Electrostatic chuck and substrate holding apparatus

Abstract

The present disclosure relates to an electrostatic chuck and a substrate fixing device including a base having a placement surface on which an adsorption target object is placed, and an electrode embedded in the base. The base is provided with a groove that opens to the placement surface side and does not reach the electrode. Between a bottom surface of the groove and the electrode, a low-resistance region made of ceramic and a high-resistance region made of ceramic having a volume resistivity higher than that of the low-resistance region are arranged in this order in a thickness direction of the base from a side close to the groove.

Description

Technical Field

[0001] This invention relates to an electrostatic chuck and a substrate fixing device. Background Technology

[0002] In the prior art, film deposition equipment (such as CVD equipment, PVD equipment, etc.) and plasma etching equipment used in the manufacture of semiconductor devices such as ICs and LSIs have a stage for precisely holding the wafer in a vacuum processing chamber.

[0003] As such a platform, for example, a substrate fixing device has been proposed that is configured to adsorb and hold a wafer, which is the target object of adsorption, by means of an electrostatic chuck mounted on a base plate. For example, an electrostatic electrode is embedded in the substrate of the electrostatic chuck, and the placement surface of the substrate for adsorbing and holding the wafer is formed with an unevenness structure.

[0004] Citation List

[0005] Patent documents

[0006] PTL 1: WO2016 / 158110 Summary of the Invention

[0007] However, when the placement surface of the wafer has an uneven structure to adsorb and hold it, the short distance between the bottom surface of the recess and the electrostatic electrode embedded in the substrate may easily lead to discharge.

[0008] The present invention was made in view of the above circumstances, and its purpose is to suppress the occurrence of discharge in electrostatic chucks.

[0009] Embodiments of the present invention relate to an electrostatic chuck. The electrostatic chuck includes: a substrate having a placement surface for placing and adsorbing a target object; and an electrode embedded in the substrate. The substrate is provided with a groove that opens towards the placement surface but does not reach the electrode. Between the bottom surface of the groove and the electrode, starting from the side closest to the groove and along the thickness direction of the substrate, a low-resistivity region made of ceramic and a high-resistivity region made of ceramic with a volume resistivity higher than that of the low-resistivity region are sequentially arranged.

[0010] According to the disclosed technology, it is possible to suppress the occurrence of discharge in electrostatic chucks. Attached Figure Description

[0011] Figure 1A and Figure 1B This is a simplified and illustrative diagram of the substrate fixing device according to the first embodiment.

[0012] Figures 2A to 2D This is a diagram illustrating the manufacturing process of the substrate fixing device according to the first embodiment.

[0013] Figure 3A and Figure 3B This is a simplified illustration of a substrate fixing device according to a first variant of the first embodiment. Detailed Implementation

[0014] In the following description, embodiments of the present disclosure will be illustrated with reference to the accompanying drawings. It should be noted that the same reference numerals are used in the drawings to denote parts having the same construction, and repeated descriptions may be omitted.

[0015] <First Embodiment>

[0016] [Structure of the substrate fixing device]

[0017] Figure 1A and Figure 1B This is a simplified and illustrative diagram of a substrate fixing device according to the first embodiment, wherein... Figure 1A It is a cross-sectional view and Figure 1B This is a top view. (Refer to...) Figure 1A and Figure 1B The substrate fixing device 1 has a base plate 10, an adhesive layer 20, and an electrostatic chuck 30 as main components. The substrate fixing device 1 is a device configured to adsorb and hold a substrate (e.g., a semiconductor wafer, etc.) as the adsorption target object by means of the electrostatic chuck 30.

[0018] The base plate 10 is a component used to mount the electrostatic chuck 30. The thickness of the base plate 10 is, for example, about 20 mm to 40 mm. The base plate 10 is formed of, for example, metallic materials such as aluminum and hard alloys, or composite materials of metallic materials and ceramics, and can be used as electrodes for plasma control. For example, from the viewpoints of easy availability, easy processing, and good thermal conductivity, aluminum or its alloys are used, and it is advantageous to use materials whose surfaces have already undergone anti-corrosion aluminum treatment (insulating layer formation).

[0019] For example, by supplying a predetermined high-frequency power to the base plate 10, the energy used to cause ions in the generated plasma state to collide with the substrate adsorbed on the electrostatic chuck 30 can be controlled, and etching can be performed effectively.

[0020] A coolant flow path may be provided in the base plate 10. The coolant flow path may be, for example, an annular hole formed in the base plate 10. For example, a coolant such as cooling water or heat transfer fluid (GALDEN) may be introduced into the coolant flow path from outside the substrate fixing device 1. By circulating the coolant in the coolant flow path to cool the base plate 10, the substrate adsorbed on the electrostatic chuck 30 can be cooled.

[0021] The electrostatic chuck 30 is mounted on one surface of the base plate 10 via an adhesive layer 20. The adhesive layer 20 is, for example, a silicone adhesive. The thickness of the adhesive layer 20 is, for example, about 0.01 mm to 1.0 mm. The adhesive layer 20 has the effect of bonding the base plate 10 and the electrostatic chuck 30, and reducing stress caused by the difference in the coefficients of thermal expansion between the ceramic electrostatic chuck 30 and the aluminum base plate 10. It should be noted that the electrostatic chuck 30 can also be fixed to the base plate 10 with screws.

[0022] The electrostatic chuck 30 has a substrate 31, electrostatic electrodes 32, and a high-resistance region 33 as its main components. The upper surface of the substrate 31 is a placement surface 31a for placing the target object. The planar shape of the electrostatic chuck 30 is formed according to the shape of the substrate, for example, it is circular. The diameter of the wafer used as the target object for the electrostatic chuck 30 is, for example, 8 inches, 12 inches, or 18 inches. The electrostatic chuck 30 is a Johnsen-Rahbeck type electrostatic chuck.

[0023] It should be noted that the expression "when viewed from above" means the target object is viewed from the normal direction of the placement surface 31a of the base 31, and the expression "planar shape" means the shape of the target object when viewed from the normal direction of the placement surface 31a of the base 31.

[0024] The substrate 31 is a dielectric. For example, ceramics such as alumina (Al₂O₃) and aluminum nitride (AlN) are used as the substrate 31. For example, titanium oxide is added to the substrate 31. The substrate 31 may include oxides of two or more elements selected from silicon (Si), magnesium (Mg), calcium (Ca), aluminum (Al), and yttrium (Y) as additives. The thickness of the substrate 31 is, for example, about 0.5 mm to 10 mm, and the relative permittivity (kHz) of the substrate 31 is, for example, about 9 to 10.

[0025] The electrostatic electrode 32 is a thin-film electrode and is embedded in the substrate 31. The electrostatic electrode 32 is connected to a power source located outside the substrate holder 1, and when a predetermined voltage is applied from the power source, an adsorption force is generated between the electrostatic electrode and the substrate through electrostatic discharge. This allows the substrate to be adsorbed and held on the placement surface 31a of the substrate 31 of the electrostatic chuck 30. The higher the voltage applied to the electrostatic electrode 32, the stronger the adsorption and holding force. The electrostatic electrode 32 can have a unipolar or bipolar shape. Materials used for the electrostatic electrode 32 include, for example, tungsten or molybdenum.

[0026] A heating element may be provided in the substrate 31. The heating element is configured to generate heat by applying a voltage from outside the substrate fixing device 1, and the heating causes the placement surface 31a of the substrate 31 to reach a predetermined temperature.

[0027] A gas supply unit 11 is provided in the electrostatic chuck 30 and the base plate 10. The gas supply unit 11 is configured to supply gas for cooling the substrate that is adsorbed and held on the electrostatic chuck 30. The gas supply unit 11 includes a gas flow path 111, a gas injection section 112, and a gas discharge section 113.

[0028] The gas flow path 111 is, for example, an annular hole formed in the base plate 10. The gas injection section 112 is a hole in which one end is configured to communicate with the gas flow path 111 and penetrate the interior of the base plate 10, and the other end of the hole is exposed to the outside from the lower surface of the base plate 10. The gas injection section 112 is configured to introduce an inert gas (e.g., He, Ar, etc.) into the gas flow path 111 from the outside of the substrate fixing device 1.

[0029] A groove 31x is provided in the substrate 31, opening towards the placement surface 31a but not reaching the electrostatic electrode 32. For example, when viewed from above, the groove 31x is annularly disposed in the substrate 31. The cross-sectional shape of the groove 31x in the width direction is, for example, rectangular. The width of the groove 31x is, for example, about 0.5 mm to 2 mm. The depth of the groove 31x relative to the placement surface 31a of the substrate 31 is, for example, about 0.1 mm to 0.5 mm.

[0030] One end of the gas discharge section 113 is configured to communicate with the gas flow path 111, and the other end protrudes outward from the bottom surface of the groove 31x provided on the placement surface 31a of the substrate 31. The gas discharge section 113 is configured to discharge the inert gas introduced into the gas flow path 111 toward the lower surface of the substrate. In other words, the gas discharge section 113 opens to the bottom surface of the groove 31x, penetrates the high-resistivity region 33 along the thickness direction of the substrate 31 from the bottom surface of the groove 31x, and then penetrates the adhesive layer 20 to communicate with the gas flow path 111 formed on the base plate 10.

[0031] Viewed from above, the gas exhaust portions 113 form dots on the bottom surface of the groove 31x. Specifically, when viewed from above, the gas exhaust portions 113 are arranged in a ring at predetermined intervals in the bottom surface of the groove 31x. The number of gas exhaust portions 113 can be appropriately determined as needed, for example, from about 10 to 100. By supplying gas into the groove 31x, the substrate adsorbed on the placement surface 31a can be easily removed.

[0032] Meanwhile, since the distance between the bottom surface of the groove 31x and the upper surface of the electrostatic electrode 32 is shorter than the distance between the placement surface 31a and the upper surface of the electrostatic electrode 32, discharge is likely to occur near the groove 31x. In particular, when titanium oxide or the like is added to the substrate 31 to obtain low resistance characteristics, the ceramic particles constituting the substrate 31 become larger, leading to a decrease in density and weakening of the ceramic. Therefore, voids are easily generated in the substrate 31, which becomes a cause of discharge. When the distance to the upper surface of the electrostatic electrode 32 is short, such as near the groove 31x, discharge is likely to occur even in small voids.

[0033] In the electrostatic chuck 30, a high-resistivity region 33 is provided along the thickness direction of the substrate 31 between the bottom surface of the groove 31x and the upper surface (surface on the side of the groove 31x) of the electrostatic electrode 32. The high-resistivity region 33 is, for example, arranged to contact the upper surface of the electrostatic electrode 32. The high-resistivity region 33 is a region with a higher volume resistivity than other regions of the substrate 31. It should be noted that... Figure 1A and Figure 1B For convenience, the high-resistivity region 33 is designated using a different reference numeral than that used for the substrate 31. However, the high-resistivity region 33 is part of the ceramic that constitutes the substrate 31.

[0034] Specifically, in the substrate 31, between the groove 31x and the electrostatic electrode 32, a low-resistivity region made of ceramic and a high-resistivity region 33 made of ceramic with a volume resistivity higher than that of the low-resistivity region are sequentially arranged along the thickness direction of the substrate 31, starting from the side closest to the groove 31x. In the substrate 31, the entire region except for the high-resistivity region 33 is a low-resistivity region.

[0035] The volume resistivity of the high-resistivity region 33 is, for example, 10. 15 Ωm or higher. In the substrate 31, the volume resistivity of the region other than the high-resistivity region 33 (i.e., the low-resistivity region) is, for example, about 10 Ωm. 10 Ωm to 10 12 Ωm. For example, the volume resistivity of the high-resistivity region 33 is more than 100 times that of the low-resistivity region. The high-resistivity region 33 is disposed between the groove 31x and the electrostatic electrode 32, thereby suppressing discharge near the groove 31x.

[0036] For the high-resistivity region 33, any material can be used, as long as its volume resistivity is higher than that of the low-resistivity region constituting the main part of the matrix 31. For example, it is preferable that the high-resistivity region 33 is formed of dense alumina (bauxite) with high resistance and high withstand voltage properties. For example, by using alumina in which titanium oxide or the like is not added, a region with a higher volume resistivity than the low-resistivity region can be formed. It should be noted that the material used to form the high-resistivity region 33 is not limited to alumina monomer, and oxides of Si, Ca, Mg, etc., can be added. Preferably, the main component (e.g., alumina) of the high-resistivity region and the low-resistivity region is the same. In this case, the volume resistivity can be changed by changing the type of additive.

[0037] From the viewpoint of improving the effect of suppressing discharge, it is preferable that the high-resistance region 33 is disposed in the region overlapping with the groove 31x when viewed from above. For example, if the groove 31x is disposed in a ring shape when viewed from above, the high-resistance region 33 is disposed in a ring shape in the region overlapping with the groove 31x. In addition, the width of the high-resistance region 33 can be the same as the width of the groove 31x. However, from the viewpoint of improving the effect of suppressing discharge, the width of the high-resistance region 33 is preferably greater than the width of the groove 31x. The thickness of the high-resistance region 33 is preferably 10 μm or more and 30 μm or less. When the thickness of the high-resistance region 33 is 10 μm or more, the effect of suppressing discharge is sufficiently obtained. In addition, when the thickness of the high-resistance region 33 is 30 μm or less, good adhesion is obtained between the low-resistance region surrounding the high-resistance region 33 and the electrostatic electrode 32.

[0038] [Manufacturing method of substrate fixing device]

[0039] Figures 2A to 2D The manufacturing process of the substrate fixing device according to the first embodiment is illustrated, showing the relationship with... Figure 1A The corresponding cross-section. Here, the main reference is... Figures 2A to 2D The manufacturing process of the electrostatic chuck 30 is explained.

[0040] First of all, Figure 2A In the process shown, a green sheet 311 is prepared, and a paste 331 is printed onto the green sheet 311. The paste 331 is a material that, upon firing, will become a high-resistance region 33. The paste 331 is, for example, a dense, high-resistance, and high-voltage-resistance paste of alumina (alumina paste) without the addition of titanium dioxide, etc. For example, when viewed from above, the paste 331 can be arranged to overlap with the area where grooves 31x will be formed in a subsequent process. The printing can be repeated multiple times to give the paste 331 the desired thickness.

[0041] Then, in Figure 2BIn the process shown, a metal paste 321 is printed onto a green sheet 311 in a predetermined pattern to cover the paste 331. The metal paste 321 is a material that, through firing, will become an electrostatic electrode 32. The metal paste 321 is, for example, tungsten paste or molybdenum paste. After printing the metal paste 321, the green sheet 311, on which the paste 331 and the metal paste 321 are formed, is stacked onto the green sheet 312 with the metal paste 321 facing towards the green sheet 312.

[0042] Then, in Figure 2C During the process shown, firing Figure 2B The structure shown is applied, and surface polishing is performed as needed. Through firing, the green sheet 311 and the green sheet become one, thereby forming the substrate 31. Furthermore, through firing, an electrostatic electrode 32 is formed from the metal paste 321, and a high-resistivity region 33 is formed from the paste 331.

[0043] Then, in Figure 2D In the process shown, a groove 31x and a gas discharge portion 113 opening into the bottom surface of the groove 31x are formed. The gas discharge portion 113 is formed to penetrate the high-resistivity region 33 from the bottom surface of the groove 31x along the thickness direction of the substrate 31 and to be exposed from the lower surface side of the substrate 31. The groove 31x and the gas discharge portion 113 can be formed, for example, by sandblasting, drilling, or the like.

[0044] exist Figure 2D Following the process shown, a base plate 10 pre-formed with a gas flow path 111, a gas injection section 112, a cooling mechanism, etc., is prepared, and an (uncured) adhesive layer 20 is formed on the base plate 10. Then, Figure 2D The structure shown is mounted on one surface of the base plate 10 through the adhesive layer 20, and the adhesive layer 20 is cured. Through the above process, the following is completed: Figure 1A The substrate fixing device 1 shown.

[0045] In this way, the high-resistivity region 33 is disposed between the groove 31x and the electrostatic electrode 32 along the thickness direction of the substrate 31, so that even if there is a weak part leading to the electrostatic electrode 32, the discharge path from the placement surface 31a side toward the electrostatic electrode 32 is cut off by the high-resistivity region 33. As a result, discharge near the groove 31x can be suppressed.

[0046] The high-resistivity region 33 is particularly effective when applied to Johnson-Labeck type electrostatic chucks, where the volume resistivity of the main portion of the substrate 31 is relatively low and discharge is easily generated. However, the high-resistivity region 33 can also be applied to Coulomb force type electrostatic chucks.

[0047] It should be noted that even when the groove 31x is not set as annular or the gas exhaust portion 113 is not open into the groove 31x, the high-resistance region 33 exhibits the effect of suppressing discharge.

[0048] <First variant of the first embodiment>

[0049] In a first variant of the first embodiment, an example of a substrate fixing device including an electrostatic chuck with multiple grooves is shown. It should be noted that in the first variant of the first embodiment, descriptions of components identical to those in the already described embodiments may be omitted.

[0050] Figure 3A and Figure 3B This is a simplified and illustrative diagram of a substrate fixing device according to a first variant of the first embodiment, wherein... Figure 3A It is a cross-sectional view and Figure 3B This is a top view. (Refer to...) Figure 3A and Figure 3B Viewed from above, the substrate fixing device 1A has two concentric grooves 31x so that the two grooves do not contact each other. A gas vent 113 opens on the bottom surface of each groove 31x. A high-resistance region 33 is provided between each groove 31x and the electrostatic electrode 32 along the thickness direction of the substrate 31. For example, when viewed from above, the high-resistance region 33 is arranged in a ring shape in the area overlapping with each groove 31x.

[0051] Thus, the base 31 of the electrostatic chuck 30 can be provided with two grooves 31x that open toward the placement surface 31a. In this case, since a high-resistance region 33 is also provided between each groove 31x and the electrostatic electrode 32, discharge near each groove 31x can be suppressed.

[0052] Furthermore, the gas discharge section 113 opens on the bottom surface of the groove 31x that opens into the placement surface 31a, thus effectively cooling the substrate that is the target of adsorption. In addition, by supplying gas into each groove 31x, the substrate adsorbed on the placement surface 31a can be removed more easily. It should be noted that three or more grooves 31x opening into the placement surface 31a may also be provided.

[0053] Although preferred embodiments have been described in detail, the present invention is not limited to the embodiments described above, and various changes and substitutions may be made to the embodiments described above without departing from the scope defined by the claims.

[0054] For example, in addition to semiconductor wafers (such as silicon wafers), glass substrates used in the manufacturing process of liquid crystal panels can also be used as adsorption targets for the substrate fixing device of the present invention.

[0055] This disclosure also includes various exemplary embodiments, such as those described below.

[0056] [1] An electrostatic chuck, comprising:

[0057] A substrate having a placement surface for placing and adsorbing target objects; and

[0058] Electrodes, which are embedded in the substrate.

[0059] The substrate has a groove that opens towards the placement surface but does not reach the electrode.

[0060] Between the bottom surface of the groove and the electrode, starting from the side closest to the groove and along the thickness direction of the substrate, a low-resistivity region made of ceramic and a high-resistivity region made of ceramic with a volume resistivity higher than that of the low-resistivity region are arranged sequentially.

[0061] [2] According to the electrostatic chuck of [1], the high resistance region is set in the region that overlaps with the groove when viewed from above.

[0062] [3] According to the electrostatic chuck described in [2], the groove is arranged in an annular shape when viewed from above, and

[0063] The high-resistance region is arranged in a ring shape in the area overlapping with the groove.

[0064] [4] According to the electrostatic chuck described in [3], when viewed from above, the multiple grooves are arranged concentrically so that the multiple grooves do not contact each other, and

[0065] When viewed from above, the high-resistivity region is arranged in a ring shape in the area that overlaps with each groove in the groove.

[0066] [5] The electrostatic chuck according to any one of [1] to [4], wherein the width of the high-resistance region is greater than the width of the groove.

[0067] [6] The electrostatic chuck according to any one of [1] to [5], wherein the high-resistance region is in contact with the surface of the electrode facing the groove.

[0068] [7] The electrostatic chuck according to any one of [1] to [6] further includes:

[0069] The gas discharge section opens into the bottom surface of the groove.

[0070] The gas discharge section is formed as a region with high resistance.

[0071] [8] The electrostatic chuck according to any one of [1] to [7], wherein the high-resistance region is formed of aluminum oxide and has 10 15Volume resistivity above Ωm.

[0072] [9] The electrostatic chuck according to any one of [1] to [8], wherein the electrostatic chuck is of the Johnson-Rabec type.

[0073]

[10] A substrate fixing device, comprising:

[0074] Base plate; and

[0075] The electrostatic chuck according to any one of [1] to [9] is mounted on the surface of the base plate.

Claims

1. An electrostatic chuck, comprising: The substrate has a placement surface for placing and adsorbing the target object; as well as Electrodes, which are embedded in the substrate. The substrate has a groove that opens towards the placement surface but does not reach the electrode. Between the bottom surface of the groove and the electrode, starting from the side closest to the groove and along the thickness direction of the substrate, a low-resistivity region made of ceramic and a high-resistivity region made of ceramic with a volume resistivity higher than that of the low-resistivity region are sequentially arranged. The electrostatic chuck further includes a gas discharge section that opens into the bottom surface of the groove. The gas discharge section is formed to penetrate the high-resistivity region.

2. The electrostatic chuck according to claim 1, wherein, When viewed from above, the high-resistance region is located in the area that overlaps with the groove.

3. The electrostatic chuck according to claim 2, wherein, Viewed from above, the groove is arranged in a ring shape, and The high-resistance region is arranged in a ring shape in the region overlapping with the groove.

4. The electrostatic chuck according to claim 3, wherein, Viewed from above, the plurality of grooves are arranged concentrically so that the plurality of grooves do not touch each other, and When viewed from above, the high-resistivity region is arranged in a ring shape in the area overlapping with each groove in the groove.

5. The electrostatic chuck according to any one of claims 1 to 4, wherein, The width of the high-resistivity region is greater than the width of the groove.

6. The electrostatic chuck according to any one of claims 1 to 4, wherein, The high-resistance region is in contact with the surface of the electrode facing the groove.

7. The electrostatic chuck according to any one of claims 1 to 4, wherein, The high-resistivity region is formed of aluminum oxide and has 10 15 Volume resistivity above Ωm.

8. The electrostatic chuck according to any one of claims 1 to 4, wherein, The electrostatic chuck is of the Johnson-Rabec type.

9. A substrate fixing device, comprising: Base plate; as well as The electrostatic chuck according to any one of claims 1 to 4, wherein the electrostatic chuck is mounted on the surface of the base plate.

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