CN117279741A

CN117279741A - Temperature controlled removal rate in CMP

Info

Publication number: CN117279741A
Application number: CN202280032056.8A
Authority: CN
Inventors: E·A·米克海利琴科; C·H-G·李; A·N·耶尔; H·特兰; P·A·东
Original assignee: Applied Materials Inc
Current assignee: Applied Materials Inc
Priority date: 2021-03-03
Filing date: 2022-02-22
Publication date: 2023-12-22
Also published as: US20220281061A1; TWI836361B; KR20230152727A; US20220281070A1; TW202247945A; JP2024509159A; WO2022187023A1

Abstract

A method for removing material from a substrate comprising: dispensing an abrasive slurry onto the polishing pad; storing an indication of the associated charge on the abrasive; contacting a substrate surface with the polishing pad in the presence of the slurry; generating a relative motion between the substrate and the polishing pad; measuring a removal rate of the substrate; comparing the measured removal rate to a target removal rate and, based on the comparison, determining whether to increase or decrease the removal rate; determining whether to increase or decrease the temperature of the interface between the polishing pad and the substrate based on the indication of the relative charge of the abrasive and based on whether to increase or decrease the removal rate; and controlling the determined temperature of the interface to modify the removal rate.

Description

Temperature controlled removal rate in CMP

Technical Field

The present specification relates to chemical mechanical polishing applications using cerium oxide slurries.

Background

Integrated circuits are typically formed on silicon wafers by sequentially depositing conductive, semiconductive or insulative layers. One fabrication step involves depositing a layer on a non-planar surface and planarizing the layer. For some applications, the layer is planarized until the top surface of the patterned underlying layer is exposed. For other applications, the layer is planarized until a predetermined thickness is left on the underlying layer.

Chemical Mechanical Polishing (CMP) is an accepted planarization method. This planarization method mounts the substrate on a carrier head and the surface of the substrate is placed against the surface of the rotating polishing pad. A polishing liquid, such as an abrasive slurry, is dispensed onto the rotating polishing pad to polish the layers on the substrate by mechanical and chemical means. The abrasive particles in the slurry may be silica and ceria.

Disclosure of Invention

In one aspect, a method of polishing includes: dispensing a polishing slurry onto the polishing pad, the polishing slurry comprising negatively-charged ceria oxide; contacting a surface of a substrate with the polishing pad in the presence of the slurry; generating relative motion between the substrate and the polishing pad to polish the surface of the substrate; performing a measurement at a removal rate of the substrate; determining that the measured removal rate is less than the target removal rate; and responsive to determining that the measured removal rate is less than the target removal rate, reducing a temperature of an interface between the polishing pad and the substrate.

In another aspect, a method of polishing includes: dispensing a polishing slurry onto the polishing pad, the polishing slurry comprising negatively-charged ceria oxide; contacting a surface of a substrate with the polishing pad in the presence of the slurry; generating relative motion between the substrate and the polishing pad to polish the surface of the substrate; measuring a removal rate of the substrate; determining that the measured removal rate is greater than the target removal rate; and in response to determining that the measured removal rate is greater than the target removal rate, increasing a temperature of an interface between the polishing pad and the substrate. The abrasive can include cerium oxide particles.

In another aspect, a method for removing material from a substrate includes: dispensing a slurry onto a surface of a polishing pad, wherein the slurry comprises a carrier liquid and an abrasive; storing an indication of an associated charge on the abrasive; contacting a surface of a substrate with the polishing pad in the presence of the slurry; generating relative motion between the substrate and the polishing pad to polish the surface of the substrate; measuring a removal rate of the substrate; comparing the measured removal rate to a target removal rate and determining whether to increase or decrease the removal rate based on the comparison; determining whether to increase or decrease the temperature of an interface between the polishing pad and the substrate based on the indication of the associated charge of the abrasive and based on whether to increase or decrease the removal rate; and controlling the determined temperature of the interface to modify the removal rate.

In another aspect, a method of polishing includes: polishing a layer on a substrate by dispensing a polishing slurry onto a polishing pad, contacting a surface of the layer on the substrate with the polishing pad in the presence of the slurry, and producing a relative motion between the substrate and the polishing pad; controlling the temperature of the polishing within a first temperature range for an initial portion of the polishing of the layer; obtaining a temperature transition time prior to the endpoint time; upon determining that the temperature transition time is reached, reducing the temperature of the polishing to a second, lower temperature range, the second temperature range being lower than the first temperature range; and controlling the temperature of the polishing within the second temperature range for a subsequent portion of the polishing of the same layer until the estimated endpoint time.

In another aspect, a method of polishing includes: polishing a layer on a substrate by dispensing a polishing slurry onto a polishing pad, contacting a surface of the layer on the substrate with the polishing pad in the presence of the slurry, and producing a relative motion between the substrate and the polishing pad; controlling the temperature of the polishing within a first temperature range for an initial portion of the polishing of the layer; determining a temperature transition time prior to the endpoint time; upon determining that the temperature transition time is reached, increasing the pressure on the substrate while increasing the coolant flow to continue to maintain the temperature of the polishing within the first temperature range; and maintaining the elevated pressure and controlling the temperature of the polishing within the first temperature range for a subsequent portion of the polishing of the same layer until an estimated endpoint time.

Implementations can include one or more of the following features. Dispensing the coolant fluid may include spraying the coolant fluid through a converging-diverging nozzle. Measuring the removal rate may include monitoring the substrate during polishing with an in situ optical monitoring system. The surface of the substrate may include an oxide layer, for example, silicon oxide. Controlling the temperature of the interface may include: if positively charged, increasing the polishing rate by increasing the temperature; if negatively charged, decreasing the polishing rate by decreasing the temperature; the polishing rate is reduced by decreasing the temperature if positively charged, or by increasing the temperature if negatively charged.

Advantages may include, but are not limited to, one or more of the following. CMP systems can achieve high polishing rates to meet customer production needs. The methods described herein further increase the throughput of the system by reducing the time required to polish each substrate. This results in an increase in substrate output and a reduction in consumable cost per substrate. The optimization of the CMP process temperature in combination with the charged ceria application also allows for an increase in the useful life of the polishing pad, thereby reducing the cost to the customer.

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

Drawings

FIG. 1 is a schematic cross-sectional view of a chemical mechanical polishing system.

Fig. 2 is a flow chart of a polishing method.

FIG. 3 is a flow chart of another embodiment of a polishing method.

Fig. 4 is a flow chart of yet another embodiment of a polishing method.

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

Detailed Description

The material removal rate of a CMP process depends on the choice of grinding and other components of the polishing fluid, the pressure applied to the substrate, the relative speed between the polishing pad and the substrate, and the temperature at the interface between the substrate and the polishing pad. Conventionally, chemical reaction processes (e.g., polishing processes) increase with temperature. Thus, increasing the temperature may be a technique to increase the removal rate.

However, the actual dependence of the polishing rate on temperature can be a more complex interaction between the temperature impact on the polishing pad (e.g., the modulus of elasticity of the polishing pad) and the reaction rate driven by temperature. Furthermore, for some polishing processes, the electrostatic potential of the abrasive particles is a component of this interaction.

Cerium oxide (e.g., ceria) is an abrasive material used in polishing solutions for some polishing processes. In the polishing liquid, the surface of the abrasive ceria particles can have a positive electrostatic potential, a negative electrostatic potential, or a negligible electrostatic potential on the surface of the abrasive particles. The potential may depend on the synthesis technique. The polishing process using the polishing liquid having ceria particles exhibits such a polishing rate: the response to temperature is different depending on the positive or negative potential at the particle surface in the slurry.

Techniques for performing temperature control based on charge properties of abrasive particles are described. The CMP system includes a heater or cooler for controlling the temperature at the interface of the substrate and the polishing pad. By varying the temperature of the polishing process, the material removal rate is increased or decreased depending on the surface charge of the ceria suspended in the slurry. For negatively charged ceria slurries, cooling can increase polishing rates and improve topography. Without being bound by any particular theory, cooling using negatively charged ceria may improve the material removal rate by increasing hardness and modifying the roughened (asperity) structure of the top surface of the pad. For some positively charged ceria slurries, the combination of heating and cooling can improve the polishing rate by heating at the beginning of the polishing process and cooling near the polishing endpoint to improve topography. For other positively charged ceria slurries, a combination of cooling and increased pressure is used to improve polishing rate; the increased pressure increases the polishing rate and the cooling prevents the pad from overheating and maintaining the topography.

Fig. 1 illustrates an example of a polishing system 20. The polishing system 20 can comprise a rotatable disk-shaped platen 22 with a polishing pad 30 disposed on the disk-shaped platen 22. The platform is operable to rotate about an axis 23. For example, the motor 24 may rotate the drive shaft 26 to rotate the platform 22. The polishing pad 30 can be removably secured to the platen 22 (e.g., by an adhesive layer). The polishing pad 30 may be a two-layer polishing pad having an outer polishing layer 32 and a softer backing layer 34.

The polishing system 20 can include a polishing liquid supply port 40 for dispensing a polishing liquid 42, such as an abrasive slurry, onto the polishing pad 30. The polishing system 20 can also include a polishing pad conditioner for abrading the polishing pad 30 to maintain the polishing pad 30 in a consistent abraded state.

The carrier head 50 is operable to hold the substrate 10 against the polishing pad 30. Each carrier head 50 also includes a plurality of independently controllable pressurized chambers (e.g., three chambers 52a-52 c) that can apply independently controllable pressures to associated areas on the substrate 10. The chambers 52a-52c may be defined by a flexible membrane 54, the flexible membrane 54 having a bottom surface to which the substrate 10 is mounted. The carrier head 50 also includes a retaining ring 56 for retaining the substrate 10 under the flexible membrane 54. Although only three chambers are shown in fig. 1 and 2 for convenience of explanation, there may be two chambers, or four or more chambers, for example, five chambers. Further, other mechanisms for adjusting the pressure applied to the substrate, such as piezoelectric actuators, may be used in the carrier head 50.

Each carrier head 50 is suspended from a support structure 60 (e.g., a turntable or track) and is connected by a drive shaft 62 to a carrier head rotating motor 64 such that the carrier heads are rotatable about axis 51. Optionally, each carrier head 50 may oscillate laterally by movement along a track, or by rotational oscillation of the turntable itself (e.g., on a slider on the turntable). In operation, the platen 22 rotates about the central axis 23 of the platen 22, and the carrier head 50 rotates about the central axis 51 of the carrier head 50 and translates laterally across the top surface of the polishing pad 30.

The polishing system also includes an in-situ monitoring system 70 that can be used to control polishing parameters, such as the pressure applied in one or more of the chambers 52a-52 c. The in-situ monitoring system 70 may be an optical monitoring system (e.g., a spectrographic monitoring system), particularly for polishing an oxide layer on a substrate. Alternatively, the in-situ monitoring system 70 may be an eddy current monitoring system, particularly for polishing a metal layer on a substrate.

As an optical monitoring system, in-situ monitoring system 70 may include a light source 72, a light detector 74, and circuitry 76, with circuitry 76 being used to send and receive signals between a controller 90 (e.g., a computer) and the light source 72 and the light detector 74. One or more optical fibers 78 may be used to transmit light from the light source 72 to the window 36 in the polishing pad 30 and to transmit light reflected from the substrate 10 to the detector 74. As a spectrographic system, the light source 72 is then operable to emit white light, and the detector 74 may be a spectrometer. The measured spectra may be converted into eigenvalues that indicate the thickness of the layer being polished in each of the regions.

The output of circuitry 76 may be a digital electronic signal that passes through a rotating coupler 28 (e.g., slip ring) in drive shaft 26 to a controller 90. Alternatively, circuitry 76 may be in communication with controller 90 via wireless signals. The controller 90 may be a computing device, such as a programmable computer, that includes a microprocessor, memory, and input/output circuitry. Although shown with a single block, the controller 90 may be a networked system with functions distributed across multiple computers.

The polishing system 20 includes a temperature sensor 80 for monitoring the temperature of the polishing process, such as the temperature of the polishing pad 30 and/or the polishing liquid 42 on the polishing pad, or the temperature of the substrate. For example, the temperature sensor 80 can be an Infrared (IR) sensor (e.g., an IR camera) positioned above the polishing pad 30 and configured to measure the temperature of the polishing pad 30 and/or the polishing liquid 42 on the polishing pad. In particular, the temperature sensor 64 may be configured to measure temperatures at a plurality of points along the radius of the polishing pad 30, thereby generating a radial temperature profile. For example, the IR camera can have a field of view that spans the radius of the polishing pad 30.

In some embodiments, the temperature sensor is a contact sensor rather than a non-contact sensor. For example, the temperature sensor 64 may be a thermocouple or an IR thermometer positioned on or in the platform 24. In addition, the temperature sensor 64 may be in direct contact with the polishing pad.

In some embodiments, multiple temperature sensors can be spaced at different radial positions across the polishing pad 30, providing temperatures at multiple points along the radius of the polishing pad 30. This technique may be used in place of or in addition to an IR camera.

Although the temperature sensor 64 is shown in fig. 1 as being positioned to monitor the temperature of the polishing pad 30 and/or the polishing liquid 42 on the pad 30, the temperature sensor 64 may be positioned inside the carrier head 50 to measure the temperature of the substrate 10. The temperature sensor 64 may be in direct contact with the semiconductor wafer of the substrate 10 (i.e., contact the sensor). In some embodiments, a plurality of temperature sensors are included in polishing system 20, for example, to measure the temperature of the various components.

The polishing system 20 also includes a temperature control system 100 for controlling the temperature of the polishing pad 30 and/or the polishing liquid 42 on the polishing pad. The temperature control system 100 includes a cooling system and/or a heating system. In some embodiments, both the cooling system and/or the heating system operate by delivering a temperature-controlled medium (e.g., a liquid, vapor, or spray) onto the polishing surface 36 of the polishing pad 30 (or onto a polishing liquid already present on the polishing pad).

As shown in fig. 1, the example temperature control system 100 includes an arm 110, the arm 110 extending above the platen 22 and the polishing pad 30. A plurality of nozzles 120 are suspended from the arm 110, and each nozzle 120 is configured to spray a temperature control fluid onto the polishing pad. The arm 110 can be supported by the base 112 such that the nozzle 120 is separated from the polishing pad 30 by a gap 126. Each nozzle 120 may be configured (e.g., using controller 12) to start and stop fluid flow through each nozzle 120. Each nozzle 120 can be configured to direct the atomized water in the spray 122 toward the polishing pad 30.

To operate as a cooling system, the temperature control fluid is a coolant. The coolant is a gas (e.g., air) or a liquid (e.g., water). The coolant may be at room temperature or chilled (cool) to below room temperature, for example, at 5 to 15 ℃. In some embodiments, the cooling system uses a spray of air and a liquid, e.g., an atomized spray of liquid (e.g., water). In particular, the cooling system may have a nozzle that generates an atomized spray of water chilled to below room temperature. In some embodiments, the solid material may be mixed with a gas and/or a liquid. The solid material may be a chilled material, such as ice, or a material that absorbs heat when dissolved in water, such as by a chemical reaction. When dispensed, this coolant may be below room temperature, e.g., from-100 to 20 ℃, e.g., below 0 ℃.

To operate as a heating system, the temperature control fluid is a heated fluid. The heated fluid may be a gas (e.g., steam or heated air) or a liquid (e.g., heated water), or a combination of gas and liquid. The heating fluid is above room temperature, e.g., at 40 to 120 ℃, e.g., at 90 to 110 ℃. The fluid may be water, such as substantially pure deionized water, or water including additives or chemicals. In some embodiments, the heating system uses a spray of steam. The steam may include additives or chemicals.

The temperature control system 100 may include a single arm for dispensing coolant or heating fluid, or two dedicated arms for dispensing coolant and heating fluid, respectively.

Alternatively or additionally, the temperature control system 100 may use other techniques to control the temperature of the polishing process. For example, a heated or cooled fluid (e.g., steam or cold water) may be injected into the polishing liquid 42 (e.g., slurry) to increase or decrease the temperature of the polishing liquid 42 prior to dispensing the polishing liquid 42. As another example, a resistive heater may be supported in the platen 22 to heat the polishing pad 30 and/or in the carrier head 50 to heat the substrate 10.

The temperature of the conditioning (conditioner) slurry and polishing pad during polishing of the layer allows for increased interaction between the charge-carrying abrasive (e.g., cerium oxide). By using temperature control, the material removal rate can be advantageously increased by modulating the physical parameters of the polishing pad and altering the chemical interaction characteristics between the charged ceria and filler layer.

In some embodiments, the temperature sensor measures the temperature of the polishing process, e.g., the temperature of the polishing pad or the polishing liquid on the polishing pad or the temperature of the substrate, and the controller 90 executes a closed-loop control algorithm to control the temperature control system (e.g., the flow rate or temperature of an associated coolant or heating fluid) in order to maintain the polishing process at a desired temperature.

In some embodiments, the in-situ monitoring system measures the polishing rate of the substrate and the controller 90 executes a closed-loop control algorithm to control the temperature control system (e.g., the flow rate or temperature of an associated coolant or heating fluid) in order to maintain the polishing rate at a desired rate.

Fig. 2 illustrates a method of performing this technique, which may be applied to a charged ceria slurry. Optionally, the controller 90 stores an indication of whether the slurry being used contains negatively charged milled ceria particles or positively charged milled ceria particles (202). Polishing is performed and a slurry having abrasive ceria particles is dispensed onto the polishing pad (204). The controller 90 can store a desired temperature or temperature range, for example, as part of a polishing recipe. Thus, during polishing, the controller 90 is operable to maintain the temperature of the polishing process at a desired temperature or temperature range (206), for example, using an open-loop or closed-loop algorithm. During polishing, the polishing process is monitored by an in-situ monitoring system and a removal rate is calculated from the acquired data (208). The removal rate may deviate from the desired polishing rate (210) for various reasons. For example, the controller 90 may detect whether the removal rate differs from the target polishing rate by an amount exceeding a threshold. If this occurs, the controller 90 may cause the temperature control system to modify the process temperature to compensate for the removal rate and return the removal rate to the desired polishing rate. However, what action should be taken may depend on the charge of the milled ceria particles.

In particular, referring to table 1, for negatively charged abrasive ceria particle slurries, if the removal rate is below the desired polishing rate, the temperature may be reduced to increase the polishing rate, whereas below if the removal rate is above the desired polishing rate, the temperature may be increased to decrease the polishing rate. Conversely, for positively charged abrasive ceria particle slurries, if the removal rate is below the desired polishing rate, the temperature may be increased to increase the polishing rate, whereas below if the removal rate is above the desired polishing rate, the temperature may be decreased to decrease the polishing rate.

	Negatively charged	Positively charged
			Under-polishing (polishing rate too low)	Lowering the temperature	Increasing the temperature
Overpolish (polishing rate too high)	Increasing the temperature	Lowering the temperature

TABLE 1

This data may be stored and accessed by the controller 90 (e.g., as control logic or a look-up table) to determine how to adjust the temperature if the removal rate deviates from the desired polishing rate (212). Alternatively, the decision process as to whether to raise or lower the temperature may be embedded in a process recipe associated with a particular slurry loaded by the controller.

The controller 90 then causes the temperature control system to adjust the temperature (e.g., by increasing or decreasing the temperature and/or flow rate of the temperature control fluid) to modify the process temperature, e.g., the pad temperature (214).

For increasing the process temperature, the maximum desired temperature depends on the glass transition temperature of the polishing pad. If the pad becomes too hot, it may become too viscoelastic and the polishing process may not proceed as intended, e.g., the polishing rate may drop or defects may increase. Typically, the controller can be configured to maintain the temperature at 2/3 of the melting point of the polishing layer (as compared to 0 ℃).

Apart from the problem of the effect of static charge on the dependence of polishing rate on temperature, for many polishing applications, reducing polishing rate as the polishing process approaches the polishing endpoint avoids overpolishing and reduces non-uniformities is useful. On the other hand, it is beneficial to maintain a high polishing rate during bulk polishing of thick layers. One method that has been proposed to reduce the polishing rate is to reduce the pressure on the substrate. However, this may not be practical in some applications, for example, where the carrier head has been operated at low applied pressures, such as for polishing of fragile layers.

One method that may be used in lieu of or in addition to reducing the applied pressure near the polishing endpoint is to modify the process temperature to reduce the polishing rate. For example, for a conventional silica slurry or positively charged ceria slurry, the temperature can be reduced prior to the polishing endpoint to reduce the polishing rate.

Fig. 3 illustrates a method of performing this technique. For an initial portion of polishing of a layer, a temperature of a polishing process is controlled within a first temperature range (302). The initial portion can be run from the beginning of the polishing process.

Control may be performed by the controller 90 using a feedback loop that receives temperature measurements from the sensor 60 and adjusts the operation of the temperature control system 100. It is understood that the temperature of the polishing pad, or the temperature of the slurry, or the temperature of the substrate at a particular location may be used as an alternative to the temperature of the polishing process.

Before or after polishing begins, a temperature transition time before an expected endpoint time is determined (304). The temperature transition time may be a preset value based on the recipe; in this case, the user can determine the temperature transition time before polishing starts. Alternatively, the polishing process can be monitored by an in-situ monitoring system. The in-situ monitoring system may calculate an estimated endpoint time based on the measured polishing rate of the substrate and may calculate a transition time based on the estimated endpoint time prior to the estimated endpoint time, such as a preset time (e.g., 10 seconds), or a percentage of the total polishing time (e.g., 5-10%).

Once the temperature transition time is reached, the controller 90 causes the temperature control system to reduce the polishing temperature to within a second, lower temperature range that is lower than the first temperature range (306). The lower second temperature range may not overlap the first temperature range or may overlap the first temperature range by no more than 25% of the first temperature range. The midpoint of the second temperature range may be 20 to 40 ℃ lower than the midpoint of the first temperature range. In some embodiments, the temperature of the polishing surface 36 may be reduced to 30 ℃ or less than 30 ℃, for example, at 20 ℃ or less than 20 ℃.

Once the temperature of the polishing process has reached the second temperature range, the controller 90 causes the temperature control system 100 to maintain the temperature of the polishing process within the second temperature range for subsequent portions of the polishing process for the same layer (308). The subsequent portions of the polishing process may continue until the estimated endpoint time of the layer.

Another method that may be used to instead reduce the pressure applied near the polishing endpoint is to increase the pressure on the substrate in order to reduce the non-uniformity while also increasing the temperature control flow so that the temperature control system maintains the desired temperature. For example, for a conventional silica slurry or for a positively charged ceria slurry, the pressure on the substrate and/or the rotation rate of the platen may be increased, and the flow rate of the coolant may be increased before the polishing endpoint to achieve higher non-uniformity without sacrificing the polishing rate.

Fig. 4 illustrates a method of performing this technique. For an initial portion of polishing of a layer, a temperature of a polishing process is controlled within a first temperature range (402). Before or after polishing begins, a temperature transition time before an expected endpoint time is determined (404). These two steps may be performed in a manner as discussed above for steps 302 and 304.

Once the temperature transition time is reached, the controller 90 adjusts the pressure in one or more chambers in the carrier head 50 to increase the pressure on the substrate (406). In conjunction therewith, the controller 90 causes the temperature control system to increase the flow rate of a temperature control fluid (e.g., a coolant for a silica slurry or for a positively charged ceria slurry) such that the temperature is maintained within a first temperature range (408). The subsequent portions of the polishing process may continue until the estimated endpoint time of the layer.

With respect to increasing the process temperature, the maximum desired temperature depends on the glass transition temperature of the polishing pad. If the pad becomes too hot, the pad may become too viscoelastic and the polishing process may not proceed as intended, e.g., the polishing rate may decrease or defects may increase. Typically, the controller can be configured to maintain the temperature at 2/3 of the melting point of the polishing layer (as compared to 0 ℃).

More generally, for conventional silica slurries or for positively charged ceria slurries, it may be desirable to run the polishing process at the maximum possible temperature before polishing is degraded due to the viscoelasticity of the polishing pad in order to maximize the polishing rate. Thus, rather than having the temperature ramp up due to friction between the substrate and the polishing pad, the temperature may be driven to a desired temperature by a temperature control system at the beginning of the polishing process. The temperature may then be maintained within a desired temperature range, for example, at a temperature of about 50-66% of the melting point of the polishing layer (as compared to 0 ℃).

While this specification contains many specifics of specific implementations, these should not be construed as limitations on the scope of any invention or of what may be claimed, but rather as descriptions of features specific to particular embodiments of particular inventions. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Similarly, although operations are depicted in the drawings and described in the claims in a particular order, this should not be understood as: such operations may be required to be performed in the particular order shown or in sequence, or all illustrated operations may be performed in order to achieve desirable results.

Specific embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown (or sequential order) to achieve desirable results.

Claims

1. A method of polishing, comprising:

dispensing a polishing slurry onto the polishing pad, the polishing slurry comprising negatively-charged ceria oxide;

contacting a surface of a substrate with the polishing pad in the presence of the slurry;

generating relative motion between the substrate and the polishing pad to polish the surface of the substrate;

performing a measurement at a removal rate of the substrate;

determining that the measured removal rate is less than the target removal rate; and

in response to determining that the measured removal rate is less than the target removal rate, reducing a temperature of an interface between the polishing pad and the substrate.

2. The method of claim 1, wherein reducing the temperature comprises: a coolant fluid is dispensed onto the polishing pad.

3. The method of claim 2, wherein the coolant fluid is deionized water chilled to less than 20 ℃.

4. A method of polishing, comprising:

performing a measurement at a removal rate of the substrate;

determining that the measured removal rate is greater than the target removal rate; and

in response to determining that the measured removal rate is greater than the target removal rate, increasing a temperature of an interface between the polishing pad and the substrate.

5. The method of claim 4, wherein increasing the temperature comprises dispensing a heating fluid onto the polishing pad.

6. The method of claim 5, wherein dispensing the heating fluid comprises spraying a vapor.

7. A method for removing material from a substrate, comprising:

dispensing a slurry onto a surface of a polishing pad, wherein the slurry comprises a carrier liquid and an abrasive;

storing an indication of an associated charge on the abrasive;

measuring a removal rate of the substrate;

comparing the measured removal rate to a target removal rate and determining whether to increase or decrease the removal rate based on the comparison;

determining whether to increase or decrease the temperature of an interface between the polishing pad and the substrate based on the indication of the associated charge of the abrasive and based on whether to increase or decrease the removal rate; and

controlling the determined temperature of the interface to modify the removal rate.

8. A computer program product comprising a plurality of instructions on a non-transitory computer readable medium to cause one or more computers to:

causing the polishing system to polish the substrate on the polishing pad using the slurry with the abrasive;

storing an indication of an associated charge on the abrasive;

calculating a removal rate of the substrate based on signals received from an in situ monitoring system;

comparing the measured removal rate to a target removal rate;

determining whether to increase or decrease the removal rate based on the comparison;

determining whether to increase or decrease the temperature of an interface between the polishing pad and the substrate based on the indication of the associated charge on the abrasive and based on whether to increase or decrease the removal rate; and

causing a temperature control system to adjust the determined temperature of the interface to modify the removal rate.

9. The computer program product of claim 8, wherein the instructions to control the temperature of the interface comprise: instructions to increase the polishing rate by increasing the temperature if the indication is positively charged; and instructions to increase the polishing rate by decreasing the temperature if the indication is negatively charged.

10. The computer program product of claim 8, wherein the instructions to control the temperature of the interface comprise: instructions to decrease the polishing rate by decreasing the temperature if the indication is positively charged; and instructions to decrease the polishing rate by increasing the temperature if the indication is negatively charged.

11. A method of polishing, comprising:

polishing a layer on a substrate by dispensing a polishing slurry onto a polishing pad, contacting a surface of the layer on the substrate with the polishing pad in the presence of the slurry, and producing a relative motion between the substrate and the polishing pad;

controlling the temperature of the polishing within a first temperature range for an initial portion of the polishing of the layer;

obtaining a temperature transition time prior to the endpoint time;

upon determining that the temperature transition time is reached, reducing the temperature of the polishing to a second, lower temperature range, the second temperature range being lower than the first temperature range; and

for a subsequent portion of the same polishing of the layer, the temperature of the polishing is controlled within the second temperature range until an estimated endpoint time.

12. The method of claim 11, wherein the polishing slurry comprises silica abrasive particles or positively charged ceria particles.

13. The method of claim 11, wherein obtaining the temperature transition time comprises storing a predetermined transition time.

14. The method of claim 11, comprising: monitoring the substrate during polishing with an in-situ monitoring system, determining an expected endpoint time based on a signal from the in-situ monitoring system, and wherein obtaining the temperature transition time comprises calculating the temperature transition time based on the expected endpoint time.

15. The method of claim 14, wherein calculating the temperature transition time comprises: a predetermined period of time is subtracted from the expected endpoint or a percentage of the total polishing time is subtracted from the expected endpoint time.

16. A method of polishing, comprising:

determining a temperature transition time prior to the endpoint time;

upon determining that the temperature transition time is reached, increasing the pressure on the substrate while increasing the coolant flow to continue to maintain the temperature of the polishing within the first temperature range; and

for a subsequent portion of the same polishing of the layer, the elevated pressure is maintained and the temperature of the polishing is controlled within the first temperature range until an estimated endpoint time.

17. The method of claim 16, wherein the polishing slurry comprises silica abrasive particles or positively charged ceria particles.

18. The method of claim 16, wherein obtaining the temperature transition time comprises storing a predetermined transition time.

19. The method of claim 16, comprising: monitoring the substrate during polishing with an in-situ monitoring system, determining an expected endpoint time based on a signal from the in-situ monitoring system, and wherein obtaining the temperature transition time comprises calculating the temperature transition time based on the expected endpoint time.

20. The method of claim 19, wherein calculating the temperature transition time comprises: a predetermined period of time is subtracted from the expected endpoint or a percentage of the total polishing time is subtracted from the expected endpoint time.