JP7633866B2 - Retaining material - Google Patents

Description

This disclosure relates to a holding member that holds an object.

In the semiconductor manufacturing process, electrostatic chucks (holding members) are used to hold semiconductor wafers. For example, Patent Document 1 discloses a thin electrostatic chuck that attracts and holds a semiconductor wafer during processing and can be transported between processes together with the semiconductor wafer attracted and held on the holding surface. Such an electrostatic chuck is placed on a base (a mounting surface provided on the semiconductor manufacturing equipment) during processing, and is held by a transport arm or the like during transport.

JP 2015-228406 A

Here, while the mounting surface installed on the semiconductor manufacturing equipment is manufactured to have a high degree of flatness, the holding member is prone to warping (deflection) due to the stress (residual stress) inherent in the ceramics themselves. Furthermore, if the holding member warps (deflects), it becomes difficult to install the holding member along (fit) the mounting surface due to the high bending rigidity of ceramics, and there is a risk that the flatness of the holding surface of the holding member that holds the semiconductor wafers cannot be guaranteed.

Therefore, the present disclosure has been made to solve the above-mentioned problems, and aims to provide a holding member that can be installed so as to conform to the installation surface and ensure the flatness of the holding surface that holds the object.

In order to solve the above problems, one aspect of the present disclosure is to
A ceramic member including a first surface and a second surface provided on an opposite side to the first surface;
a chuck electrode provided inside the ceramic member,
A holding member for holding an object on the first surface of the ceramic member,
the ceramic member has a plurality of through holes penetrating the first surface and the second surface,
The ceramic member is characterized in that, when viewed from the first surface toward the second surface, the total area of the multiple through holes in the ceramic member is 10% or more and 50% or less, with the area of the ceramic member being 100%.

In this holding member, a plurality of through holes are provided in the ceramic member, and the total area of the plurality of through holes is 10% to 50% of the area of the ceramic member, assuming that the area of the ceramic member is 100%. In other words, the area of the through holes in the ceramic member is 1/9 to 1/2 of the area of the ceramic member other than the through holes. Therefore, the bending rigidity of the ceramic member can be reduced. Therefore, the stress (residual stress) of the ceramic member is reduced, and warping (deflection) can be suppressed, and the required flatness of the ceramic member can be ensured. This allows the holding member to be attached with high precision so as to follow (fit) the installation surface of the device that processes the object. As a result, the flatness of the first surface (holding surface) of the holding member can be ensured, and the flatness of the object held by the holding member installed on the installation surface can be ensured.

The total area of the multiple through holes is set to 10% to 50% of the area of the ceramic member, with the area of the ceramic member being 100%. This is because if the area ratio is less than 10%, the bending rigidity of the ceramic member cannot be reduced, while if the area ratio is greater than 50%, the strength required for the ceramic member cannot be ensured. In other words, by setting the total area ratio of the multiple through holes to 10% to 50%, preferably 20% to 30%, it is possible to reduce the bending rigidity while ensuring the strength required for the ceramic member.

In the above-mentioned holding member,
It is preferable that each of the plurality of through holes has an opening area of 20 ^mm2 or more.

In this way, by providing the ceramic member with a through hole having an opening area of 20 ^mm2 or more (diameter of about 5 mm), the bending rigidity of the ceramic member can be reliably reduced. Note that lift pin holes and vacuum holes provided in the ceramic member have an opening area of less than 20 ^mm2 (diameter of about 2 to 3 mm), and therefore are not included in the through holes of the present disclosure.

In the above-mentioned holding member,
The plurality of through holes are preferably formed on concentric circles.

In this way, by forming the through holes in the ceramic member on concentric circles, the bending rigidity of the ceramic member can be reduced evenly within the surface, effectively suppressing warping (deflection) of the ceramic member.

In the above-mentioned holding member,
The ceramic member preferably includes a flat metal member disposed on the second surface side of the chuck electrode.

In this way, by providing a flat metal member on the second surface side of the chuck electrode, the chuck electrode is disposed on the first surface side, and the flat metal member is disposed on the second surface side. In other words, because plate-shaped members are disposed on both surface sides, warping (deflection) of the ceramic member can be further suppressed, and the required flatness of the ceramic member can be reliably guaranteed. This allows the holding member to be attached with greater precision along (matching) the installation surface of the device that processes the object.

In the above-mentioned holding member,
The chuck electrode is preferably a bipolar electrode.

Since a bipolar electrode has a pair of positive and negative electrodes, it can attract and hold an object by electrostatic force even when it is not connected to a power source, so such a holding member can be used as a transport holding member for transporting an object. Then, after transporting the object, such a transport holding member is attached to the installation surface of a device that processes the object.

This holding member ensures the flatness of the ceramic member, so it can be attached with high precision to fit (match) the installation surface of the device. In addition, because the ceramic member has multiple through holes, the holding member is lightweight, which improves the transport speed of the object, allowing the object to be transported efficiently.

The present disclosure provides a holding member that can be installed to conform to an installation surface and ensures the flatness of the holding surface that holds an object.

FIG. 2 is a plan view of the electrostatic chuck according to the embodiment. FIG. 2 is a cross-sectional view of an electrostatic chuck according to an embodiment. 11A and 11B are diagrams showing modified examples regarding the arrangement of through holes provided in the electrostatic chuck. 11A and 11B are diagrams showing modified examples regarding the arrangement of through holes provided in the electrostatic chuck. 11A and 11B are diagrams showing modified examples regarding the arrangement of through holes provided in the electrostatic chuck. 11A and 11B are diagrams showing modified examples regarding the arrangement of through holes provided in the electrostatic chuck.

A holding member according to an embodiment of the present disclosure will be described in detail with reference to the drawings. In this embodiment, an electrostatic chuck 1 that holds a semiconductor wafer W as an object will be described as an example. The electrostatic chuck 1 according to this embodiment will be described with reference to Figs. 1 and 2.

The electrostatic chuck 1 of this embodiment is a member for adsorbing and holding 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 or to transport the semiconductor wafer W between processes. As shown in Figures 1 and 2, the electrostatic chuck 1 has a disk-shaped ceramic member 10 made of ceramics.

As the ceramic, various ceramics are used, but from the viewpoints of strength, wear resistance, plasma resistance, etc., it is preferable to use ceramics containing aluminum oxide (alumina, Al ₂ O ₃ ) or aluminum nitride (AlN) as the main component. 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).

The ceramic member 10 has a diameter of, for example, about 150 to 350 mm, and a thickness of, for example, about 2 mm. The ceramic member 10 has a holding surface 11 that holds the semiconductor wafer W, and a bottom surface 12 that is provided on the opposite side of the holding surface 11 in the thickness direction of the ceramic member 10 (the vertical direction in FIG. 2). 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.

Such a ceramic member 10 has a plurality of cylindrical through holes 15 formed between the holding surface 11 and the lower surface 12 in the thickness direction (vertical direction in FIG. 2). In this embodiment, as shown in FIG. 2, the plurality of through holes 15 includes a plurality of through holes 15a formed on concentric circles and a through hole 15b formed at the center. The plurality of through holes 15a on the concentric circles have the same diameter, and eight of them are formed at equal intervals. The diameters of the through holes 15a and the through holes 15b may be the same or different. In this embodiment, the diameter of the through holes 15a is, for example, about 13 mm, and the diameter of the through holes 15b is, for example, about 18 mm, and the diameter of the through holes 15a is smaller than the diameter of the through holes 15b.

The multiple through holes 15 (15a, 15b) each have an opening area of 20 ^mm2 or more. In other words, even if they are through holes provided in the ceramic member 10, lift pin holes, holes for vacuum drawing, and the like, whose opening area is less than 20 ^mm2 (diameter is about 2 to 3 mm), are not included in the through holes 15.

When viewed from the holding surface 11 toward the underside 12 (in the thickness direction), the total area (total opening area) of the multiple through holes 15 is 10% to 50%, preferably 20% to 30%, when the area of the ceramic member 10 (holding surface 11) is taken as 100%. In other words, the total number of through holes 15 provided in the ceramic member 10 is determined so that the area ratio of the through holes 15 in the holding surface 11 is 10% to 50%, preferably 20% to 30%, of the area of the holding surface 11.

In addition, as shown in FIG. 2, a chuck electrode 30 formed of a conductive material (e.g., tungsten, molybdenum, platinum, etc.) is arranged on the holding surface 11 side inside the ceramic member 10. The chuck electrode 30 is a bipolar electrode and has a pair of positive and negative chuck electrodes 30a and 30b. These chuck electrodes 30a and 30b are arranged on the same plane. When viewed from the holding surface 11 toward the lower surface 12, the chuck electrode 30b has a circular ring shape, and the chuck electrode 30a has a circular ring shape surrounding the chuck electrode 30b. With such a chuck electrode 30, the semiconductor wafer W can be attracted and held on the holding surface 11 of the electrostatic chuck 1 by electrostatic attraction even without external power supply. As a result, the electrostatic chuck 1 enables the semiconductor wafer W to be transported between processes via a transport arm or the like. In order to supply power to the chuck electrodes 30a, 30b and to earth them during dechucking, bottomed holes 16, 16 that expose portions of the chuck electrodes 30a, 30b to the outside are formed in the underside 12 of the ceramic member 10.

Furthermore, as shown in FIG. 2, a flat metal member 31 (dummy electrode) is disposed on the inner lower surface 12 side of the ceramic member 10. The metal member 31 is formed of a conductor, but does not basically function as an electrode and is not electrically or physically connected to other electrodes. The metal member 31 may be formed of, for example, copper, tungsten, molybdenum, platinum, or the like, by a known method such as a subtractive method, a semi-additive method, or a full additive method. Specifically, for example, a method such as etching of copper foil, electroless copper plating, or electrolytic copper plating can be applied. The metal member 31 can be formed by forming a thin film by a method such as sputtering or CVD, and then etching, or by printing a conductive paste or the like. In order to connect the metal member 31 to earth during dechucking, a bottomed hole 17 that exposes a part of the metal member 31 to the outside is formed on the lower surface 12 of the ceramic member 10. The metal member 31 is connected to earth during dechucking because, although no power is supplied to the metal member 31, it carries a small charge due to the influence of the chuck electrode 30.

In the electrostatic chuck 1 having the above-described configuration, warping (deflection) is likely to occur due to stress (residual stress) in the ceramics constituting the ceramic member 10. If warping (deflection) occurs in the ceramic member 10, it becomes difficult to install the electrostatic chuck 1 along (in harmony with) the installation surface of the semiconductor manufacturing equipment due to the high bending rigidity of the ceramics. As a result, it may not be possible to guarantee the flatness of the holding surface 11 of the electrostatic chuck 1 installed on the installation surface of the semiconductor manufacturing equipment, that is, to ensure the required flatness.

Therefore, in the electrostatic chuck 1 of the present embodiment, a plurality of through holes 15 (15a, 15b) having an opening area of 20 mm2 or ^more are provided in the ceramic member 10 so as to occupy 10% to 50% of the area of the holding surface 11, preferably 20% to 30%, of the area of the holding surface 11, assuming that the area of the holding surface 11 is 100%. The reason why the total area of the plurality of through holes 15 is set to 10% to 50% of the area of the ceramic member 10 (holding surface 11) is 100% is that if the area ratio is less than 10%, the bending rigidity of the ceramic member 10 cannot be reduced, while if the area ratio is more than 50%, the strength required for the ceramic member 10 cannot be ensured. In other words, by setting the ratio of the total area of the plurality of through holes 15 to the area of the holding surface 11 to 10% to 50%, preferably 20% to 30%, the bending rigidity can be reduced while ensuring the strength required for the ceramic member 10.

Therefore, the residual stress of the ceramic member 10 is reduced, and warping (deflection) can be suppressed, and the required flatness of the ceramic member 10 can be ensured. Therefore, the electrostatic chuck 1 can be attached with high precision along (fitted) the installation surface of the semiconductor manufacturing apparatus. This ensures the flatness of the holding surface 11, and therefore the flatness of the semiconductor wafer W held by the electrostatic chuck 1 attached to the semiconductor manufacturing apparatus. The flatness of the holding surface 11 can be measured, for example, as follows . That is, first, a flat surface plate (preferably with an upper surface flatness of 3 μm or less) is placed on the work installation surface of the measuring device, and the electrostatic chuck 1 is placed on the surface plate. Then, the height of about 20 points on the surface of the electrostatic chuck 1 placed on the surface plate is measured with a contact or non-contact measuring device.

In addition, since the ceramic member 10 has a plurality of through holes 15, the ceramic member 10 is lightweight. Therefore, the transfer speed when the semiconductor wafer W is transferred between processes by the electrostatic chuck 1 can be increased, and the semiconductor wafer W can be transferred between processes efficiently.

In addition, since multiple through holes 15a of the same diameter are formed on concentric circles, the bending rigidity of the ceramic member 10 can be reduced evenly within the surface. This effectively suppresses warping (deflection) of the ceramic member 10.

In addition, in the electrostatic chuck 1 of this embodiment, inside the ceramic member 10, the chuck electrode 30 is arranged on the holding surface 11 side, and a flat metal member 31 is arranged on the lower surface 12 side. That is, inside the ceramic member 10, plate-shaped members are arranged on both sides in the thickness direction. Therefore, warping (deflection) of the ceramic member 10 can be further suppressed, and the required flatness of the ceramic member 10 can be reliably guaranteed. This allows the electrostatic chuck 1 to be attached more precisely along (compatible with) the installation surface of the semiconductor manufacturing device.

Now, modified examples of the arrangement of the through holes provided in the ceramic member of the electrostatic chuck will be described with reference to Figs. 3 to 6. In the above embodiment, multiple through holes are provided on one concentric circle, but as shown in Fig. 3, multiple through holes 15a, 15c may be provided on two or more concentric circles (two in Fig. 3). That is, multiple through holes 15a (eight in Fig. 3) are provided on the outer concentric circle, and multiple through holes 15c (four in Fig. 3) are provided on the inner concentric circle. This allows the bending rigidity of the ceramic member 10 to be reduced more evenly within the plane, so that warping (deflection) of the ceramic member 10 is more effectively suppressed.

Also, as shown in FIG. 4, multiple through holes 15a can be provided on a concentric circle only in the outer periphery where warping (deflection) of the ceramic member 10 is likely to occur. That is, in the above embodiment, the through hole 15b may not be provided in the center of the ceramic member 10. Alternatively, as shown in FIG. 5, multiple through holes 15 may be arranged in a lattice pattern rather than on concentric circles. Even with such an arrangement pattern of the through holes 15, the bending rigidity of the ceramic member 10 can be reduced, thereby suppressing warping (deflection) of the ceramic member 10.

In addition, in the above embodiment, the through hole 15 has a circular opening, but the through hole 15 is not limited to a circular shape, and may be a polygon (square in FIG. 6) or an ellipse, as shown in FIG. 6. By providing a plurality of through holes of such shapes in the ceramic member 10, the same effect as the above embodiment can be obtained.

As described above, according to the electrostatic chuck 1 of this embodiment, the ceramic member 10 is provided with a plurality of through holes 15 (15a, 15b), and the total area of the plurality of through holes 15 is 10% to 50% of the area of the ceramic member 10, assuming that the area of the ceramic member 10 is 100%. Therefore, the bending rigidity of the ceramic member 10 can be reduced, so that the residual stress of the ceramic member 10 is reduced and warping (deflection) can be suppressed, and the required flatness of the ceramic member 10 can be ensured. Therefore, the electrostatic chuck 1 can be attached with high precision so that the semiconductor wafer W is aligned (fitted) along the installation surface of the semiconductor manufacturing device. This ensures the flatness of the holding surface 11 of the electrostatic chuck 1, and therefore the flatness of the semiconductor wafer W held by the electrostatic chuck 1 installed on the installation surface.

The above embodiment is merely an example and does not limit the present disclosure in any way. Of course, various improvements and modifications are possible without departing from the spirit of the present disclosure. For example, the above embodiment illustrates an electrostatic chuck 1 in which the chuck electrode 30 is a bipolar electrode as a holding member, but the present disclosure can also be applied to a holding member equipped with a chuck electrode that is a monopolar electrode.

In addition, in the above embodiment, an electrostatic chuck 1 having a metal member 31 in addition to the chuck electrode 30 within the ceramic member 10 is exemplified as the holding member, but the present disclosure can also be applied to a holding member that does not have a metal member 31 (dummy electrode).

Reference Signs List 1: electrostatic chuck 10: ceramic member 11: holding surface 12: lower surface 15: through hole 30: chuck electrode 31: metal member W: semiconductor wafer

Claims (5)

A ceramic member including a first surface and a second surface provided on an opposite side to the first surface;
a chuck electrode provided inside the ceramic member,
A holding member for holding an object on the first surface of the ceramic member,
the ceramic member has a plurality of through holes penetrating the first surface and the second surface,
The ceramic member has a diameter of 150 to 350 mm,
A retaining member characterized in that, when viewed from the first surface toward the second surface, a total area of the plurality of through holes in the ceramic member is 20% or more and 50% or less, with the area of the ceramic member being 100%. 2. The holding member according to claim 1,
A holding member characterized in that each of the plurality of through holes has an opening area of 20 ^mm2 or more. The holding member according to claim 1 or 2,
A holding member, wherein the plurality of through holes are formed on concentric circles. In any one of the holding members according to claims 1 to 3,
The holding member, wherein the ceramic member has a flat metal member on the second surface side of the chuck electrode. In any one of the holding members according to claims 1 to 4,
The holding member, wherein the chuck electrode is a bipolar electrode.

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