way that spectrum strength becomes maximum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a secondary ion mass spectrometry method with improved resolution in the depth direction.

[Prior Art] A secondary ion mass spectrometer is an apparatus for performing elemental analysis of a sample. In such an apparatus, an ion beam from an ion source is focused by a focusing lens, and a deflector irradiates the ion beam onto a predetermined location on a sample. Secondary ions generated from the sample by the irradiation are extracted by an extraction electrode and introduced into a mass spectrometry unit. The ion beam energy-separated and mass-separated by the unit is detected by a secondary ion detector, processed in various ways by a signal processing means, and sent to a display means. As a result, a mass spectrum unique to the sample is displayed on the display means.

[Problems to be Solved by the Invention] Now, in order to improve the resolution in the depth direction in such a secondary ion mass spectrometer, for example, the sample is tilted and the -order ion beam is irradiated onto the sample. Either the corners are made smaller or this alone is not enough.

The present invention has been made in view of these points, and relates to a novel secondary ion mass spectrometry method that further improves the resolution in the depth direction.

[Means for Solving the Problems] The present invention provides a secondary ion mass spectrometry method in which a sample is irradiated with a primary ion beam and secondary ions emitted from the sample are measured. The voltage applied to the extraction lens for extracting secondary ions from the sample was made variable so that the intensity of the secondary ion beam from the sample was maximized.

[Operation As shown in the diagram, by irradiating the sample 1 with the primary ion beam I, a secondary ion beam is generated from the sample. A transfer lens 5 and a main slit 6 are arranged between the sample and the mass spectrometry unit 7, and the transfer lens directs the virtual light source of the secondary ion beam to the main slit 6.
The main slit 6 determines the diameter of the virtual light source image. At this time, the secondary ion uptake angle α of the mass spectrometry unit 7 is determined so as to provide the best resolution. Therefore, the incident angle α of the secondary ions to the transfer lens 5 is. The maximum detection efficiency can be obtained by matching the secondary ion uptake angle α of the mass spectrometry unit.

Emission angle α of secondary ions from the sample surface. is sample 1
Voltage V+ (voltage of sample applied voltage source 2) applied to sample 1, extraction voltage v2 (voltage of extraction voltage source 4) for extracting secondary ions from sample 1, emission energy φ of secondary ions from sample 1, and It changes as a function of the secondary ion emission angle α1. Therefore, the sample applied voltage V and the extraction voltage ■2
By controlling the incident angle α of the secondary ions emitted from the sample 1 to the transfer lens 5 as much as possible
. If it can be taken into the system, the detection efficiency for the mass spectrometry system 7 will be the best, and as a result, the resolution in the depth direction will be improved.

[Example] The figure is a schematic diagram of a secondary ion mass spectrometer shown as an example of the present invention.

In the figure, 1 is a sample, 2 is a voltage source applied to the sample, 3 is an extraction electrode,
4 is an extraction voltage source, 5 is a transfer lens, 6 is a main slit, 7 is a mass spectrometry unit, 8 is a slit, 9 is a secondary ion detector, 10 is a signal processing means, and 11 is a display means. Both the sample application voltage source 2 and the extraction voltage source 4 are variable voltage sources.

In such an apparatus, a sample is irradiated with a -order ion beam 1 from a -order ion beam irradiation system (not shown).

Now, for example, when extracting + ions from the sample, ten voltages of an appropriate magnitude are applied from the sample application voltage source 2. Then, a voltage of an appropriate magnitude is applied from the extraction voltage source 4 to the extraction electrode 3. Then, secondary ions are extracted from the primary ion beam irradiation area of the sample. The transfer lens 5 is used to image a virtual light source of secondary ions from the sample onto the main slit 6, and the secondary ions extracted from the sample are focused onto the main slit 6 by the transfer lens. Ru. The secondary ions that have passed through the slit are passed through a slit 8 in a mass spectrometry unit 7 that includes an electric field generating means for energy separation and a magnetic field generating means for mass separation. The ions are detected by a secondary ion detector 9 through the secondary ion detector 8.

The detected secondary ion beam is subjected to various processing by a signal processing means 10 and sent to a display means 11. As a result, a mass spectrum unique to the sample is displayed on the display means. Now,
While observing the mass spectrum displayed on the display means, the operator adjusts the intensity of the spectrum, that is, the intensity of the spectrum based on the secondary ions extracted from the sample and incident on the mass spectrometry unit, to the maximum. , adjusts the magnitude of the output voltage of the sample application voltage source 2, that is, the magnitude of the voltage applied to the sample 1. After this adjustment, the magnitude of the output voltage of the extraction voltage source 4, that is, the magnitude of the voltage applied to the extraction electrode 3, is similarly adjusted so that the intensity of the mass spectrum becomes maximum. Repeat this adjustment of the sample applied voltage and the extraction voltage several times,
The mass spectrum is maximized. This adjustment maximizes the secondary ions emitted from the sample by adjusting the incident angle α to the transfer lens. The detection efficiency in the mass spectrometry system is the highest, and as a result, the resolution in the depth direction is further improved.

[Effects] According to the present invention, the voltage applied to the sample and the voltage applied to the extraction lens for extracting secondary ions from the sample are made variable, so that the intensity of the secondary ion beam from the sample is maximized. Therefore, the incident angle α to the transfer lens can be adjusted to maximize the secondary ions emitted from the sample. The detection efficiency for the mass spectrometry system is the best, and as a result, the resolution in the depth direction is further improved.

[Brief explanation of the drawing]

The attached figure is a schematic diagram of a secondary ion mass spectrometer shown as an embodiment of the present invention. 1: Sample 2: Sample applied voltage source 3: Extraction electrode
4: Extraction voltage source 5: Transfer lens 6: Main slit 7: Mass spectrometry unit 8 Nislit
9th order ion detector 10: Signal processing means 11:
Display means patent applicant JEOL Ltd.

Claims (1)

[Claims] In a secondary ion mass spectrometry method in which a sample is irradiated with a primary ion beam and the secondary ions emitted from the sample are measured, the voltage applied to the sample and the extraction lens used to extract the secondary ions from the sample are A secondary ion mass spectrometry method in which the voltage applied to the sample is made variable, and the two voltages are adjusted so that the intensity of the secondary ion beam from the sample is maximized.