JP2011210714A - Plasma potential measuring method, plasma potential measuring device, plasma treating device, recording medium, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma potential measuring method and device for measuring plasma potential along with an analysis of ion species applying a mass spectrometer without depending on a probe measuring instrument at a low cost considering that both mass spectrometry and plasma potential measurement can be performed.SOLUTION: The plasma potential measuring method and device include applying at least two different voltages between a mass spectrometer 3 (or 19) capable of making mass spectrometry of ions in plasma 2, and the plasma, obtaining mass spectrometry conditions X corresponding to the mass spectrometer that can detect the same ion as the case of the other voltage for every voltage Vb, and fitting an equation Vb=aX-Vp (Vp is plasma potential) as a regression equation to obtained data of each voltage Vb and mass spectrometry conditions X using a method of least squares to compute (a) and Vp in the equation respectively, thereby obtaining the plasma potential Vp and also obtaining (a) for identifying ion species. A program for carrying out the method, and a recording medium M1 (M2) recording the program are also provided.

Description

  The present invention is one of parameters that indicate the state of plasma in order to perform a desired target process when performing processing such as film formation, ion implantation, etching, and surface cleaning processing on an article to be processed using plasma. The present invention relates to a method and apparatus for measuring a plasma potential, and further to a plasma processing apparatus, and further relates to a program used to implement the method and a recording medium on which the program is recorded.

  In processing such as film formation (film formation), ion implantation, etching, and surface cleaning processing using plasma, ion species, radical species, plasma potential, etc. in plasma are used to perform desired processing. Control is important, and monitoring is essential for that. For example, for ion species measurement, mass analysis using a mass analyzer is generally performed.

  FIG. 5 shows that a plasma analysis apparatus PA that performs a target process under the plasma 2 on an object to be processed S installed in the vacuum chamber 1 performs mass analysis on the plasma using a so-called E × B type mass analyzer. An example is shown. As shown in FIG. 5, when the plasma 2 is formed in the vacuum chamber 1, the E × B type mass analyzer 3 is installed so as to be in contact with the plasma.

  A negative voltage is normally applied to the E × B mass analyzer 3 by a bias power source 10, and positive ions 5 are drawn from the plasma 2 through the entrance slit 4 into the analyzer 3. A magnetic field 16 is formed inside the E × B type mass analyzer 3 by a magnetic field generating means (not shown), and the drawn ions 5 receive a force in a downward direction 17 in FIG.

  On the other hand, opposing deflection plates 6 and 7 that are parallel to each other are arranged with their flat surfaces aligned in the direction of the lines of magnetic force of the magnetic field 16. A positive potential is applied to the deflecting plate 6 from the deflecting power source 8 and a negative potential is applied to the deflecting plate 7 from the deflecting power source 9, whereby a direction crossing the direction of the magnetic field lines of the magnetic field (in the upward direction 18 in FIG. 5). ) An electric field is formed. The ions 5 are also subjected to a force in the upward direction 18 by this electric field.

  In this way, a force in the downward direction 17 and a force in the upward direction 18 are applied to the ion 5, and the ion 5 travels straight only when these two forces are balanced, passes through the FC slit 11, and enters the Faraday cup 13. On and detected by the ammeter 15.

  At this time, secondary electrons are emitted from the Faraday cup 13 and an accurate ion current may not be measured. Therefore, in order to suppress the influence, a suppressor 12 is installed between the FC slit 11 and the Faraday cup 13. In this case, a negative voltage is applied from the suppressor power supply 14 so that the emitted secondary electrons are pushed back to the Faraday cup 13 again.

  FIG. 6 is a diagram illustrating a plasma processing apparatus PB for performing a target process on a processing object S installed in a vacuum chamber 1 under a plasma 2. An example of implementation is shown. As shown in FIG. 6, when the plasma 2 is formed in the vacuum chamber 1, a magnetic field deflection type mass analyzer 19 is installed so as to be in contact with the plasma.

  A negative voltage is normally applied from the bias power source 22 to the magnetic field deflection type mass analyzer 19, and positive ions 21 are drawn from the plasma 2 through the entrance slit 20 into the analyzer 19. A magnetic field 28 is formed inside the magnetic field deflection type mass analyzer 19, and the drawn ions 21 receive a force in a direction 29 due to the influence of the magnetic field and fly in a circular orbit.

  Since the orbit radius r of the ions 21 is determined by the strength of the magnetic field 28, the FC slit 23 and the Faraday cup 25 are installed on the constant orbit radius, and the ions are finally detected by the ammeter 27.

  At this time, as in the case of the E × B mass analyzer 3, secondary electrons are emitted from the Faraday cup 25, and an accurate ion current may not be measured. The suppressor 24 is installed between the Faraday cup 25 and a negative voltage is applied to the suppressor power supply 26 so that the emitted secondary electrons are pushed back to the Faraday cup 25 again.

  The E × B type mass analyzer described above is described in, for example, Japanese Patent Application Laid-Open No. 4-212300, and the magnetic field deflection type mass analyzer is described in, for example, Japanese Patent Application Laid-Open No. 2000-46680.

  The probe method is generally used for measuring the plasma potential. The probe method is not shown here because it is already well known per se, but examples of the probe method include a single probe method, a double probe method compatible with a floating potential system, and a triple probe method capable of instantaneous measurement. Of these three methods, the plasma potential can be measured by the single probe method.

  These probe methods are described in, for example, “Latest Plasma Generation Technology” published by August 5, 1991, published by IPC Corporation and edited by Yoshinobu Kawai.

JP-A-4-212300 JP 2000-46680 A

August 5, 1991 published by IPC, edited by Yoshinobu Kawai, "Latest Plasma Generation Technology"

  As can be seen from the above description, both a mass analyzer and a probe measuring instrument are required to perform both ion species measurement and plasma potential measurement. However, if both of them are installed in the chamber, an installation space is required in the chamber, the chamber size increases, the installation area of the plasma processing apparatus increases, and the cost of the plasma processing apparatus increases.

  Therefore, the present invention can measure the plasma potential, which is a parameter indicating the state of the plasma, together with the analysis of the ion species by applying the mass analyzer without relying on the probe measuring instrument. A first problem is to provide a plasma potential measurement method that can be performed at a low cost for both.

  In addition, the present invention can measure the plasma potential, which is a parameter indicating the state of the plasma, together with the analysis of the ion species by applying the mass analyzer without depending on the probe measuring instrument. A second object is to provide an inexpensive plasma potential measuring apparatus that is simplified while being able to do both.

  Furthermore, the present invention is a plasma processing apparatus for generating a plasma in a vacuum chamber and performing an intended process on an object to be processed under the plasma, and a plasma potential which is a parameter indicating a plasma state is probed. Without relying on measuring instruments, mass processing can be applied in combination with analysis of ion species, so that both mass analysis and plasma potential measurement can be performed. It is a third problem to provide an apparatus.

  It is a fourth and fifth object of the present invention to provide a computer-readable recording medium and a program recording a program for implementing the plasma potential measuring method that can solve the first problem.

In order to solve the first problem, the present invention provides:
Disposing a mass analyzer capable of performing mass analysis of ions in the plasma with respect to a plasma potential measurement target plasma;
At least two different voltages are respectively applied between the mass analyzer and the plasma to perform mass analysis. In performing the mass analysis, at least two voltages Vb of the at least two different voltages are used. It is possible to detect the same ion as in the case of the other voltage among the two different voltages, and to obtain a mass analysis condition X according to the mass analyzer, and in the plasma potential calculation unit, each voltage Vb thus obtained and the voltage The equation Vb = aX ² −Vp (Vp is the plasma potential of the potential measurement target plasma) derived in advance is fitted to the corresponding data of the mass spectrometry condition X, and the regression equation is fitted using the least square method. To calculate the plasma potential Vp by calculating a and Vp in the regression equation, respectively, and to identify the ion species at the same time A method for measuring a plasma potential, comprising:

In order to solve the second problem, the present invention
A mass analyzer capable of mass analysis of ions in the plasma to be arranged with respect to the potential measurement target plasma;
A voltage application unit for applying a voltage (voltage for ion mass spectrometry) between the mass analyzer and the plasma;
A mass spectrometry condition grasping unit for obtaining mass spectrometry conditions X corresponding to the mass analyzer;
A plasma potential calculator,
The plasma potential calculation unit obtains data of at least two different voltages applied between the mass analyzer and the plasma from the voltage application unit and the mass analysis condition grasping unit when measuring the plasma potential. Data of mass analysis conditions X corresponding to the mass analyzer for each voltage Vb of at least two different voltages can be input,
The plasma potential calculation unit uses a preset formula Vb = aX ² −Vp (Vp is a plasma potential of the potential measurement target plasma) for each input voltage Vb and data of the mass spectrometry condition X corresponding to the voltage Vb. ) Is used as a regression equation, and the regression equation is fitted using the least square method to calculate a and Vp in the regression equation, thereby obtaining the plasma potential Vp and also identifying the ion species Provided is a plasma potential measuring apparatus capable of obtaining a.

In the plasma potential measurement method according to the present invention, when applying at least two different voltages between the mass analyzer and the plasma, a voltage application unit capable of applying such a voltage is provided. And, for each voltage Vb of the at least two different voltages, the same ion as in the case of the other voltages of the at least two different voltages can be detected. In obtaining X, a mass analysis condition grasping unit capable of obtaining such mass analysis condition X can be provided.
Then, at least two different voltages are respectively applied to the voltage application unit between the mass analyzer and the plasma to cause the mass analyzer to perform mass analysis. For each voltage Vb of the at least two different voltages in the grasping unit, a mass analysis condition X corresponding to the mass analyzer that can detect the same ions as in the other voltages of the at least two different voltages is provided. Can be asked.
In the plasma potential measurement apparatus according to the present invention, when measuring the plasma potential, the voltage application unit is configured to apply at least two different voltages between the mass analyzer and the plasma, respectively. Allowing the instrument to perform mass analysis of ions in the plasma and for each voltage Vb of the at least two different voltages to detect the same ions as at other voltages of the at least two different voltages; In obtaining the mass analysis condition X corresponding to the mass analyzer, the user of the potential measuring device operates the voltage application unit and the mass analysis condition grasping unit to apply the voltage between the mass analyzer and the plasma. Mass analysis conditions X may be obtained, and the user may input the data from the data input unit to the plasma potential calculation unit.

However, a portion for collecting the data of the voltage Vb and the corresponding mass analysis condition X and a plasma potential measurement unit including the plasma potential calculation unit are provided, and when the portion for collecting the data measures the potential of the plasma, A voltage application unit applies at least two different voltages between the mass analyzer and the plasma to cause the mass analyzer to perform mass analysis of ions in the plasma, and the mass analysis condition grasping unit For each voltage Vb of the at least two different voltages, a mass analysis condition X corresponding to the mass analyzer capable of detecting the same ions as in the other voltages of the at least two different voltages is obtained. ,
The plasma potential calculation unit fits the equation Vb = aX ² −Vp using the least square method to each voltage Vb and the data of the mass analysis condition X corresponding to the voltage thus obtained, The plasma potential Vp may be obtained by calculating a and Vp in the equation, and a for identifying the ion species may be obtained together.

  In any case, the plasma potential calculation unit or the plasma potential measurement unit may be provided exclusively for the plasma potential measurement device according to the present invention, or may use an external computer, for example. A computer dedicated to the plasma potential measuring device can also be used.

  In the plasma potential measurement method and apparatus according to the present invention, the voltage applied between the mass analyzer and the plasma corresponds to the voltage applied by the bias power supply 10 in the mass analysis example shown in FIG. In the example of mass spectrometry shown in FIG. 4, the voltage corresponds to the voltage applied by the bias power source 22.

  According to the method and apparatus for measuring plasma potential according to the present invention, since the plasma potential can be measured together with the analysis of the ion species by applying the mass analyzer without relying on the probe measuring instrument, mass spectrometry and plasma potential measurement can be performed. Mass spectrometry and plasma potential measurement can be performed at a low price while both can be performed.

  As a mass analyzer in the plasma potential measuring method and apparatus according to the present invention, an E × B type mass analyzer of the type illustrated in FIG. 1 and a deflection magnetic field type mass analyzer of the type illustrated in FIG. be able to.

  When the E × B type mass analyzer is employed, the relationship between the electric field intensity E in which the same ion is detected by the mass analyzer and the ratio E / B of the magnetic flux density B of the magnetic field is determined. In the case of using a detector, the plasma potential is calculated from the relationship between the product rB of the magnetic flux density B of the magnetic field in which the same ion is detected by the mass analyzer and the orbit radius r of the ion.

The case where the E × B type mass spectrometer is employed will be further described. In the plasma potential measuring method and the plasma potential measuring apparatus,
The mass analyzer is an E × B type mass analyzer, the mass analysis condition X is a ratio (E / B) of the electric field intensity E and the magnetic flux density B, and a in the regression equation is the mass analyzer. If the mass of the same ion detected by m is m, the valence of the ion is Z, and the elementary charge of the ion is e, then (m / Z) / 2e, and Vb = aX ² −Vp is
Vb = [(m / Z) / 2e] × (E / B) ² −Vp
It is.

When adopting a magnetic deflection type mass spectrometer,
The mass analyzer is a magnetic field deflection type mass analyzer, and the mass analysis condition X is a product (r × B) of a magnetic flux density B and a flight orbit radius r of ions by the mass analyzer, and a in the regression equation Is (Z / m) × e / 2, where m is the mass of the same ion detected by the mass analyzer, Z is the valence of the ion, and e is the elementary charge of the ion, and Vb = AX ² −Vp Vb = [(Z / m) × e / 2] × (r × B) ² −Vp
It is.

In order to solve the third problem, the present invention
A plasma processing apparatus capable of generating plasma in a vacuum chamber and performing an intended process on an article to be processed under the plasma, comprising a plasma potential measuring apparatus according to the present invention. provide.

  Since the plasma processing apparatus according to the present invention includes the plasma potential measuring apparatus according to the present invention, the plasma potential, which is a parameter indicating the state of the plasma, is applied to the mass spectrometer without depending on the probe measuring instrument. It can be measured together with the analysis of the ion species, and can be provided at a low cost without being increased in size while being able to perform both mass spectrometry and plasma potential measurement.

  Examples of the plasma processing apparatus according to the present invention include a plasma processing apparatus that can perform one or more processes selected from film formation, ion implantation, etching, and article surface cleaning.

Moreover, this invention solves the said 4th subject,
A computer-readable recording medium storing a program for causing a computer to execute at least a part of a procedure for performing a plasma potential measurement method according to the present invention, wherein at least two of the mass analyzer and the plasma are between Mass analysis is performed by applying different voltages, and in performing the mass analysis, for each voltage Vb of the at least two different voltages, the same ion as in the case of the other voltages of the at least two different voltages A step of reading each voltage Vb obtained by obtaining a mass analysis condition X corresponding to the mass analyzer and data of the mass analysis condition X corresponding to the voltage, and the read data to the equation Vb = aX by fitting using a least squares method ² -Vp, respectively a and Vp in the formula By leaving obtains the plasma potential Vp, also provides a computer-readable recording medium recording a program for executing the steps on a computer seeking a for identifying ionic species together.

Furthermore, in order to solve the fifth problem, the present invention is a program for causing a computer to execute at least a part of a procedure for performing the plasma potential measurement method according to the present invention. Mass analysis is performed by applying at least two different voltages between each of the two, and in performing the mass analysis, for each voltage Vb of the at least two different voltages, another voltage of the at least two different voltages is used. A step of reading each voltage Vb obtained by obtaining a mass analysis condition X corresponding to the mass analyzer capable of detecting the same ion as in the case of the above and the data of the mass analysis condition X corresponding to the voltage; by fitting using the method of least squares the formula Vb = aX ² -Vp to the data, it a and Vp in the formula By calculating calculates the plasma potential Vp, together also provides a program for executing the steps of obtaining an a for identifying ionic species to the computer.

  As described above, according to the present invention, the plasma potential, which is a parameter indicating the plasma state, can be measured together with the analysis of ion species by applying a mass analyzer without relying on a probe measuring instrument. It is possible to provide a plasma potential measurement method that can be performed at a low cost while performing both of the plasma potential measurement and the plasma potential measurement.

  In addition, according to the present invention, the plasma potential, which is a parameter indicating the state of the plasma, can be measured together with the analysis of the ion species by applying a mass analyzer without depending on the probe measuring instrument. Therefore, it is possible to provide a simplified and inexpensive plasma potential measuring device for both of the above.

  Furthermore, according to the present invention, there is provided a plasma processing apparatus capable of generating a plasma in a vacuum chamber and performing an intended process on an object to be processed under the plasma, wherein the plasma is a parameter indicating a plasma state. The potential can be measured together with the analysis of ion species by applying a mass analyzer without relying on a probe measuring instrument, and both mass analysis and plasma potential measurement can be performed. It is possible to provide a plasma processing apparatus that can be completed.

  Further, according to the present invention, there is provided a program for carrying out the plasma potential measurement method and a recording medium on which the program is recorded, which facilitates obtaining a plasma potential and identifying an ion species. it can.

It is a figure which shows the example of a plasma processing apparatus provided with one example of the plasma potential measuring apparatus which concerns on this invention. It is a figure which shows the relationship between the detection ion current and the deflection | deviation electric field (deflection electric field strength) in the example of mass spectrometry by the BxE type | mold mass analyzer shown in FIG. It is a figure which shows the data of the deflection electric field which shows the bias voltage applied between a mass spectrometer and plasma, and the detection ion current peak corresponding to this voltage. It is a figure which shows the example of a plasma processing apparatus provided with the other example of the plasma potential measuring device which concerns on this invention. It is a figure which shows the prior art example which is implementing mass spectrometry using what is called an E * B type | mold mass spectrometer. It is a figure which shows the prior art example which is implementing mass spectrometry using what is called a magnetic field deflection type mass analyzer.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows an example of a plasma processing apparatus provided with an example of a plasma potential measuring apparatus according to the present invention.
The plasma processing apparatus PA shown in FIG. 1 includes a plasma potential measuring apparatus A. The plasma potential measuring apparatus A includes the same E × B type mass analyzer 3 as the mass analyzer shown in FIG. 5 and reads the program from the recording medium M1 on which one example of the program according to the present invention is recorded. A personal computer PC1 is included as an example of a plasma potential calculation unit that calculates factors for potential and ion species identification.

1 that are substantially the same as those shown in FIG. 5 are denoted by the same reference numerals as those used in FIG. That is,
PA is a plasma processing apparatus (in this example, an object to be processed S to which a bias voltage is applied from a bias power supply (not shown) is subjected to a target process (for example, a cleaning process by irradiation with ions such as argon ions) under plasma. apparatus〕,
1 is a vacuum chamber,
2 is plasma,
3 is an E × B mass spectrometer disposed at a position in contact with the plasma 2,
4 is an entrance slit of the mass analyzer 3,
5 is a positive ion,
6 is a deflection plate to which a positive voltage is applied from an output variable deflection power source 8;
7 is a deflection plate to which a negative voltage is applied from an output variable deflection power source 9;
10 is an output variable bias power source for applying a negative voltage between the mass analyzer 3 and the plasma 2;
11 is the FC slit at the ion outlet,
12 and 14 are suppressors that push back secondary electrons, and the suppressor power supply 13 is an Faraday cup 15 that detects ions, and an ammeter (ion current measuring instrument).
Reference numeral 16 denotes a magnetic field (a magnetic field whose magnetic field lines are directed from the front to the back in FIG. 1).
17 is the direction of force (downward direction) exerted on the ions 5 by the magnetic field (magnetic flux density B).
Reference numeral 18 denotes the direction of force (upward direction) exerted on the ions 5 by the electric field (electric field intensity E) between the deflecting plates 6 and 7.
For example, the plasma 2 supplies a gas (for example, argon gas) from a gas supply device (not shown) into the chamber 1 while maintaining the gas plasma generation pressure by evacuating the chamber 1 with an exhaust device (not shown). It can be generated by hot cathode arc discharge (not shown).

The mass analyzer 3 can perform mass analysis in the same manner as the mass analyzer of FIG.
According to the plasma potential measuring apparatus A of FIG. 1, factors for identifying ion species in plasma can be obtained together with the potential of plasma 2.
That is, at least two different voltages are respectively applied between the mass analyzer 3 and the plasma 2 from the bias power source 10 with variable output, and the mass analysis is performed. For each voltage Vb, a mass analysis condition X corresponding to the mass analyzer 2 that can detect the same ions as those of the other of the at least two different voltages is obtained.
The equation Vb = aX ² −Vp (Vp is the plasma potential of the potential measurement target plasma) derived in advance for each voltage Vb and the data of the mass analysis condition X corresponding to the voltage obtained as a regression equation. By fitting the regression equation using the least square method, a and Vp in the regression equation are calculated to obtain the plasma potential Vp, and to obtain a for identifying the ion species. it can.

In this example employing the E × B type mass analyzer 3 as the mass analyzer, the mass analysis condition X at Vb = aX ² −Vp is the ratio (E / B) of the electric field strength E to the magnetic flux density B. Yes, a is (m / Z) / 2e (m is the mass of the same ion detected by the mass analyzer, Z is the valence of the ion, and e is the elementary charge of the ion). Therefore, Vb = aX ² −Vp is
Vb = [(m / Z) / 2e] × (E / B) ² −Vp.

The reason why Vb = [(m / Z) / 2e] × (E / B) ² −Vp will be described below. When the bias voltage applied from the power source 10 to the mass analyzer 3 is Vb and the plasma potential of the plasma 2 is Vp, the following equation (1) is established.

  In the above formula (1), m is the ion mass, v is the ion velocity, Z is the valence of the ion, and e is the elementary charge. Ion thermal energy was neglected because it was very small at about 0.03 eV at room temperature. In this example, the bias voltage is a negative voltage and the plasma potential is a positive potential, but both are described as absolute values.

In the E × B type mass analyzer 3, the ion detection condition is that the force received from the magnetic field (magnetic flux density B) and the electric field (electric field strength) is balanced, so the equation (3) derived from the following equation (2) ) become that way.

式(4) は、バイアス電圧Ｖｂが電界（偏向電界強度Ｅ）と磁界（磁束密度Ｂ）との比（Ｅ／Ｂ）の２次式であることを示している。 Substituting equation (3) into equation (1) and rearranging results in the following equation (4).

Expression (4) indicates that the bias voltage Vb is a quadratic expression of the ratio (E / B) between the electric field (deflection electric field strength E) and the magnetic field (magnetic flux density B).

FIG. 2 shows the following. That is,
While the chamber 1 is evacuated and reduced to an argon gas plasma generation pressure by an exhaust device (not shown), argon gas is supplied into the chamber 1 from a gas supply device (not shown), and hot cathode arc discharge (not shown) is performed. An example in which plasma is generated and analyzed by the mass analyzer 3 is shown. In FIG. 2, the vertical axis indicates the ion current detected by the ammeter 15, and the horizontal axis indicates the peak deflection electric field intensity E at which ions are detected.

In this case, when the bias voltage Vb was 380 V and the magnetic flux density B was fixed at 0.102 T, the peak deflection electric field intensity E in which ions were detected was 4.42 kV / m.
The measurement was performed in the same manner while changing the bias voltage Vb, and the result of examining the relationship between the bias voltage Vb and the peak deflection electric field strength E is shown by a black circle in FIG.
The coordinates (Vb, E) indicated by black dots in FIG. 3 are (380, 4.42), (330, 4.12), and (280, 3.82).
Generally speaking, the electric field intensity E can be adjusted by adjusting the output of at least one of the power supplies 8 and 9. However, in adjusting the electric field strength E, it is preferable to apply a voltage having the same absolute value between the power supplies 8 and 9.
As a specific example, when 380 V is applied as the bias voltage Vb as described above, a voltage having the same absolute value such as +190 V and −190 V between the power supplies 8 and 9 can be applied.
In any case, it can be said that the power supply 8 and / or the power supply 9 with variable output are at least a part of constituent members of the mass analysis condition grasping unit (mass analysis condition grasping means) of the mass analyzer.

The computer PC1 serving as the plasma potential calculation unit reads the next program from the recording medium M1. That is,
From the keyboard of the bias voltage Vb and the corresponding peak deflection field strength E to magnetic flux density B ratio (E / B) data, in FIG. 2, the combination data of Vb and E / B corresponding to at least two black circles. The data is read in response to the input, and the equation (4) is fitted to the read data using the method of least squares, so that (m / Z) / 2e and plasma for identifying the ion species in the equation are obtained. This is a program for calculating each potential Vp.

Therefore, mass analysis of the plasma by the mass analyzer 3 applies at least two bias voltages Vb and obtains (E / B) corresponding to each voltage Vb (B is known in this example) 0.102T), these data can be input to the computer PC1 to obtain the plasma potential Vp and (m / Z) / 2e for ion species identification. When Vp and the like were calculated in this way, the plasma potential Vp was 11.8 [V]. When (m / Z) / 2e was calculated as (m / Z) / (2e × B ² ), it was 20.1. In any case, since e is also known for ionic species identification, m / Z can be obtained, whereby the ionic species can be identified. The program may include a procedure for further calculating m / Z from the calculated (m / Z) / 2e.

In this example, since B is fixed, it is sufficient to actually input E for the ratio (E / B). From the combinations of Vb and E shown in FIG. By inputting at least two, it may be possible to calculate (m / Z) / (2e × B ² ) and Vp.
.

Among (m / Z) / (2e × B ² ), since e and B are known, (m / Z) can be calculated, and the ion species can be identified from this. The program may include a procedure for further calculating m / Z from the calculated (m / Z) / (2e × B ² ).

In the example described above, the electric field intensity E is changed by fixing B in the ratio (E / B). Conversely, the magnetic flux density B is changed by fixing E in the ratio (E / B). Or both may be changed. When changing the magnetic flux density, for example, an electromagnetic control type magnetic field generating unit such as an electromagnet type can be used, and the magnetic flux density B can be adjusted by controlling the energization to the magnetic field generating unit.
Further, when the electric field intensity E is changed by fixing B out of the ratio (E / B), for example, the computer PC1, for example, through the interface IFa as shown by a chain line in FIG. Depending on the interface IFa, the voltage application on / off instruction and the output voltage instruction may be output to each power source as necessary, and the information detected by the ammeter 15 may be read. Data of the deflection electric field intensity E when each bias voltage Vb and the corresponding peak ion current are detected in the computer PC1 is collected, and Vp and m / Z for ion species identification can be calculated based on the data. May be.

FIG. 4 shows an example of a plasma processing apparatus provided with another example of the plasma potential measuring apparatus according to the present invention.
The plasma processing apparatus PB shown in FIG. 4 includes a plasma potential measuring apparatus B. The plasma potential measuring apparatus B includes the same deflection magnetic field type mass analyzer 19 as the mass analyzer shown in FIG. 6, and reads the program from the recording medium M2 on which another example of the program according to the present invention is recorded. A personal computer PC2 is included as an example of a plasma potential calculation unit that calculates factors for plasma potential and ion species identification.

4 that are substantially the same as those shown in FIG. 6 are denoted by the same reference numerals as those used in FIG. That is,
PB is a plasma processing apparatus (in this example, a target process S to which a bias voltage is applied from a bias power supply (not shown) is subjected to a target process (for example, a cleaning process by irradiation with ions such as argon ions) under plasma. apparatus〕,
1 is a vacuum chamber,
2 is plasma,
19 is a deflection magnetic field type mass analyzer disposed at a position in contact with the plasma 2;
20 is an entrance slit of the mass analyzer 3,
21 is a positive ion,
22 is an output variable bias power source for applying a negative voltage between the mass analyzer 19 and the plasma 2, 23 is an FC slit at the ion exit,
Reference numerals 24 and 26 denote suppressors that push back secondary electrons, and the suppressor power supply 25 detects ions. Faraday cup 27 is an ammeter (ion current measuring instrument).
Reference numeral 28 denotes a magnetic field (magnetic field whose magnetic field lines are directed from the front to the back in FIG. 1).
29, the direction r of the force exerted by the magnetic field (magnetic flux density B) on the ion 21 is the radius of the flight locus of the ion 21.
Also in the apparatus PB, for example, the plasma 2 is gas (for example, argon gas) from a gas supply device (not shown) in the chamber 1 while maintaining the gas plasma generation pressure by evacuating the inside of the chamber 1 with an exhaust device (not shown). ), And can be generated by hot cathode arc discharge (not shown).

The mass analyzer 19 can perform mass analysis similarly to the mass analyzer of FIG.
According to the plasma potential measuring apparatus B of FIG. 4, the factor for identifying the ion species in the plasma can be obtained together with the potential of the plasma 2.
That is, at least two different voltages are respectively applied from the output variable bias power source 22 between the mass analyzer 19 and the plasma 2 to perform mass analysis. In performing the mass analysis, each of the at least two different voltages is applied. For each voltage Vb, a mass analysis condition X corresponding to the mass analyzer 19 that can detect the same ion as in the case of the other voltage of the at least two different voltages is obtained.
The equation Vb = aX ² −Vp (Vp is the plasma potential of the potential measurement target plasma) derived in advance for each voltage Vb and the data of the mass analysis condition X corresponding to the voltage obtained as a regression equation. By fitting the regression equation using the least square method, a and Vp in the regression equation are calculated to obtain the plasma potential Vp, and to obtain a for identifying the ion species. it can.

In this example in which a deflection magnetic field type mass analyzer 19 is employed as the mass analyzer, the mass analysis condition X at Vb = aX ² −Vp is the product of the magnetic flux density B and the flight trajectory radius r of ions by the mass analyzer. (R × B) where a in the above equation is m, the valence of the same ion detected by the mass analyzer is Z, the valence of the ion is e, and the elementary charge of the ion is e.
(Z / m) × e / 2, and Vb = aX ² −Vp is
Vb = [(Z / m) × e / 2] × (r × B) ² −Vp.

The reason why Vb = [(Z / m) × e / 2] × (r × B) ² −Vp is derived is as follows.
Assuming that the bias voltage applied from the power source 22 to the mass analyzer 19 is Vb and the plasma potential of the plasma 2 is Vp, the following equation (5) is established as in the case of the E × B type mass analyzer.

  In the above formula (5), m is the ion mass, v is the ion velocity, Z is the valence of the ion, and e is the elementary charge. Ion thermal energy was neglected because it was very small at about 0.03 eV at room temperature. In this example as well, the bias voltage is a negative voltage and the plasma potential is a positive potential, but both are described as absolute values.

In the deflection magnetic field type mass analyzer 19, the ion detection condition is a case where the force received by the ion due to the magnetic field (magnetic flux density B) is balanced with the centrifugal force. Therefore, the following equation (6) is derived. It becomes like this.

式(8) は、バイアス電圧Ｖｂが磁界（磁束密度Ｂ）とイオンの軌道半径ｒとの積（ｒ×Ｂ）の２次式であることを示している。 Substituting equation (7) into equation (5) and rearranging it yields the following equation (8).

Expression (8) indicates that the bias voltage Vb is a quadratic expression of the product (r × B) of the magnetic field (magnetic flux density B) and the orbital radius r of ions.

Therefore, for example, the ion orbit radius r is fixed, and at least two different bias voltages are respectively applied from the power source 22 between the mass analyzer 19 and the plasma 2 as in the case of the plasma potential measurement of FIG. Analysis is performed, and at least two sets of combination data of the product (r × B) of the magnetic flux density B and the orbital radius of the ions detected at each bias voltage Vb and its baice voltage are obtained, and the plasma potential is calculated. A factor for identifying the plasma potential Vp and the ion species can be calculated by inputting to the computer PC2 as a unit.
As the magnetic flux density B, for example, as illustrated in FIG. 4, a magnetic field generation unit 280 such as an electromagnet type that can be controlled to be energized is adopted, and the magnetic flux density B can be adjusted by controlling the power supply to the magnetic field generation unit. That is, it can be said that the magnetic field generation unit 280 capable of adjusting the magnetic flux density B is at least a part of the constituent members of the mass analysis condition grasping unit (mass analysis condition grasping means) of the mass analyzer.

The computer PC2 reads the next program from the recording medium M2. That is,
The data is read according to the input from the keyboard of the combination data of at least two different bias voltages Vb and the product (r × B) of the magnetic flux density B and ion orbit radius r corresponding to each bias voltage. Is a program for calculating (Z / m) × e / 2 and the plasma potential Vp for identifying ion species in the equation by fitting the equation (8) using the least square method.

  Therefore, mass analysis of the plasma by the mass analyzer 19 obtains at least two bias voltages Vb and (r × B) corresponding to each voltage Vb, and these data are input to the computer PC2 to obtain the plasma potential. Vp and (Z / m) × e / 2 for ion species identification can be obtained. As for ion species identification, since e is known, (Z / m) can be obtained, whereby the ion species can be identified. The program may include a procedure for further calculating Z / m from the calculated (Z / m) × e / 2.

In this example, since r is fixed, in practice, it is sufficient to input B for the product (r × B), and at least two of the combinations of Vb and B are input. by, it may be prepared to be calculated (Z / m) × e × r 2/2 and Vp.
.

(Z / m) of × e × r ^2/2, since e and r are known, it is possible to calculate the m / Z, can now be identified ion species. The program instructions may include calculating a further m / Z from the calculated (Z / m) × e × r 2/2.

In the example described above, r of the product (r × B) is fixed and the magnetic flux density B is changed, but conversely, B may be fixed and the ion orbit radius r may be changed. May be. The ion orbit radius r can be changed by moving the Faraday cup 25, suppressor 24 and FC slit 23.
When r is fixed in the product (r × B) and the magnetic flux density B is changed, for example, from the computer PC2, for example, via an interface IFb as shown by a chain line in FIG. Depending on the interface IFb, the power supply may be instructed to turn on / off the voltage, and the output voltage may be instructed as necessary, and the information detected by the ammeter 27 may be read. The computer PC2 may collect data on each bias voltage Vb and the magnetic flux density B corresponding to the bias voltage Vb, and calculate Vp and m / Z for ion species identification based on the data.

  INDUSTRIAL APPLICABILITY The present invention can be used to perform plasma mass analysis using a mass analyzer in film formation using plasma, ion implantation, etching, and the like, and can be used to obtain a plasma potential without using a probe measuring instrument. .

PA, PB Plasma processing apparatus A, B Plasma potential measuring apparatus 1 Vacuum chamber 2 Plasma 3 B × E type mass analyzer 4 Mass analyzer inlet slit,
5 positive ions,
6, 7 deflection plate,
8, 9 Bias power supply 10 Bias power supply
11 FC slit at the ion outlet,
12 Suppressor 14 Suppressor Power Supply 13 Faraday Cup 15 Ammeter (Ion Current Meter)
16 Magnetic field 17 Direction of force exerted on ion by magnetic field (downward direction)
18 Direction of force exerted on ions by electric field between deflecting plates 6 and 7 (upward direction)
PC1 computer M1 recording medium IFa interface 19 deflection magnetic field type mass analyzer,
20 Mass spectrometer inlet slit,
21 positive ions,
22 Bias power supply,
23 FC slit at the ion exit,
24 suppressor 25 Faraday cup 26 suppressor power supply 27 ammeter (ion current measuring instrument)
28 Magnetic field 280 Magnetic field generator 29 Direction of force exerted by magnetic field on ion r Radius of flight circle locus of ion PC2 Computer M2 Recording medium IFb interface

Claims (12)

Disposing a mass analyzer capable of performing mass analysis of ions in the plasma with respect to a plasma potential measurement target plasma;
At least two different voltages are respectively applied between the mass analyzer and the plasma to perform mass analysis. In performing the mass analysis, at least two voltages Vb of the at least two different voltages are used. It is possible to detect the same ion as in the case of the other voltage among the two different voltages, and to obtain a mass analysis condition X according to the mass analyzer, and in the plasma potential calculation unit, each voltage Vb thus obtained and the voltage The equation Vb = aX ² −Vp (Vp is the plasma potential of the potential measurement target plasma) derived in advance is fitted to the corresponding data of the mass spectrometry condition X, and the regression equation is fitted using the least square method. To calculate the plasma potential Vp by calculating a and Vp in the regression equation, respectively, and to identify the ion species at the same time A method for measuring a plasma potential, comprising: obtaining a.   A voltage application unit for applying a voltage for ion mass spectrometry between the mass analyzer and the plasma with respect to the mass analyzer, and a mass analysis condition for obtaining a mass analysis condition X corresponding to the mass analyzer A grasping unit is provided, and the voltage application unit is configured to perform the mass analysis by applying the at least two different voltages between the mass analyzer and the plasma, respectively. Mass corresponding to the mass analyzer capable of detecting the same ions as the other voltages of the at least two different voltages for each voltage Vb of the at least two different voltages in the mass analysis condition grasping unit. The plasma potential measurement method according to claim 1, wherein the analysis condition X is obtained. The mass analyzer is an E × B type mass analyzer, the mass analysis condition X is a ratio (E / B) of the electric field intensity E and the magnetic flux density B, and a in the regression equation is the mass analyzer. If the mass of the same ion detected by m is m, the valence of the ion is Z, and the elementary charge of the ion is e, then (m / Z) / 2e, and Vb = aX ² −Vp is
Vb = [(m / Z) / 2e] × (E / B) ² −Vp
The plasma potential measuring method according to claim 1 or 2. The mass analyzer is a magnetic field deflection type mass analyzer, and the mass analysis condition X is a product (r × B) of a magnetic flux density B and a flight orbit radius r of ions by the mass analyzer, and a in the regression equation Is (Z / m) × e / 2, where m is the mass of the same ion detected by the mass analyzer, Z is the valence of the ion, and e is the elementary charge of the ion, and Vb = AX ² −Vp Vb = [(Z / m) × e / 2] × (r × B) ² −Vp
The plasma potential measuring method according to claim 1 or 2. A mass analyzer capable of mass analysis of ions in the plasma to be arranged with respect to the potential measurement target plasma;
A voltage application unit for applying a voltage between the mass analyzer and the plasma;
A mass spectrometry condition grasping unit for obtaining mass spectrometry conditions X corresponding to the mass analyzer;
A plasma potential calculator,
The plasma potential calculation unit obtains data of at least two different voltages applied between the mass analyzer and the plasma from the voltage application unit and the mass analysis condition grasping unit when measuring the plasma potential. Data of mass analysis conditions X corresponding to the mass analyzer for each voltage Vb of at least two different voltages can be input,
The plasma potential calculation unit uses a preset formula Vb = aX ² −Vp (Vp is a plasma potential of the potential measurement target plasma) for each input voltage Vb and data of the mass spectrometry condition X corresponding to the voltage Vb. ) Is used as a regression equation, and the regression equation is fitted using the least square method to calculate a and Vp in the regression equation, thereby obtaining the plasma potential Vp and also identifying the ion species A plasma potential measuring device characterized in that a can be obtained. A part for collecting the data of the voltage Vb and the corresponding mass analysis condition X and a plasma potential measuring part including the plasma potential calculating part are provided, and the part for collecting the data is used for measuring the potential of the plasma. The voltage application unit applies at least two different voltages between the mass analyzer and the plasma to cause the mass analyzer to perform mass analysis of ions in the plasma and grasp the mass analysis conditions For each voltage Vb of the at least two different voltages, a mass analysis condition X corresponding to the mass analyzer that can detect the same ion as the other voltage of the at least two different voltages is obtained. Let
The plasma potential calculation unit fits the equation Vb = aX ² −Vp to each voltage Vb and the data of the mass analysis condition X corresponding to the voltage using the least square method, thereby obtaining the voltage Vb. 6. The plasma potential measuring apparatus according to claim 5, wherein a plasma potential Vp is obtained by calculating a and Vp in the equation, and a for identifying the ion species is also obtained. The mass analyzer is an E × B type mass analyzer, the mass analysis condition X is a ratio (E / B) of the electric field intensity E and the magnetic flux density B, and a in the regression equation is the mass analyzer. If the mass of the same ion detected by m is m, the valence of the ion is Z, and the elementary charge of the ion is e, then (m / Z) / 2e, and Vb = aX ² −Vp is
Vb = [(m / Z) / 2e] × (E / B) ² −Vp
The plasma potential measuring device according to claim 5 or 6. The mass analyzer is a magnetic field deflection type mass analyzer, and the mass analysis condition X is a product (r × B) of a magnetic flux density B and a flight orbit radius r of ions by the mass analyzer, and a in the regression equation Is (Z / m) × e / 2, where m is the mass of the same ion detected by the mass analyzer, Z is the valence of the ion, and e is the elementary charge of the ion, and Vb = AX ² −Vp Vb = [(Z / m) × e / 2] × (r × B) ² −Vp
The plasma potential measuring device according to claim 5 or 6.   9. A plasma processing apparatus capable of generating plasma in a vacuum chamber and performing a target process on an object to be processed under the plasma, wherein the plasma potential measuring apparatus according to claim 5 is used. A plasma processing apparatus comprising the plasma processing apparatus.   The plasma processing apparatus according to claim 9, wherein the apparatus is capable of performing one or more processes selected from film formation, ion implantation, etching, and article surface cleaning. A computer-readable recording medium recording a program for causing a computer to execute at least a part of a procedure for performing the plasma potential measurement method according to claim 1, 2, 3, or 4.
At least two different voltages are respectively applied between the mass analyzer and the plasma to perform mass analysis, and in performing the mass analysis, at least two different voltages for each voltage Vb of the at least two different voltages. Among the voltages, the same ions as in the case of other voltages can be detected. Each of the voltages Vb obtained by obtaining the mass analysis condition X corresponding to the mass analyzer and the mass analysis condition X corresponding to the voltage can be detected. A step of reading data, and fitting the equation Vb = aX ² −Vp to the read data using a least square method to calculate a and Vp in the equation, respectively, thereby obtaining the plasma potential Vp, At the same time, a computer reading recording a program for causing a computer to execute the step of obtaining a for identifying the ion species Recordable media. A program for causing a computer to execute at least a part of a procedure for carrying out the plasma potential measurement method according to claim 1, wherein at least two different voltages are applied between the mass analyzer and the plasma. Each is applied to perform mass analysis, and in performing the mass analysis, for each voltage Vb of the at least two different voltages, it is possible to detect the same ions as in the other voltages of the at least two different voltages. , A step of reading each voltage Vb obtained by obtaining a mass analysis condition X corresponding to the mass analyzer and data of the mass analysis condition X corresponding to the voltage, and the read data to the equation Vb = aX ² By fitting -Vp using the least squares method and calculating a and Vp in the equation, respectively, the plasma potential V The program for making a computer perform the step which calculates | requires p for calculating | requiring p and identifying ion species together.

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