JP2015044250A - Polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing method which can maintain cleanliness of a polishing pad surface by eliminating polishing agent residue and polishing product remaining on the polishing pad surface and in a polishing pad with high efficiency.SOLUTION: A polishing method includes: (A) a polishing agent pre-supply step S1 of supplying a polishing agent to a polishing pad by a polishing agent supply nozzle before a wafer is in contact with the polishing pad; (B) a polishing step S2 of polishing the wafer by pressing the wafer held on a top ring to the polishing pad and relatively moving the top ring and a polishing table while supplying the polishing agent; (C) a substrate cleaning step S3 of cleaning the wafer by an atomizer while relatively moving the wafer and the polishing table after polishing; (D) a polishing pad cleaning step S4 of conditioning the polishing pad by cleaning the polishing pad with the atomizer while rotating the polishing table with no wafer on the polishing pad and simultaneously pressing a conditioner to the polishing pad.

Description

  The present invention relates to a polishing method for polishing the surface of a substrate such as a semiconductor wafer, and more particularly to a method for maintaining the cleanliness of a polishing pad surface by polishing the polishing pad after polishing.

CMP (Chemical Mechanical Polishing) is widely known as an apparatus for polishing the surface of a substrate such as a semiconductor wafer.
In this CMP, the surface of the substrate is polished by pressing the substrate held by the top ring against the polishing pad while supplying an abrasive to the polishing pad on the rotating polishing table. Here, since this polishing pad is always exposed to the polishing agent and the polishing product after polishing in polishing the substrate, these residues accumulate on the polishing pad as the number of polished sheets increases.

  In addition, the abrasive is usually composed of abrasive grains, abrasive components and water at a certain mixing ratio. For example, when diluted with excess water, the abrasive grains may aggregate. These are also accumulated on the surface of the polishing pad as the number of polishing sheets increases. If polishing is continued in this state, the number of defects on the substrate surface due to these residues increases, so how to remove these residues remaining on or in the polishing pad after polishing and maintain the cleanness of the polishing pad. It becomes important.

  As for the cleaning of the polishing pad, for example, the polishing pad cleaning system described in JP-A-11-204469, the polishing pad cleaning system described in JP-A-2000-280165, and the polishing described in JP-A-2001-144054 A method for cleaning a polished polishing pad, such as a pad cleaning jig (brush) and a polishing pad cleaning liquid described in JP-A-2002-371300, has been conventionally known. However, when a plurality of substrates are polished continuously like a semiconductor wafer, the polishing pad cleaning step is affected by other steps before and after the polishing pad cleaning step. Unless a polishing step that takes into account the influence of the above is constructed, it is difficult to continuously maintain the cleanliness of the polishing pad surface by simply applying these conventional techniques alone.

  In addition, regarding the conditioning of the polishing pad surface after polishing, there have been many conditioners and conditioning mechanisms. That is, the condition of the polishing pad surface is performed by pressing the conditioner against the surface of the polishing pad mounted on the polishing table and moving the polishing table and the conditioner relative to each other while supplying the cleaning liquid. However, from the standpoint of maintaining the cleanliness of the polishing pad surface, how the diamond abrasive grains arranged in the conditioner fully penetrate the polishing pad surface and cut the polishing pad surface. The problem is whether to remove abrasive residues and polishing products remaining on the pad surface or in the polishing pad.

Japanese Patent Laid-Open No. 11-204469 JP 2000-280165 A JP 2001-144054 JP 2002-371300 A

  In view of the above situation, the present invention provides a polishing method capable of maintaining the cleanliness of the polishing pad surface by removing the polishing agent surface or polishing product remaining on the polishing pad surface or the polishing pad more efficiently. For the purpose.

  In order to solve the above problems, the present invention provides a top ring for holding a substrate, a polishing table on which a polishing pad for polishing the substrate is mounted, an abrasive supply means for supplying an abrasive to the polishing pad, In a polishing method for polishing the substrate held on the top ring, using a substrate processing apparatus including a conditioner for performing conditioning of the polishing pad, and a cleaning means for cleaning the substrate and the polishing pad, (A) a pre-abrasive supply step for supplying the polishing agent to the polishing pad by the abrasive supply means before the substrate contacts the polishing pad; and (B) the substrate held by the top ring. The top ring and the polishing table while the polishing agent is supplied by the polishing agent supply means. A polishing step for polishing the substrate, and (C) a substrate cleaning step for cleaning the substrate by the cleaning means while relatively moving the substrate and the polishing table after polishing, and (D) the step While the substrate is not on the polishing pad, while rotating the polishing table, the polishing pad is cleaned by the cleaning means, and at the same time, the conditioner is pressed against the polishing pad, and the polishing table and the conditioner are moved. And a polishing pad cleaning step for conditioning the polishing pad while performing relative movement.

  According to the present invention, steps (A) to (D) are repeatedly performed. Therefore, after step (D) “cleaning the polishing pad with the cleaning means and simultaneously conditioning the polishing pad (polishing pad cleaning step)”, step (A) “polishing agent before the substrate contacts the polishing pad” Supply (polishing agent pre-supply step) "is performed. That is, every time one substrate is polished, the “polishing pad cleaning step” of the present invention is always performed continuously.

  According to the present invention, the polishing pad surface and the polishing agent remaining on the polishing pad and the polishing product are efficiently removed, and the cleaned and conditioned polishing pad surface state can be maintained. Polishing can be performed without increasing the number of defects on the substrate surface due to these residues accumulated on the pad surface.

  Further, in the polishing pad cleaning step, when the relative speed between the polishing table and the conditioner is less than 2 m / sec, the diamond abrasive grains provided in the conditioner are set in the polishing pad by setting the relative speed within this range. Therefore, the polishing pad can be conditioned without being affected by slippage due to relative movement with respect to the surface, and the surface of the polishing pad can be conditioned more efficiently.

  Furthermore, in the polishing pad cleaning step, when the pressing load of the conditioner on the polishing pad is larger than 40N, the pressing load increases, so that the polishing pad surface can be more efficiently conditioned.

Also, in the polishing pad cleaning step, it is preferable that the abrasive grain size or uneven shape of the diamond abrasive grains arranged in the conditioner is # 200 (JIS abrasive grains) or less.
In the polishing step, the conditioning of the polishing pad surface may be performed simultaneously with the polishing of the substrate in a time shorter than the polishing time of the polishing step.

In the present invention, the cleaning means used in the substrate cleaning step may be different from the cleaning means used in the polishing pad cleaning step. For example, in the substrate cleaning step,
An abrasive supply means can be used as the cleaning means. In this case, the abrasive supply means supplies, for example, pure water or a chemical solution as the cleaning liquid instead of the abrasive. In the polishing pad cleaning step, an atomizer can be used as the cleaning means. In this case, the atomizer supplies pure water as a cleaning liquid, for example.

  Thus, in this invention, it is also possible to use an abrasive | polishing agent supply means as a washing | cleaning means, In this case, you may use an abrasive | polishing agent supply means as a washing | cleaning means also in a polishing pad washing | cleaning step.

It is a top view which shows the whole structure of the substrate processing apparatus which concerns on embodiment of this invention. It is a perspective view which shows a 1st grinding | polishing unit typically. It is a perspective view which shows a conditioner. It is a top view which shows a movement locus | trajectory when the conditioner is conditioning the polishing surface of a polishing pad. Fig.5 (a) is a perspective view which shows an atomizer, FIG.5 (b) is a schematic diagram which shows the lower part of an arm. FIG. 6A is a perspective view showing an abrasive supply nozzle, and FIG. 6B is an enlarged schematic view of the tip of the abrasive supply nozzle as viewed from below. It is a flowchart of a polishing cleaning step. It is a figure which shows the effect of the pad conditioning in a polishing pad washing | cleaning step. It is a figure which shows the dependence with respect to polishing elapsed time of the polishing rate of the oxide film on the surface of the wafer W. FIG. It is a figure which shows the relationship between a conditioning load and the number of defects.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing, the same or corresponding members are denoted by the same or similar reference numerals, and redundant description is omitted.

  FIG. 1 is a plan view showing the overall configuration of a substrate processing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the substrate processing apparatus includes a substantially rectangular housing 1, and the inside of the housing 1 is loaded / unloaded portion 2, polishing portion 3 and cleaning portion (not shown) by partition walls 1a and 1b. Z)). The load / unload unit 2, the polishing unit 3, and the cleaning unit are assembled independently and exhausted independently. In the polishing unit 3, the substrate is polished. The cleaning unit cleans and dries the polished substrate. The substrate processing apparatus has a control unit 5 that controls the substrate processing operation.

  The load / unload unit 2 includes two or more (four in this embodiment) front load units 20 on which wafer cassettes that stock a large number of wafers W (substrates) are placed. These front load portions 20 are arranged adjacent to the housing 1 and are arranged along the width direction (direction perpendicular to the longitudinal direction) of the substrate processing apparatus.

In addition, a traveling mechanism 21 is laid along the front load unit 20 in the load / unload unit 2, and two transfer robots that can move along the arrangement direction of the wafer cassettes on the traveling mechanism 21. A (loader) 22 is installed. The transfer robot 22 can access the wafer cassette mounted on the front load unit 20 by moving on the traveling mechanism 21. Each transfer robot 22 has two hands on the upper and lower sides. The upper hand is used to return the processed wafer W to the wafer cassette, and the lower hand is used to take out the unprocessed wafer W from the wafer cassette. It can be used for both upper and lower hands. Furthermore, the lower hand of the transfer robot 22 is configured to be able to reverse the wafer W by rotating around its axis.

  The polishing unit 3 is a region where polishing (planarization) and cleaning of the wafer W are performed, and includes a first polishing unit 3A, a second polishing unit 3B, a third polishing unit 3C, and a fourth polishing unit 3D. The first polishing unit 3A, the second polishing unit 3B, the third polishing unit 3C, and the fourth polishing unit 3D are arranged along the longitudinal direction of the substrate processing apparatus as shown in FIG.

  As shown in FIG. 1, the first polishing unit 3A includes a polishing table 30A to which a polishing pad 10 having a polishing surface is attached, and holds the wafer W and presses the wafer W against the polishing pad 10 on the polishing table 30A. A top ring 31A for polishing while polishing, an abrasive supply nozzle 32A (abrasive supply means) for supplying an abrasive or a conditioning liquid (for example, pure water) to the polishing pad 10, and a polishing surface of the polishing pad 10 A conditioner 33A for performing conditioning, and an atomizer 34A (cleaning means) that sprays a mixed fluid of liquid (for example, pure water) and gas (for example, nitrogen gas) or a liquid (for example, pure water) onto the polishing surface in the form of a mist. It has.

  Since the first polishing unit 3A, the second polishing unit 3B, the third polishing unit 3C, and the fourth polishing unit 3D have the same configuration, the first polishing unit 31A will be described below.

  FIG. 2 is a perspective view schematically showing the first polishing unit 3A. The top ring 31 </ b> A is supported by the top ring shaft 36. A polishing pad 10 is affixed to the upper surface of the polishing table 30A, and the upper surface of the polishing pad 10 constitutes a polishing surface for polishing the wafer W. Note that fixed abrasive grains may be used in place of the polishing pad 10. The top ring 31 </ b> A and the polishing table 30 </ b> A are configured to rotate around their axial centers as indicated by arrows. The wafer W is held on the lower surface of the top ring 31A by vacuum suction. At the time of polishing, the polishing agent is supplied from the polishing agent supply nozzle 32A to the polishing surface of the polishing pad 10, and the wafer W to be polished is pressed against the polishing surface by the top ring 31A and polished.

  A pressure chamber is provided in a space formed inside the top ring. A pressurized fluid such as pressurized air is supplied to the pressure chamber through a fluid path, or a vacuum is drawn. By raising and lowering the entire top ring, the entire top ring can be pressed against the polishing pad 10 with a predetermined pressing force.

  The wafer W may be polished by any one of the first polishing unit 3A, the second polishing unit 3B, the third polishing unit 3C, and the fourth polishing unit 3D, or selected in advance from these polishing units 3A to 3D. You may grind | polish continuously with a some grinding | polishing unit. For example, the wafer W may be polished in the order of the first polishing unit 3A → the second polishing unit 3B, or the wafer W may be polished in the order of the third polishing unit 3C → the fourth polishing unit 3D. Further, the wafer W may be polished in the order of the first polishing unit 3A → the second polishing unit 3B → the third polishing unit 3C → the fourth polishing unit 3D. In any case, the throughput can be improved by leveling all the polishing times of the polishing units 3A to 3D.

FIG. 3 is a perspective view showing a conditioner 33A that can be used as an embodiment of the present invention. As shown in FIG. 3, the conditioner 33 </ b> A includes a conditioner arm 85, a conditioning member 86 that is rotatably attached to the tip of the conditioner arm 85, and a swing shaft that is coupled to the other end of the conditioner arm 85. 88 and a motor 89 as a drive mechanism for swinging (swinging) the conditioner arm 85 about the swing shaft 88. The conditioning member 86 has a circular conditioning surface, and hard particles are fixed to the conditioning surface. Examples of the hard particles include diamond particles and ceramic particles. A motor (not shown) is built in the conditioner arm 85, and the conditioning member 86 is rotated by this motor. The swing shaft 88 is connected to an elevating mechanism (not shown), and the conditioning member 86 presses the polishing surface of the polishing pad 10 when the conditioner arm 85 is lowered by the elevating mechanism.

  FIG. 4 is a plan view showing the movement trajectory when the conditioner 33A is conditioning the polishing surface of the polishing pad 10. As shown in FIG. 4, the conditioner arm 85 is longer than the radius of the polishing pad 10, and the swing shaft 88 is located on the radially outer side of the polishing pad 10. When conditioning the polishing surface of the polishing pad 10, the polishing pad 10 is rotated, the conditioning member 86 is rotated by a motor, the conditioner arm 85 is lowered by an elevating mechanism, and the conditioning member 86 is rotated. Make sliding contact with the polished surface. In this state, the motor 89 causes the conditioner arm 85 to swing (swing). During conditioning of the polishing pad 10, pure water as a conditioning liquid is supplied to the polishing surface of the polishing pad 10 from the abrasive supply nozzle 32 </ b> A. Due to the swing of the conditioner arm 85, the conditioning member 86 located at the tip of the conditioner arm 85 moves across the center of the polishing surface from the end to the end of the polishing surface of the polishing pad 10, as shown in FIG. can do. By this swinging operation, the conditioning member 86 can condition the entire polishing surface of the polishing pad 10 including the center thereof, and the conditioning effect on the polishing surface can be greatly enhanced. Therefore, the entire polished surface can be uniformly conditioned, and a flat polished surface can be obtained.

  FIG. 5A is a perspective view showing the atomizer 34A. The atomizer 34 </ b> A includes an arm 90 having one or a plurality of injection holes in the lower part, a fluid flow path 91 connected to the arm 90, and a swing shaft 94 that supports the arm 90. FIG. 5B is a schematic diagram showing the lower part of the arm 90. In the example shown in FIG. 5B, a plurality of injection holes 90 a are formed at equal intervals in the lower part of the arm 90. The fluid flow path 91 can be composed of a tube, a pipe, or a combination thereof. Examples of the fluid used include a liquid (for example, pure water) or a mixed fluid of liquid and gas (for example, a mixed fluid of pure water and nitrogen gas).

  As shown in FIG. 5A, the arm 90 can pivot between a cleaning position and a retracted position about a swing shaft 94. The movable angle of the arm 90 is about 90 °. Normally, the arm 90 is at the cleaning position and is disposed along the radial direction of the polishing surface of the polishing pad 10 as shown in FIG. A rotation mechanism is connected to the swing shaft 94, and the arm 90 is turned by this rotation mechanism.

  The purpose of providing the atomizer 34A is to wash away polishing debris and abrasive grains remaining on the polishing surface of the polishing pad 10 with a high-pressure fluid. More favorable conditioning, that is, regeneration of the polishing surface, can be achieved by purifying the polishing surface by the fluid pressure of the atomizer 34A and sharpening the polishing surface by the conditioner 33A that is mechanical contact. Usually, after the conditioning by a contact type conditioner (diamond conditioner or the like), the polished surface is often regenerated by an atomizer.

FIG. 6A is a perspective view showing the abrasive supply nozzle 32A, and FIG. 6B is an enlarged schematic view of the tip of the abrasive supply nozzle 32A as viewed from below. As illustrated in FIG. 6, the abrasive supply nozzle 32 </ b> A includes a plurality of tubes 100 for supplying an abrasive such as pure water or slurry to the polishing surface of the polishing pad 10, and a pipe arm 101 that covers the plurality of tubes 100. And a rocking shaft 102 that supports the pipe arm 101. The plurality of tubes 100 are usually composed of a pure water supply tube for supplying pure water and a plurality of slurry supply tubes for supplying different types of slurry. As the plurality of tubes 100, for example, from two to four (for example, three) slurry supply tubes through which slurry passes and one or two pure water supply tubes through which pure water passes. Can be configured.

  The plurality of tubes 100 extend through the inside of the pipe arm 101 to the tip of the pipe arm 101, and the pipe arm 101 covers almost the entire tube 100. A reinforcing material 103 is fixed to the tip of the pipe arm 101. The tip of the tube 100 is located above the polishing pad 10, and an abrasive is supplied from the tube 100 onto the polishing surface of the polishing pad 10. An arrow shown in FIG. 6A represents an abrasive supplied to the polishing surface. The oscillating shaft 102 is connected to a rotation mechanism (such as a motor) (not shown), and by rotating the oscillating shaft 102, it is possible to supply an abrasive to a desired position on the polishing surface.

  Examples of pure water used in each polishing unit include cleaning of the top ring (for example, cleaning of the outer peripheral side surface of the top ring, cleaning of the substrate holding surface, cleaning of the retainer ring), cleaning of the transfer hand of the wafer W (for example, Cleaning of transfer hands of first and second linear transporters described later), cleaning of polished wafer W, conditioning of polishing pad, cleaning of conditioner (for example, cleaning of conditioning member), cleaning of conditioner arm , Cleaning of the abrasive supply nozzle, and cleaning of the polishing pad with an atomizer.

  Next, a transport mechanism for transporting the wafer W will be described. As shown in FIG. 1, a first linear transporter 6 is disposed adjacent to the first polishing unit 3A and the second polishing unit 3B. The first linear transporter 6 has four transfer positions along the direction in which the polishing units 3A and 3B are arranged (first transfer position TP1, second transfer position TP2, and third transfer in order from the load / unload unit side). This is a mechanism for transporting the wafer W between the position TP3 and the fourth transport position TP4.

Further, the second linear transporter 7 is disposed adjacent to the third polishing unit 3C and the fourth polishing unit 3D. The second linear transporter 7 has three transfer positions (a fifth transfer position TP5, a sixth transfer position TP6, and a seventh transfer in order from the load / unload unit side) along the direction in which the polishing units 3C and 3D are arranged. The lifter 11 for receiving the wafer W from the transfer robot 22 is disposed at the first transfer position TP1 which is a mechanism for transferring the wafer W between the transfer robot 22 and the position TP7. The wafer W is transferred from the transfer robot 22 to the first linear transporter 6 through the lifter 11. A swing transporter 12 is disposed between the first linear transporter 6 and the second linear transporter 7. The swing transporter 12 has a hand that can move between the fourth transfer position TP4 and the fifth transfer position TP5. The swing transporter 12 moves the wafer W from the first linear transporter 6 to the second linear transporter 7. Delivery is performed by the swing transporter 12.

  The control unit 5 shown in FIG. 1 performs operations of various members constituting the substrate processing apparatus and starts and stops and selects water and gas supplied to the wafer W. The operations of the load / unload unit 2 and the polishing unit 3 as well as the transfer of the wafer W between them are controlled. The control unit 5 performs each of these controls based on a program installed in advance.

Next, the operation of the substrate processing apparatus configured as described above, that is, the polishing method according to the present invention will be described. The following operations are controlled by the control unit 5. The wafer W set in the wafer cassette 20 is taken out by the transfer robot 22. The wafer W is transferred from the transfer robot 22 to the first linear transporter 6 through the lifter 11.

  The wafer W is transferred to the polishing units 3A and 3B by the first linear transporter 6. As described above, the top ring 31A of the first polishing unit 3A moves between the polishing position and the second transport position TP2 by the swing operation of the top ring head 60. Accordingly, the wafer W is delivered to the top ring 31A at the second transfer position TP2.

  After the top ring 31A is moved to the second transport position TP2, the pre-abrasive supply step S1 of FIG. 7, that is, the step of supplying the polishing agent before the wafer W contacts the polishing pad 10 is performed. In this step, a large amount of cleaning residue or cleaning liquid itself remains on the polishing pad 10 after the polishing pad cleaning step described later. When polishing the next wafer W in this state, the slurry ( Dilution of the abrasive) causes agglomeration of the abrasive grains and causes defects due to the aggregated abrasive liquid components. Therefore, the purpose of this step is to suppress the occurrence of defects by substituting these cleaning residues and cleaning liquid with abrasives in advance. Specifically, the abrasive is supplied by the abrasive supply nozzle 32A while rotating the polishing table 30A before polishing the wafer W (that is, in a state where the wafer W is not on the polishing pad).

  The abrasive is supplied for a predetermined time, and after the replacement of the residue and the cleaning liquid remaining on the polishing pad with the slurry (abrasive) is completed, the wafer W is brought into contact with the top ring 31A. When the wafer W comes into contact with the top ring 31A, the inside of the top ring 31A is set to a negative pressure, the wafer W is attracted to the top ring 31A, and the wafer W is held by the top ring 31A. The top ring 31A is moved, the wafer W held on the top ring 31A is moved onto the polishing table 30A, the top ring 31A is rotated at a predetermined rotation speed, and the wafer W contacts the polishing pad on the polishing table 30A. Further, the inside of the top ring 31A is set to a positive pressure and is increased to a predetermined pressure. Thus, a polishing step (step S2 in FIG. 7) is performed in which the wafer W held on the top ring 31A is pressed against the polishing pad 10 and the top ring 31A and the polishing table 30A are moved relative to each other to polish the surface of the wafer W. .

  Note that the wafer W may be held on the top ring 31A and moved onto the polishing table before the residue remaining on the polishing pad and the cleaning liquid are replaced with the slurry.

  The surface of the wafer W is polished by a predetermined amount according to the condition of the wiring formed on the wafer W. The predetermined amount to be polished is adjusted by, for example, the polishing time according to the rotation speed of the polishing table 30A and the top ring 31A, the state of the polishing table 30A, and the like. Alternatively, control for adjusting the polishing amount while detecting the state of the film to be polished by an eddy current type monitor that can detect the remaining film thickness of the metal film formed on the surface of the wafer W or an optical monitor that can detect the transmission film thickness, Alternatively, the amount of polishing may be adjusted by means such as control for grasping the polishing state from the table current for detecting the rotational torque of the polishing table 30A. When the surface of the wafer W is polished by a predetermined amount, the supply of the abrasive from the abrasive supply nozzle 32A is stopped, and Step S2 is completed.

  Further, the polishing of the wafer W may be performed by the polishing apparatus 30B, or may be performed in two stages so as to be polished by the polishing apparatus 30B after being polished by the polishing apparatus 30A. When polishing is performed in two stages, the surface of the wafer W can be finely finished using a polishing pad or a grindstone having different roughnesses while shortening the polishing time. Alternatively, the number of processed wafers per unit time may be increased by processing two wafers W in parallel by the polishing apparatus 30A and / or the polishing apparatus 30B and the polishing apparatus 30C and / or the polishing apparatus 30D.

  After the polishing, a substrate cleaning step (step S3 in FIG. 7) is performed in which the wafer W and the polishing table 30A are cleaned while being rotated while the top ring 31A and the polishing table 30A are rotated. In the substrate cleaning step, the wafer W is cleaned by spraying a cleaning liquid onto the polishing pad 10 by a cleaning means (atomizer 34A or abrasive supply nozzle 32A). In the substrate cleaning step, the polishing agent present on the surface (surface to be polished) of the wafer W after polishing is removed with the cleaning liquid supplied by the cleaning means. The cleaning solution here may be pure water (DIW (De-Ionized Water)), but a chemical solution may also be used. The cleaning means (that is, the cleaning liquid supply means) in the present invention is either one or both of the atomizer 34A and the abrasive supply nozzle 32A. That is, as the cleaning means, only one of the atomizer 34A and the abrasive supply nozzle 32A can be used, or both can be used simultaneously.

  As described above, the cleaning liquid supply means (abrasive supply nozzle 32A) can supply the chemical liquid as the cleaning liquid from one line of the slurry nozzle, and can also be used as conditioning water during conditioning from the other one line. Purified water can be supplied as a cleaning liquid. The atomizer can supply pure water, which is a cleaning liquid when used as an atomizer, and can supply pure water used as a conditioning water during conditioning as a cleaning liquid.

  At the end of the polishing step, a large amount of polishing agent is present on the polishing pad 10, and the polishing agent is diluted with a large amount of cleaning liquid supplied at the start of the substrate cleaning step S3. Aggregation may occur. For the purpose of suppressing damage to the surface to be polished by the agglomerated abrasive grains, before moving to the substrate cleaning step S3, the polishing pressure may be lowered while the polishing agent is supplied, or the table rotation speed may be reduced. good.

  After the end of step S3, the inside of the top ring 31A is set to a negative pressure to attract the wafer W to the top ring 31A. Then, the top ring 31A is raised to separate the wafer W from the polishing table 30A, and the wafer W is placed on the second transfer position TP2. The wafer W that has been polished and cleaned is transferred from the first polishing unit 3A by the transport mechanism to the next processing step (cleaning step of the wafer W in a normal cleaning unit (not shown) or a polishing table other than the polishing table 30A). Polishing step).

  Next, while the wafer W is not on the polishing pad 10, the polishing pad 10 is cleaned by the above-described cleaning means while rotating the polishing table 30A, and at the same time, the conditioner is pressed against the polishing pad 10 to condition the polishing table 30A. A polishing pad cleaning step (step S4 in FIG. 7) for conditioning the polishing pad is performed while relatively moving the nut 33A.

  In the polishing pad cleaning step, the polishing agent remaining on the polishing pad 10 and the polished polishing product are removed with the cleaning liquid supplied by the cleaning means. As the cleaning means, only one of the atomizer 34A and the abrasive supply nozzle 32A can be used, or both can be used simultaneously. The cleaning liquid basically uses pure water. In some cases, an appropriate chemical solution may be used. While rotating the polishing table 30A with the wafer W not on the polishing pad 10, the cleaning liquid is supplied.

  The polishing pad 10 is conditioned by the conditioner 33A simultaneously with the supply of the cleaning liquid. The polishing pad may be conditioned during the polishing of the wafer W (that is, during the polishing step). Alternatively, it may be performed at both timings, but from the viewpoint of maintaining the cleanliness of the surface of the polishing pad 10, conditioning after polishing (that is, only the polishing pad cleaning step) is preferable.

  As shown in FIG. 8, in the case of conditioning during polishing (in-situ), depending on the conditioning conditions, the conditioner may reverse these removals of the polishing agent and the polishing product on the polishing pad 10. This is because the surface of the polishing pad is rubbed and defects of the wafer W increase. However, on the other hand, depending on the polishing process, if only the conditioning (Ex-situ) of the polishing pad cleaning step is performed, a decrease in the polishing rate due to insufficient sharpening of the surface of the polishing pad 10 will be affected. There is a possibility of effect. In such a case, conditioning (In-situ) may be performed even during polishing. In-situ conditioning may be performed continuously from the start of polishing to the end of polishing, but may be performed only for a certain time from the start of polishing, and thereafter, polishing may be performed without conditioning. This is because even if a defect such as a scratch occurs due to in-situ conditioning, the scratch portion is polished by polishing after stopping the conditioning, and the scratch can be eliminated. Then, a polishing pad cleaning step is performed thereafter to remove the polishing agent remaining on the polishing pad and the polished polishing product. The in-situ conditioning time in this case was set by setting the conditioning time from the relationship between the polishing amount and the polishing rate because the polishing amount necessary for removal by polishing can be determined from the generated defect size. Condition the polishing pad for a period of time.

  As described above, in the present invention, the polishing pad cleaning step is always performed every time one wafer W is polished. The cleaning means in the substrate cleaning step and the cleaning means in the polishing pad cleaning step may be the same, and for example, an atomizer is used. However, as the cleaning means, an atomizer and, in some cases, an abrasive supply means can be used. When the abrasive supply means is used, the conditioning water is discharged from the abrasive supply means for cleaning. The atomizer and the abrasive supply means may be a single device. In the case of separate apparatuses, the substrate cleaning step can be cleaned only with the conditioning water from the abrasive supply means.

After the polishing pad cleaning step S4 is completed, the process returns to the pre-abrasive supply step S1 and repeats steps S1 to S4.
Next, the conditions for conditioning the polishing pad in the polishing pad cleaning step will be described. Conditioning of the polishing pad by the conditioner is usually performed with the conditioner and the polishing table at a predetermined load while using the cleaning means in a state where the conditioner and the polishing table are moved relative to each other (for example, rotational movement of the conditioner and the polishing table, arc movement of the conditioner). It is performed by pressing against the polishing pad. From the viewpoint of the cleanliness of the polishing pad surface, it is desirable that the conditioning load is a high load as the conditioning condition, and the relative speed between the conditioner and the polishing table is a low speed. Specifically, the relative motion speed is desirably less than 2 m / sec, more preferably less than 1 m / sec. The conditioning load is preferably 40N or more. Depending on the type of conditioner, the surface of the conditioner (the surface in contact with the polishing pad) may be affected by the effect of hydroplaning that tends to occur on the polishing pad surface as the relative motion speed increases or the conditioning load decreases. This is because a phenomenon occurs in which the diamond abrasive grains adhering (for example, electrodeposition) and the uneven protrusions on the conditioner surface do not sufficiently penetrate into the polishing pad.

FIG. 9 shows the dependence of the polishing rate (the amount polished per unit time, that is, the depth to be polished) of the oxide film on the surface (surface to be polished) of the wafer W on the polishing elapsed time. It shows the correlation between the relative speed and the conditioning load between the polishing pad (polishing table) and the conditioner in conditioning. The vertical axis represents the polishing rate, and the horizontal axis represents the polishing time. Graph A shows a reference condition which is a conventional technique, where the polishing table rotation speed is 3 m / sec and the conditioning load is 30 N. Graph B shows the low table rotation speed condition according to the present invention, where the polishing table rotation speed is 0.7 m / sec and the conditioning load is 30 N. Graph C is also according to the present invention and shows a high conditioning load condition: polishing table rotation speed = 3 m / sec and conditioning load = 60N.

  From these graphs, it can be seen that in the polishing pad cleaning step, when the relative speed between the polishing table and the conditioner is less than 2 m / sec, the polishing rate is higher than the conventional rate. Further, it can be seen that the polishing rate is higher than the conventional one when the pressing load on the polishing pad of the conditioner is larger than 40N.

  In general, the conditioning of the polishing pad also serves to sharpen the surface of the polishing pad and affects the amount of slurry retained in the polishing pad and hence the polishing rate. Therefore, the polishing rate is an index of the degree of conditioning of the polishing pad. As a result, an increase in the polishing rate has been confirmed, particularly when the relative speed between the polishing table and the conditioner decreases.

  FIG. 10 shows the relationship between the conditioning load and the number of defects. The vertical axis is the number of defects, and the horizontal axis is the conditioning load. From these graphs, in the polishing pad cleaning step, if the pressing load (conditioning load) of the conditioner to the polishing pad is greater than 40N, the number of defects is smaller than in the conventional condition (conditioning load is 30N). I understand. A decrease in the number of defects can be confirmed as the conditioning load increases. The reason is considered that the diamond abrasive grains of the conditioner and the concavo-convex convex portions sufficiently dig into the polishing pad, so that the polishing agent remaining on the polishing pad surface and the polishing product after polishing were sufficiently removed.

  In addition, the shape, size, and number of arrangements of the diamond or the uneven shape arranged in the conditioner greatly affect the biting into the polishing pad. The size is preferably # 200 or less. # 200 is a JIS standard "JIS B4130 (diamond / CBN tool-diamond or CBN and (abrasive) grain size)", but may have a size equivalent to this.

  As for the size, it determines the maximum amount of penetration into these abrasive grains or convex polishing pads. A larger one is desirable, but if it is too large, insufficient conditioning due to falling off of abrasive grains or reduction in the number of working abrasive grains Therefore, appropriate adjustment is necessary. In addition, for example, in the case of diamond abrasive grains, a sharp shape is desirable.

  As described above, by operating the conditioner at the relative speed and conditioning load of the present invention to condition the polishing pad surface, the conditioner's abrasive grains or uneven projections sufficiently penetrate the polishing pad. As a result, the abrasive residue and polishing product trapped in the polishing pad are efficiently removed.

  As described above, according to the present invention, high-efficiency removal of the polishing pad surface and the polishing agent and polishing product remaining in the polishing pad can be achieved, and a good cleaning state and polishing pad surface state can be maintained. Therefore, polishing can be performed without increasing the number of defects on the wafer surface due to these residues accumulated on the polishing pad surface.

10 Polishing pad 3A First polishing unit 30A, 30B, 30C, 30D Polishing table 31A, 31B, 31C, 31D Top ring 32A, 32B, 32C, 32D Abrasive supply nozzle 33A, 33B, 33C, 33D Conditioners 34A, 34B, 34C, 34D atomizer W wafer

Claims (7)

A top ring that holds the substrate;
A polishing table equipped with a polishing pad for polishing the substrate;
Abrasive supply means for supplying an abrasive to the polishing pad;
A conditioner for performing conditioning of the polishing pad;
In a polishing method for polishing the substrate held on the top ring, using a substrate processing apparatus including a cleaning means for cleaning the substrate and the polishing pad,
(A) A pre-abrasive supply step of supplying the polishing agent to the polishing pad by the abrasive supply means before the substrate contacts the polishing pad;
(B) The substrate held by the top ring is pressed against the polishing pad, and the top ring and the polishing table are moved relative to each other while the polishing agent is supplied by the polishing agent supply means, and the substrate is moved. A polishing step to polish;
(C) a substrate cleaning step of cleaning the substrate by the cleaning means while relatively moving the substrate and the polishing table after polishing;
(D) While rotating the polishing table in a state where the substrate is not on the polishing pad, the polishing pad is cleaned by the cleaning means and at the same time the conditioner is pressed against the polishing pad, And a polishing pad cleaning step of conditioning the polishing pad while relatively moving the conditioner.   The polishing method according to claim 1, wherein, in the polishing pad cleaning step, a relative speed between the polishing table and the conditioner is less than 2 m / sec.   The polishing method according to claim 1 or 2, wherein, in the polishing pad cleaning step, a pressing load of the conditioner to the polishing pad is larger than 40N.   4. The polishing pad cleaning step according to claim 1, wherein the abrasive grain size or uneven shape of the diamond abrasive grains arranged in the conditioner is # 200 (JIS) or less. 5. Polishing method.   The polishing method according to claim 1, wherein in the polishing step, conditioning of the surface of the polishing pad is performed simultaneously with polishing of the substrate in a time shorter than a polishing time of the polishing step. .   The polishing method according to claim 1, wherein the cleaning unit used in the substrate cleaning step and the cleaning unit used in the polishing pad cleaning step are different.   The polishing method according to claim 1, wherein the abrasive supply unit is used as the cleaning unit.

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