Substrate fixing device

Abstract

To provide a substrate fixing device in which a second base body having a mounting surface is disposed on a first base body, capable of facilitating replacement of the second base body.SOLUTION: A substrate fixing device includes: a base plate; and an electrostatic chuck mounted on the base plate via a first adhesive layer. The electrostatic chuck includes: a first base body containing a ceramic material as a main component; a second base body having a mounting surface on which an object to be adsorbed is mounted, being stacked on the first base body via a second adhesive layer, and containing a ceramic material as a main component; and an electrostatic electrode incorporated in the second base body. The first base body is stacked on the first adhesive layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a substrate fixing device. [Background technology]

[0002] Conventionally, film deposition equipment and plasma etching equipment used in manufacturing semiconductor devices have a stage for precisely holding a wafer in a vacuum processing chamber. As such a stage, for example, a substrate fixing device has been proposed that attracts and holds a wafer using an electrostatic chuck mounted on a base plate.

[0003] Such a substrate holding device has a structure in which a ceramic second base body with built-in electrodes is directly bonded onto a ceramic first base body with built-in heaters, and the upper surface of the second base body serves as a mounting surface on which an object to be attracted, such as a wafer, is placed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-123983 Summary of the Invention [Problem to be solved by the invention]

[0005] The substrate holding device is used in a plasma environment, and the second base having the mounting surface may be exposed to plasma and deteriorate. However, in the structure in which two ceramic bases are directly bonded as described above, even if the second base deteriorates, it is difficult to replace only the second base. On the other hand, if the second base deteriorates and parts other than the second base, such as the first base, are also replaced, the cost burden becomes large.

[0006] The present invention has been made in consideration of the above points, and aims to facilitate replacement of a second base having a mounting surface in a substrate fixing device in which the second base is placed on a first base. [Means for solving the problem]

[0007] This substrate fixing device has a base plate and an electrostatic chuck mounted on the base plate via a first adhesive layer, wherein the electrostatic chuck includes a first base made primarily of a ceramic material, a second base made primarily of a ceramic material having a mounting surface on which an object to be attracted is placed and laminated on the first base via a second adhesive layer, and an electrostatic electrode built into the second base, and the first base is laminated on the first adhesive layer. [Effects of the Invention]

[0008] According to the disclosed technique, in a substrate fixing device in which a second base having a mounting surface is placed on a first base, it is possible to facilitate replacement of the second base. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view illustrating a simplified example of a substrate fixing device according to a first embodiment. [Figure 2] 5A to 5C are views (part 1) illustrating a manufacturing process of the substrate fixing device according to the first embodiment. [Figure 3] 10A to 10C are views (part 2) illustrating the manufacturing process of the substrate fixing device according to the first embodiment. [Figure 4] FIG. 10 is a cross-sectional view illustrating a simplified example of a substrate fixing device according to a first modified example of the first embodiment. [Figure 5] FIG. 10 is a cross-sectional view illustrating a simplified example of a substrate fixing device according to a second modification of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant explanations may be omitted.

[0011] First Embodiment Fig. 1 is a simplified cross-sectional view illustrating a substrate fixing device according to a first embodiment. Referring to Fig. 1, the substrate fixing device 1 has, as its main components, a base plate 10, a first adhesive layer 20, and an electrostatic chuck 30. The substrate fixing device 1 is a device that adsorbs and holds a substrate (such as a wafer) as an object to be adsorbed by the electrostatic chuck 30 mounted on one surface of the base plate 10.

[0012] The base plate 10 is a member on which the electrostatic chuck 30 is mounted. The thickness of the base plate 10 is, for example, about 20 to 50 mm. The base plate 10 can be made of metal such as aluminum, copper, or titanium. Among these, it is preferable to use aluminum, which is inexpensive and easy to process.

[0013] The base plate 10 can also be used as an electrode for controlling plasma. By supplying a predetermined high-frequency power to the base plate 10, the energy for causing ions in the generated plasma state to collide with the wafer attracted to the electrostatic chuck 30 can be controlled, thereby enabling an effective etching process.

[0014] A flow path may be provided inside the base plate 10. In this case, the flow path is connected to a cooling medium control device provided outside the substrate fixing device 1, and the cooling medium control device introduces and discharges a cooling medium into the flow path. The cooling medium control device circulates the cooling medium through the flow path to cool the base plate 10, thereby cooling the wafer attracted to the electrostatic chuck 30. For example, water or Galden can be used as the cooling medium. In addition to the flow path, the base plate 10 may be provided with a gas path or the like for introducing an inert gas to cool the wafer attracted to the electrostatic chuck 30.

[0015] The electrostatic chuck 30 is mounted on the base plate 10 via a first adhesive layer 20. For example, a silicone-based resin can be used as the first adhesive layer 20. An epoxy-based resin or an acrylic-based resin may also be used as the first adhesive layer 20. An inorganic material may also be used as the first adhesive layer 20. The thickness of the first adhesive layer 20 is preferably large. The thickness of the first adhesive layer 20 may be, for example, about 0.2 to 1.5 mm. By making the first adhesive layer 20 this thick, it is possible to reduce stress caused by the difference in thermal expansion coefficient between the ceramic electrostatic chuck 30 and the aluminum base plate 10.

[0016] The thermal conductivity of the first adhesive layer 20 is preferably 2 W / mK or higher. The first adhesive layer 20 may be formed from a single layer, or may have a two-layer structure in which an adhesive with high thermal conductivity and an adhesive with low elasticity are combined. This can further reduce stress caused by the difference in thermal expansion coefficient between the ceramic electrostatic chuck 30 and the aluminum base plate 10.

[0017] The electrostatic chuck 30 is a part that attracts and holds a wafer, which is an object to be attracted. The planar shape of the electrostatic chuck 30 may be, for example, circular. The diameter of the wafer, which is an object to be attracted to the electrostatic chuck 30, may be, for example, approximately 8, 12, or 18 inches. The electrostatic chuck 30 is, for example, a Coulomb force type electrostatic chuck. However, the electrostatic chuck 30 may also be a Johnsen-Rahbek type electrostatic chuck.

[0018] The electrostatic chuck 30 includes a first base 31, a second base 32, and a second adhesive layer 33. The first base 31 is stacked on the first adhesive layer 20. The second base 32 is stacked on the first base 31 with the second adhesive layer 33 interposed therebetween. That is, the first base 31 and the second base 32 are stacked with the second adhesive layer 33 sandwiched between them.

[0019] The first substrate 31 is a dielectric material whose main component is a ceramic material. The first substrate 31 can be made mainly of aluminum oxide, for example. Here, the main component refers to a component that accounts for 90% by weight or more of the components contained in the target portion. The first substrate 31 may be made mainly of a ceramic material other than aluminum oxide. An example of a ceramic material other than aluminum oxide is mullite. The thickness of the first substrate 31 is, for example, about 2 to 10 mm.

[0020] The first base 31 may have a built-in heating element 34, for example. The heating element 34 generates heat when a voltage is applied from outside the substrate fixing device 1, and heats the mounting surface 32a (described later) of the second base 32 to a predetermined temperature. The heating element 34 may heat the mounting surface 32a of the second base 32 to a temperature of, for example, about 250°C to 300°C. The heating element 34 may be made of, for example, tungsten (W), molybdenum (Mo), or the like. The heating element 34 may have, for example, a concentric circular pattern. The thickness of the heating element 34 is, for example, about 10 to 50 μm. The first base 31 may have a built-in conductor other than the heating element 34.

[0021] The second substrate 32 has a mounting surface 32a on which an object to be adsorbed is placed. The surface of the second substrate 32 opposite to the second adhesive layer 33 is the mounting surface 32a. The second substrate 32 is a dielectric material containing a ceramic material as its main component. The second substrate 32 may contain, for example, aluminum oxide as its main component. The purity of the aluminum oxide in the second substrate 32 is, for example, 80 weight percent or more and 97 weight percent or less. The thickness of the second substrate 32 is, for example, about 1 to 5 mm. The relative dielectric constant (1 MHz) of the second substrate 32 is, for example, about 7 to 10.

[0022] The second substrate 32 and the first substrate 31 preferably have the same ceramic material as their main component. The second substrate 32 and the first substrate 31 can have aluminum oxide as their main component, for example. By having the second substrate 32 and the first substrate 31 have the same ceramic material as their main component, the physical properties (for example, thermal expansion coefficients) of the second substrate 32 and the first substrate 31 can be made closer to each other. As a result, warping due to heat can be prevented.

[0023] The second base 32 has an electrostatic electrode 35 built in. The electrostatic electrode 35 is, for example, a thin-film electrode. The electrostatic electrode 35 is connected to a power source provided outside the substrate holding device 1, and when a predetermined voltage is applied from the power source, an electrostatic attraction force is generated between the electrostatic electrode 35 and the wafer. This allows the wafer to be attracted and held on the mounting surface 32a of the second base 32. The electrostatic electrode 35 may be unipolar or bipolar. Examples of materials that can be used for the electrostatic electrode 35 include tungsten and molybdenum.

[0024] The attracting and holding force between the electrostatic electrode 35 and the object to be attracted becomes stronger as the voltage applied to the electrostatic electrode 35 increases, and also as the relative dielectric constant of the second base 32 increases. Since there is a limit to how high the voltage can be applied to the electrostatic electrode 35, it can be said that a larger relative dielectric constant of the second base 32 is preferable in terms of attracting and holding force. In this regard, it is preferable that the second base 32 contains aluminum oxide, which has a high relative dielectric constant among ceramics, as its main component in order to ensure a certain level of attracting and holding force.

[0025] The second adhesive layer 33 may be made of, for example, a silicone-based resin. The second adhesive layer 33 may be made of an epoxy-based resin or an acrylic-based resin. The second adhesive layer 33 may be made of an inorganic material. The second adhesive layer 33 may be made of the same material as the first adhesive layer 20, or may be made of a different material.

[0026] The second adhesive layer 33 may be thinner than the first adhesive layer 20. The upper and lower sides of the second adhesive layer 33 are both substrates whose main component is ceramic, and the difference in thermal expansion coefficients is small or the thermal expansion coefficients are approximately the same, so there is no need to increase the thickness to achieve the effect of reducing stress. The thickness of the second adhesive layer 33 may be, for example, approximately 0.05 to 0.2 mm.

[0027] The substrate fixing device 1 may have a first hole 10x and a second hole 10y communicating with the first hole 10x. The first hole 10x may be provided so as to continuously penetrate the base plate 10, the first adhesive layer 20, the first substrate 31, and the second adhesive layer 33, and to expose the lower surface of the second substrate 32. The second hole 10y may be provided in the second substrate 32 so as to expose the lower surface of the electrostatic electrode 35.

[0028] The second holes 10y are smaller than the first holes 10x when viewed from the bottom of the base plate 10. The first holes 10x may be, for example, circular when viewed from the bottom of the base plate 10. The second holes 10y may be, for example, circular with a smaller diameter than the first holes 10x when viewed from the bottom of the base plate 10. In this case, the diameter of the first holes 10x is, for example, about 2.5 to 4.0 mm, and the diameter of the second holes 10y is, for example, about 1.0 to 2.0 mm.

[0029] The substrate fixing device 1 may have a third hole 10z. The third hole 10z can be provided so as to continuously penetrate the base plate 10, the first adhesive layer 20, and the first base 31 and expose the lower surface of the heating element 34. When viewed from the bottom of the base plate 10, the third hole 10z can be, for example, circular. When viewed from the bottom of the base plate 10, the third hole 10z can be, for example, circular and have the same diameter as the first hole 10x.

[0030] The substrate fixing device 1 may have a power supply terminal 51 electrically connected to the lower surface of the electrostatic electrode 35 exposed in the second hole 10y. The power supply terminal 51 can be inserted into the first hole 10x and the second hole 10y, for example, and electrically connected to the lower surface of the electrostatic electrode 35 via the solder 41.

[0031] The substrate fixing device 1 may have a power supply terminal 52 electrically connected to the lower surface of the heating element 34 exposed in the third hole 10z. The power supply terminal 52 can be inserted into the third hole 10z, for example, and electrically connected to the lower surface of the heating element 34 via solder 42.

[0032] The power supply terminals 51 and 52 may be, for example, pins or wires. The power supply terminals 51 and 52 may be made of a metal such as Kovar. The power supply terminals 51 and 52 may extend from the lower surface of the base plate 10. Brazing material may be used to join the power supply terminals 51 and 52 instead of the solders 41 and 42. By providing the power supply terminals 51 and 52, power can be easily supplied to the electrostatic electrode 35 and the heating element 34 from outside the substrate fixing device 1.

[0033] 2 and 3 are diagrams illustrating the manufacturing process of the substrate holding device according to the first embodiment. First, in the process shown in FIG. 2(a), a second base 32 incorporating an electrostatic electrode 35 is formed, and second holes 10y are formed where necessary. Then, a power supply terminal 51 is electrically connected via solder 41 to the underside of the electrostatic electrode 35 exposed in the second holes 10y. The first base 31 and the electrostatic electrode 35 can be manufactured by a well-known manufacturing method including, for example, a process of forming a pattern to become the electrostatic electrode 35 on a first green sheet, a process of stacking a second green sheet on the first green sheet and firing the second green sheet, and a process of flattening the surface.

[0034] 2(b), a first base 31 incorporating a heating element 34 is formed, and first holes 11x and third holes 11z are formed in necessary locations. The first holes 11x are formed to be larger than the second holes 10y shown in FIG. 2(a). The second base 32 and the heating element 34 can be fabricated, for example, by the same method as the first base 31 and the electrostatic electrode 35.

[0035] Next, in the step shown in FIG. 2(c), an uncured second adhesive layer 33 is placed on the first base 31 fabricated in the step shown in FIG. 2(b) in an area where the first holes 11x and the third holes 11z are not formed. The second base 32 fabricated in the step shown in FIG. 2(a) is then positioned on the uncured second adhesive layer 33 in alignment with the first base 31, and the second adhesive layer 33 is cured. Since the first holes 11x are larger than the second holes 10y, a certain degree of misalignment can be tolerated, facilitating alignment between the first holes 11x and the second holes 10y. After the second adhesive layer 33 is cured, the power supply terminal 52 is electrically connected to the underside of the heating element 34 exposed in the third holes 11z via solder 42. This completes the electrostatic chuck 30.

[0036] 3(a), a base plate 10 is prepared in which first holes 12x and third holes 12z are formed. The first holes 12x and third holes 12z are formed at positions corresponding to the first holes 11x and third holes 11z shown in FIG. 2(c) and with sizes corresponding to those of the first holes 11x and third holes 11z.

[0037] Next, in the step shown in FIG. 3(b), an uncured first adhesive layer 20 is placed on the region of the base plate 10 where the first holes 12x and the third holes 12z are not formed. Then, an electrostatic chuck 30 is placed on the uncured first adhesive layer 20, and the first adhesive layer 20 is cured. The first hole 11x communicates with the first hole 12x, becoming the first hole 10x shown in FIG. 1. The third hole 11z communicates with the third hole 12z, becoming the third hole 10z shown in FIG. 1. With the above steps, the substrate fixing device 1 is completed.

[0038] As described above, in the substrate fixing device 1, the electrostatic chuck 30 has the first base 31, the second base 32 incorporating the electrostatic electrode 35, and the second adhesive layer 33 bonding the first base 31 and the second base 32 together. This structure makes it possible to easily replace the second base 32. That is, the deteriorated second base 32 can be separated from the first base 31 and discarded, and then replaced with an undeteriorated second base 32. In this case, the base plate 10 and the first base 31 can continue to be used as they are, which has the effect of reducing costs.

[0039] Furthermore, even if the second base 32 has not deteriorated, there may be cases where it is desired to change the specifications of the second base 32, such as by changing the pattern of the electrostatic electrode 35. In this case, the second base 32 with the old specifications can be separated from the first base 31 and discarded, and then replaced with a second base 32 with the new specifications. In this case, the base plate 10 and the first base 31 can be made common as general-purpose parts, which has the effect of reducing costs.

[0040] Furthermore, for example, when the main component of the first base 31 and the second base 32 is aluminum oxide, increasing the purity of the aluminum oxide can improve plasma resistance. Therefore, it is preferable that the second base 32, which deteriorates when exposed to plasma, has a higher purity of aluminum oxide than the first base 31. However, increasing the purity of aluminum oxide leads to increased costs. Therefore, in a substrate fixing device 1 in which the second base 32 is replaceable, the purity of aluminum oxide of the second base 32 may be the same as or less than the purity of aluminum oxide of the first base 31. This makes it possible to reduce the cost of the second base 32.

[0041] Furthermore, if the heating element and electrostatic electrode were built into one base, it would be difficult to optimize the distance between them because the distance between them could not be increased significantly. However, by using a structure in which the first base 31 and the second base 32 are bonded together, as in the substrate holding device 1, the degree of freedom in design is increased and the distance between the heating element 34 and the electrostatic electrode 35 can be optimized. As a result, temperature control by the heating element 34 becomes easier.

[0042] To separate the second substrate 32 from the first substrate 31, for example, a blade or the like may be prepared and used to cut the portion of the second adhesive layer 33. Polishing or grinding may be performed as necessary. From the viewpoint of facilitating cutting of the second adhesive layer 33, it is preferable that the second adhesive layer 33 be made of a relatively flexible organic material such as a silicone resin rather than an inorganic material.

[0043] <Modification 1 of the First Embodiment> In Modification 1 of the first embodiment, an example of a substrate fixing device having a sleeve is shown. Note that in Modification 1 of the first embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0044] 4 is a cross-sectional view illustrating a simplified example of a substrate fixing device according to Modification 1 of Embodiment 1. Referring to FIG. 4, the substrate fixing device 1A differs from the substrate fixing device 1 in that it has a sleeve 60.

[0045] The sleeve 60 is a cylindrical insulating member. The sleeve 60 has, for example, a hollow cylindrical shape. A power supply terminal 51 is disposed inside the sleeve 60 and is electrically connected to the lower surface of the electrostatic electrode 35 exposed in the second hole 10y. Furthermore, a power supply terminal 52 is disposed inside the other sleeve 60 and is electrically connected to the lower surface of the heating element 34 exposed in the third hole 10z.

[0046] The sleeve 60 is made of an inorganic insulator such as aluminum oxide. Alternatively, the sleeve 60 may be made of an organic insulator such as polyimide. Because the base plate 10 is made of a conductive material such as aluminum, discharge may occur from the power supply terminals 51 and / or 52 to the base plate 10. Providing the sleeve 60 can suppress discharge.

[0047] In the substrate fixing device 1A, the sleeve 60 extends from the inside of the first hole 10x located in the base plate 10 to the inside of the first holes 10x located in the first adhesive layer 20, the first base 31, and the second adhesive layer 33. An end of the sleeve 60 is adhered to the lower surface of the second base 32 exposed around the second hole 10y via an adhesive 70. In addition, in the substrate fixing device 1A, the sleeve 60 extends from the inside of the third hole 10z located in the base plate 10 to the inside of the third hole 10z located in the first adhesive layer 20 and the first base 31. An end of the sleeve 60 is adhered to the lower surface of the heating element 34 exposed in the third hole 10z via the adhesive 70. As the adhesive 70, for example, an epoxy resin can be used.

[0048] From the viewpoint of suppressing discharge, the sleeve 60 only needs to be disposed inside at least the first hole 10x and the third hole 10z located in the base plate 10. The sleeve 60 can be press-fitted into the first hole 10x and the third hole 10z located in the base plate 10, for example.

[0049] <Modification 2 of the First Embodiment> In Modification 2 of the first embodiment, an example of a substrate fixing device having a heating element different from that of Embodiment 1 is shown. Note that in Modification 2 of the first embodiment, the description of the same components as those of the already described embodiments may be omitted.

[0050] 5 is a simplified cross-sectional view illustrating a substrate fixing device according to Modification 2 of the first embodiment. Referring to FIG. 5, the substrate fixing device 1B differs from the substrate fixing device 1 in that the electrostatic chuck 30 is replaced with an electrostatic chuck 30B.

[0051] In the electrostatic chuck 30B, the heating element 34 is not built into the first base 31. The first base 31 can be used, for example, to adjust the thickness of the electrostatic chuck 30B. Alternatively, a conductor other than the heating element may be built into the first base 31. The electrostatic chuck 30B has an insulating resin layer 36 disposed between the first adhesive layer 20 and the first base 31, and the insulating resin layer 36 has a heating element 34B built into it. The heating element 34B and the insulating resin layer 36 form a so-called laminate heater.

[0052] For example, the insulating resin layer 36 may be made of an epoxy resin or a bismaleimide triazine resin, which have high thermal conductivity and high heat resistance. The insulating resin layer 36 preferably has a thermal conductivity of 3 W / mK or higher. The insulating resin layer 36 may contain a filler such as aluminum oxide or aluminum nitride, thereby improving the thermal conductivity of the insulating resin layer 36. The insulating resin layer 36 preferably has a glass transition temperature (Tg) of 250°C or higher. The insulating resin layer 36 preferably has a thickness of approximately 100 to 150 μm, and the thickness variation of the insulating resin layer 36 is preferably within ±10%.

[0053] The heating element 34B may be made of, for example, copper (Cu), tungsten (W), nickel (Ni), aluminum (Al), constantan (an alloy of Cu / Ni / Mn / Fe), geranine (an alloy of Cu / Mn / Sn), manganin (an alloy of Cu / Mn / Ni), etc. The heating element 34B may be formed, for example, in a concentric circular pattern.

[0054] In this way, the heating element 34B may be built into the insulating resin layer 36 disposed between the first adhesive layer 20 and the first base 31, without the heating element being built into the first base 31.

[0055] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0056] For example, examples of objects to be attracted by the substrate fixing device according to the present invention include glass substrates used in the manufacturing process of liquid crystal panels, etc., in addition to wafers (silicon wafers, etc.). [Explanation of symbols]

[0057] 1,1A,1B Board fixing device 10 Base Plate 10x,11x,12x 1st hole 10y 2nd hole 10z,11z,12z 3rd hole 20 1st adhesive layer 30,30B Electrostatic Chuck 31 First base 32 Second base 32a Placement surface 33 Second adhesive layer 34, 34B Heating element 35 Electrostatic Electrode 36 Insulating resin layer 41,42 Solder 51,52 Power supply terminal 60 sleeves 70 Adhesive

Claims

1. A base plate and an electrostatic chuck mounted on the base plate via a first adhesive layer; The electrostatic chuck comprises: a first substrate mainly composed of a ceramic material; a second substrate having a mounting surface on which an object to be adsorbed is placed, the second substrate being mainly made of a ceramic material and laminated on the first substrate via a second adhesive layer; an electrostatic electrode built into the second substrate; The first base is laminated on the first adhesive layer.

2. a first hole that continuously penetrates the base plate, the first adhesive layer, the first substrate, and the second adhesive layer and exposes a lower surface of the second substrate; a second hole provided in the second base so as to communicate with the first hole and exposing a lower surface of the electrostatic electrode; The substrate fixing device according to claim 1 , wherein the second hole is smaller than the first hole in a bottom view.

3. The substrate fixing device according to claim 2 , further comprising a cylindrical insulating member disposed inside the first hole located in the base plate.

4. 4. The substrate fixing device according to claim 3, wherein the insulating member extends inside the first hole located in the first adhesive layer, the first base, and the second adhesive layer, and an end portion is adhered to the underside of the second base exposed around the second hole.

5. 5. The substrate fixing device according to claim 4, further comprising a power supply terminal disposed inside the insulating member and electrically connected to a lower surface of the electrostatic electrode exposed in the second hole.

6. The substrate fixing device according to claim 1 , wherein the second adhesive layer is thinner than the first adhesive layer.

7. 6. The substrate fixing device according to claim 1, wherein the second base and the first base are made mainly of the same ceramic material.

8. The substrate fixing device according to claim 1 , wherein the second adhesive layer is made of an organic material.

9. The substrate fixing device according to claim 1 , wherein the first base includes a built-in heating element.

10. an insulating resin layer disposed between the first adhesive layer and the first base; The substrate fixing device according to claim 1 , wherein the insulating resin layer has a built-in heating element.

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