USRE39547E1

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Publication number: USRE39547E1
Application number: US10/035,828
Authority: US
Inventors: Gurtej S. Sandhu
Original assignee: Micron Technology Inc
Current assignee: Micron Technology Inc
Priority date: 1997-08-21
Filing date: 2001-12-28
Publication date: 2007-04-03
Anticipated expiration: 2017-08-21
Also published as: US6007408A

Abstract

An apparatus and method for stopping mechanical and chemical-mechanical polishing of a substrate at a desired endpoint. In one embodiment, a polishing machine has a platen, a polishing pad positioned on the platen, and a polishing medium located at a planarizing surface of the polishing pad. The polishing machine also has a substrate carrier that may be positioned over the planarizing surface of the polishing pad, and at least one heat sensor is coupled to the polishing machine to detect heat at a front side of the substrate. The heat sensor preferably measures a temperature of a component sensitive to heat at the front side of the substrate, such as the planarizing surface of the polishing pad, the back side of the substrate, or the byproducts produced by polishing the substrate. In operation, the heat sensor monitors the heat at the front side of the substrate, and the removal of material from the substrate is stopped when the heat at the front side of the substrate changes from a first heat range to a second heat range.

Description

TECHNICAL FIELD

The present invention is related to mechanical and chemical-mechanical polishing of substrates, and more particularly, to a method and apparatus for consistently stopping planarization of substrates at a desired endpoint.

BACKGROUND OF THE INVENTION

Chemical-mechanical polishing (“CMP”) processes remove material from the surface of semiconductor wafers or other substrates in the production of microelectronic devices and other products.FIG. 1 schematically illustrates aCMP machine10 with aplaten20, awafer carrier30, apolishing pad40, and a planarizingliquid44 on thepolishing pad40. Thepolishing pad40 and theplanarizing liquid44 may separately, or in combination, define a polishing medium that mechanically and/or chemically removes material from the surface of a wafer. Thepolishing pad40 may be a conventional polishing pad made from a continuous phase matrix material (e.g., polyurethane), or it may be a new generation abrasive polishing pad made from abrasive particles fixedly dispersed in a suspension medium. The planarizingliquid44 may be a conventional CMP slurry with abrasive particles and chemicals that is used with a conventional polishing pad, or the planarizingliquid44 may be a planarizing solution without atbrasive particles that is used with an abrasive polishing pad.

TheCMP machine10 may also have an under-pad25 attached to anupper surface22 of theplaten20 and the lower surface of thepolishing pad40. Adrive assembly26 rotates the platen20 (indicated by arrow A), or it reciprocates theplaten20 back and forth (indicated by arrow B). Since thepolishing pad40 is attached to the under-pad25, thepolishing pad40 moves with theplaten20 during planarization.

Thewafer carrier30 has alower surface32 to which awafer12 may be attached, or thewafer12 may be attached to aresilient pad34 positioned between thewafer12 and thelower surface32. Thewafer carrier30 may be a weighted, free-floating wafer carrier; or anactuator assembly36 may be attached to the wafer carrier to impart axial and/or rotational motion to the wafer12 (indicated by arrows C and D, respectively).

To planarize thewafer12 with theCMP machine10, thewafer carrier30 presses thewafer12 face-downward against the polishing medium. More specifically, thewafer carrier30 generally presses thewafer12 against the planarizingliquid44 on the planarizingsurface42 of thepolishing pad40, and at least one of theplaten20 or thewafer carrier30 moves relative to the other to move thewafer12 across the planarizingsurface42. As thewafer12 moves across theplanarizing surface42, material is removed from the face of thewafer12.

In the competitive semiconductor industry, it is desirable to consistently stop CMP processing of a run of wafers at a desired endpoint and to produce a uniform, planar surface on each wafer. Accurately stopping CMP processing at a desired endpoint is important to maintaining a high throughput of planarized wafers because the planarized surface must be at a desired level with respect to other layers of material and structures on the wafer. For example, if the planarized surface is above an acceptable level, the wafer must be re-planarized until it reaches a desired endpoint. Additionally, it is important to accurately produce a uniform, planar surface on each wafer to enable precise circuit and device patterns to be formed with photolithography techniques. The critical dimensions of many photo-patterns must be focused within a tolerance of approximately 0.1 μm. Focusing photo-patterns to such small tolerances, however, is difficult when the planarized surface of the wafer is not uniformly planar. Therefore, two primary objectives of CMP processing are stopping planarizing at a desired endpoint and producing a highly uniform, planar surface on each wafer.

The endpoint of CMP processing may be determined by estimating the time-to-polish the wafer based on the polishing rate of previous wafers. CMP processing, however, involves many operating parameters that affect the planarity of the surface of the wafer and the ability to estimate the time-to-polish a wafer to a desired endpoint. The rate at which the material is removed from the surface of the wafer (the “polishing rate”) often varies from one wafer to another. The most common parameters that affect the polishing rate of a wafer are: (1) the relative velocity created between the wafer and the polishing pad across the face of the wafer; (2) the distribution of slurry across the surface of the wafer; (3) the composition of materials of the wafer; (4) the topography of the wafer; (5) the parallelism between the face of the wafer and the surface of the polishing pad; (6) the temperature gradient across the face of the wafer; and (7) the condition of the planarizing surface of the polishing pad. The polishing rate may vary from one wafer to another because it is difficult to identify and correct changes in specific operating parameters. Thus, it is difficult to consistently stop CMP processing at a desired endpoint on a wafer by estimating the time-to-polish the wafer using the polishing rate of previous wafers.

The endpoint of a wafer may also be determined by stopping CMP processing and measuring a change in thickness of the wafer. In a typical process for measuring a change in thickness of the wafer, the wafer is partially or completely removed from the planarizing surface of the polishing pad, and then an interferometer or other measuring device measures a change in thickness of the wafer. However, repeatedly stopping CMP processing to measure the change in thickness of the wafer reduces the throughput of planarized wafers, or a wafer may be destroyed or impaired because it may be over-polished beyond an acceptable endpoint before the first measurement. Accordingly, it is also difficult and time-consuming to consistently stop CMP processing at a desired endpoint by continuously measuring the actual change in thickness of the water.

In light of the problems with determining the endpoint of CMP processing, it would be desirable to develop a method and apparatus that indicates when a wafer has been planarized to a desired endpoint.

SUMMARY OF THE INVENTION

The present invention is an apparatus and method for stopping mechanical and chemical-mechanical polishing of a substrate at a desired endpoint. In an embodiment, a polishing machine has a platen, a polishing pad positioned on the platen, and a polishing medium located at a planarizing surface of the polishing pad. The polishing machine also has a substrate carrier that may be positioned over the planarizing surface of the polishing pad, and at least one sensor that monitors a characteristic of a polishing component that is influenced by the type of material being removed from the substrate. In a preferred embodiment, the sensor is preferably a heat sensor that measures the temperature of a polishing component sensitive to heat at the front side of the substrate, such as the planarizing surface of the polishing pad, the back side of the substrate, or the CMP byproducts produced by polishing the substrate. A single heat sensor, for example, may either be embedded in the polishing pad, connected to the substrate carrier at the backside of the substrate, or attached to the platen at a location where the CMP byproducts flow off of the polishing pad. On the other hand, a plurality of heat sensors may be positioned at different locations on the polishing machine, including a first heat sensor embedded in the polishing pad, a second heat sensor connected to the substrate carrier, and a third heat sensor attached to the platen.

A preferred embodiment of the invention is useful to endpoint CMP processing at the uppermost interface between a cover layer on a substrate and an underlying layer on the substrate covered by the cover layer. At the beginning of the CMP process, the chemical reaction and friction between the cover layer and the polishing medium produces heat between the substrate and the polishing medium within a first heat range. After the cover layer is at least partially removed from the substrate and a portion of the underlying layer engages the polishing medium, the heat between the substrate and the polishing medium changes to within a second heat range because the chemical reaction between the underlying layer and the polishing medium is different than that of the cover layer. The heat may also change when the underlying layer engages the polishing medium because the coefficient of friction between the underlying layer and the polishing medium may also be different than that of the cover layer. The heat sensors sense the change in heat from the first heat range to the second heat range, and CMP processing is preferably stopped when the sensed heat is within the second heat range.

In another embodiment of the invention, a reactive agent is added to the planarizing solution to produce large variations between the first heat range and the second heat range when the underlying layer is exposed to the polishing medium. In still another embodiment of the invention, the CMP byproducts flowing off of the polishing pad are mixed with a reactive agent selected to react with the material of the underlying layer. Thus, by measuring the extent to which the reactive agent reacts with the CMP byproducts, this embodiment detects the presence and concentration of material from the underlying layer in the CMP byproducts to identify the endpoint of the polishing process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a semiconductor polishing machine in accordance with the prior art.

FIG. 2 is a schematic cross-sectional view of an embodiment of a polishing machine in accordance with the invention.

FIG. 3A is a partial schematic cross-sectional view of an embodiment of a substrate carrier and a polishing pad of a polishing machine in accordance with the invention at one point in an embodiment of a method in accordance with the invention.

FIG. 3B is a partial cross-sectional view of the embodiment of the substrate carrier and the polishing pad of the polishing machine ofFIG. 3B at a later point in the method of FIG.3B.

FIG. 4 is a schematic cross-sectional view of another embodiment of a polishing machine in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

The preferred embodiment of the present invention is a method and apparatus for stopping mechanical and chemical-mechanical polishing of a substrate at a desired endpoint. One aspect of an embodiment of the invention is to monitor the heat between the substrate and the polishing pad at the front side of the substrate, and to stop CMP processing when the heat changes in a manner that indicates that CMP processing has reached as interface between a cover layer and an underlying layer on the substrate. Another aspect of an embodiment of the invention is to select slurries, planarizing liquids or reactive agents that produce a large change in the heat at the front side of the substrate when the underlying layer of the substrate is exposed to the polishing medium.FIGS. 2-4, in which like reference numbers refer to like parts, illustrate various embodiments of polishing methods and apparatus for stopping mechanical and chemical-mechanical polishing of a substrate at a desired endpoint in accordance with the invention.

FIG. 2 is schematic cross-sectional view of an embodiment of apolishing machine110 for mechanical or chemical-mechanical planarization of asubstrate150. The polishingmachine110 has ahousing112, aplaten120 attached to thehousing112, and awafer carrier assembly130 that holds and moves a wafer carrier or chuck132 over theplaten120. Anunderpad125 is preferably attached to theplaten120, and apolishing pad140 is attached to theunderpad125. As discussed above with respect toFIG. 1, aplaten actuator126 moves theplaten120 and asubstrate actuator136 moves thesubstrate carrier132. In a preferred embodiment, thesubstrate actuator136 rotates thesubstrate carrier132 and moves thesubstrate carrier132 along anarm134 extending over the platen120 (indicated by arrow T) to move thesubstrate150 across thepolishing pad140.

Thepolishing pad140 has abody141 and aplanarizing surface142. In one embodiment, thepolishing pad140 is a non-abrasive polishing pad in which thebody141 is made from a matrix material. In another embodiment, thepolishing pad140 is an abrasive polishing pad in which thebody141 is made from a matrix material, and a plurality ofabrasive particles145 are bonded to the matrix material. In addition to thepolishing pad140, aplanarizing liquid148 is dispensed through adispenser149 onto theplanarizing surface142 of thepolishing pad140. Theplanarizing liquid148 preferably has chemicals that react with one or more layer of material on thesubstrate150 to enhance the removal of such layers from thesubstrate150. The planarizing liquid may also have abrasive particles, such as aluminum oxide or cesium oxide, to abrade the surface of thesubstrate150. In general, a particle-free planarizing liquid148 is preferably used with anabrasive polishing pad140, while an abrasive planarizing liquid148 (slurry) is preferably used with anon-abrasive polishing pad140. Theplanarizing liquid148 generally flows radially outwardly across theplanarizing surface142 because theplaten120 and thepolishing pad140 typically rotate (indicated by arrow R₁). In one embodiment, theplaten120 hassidewall122 spaced radially outwardly from thepolishing pad140 to catch the byproducts of the CMP process148(a) as they flow off of thepolishing pad140.

Thepolishing pad140 and/orplanarizing liquid148 define a polishing medium to remove material from thesubstrate150. In the case of anabrasive polishing pad140, either thepolishing pad140 alone defines the polishing medium or the combination of thepolishing pad140 and theplanarizing liquid148 define the polishing medium. In the case of anon-abrasive polishing pad140 and an abrasive planarizing liquid148 (generally a CMP slurry), the combination of thepolishing pad140 and theabrasive planarizing liquid148 define the polishing medium. The components of the polishing medium are accordingly the items that engage the substrate to mechanically and/or chemically remove material from the substrate. As discussed in greater detail below, the heat generated at aninterface160 between thesubstrate150 and the polishing medium changes as different layers of material on thesubstrate150 are exposed to the polishing medium.

The polishingmachine110 also has at least one heat sensor170 (identified only by reference numbers170(a)-170(c) inFIG. 2) to sense the temperature of a component sensitive to the heat at the pad/substrate interface160. A wide variety of conventional temperature sensors may be used as theheat sensor170, including those that sense temperature optically, electrically, chemically, etc. In one embodiment, a pad heat sensor170(a) is embedded into thepolishing pad140 to measure the temperature of theplanarizing surface142 or theplanarizing liquid148. In another embodiment, a substrate heat sensor170(b) is connected to thesubstrate carrier132 to measure the temperature at the backside of thesubstrate150. In still another embodiment, a byproduct heat sensor170(c) is coupled to the polishingmachine110 at a location to measure the temperature of the CMP byproducts148(a). The byproduct heat sensor170(c) is preferably attached to theplaten120 beyond the perimeter of thepolishing pad140 where the byproducts148(a) are held after they flow off of thepolishing pad140. The byproduct heat sensor170(c), however, may be attached to thearm134 of thesubstrate carrier assembly130 to engage the CMP byproducts148(a) as they flow off of the polishing pad140 (not shown).

The polishingmachine110 preferably has a plurality ofheat sensors170 with at least oneheat sensor170 attached to each of thepolishing pad140, thesubstrate carrier132 and theplaten120. Thus, it is not necessary to having a single heat sensor positioned in any single one of the components of the polishingmachine110. Furthermore, it is not necessary to position aheat sensor170 in thepolishing pad140, thesubstrate carrier132 or theplaten120, but rather aheat sensor170 may be positioned in virtually any component sensitive to heat at the pad-substrate interface160.

FIGS. 3A and 3B are partial schematic cross-sectional views of the polishingmachine110 and thesubstrate150 that further illustrate the operation of the heat sensors170(a)-170(c) in stopping CMP processing at a desired endpoint. Thesubstrate150 may be virtually any multiple layer device, such as a semiconductor wafer, a baseplate for a field emission display, or another type of substrate that requires a uniformly planar surface at a consistent endpoint. For example, as shown inFIG. 3A, thesubstrate150 is a semiconductor wafer with a plurality ofintegrated circuit components152 formed on awafer substrate151, an underlyingconformal layer154 formed over theintegrated circuit components152, and aninsulative cover layer156 formed over theunderlying layer154. Theunderlying layer154 is preferably a polish-stop layer made from a material with a relatively low polishing rate, such as silicon nitride, diamond-like carbon and other polish-resistant materials. Thecover layer156 is preferably an inter-dielectric layer made from borophosphate silicon glass (BPSG), tetraethylorthosilicate glass (TEOS), or any other suitable insulative material. In another embodiment (not shown), thesubstrate150 is a semiconductor wafer in which theunderlying layer154 is an inter-layer dielectric with vias formed over thecomponents152, and thecover layer156 is a conductive layer deposited into the vias and over theunderlying layer154 to form contact plugs to thecomponents152. The polishingmachine110, however, may be used to accurately polish and endpoint other structure of semiconductor wafers, baseplates, and other substrates.

FIG. 3A illustrates thesubstrate150 prior to the endpoint of CMP processing when only thecover layer156 is exposed to the polishingliquid148 and thepolished pad140. At this point in the CMP process, the friction and chemical reaction between anintermediate planarized surface157 of thesubstrate150 and the polishing medium produces a heat H₁at the pad/substrate interface160. The heat H₁is a function of the material of thecover layer156, the composition of theplanarizing liquid148, and the friction between thesubstrate150 and the polishing medium. To measure the heat H₁at the pad/substrate interface160, the heat sensor170(a) preferably senses the temperature of thepolishing pad140 orplanarizing liquid148, and/or the heat sensor170(b) preferably senses the temperature of thesubstrate150. It will be appreciated that the temperatures measured by the heat sensors170(a) and170(b) may not be the same, but because the temperatures at the back side of thesubstrate150 and at the planarizing surface,142 of thepolishing pad140 are both sensitive to the heat H₁at the pad/substrate interface160, the temperatures measured by theheat sensors170 are a relative indication of the heat H₁at the pad/substrate interface160.

FIG. 3B illustrates thesubstrate150 at a preferable endpoint of the CMP process when the high-points of theunderlying layer154 on top of thecomponents152 are exposed to theplanarizing liquid148 and thepolishing pad140. The friction and/or chemical reaction between a finished surface157(a) of thesubstrate150 at the desired endpoint produces a heat H₂at the pad/substrate interface160. The heat H₂is different than the heat H₁because the chemicals in theplanarizing liquid148 may react differently with the material of theunderlying layer154 than with thecover layer156, and/or the coefficient of friction of the intermediateplanarized surface157 may be different than that of the finished surface157(a). The heat at the front face of thesubstrate150 influences the temperature of many polishing components used in the polishing process, such as theplaten120,underpad125,substrate carrier132, polishingpad140, planarized liquid148 on thepolishing pad140,substrate150, and any other element that is sensitive to heat at the front side of the substrate. Thus, by knowing the temperatures of a polishing component corresponding to the first and second heats H₁and H₂at the pad/substrate interface160, the polishing process is preferably stopped at a desired endpoint. The endpoint is preferably determined by monitoring the temperature of the polishing component and stopping the removal of material from the substrate when the temperature changes from a first temperature corresponding to heat H₁to a second temperature corresponding to heat H₂. Accordingly, the second temperature of the polishing component preferably provides a predetermined temperature at which CMP processing is stopped.

The first and second temperatures of a polishing component generally vary as a function of several parameters, including the materials of thesubstrate150, the composition of thepolishing pad140 andplanarizing liquid148, the down-force of thesubstrate carrier132, and the relative velocity between thesubstrate150 and thepolishing pad140. The first and second temperatures of a polishing component are preferably determined empirically for each specific CMP process by measuring the temperature of the component during polishing of a knownintermediate surface157 on a substrate and a known finished surface157(a) on a like substrate and under like operating parameters. The actual tests to empirically determine the first and second temperatures of a given polishing component for a specific CMP process may vary and are generally known to persons skilled in the art of CMP.

The preferred embodiment of the polishingmachine110 may also be used to endpoint the CMP process at a level below the top of theunderlying layer154 because the heat H₂at the pad/substrate interface160 also varies with the extent to which theunderlying layer154 is exposed to the polishing medium. It will be appreciated that the change in heat between the first and second heats H₁and H₂is also a function of the surface area of theunderlying layer154 that is exposed to the polishing medium. In many polishing processes, one area of the wafer polishes faster than another so that only a fraction of theunderlying layer154 at the finished surface157(a) is initially exposed to the polishing medium. As polishing progresses, more material is removed from thecover layer156 to expose more of theunderlying layer154. As a result, the change in heat when theunderlying layer154 is initially exposed to the polishing medium is often different than at subsequent points in the polishing process when a different percentage of the exposed surface area on thesubstrate150 is composed of theunderlying layer154. In a preferred embodiment, therefore, theheat sensors170 indicate that the polishing process is at the desired endpoint when the temperature indicates that the heat H₂at the pad/substrate interface160 corresponds to a heat at which a sufficient percentage of the surface area on the wafer is composed of theunderlying sayer154.

In another embodiment of the invention, a reactive agent is added to the slurry orplanarizing liquid148 to increase the difference between the heats H₁and H₂at the pad/substrate interface160. The particular reactive agent is selected according to the materials of theunderlying layer154, thecover layer156, and the composition of theplanarizing liquid148. In one embodiment, the reactive agent is HCl, NH₄OH or KOH for use with anunderlying layer154 made of tungsten, acover layer156 made of silicon dioxide and an H₂O₂based planarizating liquid148 manufactured by Rodel Corporation of Newark, Del.

A preferred embodiment of the present invention accordingly provides fast, real-time direct monitoring of the polishing status of thesubstrate150. Unlike conventional endpointing techniques that remove the substrate from the polishing pad to measure a change in the thickness of the substrate, a preferred embodiment of the present invention determines the endpoint in-situ and in real-time without removing the substrate from the polishing pad and without stopping the polishing process. A preferred embodiment of the present invention, therefore, is expected to accurately endpoint CMP processing without adversely affectly the throughput of finished substrates.

Another advantage of a preferred embodiment of the present invention is that it accurately determines the endpoint of the polishing process even though the polishing parameters may change from one substrate to the next. As discussed above in the Background section, the polishing rate of a run of substrates may change from one substrate to the next for several reasons. A preferred embodiment of the present invention is expected to accurately indicate the endpoint of the polishing process even though one or more of the polishing parameters changes from one wafer to the next because the change in heat at the pad/substrate interface160 is a function of the composition of the planarized surface on the substrate that is exposed to the polishing medium. Therefore, it is expected that a preferred embodiment of the present invention will increase the accuracy of stopping CMP processing at a desired endpoint.

FIG. 4 is a schematic cross-sectional view of another embodiment of apolish machine210 for polishing thesubstrate150. As discussed above with respect toFIG. 2, thepolish machine210 has ahousing112, aplaten120, asubstrate carrier assembly130, and apolishing pad140. Thepolish machine210 also has a reactingcell220 preferably positioned in thehousing112, and afeed line230 from thecell220 to the CMP byproducts148(a) on theplaten120. Thefeed line230 is preferably movable so that it can be removed from the byproducts148(a) and/or the interior of theplaten120 during planarization when theplaten120 rotates. In operation, the CMP byproducts148(a) are pumped through thefeed line230 and into thecell220 by a pump (not shown). Once a sufficient volume of CMP byproducts148(a) is pumped into thecell220, areactive agent240 is mixed with the CMP byproducts148(a) to detect whether material of theunderlying layer154 is present in the CMP byproducts148(a). Thereactive agent240 is preferably selected to react with the material of theunderlying layer154 in a manner that indicates the quantity of theunderlying layer154 that is present in the CMP byproducts148(a).

Many differentreactive agents240 may be added to thecell220 to indicate the presence and quantity of material from theunderlying layer154 in the CMP byproducts148(a). Depending upon the specificreactive agent240, the resulting reaction may be detected by a change in temperature in thecell220 measured by a heat sensor170(d), a change in color of the reacted CMP byproducts148(a) in thecell220, or other known techniques to monitor chemical reactions. One suitablereactive agent240 to detect the presence of tungsten or compounds of tungsten in the CMP byproducts148(a) is composed of potassium chlorate (KClO₃) and aqua regia (HCl+HNO₃).

From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. For example, the heat at the front of the substrate is only one characteristic of a polishing component indicative of material being removed from the planarized surface of the substrate. When the polishing component is the CMP byproducts, the characteristics of the byproducts that may be indicative of the material at the front face of the substrate include the pH of the byproducts, the conductivity of the byproducts (especially for polishing conductive layers), the color of the byproducts, and the chemical composition of the byproducts. Predetermined values of any characteristic corresponding to the endpoint may be determined in a similar manner as described above with respect to the temperature of a polishing component sensitive to the heat at the front face of the substrate. For example, the pH level of the byproducts may be determined using a calomel electrode known in the art, or the chemical composition of the byproducts may be determined by infrared spectroscopy, elemental analysis, or atomic absorption processes known in the art. Accordingly, the invention is not limited except as by the appended claims.

Claims

1. A method for stopping polishing of a substrate at a desired endpoint, the substrate having a cover layer and an underlying layer under the cover layer, the method comprising:

monitoring a characteristic of a polishing component indicative of material being removed from a planarized surface of the substrate, wherein the component comprises byproducts produced by polishing the substrate and the characteristic is a temperature of the byproducts, and wherein the monitoring step comprises sensing the temperature of the byproducts; and

stopping removal of material from the substrate when the characteristic of the polishing component is at a predetermined value that indicates the material being removed from the planarized surface is at the desired endpoint of the substrate.

2. The method ofclaim 1 wherein the sensing step comprises measuring a temperature of a planarizing liquid flowing off of a polishing pad.

3. A method for stopping mechanical and chemical-mechaniical polishing of a substrate at an endpoint, the substrate having a cover layer and an underlying layer under the cover layer, and the method comprising:

monitoring heat transfer at a planarized surface of the substrate and a polishing component sensitive to heat at the planarized surface by measuring a temperature of the component, and wherein measuring the component temperature comprises sensing a temperature of byproducts produced by polishing the substrate; and

stopping polishing of the substrate when the characteristic of the polishing component is at a predetermined value that indicates the planarized surface is at the desired endpoint.

4. The method ofclaim 3 wherein the sensing step comprises measuring a temperature of a planarizing solution flowing off of the polishing pad.

5. A method for stopping mechanical and chemical-mechanical polishing of a substrate at an endpoint, the method comprising:

detecting a change in heat at a front side of the substrate, the heat at the front side of the substrate being different when a cover layer of the substrate engages a polishing medium than when at least a portion of an underlying layer of the substrate under the cover layer engages the polishing medium, wherein detecting a change in heat at the front side of the substrate comprises sensing a temperature of byproducts produced by polishing the substrate; and

stopping removal of material from the substrate when the heat is a predetermined value that indicates a desired portion of the underlying layer is exposed at the front side of the substrate.

6. The method ofclaim 5 wherein the sensing step comprises measuring a temperature of a planarizing solution flowing off of the polishing pad.

7. A method of stopping mechanical and chemical-mechanical polishing of a substrate at an endpoint, the method comprising:

measuring a temperature of a component sensitive to heat at a front side of the substrate, the component temperature being different when a cover layer of the substrate engages a polishing medium than when a portion of an underlying layer of the substrate under the cover layer engages the polishing medium, wherein measuring the component temperature comprises sensing a temperature of byproducts produced by polishing the substrate; and

stopping removal of material from the substrate when the component temperature changes from the first temperature to the second temperature range.

8. A method of polishing a substrate, comprising:

removing material from a front side of the substrate with a polishing medium, the polishing medium being positioned at a planarizing surface of a polishing pad;

monitoring heat at the front side of the substrate, the heat at the front side of the substrate being different when a cover layer of the substrate engages the polishing medium than when at least a portion of an underlying layer of the substrate under the cover layer engages the polishing medium, wherein monitoring the heat comprises measuring a temperature of a component sensitive to heat at the front side of the substrate, the component temperature being a first temperature when the cover layer of the substrate engages the polishing medium and the component temperature being a second temperature when at least a portion of the underlying layer of the substrate engages the polishing medium, and wherein measuring the component temperature comprises sensing a temperature of byproducts produced by polishing the substrate; and

stopping removal of material from the substrate when the heat at the front side of the substrate is a predetermined value that indicates a desired portion of the cover layer has been removed from the substrate.

9. The method ofclaim 8 wherein the sensing step comprises measuring a temperature of a planarizing solution flowing off of the polishing pad.

10. A method of polishing a substrate, comprising:

detecting a change in heat at the front side of the substrate, the heat at the front side of the substrate being in a first range when a cover layer of the substrate engages the polishing medium and the heat being in a second range when a portion of an underlying layer of the substrate under the cover layer engages the polishing medium, wherein detecting the change in heat comprises measuring a temperature of a component sensitive to heat at the front side of the substrate, the component temperature being in a first temperature range when the heat at the front side of the substrate is in the first heat range and the component temperature being in a second temperature range when the heat at the front side of the substrate is in the second heat range, and wherein measuring the component temperature comprises sensing a temperature of byproducts produced by polishing the substrate; and

stopping removal of material from the substrate when the heat at the front side of the substrate is in the second range.

11. The method ofclaim 10 wherein the sensing step comprises measuring a temperature of a planarizing solution flowing off of the polishing pad.

12. A method of polishing a substrate, comprising:

measuring a temperature of a component sensitive to heat at the front side of the substrate, the component temperature being different when a cover layer of the substrate engages the polishing medium than when at least a portion of an underlying layer of the substrate under the cover layer engages the polishing medium, wherein measuring the component temperature comprises sensing a temperature of byproducts produced by polishing the substrate; and

stopping removal of material from the substrate when the component temperature changes from the first temperature range to the second temperature range.

13. The method ofclaim 12 wherein the sensing step comprises measuring a temperature of a planarizing solution flowing off of the polished pad.

14. A method for stopping polishing of a substrate at a desired endpoint, comprising:

monitoring a characteristic of a polishing component indicative of material being removed from a planarized surface of the substrate, wherein the polishing component comprises byproducts produced by polishing the substrate and the characteristic is an emission spectrum of the byproducts, and wherein monitoring a characteristic comprises analyzing the emission spectrum; and

stopping removal of material from the substrate when the characteristic of the polishing component that is monitored indicates the material being removed from the planarized surface is at the desired endpoint of the substrate.

15. A method for determining when the polishing of a substrate has reached an endpoint, the substrate having a cover layer and an underlying layer under the cover layer, the method comprising monitoring a characteristic of a polishing component indicative of material being removed from a planarized surface of the substrate, wherein the component comprises byproducts produced by polishing the substrate and the characteristic is a temperature of the byproducts, and wherein the monitoring step comprises sensing the temperature of the byproducts.

16. A method for determining when the polishing of a substrate has reached an endpoint, the method comprising detecting a change in heat at a front side of the substrate, the heat at the front side of the substrate being different when a cover layer of the substrate engages a polishing medium than when at least a portion of an underlying layer of the substrate under the cover layer engages the polishing medium, wherein detecting a change in heat at the front side of the substrate comprises sensing a temperature of byproducts by polishing the substrate.

17. The method ofclaim 16 wherein the temperature sensing act comprises measuring a temperature of a planarizing solution flowing off of the polishing pad.

18. The method ofclaim 14 wherein the emission spectrum is characteristic of a temperature of the byproducts.

19. The method ofclaim 14 wherein the emission spectrum is characteristic of a temperature of the byproducts and wherein analyzing the emission spectrum comprises sensing the temperature with an optical temperature sensor.