Gas analyzer system having an ion source - Patent application

Abstract

The gas analyzer system of the present invention uses an ion source, which may be a hot cathode ion source. A magnet assembly is arranged to define a magnetic field, which allows ion components to be separated based on their mass-to-charge ratio. An ion beam deflector (e.g., a pair of deflection plates) is used, which allows the ion components to be scanned across the detector. The ion beam deflector defines a deflection field, which is transverse to the magnetic field and transverse to the direction of travel of ions emitted from the ion source.

Description

Related Applications

[0001] This application is a continuation of U.S. Patent Application No. 16 / 698,178, filed November 27, 2019, the entire teachings of which are incorporated herein by reference. [Background technology]

[0002] There is a constant need to facilitate troubleshooting in high vacuum processes. High vacuum processes typically follow a workflow that starts with pumping down the vacuum chamber from atmospheric pressure. Users can track the pressure of the vacuum chamber during pumping down and begin the vacuum process or experiment once the total pressure reaches the target pressure. Typically, the target pressure is expected to be reached within a pre-specified time. If the target pressure is not reached after the expected time has elapsed or if it takes longer than usual to reach the target pressure, the user of the vacuum system must troubleshoot the vacuum chamber. Often, troubleshooting requires not only the use of an ionization gauge, but also breaking the vacuum to use a helium leak detector and sometimes measuring the water level using an expensive residual gas analyzer. Summary of the Invention [Problem to be solved by the invention]

[0003] Thus, there is an ongoing need to provide equipment that reduces the time and costs associated with troubleshooting high vacuum processes. Additionally, there is a need for improvements in helium leak detection systems, water content measurement systems, magnetic sectors, quadrupole mass filters, or other systems that use ion sources. [Means for solving the problem]

[0004] The gas analyzer system uses an ion source, which may be a hot cathode ion source, a magnet assembly arranged to define a magnetic field that allows ion components to be separated based on their mass to charge ratio, and an ion beam deflector, such as a pair of deflection plates, that is capable of scanning the ion components across a detector. The ion beam deflector defines a deflection field that is transverse to the magnetic field and transverse to the direction of travel of the ions emitted from the ion source. With this configuration, ions can be produced with a narrow energy distribution, which results in a mass spectrum with sharp peaks that has high resolution. Further advantages are described below.

[0005] The gas analyzer system includes an ion source configured to generate a source electric field within an ionization region of the ion source. The ionization region receives a gas from a monitored chamber and ions of the gas are formed within the ion source. A source aperture is positioned to eject a portion of the ions of the gas out of the ion source, the ions being accelerated by the source electric field in a direction toward the source aperture. A magnet assembly is positioned to define a magnetic field that angularly displaces the ejected portion of ions based on the mass-to-charge ratio of the ions of the gas. An ion beam deflector is positioned between the source aperture and a detector, the ion beam deflector defining a deflection electric field transverse to the magnetic field and transverse to the direction of travel of the ejected portion of ions. A detector is positioned to detect the displaced ion components of the ejected portion of ions. An ion current measurement circuit is electrically connected to measure a current generated by receipt of the displaced ion components at the detector.

[0006] The ion source may include a cold cathode ion source or a hot cathode ion source. The hot cathode ion source may include a hot filament and an electron collector configured to generate an electron beam passing between the hot filament and the electron collector in the ion source. The hot filament and the electron collector may be configured to generate an electron beam in a direction parallel to a source aperture, the source aperture including an elongated aperture in a direction parallel to the electron beam. The system may further include an energy filter. The source aperture may include an elongated aperture, and the energy filter may include an energy filter grid disposed in an ion beam path of the emission of ions, the energy filter grid including conductive filaments oriented substantially perpendicular to the elongated aperture of the source aperture and substantially free of conductive filaments oriented substantially parallel to the elongated aperture of the source aperture. The energy filter may include an entrance grid disposed between the source aperture and an entrance where the emission of ions enters the ion beam deflector. The energy filter may also include an exit grid disposed between an exit where the ion beam of emitted ions exits the ion beam deflector and the detector aperture.

[0007] The ion beam deflector may be configured to align the ion beam of the ion emission onto the detector. The ion beam deflector may include a pair of parallel plates, and may include a pair of curved plates. The source aperture may be positioned such that the emission of ions of the gas from the ion source enters the ion beam deflector closer to one side of the ion beam deflector than the geometric center of the ion beam deflector. A deflector power supply may be electrically connected to the ion beam deflector to generate a deflection electric field between the pair of deflection plates of the ion beam deflector. The deflector power supply may be electrically connected to (i) provide a positive deflector bias voltage to a first plate of the ion beam deflector relative to a ground voltage of a second plate of the ion beam deflector, or (ii) provide a negative deflector bias voltage to the first plate relative to a ground voltage of the second plate, or (iii) provide a first deflector bias voltage to the first deflector plate and a second deflector bias voltage to the second deflector plate.

[0008] A deflector control circuit may be configured to provide deflector control signals to the deflector power supplies. The deflector control circuit may be configured to control a voltage of the deflector power supplies such that the ion beam deflector directs displaced ion components having different energies and such that a common ion component mass is focused through a detector aperture of the detector. The deflector control circuit may be configured to vary a voltage of the deflector power supplies such that the ion beam deflector varies a deflection of the displaced ion components of the ejection of ions. The voltage of the deflector power supplies may be varied based on (i) a triangular sawtooth variation of voltage with respect to time, or (ii) a voltage waveform to control the peak width and time position of the displaced ion components relative to other ion components. The deflector control circuit may be configured to scan the voltage of the deflector power supply to cause the ion beam deflector to deflect the plurality of ion components for sequential detection by the detector as the voltage of the deflector power supply is scanned, and may be configured to scan the voltage of the deflector power supply to enable detection of the mass spectrum of the plurality of ion components. A total current measurement circuit may be electrically connected to measure a total ion current of the ion source. [Brief description of the drawings]

[0009] The foregoing will become apparent from the following more particular description of illustrative embodiments, which are illustrated in the accompanying drawings, in which like reference characters refer to the same elements throughout the various views, and in which the drawings are not necessarily drawn to scale, emphasis instead being placed upon illustrating the embodiments. [Figure 1] FIG. 2 is a top view of a gas analyzer system according to one embodiment of the present invention showing internal components in a cutaway view of the enclosure. [Diagram 2] 2 is a perspective view of the exterior of the enclosure of the gas analyzer system of FIG. 1 showing a magnet assembly used with the gas analyzer system, according to one embodiment of the present invention; FIG. [Diagram 3] 2 is a side perspective view of the internal components and sidewall of the gas analyzer system of FIG. 1 in accordance with one embodiment of the present invention. [Figure 4] 2 is a perspective view of an ion source of the gas analyzer system of FIG. 1 in accordance with one embodiment of the present invention. [Diagram 5] 2 is a side view of the internal components and sidewall of the gas analyzer system of FIG. 1 in accordance with one embodiment of the present invention. [Figure 6] 2 is a top view of the internal components and sidewalls of the gas analyzer system of FIG. 1 in accordance with one embodiment of the present invention. [Figure 7] 1 is a schematic diagram illustrating off-center motion of a deflector plate, in accordance with one embodiment of the present invention; [Figure 8] FIG. 2 is a schematic diagram of a gas analyzer system according to one embodiment of the present invention showing electrical components and an ion beam path through a magnetic field. [Figure 9] FIG. 1 is a schematic perspective view of a gas analyzer system according to an embodiment of the present invention, which uses an ion beam deflector to deflect ion components for detection by a detector. [Figure 10] FIG. 2 is a schematic diagram illustrating energy focusing using deflection plates, according to one embodiment of the present invention. [Figure 11] FIG. 1 is a schematic perspective view of a gas analyzer system according to an embodiment of the present invention, which uses an inverted magnetron cold cathode discharge electrode configuration and an ion beam deflector to deflect ion components for detection by a detector. [Figure 12] 2 is a schematic diagram of an ion beam deflector including a pair of curved plates, in accordance with an embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Exemplary embodiments are described below.

[0011] A cold cathode ion source for a gas analyzer system was disclosed in a prior application naming some of the present inventors, see U.S. Patent Application Serial No. 16 / 397,436 (Brucker et al.), filed April 29, 2019, entitled "Gas Analysis with an Inverted Magnetron Source," the entire teachings of which are incorporated herein by reference. The disclosure of that application taught the use of a cold cathode ion source in which the magnetic field is oriented transverse to the electric field, and the use of an ion beam deflector to allow the ion beam and ion components to be swept across a detector aperture, thereby allowing the generation of a spectrum of ion components.

[0012] The cold cathode ion source taught in that application has many advantages, but the teachings of that application can be extended to hot cathode ion sources. Also, additional features can be applied to both hot and cold cathode ion sources. Taught herein is a gas analyzer system using an ion source, which can be a hot cathode ion source. A magnet assembly is arranged to define a magnetic field, which allows ion components to be separated based on their mass to charge ratio. An ion beam deflector (e.g., a pair of deflection plates) is used, which allows scanning the ion components across the detector. The ion beam deflector defines a deflection field that is transverse to the magnetic field and transverse to the direction of travel of the ions emitted from the ion source. Among other potential advantages, ions are produced with a narrow energy distribution, which produces sharp peaks in the mass spectrum, providing high resolution. Other potential advantages are also taught herein.

[0013] The gas analyzer system will now be described with reference to Figures 1-3. Figure 1 is a top view of gas analyzer system 100, showing the internal components within a cutaway view of enclosure 180. Figure 2 is a perspective view of the exterior of enclosure 180, showing magnet assembly 264. Figure 3 is a side perspective view of the internal components and sidewall 382 of the system.

[0014] In Figure 1, the gas analyzer system 100 includes an ion source 104 configured to generate a source electric field in an ionization region 110 of the ion source 104. In Figure 1, for example, the source electric field may be oriented from right to left between a source pusher electrode 108 and an anode electrode 106. The ionization region 110 receives a gas from a monitored chamber, and ions of the gas are formed in the ion source 104. A source aperture 114 is positioned to eject a portion of the ions of the gas out of the ion source 104, and the source aperture 114 may be an aperture formed in a portion of the anode electrode 106. The ions are accelerated by the source electric field in a direction toward the source aperture 114. A magnet assembly 264 (see FIG. 2) is positioned to define a magnetic field that angularly displaces ions emitted from the source aperture 114 (FIG. 1) based on the mass-to-charge ratio of the ions, for example by defining a magnetic field across the flight region of the emitted ions, as shown in FIG. 8, 860, described below. An electron beam 326 is generated by the ion source 104 of FIG. 1, as described below with respect to FIGS. 3 and 4. The electron beam collides with gas molecules to form ions of the gas within the ion source 104. The anode electrode 106 may extend to form a wall that substantially surrounds the ion source 104, except for the source pusher electrode 108. In another embodiment, the ion source 104 may be made of a wire mesh material, which allows the ion source 104 to pass gas. In this case, the solid wall of the ion source 104 is replaced with a perforated metal or sintered wire mesh. The source aperture 114 in FIG. 1 may be, for example, approximately 0.005 inches wide, although it should be appreciated that other dimensions may be used.

[0015] A vacuum port 148 allows gas from the monitored chamber to enter the gas analyzer system from the monitored chamber, such that the gas moves in a countercurrent direction to the ion beam, i.e., from the detector 116 toward the source aperture 114. In the ion source 104, gas enters the ion source 104 (e.g., through an opening in the top of the ion source 104, or possibly through an open or perforated side of the ion source 104), is then ionized within the ion source 104 to form an ion beam, and the ion beam is emitted in the reverse direction, i.e., the ion beam moves from the source aperture 114 toward the detector 116.

[0016] FIG. 2 is a perspective view of the exterior of the enclosure of the gas analyzer system of FIG. 1 according to an embodiment of the present invention, showing a magnet assembly 264 for use with the gas analyzer system. The magnet assembly 264 may include an integral magnet that extends above the ion source and extends in a longitudinal direction from the source aperture toward the detector. The example of FIG. 2 shows two integral magnets (top and bottom) that sandwich the region of the ion flight path between the source aperture and the detector, which helps to generate a uniform magnetic field in the flight path region. The magnetic field provided by the magnet assembly 264 may be, for example, 1 kilogauss throughout, and can separate the ion components to the extent that water appears separate from the remaining gases. For further mass separation, the magnetic strength in the flight path can be increased by adding another magnet 266 above the flight path, or a magnetic yoke, or both. In the hot cathode ion source embodiment of Figures 1-3, the magnet assembly 264 may extend over the ion source 104 (see Figure 1) as well as the flight region of ions between the source aperture and the detector, but this is not required. The advantage of extending the magnet assembly 264 over the ion source 104 is that the additional magnetic field over the electron beam 326 (see Figure 3) increases the circularity of the electrons, thereby lengthening their trajectories. However, in some hot cathode ion source embodiments, the magnet assembly 264 only extends over the flight region of ions between the source aperture and the detector. On the other hand, in the cold cathode ion source embodiment shown in Figure 11 below, the magnet assembly 264 may extend over the flight region of ions between the source aperture and the detector, which is required to define a cross-field arrangement across the electric field in the cold cathode ion source to facilitate mass separation of ions. Also shown in Figure 2 are electrical feedthroughs 240 (see also Figures 5 and 6), all of which may extend through one sidewall.

[0017] A detector 116 (see FIG. 1) is positioned to detect the displaced ion component of the ion ejection. The detector 116 may include, for example, a detector aperture 120, which may be approximately 0.010 inches wide, although other dimensions may of course be used. The detector 116 may include a Faraday collector 122. The detector aperture 120 may be voltage biased to act as an energy filter for the ions. Other types of energy filters may also be used, such as those described below with respect to the energy filter grids 124a / 124b, or by biasing a detector shield 1198 (FIG. 11, described below).

[0018] An ion beam deflector 118 is disposed between the source aperture 114 and the detector 116. The ion beam deflector 118 defines a deflection electric field transverse to the magnetic field (see direction 860 in FIG. 8) and transverse to the direction of travel of the ions emitted from the source aperture (i.e., transverse to the direction of travel from the source aperture 114 to the detector aperture 120 in FIG. 1). For example, in FIG. 1, the deflector 118 may define a deflection electric field in a top-to-bottom direction in FIG. 1. An ion current measurement circuit (not shown in FIG. 1, see 970 in FIG. 9) is electrically connected to measure the current resulting from receipt of the displaced ion components at the detector 116.

[0019] 1 further includes energy filters (e.g., energy filter grids 124a and 124b) disposed in the ion beam path. Energy filter grid 124a is an entrance grid, which is disposed between the source aperture 114 and the entrance where the ion beam enters the ion beam deflector 118. Energy filter grid 124b is an exit grid, which is disposed between the exit where the ion beam leaves the ion beam deflector 118 and the detector aperture 120. Of course, either or both of the entrance grid 124a and the exit grid 124b may be used.

[0020] 3 is a side perspective view of the internal components of the system and sidewall 382. Note that in some embodiments, the internal components of the system may be conveniently mounted to sidewall 382 for ease of assembly, and the electrical feedthroughs (see 240 in FIGS. 2, 5, and 6) may all extend through one sidewall. Note further that sidewall 382 (see FIGS. 3-7) and base plate 480 (see, e.g., FIG. 4) may form part of enclosure 180 (see FIGS. 1 and 2).

[0021] Figure 4 is a perspective view of the ion source 104 of the gas analyzer system of Figure 1 according to one embodiment of the present invention. The ion source 104 may be a hot cathode ion source, which may include a hot filament 428 (or other hot cathode ion source) and an electron collector 430 configured to generate an electron beam 326 that passes between the hot filament 428 and the electron collector 430 in the ion source 104. A filament deflector 432 focuses the electron beam 326. The electrons in the electron beam 326 precess in a circular orbit due to a magnetic field across the ion source. An exit hole 434 is formed in an insulator 436 that forms the bottom of the ion source 104. The hot filament 428 and electron collector 430 may be configured to generate the electron beam 326 in a direction parallel to the source aperture 114, which is elongated in a direction parallel to the electron beam, e.g., in FIG. 4, both the electron beam 326 and the source aperture 114 are aligned vertically in FIG. 4. In the most efficient electron ionization design, the electrons are injected parallel to the magnetic field and the direction of the source aperture. Ions that can reach the source aperture should be generated within a narrow range of potential energies, i.e., within the flat equipotential region of the source, which can be accounted for by modeling.

[0022] As shown in Fig. 4, the entrance grid 124a may include conductive filaments 438 oriented approximately perpendicular to the elongated aperture of the source aperture 114, i.e., horizontally oriented in Fig. 4, which is oriented vertically in Fig. 4, and which has no (or nearly no) conductive filaments oriented approximately parallel to the elongated aperture of the source aperture 114, i.e., no vertically oriented filaments in Fig. 4. In this way, there are no grid lines interfering with the path between the source aperture and the detector aperture, e.g., not present if a vertically oriented ribbon beam is scanned horizontally across the grid mesh, but which would encounter interference if used for vertically oriented filaments in the conductive mesh. This arrangement can, for example, double the signal sensitivity without affecting the resolution or peak position. The exit grid (see 124 b in FIG. 1) may use a similar arrangement of conductive filaments 438 ( FIG. 4 ) oriented approximately perpendicular to the elongated aperture of the source aperture 114 .

[0023] Figure 5 is a side view of the internal components and sidewalls of the gas analyzer system of Figure 1. Several electrical feedthroughs 240 (not individually listed) allow electrical signals and power to enter and exit the gas analyzer system enclosure. A filament power supply 542 and a filament power return 544 provide power to and from the hot filament.

[0024] Figure 6 is a top view of the internal components and sidewalls of the gas analyzer system of Figure 1, according to one embodiment of the present invention. In this view, electrical feedthrough 240 extends from outside the enclosure of the gas analyzer system to the interior of the enclosure. Also shown in this top view are source pusher electrode 108, filament power supply 542 and filament power return 544 (each with their own electrical feedthrough), and filament deflector 432. Also shown in Figure 6 is deflection plate 646a, which is one of a pair of parallel plates that form ion beam deflector 118 (of Figure 1). The other plate (see 746b in Figure 7) is not shown in Figure 6. As shown in Figure 6, entrance grid 124a and exit grid 124b are located at the entrance and exit, respectively, where the ion beam enters and exits the ion beam deflector. That is, here it is disposed between electrode deflection plate 646a and a corresponding parallel plate (see 746b in FIG. 7, not shown in FIG. 6).

[0025] 7 is a schematic diagram illustrating off-center operation of deflection plates 646a / 746b, according to one embodiment of the present invention. Here, the source aperture 114 is positioned such that the ion beam 758 emitted from the ion source 104 enters the ion beam deflector 118 closer to one side of the ion beam deflector 118 than the geometric center 750 of the ion beam deflector 118. This positioning has several potential advantages. By shortening the distance to the deflection plates to which the voltage is applied, lower voltages are required on the deflection plates, which can save on power supply costs, lower ratings are required for electrical feedthroughs, and increase component reliability. Additionally, the equipotential lines are flatter and closer to the deflection plates, which results in less distortion of the ion beam along its flight path.

[0026] FIG. 8 is a schematic diagram of a gas analyzer system according to one embodiment of the present invention, showing the electrical components and the ion beam path through the magnetic field. The system includes a source pusher electrode 108 biased at a voltage VPE=Va+VPUSH, where VPE is the voltage of the source pusher electrode 108, Va is the voltage of the anode electrode 106, and VPUSH is the bias voltage of the source pusher electrode 108, which may be, for example, around 200V. The electron beam 326 travels between the hot filament 428 and the electron collector 430. The filament heater voltage 852 is set, for example, at 2V with a current of 2A. The filament bias voltage 854 (VFB) is, for example, between 0 and 100V. The anode bias voltage 856 (Va) is, for example, between 200 and 500V. The ion beam 758 is emitted through the entrance grid 124a and travels between the deflection plates 646a / 746b. A magnetic field direction 860 is shown, and the magnitude of the magnetic field may be, for example, about 1 kilogauss (note that for simplicity of illustration, the orientation of the electron beam 326 in FIG. 8 is shown as being vertical on the page, but in other embodiments shown herein, it would be oriented out of the page, so as to be parallel to the elongated source aperture shown elsewhere herein). One deflector plate 646a (the pusher deflector plate) is biased at a voltage 862 (V(t)) (which in this example is a sawtooth pattern voltage with a peak of about 1000V) and the other deflector plate 746b is at ground voltage. The exit grid 124b is biased, for example, at VF=0-500V. The detector aperture 120 is biased at ground voltage. In another example, energy filtering may be achieved by keeping the exit grid 124b at ground potential and biasing the detector aperture 120 instead. The Faraday collector 122 receives the detected portion of the ion beam 758 and produces a detected ion current IPP(G), which may be used, for example, to measure the partial pressure of the ion constituents detected at the detector aperture 120.

[0027] In the embodiment of FIG. 8, the high energy source design creates ions in an ionization volume that is biased at a high voltage. The source pusher electrode 108 pushes the ions out of a narrow aperture in the source aperture and into the magnetic sector. The ions leave the source, gain high kinetic energy, and then fly through the mass separator, which is held at ground potential when the deflection plates 646a / 746b are off. By adjusting the bias of the source, it is possible to control the energy of the ions as they pass through the magnetic sector. An advantage of this design is that the entire flight path is held at ground potential, and only the source needs to float. Depending on the voltage bias of the ionization region, it is often possible to operate the filament close to ground potential, and the electrons gain high energy as they enter the source.

[0028] In FIG. 8, ions are generated inside the anode in an ionization region defined by the electron beam 326. The ion energy distribution is very narrow because the potential is well defined in the ionization band. To maximize the efficiency of ionization, the electron beam 326 may be parallel to the magnetic field 860 (note again, for simplicity of illustration, the source in FIG. 8 is shown in the plane of the page, but it may be parallel to the magnetic field direction 860), which causes the electrons to precess in a circular orbit and lengthen the ionization trajectory. Ions formed in the anode 106 are pushed towards the source aperture by the source pusher electrode 108. As the electrons move towards the anode 106, they accelerate and reach an energy equal to the potential difference between the anode 106 and the filament bias 854. The electron beam 326 crosses the ionization region in a band located near the anode aperture 114 (see FIG. 1). This causes the ions to form in an equipotential region which narrows the energy distribution.

[0029] 9 is a schematic perspective view of a gas analyzer system according to an embodiment of the present invention, which uses an ion beam deflector 118 to deflect ion components for detection at a detector. The ion beam deflector 118 (e.g., a pair of parallel plates 646a and 746b, or a pair of curved plates (see 646a and 746b in FIG. 12)) is placed between the source aperture 114 and the detector 116. Such an ion beam deflector 118 can be used to deflect ion components and perform energy focusing, which will be described in more detail later. The displaced ion components 968 are separated into various ion components that spread apart and disperse from each other as they move away from the source aperture 114. The source aperture 114 (e.g., a vertical slit) allows a thin sliver of ion components 968 to exit the source. The magnetic field in the ion flight region between the source aperture 114 and the detector 116 by the magnet 264 (see FIG. 2) causes a mass-dependent deflection of the ions, separating them into ion components 968b-d. Lighter ions are deflected more than heavier ions. For example, the displaced ion component 968b is made of helium ions, 968c is made of water ions, and 968d is made of residual gas (e.g. nitrogen and oxygen). Such a large deflection of the ion components with an additional magnet can, for example, allow the separation of water ions from other residual gas ions 968d. The detector 116 includes a metallic Faraday collector 122, which generates an ion current proportional to the ion flux reaching the detector 116 through the detector aperture 120. This ion current is the partial pressure current (IPP) of the ion component 968d reaching the detector. An ion current measurement circuit 970 is used to measure the partial pressure current. This partial pressure may be used to indicate the partial pressure of the gas from the monitored chamber, specifically the partial pressure of the mass separated ion components 968d reaching the detector. Additionally, a total current measurement circuit 901 may be electrically connected to measure the total ion current of the ion source. For example, the total current measurement circuit 901 may measure a total current proportional to the total ion current flowing from the ion source, which may be used to determine the total pressure of the gas from the monitored chamber.9, a total current measurement circuit 901 may measure the total current flowing into the ion source (here, the hot filament of a hot source), but may instead measure the total current in another manner, such as by measuring the current flowing through the anode 106. Based on the partial pressure current and the total pressure current, a total pressure display electrically associated with the total current measurement circuit 901 may indicate (e.g., visually indicate) the total pressure of the gas from the monitored chamber, and a partial pressure display electrically associated with the ion current measurement circuit 970 may indicate (e.g., visually indicate) the partial pressure of the gas from the monitored chamber.

[0030] Additionally, in the embodiment of FIG. 9, the ion beam deflector 118 is used to steer the ion components 968b-d entering the detector aperture 120. While the magnetic field bends the ion component trajectory downward (with respect to FIG. 9), the electric field between the deflection plates 646a and 746b electrostatically steers the ion component trajectory upward (with respect to FIG. 9) assuming a "pusher" configuration with the deflection plate 646a positively biased with respect to the grounded deflection plate 746b. In FIG. 9, for example, the potential difference between the deflection plates 646a and 746b is set such that the residual gas component 968d is detected. If both deflection plates 646a and 746b were grounded, all ions would miss the detector aperture 120 depending on the angle of the source aperture and the magnitude of the deflection of the ion component by the magnetic field. However, because the voltage of one of the deflection plates (here, pusher deflection plate 646a) is changed (here, more positive) relative to the other deflection plate 746b (which is grounded in this example), ion components 968b-d are steered upward (or downward depending on the voltage change) to allow various ion components to pass safely through detector aperture 120. In FIG. 9, pusher deflection plate 646a is set at a voltage such that residual gas ion component 968d reaches detector aperture 120. If the voltage of deflection plate 646a were increased further, water ion component 968c or helium ion component 968b would reach detector aperture 120 and generate a signal. In this manner, deflector 118 allows ion component steering, allowing multiple ion component species to be delivered sequentially to detector 116. In the example of FIG. 9, the deflection plate 646a is a pusher deflection plate, which is swept with a positive voltage relative to the grounded deflection plate 746b. Other configurations may be used, for example, one plate may be at a negative voltage relative to the other plate, which is grounded, or both plates may be biased with different voltages. In the example of FIG. 9, with the pusher deflection plate, ion components may emerge from the source aperture 114 and fly toward the pusher deflection plate 646a, for example, based on the deflection caused by the magnetic field. In this example, when the deflection plates 646a, 746b are turned off, no ion components reach the detector aperture 120.As the voltage on the pusher deflector 646a is swept with a positive voltage, the ion components begin to be pushed towards the detector aperture 120. The heavier ions enter the detector aperture 120 first, and the lighter ion components require a higher voltage to sweep them away so that they reach the detector aperture 120.

[0031] By scanning the voltage of one or both deflection plates (e.g., scanning the voltage of the pusher deflection plate 646a) and plotting the ion component signal (e.g., partial current) against the deflection plate voltage, a real-time mass spectrum can be generated. For example, a graphical display can be generated on a visual display device showing the detected partial current in volts provided by the picoammeter to the voltage converter on the vertical axis and the time in seconds that is linear with respect to the deflection plate voltage (because the deflector voltage is swept with a sawtooth waveform) on the horizontal axis. Additionally, automatic zero baseline subtraction can be performed.

[0032] 9, a deflector power supply 972 is electrically connected to the ion beam deflector 646a to generate a deflection electric field between the plates 646a, 746b of the ion beam deflector 646a. The deflector power supply 972 is electrically connected to (i) provide a positive deflector bias voltage to the first plate 646a of the ion beam deflector relative to a ground voltage of the second plate 746b of the ion beam deflector, or (ii) provide a negative deflector bias voltage to the first plate 646a relative to a ground voltage of the second plate 746b of the ion beam deflector, or (iii) provide a first deflector bias voltage to the first plate 646a and a negative deflector bias voltage to the second plate 746b of the ion beam deflector. 746b The second deflector bias voltage Pressure It may be for the sake of giving.

[0033] In FIG. 9, a deflector control circuit 974 may be configured to provide deflector control signals to a deflector power supply 972. The control circuit 974 may be configured to control the voltage of the deflector power supply 972 such that the ion beam deflector 118 directs the displaced ion components having different energies and focuses the common ion component mass through a detector aperture of a detector, as shown later in FIG. 10. Additionally, the deflector control circuit 974 may be configured to vary the voltage of the deflector power supply 972 such that the ion beam deflector varies the deflection of the displaced ion components of the ejection of ions. The voltage of the deflector power supply 972 may be varied based on (i) a triangular sawtooth variation of voltage with respect to time (as shown in FIG. 8) or (ii) a voltage waveform to control the peak width and time position of the displaced ion components relative to other ion components. The deflector control circuitry 974 may be configured to scan the voltage of the deflector power supply 972 to cause the ion beam deflector to deflect the multiple ion components 968b-d so as to be detected sequentially by the detector as the voltage of the deflector power supply 972 is scanned, and may be configured to scan the voltage of the deflector power supply 972 to enable detection of the mass spectra of the multiple ion components as described above.

[0034] In another version of the embodiment of Figure 9, the ion beam deflector 118 may be configured to align the ion beam 758 (see Figure 7) of the ejected ions onto the detector. Current beam alignment (e.g., in helium sensors) relies on mechanical adjustment of the electron beam in a hot cathode ion source, which can be a time-consuming and tedious process. However, by using the ion beam deflector 118 described herein to realign the ion beam, no mechanical adjustment is required.

[0035] Additionally, the ion beam deflector 118 can be used to determine the spectral baseline offset by measurements on top and to the sides of multiple spectral peaks, which can also be an advantage over conventional helium leak detectors.

[0036] FIG. 10 is a schematic diagram illustrating energy focusing using deflection plates according to an embodiment of the present invention. In energy focusing, ion components with different energies and a common ion component mass are focused through a detector aperture 120 of a detector. For example, low energy ions 1076 and high energy ions 1078 of a common ion component (e.g., low energy water ions and high energy water ions) can be focused through the detector aperture 120. In another example, low energy residual gas ions and high energy residual gas ions can be focused through the detector aperture 120. To perform such energy focusing, a deflector control circuit 974 (of FIG. 9) is configured to control the voltage of a deflector power supply 972 (of FIG. 9) such that the ion beam deflector directs the ion components 1076 and 1078 with different energies and the common ion component mass is focused through the detector aperture 120. For each ion component mass, there is a specific voltage of the deflector power supply that achieves energy focusing. The orientation of the ion beam corresponding to the mass of interest is determined such that the deflector voltage at which the ion beam reaches the detector is also the same as the voltage at which energy focusing is performed on the mass of interest. In hot or cold cathode ion source embodiments, this can be done by laterally displacing the detector aperture or the source aperture (or both). Additionally, in cold cathode ion source embodiments, the source may rotate.

[0037] 12 is a schematic diagram of an ion beam deflector including a pair of curved plates according to one embodiment of the present invention, where plates 646a and 746b are curved, unlike the parallel plates 646a and 746b shown elsewhere herein. Operation may be generally similar to that of the parallel plates described herein. Of course, various shapes and configurations may be used for the ion beam deflector and plates 646a and 746b, and the length and curvature of the curved plates 646a and 746b may be optimized.

[0038] In another embodiment, the ion source may include a cold cathode ion source. Figure 11 is a schematic perspective view of a gas analyzer according to an embodiment of the present invention, which uses an inverted magnetron cold cathode discharge electrode configuration and an ion beam deflector 118 to deflect ion components for detection at a detector. The ion beam deflector 118 (e.g., a pair of parallel plates 646a and 746b, or a pair of curved plates (similar to that shown in Figure 12)) is positioned between the source aperture 114 and the detector 116. As with the hot cathode ion source embodiment, the ion beam deflector 118 can be used to deflect ion components and perform energy focusing.

[0039] As with the hot cathode ion source embodiment, the displaced ion component 968 is separated into various ion components that spread apart and disperse from each other as they move away from the source aperture 114. In the inverted magnetron cold cathode discharge electrode configuration, the cathode electrode assembly 1184 surrounds the anode electrode 1186. The axial magnetic field (generated by the magnet assembly 264, not shown in FIG. 11) is centered on the anode electrode 1186, and a radial electric field is established by applying a high voltage potential (Vanode) to the anode electrode 1186. A cross-field arrangement of electric and magnetic fields (indicated by electric field direction 1188 and magnetic field direction 1190) establishes a pure electron plasma 1192 surrounding the anode electrode 1186. Gas molecules that enter the pure electron plasma 1192 are ionized by the precessing electrons to form ions, which are immediately accelerated by the radial electric field toward the cathode electrode assembly 1184. The magnetic field inside the source is strong enough (e.g., 1 kilogauss) to cause the electrons to precess in tight circular orbits, but has little effect on the heavy ions, which undergo a small mass-dependent magnetic deflection of their orbits as they fly towards the cathode electrode assembly 1184. The source aperture 114 (e.g., a vertical slit located on the cathode wall) allows a thin sliver of ion component 968 to exit the source. An additional magnet (see 264 in FIG. 2, not shown in FIG. 11) extends the magnetic field into the ion flight region between the source aperture 114 and the detector 116, which increases the mass-dependent deflection of the ions and separates them into ion components 968b-d. Lighter ions are deflected more than heavier ions. For example, displaced ion component 968b is made of helium ions, 968c is made of water ions, and 968d is made of residual gas (e.g., nitrogen and oxygen). Such a large deflection of the ionic component with the additional magnet can, for example, allow separation of water ions from other residual gas ions 968d. The detector 116 includes a metallic Faraday collector half cylinder 122, which produces an ionic current proportional to the ionic flux reaching the detector 116 through the detector aperture 1194. This ionic current is the partial pressure current (IPP) of the ionic component 968d reaching the detector.FIG. 11 also shows the total voltage current (IT).

[0040] Additionally, in the embodiment of FIG. 11, an ion beam deflector 118 is used to steer the ion components 968b-d that enter the detector aperture 1194. A detector shield electrical connector 1196 is also electrically connected between the detector shield 1198 and a voltage source 1199 that applies a detector shield bias voltage to the detector shield 1198, making the detector shield 1198 a high pass ion energy filter. The high pass ion energy filter allows only ions with energies above the detector shield bias voltage to cross the face of the detector aperture 1194 while allowing other ions to change direction. Increasing the detector shield bias voltage narrows the distribution or spread of energies of ions that are allowed to reach the detector 116 during the deflector voltage sweep, resulting in a narrower mass peak as the voltage increases. Although the embodiment of FIG. 1 uses energy filter grids 124a / 124b, other types of energy filters may also be used. For example, in the embodiment of Figure 11, a detector shield bias voltage is applied to the detector shield 1198 (while isolated from ground), making the detector shield 1198 a high pass ion energy filter. In the cold cathode ion source embodiment of Figure 11, the energy of the ions depends on the gas pressure, and generally, as the pressure increases over the useful pressure range of the analyzer (which may be, for example, 10-10 to 10-3 Torr), the energy of the ions decreases and the energy spread of the ions becomes smaller. In contrast, in the hot cathode ion sources taught herein, the energy spread of the ions is small and the energy of the ions does not change with pressure.

[0041] As used herein, hot cathode ion sources may include any hot cathode ion source, including those based on incandescent filaments and those that use thermionic emission. In addition, other ion sources may also be used, such as cold cathode ionizing emitters, such as Electron Generator Arrays and field emitters. Hot cathode ion sources are generally more complex than cold cathode ion sources. However, ions provided by hot cathode ion sources have a smaller energy distribution, which may lead to improved resolution.

[0042] The systems taught herein may be used in a variety of possible contexts, for example as helium sensors in helium leak detectors, or in mass spectrometers, or in magnetic sectors, or for multi-gas detection.

[0043] Various possible advantages can be realized using the embodiments taught herein. Ions may be generated with a narrower energy distribution, which results in sharper peaks in the mass spectrum, which allows for higher resolution. Furthermore, the energy of the ions may be independent of pressure. The ion signal is linear with pressure and therefore easier to quantify, since it does not require complex non-linear look-up tables. Since the ion energy does not change with pressure, there is no need to adjust the peak position and filter voltage with pressure, i.e., the adjustments are smaller. A smaller helium sensor may be provided in the helium leak detector, which provides an opportunity to make current mass spectrometers more compact. Compared to standard helium sensors in helium leak detectors, the scanning capability eliminates the need for a 180 degree bend, making the detector much more compact. Furthermore, no adjustment of the filament position is required, since this is commonly done when tuning a helium leak detector. Instead, with the aid of deflection plates, any changes in the position of the ion beam can be compensated for by adjusting the deflection plate voltage.

[0044] Furthermore, the high energy sources taught herein can be very efficient in that the components of the system work well together. The same anode potential that energizes the ions also attracts the electrons to the ionization region. The fact that the flight path is grounded reduces the possibility of arcing or electric shock. The voltages required are fairly small and easy to implement in electronic circuitry. Starting from a low potential, it is possible to reliably reduce the range of the ion energy distribution, thereby providing sufficient spectral resolution.

[0045] The teachings of all patents, published applications, and references cited herein are incorporated by reference in their entirety.

[0046] While exemplary embodiments have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the embodiments encompassed by the appended claims. The present invention includes the following embodiments. [Aspect 1] an ion source configured to generate a source electric field within an ionization volume of the ion source, the ionization volume receiving a gas from a monitored chamber and ions of the gas being formed within the ion source; a source aperture positioned to eject a portion of the ions of the gas out of the ion source, the ions being accelerated by the source electric field in a direction toward the source aperture; a magnet assembly arranged to define a magnetic field that angularly displaces the ejection of ions based on the mass-to-charge ratio of ions of the gas; a detector positioned to detect a displaced ion component of the ejection of ions; an ion beam deflector disposed between the source aperture and the detector, the ion beam deflector defining an electric deflection field transverse to the magnetic field and transverse to a direction of travel of the ejected portion of ions; an ion current measurement circuit electrically connected to measure a current generated by receiving the displaced ion component at the detector; 1. A gas analyzer system comprising: [Aspect 2] 2. The gas analyzer system of embodiment 1, wherein the ion source comprises a cold cathode ion source. [Aspect 3] 2. The gas analyzer system of embodiment 1, wherein the ion source comprises a hot cathode ion source. [Aspect 4] 4. The gas analyzer system of claim 3, wherein the hot cathode ion source includes a hot filament and an electron collector, the hot filament and the electron collector configured to generate an electron beam that passes between the hot filament and the electron collector within the ion source. [Aspect 5] A gas analyzer system as described in aspect 4, wherein the hot filament and the electron collector are configured to generate the electron beam in a direction parallel to the source aperture, the source aperture including an elongated aperture in a direction parallel to the electron beam. [Aspect 6] 2. The gas analyzer system of embodiment 1, further comprising an energy filter. [Aspect 7] The gas analyzer system of claim 6, wherein the source aperture includes an elongated aperture, and the energy filter includes an energy filter grid positioned in an ion beam path of the emitted portion of the ions, the energy filter grid including conductive filaments oriented approximately perpendicular to the elongated aperture of the source aperture and including substantially no conductive filaments oriented approximately parallel to the elongated aperture of the source aperture. [Aspect 8] 7. The gas analyzer system of claim 6, wherein the energy filter includes an entrance grid disposed between the source aperture and an entrance through which the ion beam of the emitted portion of the ions enters the ion beam deflector. [Aspect 9] 7. The gas analyzer system of claim 6, wherein the energy filter includes an exit grid disposed between an exit where the ion beam of the emitted portion of the ions exits the ion beam deflector and the detector aperture. [Aspect 10] 2. The gas analyzer system of claim 1, wherein the ion beam deflector is configured to align an ion beam of the ejection of ions onto the detector. [Aspect 11] 2. The gas analyzer system of claim 1, wherein the ion beam deflector comprises a pair of parallel plates. [Aspect 12] 2. The gas analyzer system of claim 1, wherein the ion beam deflector comprises a pair of curved plates. [Aspect 13] 2. The gas analyzer system of claim 1, wherein the source aperture is positioned such that the ions of the gas emitted from the ion source enter the ion beam deflector closer to one side of the ion beam deflector than the geometric center of the ion beam deflector. [Aspect 14] 2. The gas analyzer system of claim 1, further comprising a deflector power supply electrically connected to the ion beam deflector for generating the deflection electric field between a pair of deflection plates of the ion beam deflector. [Aspect 15] 15. The gas analyzer system of claim 14, wherein the deflector power supply is electrically connected to (i) provide a positive deflector bias voltage to a first deflector plate of the ion beam deflector relative to a ground voltage of a second deflector plate of the ion beam deflector, or (ii) provide a negative deflector bias voltage to the first deflector plate relative to the ground voltage of the second deflector plate, or (iii) provide a first deflector bias voltage to the first deflector plate and a second deflector bias voltage to the second deflector plate. [Aspect 16] 15. The gas analyzer system of embodiment 14, further comprising a deflector control circuit configured to provide a deflector control signal to the deflector power supply. [Aspect 17] The gas analyzer system of aspect 16, wherein the deflector control circuit is configured to control the voltage of the deflector power supply so that the ion beam deflector directs displaced ion components having various energies and so that a common ion component mass is focused through a detector aperture of the detector. [Aspect 18] 17. The gas analyzer system of claim 16, wherein the deflector control circuit is configured to vary the voltage of the deflector power supply such that the ion beam deflector changes the deflection of the displaced ion components of the ejected portion of ions. [Aspect 19] The gas analyzer system of claim 18, wherein the deflector control circuit is configured to vary the voltage of the deflector power supply based on (i) a triangular sawtooth variation of the voltage with respect to time, or (ii) a voltage waveform to control the peak width and time position of the displaced ion component relative to other ion components. [Aspect 20] The gas analyzer system of claim 16, wherein the deflector control circuit is configured to scan the voltage of the deflector power supply to cause the ion beam deflector to deflect multiple ion components so as to be detected sequentially by the detector when the voltage of the deflector power supply is scanned. [Aspect 21] 21. The gas analyzer system of claim 20, wherein the deflector control circuit is configured to scan the voltage of the deflector power supply to enable detection of a mass spectrum of the plurality of ion components. [Aspect 22] 2. The gas analyzer system of embodiment 1, further comprising a total current measurement circuit electrically connected to measure a total ion current of the ion source.

Claims

1. an ion source configured to generate a source electric field within an ionization volume of the ion source, the ionization volume receiving a gas from a monitored chamber and ions of the gas being formed within the ion source; a source aperture positioned to eject a portion of the ions of the gas out of the ion source, the ions being accelerated by the source electric field in a direction toward the source aperture; a magnet assembly arranged to define a magnetic field that angularly displaces the ejection of ions based on the mass-to-charge ratio of ions of the gas; a detector positioned to detect a displaced ion component of the ejection of ions; an ion beam deflector disposed between the source aperture and the detector, the ion beam deflector defining an electric deflection field transverse to the magnetic field and transverse to a direction of travel of the ejected portion of ions; an ion current measurement circuit electrically connected to measure a current generated by receiving the displaced ion component at the detector; the ion beam deflector is configured to direct the displaced ion components having different energies and a common ion component mass to be focused through a detector aperture of the detector; a source aperture positioned such that an emission of the ions of the gas from the ion source enters the ion beam deflector closer to one side of the ion beam deflector than a geometric center of the ion beam deflector.

2. The gas analyzer system of claim 1 , wherein the ion source comprises a cold cathode ion source.

3. The gas analyzer system of claim 1 , wherein the ion source comprises a hot cathode ion source.

4. 4. The gas analyzer system of claim 3, wherein the hot cathode ion source includes a hot filament and an electron collector configured to generate an electron beam that passes between the hot filament and the electron collector within the ion source.

5. 5. The gas analyzer system of claim 4, wherein the hot filament and the electron collector are configured to generate the electron beam in a direction parallel to the source aperture, the source aperture including an elongated aperture in a direction parallel to the electron beam.

6. The gas analyzer system of claim 1 further comprising an energy filter.

7. 7. The gas analyzer system of claim 6, wherein the source aperture includes an elongated aperture, and the energy filter includes an energy filter grid disposed in an ion beam path of the emission of ions, the energy filter grid including conductive filaments oriented substantially perpendicular to the elongated aperture of the source aperture and including no conductive filaments oriented substantially parallel to the elongated aperture of the source aperture.

8. 7. The gas analyzer system of claim 6, wherein the energy filter includes an entrance grid disposed between the source aperture and an entrance where the ion beam of the ejected portion of the ions enters the ion beam deflector.

9. 7. The gas analyzer system of claim 6, wherein the energy filter includes an exit grid disposed between an exit where the ion beam of the emission of ions exits the ion beam deflector and the detector aperture.

10. 10. The gas analyzer system of claim 1, wherein the ion beam deflector is configured to align an ion beam of the emission of ions onto the detector.

11. The gas analyzer system of claim 1 , wherein the ion beam deflector comprises a pair of parallel plates.

12. The gas analyzer system of claim 1 , wherein the ion beam deflector comprises a pair of curved plates.

13. 2. The gas analyzer system of claim 1, further comprising a deflector power supply electrically connected to said ion beam deflector for generating said deflection electric field between a pair of deflection plates of said ion beam deflector.

14. 14. The gas analyzer system of claim 13, wherein the deflector power supply is electrically connected to (i) provide a positive deflector bias voltage to a first plate of the ion beam deflector relative to a ground voltage of a second plate of the ion beam deflector, or (ii) provide a negative deflector bias voltage to the first plate relative to the ground voltage of the second plate, or (iii) provide a first deflector bias voltage to the first plate and a second deflector bias voltage to the second plate.

15. 14. The gas analyzer system of claim 13, further comprising a deflector control circuit configured to provide a deflector control signal to the deflector power supply.

16. 16. The gas analyzer system of claim 15, wherein the deflector control circuitry is configured to control a voltage of the deflector power supply such that the ion beam deflector directs the displaced ion components having different energies and the common ion component mass to be focused through the detector aperture of the detector.

17. 16. The gas analyzer system of claim 15, wherein the deflector control circuitry is configured to vary a voltage of the deflector power supply such that the ion beam deflector varies a deflection of the displaced ion component of the ejection of ions.

18. 18. The gas analyzer system of claim 17, wherein the deflector control circuitry is configured to vary the voltage of the deflector power supply based on (i) a triangular sawtooth variation of the voltage with respect to time, or (ii) a voltage waveform to control a peak width and time position of the displaced ion component relative to other ion components.

19. 16. The gas analyzer system of claim 15, wherein the deflector control circuit is configured to scan a voltage of the deflector power supply to cause the ion beam deflector to deflect a plurality of ion components for sequential detection by the detector as the voltage of the deflector power supply is scanned.

20. 20. The gas analyzer system of claim 19, wherein the deflector control circuitry is configured to scan the voltage of the deflector power supply to enable detection of a mass spectrum of the plurality of ion components.

21. 10. The gas analyzer system of claim 1, further comprising a total current measurement circuit electrically connected to measure a total ion current of said ion source.

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