JP2012011518A - Polishing apparatus, polishing pad, and method for polishing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing apparatus that efficiently polishes a substrate.SOLUTION: The polishing apparatus includes: a polishing pad; a turn table; a supply nozzle; a vibration supply unit; and a wall surface. The polishing pad is brought into press-contact with a surface to be polished of the substrate to chemically and mechanically polish the surface to be polished. The polishing pad is placed on the turn table. The supply nozzle drips a polishing agent on the polishing pad. The vibration supply unit adds vibration energy to the polishing pad. The wall surface is erected in an outer periphery of the polishing pad to surround a side surface of the polishing pad with the wall surface that is higher than the level of an upper surface of the polishing pad.

Description

  Embodiments described herein relate generally to a polishing apparatus, a polishing pad, and a polishing method.

  One of the manufacturing processes for manufacturing a semiconductor device on a substrate such as a wafer is a CMP (Chemical Mechanical Polishing) process. This CMP process is intended to flatten the surface to be polished (front surface or back surface) of a wafer. This is a process performed for the purpose, and the surface on the wafer is polished by a pad and a slurry (abrasive) provided in the CMP apparatus.

  In the CMP apparatus, the surface on the wafer is polished while dripping the slurry onto the pad. However, the used slurry used for polishing the wafer (slurry including a slurry having a reduced chemical component or a polishing powder generated during polishing) is present on the pad. Since the slurry after use penetrates deeply from the pad surface and causes a decrease in polishing rate or generation of scratches, it is desired to remove the slurry quickly and to perform efficient wafer polishing using a newly supplied slurry.

Japanese Patent Laid-Open No. 10-315122

  An object of an embodiment of the present invention is to provide a polishing apparatus, a polishing pad, and a polishing method for efficiently polishing a substrate.

  According to the embodiment, the polishing apparatus includes a polishing pad, a turntable, a supply nozzle, a vibration supply unit, and a wall surface unit. The polishing pad is subjected to chemical mechanical polishing of the surface to be polished by pressing the surface to be polished of the substrate to be processed. The turntable places the polishing pad. The supply nozzle drops an abrasive on the polishing pad. The vibration supply unit applies vibration energy to the polishing pad. The wall surface portion stands on the outer peripheral portion of the polishing pad and surrounds the side surface of the polishing pad with a wall surface having a height higher than the upper surface of the polishing pad.

FIG. 1 is a block diagram showing an overall configuration of a CMP apparatus according to an embodiment. FIG. 2 is a diagram illustrating a configuration of a polishing unit included in the CMP apparatus according to the embodiment. FIG. 3 is a cross-sectional view showing the configuration of the polishing unit. FIG. 4 is a diagram for explaining the replacement efficiency of the slurry before use and the slurry after use.

  Hereinafter, a polishing apparatus, a polishing pad, and a polishing method according to embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by this embodiment.

(Embodiment)
FIG. 1 is a block diagram showing an overall configuration of a CMP apparatus according to an embodiment. The CMP apparatus 100 is an example of a polishing apparatus (polishing apparatus), and is used in a CMP (chemical mechanical polishing) process when manufacturing a semiconductor device (semiconductor circuit) on a substrate such as a wafer WA.

  The CMP apparatus 100 includes a polishing unit 1, a cleaning unit 2, and a drying unit 3. The polishing unit 1 is a polishing chamber including a pad (polishing pad) 13 described later, and is a main part of a CMP apparatus that performs chemical mechanical polishing on the wafer WA on the pad 13. The cleaning unit 2 cleans the wafer WA polished by the polishing unit 1 using a roll sponge, a pencil sponge, or the like. The drying unit 3 dries the wafer WA cleaned by the cleaning unit 2 by spin drying or the like.

  When polishing the wafer WA, the wafer WA is carried into the CMP apparatus 100. The wafer WA is first transferred to the polishing unit 1 and polished by the polishing unit 1. In the present embodiment, the outer peripheral portion (circular outer frame portion) of the pad 13 provided in the polishing portion 1 is surrounded by a wall surface (a later-described slurry barrier) 20 having a predetermined height. Further, vibration energy is supplied to the pad 13 from the lower side of the pad 13, and the vibration energy is uniformly applied to the slurry (abrasive) through the pad 13. Thus, the wafer WA is polished while the slurry on the pad 13 is accumulated by a predetermined amount and the slurry is stirred by vibration energy.

  The wafer WA polished by the polishing unit 1 is transferred to the cleaning unit 2 and cleaned by the cleaning unit 2. Then, the wafer WA cleaned by the cleaning unit 2 is transferred to the drying unit 3 and dried by the drying unit 3. The wafer WA is dried by the drying unit 3 and then unloaded from the CMP apparatus 100.

  FIG. 2 is a diagram illustrating a configuration of a polishing unit included in the CMP apparatus according to the embodiment. The polishing unit 1 includes a slurry supply nozzle 11A, a chemical solution supply nozzle 11B, a pure water supply nozzle 11C, a turntable 10, a polishing head 15, a pad (polishing cloth) 13, and a wall surface 20. .

  The turntable 10 includes a platen (tokiwa). The turntable 10 has a substantially disk shape, and rotates around the center when the wafer WA is polished. A pad 13 is placed on the upper surface of the turntable 10, and the surface to be polished of the wafer WA is pressed on the upper side of the pad 13. The turntable 10 according to the present embodiment has a function (vibration supply unit 5 described later) that gives vibration energy to the slurry 14 or the like supplied onto the pad 13.

  The pad 13 has a member (pad surface portion) having a predetermined thickness on the upper surface, and a large number of convex portions having minute heights are uniformly formed on the surface of the pad 13 in contact with the wafer WA. Has been. When polishing the wafer WA, the polishing head 15 presses the wafer WA against the pad surface. When polishing the wafer WA, the pad 13 is rotated together with the turntable 10.

  The polishing head 15 includes a disk-shaped tip portion having a size substantially the same as the main surface of the wafer WA, and a shaft portion (polishing head shaft portion) that holds the tip portion. The wafer WA is attached to the part. The wafer WA is attached to the disk-shaped tip so that the surface opposite to the surface to be polished of the wafer WA is in contact with the bottom of the disk-shaped tip. The polishing head 15 polishes the polishing target surface of the wafer WA while pressing the polishing target surface of the wafer WA against the pad 13. When the polishing head 15 polishes the wafer WA, the polishing head 15 and the wafer WA rotate around the polishing head shaft portion.

  The slurry supply nozzle 11 </ b> A is a nozzle that supplies a slurry (abrasive) 14 onto the pad 13. The slurry 14 includes a physical component (such as alumina or silica) and a chemical component. The chemical solution supply nozzle 11 </ b> B is a nozzle that supplies a chemical solution onto the pad 13. The pure water supply nozzle 11 </ b> C is a nozzle that supplies pure water onto the pad 13.

  When the wafer WA is polished by the polishing head 15, the slurry 14, the chemical solution, and pure water are supplied onto the pad 13 from the slurry supply nozzle 11 </ b> A, the chemical solution supply nozzle 11 </ b> B, and the pure water supply nozzle 11 </ b> C, respectively. In the following description, the slurry 14, the chemical solution, and pure water may be collectively referred to as a polishing solution.

  The slurry barrier 20 is a wall surface (wall) provided so as to surround the side surface of the pad 13 on the turntable 10, and prevents unnecessary outflow of the polishing liquid supplied onto the pad 13 during polishing. It is possible to collect a fixed amount. The wall surface (slurry embankment) 20 has a substantially annular shape when viewed from the upper side, and the polishing liquid is stored inside the annular shape.

  FIG. 3 is a cross-sectional view showing the configuration of the polishing unit. As shown in the figure, the wall surface (slurry bank) 20 has a predetermined height (for example, a height of 5 mm from the polishing surface of the pad 13). Is also erected with respect to the surface of the pad 13 so as to surround the higher position. Thereby, the wall surface (slurry bank) 20 can store the polishing liquid supplied onto the pad 13 in an amount corresponding to the height of the wall surface (slurry bank) 20.

  Further, in the turntable 10, a vibration supply unit 5 that provides vibration energy to the slurry 14 and the like is disposed. The vibration supply unit 5 has a function of generating vibration energy of kHz to MHz. The vibration supply unit 5 is, for example, a piezoelectric actuator, a mechanical actuator, a megasonic transducer resonator, an ultrasonic transducer resonator, or the like. As for how to give vibration, by preparing a plurality of patterns such as strength of vibration energy, different vibration periods, and combinations thereof, it is possible to cope with various polishing conditions of CMP.

  On the upper surface of the turntable 10, water or the like (vibration energy relaxation portion 17) that relaxes vibration energy is stored, and the pad 13 is disposed on the vibration energy relaxation portion 17. When the vibration supply unit 5 generates vibration energy when polishing the surface 25 to be polished of the wafer WA, the vibration energy is used for polishing the wafer WA via the vibration energy relaxation unit 17 and the pad 13. It is transmitted to the later old slurry 14 (after-use slurry 4A described later), the new slurry 14 (after-use slurry 4B described later) before being used for polishing the wafer WA, and the like.

  The post-use slurry 4A, dust generated due to scratches (wafer WA, etc.), and pre-use slurry 4B are each agitated by vibration energy. Thereby, the old slurry 4A after use can be efficiently discharged without staying on the pad 13 (the discharge mechanism will be described later). By discharging the post-use slurry 4A in this way, the new slurry 4B before use can be replaced on the surface of the pad 13, especially the gaps of a large number of convex portions. In other words, by giving vibration energy to the pad 13 (pre-use slurry 4B, post-use slurry 4A), the post-use slurry 4A that has penetrated the details of the pad 13 can be replaced with the pre-use slurry 4B. Further, the used slurry 4A can be floated on the slurry liquid surface, and replacement of old and new slurry can be performed. As a result, the new slurry 4B can be efficiently supplied to the polished surface 25 of the wafer WA.

  FIG. 4 is a diagram for explaining the replacement efficiency of the slurry before use and the slurry after use. FIG. 4A shows a pre-use slurry 4B and a post-use slurry 4A when no slurry barrier 20 is provided on the turntable 10 and no vibration energy is applied on the pad 13. FIG. FIG. 4B shows a pre-use slurry 4B and a post-use slurry 4A in the case where a slurry barrier 20 is provided on the turntable 10 and vibration energy is applied to the pad 13. Here, the pre-use slurry 4B and the post-use slurry 4A are illustrated as granular members, but the pre-use slurry 4B and the post-use slurry 4A contain physical components and chemical components, so that the pre-use slurry is used. 4B and post-use slurry 4A are suspensions in which solid particles are dispersed in a liquid.

  As shown in FIG. 4A, when no vibration energy is applied on the pad 13, the old slurry 4A used in the previous CMP process stays in the vicinity of the convex portion 50 on the surface of the pad 13. For this reason, it is difficult for the pre-use slurry 4B to be newly supplied to reach the vicinity of the convex portion 50 on the surface of the pad 13. Further, since the slurry barrier 20 is not provided on the turntable 10, the pre-use slurry 4 </ b> B supplied on the pad 13 hardly stays on the pad 13, and the pad 13 has an outer periphery. Discharged to the outside. Therefore, the post-use slurry 4A cannot be efficiently replaced with the new pre-use slurry 4B. As a result, the pre-use slurry 4B cannot be efficiently supplied to the polished surface 25 of the wafer WA.

  On the other hand, as shown in FIG. 4B, when vibration energy is applied to the pad 13, the used slurry 4 </ b> A (chemical reaction product or the like) does not stay in the vicinity of the convex portion 50, and the polishing liquid. Move to the top side of. For this reason, the pre-use slurry 4 </ b> B newly supplied easily reaches the vicinity of the convex portion 50. Moreover, even if the slurry barrier 20 is not provided on the turntable 10, the retention of the old slurry after use can be reduced by vibration, but the new slurry supplied for replacement cannot be retained on the pad for a long time. Is bad. However, in this embodiment, since the wall surface (slurry bank) 20 is provided, the pre-use slurry 4B supplied on the pad 13 is replaced with a new pre-use slurry on the pad 13. Can be used for a relatively long time. Therefore, the post-use slurry 4A can be efficiently replaced with the pre-use slurry 4B. As a result, the pre-use slurry 4B can be efficiently supplied to the polished surface 25 of the wafer WA. Further, the collision probability and collision energy between the pre-use slurry 4B and the polished surface 25 of the wafer WA are improved.

  Here, as a mechanism of the wall surface (slurry bank) 20 for discharging old slurry, the following can be considered. For example, the wall 20 may be provided with a mechanism capable of moving up and down so that old slurry can be quickly discharged and removed. As such a mechanism, when replacing the old and new slurries, the wall surface (slurry bank) 20 is lowered to the polishing surface of the pad 13 or lower and accommodated in the turntable (dotted line portion 20a in FIG. 3), After discharging and removing the old slurry, the wall surface 20 may be raised to supply new pre-use slurry. Further, in the present embodiment, the shape of the wall surface (slurry embankment) 20 is a shape (annular shape) that surrounds the entire side surface of the pad 13, but the wall surface 20 opens a part of the annular shape (side wall). It is good also as a shape. The open part may be one place or a plurality of places, and the total size of the open part is 5% of the peripheral part length of the outer periphery of the pad 13 in consideration of both the discharge efficiency of the old slurry and the replacement efficiency with the new slurry. It is desirable that the wall surface 20 be formed on the other peripheral portion with about ˜50%. By adopting such a wall 20 mechanism, the time for slurry replacement, pad cleaning, and the like can be shortened, leading to a reduction in manufacturing cost.

  Thus, since the slurry 4B before use can be efficiently supplied to the surface 25 to be polished of the wafer WA, the wafer WA can be polished in a short time and the utilization efficiency of the slurry 14 is improved. Therefore, productivity of the semiconductor device can be improved and the amount of the slurry 14 used can be reduced.

  Further, when vibration energy is applied to the pad 13, dust or the like (not shown) generated due to scratches moves to the upper side of the polishing liquid because the particle size is large. For this reason, dust generated due to scratches is easily discharged from the outer periphery of the pad 13 to the outside of the pad 13. Therefore, it is possible to prevent the wafer WA from being scraped by dust generated due to scratches.

  The magnitude (frequency) of vibration energy supplied on the pad 13 and the height of the slurry barrier 20 are determined according to the polishing conditions of the wafer WA, the layout (density) of the pattern formed on the wafer WA, and the like. It may be changed. The polishing conditions of the wafer WA are, for example, the layer of the film to be polished, the type of the film to be polished, the type of the lower layer film formed below the film to be polished, the film thickness of the film to be polished, the polishing thickness to the film to be polished This is a condition (polishing pressure, polishing time, etc.) determined based on the above.

  Further, the magnitude of vibration energy may be changed during polishing of the wafer WA based on the polishing conditions of the wafer WA, the layout (dense / dense) of the pattern formed on the wafer WA, and the like. You may change the height.

  For example, in the first stage of polishing, vibration energy is supplied at a small frequency, thereby improving the mechanical polishing rate of the wafer WA. In the second stage of polishing, vibration energy is supplied at a large frequency, thereby improving the chemical reaction between the surface to be polished 25 of the wafer WA and the polishing liquid. By controlling these vibration frequencies, the mechanical polishing rate is improved in the first stage of polishing, so that the wafer WA is roughed. In the second stage of polishing, the chemical reaction is improved, so that the wafer WA is finished. .

  Further, the supply and stop of vibration energy may be controlled during the polishing of the wafer WA. For example, in the first stage of polishing, vibration energy is supplied, thereby performing high-speed polishing (rough cutting) of the wafer WA. In the second stage of polishing, the supply of vibration energy is stopped, thereby performing low-speed polishing (finishing) of the wafer WA.

  Further, based on the magnitude of vibration energy from the vibration supply unit 5, the height of the slurry barrier embankment 20, etc., the supply amount of the polishing liquid (slurry etc.) and the polishing conditions (polishing pressure, polishing time, etc.) of the wafer WA are changed. You may control.

  As a result, it becomes possible to perform polishing according to the polishing conditions of the wafer WA and the layout of the pattern formed on the wafer WA. Therefore, it is possible to eliminate polishing variations (such as dents in the film to be polished) depending on the pattern layout.

  The dressing of the pad 13 and the polishing of the wafer WA using the CMP apparatus 100 may be performed in any layer of the semiconductor manufacturing process. When manufacturing a semiconductor device, film forming processing on the wafer WA, polishing of the wafer WA using the CMP apparatus 100, exposure processing on the wafer WA, development processing, etching processing, and the like are repeated for each layer.

  In the present embodiment, the slurry barrier embankment 20 and the pad 13 are configured separately, but the slurry barrier embankment 20 and the pad 13 may be integrally formed. For example, the slurry barrier embankment 20 is formed of the pad 13 member, and the slurry barrier embankment 20 and the pad 13 are integrally formed. In this case, the shape of the pad 13 is composed of a substantially disc-shaped main surface portion (polishing surface) and an annular ring portion (wall surface) having a predetermined height on the outer peripheral portion of the main surface portion. The shape is concave.

  In the present embodiment, the vibration energy relaxation unit 17 is disposed between the pad 13 and the turntable 10, but the vibration energy relaxation unit 17 may not be provided. In this case, the pad 13 is disposed on the upper surface of the turntable 10.

  Further, the turntable 10 may be configured to include the vibration supply unit 5, or the vibration supply unit 5 and the turntable 10 may be configured separately.

  Thus, according to the embodiment, the periphery of the pad 13 is surrounded by the slurry barrier 20 and the vibration energy is given to the polishing liquid by the vibration supply unit 5, so that the substrate such as the wafer WA can be efficiently polished. Is possible.

  Further, since the wafer WA is polished by applying vibration energy to the pad 13, dust generated due to scratches hardly accumulates in the vicinity of the convex portion 50 of the pad 13 (near the bottom surface of the pad 13). For this reason, the dressing of the pad 13 becomes unnecessary. Accordingly, a dressing head (dresser) is not required, and the wafer WA can be polished by the polishing unit 1 having a simple configuration. Moreover, since dressing to the pad 13 becomes unnecessary, the wear of the pad 13 can be reduced, and as a result, the pad 13 can be used for a long period of time.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Polishing part, 2 ... Cleaning part, 3 ... Drying part, 4A ... Slurry after use, 4B ... Slurry before use, 5 ... Vibration supply part, 10 ... Turntable, 13 ... Pad, 14 ... Slurry, 15 ... Polishing head 20 ... wall surface, 100 ... CMP apparatus, WA ... wafer.

Claims (9)

A polishing pad for performing chemical mechanical polishing of the surface to be polished by pressing the surface to be polished of the substrate to be processed;
A turntable for placing the polishing pad;
A supply nozzle for dripping the abrasive onto the polishing pad;
A vibration supply unit that applies vibration energy to the polishing pad;
A wall surface portion standing on the outer periphery of the polishing pad and surrounding a side surface of the polishing pad with a wall surface having a height higher than the upper surface of the polishing pad;
A polishing apparatus comprising:   The polishing apparatus according to claim 1, wherein the wall surface portion is the same member as the polishing pad, and the wall surface portion and the polishing pad are integrally formed.   The polishing apparatus according to claim 1, wherein the wall surface portion has an annular wall surface that surrounds the entire side surface of the polishing pad.   The polishing apparatus according to claim 1, wherein the wall portion can be moved up and down. A polishing surface portion that is disposed on a vibration supply portion that applies vibration energy to a supplied abrasive and that is subjected to chemical mechanical polishing of the surface to be polished by pressing the surface to be polished of the substrate to be processed;
A wall surface portion standing on the outer periphery of the polishing surface portion and surrounding a side surface of the polishing surface portion with a wall surface higher than the upper surface of the polishing surface portion;
A polishing pad comprising:   The polishing pad according to claim 5, wherein the wall surface portion has an annular wall surface that surrounds the entire side surface of the polishing surface portion.   A polishing surface portion that is subjected to chemical mechanical polishing of the surface to be polished by being pressed against the surface to be processed of the substrate to be processed, and an outer peripheral portion of the polishing surface portion, the wall surface being higher than the upper surface of the polishing surface portion And applying vibration energy to the polishing pad when polishing by pressing the surface to be polished of the substrate against the polishing pad while supplying an abrasive onto the polishing pad provided with a wall surface portion surrounding the side surface of the polishing surface portion. A polishing method characterized by the above.   The polishing method according to claim 7, wherein the wall surface portion is the same member as the polishing pad, and the wall surface portion and the polishing pad are integrally formed.   The polishing method according to claim 7, wherein the wall surface portion has an annular wall surface that surrounds the entire side surface of the polishing pad.

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