JP7565591B2 - Wafer polishing carrier and wafer polishing device - Google Patents

Description

The present invention relates to a wafer polishing carrier and a wafer polishing device, and more specifically to a wafer polishing carrier that holds a wafer and rotates it on a platen to polish the wafer, and a wafer polishing device that is configured with the wafer polishing carrier.

As an example of an apparatus for polishing wafers such as silicon wafers, a wafer polishing apparatus capable of polishing both sides of a wafer simultaneously has been conventionally known (see Patent Document 1: JP 2011-066342 A). In this wafer polishing apparatus, a carrier holding a wafer, which is the workpiece, in a work hole is sandwiched between upper and lower surface plates, and both sides of the wafer are polished simultaneously by rotating the surface plates and the carrier.

JP 2011-066342 A JP 2000-024912 A

In the wafer polishing device exemplified in Patent Document 1, a suitable configuration is one in which a resin inner liner is provided on the inner periphery of the work hole of the carrier in order to prevent defects (scratches) on the wafer caused by collision between the wafer and the metal carrier during polishing. For example, the configuration disclosed in Patent Document 2 (see JP 2000-024912 A) is known as an example of a conventional polishing device in which the carrier has an inner liner.

As a result of intensive research by the inventors of the present application, it has been confirmed that in a configuration with the above-mentioned inner, it is preferable to form the inner thin (with small radial dimensions) and in a shape close to a ring (with few radial irregularities in plan view) so that there is less damage to the carrier (specifically, the body) to which the inner is attached (i.e., the damaged area is small in plan view). This is because such a shape can prevent the occurrence of a defect in which the polishing cloth sinks in the damaged area and the edge of the wafer is ground into a rounded shape (a defect that creates a so-called "droop" shape).

On the other hand, it has been found that if the inner is thin and has a shape close to a ring, the engagement force between the body and the inner is weak, increasing the risk that the inner will fall off the body during wafer polishing and damage the wafer. In particular, as in the configuration exemplified in Patent Document 2, when the inner shape at the engagement part is circular in plan view, the smaller the missing area, the weaker the engagement force and the easier it is for the inner to fall off. Also, when the inner shape at the engagement part is wedge-shaped in plan view, the smaller the included angle between the opposite sides sandwiching the missing area, the weaker the engagement force and the easier it is for the inner to fall off, and the larger the included angle, the easier it is for the edge to sag due to the increased missing area. Also, during insert molding, unfilled areas of resin may occur, allowing foreign matter to get in, and the wafer may be more likely to be scratched during polishing.

The present invention was made in consideration of the above circumstances, and aims to realize a wafer polishing carrier and wafer polishing device that can reduce the defective area in the engagement portion between the carrier body and the inner member, suppress the occurrence of unfilled resin areas, and generate a high engagement force.

The present invention solves the above problems by the solution described below as one embodiment.

The wafer polishing carrier of the present invention is a wafer polishing carrier for holding a wafer in a work hole formed as an opening in a disk-shaped body and rotating the wafer on a surface plate to polish the wafer, the body having a notch cut out radially outward from the inner periphery of the work hole, and an annular inner is provided which is engaged with the notch and held on the inner periphery, the notch is formed in a shape having, in a plan view, two base lines respectively connected to two starting points provided on the inner periphery, two intermediate lines respectively connected to the terminal ends of the two base lines and arranged so that the circumferential distance between them increases radially outward, two first circular arcs respectively connected to the terminal ends of the two intermediate lines and arranged so that their inner circular portions face each other, and a connecting line connecting the terminal ends of the two first circular arcs , the connecting line being required to be formed in a circular arc shape with a constant radius from the center of the work hole in a plan view .

The wafer polishing apparatus according to the present invention comprises the wafer polishing carrier, a lower platen having a polishing surface on its upper surface, an upper platen supported above the lower platen so as to be movable up and down and having a polishing surface on its lower surface, a drive device for rotating the lower platen and the upper platen, a carrier drive device for rotating the wafer polishing carrier, and a slurry supply device for supplying slurry, and is required to rotate the lower platen, the upper platen, and the wafer polishing carrier in a set direction to polish both sides of the wafer while supplying the slurry onto the lower platen while the wafer polishing carrier with the wafer held in the work hole is sandwiched between the lower platen and the upper platen.

According to the present invention, the defective area can be reduced in the engagement portion between the body of the carrier and the inner liner, which prevents the polishing cloth from sinking in the defective area and causing the edge of the wafer to be cut into a rounded shape (drooping), thereby improving the flatness of the wafer. In addition, the occurrence of unfilled resin areas during insert molding can be prevented, which prevents foreign matter from entering the unfilled areas and scratching the wafer during polishing. Furthermore, a high engagement force can be generated, which reduces the risk of the inner liner falling off the body during polishing and damaging the wafer.

1 is a front view showing an example of a wafer polishing apparatus according to an embodiment of the present invention. FIG. 2 is a plan view of the wafer polishing apparatus of FIG. 1 . 2 is a plan view showing an example of a wafer polishing carrier of the wafer polishing apparatus of FIG. 1. 1. FIG. 4 is a plan view showing another example of the wafer polishing carrier of the wafer polishing apparatus of FIG. 2 is a plan view showing an example of a cutout portion of a wafer polishing carrier of the wafer polishing apparatus of FIG. 1 . 1. FIG. 4 is a plan view showing another example of the notch portion of the wafer polishing carrier of the wafer polishing apparatus of FIG.

The following describes in detail the embodiments of the present invention with reference to the drawings. FIG. 1 is a front view (schematic diagram) showing an example of a wafer polishing apparatus 1 according to an embodiment of the present invention. FIG. 2 is a plan view (schematic diagram) of the wafer polishing apparatus 1 shown in FIG. 1, in which the mechanism above the upper platen 14 is omitted to facilitate understanding of the carrier 20 and its surrounding structure. In all the drawings used to explain each embodiment, members having the same function are given the same reference numerals, and repeated explanations may be omitted.

The wafer polishing apparatus 1 according to this embodiment is a so-called double-sided polishing apparatus in which a wafer polishing carrier (sometimes simply referred to as a "carrier") 20, in which a wafer W is held in a work hole 22, is sandwiched between upper and lower base plates 12, 14, and both sides of the wafer W are polished simultaneously by rotating the base plates 12, 14 and the carrier 20. The wafer W to be processed (polished) is mainly, but not limited to, a wafer with a size of about 8 to 12 inches.

More specifically, the wafer polishing apparatus 1 comprises a lower platen 12 having a polishing surface on its upper surface, and an upper platen 14 supported above the lower platen 12 so as to be movable up and down, and having a polishing surface on its lower surface. Both the lower platen 12 and the upper platen 14 are formed in a circular shape in a plan view using a metal material (stainless steel alloy, for example). Note that the polishing process is usually carried out with a polishing cloth (not shown) attached to the polishing surface (therefore, the "polishing surface" in this application refers primarily to the state in which the polishing cloth is attached).

The upper and lower surface plates 12 and 14 are rotated in opposite directions around the axis by a drive device. That is, the upper surface plate 14 is rotatable around the axis by a drive device (e.g., a drive mechanism equipped with an electric motor) 40 arranged on the support frame 10. The upper surface plate 14 can be moved up and down by a vertical movement mechanism, such as a cylinder device 41. Meanwhile, the lower surface plate 12 is rotated by a drive device (e.g., a drive mechanism equipped with an electric motor) 42. The lower surface plate 12 is supported on its underside by a ring-shaped support bearing 43. A rotating disk 52 is attached to the upper surface plate 14 via a number of support rods 50 and is arranged on the upper surface plate 14, rotating together with the upper surface plate 14.

In addition, a carrier 20 having a work hole 22 for holding a wafer W is disposed between the lower platen 12 and the upper platen 14. Here, an example of a carrier drive device for rotating the carrier 20 while it is sandwiched between the lower platen 12 and the upper platen 14 has the following configuration. Specifically, the carrier 20 is rotated and revolved by a sun gear (inner pin gear) 16 and an internal gear (outer pin gear) 18, which are disposed with their axes aligned with the central hole of the lower platen 12. The sun gear 16 and the internal gear 18 are also rotated by a known mechanism. In this embodiment, five carriers 20 are disposed between the sun gear 16 and the internal gear 18, but this is not limiting.

The wafer polishing apparatus 1 also includes a slurry supplying device that supplies slurry. As an example of the configuration, a plurality of (two in this embodiment) ring-shaped gutters 54, 56 are fixed concentrically on the rotating disk 52. Furthermore, the bottom surfaces of the ring-shaped gutters 54, 56 are provided with slurry flow holes (not shown). Slurry is supplied to the ring-shaped gutters 54, 56 from a slurry storage section (not shown) via a pipe 62. Furthermore, the upper surface plate 14 is formed with radially arranged slurry flow holes 76, and the flow holes 76 of the upper surface plate 14 and the flow holes provided in the ring-shaped gutters 54, 56 are connected by a supply pipe 78. Slurry is supplied onto the polishing surface of the lower surface plate 12 through the supply pipe 78.

Therefore, while supplying the slurry onto the lower platen 12 through the supply pipe 78, the upper platen 14 is rotated in the direction of arrow A (here, counterclockwise) and the lower platen 12 is rotated in the direction of arrow B (here, clockwise), and the carrier drive device is operated to rotate the carrier 20 in the direction of arrow C (here, counterclockwise), whereby the wafer W moves relative to the upper and lower platens 12, 14, and both sides of the wafer W sandwiched between the upper and lower platens 12, 14 can be polished. Note that, although two ring-shaped troughs are provided in the above embodiment, a configuration in which one ring-shaped trough is provided may be used, or three or more ring-shaped troughs may be arranged concentrically.

The wafer polishing apparatus 1 also includes a storage means (here, a wafer cassette) 19 capable of storing multiple wafers W. It also includes a transport means (here, a robot hand) 58 for transporting the wafers W between the wafer cassette 19 and the carrier 20 (work hole 22). In summary, the robot hand 58 takes out one of the specified wafers W to be polished from the wafer cassette 19, transports the wafer W to the work hole 22 of the carrier 20, and holds it there. It also takes out the wafer W that has been polished from the work hole 22 of the carrier 20, transports the wafer W to the wafer cassette 19, and stores it in a specified storage position.

Next, the configuration of the carrier 20 will be described in detail. As described above, the carrier 20 holds the wafer W and rotates it on the platen (while being sandwiched between the lower platen 12 and the upper platen 14) to polish the wafer W. FIG. 3 is a plan view (schematic diagram) showing an example of the carrier 20. The carrier 20 in this embodiment has a work hole 22 that is formed in a circular or polygonal shape (a hole penetrating the plate surface) in a disk-shaped body 21, and the wafer W is held in this work hole. The thickness of the body 21 is configured to be approximately the same as the finished dimension of the wafer W, for example, 0.7 mm to 0.8 mm. In this embodiment, an example is given in which three work holes 22 are provided at equal intervals in the circumferential direction, but this is not limited to this. Meanwhile, FIG. 4 is a plan view (schematic diagram) showing another example of the carrier 20. In this way, a configuration in which only one work hole 22 is provided may be used. In any of the above examples, a through hole 24 is provided to allow the slurry to pass through.

The body 21 is formed using a metal material such as titanium or stainless steel alloy. Here, a coating layer (not shown) of a predetermined width and thickness is provided on the periphery of the work hole 22 (upper and lower surfaces of the body 21) using a material having wear resistance. As an example, the coating layer is formed to a thickness of about 2 μm and a width of about 8 mm to 15 mm (more preferably, 10 mm). A specific material for the coating layer is preferably DLC (diamond-like carbon). Here, the formation of the DLC film can be performed by a known plasma CVD method. The DLC film has a high hardness comparable to that of diamond, and also has excellent smoothness and wear resistance that diamond does not have. Therefore, by forming the DLC film on the body 21, wear of the body 21 can be reduced and the life of the carrier 20 can be extended. However, the above configuration is not limited to this, and the body may be formed using a hard ceramic with high hardness instead of DLC, or a configuration without a coating layer may be used.

The carrier 20 also has an annular inner 26 on the inner periphery of the work hole 22 formed in the body 21. Specifically, a notch 30 is provided that is cut out radially outward from the inner periphery of the work hole 22, and the inner 26 is held in the inner periphery of the work hole 22 by engaging with this notch 30. As an example, the inner 26 is formed using a resin material (e.g., nylon, POM, etc.) and is formed into a shape that has approximately the same thickness as the body 21 and a width (radial dimension) of about 1 mm to 2 mm. By providing the inner 26, it acts as a cushioning material for the wafer W held inside, and can prevent the outer periphery of the wafer W from being scratched.

In this embodiment, the inner 26 is configured to be engaged with the body 21 (here, the notch 30 on the inner circumference of the work hole 22) by insert molding. However, this is not limited to this configuration, and the inner 26 may be configured to be engaged with the body 21 by adhesion (including fusion, etc.).

Here, as shown in FIG. 5 (enlarged view of part V in FIG. 3), the cutout portion 30 according to this embodiment is formed in a shape having, in a plan view, two base lines 31A, 31B connected to two starting points a, b provided on the inner periphery of the work hole 22, two intermediate lines 32A, 32B connected to the terminal ends c, d of the two base lines 31A, 31B, respectively, and arranged so that the circumferential distance between them increases radially outward, two first arcs (for example, radii of about 0.1 mm to 0.8 mm) 33A, 33B connected to the terminal ends e, f of the two intermediate lines 32A, 32B, respectively, and arranged so that the inner circular portions 33a, 33b face each other, and a connection line 34 connecting the terminal ends g, h of the two first arcs 33A, 33B. The above configuration includes a shape in which the baseline and intermediate lines (31A and 32A, and/or 31B and 32B) are straight and arranged on the same line, making them look like a single straight line.

This allows for a configuration in which the missing area of the carrier 20 (here, the body 21) to which the inner 26 is attached is small (i.e., the area of the cutout portion 30 is small in a plan view), and the inner 26 is thin (the radial dimension is small) and has a shape close to a ring (annular) (a shape with few radial irregularities in a plan view). This makes it possible to prevent the polishing cloth from sinking in the missing area and causing the edge of the wafer W to be ground into a rounded shape (a problem resulting in a so-called "drooping" shape), and increases the flatness of the wafer W in its polished state.

However, as described above, in the case of the inner 26 having a small missing area of the body 21 (here, the notch 30) to which the inner 26 is engaged and a thin ring-shaped inner 26, this increases the risk of the inner 26 falling off during polishing the wafer W. The above-described configuration of this embodiment can also solve this problem. In particular, the two intermediate lines 32A, 32B arranged so that the circumferential distance between them increases the effect of preventing the inner 26 from falling off the body 21, and the first arcs 33A, 33B connected to the end portions e, f of the intermediate lines 32A, 32B, respectively, can further reduce the missing area (planar view area of the notch 30), while suppressing the occurrence of an unfilled portion of resin in the notch 30 during insert molding, thereby preventing foreign matter from entering the unfilled portion and causing scratches on the wafer W during polishing. As a secondary effect, there is no need to increase the resin injection pressure during insert molding, which helps prevent problems such as the inner 26 becoming unintentionally thick or uneven in thickness.

Here, the two intermediate lines 32A, 32B according to this embodiment are formed in a shape such that the angle θ formed is approximately 30° to 90° (for example, 50°) in a plan view. For example, if the intermediate lines 32A, 32B have a main straight line, the angle θ can be defined as the angle between the straight lines, and if they do not have a main straight line (if they are composed of a curve or a series of short straight lines, etc.), the angle θ can be defined as the angle between the straight line connecting the end portions c and e and the straight line connecting the end portions d and f.

This provides a high level of effectiveness in preventing the inner 26 from falling off. In particular, in this embodiment, as described above, the provision of the first circular arcs 33A and 33B makes it possible to reduce the loss area (area in plan view of the cutout portion 30) and to prevent the occurrence of unfilled areas of resin in the cutout portion 30 during insert molding. This allows the angle θ to be set larger than in the conventional technology, thereby further improving the effectiveness in preventing the inner 26 from falling off.

The two base lines 31A, 31B according to this embodiment are configured to have two second arcs 35A, 35B (with a radius of about 0.1 mm to 0.8 mm, for example) arranged so that the outer circular portions 35a, 35b face each other in a plan view. The above configuration includes curved surfaces (curves in a plan view) formed by corner rounding of the base lines 31A, 31B, and curved surfaces with non-constant radii.

This allows the resin to flow well around the starting points a, b and their adjacent positions when the inner 26 is formed by insert molding. This prevents the occurrence of unfilled resin areas during insert molding, preventing foreign matter from entering the unfilled areas and scratching the wafer W during polishing. Furthermore, if the second arcs 35A, 35B are not provided, the shapes of the starting points a, b will be sharply pointed, increasing the possibility of damaging the polishing cloth, etc., during polishing of the wafer W, but this can be prevented.

Next, as shown in FIG. 5, the connection line 34 according to this embodiment is configured to be formed in a circular arc shape with a constant radius r1 from the center of the work hole 22 in a plan view. This allows the radial width dimension of the cutout portion 30 to be constant. This makes it possible to avoid variations in the sinking state of the polishing cloth depending on the circumferential position, and prevents sagging of the edge portion when polishing the wafer W.

On the other hand, as another example of the connection line 34, as shown in FIG. 6 (a view corresponding to the same position as FIG. 5), in plan view, the connection line 34 may be configured to be formed in an arc shape in which the radii r2, r3 at the two connection positions (specifically, g, h) connected to the two first arcs 33A, 33B are relatively small, and the radius r4 at the intermediate position between the two connection positions (g, h) is relatively large. This allows the resin to flow more easily around the terminal ends g, h and their neighboring positions when the inner 26 is formed by insert molding, particularly when the radii of the first arcs 33A, 33B are small, compared to the configuration shown in FIG. 5.

As explained above, according to the present invention, the defective area can be reduced in the engagement portion between the carrier body and the inner liner, which prevents the polishing cloth from sinking in the defective area and causing the edge of the wafer to be cut into a rounded shape (drooping). In addition, the occurrence of unfilled areas of resin during insert molding can be prevented, which prevents foreign matter from entering the unfilled areas and scratching the wafer during polishing. Furthermore, a high engagement force can be generated, which reduces the risk of the inner liner falling off the body during polishing and damaging the wafer.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. For example, the above description has been given using a wafer (silicon wafer) as an example of the object to be polished, but the present invention is not limited to this, and can be similarly applied to other flat (particularly disc-shaped) workpieces.

Reference Signs List 1 Wafer polishing device 12 Lower surface plate 14 Upper surface plate 20 Wafer polishing carrier 21 Body 22 Work hole 26 Inner 30 Notch portion 31A, 31B Base line 32A, 32B Intermediate line 33A, 33B First circular arc 34 Connection line 35A, 35B Second circular arc W Wafer

Claims (5)

A wafer polishing carrier for holding a wafer in a work hole formed in a disk-shaped body and rotating the wafer on a surface plate to polish the wafer, comprising:
the body has a notch portion that is notched radially outward from an inner periphery of the work hole, and an annular inner is provided that is engaged with the notch portion and held by the inner periphery,
the cutout portion is formed in a shape having, in a plan view, two base lines respectively connected to two starting points provided on the inner peripheral portion, two intermediate lines respectively connected to end portions of the two base lines and arranged such that the circumferential distance between them increases radially outward, two first circular arcs respectively connected to end portions of the two intermediate lines and arranged such that inner circular portions face each other, and a connecting line connecting the end portions of the two first circular arcs ,
The connection line is formed in a circular arc shape having a constant radius from the center of the work hole in a plan view.
A carrier for wafer polishing comprising: 2. The wafer polishing carrier according to claim 1, wherein the two base lines are formed in a shape having two second arcs arranged so that their outer circular portions face each other when viewed in a plane. A wafer polishing carrier as described in claim 1 or claim 2, characterized in that, when viewed in a plane, the connection line is formed into an arc shape in which the radius at the two connection positions connected to the two first arcs is relatively small, and the radius at the intermediate position between the two connection positions is relatively large. 4. The carrier for polishing wafers according to claim 1 , wherein the two intermediate lines are formed so that the angle θ between the two intermediate lines is 30° to 90° in a plan view. A carrier for polishing a wafer according to any one of claims 1 to 4 ,
A lower surface plate having a polishing surface on an upper surface thereof;
an upper surface plate supported above the lower surface plate so as to be movable up and down and having a polishing surface on its lower surface;
A drive device that rotates the lower platen and the upper platen;
a carrier driving device that rotates the wafer polishing carrier;
A slurry supplying device that supplies a slurry,
A wafer polishing apparatus characterized in that the wafer polishing carrier with the wafer held in the work hole is clamped between the lower platen and the upper platen, and the slurry is supplied onto the lower platen while the lower platen, the upper platen, and the wafer polishing carrier are rotated in respective set directions to polish both sides of the wafer.

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