Patent Application
20140113533
The present disclosure relates to conditioning of polishing pads.
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.
In some conditioning systems with some polishing recipes, the pad conditioner, particularly the pad conditioner arm, will exhibit significant vibration. The vibration is detrimental to the arm can reduces the effectiveness of the conditioning process. In addition, this vibration is often audible, and in fact can be unacceptably loud. However, by placing a tuned mass damper on the base of the conditioner, vibrations can be significantly reduced or eliminated.
In one aspect, a conditioner apparatus for use in substrate polishing includes a conditioner head constructed to receive an end effector for conditioning a surface of a polishing pad, an arm that supports the conditioner head, a base that supports the arm, and a damper system secured to the base. The base includes an actuator connected to the arm to move the arm and the conditioner head laterally over the polishing pad. The damper system is configured to reduce vibration of the arm.
Implementations can include on or more of the following features. The actuator comprises may be a rotary actuator configured to sweep the arm over the polishing pad. The damper system may be secured to and rotate with the rotary actuator. The damper system may include a damper mass. The damper mass may be attached to the base by at least one damper. The at least one damper may be a layer of damping material. The damper mass may be attached to the base by a plurality of dampers. The plurality of dampers may include dashpots. The plurality of dampers may be arranged to define a primary axis parallel to an axis of a primary mode of vibration of the arm. The plurality of dampers may be are arranged to define a primary axis parallel to a longitudinal axis of the arm. The conditioner head may include a vertical actuator connected to the end effector to control a vertical position of the end effector. In another aspect, a non-transitory computer program product, tangibly embodied in a machine readable storage device, includes instructions to carry out the method.
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.
Like reference numbers and designations in the various drawings indicate like elements.
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, e.g., an IC-1000 material.
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
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. 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
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
Vertical motion of the end effector 170 and control of the pressure of conditioning disk 172 can be provided 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. Alternatively, 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 pivot connection between the arm 164 and the base 162 that permits a controllable angle of inclination of the arm 164 and thus height of the conditioner head 166 above the polishing pad 110.
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.
A controller 190 (see
The base 162 includes a rotary actuator 180 held on a support 182 that is secured to the frame. The arm 164 is affixed to the rotary actuator 180, and rotation of the actuator 180 causes the lateral sweep of the arm 162 across the polishing pad.
A damper system 190 is attached to the base 162 of the conditioner apparatus 160. For example, the damper system 190 can be attached to the rotary actuator 180. In this case, the damper system 190 can rotate with the actuator 180.
The damper system 190 includes a damper mass 192. The damper mass 192 is a heavy body, e.g., formed of metal. The mass of the damper 192 is selected to increase the stability threshold of the arm. A cover 184 can extend over the damper mass 192 to protect the damper mass 192 from slurry and other contaminants, e.g., to prevent corrosion.
The damper mass 192 can either be secured with a rigid connection to the base 162, e.g., by mechanical fasteners, or one or more dampers 194 can be positioned between the damper mass 192 and the base 162.
Each damper 194 can be a dashpot, e.g., a hydraulic or mechanical damper, or simply a layer of viscoelastic material.
Typically the primary mode of vibration is parallel to the longitudinal axis of the arm 164. Thus, the dampers 194 can be positioned to preferentially reduce vibration in this mode. As shown in
In general, if the damper mass 190 is secured with no or a minimal damping, the natural frequency of the arm 164 can be altered such that vibration of the conditioner arm 164 is significantly reduced. For example, of the conditioner apparatus 160 can run with an acceptable degree of vibration over a different consumable set and down force range. In general, if the damper mass 190 is connected to the base 162 by a sufficient damper 192, problem vibrations can be significantly reduced or effectively eliminated. Thus the use of the damper system 190 dramatically increases the range of applications the arm can be used under without causing any problem vibrations.
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.
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.
Embodiments of the invention and all of the functional operations described in this specification can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structural means disclosed in this specification and structural equivalents thereof, or in combinations of them. Embodiments of the invention can be implemented as one or more computer program products, i.e., one or more computer programs tangibly embodied in a non-transitory machine readable storage media, for execution by, or to control the operation of, data processing apparatus, e.g., a programmable processor, a computer, or multiple processors or computers.
Particular embodiments of the invention have been described. Other embodiments are within the scope of the following claims.
This application is a non-provisional of and claims priority to U.S. Provisional Patent Application No. 61/715,750, filed on Oct. 18, 2012, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61715750 | Oct 2012 | US |
