JPH03129656A - Secondary ion mass spectrometer - Google Patents

Abstract

PURPOSE:To simplify the constitution of a power system and also simplify operation thereof by dividing voltages from positive and negative high-voltage stabilized power supplies into voltages to be applied to each electrode by means of a group of partial pressure resistors. CONSTITUTION:The voltages of a positive high-voltage stabilized power supply 16 and a negative high voltage stabilized power supply 17 are divided by a group of partial pressure resistors into voltages required at respective electrodes of a first accelerating system, a second accelerating system, a spectrometry system and a secondary ion observing system and are then supplied to each part. This constitution makes it possible to supply stabilized voltages from a small number of power supplies to the respective electrodes of the first accelerating system and the second accelerating system etc., and simplify and miniaturize the constitution of the power system and besides simplify operation thereof.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a secondary ion mass spectrometer that analyzes solid or liquid samples, and in particular, to a secondary ion mass spectrometer that analyzes a solid or liquid sample. The present invention relates to a power supply means capable of substantially reducing the number of voltage power supplies and increasing the stability of the power supply voltage.

[Prior Art] Recent mass spectrometry technology has moved from gas analysis to solid or liquid analysis, and has further progressed to the analysis of the molecular weight of polymers.
Secondary ion mass spectrometry and post-acceleration detection technologies are becoming essential. Accordingly, the device configuration has become complicated, and a large number of power supplies are arranged in each part.

[Problems to be Solved by the Invention] A conventional positive secondary ion mass spectrometer requires 12 types of voltages, as shown in Table 1, for example. In the case of measuring negative ions, a negative secondary acceleration voltage and a positive post-acceleration voltage are additionally added, making it necessary to supply 16 types of voltage in total.

If these voltages were supplied independently, as shown in Figure 5, not only would there be a large number of power supplies, but the adjustment would be complicated, stability would decrease, and it would be difficult to obtain the required resolution. . That is, the first electrode 1. The power supplies IA, 2A, 3A, and 12A of the extraction electrode 2, primary lens 3, and secondary electron multiplier tube 12 can be controlled independently, but the power supplies g4A to IIA surrounded by dotted lines are controlled by the control unit 30. Without proportional control, the required stability and resolution will not be achieved. Furthermore, ripples and voltage fluctuations in commercial AC power sources do not necessarily affect each power source proportionally.

Therefore, the electric fields of the primary acceleration system, secondary acceleration system, and mass spectrometry system,
A system has also been proposed in which each of the quadrupole lenses in the mass spectrometry system is supplied separately from one power supply, but if you add two power supplies for the secondary ion observation system, that is, the detector part, it still requires six types of power supplies. It was necessary. It is desirable to have as few types of power supplies as possible not only from the cost standpoint but also from the standpoint of operation and maintenance.

An object of the present invention is to provide a secondary ion mass spectrometer equipped with a power supply means that can supply stable voltage to each electrode of the primary acceleration system, secondary acceleration system, etc. from a small number of power sources. .

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a primary acceleration system that accelerates and focuses primary ions, and a sample stage that irradiates the accelerated primary ions. 2, which includes a secondary acceleration system that accelerates and focuses secondary ions sputtered from a secondary ion, a mass spectrometry system that performs mass analysis of the accelerated secondary ions, and a secondary ion observation system that detects the analyzed secondary ions. Next, in the ion mass spectrometer, there are high voltage stabilized power supplies, one positive and one negative, and the voltages from these power supplies are connected to the primary acceleration system and the secondary acceleration system.

This paper proposes a secondary ion mass spectrometer equipped with a power supply means consisting of a voltage dividing resistor group that divides the voltage to be applied to each electrode of the mass spectrometry system and the secondary ion a festival system.

If a positive/negative switching device is provided for reversing the polarity of the voltage to be applied to the sample stage and secondary lens of the secondary acceleration system and the fan-shaped electric field and quadrupole lens of the mass spectrometry system, one device can convert positive ions and negative ions. It becomes possible to analyze ions.

Further, a post-acceleration system for further accelerating secondary ions may be included between the mass spectrometry system and the secondary ion am system. In that case, a voltage dividing resistor is added to apply an acceleration voltage to the subsequent stage acceleration system.

Furthermore, when analyzing positive and negative surface ions with an apparatus including a post-acceleration system, the sample stage and secondary lens of the secondary acceleration system, the fan-shaped electric field and quadrupole lens of the mass spectrometry system, and the post-acceleration system are A positive/negative switching device is provided to reverse the polarity of the voltage to be applied.

[Function] In the present invention, there are high voltage stabilized power supplies, one positive and one negative, and the voltages from these power supplies are applied to each electrode of the primary acceleration system, secondary acceleration system, mass spectrometry system, and secondary ion wA detection system. Since it is equipped with a power supply consisting of a group of voltage dividing resistors that divide the voltage to be applied to the becomes simpler, smaller, and easier to operate.

In particular, since the voltage of a common power supply (positive and negative) is divided by resistors, the ripples and drifts of the voltage applied to each electrode are aligned in phase, resulting in a proportionally controlled ratio of each electrode voltage. The effects are significantly reduced and the resolution of mass spectrometry is increased.

[Example] Next, the present invention will be described in detail with reference to FIGS. 1 to 4 of the drawings.

FIG. 1 is a system diagram showing only the power supply section of an embodiment of the secondary ion mass spectrometer according to the present invention. The power supply of this embodiment is composed of a positive stabilized power supply 16, a negative stabilized power supply 17, and a voltage dividing resistor group 18. By 18,
The voltage is divided to the required voltage at each electrode of the secondary ion mass spectrometer,
Supply to each part.

In addition, although all the resistors 18 are shown as variable resistors here due to the drawing space, they are actually a combination of fixed resistors and variable resistors. Considering the long-term stability of resistance value, temperature coefficient, etc., it is better to configure all the resistors with fixed resistors.

On the other hand, it is not always possible to obtain a fixed resistor with a desired resistance value, and it is also necessary to balance the left and right sides of the secondary lens, so a variable resistor must also be used. Therefore, it is desirable to have the fixed resistor share most of the resistance value, and have the variable resistor share only the minimum necessary variable width.

Explaining with specific numerical values shown in FIG. 1, the specifications of the maximum voltages of the positive and negative stabilized power supplies are determined by the primary acceleration anode voltage and the post-acceleration voltage.

Here, it is assumed to be +30kV and -30kV.

The output current of currently commercially available high voltage stabilized power supplies is 1
Since it is about mA, each resistance value of the voltage dividing resistor is set to LM
Ω and connecting 30 stages in series is just right. if,
If a variable resistor of 1 MΩ and IW is used as the variable range of the entire division part for IMQ, a voltage variable range of about 3% (900 V) will be obtained.

Power supply stability specifications are determined by the resolution requirements of the mass spectrometer. To obtain a resolution of 10,000, the ripple must be less than 10-4. A stabilized power source of this level can be obtained relatively easily even as a commercial product. In order to obtain the above resolution, the voltage drift must also be kept below 10-'.

Here, it is necessary to pay attention not only to the drift of the power supply alone, but also to the temperature drift of the resistance value of the voltage dividing resistor, and it may be necessary to consider installing a cooler to limit temperature fluctuations of the resistor.

Once the mechanical parts are fixed, the fan electric field, quadrupole lens voltage, and post-acceleration voltage required for mass spectrometry of secondary ions must be controlled to a voltage proportional to the secondary acceleration voltage after adjustment. There is.

In the conventional independent power supply system, a special control unit 30 was required to change each voltage in proportion to the secondary acceleration voltage, but in this embodiment, the voltage from one common power supply for each positive and negative voltage is connected to a voltage dividing resistor. Since the amount is distributed proportionally, no special control system is required. Therefore, after the - degree adjustment, there is no need to readjust the yA before each mass spectrometry operation.

In addition, even if the positive and negative power supply voltages fluctuate over a long period of time, the fluctuations in the power supply voltage change proportionally for each voltage, so the overall trajectory change of the ion beam is much smaller than with conventional methods. Become.

FIG. 2 shows the overall system configuration of a more specific embodiment of the present invention for analyzing positive secondary ions.

The structure of the mechanical parts of this embodiment is the same as that of the conventional example shown in FIG. That is, ions emitted from the primary ion source are accelerated by the anode electrode 1 and the extraction electrode 2, and are focused by the primary lens 3 to become the primary ion beam 13.
, collides with the sample stage 4 and generates secondary ions of the sample.

This secondary ion beam 14 is accelerated by secondary lenses 5, 6, fan-shaped electric fields 7, 8 and quadrupole lenses 9, 10.
and a magnetic field 15 for analysis. The analyzed secondary ions are attracted to and collide with the second-stage accelerating electrode 11 of opposite polarity, and are captured and detected by the secondary electron multiplier 12.

In this embodiment, +30kV positive power supplies 16 and -30
The voltage of the kV negative power supply 17 is divided by a voltage dividing resistor 18, and the necessary voltage is supplied to each electrode. As is clear from a comparison with the conventional example shown in Figure 5, the number of individual power supplies is greatly reduced, which simplifies the system configuration, and since the power supply voltage fluctuations change proportionally at each voltage, the overall The change in the trajectory of the ion beam is much smaller than in the conventional method.

FIG. 3 shows the overall system configuration of a more specific embodiment of the present invention for analyzing negative secondary ions.

The structure of the mechanical parts of this embodiment is the same as that of the embodiment shown in FIG. 2 and the conventional example shown in FIG.

This embodiment differs from the embodiment shown in FIG. 2, which analyzes positive secondary ions, in that it includes a sample stage 4, a secondary lens 5.6, a fan-shaped electric field 7, 8. Quadrupole lenses 9, 10. and rear acceleration electrode 1
1, the polarity of the voltage is reversed.

Therefore, as shown in FIG. 4, when detecting positive and negative ions, a positive/negative switching bag applies voltages with appropriate polarities to the electrodes whose polarities are to be reversed, respectively! 40, it is possible to quickly switch between positive secondary ion analysis and negative secondary ion analysis with one mechanical unit.

A secondary ion mass spectrometer capable of mass spectrometry of positive or negative secondary ions is obtained.

Note that the specific voltage values used in each of the above embodiments are merely examples, and the present invention is not limited to these values.

〔Effect of the invention〕

According to the present invention, a high voltage stabilized power supply with one positive and one negative power supply,
Since it is equipped with a power supply consisting of a group of voltage dividing resistors that divide the voltage from the power supply into the voltage to be applied to each electrode, it is different from the conventional complicated power supply system that had one power supply for each electrode. Compared to the configuration of , the configuration is simpler and smaller, and the operation is also simplified.

In particular, since the voltage of a common power supply (positive and negative) is divided by resistors, the ripples and drifts of the voltage applied to each electrode are aligned in phase, resulting in a proportionally controlled ratio of each electrode voltage. The effects are significantly reduced and the resolution of mass spectrometry is increased.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing only the power supply section of an embodiment of the secondary ion mass spectrometer according to the present invention, and Fig. 2 shows a more specific diagram of the present invention when analyzing positive secondary ions. FIG. 3 is a diagram showing the entire system configuration of a more specific embodiment of the present invention when negative secondary ions are analyzed, and FIG. 4 is a diagram showing the overall system configuration of the embodiment. A diagram showing the system configuration of an embodiment equipped with a positive/negative switching device that applies a voltage with the appropriate polarity to each electrode whose polarity should be reversed during ion detection. Figure 5 shows the system of an example of a conventional secondary ion mass spectrometer. FIG. 3 is a diagram showing the configuration. 1...Anode electrode, 2...Leader electrode, 3...1
Next lens, 4... sample stage, 5.6... secondary lens,
7, 8... Fan-shaped electric field. 9.10... Quadrupole lens, 11... Post-acceleration electrode, 12... Secondary electron multiplier. 13... Primary ion beam, 14... Secondary ion beam, 15... Magnetic field, 16...
... Positive voltage power supply, 17... Negative voltage power supply, 18... Voltage dividing resistor, 30... Conventional control unit, 40... Positive/negative switching device.

Claims (1)

[Claims] 1. A primary acceleration system that accelerates and focuses primary ions, and a sample stage that irradiates the accelerated primary ions, and 2 that accelerates and focuses secondary ions sputtered from the sample. In a secondary ion mass spectrometer including a secondary acceleration system, a mass spectrometry system that performs mass analysis of the accelerated secondary ions, and a secondary ion observation system that detects the analyzed secondary ions, one for each positive and negative one. a high-voltage stabilized power supply, and a group of voltage dividing resistors that divide the voltage from the power supply into voltages to be applied to each electrode of the primary acceleration system, secondary acceleration system, mass spectrometry system, and secondary ion observation system. A secondary ion mass spectrometer comprising a power supply means comprising: 2. A positive/negative switching device is provided for reversing the polarity of the voltages to be applied to the sample stage and secondary lens of the secondary acceleration system and the fan-shaped electric field and quadrupole lens of the mass spectrometry system; Claim 1 characterized in that it analyzes
The secondary ion mass spectrometer described in . 3. Between the mass spectrometry system and the secondary ion observation system,
The secondary ion mass spectrometer according to claim 1, further comprising a post-acceleration system that further accelerates the next ions, and wherein the power supply means has a voltage dividing resistor that applies an accelerating voltage to the post-acceleration system. Total. 4. A positive/negative switching device for reversing the polarity of the voltage to be applied to the sample stage and secondary lens of the secondary acceleration system, the fan-shaped electric field and quadrupole lens of the mass spectrometry system, and the post-acceleration system, The secondary ion mass spectrometer according to claim 3, wherein the secondary ion mass spectrometer analyzes positive ions and negative ions.