Ion milling apparatus

Abstract

The purpose of the present invention is to provide an ion milling device in which a horizontally movable stage is disposed on a sample rotating stage and in which it is possible to supply power to the horizontally movable stage. An ion milling device according to the present invention is provided with: a rotary stage; a movable stage installed on the top face of the rotary stage; and a fixed base part supporting the rotary stage. The rotary stage is provided with a first power transmission part, and the fixed base part is provided with a second power transmission part. The ion milling device is further provided with a member for exerting a force for pressing the first power transmission part and the second power transmission part against each other (see fig. 1C).

Description

Technical Field

[0001] The present invention relates to an ion milling apparatus.

Background Art

[0002] An ion milling apparatus irradiates a non-focused ion beam onto a sample (such as metal, semiconductor, glass, ceramic, etc.) that is an observation target of an electron microscope. By knocking off the atoms on the sample surface due to the sputtering phenomenon accompanying the ion beam irradiation, the sample surface can be polished without stress or the internal structure of the sample can be exposed. Since the polished or exposed surface becomes the observation surface of a scanning electron microscope or a transmission electron microscope, the ion milling apparatus is applied as a sample pretreatment apparatus.

[0003] There are multiple methods for processing a sample using an ion milling apparatus. A method of ion milling the sample surface by irradiating an ion beam obliquely onto the surface of a rotating sample is called a planar milling method. In addition to polishing the sample surface, when planar milling is performed with the sample rotation center and the ion beam center aligned, it is possible to process in a conical shape. Therefore, in recent years, planar milling has been applied in the delayering of semiconductors (flash memories).

[0004] With the recent increase in the capacity of flash memories, the demand for wide-area processing has been increasing. However, the current milling method has no way to expand the processing range other than moving the processing position little by little and performing milling multiple times. As a result, there is a concern about the lengthening of the processing time.

[0005] Patent Document 1 below describes a technology related to the sample stage in a charged particle beam apparatus. The document states that the objective is to "enable rapid placement and replacement of samples in a charged particle beam apparatus," and describes a technology that "includes a charged particle beam apparatus which includes a charged particle beam tube for irradiating a sample with a charged particle beam, a rotating stage 5A having a base portion 5d and a rotating moving portion that rotates around a rotation axis R1 relative to the base portion 5d, a sample stage for moving the sample relative to the charged particle beam tube, a rotating connector 56 arranged coaxially with the rotation axis R1 and interposed between the base portion 5d and the rotating moving portion, and a contact pin 55a arranged on the upper part of the sample stage and electrically connected to the rotating connector 56." (See abstract). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2018-166042 [Overview of the project] [Problems that the invention aims to solve]

[0007] In an ion milling apparatus, in order to process a line shape using the planar milling method, it is necessary to have a structure in which the stage rotation part of the sample stage is placed at the bottom, and the sample moving stage (hereinafter referred to as the single-axis horizontal movable stage) is placed above it. This is because the sample is sputtered into a cone shape by irradiating it with an ion beam while rotating the rotating stage, and the processing position is moved horizontally by the horizontal movable stage, thereby forming a line shape.

[0008] A horizontally movable stage moves horizontally, for example, by a motor, so it is necessary to supply power to its drive mechanism. In other words, wiring for power supply must be connected to the horizontally movable stage, and power must be supplied to that wiring. If this wiring is connected directly to the power supply, the wiring may twist as the stage rotates. Therefore, when a horizontally movable stage is placed on a rotating stage, it is considered necessary to use rotary contacts to secure the power path.

[0009] Rotary contact type wiring uses mercury in the contact points to ensure contact. High vacuum (~10 -3 Introducing a rotary contact structure into the sample chamber of an ion milling apparatus (below Pa) will cause mercury to sublimate, making it difficult to use rotary contact type wiring in the sample chamber of an ion milling apparatus.

[0010] Patent Document 1 describes a structure in which a single-axis horizontal movable stage is mounted on a rotating body. However, in the structure described in that document, there is a high risk of the wiring twisting and breaking if the single-axis horizontal movable stage is placed on the sample rotation axis, making power supply difficult. It is possible that the document did not adequately consider this point.

[0011] The present invention has been made in view of the above-mentioned problems, and aims to provide an ion milling apparatus that arranges a horizontally movable stage on a sample rotation stage and is capable of supplying power to the horizontally movable stage. [Means for solving the problem]

[0012] The ion milling apparatus according to the present invention comprises a rotating stage, a movable stage installed on the upper surface of the rotating stage, and a fixed base supporting the rotating stage, wherein the rotating stage is equipped with a first power transmission unit, the fixed base is equipped with a second power transmission unit, and the ion milling apparatus further comprises a member that exerts a force pressing the first power transmission unit and the second power transmission unit against each other. [Effects of the Invention]

[0013] According to the ion milling apparatus of the present invention, it is possible to provide an ion milling apparatus in which a horizontally movable stage is arranged on a sample rotation stage and power can be supplied to the horizontally movable stage.

Brief Description of Drawings

[0014] [Figure 1A] It is a top view of an ion milling apparatus 100 according to Embodiment 1. [Figure 1B] It is a front view of the ion milling apparatus 100. [Figure 1C] It is an enlarged view of the stage mechanism in FIG. 1B. [Figure 2A] It is a schematic diagram showing an ion source 101 adopting a Penning method and a power supply circuit for applying a control voltage to an electrode component of the ion source 101. [Figure 2B] It shows a state where a beam measuring device is scanned with respect to an ion beam irradiated from an ion source. [Figure 2C] It shows the profile of an ion beam. [Figure 2D] It shows a processed shape when the sample rotation center axis and the ion beam center axis are eccentric. [Figure 3] It shows the processed shape of a sample when the X coordinate is gradually moved using the stage having the structure shown in FIG. 1. [Figure 4] It shows a flowchart for explaining a procedure for processing a sample using the stage having the structure of FIG. 1. [Figure 5] It is an enlarged view of the periphery of the stage of the ion milling apparatus 100 according to Embodiment 2.

Modes for Carrying Out the Invention

[0015] <Embodiment 1> FIG. 1A is a top view of an ion milling apparatus 100 according to Embodiment 1 of the present invention. The ion milling apparatus 100 includes an ion source 101, a sample chamber 102, a stage inclination section 103, a one-axis horizontal movable stage 104, a one-axis horizontal movable stage holder 105, a control unit 114, and a vacuum evacuation section 115.

[0016] The ion milling apparatus 100 is used as a pretreatment apparatus for observing the surface or cross-section of a sample by a scanning electron microscope or a transmission electron microscope, and is also applied to semiconductor layering. The sample chamber 102 during ion milling is always maintained at a high vacuum (10 -3 Pa or less) by the vacuum evacuation section 115. The Ar gas introduced from the outside is ionized by discharging in the ion source 101 and irradiated onto the sample as an ion beam. The control unit 114 controls each part included in the ion milling apparatus 100.

[0017] FIG. 1B is a front view of the ion milling apparatus 100. The ion milling apparatus 100 further includes a power transmission section 106 (first power transmission section) of a rotary stage, a power transmission section 107 (second power transmission section) of a fixed base section, an insulator section 108, a permanent magnet 109 (contact maintaining member), a fixed base section 110, a stage rotation bearing 111, a stage rotation section 112, a stage rotation shaft 113, and a rotation sensor 116.

[0018] The sample is placed on the one-axis horizontal movable stage 104. The one-axis horizontal movable stage 104 is placed on the one-axis horizontal movable stage holder 105. The wiring of the one-axis horizontal movable stage 104 is connected to the power transmission section 106 of the rotary stage. Since the one-axis horizontal movable stage holder 105 is arranged on the stage rotation section 112 and the stage rotation shaft 113, it can rotate freely (that is, it can operate as a rotary stage). The stage rotation section 112 is fixed inside the stage rotation bearing 111, and the power transmission section 107 of the fixed base section is fixed outside the stage rotation bearing 111.

[0019] The rotation sensor 116 is composed of two members. The first member is attached to the fixed base 110 side (for example, the power transmission unit 107), and the second member is attached to the rotating stage side (for example, the power transmission unit 106). As the rotating stage rotates, the second member rotates. The first member detects the rotation of the second member. For example, the second member is made of a permanent magnet, and the first member is configured as a sensor that detects the magnetic force of the second member each time it approaches. This makes it possible to detect the rotation of the rotating stage. Since the first member operates as a sensor, it is desirable to place it in a position where it can receive power (in this example, in contact with the power transmission unit 107). The rotation sensor 116 only needs to be able to detect the rotation of the rotating stage, and is not limited to the configuration shown in Figure 1B.

[0020] Figure 1C is an enlarged view of the stage mechanism shown in Figure 1B. A magnetic material (Fe, Ni, etc.) is embedded in the power transmission section 106 of the rotating stage, and as shown in Figure 1C, the power transmission section 106 is attracted by a permanent magnet 109 positioned between the power transmission section 107 and the insulator section 108. As a result, the power transmission section 106 of the rotating stage can rotate while sliding, maintaining close contact with the power transmission section 107.

[0021] The power transmission unit 107, the insulator unit 108, and the permanent magnet 109 are fixed to the fixed base unit 110. By supplying power to the power transmission unit 107 from the control unit 114, the single-axis horizontal movable stage 104 can be moved via the power transmission unit 106 of the rotating stage.

[0022] Attractive force F due to magnets mag In addition, as the mass of the sample increases, gravity F gAs these forces increase, the frictional force f acting between the power transmission unit 106 of the rotating stage and the power transmission unit 107 of the fixed base increases in proportion to these forces. In this case, depending on the maximum torque value of the motor that rotates the stage, the stage may not rotate. If it does not rotate, the rotation sensor 116 provided on the side sends a feedback to the control unit 114 to stop the rotation.

[0023] In this embodiment, a configuration including a single-axis horizontal movable stage is used, but a two-axis horizontal movable stage may also be used. Furthermore, since the purpose of the permanent magnet 109 is to attract the power transmission unit 106 of the rotating stage and bring it into contact with the power transmission unit 107 of the fixed base, it is desirable to use a magnet with low magnetic properties (such as a samarium-cobalt magnet).

[0024] Figure 2A is a schematic diagram showing an ion source 101 employing a Penning method and a power supply circuit that applies a control voltage to the electrode components of the ion source 101. The ion source 101 mainly consists of a first cathode 201, a second cathode 202, an anode 203, a permanent magnet 204, an accelerating electrode 205, a gas piping 206, and a gas flow control unit 207.

[0025] To generate an ion beam, argon gas is injected into the ion source 101 through the gas pipe 206. Inside the ion source 101, a first cathode 201 and a second cathode 202 are arranged opposite each other via a permanent magnet 204, and an anode 203 is positioned between the first cathode 201 and the second cathode 202. A discharge voltage V is supplied to the first cathode 201, the second cathode 202, and the anode 203 from the high-voltage power supply in the control unit 114. d A force is applied, generating electrons. A Lorentz force acts on the generated electrons due to the permanent magnet 204 placed inside the ion source 101, causing the electrons to move in a helical motion.

[0026] Electrons collide with argon gas injected from the gas pipe 206, controlled by the gas flow control unit 207, to form a plasma and generate argon ions. An acceleration voltage V is supplied between the anode 203 and the accelerating electrode 205 from the high-voltage power supply contained in the control unit 114. a A voltage is applied. As a result, the generated argon ions are drawn out by the accelerating electrode 205 and emitted as an ion beam.

[0027] Figure 2B shows the scanning of the beam detector against the ion beam irradiated from the ion source.

[0028] Figure 2C shows the ion beam profile. When the beam analyzer is scanned as shown in Figure 2B, a profile following a Gaussian distribution is obtained as shown in Figure 2C. Therefore, if the sample rotation axis and the ion beam axis coincide, the processed shape will follow the beam profile.

[0029] Figure 2D shows the processed shape when the sample rotation axis and the ion beam axis are eccentric. Eccentricity allows for processing over a wider area. It has been confirmed that increasing the amount of eccentricity results in a flat surface (2.0 mm eccentricity in Figure 2D), and that excessive eccentricity causes the flat surface to be lost (2.5 mm and 3.0 mm eccentricity in Figure 2D). Applying this result, linear processing can be achieved by moving the sample while maintaining the alignment of the sample rotation axis and the ion beam axis. As shown in Figure 2D, as the amount of eccentricity increases, the processed shape gradually deviates from the Gaussian distribution shape. Therefore, considering the ease of controlling the processed shape, it is desirable for the amount of eccentricity to be 0. In other words, it is desirable for the sample rotation axis and the ion beam axis to be aligned.

[0030] Figure 3 shows the processed shape of the sample when the X-coordinate is moved little by little using the stage structure shown in Figure 1. The sample rotation axis is assumed to coincide with the ion beam central axis and is always rotating. The X-coordinate of the starting point of processing is -a (mm). At this point, the processed shape follows the shape of the beam profile, so it is machined into a shape that can be approximated as a cone. When the X-axis is moved in the range of -a to 0 (mm), the processed shape of the sample can be seen from above as being machined into an elongated hole shape. The length of the elongated hole shape (in this case, the length is the distance between the centers of the circles at both ends) is the same as the distance moved on the X-axis, a (mm). Similarly, when the X-coordinate is moved in the range of -a to a (mm), the processed shape is an elongated hole shape with a length of 2a. Although Figure 3 uses a single-axis movable stage for explanation, a two-axis movable stage may be used to further expand the range of motion.

[0031] Figure 4 shows a flowchart illustrating the procedure for processing a sample using a stage having the structure shown in Figure 1. Each step is carried out by the control unit 114 controlling each part. The steps in Figure 4 are described below.

[0032] S301: Place the sample on the uniaxial horizontal movable stage 104. Considering that the sample rotation axis and the ion beam center are aligned, determine the processing start point.

[0033] S302: Vacuum evacuation of the sample chamber 102 is performed by the vacuum evacuation unit 115.

[0034] S303: Set the drive range of the 1-axis horizontal movable stage 104. In principle, during machining, the 1-axis horizontal movable stage 104 will reciprocate within the drive range set in this flow. In the case of a 2-axis horizontal stage, you may set the drive range to be a single continuous line and configure it to reciprocate between its start and end points.

[0035] S304: Check whether the drive range set in S303, including the rotary contact section (referring to the part where the power transmission section 106 of the rotating stage and the power transmission section 107 of the fixed base rotate while in contact), is being driven without any problems. If the single-axis horizontal movable stage 104 does not move, the sensor built into the single-axis horizontal movable stage 104 detects this and the process proceeds to S305. If the rotary contact section does not move, the rotation sensor 116 detects this and the process proceeds to S305. If it moves without any problems, the process proceeds to S306.

[0036] S305: Stop processing.

[0037] S306: The output conditions for the ion beam are set, and the stage tilt section 103 is tilted to set the irradiation angle of the ion beam.

[0038] S307: The ion beam is activated and processing begins.

[0039] S308: Check whether machining has been sufficiently performed based on the drive range set in S303. If it is insufficient, return to S303, reset the drive range of the single-axis horizontal movable stage 104, and resume machining. If machining has been sufficiently performed, proceed to S309.

[0040] S309: The sample chamber 102 is opened to the atmosphere, and processing is terminated.

[0041] <Embodiment 1: Summary> In the ion milling apparatus 100 according to this first embodiment, a power transmission unit 106 is placed within a single-axis horizontal movable stage holder 105 that constitutes the rotating stage, and power is supplied to the single-axis horizontal movable stage 104 via the power transmission units 106 and 107. A magnetic material is embedded in the power transmission unit 106, and a permanent magnet 109 attracts the power transmission unit 106, generating a force that presses the power transmission units 106 and 107 against each other, thereby maintaining close contact between the power transmission units 106 and 107. Therefore, the rotating stage can be rotated while sliding. This structure rotates while in contact with the conductive part, similar to rotary contact type wiring. Therefore, it is possible to install a single-axis movable stage on the sample rotating stage without using mercury.

[0042] <Embodiment 2> Figure 5 is an enlarged view of the area around the stage of the ion milling apparatus 100 according to Embodiment 2 of the present invention. In Embodiment 1, a structure was described in which a magnet was embedded in the fixed base to ensure contact between the power transmission units 106 and 107. In Embodiment 2, instead of embedding a magnet in the fixed base, a pin 502 incorporating a compression spring 501 is incorporated into the power transmission unit 106 of the rotating stage. When the power transmission units 106 and 107 slide, the incorporated spring presses the pin against the power transmission unit 107, creating a structure that keeps them in constant contact. This allows for rotational operation while maintaining contact between the power transmission units 106 and 107, as in Embodiment 1, and also allows power to be supplied to the single-axis horizontal movable stage 104. The other configurations are the same as in Embodiment 1. The compression spring 501 and pin 502 act as contact-maintaining members, exerting a force that presses the power transmission units 106 and 107 against each other, thereby maintaining contact between them.

[0043] The power transmission unit 107 provides point support to the power transmission unit 106 via the pin 502 (protrusion). This minimizes the contact area between the power transmission unit 106 and 107. Therefore, frictional heat generated as the rotating stage rotates can be suppressed. Power supplied from the power transmission unit 107 is transmitted to the single-axis horizontal movable stage 104 via the pin 502 and the compression spring 501 (and wiring).

[0044] <Regarding variations of the present invention> The present invention is not limited to the embodiments described above, but includes various modifications. For example, the embodiments described above are described in detail for the purpose of clearly illustrating the present invention, and it is not necessary to have all the configurations described, and modifications can be made without departing from the spirit of the invention.

[0045] In Embodiment 2, the power transmission unit 107 was described as providing point support to the power transmission unit 106 via the pin 502. A similar structure can also be provided in Embodiment 1. That is, the bottom surface of the power transmission unit 106 can be partially made to protrude to form a convex portion, and the power transmission unit 107 can be configured to provide point support to the power transmission unit 106 via this convex portion. This allows frictional heat to be suppressed in the same way as in Embodiment 2.

[0046] In the embodiments described above, the flowchart in Figure 4, which shows the process up to the completion of sample processing, depicts continuous processing while constantly moving back and forth within the pre-set drive range of the single-axis horizontal movable stage. However, it is also possible to perform planar milling of the sample at one point, and after the processing is completed, move the single-axis horizontal movable stage to perform planar milling of the sample again at another point.

[0047] In the embodiments described above, the control unit 114 can be configured by hardware such as a circuit device that implements its function, or by a computing device such as a CPU (Central Processing Unit) executing software that implements its function. [Explanation of symbols]

[0048] 100: Ion milling apparatus 104: 1-axis horizontal movable stage 105: 1-axis horizontal movable stage holder 106: Power transmission section of the rotating stage 107: Power transmission section of the fixed base 108: Insulator 109: Permanent Magnet 114: Control Unit 501: Compression spring 502: Pin

Claims

1. An ion milling apparatus that irradiates a sample with an ion beam, A rotating stage that rotates around an axis of rotation, A movable stage, which is installed on the upper surface of the rotating stage and moves in a direction not parallel to the axis of rotation, A fixed base supporting the aforementioned rotating stage, Equipped with, The rotating stage includes a first power transmission unit capable of transmitting power to the movable stage, The aforementioned fixed base section includes a second power transmission section that receives power from a power source, The first power transmission unit and the second power transmission unit are configured to transmit power supplied by the power source to the movable stage by contacting each other. The ion milling apparatus further includes a contact maintenance member that maintains contact between the first power transmission unit and the second power transmission unit by exerting a force that presses the first power transmission unit and the second power transmission unit against each other. The ion milling apparatus further includes a sensor for detecting the rotation of the rotating stage, The aforementioned sensor is The first member attached to the aforementioned fixed base portion, A second member attached to the aforementioned rotating stage, Equipped with, The second member rotates together with the rotating stage, The first member detects the rotation of the second member by receiving power through the second power transmission unit. An ion milling apparatus characterized by the following features.

2. The first power transmission section has a portion made of a magnetic material, The contact maintenance member is composed of a magnet that exerts a magnetic force that attracts the magnetic material, thereby exerting a force that presses the first power transmission unit and the second power transmission unit against each other. The ion milling apparatus according to claim 1, characterized in that it is a feature of the present invention.

3. The aforementioned contact maintenance member is composed of a pin incorporating a compression spring. The contact maintenance member is configured such that the action of the compression spring causes the pin to exert a force that presses the first power transmission unit and the second power transmission unit against each other. The ion milling apparatus according to claim 1, characterized in that it is a feature of the present invention.

4. The movable stage is configured to hold the sample, The ion milling apparatus further includes an ion source that emits the ion beam, The ion milling apparatus further includes a control unit that controls the rotating stage and the movable stage, The control unit aligns the beam center axis of the ion beam with the rotation axis, and then moves the movable stage to process the sample with the ion beam. The ion milling apparatus according to claim 1, characterized in that it is a feature of the present invention.

5. The ion milling apparatus further includes a control unit for controlling the operation of the ion milling apparatus. When the sensor detects that the rotational movement of the rotating stage is not as specified, the control unit stops processing the sample with the ion beam. The ion milling apparatus according to claim 1, characterized in that it is a feature of the present invention.

6. The first power transmission unit includes a protrusion that contacts the second power transmission unit, The second power transmission unit is configured to point-support the first power transmission unit via the protrusion. The ion milling apparatus according to claim 1, characterized in that it is a feature of the present invention.

7. The first power transmission unit includes a protrusion that contacts the second power transmission unit, The second power transmission unit is configured to point-support the first power transmission unit via the protrusion, The aforementioned protrusion is formed by the aforementioned pin. The ion milling apparatus according to claim 3, characterized in that it is as described above.

8. The control unit moves the movable stage while rotating the rotary stage, thereby processing a line shape on the sample using the ion beam. The ion milling apparatus according to feature 4.

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