Chemical-mechanical polishing system with a potentiostat and pulsed-force applied to a workpiece

Abstract

Shortcomings associated with insufficient control of a conventional CMP-process are obviated by providing an CMP-apparatus configured to complement a constant force (to which a workpiece that is being polished is conventionally exposed) with a time-alternating force and/or means for measuring an electrical characteristic of the CMP-process. The time-alternating force is applied with the use of a system component that is electrically isolated from the workpiece and that is disposed in the carrier-chick in which the workpiece is affixed for CMP-process, while the electrical characteristic is measured with the use of a judiciously-configured reservoir in which the used fluid is collected. The use of such CMP-apparatus.

What is claimed is: 
     
         1 . A chemical-mechanical-polishing apparatus for polishing a workpiece, the apparatus comprising:
 a table rotatably supported about an axis of rotation and operably connected with a motor drive of the apparatus;   a support component carried by the table and having a recess that forms a reservoir therein;   a measurement system including a first electrode that extends into the reservoir;   an electronic circuitry including a microcontroller that is configured to govern an operation of the motor drive and to modify one or more of parameters of the polishing; and   a carrier chuck having a chuck head with a working electrode that is electrically connected to the microcontroller.   
     
     
         2 . An apparatus according to  claim 1 ,
 configured to have the working electrode electrically connected (i) to a potentiometer of the electronic circuitry and/or (ii) to a back surface of the workpiece when the workpiece is secured in the chuck head.   
     
     
         3 . An apparatus according to  claim 1 ,
 wherein the carrier chuck contains a workpiece holder removably attached to the chuck head, and   wherein the microcontroller is configured to control a force exerted by a first component located within the carrier chuck onto the workpiece holder, to collect measurement data acquired by the measurement system of the apparatus, and to modify one or more of parameters of the polishing based on said measurement data.   
     
     
         4 . An apparatus according to  claim 1 , wherein the chuck head includes a piezoelectric element that is electrically connected to the microcontroller, and wherein one or more of the following conditions is satisfied:
 (a) the piezoelectric element is sandwiched between first and second electrically-insulating pads located in the chuck head;   (b) the apparatus is configured to tune a frequency of operation of the piezoelectric element;   (c) the piezoelectric element is dimensioned as a disk.   
     
     
         5 . An apparatus according to  claim 1 ,
 wherein the chuck head includes an acoustic sensor disposed therein and electrically connected with the microcontroller through a slip-ring,   wherein the microcontroller is configured to receive a signal, from the acoustic sensor, representing mechanical vibrations of a component of the apparatus during an operation of the apparatus and to determine an eigenfrequency of said mechanical vibrations.   
     
     
         6 . An apparatus according to  claim 1 ,
 wherein the chuck head includes a piezoelectric element electrically connected to the microcontroller and a workpiece holder,   wherein the microcontroller is configured to perform one or more of the following:
 (i) adapting voltage applied to the piezoelectric element based at least in part on measurement data acquired by the measurement system; 
 (3B) determining an eigenfrequency of mechanical vibrations of the apparatus; 
 (3B) when the eigenfrequency of the mechanical vibrations of the apparatus has been determined based on the signal received by the microcontroller from an acoustic sensor of the apparatus, applying electrical pulses to the piezoelectric element at a frequency within a +/−30% range or within a +/−20% range or within a +/−10% range or within a +/−5% range from the eigenfrequency to increase an amplitude of a time-alternating force transferred from the piezoelectric element to the workpiece holder. 
   
     
     
         7 . An apparatus according to  claim 1 ,
 wherein said reservoir has a bottom facing the table and an opening facing the carrier chuck,   wherein the reservoir is dimensioned to have at least a portion thereof that is rotationally symmetric about the axis of rotation,   wherein the reservoir is centered on the axis of rotation and/or dimensioned as a rotationally symmetric groove.   
     
     
         8 . An apparatus according to  claim 7 , wherein the rotationally symmetric groove is in a peripheral portion of the support component, and further comprising a polishing pad having an extent, in an up-facing surface of the supporting component, that does not exceed a diameter of the groove. 
     
     
         9 . An apparatus according to  claim 1 , wherein at least one of the following conditions is satisfied:
 (a) wherein the apparatus further comprises a potentiometer cooperated with at least the first electrode,   (b) wherein the reservoir has an opening and said first electrode extends into the reservoir from an electrode holder through the opening,   (c) wherein the measurement system includes an additional electrode that either extends into the reservoir from the electrode holder through the opening or is firmly embedded in the reservoir; and   (d) wherein the additional electrode is operably coupled to the microcontroller and the potentiometer through the slip-ring and is either embedded in a wall of the reservoir or protrudes into the reservoir from the bottom.   
     
     
         10 . An apparatus according to  claim 9 , wherein, when the apparatus includes said additional, the additional electrode is fluidly-sealed in the reservoir at least with respect to the table. 
     
     
         11 . An apparatus according to  claim 1 , further comprising:
 at least one port dimensioned to deliver a slurry-containing liquid towards an up-facing surface through an outlet of said at least one port, said liquid including an electrolyte;   a rotary drive operably connected to the carrier chuck and to the microcontroller, the carrier chuck being rotatably connected to the rotary drive, the microcontroller being configured to control the rotary drive to apply a pressure to a workpiece holder at the carrier chuck to force the workpiece holder towards the support component,   wherein the parameters of polishing include at least one or more of:
 (i) the pressure applied to the workpiece holder via the rotary drive; 
 (ii) an electrical signal delivered to a piezoelectric element of the chuck head to cause said piezoelectric element to apply time-alternating force to the workpiece holder to displace the workpiece along the axis of rotation; 
 (iii) an electrical conductivity of the slurry-containing liquid; and 
 (iv) at least one of a spatial orientation parameter and a spatial position parameter of a first component of the carrier chuck with respect to the support component. 
   
     
     
         12 . An apparatus according to  claim 1 ,
 wherein at least one of the following conditions is satisfied:
 (a) the support component is electrically insulated with respect to at least the table; 
 (b) an inlet of the reservoir is defined by a reservoir aperture such that the axis of rotation of the table passes through the reservoir aperture; 
 (c) the inlet of the reservoir is defined at a location of an up-facing surface of the support component, wherein said location is between the axis of rotation and an outer edge of the support component; 
 (d) the inlet of the reservoir is between the outer perimeter of a polishing pad, operably positioned on and adhered to the up-facing surface of the support component, and the outer edge of the support component; and 
 (e) an opening in the polishing pad and the inlet of the reservoir overlap at least in part when the polishing pad is operably positioned on and adhered to the up-facing surface of the support component. 
   
     
     
         13 . A method for chemical-mechanical polishing of a workpiece, wherein the method comprises:
 using the apparatus of  claim 1 :
 (i) positioning a support component on the table of the apparatus; 
 (ii) securing the workpiece in the apparatus; 
 (iii) polishing the workpiece by at least: 
 a. rotating the support component and a polishing pad, adhered to an up-facing surface thereof on the table, while the workpiece is in contact with the polishing pad, and 
 b. delivering a slurry-containing liquid to the polishing pad. 
   
     
     
         14 . A method according to  claim 13 , further comprising:
 during said polishing the workpiece:
 electrically-biasing the working electrode, which is electrically connected to a back-side of the workpiece, with respect to an additional electrode that is in contact with the slurry-containing liquid based on an electrical data that has been acquired with the use of the first electrode, the working electrode, and the additional electrode; 
 wherein the additional electrode either extends into the reservoir through an opening in the reservoir or is firmly embedded in the reservoir. 
   
     
     
         15 . A method according to  claim 13 , further comprising changing ionic conductivity of the slurry-containing liquid by said electrically-biasing. 
     
     
         16 . A method according to  claim 13 , further comprising:
 during said rotating the support component:   (i) measuring an eigenfrequency of mechanical vibrations of the apparatus with an acoustic sensor when no voltage is applied to a piezoelectric element that is electrically connected to the microcontroller, and   (ii) adjusting frequency of electrical pulses, delivered through a slip-ring to the piezoelectric element, to the eigenfrequency within +/−20% or +/−10% or +/−5% of a value of the eigenfrequency based on said measuring.   
     
     
         17 . A method according to  claim 13 ,
 further comprising adjusting at least one of a speed of rotation of the table and a speed of rotation of a workpiece holder.   
     
     
         18 . A method according to  claim 13 , wherein said securing includes securing the workpiece in a workpiece holder of the apparatus with magnets. 
     
     
         19 . A method according to  claim 13 , further comprising:
 during said rotating, applying pulsed pressure to the workpiece in a direction of the polishing pad by delivering electrical pulses through a slip-ring from a signal generator of the electrical circuitry to a piezoelectric element contained in a carrier chuck of the apparatus.