electrostatic chuck

Abstract

The present invention provides an electrostatic chuck that can be easily manufactured, despite having a configuration in which a conductive member is placed between a dielectric substrate and a base plate. [Solution] The electrostatic chuck 10 comprises a dielectric substrate 100, an RF electrode 140 provided inside the dielectric substrate 100, a base plate 200 made of metal and bonded to the dielectric substrate 100, and a conductive member 400 that electrically connects the RF electrode 140 and the base plate 200. A recess 270 is formed on the surface 210 of the base plate 200 that faces the dielectric substrate 100, and accommodates a portion of the conductive member 400. In this electrostatic chuck 10, the length (L2) of the portion of the conductive member 400 that is accommodated in the recess 270 is 1 / 2 or more of the total length (L1) of the conductive member 400.

Description

Technical Field

[0001] The present invention relates to an electrostatic chuck.

Background Art

[0002] For example, in a semiconductor manufacturing apparatus such as an etching apparatus, an electrostatic chuck is provided as a device for adsorbing and holding a substrate such as a silicon wafer to be processed. The electrostatic chuck includes a dielectric substrate provided with an adsorption electrode and a base plate that supports the dielectric substrate, and these are joined to each other. When a voltage is applied to the adsorption electrode, an electrostatic force is generated, and the substrate placed on the dielectric substrate is adsorbed and held.

[0003] As described in Patent Document 1 below, the dielectric substrate may incorporate an RF electrode, which is one of a pair of opposing electrodes for generating plasma in a semiconductor manufacturing apparatus. In this case, the RF electrode and the base plate are electrically connected via a conductive member. Thereby, the potential of the RF electrode during substrate processing is maintained at the potential of the base plate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] To electrically connect a conductive member and an RF electrode, for example, a recess can be formed on the base plate side of the dielectric substrate, the RF electrode can be exposed at its bottom, and the conductive member can be housed inside the recess. Similarly, to electrically connect a base plate and an RF electrode, for example, a recess can be formed on the dielectric substrate side of the base plate, and the conductive member can be housed inside the recess. In this case, a portion of the conductive member will be housed in the recess of the dielectric substrate, and the other portion will be housed in the recess of the base plate.

[0006] When manufacturing an electrostatic chuck with the above configuration, a portion of the conductive member is inserted into a recess provided on the upper surface of the base plate, causing the conductive member to protrude from the upper surface of the base plate. Then, the base plate and the dielectric substrate are joined using a silicone adhesive or the like. However, if the recess formed on the upper surface of the base plate is too shallow, the conductive member is prone to tipping over during joining, significantly reducing work efficiency.

[0007] This invention has been made in view of these problems, and its objective is to provide an electrostatic chuck that can be easily manufactured, while having a configuration in which a conductive member is placed between a dielectric substrate and a base plate. [Means for solving the problem]

[0008] To solve the above problems, the electrostatic chuck according to the present invention comprises a dielectric substrate having a mounting surface on which an object to be adsorbed is placed, an internal electrode provided inside the dielectric substrate, a base plate made of metal and bonded to the dielectric substrate, and a conductive member that electrically connects the internal electrode and the base plate. A recess is formed on the surface of the base plate facing the dielectric substrate to accommodate a part of the conductive member. In this electrostatic chuck, the length of the portion of the conductive member housed in the recess, along the direction perpendicular to the mounting surface, is 1 / 2 or more of the total length of the conductive member along the same direction.

[0009] In an electrostatic chuck with this configuration, the recess formed in the base plate is sufficiently deep, reaching a depth of more than half the total length of the conductive member. This prevents the conductive member, which is inserted into the recess before joining, from falling over afterward, thus facilitating operations such as joining the dielectric substrate and the base plate. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an electrostatic chuck that can be easily manufactured, even though it has a configuration in which a conductive member is placed between a dielectric substrate and a base plate. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view showing the configuration of the electrostatic chuck according to this embodiment. [Figure 2] This figure shows an enlarged view of the conductive member and its vicinity within the electrostatic chuck shown in Figure 1. [Figure 3] This is a perspective view showing the configuration of the conductive component. [Modes for carrying out the invention]

[0012] This embodiment will now be described with reference to the attached drawings. To facilitate understanding of the explanation, the same reference numerals are used for identical components in each drawing whenever possible, and redundant explanations are omitted.

[0013] The electrostatic chuck 10 according to this embodiment is used to attract and hold a substrate W to be processed by electrostatic force inside a semiconductor manufacturing apparatus (not shown), such as an etching apparatus. The substrate W to be attracted is, for example, a silicon wafer. The electrostatic chuck 10 may also be used in apparatus other than semiconductor manufacturing apparatus.

[0014] Figure 1 shows a schematic cross-sectional view of the electrostatic chuck 10 in a state where the substrate W is adsorbed and held. The electrostatic chuck 10 comprises a dielectric substrate 100 and a base plate 200.

[0015] The dielectric substrate 100 is a substantially disc-shaped component made of a ceramic sintered body. The dielectric substrate 100 contains, for example, high-purity aluminum oxide (Al2O3), but may also contain other materials. The purity and type of ceramics in the dielectric substrate 100, as well as the additives, can be appropriately set considering the plasma resistance and other properties required of the dielectric substrate 100 in semiconductor manufacturing equipment.

[0016] The upper surface 110 of the dielectric substrate 100 in Figure 1 is the "mounting surface" on which the substrate W is placed. The lower surface 120 of the dielectric substrate 100 in Figure 1 is the "bonded surface" to which it is bonded to the base plate 200 via the bonding layer 300. The viewpoint from which the electrostatic chuck 10 is viewed from the surface 110 side, along a direction perpendicular to surface 110, will also be referred to as the "top view" below.

[0017] An adsorption electrode 130 is embedded inside the dielectric substrate 100. The adsorption electrode 130 is a thin, flat layer formed of a metallic material such as tungsten, and is arranged parallel to the surface 110. In addition to tungsten, molybdenum, platinum, palladium, etc. may be used as the material for the adsorption electrode 130. When a voltage is applied to the adsorption electrode 130 from the outside via a power supply circuit (not shown), an electrostatic force is generated between the surface 110 and the substrate W, thereby adsorbing and holding the substrate W. Various known configurations can be used for the power supply circuit. The adsorption electrode 130 may be provided as a single so-called "monopolar" electrode as in this embodiment, or it may be provided as two so-called "bipolar" electrodes.

[0018] Inside the dielectric substrate 100, in addition to the above-described adsorption electrode 130, an RF electrode 140 is also embedded. The RF electrode 140 is provided as one of a pair of opposing electrodes for generating plasma in a semiconductor manufacturing apparatus. The other of the opposing electrodes is provided at a position above the electrostatic chuck 10 in the semiconductor manufacturing apparatus. When a high-frequency alternating voltage is applied between these opposing electrodes, plasma is generated above the substrate W and is used for processes such as film formation and etching on the substrate W. The RF electrode 140 corresponds to the "internal electrode" in the present embodiment.

[0019] The RF electrode 140 is, like the adsorption electrode 130, a thin flat plate-shaped layer formed of a metal material such as tungsten. As the material of the RF electrode 140, in addition to tungsten, molybdenum, platinum, palladium, etc. may also be used. The RF electrode 140 is embedded at a position closer to the surface 120 side than the adsorption electrode 130. The RF electrode 140 is arranged parallel to the surface 110, like the adsorption electrode 130. The RF electrode 140 is a substantially circular single electrode in a top view. The center of the RF electrode 140 in a top view coincides with the center of the dielectric substrate 100.

[0020] A conductive member 400 is provided on the electrostatic chuck 10. The conductive member 400 is a member for electrically connecting between the RF electrode 140 and a base plate 200 described later. Due to the conductive member 400, the potential of the RF electrode 140 during the processing of the substrate W becomes the same as the potential of the base plate 200. A plurality of conductive members 400 are provided in the electrostatic chuck 10, but only two of them are shown in FIG. 1. The number of conductive members 400 provided on the electrostatic chuck 10 may be only one. The specific shape etc. of the conductive member 400 will be described later.

[0021] As shown in FIG. 1, a space SP is formed between the dielectric substrate 100 and the substrate W. When processing such as etching is performed in the semiconductor manufacturing apparatus, helium gas for temperature adjustment is supplied from the outside to the space SP through a gas hole (not shown). By interposing helium gas between the dielectric substrate 100 and the substrate W, the thermal resistance between the two is adjusted, and thereby the temperature of the substrate W is maintained at an appropriate temperature. Note that the gas for temperature adjustment supplied to the space SP may be a gas of a type different from helium.

[0022] A seal ring 111 and dots 112 are provided on the surface 110 which is the mounting surface, and the above-described space SP is formed around these.

[0023] The seal ring 111 is a wall that partitions the space SP at the outermost peripheral position. The seal ring 111 is an annular protrusion formed on the surface 110 side. The tip of the seal ring 111 is a part of the surface 110 and abuts on the substrate W. Note that a plurality of seal rings 111 may be provided so as to divide the space SP. With such a configuration, the pressure of the helium gas in each space SP can be individually adjusted, and the surface temperature distribution of the substrate W during processing can be made closer to uniform.

[0024] The portion marked with reference numeral "116" in FIG. 1 is the bottom surface of the space SP. Hereinafter, this portion is also referred to as the "bottom surface 116". The seal ring 111 is formed as a result of digging down a part of the surface 110 to the position of the bottom surface 116 together with the dots 112 described below.

[0025] The dots 112 are circular protrusions protruding from the bottom surface 116. A plurality of dots 112 are provided and are arranged substantially evenly and dispersedly on the mounting surface of the dielectric substrate 100. The tip of each dot 112 is a part of the surface 110 and abuts on the substrate W. By providing a plurality of such dots 112, the deflection of the substrate W is suppressed.

[0026] The base plate 200 is a substantially disc-shaped member that supports the dielectric substrate 100. The base plate 200 is made of a metallic material such as aluminum. The base plate 200 is bonded to the surface 120 of the dielectric substrate 100 via a bonding layer 300. Of the base plate 200, the upper surface 210 in Figure 1 is the "bonded surface" that is bonded to the dielectric substrate 100.

[0027] The bonding layer 300 is a layer provided between the dielectric substrate 100 and the base plate 200, and it bonds the two together. The bonding layer 300 is made by curing an adhesive made of an insulating material. In this embodiment, a silicone adhesive is used as the adhesive. However, the bonding layer 300 may be made by curing another type of adhesive. In any case, it is preferable to use a material with the highest possible thermal conductivity for the bonding layer 300 so that the thermal resistance between the dielectric substrate 100 and the base plate 200 is reduced.

[0028] An insulating film may be formed on the surface of the base plate 200. As the insulating film, for example, an alumina film formed by thermal spraying can be used. By covering the surface of the base plate 200 with an insulating film, the dielectric strength of the base plate 200 can be increased.

[0029] A refrigerant channel 250 is formed inside the base plate 200 for passing a refrigerant. When etching or other processes are performed in the semiconductor manufacturing equipment, a refrigerant is supplied from the outside to the refrigerant channel 250, thereby cooling the base plate 200. During processing, the heat generated in the substrate W is transferred to the refrigerant via the helium gas in the space SP, the dielectric substrate 100, and the base plate 200, and is discharged to the outside together with the refrigerant. The supply and discharge of refrigerant to and from the refrigerant channel 250 is performed through an opening (not shown) formed on the surface 220 of the base plate 200 opposite to the surface 210.

[0030] The specific configuration of the conductive member 400 and its vicinity will now be described. Figure 2 shows an enlarged view of the conductive member 400 and its vicinity within the electrostatic chuck 10 of Figure 1. As shown in Figure 2, a recess 170 is formed on the surface 120 of the dielectric substrate 100 on the base plate 200 side. The recess 170 is a portion of the surface 120 that has been recessed toward the surface 110 in order to allow the conductive member 400 to be placed therein. In this embodiment, the recess 170 is formed to a depth position that exposes the RF electrode 140. Therefore, the RF electrode 140, which is an internal electrode, is exposed at the bottom surface (also called the upper end surface) of the recess 170. In a top view, the shape of the recess 170 is circular, and a roughly cylindrical space is formed inside it.

[0031] A recess 270 is formed on the surface 210 of the base plate 200 that faces the dielectric substrate 100. The recess 270 is formed on the surface 210 in the portion that overlaps with the recess 170 when viewed from above. The recess 270 is a portion of the surface 210 that has been recessed toward the surface 220 in order to allow the conductive member 400 to be placed therein. The metal portion of the base plate 200 is exposed throughout the inside of the recess 270. The shape of the recess 270 when viewed from above is circular, and a roughly cylindrical space is formed inside it. The central axis of the recess 270 coincides with the central axis of the recess 170. The inner diameter of the recess 270 is smaller than the inner diameter of the recess 170.

[0032] Within the bonding layer 300, a circular opening is formed in the portion between the recess 170 and the recess 270. The recess 170 and the recess 270 are connected through this opening, and the entire area forms a single space.

[0033] The conductive member 400 is a substantially cylindrical member formed from a fibrous metal member and is housed inside the recesses 170 and 270. In other words, a portion of the conductive member 400 is housed in the recess 170, and another portion of the conductive member 400 is housed in the recess 270. In a top view, the diameter of the portion of the conductive member 400 housed in the recess 270 is approximately equal to the inner diameter of the recess 270.

[0034] The conductive member 400 is in contact with the RF electrode 140, which is exposed at the bottom surface of the recess 170. The conductive member 400 is also in contact with the metal portion of the base plate 200, which is exposed at the bottom surface of the recess 270. The conductive member 400, positioned in this manner, electrically connects the RF electrode 140 and the metal portion of the base plate 200.

[0035] As shown in Figure 3, the conductive member 400 has a substantially cylindrical main body portion 410 and a plurality of protrusions 420, and the entire body is integrally formed from a fibrous metal member. The protrusions 420 are substantially cylindrical projections formed so as to extend from the surface of the main body portion 410 facing the dielectric substrate 100, and further toward the dielectric substrate 100. In this embodiment, a total of four protrusions 420 are formed, but the number of protrusions 420 may be different.

[0036] The conductive member 400, which is made of fibrous metal material, has some degree of permeability, allowing fluids such as air to enter its interior. In other words, the fibrous metal material is not sufficiently dense, and there are gaps between the fibers. With this configuration, each part of the conductive member 400, including the protruding portion 420, is an elastic body that can be easily deformed by external forces.

[0037] When no external force is being applied, the vertical dimension of the conductive member 400 (in the direction in which the protrusion 420 extends) is larger than the dimension in the same direction in the state shown in Figure 2 (L1 in Figure 2). In other words, the conductive member 400 is compressed along the direction from the dielectric substrate 100 toward the base plate 200, housed inside the recesses 170 and 270, and sandwiched between the RF electrode 140 and the base plate 200. The tip of each protrusion 420 is elastically deformed so as to be crushed by being pressed against the bottom surface of the recess 170 (i.e., the RF electrode 140).

[0038] The conductive member 400 is pressed against the RF electrode 140 and the base plate 200 by its own restoring force. Therefore, even if thermal expansion or contraction occurs in various parts of the electrostatic chuck 10 during processing of the substrate W, the electrical connection between the RF electrode 140 and the base plate 200 is always maintained.

[0039] The conductive member 400 may have a different shape than that of this embodiment. For example, the conductive member 400 may be substantially cylindrical in shape and may not have a protruding portion 420.

[0040] Let's return to Figure 2 and continue the explanation. "L1" shown in the figure is the total length of the conductive member 400 along the direction perpendicular to the mounting surface. Specifically, it is the total length of the conductive member 400 when it is housed and compressed inside the recesses 170 and 270. L1 is equal to the distance from the bottom surface of recess 170 to the bottom surface of recess 270.

[0041] "L2" shown in Figure 2 is the length of the portion of the conductive member 400 that is housed in the recess 270, along the direction perpendicular to the mounting surface. L2 is equal to the distance from the surface 210 to the bottom surface of the recess 270, that is, the depth of the recess 270.

[0042] In this embodiment, the shapes of the conductive member 400, the recess 170, and the recess 270 are adjusted so that L2 is at least half the length of L1. The reason for this configuration is as follows.

[0043] When manufacturing the electrostatic chuck 10, a portion of the conductive member 400 is inserted into a recess 270 provided on the surface 210 of the base plate 200, causing the conductive member 400 to protrude from the surface 210. Then, the base plate 200 and the dielectric substrate 100 are joined using a silicone adhesive or the like. At this time, if the recess 270 formed on the surface 210 is too shallow, the conductive member 400 is prone to tipping over during joining, which significantly reduces work efficiency.

[0044] Therefore, in this embodiment, as described above, the depth (L2) of the recess 270 formed in the surface 210 is sufficiently deep, being at least half the total length (L1) of the conductive member 400. In this configuration, the conductive member 400 inserted into the recess 270 before joining is prevented from falling over afterward, making it easier to perform operations such as joining the dielectric substrate 100 and the base plate 200.

[0045] Furthermore, even if L1 is the length of the conductive member 400 before it is compressed, the depth of the recess 270 may be adjusted so that L2 ≥ L1 holds true.

[0046] In this embodiment, the RF electrode 140 is exposed at the bottom surface of the recess 170, and the upper end of the conductive member 400 is in direct contact with the RF electrode 140. Alternatively, the recess 170 may be formed shallower than in this embodiment, so that the RF electrode 140 is not exposed at its bottom surface. In this case, for example, a via (a hole filled with a conductor) can be formed extending from the bottom surface of the recess 170 to the RF electrode 140, and the upper end of the conductive member 400 and the RF electrode 140 can be electrically connected via this via.

[0047] The embodiments have been described above with reference to specific examples. However, this disclosure is not limited to these specific examples. Modifications made to these specific examples by those skilled in the art are also included within the scope of this disclosure, as long as they retain the features of this disclosure. The elements, their arrangement, conditions, shapes, etc., of each of the aforementioned specific examples are not limited to those illustrated and can be modified as appropriate. The elements of each of the aforementioned specific examples can be combined in different ways as appropriate, as long as no technical inconsistencies arise. [Explanation of symbols]

[0048] 10: Electrostatic Chuck 100: Dielectric substrate 110: Face 140:RF electrode 200: Base plate 210: Face 270: Recess 400: Conductive material W: Circuit board

Claims

[Claim 1] A dielectric substrate having a mounting surface on which an object to be adsorbed is placed, An internal electrode provided inside the dielectric substrate, A base plate formed of metal and bonded to the dielectric substrate, The system includes a conductive member that electrically connects the internal electrode and the base plate, A recess is formed on the surface of the base plate facing the dielectric substrate, which accommodates a portion of the conductive member. The length of the portion of the conductive member housed in the recess, along the direction perpendicular to the aforementioned mounting surface, An electrostatic chuck characterized in that the conductive member is at least half the total length of the conductive member along the same direction.

Images