DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Claim Rejections - 35 USC § 103
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention.
Claims 1-6, 8-9, and 11-20 are rejected under 35 U.S.C. 103 as being unpatentable over Benvegnu et al. (US PG Pub No. 20150147940) in view of Wiswell et al. (US PG Pub No. 20200070306).
In regards to claim 1, Benvegnu discloses
a computer program product (remote controller 190; [0033]: a computer), comprising a non-transitory computer readable medium (memory [0007], [0114], [0118]: Generally, a central processing unit will receive instructions and data from a read only memory or a random access memory or both) encoded with instructions to cause one or more processors to perform a method of controlling polishing, comprising:
receive from an in-situ eddy current monitoring system (in-situ monitoring system 160; [0031]: eddy current) a sequence of signal values during polishing ([0040]) of a stack of adjacent conductive layers on a substrate;
[0040] In operation, the controller 190 can receive, for example, a signal that carries information describing a spectrum of the light received by the light detector for a particular flash of the light source or time frame of the detector. Thus, this spectrum is a spectrum measured in-situ during polishing (but applying eddy current modification).
convert the sequence of signal values into a sequence of thickness values ([0046]) for the stack of adjacent conductive layers;
[0045] For each measured spectrum, the controller 190 can calculate a characterizing value. The characterizing value is typically the thickness of the outer layer, but can be a related characteristic such as thickness removed. In addition, the characterizing value can be a physical property other than thickness, e.g., metal line resistance….
[0046] One technique to calculate a characterizing value is, for each measured spectrum, to identify a matching reference spectrum from a library of reference spectra. Each reference spectrum in the library can have an associated characterizing value, e.g., a thickness value or an index value indicating the time or number of platen rotations at which the reference spectrum is expected to occur.
repeatedly calculate a polishing rate ([0057], [0064], [0069]) from the sequence of thickness values during polishing of the substrate;
[0057] During the polishing process, measured thicknesses and measured polishing rates of multiple zones can be determined in-situ for each rotation of the platen, based on the in-situ measurements of completed rotation(s). The relationship among the measured thicknesses can be compared with the relative thickness relationship and the actual polishing rates can be adjusted so that the actual (or physical) thicknesses are changed in future rotation(s) to more closely follow the relative thickness relationship.
[0064] As briefly explained previously, for each zone, the measured thickness in each rotation can be determined as the average or median value of all derived thicknesses in the rotation, or can be a fitted value. A measured polishing rate for each zone can be determined in each rotation using a function that fits the derived thicknesses of each zone.
for an initial time period (t. sub. 0; [0060-0062]), calculate one or more first adjustments ([0057], [0060-0062])) for one or more polishing parameters ([0026]), based on the polishing rate using a first control algorithm;
[0057] During the polishing process, measured thicknesses and measured polishing rates of multiple zones can be determined in-situ... In one example, the actual polishing rates of certain zones can be changed by changing the pressure of the corresponding chambers and the amount of pressure changes can be derived from the amount of polishing rates to be changed, as explained further below.
[0060] Referring to FIG. 4, the derived thicknesses (or the thicknesses derived from in-situ measurements, such as optical spectra) for a reference zone and a control zone are plotted to facilitate the visualization of a process for adjusting the chamber pressure and the polishing rate of the control zone.
[0061] In particular, along the time axis (horizontal axis), three predetermined pressure update time t.sub.0, t.sub.1, and t.sub.2 have been marked. The time axis can also be mapped to the number of rotations completed by the platen. The current time point of the polishing process shown in the plot is t.sub.1, at which time the platen has completed k+n rotations, (n+1) of which have been completed between the two pressure update time t.sub.0 (exclusive) and t.sub.1 (inclusive). In the example shown in the plot, n is 9, and a total of 10 rotations have been completed in the time period t.sub.1-t.sub.0. Of course, n could be a value other than 9, e.g., 5 or more, depending on the rate at which adjustments are performed and the rotation rate of the platen.
[0062] The chamber pressure adjustment and polishing rate adjustment for the control zone is to be determined so that during the time period t.sub.1 to t.sub.2, the control zone is polished at the adjusted polishing rate. Before the pressure update time t.sub.1, one or more chamber pressure/polishing rate updates have been performed for the control zone, in a manner similar to the adjustments to be determined and to be made at t.sub.1, and after the pressure update time t.sub.1, zero or one or more additional pressure updates may be performed, also in a manner similar to the adjustments determined and to be made at t.sub.1, until the endpoint time of the polishing process.
and for a subsequent time period after detection of the change in the polishing rate, calculate one or more second adjustments ([0057], [0060-0062]) for the one or more polishing parameters based on the polishing rate using a different second control algorithm.
Benvegnu fails to disclose a step wherein the controller is configured to determine that detecting “a change in the polishing rate that meets at least one first predetermined criterion that indicates exposure of an underlying conductive layer in a stack of adjacent conductive layers on the substrate that is being polished.”
Wiswell discloses a polishing system that uses in situ polishing monitoring employing optical or eddy current sensors. Wiswell teaches how a change in polishing rate indicates layer exposure:
[0005] One problem in CMP is determining whether the polishing process is complete, i.e., whether a substrate layer has been planarized to a desired flatness or thickness, when a desired amount of material has been removed, or when an underlying layer has been exposed. Variations in the initial thickness of the substrate layer, the slurry composition, the polishing pad condition, the relative speed between the polishing pad and the substrate, and the load on the substrate can cause variations in the material removal rate…
[0040] In operation, the CMP apparatus 100 can use the in-situ monitoring system 200 to determine when the bulk of the filler layer has been removed and/or to determine when the underlying stop layer has been substantially exposed. In particular, when an underlying layer is exposed, there should be a sudden change in the coefficient of friction. This change can be detected, e.g., by detecting changes in slope of the trace, or by detecting that the amplitude or slope of the trace passes a threshold value. Detection of exposure of the underlying layer can trigger the polishing endpoint and halt polishing.
[0041] ... In addition, the computer 190 can be programmed to divide the measurements from the sensor 202 from each sweep beneath the substrate into a plurality of sampling zones 194, to calculate the radial position of each sampling zone, and to sort the amplitude measurements into radial ranges. After sorting the measurements into radial ranges, information on the film thickness can be fed in real-time into a closed-loop controller to periodically or continuously modify the polishing pressure profile applied by a carrier head in order to provide improved polishing uniformity.
[0059] Different substrate layers have different coefficients of friction between the deposited layers and the substrate contacting portion 214. This difference in coefficients of friction means that different deposited layers will generate different amounts of frictional force, and thus different amounts of shear on the sensor 202. If the coefficient of friction increases, the shear will increase. Similarly, if the coefficient of friction decreases, the shear will decrease. When deposited layer 16 has been polished down to expose the patterned layer 14, the shear will change to reflect the different coefficient of friction between the material of the deposited layer 14 and the polishing pad 30. Consequently, a computing device, such as the controller 190, can be used to determine the polishing endpoint by monitoring the changes in shear, and thus friction, detected by the in-situ monitoring system.
Benvegnu and Wiswell are from the same field of endeavor as the claimed invention, in-situ chemical mechanical polishing systems that employ eddy current sensors.
Therefore, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed invention to have modified Benvegnu to incorporate the teachings of Wiswell, and provide controller logic to determine when a conductive layer of a substrate had been exposed in order to improve endpoint detection, improve wafer uniformity in polishing and increase wafer quality consistently.
In regards to claim 2, Benvegnu as modified discloses
the computer program product of claim 1, wherein the instructions to calculate ([0078], [0084]) the one or more first adjustments for the one or more polishing parameters use a first matrix (matrix [0078]), and
wherein the instructions to calculate the one or more second adjustments ([0057], [0060-0062]) for the one or more polishing parameters use a second matrix (matrix [0078] with different values as the inputs have changed resultant of performed polishing).
[0078] The polishing rate of the control zone is adjusted by adjusting the pressure of its corresponding chamber. The amount of the pressure adjustment can be determined based on the amount of polishing rate adjustment using a Preston matrix…
[0084] When the rate is adjusted from one rotation to the next rotation, .DELTA.rate can be calculated as:
.DELTA.rate=.rho.P.DELTA.p,
where .rho. is the nominal polishing rate for the zone, P is the Preston matrix, which is discussed further below, and .DELTA.p is the pressure change made in the corresponding chamber.
In regards to claim 3, Benvegnu as modified discloses
the computer program product of claim 1, comprising instructions to iterate calculation of a first polishing rate and calculation of the one or more first adjustments prior to detecting the change in the polishing rate at a first frequency ([0059]),
[0059] … the controller and/or computer can schedule to adjust the polishing rates of the control zones at a predetermined rate, e.g., every given number of rotations, e.g., every 5 to 50 rotations, or every given number of seconds, e.g., every 3 to 30 seconds. In some ideal situations, the adjustment may be zero at the prescheduled adjustment time. In other implementations, the adjustments can be made at a rate determined in-situ. For example, if the measured thicknesses of different zones are vastly different from the desired thickness relationships, then the controller and/or the computer may decide to make frequent adjustments for the polishing rates.
and instructions to iterate calculation of a second polishing rate and calculation of the one or more second adjustments ([0057], [0060-0062]) after to detecting the change in the polishing rate at a second frequency ([0059]: adjusted in-situ based upon values received).
In regards to claim 4, Benvegnu as modified discloses
the computer program product of claim 3, wherein the first frequency ([0059]) is different from the second frequency ([0059]: adjusted in-situ based upon values received).
In regards to claim 5, Benvegnu as modified discloses
the computer program product of claim 1, comprising instructions to, after detection of the change in the polishing rate, detect a second change (when another layer is exposed) in the polishing rate that meets at least one second predetermined criterion that indicates exposure of a further layer below the underlying conductive layer (Wiswell [0059]).
[0059] Different substrate layers have different coefficients of friction between the deposited layers and the substrate contacting portion 214. This difference in coefficients of friction means that different deposited layers will generate different amounts of frictional force, and thus different amounts of shear on the sensor 202. If the coefficient of friction increases, the shear will increase. Similarly, if the coefficient of friction decreases, the shear will decrease. When deposited layer 16 has been polished down to expose the patterned layer 14, the shear will change to reflect the different coefficient of friction between the material of the deposited layer 14 and the polishing pad 30. Consequently, a computing device, such as the controller 190, can be used to determine the polishing endpoint by monitoring the changes in shear, and thus friction, detected by the in-situ monitoring system.
In regards to claim 6, Benvegnu as modified discloses
the computer program product of claim 1, wherein the instructions to calculate the one or more first adjustments comprise instructions to limit the first adjustments to a first maximum change ([0023] predetermined pressure range; affects adjustment in a limited manner) , and wherein the instructions to calculate the one or more second adjustments ([0057], [0060-0062]) comprise instructions to limit the second adjustments to a different second maximum change ([0023]).
[0023] In some implementations, one or more predictive filters are applied to the results of the in-situ measurement to provide filtered thicknesses and polishing rates that can have improved precision over unfiltered thicknesses and polishing rates. An example of the predictive filter is a Kalman filter. Multiple pressure adjustments, and therefore, polishing rate adjustments, can be made for one or more substrate zones and the overall polishing precision for the substrate(s) can be improved. In some implementations, each pressure adjustment is additionally controlled such that the pressure remains within a predetermined pressure range, and/or the pressure adjustment do not exceed a predetermined pressure adjustment range, so that the possible imprecision in the determined pressure adjustment affects the actual pressure adjustment in a limited manner.
In regards to claim 8, Benvegnu discloses
a polishing system, comprising:
a platen (platen 120, fig. 1) to support a polishing pad (polishing pad 110, fig. 1);
a carrier head (carrier head 140, fig. 1) to hold a substrate;
a motor (rotation motor 154, fig. 1) to generate relative motion between the platen (platen 120, fig. 1) and the carrier head (carrier head 140, fig. 1);
an in-situ eddy current monitoring system (in-situ monitoring system 160; [0031]: eddy current) to monitor the substrate during polishing ([0040]) of the substrate; and a controller configured to:
receive a sequence of signal values from the in-situ eddy current monitoring system (in-situ monitoring system 160; [0031]) during polishing of a stack of adjacent conductive layers on a substrate;
convert the sequence of signal values into a sequence of thickness values ([0046]) for the stack of adjacent conductive layers;
repeatedly calculate a polishing rate ([0057], [0064], [0069]) from the sequence of thickness values during polishing of the substrate; for an initial time period (t. sub. 0; [0060-0062]), calculate one or more first adjustments ([0057], [0060-0062])) for one or more polishing parameters ([0026]), based on the polishing rate using a first control algorithm;
for a subsequent time period after detection of the change in the polishing rate, calculate one or more second adjustments ([0057], [0060-0062]) for the one or more polishing parameters based on the polishing rate using a different second control algorithm.
Benvegnu fails to disclose being configure to “detect a change in the polishing rate that meets at least one first predetermined criterion that indicates exposure of an underlying conductive layer in a stack of adjacent conductive layers on the substrate that is being polished.”
Wiswell discloses a polishing system that uses in situ polishing monitoring employing optical or eddy current sensors. Wiswell teaches how a change in polishing rate indicates layer exposure:
[0005] One problem in CMP is determining whether the polishing process is complete, i.e., whether a substrate layer has been planarized to a desired flatness or thickness, when a desired amount of material has been removed, or when an underlying layer has been exposed. Variations in the initial thickness of the substrate layer, the slurry composition, the polishing pad condition, the relative speed between the polishing pad and the substrate, and the load on the substrate can cause variations in the material removal rate…
[0040] In operation, the CMP apparatus 100 can use the in-situ monitoring system 200 to determine when the bulk of the filler layer has been removed and/or to determine when the underlying stop layer has been substantially exposed. In particular, when an underlying layer is exposed, there should be a sudden change in the coefficient of friction. This change can be detected, e.g., by detecting changes in slope of the trace, or by detecting that the amplitude or slope of the trace passes a threshold value. Detection of exposure of the underlying layer can trigger the polishing endpoint and halt polishing.
[0041] ... In addition, the computer 190 can be programmed to divide the measurements from the sensor 202 from each sweep beneath the substrate into a plurality of sampling zones 194, to calculate the radial position of each sampling zone, and to sort the amplitude measurements into radial ranges. After sorting the measurements into radial ranges, information on the film thickness can be fed in real-time into a closed-loop controller to periodically or continuously modify the polishing pressure profile applied by a carrier head in order to provide improved polishing uniformity.
[0059] Different substrate layers have different coefficients of friction between the deposited layers and the substrate contacting portion 214. This difference in coefficients of friction means that different deposited layers will generate different amounts of frictional force, and thus different amounts of shear on the sensor 202. If the coefficient of friction increases, the shear will increase. Similarly, if the coefficient of friction decreases, the shear will decrease. When deposited layer 16 has been polished down to expose the patterned layer 14, the shear will change to reflect the different coefficient of friction between the material of the deposited layer 14 and the polishing pad 30. Consequently, a computing device, such as the controller 190, can be used to determine the polishing endpoint by monitoring the changes in shear, and thus friction, detected by the in-situ monitoring system.
Benvegnu and Wiswell are from the same field of endeavor as the claimed invention, in-situ chemical mechanical polishing systems that employ eddy current sensors.
Therefore, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed invention to have modified Benvegnu to incorporate the teachings of Wiswell, and provide controller logic to determine when a conductive layer of a substrate had been exposed in order to improve endpoint detection, improve wafer uniformity in polishing and increase wafer quality consistently.
In regards to claim 9, Benvegnu as modified discloses
the system of claim 8, wherein the carrier head (carrier head 140, fig. 1) comprises a plurality of independently controllable chambers ([0027]), and the one or more polishing parameters include one or more pressures for one or more of the chambers ([0057]).
[0027] In particular, each carrier head 140 can include a retaining ring 142 to retain the substrate 10 below a flexible membrane 144. Each carrier head 140 also includes a plurality of independently controllable pressurizable chambers defined by the membrane, e.g., three chambers 146a-146c, which can apply independently controllable pressurizes to associated zones 148a-148c on the flexible membrane 144 and thus on the substrate 10 (see FIG. 2).
[0057]:… In one example, the actual polishing rates of certain zones can be changed by changing the pressure of the corresponding chambers and the amount of pressure changes can be derived from the amount of polishing rates to be changed, as explained further below.
In regards to claim 11, Benvegnu discloses
a computer program product (remote controller 190; [0033]: a computer), comprising a non-transitory computer readable medium (memory [0007], [0114], [0118]: Generally, a central processing unit will receive instructions and data from a read only memory or a random access memory or both) encoded with instructions to cause one or more processors to perform a method of controlling polishing, comprising:
receive from an in-situ eddy current monitoring system (in-situ monitoring system 160; [0031]) a sequence of characterizing values during polishing ([0040]) of a stack of adjacent layers on a substrate by a polishing system that has one or more polishing control parameters that affect a polishing rate of the stack of adjacent layers;
detect a polishing endpoint for the substrate that is being polished using a second detection algorithm on the sequence of characterizing values, the second detection algorithm having a different detection criterion to indicate the polishing endpoint;
for an initial time period (t. sub. 0; [0060-0062]) prior to detection of the exposure of the underlying layer, calculate one or more first adjustments ([0057], [0060-0062])) for one or more polishing control parameters based on a first target polishing rate and using a first control algorithm that includes a control variable other than the first target polishing rate and the first detection criterion; and
for a subsequent time period after detection of the exposure of the underlying layer and before detection of the polishing endpoint, calculate one or more second adjustments ([0057], [0060-0062]) for the one or more polishing control parameters based on a second target polishing rate that is different from the first target polishing rate and using a second control algorithm that includes the control variable set to a different value than in the first control algorithm.
Benvegnu fails to disclose “detect exposure of an underlying layer in the stack of adjacent layers on the substrate that is being polished using a first detection algorithm on the sequence of characterizing values, the first detection algorithm having a first detection criterion to indicate exposure of the underlying layer.
Wiswell discloses a polishing system that uses in situ polishing monitoring employing optical or eddy current sensors. Wiswell teaches how a change in polishing rate indicates layer exposure:
[0005] One problem in CMP is determining whether the polishing process is complete, i.e., whether a substrate layer has been planarized to a desired flatness or thickness, when a desired amount of material has been removed, or when an underlying layer has been exposed. Variations in the initial thickness of the substrate layer, the slurry composition, the polishing pad condition, the relative speed between the polishing pad and the substrate, and the load on the substrate can cause variations in the material removal rate…
[0040] In operation, the CMP apparatus 100 can use the in-situ monitoring system 200 to determine when the bulk of the filler layer has been removed and/or to determine when the underlying stop layer has been substantially exposed. In particular, when an underlying layer is exposed, there should be a sudden change in the coefficient of friction. This change can be detected, e.g., by detecting changes in slope of the trace, or by detecting that the amplitude or slope of the trace passes a threshold value. Detection of exposure of the underlying layer can trigger the polishing endpoint and halt polishing.
[0041] ... In addition, the computer 190 can be programmed to divide the measurements from the sensor 202 from each sweep beneath the substrate into a plurality of sampling zones 194, to calculate the radial position of each sampling zone, and to sort the amplitude measurements into radial ranges. After sorting the measurements into radial ranges, information on the film thickness can be fed in real-time into a closed-loop controller to periodically or continuously modify the polishing pressure profile applied by a carrier head in order to provide improved polishing uniformity.
[0059] Different substrate layers have different coefficients of friction between the deposited layers and the substrate contacting portion 214. This difference in coefficients of friction means that different deposited layers will generate different amounts of frictional force, and thus different amounts of shear on the sensor 202. If the coefficient of friction increases, the shear will increase. Similarly, if the coefficient of friction decreases, the shear will decrease. When deposited layer 16 has been polished down to expose the patterned layer 14, the shear will change to reflect the different coefficient of friction between the material of the deposited layer 14 and the polishing pad 30. Consequently, a computing device, such as the controller 190, can be used to determine the polishing endpoint by monitoring the changes in shear, and thus friction, detected by the in-situ monitoring system.
Benvegnu and Wiswell are from the same field of endeavor as the claimed invention, in-situ chemical mechanical polishing systems that employ eddy current sensors.
Therefore, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed invention to have modified Benvegnu to incorporate the teachings of Wiswell, and provide controller logic to determine when a conductive layer of a substrate had been exposed in order to improve endpoint detection, improve wafer uniformity in polishing and increase wafer quality consistently.
Examiner’s Note: While Benvegnu doesn’t use the term “algorithm”, a skilled artisan would recognize that a series of steps are used to solve a problem/perform a computation. Therefore, while not explicitly defined as such, Benvegnu as modified applies an algorithm in order to determine the exposure of layers by taking in-situ measurements and comparing them to stored threshold values.
In regards to claim 12, Benvegnu as modified discloses
the computer program product of claim 11, wherein the instructions to calculate ([0078], [0084]) the one or more first adjustments for the one or more polishing control parameters use a first matrix (matrix [0078]), and
wherein the instructions to calculate the one or more second adjustments ([0057], [0060-0062]) for the one or more polishing control parameters use a second matrix (matrix [0078] with different values as the inputs have changed resultant of performed polishing).
In regards to claim 13, Benvegnu as modified discloses
the computer program product of claim 11, comprising instructions to iterate calculation of the one or more first adjustments prior to detecting the exposure of the underlying layer at a first frequency ([0059]), and instructions to iterate calculation of a second polishing rate and calculation of the one or more second adjustments after detecting the exposure of the underlying layer at a second frequency ([0059]).
In regards to claim 14, Benvegnu as modified discloses
the computer program product of claim 13, wherein the first frequency ([0059]) is different from the second frequency ([0059]: adjusted in-situ based upon values received).
In regards to claim 15, Benvegnu as modified discloses
the computer program product of claim 11, comprising instructions to, after detection of the exposure of the underlying layer (Wiswell [0059]), detect a second change in the polishing rate that meets at least one second predetermined criterion that indicates exposure of a further layer below the underlying layer (Wiswell [0059]).
In regards to claim 16, Benvegnu as modified discloses
the computer program product of claim 11, wherein the instructions to calculate the one or more first adjustments comprise instructions to limit the first adjustments to a first maximum change ([0023]), and wherein the instructions to calculate the one or more second adjustments ([0057], [0060-0062]) comprise instructions to limit the second adjustments to a different second maximum change ([0023]).
In regards to claim 17, Benvegnu discloses
a polishing system, comprising:
a platen (platen 120, fig. 1) to support a polishing pad (polishing pad 110, fig. 1);
a carrier head (carrier head 140, fig. 1) to hold a substrate;
a motor (rotation motor 154, fig. 1) to generate relative motion between the platen (platen 120, fig. 1) and the carrier head (carrier head 140, fig. 1);
an in-situ eddy current monitoring system (in-situ monitoring system 160; [0031]) to monitor the substrate during polishing ([0040]) of the substrate; and a controller configured to:
receive from the in-situ eddy current monitoring system (in-situ monitoring system 160; [0031]) a sequence of characterizing values during polishing ([0040]) of a stack of adjacent layers on a substrate that has one or more polishing control parameters that affect a polishing rate of the stack of adjacent layers,
calculate one or more first adjustments ([0057], [0060-0062])) for one or more polishing control parameters based on a first target polishing rate and using a first control algorithm that includes a control variable other than the first target polishing rate and first detection criterion, and for a subsequent time period after detection of the exposure of the underlying layer and before detection of the polishing endpoint, calculate one or more second adjustments ([0057], [0060-0062]) for the one or more polishing control parameters based on a second target polishing rate that is different from the first target polishing rate and using a second control algorithm that includes the control variable set to a different value than in the first control algorithm.
Benvegnu fails to explicitly disclose “detecting exposure of an underlying layer in the stack of adjacent layers on the substrate that is being polished using a first detection algorithm on the sequence of characterizing values, the first detection algorithm having a first detection criterion to indicate exposure of the underlying layer, detect a polishing endpoint for the substrate that is being polished using a second detection algorithm on the sequence of characterizing values, the second detection algorithm having a different detection criterion to indicate the polishing endpoint”, for an initial time period (t. sub. 0; [0060-0062]) prior to detection of the exposure the underlying layer.
Benvegnu fails to disclose “detect exposure of an underlying layer in the stack of adjacent layers on the substrate that is being polished using a first detection algorithm on the sequence of characterizing values, the first detection algorithm having a first detection criterion to indicate exposure of the underlying layer.
Wiswell discloses a polishing system that uses in situ polishing monitoring employing optical or eddy current sensors. Wiswell teaches how a change in polishing rate indicates layer exposure:
[0005] One problem in CMP is determining whether the polishing process is complete, i.e., whether a substrate layer has been planarized to a desired flatness or thickness, when a desired amount of material has been removed, or when an underlying layer has been exposed. Variations in the initial thickness of the substrate layer, the slurry composition, the polishing pad condition, the relative speed between the polishing pad and the substrate, and the load on the substrate can cause variations in the material removal rate…
[0040] In operation, the CMP apparatus 100 can use the in-situ monitoring system 200 to determine when the bulk of the filler layer has been removed and/or to determine when the underlying stop layer has been substantially exposed. In particular, when an underlying layer is exposed, there should be a sudden change in the coefficient of friction. This change can be detected, e.g., by detecting changes in slope of the trace, or by detecting that the amplitude or slope of the trace passes a threshold value. Detection of exposure of the underlying layer can trigger the polishing endpoint and halt polishing.
[0041] ... In addition, the computer 190 can be programmed to divide the measurements from the sensor 202 from each sweep beneath the substrate into a plurality of sampling zones 194, to calculate the radial position of each sampling zone, and to sort the amplitude measurements into radial ranges. After sorting the measurements into radial ranges, information on the film thickness can be fed in real-time into a closed-loop controller to periodically or continuously modify the polishing pressure profile applied by a carrier head in order to provide improved polishing uniformity.
[0059] Different substrate layers have different coefficients of friction between the deposited layers and the substrate contacting portion 214. This difference in coefficients of friction means that different deposited layers will generate different amounts of frictional force, and thus different amounts of shear on the sensor 202. If the coefficient of friction increases, the shear will increase. Similarly, if the coefficient of friction decreases, the shear will decrease. When deposited layer 16 has been polished down to expose the patterned layer 14, the shear will change to reflect the different coefficient of friction between the material of the deposited layer 14 and the polishing pad 30. Consequently, a computing device, such as the controller 190, can be used to determine the polishing endpoint by monitoring the changes in shear, and thus friction, detected by the in-situ monitoring system.
Benvegnu and Wiswell are from the same field of endeavor as the claimed invention, in-situ chemical mechanical polishing systems that employ eddy current sensors.
Therefore, it would have been obvious to someone of ordinary skill in the art before the effective filing date of the claimed invention to have modified Benvegnu to incorporate the teachings of Wiswell, and provide controller logic to determine when a conductive layer of a substrate had been exposed in order to improve endpoint detection, improve wafer uniformity in polishing and increase wafer quality consistently.
Examiner’s Note: While Benvegnu doesn’t use the term “algorithm”, a skilled artisan would recognize that a series of steps are used to solve a problem/perform a computation. Therefore, while not explicitly defined as such, Benvegnu as modified applies an algorithm in order to determine the exposure of layers by taking in-situ measurements and comparing them to stored threshold values.
In regards to claim 18, Benvegnu as modified discloses
the system of claim 17, wherein the carrier head (carrier head 140, fig. 1) comprises a plurality of independently controllable chambers ([0027]), and the one or more polishing control parameters include one or more pressures for one or more of the chambers ([0057]).
In regards to claim 19, Benvegnu as modified discloses
the computer program product of claim 1, wherein the first control algorithm function and the second control algorithm use running windows of different durations ([0086-0087]).
[0086] The controller and/or computer also calculates (606) a predicted error covariance P.sub.m.sup.- for the m.sup.th rotation:
[0087] Based on the predicted error covariance for the m.sup.th rotation, P.sub.m.sup.-, the controller and/or computer calculates (608) a Kalman weight, K.sub.m, for the m.sup.th rotation)
Examiner’s Note: As the polishing rate is adjusted, the characterizing values and rates as which they are received is dependent upon that rate, and will resultingly have different durations.
In regards to claim 20, Benvegnu as modified discloses
the computer program product of claim 2, wherein the first matrix (matrix [0078]) and second matrix (matrix [0078] with different values as the inputs have changed resultant of performed polishing) include different values for at least one element at the same row and column in the first matrix and second matrix.
Examiner’s Note: As each row would have its own matrix, a skilled artisan, for efficiency and clarity, would populate the first row with values reflective the zone having its polishing rate adjusted.
Claims 7 and 10 are rejected under 35 U.S.C. 103 as being unpatentable over Benvegnu in view of Wiswell as applied to claims 1 and 8 above, and further in view of Huang et al. (US PG Pub No. 20050225898).
In regards to claim 7, Benvegnu as modified discloses
the computer program product of claim 1, but fails to disclose the instructions to calculate the polishing rate from the sequence of thickness values use a correlation curve based on a “resistivity” of a layer from the stack of adjacent conductive layers.
However, Huang, which discloses a CMP device concerned with endpoint detection, teaches that both friction and eddy current sensing, which would rely upon resistivity, can be used in determining layer exposure through detecting a change in polishing rates.
[0022] Stop layer 16 provides a means for accurately detecting the endpoint of a CMP process, which may be accomplished in several manners. First, the CMP endpoint may be detected based upon measurable fluctuations in the motor current of a CMP apparatus (not shown). These fluctuations are induced by changes in polishing friction during a polishing process (i.e., changes in removal rates), and correlate to the differences in removal rate selectivities between the layers. Additionally, the CMP endpoint may also be detected by changes in surface optical reflectivity and changes in eddy currents induced through the layers. The detection of the CMP endpoint through these techniques allows top surface 16a and surface 12a to be evenly planarized for providing a smooth surface for magnetic feature 10.
Huang and Benvegnu are analogous to the claimed invention as they are in the same field of endeavor. Therefore it would have been obvious before the effective filing date, through simple substation, to use eddy current sensors to detect the change in polishing rate and apply resistivity values for detecting the change in layers and using in calculating the polishing rate from the thickness values.
In regards to claim 10, Benvegnu as modified discloses
the system of claim 8, but fails to disclose the instructions to calculate the polishing rate from the sequence of thickness values use a correlation curve based on a “resistivity” of a layer from the stack of adjacent conductive layers.
However, Huang, which discloses a CMP device concerned with endpoint detection, teaches that both friction and eddy current sensing, which would rely upon resistivity, can be used in determining layer exposure through detecting a change in polishing rates.
[0022] Stop layer 16 provides a means for accurately detecting the endpoint of a CMP process, which may be accomplished in several manners. First, the CMP endpoint may be detected based upon measurable fluctuations in the motor current of a CMP apparatus (not shown). These fluctuations are induced by changes in polishing friction during a polishing process (i.e., changes in removal rates), and correlate to the differences in removal rate selectivities between the layers. Additionally, the CMP endpoint may also be detected by changes in surface optical reflectivity and changes in eddy currents induced through the layers. The detection of the CMP endpoint through these techniques allows top surface 16a and surface 12a to be evenly planarized for providing a smooth surface for magnetic feature 10.
Huang and Benvegnu are analogous to the claimed invention as they are in the same field of endeavor. Therefore it would have been obvious before the effective filing date, through simple substation, to use eddy current sensors to detect the change in polishing rate and apply resistivity values for detecting the change in layers and using in calculating the polishing rate from the thickness values.
Conclusion
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/JASON KHALIL HAWKINS/Examiner, Art Unit 3723
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