Patent Description:
Chemical mechanical polishing (CMP) is one of many processes used in the fabrication of high density integrated circuits. Chemical mechanical polishing is generally performed by moving a substrate against a polishing material in the presence of a polishing fluid. In many polishing applications, the polishing fluid contains an abrasive slurry to assist in the planarization of the feature side of the substrate that is pressed against the polishing material during processing.

The substrate is generally retained during polishing operations by a carrier head. Conventional carrier heads include a retaining ring that bounds a substrate retaining pocket. The substrate may be held in the substrate retaining pocket by stiction to a flexible membrane. The retaining ring prevents the substrate from slipping out from under the polishing head during polishing.

During polishing, the retaining ring is typically pressed against the polishing pad. A pressurizable chamber in the carrier head can control the vertical position of the retaining ring. The retaining ring is typically formed of a wearable material, and as polishing progresses, the bottom surface of the retaining ring is worn away. Consequently, the thickness of the retaining ring can change over the course of processing multiple substrates. Eventually the retaining ring may need to be replaced.

In addition, after the CMP process is performed for a certain period of time, the surface of the polishing pad can become glazed due to accumulation of slurry by-products and/or material removed from the substrate and/or the polishing pad. Glazing can reduce the polishing rate or increase non-uniformity on the substrate.

Typically, the polishing pad is maintained in with a desired surface roughness (and glazing is avoided) 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 disk generally embedded with diamond abrasives which can be scraped against the polishing pad surface to retexture the pad. However, the conditioning process also tends to wear the conditioner disk itself. Consequently, after a certain number of cycles of polishing and conditioning, the conditioner disk may need to be replaced.

Patent application <CIT> discloses a polishing apparatus including a polishing station and an abrasion control part for controlling a polishing process. A camera screen read station transmits a grinding stop signal based on a camera screen of an image pickup camera to the abrasion control part. Patent application <CIT>discloses a polishing system including a polisher. The polisher may include three polishing stations, each having a platen that supports a polishing material on which a substrate is processed. A conditioning mechanism is disposed proximate each polishing station and is adapted to dress or condition the polishing material disposed on each platen. The conditioning element is moved to a rinse station when not in use. The rinse station includes a body, one or more sensors, and a rinse nozzle. Patent application <CIT>relates to inspection processes used during a semiconductor manufacturing process and to defect review involving re-detection of defects detected by an inspection process and generation of additional information at a higher resolution.

<CIT> discloses a polishing apparatus comprising: a polishing table having a polishing surface; a top ring to hold a substrate and press the substrate against the polishing surface, the top ring including a retaining ring; a CCD camera positioned to image the inner circumferential surface of the retaining ring when the top ring moves away from the polishing table; wherein the top ring is movable between the polishing table and a substrate transfer position, and wherein the CCD camera is positioned to image the inner circumferential surface of the retaining ring at a location between the polishing table and the substrate transfer position; and an image processor processing an image obtained by the CCD camera to judge whether there is a foreign matter on the inner circumferential surface of the retaining ring.

A polishing apparatus according to the features of claim <NUM> and a polishing apparatus according to the features of claim <NUM> are provided.

Advantages of implementations can include one or more of the following. A retaining ring and/or conditioning disk of a chemical mechanical polishing system may be replaced before damage to such parts impacts the polishing process. This can reduce scratches and defects, and improve polishing uniformity.

<FIG> is a simplified side view, partially in section, of an implementation of a chemical mechanical polishing system.

In addition to general wear (e.g., thickness reduction) of consumable parts such as the retaining ring or conditioning disk, it is also possible for such consumable parts to be damaged in a manner that does not particularly change their thickness. For example, the inner surface of a retaining ring can be notched or cracked, which can introduce polishing non-uniformity. Similarly, abrasive particles on the conditioning disk can come loose, which can introduce non-uniformity into the conditioning process.

However, by placing a camera in the polishing system in a position to periodically scan the consumable part, it is possible to capture an image of the consumable part. This image can then be subject to image analysis software, e.g., an algorithm trained by a machine learning technique, to identify a damaged consumable part.

<FIG> depicts a partially sectional view of a simplified chemical mechanical polishing system <NUM> that includes a polishing station <NUM>, a carrier head <NUM> and a load cup <NUM>. The various components can be supported on a base <NUM>. Examples of suitable polishing systems which may be adapted to benefit from the invention include MIRRA™ and REFLEXION™ chemical mechanical polishing systems available from Applied Materials.

In one implementation, the polishing station <NUM> includes a rotatable platen <NUM> having a polishing pad <NUM> disposed thereon. The platen <NUM> is operable to rotate about an axis. For example, a motor <NUM> can turn a drive shaft to rotate the platen <NUM>.

The polishing pad <NUM> may be a conventional polyurethane polishing pad, a fixed abrasive material, or another pad suitable for chemical mechanical polishing. The polishing pad <NUM> can be a two-layer polishing pad with an outer polishing layer and a softer backing layer.

The polishing station <NUM> additionally includes a polishing liquid source <NUM> adapted to provide a polishing liquid to the working surface of the polishing pad <NUM> during processing. In the embodiment depicted in <FIG>, an arm <NUM> having at least one nozzle <NUM> is positioned to flow polishing fluid onto the polishing material <NUM> during processing. The polishing liquid can include abrasive particles, e.g., the polishing liquid can be a polishing slurry.

The polishing station <NUM> can also include a polishing pad conditioner <NUM> to abrade the polishing pad <NUM> to maintain the polishing pad <NUM> in a consistent abrasive state. The polishing pad conditioner <NUM> includes a conditioner base, an arm <NUM> that can sweep laterally over the polishing pad <NUM>, and a conditioner head <NUM> connected to the base by the arm <NUM>. The conditioner base can be supported on the polishing system machine base <NUM>. The conditioner head <NUM> brings an abrasive surface, e.g., a lower surface of a disk <NUM> held by the conditioner head <NUM>, into contact with the polishing pad <NUM> to condition it. The abrasive surface can be rotatable, and the pressure of the abrasive surface against the polishing pad can be controllable.

In some implementations, the arm <NUM> is pivotally attached to the conditioner base and sweeps back and forth to move the conditioner head <NUM> in an oscillatory sweeping motion across the polishing pad <NUM>. The motion of the conditioner head <NUM> can be synchronized with the motion of carrier head <NUM> to prevent collision. Vertical motion of the conditioner head <NUM> and control of the pressure of conditioning surface on the polishing pad <NUM> can be provided by a vertical actuator above or in the conditioner head <NUM>, e.g., a pressurizable chamber positioned to apply downward pressure to the conditioner head <NUM>, or by a vertical actuator in the base that lifts the entire arm <NUM> and conditioner head <NUM>, or by a pivot connection between the arm <NUM> and the base that permits a controllable angle of inclination of the arm <NUM> and thus height of the conditioner head <NUM> above the polishing pad <NUM>.

The polishing station <NUM> can also include a conditioner rinse cup <NUM> positioned to the side of the platen <NUM>. After a polishing operation, the arm <NUM> can swing around to place the conditioner head <NUM>, including the conditioner disk <NUM>, into the rinse cup <NUM>. The rinse cup <NUM> can include nozzles configured to spray the head <NUM> and disk <NUM> with a cleaning fluid, e.g., deionized water, to rinse off any debris, particulates or contamination.

The carrier head <NUM> is suspended from a support structure <NUM>, e.g., a carousel or a track, which can act as a transfer mechanism, that is coupled to the base <NUM>. The transfer mechanism is generally adapted to position the carrier head <NUM> selectively between a processing position over the polishing pad <NUM> and a transfer position over the load cup <NUM>. The carrier head <NUM> can be connected by a drive shaft to a carrier head drive mechanism <NUM>, e.g., a rotary motor, so that the carrier head <NUM> can rotate.

In operation, the platen is rotated about its central axis, and the carrier head <NUM> is rotated about its central axis and translated laterally across the top surface of the polishing pad <NUM>. Optionally, during polishing, the carrier head <NUM> can oscillate laterally, e.g., on sliders on the carousel or track; or by rotational oscillation of the carousel itself.

In the implementation depicted in <FIG>, the transfer mechanism <NUM> includes a stanchion <NUM> having a cantilevered arm <NUM> that may be rotated to laterally position the carrier head <NUM>. The carrier head <NUM> can be coupled to the arm <NUM> by the motor <NUM>. The elevation of the polishing head <NUM> relative to the base <NUM> can be controlled by the drive mechanism <NUM> or by a pressurizable chamber inside the carrier head <NUM>.

Generally, the polishing head <NUM> comprises a housing <NUM> and a retaining ring <NUM> secured near an edge of the housing, e.g., to a rim <NUM>, to retain the substrate within a recess <NUM> in the polishing head <NUM> during polishing. In some implementations, the carrier head <NUM> includes a flexible membrane <NUM>, behind which are a plurality of independently pressurizable chambers, which can apply different pressures to different radial zones of the substrate. For example, the carrier head can include a first chamber 152a to apply pressure to a central portion of the substrate and a second chamber 152b to apply pressure to an edge portion of the substrate. The chambers 152a, 152b are coupled to pressure sources <NUM> (only one is shown in <FIG> for simplicity) such that the chambers 152a, 152b can be independently controllably inflated or deflated.

In order to perform a transfer operation, the flexible membrane <NUM> can be brought in contact with the substrate, and one or more the chambers 152a, 152b can be deflated, thus creating a vacuum between the substrate and the flexible membrane and thereby securing the substrate on the carrier head <NUM>. In order to perform a polishing operation, one or more the chambers 152a, 152b can be inflated, thus pressing the substrate against the polishing pad <NUM>.

The vertical position of the retaining ring <NUM>, and the pressure of the retaining ring <NUM> against the polishing pad <NUM>, can also be adjustable, e.g., by the drive mechanism <NUM> or by another pressurizable chamber inside the carrier head <NUM>. Pressure in the pressurizable chamber inside the carrier head <NUM> that controls the vertical position of the retaining ring <NUM> can be controlled by the pressure source <NUM>.

The load cup <NUM> generally includes a pedestal assembly <NUM> and a cup <NUM>. The pedestal assembly <NUM> provides a structure that mates with the polishing head <NUM> to insure alignment therebetween during substrate transfer. The pedestal assembly <NUM> is generally extended to transfer the substrate to the polishing head <NUM> and retracts from the extended position to receive the substrate during the process of de-chucking.

A controller <NUM>, e.g., a programmed computer including a microprocessor, is configured to control the various components of the polishing system <NUM>. For example, the controller <NUM> can be coupled to the coupled to the motors <NUM>, <NUM> to control the rotational speeds of the carrier head <NUM> and platen <NUM> respectively, to pressure source <NUM> to control the pressure in the carrier head <NUM>, to an actuator that controls the positioning of the transfer device <NUM>, to actuators <NUM>, <NUM> to control operation of the load cup <NUM>, to actuators in the conditioner system <NUM> to control the position of the conditioner head <NUM> and down-force of the conditioner disk <NUM> on the polishing pad <NUM>, to the polishing liquid supply <NUM> to control the flow rate of the polishing liquid onto the polishing pad, and/or to the conditioner rinse disk <NUM> to control operation of nozzles to spray cleaning fluid on the conditioner head <NUM>.

Although the controller <NUM> is illustrated as a single part, the controller <NUM> can be a distributed across multiple processing components connected a computer network.

As noted above, it is possible for consumable parts, e.g., the retaining ring <NUM> and/or the conditioner disk <NUM>, to be damaged or overly worn. The polishing system <NUM> also includes a consumable part monitoring system to detect whether the consumable parts are damaged.

In particular, the polishing system <NUM> includes one or more cameras <NUM> positioned to capture an image of the underside of a consumable part. Each camera can be positioned in a spot in a path where the consumable part is be carried. For example, a camera to monitor the retaining ring can be positioned on a path that the carrier head travels between the platen <NUM> and the load cup <NUM>. Similarly, a camera to monitor the conditioner disk can be positioned on a path that the conditioner head travels between the platen <NUM> and the rinse cup <NUM>. Each camera can have a field of view (indicated by the broken lines) through which the consumable part travels.

As one example, a camera 200a can be positioned on the base <NUM> adjacent the platen <NUM>. This camera 200a can capture of an image of the underside of the retaining ring <NUM> as the carrier head <NUM> moves from the polishing station <NUM> to the load cup <NUM>, or vice versa.

As another example, a camera 200b can be positioned on the base <NUM> adjacent the load cup <NUM>. This camera 200b can capture of an image of the underside of the retaining ring <NUM> as the carrier head <NUM> moves from the polishing station <NUM> to the load cup <NUM>, or vice versa.

As another example, a camera 200c can be positioned on the base <NUM> adjacent the rinse cup <NUM>. This camera 200c can capture of an image of the underside of the conditioner disk <NUM> as the conditioner head <NUM> moves from the polishing station <NUM> to the rinse cup <NUM>, or vice versa.

In some implementations, the field of view is sufficiently wide that the entire underside of the consumable part can be captured in a single image. In some implementations, the field of view does not cover the entire underside of the consumable part, and multiple images are taken by the camera as the consumable part moves through the field of view; the multiple images include the entire underside of the part. Optionally, these multiple images can be stitched together to form a single image that covers the entire underside of the consumable part. This image stitching can be performed using known image processing techniques.

The image from the camera <NUM> is subject to an image processing algorithm run by software in the controller <NUM> to determine whether there is damage to the consumable part. For example, the image processing program can be configured to detect cracks or chips in an inner edge of the lower surface of the retaining ring <NUM> from the image. As another example, the image processing program can be configured to stains, scratches or unusual surface texture on the lower surface of the retaining ring <NUM> from the image. As another example, the image processing program can be configured to detect missing abrasive particles, or patterns of wear or stains, in the lower surface of the conditioner disk <NUM> from the image.

In some implementations, if the controller <NUM> detects a damaged consumable part, it can signal an operator that replacement is needed. Alternatively, if the controller <NUM> detects a damaged consumable part, it may be able to adjust an operating parameter of another component in the polishing system to compensate for non-uniformity introduced by the damage.

In some implementations, the image processing algorithm can be generated by training a machine learning system. For example, the machine learning system can be trained with images of normal and "defective" consumable parts. The image processing algorithm can be implemented as a generic neural network. For example, the neural network can be a convolutional neural network or a fully connected neural network. The training can be performed by operating in a backpropagation mode.

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 an information carrier, e.g., in a non-transitory machine readable storage medium or in a propagated signal, for execution by, or to control the operation of, data processing apparatus, e.g., a programmable processor, a computer, or multiple processors or computers. A computer program (also known as a program, software, software application, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A program can be stored in a portion of a file that holds other programs or data, in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code).

Claim 1:
A polishing apparatus, comprising:
a polishing station (<NUM>);
a carrier head (<NUM>) to hold a substrate in contact with a polishing pad (<NUM>) at the polishing station (<NUM>), the carrier head (<NUM>) including a retaining ring (<NUM>);
a camera (200a, 200b, 200c) positioned to capture an image of a lower surface of the retaining ring (<NUM>) when the carrier head (<NUM>) moves away from the polishing pad (<NUM>); and
a substrate transfer station to load and/or unload the substrate from the carrier head (<NUM>), wherein the carrier head (<NUM>) is movable between the polishing station (<NUM>) and the transfer station, and wherein the camera (200a, 200b, 200c) is positioned to capture the image of the lower surface of the retaining ring (<NUM>) at a position between the polishing station (<NUM>) and the transfer station;
a controller (<NUM>) configured to perform an image processing algorithm generated by training a machine learning system with images of normal and "defective" consumable parts on the image to determine whether the retaining ring (<NUM>) is damaged, the image processing algorithm being implemented as a generic neural network, wherein the training is performed by operating in a backpropagation mode.