electrostatic chuck

Abstract

The present invention provides an electrostatic chuck that allows for the selection of the optimal material for both the bonding layer and the sealing portion with a high degree of freedom. [Solution] The electrostatic chuck 10 comprises a dielectric substrate 100, a base plate 200 supporting the dielectric substrate 100, a bonding layer 300 joining the dielectric substrate 100 and the base plate 200, and a sealing portion 350 covering the bonding layer 300 from the outer periphery. In this electrostatic chuck 10, there is a gap between the bonding layer 300 and the sealing portion 350.

Description

Technical Field

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

Background Art

[0002] For example, in semiconductor manufacturing apparatuses such as etching apparatuses, 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 has a configuration in which these are joined to each other via a joining layer. 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 the above joining layer, for example, a silicone-based resin, an acrylic-based resin, or the like is used. However, a joining layer made of such a material often has low durability against plasma. Therefore, there is a possibility that problems such as the joining layer deteriorating from the outer peripheral side and peeling off from the dielectric substrate may occur with long-term use.

[0004] Therefore, as described in Patent Document 1 below, it has become common in an electrostatic chuck to provide a sealing portion (protective member) for covering and protecting the joining layer from the outer peripheral side.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The bonding layer is used to join the dielectric substrate and the base plate, so adhesive and heat transfer properties are required. On the other hand, the sealing portion is used to protect the bonding layer from plasma, so plasma resistance is required. The materials for the bonding layer and the sealing portion are selected individually according to the required performance, so they are generally different from each other.

[0007] For example, in the case of an electrostatic chuck described in Patent Document 1 above, where the bonding layer and the sealing part are in contact with each other, there is a possibility that the respective materials will react with each other through solid diffusion or the like, causing a part of the bonding layer or sealing part to be altered.

[0008] When selecting materials for the bonding layer and the sealing portion, attempting to choose combinations of materials that prevent the above-mentioned phenomena from occurring reduces the degree of freedom in selection. Therefore, there is a possibility that it may become impossible to select the optimal materials for the bonding layer and the sealing portion to fully perform their respective functions.

[0009] This invention has been made in view of these problems, and its objective is to provide an electrostatic chuck that can select the optimal material for both the bonding layer and the sealing portion with a high degree of freedom. [Means for solving the problem]

[0010] To solve the above problems, the electrostatic chuck according to the present invention comprises a dielectric substrate, a base plate supporting the dielectric substrate, a bonding layer joining the dielectric substrate and the base plate, and a sealing portion covering the bonding layer from the outer periphery. In this electrostatic chuck, there is a gap between the bonding layer and the sealing portion.

[0011] In the electrostatic chuck with the above configuration, the bonding layer and the sealing portion are separated, preventing the two materials from reacting with each other. As a result, it becomes possible to select each material with a high degree of freedom. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide an electrostatic chuck that allows for the selection of the optimal material for both the bonding layer and the sealing portion with a high degree of freedom. [Brief explanation of the drawing]

[0013] [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 a part of the configuration in Figure 1. [Modes for carrying out the invention]

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] Of the dielectric substrate 100, the upper surface 110 in FIG. 1 serves as the "mounting surface" on which the substrate W is placed. Also, the lower surface 120 of the dielectric substrate 100 in FIG. 1 serves as the "surface to be joined" that is joined to the base plate 200 via the joining layer 300. Along the direction perpendicular to the surface 110, the perspective when viewing the electrostatic chuck 10 from the side of the surface 110 will also be hereinafter referred to as "top view".

[0019] An adsorption electrode 130 is embedded inside the dielectric substrate 100. The adsorption electrode 130 is a thin flat plate-like layer formed of a metal material such as tungsten, for example, and is arranged parallel to the surface 110. As the material of the adsorption electrode 130, in addition to tungsten, molybdenum, platinum, palladium, etc. may also be used. When a voltage is applied to the adsorption electrode 130 from the outside via a power supply path (not shown), an electrostatic force is generated between the surface 110 and the substrate W, and thereby the substrate W is adsorbed and held. As the configuration of the power supply path, various known configurations can be adopted. The adsorption electrode 130 may be provided only one as a so-called "unipolar" electrode as in the present embodiment, or may be provided two as a so-called "bipolar" electrode.

[0020] A space SP1 is formed between the dielectric substrate 100 and the substrate W. When processes such as etching are performed in the semiconductor manufacturing apparatus, helium gas for temperature adjustment is supplied from the outside to the space SP1 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 SP1 may be a different type of gas from helium.

[0021] A seal ring 111 and dots 112 are provided on the surface 110 which is the mounting surface, and the above space SP1 is formed around these.

[0022] The seal ring 111 is a wall that partitions the space SP1 at the outermost peripheral position. The upper end of the seal ring 111 forms a part of the surface 110 and abuts against the substrate W. Incidentally, a plurality of seal rings 111 may be provided so as to divide the space SP1. With such a configuration, it becomes possible to individually adjust the pressure of the helium gas in each space SP1 and to make the surface temperature distribution of the substrate W during processing closer to uniform.

[0023] In FIG. 1, the portion labeled with the reference numeral "116" is the bottom surface of the space SP1. Hereinafter, this portion will also be 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 dot 112 described below.

[0024] The dot 112 is a circular protrusion protruding from the bottom surface 116. A plurality of dots 112 are provided and are arranged approximately evenly dispersed on the mounting surface of the dielectric substrate 100. The tip surface of each dot 112 forms a part of the surface 110 and abuts against the substrate W. By providing a plurality of such dots 112, the deflection of the substrate W is suppressed. The shapes of the respective dots 112 in a top view are the same as each other.

[0025] The base plate 200 is a substantially disk-shaped member that supports the dielectric substrate 100. The base plate 200 is formed of a metal material such as aluminum, for example. Among the base plate 200, the upper surface 210 in FIG. 1 is a "bonding surface" that is bonded to the dielectric substrate 100 via the bonding layer 300.

[0026] 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 of an adhesive made of an insulating material that has been cured. In this embodiment, a silicone adhesive is used as the adhesive, but other types of adhesives, such as acrylic adhesives, may also be used. 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.

[0027] In this embodiment, in order to increase the thermal conductivity of the bonding layer 300, multiple particulate fillers are arranged inside the bonding layer 300. As the material for the filler, for example, metallic materials such as silver, nickel, gold, platinum, copper, tin, iron, aluminum, and titanium, or materials such as carbon can be used.

[0028] If it is necessary to further increase the thermal conductivity of the bonding layer 300, for example, indium may be used as the bonding layer 300. In other words, a metal material may be used as the material for the bonding layer 300 instead of a resin material.

[0029] A refrigerant channel 250 for circulating refrigerant is formed inside the base plate 200. When etching or other processes are performed in the semiconductor manufacturing equipment, 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 SP1, 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] 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.

[0031] Incidentally, when the substrate W is being processed in the semiconductor manufacturing equipment, the electrostatic chuck 10 is exposed to plasma. At this time, if the edge of the bonding layer 300 is exposed to the outer periphery, that portion will also be exposed to plasma. However, the material constituting the bonding layer 300 often has low durability against plasma. Therefore, with long-term use, the bonding layer 300 may deteriorate from the outer periphery, potentially leading to problems such as delamination from the surface 120 of the dielectric substrate 100. To address this, the electrostatic chuck 10 according to this embodiment is provided with a sealing portion 350 on the outer periphery of the bonding layer 300.

[0032] Figure 2 shows an enlarged view of a part of the configuration of the electrostatic chuck 10 shown in Figure 1. Figure 2 shows a cross-section of the electrostatic chuck 10 near the outermost end. As shown in the figure, in addition to the bonding layer 300, a sealing portion 350 is provided between the dielectric substrate 100 and the base plate 200. The sealing portion 350 is an annular member provided to cover the entire bonding layer 300 from the outer periphery, and is sandwiched between surfaces 120 and 210, similar to the bonding layer 300. The sealing portion 350 is a member provided to cover and protect the bonding layer 300 from the outer periphery so that the bonding layer 300 is not directly exposed to plasma. As the material of the sealing portion 350, for example, resin materials such as silicone resin, epoxy resin, fluororesin, and acrylic resin, or materials mainly composed of these resin materials can be used.

[0033] The bonding layer 300 and the sealing portion 350 are spaced apart all around, and an annular space SP2 is formed between them. The reason for this configuration is as follows.

[0034] The bonding layer 300 is intended to bond the dielectric substrate 100 and the base plate 200, and therefore requires adhesive and heat transfer properties. On the other hand, the sealing portion 350 is intended to protect the bonding layer 300 from plasma, and therefore requires plasma resistance. The materials for the bonding layer 300 and the sealing portion 350 are selected individually according to their required performance, and are therefore generally different from each other.

[0035] If the bonding layer 300 and the sealing portion 350 are in contact with each other, the materials may react with each other through solid diffusion or other means, potentially causing alteration of parts of the bonding layer 300 and the sealing portion 350. Furthermore, if particulate metal or the like is placed inside the bonding layer 300 for purposes such as increasing thermal conductivity, this metal or the like may act as a catalyst, potentially altering the sealing portion 350.

[0036] When selecting materials for the bonding layer 300 and the sealing portion 350, attempting to select material combinations that prevent the above-mentioned phenomena from occurring reduces the degree of freedom in selection. Therefore, there is a possibility that it may become impossible to select the optimal materials for each of the bonding layer 300 and the sealing portion 350 to fully perform their respective functions.

[0037] Therefore, in the electrostatic chuck 10 according to this embodiment, the bonding layer 300 and the sealing portion 350 are separated to prevent the materials of the two from reacting with each other. As a result, it is possible to select the optimal material for each to perform its respective function with a high degree of freedom.

[0038] In a configuration where the bonding layer 300 contains metal or carbon (as a filler) and the sealing portion 350 contains resin, the effect of keeping the bonding layer 300 and the sealing portion 350 separated from each other, as described above, is particularly significant.

[0039] Other solid materials may be interposed between the bonded layer 300 and the sealing portion 350, which are spaced apart from each other. However, in order to reliably prevent interactions such as solid diffusion between the bonded layer 300 and the sealing portion 350, it is preferable to have a configuration in which a space SP2 is formed between them, as in this embodiment.

[0040] The material used for the bonding layer 300 is often a material with a larger coefficient of thermal expansion than the material used for the sealing portion 350. Therefore, if a space SP2 is not formed, the sealing portion 350 on the outer periphery may suppress the bonding layer 300, which is trying to expand, potentially causing excessive stress.

[0041] As in this embodiment, by forming a space SP2 between the bonding layer 300 and the sealing portion 350, the thermal expansion of the bonding layer 300 can be absorbed by the space SP2. As a result, even if the temperature of the bonding layer 300 rises and it expands, the generation of the above-mentioned stress can be suppressed. In this respect as well, the configuration in which a space SP2 is formed between the bonding layer 300 and the sealing portion 350 is preferable.

[0042] In this embodiment, the entire sealing portion 350 is sandwiched between the dielectric substrate 100 and the base plate 200. Alternatively, part or all of the sealing portion 350 may be positioned on the outer periphery of the space between the dielectric substrate 100 and the base plate 200. In this configuration as well, the same effects as in this embodiment can be achieved by maintaining a distance between the bonding layer 300 and the sealing portion 350.

[0043] 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]

[0044] 10: Electrostatic Chuck 200: Base plate 300: Bonding layer 350: Sealing part SP2: Space

Claims

1. Dielectric substrate and A base plate supporting the dielectric substrate, A bonding layer that joins the dielectric substrate and the base plate, The bonding layer comprises a sealing portion that covers the outer periphery, An electrostatic chuck characterized in that there is a gap between the bonding layer and the sealing portion.

2. The electrostatic chuck according to claim 1, characterized in that a space is formed between the bonding layer and the sealing portion.

3. The material of the bonding layer includes metal or carbon. The electrostatic chuck according to claim 2, characterized in that the material of the sealing portion includes resin.

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