Quadrupole mass spectrometer and residual gas analysis method

Abstract

The present invention is for reducing temperature influence caused by a transformer, in a quadrupole mass spectrometer. The present invention comprises: an ionization unit (21) for ionizing a sample; a quadrupole unit (23) having two sets of counter electrodes (23P) that selectively pass ions generated by the ionization unit (21); a voltage applying unit (32) for applying, to each of the two sets of counter electrodes (23P), voltage obtained by superimposing DC voltage U and high frequency voltage Vcosωt; and an ion detection unit (24) for detecting ions having passed through the quadrupole unit (23). The voltage applying unit (32) has a transformer (4) for transforming the high frequency voltage Vcosωt. The transformer (4) is formed by winding a primary winding (42) and a secondary winding (43) around a toroidal core (41). The primary winding (42) is formed of a plate-like metallic conductor.

Description

Technical Field

[0001] The present invention relates to a quadrupole mass spectrometer and a residual gas analysis method.

Background Art

[0002] Conventionally, as a quadrupole mass spectrometer, as shown in Patent Document 1, it has a quadrupole section that selectively passes ions. In the quadrupole section, a voltage obtained by superimposing a DC voltage and a high-frequency voltage is applied to each of two pairs of opposing electrodes. Here, the high-frequency voltage applied to the opposing electrodes is boosted using a transformer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, when the present inventors continuously measured a specific mass-to-charge ratio (m / z = 40 AMU) over a predetermined period using the above quadrupole mass spectrometer, as shown in FIG. 9, it was found that the peak of the output current shifted with the passage of time, resulting in a measurement error. As a result of intensive investigation of the cause, it was found that the circuit components on the surrounding circuit board were affected by heat due to the heat generated by the transformer.

[0005] Therefore, the present invention has been made to solve the above problems, and its main object is to reduce the temperature influence caused by a transformer that transforms a high-frequency voltage in a quadrupole mass spectrometer.

Means for Solving the Problems

[0006] That is, the quadrupole mass spectrometer according to the present invention includes an ionization unit that ionizes a sample, a quadrupole unit having two pairs of opposing electrodes that selectively pass the ions generated in the ionization unit, a voltage application unit that applies a voltage in which a DC voltage and a high-frequency voltage are superimposed on each of the two pairs of opposing electrodes, and an ion detection unit that detects the ions that have passed through the quadrupole unit. The voltage application unit has a transformer that transforms a high-frequency voltage. The transformer is configured by winding a primary winding and a secondary winding around a toroidal core. The primary winding is formed of a plate-shaped metal conductor.

[0007] In such a quadrupole mass spectrometer, a transformer is configured by winding a primary winding and a secondary winding around a toroidal core. In this transformer, since the primary winding is formed of a plate-shaped metal conductor, the effective cross-sectional area through which a high-frequency current flows in the primary winding can be increased. As a result, the heat loss in the primary winding can be reduced, and the temperature influence caused by the transformer can be reduced. Further, since the primary winding is a plate-shaped metal conductor, the number of turns of the primary winding can be reduced, the winding operation can be facilitated, and the productivity can be improved.

[0008] As a specific embodiment of the secondary winding wound around the toroidal core, it is conceivable to have a first secondary winding connected to one of the two pairs of opposing electrodes and a second secondary winding connected to the other of the two pairs of opposing electrodes. In the present invention, by using a plate-shaped metal conductor for the primary winding to form a radial current path, the variation in magnetic coupling between the primary winding and the first secondary winding and the variation in magnetic coupling between the primary winding and the second secondary winding can be reduced, and the variation in the output high-frequency voltage can be reduced.

[0009] In order to reduce the loss (iron core) and heat generation in the toroidal core by increasing the cross-sectional area to increase the allowable magnetic flux while reducing the footprint of the transformer (specifically, the mounting area of the high-frequency circuit board), it is desirable that the toroidal core is configured by laminating two or more toroidal core elements.

[0010] It is desirable that the primary winding is wound so as to be radial with respect to the toroidal core. With this configuration, the cross-sectional area of the plate-shaped metal conductor that is the primary winding can be increased, and the effects of the present invention can be made even more remarkable.

[0011] As a specific embodiment of the primary winding, it is conceivable that the primary winding has a plurality of belt-like portions arranged radially in a developed state, and the plurality of belt-like portions are wound around the toroidal core. With this configuration, the operation of winding the primary winding radially can be facilitated.

[0012] Further, as another specific embodiment of the primary winding, the primary winding preferably includes a substrate provided with a metal conductor on one surface, a center pin member composed of a metal conductor connected to the central portion of the substrate and disposed at the center of the toroidal core, and a plurality of peripheral pin members composed of metal conductors connected to the peripheral edge portion of the substrate and disposed around the toroidal core. With this configuration, the primary winding can be easily assembled.

[0013] It is conceivable that the toroidal core, which is the iron core, generates heat due to iron loss. In order to efficiently radiate heat of this toroidal core to the outside, it is desirable that the space between the toroidal core and the primary winding is filled with an adhesive having thermal conductivity.

[0014] In order to simplify the configuration of fixing the transformer to the circuit board and radiate the heat generated by the primary winding from the circuit board to the outside, it is desirable that the transformer is fixed to the circuit board by fixing the primary winding to the circuit board.

[0015] The present invention further includes a control unit that controls the voltage application unit, and when the control unit controls the voltage application unit to continuously measure a specific mass-to-charge ratio over a predetermined period, the effects of the present invention can be made even more remarkable.

[0016] The residual gas analysis method according to the present invention is characterized by analyzing the residual gas in the vacuum chamber using the quadrupole mass spectrometer described above.

Effects of the Invention

[0017] According to the present invention described above, it is possible to reduce the temperature influence caused by the transformer in the quadrupole mass spectrometer.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 8

Figure 9

Figure 10

Explanation of Symbols

[0019] 100 ··· Quadrupole mass spectrometer VC ··· Vacuum chamber 21 ··· Ionization section 23 ··· Quadrupole section 24 ··· Ion detector 23P ··· Opposing electrode 32 ··· Voltage application section 33 ··· Control section 4 ··· Transformer 41 ··· Toroidal core 41a, 41b ··· Toroidal core elements 42 ··· Primary winding 43a ··· First secondary winding 43b ··· Second secondary winding 421 ··· Strip portion 44 ··· Adhesive 5 ··· High-frequency circuit board

Embodiments for Carrying Out the Invention

[0020] Hereinafter, a quadrupole mass spectrometer according to an embodiment of the present invention will be described with reference to the drawings.

[0021] <1. Overall Configuration> The quadrupole mass spectrometer 100 of this embodiment is used, for example, for gas monitoring in a vacuum chamber VC during a semiconductor manufacturing process or after apparatus cleaning. As shown in FIG. 1, it is attached to the vacuum chamber VC and analyzes residual gas, which is the sample gas in the vacuum chamber VC.

[0022] Specifically, as shown in FIGS. 1 and 2, the quadrupole mass spectrometer 100 includes a sensor unit 2 that detects sample gas such as process gas or residual gas in the vacuum chamber VC, and an arithmetic unit 3 that controls the sensor unit 2 and performs analysis processing of the residual gas based on the output of the sensor unit 2.

[0023] As shown in FIG. 2, the sensor unit 2 includes an ionization unit 21 that ionizes the residual gas, which is the sample gas, an ion extraction electrode 22 provided outside the ionization unit 21 to extract ions, a quadrupole unit 23 that selectively allows the ions derived from the ionization unit 21 by the ion extraction electrode 22 to pass through, and an ion detection unit 24 that detects the ions that have passed through the quadrupole unit 23.

[0024] The sensor unit 2 further includes a casing 25 that houses and protects the ionization unit 21, the ion extraction electrode 22, the quadrupole unit 23, and the ion detection unit 24 in this order from the tip side. Inside the casing 25, the ionization unit 21, the ion extraction electrode 22, the quadrupole unit 23, and the ion detection unit 24 are arranged in a straight line. On the tip wall of this casing 25, a gas inlet 25H is provided for introducing the residual gas in the vacuum chamber VC into the sensor unit 2 when the casing 25 is attached to the vacuum chamber VC. The casing 25 is airtightly attached to the attachment hole provided in the vacuum chamber VC via a sealing member or the like. As a result, the inside of the casing 25 has the same pressure as the atmospheric pressure in the vacuum chamber VC via the gas inlet 25H, and the ionization unit 21, the ion extraction electrode 22, the quadrupole unit 23, and the ion detection unit 24 are exposed to the atmospheric pressure in the vacuum chamber VC.

[0025] The ionization unit 21 has a filament inside and ionizes the sample gas by the thermoelectrons emitted from the filament. Then, the ions generated by the ionization unit 21 are drawn out to the outside by the ion extraction electrode 22.

[0026] The ion extraction electrode 22 is composed of a single or a plurality of electrodes. The ion extraction electrode 22 is provided between the ionization unit 21 and the quadrupole unit 23, draws out the ions generated by the ionization unit 21 to the side of the quadrupole unit 23 and the ion detection unit 24, and accelerates and converges the ions.

[0027] The quadrupole section 23 separates the ion beam accelerated and converged by the ion extraction electrode 22 according to the ion charge-to-mass ratio (m / z). Specifically, as shown in FIG. 3, the quadrupole section 23 has two sets of opposing electrodes 23P arranged at 90° intervals.

[0028] This quadrupole section 23 has a voltage applied to it by a voltage application section 32 described later. After setting the opposing electrodes to the same potential, a voltage obtained by superimposing a DC voltage U and a high-frequency voltage Vcosωt is applied between each pair of sets of electrodes that are 90° different from each other. Then, by changing V while keeping the U / V ratio constant by the voltage application section 32, the quadrupole section 23 selectively passes the ions incident into the opposing electrodes 23P according to the charge-to-mass ratio (m / z).

[0029] The ion detection section 24 is a Faraday cup that captures the ions separated by the quadrupole section 23 and detects them as an ion current. Specifically, the ion detection section 24 is for detecting the ions of a specific component separated by the quadrupole section 23 and detecting the absolute value of the partial pressure of the specific component in the sample gas. It is also for detecting all the ions of the sample gas ionized by the ionization section 21 and detecting the absolute value of the total pressure of the sample gas.

[0030] As described above, the arithmetic unit 3 has an arithmetic processing function and a control function. As shown in FIG. 2, this arithmetic unit 3 includes an amplifier, an A / D converter, a D / A converter, a CPU, a memory, a communication port, etc. And the arithmetic unit 3 has a data processing section 31 that performs mass spectrometry based on the current value of the ion current output from the ion detection section 24 of the sensor section 2. Also, if necessary, the data processing section 31 can transmit the analysis result to a general-purpose computer 200 (see FIG. 1), etc.

[0031] Also, as shown in FIG. 2, the arithmetic unit 3 functions as a voltage application section 32 that applies a voltage obtained by superimposing a DC voltage U and a high-frequency voltage Vcosωt to the two sets of opposing electrodes 23P of the quadrupole section 23, and a control section 33 that controls the voltage application section 32.

[0032] The voltage application unit 32 applies a voltage obtained by superimposing a DC voltage U and a high-frequency voltage Vcosωt across each pair of opposing electrodes 23P that are 90° different from each other, makes the U / V ratio constant, and changes V, and is controlled by the control unit 33. This control unit 33 controls the DC voltage U and the high-frequency voltage Vcosωt according to a specific mass-to-charge ratio. For example, it can control the voltage application unit 32 to continuously measure a specific mass-to-charge ratio over a predetermined period.

[0033] Specifically, as shown in FIG. 4, the voltage application unit 32 has a transformer 4 for boosting the high-frequency voltage and is mounted on a high-frequency circuit board 5 for feedback control to a desired high-frequency voltage.

[0034] As shown in FIGS. 4 and 5, the transformer 4 is configured by winding a primary winding 42 and a secondary winding 43 around an annular toroidal core 41. The primary winding 42 is connected to the power supply side, and the secondary winding 43 is connected to the opposing electrode side. The toroidal core 41 of the present embodiment has a double structure by stacking two toroidal core elements 41a and 41b, thereby increasing the cross-sectional area of the toroidal core 41 to increase the allowable magnetic flux and reducing the loss (iron loss) in the toroidal core 41, that is, the heat generation of the toroidal core 41.

[0035] And the primary winding 42 is formed of a plate-shaped metal conductor made of, for example, copper. Also, the secondary winding 43 is formed of a linear metal conductor. Here, as shown in FIG. 5, the secondary winding 43 has a first secondary winding 43a connected to one of the two pairs of opposing electrodes 23P and a second secondary winding 43b connected to the other of the two pairs of opposing electrodes 23P.

[0036] In the transformer 4 of this embodiment, after the secondary winding 43 is wound around the toroidal core 41 with a predetermined number of turns, the primary winding 42 is wound around the outside thereof. That is, the secondary winding 43 is wound inside the toroidal core 41, and the primary winding 42 is wound outside. The first secondary winding 43a and the second secondary winding 43b are wound around the toroidal core 41 along each other, thereby reducing the variation in magnetic coupling with the primary winding 42.

[0037] Here, the primary winding 42 is wound around the toroidal core 41 so as to be radial (see FIG. 5). By winding radially, the cross-sectional area of the primary winding 42 can be increased. Specifically, as shown in FIG. 6, in the unfolded state, the primary winding 42 is composed of a plurality of strip portions 421 arranged radially, and is wound by winding the plurality of strip portions 421 around the toroidal core 41. With this configuration, the operation of winding the primary winding 42 radially is facilitated.

[0038] More specifically, a core portion 422 disposed at the center of the toroidal core 41 is provided at the center of the primary winding 42, and a plurality of strip portions 421 extend radially from the core portion 422. Further, an insertion portion 421x to be inserted into the wiring through hole 51 (see FIG. 4) of the high-frequency circuit board 5 is formed at the free end portion 421a of the strip portion 421.

[0039] Then, while inserting the core portion 422 into the center of the toroidal core 41, the strip portion 421 is bent along the outer surface of the toroidal core 41, and the insertion portion 421x is inserted into the wiring through hole 51 and soldered, whereby the transformer 4 is fixed to the high-frequency circuit board 5. That is, the transformer 4 is configured to be fixed to the high-frequency circuit board 5 by fixing the primary winding 42 to the high-frequency circuit board 5. Thereby, while simplifying the configuration for fixing the transformer 4 to the high-frequency circuit board 5, the heat generated by the primary winding 42 can be easily dissipated from the high-frequency circuit board 5 to the outside.

[0040] Furthermore, in the transformer 4, as shown in FIG. 4, the space between the toroidal core 41 and the primary winding 42 is filled with a thermally conductive adhesive 44. This makes it easier for the heat generated by the loss (iron loss) in the toroidal core 41 to be transferred to the primary winding 42. Also, since the primary winding 42 is connected to the high-frequency circuit board 5, the heat from the toroidal core can be transferred to the high-frequency circuit board 5 via the primary winding 42, making it easier to dissipate heat to the outside from the high-frequency circuit board 5. In this embodiment, since the secondary winding 43 is arranged between the toroidal core 41 and the primary winding 42, the secondary winding 43 will be surrounded by the adhesive 44.

[0041] Also, as shown in FIG. 7, the high-frequency circuit board 5 of this embodiment is provided with a high-frequency power supply circuit for applying a desired high-frequency voltage to the transformer. Note that the upper diagram in FIG. 7 is the high-frequency power supply circuit of this embodiment, and the lower diagram in FIG. 7 is the conventional high-frequency power supply circuit.

[0042] In the conventional high-frequency power supply circuit, the number of components is large, and a configuration that requires the use of high-frequency components is adopted. Also, a diode with temperature characteristics is used for the high-frequency amplitude detector, and the high-frequency power supply circuit is configured such that the high-frequency amplitude is greatly affected by temperature.

[0043] In contrast, the high-frequency power supply circuit of this embodiment includes a DDS (Direct Digital Synthesizer), an amplifier that amplifies the output from the DDS and outputs it to the transformer, a detector that detects the high-frequency amplitude from the amplifier, and a subtractor that inputs an amplitude setting signal to the DDS based on the difference between the detected amplitude of the detector and the amplitude setting value. Then, a bipolar transistor is connected to the amplitude setting pin of the DDS (the current flowing out of the amplitude setting pin changes according to the connected resistance value, and the output is the current that mirrors it, causing the high-frequency amplitude to change), and the current flowing out of the amplitude setting pin is changed from another circuit. This changes the high-frequency amplitude output from the DDS and simplifies the circuit configuration.

[0044] <Effects of this Embodiment> According to the quadrupole mass spectrometer 100 of this embodiment configured as described above, a transformer 4 is formed by winding a primary winding 42 and a secondary winding 43 around a toroidal core 41. Since the primary winding 42 is formed of a plate-shaped metal conductor in this transformer 4, the effective cross-sectional area through which a high-frequency current flows in the primary winding 42 can be increased. As a result, the heat loss in the primary winding 42 can be reduced, and the temperature influence caused by the transformer 4 can be reduced. Further, since the primary winding 42 is a plate-shaped metal conductor, the number of turns of the primary winding 42 can be reduced, the winding operation can be facilitated, and the productivity can be improved.

[0045] Next, the experimental results of the heat generation temperatures of the transformer of the conventional configuration and the transformer of this embodiment are shown. Here, the frequency of the high-frequency voltage was set to 14 [MHz], and the amplitude of the high-frequency voltage was set to 900 [V]. As shown in FIG. 8, while the heat generation temperature of the transformer of the conventional configuration was 138.9 degrees, the heat generation temperature of the transformer of this embodiment could be suppressed to 81.2 degrees.

[0046] <Other Embodiments> For example, although the primary winding in the above embodiment has a configuration in which a plurality of strip portions are provided radially, it may have a configuration in which a single strip is wound spirally around a toroidal coil.

[0047] Also, the configuration of the primary winding 42 may be as shown in FIG. 10. Specifically, the primary winding 42 includes a substrate 42a provided with a metal conductor 42a1 on one surface, a center pin member 42b formed of a metal conductor that is connected to the central portion of the substrate 42a and disposed at the center of the toroidal core 41, and a plurality (here, four) of peripheral pin members 42c formed of metal conductors that are connected to the peripheral edge portion of the substrate 42a and disposed around the toroidal core 41. It is conceivable to attach a metal conductor 42a1 such as a copper foil to the surface of the substrate 42a facing the toroidal core 41. With this configuration, current flows radially from the center pin member 42b through the substrate 42a to the plurality of peripheral pin members 42c. With such a configuration, the primary winding 42 can be made easier to assemble.

[0048] Also, in the above embodiment, the secondary winding was wound inside the toroidal core and the primary winding was wound outside the toroidal core. However, the primary winding may be wound inside the toroidal core and the secondary winding may be wound outside the toroidal core, or the primary winding may be wound around a part of the circumferential direction of the toroidal core and the secondary winding may be wound around a part other than the part where the primary winding is wound in the circumferential direction.

[0049] Furthermore, in the above embodiment, the transformer was fixed to the circuit board by fixing the primary winding to the circuit board. However, the transformer may be fixed to the circuit board by other methods such as using fixing screws.

[0050] In addition, various modifications and combinations of embodiments may be made as long as they do not contravene the spirit of the present invention.

Industrial Applicability

[0051] According to the present invention, it is possible to reduce the temperature influence caused by the transformer in the quadrupole mass spectrometer.

Claims

1. An ionization section for ionizing a sample, a quadrupole section having two pairs of opposing electrodes for selectively passing the ions generated in the ionization section, a voltage application section for applying a voltage in which a DC voltage and a high-frequency voltage are superimposed on each of the two pairs of opposing electrodes, and an ion detection section for detecting the ions that have passed through the quadrupole section, wherein the voltage application section has a transformer for transforming a high-frequency voltage, the transformer is configured by winding a primary winding and a secondary winding around a toroidal core, and the primary winding is formed of a plate-shaped metal conductor, a quadrupole mass spectrometer.

2. The secondary winding wound around the toroidal core has a first secondary winding connected to one of the two pairs of opposing electrodes and a second secondary winding connected to the other of the two pairs of opposing electrodes, the quadrupole mass spectrometer according to claim 1.

3. The toroidal core is configured by laminating two or more toroidal core elements, the quadrupole mass spectrometer according to claim 1 or 2.

4. The primary winding is wound around the toroidal core in a radial manner, the quadrupole mass spectrometer according to any one of claims 1 to 3.

5. In a developed state, the primary winding has a plurality of strip-shaped portions arranged radially, and the plurality of strip-shaped portions are wound around the toroidal core, the quadrupole mass spectrometer according to any one of claims 1 to 4.

6. The primary winding includes a substrate provided with a metal conductor on one surface, a center pin member formed of a metal conductor connected to the central portion of the substrate and disposed at the center of the toroidal core, and a plurality of peripheral pin members formed of a metal conductor connected to the peripheral edge portion of the substrate and disposed around the toroidal core, the quadrupole mass spectrometer according to any one of claims 1 to 4.

7. The space between the toroidal core and the primary winding is filled with an adhesive having thermal conductivity, the quadrupole mass spectrometer according to any one of claims 1 to 6.

8. The transformer is fixed to the circuit board by fixing the primary winding to the circuit board, the quadrupole mass spectrometer according to any one of claims 1 to 7.

9. further comprising a control section for controlling the voltage application section, The quadrupole mass spectrometer according to any one of claims 1 to 8, wherein the control unit controls the voltage application unit to continuously measure a specific mass-to-charge ratio over a predetermined period.

10. A residual gas analysis method for analyzing residual gas in a vacuum chamber using the quadrupole mass spectrometer according to any one of claims 1 to 9.

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