JP2011228069A - Time-of-flight secondary ion mass spectrometer using gas cluster ion beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a time-of-flight secondary ion mass spectrometer using a gas cluster ion beam in which secondary ions with a high mass-number can be pulsed while holding the two-dimensional information of the irradiation surface.SOLUTION: Secondary ions emitted from the irradiation surface of an analysis sample 5 are extracted by an extraction electrode 15 while holding the two-dimensional information of the irradiation surface and enter a pulse gate electrode. The secondary ions entered between first and second electrodes 21a and 21b from a first passage hole 23a are accelerated by the pulse voltage. The secondary ions passed through a second passage hole 23b enter an analyzer 40 consisting of a plurality of fan-shaped electrostatic analyzers which perform spatial and temporal convergence. A plurality of electrostatic analyzers are arranged so that only the secondary ions accelerated by the pulse gate electrode are selected, and the secondary ions having the same charge-to-mass ratio enter an ion detector 50 simultaneously while holding the two-dimensional information of the irradiation surface and the position and time are detected.

Description

  The present invention relates to a time-of-flight secondary ion mass spectrometer using a gas cluster ion beam as a primary ion beam.

Time-of-flight secondary ion mass spectrometry (hereinafter referred to as TOF-SIMS) is generated from a sample by irradiating the sample with primary ions extracted from an ion source with acceleration energy of several tens of keV. In this method, the mass of secondary ions is identified according to the time of flight and the atomic / molecular composition of the sample surface is clarified. When the sample surface is two-dimensionally scanned with a liquid ion beam such as Ga ions or Au ions, a two-dimensional distribution of mass can be obtained with a spatial resolution of several μm or less. Recently, Bi ions and C ₆₀ ions have begun to be used instead of Ga ions and Au ions for the purpose of improving the yield of secondary ions for organic substances.

  On the other hand, a gas cluster ion beam (GCIB) having a size of hundreds to thousands of atoms / molecules has a small energy of several eV or less, so that GCIB is used as a primary ion. If it is possible, the polymer sample is hardly decomposed into fragments, and detection of molecular ions can be expected. Moreover, since the secondary ion yield is large, an improvement in sensitivity can be expected, and the application range of TOF-SIMS is considered to be expanded.

However, when GCIB is used as a primary ion beam in place of conventional liquid metal ions, the following two problems arise.
The first problem is that GCIB has an energy distribution of about several tens of eV corresponding to the cluster size, and the beam spread due to the chromatic aberration of the lens is inevitable, so that a beam diameter of about several μm can be obtained. It is difficult. Therefore, when the sample surface is two-dimensionally scanned by GCIB, it is difficult to obtain a spatial resolution like the above-described liquid ion beam because the beam optical system is complicated.

The second problem is that since GCIB has a wide size distribution, the speed of GCIB accelerated by a constant energy differs depending on the size, and the drift space to the sample is separated according to the size while traveling. It is difficult to generate a short ion packet of several nsec or less like a beam. As will be described later, in TOF-SIMS, the smaller the time width of the ion beam of the primary beam, the larger the mass resolution can be obtained, but in GCIB, only an ion packet of several μsec at most can be obtained. Therefore, there is a need for a technique for continuously irradiating the sample with GCIB and pulsing the secondary ions emitted from the irradiated surface.
In order to use GCIB as a primary ion beam of TOF-SIMS, it is necessary to solve these two problems.

  In Patent Document 2, in an imaging mass spectrometer, a sample is irradiated with a primary ion beam having a beam diameter of about 0.5 to 1 mm, and the relative positional relationship of secondary ions desorbed from a wide irradiation surface is maintained. A method for obtaining a two-dimensional mass distribution of a sample using TOF-SIMS is disclosed. In other words, it is considered that the first problem can be solved by a method in which the relative positional relationship of secondary ions emitted from different positions on the irradiation surface is maintained as it is rather than two-dimensionally scanning the sample surface with an ion beam. .

However, Patent Document 2 does not describe a secondary ion pulsing technique when the primary ion beam, which is the second problem, is continuous.
An orthogonal acceleration method used in gas chromatography (GC-MS) or the like is widely known in this field as a method for pulsing secondary ions generated continuously. In this method, a two-dimensional position of a sample is used. There is a problem that information is lost.

  Further, in order to generate a continuous ion beam into an ion packet with a short pulse width, a lateral beam deflection method (lateral gate) using a mass gate (see Non-Patent Document 1) is also well known. In the case of large ions, there is a disadvantage that a non-negligible time is required to pass through the deflection electric field, and the pulse width becomes long. For example, the time required for an ion having a mass number of 5000 having an acceleration energy of 2 keV to pass through an effective deflection electric field region of 2 mm is 230 nsec. Therefore, a voltage pulse having a pulse width of 115 nsec or more must be applied to the deflection electrode. In order to shorten the pulse width, it is necessary to extremely shorten the beam traveling direction (axial direction) length of the deflection electric field, but in order to obtain a sufficient deflection angle for turning on / off the beam, a high deflection voltage is required. Therefore, the axial length of the deflection electric field cannot be made extremely short.

In general, the resolution R of a time-of-flight mass spectrometer is given by R = M / ΔM = T / 2ΔT. Here, T is the flight time of the secondary ions, and ΔT is the time width of the secondary ion packet.
In order to increase the resolution, it is only necessary to increase T while keeping ΔT constant. As a method of increasing the flight time T without increasing the size of the analyzer, a method of circulating the same orbit (see Non-Patent Document 2) or a multiple reflection method using an ion mirror (see Patent Document 1) is known. However, it is currently unknown whether multiple rounds and multiple reflections are possible while maintaining two-dimensional information.
In other words, in order to use GCIB as a primary ion beam of TOF-SIMS, a technique for pulsing high-mass secondary ions while retaining the two-dimensional information of the sample is necessary. No technology has been found.

JP 2009-512162 A JP 2007-157353 A

P. R. Vlasak, et al. Rev. Sci. Instrument. , 1996, 67 (1), p68. Toyoda, J.H. Vac. Soc. Jpn (vacuum), 2007, 50, No24, p246 W. P. Poschenrieder, Int. J. et al. Mass Spectrom. Ion Phys. , 1972, 9, p357

  The present invention was created in order to solve the above-mentioned disadvantages of the prior art, and its purpose is a TOF using GCIB capable of pulsing secondary ions having a high mass number while maintaining the two-dimensional information of the irradiated surface. -To provide a SIMS device.

  In order to solve the above problems, the present invention irradiates a surface of an analysis sample disposed in a vacuum chamber, a vacuum exhaust device that evacuates the vacuum chamber, and a gas cluster ion beam, An ion gun for emitting secondary ions having positive or negative charges made of ions of the analysis sample from an irradiation surface irradiated with a gas cluster ion beam, and the secondary ions emitted from the irradiation surface of the analysis sample An extraction electrode drawn from above, a pulse gate electrode portion in which the secondary ions extracted by the extraction electrode are pulse-accelerated, and spatial and temporal convergence of the secondary ions accelerated by the pulse gate electrode portion Ion detection that detects a plurality of sector electrostatic analyzers to be performed and an incident position of the secondary ions that have passed through the plurality of sector electrostatic analyzers according to an incident time The pulse gate electrode portion is arranged in the traveling direction of the secondary ions accelerated by the extraction electrode, and is provided with first and second passage holes, respectively. A pulsed voltage is applied to the first and second electrodes and the first electrode, and the secondary ions that have entered between the first and second electrodes from the first passage hole are moved to the first electrode. The secondary ion accelerated by the pulse gate electrode portion converges at a predetermined convergence position at a time corresponding to a charge mass ratio. Thereafter, the secondary ions are incident on the plurality of sectoral electrostatic analyzers that perform spatial and temporal convergence of the secondary ions, and the plurality of sectoral electrostatic analyzers each include an annular outer circumferential electrode and the outer circumferential surface. Formed by the inner circumference electrode located on the inner circumference of the electrode. And the secondary ions incident on the ion passages pass through the ion passages in a time corresponding to a charge-mass ratio by a voltage applied between the outer peripheral electrode and the inner peripheral electrode. It is a TOF-SIMS device that is allowed to pass through.

  The present invention is a TOF-SIMS device, wherein the plurality of fan-shaped electrostatic analyzers are configured to allow a longer time to pass as the energy increases even if the charge mass ratio of the incident secondary ions is the same. .

Since the two-dimensional mass distribution of the sample can be detected without scanning the primary ion beam on the sample surface, the measurement time is greatly shortened.
When GCIB is used for a primary ion beam, a two-dimensional mass distribution can be detected even for a polymer and a biological sample, so that the application range is greatly expanded in the medical field and the like.

The internal block diagram of an example of the TOF-SIMS apparatus of this invention

The structure of the TOF-SIMS device using the GCIB according to the present invention will be described. FIG. 1 shows an internal configuration diagram of an example of a TOF-SIMS device 10 according to the present invention.
The TOF-SIMS device 10 includes a vacuum chamber 11 and a vacuum exhaust device 12. The vacuum evacuation device 12 is connected to the vacuum chamber 11 so that the inside of the vacuum chamber 11 can be evacuated.
A sample stage 14 is arranged in the vacuum chamber 11, and the analysis sample 5 is placed on the sample stage 14.

The TOF-SIMS apparatus 10 has an ion gun 13 that can emit GCIB from the muzzle. The ion gun 13 is installed air-tightly through the inner wall of the vacuum chamber 11 so that the muzzle is positioned in the vacuum chamber 11, and is configured to irradiate the GCIB on the surface of the analysis sample 5 in the vacuum chamber 11.
A plate-like extraction electrode 15 having an opening diameter of several Φ is disposed at a position facing the surface of the analysis sample 5 in the vacuum chamber 11.

  A sample power source 16 is electrically connected to the sample stage 14 on which the analysis sample 5 is placed, and a negative or positive DC voltage is applied corresponding to the positive or negative charge of the secondary ions. The extraction electrode 15 is electrically grounded so that an electric field can be formed between the sample stage 14 and the extraction electrode 15.

  As will be described later, when GCIB is irradiated to the analysis sample 5, secondary ions released from the irradiation surface are extracted from the analysis sample 5 on the irradiation surface by the electric field between the analysis sample 5 and the extraction electrode 15. It is accelerated toward the electrode 15 and pulled out.

  Flat plate-shaped first and second electrodes 21a and 21b are arranged in this order on the beam downstream side of the extraction electrode 15 (the traveling direction of secondary ions extracted by the extraction electrode 15). The first and second electrodes 21a and 21b are provided with first and second passage holes 23a and 23b, respectively. Here, the first and second passage holes 23a and 23b are both Φ3, and the distance between the first and second electrodes 21a and 21b is 10 mm.

  A pulse power source 22 is electrically connected to the first electrode 21a, and the second electrode 21b is electrically grounded. The pulse power source 22 is configured to apply a pulse voltage to the first electrode 21a to form an electric field between the first and second electrodes 21a, 21b.

  As will be described later, the secondary ions that enter between the first and second electrodes 21a and 21b from the first passage hole 23a while maintaining the relative two-dimensional positional relationship on the irradiation surface are the first and second The electric field between the electrodes 21a and 21b is accelerated toward the second electrode 21b grounded from the first electrode 21a, and after passing through the second passage hole 23b, the charge mass ratio (q / M) at a predetermined convergence position (hereinafter referred to as a spatial convergence point 30). Here, q and m indicate the charge and mass of the secondary ions, respectively.

  The secondary ions located between the first and second electrodes 21a and 21b are kept at a predetermined time at a time corresponding to the charge mass ratio while maintaining a relative two-dimensional positional relationship in a plane perpendicular to the traveling direction. Acceleration that converges at the spatial convergence point 30 is called pulse acceleration.

  When a device for accelerating the secondary ions extracted by the extraction electrode 15 is called a pulse gate electrode section, the pulse gate electrode section is composed of first and second electrodes 21 a and 21 b and a pulse power source 22.

  A plurality of fan-shaped electrostatic analyzers 40 capable of temporal and spatial convergence are arranged on the beam downstream side of the spatial convergence point 30. Here, a TRIFT type analyzer is arranged as an example of such an analyzer 40 (Non-Patent Document 4).

  Here, “temporal convergence” means that the flight time from the incident point of the secondary ions to the analyzer 40 to the ion detector 50 is other than the time difference caused by the difference in the mass of the incident secondary ions. Even if the initial conditions (position coordinates, angle and energy in a plane perpendicular to the optical axis) are different, if the mass and charge are the same, the ion detector 50 is reached at exactly the same time. Means.

  “Spatial convergence” refers to the initial condition of energy while maintaining the relative two-dimensional positional relationship (secondary ion image) in a plane perpendicular to the optical axis (center trajectory) at the incident point of the analyzer 40. This means that the light is incident on the ion detector 50 without being enlarged or reduced, that is, is imaged. That is, it means that the detection surface of the ion detector 50 is reached with the same two-dimensional positional relationship as the relative two-dimensional positional relationship on the sample of a plurality of secondary ions.

A path from the spatial convergence point 30 to the TRIFT analyzer 40 is referred to as a first drift distance L ₃ . The secondary ions accelerated by the pulse gate electrode portion converge at the space convergence point 30 at a time corresponding to the charge mass ratio, and are then collimated by the lens 35 installed in the first drift distance L ₃ path. The light enters the TRIFT type analyzer 40. In the TRIFT type analyzer 40, the incident secondary ions must be parallelized so that the secondary ion image from the analysis sample 5 is formed at the detection position.
(Non-Patent Document 4) B. W. Schueler, Microsc. Microanal. Microstruct, 3 (1992) p119
Here, the TRIFT type analyzer 40 has three curved portions 41 ₁ , 41 ₂ , 41 ₃ and four straight portions D ₁ , D ₂ , D ₃ , D ₄ , and the straight portions and the curved portions are in the vacuum chamber 11. Are arranged side by side so as to form a ring as a whole. Assuming that the curvature R ₀ = D of the TRIFT type analyzer 40, the lengths of the linear portions of the codes D ₁ , D ₂ , D ₃ , and D ₄ are D / 2, D, D, and D / 2, respectively.

The curved portions 41 ₁ , 41 ₂ , 41 ₃ are respectively the outer peripheral electrodes 41a ₁ , 41a ₂ , 41a ₃ and the inner peripheral electrodes 41b ₁ , 41b ₂ , 41b located on the inner periphery of the outer peripheral electrodes 41a ₁ , 41a ₂ , 41a _3. Has _three . Hereinafter, an annular passage formed at a position between the outer peripheral electrodes 41a ₁ , 41a ₂ , 41a ₃ and the inner peripheral electrodes 41b ₁ , 41b ₂ , 41b ₃ is called an ion passage.

A power supply device (not shown) is electrically connected to the outer peripheral electrodes 41a ₁ , 41a ₂ , 41a ₃ and the inner peripheral electrodes 41b ₁ , 41b ₂ , 41b _3, and the power supply devices are connected to the outer peripheral electrodes 41a ₁ , 41a ₂ , 41a ₃ . An electric field is formed in the ion passage between the inner peripheral electrodes 41b ₁ , 41b ₂ , and 41b ₃ .

  The secondary ions incident on the analyzer 40 pass through the ion passage in a time corresponding to the charge mass ratio of the secondary ions, and the secondary ions having a large energy even at the same charge mass ratio are longer than the secondary ions having a small energy. It passes through the ion passage in time.

Specifically, in the ion passage, among a plurality of secondary ions having the same charge-mass ratio, a secondary ion having a higher energy is applied to the outer peripheral electrodes 41a ₁ , 41a ₂ , 41a ₃ than a secondary ion having a lower energy. It takes a long time to pass through the ion path because it flies along a close path and flies over a substantially long flight distance.

When a route from TRIFT analyzers 40 to the ion detector 50 is called a second drift distance L _4, secondary ions having passed through the analyzer 40, ion detector flying the second drift distance L ₄ 50 is incident.

Among a plurality of secondary ions having the same charge-mass ratio, a secondary ion having a high energy passes through the first drift distance L ₃ and the second drift distance L ₄ in a shorter time than a secondary ion having a low energy. However, it takes a long time to pass through the ion passage by the time difference.

In other words, secondary ions having the same charge-mass ratio pass through the first drift distance L ₃ , the ion path, and the entire second drift distance L _{4 in} the same time regardless of the energy difference. Has been.

  Furthermore, the analyzer 40 allows the plurality of secondary ions incident from one end to have the same two-dimensional positional relationship as the relative two-dimensional positional relationship in a plane perpendicular to the traveling direction (optical axis) when entering. It is comprised so that it may inject from an end.

Since the secondary ions are incident on one end of the analyzer 40 while maintaining the relative two-dimensional positional relationship on the irradiation surface, the analyzer 40 has the same two-dimensional positional relationship as the relative two-dimensional positional relationship on the irradiation surface. the injection from the other end, is incident on the second drift distance L ₄ after flying parallel to each other, while the ion detector 50 and holds the same two-dimensional position relationship between the relative two-dimensional positional relationship between the irradiation surface .

  The ion detector 50 is a microchannel plate (MCP) having a large number of channel-type secondary electron multipliers bundled in a plane, and detects the incident position of incident secondary ions corresponding to the incident time. It is configured.

  A data processing unit 51 is disposed outside the vacuum chamber 11. The data processing unit 51 is connected to the ion detector 50 and the pulse power source 22, and the secondary voltage is determined from the application start time of the pulse voltage at the pulse power source 22 and the incident time of the secondary ions detected by the ion detector 50. The charge-mass ratio of ions is calculated. Therefore, a two-dimensional distribution of the charge-mass ratio of atoms / molecules constituting the irradiation surface of the analysis sample 5 can be obtained from the calculation result.

A mass spectrometry method using the TOF-SIMS apparatus 10 of the present invention will be described.
The inside of the vacuum chamber 11 is evacuated. Thereafter, evacuation is continued and the vacuum atmosphere in the vacuum chamber 11 is maintained.
While maintaining the vacuum atmosphere in the vacuum chamber 11, the analysis sample 5 is loaded into the vacuum chamber 11 by a loading mechanism (not shown) and placed on the sample table 14 facing the extraction electrode 15. Here, a voltage of 2000 V is applied to the sample stage 14 to form an electric field with the extraction electrode 15 that is electrically grounded.

The irradiation surface of the analysis sample 5 is irradiated from the ion gun 13 with GCIB. Thereafter, the GCIB irradiation is continued until the mass analysis of the irradiated surface is completed.
Secondary ions having positive or negative charges made of ions of the analysis sample 5 are released from the irradiation surface irradiated with GCIB. The secondary ions fly parallel to each other from the analysis sample 5 toward the extraction electrode 15 while maintaining the relative two-dimensional positional relationship on the irradiation surface by the electric field between the analysis sample 5 and the extraction electrode 15. To be accelerated.

The energy distribution of the monovalent secondary ions accelerated by the extraction electrode 15 is a distribution obtained by adding an initial energy of several eV to several tens of eV to the center value of 2000 eV.
The secondary ions extracted by the extraction electrode 15 are first and second electrodes 21a, 21a from the first passage hole 23a of the pulse gate electrode portion while maintaining the relative two-dimensional positional relationship on the irradiation surface. It enters between 21b and passes through the second passage hole 23b.

The three curved portions 41 ₁ , 41 ₂ , 41 ₃ of the TRIFT type analyzer 40 are connected to the first, second, and third electrostatic analyzers in order from the upstream side to the downstream side in the secondary ion traveling direction. Call.
A positive voltage is applied to the outer peripheral electrodes 41a ₁ , 41a ₂ and 41a ₃ of the first, second and third electrostatic analyzers 41 ₁ , 41 ₂ and 41 ₃ , and a negative voltage is applied to the inner peripheral electrodes 41b ₁ , 41b ₂ and 41b ₃ . A voltage is applied, and an electric field is formed in the ion passage so that secondary ions having energy greater than 2100 eV and less than 2200 eV can pass.

Here, a slit 43 is arranged in the straight line portion D ₂ on the downstream side of the first electrostatic analyzer 41 ₁ . The slit 43 is disposed so as to intersect with the flight path of secondary ions whose energy is 2100 eV or less or 2200 eV or more among the secondary ions incident on the first electrostatic analyzer 41 ₁ .

Secondary ions have passed through the second passage hole 23b of the pulse gate electrode portion, while maintaining the relative two-dimensional positional relationship between the irradiation surface, after flying a first drift distance L _3, the first The light enters the electrostatic analyzer 41 ₁ .

Before the pulse voltage application step described later, monovalent secondary ions are incident on the first electrostatic analyzer 41 ₁ with energy smaller than 2100 eV. Will not reach.
Further, since secondary ions having a valence of 2 or more are incident on the first electrostatic analyzer 41 ₁ with energy larger than 2200 eV, they collide with the slit 43 and are absorbed and do not reach the ion detector 50.

  Next, as a pulse voltage application step, a positive voltage of 200 V (referred to as a pulse voltage) is applied to the first electrode 21a with a steep rise, and at least when the pulse voltage application starts, the first electrode 21a passes through the first passage hole 23a. The pulse voltage is continuously applied until the secondary ions pass through the second passage hole 23b.

An electric field having a magnitude of E ₁ = 2 × 10 ⁴ V / m is formed between the first and second electrodes 21a and 21b. First and second electrodes 21a, 21b the secondary ions located between the electric field E ₁ that is formed, are accelerated towards the second electrode 21b from the first electrode 21a, the second passage hole 23b Pass through.

When the flight distance of the secondary ions having passed through the second passage hole 23b and L _2, first and second electrodes 21a, secondary ions from the start of application of the pulse voltage to 21b the distance L ₂ The time t _1-2 required to fly up to is given by the following equation. The first term is the required time between the first and second electrodes 21a and 21b, and the second term is the required time after passing through the second passage hole 23b.

Where U ₁ = U ₀ (1 + δ)
U ₀ : acceleration voltage δ at the extraction electrode 15 δ = ΔU / U ₀ ΔU: full width at half maximum U ₂ = U ₁ + E ₁ × secondary energy (initial energy) distribution when incident on the first passage hole 23a s
s: The position of the secondary ion between the first and second electrodes 21a and 21b at the time when the application of the pulse voltage is started (distance measured from the second electrode 21b)
When δ << 1 and E ₁ × s / U ₀ << 1 are expanded in series, the first order term is obtained.

The first term becomes zero by choosing L ₂ = 2U ₀ / E ₁ = 200 mm. That is, t _1-2 does not depend on the position s of the secondary ion at the time when the application of the pulse voltage is started. If δ = 0, the secondary ion having the same charge mass ratio (q / m) is L _2. = A position of 200 mm is reached at the same time. The position where L ₂ = 200 mm is the aforementioned spatial convergence point 30.

Paragraph is the same charge-to-mass ratio the time difference at the location of the initial energy distribution based on .DELTA.U L ₂ of (q / m) secondary ions having a (full width at half maximum of the distribution of the time that passes through the position of the L ₂₎ . Hereinafter, the value of the second term is referred to as a time difference of δ.

As described above, the full width at half maximum ΔU of the initial energy distribution may reach several tens of eV. If the acceleration voltage U _{0 of} secondary ions is 2000 V and ΔU = 20 V, δ = ΔU / U ₀ = 0.01 (1%).

The monovalent secondary ions accelerated by the pulse voltage are accelerated to energy in a range larger than 2000 eV and smaller than 2200 eV when δ = 0 before passing through the second passage hole 23b. The aircraft enters the TRIFT analyzer 40 after flying the first drift distance L ₃ while maintaining the dimensional relative positional relationship.

  As described above, the electric field in the ion passage of the TRIFT type analyzer 40 is set so as to pass secondary ions having an energy larger than 2100 eV and smaller than 2200 eV. It passes through the ion passage without colliding with.

In addition, since the bivalent or more secondary ions accelerated by the pulse voltage are incident on the first electrostatic analyzer 41 ₁ with energy larger than 2200 eV, they are absorbed by colliding with the slit 43 and do not pass through the ion passage.

When δ = 0, among the plurality of secondary ions having the same charge-mass ratio that simultaneously pass through the space convergence point 30, the secondary ion having a high energy is the first drift in a shorter time than the secondary ion having a low energy. It passes the distance L ₃ and enters one end of the first electrostatic analyzer 41 ₁ at an early time, but it passes through the ion passage in a long time due to the large radius of curvature, so it is slower than the secondary ion with low energy. It is ejected from the other end of the third electrostatic analyzer 41 ₃ at the time, passes through the second drift distance L ₄ in a short time, and enters the ion detector 50 at the same time as the secondary ion with low energy. .

However, since a plurality of secondary ions having the same charge mass ratio have a time difference of δ when passing through the spatial convergence point 30, they reach the TRIFT type analyzer 40 with the time difference of δ. .
The ion detector 50 detects the incident position of incident secondary ions corresponding to the incident time.

  The charge mass ratio of the secondary ions is calculated from the application start time of the pulse voltage at the pulse power source 22 and the incident time of the secondary ions detected by the ion detector 50. Here, since the secondary ions reaching the ion detector 50 are monovalent, the mass may be calculated from the charge mass ratio. From the calculation result, it is possible to simultaneously obtain both the two-dimensional relative position information of the atoms and molecules constituting the irradiation surface of the analysis sample 5 and the charge mass ratio information.

Next, the mass resolution R = m / Δm of the TOF-SIMS apparatus 10 according to the present invention is evaluated. Here, Δm is the full width at half maximum of the peak in the mass distribution.
If the flight distance from the spatial convergence point 30 to the ion detector 50 via the TRIFT type analyzer 40, that is, the sum of the first drift distance L ₃ , the ion path and the second drift distance L ₄ is L _5. The mass resolution R is expressed by the following equation.

Here, v ₀ = √ (2qU ₀ / m).
Here, the flight distance is L ₅ = 2 m, and when the mass resolution R is evaluated, it is understood that a mass resolution of R = 1000 is obtained from L ₅ / L ₂ = 10 and δ = 0.01.

  In the TOF-SIMS apparatus 10 of the present invention, an energy filter that reduces the full width at half maximum ΔU of the initial energy distribution of secondary ions may be disposed between the pulse gate electrode portion and the extraction electrode 15. In this case, the mass resolution R is improved from the result of the above equation, which is preferable.

5 ... Analytical sample 10 ... Time-of-flight secondary ion mass spectrometer (TOF-SIMS)
DESCRIPTION OF SYMBOLS 11 ... Vacuum chamber 12 ... Vacuum exhaust apparatus 15 ... Extraction electrode 21a, 21b ... 1st, 2nd electrode 22 ... Pulse power supply 23a, 23b ... 1st, 2nd passage hole 40 ... Plurality Fan-shaped electrostatic analyzer (TRIFT analyzer, analyzer)
41a ₁ , 41a ₂ , 41a ₃ ... outer peripheral electrode 41b ₁ , 41b ₂ , 41b ₃ ... inner peripheral electrode 50 ... ion detector

Claims (1)

A vacuum chamber;
An evacuation device for evacuating the vacuum chamber;
A surface of an analysis sample disposed in the vacuum chamber is irradiated with a gas cluster ion beam, and secondary ions having positive or negative charges made of ions of the analysis sample are irradiated from the irradiation surface irradiated with the gas cluster ion beam. An ion gun that emits
An extraction electrode for extracting the secondary ions emitted from the irradiation surface from the analysis sample;
A pulse gate electrode portion in which the secondary ions extracted by the extraction electrode are pulse-accelerated;
A plurality of fan-shaped electrostatic analyzers that perform spatial and temporal convergence of the secondary ions accelerated by the pulse gate electrode unit;
A time-of-flight secondary ion mass spectrometer comprising: an ion detector that detects an incident position of the secondary ion that has passed through the plurality of sector electrostatic analyzers according to an incident time;
The pulse gate electrode portion is arranged in the traveling direction of the secondary ions accelerated by the extraction electrode, and the first and second electrodes respectively provided with first and second passage holes, and the first A pulsed voltage is applied to the first electrode, and the secondary ions entering between the first and second electrodes through the first passage hole are accelerated from the first electrode toward the second electrode. A pulse power supply
The secondary ions accelerated by the pulse gate electrode portion are converged at a predetermined convergence position at a time corresponding to a charge mass ratio, and then the plurality of sectors for performing spatial and temporal convergence of the secondary ions. To enter the electrostatic analyzer,
The plurality of sector electrostatic analyzers each have an annular ion passage formed by an annular outer peripheral electrode and an inner peripheral electrode located on the inner periphery of the outer peripheral electrode, and the outer peripheral electrode and the inner peripheral electrode A time-of-flight secondary ion mass spectrometer configured such that the secondary ions incident on the ion passage pass through the ion passage in a time corresponding to a charge-mass ratio by a voltage applied therebetween.

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