Electropolishing assembly and methods for electropolishing conductive layers

Abstract

In one aspect of the present invention, an exemplary apparatus and method are provided for electropolishing a conductive film on a wafer. An apparatus includes a wafer chuck for holding a wafer, an actuator for rotating the wafer chuck, and a nozzle configured to electropolish the wafer. The apparatus may further include a conductive ring or a shroud. A method of electropolishing a conductive film on a wafer includes rotating a wafer chuck with sufficient speed such that electrolyte fluid incident upon the wafer flows on the surface of the wafer towards the edge of the wafer.

1 . An apparatus for electropolishing a wafer, comprising: 
 a wafer chuck for holding the wafer;    an actuator for rotating the wafer chuck;    a nozzle configured to electropolish the wafer; and    a shroud positioned around the edge of the wafer.    
     
     
         2 . The apparatus of  claim 1 , wherein the actuator is configured to rotate the wafer chuck with sufficient rotational speed such that a stream of electrolyte fluid incident on the wafer flows towards the edge of the wafer.  
     
     
         3 . The apparatus of  claim 2 , wherein the electrolyte fluid flows past the edge of the wafer and is incident upon the shroud.  
     
     
         4 . The apparatus of  claim 2 , wherein the wafer is oriented facing down and the stream of electrolyte fluid incident on the wafer flows to the edge of the wafer before falling from the surface of the wafer.  
     
     
         5 . The apparatus of  claim 1 , wherein the actuator is configured to vary the rotation of the chuck depending on the portion of the wafer that is being electropolished.  
     
     
         6 . The apparatus of  claim 5 , wherein the actuator is configured to rotate the chuck at a higher speed when electropolishing portions of the wafer near the center.  
     
     
         7 . The apparatus of  claim 1 , wherein the wafer chuck is configured to translate in relation to the nozzle.  
     
     
         8 . The apparatus of  claim 7 , wherein the shroud is configured to move with the wafer chuck in relation to the nozzle.  
     
     
         9 . The apparatus of  claim 7 , wherein the shroud and the wafer chuck are mechanically coupled to move together in relation to the nozzle.  
     
     
         10 . The apparatus of  claim 1 , wherein the nozzle is configured to move in relation to the wafer chuck.  
     
     
         11 . The apparatus of  claim 1 , wherein the shroud is positioned about 1 mm to about 10 mm from the edge of the chuck.  
     
     
         12 . The apparatus of  claim 1 , wherein the shroud is positioned about 5 mm from the edge of the chuck.  
     
     
         13 . The apparatus of  claim 1 , wherein the sidewall of the shroud includes an L-shape cross-section.  
     
     
         14 . The apparatus of  claim 1 , wherein the sidewall of the shroud is tapered.  
     
     
         15 . The apparatus of  claim 1 , wherein the sidewall of the shroud extends above or below the chuck.  
     
     
         16 . The apparatus of  claim 1 , wherein the shroud includes plastic or ceramic material.  
     
     
         17 . The apparatus of  claim 1 , wherein the shroud includes anticorrosive metals or alloys.  
     
     
         18 . The apparatus of  claim 1 , wherein the shroud is coated with an electrolyte fluid-resistant material.  
     
     
         19 . A method for electropolishing a semiconductor wafer, comprising the acts of: 
 electropolishing the wafer with a stream of electrolyte fluid;    rotating the wafer such that the electrolyte fluid incident upon the wafer flows across the surface of the wafer towards the edge of the wafer; and    positioning a shroud adjacent the edge of the wafer.    
     
     
         20 . The method of  claim 19 , wherein the wafer is rotated with sufficient rotational speed such that electrolyte fluid incident on the wafer flows to the edge of the wafer without leaving the surface of the wafer.  
     
     
         21 . The method of  claim 19 , wherein the electrolyte fluid flows past the edge of the wafer and is incident upon the shroud.  
     
     
         22 . The method of  claim 19 , further including varying the rotation of the chuck depending on the portion of the wafer that is being electropolished.  
     
     
         23 . The method of  claim 22 , wherein the wafer is rotated at a higher speed when electropolishing portions of the wafer near the center.  
     
     
         24 . The method of  claim 19 , further including translating the wafer in relation to the nozzle.  
     
     
         25 . The method of  claim 19 , further including moving the shroud in relation to the nozzle.  
     
     
         26 . The method of  claim 19 , further including moving the shroud and the wafer together in relation to the nozzle.  
     
     
         27 . The method of  claim 19 , further including moving the nozzle in relation to the wafer.  
     
     
         28 . An apparatus for holding a wafer, comprising: 
 a body to support the wafer and expose one side of the wafer to a stream of electrolyte fluid;    a first conductive member configured to apply a charge to the wafer; and    a second conductive member configured to be exposed to the stream of electrolyte fluid.    
     
     
         29 . The apparatus of  claim 28 , wherein the first conductive member is further configured to be isolated from the stream of electrolyte fluid.  
     
     
         30 . The apparatus of  claim 28 , wherein an electric charge is applied to the second conductive member.  
     
     
         31 . The apparatus of  claim 28 , wherein the electric charge applied to the second conductive member is not equal to the conductive charge applied to the wafer.  
     
     
         32 . The apparatus of  claim 28 , wherein the second conductive member is a ring.  
     
     
         33 . The apparatus of  claim 28 , wherein the second conductive member is positioned near a perimeter of the wafer.  
     
     
         34 . The apparatus of  claim 28 , wherein the second conductive member includes metal.  
     
     
         35 . The apparatus of  claim 28 , wherein the second conductive member is in contact with the wafer.  
     
     
         36 . The apparatus of  claim 28 , wherein an insulative member is positioned between the wafer and the second conductive member.  
     
     
         37 . The apparatus of  claim 36 , wherein the insulative member forms a seal between the conductive member and the wafer.  
     
     
         38 . The apparatus of  claim 36 , wherein the insulative member includes an o-ring.  
     
     
         39 . The apparatus of  claim 36 , wherein the insulative member includes synthetic rubber.  
     
     
         40 . The apparatus of  claim 28 , wherein the first conductive member inlclues a spring member  
     
     
         41 . The apparatus of  claim 40 , wherein the spring member is configured to contact an outer perimeter of the wafer.  
     
     
         42 . The apparatus of  claim 40 , wherein the spring member includes a spring.  
     
     
         43 . The apparatus of  claim 40 , wherein the spring member includes a plurality of coiled springs arranged around the perimeter of the wafer.  
     
     
         44 . The apparatus of  claim 40 , wherein a second insulative member is inserted between the spring member and the second conductive member.  
     
     
         45 . The apparatus of  claim 28 , wherein one of the electrical charge applied by the first conductive member and a electrical charge applied by the second conductive member may be varied with respect to each other.  
     
     
         46 . The apparatus of  claim 28 , further including a DC power supply configured to apply the electrical charge.  
     
     
         47 . The apparatus of  claim 28 , further including an AC power supply configured to apply the electrical charge.  
     
     
         48 . The apparatus of  claim 28 , wherein the second conductive member is positioned within an insulative member.  
     
     
         49 . The apparatus of  claim 48 , wherein the insulative member is a ring.  
     
     
         50 . The apparatus of  claim 28 , further including at least one resistor to vary the electric charge applied to the wafer or an electric charge applied to the second conductive member.  
     
     
         51 . The apparatus of  claim 28 , wherein the second conductive member has an insulative coating layer.  
     
     
         52 . The apparatus of  claim 28 , wherein a second insulative member is positioned on a side of the second conductive member opposite of the wafer.  
     
     
         53 . A method for holding a semiconductor wafer during an electropolishing process, comprising the acts of: 
 positioning a surface of the wafer in a stream of electrolyte fluid;    applying an electric charge to the wafer with a first conductive member; and    applying an electric charge to a second conductive member, wherein the second conductive member is configured to draw a current from the electrolyte fluid on the surface of the wafer.    
     
     
         54 . The method of  claim 53 , wherein the second conductive member draws current near the edge of the wafer to reduce the polishing rate.  
     
     
         55 . The method of  claim 53 , wherein the wafer is rotated such that the electrolyte fluid flows towards the edge of the wafer.  
     
     
         56 . The method of  claim 53 , wherein the second conductive member is positioned near the edge of the wafer.  
     
     
         57 . The method of  claim 53 , wherein the second conductive member is a ring of metal.  
     
     
         58 . The method of  claim 53 , further including an insulative member positioned between the wafer and the second conductive member.  
     
     
         59 . The method of  claim 53 , wherein the conductive member is positioned adjacent the wafer.  
     
     
         60 . The method of  claim 53 , further including adjusting one of the electric charge applied to the wafer and the electric charge applied to the second conductive member relative to the other.  
     
     
         61 . The method of  claim 53 , wherein the electric charges are applied with a DC power supply.  
     
     
         62 . The method of  claim 53 , wherein the electric charges are applied with an AC power supply.  
     
     
         63 . The method of  claim 53 , wherein the second conductive member is positioned within an insulative member.  
     
     
         64 . The method of  claim 53 , wherein the insulative member is a ring.  
     
     
         65 . An apparatus for monitoring the end-point of an electropolishing process of a metal layer formed on a wafer, comprising: 
 a nozzle configured to electropolish the metal layer;    an end-point detector disposed adjacent to said nozzle;    a reservoir containing an electrolyte fluid and coupled to said nozzle;    a fluid detector disposed in the reservoir, wherein    the fluid detector measures a property of the fluid, and    the end-point detector is configured to measure wafer properties taking into consideration the measured property of the fluid.    
     
     
         66 . The apparatus of  claim 65 , wherein said apparatus is further configured to end the electropolishing process when a measured property of the wafer reaches a target value.  
     
     
         67 . The apparatus of  claim 65 , wherein the nozzle and the end-point detector are configured to move together to electropolish discrete portions of the wafer.  
     
     
         68 . The apparatus of  claim 65 , wherein the nozzle is configured as a stationary nozzle and the wafer is translated relative to the nozzle.  
     
     
         69 . The apparatus of  claim 65 , further comprising a wafer chuck configured to rotate the wafer.  
     
     
         70 . The apparatus of  claim 65 , wherein the fluid detector measures a metal ion concentration in the fluid.  
     
     
         71 . The apparatus of  claim 70 , further including electrodes immersed in the electrolyte fluid configured to remove metal ions from the electrolyte fluid if the metal ion concentration reaches a pre-set value.  
     
     
         72 . The apparatus of  claim 71 , wherein if the metal ion concentration reaches a second pre-set value the electrodes are configured to stop removing metal ions from the electrolyte fluid.  
     
     
         73 . The apparatus of  claim 65 , wherein the fluid detector includes an optical detector.  
     
     
         74 . The apparatus of  claim 73 , wherein the optical detector includes a red light.  
     
     
         75 . The apparatus of  claim 73 , wherein the optical detector includes a white light.  
     
     
         76 . The apparatus of  claim 73 , further including a reflector wherein the optical detector reflects light from.  
     
     
         77 . The apparatus of  claim 65 , wherein the end-point detector includes an optical reflection detector.  
     
     
         78 . The apparatus of  claim 65 , wherein the end-point detector includes an ultrasonic detector.  
     
     
         79 . The apparatus of  claim 65 , wherein the end-point detector includes an electromagnetic detector.  
     
     
         80 . The apparatus of  claim 65 , wherein the end-point detector includes an Eddy-current detector.  
     
     
         81 . The apparatus of  claim 65 , further comprising a second fluid detector to measure a second property of the fluid.  
     
     
         82 . The apparatus of  claim 81 , wherein the end-point detector is configured to measure wafer properties taking into consideration the second measured property of the fluid.  
     
     
         83 . The apparatus of  claim 81 , wherein the second fluid detector includes an optical detector.  
     
     
         84 . The apparatus of  claim 81 , wherein the optical detector includes a blue light.  
     
     
         85 . The apparatus of  claim 81 , wherein the optical detector includes a white light.  
     
     
         86 . The apparatus of  claim 81 , wherein the optical detector detects bubbles in the electrolyte fluid.  
     
     
         87 . A method of detecting the end-point of an electropolishing process of a wafer, comprising the acts of: 
 electropolishing the wafer using an electrolyte fluid;    measuring properties of the wafer using an end-point detector;    measuring properties of the electrolyte fluid using a fluid detector; and    evaluating the properties of the wafer measured by the end-point detector taking into consideration the properties of the fluid measured by the fluid detector.    
     
     
         88 . The method of  claim 87 , wherein the act of electropolishing is ended when a measured property of the wafer reaches a target value.  
     
     
         89 . The method of  claim 87 , wherein a nozzle and the end-point detector are configured to move together to electropolish discrete portions of the wafer.  
     
     
         90 . The method of  claim 87 , further including translating the wafer relative to a stationary nozzle.  
     
     
         91 . The method of  claim 87 , further including rotating the wafer with a wafer chuck.  
     
     
         92 . The method of  claim 87 , further including measuring a metal ion concentration of the fluid with the fluid detector.  
     
     
         93 . The method of  claim 92 , further including removing metal ions from the electrolyte fluid if the metal ion concentration reaches a pre-set value.  
     
     
         94 . The apparatus of  claim 92 , wherein if the metal ion concentration reaches a second pre-set value metal ions are no longer removed from the electrolyte fluid.  
     
     
         95 . The method of  claim 87 , wherein the fluid detector includes an optical detector.  
     
     
         96 . The method of  claim 87 , wherein the optical detector includes a red light.  
     
     
         97 . The method of  claim 96 , wherein the optical detector includes a white light.  
     
     
         98 . The method of  claim 96 , further including reflecting light from a reflector to the optical detector.  
     
     
         99 . The method of  claim 87 , wherein the end-point detector includes an optical reflection detector.  
     
     
         100 . The method of  claim 87 , wherein the end-point detector includes an ultrasonic detector.  
     
     
         101 . The method of  claim 87 , wherein the end-point detector includes an electromagnetic detector.  
     
     
         102 . The method of  claim 87 , further including measuring a second property of the fluid.  
     
     
         103 . The method of  claim 102 , wherein the end-point detector is configured to measure wafer properties taking into consideration the second measured property of the fluid.  
     
     
         104 . The method of  claim 103 , wherein the second property of the fluid is measured with a second detector.  
     
     
         105 . The method of  claim 102 , wherein the second fluid detector includes an optical detector.  
     
     
         106 . The method of  claim 102 , wherein the second optical detector includes a blue light.  
     
     
         107 . The method of  claim 102 , wherein the second optical detector includes a white light.  
     
     
         108 . The method of  claim 102 , wherein the second optical detector detects bubbles in the electrolyte fluid.  
     
     
         109 . An apparatus for electropolishing a fragmented metal layer on a semiconductor wafer, comprising: 
 a wafer chuck for holding the wafer;    a conductive member around the perimeter of the wafer chuck;    a nozzle configured to direct a stream of electrolyte fluid to a surface of the wafer; and    an actuator configured to rotate the wafer chuck with sufficient rotational speed to form a thin film of electrolyte fluid across the surface of the wafer to electrically connect the fragmented metal layer.    
     
     
         110 . The apparatus of  claim 109 , wherein the thin film of electrolyte fluid forms a path to conduct a current between the electrolyte fluid and the conductive member.  
     
     
         111 . The apparatus of  claim 109 , wherein the wafer is oriented facing down and the stream of electrolyte fluid incident on the wafer flows to the edge of the wafer before falling from the surface of the wafer.  
     
     
         112 . The apparatus of  claim 109 , wherein the actuator is configured to vary the rotation of the chuck depending on the portion of the wafer that is being electropolished.  
     
     
         113 . The apparatus of  claim 112 , wherein the actuator is configured to rotate the chuck at a higher speed when electropolishing portions of the wafer near the center.  
     
     
         114 . The apparatus of  claim 109 , wherein the wafer chuck is configured to translate the wafer in relation to the nozzle.  
     
     
         115 . The apparatus of  claim 109 , wherein the nozzle is configured to move in relation to the wafer chuck.  
     
     
         116 . The apparatus of  claim 109 , further including a shroud surround the wafer chuck.  
     
     
         117 . The apparatus of  claim 116 , wherein the shroud moves with the wafer chuck in relation to the nozzle.  
     
     
         118 . The apparatus of  claim 116 , wherein the shroud and the wafer chuck are mechanically coupled to move together in relation to the nozzle.  
     
     
         119 . The apparatus of  claim 116 , wherein the shroud is positioned about 1 mm to about 10 mm from the edge of the wafer chuck.  
     
     
         120 . The apparatus of  claim 116 , wherein the shroud is positioned about 5 mm from the edge of the chuck.  
     
     
         121 . The apparatus of  claim 116 , wherein the sidewall of the shroud includes an L-shape cross-section.  
     
     
         122 . The apparatus of  claim 116 , wherein the sidewall of the shroud is tapered.  
     
     
         123 . The apparatus of  claim 116 , wherein the sidewall of the shroud extends above or below the chuck.  
     
     
         124 . The apparatus of  claim 116 , wherein the shroud includes plastic or ceramic material.  
     
     
         125 . The apparatus of  claim 116 , wherein the shroud includes anticorrosive metals or alloys.  
     
     
         126 . The apparatus of  claim 116 , wherein the shroud is coated with an electrolyte fluid-resistant material.  
     
     
         127 . A method for electropolishing a fragmented metal layer on a semiconductor wafer, comprising the acts of: 
 holding a wafer with a wafer chuck that includes a conductive member positioned around the perimeter of the wafer;    electropolishing the wafer with a stream of electrolyte fluid; and    rotating the wafer such that the electrolyte fluid incident upon the wafer forms a thin film of electrolyte fluid on the surface of the wafer.    
     
     
         128 . The method of  claim 127 , wherein the wafer is rotated with sufficient rotational speed such that electrolyte fluid incident on the wafer flows to the edge of the wafer without leaving the surface of the wafer.  
     
     
         129 . The method of  claim 127 , further including varying the rotation of the chuck depending on the portion of the wafer that is being electropolished.  
     
     
         130 . The method of  claim 129 , wherein the wafer is rotated at a higher speed when electropolishing portions of the wafer near the center.  
     
     
         131 . The method of  claim 127 , further including translating the wafer in relation to the nozzle.  
     
     
         132 . The method of  claim 127 , further including positioning a shroud around the wafer chuck.  
     
     
         133 . The method of  claim 127 , wherein the electrolyte fluid flows past the edge of the wafer and is incident upon the shroud.  
     
     
         134 . The method of  claim 127 , further including moving the shroud in relation to the nozzle.  
     
     
         135 . The method of  claim 127 , further including moving the shroud and the wafer together in relation to the nozzle.  
     
     
         136 . The method of  claim 127 , further including moving the nozzle in relation to the wafer.  
     
     
         137 . An apparatus for electropolishing a wafer, comprising: 
 a nozzle holder configured to hold one two or more nozzles adjacent to a supply line of electrolyte fluid, wherein    at least one of the nozzle holder and the supply line move relative to the other to couple one of the two or more nozzles to the supply line of electrolyte fluid.    
     
     
         138 . The apparatus of  claim 137 , further including an actuator, wherein the actuator is configured to rotate the nozzle holder to couple one of the two or more nozzles.  
     
     
         139 . The apparatus of  claim 137 , wherein the nozzle holder includes an insulative material.  
     
     
         140 . The apparatus of  claim 137 , wherein the nozzle holder includes a non-corrosive material.  
     
     
         141 . The apparatus of  claim 137 , wherein the nozzle holder is made of plastic.  
     
     
         142 . The apparatus of  claim 137 , wherein the nozzle holder and the one or more nozzles are integrally formed.  
     
     
         143 . The apparatus of  claim 137 , wherein the two or more nozzles include at least two different profiles.  
     
     
         144 . The apparatus of  claim 137 , further including an end-point detector positioned adjacent the nozzle holder.  
     
     
         145 . The apparatus of  claim 137 , further including a movable base, wherein said nozzle holder is coupled to said movable base.  
     
     
         146 . The apparatus of  claim 145 , wherein the movable base is configured to move in a linear direction and the nozzle holder is configured to rotate.  
     
     
         147 . A method for electropolishing a semiconductor wafer, comprising the acts of: 
 providing a wafer;    providing a supply of electrolyte fluid;    providing two or more nozzles that are mechanically coupled together;    movably positioning one of the two or more nozzles to the supply of electrolyte fluid to direct a stream of electrolyte fluid towards the wafer.    
     
     
         148 . The method of  claim 147 , wherein the two or more nozzles are mechanically coupled through a nozzle holder.  
     
     
         149 . The method of  claim 148 , wherein the act of movably positioning one of the two or more nozzles includes rotating the nozzle holder.  
     
     
         150 . The method of  claim 148 , wherein the act of movable positioning the nozzles includes translating the nozzle holder in a linear direction.  
     
     
         151 . The method of  claim 147 , wherein the two or more nozzles include at least two different nozzle profiles.  
     
     
         152 . The method of  claim 147 , further including: 
 determining the profile of a metal layer on the wafer; and    directing a stream of electrolyte fluid at the metal layer with varying nozzle profiles depending on the particular profile of the metal layer.    
     
     
         153 . The method of  claim 152 , wherein the varying nozzles include two or more different nozzle profiles.  
     
     
         154 . The method of  claim 152 , wherein the varying nozzles produce varying polishing rates.  
     
     
         155 . The method of  claim 152 , wherein the varying nozzles are selected to include relatively high polishing rates on thick portions of the metal layer and relatively low polishing rates on thin portions of the metal layer.  
     
     
         156 . The method of  claim 152 , wherein the profile of the metal layer is determined with an end-point detector positioned adjacent the two or more nozzles.  
     
     
         157 - 182  (Canceled).