JPH0359545B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a secondary ion mass spectrometer that irradiates a sample to be subjected to mass spectrometry with ions and performs mass spectrometry based on the secondary ions generated by the irradiation.

Secondary ion mass spectrometers that irradiate a sample with ions and use the secondary ions generated from the sample to sequentially analyze the surface layer in the depth direction of the sample are generally SIMS (Secondary Ion Mass Spectrometers).
Spectroscopy). By the way, in order to obtain a practical surface layer analysis speed in the depth direction (practical depth analysis speed), the voltage and current for driving the ion gun must be increased to increase the speed of the irradiated ions toward the sample. There is a need. On the other hand, when a sample is irradiated with irradiation ions at high speed, the secondary ions generated from the sample contain a large proportion of atomic ions to molecular ions. However, with only analysis information based on atomic ions, it is possible to know what elements are present in a sample and in what proportions, but it is difficult to know what form these elements have with other elements. In other words, it is not possible to accurately know what compounds (molecules) are present in the sample and in what proportions. Therefore, in order to know exactly what kind of compounds are present in a sample, it is necessary to reduce the ion irradiation rate to the sample to suppress the decomposition of molecules into atoms as much as possible. It is necessary to increase the proportion of ions included. By the way, in addition to analytical information based on atomic ions, in order to obtain analytical information based on molecular ions,
In the prior art, even with one ion gun, the voltage and current for driving the ion gun are changed and controlled in accordance with each analysis information, or the ion gun is controlled to be changed in a manner suitable for obtaining each analysis information. Gas replacement is performed to change the type of ions emitted. However, it actually takes time to change and control the voltage and current to drive the ion gun to accurately obtain ion irradiation conditions that correspond to each analysis information, and gas replacement takes a very long time and is not practical. There are problems such as difficulty in obtaining depth analysis speed and undesirability.

In other words, each time the irradiation conditions are changed as described above, a time-consuming task is required to confirm whether the ion beam is accurately irradiating the sample placed in the analysis room, or In some cases, it may be necessary to temporarily change the ion beam irradiation position on the sample and move the sample within the analysis chamber to ensure that the ions do not damage the target part of the sample. There were also some undesirable problems.

Therefore, an object of the present invention is to solve the above-mentioned technical problems by providing at least two ion guns and irradiating samples by alternately switching the ion beams constantly emitted from these ion guns. , there is no need for gas replacement and no need to change or control voltage or current; therefore, it is possible to contain secondary ions in the form of molecular ions in addition to atomic ions in a very short time, accurately and easily. It is an object of the present invention to provide a secondary ion mass spectrometer in which a desired analysis can be performed by generating secondary ions alternately based on the ratio.

FIG. 1 is a schematic diagram of an apparatus according to an embodiment of the present invention. The ion gun 1 irradiates the surface layer of the sample 2 with ions. The ion gun 1 contains active gas such as oxygen and nitrogen, and the sample 2 is irradiated with ions corresponding to the active gas. The ion gun 1 is also configured to be driven by a large voltage or current from a voltage source or current source (not shown).
The ion beam (dashed line 3 in the figure) fired from the ion gun 1 collides with the sample 2 at high speed, and as a result, the surface layer of the sample 2 is exposed in the form of atomic ions (based on the proportion of ions contained). Secondary ions are generated. The sample 2 is placed at a predetermined location within the analysis chamber 4, and the beam 5 of secondary ions generated from the sample 2 passes into the mass spectrometer 6 as shown by the arrow. Mass spectrometry section 6
analyzes the mass based on the incoming secondary ion beam 5, and sends the analysis data to a data analysis device such as a microcomputer (not shown). The data analysis device analyzes the type of element, the content ratio of the element, etc. in the depth direction of the surface layer of the sample 2 based on the sent analysis data. By the way, since the high-speed ion beam 3 from the ion gun 1 generates many secondary ions in the form of atomic ions from the sample 2, the mass spectrometer 6 and data analysis device
It is not possible to know what compounds (molecules) are present in the sample and in what proportion. Therefore, in this embodiment, in addition to the ion gun 1, another ion gun 7 is provided.

Like the ion gun 1, the ion gun 7 is connected to the analysis chamber 4.
The ion beam 8 is irradiated onto the surface of the sample 2 placed inside the chamber. ion gun 7
is arranged so that the irradiation location of the ion beam 8 on the surface of the sample 2 coincides with the irradiation location of the ion beam 3 from the ion gun 1. The ion gun 7 contains an inert gas such as argon, a reactive gas such as methane, etc., and the ion beam 8 corresponding to these gases is
Sample 2 is irradiated from In addition, ion gun 7
The reason why an inert gas such as argon is included in the ion gun 7 is to prevent the ions constituting the ion beam 8 from having an unfavorable reaction with the surface material of the sample 2. The reason for including reactive gas is
Contrary to the above, this is to make the ions constituting the ion beam 8 react with secondary ions on the surface material of the sample 2 to make it suitable for analysis. The ion gun 7 is also configured to be driven by a low voltage or current from a voltage source or current source (not shown) so as to irradiate the sample 2 with the ion beam 8 at a low speed.

Therefore, from the surface of the sample 2 irradiated with the low-velocity ion beam 8 from the ion gun 7, secondary ions are generated in the form of molecular ions based on the content ratio. The secondary ions 5 in the form of molecular ions are subjected to mass analysis in the mass spectrometer 6 and then analyzed in the data analysis device described above. This makes it possible to accurately determine whether a compound is present.

Next, the surface layer from the sample is peeled off by the high-speed ion beam 3 from the ion gun 1, but the peeling speed (sputtering speed) is controlled by the voltage and current used to drive the ion gun. In this embodiment, the sputtering speed is controlled so as to obtain a practical sputtering speed. In addition, since the ion gun 1 is constantly driven to stabilize the ion beam, an ion beam stopper 9 is connected to the ion gun 1 to prevent the ion beam 3 from irradiating the surface of the sample 2. It is inserted in the middle of the ion path section 10 interposed between the chamber 4 and the ion path section 10 . The ion beam stopper 9 includes an ion beam shielding moving body 93 equipped with an O-ring 91 and a bellows 9.
4. In the illustrated state, the bellows 94 of the ion beam stopper 9 is compressed and the ion beam shielding moving body 93 blocks the ion path in the ion path section 10, so that the ion gun 1 is constantly ejected. The ion beam 3 is covered by an ion beam shielding moving body 93
shielded by. By doing so, the ion beam 3 is prevented from irradiating the surface of the sample 2. The broken line 3 is for showing the progress of the ion beam, and in the illustrated state, the surface of the sample 2 is not irradiated with the ion beam.

On the other hand, the surface layer of the sample 2 is also peeled off by the low-speed ion beam 8 from the other ion gun 7, but the practical sputtering speed depends on the voltage and current from the voltage source and current source mentioned above. Controlled by electric current. Also, in order to stabilize the ion beam, the ion gun 7, like the ion gun 1, always
In order to prevent the ion beam 8 from irradiating the surface of the sample 2 as it is being driven, another ion beam stopper 11 is installed.
It is inserted in the middle of the ion path section 12. The ion beam stopper 11 includes an ion beam shielding moving body 113 equipped with an O-ring 111 and a bellows 1.
14, and in the illustrated state, the ion beam stopper 11 is placed in a position retracted from the ion path section 12.

The switching operation of the ion beam stoppers 9 and 11 is controlled by a switching device (not shown) so that the ion beam stoppers 9 and 11 alternately close the respective ion path sections 10 and 12. Therefore, by alternately switching the ion beam stoppers 9 and 11, the surface of the sample 2 is alternately irradiated with the high speed ion beam 3 and the low speed ion beam 8. In this way, from the surface of sample 2,
Secondary ions containing a large proportion of atomic ions and secondary ions containing a large proportion of molecular ions alternately enter the mass spectrometer 6 .

Next, the operation of this embodiment will be explained with reference to FIG.

The voltage and current are controlled so that high-speed and low-speed ion beams 3 and 8 are emitted from the ion guns 1 and 7, respectively. Ion beam stopper 9
The ion beam shielding moving body 93 is moved away from the ion path section 10, and the ion beam shielding moving body 113 of the other ion beam stopper 11 is moved so as to block the ion path section 12. . The sample 2 is placed at a predetermined location inside the analysis chamber 4 .

In this state, the high-speed ion beam 3 from one of the ion guns 1 irradiates the surface of the sample 2. Then, from the surface layer of sample 2,
Secondary ions in the form of atomic ions are generated, and the secondary ions enter the mass spectrometer 6 where they are subjected to mass analysis, and the data of the analysis is further analyzed by a data analysis device. In this analysis, as shown in the graph [see Figure 2 (1)], where the vertical axis represents the intensity and the horizontal axis represents the depth from the original surface layer of the sample, the intensity varies depending on the depth. How it changes in response is measured. First, in the first analysis stage, at the depth a,
You can see how much of a certain element, for example iron, is contained as a single element. Next, the ion beam shielding moving bodies 93 and 113 of the ion beam stoppers 9 and 11 are moved, so that one of the ion beam shielding moving bodies 93 blocks the ion path section 10. At the same time, the other ion beam shielding moving body 113
Evacuate from the ion path section 12. By doing so, the low-velocity ion beam 8 from the other ion gun 7 irradiates the surface of the sample 2, thereby causing secondary ions in the form of molecular ions to be removed from the surface of the sample 2. Ions are generated, and after entering the mass spectrometer 6, the secondary ions are analyzed by a data analysis device.

As a result, as shown in the qualitative chart (see Figure 2), where the vertical axis represents the intensity and the horizontal axis represents the mass number, a certain element at a depth a from the original surface of the sample 2, e.g. The types of compounds in which iron exists with other elements will be analyzed. That is, according to this qualitative chart, α,
It can be seen that among the three types of iron compounds β and γ, the β iron compound is contained in the sample the most. Next, each of the ion beam shielding moving bodies 9 of the ion beam stoppers 9 and 11
3 and 113 are moved to the state of reaction shown in FIG. 1 to block and evacuate the ion path sections 10 and 12, respectively. Then, this time, the high-speed ion beam 3 from the ion gun 1
The surface of the sample 2 is irradiated, thereby analyzing the content of elements such as iron in the sample at a depth b from the original surface layer of the sample 2, as shown in FIG. . In this second analysis, when the ion beam stoppers 9 and 11 are switched and moved in the opposite direction, a qualitative chart [Second As shown in the graph in Figure 3], elements such as iron compounds (α, β, γ) at a depth b from the original surface of the sample
The content ratio of three types) is analyzed. In this way, the qualitative chart of FIG. 2 also shows the content of a compound of an element, for example iron, at a depth c from the original surface of the sample.

In the above embodiment, the gas contained in the ion gun 1 is an active gas, but this active gas can be used as long as it can generate secondary ions in the form of atomic ions from the surface of the sample. It is not limited to.

Further, in the above embodiments, a mechanical ion beam stopper equipped with an O-ring or a bellows is used to shield the ion beam, but the O-ring is not necessarily necessary, and the bellows is not necessarily required. It is also possible to use other mechanisms other than mechanical ion beam stoppers, and instead of mechanical ion beam stoppers, electrical or magnetic ion beam stoppers that deflect the ion beam and shield the ion beam may also be used. A beam stopper may be used. Furthermore, the above-mentioned embodiment is a SIMS [ion microprobe analyzer,
(also referred to as IMA)].

As explained above, according to the present invention, at least two ion guns are provided, one for emitting high-speed ion beams and the other for emitting low-speed ion beams, and the ion beams are alternately emitted from each ion gun. Since the sample is irradiated at the same time, there is no need for gas replacement, and there is no need to change the voltage or current to control the speed of the ion beam. Therefore, it is very quick, accurate and simple. In addition, secondary ions can be generated alternately in the form of both atomic ions and molecular ions from the sample surface layer, and the desired analysis can be performed accurately. .

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a device according to an embodiment of the present invention, and FIG. 2 is a graph for explaining the operation of the device. 1,7...Ion gun, 2...Sample, 3,8
...Ion beam, 5...Secondary ion beam, 6
... Mass spectrometry section, 9, 11 ... Ion beam stopper, 10, 12 ... Ion path section.

Claims (1)

[Claims] 1. A high-speed ion gun that constantly fires a high-speed ion beam, a low-speed ion gun that constantly fires a low-speed ion beam, an analysis room where the sample can be placed at the ion beam irradiation position, and a combination of the high-speed ion gun and the analysis room. A fast ion beam and a slow ion beam are placed between the ion path section between the ion gun and the analysis chamber, and the ion path section between the slow ion gun and the analysis room, and are emitted from the fast ion gun and the slow ion gun, respectively. and an ion beam stopper that electromagnetically or mechanically shields the ion beam so that the ion beam is alternately irradiated onto the sample, thereby obtaining analysis information based on atomic ions and molecular ions of the sample. A secondary ion mass spectrometer characterized by: