Patent Publication Number: US-2022228287-A1

Title: Electrochemical deposition system including optical probes

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/852,497, filed on 24 May 2019. The entire disclosure of the application referenced above is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to electrochemical plating systems and more particularly to electrochemical plating systems including optical probes. 
     BACKGROUND 
     The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     Electrochemical deposition may be used to fill features (e.g., trenches and/or vias) in a substrate with material from the bottom of the features to the top of the features (i.e., bottom-up). Excess material deposited above the tops of the features can be removed, for example, by a chemical-mechanical planarization (CMP) process. In some examples, the material may be a metal, such as copper, cobalt, tungsten, tin, silver, gold, ruthenium, titanium, tantalum, and oxides, nitrides, and alloys of the above. 
     Control of the deposition uniformity may help to provide a uniform film for CMP and to minimize voids in the features. If the material does not have a uniform thickness, under-polishing or over-polishing may occur during CMP. For example, over-polishing may occur in thin regions, and under-polishing may occur in thick regions. Over-polishing or under-polishing may increase voids and/or other defects. An increase in voids and/or other defects may additionally or alternatively occur if there is a difference between a first feature fill rate near the edges of a substrate and a second feature fill rate near a center of the substrate. Defects in an integrated circuit can lead to an electrical failure of the integrated circuit. 
     SUMMARY 
     In a feature, an electrochemical deposition system includes: an electrochemical deposition chamber including an electrolyte for electrochemical deposition; a substrate holder configured to hold a substrate and including a first cathode that is electrically connected to the substrate; a first actuator configured to adjust a vertical position of the substrate holder within the electrochemical deposition chamber; an anode that is submerged in the electrolyte; a second cathode that is arranged between the first cathode and the anode; a first optical probe configured to measure a first reflectivity of the substrate at a first distance from a center of the substrate while the substrate is submerged within the electrolyte during the electrochemical deposition; and a controller configured to, during the electrochemical deposition, based on the first reflectivity of the substrate, selectively adjust at least one of (i) power applied to the first cathode, (ii) power applied to the second cathode, (iii) power applied to the anode, and (vi) the vertical position of the substrate holder. 
     In a feature, a second optical probe is configured to measure a second reflectivity of the substrate at a second distance from the center of the substrate while the substrate is submerged within the electrolyte during the electrochemical deposition. The controller is configured to, during the electrochemical deposition, further based on the second reflectivity of the substrate, selectively adjust at least one of (i) the power applied to the first cathode, (ii) the power applied to the second cathode, (iii) the power applied to the anode, and the (vi) vertical position of the substrate holder. 
     In a feature, the first distance is different than the second distance. 
     In a feature, the controller is configured to, during the electrochemical deposition, based on a difference between the first reflectivity and the second reflectivity, selectively adjust at least one of (i) the power applied to the first cathode, (ii) the power applied to the second cathode, (iii) the power applied to the anode, and the (vi) vertical position of the substrate holder. 
     In a feature, the controller is configured to, during the electrochemical deposition: determine a first adjustment based on the difference; and apply power to the first cathode based on the first adjustment and a value selected from a first profile. 
     In a feature, the controller is configured to, during the electrochemical deposition: determine a second adjustment based on the difference; and apply power to the second cathode based on the second adjustment and a value selected from a second profile. 
     In a feature, the controller is configured to, during the electrochemical deposition: determine a third adjustment based on the difference; and adjust the vertical position of the substrate holder based on the third adjustment and a value selected from a third profile. 
     In a feature, the first optical probe includes: a first light source configured to transmit light normal to a surface of the substrate while the substrate is submerged within the electrolyte during the electrochemical deposition; and a first light detector configured to receive light normal to the surface of the substrate while the substrate is submerged within the electrolyte during the electrochemical deposition. 
     In a feature, the first optical probe includes: a first light source configured to transmit light at a non-90 degree angle with respect to a surface of the substrate while the substrate is submerged within the electrolyte during the electrochemical deposition; and a first light detector configured to receive light at a non-90 degree angle with respect to the surface while the substrate is submerged within the electrolyte during the electrochemical deposition. 
     In a feature, a window is located between the first optical probe and the substrate. The first optical probe is configured to transmit and receive light through the window while the substrate is submerged within the electrolyte during the electrochemical deposition. 
     In a feature, the first optical probe includes: a first light source configured to transmit light normal to a surface of the substrate while the substrate is submerged within the electrolyte during the electrochemical deposition; and a first light detector configured to receive light through the substrate while the substrate is submerged within the electrolyte during the electrochemical deposition. 
     In a feature, the first optical probe is located on a horizontally extending bar. 
     In a feature, the first optical probe is mounted to a wall of the electrochemical deposition chamber. 
     In a feature, the first optical probe is configured to transmit and receive only a single wavelength of light. 
     In a feature, the first optical probe is configured to transmit and receive light within a wavelength range. 
     In a feature, a second actuator is configured to rotate the substrate holder during the electrochemical deposition. 
     In a feature, the controller is further configured to, during the electrochemical deposition: based on the first reflectivity of the substrate, detect an endpoint of the electrochemical deposition; and in response to the detection of the endpoint, selectively adjust at least one of (i) the power applied to the first cathode, (ii) the power applied to the second cathode, (iii) the power applied to the anode, and (vi) the vertical position of the substrate holder. 
     In a feature, the controller is further configured to, during the electrochemical deposition: based on the first reflectivity of the substrate, determine a depth of features formed in the substrate; and based on the depth of the features formed in the substrate, selectively adjust at least one of (i) the power applied to the first cathode, (ii) the power applied to the second cathode, (iii) the power applied to the anode, and (vi) the vertical position of the substrate holder. 
     In a feature, the controller is further configured to, during the electrochemical deposition: based on the first reflectivity of the substrate, detect a fault; and in response to the detection of the fault, display an indicator of the fault on a display. 
     In a feature, the controller is configured to: determine an average of a plurality of first reflectivities of the substrate measured during an amount of rotation of the substrate during the electrochemical deposition; and during the electrochemical deposition, based on the average, selectively adjust at least one of (i) the power applied to the first cathode, (ii) the power applied to the second cathode, (iii) the power applied to the anode, and (vi) the vertical position of the substrate holder. 
     In a feature, an actuator is configured to, while the substrate is submerged within the electrolyte, move the first optical probe from the first distance from the center of the substrate to a second distance from the center of the substrate that is different than the first distance. The controller is configured to, during the electrochemical deposition, based on a first value of the first reflectivity measured when the first optical probe is the first distance from the center of the substrate and a second value of the first reflectivity measured when the first optical probe is the second distance from the center of the substrate, selectively adjust the at least one of (i) the power applied to the first cathode, (ii) the power applied to the second cathode, (iii) the power applied to the anode, and (vi) the vertical position of the substrate holder. 
     In a feature, the controller is configured to, during the electrochemical deposition, based on the first reflectivity of the substrate, selectively adjust at least one of (i) the power applied to the first cathode, (ii) the power applied to the second cathode, (iii) the power applied to the anode, (vi) the vertical position of the substrate holder, (v) an angle of the substrate, and (vi) a distance between the first cathode and the second cathode. 
     In a feature, an electrochemical deposition system includes: an electrochemical deposition chamber configured to contain an electrolyte for electrochemical deposition; a substrate holder including a first cathode; a first actuator configured to adjust a vertical position of the substrate holder within the electrochemical deposition chamber; an anode; a second cathode that is arranged between the first cathode and the anode; and an optical probe configured to measure a reflectivity of a substrate during the electrochemical deposition. 
     In further features, the electrochemical deposition system further includes a second optical probe configured to measure a second reflectivity of the substrate during the electrochemical deposition. 
     In further features, the optical probe includes: a light source configured to transmit light normal to a surface of the substrate; and a light detector configured to receive light normal to the surface of the substrate. 
     In further features, the optical probe includes: a light source configured to transmit light at a non-90 degree angle with respect to a surface of the substrate; and a light detector configured to receive light at a non-90 degree angle with respect to the surface. 
     In further features, the electrochemical deposition system further includes a window located between the optical probe and the substrate, where the optical probe is configured to transmit and receive light through the window. 
     In further features, the optical probe includes: a light source configured to transmit light normal to a surface of the substrate; and a light detector configured to receive light through the substrate. 
     In further features, the electrochemical deposition system further includes a bar, where the optical probe is located on the bar. 
     In further features, the optical probe is mounted to a wall of the electrochemical deposition chamber. 
     In further features, the optical probe is configured to transmit and receive only a single wavelength of light. 
     In further features, the optical probe is configured to transmit and receive light within a wavelength range. 
     In further features, the electrochemical deposition system further includes a second actuator configured to move the optical probe one of toward and away from a center of the substrate. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a flowchart depicting an example method of processing a substrate to produce an integrated circuit; 
         FIGS. 2A-2B  are a functional block diagram of an example implementation of an electrochemical deposition system; 
         FIG. 3A  illustrates a first example distance between a substrate and an anode and an example electric field at a beginning of electrochemical deposition; 
         FIG. 3B  illustrates a second example distance between a substrate and an anode and an example electric field nearer to an end of electrochemical deposition; 
         FIG. 4  includes an example graph of reflectivity of a substrate versus thickness of material deposited on the substrate; 
         FIGS. 5-10  include cross-sectional views including an example portion of a chamber including one or more optical probes; 
         FIG. 11  includes an example graph of normalized reflectivity at a location on a substrate as a function of plating time; 
         FIG. 12A  includes an example graph of normalized reflectivity at three different locations on a substrate as a function of plating time; 
         FIG. 12B  includes an example graph of normalized reflectivity at three different locations on a substrate as a function of plating time with at least one of current of the second cathode, and distance between the substrate and the anode adjusted during electrochemical deposition; 
         FIG. 13  includes a functional block diagram of an example implementation of a system controller; 
         FIG. 14  includes an example graph illustrating the interference for the example where the incident and reflected light is normal to the substrate and an example graph of wavelength averaged reflectivity as a function of time; 
         FIG. 15  includes an example graph of a first reflectivity over time during the electrochemical deposition; 
         FIG. 16  includes an example of a rolling standard deviation of the first average reflectivity over time during the electrochemical deposition; 
         FIG. 17  includes a flowchart depicting an example method of controlling power applied to a first cathode, a second cathode, and a distance between a substrate and an anode during electrochemical deposition; and 
         FIGS. 18-24  include cross-sectional views including an example portion of a chamber including one or more optical probes. 
     
    
    
     In the drawings, reference numbers may be reused to identify similar and/or identical elements. 
     DETAILED DESCRIPTION 
     Features formed in a dielectric layer of a substrate can be filled with material (e.g., metal) using electrochemical deposition within a processing chamber. The substrate contacts a first electrode. An anode is located at a bottom of the processing chamber. An electric field within the processing chamber can be varied by varying at least one of (a) distance between the substrate and (b) at least one of power applied to the first electrode, power applied to a second electrode, and power applied to the anode. Trial and error based on characteristics of substrates before and after deposition can be used to calibrate a target first cathode current profile, a target second cathode current profile, and a target distance profile to be followed during electrochemical deposition. 
     According to the present disclosure, in-situ characteristics measured during deposition are used to increase thickness uniformity and increase fill rate uniformity of the deposited material. For example, one or more optical probes measure one or more reflectivities of a substrate during deposition of the material on the substrate. Reflectivity generally increases as material (e.g., metal) is deposited on the substrate. A controller selectively adjusts the distance between the substrate based on the one or more reflectivities. Additionally or alternatively, the controller may selectively adjust at least one of the power applied to the first electrode, the power applied to the second electrode, and the power applied to the anode based on the one or more reflectivities. The closed-loop adjustment during deposition may increase thickness uniformity and increase fill rate uniformity of the deposited material. Increasing thickness uniformity and/or increasing fill rate uniformity may decrease defect counts. 
       FIG. 1  is a flowchart depicting an example method of processing a substrate to produce an integrated circuit. At  104 , a dielectric layer is deposited on the substrate. At  108 , features (e.g., trenches and/or vias) are formed in the dielectric layer, such as by patterning and etching. At  112 , a diffusion barrier is applied to the substrate, such as by chemical vapor deposition (CVD) or physical vapor deposition (PVD). 
     At  116 , a seed layer for a material (e.g., metal) is applied to the substrate. The seed layer may be applied, for example, via CVD or PVD. The seed layer may include, for example, titanium nitride or another suitable seed material for the material. Examples of the metal include copper, cobalt, tungsten, tin, silver, gold, ruthenium, titanium, tantalum, and oxides, nitrides, and alloys of the above. At  120 , the features are filled with the material. The features may be filled, for example, using electrochemical deposition, from the bottom of the features to the tops of the features. The electrochemical deposition is discussed further below. At  124 , excess of the electrically conductive material is removed, such as by chemical-mechanical planarization (CMP). Control may then return to  104 . 
       FIG. 2A  is a functional block diagram of an example implementation of an electrochemical deposition system  200  including an electrochemical deposition chamber  204 . The chamber  204  contains a bath of an electrolyte  208  that is used to deposit the material (e.g., metal) within features formed in a lower surface  212  of a substrate  216 . The electrolyte  208  may include ions of the material (e.g., metal) that is deposited onto the substrate  216 . 
     The substrate  216  is suspended from the substrate holder  218  that includes a first cathode  220 . The first cathode  220  electrically contacts outer edges of the substrate  216 . For example, the first cathode  220  may include one or more clamping elements  224 , such as a plurality of gripping elements, that hold the substrate  216  to the substrate holder  218 . The first cathode  220  may be made of an electrically conductive material. The clamping elements  224  may also be made of an electrically conductive material. The first cathode  220  may electrically contact outer edges of the substrate  216  via the clamping elements  224 . 
     The substrate holder  218  may also include a second cathode  228  that is electrically isolated from the first cathode  220 , such as via isolator  230 . For example, the second cathode  228  may be an annular ring. The second cathode  228  may be made of an electrically conductive material, such as platinum coated titanium. 
     An anode  232  is submerged in the electrolyte  208  and is electrically isolated from the first cathode  220 . The anode  232  may be fixed to a bottom surface of the chamber  204 . The anode  232  may be made of an electrically conductive material, such as copper or cobalt. 
     A first actuator  236  raises and lowers the substrate holder  218 . The first actuator  236  therefore controls a distance between the substrate  216  and the anode  232 . For example only, the first actuator  236  may include a linear actuator or another suitable type of actuator.  FIG. 2A  illustrates an example where the first actuator  236  lowered the substrate  216  to a first position such that the substrate  216  is submerged in the electrolyte  208  for deposition of the material within the features formed in the lower surface  212  of the substrate  216 .  FIG. 2B  illustrates an example where the first actuator  236  raised the substrate  216  to a second position such that the substrate  216  is not submerged in the electrolyte  208 . 
     A second actuator  240  rotates substrate holder  218 . The second actuator  240  may include, for example, an electric motor that drives rotation of the substrate holder  218  at a rotational speed. The second cathode  228  may rotate with the substrate holder  218  or may not rotate while the substrate holder  218  rotates. 
     A power supply  250  applies power to the first cathode  220 , the second cathode  228 , and the anode  232 . The power applied to the first cathode  220 , the second cathode  228 , and the anode  232 , and locations of the first and second cathodes  220  and  228  relative to the anode  232 , dictate the shape of the electric field within the chamber  204 . A system controller  260  controls the power applied to the first cathode  220 , the second cathode  228 , and the anode  232  by the power supply  250 . The system controller  260  also controls the distance between the substrate  216  and the anode  232  via the first actuator  236 . The system controller  260  also controls rotation of the substrate holder  218  via the second actuator  240 . 
     Based on measurements from one or more optical probes  264  within the chamber  204 , the system controller  260  controls the distance between the substrate  216  and the anode  232 , and the power applied to the first cathode  220 , the second cathode  228 , and the anode  232 . The one or more optical probes  264  measure, for example, reflectivity of the lower surface  212  of the substrate  216  while the substrate  216  is within the electrolyte  208 . Controlling the position of the first cathode  220  and the power applied may increase a uniformity of a thickness of the material deposited on the substrate  216  and increase a uniformity of fill rates across the substrate  216 . 
     The one or more optical probes  264  may be located on a horizontally extending bar  266  or tab. The bar  266  may be suspended from the substrate holder  218 . The bar  266  may rotate with the substrate holder  218  or may be fixed and not rotate while the substrate holder  218  rotates. Alternatively, the bar  266  may be fixed, such as to a wall of the chamber  204 . 
     A robot  270  may deliver substrates to and remove substrates from the substrate holder  218 . For example, the robot  270  may transfer substrates to and from the substrate holder  218 . The system controller  260  may control operation of the robot  270 . 
       FIGS. 3A and 3B  include cross-sectional views illustrating example positions and electric fields during electrochemical deposition of the material within the features of the substrate  216 . A first resistance of the substrate  216  at a beginning of the electrochemical deposition is higher than a second resistance of the substrate  216  at an end of the electrochemical deposition. As the material (e.g., metal) is deposited on the substrate  216 , the resistance of the substrate  216  generally decreases. 
       FIG. 3A  illustrates a first example distance between the substrate  216  and the anode  232  and an example electric field at a beginning of the electrochemical deposition. At the beginning of the electrochemical deposition, the electric field and current density will naturally be higher near where the substrate  216  is electrically contacted at its edge. The system controller  260  compensates for this by applying a first current to the second cathode  228  that results in a more uniform electric field and current density to the first cathode  220 . 
       FIG. 3B  illustrates a second example distance between the substrate  216  and the anode  232  and an example electric field nearer to an end of the electrochemical deposition. At the end of the electrochemical deposition, the resistance of the substrate  216  may be negligible. The system controller  260  may decrease or increase the distance between the substrate  216  and the anode  232  as the end of the electrochemical deposition nears and decrease or disable current to the second cathode  228 . The adjusted distance and the decreased current to the second cathode  228  results in a more uniform electric field and current density to the first cathode  220 . 
       FIG. 4  includes an example graph of reflectivity of a substrate versus thickness of material deposited on the substrate. As shown, reflectivity increases as material (e.g., metal) thickness increases on a substrate. Reflectivity plateaus once the material thickness is thick enough to fully reflect incident electromagnetic radiation from the one or more optical probes  264 . 
       FIG. 5  includes a cross-sectional view including an example portion of the chamber  204 . In various implementations, the one or more optical probes  264  may include two or more optical probes. For example, a first optical probe may include a first light source  504  and a first light detector  508 . The first light source  504  and the first light detector  508  are configured to transmit and receive light from a first location near or at the outer edge of the substrate  216 . The first light source  504  outputs light toward the substrate  216 . The first light detector  508  receives light from the first light source  504  that is reflected by the substrate  216 . 
     A second optical probe may include a second light source  512  and a second light detector  516 . The second light source  512  and the second light detector  516  are arranged radially inwardly from the first light source  504  and the first light detector  508 . The second light source  512  and the second light detector  516  are configured to transmit and receive light from a second location that is radially inward of the first location. The second location may be near or at a center of the substrate  216 . The second light source  512  outputs light toward the substrate  216 . The second light detector  516  receives light from the second light source  512  that is reflected by the substrate  216 . 
     In various implementations, one or more other optical probes may be arranged radially between the first optical probe and the second optical probe. For example, a third optical probe may include a third light source  520  and a third light detector  524 . The third light source  520  and the third light detector  524  are arranged radially inwardly from the first light source  504  and the first light detector  508  and radially outwardly from the second light source  512  and the second light detector  516 . The third light source  520  and the third light detector  524  are configured to transmit and receive light from a third location that is radially outward of the second location and radially inward of the first location. The third light source  520  outputs light toward the substrate  216 . The third light detector  524  receives light from the third light source  520  that is reflected by the substrate  216 . 
     A fourth optical probe may include a fourth light source  528  and a fourth light detector  532 . The fourth light source  528  and the fourth light detector  532  are arranged radially inwardly from the third light source  520  and the third light detector  524  and radially outwardly from the second light source  512  and the second light detector  516 . The fourth light source  528  and the fourth light detector  532  are configured to transmit and receive light from a fourth location that is radially outward of the second location and radially inward of the third location. The fourth light source  528  outputs light toward the substrate  216 . The fourth light detector  532  receives light from the fourth light source  528  that is reflected by the substrate  216 . 
     A fifth optical probe may include a fifth light source  536  and a fifth light detector  540 . The fifth light source  536  and the fifth light detector  540  are arranged radially inwardly from the fourth light source  528  and the fourth light detector  532  and radially outwardly from the second light source  512  and the second light detector  516 . The fifth light source  536  and the fifth light detector  540  are configured to transmit and receive light from a fifth location that is radially outward of the second location and radially inward of the fourth location. The fifth light source  536  outputs light toward the substrate  216 . The fifth light detector  540  receives light from the fifth light source  536  that is reflected by the substrate  216 . 
     In various implementations, one or more of the third, fourth, and fifth optical probes may be omitted. In various implementations, more than five optical probes may be included. 
     The first, second, third, fourth, and fifth light detectors  508 ,  516 ,  524 ,  532 , and  540  generate and output signals based on the light reflected off of the substrate  216  to the first, second, third, fourth, and fifth light detectors  508 ,  516 ,  524 ,  532 , and  540 . The outputs of the first, second, third, fourth, and fifth light detectors  508 ,  516 ,  524 ,  532 , and  540  correspond to reflectivities of the substrate  216  at the first, second, third, fourth, and fifth locations, respectively. The outputs of the first, second, third, fourth, and fifth light detectors  508 ,  516 ,  524 ,  532 , and  540  therefore correspond to thicknesses of the material deposited at the first, second, third, fourth, and fifth locations, respectively. 
     The first, second, third, fourth, and fifth light sources  504 ,  512 ,  520 ,  528 , and  536  may transmit light normal to the lower surface  212  of the substrate  216 . The first, second, third, fourth, and fifth light detectors  508 ,  516 ,  524 ,  532 , and  540  may receive light normal to the lower surface  212  of the substrate  216 . In this example, both the incident (transmitted) and reflected light are normal to the lower surface  212  of the substrate  216 . 
       FIG. 6  includes a cross-sectional view including an example portion of the chamber  204 . In the example of  FIG. 6 , the first, second, third, and fourth light sources  504 ,  512 ,  520 , and  528  transmit light at a non-90 degree angle with respect to the lower surface  212  of the substrate  216 . The first, second, third, and fourth light detectors  508 ,  516 ,  524 , and  532  receive light at a non-90 degree angle with respect to the lower surface  212  of the substrate  216 . 
     The first, second, third, and fourth light sources  504 ,  512 ,  520 , and  528  transmit light at different locations on the substrate  216 , as shown. For example, the first light source  504  transmits light near the edge of the substrate  216  and the second light source  512  transmits light at or near the center of the substrate  216 . The third and fourth light sources  520  and  528  transmit light at locations between the edge and the center of the substrate  216 . 
       FIG. 7  includes a cross-sectional view including an example portion of the chamber  204 . In various implementations, a window  704  may be located between the one or more optical probes and the substrate  216 . In this example, the electrolyte  208  may be circulated above and below the window  704 . The window  704  may be fixed to the walls of the chamber  204  or to the substrate holder  218 . 
       FIG. 8  includes a cross-sectional view including an example portion of the chamber  204 . In various implementations, the optical probes may be fixed to walls of the chamber  204 . The first, second, third, and fourth light sources  504 ,  512 ,  520 , and  528  transmit light at a non-90 degree angle with respect to the lower surface  212  of the substrate  216 . The first, second, third, and fourth light detectors  508 ,  516 ,  524 , and  532  receive light at a non-90 degree angle with respect to the lower surface  212  of the substrate  216 . 
     The first, second, third, and fourth light sources  504 ,  512 ,  520 , and  528  transmit light at different locations on the substrate  216 , as shown. For example, the first light source  504  transmits light to the first location near the edge of the substrate  216  and the second light source  512  transmits light to the second location at or near the center of the substrate  216 . The third and fourth light sources  520  and  528  transmit light to second and third locations between the edge and the center of the substrate  216 . 
       FIG. 9  includes a cross-sectional view including an example portion of the chamber  204 . In various implementations, The first, second, third, and fourth light sources  504 ,  512 ,  520 , and  528  transmit light normal to the lower surface  212  of the substrate  216 . The first, second, third, and fourth light sources  504 ,  512 ,  520 , and  528  may transmit light through the substrate  216  and the first cathode  220 . The first, second, third, and fourth light detectors  508 ,  516 ,  524 , and  532  may be arranged above the first cathode  220  and receive light from the first, second, third, and fourth light sources  504 ,  512 ,  520 , and  528  through the substrate  216  and the first cathode  220 . As thickness of material deposited at a location on the substrate  216  increases, light transmission through the substrate  216  at that location decreases as more light is reflected (by the material). The amount of light received by the first, second, third, and fourth light detectors  508 ,  516 ,  524 , and  532  may decrease as thickness of the material at the locations where the first, second, third, and fourth light sources  504 ,  512 ,  520 , and  528  output light increases. 
       FIG. 10  includes a cross-sectional view including an example portion of the chamber  204 . In the example of  FIG. 10 , the first light source  504  and the first light detector  508  move radially inwardly and outwardly. For example, the first light source  504  and the first light detector  508  may sit on a trolley  1004  that slides along a track in the bar  266 . An actuator  1008  may push and pull the trolley  1004 , thereby moving the first light source  504  and the first light detector  508  radially inwardly and outwardly. The actuator  1008  may move the first light source  504  and the first light detector  508  from a radially outer position to a radially inner position and back to the radially outer position at a frequency. 
     The optical probes may be configured to transmit and receive light of only a single wavelength or light within a range of wavelengths. 
       FIG. 11  is an example graph of normalized reflectivity at a location on the substrate  216  as a function of plating time. As shown, normalized reflectivity is 0 at the start of the deposition of the material. As time passes, the normalized reflectivity increases. The normalized reflectivity reaches 1 when deposition of the material is complete. 
       FIG. 12A  includes an example graph of normalized reflectivity at three different locations on the substrate  216  as a function of plating time. Trace  1204  tracks normalized reflectivity at a first location near the edge of the substrate  216  (e.g., measured by the first light detector  508 , radius r=135 mm from center). Trace  1208  tracks normalized reflectivity at a second location near the center of the substrate  216  (e.g., measured by the second light detector  516 , radius r=15 mm from center). Trace  1212  tracks normalized reflectivity at a third location between the first and second locations (e.g., measured by the fourth light detector  532 , radius r=95 mm from center). As illustrated, normalized reflectivity increases and approaches 1 more quickly near the edges of the substrate  216  than near the center of the substrate  216 . 
       FIG. 12B  includes an example graph of normalized reflectivity at three different locations on the substrate  216  as a function of plating time with at least one of current of the second cathode  228  and distance between the substrate  216  and the anode  232  adjusted during electrochemical deposition, as discussed further below. As shown, the deposition occurs at approximately the same rate across the surface of the substrate  216 . In other words, fill rate is approximately uniform across the substrate  216 . The substrate  216  may therefore have a more uniform thickness of the material deposited. 
       FIG. 13  includes a functional block diagram of an example implementation of the system controller  260 . A sampling module  1304  samples and digitizes a first reflectivity measured by a first one of the light detectors and a second reflectivity measured by a second one of the light detectors a number of times per revolution of the substrate holder  218 . For example only, the sampling module  1304  may sample the first reflectivity and the second reflectivity  40  the number of equally spaced times per revolution of the substrate holder  218  or at another suitable rate. The first one of the light detectors (e.g., the second light detector  516 ) and the second one of the light detectors (e.g., the first light detector  508 ) receive light from different radial locations on the substrate  216  during deposition of the material on the substrate  216 . 
     An averaging module  1308  averages the first reflectivities measured over a period to determine a first average reflectivity. The averaging module  1308  also averages the second reflectivities measured over the period to determine a second average reflectivity. The period may be, for example, one revolution of the substrate holder  218  or another suitable period. The period may be moving or non-moving. 
     An error module  1312  determines an error between the first average reflectivity and the second average reflectivity. For example, the error module  1312  may set the error based on or equal to the first average reflectivity minus the second average reflectivity. In the example of  FIG. 10 , the error module  1312  may set the error based on or equal to a difference between a first reflectivity measured by the first light detector  508  at a first time when the first light detector  508  is at a first radial position and a second reflectivity measured by the first light detector  508  at a second time when the first light detector  508  is at a second radial position that is different than the first radial position. 
     A filtering module  1316  applies one or more filters to the error to produce a filtered error. For example, the filtering module  1316  may apply (e.g., multiply) one or more weighting values to the error based on the locations on the substrate  216  associated with the first and second light detectors. The filtering module  1316  may additionally or alternatively apply a rate limit to changes in the error to smooth the filtered error. 
     An adjustment module  1320  selectively sets one or more adjustments based on the filtered error. For example, the adjustment module  1320  may increase or decrease at least one of a first cathode adjustment, a second cathode adjustment, or a distance adjustment based on the filtered error. The adjustment module  1320  adjusts at least one of the first cathode adjustment, the second cathode adjustment, or the distance adjustment to adjust the filtered error (and the error) toward zero. The first cathode adjustment may be used to vary current of the first cathode  220  relative to a first cathode profile. The first cathode profile includes a series of values of power to apply to the first cathode  220  over time during the deposition of the material on the substrate  216 . 
     A first cathode control module  1324  controls power applied by the power supply to the first cathode  220  based on the first cathode profile and the first cathode adjustment. For example, the first cathode control module  1324  may multiply or add the first cathode adjustment to the values of the first cathode profile and control the power applied to the first cathode  220  over time based on the result of the multiplication or addition. 
     The second cathode adjustment may be used to vary current of the second cathode  228  relative to a second cathode profile. The second cathode profile includes a series of values of power to apply to the second cathode  228  over time during the deposition of the material on the substrate  216 . 
     A second cathode control module  1328  controls power applied by the power supply to the second cathode  228  based on the second cathode profile and the second cathode adjustment. For example, the second cathode control module  1328  may multiply or add the second cathode adjustment to the values of the second cathode profile and control the power applied to the second cathode  228  over time based on the results of the multiplication or addition. 
     The distance adjustment may be used to vary the distance between the substrate  216  and the anode  232  relative to a distance profile. The distance profile includes a series of distances between the substrate and the anode  232  over time during the deposition of the material on the substrate  216 . 
     A distance control module  1332  actuates the first actuator  236  based on the distance profile and the distance adjustment. For example, the distance control module  1332  may multiply or add the distance adjustment to the values of the distance profile and actuate the first actuator  236  over time based on the results of the multiplication or addition. 
     Adjusting the power applied to the first cathode  220 , the power applied to the second cathode  228 , and/or the distance between the substrate  216  and the anode  232  during the electrochemical deposition based on the in-situ optical measurements of the optical probes may decrease defect counts of the substrate  216  and/or increase uniformity of the deposited material. While the example of the first and second reflectivities is provided, at least one of the first cathode adjustment, the second cathode adjustment, and the distance adjustment may additionally or alternatively be set based on one or more other pairs of reflectivities measured by one or more other pairs of light detectors. Furthermore, at least one of the first cathode adjustment, the second cathode adjustment, and the distance adjustment may be additionally or alternatively set based on more than two reflectivity signals. In the example of more than two reflectivity signals, the error module  1312  may weight each of the reflectivity signals to produce the error. 
     While the example of the distance between the substrate  216  and the anode  232  is discussed above, geometry may be additionally or alternatively adjusted in one or more ways based on the error. For example, the system controller  260  may adjust a distance between the first cathode  220  and the second cathode  228 , a position or dimension of one or more field-shaping components (e.g., the first cathode  220 , the second cathode  228 , and/or the anode  232 ), and/or an angle of the substrate  216  in electrolyte  208  may be adjusted. 
     An endpoint module  1336  detects endpoints of the electrochemical deposition during the electrochemical deposition based on at least one of the reflectivities, such as the first reflectivity. The endpoint module  1336  may detect an endpoint, for example, when a reflectivity crosses an endpoint reflectivity, a rate of change of the reflectivity becomes less than an endpoint rate of change, or when the reflectivity achieves another suitable criteria. 
     At least one of the first cathode control module  1324 , the second cathode control module  1328 , and the distance control module  1332  may adjust the power applied to the first cathode  220 , the power applied to the second cathode  228 , and the distance, respectively, when an endpoint is detected. For example, the first cathode control module  1324  may select a different first profile when an endpoint is detected. Additionally or alternatively, the second cathode control module  1328  may select a different second profile when an endpoint is detected. Additionally or alternatively, the distance control module  1332  may select a different distance profile when an endpoint is detected. 
     While the example of use of an average reflectivity is shown, a non-averaged reflectivity may be used. The use of a non-averaged reflectivity (e.g., the first reflectivity) may allow for a reflectivity of the substrate surface to be mapped for each revolution. This would provide a series of detailed snapshots that could be used to monitor the evolution (over time) of local differences in reflectivity on the substrate  216 . This may be useful where the substrate is initially more resistive and therefore more prone to more rapid deposition of the material in less resistive pathways. These less resistive pathways may form at the azimuthal positions on the edge of the substrate  216  where either nucleation stochastically initiates before other areas or the contact resistance is minimized. This may allow for observation of pathway formation in real time, and allow for tuning of at least one of the adjustments based on the in-situ data from the light detectors to avoid the potentially defect-causing phenomenon of pathway formation. 
     A fault module  1340  diagnoses the presence of one or more faults during the electrochemical deposition based on the first reflectivity. A reference profile includes a series of reference first reflectivities over time during the electrochemical deposition when no faults are present. When a value of the first reflectivity at a given time is greater than or less than the reference first reflectivity at that time by at least a predetermined amount, the fault module  1340  may diagnose the presence of a fault. While the example of the first reflectivity is used, the fault module  1340  may diagnose the presence of a fault additionally or alternatively based on one or more other reflectivities. 
     The fault module  1340  may take one or more actions when a fault is diagnosed. For example, the fault module  1340  may display a predetermined fault message on a display  1344 . 
     In the example of the light detectors detecting only a single wavelength of light, the presence of interference fringes may be observed as the features fill from bottom-up. For example, destructive interference may occur when the average distance between the top reflecting surface (e.g., an unetched area) and the bottom reflecting surface (an etched area) is equal to or approximately equal to nλ/4, where n is an integer and λ is the wavelength of the light. Constructive interference may occur when the average distance is equal to or approximately equal to nλ/2. 
       FIG. 14  includes an example graph illustrating the destructive interference when the average distance is equal to nλ/4 for the example where the incident and reflected light is normal to the substrate  216 .  FIG. 14  also includes an example graph of wavelength averaged reflectivity as a function of time. 
     As shown in  FIG. 13 , an average depth module  1350  may compare the averaged reflectivity versus time profile to a reference average reflectivity versus time profile to determine where constructive and destructive interference occur and, therefore feature depth. This can be performed for each wavelength sampled. This may improve estimates of a mean and a standard deviation of feature depths in a sample area. 
     The adjustment module  1320  may determine the first cathode adjustment additionally or alternatively based on the average depth. For example, the adjustment module  1320  may determine the first cathode adjustment using one of a lookup table and an equation that relates average depths to first cathode adjustments. The adjustment module  1320  may additionally or alternatively determine the second cathode adjustment and/or the distance adjustment based on the average depth. Adjustment based on the average depth may remove variation due to azimuthal non-uniformity and may increase a signal to noise ratio for any changes in radial (e.g., center to edge) non-uniformity. 
       FIG. 15  includes an example graph of the first (non-averaged) reflectivity over time during the electrochemical deposition.  FIG. 16  includes an example of a rolling standard deviation of the first average reflectivity over time during the electrochemical deposition. The endpoint module  1336  may detect an endpoint based on the first average reflectivity, the first reflectivity, or the rolling standard deviation of the first average reflectivity becoming greater or less than a respective value. 
       FIG. 17  includes a flowchart depicting an example method of controlling power applied to the first cathode  220 , the second cathode  228 , and the distance between the substrate  216  and the anode  232  during electrochemical deposition. Control begins with  1704  where the first and second light detectors  508  and  516  measure the first and second reflectivities of the substrate  216  at the first and second locations, respectively. The first and second light detectors  508  and  516  measure the first and second reflectivities while the substrate  216  is being rotated within the electrolyte  208 , the first and second light sources  504  and  512  are outputting light to the first and second locations, and the substrate  216  is held to the substrate holder  218 . 
     At  1708 , the averaging module  1308  determines the first and second average reflectivities. At  1712 , the error module  1312  determines the error based on a difference between the second average reflectivity and the first average reflectivity. At  1716  the filtering module  1316  generates the filtered error based on the error. At  1720 , the adjustment module  1320  determines the first cathode adjustment, the second cathode adjustment, and the distance adjustment based on the filtered error. 
     At  1724 , the first cathode control module  1324  selects a first value (for applying power to the first cathode  220 ) for the present time during the deposition from the first profile. Also, the second cathode control module  1328  selects a second value (for applying power to the second cathode  228 ) for the present time during the deposition from the second profile. Also, the distance control module  1332  selects a third value (for the distance between the substrate  216  and the anode  232 ) for the present time during the deposition from the third profile. 
     At  1728 , the first cathode control module  1324  controls the power applied to the first cathode  220  based on the first value and the first cathode adjustment. For example, the first cathode control module  1324  may apply power to the first cathode  220  based on or equal to (i) the first cathode adjustment plus the first value or (ii) the first cathode adjustment multiplied by the first value. The second cathode control module  1328  controls the power applied to the second cathode  228  based on the second value and the second cathode adjustment. For example, the second cathode control module  1328  may apply power to the second cathode  228  based on or equal to (i) the second cathode adjustment plus the second value or (ii) the second cathode adjustment multiplied by the second value. The distance control module  1332  controls the controls the distance between the substrate  216  and the anode  232  based on the third value and the distance adjustment. For example, the distance control module  1332  may actuate the first actuator  236  to achieve a distance that is based on or equal to (i) the distance adjustment plus the third value or (ii) the distance adjustment multiplied by the third value. 
     At  1732 , the system controller  260  may determine whether deposition of the material on the substrate  216  is complete. If  1732  is true, the system controller  260  may disable the first cathode  220  and the second cathode  228 . The system controller  260  may also remove the substrate  216  from the electrolyte  208 . If  1732  is false, control may return to  1704 . 
       FIG. 18  includes a cross-sectional view of an electrochemical deposition system including an example portion of the chamber  204 . In the example of  FIG. 18 , the chamber  204  is an electrochemical deposition chamber and is configured to contain the electrolyte  208  for electrochemical deposition. The substrate holder  218  includes the first cathode  220 . The first actuator  236  is configured to raise and lower the substrate holder  218  and thereby to adjust a vertical position of the substrate holder  218  within the chamber  204 . The chamber  204  also includes the anode  232  and the second cathode  228 . The second cathode  228  is arranged between the first cathode  220  and the anode  232 . The optical probe  264  is configured to measure a reflectivity of the substrate  216  during electrochemical deposition. While an example location of the optical probe  264  is provided, the optical probe  264  may be located in another suitable location. 
       FIG. 19  includes a cross-sectional view of an electrochemical deposition system including an example portion of the chamber  204  of  FIG. 18 . As shown in  FIG. 19 , a second one of the optical probes  264  is included. The second one of the optical probes  264  is configured to measure a second reflectivity of the substrate during the electrochemical deposition. 
     In  FIG. 18 , the optical probe  264  includes: the first light source  504  configured to transmit light normal to a surface of the substrate; and the first light detector  508  configured to receive light normal to the surface of the substrate. 
       FIG. 20  includes a cross-sectional view of an electrochemical deposition system including an example portion of the chamber  204  of  FIG. 18 . In  FIG. 20 , the optical probe  264  includes: the first light source  504  configured to transmit light at a non-90 degree angle with respect to a surface of the substrate; and the first light detector  508  configured to receive light at a non-90 degree angle with respect to the surface. 
       FIG. 21  includes a cross-sectional view of an electrochemical deposition system including an example portion of the chamber  204  of  FIG. 18 . In the example of  FIG. 21 , the window  704  is located between the optical probe  264  and the substrate  216 . The optical probe  264  is configured to transmit and receive light through the window  704 . 
       FIG. 22  includes a cross-sectional view of an electrochemical deposition system including an example portion of the chamber  204  of  FIG. 18 . In the example of  FIG. 22 , the optical probe  264  includes: the first light source  504  configured to transmit light normal to a surface of the substrate  216 ; and the first light detector  508  configured to receive light through the substrate  216 . 
     In the example of  FIG. 18 , the optical probe  264  is located on the bar  266 . 
       FIG. 23  includes a cross-sectional view of an electrochemical deposition system including an example portion of the chamber  204  of  FIG. 18 . In the example of  FIG. 23 , the optical probe  264  includes the first light source  504  and the first light detector  508  and is mounted to a wall of the electrochemical deposition chamber  204 . 
     In the example of  FIG. 18 , the optical probe  264  is configured to transmit and receive only a single wavelength of light or light within a wavelength range. 
       FIG. 24  includes a cross-sectional view of an electrochemical deposition system including an example portion of the chamber  204  of  FIG. 18 . In the example of  FIG. 24 , the second actuator  266  is configured to move the optical probe  264  one of toward and away from a center of the substrate  216 . 
     The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure. 
     Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.” 
     In some implementations, a controller is part of a system, which may be part of the above-described examples. Such systems can comprise semiconductor processing equipment, including a processing tool or tools, chamber or chambers, a platform or platforms for processing, and/or specific processing components (a wafer pedestal, a gas flow system, etc.). These systems may be integrated with electronics for controlling their operation before, during, and after processing of a semiconductor wafer or substrate. The electronics may be referred to as the “controller,” which may control various components or subparts of the system or systems. The controller, depending on the processing requirements and/or the type of system, may be programmed to control any of the processes disclosed herein, including the delivery of processing gases and/or liquids, temperature settings (e.g., heating and/or cooling), pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, positional and operation settings, wafer transfers into and out of a tool and other transfer tools and/or load locks connected to or interfaced with a specific system. 
     Broadly speaking, the controller may be defined as electronics having various integrated circuits, logic, memory, and/or software that receive instructions, issue instructions, control operation, enable cleaning operations, enable endpoint measurements, and the like. The integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and/or one or more microprocessors, or microcontrollers that execute program instructions (e.g., software). Program instructions may be instructions communicated to the controller in the form of various individual settings (or program files), defining operational parameters for carrying out a particular process on or for a semiconductor wafer or to a system. The operational parameters may, in some embodiments, be part of a recipe defined by process engineers to accomplish one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and/or dies of a wafer. 
     The controller, in some implementations, may be a part of or coupled to a computer that is integrated with the system, coupled to the system, otherwise networked to the system, or a combination thereof. For example, the controller may be in the “cloud” or all or a part of a fab host computer system, which can allow for remote access of the wafer processing. The computer may enable remote access to the system to monitor current progress of fabrication operations, examine a history of past fabrication operations, examine trends or performance metrics from a plurality of fabrication operations, to change parameters of current processing, to set processing steps to follow a current processing, or to start a new process. In some examples, a remote computer (e.g. a server) can provide process recipes to a system over a network, which may include a local network or the Internet. The remote computer may include a user interface that enables entry or programming of parameters and/or settings, which are then communicated to the system from the remote computer. In some examples, the controller receives instructions in the form of data, which specify parameters for each of the processing steps to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool that the controller is configured to interface with or control. Thus as described above, the controller may be distributed, such as by comprising one or more discrete controllers that are networked together and working towards a common purpose, such as the processes and controls described herein. An example of a distributed controller for such purposes would be one or more integrated circuits on a chamber in communication with one or more integrated circuits located remotely (such as at the platform level or as part of a remote computer) that combine to control a process on the chamber. 
     Without limitation, example systems may include a plasma etch chamber or module, a deposition chamber or module, a spin-rinse chamber or module, a metal plating chamber or module, a clean chamber or module, a bevel edge etch chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etch (ALE) chamber or module, an ion implantation chamber or module, a track chamber or module, and any other semiconductor processing systems that may be associated or used in the fabrication and/or manufacturing of semiconductor wafers. 
     As noted above, depending on the process step or steps to be performed by the tool, the controller might communicate with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout a factory, a main computer, another controller, or tools used in material transport that bring containers of wafers to and from tool locations and/or load ports in a semiconductor manufacturing factory.