JP4172561B2 - Gas analyzer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas analyzer intended to perform mass analysis of gases used in thin film processing processes for semiconductors and electronic parts such as CVD / etching without damaging the apparatus.
[0002]
[Prior art]
Conventional gas analyzers separate an excitation source that generates an excitation beam, an ionization unit that ionizes the introduced analyte gas using the excitation beam, and an ion beam that is generated in the ionization region inside the ionization unit according to mass. -It consists of a mass spectrometer to detect. Usually, an electron source is used as the excitation source, and a quadrupole mass spectrometer is used as the mass analyzer. At this time, the kinetic energy of electrons is often 70 eV, and the kinetic energy of ions is often 20 eV.
[0003]
Furthermore, a necessary configuration of the in-process gas analyzer that performs analysis during the process is that the ionization unit is a closed type. This closed ionization source is a low pressure of 10 ⁻⁵ torr or less by differential evacuation between the excitation source and the mass analyzer while the inside of the ionization unit is about 10 ⁻³ torr which is the same as the atmosphere in the process chamber or in a reduced pressure state. It can be kept in a state. This is because at a high pressure of 10 ⁻⁵ torr or more, discharge occurs in the excitation source unit and the mass analysis unit, resulting in damage. Such a conventional in-process gas analyzer is shown in FIG.
[0004]
Sputtering, which is one of thin film processing processes for semiconductor / electronic parts, can be operated without any problem even in this conventional in-process gas analyzer.
[0005]
Further, as a prior art, there is disclosed a gas analyzer connected to a gas conduction amount control device that is provided with an orifice or a valve and can control the conduction amount of an analysis target gas in a stepwise manner (Japanese Patent Laid-Open No. 10-89599). .
[0006]
[Problems to be solved by the invention]
In the conventional gas analyzer, in the CVD using the adhesive gas and the etching using the corrosive gas, although the conventional in-process gas analyzer is within the operating pressure range, the excitation source unit and the mass analyzer unit Since these gases flow directly into each part of the battery, a great deal of damage occurs and it cannot be used immediately. The excitation source section and mass spectrometry section are composed of a high-temperature section such as a filament, electrodes that generate a precise electric field, a detector that utilizes secondary electron generation on the surface, and the like. There was a problem that normal operation could not be performed due to adhesion or corrosion.
[0007]
[Means for solving the problems]
The average value of the stroke (length) in which a certain particle can fly freely without colliding with other particles in the original space is called an average free stroke. The magnitude of the mean free path of a gas molecule that is neutral is inversely proportional to the density (pressure) of the gas and inversely proportional to the square of the diameter of the gas molecule.
[0008]
The value obtained by dividing the mean free path by the representative dimension of the container space is called the Knudsen number. When the Knudsen number is smaller than 0.01, the gas flow becomes a viscous flow, and the gas molecules flow in one direction while colliding with each other, which is similar to a river flow. On the other hand, when the Knudsen number is larger than 1, the gas flow becomes a molecular flow, and the gas diffuses quickly in all directions. There is an intermediate flow between the two.
[0009]
Therefore, it is known that when it is not desired to allow a certain gas to enter a specific region, another gas may flow out from the specific region in a viscous flow state. This is a technique that has been widely used as a shield for adhesive and corrosive gases.
[0010]
However, recent precise research has demonstrated that the diffusion of a specific gas can be sufficiently prevented even in an intermediate flow region having a Knudsen number of about 0.6, even if it is not a perfect viscous flow. If so, it is presumed to have a diffusion preventing effect.
[0011]
Here, the present inventor has found that the effective mean free path of electrons and ions with high energy can be made considerably longer than the mean free path of neutral gas. Therefore, by setting a certain area to a specific pressure and thickness, electrons and ions can pass therethrough but gas cannot pass easily. Then, it was conceived that if an inert gas flows out with a Knudsen number of 1 or less, this region can be used as a barrier against adhesive gas and corrosive gas.
[0012]
That is, by providing the barrier region in such a state at the connection between the excitation source unit and the ionization unit and the mass analysis unit and the ionization unit, the adhering gas and the corrosive gas do not enter the excitation source unit and the mass analysis unit. Can be made.
[0013]
In the above, the adhesion gas or corrosive gases will be entering the only mass analyzer as the ion, this ion will be capable of damaging the device. However, no matter what excitation source is used, the rate at which the gas is ionized is very small, 5 digits or less, and in the present invention, only a very small amount of ions enter the mass spectrometer. In other words, the present invention has been completed as a result of earnest research, with the conviction that it has a life longer by 5 digits or more than the conventional example and can be practically ignored.
[0014]
That is, the present invention ionizes the analyte gas introduced into the ionization region of about 10 ⁻³ torr, which is equivalent to the atmosphere in the process chamber or in a reduced pressure state, by the excitation beam emitted from the excitation source portion in the low pressure state of 10 ⁻⁵ torr or less . A gas analyzer that performs mass spectrometry by separating and detecting the ion beam generated thereby in accordance with the mass in a low-pressure mass analyzer of 10 ⁻⁵ torr or less ,
A first barrier region into which the barrier gas is introduced, a first differential pressure region to which a suction side of a vacuum pump is connected, and the mass spectrometer are sequentially connected in series to the ionization region, and a barrier gas is introduced into the ionization region. A second barrier region, a second differential pressure region to which the suction side of the vacuum pump is connected, and the excitation source unit sequentially connected in series;
Both of the first barrier region and the second barrier region are (1) the length of the excitation beam and the ion beam that are longer than the length of the barrier region that is the length that the excitation beam passes and the length that the ion beam passes. The effective mean free path in the barrier area is large,
(2) The mean free path in the barrier region of the gas to be analyzed is smaller than the thickness of the barrier region,
(3) The Knudsen number in the barrier region of the gas to be analyzed is 1 or less,
(4) The pressure in the barrier region is higher than the pressure in the ionization region, and the barrier gas flows from the barrier region to the ionization region.
By satisfying the conditions, an excitation beam and an ion beam can pass through each barrier region, but a gas to be analyzed cannot pass through each barrier region.
In addition, when the ion beam and the excitation beam are charged beams, a converging lens for converging these beams is provided so that the area of the barrier region that passes through the at least one including the excitation beam is reduced. When the ion beam and the excitation beam are charged beams, the at least one including the excitation beam is provided with an acceleration mechanism so that the transit time of the barrier region is reduced. The kinetic energy of the beam is increased. Furthermore, when the beam is positively charged, a gas that is unlikely to become positive ions is selected as a barrier gas, and when these beams are negatively charged, a gas that is unlikely to become negative ions is selected as a barrier gas. The mass spectrometer is a quadrupole mass spectrometer.
[0015]
The effective mean free path of electrons and ions will be described. In a region where argon (Ar) gas is at a pressure of 1 × 10 ⁻² torr (10 mtorr) at room temperature, the mean free path of Ar gas itself is 8 mm. On the other hand, the mean free path of electrons in Ar gas at the same pressure is 11 mm when the kinetic energy is 15 eV, about 50 mm when 100 eV, and about 200 mm when 1000 eV.
[0016]
In the case of charged particles as compared with neutral gases, the interaction due to the Coulomb force becomes stronger. On the other hand, the higher the kinetic energy, the faster the passing speed and the shorter the time for acting with the gas. Therefore, in the case of charged particles, the mean free path can be lengthened by accelerating.
[0017]
However, in the case of ions, since the diameter is larger than the electron, the probability of collision increases, and the effect of losing the charge due to the charge exchange with the gas appears, so that the mean free path becomes longer as the electron. I can't. The average free path of Ar ions in Ar gas at the same pressure of 1 × 10 ⁻² torr is about 8 mm when the kinetic energy is −400 eV, which is the same as that of the gases.
[0018]
However, it is known that the effect of this charge exchange decreases when the types of gas and ion are different. For example, for N ₂ ions in NO gas under almost the same conditions, the mean free path is about 40 mm, and for Na ions in Ar gas, the length is as long as 28 mm even at 50 eV.
[0019]
In particular, when the ionization potential of the gas is higher than that of the ions, it is easily assumed that charge exchange hardly occurs. This is because such charge exchange increases the overall energy. In general, many adhesive gases and corrosive gases have a low ionization potential and are easily ionized. Therefore, if a gas that is difficult to ionize is used as the barrier gas, the mean free path can be lengthened with respect to the charge exchange effect.
[0020]
Further, in the case of ions having a large kinetic energy, it is considered that the traveling direction hardly changes even if they collide with a gas. This is because the kinetic energy of the gas is only about 0.04 eV, so there is a difference of 4 orders of magnitude in kinetic energy from the ions accelerated to 400 eV. Therefore, the length of the ion that travels without changing greatly from the accelerated direction, that is, the effective mean free path (effective mean free path) is orders of magnitude larger than the normally defined mean free path.
[0021]
From the above, it has been estimated that the effective mean free path of electrons and ions can be made many times larger than the mean free path of gases by selecting a barrier gas that is difficult to ionize and appropriately accelerating electrons and ions.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
The present invention ionizes a gas to be analyzed introduced into an ionization region of about 10 ⁻³ torr equivalent to the atmosphere in a process chamber or in a reduced pressure state by an excitation beam emitted from an excitation source portion in a low pressure state of 10 ⁻⁵ torr or less . A gas analyzer that performs mass spectrometry by separating and detecting the ion beam generated thereby in accordance with the mass in a low-pressure mass analyzer of 10 ⁻⁵ torr or less ,
A first barrier region into which the barrier gas is introduced, a first differential pressure region to which a suction side of a vacuum pump is connected, and the mass spectrometer are sequentially connected in series to the ionization region, and a barrier gas is introduced into the ionization region. A second barrier region, a second differential pressure region to which the suction side of the vacuum pump is connected, and the excitation source unit sequentially connected in series;
Both of the first barrier region and the second barrier region are (1) the length of the excitation beam and the ion beam that are longer than the length of the barrier region that is the length that the excitation beam passes and the length that the ion beam passes. The effective mean free path in the barrier area is large,
(2) The mean free path in the barrier region of the gas to be analyzed is smaller than the thickness of the barrier region,
(3) The Knudsen number in the barrier region of the gas to be analyzed is 1 or less,
(4) The pressure in the barrier region is higher than the pressure in the ionization region, and the barrier gas flows from the barrier region to the ionization region.
By satisfying the conditions, an excitation beam and an ion beam can pass through each barrier region, but a gas to be analyzed cannot pass through each barrier region.
[0023]
In the above, when the ion beam and the excitation beam are charged beams, a focusing lens is provided for at least one including the excitation beam, and these beams are converged so that the area of the barrier region passing therethrough becomes small. It is the gas analyzer which was made to do.
[0024]
Further, when the ion beam and the excitation beam are charged beams, the motion of these beams is reduced so that the transit time of the barrier region passing through the acceleration mechanism is reduced for at least one including the excitation beam. When the energy is increased and the beam is positively charged, a gas that does not easily become positive ions is selected as a barrier gas, and when these beams are negatively charged, a gas that is unlikely to become negative ions is selected as a barrier gas. This is a gas analyzer.
[0025]
[Example 1]
An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an overall view, and FIG. 2 is an enlarged and detailed view of the vicinity of a connecting portion between a mass analyzing unit and an ionizing unit. Although an enlarged and detailed view of the vicinity of the connection portion between the electron generating portion and the mass analyzing portion, which is an excitation source portion, is omitted, the basics are the same as FIG.
[0026]
That is, one side of the ionization unit 3 is connected to the process chamber 1 via the orifice 2, the focusing lens 4 is installed on the ionization unit 3, and the barrier region 6 is connected to the other side of the ionization unit 3 via the orifice 5. The differential pressure region 8 is connected to the barrier region 6 via the orifice 7, and the mass spectrometer 10 is connected to the differential pressure region 8 via the orifice 9.
[0027]
A barrier region 14, a differential pressure region 15, and an electron generator 16 are sequentially connected in series to the ionization unit 3 through orifices 11, 12, and 13. The ionization unit 3, the differential pressure regions 8, 1 5 , the electron generation unit 16, and the mass analysis unit 10 are connected to the suction sides of the vacuum pumps 17, 18, and 19, respectively.
[0028]
The barrier regions 6 and 14 are introduced with Ar and maintained at a pressure of 1 × 10 ⁻¹ torr. Ar flows from the barrier regions 6 and 14 through the orifices 5 and 11 to the ionization unit 3 having a pressure of 1 × 10 ⁻³ torr. Both the thickness of the barrier regions 6 and 14 and the diameter of the orifices 5 and 11 are about 2 mm. In the barrier regions 6 and 14, the mean free path of gas is about 0.8 mm and the Knudsen number is about 0.4. Therefore, the gas can hardly pass through the barrier regions 6 and 14. That is, the adherent / corrosive gas to be analyzed present in the ionization unit 3 hardly enters the electron generation unit 16 or the mass analysis unit 10.
[0029]
However, electrons and ions having a large effective mean free path can pass through the barrier regions 6 and 14. That is, the electron beam emitted from the electron generator 16 and the ion beam emitted from the ionizer 3 (ionized analyte gas) can pass through the barrier regions 6 and 14 and perform their original functions.
[0030]
The electron beam and the ion beam are converged by the converging lenses 4 and 20 so as to have a minimum diameter in the barrier regions 6 and 14. Thereby, the opening diameters of the orifices 5 and 11 through which these beams pass are reduced, the outflow amount of the barrier gas is reduced, and the load on the vacuum pumps 17, 18 and 19 is reduced.
[0031]
Ar gas also flows out from the orifices 7, 9, 12, and 13 into the electron generation unit 16 and the mass analysis unit 10 on the opposite side, but this is differentially evacuated in the differential pressure regions 8 and 15. For this reason, the pressure of the electron generation part 16 and the mass spectrometry part 10 is 10 < ^-5 > torr, The main component is Ar. Incidentally, the pressure of the mass analyzing unit and the electron generating unit in the conventional example is also 10 ⁻⁵ torr, but this main component is an adherent / corrosive gas to be analyzed and is decisively different. Other operations are the same as in the conventional example. In addition, 30 is an ionization area | region, Comprising: Analytical gas is ionized by an electron beam. An ion beam is generated from this ionization region. In FIG. 2, 25 and 26 are exhaust pipes, and 27 is a barrier gas feed pipe.
[0032]
[Example 2]
Another embodiment of the present invention will be described with reference to FIG. Only an enlarged and detailed view of the vicinity of the connecting portion between the mass spectrometric section and the ionizing section corresponding to FIG. 2 is shown. Although an enlarged and detailed view of the vicinity of the connecting portion between the electron generating unit and the mass analyzing unit is omitted, the basics are the same as in FIG. In this embodiment, an electron generator (second electron generator 24) is added to the first embodiment. Other configurations and operations are the same as those in the first embodiment.
[0033]
In the embodiment shown in FIG. 3, the second ionization region 21 is connected to the differential pressure region 8 of the first embodiment via an orifice 9, and the mass analyzer 10 is connected to the second ionization region via orifices 22 and 23. The second electron generator 24 is connected, and other devices are the same as those in the first embodiment. In FIG. 3, 25 and 26 are exhaust pipes connected to the vacuum pumps 17 and 18, respectively, 27 is a barrier gas feed pipe, and 28 is a quadrupole mass spectrometer.
[0034]
In the above, the ion beam that has passed through the orifice 9 includes the analyte gas that has been neutralized due to charge exchange when it has passed through the barrier region 6. Cannot be separated or detected. Therefore, in Example 2, the gas to be analyzed that has become neutral is ionized again by the second electron generator 24. The analyte gas ionized in the second ionization region 21 is subjected to mass analysis by a quadrupole mass spectrometer 28. The configuration and operation of the second electron generator 24, the second ionization region 21, and the quadrupole mass spectrometer 28 are the same as in the conventional example of FIG. Thereby, sensitivity can be improved.
[0035]
In addition, the optimum amount of introduced barrier gas can be set by using the second electron generation unit 24. That is, only the second electron generating unit 24 is operated without operating the electron generating unit 16, and the pressure in the barrier region 6 is decreased by gradually reducing the amount of introduced barrier gas. At this time, the gas to be analyzed begins to enter from a certain introduction amount, and the gas to be analyzed is detected. Therefore, a value slightly higher than this value is the optimum barrier gas introduction amount that prevents the gas to be analyzed and allows ions to easily pass through.
[0036]
[Example 3]
Another embodiment of the present invention will be described with reference to FIG. Only an enlarged and detailed view of the vicinity of the connecting portion between the mass spectrometric section and the ionizing section corresponding to FIG. 2 is shown. Although an enlarged and detailed view of the vicinity of the connecting portion between the electron generating unit and the mass analyzing unit 1 is omitted, the basics are the same as in FIG. That is, a barrier gas flow path is added to Example 1, and the barrier region is localized in the vicinity of the ionization portion outlet. Also, the differential pressure region and the differential pressure vacuum pump are excluded. The acceleration electrode increases the kinetic energy of the ion beam and reduces the opening angle. Furthermore, the converging lens is embodied as an electromagnetic type. Other configurations and operations are the same as those in the first embodiment.
[0037]
The input of the acceleration electrode 29 passes through the shielding gas introduction system 31 and is connected to the power source 32. One end face of the barrier gas flow path 33 is connected to the tip of the barrier gas supply pipe 27, and the other end of the barrier gas flow path 33 enters the barrier region 38. Further, the barrier gas flow path 33 is communicated with the mass spectrometer 10 via the tube 35.
[0038]
The barrier gas flow path 33 is composed of a plurality of axially symmetric or annular flow paths, and has a structure in which the barrier gas concentrates in the vicinity of the ionization portion outlet. Therefore, the barrier region 38 is localized at the outlet of the ionization part 3 and serves as a plug that completely seals the outlet of the ionization part 3. Further, here, a strong flow toward the ionization unit 3 is generated. For this reason, invasion of the gas to be analyzed into the mass spectrometer 10 is completely prevented. However, electrons and ions having a large effective mean free path can pass through the barrier region 38.
[0039]
Further, the ease of gas passage, that is, the conductance of the barrier region 38 and the mass analysis unit 10 is considerably smaller than that of the first embodiment. This is because the distance from the barrier region 38 to the mass analyzer 10 is increased, the shape is changed from a simple orifice to the tube 35, and the inner diameter of the tube 35 is made smaller. The differential pressure region 8 and the differential pressure vacuum pump 18 are not required due to the effect of the decrease in conductance and the strong flow toward the ionization unit 3 in the barrier region 38.
[0040]
The ionization region 30 of this embodiment is surrounded by an acceleration electrode 29 to which a positive potential of about 400 V is applied. For this reason, the kinetic energy of an ion beam having a positive charge is 400 eV or more, and the effective mean free path becomes long. As a result, the loss in the barrier region 38 is reduced, and the proportion of the ion beam that passes through is increased. However, if the ion beam passes through the quadrupole mass spectrometer 28 with this high kinetic energy, normal mass analysis cannot be performed. Therefore, a positive potential of about 400 V is set as the base potential of the quadrupole mass spectrometer 28. When applied, the ion beam is decelerated in the quadrupole mass spectrometer. This deceleration / measurement technique is a well-known technique. In the case of an ion beam having a negative charge, a negative potential is applied to the acceleration electrode 29.
[0041]
The exit of the acceleration electrode 29 is narrowed down, and the extraction electrode is installed just outside. For this reason, the ion beam is efficiently extracted from the ionization region 30, and the opening angle of the ion beam is reduced. Therefore, although the inner diameter of the tube is small, the amount of passing ion beam does not decrease so much. A shield gas is passed through the wiring portion of the acceleration electrode 29 to prevent deterioration due to the gas to be analyzed.
[0042]
The electromagnetic converging lens is composed only of a coil using a covered wire and a magnetic pole. Therefore, unlike the electrostatic type that requires high-voltage electrodes and insulating stones, there is little deterioration due to the gas to be analyzed.
[0043]
[Example 4]
Another embodiment of the present invention will be described with reference to FIG. Only an enlarged and detailed view of the vicinity of the connecting portion between the mass analyzing unit 10 and the ionizing unit corresponding to FIG. 2 is shown. Although an enlarged and detailed view of the vicinity of the connecting portion between the electron generating unit and the mass analyzing unit is omitted, the basics are the same as in FIG. In contrast to Example 3, the converging lens is an electrostatic type, and a barrier gas flow path 37 is incorporated therein. Moreover, the whole ionization part 3 becomes elongate, and the connection port of the exhaust pipe 25 is attached to the left end. The distance between the ionization region 39 and the pipe is about 40 mm, and the effective inner diameter is about 5 mm. In addition, the barrier gas spreads over almost the entire ionization portion, and is approximately 1 × 10 ⁻² torr.
[0044]
Reference numeral 43 denotes an analysis gas feed pipe, which is attached to the right side of the ionization region 39. The pressure contribution in the ionization region of the gas to be analyzed is about 1 × 10 ⁻³ torr, which is 1 as compared with the barrier gas.
[0045]
In addition, although the installation presence or absence of an acceleration electrode is arbitrary, it is removed in FIG. Other configurations and operations are the same as those in the third embodiment. That is, the mass analyzer 10 in which the quadrupole mass spectrometer 28 is installed and the ionization unit 3 are connected by a tube 40, and a barrier gas channel 37 is connected to the outside of the ionization unit 3 through a converging lens 42. is set up. An ionization region 39 is connected to the tip of the ionization unit 3, and the exhaust pipe 25 of the vacuum pump 17 is connected to the ionization region 39. In FIG. 5, reference numeral 41 denotes an insulating stone.
[0046]
The situation inside the ionization unit will be described in detail. The barrier gas channel 37 is located in a region near the mass analyzer 10, and the ionization region 39 is near the connection port of the vacuum pump 17. For this reason, the pressure in the ionization region 39 is slightly lower than the “most region near the mass analysis unit 10 (rightward)” in the ionization unit. In addition, the barrier gas flows from the “most region near the mass analysis unit 10 (rightward)” to the ionization region 39. Therefore, in this embodiment, “a large area near the mass analyzer 10 (rightward)” can be regarded as the barrier area 38. The mean free path of gas in the barrier region 38 is 8 mm, and the Knudsen coefficient is 0.2. Further, since the effective inner diameter of the ionization unit 3 is as short as a quarter of the distance in the longitudinal direction and the barrier gas flow path 37 is axisymmetric, the flow of the barrier gas in the barrier region 38 becomes substantially uniform. Therefore, the gas to be analyzed moves only from the inlet to the ionization region 39 side (left side) according to the flow of the barrier gas, and does not diffuse to the mass analyzer 10 side (right side). That is, the gas to be analyzed does not enter the mass spectrometer 10. However, electrons and ions having a large effective mean free path can pass through the barrier region 38.
[0047]
Further, the converging lens 42 is not exposed to the gas to be analyzed. For this reason, the insulating stone 41 is not deteriorated, and the convergent lens 42 can be an electrostatic type that is simple in structure and inexpensive. Further, since the pressure difference with the mass analyzer 10 is as small as two digits, a differential pressure region is not required, and the connection port tube 40 does not need to be as elongated as in the third embodiment.
[0048]
The present invention is not limited to the first, second, third, and fourth embodiments, and can be modified as follows. As an excitation source for ionization of the gas to be analyzed, heating or discharge using ions, light (ultraviolet light, laser, etc.) or plasma can be used in addition to electrons. Some types of excitation sources are not degraded by the gas to be analyzed, but in that case, no barrier region is provided. On the other hand, in the case of an excitation source that is very easily deteriorated, a barrier region can be provided only in the excitation source.
[0049]
In order to increase the energy of the ion beam, a mechanism for lowering the potential between the ionization region and the mass analyzer can be used in addition to the mechanism for raising the potential of the ionization region by the acceleration electrode.
[0050]
As a mass spectrometry method, a magnetic field type can be used in addition to the quadrupole type. As the barrier gas, various gases such as He · N ₂ or SF ₆ can be used in addition to Ar. Introducing the gas to be analyzed into the ionization part is a method of introducing a molecular beam by combining a very small diameter orifice and a large exhaust vacuum pipe in addition to the gas flow through the orifice or pipe, or pressure. A method in which no partition wall is provided between a sufficiently low process chamber and an ionization part can be used.
[0051]
Further, the gas to be analyzed can be applied to any pressure in any place other than the process chamber of 10 to 10 ⁻¹ torr. That is, it can be used not only for a vacuum apparatus but also for analysis of a gas to be analyzed in an atmospheric pressure state such as a direct analysis of an atmospheric environment or a connection with a gas chromatography apparatus. However, in any case, the pressure in the ionization region is lower than the pressure in the barrier region, and the barrier gas needs to flow from the mass analyzer or the excitation source side to the ionization region side.
[0052]
【The invention's effect】
According to the present invention, the adhering gas and the corrosive gas can be prevented from entering the excitation source unit and the mass analyzing unit, so that the in-process can be performed without damaging the mass analyzing unit and the electron generating unit. The gas can be easily analyzed.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of an embodiment of the present invention.
2 is an enlarged conceptual view of the ionization unit, barrier region, differential pressure region, and mass analysis unit of FIG.
FIG. 3 is an enlarged conceptual diagram of an ionization unit, a barrier region, a differential pressure region, and a mass analysis unit of another embodiment.
FIG. 4 is an enlarged conceptual diagram of an ionization unit, an ionization region, a barrier gas channel, and a mass analysis unit of another embodiment.
FIG. 5 is an enlarged conceptual diagram of an ionization unit, a barrier region, a converging lens, and a mass analysis unit of another embodiment.
FIG. 6 is a conceptual diagram of a conventional mass spectrometer.
[Explanation of symbols]
1 Process chamber 2, 5, 7, 9, 11, 12, 13 Orifice 3 Ionization unit 4, 20, 42 Converging lens 6, 14, 38 Barrier region 8, 15 Differential pressure region 10 Mass analysis unit 16 Electron generation unit 17, 18, 19 Vacuum pump 21 Second ionization region 22, 23 Orifice 24 Second electron generator 25, 26 Exhaust pipe 27 Barrier gas feed pipe 28 Quadrupole mass spectrometer 29 Accelerating electrode 30, 39 Ionization region 31 Shielding gas Gas introduction system 32 Power source 33, 37 Barrier gas flow path 34 Orifice 35, 40 Tube 41 Insulating stone

Claims (5)

The gas to be analyzed introduced into the ionization region of about 10 ⁻³ torr equivalent to the atmosphere in the process chamber or in a reduced pressure state is ionized by an excitation beam emitted from an excitation source portion in a low pressure state of 10 ⁻⁵ torr or less. A gas analyzer that performs mass spectrometry by separating and detecting the generated ion beam according to mass in a low-pressure mass analyzer of 10 ⁻⁵ torr or less ,
A first barrier region into which the barrier gas is introduced, a first differential pressure region to which a suction side of a vacuum pump is connected, and the mass spectrometer are sequentially connected in series to the ionization region, and a barrier gas is introduced into the ionization region. A second barrier region, a second differential pressure region to which the suction side of the vacuum pump is connected, and the excitation source unit sequentially connected in series;
Both of the first barrier region and the second barrier region are (1) the length of the excitation beam and the ion beam that are longer than the length of the barrier region that is the length that the excitation beam passes and the length that the ion beam passes. The effective mean free path in the barrier area is large,
(2) The mean free path in the barrier region of the gas to be analyzed is smaller than the thickness of the barrier region,
(3) The Knudsen number in the barrier region of the gas to be analyzed is 1 or less,
(4) The pressure in the barrier region is higher than the pressure in the ionization region, and the barrier gas flows from the barrier region to the ionization region.
By satisfying the conditions, an excitation beam and an ion beam can pass through each barrier region, but a gas to be analyzed cannot pass through each barrier region.   When the ion beam and the excitation beam are charged beams, a converging lens for converging these beams is provided so that the area of the barrier region that passes through the at least one including the excitation beam is reduced. The gas analyzer according to claim 1.   When the ion beam and the excitation beam are charged beams, the kinetic energy of these beams is reduced so that the transit time of the barrier region passing through the acceleration mechanism is reduced for at least one including the excitation beam. The gas analyzer according to claim 1, wherein the gas analyzer is increased.   When the beam has a positive charge, a gas that does not easily become positive ions is selected as a barrier gas. When these beams have a negative charge, a gas that does not easily become negative ions is selected as a barrier gas. The gas analyzer according to any one of claims 1, 2, and 3.   The gas analyzer according to claim 1, wherein the mass analyzer is a quadrupole mass spectrometer.

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