Retaining material

Abstract

To provide a holding member that can improve the heat homogeneity of an object.SOLUTION: An electrostatic chuck 1 holding a semiconductor wafer W on a holding surface 11 of a ceramic member 10 includes a ceramic member 10, a heater layer 17, and an internal electrode 41. When viewed from a Z-axis direction, the ceramic member 10 includes a first region 10a including an internal electrode 41 and a second region 10b not including the internal electrode 41. When viewed from the Z-axis direction, at least a part of a convex part 14 overlaps with the second region 10b.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a holding member for holding an object. [Background technology]

[0002] As a conventional technique relating to a holding member, Patent Document 1 discloses an electrostatic chuck having a ceramic substrate equipped with an electrostatic electrode and a heat generating portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-201669 A Summary of the Invention [Problem to be solved by the invention]

[0004] The electrostatic chuck disclosed in Patent Document 1 holds a semiconductor wafer, which is an object to be held, by contacting it with a protrusion formed on a first main surface of a ceramic substrate. Therefore, heat transfer between the semiconductor wafer and the ceramic substrate is likely to occur in the area of ​​the protrusion, but may be difficult to occur in areas other than the protrusion. Therefore, there is a risk that the thermal uniformity of the semiconductor wafer may decrease.

[0005] Therefore, the present disclosure has been made to solve the above-mentioned problems, and has an object to provide a holding member that can improve the thermal uniformity of an object. [Means for solving the problem]

[0006] One form of the present disclosure made to solve the above problems is characterized in that it comprises a ceramic member having a first surface on which a plurality of convex portions are formed and a second surface provided on the opposite side of the first surface in a first direction, a heating resistor for heating the ceramic member, and an internal electrode arranged inside the ceramic member and on the first surface side of the heating resistor, and in a holding member for holding an object on the first surface of the ceramic member, when viewed from the first direction, the ceramic member has a first region having the internal electrode and a second region not having the internal electrode, and when viewed from the first direction, at least a portion of the convex portions overlap with the second region.

[0007] According to this embodiment, since the second region having no internal electrode is disposed below the protrusion, a portion where no internal electrode exists is formed below the protrusion, and heat transfer to the protrusion is suppressed. Therefore, heat transfer between the protrusion and the object is suppressed. Therefore, the temperature difference between the portion of the held object that is in contact with the protrusion and the other portion can be reduced, and the temperature uniformity of the object can be improved.

[0008] In the above aspect, it is preferable that all of the plurality of protrusions overlap at least a portion of the second region when viewed from the first direction.

[0009] According to this aspect, since the second region is disposed on all of the plurality of protrusions, heat transfer between all of the protrusions and the object is suppressed, so that the temperature difference between the part of the held object that is in contact with the protrusions and the other part can be reduced, thereby further improving the thermal uniformity of the object.

[0010] In the above aspect, it is preferable that the entire area of ​​the protrusion overlaps with the second area when viewed from the first direction.

[0011] According to this aspect, by forming the second region so as to overlap the entire region of the protrusion when viewed from the first direction, heat transfer is suppressed over the entire region of the protrusion, so that the temperature difference between the part of the held object that is in contact with the protrusion and the other part can be further reduced, thereby further improving the thermal uniformity of the object.

[0012] In the above aspect, it is preferable that an annular convex portion is formed on the first surface so as to surround all of the plurality of convex portions, and that when viewed from the first direction, the annular convex portion does not overlap with the first region.

[0013] According to this aspect, by arranging the internal electrodes so as not to overlap the annular protrusion when viewed from the first direction, heat transfer is also suppressed in the annular protrusion that contacts the object, so that the temperature difference between the protrusion and the part of the object that contacts the annular protrusion and the other part can be reduced, thereby improving thermal uniformity even in the outer periphery of the object. Effect of the Invention

[0014] The holding member of the present disclosure can improve the thermal uniformity of an object. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic perspective view of an electrostatic chuck according to an embodiment of the present invention. [Diagram 2] 2 is a schematic diagram of the XZ side surface (partial cross section) of the electrostatic chuck of the present embodiment. FIG. [Diagram 3] 1 is a schematic configuration diagram of an electrostatic chuck of the present embodiment in an XY plane. [Figure 4] 2 is an enlarged view of a portion of an XZ cross section of the ceramic member of the present embodiment. FIG. [Diagram 5] FIG. 1 is an enlarged view of a portion of an XZ cross section of a conventional ceramic member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] A holding member according to an embodiment of the present disclosure will be described below. In this embodiment, an electrostatic chuck 1 for holding a semiconductor wafer W as an object will be described as an example of the holding member.

[0017] <Overall explanation of electrostatic chuck> The electrostatic chuck 1 of this embodiment is a device that attracts and holds a semiconductor wafer W (object) by electrostatic attraction, and is used, for example, to fix the semiconductor wafer W in a vacuum chamber of a semiconductor manufacturing device. As shown in Fig. 1, the electrostatic chuck 1 has a ceramic member 10, a base member 20, and a bonding layer 30 that bonds the ceramic member 10 and the base member 20 together.

[0018] For the sake of convenience, in the following description, the X, Y and Z axes are defined as shown in Fig. 1. Here, the Z axis is an axis in the axial direction of the electrostatic chuck 1 (the vertical direction in Fig. 1), and the X and Y axes are axes in the radial directions of the electrostatic chuck 1.

[0019] The ceramic member 10 is a disk-shaped member made of ceramics, as shown in Fig. 1. Various ceramics can be used as the ceramic, but from the viewpoints of strength, wear resistance, plasma resistance, etc., it is preferable to use ceramics whose main component is, for example, aluminum oxide (alumina, Al2O3) or aluminum nitride (AlN). Note that the main component here means the component with the highest content (for example, a component with a volume content of 90 vol% or more).

[0020] The ceramic member 10 has a diameter of, for example, about 150 to 300 mm. The ceramic member 10 has a thickness of, for example, about 2 to 6 mm. The ceramic member 10 desirably has a thermal conductivity in the range of 10 to 50 W / mK (more preferably, 18 to 30 W / mK).

[0021] 1 and 2, the ceramic member 10 includes a holding surface 11 that holds a semiconductor wafer W, and a bottom surface 12 that is provided on the opposite side to the holding surface 11 in the thickness direction (Z-axis direction, up-down direction) of the ceramic member 10. Note that the Z-axis direction is an example of a "first direction" in the present disclosure, the holding surface 11 is an example of a "first surface" in the present disclosure, and the bottom surface 12 is an example of a "second surface" in the present disclosure.

[0022] The holding surface 11 of the ceramic member 10 has an uneven shape. Specifically, as shown in FIG. 2 and FIG. 3, the holding surface 11 has an annular convex portion 13 formed in the vicinity of its outer edge, and a plurality of independent columnar convex portions 14 formed inside the annular convex portion 13. In this way, the holding surface 11 has the annular convex portion 13 arranged so as to surround all of the plurality of convex portions 14. The annular convex portion 13 is also called a seal band. The cross section (XZ cross section) of the annular convex portion 13 has a substantially rectangular shape as shown in FIG. 2. The height (dimension in the Z-axis direction) of the annular convex portion 13 is, for example, about 10 μm to 20 μm. The width (dimension in the X-axis direction) of the annular convex portion 13 is, for example, about 0.5 mm to 5.0 mm.

[0023] Although not shown, through holes for lift pins and the like are formed in the ceramic member 10, and annular protrusions are formed on the holding surface 11 so as to surround each of the through holes.

[0024] As shown in FIG. 3, each of the protrusions 14 has a substantially circular shape when viewed in the Z-axis direction (plan view), and is disposed at substantially equal intervals. The shape of the cross section (XZ cross section) of each of the protrusions 14 is substantially rectangular, as shown in FIG. 2. The height of the protrusions 14 is substantially the same as the height of the annular protrusion 13, and is, for example, about 10 to 20 μm. The width of the protrusions 14 (maximum diameter of the protrusions 14 when viewed in the Z-axis direction) is, for example, about 0.5 to 1.5 mm. The portion of the holding surface 11 of the ceramic member 10 on the inner side of the annular protrusion 13 where the protrusions 14 are not formed is a recess 15.

[0025] The semiconductor wafer W is supported by the annular convex portion 13, the multiple convex portions 14, and an annular convex portion (not shown) formed to surround the through holes for lift pins on the holding surface 11 of the ceramic member 10, and is held by the electrostatic chuck 1. When the semiconductor wafer W is held by the electrostatic chuck 1, a space S exists between the surface (lower surface) of the semiconductor wafer W and the holding surface 11 of the ceramic member 10 (more specifically, the concave portion 15 of the holding surface 11) (see FIG. 2). An inert gas (e.g., helium gas) is supplied to this space S through a gas hole 16 shown in FIG. 3.

[0026] 2, the ceramic member 10 includes a heater layer 17 and an internal electrode portion 18 therein. The heater layer 17 heats the ceramic member 10 to adjust the temperature of the semiconductor wafer W held on the holding surface 11 of the ceramic member 10. The heater layer 17 may be formed on the lower surface 12 of the ceramic member 10. The heater layer 17 is an example of a "heating resistor" in the present disclosure.

[0027] The internal electrode portion 18 is disposed inside the ceramic member 10 at a position closer to the support surface 11 than the heater layer 17 is.

[0028] In this embodiment, the internal electrode portion 18 is formed in a plate shape, and includes an internal electrode 41 in which an electrode is formed, and a through hole 42 formed so as to penetrate the internal electrode portion 18 in its thickness direction. The internal electrode 41 and the through hole 42 are disposed inside the ceramic member 10, at a position closer to the holding surface 11 than the heater layer 17.

[0029] The internal electrode 41 is, for example, a chuck electrode, an RF electrode, a land electrode, etc. The internal electrode 41 is made of a metal, and the metal material of the internal electrode 41 is, for example, tungsten, molybdenum, or an alloy thereof.

[0030] The through holes 42 are formed, for example, as round holes having a circular outer shape when the ceramic member 10 is viewed from the Z-axis direction. Moreover, the through holes 42 are formed, for example, by using a mask when the ceramic member 10 is formed by stacking sheet members.

[0031] In this embodiment, the outer circumferential portion 18a of the internal electrode portion 18 is formed at a position on the inner circumferential surface 13a of the annular convex portion 13 that is located outside the outermost convex portion 14 in the radial direction of the ceramic member 10, or at a position slightly inside from that position. As a result, when the ceramic member 10 is viewed from the Z-axis direction, all of the convex portions 14 and the concave portions 15 are formed inside the outer circumferential portion 18a of the internal electrode portion 18.

[0032] The base member 20 is formed in a cylindrical shape as shown in Fig. 1. The base member 20 is preferably formed from a metal (for example, aluminum or an aluminum alloy), but may be formed from a material other than metal.

[0033] The diameter of the base member 20 is, for example, about 180 mm to 350 mm. The thickness (dimension in the Z-axis direction) of the base member 20 is, for example, about 20 mm to 50 mm. The thermal conductivity of the base member 20 (assumed to be aluminum) is greater than that of the ceramic member 10, and is desirably within the range of 180 to 250 W / mK (preferably, about 230 W / mK).

[0034] The bonding layer 30 is disposed between the lower surface 12 of the ceramic member 10 and the base member 20, and bonds the ceramic member 10 and the base member 20. The lower surface 12 of the ceramic member 10 and the base member 20 are thermally connected via the bonding layer 30. The bonding layer 30 is made of an adhesive material such as a silicone resin, an acrylic resin, or an epoxy resin. The thickness (dimension in the Z-axis direction) of the bonding layer 30 is, for example, about 0.1 to 1.0 mm. The thermal conductivity of the bonding layer 30 is, for example, 1.0 W / mK. The thermal conductivity of the bonding layer 30 (assuming a silicone resin) is preferably within a range of 0.1 to 2.0 W / mK (preferably, 0.5 to 1.5 W / mK).

[0035] <Methods for improving thermal uniformity of semiconductor wafers> Next, a method for improving the temperature uniformity of the semiconductor wafer W will be described.

[0036] As shown in FIG. 5, in the holding surface 11 of the ceramic member 10, the semiconductor wafer W is in direct contact with the region of the convex portion 14 and the annular convex portion 13, so that heat transfer is likely to occur between the semiconductor wafer W and the ceramic member 10. On the other hand, in the region other than the convex portion 14 and the annular convex portion 13, that is, the region of the concave portion 15, an inert gas is filled, but the semiconductor wafer W is not in direct contact with the region, so that heat transfer is unlikely to occur between the semiconductor wafer W and the ceramic member 10. Therefore, in the conventional method, while the heat of the heater layer 17 is easily transferred from the region of the convex portion 14 and the annular convex portion 13 to the semiconductor wafer W, the heat of the heater layer 17 is unlikely to be transferred from the region of the concave portion 15 to the semiconductor wafer W via the helium gas. Therefore, there was a risk that the temperature distribution of the semiconductor wafer W would deteriorate, and the thermal uniformity of the semiconductor wafer W would decrease.

[0037] Therefore, in this embodiment, the internal structure of the ceramic member 10 is devised to improve the temperature uniformity of the semiconductor wafer W.

[0038] Specifically, as shown in Fig. 4, the ceramic member 10 includes a first region 10a having an internal electrode 41 of the internal electrode portion 18 and a second region 10b not having the internal electrode 41, arranged in the XY plane direction below the internal convex portion 14 and concave portion 15. That is, the ceramic member 10 includes the first region 10a in which the internal electrode 41 is formed, and the second region 10b in which the through hole 42 is formed. In this way, when viewed from the Z-axis direction, the ceramic member 10 includes the first region 10a and the second region 10b.

[0039] 4, the second region 10b, i.e., the through hole 42, is disposed below (toward the lower surface 12) the protrusion 14. In this way, the protrusion 14 overlaps with the through hole 42 when the ceramic member 10 is viewed from the Z-axis direction (from above in FIG. 4).

[0040] In this embodiment, since the through holes 42 are disposed below the protrusions 14 in this manner, a portion where the internal electrode 41 is not present, i.e., a portion formed of a ceramic having a lower thermal conductivity than the metal forming the internal electrode 41, is formed below the protrusions 14, and heat transfer from the heater layer 17 to the protrusions 14 is suppressed. This suppresses heat transfer between the protrusions 14 and the semiconductor wafer W. This makes it possible to reduce the temperature difference between the portion of the held semiconductor wafer W that is in contact with the protrusions 14 and the other portions, thereby improving the thermal uniformity of the semiconductor wafer W.

[0041] Here, in the example shown in FIG. 4, the through holes 42 are arranged below the entire area of ​​each protrusion 14 in the radial direction of the ceramic member 10 (i.e., the X-axis direction in FIG. 4). In this way, when viewed from the Z-axis direction, the through holes 42 are formed so as to include the entire area of ​​each protrusion 14 within the hole, and the entire area of ​​each protrusion 14 overlaps with the through holes 42. This suppresses heat transfer in the entire area of ​​each protrusion 14, so that the temperature difference between the part of the held semiconductor wafer W that is in contact with the protrusion 14 and the other part can be further reduced. This makes it possible to further improve the thermal uniformity of the semiconductor wafer W.

[0042] Moreover, the through holes 42 are formed in a one-to-one correspondence with all of the protrusions 14, and all of the multiple protrusions 14 overlap with the through holes 42 when viewed from the Z-axis direction. That is, the through holes 42 are formed in 100% of the total area of ​​all of the protrusions 14. As a result, by forming the through holes 42 in all of the multiple protrusions 14, heat transfer between all of the protrusions 14 and the semiconductor wafer W is suppressed, and therefore the temperature difference between the parts of the held semiconductor wafer W that come into contact with the protrusions 14 and the other parts can be made smaller. This makes it possible to further improve the thermal uniformity of the semiconductor wafer W.

[0043] The through hole 42 may be larger than the area of ​​one of the protrusions 14. This allows for misalignment between the protrusions 14 and the through hole 42 during the manufacture of the ceramic member 10. However, if the area of ​​the through hole 42 is too large, the through hole 42 is provided below the recess 15, which reduces the effect of improving the thermal uniformity of the semiconductor wafer W of the present application, so there is an upper limit to the area of ​​the through hole 42. For example, if the diameter of one of the protrusions 14 is 1 mm, the area of ​​the through hole 42 is set to an upper limit such that the outer periphery of the through hole 42 is formed outside the outer periphery of the protrusion 14 within a range of 1 mm or less.

[0044] 4, the outer peripheral portion 18a of the internal electrode portion 18 is formed at the position of the inner peripheral surface 13a of the annular protrusion 13 in the radial direction of the ceramic member 10 or at a position slightly inside the position. As a result, similar to the protrusion 14, the internal electrode 41 is not present below the annular protrusion 13. In this way, when viewed from the Z-axis direction, the annular protrusion 13 does not overlap the first region 10a, i.e., the internal electrode 41. The heater layer 17 is also disposed below the annular protrusion 13.

[0045] In this way, since the internal electrode 41 is not present below the annular protrusion 13, a portion made of ceramic having a lower thermal conductivity than the metal forming the internal electrode 41 is formed below the annular protrusion 13, and heat transfer from the heater layer 17 to the annular protrusion 13 is suppressed. Therefore, heat transfer between the annular protrusion 13 and the semiconductor wafer W is also suppressed. Therefore, it is possible to reduce the temperature difference between the portion of the held semiconductor wafer W that is in contact with the protrusion 14 and the annular protrusion 13 and the other portion. This makes it possible to improve thermal uniformity even in the outer periphery of the semiconductor wafer W.

[0046] Furthermore, when viewed from the Z-axis direction, it is sufficient that at least a portion of the protrusion 14 overlaps with the through-hole 42, and not the entire area of ​​the protrusion 14 but only a portion thereof may overlap with the through-hole 42.

[0047] Moreover, when viewed from the Z-axis direction, all of the multiple protrusions 14 need only overlap at least a portion of the through hole 42, and all of the multiple protrusions 14 may overlap a portion of the through hole 42. For example, the through holes 42 are preferably formed in 30% or more of the total area of ​​all the protrusions 14, and more preferably, are formed in 50% or more of the total area of ​​all the protrusions 14. As a specific example, when the through holes 42 are formed in a range of 50% of the total area of ​​all the protrusions 14, the through holes 42 may be formed in the entirety of one of the two protrusions 14, or in half of each of the two protrusions 14.

[0048] Furthermore, the through hole 42 may be formed at an angle such that its central axis is oblique to the Z-axis direction. In this case, when viewed from the Z-axis direction, at least a part of the protrusion 14 overlaps with the part of the through hole 42 that penetrates in the Z-axis direction.

[0049] In addition, when viewed from the Z-axis direction, the through holes 42 may be formed as linear holes, but it is more preferable to form them as circular holes in order to improve the thermal uniformity of the semiconductor wafer W.

[0050] In addition, when viewed from the Z-axis direction, at least a portion of a ring-shaped protrusion (not shown, an example of a "protrusion" in the present disclosure) formed to surround a through hole for a lift pin, etc., may overlap the second region 10b of the internal electrode portion 18, i.e., the through hole 42.

[0051] It should be noted that the above-described embodiments are merely examples and do not limit the present disclosure in any way. Needless to say, various improvements and modifications are possible without departing from the spirit and scope of the present disclosure. [Explanation of symbols]

[0052] 1. Electrostatic chuck 10 Ceramic materials 10a First Area 10b The second area 11 Holding surface 12 Bottom side 13 Annular protrusion 13a Inner surface 14 Convex 15 Recess 16 Gas hole 17 Heater layer 18 Internal electrode section 18a outer periphery 20 Base material 30 Bonding layer 41 Internal electrode 42 Through hole W Semiconductor wafer S space Ca central axis

Claims

1. A ceramic member including a first surface on which a plurality of protrusions are formed and a second surface provided on an opposite side to the first surface in a first direction; A heating resistor for heating the ceramic member; an internal electrode disposed inside the ceramic member on the first surface side of the heating resistor; A holding member for holding an object on the first surface of the ceramic member, When viewed from the first direction, the ceramic member includes a first region having the internal electrode and a second region not having the internal electrode, When viewed from the first direction, at least a portion of the protrusion overlaps with the second region, When viewed from the first direction, the convex portion has a circular shape, and the second region has a circular shape; A holding member comprising:

2. The holding member according to claim 1, When viewed from the first direction, all of the plurality of protrusions overlap at least a portion of the second region; A holding member comprising:

3. The holding member according to claim 1 or 2, When viewed from the first direction, an entire area of ​​the protrusion overlaps with the second area; A holding member comprising:

4. 4. The holding member according to claim 1, an annular convex portion is formed on the first surface so as to surround all of the plurality of convex portions; When viewed from the first direction, the annular convex portion does not overlap with the first region; A holding member comprising:

5. In the retaining member of claim 1, the second region has an area larger than that of the protrusion; A holding member comprising:

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