JP2014181934A - Height standard sample, method for manufacturing the same, and device for manufacturing height standard sample - Google Patents

Abstract

A highly accurate standard sample is produced.
According to the present invention, the first region 20 and the second region 22 of the first region 20 and the second region 22 are formed such that a step is formed at the boundary between the first region 20 and the second region 22 on the surface of the silicon substrate 10. This is a method for producing a height standard sample including a step of selectively irradiating one region 20 with oxygen ions 42.
[Selection] Figure 2

Description

  The present invention relates to a height standard sample and a manufacturing method thereof, and a height standard sample manufacturing apparatus, and more particularly to a height standard sample, a manufacturing method thereof, and a height standard sample manufacturing apparatus that irradiates a silicon substrate with oxygen ions. .

  A height standard sample is used for height calibration of a measuring device such as an atomic force microscope. It is known that a terrace on the surface of a silicon substrate is used as a height standard sample (for example, Patent Document 1). It is also known to use a height standard sample formed by etching (for example, Patent Document 2).

  On the other hand, it is known that the surface position of a silicon substrate changes by irradiating the silicon substrate with oxygen ions (for example, Non-Patent Document 1).

JP-A-6-58753 JP-A-5-196559

SURFACE AND INTERFACE ANALYSIS, VOL. 24, 389-398 (1996)

  In the method of producing a height standard sample using a terrace on the surface of a silicon substrate, it is difficult to produce a standard sample having an arbitrary height. In the method for producing a height standard sample by etching, a standard sample having an arbitrary height can be produced. However, a mask for etching is formed on the surface of the substrate, and the mask is removed. During mask formation and removal, the surface of the substrate is affected. For this reason, it is difficult to produce a highly accurate standard sample.

  This height standard sample, its production method, and the height standard sample production apparatus are intended to produce a highly accurate height standard sample.

  Selectively irradiating the first region of the first region and the second region with oxygen ions such that a step is formed at the boundary between the first region and the second region on the surface of the silicon substrate; A method for producing a height standard sample is used.

  A height standard sample including a silicon substrate in which a step is formed at the boundary between a first region where a silicon oxide film is formed by irradiation with oxygen ions and a second region where no oxygen ions are irradiated is used. .

  Ion irradiation for selectively irradiating oxygen ions to the first region of the first region and the second region so that a step is formed at the boundary between the first region and the second region on the surface of the silicon substrate. A height standard sample manufacturing apparatus including a unit is used.

  According to the present height standard sample, its production method, and the height standard sample production apparatus, a highly accurate standard sample can be produced.

FIG. 1 is a schematic diagram of a production apparatus for producing a standard sample in Example 1. FIG. 2A to FIG. 2C are cross-sectional views showing a method for manufacturing a standard sample according to Example 1. FIG. 3A and FIG. 3B are flowcharts showing a method for preparing a standard sample according to Example 1. FIG. 4A to FIG. 4C are cross-sectional views of a silicon substrate irradiated with oxygen ions. FIG. 5 is a diagram showing the surface height with respect to the oxygen dose.

  When oxygen ions are implanted into the silicon substrate, a silicon oxide film is formed at a certain dose or more. This phenomenon is applied to a SIMOX (Separation by Implantation of Oxygen) technique for forming a silicon oxide layer in a silicon substrate. The SIMOX technique is a technique for forming a silicon oxide film inside a silicon substrate by implanting oxygen ions with high energy. When oxygen ions are implanted at low energy, a silicon oxide film can be formed on the surface of the silicon substrate. The implantation of oxygen ions can be selectively performed on the silicon substrate. For this reason, compared with the case where a step is formed on the surface of the substrate using etching, a mask forming and removing process is unnecessary. Therefore, a highly accurate height standard sample can be produced.

  FIG. 1 is a schematic diagram of a production apparatus for producing a standard sample in Example 1. Referring to FIG. 1, the manufacturing apparatus 30 includes a stage 32, a vacuum chamber 34, an ion gun 36, an ammeter 38 and a control unit 40. The stage 32 holds the substrate 10 on the upper surface. The stage 32 and the substrate 10 are disposed in the vacuum chamber 34. The atmosphere in the vacuum chamber 34 is exhausted as indicated by an arrow 44 by a vacuum pump. The ion gun 36 which is an ion irradiation unit irradiates the surface of the substrate 10 with oxygen ions 42. The ion gun 36 may irradiate oxygen ions 42 perpendicularly to the surface of the substrate 10 or may irradiate the substrate 10 surface obliquely. The ammeter 38 measures a current flowing from the substrate 10 to the ground via the stage 32. The control unit 40 irradiates the ion gun 36 with oxygen ions 42. Also, the ion gun 36 is stopped from irradiating the oxygen ions 42 based on the amount of current measured by the ammeter 38. The stage 32 is driven by a drive unit. Thereby, an oxygen ion can be irradiated to the arbitrary area | regions of the board | substrate 10 surface.

  FIG. 2A to FIG. 2C are cross-sectional views showing a method for manufacturing a standard sample according to Example 1. Referring to FIG. 2A, a single crystal silicon substrate 10 is prepared. For example, the silicon substrate 10 is disposed on the stage 32 in FIG. The silicon substrate 10 has, for example, a (100) or (111) plane as a main surface. With reference to FIG. 2B, the surface of the silicon substrate 10 is irradiated with oxygen ions 42. For example, the ion gun 36 in FIG. 1 irradiates the surface of the silicon substrate 10 with oxygen ions 42. With reference to FIG. 2C, the silicon oxide film 12 is formed on the surface of the silicon substrate 10 in the first region 20 irradiated with the oxygen ions 42. In the second region where the oxygen ions 42 are not irradiated, the silicon oxide film 12 is not formed on the surface of the silicon substrate 10.

  The beam diameter of the oxygen ions 42 is 5 μm, for example. The oxygen ion beam may be scanned relative to the silicon substrate 10. In this case, the size of the first region 20 can be made larger than the oxygen ion beam diameter. The size of the first region 20 is, for example, several tens μm to several hundreds μm. When the intensity distribution in the oxygen ion beam is a Gaussian distribution, the amount of oxygen ions irradiated into the first region 20 can be made uniform by scanning the oxygen ion beam.

  FIG. 3A and FIG. 3B are flowcharts showing a method for preparing a standard sample according to Example 1. With reference to Fig.3 (a), the acceleration energy and dose amount of oxygen ion are determined (step S10). Next, as shown in FIG. 2B, the ion gun 36 irradiates the silicon substrate with oxygen ions 42 (step S12).

  FIG. 3B shows a process performed by the control unit 40 corresponding to step S12 of FIG. Referring to FIG. 3B, the control unit 40 determines a set current amount corresponding to the dose amount of oxygen ions determined in step S10 (step S14). The control unit 40 causes the ion gun 36 to start irradiation with oxygen ions with the acceleration energy determined in step S10 (step S16). The control unit 40 determines whether the accumulated current amount of the current measured by the ammeter 38 has reached the set current amount (step S18). If No, the process returns to step S18. In the case of Yes, the control unit 40 causes the ion gun 36 to stop irradiating oxygen ions (step S20). Thereby, a dose amount of oxygen ions set in the first region 20 of the silicon substrate 10 is irradiated.

FIG. 4A to FIG. 4C are cross-sectional views of a silicon substrate irradiated with oxygen ions. Referring to FIG. 4A, when the silicon substrate 10 is irradiated with oxygen ions, oxygen atoms are implanted into the silicon substrate 10 in the first region 20. Oxygen atoms are combined with silicon atoms to form a silicon oxide film 12. The volume of the silicon layer expands by becoming a silicon oxide film. For example, a Si layer having a thickness of 4.4 nm becomes a SiO ₂ layer having a thickness of 10 nm. Therefore, the surface height of the first region 20 is higher than that of the second region 22 by H1. Thereby, a step is formed at the boundary between the first region 20 and the second region 22. Note that the silicon substrate 10 may be heat-treated after the implantation of oxygen ions, but the silicon oxide film 12 is formed without heat treatment.

  Referring to FIGS. 4B and 4C, when oxygen ions are applied to the surface of the silicon substrate 10 or the silicon oxide film 12, oxygen atoms are implanted into the silicon substrate 10 or the silicon oxide film 12. At the same time, the surface of the silicon oxide film 12 is sputter etched. Therefore, the surface of the silicon oxide film 12 is lowered. The position of the surface of the silicon oxide film 12 changes depending on the balance between the sputtering yield Y of oxygen ions in the silicon oxide film 12 and the rate α at which oxygen ions stay in the silicon oxide film 12. In FIG.4 (b), the surface of the 1st area | region 20 and the 2nd area | region 22 is the same height. In FIG. 4C, the surface of the first region 20 is H2 lower than the second region 22.

The amount of oxygen atoms remaining in the silicon substrate 10 or the silicon oxide film 12 affects the volume expansion and the sputtering yield. Thereby, the etching amount of the surface depends on the amount of oxygen atoms. Until the dose of oxygen ions [Phi becomes constant amount [Phi _tr, the amount of oxygen remains in the silicon substrate 10 or silicon oxide film 12 is growing. When the dose amount Φ exceeds a certain amount _Φtr , the amount of oxygen remaining in the silicon substrate 10 or the silicon oxide film 12 becomes constant (steady state).

According to Non-Patent Document 1, when the acceleration energy of oxygen ions is constant, the oxygen sputtering rate Y and the oxygen retention rate α in the silicon oxide film 12 are functions of the oxygen ion dose Φ. The sputtering rate Y (Φ) is expressed by the following formula.
When Φ / Φ _tr ≦ 1, Y (Φ) = Y ⁰ [1 + a (Φ / Φ _tr ) ^p ]
When Φ / Φ _tr ≧ 1, Y (Φ) = Y ^{∞
Here, a = (Y ∞ -Y 0} ) / Y 0, Y 0 = Y (Φ → 0), is ^{Y = Y ∞ (Φ → ∞} ). Y (Φ → 0) and Y ^∞ (Φ → ∞) are constant values. p is the power depending on the impact energy.

The rate α (Φ) at which oxygen remains is expressed by the following equation.
When Φ / Φ _tr ≦ 1, α (Φ) = α ⁰ [1- (Φ / Φ _tr ) ^p ]
When Φ / Φ _tr ≧ 1, α (Φ) = 0
Here, α ⁰ = α (Φ → 0). α (Φ → 0) is a constant value.

The movement of the surface of the silicon oxide film 1 (that is, the amount of etching per irradiated oxygen element + the amount of expansion due to volume expansion) v _s (Φ) is a function of the dose amount Φ as follows.
v _s (Φ) = v _Si (Φ) + v _Ox (Φ) = Ω _Si × Y (Φ) −Ω _Ox × α (Φ)
Here, Ω _Si and Ω _Ox are atomic volumes of silicon and oxygen, respectively. Ω _Ox is obtained from Ω _SiO2 = Ω _Si + 2Ω _Ox .

The height z _s (Φ) of the surface of the silicon oxide film 12 can be obtained by integrating v _s from 0 to Φ as shown in Equation 1.

From the experiment, by obtaining Y ⁰ , Y ^∞ and α, the surface height z _s (Φ) of the silicon oxide film 12 can be calculated from the dose Φ of oxygen ions.

FIG. 5 is a diagram showing the surface height with respect to the oxygen dose. It is the figure which calculated the surface height with respect to the dose amount using Formula 1 when oxygen ion is O ₂ ⁺ and acceleration energy is 250 eV, 500 eV, 750 eV, 1 keV, and 3 keV. In this case, oxygen ions are irradiated from the normal direction of the surface of the silicon substrate 10 having the (001) plane as the main surface. A surface height of 0 indicates that the surface of the silicon substrate 10 before irradiation with oxygen ions and the surface of the silicon oxide film 12 after irradiation with oxygen ions have the same height. That is, it corresponds to FIG. The range where the surface height is positive indicates that the surface of the silicon oxide film 12 is higher than the surface of the silicon substrate 10 before being irradiated with oxygen ions. That is, it corresponds to FIG. The range where the surface height is negative indicates that the surface of the silicon oxide film 12 is lower than the surface of the silicon substrate 10 before being irradiated with oxygen ions. That is, it corresponds to FIG.

Referring to FIG. 5, when the acceleration energy is 250 eV to 1 keV, when the oxygen dose exceeds 10 ¹⁵ cm ⁻² , silicon oxide film 12 is formed and the surface becomes high. When the oxygen dose exceeds 10 ¹⁶ cm ⁻² and reaches the oxygen dose indicated by the down arrow, sputtering and volume expansion are balanced. At acceleration energy of 250 eV, 500 eV, 750 eV and 1 keV, the maximum height of the surface is about 1.3 nm, about 1.0 nm, about 0.5 nm and about 0.1 nm, respectively. When the oxygen dose is larger than the downward arrow, the surface of the silicon oxide film 12 is lowered by sputtering while the film thickness of the silicon oxide film 12 remains constant. When the oxygen dose is between 10 ¹⁷ cm ⁻² and 10 ¹⁸ cm ⁻² , the surface height decreases rapidly.

In step S10 of FIG. 3A, the acceleration energy and the dose amount of oxygen ions are determined so as to achieve the target height using FIG. Thereby, the height standard sample which has arbitrary height can be produced. The current corresponding to a dose rate of O ₂ ⁺ ions of 6.25 × 10 ¹² ions / second is 1 μA. Therefore, in step S14 of FIG. 3B, the set current amount is set from the target dose amount using the relationship between the dose rate and the current.

  According to the first embodiment, as shown in FIGS. 2B and 2C, the first region 20 on the surface of the silicon substrate 10 is irradiated with oxygen ions, and the second region 22 is not irradiated with oxygen ions. For example, the first region 20 and the second region 22 are selectively irradiated with oxygen ions 42 in the first region 20. As a result, a step is formed at the boundary between the first region 20 and the second region 22. Thereby, the height standard sample which has the level | step difference of arbitrary height is producible.

  For example, when an atomic level step is fabricated by heating a silicon substrate in an ultrahigh vacuum, the height of the step is 0.31 nm in the (111) plane silicon substrate. In the (0001) plane sapphire substrate, the height of the step is 0.22 nm. When the silicon carbide molecular step is used, the height of the step is 0.50 nm. Furthermore, there is a standard sample having a height of 8 nm using a quartz sample. On the other hand, the height standard sample of 0.50 nm to 8 nm has low accuracy. In the standard sample according to Example 1, a height standard sample in which the height of the step is larger than 0.50 nm and smaller than 8.0 nm can be produced. Furthermore, the method of Embodiment 1 does not require mask formation and removal steps. Therefore, a highly accurate height standard sample can be produced.

  Further, as in step S10 of FIG. 3A, the dose amount of oxygen ions and the acceleration energy are determined so that the height of the step becomes the target height. As shown in FIG. 5, the acceleration energy and the dose amount are determined from the sputtering yield Y of oxygen ions in the first region 20 and the rate α at which oxygen ions stay on the silicon substrate. Thereby, the height of the step can be arbitrarily set.

  As shown in FIG. 4A, the surface of the first region 20 is preferably higher than the second region 22. Referring to FIG. 5, in the region where the surface height is positive, the amount of change in the surface height with respect to the oxygen dose can be reduced. That is, the accuracy of the height of the step can be increased. As shown in FIG. 5, when the step height is 1.3 nm or less, the accuracy of the step height can be increased. Furthermore, by making the acceleration energy smaller than 250 eV, the maximum value of the surface height (the height of the surface of the down arrow) can be increased. Thereby, the value of 1.3 nm or more which is the maximum value of the surface height of 250 eV can also be realized.

  As in step S10 of FIG. 3A, the dose amount of oxygen ions is determined so that the step becomes the target height. As in step S14 in FIG. 3B, the set current amount is determined from the dose amount. As in step S18, it is determined whether or not the amount of current flowing through the silicon substrate 10 exceeds the set amount of current. When the amount of current flowing through the silicon substrate 10 exceeds the set current amount as in step S20, the irradiation of oxygen ions is stopped. Thereby, the accuracy of the oxygen dose can be increased, and the accuracy of the height of the step can be increased.

  The height standard sample produced by Example 1 can be used as a standard sample for height calibration of an apparatus that evaluates a fine height such as an atomic force microscope.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

In addition, the following additional notes are disclosed regarding the above description.
(Supplementary Note 1) The first region and the second region are selectively formed in the first region so as to form steps having different heights at the boundary between the first region and the second region on the surface of the silicon substrate. A method for producing a height standard sample, comprising a step of irradiating oxygen ions.
(Appendix 2) A method for producing a height standard sample according to appendix 1, wherein a silicon oxide film is formed on the silicon substrate in the first region by irradiating the first region with oxygen ions. .
(Supplementary Note 3) From the sputtering yield of oxygen ions in the first region and the rate at which oxygen ions remain in the silicon substrate so that the height of the step becomes the target height, the dose amount and acceleration of the oxygen ions The method for producing a height standard sample as set forth in appendix 1 or 2, comprising a step of determining energy.
(Supplementary note 4) The method for producing a height standard sample according to any one of supplementary notes 1 to 3, wherein a surface of the first region is higher than that of the second region.
(Additional remark 5) The said height standard sample is used for atomic force microscope, The preparation method of the height standard sample as described in any one of Additional remark 1 to 4 characterized by the above-mentioned.
(Additional remark 6) The step which determines the dose amount of the said oxygen ion so that the height of the said level | step difference becomes a target height, and the step which selectively irradiates an oxygen ion to the said 1st area | region includes the said dose amount Determining a set current amount from step, determining whether the amount of current flowing through the silicon substrate exceeds the set current amount, and if the amount of current flowing through the silicon substrate exceeds the set current amount, The method for producing a height standard sample according to any one of appendices 1 to 5, further comprising a step of stopping irradiation of the oxygen ions.
(Supplementary note 7) The height standard sample manufacturing method according to any one of supplementary notes 1 to 6, wherein a height of the step is larger than 0.50 nm and smaller than 8 nm.
(Supplementary Note 8) Steps having different surface heights are formed at the boundary between the first region where the silicon oxide film is formed by irradiation with oxygen ions and the second region where the oxygen ions are not irradiated. Standard height sample equipped with a silicon substrate.
(Supplementary Note 9) The first region and the second region are selectively formed in the first region so as to form steps having different heights at the boundary between the first region and the second region on the surface of the silicon substrate. A height standard sample manufacturing apparatus comprising an ion irradiation unit for irradiating oxygen ions.

DESCRIPTION OF SYMBOLS 10 Silicon substrate 12 Silicon oxide film 20 1st area | region 22 2nd area | region 30 Production apparatus 32 Stage 34 Vacuum chamber 36 Ion gun 38 Ammeter 40 Control unit

Claims (7)

  Selectively irradiating the first region of the first region and the second region with oxygen ions such that a step is formed at the boundary between the first region and the second region on the surface of the silicon substrate; A method for producing a height standard sample, comprising:   The method for producing a height standard sample according to claim 1, wherein a silicon oxide film is formed on the silicon substrate in the first region by irradiating the first region with oxygen ions.   The acceleration energy and dose amount of the oxygen ions are determined from the sputtering yield of oxygen ions in the first region and the rate at which the oxygen ions remain in the silicon substrate so that the height of the step becomes the target height. The method for producing a height standard sample according to claim 1, further comprising a step.   The method for producing a height standard sample according to any one of claims 1 to 3, wherein a surface of the first region is higher than that of the second region.   The method for producing a height standard sample according to any one of claims 1 to 4, wherein the height standard sample is used in an atomic force microscope.   A silicon substrate having a step formed at a boundary between a first region in which a silicon oxide film is formed by irradiation with oxygen ions and a second region in which the oxygen ions are not irradiated is provided. Standard height sample.   Ion irradiation for selectively irradiating oxygen ions to the first region of the first region and the second region so that a step is formed at the boundary between the first region and the second region on the surface of the silicon substrate. A height standard sample manufacturing apparatus comprising a unit.

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