Electrostatic chuck

Abstract

An electrostatic chuck (101) having a monopolar structure is provided with: a dielectric body (2) having an electrode (23) and a dielectric layer (25) covering the electrode (23) and having a volume resistivity of 109 to 1013 Omega cm; and an unclamping mechanism having an unclamping member 1 belonging to the conductor. The disengagement member (1) is connected to the ground and is an opposite electrode of the electrode (23).

Description

Technical Field

[0001] The present invention relates to an electrostatic chuck that can be used in a robot arm, a fixing auxiliary tool, etc. to adsorb an adsorption object (workpiece). Background Art

[0002] Electrostatic chucks have been primarily used in semiconductor manufacturing equipment. Electrostatic chucks can be broadly categorized into three types of adsorption: Coulomb, Johnson-Rahbek, and gradient. The Coulomb, gradient, and Johnson-Rahbek forces exerted by each electrostatic chuck do not act independently to hold the object. Rather, the balance of these three forces differs for each adsorption method, and the distinction is made based on which force predominantly affects the object.

[0003] Generally speaking, the so-called Coulomb force type refers to a force with a force of 10 14 Electrostatic chucks with a dielectric layer having a volume resistivity of Ω˙cm or higher and using a unipolar or bipolar charging method.

[0004] A simple understanding of the Coulomb force primarily generated in a Coulomb-type electrostatic chuck is that, in a configuration where a first electrode, a dielectric layer, and an object to be attracted are arranged in parallel, by simulating the object to be attracted with the second electrode, the parallel first and second electrodes, and the dielectric between them, can be considered a so-called capacitor. When a voltage is applied to the first and second electrodes, the energy generated by the electric field between them generates a force F that attracts the first and second electrodes.

[0005] According to the basic principle of capacitors, the attractive force F can be expressed as F = 1 / 2˙V 2 ˙S˙ ε / D 2 That is, the attractive force F is proportional to the square of the potential difference V between the first and second electrodes, and inversely proportional to the square of the distance D between the electrodes, and is proportional to the electrode area S and the relative dielectric constant between the first and second electrodes. ε Directly proportional.

[0006] If the attractive force F is regarded as the adsorption force in the electrostatic chuck, the adsorption force can be understood as: the higher the applied voltage, the thinner the thickness of the dielectric layer, and the smaller the relative dielectric constant of the dielectric layer. ε The higher the voltage, the stronger it is, and the higher the voltage used to charge the adsorbate.

[0007] In summary, it is more preferable to use a material having a high dielectric constant and a high dielectric breakdown strength, such as polyimide, for the dielectric layer of a Coulomb type electrostatic chuck.

[0008] In addition, Johnson's Rabec force type electrostatic chuck uses a volume resistivity of 10 9 to 10 13 An electrostatic chuck with a dielectric layer in the Ω˙cm range and a bipolar charging method.

[0009] In a Johnson-Rabec force-type electrostatic chuck, the dominant Johnson-Rabec force manifests based on the same capacitor-like adsorption principle as the Coulomb force. Simply put, when a voltage is applied to the internal electrode, a very small current flows from the back of the dielectric layer in contact with the internal electrode due to its low volume resistivity, reaching the surface of the dielectric layer. This makes the surface of the dielectric layer a virtual electrode. The energy accumulated due to the rapid potential change caused by the contact resistance at the slight distance between the adsorbate and the virtual electrode generates a force that attracts the internal electrode and the virtual electrode. In other words, while the adsorption force due to the Johnson-Rabec force is inversely proportional to the square of the distance between the electrodes, it is still greater than the adsorption force due to the Coulomb force because the distance between the electrodes is infinitesimally small.

[0010] However, since the current flows slightly into the adsorbate, the potential is continuously supplied to the adsorbate. Therefore, when a unipolar charging method is used, the potential difference between the electrode and the adsorbate continuously decreases, causing the adsorption force to decrease. Therefore, in general, a bipolar charging method is used in a Johnson-Rabec force type electrostatic chuck. In addition, the charge has the characteristic (current) of moving to areas with lower volume resistivity, so the charge will not move to an object with a volume resistivity higher than that of the dielectric layer. Therefore, Johnson-Rabec force type electrostatic chucks are only suitable for adsorption objects with a volume resistivity lower than that of the dielectric layer.

[0011] Finally, gradient-force electrostatic chucks utilize a bipolar charging method. The + and - (positive and negative) electrodes have a comb-like pattern, with alternating positive and negative electrodes. This configuration generates a highly nonuniform electric field near the dielectric layer. In gradient-force electrostatic chucks, the primary gradient force is the force that attracts adsorbates to the electrode with the stronger electric field within the nonuniform electric field between the positive and negative electrodes. This gradient force polarizes the adsorbate within the electric field, and, in accordance with Coulomb's law, attracts the adsorbate to the electrode with the stronger electric field.

[0012] When electric lines of force in an inhomogeneous electric field are concentrated, the gradient force increases. Therefore, shortening the distance between the positive and negative electrodes can enhance the suction force of a gradient-force electrostatic chuck. Furthermore, in electrostatic chucks with plate-shaped electrodes, these electrodes are typically arranged horizontally. Therefore, arranging the positive and negative electrodes in a comb-like pattern with shorter spacing increases the suction force of a gradient-force electrostatic chuck.

[0013] Furthermore, since the shorter the distance between the horizontally spaced positive and negative electrodes and the adsorbed object, the more concentrated the lines of electric force become, the stronger the electrostatic chuck's adsorption force can be, even with a thinner dielectric layer. Therefore, when the distance between the electrodes and the adsorbed object is shortened, it is preferable to select a dielectric layer with a relatively high volume resistivity and a high dielectric breakdown strength to maintain insulation from the electrodes.

[0014] As is clear from the description so far, Coulomb-type or Johnson-Rabec-type (JR) electrostatic chucks utilize high voltages, generating a nonuniform electric field between the electrodes and exhibiting gradient forces, making precise calculations of the adsorption force extremely difficult. Similarly, in gradient-type electrostatic chucks, objects contacting the dielectric layer are attracted by the principle of a capacitor, as described above with respect to the Coulomb force, making precise calculations of the adsorption force extremely difficult.

[0015] Generally speaking, when the object being attracted and fixed is a conductor or semiconductor, JR-type electrostatic chucks offer the strongest attraction per unit area at the same voltage. Therefore, JR-type electrostatic chucks are suitable for attracting and fixing objects with relatively small contact areas, such as small or elongated conductor or semiconductor workpieces (hereinafter referred to as small workpieces).

[0016] Electrostatic chucks are also finding applications beyond semiconductor manufacturing equipment, in applications that are difficult to address with conventional fixed handling methods such as vacuum devices (adsorption devices) or robotic arms. However, conventional electrostatic chucks are limited by cost and takt time (the speed of adsorption and detachment), failing to achieve the performance expected by users and hindering their introduction.

[0017] For example, in a vacuum device that uses the pressure difference from atmospheric pressure to adsorb and hold the adsorption object, when the adsorption object is a metal mesh or cloth, air may leak from the gap between the adsorption pad that supplies negative pressure and the adsorption object, making it difficult to pick up the above-mentioned adsorption object.

[0018] There are also existing robotic arms that have a pair of claws and use them to hold an object. However, it is important to avoid using robotic arms to hold metal mesh or cloth. This is because if the object has weak areas, such as the mesh holes of a metal mesh or the grain of a cloth, there is a risk of deformation or wrinkling of the object.

[0019] Regarding the use of a vacuum device for transporting large quantities of small workpieces, this would require installing a vacuum hole for each small workpiece to provide negative pressure, making it impractical. On the other hand, using a robot for transporting large quantities of small workpieces would require a pair of claws to pick up the small workpieces one by one, making it difficult to shorten transport time.

[0020] [Prior art literature]

[0021] [Patent Document]

[0022] Patent Document 1: Japanese Patent Application No. 2003-401841

[0023] Patent Document 2: Japanese Patent Application Laid-Open No. 2004-031599. Summary of the Invention

[0024] [Problems to be Solved by the Invention]

[0025] Electrostatic chucks can handle large quantities of small workpieces, a type of transport that is difficult to perform using vacuum equipment or robotic arms. Considering the aforementioned adsorption characteristics of electrostatic chucks, the following conclusions emerge: Coulomb or JR types are preferred for adsorbing and transporting metal mesh, Coulomb or gradient types are preferred for adsorbing and transporting cloth, and JR or gradient types are preferred for adsorbing and transporting small workpieces.

[0026] However, in the Coulomb type and the gradient type, a material such as polyimide having a high volume resistivity is used for the dielectric layer, and therefore there is a problem that it is difficult to reduce the potential through the dielectric layer.

[0027] Furthermore, because the object being held is dielectrically polarized during the process, the holding force on the holding surface tends to remain long after the electrostatic chuck is powered off. Consequently, with lightweight objects such as small components, this residual holding force can make it difficult to de-chuck the object.

[0028] On the other hand, the conventional JR type has the characteristic of being able to reduce the potential more easily than the Coulomb type and gradient type, which can shorten the time it takes for the adsorbed object to detach from the adsorption surface. However, further shortening the de-adhesion time is difficult with the conventional JR type. Furthermore, if the size of the adsorbed object is further minimized, the adsorbed object will not be able to cross the positive and negative electrodes and will not be adsorbed, resulting in the concern that the adsorbed object cannot be transported reliably.

[0029] Patent Document 1 discloses a JR-type electrostatic chuck that addresses the aforementioned issues. The electrostatic chuck of Patent Document 1 features a monopole structure that imparts an electric charge to the wafer through plasma discharge to hold the wafer in the chuck body. However, this structure is limited to wafer processing using plasma discharge for wafer holding, thus limiting the electrostatic chuck's intended applications.

[0030] Furthermore, Patent Document 2 discloses an electrostatic chuck for mounting insulating substrates such as wafers. This electrostatic chuck has a structure in which a monopolar electrostatic electrode is exposed on a mounting surface for the insulating substrate. Therefore, the electrostatic chuck of Patent Document 2 can only be used to attract objects with insulating surfaces, limiting its use and preventing it from attracting conductors through which current flows.

[0031] As described above, conventional electrostatic chucks capable of reliably clamping and unclamping a large number of small workpieces have problems such as high introduction costs, limited suction targets, and increased equipment size.

[0032] Therefore, an object of the present invention is to provide an electrostatic chuck that is inexpensive and highly versatile, does not increase the size or complexity of the equipment, and has excellent locking and de-locking properties.

[0033] [Methods used to solve the problem]

[0034] The inventors have focused on the fact that a physical release mechanism will inevitably contact an adsorbed object, and have provided an electrostatic chuck to solve the above problem.

[0035] A first aspect of the electrostatic chuck of the present invention is a monopolar electrostatic chuck having:

[0036] A dielectric body comprising: an electrode, and a dielectric covering the electrode and having a volume resistivity of 10 9 to 10 13 Ω˙cm dielectric layer; and

[0037] The unfastening mechanism has an unfastening member belonging to the conductor; and

[0038] The unfastening member is connected to the earth and serves as an opposite electrode to the electrode.

[0039] The unfastening member is a conductor connected to the ground, and functions as a counter electrode of the electrostatic chuck, thereby enabling the JR type electrostatic chuck to adsorb an object.

[0040] A second aspect of the electrostatic chuck of the present invention is the electrostatic chuck according to the first aspect, wherein the dielectric body is disposed vertically above the unclamping member.

[0041] A third aspect of the electrostatic chuck of the present invention is the electrostatic chuck of the first or second aspect, wherein the de-clamping member is a metallic mesh.

[0042] A fourth aspect of the electrostatic chuck of the present invention is the electrostatic chuck according to the third aspect, wherein the mesh has a thickness of 20 μm to 100 μm.

[0043] A fifth aspect of the electrostatic chuck of the present invention is the electrostatic chuck of the first or second aspect, wherein the unclamping member and the dielectric layer are arranged side by side in one direction.

[0044] A sixth aspect of the electrostatic chuck of the present invention is the electrostatic chuck according to the first aspect, wherein the de-clamping mechanism comprises a driving portion for driving the de-clamping member, and the driving portion is a motor or a power cylinder.

[0045] A seventh aspect of the electrostatic chuck of the present invention is the electrostatic chuck according to the second aspect, wherein the de-clamping member has elasticity and functions as a driving portion for driving the de-clamping member, or the de-clamping mechanism has a spring connected to the de-clamping member.

[0046] The Coulomb force, which contributes to adsorption, weakens inversely with the square of the mesh thickness, so a thin mesh is preferred. The inventors have diligently examined and determined that a mesh with a maximum thickness greater than 100 μm cannot achieve the desired adsorption force. Furthermore, if the mesh thickness is less than 20 μm, there is a risk of tangling during unfastening or wrinkling during adsorption. Therefore, a mesh thickness of 20 μm or greater is more preferred.

[0047] In addition, the mesh refers to a shape having many fine pores.

[0048] A seventh aspect of the electrostatic chuck of the present invention is the electrostatic chuck according to the second aspect, further comprising a drive unit for driving the aforementioned de-clamping mechanism or dielectric layer, wherein the drive unit is a motor or a power cylinder. The motor includes an electric motor such as a DC motor, a direct current motor, a servo motor, or a stepper motor, and the power cylinder includes an actuator capable of extension and contraction by, for example, oil pressure, air pressure, or water pressure.

[0049] [Effects of the invention]

[0050] Conventional JR-type electrostatic chucks require a special charge supply device to implement a bipolar charging method, which tends to complicate the design. However, the present invention utilizes a unipolar charging method, resulting in a simpler structure. Furthermore, the counter electrode in the electrostatic chuck of the present invention also serves as the release mechanism, simplifying the design and reducing costs. Furthermore, the unipolar structure ensures that the object being attracted reliably contacts the bipolar release mechanism.

[0051] Furthermore, according to the present invention, even in the event of unintended discharge and charge transfer during the physical release of the clamping mechanism, the relatively low volume resistivity of the dielectric layer allows for charge removal through charge transfer. Consequently, the electrostatic chuck's holding force is not reduced. Furthermore, the electrostatic chuck of the present invention does not require a charge removal mechanism, simplifying its components and reducing its cost.

[0052] Furthermore, when the object is a conductor, since the current flows between the counter electrode and the object without passing through the dielectric layer, no voltage drop occurs, and no attraction force is generated at the point of contact between the object and the counter electrode. However, compared to a configuration in which a dielectric layer is provided on the counter electrode, this allows for better current flow, so minimal contact between the object and the counter electrode is required. This results in an electrostatic chuck that is versatile and offers excellent locking and release properties.

[0053] According to the second aspect of the electrostatic chuck, when a voltage is applied to the electrostatic chuck, the unfastening portion is pulled toward the dielectric by a gradient force, thereby simplifying the unfastening mechanism.

[0054] In addition, according to the seventh aspect of the electrostatic chuck, if the deflection or spring of the release clamping member itself is used to set the release clamping member in a position where it is slightly separated from the dielectric by a tension weaker than the gradient force, the action of releasing the attachment or peeling off the release clamping member from the dielectric can be performed by the gradient force depending on whether a voltage is applied. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 FIG. 1 is a schematic diagram showing an electrostatic chuck according to a first embodiment of the present invention.

[0056] Figure 2 for Figure 1 A partial cross-sectional view of the main parts of the electrostatic chuck. Figure 2 Part (a) shows the fixed state of the adsorption object. Figure 2 Part (b) shows the released state of the adsorbed object.

[0057] Figure 3 Part (a) of Figure 1 A top view of the dielectric and electrodes of the electrostatic chuck is shown. Figure 3 Part (b) of Figure 1 A top view of the unclamping member of the electrostatic chuck is shown.

[0058] Figure 4 FIG. 1 is a schematic diagram showing an electrostatic chuck according to a second embodiment of the present invention.

[0059] Figure 5 Part (a) is a schematic diagram showing an electrostatic chuck according to a third embodiment. Figure 5 Part (b) is a schematic diagram showing an electrostatic chuck according to a fourth embodiment. DETAILED DESCRIPTION

[0060] Hereinafter, the embodiment and examples of the present invention will be described with reference to the accompanying drawings. In addition, the present invention is not limited to the embodiment. In the following description, the same reference numerals are given to the same components, and their descriptions are omitted or simplified.

[0061] (First embodiment)

[0062] Figure 1 Schematic diagram showing an electrostatic chuck 101 according to a first embodiment of the present invention. Figure 2 for Figure 1 A partial cross-sectional view of the main portion of the electrostatic chuck 101, Figure 2 Part (a) shows the fixed state of the adsorption object T after being adsorbed. Figure 2 Part (b) shows the released state after the adsorption object T is removed. Figure 3 Part (a) of Figure 1 A top view of the electrode 23 of the dielectric body 2 of the electrostatic chuck 101 is shown. Figure 3 Part (b) of Figure 1 A top view of the unclamping member 1 of the electrostatic chuck 101 is shown.

[0063] The electrostatic chuck 101 mainly includes a release mechanism and a dielectric body 2. Figure 2As shown, dielectric body 2 has a laminated structure comprising an insulating layer 21, an electrode 23 laminated on insulating layer 21, and a dielectric layer 25 completely covering electrode 23 and laminated on insulating layer 21. Furthermore, the de-clamping mechanism includes a de-clamping member 1, a device for moving or driving de-clamping member 1, and a support member for supporting de-clamping member 1. The de-clamping mechanism of this embodiment includes a lifting portion 112 connected to de-clamping member 1 and an electric motor 103 for driving lifting portion 112.

[0064] The dielectric layer 25 of the dielectric body 2 is made of a material having a volume resistivity of 1.0×10 9 to 1.0×10 13 Insulators with a resistance of Ω˙cm. Examples include ceramics, soft PVC (polyvinyl chloride), paper phenol (paper impregnated with phenolic resin), polyacetal, glass epoxy (glass fiber impregnated with liquid epoxy resin and cured by heat), conductive PE (polyethylene), polyurethane, EVA (ethylene-vinyl acetate), or insulating resins with a conductor mixed in and adjusted for volume resistivity.

[0065] The electrode 23 is made of a conductive material. Figure 3 As shown in part (a) of FIG, electrode 23 of this embodiment is planar when viewed from above. The shape of electrode 23 can, of course, be appropriately modified depending on the shape of the laminated insulating layer 21. Electrode 23 is connected to the negative electrode of power supply 108, which generates a DC voltage. Therefore, when switch 110 is turned on, the DC voltage at the negative electrode is applied to electrode 23.

[0066] The dielectric layer 25 is made of a material having a volume resistivity higher than that of the adsorbed object T. In addition, the amount of charge moving in the dielectric layer 25 increases as the volume resistivity of the dielectric layer 25 decreases, thereby increasing the generated JR force.

[0067] The volume resistivity of the insulating layer 21 needs to be equal to or higher than that of the dielectric layer 25. The inventors have found that the volume resistivity of the insulating layer 21 is preferably 1.0×10 15 Ω˙cm or more, more preferably 1.0×10 18 Ω˙cm or more.

[0068] If the volume resistivity of insulating layer 21 is lower than that of dielectric layer 25, charges will not migrate to dielectric layer 25 but will migrate to insulating layer 21. Consequently, charges cannot be accumulated in dielectric layer 25. Consequently, electrostatic chuck 101 cannot exert an attractive force and cannot attract an object.

[0069] In addition, the higher the planarity of the dielectric layer 25 is, the wider the contact area with the adsorption object T can be. Therefore, the dielectric body 2 is preferably manufactured by a hot stamping process with thermocompression bonding or a lamination process with lamination.

[0070] like Figure 3 As shown in part (b) of the figure, the release member 1 of the release mechanism is made of a metal film having multiple openings 11. The release member 1 is secured to the housing 106 of the electrostatic chuck 101 via a fixing member 104. Furthermore, the release member 1 is grounded. By setting the diameter of the openings 11 smaller than the outer dimensions of the object T to be attracted, contact between the object T and the release member 1 is ensured, ensuring reliable attraction.

[0071] The thickness of the metal film is preferably thinned to minimize the distance to the adsorbed object T, preferably 100 μm or less, and even more preferably 60 μm or less. This is because the gradient force weakens inversely proportional to the square of the distance. Therefore, if the metal film is thicker than 100 μm, there is a concern that the adsorption rate for the adsorbed object T, as envisioned by the inventors, may not be maintained. On the other hand, if the metal film is less than 20 μm, there is a concern that the metal film may become tangled during unfastening or wrinkled during adsorption, thereby reducing the unfastening rate for the adsorbed object T.

[0072] The release clamping member 1 having an opening 11 is preferably made by etching, laser processing, wire discharge processing or electric casting of a metal film. In contrast, if the opening of the metal film is made by mechanical processing such as punching, there is a concern that the peripheral portion of the punched hole will be deformed into a convex or concave shape, making the contact between the adsorption object T and the release clamping member 1 unstable, and the adsorption object cannot be stably adsorbed. It is not ideal to use a metal mesh made by weaving metal wires in the release clamping member. This is because the metal mesh becomes a convex or concave shape by crossing the wires, so similar to the aforementioned mechanical processing, there is a concern that the contact between the adsorption object T and the release clamping member 1 will be unstable, and the adsorption object cannot be stably adsorbed.

[0073] Furthermore, the housing 106 is provided with an electric motor 103, which is connected to the lifting unit 112 via a mechanism that converts rotational force into linear motion (e.g., rack and pinion). The lifting unit 112 can be moved in the Z direction ( Figure 1 The lifting part 112 of this embodiment is moved in the vertical direction. Figure 1The lifting portion 112 is connected to the release member 1. When a driving signal is received from a control unit (not shown), the release member 1 is moved in the Z direction by the rotational force of the electric motor 103, and the release member 1 is brought into contact with the dielectric layer 25.

[0074] Furthermore, the unfastening member 1 functions as a counter electrode that is grounded (0 V). Therefore, in this embodiment, a negative voltage is applied to the electrostatic chuck 101 , but a positive voltage may be applied.

[0075] Figure 2 Part (a) of Figure 2 Part (b) is a schematic cross-sectional view showing the action and effect of the adsorption step and the de-chucking step when the electrostatic chuck 101 is used.

[0076] The adsorption step of this embodiment starts from the state where the electric motor 103 is driven to move the lifting part 112 upward in the Z direction and the unfastening member 1 is brought into contact with or close to the dielectric 2. In this state, if the switch 110 of the power supply 108 provided in the electrostatic chuck 101 is turned on, the adsorption step starts and a predetermined DC voltage is applied to the electrode 23. As a result, a charge of "-" is induced on the electrode 23 (see Figure 2 (a) of the .

[0077] In this state, if Figure 2 As shown in part (a), when the clamping member 1, the insulating layer 21 and the dielectric layer 25 have the aforementioned volume resistivity characteristics, the adsorption object T ( Figure 2 T) shown on the right side of part (a) is adsorbed on the dielectric layer 25.

[0078] At this time, the "-" charge is supplied from the electrode 23 side to the dielectric layer 25, and the "-" charge moves to the unfastening member 1 side of the dielectric layer 25. In addition, when the charge moves to the attraction object T which becomes 0V, a rapid voltage drop occurs, and an attraction force as a JR-type attraction is generated on the dielectric layer 25, which pulls the attraction object T ( Figure 2 The right side of part (a) illustrates T) adsorption.

[0079] Since the unfastening member 1 is grounded, the charge transferred to the attracted object T is rejected by the unfastening member 1 , maintaining the attracted object T at 0 V. As a result, a potential difference sufficient to generate an attracting force to attract the attracted object T is maintained between the dielectric layer 25 and the attracted object T.

[0080] In addition, even if the adsorption object T( Figure 2Even when the object T shown on the left side of part (a) does not contact the dielectric layer 25, the gradient force generated between the electrode 23 and the release clamping member 1 causes the adsorbed object T to be pulled to the electrode 23 side, thereby allowing it to remain on the electrostatic chuck (release clamping member 1).

[0081] Furthermore, during the adsorption step, the releasing clamp member 1 is vibrated or swung, and pressure is applied to the adsorption object T. This assists the adsorption object T in moving in a direction with a stronger electric field, resulting in an extremely excellent adsorption rate.

[0082] In the case where the adsorption object T is a very small workpiece, the adsorption object T ( Figure 2 This is because the gradient force is correlated with the surface area of the dielectric layer, and because the surface area increases relatively as the volume (weight) of the adsorption target T decreases, the gradient force becomes relatively larger.

[0083] In addition, the gradient force is determined by the potential difference, so when the volume resistivity is 1.0×10 14 Coulomb or gradient electrostatic chucks with dielectric layers of Ω˙cm or greater can also be adsorbed using a gradient force and released using the same de-caulking mechanism as in this embodiment. However, when de-caulking an adsorbed object from an electrostatic chuck with residual adsorption force, frictional charging or peeling charge can lead to an opposite potential, making repeated adsorption impossible. To avoid this, a special power supply with switchable polarity is required, or a step is required to remove the charge accumulated in the dielectric layer each time the chuck is released. Therefore, the JR type configuration is superior.

[0084] Then, in the unfastening step, Figure 2 As shown in part (b) of FIG. 1 , the electric motor 103 is driven to move the lifting portion 112 downward in the Z direction, and the release clamping member 1 is separated from the dielectric body 2. At the same time, if the switch 110 (see FIG. 1 ) is turned off, Figure 1 . ), when the application of the voltage to the electrode 23 stops, the adsorbed object T is detached from the unfastening member 1.

[0085] [Example]

[0086] The inventors conducted a verification test on the adsorption rate of an electrostatic chuck under the following conditions.

[0087] (Empirical Test 1)

[0088] The insulating layer 21 of Examples 1 and 2 is made of NC nylon, which is a resin material, and has a thickness of 5 mm.

[0089] The electrodes 23 in Examples 1 and 2 are made of copper and have a thickness of 7 μm.

[0090] The dielectric layer 25 of Example 1 has a volume resistivity of 1.0×10 13 Ω˙cm, 300μm thick polyacetal plate, the dielectric layer 25 of Example 2 is made of a volume resistivity of 1.0×10 9 Made of soft PVC with a thickness of 500μm and a thickness of Ω˙cm.

[0091] The unfastening member 1 (counter electrode) of the unfastening mechanism is a plate-like member formed by etching a plurality of openings 11 with a diameter of 1 mm at 100 μm intervals in a 20 μm SUS foil. A pneumatic cylinder is used as a driving unit for the unfastening member 1 .

[0092] In addition, as the adsorption objects T, 30 pieces of the adsorption objects T with a size of 1.7 × 2.1 × 0.7 mm and a surface resistivity of 3 × 10 -1 Ω / sq three-dimensional component. Furthermore, a voltage of 2.2 kV was applied from power supply 108. Under atmospheric pressure at room temperature of 22°C and humidity of 30 to 35%, a cycle consisting of three steps: an adsorption step in which the electrostatic chuck 101 adsorbs the adsorbed object T; a movement step in which the electrostatic chuck 101 is moved while retaining the adsorbed object T; and a de-clamping step in which the adsorbed object T is released from the electrostatic chuck 101. This cycle was repeated five times for 30 adsorbed objects T, and the changes in the adsorption rate and de-clamping rate were observed. The adsorption step, movement step, and de-clamping step each required 5 seconds. Furthermore, in the movement step, the electrostatic chuck 101 was moved on a plane from a first predetermined position to a second predetermined position, requiring 5 seconds.

[0093] In addition, when an adsorbed object T falls in the moving step, it is excluded from the adsorbed objects T that can be adsorbed in the adsorption step. Therefore, it is not included in the number of adsorbed objects T released in the desorption step.

[0094] [Comparative Example]

[0095] In the comparative example, the volume resistivity ratio of the dielectric layer used was 1.00×10 9 Still small 1.0×10 6 Ω˙cm dielectric layer (Comparative Example 1) and volume resistivity ratio 1.00×10 13 Still larger than 1.0×10 18 An evaluation test was conducted on a dielectric layer with a thickness of Ω˙cm (Comparative Example 2).

[0096] The following results were obtained from Experimental Test 1 (see Table 1). The average adsorption rate for Example 1 over five runs was 99%, and the average adsorption rate for Example 2 over five runs was 94%. In contrast, the adsorption rates for Comparative Example 1 were 0%, and 48%, respectively. Therefore, it was confirmed that the electrostatic chuck of Example 1 achieved even better adsorption performance than Comparative Example 1.

[0097] [Table 1]

[0098]

[0099]

[0100] (Empirical Test 2)

[0101] The insulating layer 21 is made of NC nylon, which is a resin material, and has a thickness of 5 mm.

[0102] The electrode 23 is made of copper and has a thickness of 7 μm.

[0103] The volume resistivity of the dielectric layer 25 is 1.0×10 13 Polyacetal plate with a thickness of Ω˙cm and a thickness of 300μm.

[0104] The unfastening member 1 (counter electrode) of the unfastening mechanism is a plate-like member formed by etching multiple openings 11 with a diameter of 1 mm at 100 μm intervals in 20 μm, 60 μm, 100 μm, and 200 μm SUS foils. A pneumatic cylinder is used as the driving unit for the unfastening member 1.

[0105] In addition, as the adsorption objects T, 30 pieces of the adsorption objects T with a size of 1.7 × 2.1 × 0.7 mm and a surface resistivity of 3 × 10 -1 Ω / sq three-dimensional component. Furthermore, a voltage of 2.2 kV was applied from power supply 108. Under atmospheric pressure at room temperature of 22°C and humidity of 30 to 35%, a cycle consisting of three steps: an adsorption step in which the electrostatic chuck 101 adsorbs the adsorbed object T; a movement step in which the electrostatic chuck 101 is moved while retaining the adsorbed object T; and a de-clamping step in which the adsorbed object T is released from the electrostatic chuck 101. This cycle was repeated five times for 30 adsorbed objects T, and the changes in the adsorption rate and de-clamping rate were observed. The adsorption step, movement step, and de-clamping step each required 5 seconds. Furthermore, in the movement step, the electrostatic chuck 101 was moved on a plane from a first predetermined position to a second predetermined position, requiring 5 seconds.

[0106] In addition, when an adsorbed object T falls in the moving step, it is excluded from the adsorbed objects T that can be adsorbed in the adsorption step. Therefore, it is not included in the number of adsorbed objects T released in the desorption step.

[0107] The following results were obtained from empirical experiment 2 (refer to Figure 2 The adsorption rate averaged over five runs at 20 μm was 100%, at 60 μm was 99%, and at 100 μm was 86%. In contrast, the adsorption rate averaged over five runs at 200 μm was 17%. Therefore, it can be confirmed that the electrostatic chuck of the embodiment also achieved good adsorption results at 20 μm to 100 μm.

[0108] [Table 2]

[0109]

[0110] The material of the dielectric layer used in Experimental Tests 1 and 2 can of course be changed as appropriate. This is because the same results as those in Experimental Tests 1 and 2 can be obtained if the material has a desired volume resistivity.

[0111] [Second embodiment]

[0112] The electrostatic chuck 201 of the second embodiment includes a drive unit 203, which differs from the drive unit 103 of the first embodiment in that it moves a support unit 205 in the direction indicated by arrow Z (vertical direction). The dielectric member 2 is coupled to the support unit 205, and the drive unit 203 allows the dielectric member 2 to contact or separate from the unfastening member 1. Furthermore, the drive unit 203 is disposed within the housing 204 of the electrostatic chuck 201.

[0113] The structure and function of the electrostatic chuck 201 of the second embodiment are the same as those of the first embodiment. As described in the first and second embodiments, the structure of the drive unit can be modified as appropriate, provided that the drive unit can move the unclamping member 1 and the dielectric body 2 in a relative direction toward and away from each other. Furthermore, the drive unit of the first and second embodiments, as well as the embodiments described below, can be an electric motor or a power cylinder, as appropriate.

[0114] [Third embodiment]

[0115] The drive unit 303 of the third embodiment is different from the drive unit 103 of the first embodiment and does not have a power cylinder or a motor. The drive unit 303 installs the release clamping member 302 on the housing 112 of the electrostatic chuck 301 via the spring 303. The elastic force of the spring 303 used is weaker than the Coulomb force that causes the release clamping member 302 (for example, a metal mesh) to be attracted upward in the Z direction by applying a voltage from the power supply 108. If the power supply 108 is turned off during the release step, the Coulomb force caused by the electrostatic chuck 301 no longer takes effect, and the release clamping member 302 is detached from the dielectric body 2 due to the elastic force of the spring 303. In other words, the spring 303 extends downward in the Z direction and returns to its initial position.

[0116] According to the third embodiment, the structure of the electrostatic chuck 301 can be simplified and reduced in cost.

[0117] [Fourth embodiment]

[0118] The driving unit of the fourth embodiment is different from the driving unit 103 of the first embodiment and does not include a cylinder or a motor. Figure 5 Part (b) is a schematic diagram showing an electrostatic chuck 401 according to a fourth embodiment.

[0119] Furthermore, the drive unit 402 of the fourth embodiment, similar to the first embodiment, mounts a de-clamping member 402 on the housing 112 of the electrostatic chuck 401. Unlike the de-clamping member 302 of the first embodiment, the de-clamping member 402 of the fourth embodiment is constructed from a member having a predetermined elastic force. The de-clamping member 402 (e.g., a metal mesh) is constructed from a member having an elastic force weaker than the Coulomb force (upward in the Z direction) that is applied when a voltage is applied from the power supply 108. In other words, if the power supply is turned off during the de-clamping step, the Coulomb force generated by the electrostatic chuck 401 no longer acts on the de-clamping member 402, and the de-clamping member 402 is released from the dielectric body 2 by the elastic force of the de-clamping member 402. That is, when the power source 108 is on, the release fastening member 402 contacts the dielectric body 2 while being bent upward in the Z direction. When the power source 108 is off, the release fastening member 402 bends downward in the Z direction and separates from the dielectric body 2.

[0120] According to the fourth embodiment, the structure of the electrostatic chuck 401 can be simplified and reduced in cost compared to the electrostatic chuck 301 of the third embodiment.

[0121] While the aforementioned embodiments and examples employ a configuration in which the release member 1 and dielectric body 2 are arranged vertically face-to-face, the electrostatic chuck of the present invention is not limited to this configuration. For example, the positional relationship between the release member 1 and dielectric body 2 can be such that the release mechanism can physically engage and release the object being attracted. Therefore, the release member 1 and dielectric body 2 can be arranged horizontally, side by side, or parallel to each other in a direction oblique to the horizontal (i.e., in one direction).

[0122] Description of Reference Numerals

[0123] 1.302,402 release the fixed components

[0124] 2 Dielectric

[0125] 101, 201, 301, 401 electrostatic chucks

[0126] 103, 203, 303 electric motors (drive units)

[0127] 104 fixed components

[0128] 106, 204 shell

[0129] 108 Power Supply

[0130] 110 switch

[0131] 112 lifting part / housing

[0132] 205 Support

[0133] T Attach object.

Claims

1. An electrostatic chuck having a monopolar structure, comprising: A dielectric body comprising: an electrode, and a dielectric covering the electrode and having a volume resistivity of 10 9 to 10 13 Ω˙cm dielectric layer; and The unfastening mechanism has an unfastening member belonging to the conductor; and The aforementioned unfastening member is connected to the ground and serves as an opposite electrode to the aforementioned electrode.

2. The electrostatic chuck according to claim 1, wherein: The dielectric body is provided vertically above the unfastening member.

3. The electrostatic chuck according to claim 1 or 2, wherein: The aforementioned clamp release member is a metallic mesh.

4. The electrostatic chuck according to claim 3, wherein: The mesh has a thickness of 20 μm to 100 μm.

5. The electrostatic chuck according to claim 1 or 2, wherein: The unfastening member and the dielectric layer are arranged side by side in one direction.

6. The electrostatic chuck according to claim 1, wherein The aforementioned unfastening mechanism has a driving portion for driving the aforementioned unfastening member, and the aforementioned driving portion is a motor or a power cylinder.

7. The electrostatic chuck according to claim 2, wherein: The unfastening member has elasticity and functions as a driving portion for driving the unfastening member, or the unfastening mechanism includes a spring connected to the unfastening member.

Images