# US 6,725,120 B2 · Apparatus and methods with resolution enhancement feature for improving accuracy of conversion of required chemical mechanical polishing pressure to force to be applied by polishing head to wafer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,725,120 B2 - Document ID: US6725120B2 - Status: Granted - Kind: B2 - Application number: 09/823,151 - Filed: 2001-03-29 - Published: 2002-12-19 - Granted: 2004-04-20 - Earliest claimed: 2001-03-29 - Assignees: Lam Research Corporation - Inventors: Miguel Angel Saldana - Web page: https://patentgrep.com/patent/US6725120B2 ## CPC - G05B 19/408: characterised by data handling or data format, e.g. reading, buffering or conversion of data - B24B 37/005: Control means for lapping machines or devices - B24B 37/30: for single side lapping of plane surfaces - B24B 49/16: taking regard of the load - Y10S 438/959: Mechanical polishing of wafer - G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G) - B24B: MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING (grinding of gear teeth B23F, of screw-threads B23G1/36; by electro-erosion B23H; abrasive or related blasting B24C; tools for grinding, buffing or sharpening B24D; polishing compositions C09G1/00; abrasives C09K3/14; electrolytic etching or polishing C25F3/00; grinding arrangements for use on assembled railway tracks E01B31/17); DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract CMP systems and methods in which a polishing pad is moved relative to a wafer and a retainer ring implement instructions for applying required pressure to the wafer for CMP operations. Accuracy of computations of the pressures, and of conversion of the pressure to force, is improved without use of high resolution components, such as high resolution digital devices. Such improved accuracy is achieved using both digital and analog operations, and by converting values of required pressure or force from one set of units to a second set of units and then back to the first set of units. A quantization process is performed using data processed by average resolution digital devices. The process transfers both pressure/force scale and pressure/force set point data between separate processors to obtain computed values of pressure and force having acceptable accuracy, such that quantization errors are eliminated or significantly reduced. ## Claims ### Claim 1 Apparatus for processing a desired value among a range of pressure values to be applied to a wafer in chemical mechanical polishing, the processing providing improved accuracy in representing the desired value, the apparatus comprising: a processor programmed to divide the pressure range by the value of a component resolution to define scale portions of the pressure range; the processor being programmed to generate a first output signal to identify one of the scale portions that includes the desired value; and the processor being programmed to generate a second output signal to identify a set point that defines the requested value in the identified scale portion. ### Claim 2 (depends on 1) Apparatus as recited in claim 1, wherein the component resolution is the resolution of a digital device that outputs data representing the identity of the one of the scale portions and of the set point. ### Claim 3 (depends on 2) Apparatus as recited in claim 2, wherein the programming of the processor to generate the first output signal comprises programming for: converting the identified scale portion to resolution units; dividing a range of the first output signal by the component resolution to define a first signal conversion factor; and converting the identified scale portion in resolution units to the first output signal by multiplying the count value of the identified scale portion times the first signal conversion factor. ### Claim 4 (depends on 2) Apparatus as recited in claim 2, wherein the programming of the processor to generate the second output signal comprises programming for: converting the identified set point to resolution units; dividing a range of the second output signal by the component resolution to define a second signal conversion factor; and converting the identified set point in resolution units to the second output signal by multiplying the count value of the identified set point times the second signal conversion factor. ### Claim 5 Apparatus for reducing quantization error in a computation of a chemical mechanical polishing parameter, the apparatus comprising: first and second digital data processors each provided with data storage for storing synchronization data for synchronization operations of the first and second digital processors, the synchronization data defining a computational resolution, a set of values of the parameter to be used in computations, a set of values of output parameter data for communications between the first and second digital processors, a scale data conversion function that defines a relationship between the parameter and each one of a plurality of scales into which the set of values of the parameter is divided; a set point data conversion function that defines a relationship between a range of values of the parameter in a particular one of the scales and a set point that defines a required value of the parameter in the particular scale; the first processor being programmed to use the synchronization data to first convert a required value of the parameter to first output pressure digital data representing a particular one of the scales; the first processor being further programmed to use the synchronization data to second convert the required value of the parameter to second output pressure digital data representing the set point that defines the parameter in the particular scale; the second processor being further programmed to use the synchronization data to third convert the first output parameter digital data to scale data representing the particular one of the scales; and the second processor being further programmed to use the synchronization data to fourth convert the second output pressure digital data to digital data representing the required value of the parameter. ### Claim 6 (depends on 5) Apparatus as recited in claim 5, wherein the programming of the first processor to first convert includes: instructions for dividing the computational resolution into the highest value of the set of values of the parameter to define the scale data conversion function in terms of a number of the plurality of the scales, each of the scales having a range within the set of values; each range being of equal-value, and instructions for identifying which of the scales corresponds to the required value of the parameter. ### Claim 7 (depends on 5) Apparatus as recited in claim 5, wherein the set point data conversion function is based on the ratio of the required value of the parameter to the range of values of the parameter in the particular scale. ### Claim 8 (depends on 5) Apparatus as recited in claim 5, wherein the synchronization data further includes a definition of a voltage conversion value in terms of numbers of counts per voltage value, and wherein the programming of the second processor to third convert includes instructions for: multiplying a voltage value of the first output parameter digital data by the voltage conversion value to convert the first output parameter digital data to digital count data, wherein the synchronization data further includes a definition of a count conversion value in terms of numbers of counts per particular ones of the scales, and wherein the programming of the second processor to third convert includes instructions for multiplying the digital count data value of the first output parameter digital data by the count conversion value to convert the digital count data to the scale data. ### Claim 9 (depends on 5) Apparatus as recited in claim 5, wherein the set point data conversion function further includes a definition of a voltage conversion value in terms of numbers of counts per voltage value, and wherein the programming of the second processor to fourth convert includes instructions for multiplying a voltage value of the second output pressure digital data by the voltage conversion value to convert the second output parameter digital data to digital count data. ### Claim 10 Apparatus for reducing quantization error in specifying chemical mechanical polishing pressure in which a computational resolution is to be used in processing a required value of the pressure to obtain a computed value of the pressure, the apparatus comprising: a chemical mechanical polishing system configured with a polishing pad for applying pressure to a wafer, the pressure being within a set of pressure values that includes the required value of the pressure; a first digital processor programmed with a computational resolution having a relatively average value, the first processor being further programmed to divide the highest value of pressure of the set by the value of the computational resolution to obtain a series of pressure scales of the set, the pressure scales representing uniformly increasing possible values of the pressure, the scales having equal ranges of pressure each of which ranges has a value in excess of the value of the required pressure; the first digital processor being further programmed to provide a different first identifier for each of the scales of the pressure, the number of different first identifiers being equal to the value of the computational resolution; and the first digital processor being further programmed to specify the required value of the pressure by providing a different second identifier to indicate a set point value within any specific one of the scales, the set point corresponding to any particular pressure value, the number of different second identifiers being equal to the value of the computational resolution. ### Claim 11 (depends on 10) Apparatus as recited in claim 10, wherein the specific required value of the pressure is to be communicated to a second digital processor for processing the required value of the pressure, the apparatus comprising: the first digital processor being further programmed for generating a two-part output representing the required value of the pressure, the output including first data representing the first identifier that corresponds to the specific one of the scales that includes the required value of the pressure, the output further including second data representing the second identifier that corresponds to the required value of the pressure within the specific one of the scales. ### Claim 12 (depends on 11) Apparatus as recited in claim 11, wherein: the second digital processor is configured to receive the first and second data of the output, the second digital processor is programmed with the computational resolution having the relatively average value; and the second digital processor is programmed to convert the output to the exact amount of the required value of the pressure by selecting one of the pressure scales corresponding to the first identifier and by selecting a value within the selected pressure scale corresponding to the second identifier. ### Claim 13 Apparatus for processing a desired value among an entire range of pressure values to be applied to a wafer in chemical mechanical polishing, the processing providing improved accuracy in representing the desired value, the apparatus comprising: a processor programmed to computationally divide the pressure range by the value of a component resolution to define scale portions of the pressure range; the processor being programmed to generate a first output signal to identify one of the computationally defined scale portions that includes the desired value; and the processor being programmed to computationally generate a second output signal to identify a set point that defines the requested value in the identified scale portion. ### Claim 14 (depends on 13) Apparatus as recited in claim 13, wherein the component resolution is the resolution of a digital device that outputs data representing the identity of the one of the scale portions and of the set point. ### Claim 15 (depends on 14) Apparatus as recited in claim 14, wherein the programming of the processor to generate the first output signal comprises programming for: converting the identified scale portion to resolution units; dividing a range of the first output signal by the same relatively average component resolution to define a first signal conversion factor; and converting the identified scale portion in resolution units to the first output signal by multiplying the count value of the identified scale portion times the first signal conversion factor. ### Claim 16 (depends on 14) Apparatus as recited in claim 14, wherein the programming of the processor to generate the second output signal comprises programming for: converting the identified set point to resolution units; dividing a range of the second output signal by the same relatively average component resolution to define a second signal conversion factor; and converting the identified set point in resolution units to the second output signal by multiplying the count value of the identified set point times the second signal conversion factor. ### Claim 17 Apparatus for reducing quantization error in a computation of a value of desired pressure as a chemical mechanical polishing parameter, the apparatus comprising: first and second digital data processors each provided with data storage for storing synchronization data for synchronization operations of the first and second digital processors, the synchronization data defining a particular relatively average computational resolution, a range of values of the pressure parameter to be used in computations, a set of values of output parameter data for communications between the first and second digital processors, a scale data conversion function that defines a relationship between the pressure parameter and each one of a plurality of scales into which the set of values of the pressure parameter is divided; a set point data conversion function that defines a relationship between a range of values of the pressure parameter in a particular one of the scales and a set point that defines a required value of the pressure parameter in the particular scale; the first processor being programmed to use the synchronization data to first convert a required value of the parameter to first output pressure digital data representing a particular one of the scales; the first processor being further programmed to use the synchronization data to second convert the required value of the parameter to second output pressure digital data representing the set point that defines the parameter in the particular one of the scales; the second processor being further programmed to use the synchronization data to third convert the first output parameter digital data to scale data representing the particular one of the scales; and the second processor being further programmed to use the synchronization data to fourth convert the second output pressure digital data to digital data representing the exact value of the pressure parameter in the particular scale. ### Claim 18 (depends on 17) Apparatus as recited in claim 17, wherein the programming of the first processor to first convert includes: instructions for dividing the particular relatively average computational resolution into the highest value of the range of values of the pressure parameter to define the scale data conversion function in terms of a number of the plurality of the scales, each of the scales having a range within the set of values; each range being of equal-value, and instructions for identifying which of the scales corresponds to the desired value of the parameter. ### Claim 19 (depends on 17) Apparatus as recited in claim 17, wherein the set point data conversion function is based on the ratio of the desired value of the parameter to the range of values of the pressure parameter in the particular scale. ### Claim 20 (depends on 17) Apparatus as recited in claim 17, wherein the synchronization data further includes a definition of a voltage conversion value in terms of numbers of counts per voltage value, and wherein the programming of the second processor to third convert includes instructions for: multiplying a voltage value of the first output parameter digital data by the voltage conversion value to convert the first output parameter digital data to digital count data, wherein the synchronization data further includes a definition of a count conversion value in terms of numbers of counts per particular ones of the scales, and wherein the programming of the second processor to third convert includes instructions for multiplying the digital count data value of the first output parameter digital data by the count conversion value to convert the digital count data to the scale data. ### Claim 21 (depends on 17) Apparatus as recited in claim 17, wherein the set point data conversion function further includes a definition of a voltage conversion value in terms of numbers of counts per voltage value, and wherein the programming of the second processor to fourth convert includes instructions for multiplying a voltage value of the second output pressure digital data by the voltage conversion value to convert the second output parameter digital data to digital count data.