Ion milling device

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

Ion milling equipment

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

[0002] Ion milling equipment irradiates a sample (e.g., metal, semiconductor, glass, ceramic, etc.) to be observed with an electron microscope with an unfocused ion beam. The sputtering phenomenon that accompanies ion beam irradiation ejects atoms from the sample surface, allowing for stress-free polishing of the sample surface or exposure of the sample's internal structure. Because the polished or exposed surface becomes the observation surface for scanning electron microscopes or transmission electron microscopes, ion milling equipment is used as a sample pretreatment device.

[0003] There are several methods for processing samples using ion milling equipment, but the method of ion milling the surface of a rotating sample by irradiating it with an ion beam at an angle is called planar milling. In addition to polishing the sample surface, planar milling can be performed by aligning the center of sample rotation with the center of the ion beam, resulting in a conical shape. In recent years, planar milling has been applied to delayering semiconductors (flash memory).

[0004] With the recent increase in flash memory capacity, there is an increasing demand for wide-area processing, but with current milling methods, there is no way to expand the processing area other than by moving the processing position slightly and performing milling multiple times, which raises concerns about the lengthening of processing time.

[0005] Japanese Patent Application Laid-Open No. 2006-103662 (Patent Document 1) describes a technique related to a sample stage in a charged particle beam device. The document aims to "enable rapid sample placement and replacement in a charged particle beam device," and describes the following technology: "A charged particle beam device includes a charged particle beam column that irradiates a sample with a charged particle beam, a rotary stage 5A having a base 5d and a rotary moving part that rotates about a rotation axis R1 relative to the base 5d, and the sample stage moves the sample relative to the charged particle beam column, a rotary connector 56 that is arranged coaxially with the rotation axis R1 and interposed between the base 5d and the rotary moving part, and a contact pin 55a that is arranged above the sample stage and electrically connected to the rotary connector 56" (see Abstract).

[0006] Japanese Patent Application Laid-Open No. 2018-166042

[0007] In order to process a line shape using the planar milling method in an ion milling device, it is necessary to place the rotating part of the sample stage at the bottom and place a sample movement stage (hereinafter referred to as the one-axis horizontally movable stage) 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 horizontally movable stage to form the line shape.

[0008] The horizontally movable stage is moved horizontally by a motor, for example, and therefore requires a power supply to its drive mechanism. This means that power supply wiring must be connected to the horizontally movable stage, and then power must be supplied to this wiring. If this wiring is connected directly to the power supply, there is a possibility that it will become twisted as the stage rotates. Therefore, when placing the horizontally movable stage on a rotating stage, it is considered necessary to use rotary contacts to ensure a power path.

[0009] The rotary contact type wiring uses mercury in the contact area to ensure contact. －３If a rotary contact structure is brought into the sample chamber of an ion milling apparatus (pressures below 100 Pa), mercury will sublime, 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 one-axis horizontally movable stage is mounted on a rotating body. However, in the structure described in this document, if the one-axis horizontally movable stage is placed on the sample rotation axis, there is a high risk of the wiring becoming twisted and breaking, which is thought to make it difficult to supply power. It is possible that this point has not been fully considered in this document.

[0011] The present invention has been made in consideration of the above-mentioned problems, and aims 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.

[0012] The ion milling apparatus of the present invention comprises a rotary stage, a movable stage installed on the upper surface of the rotary stage, and a fixed base portion supporting the rotary stage, wherein the rotary stage comprises a first power transmission portion and the fixed base portion comprises a second power transmission portion, and the ion milling apparatus further comprises a member that exerts a force pressing the first power transmission portion and the second power transmission portion against each other.

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

[0014] 1B is a top view of the ion milling apparatus 100 according to the first embodiment. FIG. 1C is a front view of the ion milling apparatus 100. FIG. 1D is an enlarged view of the stage mechanism of FIG. 1B. FIG. 1E is a schematic diagram showing an ion source 101 employing the Penning method and a power supply circuit that applies a control voltage to electrode components of the ion source 101. FIG. 1F is a diagram showing a state in which a beam probe is scanned with respect to an ion beam irradiated from the ion source. FIG. 1G is a profile of an ion beam. FIG. 1H is a diagram showing a processed shape when the sample rotation central axis and the ion beam central axis are eccentric. FIG. 1I is a diagram showing a processed shape of a sample when the X coordinate is moved little by little using a stage having the structure shown in FIG. 1. FIG. 1J is a flowchart illustrating the procedure for processing a sample using a stage having the structure shown in FIG. 1. FIG. 1J is an enlarged view of the periphery of the stage of the ion milling apparatus 100 according to a second embodiment.

[0015] 1A is a top view of an ion milling apparatus 100 according to a first embodiment of the present invention. The ion milling apparatus 100 includes an ion source 101, a sample chamber 102, a stage tilt unit 103, a one-axis horizontally movable stage 104, a one-axis horizontally movable stage holder 105, a control unit 114, and a vacuum pumping unit 115.

[0016] The ion milling apparatus 100 is used as a pretreatment device for observing the surface or cross section of a sample using a scanning electron microscope or a transmission electron microscope, and is also used for semiconductor delayering. During ion milling, the sample chamber 102 is always kept at a high vacuum (10 －３ The pressure in the ion source 101 is maintained at 100 Pa or less. Ar gas introduced from the outside is ionized by discharging within the ion source 101, and the ion beam is irradiated onto the sample. The control unit 114 controls each component of the ion milling apparatus 100.

[0017] 1B is a front view of the ion milling apparatus 100. The ion milling apparatus 100 further includes a rotary stage power transmission section 106 (first power transmission section), a fixed base power transmission section 107 (second power transmission 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 a single-axis horizontally movable stage 104. The single-axis horizontally movable stage 104 is placed on a single-axis horizontally movable stage holder 105. The wiring of the single-axis horizontally movable stage 104 is connected to a rotary stage power transmission unit 106. The single-axis horizontally movable stage holder 105 is disposed on a stage rotation unit 112 and a stage rotation shaft 113, and is therefore able to rotate freely (i.e., it can operate as a rotary stage). The stage rotation unit 112 is fixed inside a stage rotation bearing 111, and a power transmission unit 107 of the fixed base 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 (e.g., the power transmission unit 107), and the second member is attached to the rotation stage (e.g., the power transmission unit 106). As the rotation stage rotates, the second member rotates. The first member detects the rotation of the second member. For example, the second member may be composed of a permanent magnet, and the first member may be configured as a sensor that detects the magnetic force of the second member each time the second member approaches. This makes it possible to detect the rotation of the rotation stage. Because 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 is not limited to the configuration shown in FIG. 1B as long as it can detect the rotation of the rotation stage.

[0020] Fig. 1C is an enlarged view of the stage mechanism of Fig. 1B. A magnetic material (Fe, Ni, etc.) is embedded in the power transmission unit 106 of the rotary stage, and as shown in Fig. 1C, the power transmission unit 106 is attracted by a permanent magnet 109 disposed between the power transmission unit 107 and the insulator unit 108. This allows the power transmission unit 106 of the rotary stage to rotate while sliding against the power transmission unit 107 while maintaining close contact with it.

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

[0022] Magnetic attraction F ｍａｇ In addition, as the mass of the sample increases, the force of gravity F ｇ increases, the friction 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. At this time, depending on the maximum torque value of the motor that rotates the stage, there is a risk that the stage will not rotate. If it does not rotate, a rotation sensor 116 provided on the side sends feedback to the control unit 114 to stop the rotation.

[0023] In this embodiment, the configuration includes a one-axis horizontally movable stage, but a two-axis horizontally movable stage may also be used. Also, 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 that is not highly magnetic (such as a samarium-cobalt magnet).

[0024] 2A is a schematic diagram showing an ion source 101 employing the 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 has, as its main components, a first cathode 201, a second cathode 202, an anode 203, a permanent magnet 204, an accelerating electrode 205, a gas pipe 206, and a gas flow rate control unit 207.

[0025] To generate an ion beam, argon gas is injected into the ion source 101 through a gas pipe 206. Inside the ion source 101, a first cathode 201 and a second cathode 202, which are set to the same potential via a permanent magnet 204, are arranged facing each other, and an anode 203 is arranged between the first cathode 201 and the second cathode 202. A discharge voltage V is applied to the first cathode 201, the second cathode 202, and the anode 203 from a high-voltage power supply in the control unit 114. ｄA permanent magnet 204 disposed in the ion source 101 applies a Lorentz force to the generated electrons, causing the electrons to move in a spiral motion.

[0026] The electrons collide with argon gas injected from a gas pipe 206 under the control of a gas flow rate control unit 207, generating plasma and generating argon ions. An acceleration voltage V ａ is applied to the argon ions, which are then extracted by the accelerating electrode 205 and emitted as an ion beam.

[0027] FIG. 2B shows how the beam probe is scanned with respect to the ion beam emitted from the ion source.

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

[0029] Figure 2D shows the processed shape when the central axis of the sample rotation and the central axis of the ion beam are offset. Eccentricity allows for wider processing. Increasing the amount of offset results in a flat surface (2.0 mm in Figure 2D), whereas excessive offset results in a loss of flatness (2.5 mm and 3.0 mm in Figure 2D). Applying this result, linear processing can be achieved by moving the sample while maintaining the alignment of the central axis of the sample rotation and the central axis of the ion beam. As shown in Figure 2D, as the amount of offset increases, the processed shape gradually deviates from a Gaussian distribution. Therefore, considering the ease of control of the processed shape, it is desirable to have an offset of zero. In other words, it is desirable for the central axis of the sample rotation and the central axis of the ion beam to be aligned.

[0030] Figure 3 shows the processed shape of a sample when the X coordinate is moved little by little using a stage with the structure shown in Figure 1. The sample rotation axis coincides with the central axis of the ion beam and is constantly rotating. The X coordinate of the starting point of processing is set to -a (mm). The processed shape at this time follows the shape of the beam profile, resulting in a shape that approximates 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 to be an elongated hole when viewed from above. The length of the elongated hole (the distance between the centers of the circles at both ends) is a (mm), the same as the movement distance along the X axis. Similarly, when the X coordinate is moved in the range of -a to a (mm), the processed shape is an elongated hole with a length of 2a. While Figure 3 uses a single-axis movable stage, a two-axis movable stage may be used to further expand the movable range.

[0031] Fig. 4 shows a flowchart explaining the procedure for processing a sample using a stage having the structure shown in Fig. 1. Each step is performed by controlling each part using the control unit 114. Each step in Fig. 4 will be explained below.

[0032] S301: A sample is placed on the one-axis horizontally movable stage 104. Taking into consideration that the sample rotation axis and the center of the ion beam coincide with each other, a processing start point is determined.

[0033] S302: The sample chamber 102 is evacuated by the evacuation unit 115.

[0034] S303: Set the driving range of the single-axis horizontally movable stage 104. In principle, during processing, the single-axis horizontally movable stage 104 moves back and forth within the driving range set in this flow. In the case of a two-axis horizontal stage, the driving range may be set to be a single stroke, and the stage may be set to move back and forth between the start point and the end point.

[0035] S304: The drive range set in S303 is checked to see if the rotary contact portion (the portion where the power transmission portion 106 of the rotary stage and the power transmission portion 107 of the fixed base portion rotate while in contact) can be driven without any problems. If the single-axis horizontally movable stage 104 does not move, a sensor built into the single-axis horizontally movable stage 104 detects this, and the process proceeds to S305. If the rotary contact portion 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: Processing is stopped.

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

[0038] S307: An ion beam is output to start processing.

[0039] S308: It is confirmed whether or not the machining has been performed sufficiently based on the drive range set in S303. If it has not been performed sufficiently, the process returns to S303, the drive range of the single-axis horizontally movable stage 104 is reset, and machining is resumed. If it has been performed sufficiently, the process proceeds to S309.

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

[0041] Summary of First Embodiment The ion milling apparatus 100 according to the first embodiment includes a power transmission unit 106 disposed within a single-axis horizontally movable stage holder 105 that constitutes a rotary stage. Power is supplied to the single-axis horizontally movable stage 104 via the power transmission units 106 and 107. A magnetic material is embedded within 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. This allows the rotary stage to be rotated while sliding. This structure rotates while in contact with a conductive portion, similar to rotary contact wiring. This makes it possible to install the single-axis movable stage on the sample rotary stage without using mercury.

[0042] Second Embodiment FIG. 5 is an enlarged view of the stage and its surroundings of an ion milling apparatus 100 according to a second embodiment of the present invention. In the first embodiment, a magnet is embedded in the fixed base to ensure contact between the power transmission units 106 and 107. In the second embodiment, 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, maintaining constant contact between the two. This allows rotation while maintaining contact between the power transmission units 106 and 107, as in the first embodiment, and also allows power to be supplied to the one-axis horizontally movable stage 104. The remaining configuration is the same as in the first embodiment. The compression spring 501 and the pin 502 function as contact maintaining members that maintain contact between the power transmission units 106 and 107 by exerting a force pressing the power transmission units 106 and 107 against each other.

[0043] The power transmission unit 107 supports the power transmission unit 106 at points via the pins 502 (protrusions). This minimizes the contact area between the power transmission units 106 and 107. This makes it possible to suppress frictional heat generated as the rotary stage rotates. The power supplied from the power transmission unit 107 is transmitted to the single-axis horizontally movable stage 104 via the pins 502 and compression springs 501 (and wiring).

[0044] <Modifications of the present invention> The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail to clearly explain the present invention, and it is not necessary to include all of the described configurations, and modifications can be made within the scope of the gist thereof.

[0045] In the second embodiment, it has been described that the power transmission unit 107 supports the power transmission unit 106 at points via the pins 502. A similar structure can also be provided in the first embodiment. That is, the bottom surface of the power transmission unit 106 can be partially protruded to form a convex portion, and the power transmission unit 107 can be configured to point-support the power transmission unit 106 via the convex portion. This makes it possible to suppress frictional heat, as in the second embodiment.

[0046] In the above embodiment, in the flowchart up to the completion of sample processing explained in FIG. 4, continuous processing is performed while constantly moving back and forth within a preset driving range of the 1-axis horizontally movable stage. However, it is also possible to perform flat milling of the sample at a certain point, and after processing is completed, move the 1-axis horizontally movable stage and perform flat milling of the sample again at a different point.

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

[0048] 100: Ion milling device 104: One-axis horizontally movable stage 105: One-axis horizontally movable stage holder 106: Power transmission part of rotary stage 107: Power transmission part of fixed base part 108: Insulator part 109: Permanent magnet 114: Control unit 501: Compression spring 502: Pin

Claims

1. An ion milling apparatus for irradiating a sample with an ion beam, a rotation stage that rotates around a rotation axis; a movable stage that is disposed on an upper surface of the rotation stage and moves in a direction not parallel to the rotation axis; a fixed base portion supporting the rotary stage; Equipped with the rotary stage includes a first power transmission unit capable of transmitting power to the movable stage; the fixed base portion includes a second power transmission portion that receives power from a power source; the first power transmission unit and the second power transmission unit are configured to contact each other to transmit power supplied by the power source to the movable stage, the ion milling apparatus further includes a contact maintaining member that maintains contact between the first power transmission portion and the second power transmission portion by exerting a force that presses the first power transmission portion and the second power transmission portion against each other; The ion milling apparatus further includes a sensor for detecting rotation of the rotary stage; The sensor a first member attached to the fixed base; a second member attached to the rotary stage; Equipped with the second member rotates together with the rotary stage; The first member receives power supply via the second power transmission unit to detect rotation of the second member. An ion milling apparatus characterized by:

2. the first power transmission unit has a portion made of a magnetic material, The contact maintaining member is configured by 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.

2. The ion milling apparatus according to claim 1.

3. The contact maintaining member is constituted by a pin incorporating a compression spring, The contact maintaining member is configured so that the pin exerts a force pressing the first power transmission portion and the second power transmission portion against each other under the action of the compression spring.

2. The ion milling apparatus according to claim 1.

4. the movable stage is configured to mount 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 for controlling the rotary stage and the movable stage; The control unit causes the beam center axis of the ion beam to coincide with the rotation axis, and then moves the movable stage, thereby processing the sample with the ion beam.

2. The ion milling apparatus according to claim 1.

5. The ion milling apparatus further includes a control unit that controls an operation of the ion milling apparatus. The control unit stops processing the sample with the ion beam when the sensor detects that the rotational movement of the rotary stage is not as specified.

2. The ion milling apparatus according to claim 1.

6. the first power transmission portion includes a protrusion that contacts the second power transmission portion, The second power transmission unit is configured to point-support the first power transmission unit via the protrusion.

2. The ion milling apparatus according to claim 1.

7. the first power transmission portion includes a protrusion that contacts the second power transmission portion, the second power transmission unit is configured to point-support the first power transmission unit via the protrusion, The protrusion is formed by the pin.

4. The ion milling apparatus according to claim 3.

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.

5. The ion milling apparatus according to claim 4.