阅读说明：本技术 离子铣削装置及离子铣削装置的离子源调整方法 (Ion milling device and ion source adjusting method of ion milling device ) 是由 鸭志田齐 高须久幸 上野敦史 岩谷彻 于 2018-02-28 设计创作，主要内容包括：本发明提高通过向试样照射非聚焦的离子束加工试样的离子铣削装置的加工精度、或加工面形状的再现精度。为此,具有试样室(6)、设置于试样室的离子源位置调整机构(5)、经由离子源位置调整机构安装于试样室且射出离子束的离子源(1)、以及以旋转中心为轴旋转的试样台(2),若将离子束的离子束中心(B<Sub>0</Sub>)和旋转中心(R<Sub>0</Sub>)一致时的旋转中心的延伸方向设为Z方向,且将与Z方向垂直的面设为XY面,则离子源位置调整机构(5)能够调整离子源(1)的XY面上的位置及Z方向的位置。(The invention provides an ion milling device for processing a sample by irradiating the sample with a non-focused ion beam, which can improve the processing precision or the reproduction precision of the processing surface shape. The ion source device is provided with a sample chamber (6), an ion source position adjusting mechanism (5) arranged in the sample chamber, an ion source (1) which is arranged in the sample chamber through the ion source position adjusting mechanism and emits ion beams, and a sample table (2) which rotates by taking a rotation center as an axis, and the ion beam center (B) of the ion beam is determined 0 ) And center of rotation (R) 0 ) The extending direction of the rotation center when the rotation centers are aligned is the Z direction, and the surface perpendicular to the Z direction is the XY surfaceThe ion source position adjusting mechanism (5) can adjust the position on the XY plane and the position in the Z direction of the ion source (1).)

1. An ion milling apparatus for processing a sample by irradiating the sample with an unfocused ion beam, comprising:

a sample chamber;

an ion source position adjusting mechanism provided in the sample chamber;

an ion source that is attached to the sample chamber via the ion source position adjustment mechanism and emits the ion beam; and

a sample table rotating with the rotation center as an axis,

when the direction in which the rotation center extends when the ion beam center of the ion beam and the rotation center coincide is a Z direction and a plane perpendicular to the Z direction is an XY plane, the ion source position adjustment mechanism can adjust the position of the ion source in the XY plane and the position in the Z direction.

2. The ion milling apparatus of claim 1, having:

a target plate provided on the sample stage and provided with a conductive material in a range including the rotation center; and

and an ammeter for measuring an ion beam current received by the conductive material.

3. The ion milling apparatus of claim 2,

the conductive material has a circular shape centered on the rotation center.

4. The ion milling apparatus of claim 2, having:

the conductive material has a first conductive material in a circular shape arranged concentrically about the rotation center and a second conductive material in an annular shape having a larger diameter than the first conductive material,

the ion beam current received by the first conductive material and the ion beam current received by the second conductive material are measured independently.

5. The ion milling apparatus of claim 2, having:

a power supply unit for applying a predetermined voltage to the ion source;

a control unit; and

a display part for displaying the display position of the display part,

the control unit collects and displays on the display unit sensing data including a discharge voltage value, a discharge current value, an acceleration voltage value, and an ion beam current value measured by the ammeter, which are applied to the ion source by the power supply unit.

6. The ion milling apparatus of claim 2,

a power supply unit for applying a predetermined voltage to the ion source; and

a control part for controlling the operation of the display device,

the control unit adjusts the position of the ion source on the XY plane and the position in the Z direction by the ion source position adjustment mechanism based on the ion beam current value measured by the galvanometer.

7. The ion milling apparatus of claim 6,

the control unit may adjust the discharge voltage applied to the ion source by the power supply unit instead of adjusting the position in the Z direction by the ion source position adjustment mechanism or in addition to adjusting the position in the Z direction by the ion source position adjustment mechanism.

8. An ion source adjusting method for an ion milling apparatus for processing a sample by irradiating the sample placed in a sample chamber with an unfocused ion beam,

the sample stage rotation driving source rotates a sample stage provided with a target plate provided with a conductive material in a range including a rotation center around the rotation center as an axis,

the ion source irradiates the ion beam toward the target plate,

the galvanometer measures the ion beam current received by the conductive material,

the ion source is mounted to the sample chamber via an ion source position adjustment mechanism capable of adjusting a position of the ion source,

the position of the ion source adjusted by the ion source position adjusting mechanism is set such that the ion beam current value measured by the galvanometer satisfies a predetermined target.

9. The ion source tuning method of claim 8,

when the direction in which the rotation center extends when the ion beam center of the ion beam and the rotation center coincide is a Z direction and a plane perpendicular to the Z direction is an XY plane, the position of the ion source adjusted by the ion source position adjustment mechanism includes a position on the XY plane of the ion source and a position in the Z direction.

10. The ion source tuning method of claim 8,

the value of the discharge voltage of the ion source is set so that the ion beam current value measured by the ammeter satisfies the predetermined target.

11. The ion source tuning method of claim 8,

the emission conditions of the ion source when the ion beam is irradiated to the target plate are equal to the emission conditions of the ion source when the sample is processed.

12. The ion source tuning method of claim 8,

the predetermined target is a maximum value of the ion beam current or a value of the ion beam current at the time of the previous machining.

13. An ion source adjusting method for an ion milling apparatus for processing a sample by irradiating the sample placed in a sample chamber with an unfocused ion beam,

a sample stage rotation drive source for rotating a sample stage having a mirror member provided in a range including a rotation center, with the rotation center as an axis, while inclining an inclination angle of the sample stage by 45 degrees,

the ion source irradiates the ion beam toward the mirror member,

the ion source is mounted to the sample chamber via an ion source position adjustment mechanism capable of adjusting a position of the ion source,

the position of the ion source adjusted by the ion source position adjusting mechanism is set to a state where the vicinity of the rotation center of the mirror member appears to emit light in a dot or annular shape.

14. The ion source tuning method of claim 13,

instead of the mirror member, a light emitting member that emits light by reacting with the ion beam is provided on the sample stage.

15. The ion source tuning method of claim 13 or 14,

the emission condition of the ion source when the ion beam is irradiated to the mirror member or the light emitting member is equal to the emission condition of the ion source when the sample is processed.

Technical Field

The present invention relates to an ion milling apparatus and an ion source adjustment method for the ion milling apparatus.

Background

In order to observe and analyze the internal structure of the sample, the target internal structure needs to be exposed on the surface. Conventionally, there are methods of preparing a sample by cutting or mechanical polishing, but these methods cannot avoid the occurrence of deformation or damage due to the application of physical pressure to the sample. The ion milling apparatus irradiates a surface or a cross section of a sample (for example, metal, semiconductor, glass, ceramic, or the like) with an unfocused argon ion beam accelerated to, for example, several kV, and can eject atoms on the surface of the sample without stress by utilizing a sputtering phenomenon to smooth the surface of the sample. This is an excellent characteristic because the surface or the cross section of the sample is smoothed by Electron microscopy represented by Scanning Electron Microscopy (SEM) or Transmission Electron Microscopy (TEM).

In an ion milling apparatus, an ion beam irradiation unit that generates an ion beam is attached to a vacuum container in order to process a sample in a vacuum atmosphere. When a sample is processed, fine particles from the sample generated from a processed surface adhere to an ion beam irradiation portion, and therefore the ion milling apparatus needs to perform periodic cleaning. Therefore, although the ion beam irradiation unit is configured to be detached from the vacuum container and reattached after maintenance, there is a possibility that an attachment error occurs in the ion beam irradiation unit at the time of reattachment, and the irradiation direction of the ion beam irradiated from the ion beam irradiation unit may be changed from before.

Patent document 1 discloses an ion beam irradiation apparatus in which a sample (here, a substrate) is held by a substrate holder and reciprocated so as to traverse an irradiation region of an ion beam, and an ion beam irradiation portion irradiates the substrate with the ion beam. In order to solve the above problem, an ion beam measuring mechanism for measuring a beam current density distribution of an irradiated ion beam is provided on a wall surface of a vacuum chamber facing an ion beam irradiation unit. The ion beam center position is measured by an ion beam measuring mechanism, and the stroke center position of the reciprocating motion of the substrate is set at the ion beam center position or a predetermined position determined based on the position, thereby ensuring the uniformity of the ion irradiation amount to the substrate even if the ion beam irradiation part generates a mounting error.

On the other hand, in recent semiconductor devices, since the degree of integration has been dramatically increased, semiconductor devices in which patterns having a fine three-dimensional structure are three-dimensionally integrated have been developed. In order to manage the manufacture of a device in which such a three-dimensional structure (three-dimensional structure) pattern is integrated, it is necessary to evaluate the pattern in the cross-sectional direction. Patent document 2 discloses the following technique: in order to realize such highly accurate measurement of the depth direction (or height direction) of the three-dimensional structure pattern, an inclined surface is formed on the surface of the sample, and the depth direction (height direction) of the pattern is measured.

Disclosure of Invention

Problems to be solved by the invention

In patent document 2, a Focused Ion Beam (FIB) device is used to form an inclined surface on the surface of a sample to expose the cross section of a three-dimensional structure pattern. However, since the focused ion beam apparatus has a low processing speed and a narrow processing range, it takes time to form a target inclined surface on the surface of a sample. Therefore, the inventors have studied to form an inclined surface by an ion milling apparatus using an unfocused ion beam having a high processing speed.

When an unfocused ion beam is used for processing a sample, the processing speed depends on the intensity of the ion beam irradiated to the sample, specifically, the speed of ions applied by an acceleration voltage, the number of ions, and the irradiation angle of the ions. Here, the intensity of the ion beam emitted from the ion source is ideally considered to have a shape of a binomial distribution in which the intensity is highest at the center of the ion beam and gradually decreases toward the periphery. However, the ion beam emitted from the ion source is affected by the contamination of the electrode members constituting the ion source, the fluctuation in the number of ions due to the consumption of the electrode members, and the disturbance of the electric field due to the environment, and it is difficult to keep the intensity of the ion beam irradiating the sample constant. Further, since the unevenness is formed due to the difference in milling speed caused by the composition and the incident angle of the sample, when the sample is irradiated with the unfocused ion beam to perform the processing, the ion milling apparatus irradiates the ion beam while rotating the sample about the ion beam center as an axis, thereby suppressing the formation of the unevenness, and obtaining a smooth processed surface suitable for observation and measurement by the electron microscope.

The problem of the present invention will be explained. Fig. 2A shows the main part of the ion milling apparatus. Comprises an ion source 21, a sample stage 22 on which a sample 20 is placed, and a rotation center R of the sample stage 22₀A sample stage rotation drive source 23 whose axis rotates in the R direction. The ion beam from the ion source 21 is centered at the ion beam center B₀The sample 20 placed on the sample placement surface of the sample stage 22 is irradiated with the sample extending radially at the center. Essentially, the premise is that the center of rotation R₀And ion beam center B₀In agreement, but sometimes due to mounting errors of the ion source 21, the rotation center R is as shown in fig. 2A₀And ion beam center B₀The state of deviation is obtained. Fig. 2B shows the depth of the machining formed on the surface of the sample 20 at this time. As shown by the waveform 25, at the center R of rotation₀Ion beam center B with highest ion beam intensity at deviated position₀The depth of the work is deepest, and the work depth becomes smaller as separating therefrom.Correspondingly, the rotation center R is adjusted₀And ion beam center B₀The machining depth in the case of coincidence is represented as a waveform 26. As described above, it is found that, when the shape of the processing surface is smoother and more extreme than the originally intended processing surface due to the mounting error of the ion source 21, the processing surface fluctuates as shown by the waveform 25 in fig. 2B. In particular, when an observation surface or an inclined surface is intentionally formed on a sample for observation or measurement of a fine three-dimensional structure pattern, such a change in the shape of a processed surface can be ignored.

In the example of fig. 2A, the ion beam center B is used₀The ion beam is irradiated perpendicularly to the surface of the sample 20 (or the sample mounting surface of the sample stage 22), but the sample stage 22 may be inclined in the C direction to irradiate the ion beam at a low incident angle to the surface of the sample 20. This makes it possible to obtain a wide range of machined surfaces. In this case, the sample table 22 is tilted about the rotation center R₀Since the ion beam is irradiated to the sample 20 while rotating the axis, the rotation center R is set to be the center of rotation₀And ion beam center B₀Offset (on the surface of the sample 20, center of rotation R₀And ion beam center B₀Do not intersect), then the center R is likewise rotated₀And the center B of the ion beam₀The deviation of (a) is caused by a change in the shape of the machined surface, and there is a problem that a desired observation surface or inclined surface cannot be obtained.

In the case of a structure in which an ion source is directly attached to a vacuum container as in the conventional apparatus, the ion source needs to be detachable due to periodic cleaning, and the machining tolerance of the ion source and the ion source mounting portion of the sample chamber cannot be set to 0. Therefore, it is impossible to avoid the occurrence of misalignment when the ion source is mounted again. As described with reference to fig. 2A, B, this causes unevenness in the processing accuracy of the ion milling apparatus and reduces the reproducibility of the processed surface shape.

In addition, in the ion beam, as the distance from the exit of the ion source is longer, the beam diameter is expanded, and the current and ion density are reduced. Therefore, it is considered that when the ion beam measurement position is separated from the actual sample processing position as in patent document 1In order to measure the ion beam, it is necessary to measure the voltage applied to the ion source higher than the conditions under which the actual processing is performed. However, when the emission conditions of the ion beam are changed, the milling speed is changed due to the change in the energy of the ion beam, the density distribution of the ions is also changed, and the magnitude of the influence of the disturbance is also changed, and therefore, it is desirable that the adjustment is performed under the same conditions as the emission conditions in the actual processing. Therefore, in order to adjust the position under the emission conditions during actual processing, an operator of the ion milling apparatus may mount a processing object such as a copper foil on a sample stage, and irradiate the sample stage with an ion beam under the actual processing conditions to leave a beam mark on the copper foil so that the beam mark and the rotation center R are aligned₀A consistent approach implements position adjustment of the ion source. However, such adjustment by visual observation or microscopic observation of the beam mark has a limit to accuracy, and in many cases, it is necessary to perform positioning by repeating attachment and detachment of the ion source a plurality of times, and the real-time performance is poor, so that the adjustment load on the operator is large.

In view of the above problems, the present invention provides an ion milling apparatus and an ion source adjustment method that can easily and accurately adjust the center of an ion beam and the center of rotation of a sample after the ion source is attached and detached.

Means for solving the problems

An ion milling apparatus according to an embodiment of the present invention is an ion milling apparatus for processing a sample by irradiating the sample with an unfocused ion beam, the ion milling apparatus including: a sample chamber; an ion source position adjusting mechanism provided in the sample chamber; an ion source which is installed in the sample chamber via the ion source position adjusting mechanism and emits an ion beam; and a sample stage that rotates about a rotation center as an axis, wherein the ion source position adjustment mechanism is capable of adjusting a position on an XY plane and a position in a Z direction of the ion source, when a direction in which the rotation center extends when the ion beam center of the ion beam and the rotation center are aligned is the Z direction and a plane perpendicular to the Z direction is the XY plane.

Other objects and novel features will become apparent from the description of the specification and the accompanying drawings.

ADVANTAGEOUS EFFECTS OF INVENTION

The machining accuracy of the ion milling device or the reproduction accuracy of the shape of the machined surface can be improved. In addition, the maintenance time of the ion milling apparatus can be shortened.

Drawings

Fig. 1 is a configuration diagram of a main part of an ion milling apparatus according to embodiment 1.

Fig. 2A is a diagram for explaining the problem of the present invention.

Fig. 2B is a diagram for explaining the problem of the present invention.

Fig. 3 is a diagram showing a configuration example of the sample stage.

Fig. 4 is a block diagram of position adjustment of the ion source.

Fig. 5 is a flow of adjusting the position of the ion source in embodiment 1.

Fig. 6A shows an example of the shape of the conductor of the target plate.

Fig. 6B shows another example of the shape of the conductor of the target plate.

Fig. 7 is a main part configuration diagram of an ion milling apparatus according to embodiment 2.

Fig. 8 is a flow of adjusting the position of the ion source according to embodiment 2.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.