KR100827871B1 - In-situ endpoint detection and process monitoring method and apparatus for chemical mechanical polishing - Google Patents

Abstract

A chemical mechanical polishing apparatus has a polishing pad (30), a carrier (70) to hold a substrate (10) against a first side of the polishing surface, and a motor coupled to at least one of the polishing pad (30) and carrier head (70) for generating relative motion therebetween. An eddy current monitoring system (40) is positioned to generate an alternating magnetic field in proximity to the substrate (10), an optical monitoring system (140) generates a light beam and detects reflections of the light beam from the substrate (10), and a controller (90) receives signals from the eddy current monitoring system (40) and the optical monitoring system (140).

Description

IN-SITU ENDPOINT DETECTION AND PROCESS MONITORING METHOD AND APPARATUS FOR CHEMICAL MECHANICAL POLISHING}

The present invention broadly relates to chemical mechanical polishing of substrates, and more particularly to methods and apparatus for monitoring metal layers during chemical mechanical polishing.

Integrated circuits are typically formed by continuously depositing a conductive layer, a semiconductor layer, or an insulating layer on a substrate. In one step of the manufacturing process, a filler layer is deposited on an uneven surface and the filler layer is polished until a flat layer appears. For example, the conductive filler layer is deposited on the patterned insulating layer to form holes or trenches in the insulating layer. The filler layer is then polished until the raised pattern of the insulating layer is exposed. After planarization, some of the conductive layer remaining between the raised portions of the insulating layer forms vias, plugs, and lines, which provide conductive paths between thin circuits on the substrate. Furthermore, planarization is also necessary to planarize the substrate surface for photolithography.

Chemical mechanical polishing (CMP) is one of the methods employed for planarization. This planarization method usually requires the substrate to be mounted on a carrier or polishing head. The exposed surface of the substrate lies against the rotating polishing disk pad or belt pad. The polishing pad can be a "standard" pad or a fixed-abrasive pad. Standard pads have a durable rough surface, while fixed abrasive pads have abrasive particles that are supported in containment media. The carrier head provides a controllable load to the substrate to press the substrate against the polishing pad. If a standard pad is used, a polishing slurry comprising abrasive particles and at least one chemically-reactive agent is supplied to the polishing pad surface.

One problem with CMP is to determine if the polishing process is finished, i.e., if the substrate layer has been planarized to the desired flatness or thickness, or when the desired amount of material has been removed. Overpolishing (removing too much) the conductive layer or film can result in high circuit resistance. Conversely, under-polishing (too little removal) of the conductive layer can result in electrical shorting. As the initial thickness of the substrate layer, the slurry composition, the state of the polishing pad, the relative speed of the polishing pad and the substrate, and the load on the substrate change, the time required to reach the polishing endpoint may change. Therefore, the polishing endpoint should not simply be determined as a function of polishing time.

There is a method of removing and inspecting a substrate from the polishing surface to measure the polishing endpoint. For example, the substrate is transferred to a metrology station, where the thickness of the substrate layer can be measured, for example, by profilometer or resistivity measurement. If the required specifications are not achieved, the substrate is remounted in the CMP apparatus for further processing. This consumes significant time and lowers the efficiency of the CMP device. In contrast, if the inspection reveals that an excessive amount of material has been removed, the substrate is unruly.

More recently, polishing endpoints have been detected by in-situ monitoring the substrate with, for example, optical or capacitive sensors. Other proposed endpoint detection techniques relate to friction, motor current, chemical composition of the slurry, acoustic or conductivity, and the like. One detection method that is considered is the flow of vortices in the metal layer and measuring the change in the vortex as the metal layer is removed.

Another problem arising in CMP processing is dishing of the substrate surface when polishing the filler layer exposed to the underlying layer. Specifically, once the bottom layer is exposed, portions of the filler layer located between the raised portions of the patterned bottom layer may be overpolished to form recesses in the substrate surface. Dicing occurs, the substrate becomes unsuitable for integrated circuit fabrication, resulting in low process yield.

One feature of the present invention is a sensor for monitoring a conductive film in a substrate. The sensor includes a core, which may be located near the substrate, an oscillator electrically coupled to the first coil to induce alternating current in the first coil and generating an alternating magnetic field near the substrate, and a second winding around the second portion of the core. It includes a coil. The capacitor is electrically coupled to the second coil, and the amplifier is electrically coupled to the second coil and the capacitor to produce an output signal.

Embodiments of the present invention include one or more of the following features. The oscillator includes an alternating current whose frequency is selected to provide a resonant frequency when the substrate is not near the core. The core may consist of ferrite as an essential component and may comprise two prongs and a connection between these prongs. The first coil may be wound around the connection and the second coil may be wound around at least one of the two branches. The second coil and the capacitor can be connected in parallel. The sensor may be located on the polishing pad opposite the substrate. The polishing pad may include an upper layer and a lower layer, and apertures may be formed in at least a portion of the lower layer adjacent to the core. The computer can receive the output signal.

Another feature of the invention resides in a chemical mechanical polishing apparatus. The apparatus includes a polishing pad, a carrier for holding the substrate relative to the first side of the polishing side, a vortex sensor, and a motor coupled to the at least one polishing pad and the carrier head to generate relative motion therebetween. The sensor is coupled to at least one inductor opposite the substrate, the at least one inductor located on the second side of the polishing pad, an oscillator electrically coupled to the at least one inductor to induce current in the coil and generate an alternating magnetic field, and at least one inductor. It includes a capacitor.

The present invention may include one or more of the following features. The platen may support the polishing pad and at least one inductor may be located in a recess in the platen top surface. The platen can rotate, and the position sensor determines each position of the platen and controller, sampling data from the vortex when at least one inductor is located near the substrate. The recess may be formed in the second side of the polishing pad. The polishing pad can include a cover layer on its first face and a backing layer on its second face, and the recess can be formed by removing a portion of the support layer. The eddy current sensor may comprise a core having two poles located adjacent to a recess in the polishing pad, wherein at least one inductor is wound around the first portion of the core. The eddy current sensor may comprise a core and the at least one inductor may comprise a first inductor wound around a first portion of the core and a second inductor wound around a second portion of the core. The oscillator may be electrically coupled to the first coil to induce alternating current in the first coil. The capacitor may be electrically coupled to the second coil. The oscillator may induce alternating current at a frequency selected to provide a resonant frequency when the substrate is not near the core. An endpoint detection device may receive an output signal from the eddy current sensor. The endpoint detection device may be configured to signal a polishing endpoint if the output signal exceeds a predetermined threshold.

In another aspect, the present invention may relate to a method of monitoring the thickness of a conductive layer on a substrate during a polishing operation. In this method, an alternating magnetic field is generated from an inductor located on the first side of the polishing side and located on the second side of the polishing side opposite the substrate. This magnetic field extends through the polishing surface to induce vortices in the conductive layer. The change in the alternating magnetic field due to the change in the conductive layer thickness is detected.

The practice of the present invention may include one or more of the following features. The first coil may be driven at the first frequency with an oscillator. This first frequency may be the resonance frequency when the substrate is not near the magnetic field. The alternating magnetic field may be sensed by the second coil. The second coil may be connected in parallel with the capacitor. The first coil may be wound around the first portion of the core while the second coil may be wound around the second portion of the core. It can be determined when the inductor is adjacent to the substrate. The inductor can be driven by the first signal and a second signal can be generated from the alternating magnetic field. The change in the amplitude of the second signal can be determined. A change in phase difference between the first signal and the second signal may be determined.

In another aspect, the present invention relates to a chemical mechanical polishing method. In this method, a substrate having a conductive layer is located at the first side of the polishing surface. An alternating magnetic field is generated from the inductor located at the second edge opposite the substrate of the polishing surface. This magnetic field extends through the polishing surface to induce eddy currents in the conductive layer. Relative motion occurs between the substrate and the polishing surface to polish the conductive layer. Vortex in the substrate is sensed and polishing stops when the sensed vortex indicates an endpoint criteria.

The practice of the present invention may include one or more of the following features. The endpoint criterion may be a vortex beyond or equal to the threshold intensity.

In another aspect, the present invention relates to a chemical mechanical polishing apparatus. Such a device has a polishing pad with a polishing surface, a carrier supporting a substrate with respect to the polishing surface, a motor coupled to at least one of the polishing pad and the carrier head to generate relative motion, and a conductive layer thickness monitoring device. Such a conductive layer thickness monitoring device includes at least one inductor, a current source generating a drive signal and coupled to the at least one inductor to induce alternating current in the at least one inductor and to generate an alternating magnetic field; A sensing circuit comprising a capacitor electrically coupled to sense an alternating magnetic field and generating a sense signal, and a phase comparison circuit coupled to the current source and the sense circuit to measure a phase difference between the sense signal and the drive signal.

The practice of the present invention may include one or more of the following features. At least one first gate, such as an XOR gate, may convert sinusoidal signals from the inductor and oscillator into first and second square-wave signals. A comparator, such as an XOR gate, may compare the first square wave signal with the second square wave signal to generate a third square wave signal. A filter may convert the third square wave signal into a differential signal having an amplitude proportional to the phase difference between the first and second square wave signals. The phase comparison circuit may generate a signal having a duty cycle proportional to the phase difference.

In another aspect, the present invention may relate to a method of monitoring the thickness of a conductive layer on a substrate in a chemical mechanical polishing operation. In this method, the coil is powered by the first signal to create an alternating magnetic field. The alternating magnetic field induces vortices in the conductive layer of the substrate. The alternating magnetic field is measured and a second signal representing the magnetic field is generated. The first and second signals are compared to determine the phase difference therebetween.

In another aspect, the present invention relates to a chemical mechanical polishing apparatus. The apparatus includes a polishing pad, a carrier for supporting the substrate with respect to the first edge of the polishing surface, a vortex monitoring device positioned to generate an alternating magnetic field in the vicinity of the substrate, and an optical for generating the light beam and detecting the reflection of the light beam from the substrate. A monitoring device, a controller for receiving signals from the eddy current monitoring device and the optical monitoring device, and a motor coupled to at least one of the polishing pad and the carrier head to generate relative motion therebetween.

The practice of the present invention may include one or more of the following features. The eddy current monitoring device can include an inductor located at a second edge opposite the substrate of the polishing pad. This inductor may be located in a first cavity in a platen under the polishing pad. The optical monitoring device may include a light source and a photodetector located at a second edge opposite the substrate of the polishing pad. The light source and photodetector may be located within the first cavity in the platen or within the second cavity under the polishing pad. The vortex monitoring device and the optical monitoring device can be positioned to monitor almost the same radial position on the substrate. The controller may be configured to detect endpoint references in signals from both the eddy current monitoring device and the optical monitoring device.

In another aspect, the present invention relates to a chemical mechanical polishing method. In this method, the substrate is positioned at the first edge of the polishing surface, relative motion is generated between the substrate and the polishing surface to polish the substrate, a first signal is generated from the eddy current monitoring device, and the second from the optical monitoring device. A signal is generated and the first and second signals are monitored for endpoint criteria.

The practice of the present invention may include one or more of the following features. Polishing may be stopped when an endpoint reference is detected in both the first and second signals, or when an endpoint reference is detected in either of the first and second signals. The substrate may comprise a metal layer, and the step of monitoring may include monitoring the signal from the eddy current monitoring device until the metal layer reaches a predetermined thickness, and then monitoring the signal from the optical monitoring device.

In another aspect, the present invention provides a method for chemical mechanical polishing of a metal layer on a substrate. The substrate is polished from the first polishing station to the first polishing face at a first polishing rate. Polishing at the first polishing station is monitored with an eddy current monitoring system, and then the substrate is transferred to the second polishing station when the vortex monitoring system indicates that a metal layer of a predetermined thickness remains on the substrate. . The substrate is polished from the second polishing station to the second polishing face at a second polishing rate slower than the first polishing rate. Polishing is monitored at the second polishing station with an optical monitoring system, where the polishing is stopped if the optical monitoring system indicates that the first underlying layer has been at least partially exposed.

The practice of the present invention may include one or more of the following features. The first lower layer may be a barrier layer. The substrate may be transferred to a third polishing station and polished to the third polishing surface. Polishing at the third polishing station may be monitored with a second optical monitoring system, and polishing may be stopped if the second optical monitoring system indicates that the second underlayer has been at least partially exposed. Polishing at the third polishing station may continue until the second underlayer is almost entirely exposed. Polishing at the second polishing station may continue until the first underlayer is almost entirely exposed. Polishing the substrate at the second polishing station may include an initial polishing step at a higher pressure than the remaining polishing at the second polishing station.

In another aspect, the present invention provides a method for chemical mechanical polishing of a metal layer on a substrate. The substrate is polished from the first polishing station to the first polishing face at a first polishing rate. Polishing at the first polishing station is monitored with a vortex monitoring system, and the polishing rate at the first polishing station is reduced when the vortex monitoring system indicates that a metal layer of a predetermined thickness remains on the substrate. Polling at the first polishing station is monitored by the optical monitoring system and polishing is stopped when the optical monitoring system indicates that the first underlayer is at least partially exposed.

The practice of the present invention may include one or more of the following features. The first lower layer may be a boundary layer. The substrate may be transferred to a second polishing station and polished to the second polishing side. Polishing at the second polishing station may be monitored with a second optical monitoring system and polishing may be stopped if the second optical monitoring system indicates that the second underlayer is at least partially exposed. The substrate may be transferred to a third polishing station and buffed to a buffing surface. Polishing at the second polishing station may continue until the first underlayer is exposed almost entirely.

In another aspect, the present invention provides a method for chemical mechanical polishing of a metal layer on a substrate on which the substrate is polished at a first polishing rate. Polishing is monitored with a vortex monitoring system and the polishing rate is reduced when the vortex monitoring system indicates that a metal layer of a predetermined thickness remains on the substrate. Polishing is monitored with an optical monitoring system, and polishing is stopped when the optical monitoring system indicates that the underlying layer is at least partially exposed.

Possible advantages of embodiments of the present invention may include one or more of the following. During bulk polishing of the metal layer, the pressure profile applied by the carrier head may be adjusted to compensate for the non-uniform thickness and non-uniform polishing rate of the inlet substrate. In addition, the polishing monitoring system can detect the polishing endpoint of the metal layer in place. Moreover, the polishing monitoring system can determine the point at which the polishing apparatus switches the polishing parameters. For example, a polishing monitoring system may be used to trigger to slow down the polishing rate while polishing the metal layer prior to the polishing endpoint. Polishing can be stopped with high precision. Overpolishing and underpolishing, such as dishing and erosion, may be reduced, thereby improving yield and throughput.

Other features and advantages of the invention will be apparent from the following description, including the drawings and the claims.

1 shows an exploded schematic perspective view of a chemical mechanical polishing apparatus,

2 shows a schematic cross sectional view of a carrier head,

3 shows a schematic side view, partially in cross section, of a chemical mechanical polishing station including a vortex monitoring system and an optical monitoring system,

4A-4E show a schematic plan view of the platen from the polishing station of FIG. 3,

delete

5 shows a schematic cross sectional view showing a magnetic field generated by the vortex monitoring system,

6 shows a schematic perspective view of the core from the vortex sensor,

7A-7D schematically illustrate a polishing endpoint sensing method using a vortex sensor,

8 shows a graph showing amplitude traces from a vortex monitoring system,

9A and 9B show schematic circuit diagrams of a vortex monitoring system,

10 shows a graph showing a phase transition trace from a vortex monitoring system,

11 shows a graph representing an amplitude trace from an optical monitoring system,                 

12 is a flowchart illustrating a method of polishing a metal layer,

13 is a flow diagram illustrating an alternative method of polishing a metal layer,

14 shows a schematic side view with a partially cross-sectional view of a chemical mechanical polishing station including a vortex monitoring system,

15A-15B show a schematic cross sectional view of a polishing pad.

Referring to FIG. 1, one or more substrates 10 may be polished by the CMP apparatus 20. A description of a similar polishing apparatus 20 can be found in US Pat. No. 5,738,574, the entire specification of which is hereafter referred to. The polishing apparatus 20 includes a series of polishing stations 22a, 22b, and 22c and a transfer station 23. The transfer station 23 transfers the substrate between the carrier head and the loading device.

Each polishing station includes a rotatable platen 24, on which a polishing pad 30 is disposed. The first station 22a and the second station 22b may comprise two layers of polishing pads having a hard durable outer surface or a fixed-wear pad having embedded abrasive particles. have. The final polishing station 22c may include relatively soft pads or two layer pads. Each polishing station may include a pad conditioner device 28 to maintain the conditions of the polishing pad to effectively polish the substrate.

Referring to FIG. 3, a two-layer polishing pad 30 typically has a backing layer 32, which is the surface and covering layer 24 of the platen 24. In contact with, the cover layer is used to polish the substrate 10. Cover layer 34 is typically harder than back layer 32. However, some pads have only a cover layer and no back layer. The cover layer 34 may be composed of polyurethane foamed or cast, such as hollow microspheres and / or grooved surfaces, possibly with filler. The back layer 32 may be composed of compressed felt fibers leached with urethane. Polishing pads with two layers of cover layer consisting of IC-1000 and back layer consisting of SUBA-4 are available from Rodel, Inc., Newark, Delaware (IC-1000 and SUBA-). 4 is a product name of Rodel, Inc.).

During the polishing step, a liquid (eg deionized water for oxide polishing) and a pH adjuster (eg potassium hydroxide for oxidative polishing) are included. Slurry 38 may be supplied to the surface of polishing pad 30 by slurry supply port or slurry / rinse arm 39. When the polishing pad 30 is a conventional pad, the slurry 38 may include abrasive particles (eg, silicon dioxide for oxidative polishing).

Returning to FIG. 1, a rotatable multi-head carousel 60 supports four carrier heads 70. The carousel is rotated by a carousel motor assembly (not shown) about the carousel shaft 64 through the center post 62 to pivot the carrier head system and to the polishing station 22 and the delivery station 23. Rotate the substrate attached in between. Three carrier head systems receive and hold substrates and polish them by pressing them against a polishing pad. On the other hand, one carrier head system receives the substrate from the delivery station 23 and delivers the substrate to the delivery station 23.

Each carrier head 70 is connected to a carrier head rotary motor 76 (shown with a quarter of the lid 68 removed) by a carrier drive shaft 74, so that each carrier head is adapted to its own axis. Can be rotated independently from the center. In addition, each carrier head 70 vibrates laterally independently in a radial slot 72 formed in the carousel support plate 66. Techniques for suitable carrier heads 70 can be found in US Patent Application Nos. 09 / 470,820 and 09 / 535,575, filed December 23, 1999 and March 27, 2000, which are incorporated herein by reference. . In operation, the platen is rotated about its central axis 25, and the carrier head rotates about its central axis 71 and translates transversely across the surface of the polishing pad.

As described in the foregoing patent application specification and shown in FIG. 2, the exemplary carrier head 70 may include a housing 202, a base assembly 204, a gimbal (which may be considered as part of the base assembly 204). Three pressable chambers, such as the instrument 206, the loading chamber 208, the retaining ring 210, and the floating upper chamber 236, the floating lower chamber 234, and the outer chamber 238. Substrate rear assembly 212. The loading chamber 208 is positioned between the housing 202 and the base assembly 204 to apply a load and control the vertical position of the base assembly 204. A first pressure regulator (not shown) is fluidly connected to the loading chamber by passage 232 to control the pressure of the loading chamber and the vertical position of the base assembly 204.

Substrate back assembly 212 includes flexible inner film 216, flexible outer film 218, inner support structure 220, outer support structure 230, inner spacer ring 222, and outer spacer ring 232. It includes. Flexible outer film 216 includes a central portion that applies pressure to wafer 10 in a controllable region. The volume between the inner membrane 216 and the base assembly 204 sealed by the inner flap 244 provides a pressurizable floating lower chamber 234. The annular volume between the inner membrane 216 and the base assembly 204 sealed by the inner flap 244 and the outer flap 246 forms a pressurized floating upper chamber 236. The sealed volume between the inner membrane 216 and the outer membrane 218 forms a pressurizable outer chamber 238. Three pressure regulators (not shown) are independently connected to the floating lower chamber 234, the floating upper chamber 236, and the outer chamber 238. Thus, a fluid such as a gas can be directed so that it can flow out or flow into each chamber independently.

The pressure and contact area of the inner membrane 216 against the top surface of the outer membrane 218 is controlled by combining the pressures inside the floating upper chamber 236, the floating lower chamber 234 and the outer chamber 238. . For example, by pumping the fluid in the floating upper chamber 236 to the outside, the edge of the inner membrane 216 is lifted from the outer membrane 218, so that the contact diameter D _c of the contact region between the inner membrane and the outer membrane Decrease). Conversely, by pumping the fluid in the floating upper chamber 236 inwards, the edge of the inner membrane 216 is lowered toward the outer membrane 218 to increase the contact diameter D _c of the contact region. In addition, the pressure of the inner membrane 216 against the outer membrane 218 is controlled by pumping fluid into and out of the floating lower chamber 234. However, the diameter of the area where the carrier head is loaded and the pressure therein are not controlled.

Referring to FIG. 3, a recess 26 is formed in the platen 24 and a transparent portion 36 is formed in the polishing pad 30 overlying the recess. The hole 26 and the transparent portion 36 are positioned to pass under the substrate 10 during a portion of the platen's rotation regardless of the translational position of the carrier head. Assuming the polishing pad 32 is a two-layer pad, a thin pad portion 36 can be constructed by removing a portion of the back layer 32 and inserting a transparent plug 36 inside the cover layer 34. . Plug 36 may be a fairly pure polymer or polyurethane that may be formed, for example, without filler. In general, the material of the transparent portion 36 should be non-magnetic and geo-conductive.

3 and 4A-4E, the first polishing station 22a includes an in-situ vortex monitoring system 40 and an optical monitoring system 140. Vortex monitoring system 40 and optical monitoring system 140 may serve as a polishing process control and endpoint detection system. The second polishing station 22b and the final polishing station 22c both comprise an optical monitoring system, but the vortex monitoring system may further comprise only one station.

Vortex monitoring system 40 includes a drive system 48 for inducing vortices in the metal layer of the substrate and a sensing system 58 for detecting vortices induced in the metal layer by the drive system. The monitoring system 40 includes a core located inside a recess 26 that rotates with the platen, a drive coil 44 wound around one portion of the core 42, and a sensing wound around the other portion of the core 42. Coil 46. For drive system 48, monitoring system 40 includes an oscillator 50 coupled to drive coil 44. For the sensing system 58, the monitoring system 40 includes a capacitor 52 connected in parallel to the sense coil 46, an RF amplifier 54 connected to the sense coil 46, and a diode 56. The oscillator 50, the capacitor 52, the RF amplifier 54, and the diode may be located away from the platen 24 and may be connected with components in the platen via a rotating electrical union 29.

Referring to FIG. 5, in operation, the oscillator 50 drives the drive coil 44 to generate a vibrating magnetic field 48 that extends between the two poles 42a and 42b of the core through the body of the core 42. . At least a portion of the magnetic field 48 extends into the substrate 10 through the thin portion 36 of the polishing pad 30. If the metal layer 12 is present on the substrate, the vibrating magnetic field 48 generates a vortex in the metal layer 12. Vortex causes metal layer 12 to act as an impedance source in parallel with sense coil 46 and capacitor 52. As the thickness of the metal layer changes, so does the impedance, which results in a change in the Q-factor of the sensing mechanism. By detecting a change in the cue-factor of the sensing mechanism, the eddy current sensor detects a change in the eddy current intensity to detect a change in thickness of the metal layer 12.

Referring to FIG. 6, the core 42 may be a U-shaped body formed of a non-conductive material having a fairly high permeability (eg, about 2500). In particular, the core 42 may be ferrite. In one embodiment, the two poles 42a and 42b are about 0.6 inches apart, the core has a depth of about 0.6 inches, and the cross section of the core is a square with about 0.2 inches on one side.

Generally, the in-situ eddy current monitoring system 40 is configured to have a resonant frequency of about 50 Hz to about 10 MHz, for example 2 MHz. For example, sense coil 46 may have an inductance of about 0.3-30 μH and capacitor 52 may have a capacitance of about 0.2-20 mA. The drive coil can be designed to tune the drive signal from the oscillator. For example, if the oscillator has a low voltage and low impedance, the drive coil may have only a few turns to provide low impedance. On the other hand, if the oscillator has a high voltage and a high impedance, the drive coil may have more winding counts to provide a large impedance.

In one embodiment, the sense coil 46 has nine turns around each branch of the core and the drive coil 44 has two turns around the base of the core and the oscillator has a magnitude of about 0.1 to 5.0 V. The furnace driving coil 44 is driven. In addition, in one embodiment, sense coil 46 has an impedance of about 2.8 μH, capacitor 52 has a capacitance of about 2.2 Hz, and a resonance frequency is about 2 MHz. In another embodiment, the sense coil has an impedance of about 3 μH and the capacitor 52 has a capacitance of about 400 pF. Of course, these values are merely exemplary values that are highly sensitive to the exact winding shape, the composition and shape of the core, and the size of the capacitor.

In general, the greater the expected initial thickness of the conductive film, the lower the predetermined resonance frequency. For example, in the case of a fairly thin thickness, for example 2000 kHz, the capacitance and inductance can be chosen to have a fairly high resonance frequency, for example about 2 MHz. On the other hand, in the case of a fairly low thickness, for example 20000 Hz, the capacitance and inductance can be chosen to have a fairly low resonance frequency, for example about 50 Hz. However, high resonance frequencies can still work well for thick copper layers. In addition, very high frequencies (above 2 MHz) can be used to reduce background noise from metal parts of the carrier head.

First, referring to FIGS. 3, 4A-4E and 7A, the oscillator 50 is rotated to the resonant frequency of the LC circuit without the presence of any substrate prior to guiding polishing. This resonant frequency maximizes the output signal from the RF amplifier 54.

As shown in FIGS. 7B and 8, the substrate 10 is placed in contact with the polishing pad 30 for a polishing operation. Substrate 10 may include a silicon wafer 12 and a conductive layer 16, the conductive layer being a metal layer such as copper arranged over one or more patterned underlying layers 14, which may be semiconductor conductors or insulators. . Barrier layer 18, such as titanium or titanium nitride, may separate the metal layer from the underlying dielectric. Patterned underlayers may include metal features such as, for example, biases, pads, and interconnects. Since the large conductive layer 16 is initially quite thick and continuous before polishing, a low resistance and fairly strong vortex can be generated in the conductive layer. As mentioned above, the vortex acts as an impedance source in parallel with the sense coil 46 and the capacitor 52. Thus, the presence of the conductive film 16 reduces the cue-factor of the sensor circuit, thereby significantly reducing the signal magnitude from the RF amplifier 56.

7C and 8, as the substrate 10 is polished, the bulk portion of the conductive layer 16 is thinned. As the conductive layer 16 becomes thinner, the sheet resistance increases and the vortices in the metal layer cancel out. Thus, the coupling between the metal layer 16 and the sensor circuit 58 is reduced (ie, increases the resistance of the actual impedance source). As the coupling decreases, the cue factor of the sensor circuit 58 increases toward its original value.

7D and 8, the bulk portion of the conductive layer 16 is finally removed leaving a conductive interconnect 16 ′ in the trench between the patterned insulating layer 14. At this point, the coupling between the sensor circuit 58 and the conductive portion in a generally small, generally continuous substrate is minimized. Thus, the cue-factor of the sensor circuit reaches its maximum (though not as large as the cue-factor when the substrate is entirely absent). This amplifies the output signal from the sensor circuit to the platen.

As such, the computer 90 can detect the polishing endpoint by detecting when the amplification of the output signal no longer increases and reaches a level off (eg, local plateau). Alternatively, by polishing one or more test substrates, the operator of the polishing machine can determine the magnitude of the output signal as a function of the thickness of the metal layer. Thus, the endpoint detector can stop polishing when a certain thickness of the metal layer is maintained on the substrate. In particular, the computer 90 may adjust the endpoint when the output signal from the amplifier exceeds a voltage threshold corresponding to a predetermined thickness. Alternatively, a vortex monitoring system can also be used to adjust for changes in polishing parameters. For example, when a monitoring system detects a polishing condition, the CMP apparatus can change the composition of the slurry (eg, from a high selectivity slurry to a low selectivity slurry). In another embodiment, the CMP apparatus can change the pressure profile applied to the carrier head as described below.

Referring to FIG. 9A, in addition to the detection of a magnitude change, the eddy current monitoring system may include a phase displacement sensor 94 for calculating the phase displacement in the sensed signal. As the metal layer is polished the phase of the sensed signal changes with respect to the drive signal from the oscillator 50. This retardation can be corrected for the thickness of the polished layer.

An embodiment of the magnitude and phase shift portions of the vortex monitoring system is shown in FIG. 9B. In this embodiment, as shown in Fig. 9B, the drive and sensor signals are combined to generate a phase shift signal having a duty cycle or pulse width proportional to the phase difference. In this embodiment two XOR gates 100 and 102 are used to convert the sinusoidal signals from each of sense coil 46 and oscillator 50 into square wave signals. Two square wave signals are supplied to the input side of the third XOR gate 104. The output of the third XOR gate 104 is a phase shift signal having a pulse width and a duty cycle proportional to the phase difference between two square wave signals. The phase shift signal is filtered by an RC filter to generate a DC type signal having a voltage proportional to the phase difference. Alternatively, the signal is fed into a programmable digital logic, such as a complex programmable logic device (CPLD) or field programmable gate array (FGPA) that performs phase shift measurements. Another embodiment of the size sensing of the vortex monitoring system is shown in FIG. 9C. An example of a trace generated by the eddy current monitoring system measuring the phase difference between the drive and sense signals is shown in FIG. 10. Since phase measurements are quite sensitive to drive frequency, phase locked loop electronics can be added.

A potential advantage of phase measurements is that the dependence of the phase difference on the metal layer thickness is more linear than the dependency of size. In addition, the absolute thickness of the metal layer can be determined for a range of possible thicknesses of the thickness.

Referring to FIG. 3, an optical monitoring system 140, which may function as a reflectometer or interferometer, may be secured relative to the platen 24 in the recess 26 adjacent to the vortex monitoring system 40. Thus, the optical monitoring system 140 can measure the reflectance for a location on the substrate that is about the same as when monitored by the vortex monitoring system 40. In particular, the optical monitoring system 140 may be positioned to measure the substrate portion at the same distance as the vortex monitoring system 40 from the axis of rotation of the platen 24. Thus, the optical monitoring system 140 can pass through the substrate in the same passageway as the vortex monitoring system 40.

Optical monitoring system 140 includes a light source 144 and a detector 146. The light source generates a light beam 142 that propagates through the transparent window 36 and the slurry so as to collide with the exposed surface of the substrate 10. For example, light source 144 may be a laser and light beam 142 may be an aimed laser beam. The optical laser beam 142 may be projected from the laser 144 to be angled from an axis perpendicular to the surface of the substrate 10. Also, if the aperture 26 and the window 36 are long, a beam enlarger (not shown) may be located within the path of the light beam to enlarge the light beam along the long axis of the window. In general, the optical monitoring system serves as described in US Patent Application No. 09 / 184,767 and US Patent No. 6,159,073, filed November 2, 1998, the entire contents of which are incorporated herein by reference.

An example of a trace 250 generated by an optical monitoring system that measures the phase difference between the drive and sense signals is shown in FIG. 11. The overall shape of the trace 250 can be described as follows. First, metal layer 16 has some initial shape due to the shape of lower patterned layer 14. Due to this shape, the light beam is scattered when it collides with the metal layer. As the polishing operation proceeds at portion 252 of the trace, the metal layer becomes flatter and the reflectivity of the polished metal layer increases. The intensity is relatively stabilized as the bulk of the metal layer is removed from the portion 254 of the trace. Once the oxide layer is exposed to the trace, the overall signal strength drops rapidly at portion 256 of the trace. Once the oxide layer is fully exposed in the trace, the intensity is again stabilized in the portion 258 of the trace even though there is a slight vibration due to the interference effect when the oxide layer is removed.

Referring again to FIGS. 3 and 4A-4E, the CMP apparatus 20 includes a position detector, such as a light blocker, to detect when the core 42 and light source 44 are below the substrate 10. . For example, the light blocker may be mounted at a fixed point opposite the carrier head 70. The flag 82 is attached to the periphery of the platen. The length and attachment point of the flag 82 is selected to block the optical signal of the sensor 80 while the transparent portion 36 passes under the substrate 10. Alternatively, the CMP apparatus may include an encoder for determining the angular position of the platen.

General-purpose programmable digital computer 90 receives intensity and phase shift signals from an eddy current sensing system and intensity signals from an optical monitoring system. As the monitoring system sweeps under the substrate for each rotation of the platen, information about the thickness of the metal layer and the exposure of the underlying layer is accumulated in-situ and in continuous real time (once per rotation of the plate). . The computer 90 may be programmed for sample measurements from the monitoring system when the substrate is placed on the transparent portion 36 (as determined by the position sensor). As polishing proceeds, the thickness or reflectivity of the metal layer changes and the sample signal changes over time. Sample signals that change over time may be referred to as traces. Measurements from the monitoring system can be displayed on the output device 92 during polishing so that the operator of the device can visually monitor the progress of the polishing operation. In addition, as described below, traces may be used to control the polishing process and determine the endpoint of the polishing operation of the metal layer.                 

Since signals from the eddy current monitoring system 40 and the optical monitoring system 140 are supplied to the computer 90, either or both of the monitoring systems can be used for endpoint determination. This results in a powerful endpoint detection capability for chemical mechanical polishing machines for polishing dielectric and metal materials. Signals from the two systems can be monitored for endpoint criteria, and detection of endpoint criteria from the two systems can cause various Boolean logic operations (e.g., AND) to generate a change in the polishing endpoint or process variable. Or OR). Endpoint criteria for possible process control and detector logic include local minimum or maximum, slope change, threshold of amplitude or slope, or a combination thereof. One monitoring system may be provided to identify another monitoring system. For example, the polishing apparatus may stop polishing when detecting an appropriate endpoint reference in the eddy current signal and the optical intensity signal. Optionally, one system may act as a backup endpoint detector. The polishing apparatus may stop polishing when detecting the first endpoint criterion from one system, for example a vortex monitoring system, and if the endpoint criterion is not detected within a predetermined time range, then the polishing may be performed on another system, for example And may be stopped when detecting a second endpoint reference from the optical monitoring system. In addition, the two systems may be used for different parts of the polishing operation. For example, during metal polishing (especially copper polishing) most substrates can be polished while being monitored by a vortex monitoring system.

In polishing operations on the metal layer, the CMP apparatus 20 determines the vortex monitoring system 40 and the optical monitoring system 140 to determine when the packed bed bulk is removed and to determine when the lower stop layer is substantially exposed. Use Computer 90 applies process control and endpoint detection logic to the sample signal to determine when to change process variables and when to detect a polishing endpoint. When the eddy current monitoring system determines that the metal film has reached a predetermined thickness, the optical monitoring system may be used to detect when the lower insulating layer will be exposed.

In addition, as disclosed in US Patent Application No. 09 / 460,529, incorporated herein by reference on Dec. 13, 1999, computer 90 includes a vortex monitoring system 40 and a respective sweep under the substrate. Separate the measurements from the optical monitoring system 140 into a plurality of sample regions 96, calculate the radial position of each sample region, classify the amplitude measurements into the radial range, and minimum and maximum values for each sample region. And determine the average and use multiple radius ranges to determine the polishing endpoint.

The computer 48 is applied to the carrier head rotation motor 76 to control the rotation rate of the carrier head by the carrier head 70, and to the platen rotation motor (not shown) to control the platen rotation rate, or It may also be connected to a pressure mechanism that controls the pressure applied to the slurry dispensing system 39 to control the slurry composition supplied to the polishing pad. In particular, as disclosed in US Patent Application No. 09 / 609,426, filed on July 5, 2000, after categorizing the measurements into a radius range, the information about the metal film thickness is applied by a carrier head to polishing It may be supplied to the closed loop controller in real time to modify the pressure profile periodically or continuously. For example, the computer can determine whether the endpoint criterion satisfies the outer radius range, not the inner radius range. This indicates that the underlying layer is exposed to the annular outer region rather than the inner region of the substrate. In this case, the computer applies pressure to reduce the diameter of the region where the pressure is applied only to the inner region of the substrate, thereby reducing corrosion and dishing on the outer region of the substrate.

A method of polishing a metal layer, such as a copper layer, is shown in the flowchart of FIG. First, the substrate is polished at the first polishing station 22a to remove the metal layer bulk. The polishing process is monitored by the vortex monitoring system 40. When a copper layer 14 of a predetermined thickness, for example 2000 kPa, remains on the lower barrier layer 16 (see drawing), the polishing process is stopped and the substrate is transferred to the second polishing station 22b. An endpoint of the first polishing may be generated when the phase shift signal exceeds an experimentally determined threshold. Exemplary polishing parameters for the first polishing station include platen turnover of 93 rpm, carrier head pressure of about 3 psi, and IC-1010 polishing pad. As polishing proceeds in the first polishing station, the radial thickness information from the vortex monitoring system 40 can be supplied to the closed loop feedback system to control the mounting area and / or pressure of the carrier head 200 on the substrate. have. The pressure of the retaining ring on the polishing pad may be adjusted to adjust the polishing rate. This allows the carrier head to compensate for nonuniformity in polishing rate or nonuniformity in the thickness of the metal layer of the incoming substrate. As a result, after polishing at the first polishing station, most of the metal layer is removed and the surface of the metal layer remaining on the substrate is substantially planarized.

In the second polishing station 22b, the substrate is polished at a polishing rate lower than the polishing rate at the first polishing station. For example, the polishing rate is reduced by about 2 to 4 times, ie about 50% to 75%. To reduce the polishing rate, the carrier head pressure can be reduced, the turnover of the carrier head can be reduced, the composition of the slurry can be changed to introduce the polishing slurry more slowly, or the turnover of the platen is reduced. Can be. For example, the pressure on the substrate from the carrier head may be reduced by about 33% to 50%, and the plate turn rate and rotation rate of the carrier head may be reduced by about 50%. Exemplary polishing parameters for the second polishing station 22b include platen turnover of 43 rpm, carrier head pressure of about 2 psi, and IC-1010 polishing pad.

Optionally, when polishing begins at the second polishing station, the substrate may simply be polished at some high pressure and rotation rate, for example 3 psi and 93 rpm, for example for about 10 seconds. This initial polishing, which may be referred to as the "early" stage, is required to remove natural oxides formed on the metal layer to compensate for the expected throughput or to compensate for ramp-up of platen turnover and carrier head pressure. May be

The polishing process is monitored at the second polishing station 22b by the optical monitoring system. Polishing proceeds in the second polishing station 22b until the metal layer is removed and the lower barrier layer is exposed. Of course, a minute portion of the metal layer may remain on the substrate, but the metal layer is substantially removed. Optical monitoring systems are useful in determining these endpoints because they can detect changes in reflectivity when the barrier layer is exposed. In particular, an endpoint for the second polishing station may occur when the amplitude or slope of the optical monitoring signal falls below an experimentally determined threshold over the entire radius range monitored by the computer. This indicates that the barrier metal layer has been removed substantially across all substrates. Of course, when polishing is performed at the second polishing station 22b, the reflectivity information from the optical monitoring system 40 may be applied to the carrier head 200 on the substrate to prevent overpolishing of the area of the barrier layer that is first exposed. It can be supplied to a closed loop feedback system that controls the mounting area and / or pressure.

By reducing the polishing rate before the barrier layer is exposed, dishing and corrosion effects can be reduced. In addition, the relative reaction time of the polishing machine is improved, which results in less material being removed after the final endpoint criterion is detected, causing the polishing machine to stop polishing and move to the third polishing station. In addition, higher intensity measurements can be collected near the predicted polishing end time, thereby potentially improving the accuracy of the polishing endpoint calculation. However, by maintaining a high polishing rate throughout most polishing operations at the first polishing station, high yields are achieved. Preferably, at least 75%, such as 80-90%, of bulk polishing is completed before the carrier head pressure is reduced or other polishing parameters are changed.

Once the metal layer has been removed at the second polishing station 22b, the substrate is transferred to the third polishing station 22c to remove the barrier layer. Exemplary polishing parameters for the second polishing station include a platen turnover of 103 rpm, a carrier pressure head of about 3 psi, and an IC-1010 polishing pad. Optionally, the substrate will be temporarily polished by, for example, an initiation step for about 5 seconds, such as a rather high pressure of 3 psi, and a platen turnover of, for example, 103 rpm. The polishing process is monitored by the optical monitoring system at the third polishing station 22c and continues until the barrier layer is nearly removed and the underlying dielectric layer is barely exposed. The same slurry solution is used in the first and second polishing stations, while another slurry solution is used in the third polishing station.

Another method of polishing a metal layer, such as a copper layer, is shown in flowchart form in FIG. 13. This method is similar to the method shown in FIG. However, both the fast polishing step and the slow polishing step are performed at the first polishing station 22a. Removal of the barrier layer is performed at the second polishing station 22b, and a buffing step is performed at the final polishing station 22c.

Eddy current and optical monitoring systems can be used in various polishing systems. Either or both of the polishing pad or the carrier head can be moved to provide relative motion between the polishing surface and the substrate. The polishing pad may be a platen, a tape extending between the feed roller and the take-up roller, or a circular (or some other shape) pad fixed to an endless belt. The polishing pad may be fixed on the platen, progressively advanced over the platen between polishing operations, or continuously driven over the platen during polishing. Such polishing pads may be secured to the platen during polishing, or there may be fluid bearing between the platen and the polishing pad during polishing. The polishing pad can be a standard (eg, polyurethane with or without additives) rough pads, soft pads, or fixed-abrasive pads. If no substrate is present, the drive frequency of the oscillator can be tuned to the resonance frequency with no tuning and with a polished or unpolished substrate (with or without carrier head), or Tuning is somewhat different.

The optical monitoring system 140 may be located at a location on a platen different from the vortex monitoring system 40, although described above as being located in the same aperture. For example, the optical monitoring system 140 and the vortex monitoring system 40 can be located on opposite sides of the platen so that they can alternately scan the substrate surface.

Referring to FIG. 14, in another embodiment, the first polishing station includes only the eddy current monitoring system 40 and does not include the optical monitoring system. In this case, the section 36 'of the pad is not necessary for the transfer. However, it would be advantageous for the section 36 'to be relatively thin. For example, assuming the polishing pad 30 is a two layer pad, the thin pad section 36 'is constructed as shown in FIG. 15A by removing a portion 33' of the backing layer 32 '. Can be. Alternatively, as shown in FIG. 15B, a thin pad section 36 ″ may be formed by removing both a portion of the lid layer 34 ″ and a portion 33 ″ of the back layer 32 ″. Thus, this embodiment has recesses in the bottom surface of the cover layer 34 "in the thin pad section 36". If the polishing pad is a monolayer pad, a thin pad section 36 may be formed by removing a portion of the pad material to form a recess in the bottom surface of the pad. If the polishing pad is itself thin enough or has magnetic permeability (and conductivity) that does not interfere with the vortex measurement, the pad does not require any modifications or recesses.

If the eddy current sensor uses a single coil, various aspects of the present invention still apply, such as the measurement of the phase difference or the placement of the coil on one edge of the polishing surface opposite the substrate. In a single coil system, both the oscillator and sense capacitor (or other sensor circuit) are connected to the same coil.

So far, the present invention has been described through preferred embodiments. However, the present invention is not limited to the above-described embodiment, and the scope of the present invention is defined by the appended claims.

Claims (84)

As a chemical mechanical polishing apparatus, A carrier for holding the substrate on the polishing surface of the polishing pad; A sensor for monitoring a conductive film in a substrate, the sensor comprising: a core positionable proximate to the substrate, a first coil wound around the first portion of the core, inducing an alternating current in the first coil to be adjacent to the substrate. An oscillator electrically coupled to the first coil to generate an alternating magnetic field, a second coil wound around a second portion of the core, a capacitor electrically coupled to the second coil, and the second to generate an output signal A sensor comprising a coil and an amplifier electrically coupled to the capacitor, When the substrate is not near the core, the oscillator induces an alternating current having a substantially constant frequency selected to provide a resonant frequency, Chemical mechanical polishing device. delete delete The method of claim 1, Wherein the core comprises two prongs and a connection between the two prongs, Chemical mechanical polishing device. The method of claim 4, wherein Wherein the first coil is wound around the connecting portion and the second coil is wound around at least one of the two branches, Chemical mechanical polishing device. delete delete delete delete As a chemical mechanical polishing apparatus, A polishing pad having a polishing surface, a bottom surface and a recess formed in the bottom surface; A carrier for holding a substrate on the polishing surface; A vortex sensor opposite the substrate, the core positioned on an edge of the polishing surface and extending into the recess at least partially through the polishing surface; and A motor coupled to at least one of the polishing pad and the carrier head to produce a relative movement between the polishing pad and the carrier head, Chemical mechanical polishing device. The method of claim 10, Further comprising a rotatable platen for supporting the polishing pad, Chemical mechanical polishing device. delete delete delete delete The method of claim 10, The polishing pad comprises a cover layer and a backing layer having the polishing surface, wherein the recess is formed by removing a portion of the backing layer, Chemical mechanical polishing device. The method of claim 10, The core includes two poles positioned adjacent the recess in the polishing pad, Chemical mechanical polishing device. delete delete delete delete The method of claim 10, And an endpoint detection system for receiving an output signal from the vortex sensor, wherein the endpoint detection system is configured to determine a polishing endpoint based on the output signal. Chemical mechanical polishing device. A method of monitoring the thickness of a conductive layer in a substrate during a polishing operation, the method comprising: Positioning the substrate on the first edge of the polishing surface of the polishing pad; From the inductor wound around a core positioned on a second edge of the polishing surface opposite the substrate and extending into a recess on the bottom surface of the polishing pad, the polishing surface is induced to induce vortex in the conductive layer. Generating a magnetic field that extends through it, and Detecting a change in the magnetic field generated by a change in the thickness of the conductive layer, A method of monitoring the thickness of a conductive layer in a substrate during a polishing operation. delete delete delete delete delete delete delete delete delete delete delete delete As a chemical mechanical polishing device, A carrier for holding the substrate on the polishing surface of the polishing pad; A motor coupled to at least one of the polishing pad and the carrier head to produce a relative movement between the polishing pad and the carrier head, and A conductive layer thickness monitoring system, The conductive layer thickness monitoring system, One or more inductors, A current source electrically coupled to the one or more inductors to generate eddy currents in the one or more inductors and generate an alternating magnetic field, A sensing circuit comprising a capacitor electrically coupled to the at least one inductor to sense the alternating magnetic field and generate a sense signal; and A phase comparison circuit coupled to the current source and the sense circuit to measure a phase difference between the sense signal and the drive signal; Chemical mechanical polishing device. The method of claim 36, At least one first gate for converting a sinusoidal signal from the inductor and the current source into first and second square wave signals, and a comparator for comparing the first square wave signal and the second square wave signal to generate a third square wave signal; Including more, Chemical mechanical polishing device. delete delete delete The method of claim 37, wherein And a filter for converting the third square wave signal into a differential signal having an amplitude proportional to a phase difference between the first square wave signal and the second square wave signal. Chemical mechanical polishing device. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete A method of chemical mechanical polishing a metal layer on a substrate, Polishing the substrate at a first polishing rate; Monitoring the polishing with a vortex monitoring system, Decelerating the polishing rate and polishing the substrate at a second polishing rate when the eddy current monitoring system indicates that a predetermined thickness of the metal layer remains on the substrate; Monitoring the polishing with an optical monitoring system, and Stopping the polishing when the optical monitoring system informs that the underlying layer is at least partially exposed; A method of chemical mechanical polishing a metal layer on a substrate. The method of claim 71 wherein Polishing the substrate at the first polishing rate is performed with a first polishing surface at a first polishing station, Polishing the substrate at the second polishing rate is performed with a second polishing surface at a second polishing station, The method includes transferring the substrate to a second polishing station when the vortex monitoring system informs that a predetermined thickness of the metal layer remains on the substrate. A method of chemical mechanical polishing a metal layer on a substrate. The method of claim 72, Transferring the substrate to a third polishing station to polish the substrate to a third polishing surface, Monitoring polishing at the third polishing station with a second optical monitoring system, and Stopping the polishing when the second optical monitoring system indicates that the second sublayer is at least partially exposed; A method of chemical mechanical polishing a metal layer on a substrate. The method of claim 71 wherein Polishing the substrate at the first polishing rate is performed with a first polishing surface at a first polishing station, Polishing the substrate at the second polishing rate is performed with a first polishing surface at a first polishing station, The method includes reducing the polishing rate at the first polishing station, A method of chemical mechanical polishing a metal layer on a substrate. The method of claim 74, wherein Transferring the substrate to a second polishing station, Polishing the substrate at the second polishing station to a second polishing surface, Monitoring polishing at the second polishing station with a second optical monitoring system, Stopping polishing when the second optical monitoring system informs that the second sublayer is at least partially exposed, Transferring the substrate to a third polishing station, and Buffing the substrate to a buffing surface, A method of chemical mechanical polishing a metal layer on a substrate. The method of claim 71 wherein The lower layer is a barrier layer, A method of chemical mechanical polishing a metal layer on a substrate. The method of claim 10, The eddy current sensor comprises one or more coils wound around a portion of the core and an oscillator electrically coupled to the one or more inductors to induce alternating current in the coils, Chemical mechanical polishing device. As a polishing apparatus, A platen having a top surface configured to support a polishing pad having a flicking surface, A carrier configured to hold a substrate on the polishing surface, and A eddy current monitoring system comprising a core supported by the platen and extending over the top surface of the platen, Polishing device. The method of claim 78, The core comprises ferrite, Polishing device. The method of claim 78, An endpoint detection system for receiving an output signal from the vortex monitoring system to determine a polishing endpoint, Polishing device. A method of monitoring the thickness of a conductive layer in a substrate during a polishing operation, the method comprising: Positioning the substrate on the first edge of the polishing surface of the polishing pad supported on the platen; From the inductor wound around a core positioned on a second edge of the polishing surface opposite the substrate and extending over a surface of the platen supporting the polishing pad, the polishing to induce vortex in a conductive layer Generating a magnetic field extending through the plane, and Detecting a change in the magnetic field generated by a change in the thickness of the conductive layer, A method of monitoring the thickness of a conductive layer in a substrate during a polishing operation. 82. The method of claim 23 or 81, Generating a signal responsive to a charge sensed in the magnetic field, and Stopping polishing when the signal indicates an endpoint reference, A method of monitoring the thickness of a conductive layer in a substrate during a polishing operation. 83. The method of claim 82, Wherein the endpoint reference includes the vortex signal passing through a threshold intensity, A method of monitoring the thickness of a conductive layer in a substrate during a polishing operation. 83. The method of claim 82, The endpoint reference includes a slope that flattens the eddy current signal, A method of monitoring the thickness of a conductive layer in a substrate during a polishing operation.

Images