JP2005114388A - Method of measuring moisture amount in gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure a very small moisture amount, for example, of 1wt.ppm or lower, in a gas of a compound containing fluorine and carbon, for example, C5F8 gas for production of a semiconductor, to guarantee specifications as to the moisture amount. <P>SOLUTION: A lithium ion is attached to the sample gas, for example, C5F8 gas, to ionize the sample gas. C5F8 gas is a neutral molecule but since it is polarized to some extent, the lithium ion attaches to it. Lithium ion is also attached to moisture contained in the sample gas. The C5F8 will not dissociate, because cohesive energy of the lithium ion is low, and fluorine ions "19" near to mass 18 of water are thus not generated. The very trace amount of moisture in the sample gas is thereby measured accurately, by mass-analyzing the sample gas irradiated with the lithium ions. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for measuring a moisture content in a fluorine-containing compound gas, for example, a raw material gas for semiconductor production.

  As a technique for achieving high integration of semiconductor devices, there is a technique of multilayering wiring. In order to take a multilayer wiring structure, an nth wiring layer and an (n + 1) th wiring layer are connected to a conductive layer. In addition, a thin film called an interlayer insulating film is formed in the region other than the conductive layer. A typical example of the interlayer insulating film is a SiO2 film. In recent years, it has been required to lower the relative dielectric constant of the interlayer insulating film in order to further increase the operation speed of the device.

  Due to such a demand, a fluorine-added carbon film (fluorocarbon film) which is a compound of carbon (C) and fluorine (F) has attracted attention. Whereas the relative dielectric constant of the SiO2 film is around 4, the fluorine-added carbon film is a very effective film as an interlayer insulating film because the relative dielectric constant becomes 2 or less if the type of source gas is selected. . Various gases are known as source gases for the fluorine-added carbon film. For example, C5F8 (perfluorocyclopentene) gas is an excellent source gas in that a film composed of a network structure can be formed.

  By the way, when such raw material gas contains moisture, hydrogen is taken into the fluorine-added carbon film, and this hydrogen is combined with fluorine to generate hydrogen fluoride. When heated as described above, hydrogen fluoride escapes from the film, resulting in a decrease in the weight of the fluorine-added carbon film, and the function as an interlayer insulating film is impaired. In other words, when moisture is contained in the source gas, there is a problem that the fluorine-added carbon film lacks thermal stability. The C5F8 gas is manufactured with a purity of 99.99% as an etching gas. If this etching grade C5F8 gas is used, the amount of water is not more than 10 ppm by weight and is extremely small.

  However, when a fluorine-added carbon film is formed using C5F8 gas having a low water content, the hydrogen content in the film becomes a value of several percent (atomic%). This is presumably because hydrogen is selectively bonded to fluorine dangling bonds. Therefore, when C5F8 gas is used as a raw material gas for the fluorine-added carbon film, the amount of water in the raw material gas is desirably 1 ppm by weight or less, and more desirably 100 ppm by weight or less.

  FIG. 8 shows the result of examining the weight reduction by heating a 500 nm fluorine-added carbon film on a bare silicon wafer by performing plasma treatment using C5F8 gas. The dotted line (1) shows the case where an etching great C5F8 gas having a moisture content of 10 ppm by weight or less is used, and the solid line (2) shows the above-described moisture removal treatment performed on the etching grade C5F8 gas. This is the case of using a different gas. From this result, it can be understood that when the fluorine-added carbon film is heated to a temperature between about 350 ° C. and about 420 ° C., a slight difference in the moisture content of the source gas greatly affects the weight reduction of the thin film. Therefore, when the process of heating to such a temperature is included in the manufacturing process of the semiconductor device after forming the fluorine-added carbon film, it is important to reduce the amount of water in the source gas as much as possible.

  On the other hand, since the boiling point of water is 100 ° C. and the boiling point of C 5 F 8 is 27 ° C., most of the water can be removed by distilling a liquefied C 5 F 8 having a purity of 99.99%. The moisture content in the raw material gas can be suppressed to a very small value, for example, 100 weight ppb or less by performing a plurality of stages of moisture removal processes using the molecular sieve.

  By the way, when using the raw material gas that has been subjected to the above water removal treatment as a gas for semiconductor production, it is natural to guarantee its specifications, that is, to guarantee that the water content is, for example, 1 ppm by weight or less. For this purpose, the moisture in the raw material gas must be quantified. Karl Fischer method and mass spectrometry (Non-patent Document 1) are known as methods for quantifying a very small amount of water. The Karl Fischer method is a method of measuring moisture using a Karl Fischer reagent (a reagent comprising a solvent such as iodine, sulfur dioxide, base and alcohol) that selectively and quantitatively reacts with water. Mass spectrometry is a method in which, for example, thermoelectrons collide with gas phase molecules to ionize the molecules, and measure a mass spectrum arranged in order of mass / charge number with a magnetic field type or quadrupole type device. The water content can be measured from the peak intensity corresponding to the water content.

"Instrumental analysis" (Tatsukabo Publishing), pages 214-217

  Since the Karl Fischer method has a detection limit of about 5 ppm by weight, it cannot be applied to guarantee that the amount of water in the raw material gas is 1 ppm by weight or less. On the other hand, mass spectrometry can detect up to 1 ppm by weight of water, and particularly 10 wt ppb of water can be detected according to the method of measurement in an atmospheric pressure atmosphere. However, in mass spectrometry, molecules are dissociated when gas molecules are ionized, so that when the gas is a compound of carbon and fluorine, fluorine ions are generated. Since the mass of fluorine is “19” and the mass of water molecule (H 2 O) is “18”, these masses are the most different, so their mass spectra overlap, and the moisture content is accurate. Cannot be measured.

  Thus, when the moisture in the sample gas containing fluorine was 5 ppm by weight or less, the amount of moisture could not be measured. For this reason, for example, a raw material gas for semiconductor production containing carbon and fluorine cannot be measured for a moisture content of 5 ppm by weight or less, for example, a moisture content of 1 ppm by weight or less, and the specifications regarding the moisture content in the gas are guaranteed. There was a problem that could not be done.

  The present invention has been made based on such a background, and an object thereof is to provide a method capable of measuring a trace amount of water in a gas of a compound containing fluorine.

The present invention relates to a method for measuring a moisture content in a gas of a compound containing fluorine,
A sample gas of a compound containing fluorine, and a step of ionizing the sample gas by attaching a positively charged metal ion to a sample gas containing a trace amount of moisture;
A method for measuring the amount of moisture in the gas, comprising: performing mass spectrometry of the ionized sample gas and measuring the amount of moisture.

The sample gas is, for example, a gas for manufacturing a semiconductor, and the moisture content is measured in order to guarantee specifications relating to the moisture content in the gas. The gas for manufacturing a semiconductor is, for example, a gas for manufacturing a fluorine-added carbon film constituting a semiconductor device. Since the measurement limit of moisture by the Karl Fischer method is about 5 ppm by weight, the present invention This is particularly effective when the water content is 5 ppm by weight or less. The positively charged metal ions adhering to the sample gas (or source gas) are, for example, lithium ions. The compound containing fluorine is, for example, a compound of carbon and fluorine, and examples of the compound of carbon and fluorine include C5F8.

  According to the present invention, positively charged metal ions are attached to a sample gas of a compound containing fluorine to perform ionization and mass spectrometry. Therefore, it is not necessary to dissociate compound molecules of the gas, and fluorine ions are not generated. Accordingly, since there is no fluorine ion having a molecular weight “19” close to the molecular weight “18” of water (H 2 O), it is possible to perform accurate mass analysis on the moisture, and as a result, the moisture contained in a trace amount in the sample gas can be obtained. Accurate quantification is possible. For this reason, for example, it becomes possible to guarantee the specifications regarding the moisture content of the raw material gas for semiconductor manufacturing, and it is possible to supply the semiconductor manufacturing raw material gas with a very small moisture content to the semiconductor manufacturing equipment manufacturer.

  Next, embodiments of the present invention will be described with reference to the drawings. First, FIG. 1 shows a configuration diagram of a mass spectrometer 1 applied to an embodiment of a moisture content measuring method of the present invention. The mass spectrometer 1 includes an ionization chamber 2, a differential exhaust chamber 3, and a measurement chamber 4. The ionization chamber 2 includes an ion radiation chamber 22 partitioned by a partition wall 21 on the rear side (left side in FIG. 1), and an ion attachment region 23 located on the front side (right side in FIG. 1) of the partition wall 21. Yes.

In the ion radiation chamber 22, there is provided an emitter 24 for depositing ions formed by applying a spherical metal oxide in a thin film form to a linear filament. As the metal oxide, lithium oxide (LiO2) is provided. A sintered body made of aluminum oxide (Al2O3) and silicon dioxide (SiO2) is used. The emitter 24 is for discharging positively charged metal ions such as Li ⁺ from the ion passage opening 25 of the partition wall 21 to the ion adhesion region 23 by heating. Although not shown, the emitter 24 is used to heat the emitter 24. A power supply for power supply (not shown) is connected.

A nitrogen (N 2) gas introduction pipe 26 is connected to the ion radiation chamber 22, and nitrogen gas is blown out from the ion passage port 25 of the partition wall 21. This is to prevent the sample gas described later from entering the ion emission chamber 22 and coming into contact with the emitter 24. If the sample gas is corrosive or depositable, the surface of the emitter 24 that is at high temperature may react with the sample gas to reduce the amount of metal ions generated, and metal ions (for example, Li ⁺ ) may be N 2. It is discharged from the ion passage port 25 by the gas flow.

  The ionization chamber 2 is connected to a sample gas introduction tube 11 for introducing a sample gas into the ion adhesion region 23, and a mixing chamber 12 is provided on the base end side of the sample gas introduction tube 11. . A first gas supply pipe 13 and a second gas supply pipe 14 are connected to the mixing chamber 12, and a C5F8 gas is supplied from a C5F8 gas supply source 15 as a sample gas supply source through the first gas supply pipe 13. The argon gas is supplied into the mixing chamber 12 from the argon (Ar) gas supply source 16 through the second gas supply pipe 14. MFC1 and MFC2 are mass flow controllers that are flow rate adjusting units, and V1 and V2 are valves.

  The reason why the argon gas is introduced into the mass spectrometer 1 together with the sample gas is to dilute the sample gas, but the diluent gas is not limited to the argon gas, and other inert gas that does not affect the determination of the sample gas. It may be.

  The differential exhaust chamber 3 is divided into a first chamber 32 and a second chamber 33 by a partition wall 31, and the first chamber 32 communicates with the ionization chamber 2 through the aperture 27 and is in the second chamber 33. Are provided with three ring-shaped focusing lenses 34. The measurement chamber 4 communicates with the second chamber 33 via a partition wall 41. The measurement chamber 4 includes a Q pole type (quadrupole type) mass analysis mechanism 42 that performs mass analysis of the sample gas, and a Q chamber. A detector 43 including an electron multiplier for detecting ions of m (mass) / z (number of charges) selected by the pole-type mass spectrometry mechanism 42 is provided.

  In addition, turbo molecular pumps TP1 and TP2 are connected to the first chamber 32 and the second chamber 33 of the differential exhaust chamber 3 via exhaust passages 35 and 36, respectively, and to the measurement chamber 4 via an exhaust passage 44. A turbo molecular pump TP3, which is an evacuation means, is connected to each other so that a predetermined pressure state can be created. DP1 to DP3 are dry pumps.

Regarding the pressure in each chamber during the mass spectrometric determination, the ionization chamber 2 is evacuated by the turbo molecular pump TP1 through the aperture 23 and maintained at 100 Pa, and the first chamber 32 and the first chamber 32 of the differential exhaust chamber 3 are maintained. The two chambers 33 are maintained at 0.1 Pa and 10 ⁻³ Pa, respectively, and in the measurement chamber 4 are maintained at 10 ⁻⁵ Pa. This is because a low pressure of about 10 ⁻⁵ is necessary for the Q pole type mass spectrometry mechanism 21 to operate normally. In order to obtain this pressure, an independent evacuation means is provided, The pressure is gradually reduced toward the front.

  Next, a method for measuring the moisture content in the C5F8 gas, which is the sample gas, using the mass spectrometer 1 will be described. In this example, the C5F8 gas is a raw material gas for manufacturing a semiconductor, for example, a raw material gas for forming an interlayer insulating film made of a fluorine-added carbon film (hereinafter referred to as a CF film), and has an purity of 99.99%. Water removal treatment was performed on grade C5F8 gas. For example, most of the water is removed by distilling the liquid obtained by liquefying the C5F8 gas, and the water is adsorbed and removed by applying C5F8 to a molecular sieve. The amount of water is suppressed to a very small value, for example, 100 weight ppb or less. The C5F8 gas, which is predicted to have a moisture content of 100 weight ppb or less, is measured in the following manner to assure specifications regarding the moisture content of the gas.

Accordingly, in this example, the C5F8 gas supply source 15 is a container filled with a gas sample to be shipped to a semiconductor manufacturer. The sample gas from the C5F8 gas supply source 15 and the argon gas from the argon gas supply source 16 are used. Are mixed in the mixing chamber 12 at flow rates of, for example, 150 sccm and 300 sccm, respectively, and the sample gas is introduced into the ionization chamber 2 together with the argon gas. The pressure of the sample gas in the ionization chamber 2 is 100 Pa, and the emitter 24 is heated to about 600 ° C. to 1000 ° C., for example, and Li ⁺ is released. Although C5F8 and H2O are neutral molecules, since they are polarized to some extent, Li ⁺ adheres to the C5F8 molecules and H2O molecules, which are sample gases, in the ionization chamber 2 as shown in FIG. And H2O molecules are charged positively and ionized for each molecule.

The sample gas molecules attached with Li ⁺ are in an unstable state with surplus energy immediately after the attachment, but when the pressure in the ionization chamber 2 is 100 Pa, the mean free path of the gas molecules is 0. It is about 07 mm and collides with gas molecules 10 ⁷ times per second. Therefore, the surplus energy is immediately taken away by a large number of gas molecules that collide, and the sample gas molecules with stable Li ⁺ are obtained.

  For example, a voltage of +20 V is applied to the emitter 24, and a voltage of +10 V is applied to the partition wall 21, for example. Further, the front and rear lenses of the focusing lens 34 are held at 0 V, and a voltage of +10 V, for example, is applied to the central lens. The center potential of the Q-pole mass spectrometer 21 is 0V.

Li ⁺ with C5F8 gas molecules and Li ⁺ with H2O molecule is drawn in an electric field formed by the left end of the lens of the partition wall 21 and the focusing lens 34, to the right in FIG. 1, it passes through the aperture 27 from the ionization chamber 2 Then, it is drawn out to the differential exhaust chamber 3. Li ⁺ -attached C 5 F 8 gas molecules and Li ⁺ -attached H 2 O molecules that have entered the region surrounded by the focusing lens 34 are focused by the positive potential of the central lens and then transported into the measurement chamber 4 to be Q-pole type mass analysis mechanism 42. And the amount of each ion is measured by the electron multiplier 43.

In the mass spectrum thus obtained, as shown in FIG. 3, a portion of “219” in which 7 amu (atomic mass unit), which is the mass of Li ^+, is added to the molecular weight of C ₅ F ₈ , and the H ₂ O molecular weight. A peak of relative sensitivity appears at the portion of “25” where 7 amu is added. In addition, a peak is also observed in the molecular weight “43” portion, which is a Li ⁺ adhering to a water dimer. The amount of water in the C5F8 gas can be quantified by, for example, preparing a calibration curve for the relative value of the peak intensity of the molecular weight “25”, but creating a calibration curve for the peak portion of the molecular weight “43”. You may make it quantify.

According to the above-described embodiment, Li ⁺ is attached to the sample gas molecules to ionize the molecules, and in this case, since the adhesion energy of Li ⁺ is small, the molecules are ionized without being broken. Since a fluorine ion having a molecular weight of 19 close to the molecular weight of 18 is not formed, a peak of a water molecule appears in the mass spectrum without being disturbed by the peak of the fluorine ion. Can be measured. As a result, for C5F8 gas, for example, it is possible to guarantee the specification that the moisture content is 1 ppm by weight or less, and the semiconductor manufacturing apparatus manufacturer can purchase and use this gas from, for example, the gas manufacturer. By using C5F8 gas with a very low moisture content, an insulating film with excellent thermal stability, such as an interlayer insulating film, can be formed. This ultimately increases the speed of semiconductor devices. can do.

  Here, in the embodiment of the present invention, the emitter 24 for the ion attachment ionization method is formed by applying a spherical metal oxide to a linear filament in the form of a thin film. Various shapes and structures, such as those using plates, can be used.

In addition, as the metal ions to be attached, Li ⁺ is applied in the example because it has the highest affinity among the current metal ions, that is, the sensitivity is high, but as the alkali metal ions, K ⁺ , Na ⁺ , Rb ⁺ , Cs ⁺ , and other metal ions such as Al ⁺ , Ga ⁺ , and In ⁺ can also be used.

  As the mass analysis mechanism, the Q-pole type mass analysis mechanism has been described, but other external ion trap type mass analysis mechanism, magnetic sector type mass analysis mechanism, and TOF (time-of-flight) type mass analysis mechanism should be used. Can do.

  Further, all the samples to be measured have been described as gaseous, but the sample itself may be solid or liquid. Any solid or liquid sample may be used as long as it is gasified by some means and the gas is analyzed as a sample gas. Further, the gas of the compound of carbon and fluorine is not limited to C5F8 gas, but may be C4F8 gas, C2F2 gas, C (CF3) 4 gas, or the like. Furthermore, in the present invention, the gas is not limited to a compound gas of carbon and fluorine, but may be another gas containing fluorine, such as NF3.

  Here, in order to create a calibration curve for the moisture content, a predetermined amount of moisture is contained in a nitrogen gas that does not substantially contain moisture to obtain a sample gas, and the mass spectrum is obtained through the above-described mass spectrometer, and the molecular weight “ The relative sensitivity of the peak corresponding to “25” was determined. When the moisture content was set to 5 types of 60 ppb, 80 ppb, 100 ppb, 1000 ppb, and 3000 ppb, and the relative sensitivity of the peak in each sample gas was plotted, the calibration curve shown in FIG. 4 was obtained. The moisture content in the sample gas was set by measuring the amount of moisture mixed with nitrogen gas with a laser moisture meter. Therefore, by using this calibration curve, for example, the amount of water in the C5F8 gas can be determined, and for example, it can be ensured that the amount of water is 5 ppm by weight or less or 1 ppm by weight or less.

  Next, a process for forming an interlayer insulating film using a source gas, for example, C5F8 gas, whose water content is guaranteed as described above will be described. First, the configuration of the plasma film forming apparatus will be briefly described with reference to FIGS. This plasma film forming apparatus is a chemical vapor deposition (CVD) apparatus that generates plasma using a radial line slit antenna. In the figure, 101 is a processing vessel (vacuum chamber), 100 is an insulating material, and 111 is a mounting table. Inside the mounting table 111, temperature control means (not shown) such as a cooling medium flow path and a heater are provided. ing. Further, for example, a high frequency power supply 112 for bias of 13.56 MHz is connected to the mounting table 111.

  A first gas supply unit 102 made of alumina, for example, whose planar shape is formed in a substantially circular shape is provided at the upper portion of the processing container 101 so as to face the mounting table 111. A number of first gas supply holes 121 are formed on the surface of the gas supply unit 102 facing the mounting table 111. The gas supply hole 121 communicates with the first gas supply path 123 through the gas flow path 122. The first gas supply path 123 is connected to a supply source such as argon (Ar) gas or krypton (Kr) gas, which is a plasma gas, or a supply source of hydrogen (H2) gas.

  Further, a second gas supply unit 103 made of a conductor having a substantially circular planar shape is provided between the mounting table 111 and the first gas supply unit 102. A large number of second gas supply holes 131 are formed on the surface facing the mounting table 111. For example, as shown in FIG. 6, a lattice-like gas flow path 132 that communicates with one end side of the gas supply hole 131 is formed in the gas supply section 103. One end side of the gas supply path 133 is connected. The second gas supply unit 103 is formed with a large number of openings 134 so as to penetrate the gas supply unit 103. The opening 134 is for passing plasma or a source gas in the plasma through a space below the gas supply unit 103, and is formed, for example, between adjacent gas flow paths 132.

  Here, the second gas supply unit 103 is connected via a second gas supply path 133 to a supply source 135 of a source gas containing fluorine and carbon as source gases, for example, C5F8 gas. The second gas supply passage 133 sequentially passes through the gas flow passage 132 and is uniformly supplied to the space below the second gas supply portion 103 via the gas supply hole 131. Reference numeral 114 denotes an exhaust pipe, which is connected to a vacuum exhaust means (not shown).

  A cover plate 113 made of a dielectric material such as alumina is provided on the upper side of the second gas supply unit 103, and the upper side of the cover plate 113 is in close contact with the cover plate 113. An antenna unit 104 is provided. As shown in FIG. 7, the antenna portion 104 is provided so as to close a flat antenna main body 141 having a circular planar shape whose lower surface side opens, and an opening on the lower surface side of the antenna main body 141, and includes a plurality of slits. The antenna main body 141 and the planar antenna member 142 are made of a conductor and constitute a flat hollow circular waveguide. Yes.

  Further, a slow phase plate 143 made of a low-loss dielectric material such as alumina, silicon oxide, or silicon nitride is provided between the planar antenna member 142 and the antenna main body 141. The retardation plate 143 is for shortening the wavelength of the microwave to shorten the guide wavelength in the waveguide. In this embodiment, the antenna main body 141, the planar antenna member 142, and the slow phase plate 143 constitute a radial line slit antenna.

  The antenna unit 104 configured as described above is attached to the processing container 101 via a seal member (not shown) so that the planar antenna member 142 is in close contact with the cover plate 113. The antenna unit 104 is connected to an external microwave generation means 145 via a coaxial waveguide 144, and for example, a microwave having a frequency of 2.45 GHz or 8.3 GHz is supplied. At this time, the waveguide 144A outside the coaxial waveguide 144 is connected to the antenna body 141, and the center conductor 144B is connected to the planar antenna member 142 through an opening formed in the slow phase plate 143.

  The planar antenna member 142 is made of, for example, a copper plate having a thickness of about 1 mm, and a plurality of slits 146 for generating, for example, circularly polarized waves are formed as shown in FIG. The slit 146 is formed, for example, concentrically or spirally along the circumferential direction, with a pair of slits 146a, 146b arranged in a substantially T-shape and slightly spaced apart. Since the slits 146a and the slits 146b are arranged so as to be substantially orthogonal to each other in this way, circularly polarized waves including two orthogonal polarization components are radiated. At this time, by arranging the slit pairs 146 a and 146 b at an interval corresponding to the wavelength of the microwave compressed by the retardation plate 143, the microwave is radiated from the planar antenna member 142 as a substantially plane wave.

  Next, an example of a film forming process performed by the above film forming apparatus using the C5F8 gas whose moisture content is measured in the above embodiment will be described. First, a wafer W, which is a substrate on which aluminum wiring is formed, is loaded and placed on the mounting table 111. Subsequently, the inside of the processing vessel 101 is evacuated to a predetermined pressure, and a plasma gas such as Ar gas is supplied to the first gas supply unit 102 via the first gas supply path 123 at a predetermined flow rate such as 300 sccm. A source gas, for example, C5F8 gas is supplied at a predetermined flow rate, for example, 150 sccm, to the second gas supply unit 103, which is a source gas supply unit, via the second gas supply path 133. Then, the inside of the processing vessel 101 is maintained at a process pressure of 13.3 Pa, for example, and the surface temperature of the mounting table 111 is set to 350 ° C.

  On the other hand, when a high frequency (microwave) of 2.45 GHz and 2000 W is supplied from the microwave generation means 145, the microwave propagates in the coaxial waveguide 144 in the TM mode, the TE mode, or the TEM mode, and the antenna unit 104 While reaching the planar antenna member 142 and propagating radially from the central portion of the planar antenna member 142 toward the peripheral region via the central conductor 144B of the coaxial waveguide, microwaves are transmitted from the slit pairs 146a and 146b. The gas is discharged toward the processing space below the gas supply unit 102 via the cover plate 113 and the first gas supply unit 102. At this time, since the slit pairs 146a and 146b are arranged as described above, the circularly polarized wave is uniformly emitted over the plane of the planar antenna member 142, and the electric field density in the space below (the film formation space) becomes uniform. Is done. The microwave energy excites high density and uniform plasma over the entire wide space. This plasma flows into the film formation space below the gas supply unit 103 through the opening 134 of the second gas supply unit 103 and is supplied from the second gas supply unit 103 to the film formation space. The C5F8 gas circulates to the upper side of the second gas supply unit 103 and is activated and then descends. As a result, the C5F8 gas is activated in the film forming space below the second gas supply unit 103. There is a group of active species obtained.

  The active species transported onto the wafer W is formed as a CF film. At this time, Ar ions drawn into the wafer W by the bias voltage for plasma attraction are sputter-etched on the pattern on the surface of the wafer W. The CF film formed at the corners of the film is scraped off, and the CF film is formed from the bottom of the pattern groove while widening the opening, and the CF film is embedded in the recess.

It is a block diagram of the mass spectrometer used for embodiment of this invention. It is a schematic diagram which shows a mode that the lithium ion in embodiment of this invention adheres. It is a figure which shows the mass spectrum obtained in embodiment of this invention. In embodiment of this invention, it is a calibration curve which shows the relationship between the moisture content in source gas, and the relative sensitivity in a mass spectrum. It is a vertical side view which shows an example of the plasma film-forming apparatus which forms a fluorine addition carbon film | membrane using C5F8 gas with which the moisture content was ensured in embodiment of this invention. It is a top view which shows the 2nd gas supply part used for said plasma film-forming apparatus. It is a perspective view which shows the antenna part used for said plasma film-forming apparatus in a partial cross section. It is the graph which compared the relationship between the heating temperature of a fluorine addition carbon film, and the weight reduction of the film | membrane based on the difference in the moisture content in source gas.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mass spectrometer 2 Ionization chamber 3 Differential exhaust chamber 4 Mass analysis chamber 12 Mixing chamber 15 Sample gas supply source 24 Emitter 25 Ion passage port 27 Aperture 34 Focusing lens 42 Q pole type mass analysis mechanism 43 It consists of an electron multiplier Detectors TP1 to TP3 Vacuum pump 101 Processing vessel 102 First gas supply unit 103 Second gas supply unit 104 Antenna unit 111 Mounting table 114 Exhaust pipe 141 Antenna main body 142 Planar antenna member 143 Slow phase plate 144 Coaxial waveguide 146 146a, 146b Slit W Wafer

Claims (7)

In the method for measuring the amount of water in the gas of a compound containing fluorine,
A sample gas of a compound containing fluorine, and a step of ionizing the sample gas by attaching a positively charged metal ion to a sample gas containing a trace amount of moisture;
A method for measuring the amount of moisture in the gas, comprising: performing mass spectrometry of the ionized sample gas and measuring the amount of moisture. The method for measuring the amount of moisture in a gas according to claim 1, wherein the amount of moisture in the sample gas is 5 ppm by weight or less. 3. A method for measuring the amount of moisture in a gas according to claim 1, wherein the sample gas is a gas for manufacturing a semiconductor, and the measurement of the amount of moisture is performed in order to guarantee specifications relating to the amount of moisture in the gas. . 4. The method for measuring a moisture content in a gas according to claim 3, wherein the sample gas is a gas for producing a fluorine-added carbon film constituting the semiconductor device. 5. The method for measuring a moisture content in a gas according to claim 1, wherein the positively charged metal ions are lithium ions. 6. The moisture content measuring method according to claim 1, wherein the fluorine-containing compound is a compound of carbon and fluorine. The method for measuring a moisture content in a gas according to claim 6, wherein the compound of carbon and fluorine is C5F8.

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