JP4629722B2 - Surface analyzer - Google Patents

Description

  The present invention relates to a surface analyzer, and more particularly to a surface analyzer using an ion beam.

Conventionally, a device for irradiating a sample surface with an ion beam and measuring and evaluating secondary electrons emitted from the sample is used for surface analysis.
Reference numeral 101 in FIG. 6 is an example of a surface analyzer used for evaluation of a protective film for a plasma display device, and has an ion source (not shown) on the left side of the drawing.

  A beam shaper (hereinafter referred to as a shaper) 111 is disposed downstream of the ion source, and ions generated and extracted in the ion source are incident on the shaper 111 and are ionized in the shaper 111. Shaped into a beam 105.

  A speed reducer unit (112 to 114) is arranged on the downstream side of the molding device 111, and the suppressor electrode 112, the intermediate electrode 113, and the final electrode 114 are arranged in this order in the speed reduction device unit. The shaped ion beam 105 is emitted toward the suppressor electrode 112 on the downstream side, passes through holes formed in the electrodes 112 to 114, and is irradiated toward the sample 121.

  A ground electrode 115 is disposed between the sample 121 and the final electrode 114 on the front surface of the sample 121, and the ion beam 105 has a beam diameter due to an electric field formed by the hole formed in the ground electrode 115 and the final electrode 114. , And enters the surface of the sample 121.

  A collector electrode 118 is disposed between the ground electrode 115 and the sample 121, and a positive voltage is applied to the collector 118. The sample 121 is irradiated with the ion beam 105, and secondary electrons jumping out from the surface are collected by the collector electrode 118.

When the current flowing through the collector electrode 118 when the ion beam 105 is irradiated is I _C and the current flowing through the sample 121 is I _S , the total current I _ion of the ion beam 105 irradiated onto the sample 121 is
I _ion = I _C -I _S
It is represented by

Since the currents I _c and I _s flowing through the collector electrode 118 and the sample 121 can be measured, the total current I _ion of the ion beam 105 can be calculated, thereby _{obtaining the} secondary electron emission ratio I _s / I _ion for the ion beam. Can do. Thereby, the sample 121 can be evaluated.
JP-A-10-261378 Japanese Utility Model Publication No. 6-22916 Yoshiaki Agawa, Yasuhiro Hara, Yoshihiro Yamamoto, Shigeru Amano, “Development of MgO protective film evaluation device”, 1997 Vol.4, Electrochemical Society Particle Beam Technology Development Study Group, Electrochemical Society Particle Beam Technology Development Study Group Secretariat Ionics Corporation, 1998, p. 51-55

  However, in the surface analysis apparatus 101 as described above, the ion beam 105 hits the ground electrode 115, and secondary electrons are also emitted from the ground electrode 115. When the secondary electrons are collected by the collector electrode 118, the secondary electron emission ratio of the sample 121 becomes inaccurate.

In addition, a positive voltage is applied to the collector electrode 118 with respect to the potential of the sample 121 so that secondary electrons can be efficiently collected . When the sample 121 is an insulator, irradiation with an ion beam is performed. Therefore, when the sample 121 is charged to a positive potential and the potential difference from the collector electrode 118 is reduced, the electron collection efficiency of the collector electrode 118 is lowered, and the measurement of the secondary electron emission ratio becomes inaccurate.

  The present invention was created to solve the above-described disadvantages of the prior art, and an object thereof is to provide a technique capable of accurately obtaining the secondary electron emission ratio.

In order to solve the above problem, the invention according to claim 1 is a sample stage on which a sample is arranged, a ground electrode in which a first hole is formed, a collector electrode in which a second hole is formed, and the sample. A first ammeter that measures the current flowing through the table and a second ammeter that measures the current flowing through the collector electrode, the sample table and the ground electrode are connected to a ground potential, and the ion beam is A surface analyzer that collects secondary electrons emitted from the surface that pass through the first hole and then pass through the second hole and are emitted to the surface of the sample. A first variable power source connected to the collector electrode, and a third ammeter for measuring a current flowing through the ground electrode, the ion beam being adapted to change the diameter , While heating the sample Is configured to be capable of irradiating the ion beam on the surface, the sample side surface of the collector electrode is a surface analyzer that is molded into the concave mirror.

According to a second aspect of the invention includes an adjustment electrodes fourth holes are formed, claims wherein the ion beam having passed through the fourth hole is configured to pass through the first hole The surface analysis apparatus according to claim 1, further comprising a second variable power supply connected to the adjustment electrode, wherein the ion beam can change the diameter by changing an output voltage of the second variable power supply. It was configured as described above.

The invention according to claim 3 is the surface analysis apparatus according to claim 1 or 2, wherein a light transmitting window is provided in the sample stage, and an infrared lamp is disposed behind the sample stage, infrared rays emitted from the infrared lamp, characterized in that through the transparent window is configured so that is irradiated to the sample back surface.

The invention according to claim 4 is the surface analysis apparatus according to claim 3 , wherein the infrared light transmitted through the sample is reflected by the concave mirror of the collector electrode and re- irradiated to the sample . It is characterized by that.

  When the sample is irradiated with an ion beam, the current flowing through the ground electrode placed in front of the collector electrode is measured, and the ion beam diameter is adjusted so that no current flows through the ground electrode. The secondary electrons that are not irradiated are not emitted from the ground electrode.

  When a control electrode is provided between the ground electrode and the collector electrode and a voltage lower than the ground electrode and the collector electrode is applied to the control electrode, the secondary electrons emitted from the ground electrode do not reach the collector electrode, The secondary electrons emitted from the sample and leaking from the collector electrode are pushed back to the collector electrode side and collected by the collector electrode, so that the amount of secondary electrons emitted can be accurately measured.

  When the ion beam is irradiated while heating the sample, the resistivity of the glass substrate is low, so that the increase in the potential of the sample is small even if the charge accumulated in the sample flows.

  When an infrared lamp is provided at the back of the sample and the back surface of the sample is irradiated with infrared rays for heating, if the collector electrode placed in front of the sample is a concave mirror, the infrared light transmitted through the sample is reflected by the concave mirror and collected. In this state, the sample surface is reirradiated, so that the heating efficiency of the sample is improved.

  When the ion beam emitted from the shaper passes through at least a suppressor electrode to which a negative voltage is applied to the shaper and a ground electrode having a positive potential with respect to the suppressor electrode, and irradiates the sample surface, When the potential of the sample rises, if the suppressor electrode is placed at an intermediate potential between the shaper and the ground electrode to form a positive potential gradient from the shaper to the ground electrode, electrons are emitted to the sample and accumulated in the sample. The positive charge can be neutralized.

  On the other hand, if a metal is placed around the sample and an ion beam is irradiated to a portion where the metal does not exist, the charge accumulated in the sample can flow to the ground potential via the metal. The potential can be prevented from rising. The metal may be a plate-like object or a metal thin film formed on the sample surface.

According to the present invention, the positive potential accumulated in the sample can be neutralized even when the potential of the sample does not increase and increases.
Further, the collection efficiency of secondary electrons emitted from the sample is increased, and on the other hand, secondary electrons emitted from the ground electrode need not be collected, so that measurement accuracy is improved.

Embodiments of the present invention will be described with reference to the drawings.
Referring to FIG. 1, reference numeral 1 denotes a surface analysis apparatus according to a first example of the present invention.

  This surface analysis apparatus 1 has an ion source (not shown) arranged on the left side of the drawing and a molding device 11 arranged on the downstream side of the ion source. Positive ions such as xenon generated in the ion source are extracted by an extraction electrode (not shown) and irradiated toward the molding device 11. The ions are shaped into an ion beam 5 when passing through the shaping device 11 and irradiated toward the downstream side.

  In the surface analyzer 1, a suppressor electrode 12, an intermediate electrode 13, and a final electrode 14 are disposed on the downstream side of the molding device 11. A hole is provided in the center of each of the electrodes 12 to 14, and the ion beam 5 emitted from the molding device 11 is first irradiated toward the hole of the suppressor electrode 12.

A variable power source is connected to the molding device 11 and each of the deceleration electrodes 12 to 14, and a negative voltage is applied thereto. Sign E ₁ in FIG. 2 shows a potential change of the ion beam emitted from the shaper 11, -20 kV to shaper 11, the suppressor electrode 12 -25 kV, the intermediate electrodes 13 -10 kV, the final electrode 14 is applied with −1 kV.

  A ground electrode 15 is disposed on the downstream side of the final electrode 14. The ground electrode 15 is formed by molding a metal into a bottomed cylindrical shape, and a hole 25 is provided in a substantially central portion of the bottom surface.

  The ground electrode 15 has a bottom side directed toward the final electrode 14 (upstream direction of the ion beam 5) and an opening side directed toward the sample 21 (downstream direction of the ion beam 5). A collector electrode 18 in which a metal material is formed into a bottomed cylindrical shape is disposed inside the ground electrode 15.

  The collector electrode 18 also has a bottom surface directed in the upstream direction of the ion beam 5 and an opening portion directed in the downstream direction.

A metal sample stage 20 is disposed at the opening of the collector electrode 18, and a sample 21 to be measured is disposed on the sample stage 20. The sample 21 is composed of a transparent glass substrate and an MgO film formed on the surface thereof.
A hole 26 is formed on the bottom surface of the collector electrode 18 at a position on the same axis as the hole 25 of the ground electrode 15.

  When the voltage applied to the molding device 11 and the voltage applied to the suppressor electrode 12 to the final electrode 14 are appropriate, the ion beam 5 is focused to a smaller diameter than the hole 25 of the ground electrode 15, and the ground electrode The MgO film on the surface of the sample 21 is irradiated through the 15 holes 25 and the hole 26 of the collector electrode 18.

Secondary electrons that have jumped out of the MgO film on the surface of the sample 21 by the irradiation of the ion beam 5 are collected by the collector electrode 18 disposed between the sample 21 and the ground electrode 15, and the secondary electron emission ratio is obtained.

On the other hand, when the ion beam 5 has a larger diameter than the hole 25, the peripheral portion of the ion beam 5 is irradiated to the ground electrode 15 in the peripheral portion of the hole 25. Reference numeral 29 in FIG. 1 indicates the ion beam 5 irradiated around the hole 25. When the ion beam 5 is irradiated to the ground electrode 15, secondary electrons are emitted from that portion, and when the ion beam 5 is collected by the collector electrode 18, the measurement accuracy deteriorates.

  In this surface analysis apparatus 1, the ground electrode 15 is connected to the ground potential via the adjustment ammeter 37, and the diameter of the ion beam 5 is large so that it cannot pass through the hole 25 of the ground electrode 15. The current flows through the adjustment ammeter 37 according to the irradiation amount of the ion beam 5 to the ground electrode 15.

When no current flows through the adjustment ammeter 37, the ion beam 5 is not applied to the ground electrode 15. Conversely, when a current flows through the adjustment ammeter 37, the intermediate electrode 13 The voltage applied to the first electrode 14 and the voltage applied to the final electrode 14 are adjusted, and when the diameter of the ion beam 5 is reduced until no current flows through the adjustment ammeter 37, the collector electrode 18 protrudes from the ground electrode 15. Secondary electrons are not collected and can be measured accurately.
In this case, both the voltage applied to the intermediate electrode 13 and the voltage applied to the final electrode 14 may be adjusted, or only the voltage applied to one of the electrodes may be adjusted.

  In the surface analysis apparatus 1, an infrared lamp 30 is arranged at the back surface position of the sample 21 behind the sample stage 20. A translucent window 27 made of a hole is provided at the center of the sample stage 20.

  The infrared lamp 30 has a filament 31 and a condensing mirror 32, and the infrared ray 35 that is energized and radiated to the filament 31 is reflected directly or by the condensing mirror 32 as shown in FIG. It passes through the optical window 27 and is configured to be irradiated on the back surface of the substrate 21.

  The glass substrate of the sample 21 is an insulator, and the MgO film formed on the surface is also an insulator. Therefore, when the ion beam is irradiated on the surface of the MgO film, it is charged up.

When the glass substrate is soda lime glass, the specific resistance is about 10 ¹³ Ωcm at room temperature. When the size is 25 mm × 25 mm and the thickness is 2 mm, the resistance value in the thickness direction is
10 ¹³ × 0.2 / (2.5 × 2.5) = 3.2 × 10 ¹¹ Ω
It becomes.

When the current flowing through the sample 21 is about 60 nA, the surface potential is
3.2 × 10 ¹¹ × 60 nA = 1.9 × 10 ⁴ V (= 19 kV)
It becomes. The ion beam of 100 to 1000 eV cannot reach the surface of the sample 21 and the surface analysis of the MgO film cannot be performed (in fact, the surface potential of the sample 21 rises only up to the incident voltage of the ion beam). , It will not be a potential of 19 kV.)

  In the surface analysis apparatus 1, the filament 31 is energized in advance, the infrared rays 35 are emitted, and the sample 21 is heated. Further, since the sample 21 is a glass substrate and the infrared rays 35 are transmitted and the efficiency of heating is reduced, the portion facing the sample 21 on the bottom surface of the collector electrode 18 is formed in a concave shape, and a gold thin film is formed on the surface. A concave mirror 19 is formed by forming a film.

  Therefore, the infrared ray 35 that has passed through the sample 21 is reflected by the concave mirror 19 and condensed, and is re-irradiated on the surface of the sample 21 so that the sample 21 is efficiently heated.

FIG. 4 shows the relationship between the temperature of the soda lime glass substrate and the specific resistance. When heated to about 100 ° C., a specific resistance of 10 ¹⁰ [Omega] cm approximately, when heated to about 300 ° C., drops to about 10 ⁶ [Omega] cm.

When heated to 300 ° C., the resistance value of sample 21 is
10 ⁶ × 0.2 / (2.5 × 2.5) = 3.2 × 10 ⁴ Ω
It becomes. When a current of 60 nA flows,

3.2 × 10 ⁴ × 60 nA = 192 × 10 ⁻⁵ V (= 1.9 mV)
Thus, the charge applied by the ion beam 5 flows in the vertical direction from the surface of the sample 21 through the glass substrate and to the ground via the sample stage 20 because it is sufficiently smaller than the incident voltage of the ion beam 5.

  Thermocouples and thermometers 40 and 38 are attached to the sample stage 20 and the infrared lamp 30, and the ion beam 5 is irradiated after the temperature is raised to about 300 ° C.

  When the sample 21 is heated, the surface potential is close to the ground potential even when the ion beam 5 is irradiated. Therefore, the potential difference between the sample 21 and the collector electrode 18 is large.

  As described above, in the surface analysis apparatus 1, the surface of the sample 21 is not charged up, the focused ion beam 5 is irradiated onto the sample 21, and secondary electrons generated on the surface of the sample 21 are collected by the collector electrode 18. Currents flowing through the collector electrode 18 and the sample 21 are measured by ammeters 35 and 36 that are efficiently collected and connected to the collector electrode 18 and the sample 21, respectively, and the secondary electron emission ratio is accurately obtained. .

  Note that the specific resistance of the MgO film is small and the film thickness is as small as about 1000, and can be ignored.

  Next, another surface analysis apparatus of the present invention will be described. Reference numeral 2 in FIG. 5 indicates the surface analyzer, and the same members as those in the analyzer 1 of the first example are denoted by the same reference numerals and description thereof is omitted.

  The surface analyzer 2 has a control electrode 17. The control electrode 17 is a bottomed cylindrical metal electrode and is disposed in the ground electrode 15.

  The bottom surface side of the control electrode 17 is directed in the upstream direction of the ion beam 5, and the collector electrode 18 is disposed therein. Therefore, the control electrode 17 and the collector electrode 18 are disposed in the ground electrode 15 in a cage shape.

  A hole 28 is formed in the bottom surface of the control electrode 17, and the holes 25, 28, and 26 formed in the ground electrode 15, the control electrode 17, and the collector electrode 18 are arranged on the same central axis. Therefore, the ion beam 5 that has passed through the suppressor electrode 12, the intermediate electrode 13, and the final electrode 14 passes through the holes 25, 28, and 26 and is irradiated on the surface of the sample 21.

  The control electrode 17 is connected to a variable power source 39 so that a negative voltage can be applied. When a voltage lower than the potential of the ground electrode 15 and the collector electrode 18 is applied to the control electrode 17, when the peripheral portion of the ion beam 5 collides with the ground electrode 15 and the secondary electrons 44 are generated, the secondary electrons 44 are generated. Is pushed back by the electric field formed by the control electrode 17 so as not to enter the collector electrode 18.

  The secondary electrons 45 emitted from the surface of the sample 21 and leaking upstream from the hole 26 of the collector electrode 18 are also pushed back by the electric field formed by the control electrode 17 and enter the collector electrode 18. Therefore, secondary electrons emitted from the ground electrode 15 are not measured, and on the other hand, the collection efficiency of secondary electrons emitted from the sample 21 is increased. As a result, the secondary electron emission coefficient is accurately measured.

  When the potential of the ground electrode 15 is zero, the potential of the collector electrode 18 is positive. Therefore, the potential of the control electrode 17 may be applied with a negative voltage lower than that of the ground electrode 15, and specifically, −30 to 30. It is appropriate to apply a negative voltage of about −50V.

  The sample 21 is pressed against a metal pedestal 20 by a metal clamp 22. Reference numeral 41 denotes a glass substrate of the sample 21, and an MgO film 42 is formed on the surface thereof. A ring-shaped metal plate 50 is disposed between the clamp 22 and the MgO film 42, and the sample 21 is configured to be pressed against the pedestal 20 by the clamp 22 and the metal plate 50.

  The pedestal 20 is connected to the ground potential with the ammeter 36 inserted, and the clamp 22 is attached to the pedestal 20. Therefore, the metal plate 50 is connected to the ground potential via the clamp 22 and the pedestal 20. The MgO film 42 is irradiated with the ion beam 5 and the charge generated on the surface flows to the ground potential through the metal plate 50 in contact with the surface of the MgO film 42. Therefore, the metal plate 50 makes it difficult for the sample 21 to be charged up.

  The metal plate 50 is separate from the sample 21 and is disposed on the sample 21. However, a ring-shaped metal thin film is formed on the surface of the MgO film 42 of the sample 21, and the clamp 22 is used as the metal thin film. You may contact | abut.

Next, the case where the potential of the sample 21 is increased by the irradiation of the ion beam 5 will be described. Sign E ₂ of Figure 2 shows the space potential after the ion beam 5 irradiation, whereas the potential of the sample 21 of the ion beam 5 irradiation start time was zero V (space potential code E _1.) The voltage V _{U is} charged up.

As can be seen from the space potentials E ₁ and E ₂ , the potential of the molding device 11 is −20 kV, whereas the potential of the suppressor electrode 12 is −25 kV, which is larger in the negative direction than the potential of the molding device 11. It is at potential. In this way, a negative potential gradient is formed between the shaper 11 and the suppressor electrode 12, and electrons that have passed through the shaper 11 are pushed back by the potential gradient and do not reach the sample 21. ing.

Therefore, conversely, when the suppressor electrode 12 is brought closer to the ground potential than the molding device 11, electrons are not pushed back by the suppressor electrode 12. Symbol E _{3 in} FIG. 2 is a potential gradient when the potential of the molding device 11 is set to -15 kV between the molding device 11 and the intermediate electrode 13 of −20 kV and −10 kV, and the molding device 11 and the suppressor. L between the electrodes 12 also has a positive potential gradient. This potential gradient E ₃ is positive from the molding device 11 to the collector electrode 18 and, as described above, is discharged from the molding device 11 even when the sample 21 is charged to a positive voltage. Electrons are accelerated by the positive potential gradient and irradiated on the surface of the sample 21. As a result, the positive charge accumulated in the sample 21 is neutralized and the positive charge-up is eliminated.

The figure for demonstrating an example of the surface analyzer of this invention A diagram for explaining the space potential of the device Diagram for explaining sample heating method Graph showing the relationship between glass substrate temperature and resistivity The figure for demonstrating the control electrode provided between the collector electrode and the ground electrode The figure for demonstrating the surface analysis apparatus of a prior art

Explanation of symbols

1, 2 ... Surface analyzer 5 ... Ion beam 11 ... Molder 12 ... Suppressor electrode 15 ... Ground electrode 17 ... Control electrode 18 ... Collector electrode 19 ... Concave mirror 20 ... Base 21 ... Sample 27 …… Transparent windows 25, 26 …… Hole 30 …… Infrared lamp 35 …… Infrared

Claims (4)

A sample stage on which the sample is placed;
A ground electrode formed with a first hole;
A collector electrode formed with a second hole;
A first ammeter for measuring the current flowing through the sample stage;
A second ammeter for measuring the current flowing through the collector electrode;
The sample stage and the ground electrode are connected to a ground potential,
A surface in which an ion beam passes through the first hole and then passes through the second hole and is irradiated onto the surface of the sample, and secondary electrons emitted from the surface are collected by the collector electrode. An analyzer,
A first variable power source connected to the collector electrode;
A third ammeter that measures the current flowing through the ground electrode;
The ion beam can be changed in diameter ,
Configured to irradiate the surface with the ion beam while heating the sample;
The surface of the collector electrode on the sample side is a surface analyzer formed into a concave mirror. Having an adjustment electrode in which a fourth hole is formed;
The surface analysis apparatus according to claim 1, wherein the ion beam that has passed through the fourth hole is configured to pass through the first hole.
A second variable power source connected to the adjustment electrode;
The ion beam, the second variable power source front surface analyzer output voltage by changing the configured to be able to change the size of the. The sample stage is provided with a translucent window, an infrared lamp is disposed behind the sample stage, and the infrared ray emitted from the infrared lamp is configured to be irradiated to the back surface of the sample through the translucent window. The surface analysis apparatus of any one of Claim 1 or Claim 2 . The surface analysis apparatus according to claim 3, wherein the infrared ray transmitted through the sample is reflected by the concave mirror of the collector electrode and re-irradiated to the sample.

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