TECHNICAL FIELD

The present disclosure relates to conditioning of polishing pads.

BACKGROUND

An integrated circuit is typically formed on a substrate by the sequential deposition of conductive, semiconductive, or insulative layers on a silicon wafer. A variety of fabrication processes require planarization of a layer on the substrate. For example, for certain applications, e.g., polishing of a metal layer to form vias, plugs, and lines in the trenches of a patterned layer, an overlying layer is planarized until the top surface of a patterned layer is exposed. In other applications, e.g., planarization of a dielectric layer for photolithography, an overlying layer is polished until a desired thickness remains over the underlying layer.

Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head. The exposed surface of the substrate is typically placed against a rotating polishing pad. The carrier head provides a controllable load on the substrate to push it against the polishing pad. Abrasive polishing slurry is typically supplied to the surface of the polishing pad.

After the CMP process is performed for a certain period of time, the surface of the polishing pad becomes glazed due to accumulation of slurry by-products and/or material removed from the substrate and/or the polishing pad. Glazing reduces pad asperity, provides less localized pressure, thus reducing the polishing rate. In addition, glazing may cause the polishing pad to lose some of its capacity to hold the slurry, further reducing the polishing rate.

Typically, the properties of the glazed polishing pad can be restored by a process of conditioning with a pad conditioner. The pad conditioner is used to remove the unwanted accumulations on the polishing pad and regenerate the surface of the polishing pad to a desirable asperity. Typical pad conditioners include an abrasive head generally embedded with diamond abrasives which can be rubbed against the pad surface of the glazed polishing pad to retexture the pad.

SUMMARY

In some conditioning systems with some polishing recipes and consumable sets, the pad conditioner, particularly the pad conditioner arm, will exhibit significant vibration. The vibration, which is detrimental to the arm, can reduce the effectiveness of the conditioning process. In addition, this vibration is often audible, and in fact can be unacceptably loud. However, by appropriate selection of the pivot point between the conditioner arm and the conditioner base, vibrations can be significantly reduced or eliminated.

In one aspect, a polishing system includes a platen having a top surface to support a polishing pad and a conditioner apparatus. The conditioner apparatus includes a conditioner head constructed to receive a conditioning disk for conditioning a surface of the polishing pad, an arm that supports the conditioner head, and a base that supports the arm. The arm is pivotally connected to the base such that the arm is pivotable about a pivot point to change an angle of inclination of the arm. The pivot point is positioned below a plane parallel to and positioned 130 mils above the top surface of the platen.

Implementations may include one or more of the following features. The pivot point may be positioned between 0.05 and 2 inches below the plane. The pivot point may be positioned about 0.1 inch below the plane. The pivot point may be positioned below the top surface of the platen. An actuator may be configured to sweep the arm over the polishing pad. A linear actuator may connect the base to the arm to control an angle of inclination of the arm.

In another aspect, a polishing system includes a polishing pad having a polishing surface and a conditioner apparatus. The conditioner apparatus includes a conditioner head constructed to receive a conditioning disk for conditioning a surface of the polishing pad, an arm that supports the conditioner head, a base that supports the arm, the arm pivotally connected to the base such that the arm is pivotable about a pivot point to change an angle of inclination of the arm, wherein the pivot point is positioned below the polishing surface of the polishing pad.

Implementations may include one or more of the following features. The pivot point may be positioned between 0.05 and 2 inches below the polishing surface. The pivot point may be positioned about 0.1 inch below the polishing surface. The pivot point may be positioned below the top surface of the platen. An actuator may be configured to sweep the arm over the polishing pad. A linear actuator may connect the base to the arm to control an angle of inclination of the arm.

In another aspect, a polishing system includes a platen having a top surface to support a polishing pad and a conditioner apparatus. The conditioner apparatus includes a conditioner head constructed to receive a conditioner disk for conditioning a surface of the polishing pad, an arm that supports the conditioner head, and a base that supports the arm. The arm is pivotally connected to the base such that the arm is pivotable about a pivot point to change an angle of inclination of the arm. The pivot point is positioned the top surface of the platen.

Implementations may optionally include one or more of the following advantages. Vibration of the pad conditioner, particularly the pad conditioner arm, can be reduced. Effectiveness of the conditioning process can be improved. Noise generated by the pad conditioner can be reduced.

The details of one or more implementations are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic cross-sectional side view of an example of a polishing apparatus.

FIG. 2 is a top view of a polishing station of a polishing apparatus.

FIG. 3 is a cross-sectional view of a conditioner apparatus.

FIGS. 4A and 4B are graphs of oscillation intensity as a function of frequency for a conditioner apparatus with a pivot point at the top of the platen and below the top of the platen, respectively.

FIG. 5 is a cross-sectional view of a prior art conditioner apparatus.

Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

FIG. 1 illustrates an example of a polishing apparatus 100. The polishing apparatus 100 includes a rotatable disk-shaped platen 120 on which a polishing pad 110 is situated. The polishing pad 120 can sit on, e.g., be adhesively attached to, a top surface 126 of the platen 120.

The platen 120 is operable to rotate about an axis 125. For example, a motor 122 can turn a drive shaft 124 to rotate the platen 120. The platen 120 can rotate at about 30-200 rpm.

The polishing pad 110 can has a polishing surface 116. The polishing pad 110 can be a two-layer polishing pad with an outer polishing layer 112 and a softer backing layer 114. The layer that provides the polishing surface 116, e.g., the outer polishing layer 112, can be a porous polyurethane. For example, the polishing pad can be an IC-1000 or IC-1010 polishing pad.

The polishing apparatus 100 can include a port 130 to dispense polishing liquid 132, such as slurry, onto the polishing pad 110 to the pad. The slurry 132 can include silica abrasive particles, e.g., the slurry can be SS-12.

The polishing apparatus 100 includes at least one carrier head 140. While only one carrier head 140 is shown, more carrier heads can be provided to hold additional substrates so that the surface area of polishing pad 110 may be used efficiently.

The carrier head 140 is operable to hold a substrate 10 against the polishing pad 110. The carrier head 140 can have independent control of the polishing parameters, for example pressure, associated with each respective substrate. The carrier head 140 can include a retaining ring 142 to retain the substrate 10 below a flexible membrane 144. Pressurization of one or more chambers behind the membrane 144 controls the pressure applied to the substrate 10. Although only three chambers are illustrated in FIG. 1 for ease of illustration, there could be one or two chambers, or four or more chambers, e.g., five chambers.

The carrier head 140 is suspended from a support structure 150, e.g., a carousel or a track, and is connected by a drive shaft 152 to a carrier head rotation motor 154 so that the carrier head can rotate about an axis 155. The carrier head 140 can rotate at about 30-200 rpm. Optionally the carrier head 140 can oscillate laterally, e.g., on sliders on the carousel 150 or track; or by rotational oscillation of the carousel itself. In operation, the platen is rotated about its central axis 125, and the carrier head is rotated about its central axis 155 and translated laterally across the top surface of the polishing pad.

The polishing apparatus can also include a polishing pad conditioner 160 to abrade the polishing pad 110 to maintain the polishing pad 110 in a consistent abrasive state. A description of a similar conditioner can be found in U.S. Pat. No. 7,963,826, which is incorporated by reference. The polishing pad conditioner 160 includes a base 162, an arm 164 that can sweep laterally over the polishing pad 110, and a conditioner head 166 connected to the base 162 by the arm 164. The base 162 is mounted on a frame 102 of the polishing apparatus 100 that can also support the other components, e.g., the platen 120 and the support structure 150. The conditioner head 166 includes an abrasive surface configured to condition the surface 116 of the polishing pad 110. The abrasive surface can be rotatable, and the pressure of the abrasive surface against the polishing pad can be controllable.

Referring to FIG. 2, in one mode of operation, the polishing pad 110 is conditioned by the conditioner head 166 while the polishing pad 110 polishes a substrate 10 which is mounted on carrier head 140. In some implementations, the base 162 is pivotally attached to the frame 102 and can rotate about a vertical axis so that arm 164 and sweeps back and forth to move the conditioner head 166 in an oscillatory sweeping motion (shown by arrows S) across polishing pad 110. The motion of the conditioner head 166 can be synchronized with the motion of carrier head 140 to prevent collision.

Optionally, the polishing apparatus 100 can include a rinsing cup 168 supported on the frame 102 and positioned in a location such that the arm 164 can position the conditioner head 166 in the cup 168. The rinsing cup 168 can contain a fluid for rinsing the conditioner head 166, or a set of nozzles can be mounted in the cup to spray cleaning fluid on the conditioner head 166. Before and after the conditioning operation, the conditioner head 166 can be positioned in the rinsing cup 168 for cleaning.

Referring to FIG. 3, the conditioner head 166 includes a rotatable end effector 170 that holds a conditioning disk 172. The conditioning disk 172 has a bottom surface embedded with diamond abrasives which can be rubbed against the surface of the polishing pad to retexture the pad. The conditioning disk 172 can be held in the end effector by magnets, or by mechanical fasteners. A gimbal mechanism can be coupled between the end effector 170 and the conditioner head 166, the gimbal mechanism allowing the end effector 170 to tilt at an angle relative to the arm 164. Optionally the end effector 170 is also rotatable.

Rotation of the end effector 170 can be provided by a motor in the base 162 that is connected by a belt drive that extends through the arm 164 to engage a drive shaft 174 connected to the end effector 170. A description of a conditioner head can be found in U.S. Pat. No. 6,036,583, incorporated herein by reference.

The base 162 includes a rotary actuator that includes a rotatable upper portion 180 and a lower portion 182 that is fixed relative to the frame 102. The arm 164 is affixed to the rotatable upper portion 180, and rotation of the upper portion 180 causes the lateral sweep of the arm 162 across the polishing pad.

The rotary actuator includes a sweep motor 184. The sweep motor 184 can be housed in the lower portion 182. For example, the sweep motor 184 can drive a drive shaft that is fixed to the upper portion 180 and extends from the upper portion 180 into the lower portion 182. Alternatively, the sweep motor can be housed in the upper portion 180. For example, the sweep motor 184 can cause the upper portion 180 to be driven relative to a drive shaft that is fixed to the lower portion 182 and extends from the lower portion 182 into the upper portion 180.

Vertical motion of the end effector 170 and control of the pressure of conditioning disk 172 can be provided by a pivot connection 186 between the arm 164 and the upper portion 180 of the base 162. The pivot connection 186 permits pivoting of the arm 164 about a substantially horizontal axis, so that the arm 164 can swing up and down as shown by arrows A. An actuator 188, e.g., a pneumatic linear actuator positioned between the upper portion 180 and the arm 164, permits a controllable angle of inclination of the arm 164, and thus a controllable height of the conditioner head 166 above the polishing pad 110 and/or controllable pressure of the conditioner disk 172 against the polishing pad 110.

Various components, such as the pivot connection 186, the portion of the arm 164 adjacent the pivot connection, the actuator 188, the upper portion 180, and the lower portion 182 can be enclosed in by a cover 189.

The pivot point 186a of the pivot connection 186 is located below the polishing surface 116 of the polishing pad 110. The thickness of a typical polishing pad is 130 mils; consequently the pivot point 186a of the pivot connection 186 can be located below a reference plane that is parallel to and positioned 130 mils above the top surface 126 of the platen 120. For example, there can be a distance D of about 0.05 to 2.0 inches between the pivot point 186a and the reference plane. In some implementations, the pivot point 186a of the pivot connection 186 is located below the top surface 126 of the platen 120. In some implementations, the pivot point 186a of the pivot connection 186 is located above the top surface 126 of the platen 120 but below the polishing surface 116 of the polishing pad 110.

Referring to FIGS. 4A and 4B, a conditioner system with the interface 188 located below the top surface 126 of the platen 120 can exhibit less vibration, e.g., in the 50-75 Hz range, as compared to a conditioner system with the interface 188 coplanar with the polishing surface 116 of the polishing pad 110 (see FIG. 5).

Without being limited to any particular theory, if the pivot point of the arm is level with the polishing surface of the polishing pad, the friction and force interaction of the conditioner disk and polishing pad can cause stick-slip vibration and chattering of the pad conditioner. By lowering the pivot point below the polishing surface, e.g., below the top surface of the platen, frictional force will tend to reduce the down-force applied by the pad conditioner arm, thus reducing or eliminating stick-slip vibration and chattering.

A controller 190 (see FIG. 1), e.g., a computer, can be connected to the conditioning apparatus 160 to control the lateral sweep of the arm 164, the inclination or vertical position of the arm 164, the rotation rate of the end effector 170, and the downward force of the end effector 170 on the polishing pad. The computer can include an output device 192, e.g., a display, and an input device 194, e.g., a keyboard.

Although the description above focuses on a conditioner head, the damper system could be applied to other cantilever parts in a polishing system that are susceptible to vibration. For example, the damper system could be applied to an arm that holds a polishing head.

In some implementations, the vertical motion and pressure control can be provided by a vertical actuator in the base 162 that lifts the entire arm 164 and conditioner head 166, or by a vertical actuator in the conditioner head 166, e.g., a pressurizable chamber 174 positioned to apply downward pressure to the end effector 170.

The above described polishing apparatus and methods can be applied in a variety of polishing systems. Either the polishing pad, or the carrier heads, or both can move to provide relative motion between the polishing surface and the substrate. For example, the platen may orbit rather than rotate. The polishing pad can be a shape other than circular. Some aspects of the endpoint detection system may be applicable to linear polishing systems, e.g., where the polishing pad is a continuous or a reel-to-reel belt that moves linearly. The polishing layer can be a standard (for example, polyurethane with or without fillers) polishing material, a soft material, or a fixed-abrasive material. The arm could undergo a linearly extension motion rather than an angular sweep.

As used in the instant specification, the term substrate can include, for example, a product substrate (e.g., which includes multiple memory or processor dies), a test substrate, a bare substrate, and a gating substrate. The substrate can be at various stages of integrated circuit fabrication, e.g., the substrate can be a bare wafer, or it can include one or more deposited and/or patterned layers. The term substrate can include circular disks and rectangular sheets.

Particular embodiments of the invention have been described. Other embodiments are within the scope of the following claims.