Electrostatic chuck

Abstract

Provided is an electrostatic chuck that enables, with respect to a bonding layer and a sealing part, the selection of an optimum material with a high degree of freedom. An electrostatic chuck 10 comprises: a dielectric substrate 100; a base plate 200 that supports the dielectric substrate 100; a bonding layer 300 that bonds together the dielectric substrate 100 and the base plate 200; and a sealing part 350 that covers the bonding layer 300 from an outer peripheral side. In the electrostatic chuck 10, the bonding layer 300 and the sealing part 350 are separated from each other.

Description

Electrostatic chuck

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

[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 supporting 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. For this reason, 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 due to 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.

[0005] Japanese Patent Application Laid-Open No. 2006-80389

[0006] Since the joining layer is for joining the dielectric substrate and the base plate, adhesiveness and heat conductivity are required. On the other hand, since the sealing portion is for protecting the joining layer from plasma, durability against plasma is required. Since the materials of the joining layer and the sealing portion are individually selected according to the required performance, they are generally different from each other.

[0007] For example, when the joining layer and the sealing portion are in contact with each other as in the electrostatic chuck described in Patent Document 1 above, there is a possibility that the respective materials react with each other by solid diffusion or the like, and a part of the joining layer or the sealing portion may 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.

[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.

[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.

[0013] This is a schematic cross-sectional view showing the configuration of the electrostatic chuck according to this embodiment. This is an enlarged view showing a part of the configuration of Figure 1.

[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 member made of a ceramic sintered body. The dielectric substrate 100 is made of, for example, high-purity aluminum oxide (Al ２ O ３ ) may include other materials. The purity, type, and additives of the ceramics in the dielectric substrate 100 can be appropriately set considering the plasma resistance and other properties required for the dielectric substrate 100 in semiconductor manufacturing equipment.

[0018] 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" that 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.

[0019] An adsorption electrode 130 is embedded inside the dielectric substrate 100. The adsorption electrode 130 is a thin, flat layer made 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.

[0020] A space SP1 is formed between the dielectric substrate 100 and the substrate W. When etching or other processes are performed in the semiconductor manufacturing apparatus, helium gas for temperature control is supplied to space SP1 from the outside through a gas hole (not shown). By interposing helium gas between the dielectric substrate 100 and the substrate W, the thermal resistance between them is adjusted, thereby maintaining the temperature of the substrate W at an appropriate temperature. Note that the gas supplied to space SP1 for temperature control may be a different type of gas than helium.

[0021] A sealing ring 111 and dots 112 are provided on the mounting surface 110, and the space SP1 is formed around them.

[0022] The seal ring 111 is a wall that partitions the space SP1 at its outermost position. The upper end of the seal ring 111 is part of the surface 110 and contacts the substrate W. Multiple seal rings 111 may be provided to divide the space SP1. This configuration allows for individual adjustment of the helium gas pressure in each space SP1, making the surface temperature distribution of the substrate W more uniform during processing.

[0023] In Figure 1, the portion labeled "116" is the bottom surface of space SP1. Hereafter, this portion will also be referred to as "bottom surface 116". The seal ring 111, along with the dot 112 described below, is formed as a result of excavating a portion of surface 110 down to the position of bottom surface 116.

[0024] The dots 112 are circular protrusions that extend from the bottom surface 116. Multiple dots 112 are provided and are distributed approximately evenly on the mounting surface of the dielectric substrate 100. The tip surface of each dot 112 is part of the surface 110 and contacts the substrate W. By providing multiple such dots 112, the bending of the substrate W is suppressed. In a top view, the shape of each dot 112 is identical to that of the others.

[0025] 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. Of the base plate 200, the upper surface 210 in Figure 1 is the "bonded surface" which 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 apparatus, 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 the surface 120 and the surface 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 used to bond the dielectric substrate 100 and the base plate 200, so adhesiveness and heat transfer properties are required. On the other hand, the sealing portion 350 is used to protect the bonding layer 300 from plasma, so plasma resistance is required. The materials for the bonding layer 300 and the sealing portion 350 are selected individually according to the required performance, so they are 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. As a result, there is a possibility that it may become impossible to select the optimal material 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 bonding 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 bonding layer 300 and the sealing portion 350, a configuration in which a space SP2 is formed between the two, as in the present embodiment, is preferable.

[0040] As the material of the bonding layer 300, a material having a larger coefficient of thermal expansion than the material of the sealing portion 350 is often used. For this reason, when the space SP2 is not formed, the sealing portion 350 on the outer peripheral side may suppress the expanding bonding layer 300, and excessive stress may occur.

[0041] If a space SP2 is formed between the bonding layer 300 and the sealing portion 350 as in the present embodiment, the thermal expansion of the bonding layer 300 can be absorbed by the space SP2. As a result, even when the temperature of the bonding layer 300 rises and expands, the generation of stress as described above can be suppressed. Also in this regard, a configuration in which a space SP2 is formed between the bonding layer 300 and the sealing portion 350 is preferable.

[0042] The entire sealing portion 350 of the present embodiment is sandwiched between the dielectric substrate 100 and the base plate 200. Instead of such an aspect, a part or all of the sealing portion 350 may be disposed at a position on the outer peripheral side rather than between the dielectric substrate 100 and the base plate 200. Even in such a configuration, by separating the bonding layer 300 and the sealing portion 350, the same effect as in the present embodiment can be achieved.

[0043] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Those obtained by appropriately making design changes by those skilled in the art to these specific examples are also included in the scope of the present disclosure as long as they have the features of the present disclosure. Each element, its arrangement, conditions, shape, etc. included in each of the above-described specific examples are not limited to those illustrated and can be appropriately changed. Each element included in each of the above-described specific examples can be appropriately combined as long as no technical contradiction occurs.

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

Claims

1. An electrostatic chuck comprising: 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, wherein the bonding layer and the sealing portion are spaced apart.

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

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