JPH09236582A - Mass spectrometry method and apparatus - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] In gas mass spectrometry, the preparation time of an object to be inspected and the analysis time of the adhered matter are shortened. A thermal desorption unit (5) that heats and desorbs a semiconductor wafer (1) in a quartz chamber (3) supplied with an ionizable nitrogen gas (2) to thermally desorb an adhering substance and form a desorbed gas (4).
The desorbed gas 4 discharged from the quartz chamber 3 is discharged from the quartz chamber 3, and a first mass analysis unit 7 that includes a first ion forming unit 6 that performs positive ionization in an atmospheric pressure atmosphere and that mass-analyzes positive ions. A second mass spectrometric apparatus that includes a second ion forming unit 10 that performs negative ionization of a mixed desorption gas 9 formed by supplying an ionizable oxygen gas 8 to the desorption gas 4 in an atmosphere of atmospheric pressure and mass-analyses negative ions It consists of part 11 and
Positive and negative ionization is simultaneously performed by using the same desorption gas 4 in the first ion forming unit 6 and the second ion forming unit 10, and both positive and negative ions are simultaneously mass analyzed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for analyzing an object to be inspected, and more particularly to a mass spectrometric method and apparatus for ionizing and analyzing a deposit desorbed by a thermal desorption method.

[0002]

2. Description of the Related Art The technology described below studies the present invention,
The present invention was studied by the present inventors upon completion, and its outline is as follows.

When analyzing an adhering substance attached to an object to be inspected using an atmospheric pressure mass spectrometer, it is necessary to ionize the adhering substance by a carrier gas.

Here, the positive (plus) ionization of the deposit is performed by the movement of the electrons using the positive ions generated by the corona discharge of the carrier gas.

At this time, for example, nitrogen gas is used as the carrier gas.

Negative ionization of the deposit is performed by moving the electrons of the negative ions generated by the corona discharge of the carrier gas.

At this time, for example, a nitrogen-oxygen mixed gas is used as the carrier gas.

In the method of mass-analyzing a carrier gas by using an atmospheric pressure mass spectrometer, the desorbed gas formed by desorbing an adhering material at elevated temperature is formed together with the carrier gas by the atmospheric pressure mass spectrometer. There is a method of introducing into and ionizing.

The gas analysis method using thermal desorption is described in, for example, pages 93 to 94, "Monthly Semiconductor World, August 1994", published by Press Journal, Inc., July 20, 1994. Has been done.

[0010]

However, in the above-mentioned technique, when the desorbed gas due to the temperature programmed desorption is ionized by the atmospheric pressure mass spectrometer and then mass-analyzed, a carrier gas that can be positively ionized and a negative ionized gas can be used. Since the possible carrier gases are different, it is a problem that positive ions and negative ions cannot be detected at the same time.

As a result, since the detection of positive ions and the detection of negative ions are performed separately, there is a problem that the preparation time of the object to be inspected and the analysis time of the adhering substance are significantly increased.

Further, since two inspection objects are required for each analysis, there is a problem that the amount is wasted.

An object of the present invention is to provide a mass spectrometric method and apparatus for shortening the preparation time of the object to be inspected and the analysis time of the attached matter.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0015]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, the mass spectrometric method of the present invention is for ionizing and analyzing the adhering matter adhering to the object to be inspected, and supplying the first carrier gas into the processing container to heat the object to be inspected. Thereby desorbing the adhering material at elevated temperature to form a desorbed gas, and the desorbed gas is discharged together with the first carrier gas from the processing container and introduced into a first mass spectrometric section, where the first mass In the analysis unit, either positive or negative ionization of the desorbed gas is performed in the atmospheric pressure atmosphere, and then the ions are subjected to mass spectrometry. The desorbed gas discharged from the processing container together with the first carrier gas is supplied with the second carrier gas. The mixed desorbed gas formed by the supply is introduced into the second mass spectrometric section, and either positive or negative ionization of the mixed desorbed gas is performed in the second mass spectrometric section in the atmospheric pressure atmosphere, and then the ions are removed. Mass spectrometry .

Thus, positive and negative ionization can be performed simultaneously in different ion forming sections using the same desorption gas, and further, positive and negative ions can be simultaneously mass analyzed in different mass spectrometric sections.

As a result, it is not necessary to separately perform positive and negative ionization and mass analysis of positive and negative ions in two steps, positive and negative, so that positive and negative ion analysis can be performed by one inspection object. It is possible to reduce the preparation time of the inspection object and the analysis time of the deposits by almost half.

Further, the mass spectrometer of the present invention is for carrying out an analysis by ionizing the adhering matter adhering to the object to be inspected, and inspecting the object to be inspected in the processing container supplied with the ionizable first carrier gas. A thermal desorption unit for heating and desorbing the adhering substances to form desorbed gas, and positive or negative ionization of the desorbed gas discharged together with the first carrier gas from the processing container. A first mass analysis unit that includes a first ion formation unit that performs either one of them in an atmospheric pressure atmosphere, and that mass-analyzes the ions formed in the first ion formation unit; and discharges from the processing container together with the first carrier gas. A deionized gas is supplied with a second carrier gas that can be ionized, and a positive ionization or negative ionization of the mixed desorption gas that is formed is performed in an atmospheric pressure atmosphere. Formation Is the in formed ions as it has a second mass analyzer for mass analysis.

Furthermore, in the mass spectrometer of the present invention, in the first or second ion forming section or both,
The desorbed gas or the mixed desorbed gas is ionized by corona discharge.

The mass spectrometer of the present invention comprises the first
Alternatively, a data processing unit for digitizing and storing the ion intensity data as a result of the mass analysis is connected to the second mass analysis unit or both.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a structural conceptual diagram showing an example of an embodiment of the structure of a mass spectrometer according to the present invention.

The mass spectroscope described in the present embodiment is equipped with a deposit (moisture in a fine pattern groove, dry etching residue, CVD (Chemical Vapor) attached to a semiconductor wafer 1 which is an example of an object to be inspected. Deposition) Moisture in the film is ionized to analyze the surface state of the semiconductor wafer 1 by mass spectrometry, and the ionic strength is output as the analysis result.

The structure of the mass spectrometer will be described. The semiconductor wafer 1 is placed in a quartz chamber 3 (processing container) to which a nitrogen gas 2 which is an ionizable first carrier gas is supplied.
And a nitrogen gas 2 from the quartz chamber 3 to heat the desorbed material by heating to desorb the deposited material and form a desorbed gas 4.
A first mass spectrometric section 7 for mass spectrometric analysis of the positive ions formed by the first ion formation section 6 for positive ionization of the desorbed gas 4 discharged together with it in an atmosphere of atmospheric pressure; Secondly, the mixed desorbed gas 9 formed by supplying the ionizable second carrier gas oxygen gas 8 to the desorbed gas 4 discharged together with the nitrogen gas 2 from the quartz chamber 3 is negatively ionized in the atmospheric pressure atmosphere. The second mass analysis unit 11 includes the ion formation unit 10 and performs mass analysis of the negative ions formed in the second ion formation unit 10.

The thermal desorption unit 5, the first mass analysis unit 7, and the second mass analysis unit 11 are connected to the second pipe 21 and the third pipe 22.
And a fourth pipe 23.

That is, the quartz chamber 3 of the thermal desorption unit 5
The second pipe 21 connected to the exhaust system 3b of the
2 and the fourth pipe 23, and splits the desorbed gas 4 flowing through the second pipe 21 into two directions of the third pipe 22 and the fourth pipe 23.

Further, one of the split desorbed gases 4 is
It is introduced into the first ion forming unit 6 of the first mass analysis unit 7 via the third pipe 22, and the other desorbed gas 4 is supplied to the fourth pipe 2
The second ion forming unit 10 of the second mass spectrometric unit 11
Will be introduced.

The other desorbed gas 4 flowing through the fourth pipe 23 is supplied with the oxygen gas 8 as the second carrier gas through the fifth pipe 24 and contains the desorbed gas 4. A mixed desorbed gas 9 is formed by the nitrogen gas 2 and the oxygen gas 8.

As a result, the mixed desorbed gas 9 is fed to the fourth pipe 2
The second ion forming unit 10 of the second mass spectrometric unit 11
Will be introduced.

The mixed desorbed gas 9 is, for example, a gas in which the nitrogen gas 2 is 80% and the oxygen gas 8 is 20%, but the mixing ratio is not limited to this, and other ratios can be used. It may be.

The first mass spectrometric section 7 comprises a first ion forming section 6 and a quadrupole mass spectrometric section 12 for mass spectrometric analysis of positive ions formed by the first ion forming section 6,
The mass spectrometric section 11 is composed of a second ion forming section 10 and a quadrupole mass spectrometric section 13 that mass-analyzes the negative ions formed in the second ion forming section 10.

Here, each of the first ion forming unit 6 and the second ion forming unit 10 is provided with a needle-shaped ion source 6a and an ion source 10a, and the first ion forming unit 6 in an atmospheric pressure atmosphere.
The desorbed gas 4 is introduced into the chamber to perform positive ionization, and the mixed desorbed gas 9 is introduced into the second ion forming unit 10 in the atmospheric pressure atmosphere to perform negative ionization.

The interiors of the quadrupole mass spectrometers 12 and 13 are divided into two processing sections 12a and 12b and processing sections 13a and 13b, respectively, so that the vacuum can be drawn in two steps. , The respective processing units 12a, 12b,
Vacuum evacuation means 14 such as a vacuum pump is connected to 13a and 13b.

As a result, the respective vacuum exhaust means 14
Can be reduced.

The quadrupole mass spectrometers 12 and 13 perform mass analysis of ions in a vacuum atmosphere by utilizing only the action of an electric field without using a magnetic field, but can perform mass analysis of ions. The number of electrodes is not limited to the quadrupole, and any other number of electrodes may be used.

Further, each of the quadrupole mass spectrometric sections 12, 13 has an orifice 12c, which is a partition plate that determines the flow rate and the moving direction of the desorbed gas 4 or the mixed desorbed gas 9.
13c, four electrodes 12d and 13d, deflectors 12e and 13e that change the moving direction of ions, and ion detectors 12f and 13f that detect ions are installed.

Further, an infrared lamp 15 as a heating means is installed in the thermal desorption section 5. As a result, various temperature rising conditions can be set according to the material and size of the inspection object (the semiconductor wafer 1 in the present embodiment).

For example, the temperature rising conditions in the case of the semiconductor wafer 1 made of silicon are in the range of several degrees Celsius to 20 degrees Celsius per minute.

That is, the temperature-controlled desorption unit 5 is the quartz chamber 3
Nitrogen gas 2 is supplied to the inside of the semiconductor wafer 1, and the infrared lamp 15 heats the semiconductor wafer 1 to cause the deposits adhering to the semiconductor wafer 1 to be desorbed by heating to form the desorbed gas 4.

In the first ion forming part 6 and / or the second ion forming part 10 of the mass spectrometer according to this embodiment, the desorbed gas 4 or the mixed desorbed gas 9 is generated by corona discharge under atmospheric pressure. Is ionized.

However, if ionization is performed under atmospheric pressure, it may be ionized by a method other than corona discharge.

Further, each of the first mass analysis section 7 and the second mass analysis section 11 of the mass spectrometer is connected to a data processing section 16 for digitizing and storing the ion intensity data as a result of the mass analysis. ing.

Further, the mass spectrometer is provided with a first gas supply section 17 for supplying a nitrogen gas 2 which is a first carrier gas.
And a second gas supply unit 18 for supplying the oxygen gas 8 which is the second carrier gas.
Alternatively, a mass flow controller 19 which is a flow rate adjusting means for adjusting the flow rate of the oxygen gas 8 is connected.

That is, the quartz chamber 3 of the thermal desorption unit 5
A first gas supply unit 17 is connected to the introduction system 3 a of FIG. 1 through a first pipe 20, and a mass flow controller 19 is attached to the first pipe 20.

Further, the fourth pipe 23 connected to the second pipe 21 connected to the discharge system 3b of the quartz chamber 3 is connected to the second gas supply unit 18 via the fifth pipe 24, and the fifth gas supply unit 18 is connected to the fourth pipe 23. A mass flow controller 19 is attached to the pipe 24.

Next, the mass spectrometric method according to the present embodiment will be described.

First, the nitrogen gas 2 is supplied into the quartz chamber 3 from the first gas supply unit 17 through the first pipe 20.

At this time, the mass flow controller 19 adjusts the flow rate of the nitrogen gas 2 to a predetermined flow rate.

Subsequently, the semiconductor wafer 1 is heated by the infrared lamp 15 under a predetermined temperature rising condition.

As a result, the deposit adhered to the semiconductor wafer 1 is desorbed by heating to form the desorbed gas 4.

After that, the desorbed gas 4 is discharged from the quartz chamber 3 together with the nitrogen gas 2 and flowed into the second pipe 21.

As a result, the nitrogen gas 2 flowing through the second pipe 21 is divided into the third pipe 22 and the fourth pipe 23.

Here, the nitrogen gas 2 flowing through the third pipe 22
Are introduced into the first ion forming section 6 of the first mass spectrometric section 7.

Further, nitrogen gas 2 flowing through the fourth pipe 23
The oxygen gas 8 is supplied from the second gas supply unit 18 through the fifth pipe 24 to mix the nitrogen gas 2 and the oxygen gas 8 to form the mixed desorbed gas 9.

At this time, the mass flow controller 19 adjusts the flow rate of the oxygen gas 8 to a predetermined flow rate.

As a result, the mixed desorbed gas 9 is fed to the fourth pipe 2
The second ion forming unit 10 of the second mass spectrometric unit 11
To be introduced.

After that, in the first ion forming section 6, the desorbed gas 4 is positively ionized by corona discharge in the atmospheric pressure atmosphere.

At the same time, in the second ion forming section 10, the mixed desorbed gas 9 containing the desorbed gas 4 is negatively ionized by corona discharge in the atmospheric pressure atmosphere.

Further, in the quadrupole mass spectrometric section 12 in which a vacuum atmosphere is formed by the vacuum exhaust means 14, mass analysis of positive ions is performed.

At the same time, in the quadrupole mass spectrometric section 13 in which a vacuum atmosphere is formed by the vacuum evacuation means 14, mass analysis of negative ions is performed.

After that, the ion intensity data as the result of the mass spectrometry is used for the first mass spectrometric section 7 and the second mass spectrometric section 11.
After being amplified by the amplifier 25 connected to each of the above, the digitized ion intensity data is stored in the data processing unit 16 connected to each of the amplifiers 25.

According to the mass spectrometry method and apparatus of the present embodiment, the following operational effects can be obtained.

That is, the desorption gas 4 discharged from the quartz chamber 3 is provided with a first ion forming section 6 for positive ionization in an atmospheric pressure atmosphere, and the desorption gas is a desorption gas. The negative deionization of the mixed desorption gas 9 formed by supplying the oxygen gas 8 to the No. 4 in the atmospheric pressure atmosphere
The second which is provided with the ion forming unit 10 and which performs mass spectrometry of ions
By including the mass spectrometric section 11, positive and negative ionization can be performed simultaneously by the same desorbed gas 4 in the first ion forming section 6 and the second ion forming section 10, and further positive and negative ions can be generated. At the same time, mass analysis can be performed by the first mass analysis unit 7 and the second mass analysis unit 11.

This eliminates the need to separately perform positive and negative ionization and mass analysis of positive and negative ions in two steps, positive and negative, so that positive and negative ion analysis can be performed by one semiconductor wafer 1. It is possible to reduce the preparation time of the semiconductor wafer 1 and the analysis time of the adhered substance thereof by almost half.

Further, the amount used for mass spectrometric analysis of the semiconductor wafer 1 can be reduced to almost half.

Further, since the positive and negative ion analysis can be performed by one semiconductor wafer 1, as compared with the case where the positive and negative ion analysis is performed by two semiconductor wafers 1, It is possible to eliminate the physical property error originally included in, and improve the reliability of the analysis result.

Since positive and negative ion analysis can be performed by one inspected object, the inspected object under the same conditions can be repeatedly used, such as analysis of industrial defective products other than semiconductors. The amount of information obtained from the analysis result can be increased when manufacturing is impossible or when there is only one inspection object.

Further, the desorption gas 4 or the mixed desorption gas 9 is ionized by corona discharge,
Positive and negative ionization can be performed in an atmospheric pressure atmosphere.

Since the data processing unit 16 for digitizing and storing the ion intensity data as the result of the mass spectrometry is connected, the ion intensity data for each semiconductor wafer 1 can be stored.

Further, since the mass flow controller 19 which is a flow rate adjusting means for adjusting the flow rate of the nitrogen gas 2 or the oxygen gas 8 is provided, the flow rate of the nitrogen gas 2 or the oxygen gas 8 is controlled by the material of the semiconductor wafer 1 or the like. The flow rate can be adjusted according to the size.

As a result, it is possible to improve the accuracy of ion mass analysis.

Although the invention made by the present inventor has been specifically described based on the embodiments of the present invention, the present invention is not limited to the embodiments of the present invention, and does not depart from the scope of the invention. It goes without saying that various changes can be made with.

For example, in the above-described embodiment, the case where the data processing section connected to the amplifier is provided in each of the first mass analysis section and the second mass analysis section of the mass spectrometer has been described. Like the mass spectrometer of the other embodiment shown in FIG. 2, the data processing unit 16 (see FIG. 1) may not be connected and the ionic strength data may not be stored.

In this case, the output of the ion intensity data is a waveform output in an analog format.

Further, in the above embodiments and other embodiments, the case where the inspection object is a semiconductor wafer has been described, but the inspection object is not limited to the semiconductor wafer, but a wafer carrier formed of fluororesin or the like. It may be a resin member.

Furthermore, the mass spectrometer shown in FIG.
A check valve 26 is installed in the pipe 23.

This makes it possible to prevent the oxygen gas 8 as the second carrier gas from flowing into the third pipe 22, that is, the oxygen gas 8 from flowing into the first mass spectrometric section 7.

However, the check valve 26 does not have to be installed as in the mass spectrometer shown in FIG.

Further, in the mass spectrometers of the above-mentioned embodiment and other embodiments, the first mass analysis section performs positive ionization and mass analysis of positive ions, and further the second mass analysis section carries out negative ionization. The first mass spectrometric section performs negative ionization and mass spectrometric analysis of negative ions according to the first and second carrier gases used, and further the second mass spectrometric section It is also possible to perform positive ionization with and mass analyze the positive ions.

The mass spectroscopes in the above-mentioned embodiments and other embodiments analyze the adhering substances adhering to the surface of the semiconductor wafer. It can be used as a means for analyzing the adhered matter adhered to and the surface state thereof. For example, the inspected object may be a resin member formed of a polymer material or another catalyst.

The first or second carrier gas used in the mass spectrometer may be a gas other than nitrogen gas or oxygen gas, such as argon gas or helium gas, or other inert gas. It may be.

[0083]

Advantageous effects obtained by typical ones of the inventions disclosed by the present application will be briefly described as follows.
It is as follows.

(1). A first mass spectrometric section having a first ion forming section for performing either positive or negative ionization of the desorbed gas and for mass spectrometric analysis of ions; and a mixed desorption formed by supplying a second carrier gas to the desorbed gas. By providing a second ion forming unit for performing either positive or negative ionization of the separated gas, and having a second mass analysis unit for mass-analyzing the ions, positive and negative ionization can be performed simultaneously by using the same desorbed gas. Can be carried out by the ion forming section of the above, and both ions can be analyzed simultaneously by separate mass spectrometric sections. As a result, since both positive and negative ions can be analyzed by one inspected object, the preparation time of the inspected object and the analysis time of the adhered substance can be shortened to almost half.

(2). Since positive and negative ion analysis can be performed by one inspected object, the amount of the inspected object used for mass spectrometry can be reduced to almost half.

(3). Since the positive and negative ion analysis can be performed by one inspected object, the physical property error originally included between the inspected objects can be compared with the case where the positive and negative ion analysis is performed by two inspected objects. It can be omitted and the reliability of the analysis result can be improved.

(4). Since positive and negative ion analysis can be performed by one inspected object, when it is impossible to repeatedly manufacture the inspected object under the same conditions as in the case of industrially defective products, or The amount of information obtained from the analysis result can be increased when there is only one inspected object.

(5). By ionizing the desorbed gas or the mixed desorbed gas by corona discharge, positive and negative ionization can be performed in the atmospheric pressure atmosphere.

(6). Since the data processing unit for digitizing and storing the ion intensity data as the result of the mass spectrometry is connected, it is possible to store the ion intensity data for each inspection object.

(7). Since the flow rate adjusting means for adjusting the flow rate of the first or second carrier gas is provided, the flow rate can be adjusted to a suitable flow rate based on the material and size of the inspection object. As a result, it is possible to improve the accuracy of ion mass analysis.

[Brief description of drawings]

FIG. 1 is a structural conceptual diagram showing an example of an embodiment of a structure of a mass spectrometer according to the present invention.

FIG. 2 is a structural conceptual diagram showing an example of a structure of a mass spectrometer according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor wafer (inspection object) 2 Nitrogen gas (1st carrier gas) 3 Quartz chamber (processing container) 3a Introduction system 3b Discharge system 4 Desorption gas 5 Temperature rising desorption part 6 1st ion formation part 6a Ion source 7 First mass spectrometric section 8 Oxygen gas (second carrier gas) 9 Mixed desorption gas 10 Second ion forming section 10a Ion source 11 Second mass spectrometric section 12 Quadrupole mass spectrometric section 12a Treatment section 12b Treatment section 12c Orifice 12d Electrode 12e Deflector 12f Ion detector 13 Quadrupole mass spectrometric section 13a Processing section 13b Processing section 13c Orifice 13d Electrode 13e Deflector 13f Ion detector 14 Vacuum exhaust means 15 Infrared lamp (heating means) 16 Data processing section 17 First gas supply Part 18 Second gas supply part 19 Mass flow controller (flow rate adjusting means) 20 1 pipe 21 the second pipe 22 third pipe 23 fourth pipe 24 fifth pipe 25 amplifier 26 check valve

Claims (5)

[Claims] 1. A mass spectrometric method for ionizing and analyzing a deposit adhered to an object to be inspected, comprising supplying a first carrier gas into a processing container to heat the object to be inspected. The desorption gas is desorbed by heating to form a desorbed gas, and the desorbed gas is discharged from the processing container together with the first carrier gas and introduced into a first mass analysis unit, and the first mass analysis unit described above. After performing either positive or negative ionization of the desorbed gas in an atmosphere of atmospheric pressure, mass analysis of ions is performed, and a second carrier gas is supplied to the desorbed gas discharged from the processing container together with the first carrier gas. The formed mixed desorption gas is introduced into the second mass spectrometric unit, and either positive or negative ionization of the mixed desorption gas is performed in the second mass spectrometric unit in the atmospheric pressure atmosphere, and then the ions are mass analyzed. Mass fraction characterized by Method. 2. A mass spectrometer for ionizing and analyzing an adhered matter adhered to an object to be inspected, wherein the object to be inspected is heated in a processing container to which an ionizable first carrier gas is supplied. One of a positive temperature and a negative ionization of the desorption gas discharged from the processing container together with the first carrier gas is large, and the desorption gas is heated and desorbed to form a desorption gas. A first ion forming unit for performing in a pressure atmosphere, and
A first mass spectrometric section for mass spectrometrically analyzing the ions formed in the ion forming section, and a mixture formed by supplying an ionizable second carrier gas to the desorbed gas discharged from the processing container together with the first carrier gas. A second ion forming unit for performing either positive or negative ionization of the desorbed gas in an atmospheric pressure atmosphere,
And a second mass spectrometric section for mass spectrometrically analyzing the ions formed in the second ion forming section. 3. The mass spectrometer according to claim 2, wherein:
A mass spectrometer, wherein the desorbed gas or the mixed desorbed gas is ionized by corona discharge in the first or second ion forming unit or both. 4. The mass spectrometer according to claim 2 or 3, wherein the first or second mass spectrometric section or both digitize and store the ion intensity data resulting from the mass spectrometric analysis. A mass spectrometer characterized in that the parts are connected. 5. The mass spectrometer according to claim 2, 3 or 4, wherein flow rate adjusting means for adjusting the flow rate of the first or second carrier gas is provided. .