Abstract:
The present invention relates to applying at least one ultra/mega sonic device and its reflection plate for forming standing wave in a metallization apparatus to achieve highly uniform metallic film deposition at a rate far greater than conventional film growth rate in electrolyte. In the present invention, the substrate is dynamically controlled so that the position of the substrate passing through the entire acoustic field with different power intensity in each motion cycle. This method guarantees each location of the substrate to receive the same amount of total sonic energy dose over the interval of the process time, and to accumulatively grow a uniform deposition thickness at a rapid rate.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to an apparatus and a method for metallization of substrate from electrolyte solutions. More particularly, it relates to applying at least one ultra/mega sonic device to a metallization apparatus, incorporating a dynamical controlling mechanism of substrate motions for uniform applying the acoustic wave across the substrate surface, to achieve highly uniform metallic film deposition at a rate far greater than conventional film growth rate in electrolyte solutions. 
       BACKGROUND 
       [0002]    Forming of a metallic layer onto a substrate bearing a thin conductive layer, usually copper, in an electrolyte environment, is implemented to form conductive lines during VLSI (ultra large scale integrated) circuit fabrication. Such a process is used to fill cavities, such as vias, trenches, or combined structures of both by electrochemical methods, with an overburden film covering the surface of the substrate. It is critical to obtain a uniform final deposit film because the subsequent process step, commonly a planarization step (such as CMP, chemical-mechanical planarization) to remove the excess conductive metal material, requires a high degree of uniformity in order to achieve the equal electrical performance from device to device at the end of production line. 
         [0003]    Currently, metallization from electrolyte solutions is also employed in filling TSV (through silicon via) to provide vertical connections to the 3-D package of substrate stacks. In TSV application, via opening has a diameter of a few micrometers or larger, with via depth as deep as several hundreds of micrometers. The dimensions of TSV are orders of magnitude greater than those in a typical dual damascene process. It is a challenge in TSV technology to perform metallization of cavities with such high aspect ratio and depth close to the thickness approaching that of the substrate itself. The deposition rates of metallization systems designed for use in typical dual damascene process, usually a few thousand angstroms per minute, is too low to be efficiently applied in TSV fabrication. 
         [0004]    To achieve the void-free and bottom-up gapfill in deep cavities, multiple organic additives are added in the electrolyte solutions to control the local deposition rate. During deposition, these organic components often break down into byproduct species that can alter the desired metallization process. If incorporated into deposited film as impurities, they may act as nuclei for void formation, causing device reliability failure. Therefore, during the deposition process high chemical exchange rate of feeding fresh chemicals and removing break-down byproducts in and near the cavities is needed. In addition, with high aspect ratio, vortex is formed inside the cavities below where steady electrolyte flow passes on top of the cavity openings. Convection hardly happens between the vortex and the main flow, and the transport of fresh chemicals and break-down byproducts between bulk electrolyte solution and cavity bottom is mainly by diffusion. For deep cavity such as TSV, the length for diffusion path is longer, further limiting the chemical exchange within the cavity. Moreover, the slow diffusion process along the long path inside TSV hinders the high deposition rate required by economical manufacturing. The maximum deposition rate by electrochemical methods in a mass-transfer limited case is related to the limiting current density, which is inversely proportional to diffusion double layer thickness for a given electrolyte concentration. The thinner the diffusion double layer, the higher the limiting current density, thus the higher the deposition rate possible. Patent WO/2012/174732, PCT/CN2011/076262 discloses an apparatus and method by using ultra/mega sonic in the substrate metallization to conquer the above issues. 
         [0005]    In the plating bath used a piece of ultra/mega sonic device, the wave distribution across the ultra/mega device length is not uniform, which is proved by the power intensity test of acoustic sensor and other optical-acoustic inspection tool. To apply it on the substrate, the acoustic energy dose on each point of the substrate is not the same. 
         [0006]    In addition, in the plating bath with an acoustic field, the wave energy lost occurs due to wave propagation absorbed by the bath wall and diffraction around the additives and byproducts. So that the power intensity of acoustic wave in the areas near the acoustic source are different from those far away from the acoustic source. A standing wave formed in two parallel planes maintains the energy within the bath to minimize the energy lost. And the energy transfer only occurs between the node and anti-node within a standing wave. However, the power intensity of wave in its node and anti-node are different, which leads to not uniform acoustic performance across substrate during process. What&#39;s more, it is difficult to control the standing wave during the entire process due to the difficulty in adjustment for the parallelism and distance between the surfaces forming standing wave. 
         [0007]    With this method; however, a way of controlling uniformity of acoustic energy distribution further the uniformity of plating deposition must be found. And a way of controlling the acoustic field with low energy lost in the plating bath is further required. 
       SUMMARY 
       [0008]    The present invention relates to applying at least one ultra/mega sonic device and its coupling reflection plate for forming standing wave in a metallization apparatus to achieve highly uniform metallic film deposition at a rate far greater than conventional film growth rate in electrolyte solutions. In the present invention, the substrate is dynamically controlled so that the position of the substrate passing through the entire acoustic field with different power intensity in each motion cycle. This method guarantees each location of the substrate to receive the same amount of total sonic energy dose over the interval of the process time, and to accumulatively grow a uniform deposition thickness at a rapid rate. 
         [0009]    One embodiment of the present invention of an apparatus for substrate metallization from electrolyte by using ultra/mega sonic device in the bath is disclosed. It comprises an immersion bath containing at least one metal salt electrolyte, at least one electrode with individual power supply, an electricity conducting substrate holder, at least one substrate held by the substrate holder with the conductive side facing to the electrode, and an ultra/mega sonic device. The apparatus avoids the standing wave formation. The substrate holder and the electrode are oscillated by a dynamical motion actuator to pass through the acoustic area with different acoustic wave power intensity in the immersion bath. It ensures the same sonic energy dose on substrate surface in a certain cumulative time, which enhances the deposited film uniformity. 
         [0010]    One embodiment of the present invention of an apparatus for substrate metallization from electrolyte by using ultra/mega sonic device with controlling standing wave in the bath is disclosed. It comprises an immersion bath containing at least one metal salt electrolyte, at least one electrode with individual power supply, an electricity conducting substrate holder, at least one substrate held by the substrate holder with the conductive side facing to the electrode, an ultra/mega sonic device, and a reflection plate parallel to the ultra/mega sonic device to form standing wave in the space between the reflection plate and the ultra/mega sonic device. The substrate holder and the electrode are oscillated by a dynamical motion actuator to pass through the acoustic area with different standing wave power intensity in the immersion bath. It ensures the same sonic energy dose on substrate surface in a certain cumulative time, which enhances the deposited film uniformity. In another embodiment, the space distance of the ultra/mega sonic device and the reflection plate for controlling the standing wave&#39;s formation is controlled by an oscillating actuator for further dynamic stabilizing the standing wave formation in the immersion bath. 
         [0011]    One embodiment of the present invention of an apparatus for substrate metallization from electroless electrolyte by using ultra/mega sonic device in the bath is disclosed. It comprises an immersion bath containing at least one metal salt electrolyte, at least one substrate held by a substrate holder, and an ultra/mega sonic device. The apparatus avoids the standing wave formation. The substrate is oscillated by a dynamical motion actuator to pass through the acoustic area with different acoustic wave power intensity in the immersion bath. It ensures the same sonic energy dose on substrate surface in a certain cumulative time, which enhances the deposited film uniformity. 
         [0012]    One embodiment of the present invention of an apparatus for substrate metallization from electroless electrolyte by using ultra/mega sonic device with controlling standing wave in the bath is disclosed. It comprises an immersion bath containing at least one metal salt electrolyte, at least one substrate held by a substrate holder, an ultra/mega sonic device, and a reflection plate parallel to the ultra/mega sonic device. The substrate is oscillated by a dynamical motion actuator to pass through the acoustic area with different standing wave power intensity in the immersion bath. It ensures the same sonic energy dose on substrate surface in a certain cumulative time, which enhances the deposited film uniformity. In another embodiment, the space distance of the ultra/mega sonic device and the reflection plate for controlling the standing wave&#39;s formation is controlled by an oscillating actuator for further dynamic stabilizing the standing wave formation in the immersion bath. 
         [0013]    According to one embodiment of the present invention, a method for substrate metallization from electrolyte is provided. The method comprises: flowing a metal salt electrolyte into an immersion bath; transferring at least one substrate to a substrate holder that is electrically in contact with a conductive side on a surface of the substrate; applying a first bias voltage to the substrate; bringing the substrate into contact with the electrolyte; applying an electrical current to electrode; applying ultra/mega sonic to the substrate and oscillating the substrate holder; oscillating the substrate holder up and down for passing through acoustic area with different intensity; stopping applying the ultra/mega sonic and stopping oscillation of the substrate holder; applying a second bias voltage on the substrate; bringing the substrate out of the metal salt electrolyte. 
         [0014]    According to one embodiment of the present invention, a method for substrate metallization from electrolyte is provided. The method comprises: flowing a metal salt electrolyte into an immersion bath; transferring at least one substrate to a substrate holder that is electrically in contact with a conductive side on a surface of the substrate; applying a first bias voltage to the substrate; bringing the substrate into contact with the electrolyte; applying an electrical current to electrode; applying ultra/mega sonic to the substrate and oscillating the substrate holder; oscillating the substrate holder up and down passing through acoustic area with different intensity, meanwhile, periodically changing the distance of space between the ultra/mega sonic device and the reflection plate; stopping applying the ultra/mega sonic and stopping oscillation of the substrate holder; applying a second bias voltage on the substrate; bringing the substrate out of the metal salt electrolyte. 
         [0015]    According to one embodiment of the present invention, methods for substrate metallization from electroless electrolyte are provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  shows power intensity distribution at the acoustic area at front of megasonic device. 
           [0017]      FIGS. 2A and 2B  show one exemplary apparatus for metallization of substrate from electrolyte solutions. 
           [0018]      FIG. 3  shows another exemplary apparatus for metallization of substrate from electrolyte solutions and the solution distribution plate in the apparatus. 
           [0019]      FIG. 4  shows another exemplary apparatus for metallization of substrate from electrolyte solutions. 
           [0020]      FIGS. 5A to 5B  show power intensity distribution along the space between an ultra/mega sonic device and a reflection plate in an exemplary apparatus.  FIG. 5C  shows power intensity of a fixed point within the space between the ultra/mega sonic device and the reflection plate in an exemplary apparatus. 
           [0021]      FIGS. 6A and 6B  show one exemplary apparatus for metallization of substrate from electrolyte solutions. 
           [0022]      FIG. 7  shows another exemplary apparatus for metallization of substrate from electrolyte solutions. 
           [0023]      FIG. 8  shows another exemplary apparatus for metallization of substrate from electrolyte solutions. 
           [0024]      FIG. 9  shows another exemplary apparatus for metallization of substrate from electrolyte solutions. 
           [0025]      FIGS. 10A and 10B  show the power intensity between an ultra/mega sonic device and a reflection plate changes while the distance of the space between the ultra/mega sonic device and the reflection plate changing. 
           [0026]      FIGS. 11A and 11B  illustrate the motion of substrate along Z axis and the motion of reflection plate along X′ direction. 
           [0027]      FIGS. 12A to 12C  show another exemplary apparatus for metallization of substrate from electrolyte solutions. 
           [0028]      FIG. 13  shows another exemplary apparatus for metallization of substrate from electrolyte solutions. 
           [0029]      FIG. 14  shows one exemplary reflection plate in the apparatus for metallization of substrate from electrolyte solutions. 
           [0030]      FIG. 15  shows another exemplary apparatus for metallization of substrate from electrolyte solutions. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    According to embodiments of the present invention, ultra/mega sonic devices are utilized, and an exemplary ultra/mega sonic device that may be applied to the present invention is described in U.S. Pat. No. 6,391,166 and WO/2009/055992. 
         [0032]      FIG. 1  shows power intensity distribution at the area at front of a bar-shaped megasonic device. This map is obtained by a hydrophone sensor, wherein the dark area indicates high power intensity and the bright area indicates low power intensity. The power intensity distribution from the megasonic device center to edge is not uniform, wherein a plurality of dark strips with higher power intensity exit. And the power intensity distribution from the D axis normal to megasonic device surface is also not uniform, wherein power intensity is high at the area near the megasonic device and low at the area far away from the megasonic device. 
         [0033]      FIGS. 2A-2B  show one exemplary apparatus for substrate metallization from electrolyte by using ultra/mega sonic according to an embodiment of the present invention. The apparatus includes an immersion bath  2021  containing at least one metal salt electrolyte  2020 , one or two sets of electrodes  2002   a  and  2002   b  connecting to individual power supplies  2024   a  and  2024   b , an electricity conducting substrate holder  2003  holding one or two substrates  2001   a  and  2001   b  to expose the conductive sides of the substrates  2001   a  and  2001   b  to face the electrodes  2002   a  and  2002   b , an ultra/mega sonic device  2004 , and a vertical oscillating actuator  2013  named as first actuator for moving the substrate holder  2003  and the electrodes  2002   a  and  2002   b  passing through the ultra/mega sonic area and non ultra/mega sonic area. The apparatus can be designed for processing the two substrates  2001   a  and  2001   b  at the same time or only processing one of them in the immersion bath  2021 . The metal salt electrolyte  2020  flows from the immersion bath  2021  bottom to immersion bath  2021  top. At least one inlet and one outlet are positioned in the immersion bath  2021  for the metal salt electrolyte  2020  circulation. The ultra/mega sonic device  2004  is mounted on the immersion bath  2021  side wall with its surface immersed into the metal salt electrolyte  2020 . An ultra/mega sonic generator is connected to the ultra/mega sonic device  2004  for generating the acoustic wave with a frequency from 20 KHz to 10 MHz and power intensity from 0.01 to 3 W/cm 2 . The ultra/mega sonic device  2004  is made of at least one piece of piezo crystal. The acoustic wave field is formed in the space at front of the ultra/mega sonic device  2004 , which is named as zone B. And the Zone A and Zone C out of the said space are non ultra/mega sonic areas. An acoustic absorption surface  2040  is facing the ultra/mega sonic device  2004  to avoid the standing wave formation. The independent power supplies  2024   a  and  2024   b  connect to each set of the electrodes  2002   a  and  2002   b , and work in voltage-controlled mode or current-controlled mode with pre-programmed waveforms, and switch between the two modes at desired time. The applying electrical current is operable in DC mode or pulse reverse mode with pulse period from 5 ms to 2 s. Each set of electrodes  2002   a  and  2002   b  can be made in one piece or multi pieces with independent power supplies for each piece. Permeable membranes  2011   a  and  2011   b  with one layer or multi layers are set between the electrodes  2002   a  and  2002   b  and the substrate holder  2003 . The substrate holder  2003  is connected to a vertical movement actuator  2012  for the substrates  2001   a  and  2001   b  loading into or unloading out of the immersion bath  2021 . The actuator  2012  and the electrodes  2002   a  and  2002   b  are connected to the first oscillating actuator  2013  with amplitude from 1 to 300 mm and a frequency from 0.001 to 0.5 Hz. The first oscillating actuator  2013  oscillates the electrodes  2002   a  and  2002   b  and the substrates  2001   a  and  2001   b  up and down along Z axis which is perpendicular to the acoustic wave propagation direction. It oscillates the substrates  2001   a  and  2001   b  to ensure each point on the substrates  2001   a  and  2001   b  can pass through the entire acoustic wave field named as zone B with different power intensity, from zone B to zone A then back to zone B, from zone B to zone C then back to zone B. In this case, the sonic energy dose on each point of the substrates  2001   a  and  2001   b  is uniform over the course of process. An example of the metallization apparatus from electrolyte solutions to apply the ultra/mega sonic device is described in U.S. Pat. No. 6,391,166 and WO/2009/055992. 
         [0034]      FIG. 3  shows another exemplary apparatus for substrate metallization from electrolyte by using ultra/mega sonic according to an embodiment of the present invention. The apparatus includes an immersion bath  3021  containing at least one metal salt electrolyte  3020 , at least one set of electrode connecting to a corresponding power supply, an electricity conducting substrate holder  3003  holding at least one substrate  3001  to expose the conductive side of the substrate  3001  to face the electrode, an ultra/mega sonic device  3004  for forming an acoustic wave field in zone B, and a vertical oscillating actuator named as first actuator for moving the substrate holder  3003  and the electrode passing through the entire ultra/mega sonic area and non ultra/mega sonic area. An acoustic absorption surface  3040  is facing the ultra/mega sonic device  3004  to avoid the standing wave formation. A rotating actuator  3017  named as second actuator is connected to the substrate holder  3003  to flip the substrate holder  3003  180 degree around the axis of the substrate holder  3003  while the substrate holder  3003  is oscillated by the first oscillating actuator to non-acoustic zone A and zone C, so as to further uniform the acoustic wave distribution across the substrate  3001  when it passing through the acoustic zone B. 
         [0035]      FIG. 4  shows another exemplary apparatus for substrate metallization from electrolyte by using ultra/mega sonic according to an embodiment of the present invention. The apparatus includes an immersion bath  4021  containing at least one metal salt electrolyte  4020 , at least one set of electrode connecting to a corresponding power supply, an electricity conducting substrate holder  4003  holding at least one substrate  4001  to expose the conductive side of the substrate  4001  to face the electrode, an ultra/mega sonic device  4004  for forming an acoustic wave field in zone B, and a vertical oscillating actuator named as first actuator for moving the substrate holder  4003  and the electrode passing through the ultra/mega sonic area and non ultra/mega sonic area. A slope surface  4040  with its angle α(0&lt;α&lt;45) at the other side of the immersion bath  4021 , facing the ultra/mega sonic device  4004  is used to reflect the primary acoustic wave out of the immersion bath  4021 , so as to avoid the standing wave formation. 
         [0036]      FIG. 5A  illustrates a substrate  5001  is processed in a plating bath with standing wave across its surface. As the acoustic wave propagating in the space between the ultra/mega sonic device  5004  and its parallel reflection plate  5005 , a standing wave is formed by the propagating wave interfering with its reflection wave when the distance of the space equals to 
         [0000]    
       
         
           
             
               N 
               · 
               
                 λ 
                 2 
               
             
             , 
             
               N 
               = 
               1 
             
             , 
             2 
             , 
             
               3 
                
               
                   
               
                
               … 
             
           
         
       
     
         [0037]    where λ is the wavelength of the ultra/mega sonic wave and N is integers, the standing wave with highest power intensity is formed within the space. Under the condition with the space distance near the multiple half wave lengths, the standing wave is also formed but it is not that strong. The standing wave maintains the energy of within the space with high uniformity along the wave direction. The energy lost by the wave propagation in the electrolyte is minimized. In this case, the uniformity of acoustic power intensity distribution from the area near the acoustic source to that far away from the acoustic source is enhanced, and the efficiency of the acoustic generator is enhanced as well as. 
         [0038]    However, the energy distribution within a single length of standing wave is not uniform, due to the energy transferring between the node and anti-node of standing wave.  FIG. 5B  shows the substrate  5001  oscillating in the distance of a quarter of wave length, from node to anti-node, so as to get uniform wave power intensity across its surface in an accumulation time. Further, in order to keep the total sonic energy dose of the ultra/mega sonic wave on each point of the substrate  5001  the same, the oscillating distance of the substrate  5001  equals to 
         [0000]    
       
         
           
             
               N 
               · 
               
                 λ 
                 4 
               
             
             , 
             
               N 
               = 
               1 
             
             , 
             2 
             , 
             
               3 
                
               
                   
               
                
               … 
             
           
         
       
     
         [0039]    where λ is the wavelength of the ultra/mega sonic wave and N is integers, each point of the substrate  5001  cross its surface obtains equal total power intensity of operating acoustic wave during an accumulation plating time. As the uniform ultra/mega sonic wave working across the substrate  5001  with low energy lost, the high plating rate and uniformity of the plated film can be achieved. 
         [0040]      FIG. 5C  shows power intensity distribution along the space between the ultra/mega sonic device and the reflection plate in an exemplary apparatus. The results are obtained by an acoustic sensor and the measurement is performed in a plating bath with a megasonic source. It proves the power intensity changing periodically along the distance of the space between the ultra/mega sonic device and the reflection plate in the plating bath. The node to node distance is the half wave length of the megasonic source and the node to anti-node distance is a quarter of wave length of the megasonic source. 
         [0041]      FIGS. 6A to 6B  show an exemplary apparatus for substrate metallization from electrolyte by using ultra/mega sonic, standing wave in particular, according to an embodiment of the present invention. The apparatus includes an immersion bath  6021  containing at least one metal salt electrolyte  6020 , two sets of electrodes  6002   a  and  6002   b  connecting to corresponding power supplies  6024   a  and  6024   b , an electricity conducting substrate holder  6003  holding two substrates  6001   a  and  6001   b  to expose the conductive sides of the substrates  6001   a  and  6001   b  to face the electrodes  6002   a  and  6002   b , an ultra/mega sonic device  6004  and a coupling reflection plate  6005  parallel to the ultra/mega sonic device  6004 , and a vertical oscillating actuator  6013  named as first actuator for moving the substrate holder  6003  and the electrodes  6002   a  and  6002   b  passing through the ultra/mega sonic area and non ultra/mega sonic area. The apparatus can be designed for processing the two substrates  6001   a  and  6001   b  at the same time or only processing one of them in the immersion bath  6021 . The metal salt electrolyte  6020  flows from the immersion bath  6021  bottom to immersion bath  6021  top. At least one inlet and one outlet are positioned in the immersion bath  6021  for the metal salt electrolyte  6020  circulation. The substrate holder  6003  is connected to a vertical movement actuator  6012  for the substrates  6001   a  and  6001   b  loading into or unloading out of the immersion bath  6021 . The actuator  6012  and the electrodes  6002   a  and  6002   b  are connected to the first oscillating actuator  6013  with amplitude from 1 to 300 mm and a frequency from 0.001 to 0.5 Hz. The first oscillating actuator  6013  oscillates the electrodes  6002   a  and  6002   b  and the substrates  6001   a  and  6001   b  along Z axis which is perpendicular to the bottom plane of the immersion bath  6021  during process. The first oscillating actuator  6013  oscillates the substrates  6001   a  and  6001   b  to ensure each point on the substrates  6001   a  and  6001   b  passing through the entire acoustic wave field named as zone B with different power intensity, from zone B to zone A then back to zone B, and from zone B to zone C then back to zone B. In this case, the acoustic power intensity received by each point of the substrates  6001   a  and  6001   b  is uniform over the course of process. The ultra/mega sonic device  6004  and the reflection plate  6005  which is parallel to the ultra/mega sonic device  6004 , are mounted on the opposite side walls of the immersion bath  6021  with a small angle θ(0&lt;θ&lt;45) to the substrate holder  6003  oscillating direction. The surfaces of the ultra/mega sonic device  6004  and its reflection plate  6005  are immersed in the metal salt electrolyte  6020 , and the standing wave is formed in the space of the parallel surfaces of the ultra/mega sonic device  6004  and its reflection plate  6005 . The propagation direction of the standing wave is parallel to the surfaces of the substrates  6001   a  and  6001   b . The standing wave also tilted a said angle θ from perpendicular to the substrate holder  6003  oscillating direction. When the lateral component ΔX′, along the acoustic wave direction, of oscillating distance of substrate  6001  is integral times of a quarter wave length, each point of the substrate  6001  surface is passing through nodes and anti-nodes during oscillating, obtaining the same total sonic energy dose of ultra/mega sonic wave in each cycle of oscillation. In this case, the oscillation amplitude ΔZ should equals to: 
         [0000]    
       
         
           
             
               
                 Δ 
                  
                 
                     
                 
                  
                 Z 
               
               = 
               
                 
                   N 
                   · 
                   
                     λ 
                     4 
                   
                 
                 
                   sin 
                    
                   
                       
                   
                    
                   θ 
                 
               
             
             , 
             
               N 
               = 
               1 
             
             , 
             2 
             , 
             
               3 
                
               
                   
               
                
               … 
             
           
         
       
     
         [0042]    where λ is the wavelength of the ultra/mega sonic wave and N is integers. The reflection plate  6005  is made of one layer or multiple layers and the space can be provided between layers of the reflection plate  6005  for minimizing the acoustic energy lost. In order to keep the surface of the reflection plate  6005  parallel to the surface of the ultra/mega sonic device  6004 , an adjusting component is used to set the reflection plate  6005  position. 
         [0043]    In another embodiment of the apparatus, it further includes a rotating actuator named as second actuator to rotate the substrate holder 180 degree around the axis of the substrate holder while the substrate is within the non-acoustic areas, such as zone A or zone C. 
         [0044]      FIG. 7  shows an exemplary apparatus for substrate metallization from electrolyte by using ultra/mega sonic, standing wave in particular, according to an embodiment of the present invention. The apparatus includes an immersion bath  7021  containing at least one metal salt electrolyte  7020 , at least one set of electrode connecting to a corresponding power supply, an electricity conducting substrate holder  7003  holding at least one substrate  7001  to expose the conductive side of the substrate  7001  to face the electrode, an ultra/mega sonic device  7004  and an reflection plate  7005  parallel to the ultra/mega sonic device  7004 , and a vertical oscillating actuator  7013  named as first actuator for moving the substrate holder  7003  and the electrode passing through the ultra/mega sonic area and non ultra/mega sonic area. The ultra/mega sonic device  7004  and the reflection plate  7005  parallel to the ultra/mega sonic device  7004 , are mounted on the opposite side walls of the immersion bath  7021  perpendicular to the bottom plane of the bath. The surfaces of the ultra/mega sonic device  7004  and its reflection plate  7005  are immersed in the metal salt electrolyte  7020 , and the standing wave is formed between the space of the parallel surfaces of the ultra/mega sonic device  7004  and its reflection plate  7005 . The substrate holder  7003  is connected to the first oscillating actuator  7013 , and the substrate holder  7003  is oscillated by the first oscillating actuator  7013  with an amplitude from 1 to 300 mm and a frequency from 0.001 to 0.5 Hz. The substrate holder  7003  holds the substrate  7001  to move up and down periodically along a Z′ direction which is tilted a small angle θ (0&lt;θ&lt;45) from Z axis that is perpendicular to the standing wave propagation direction. When the lateral component ΔX′, along the standing wave direction, of oscillating distance of the substrate  7001  is integral times of a quarter wave length, each point of the substrate  7001  surface is passing through nodes and anti-nodes during oscillating, obtaining the same total power intensity of ultra/mega sonic wave in each cycle of oscillation. In this case, the oscillation amplitude ΔZ′ should equals to: 
         [0000]    
       
         
           
             
               
                 Δ 
                  
                 
                     
                 
                  
                 
                   Z 
                   ′ 
                 
               
               = 
               
                 
                   N 
                   · 
                   
                     λ 
                     4 
                   
                 
                 
                   sin 
                    
                   
                       
                   
                    
                   θ 
                 
               
             
             , 
             
               N 
               = 
               1 
             
             , 
             2 
             , 
             
               3 
                
               
                   
               
                
               … 
             
           
         
       
     
         [0045]    where λ is the wavelength of the ultra/mega sonic wave and N is integers. Meanwhile, the lateral component ΔZ of oscillation along Z axis ensures each point on the substrate  7001  passing through entire acoustic wave field zone B with different power intensity, from zone B to zone A then back to zone B, and from zone B to zone C then back to zone B. In this case, the power intensity on each point of the substrate  7001  is uniform over the course of process. 
         [0046]      FIG. 8  shows an exemplary apparatus for substrate metallization from electrolyte by using ultra/mega sonic, standing wave in particular, according to an embodiment of the present invention. The apparatus includes an immersion bath  8021  containing at least one metal salt electrolyte  8020 , at least one set of electrode connecting to a corresponding power supply, an electricity conducting substrate holder  8003  holding at least one substrate  8001  to expose the conductive side of the substrate  8001  to face the electrode, an ultra/mega sonic device  8004  and an reflection plate  8005  parallel to the ultra/mega sonic device  8004 , and a vertical oscillating actuator  8013  named as first actuator for moving the substrate holder  8003  and the electrode passing through the ultra/mega sonic area and non ultra/mega sonic area. The ultra/mega sonic device  8004  and the reflection plate  8005  parallel to the ultra/mega sonic device  8004 , are mounted on the opposite side walls of the immersion bath  8021  and are perpendicular to the bottom plane of the immersion bath  8021 . The surfaces of the ultra/mega sonic device  8004  and its reflection plate  8005  are immersed in the electrolyte  8020 , and the standing wave is formed between the space of the parallel surfaces of the ultra/mega sonic device  8004  and the reflection plate  8005 . The substrate holder  8003  is connected to the first oscillating actuator  8013 , and the substrate holder  8003  and the electrode are oscillated by the first oscillating actuator  8013  along Z axis with an amplitude from 1 to 300 mm and a frequency from 0.001 to 0.5 Hz. Another oscillating actuator  8015  named as third actuator is further connected to the first oscillating actuator  8013  to oscillate the substrate holder  8003  along X axis while the first oscillating actuator  8013  oscillating along Z axis. These two oscillating actuators oscillate the substrate holder  8003  to move up and down periodically perpendicular to wave propagation direction while back and forth periodically along wave propagation direction, wherein the frequency of the oscillation along the wave propagation direction is larger than that perpendicular to wave propagation direction. When the substrate  8001  is oscillated by the oscillating actuator  8015  along X axis with an amplitude of integral times of a quarter wave length of ultra/mega sonic wave, each point of the substrate  8001  surface is passing through nodes and anti-nodes during oscillating, obtaining the same total power intensity of ultra/mega sonic wave in each cycle of oscillation along X axis. 
         [0047]      FIG. 9  shows an exemplary apparatus for substrate metallization from electrolyte by using ultra/mega sonic, standing wave in particular, according to an embodiment of the present invention. The apparatus includes an immersion bath  9021  containing at least one metal salt electrolyte  9020 , at least one electrode  9002  connecting to its individual power supply  9024 , an electricity conducting substrate holder  9003  holding at least one substrate  9001  to expose the conductive side of the substrate  9001  to face the electrode  9002 , an ultra/mega sonic device  9004  and a reflection plate  9005  parallel to the ultra/mega sonic device  9004 , and a vertical oscillating actuator  9013  named as first actuator for moving the substrate holder  9003  passing through the ultra/mega sonic area with different power intensity. The metal salt electrolyte  9020  flows from the immersion bath  9021  bottom to immersion bath  9021  top. At least one inlet and one outlet are positioned in the immersion bath  9021  for electrolyte  9020  circulation. The ultra/mega sonic device  9004  and the reflection plate  9005  parallel to the ultra/mega sonic device  9004 , are mounted on the opposite side walls of the immersion bath  9021 . The surfaces of the ultra/mega sonic device  9004  and its reflection plate  9005  are immersed in the electrolyte  9020 , and the standing wave is formed between the space of the parallel surfaces of the ultra/mega sonic device  9004  and its reflection plate  9005 . A rotation component  9036  is connected to the substrate holder  9003  with the rotation speed in the range of 10 rpm to 300 rpm. A rotating actuator  9033  named as fourth actuator placed at outside wall of the immersion bath  9021  provides the force to drive the rotation component  9036  by the magnetic coupling mechanism. A connecting component  9030  is used to connect the first oscillating actuator  9013  and the rotation component  9036  together with good sealing. The substrate holder  9003  is oscillated by the first oscillating actuator  9013  along the Z axis with the amplitude in range of 1 to 300 mm while it is rotated by the rotation component  9036 . In this case, the acoustic power intensity received by each point of the substrate  9001  is uniform over the course of process. The connecting component  9030  also provides electrical conduction to the substrate through the contact  9034  during the substrate  9001  rotation. A gas line  9038  provides gas in to the connecting component  9030 , maintaining a positive pressure inside so as to keep the electrolyte  9020  outside. 
         [0048]      FIG. 10A  shows power intensity distribution map within the space between the ultra/mega sonic device and the reflection plate in an exemplary apparatus while the distance of the space changing. The power intensity distribution map of the space between the ultra/mega sonic device and its reflection plate is measured by an acoustic testing station, wherein the dark area indicates low power intensity and bright area indicates high power intensity. The alternative dark and bright lines along the Z axis in the power intensity distribution map discloses the formation of the standing wave, wherein the node at darkest line and anti-node at brightest line. The dark strips along D axis in the power intensity distribution map disclose a not uniform power intensity distribution across the megasonic device length. The distance of space between the ultra/mega sonic device and its reflection plate is marked as d. To change the distance d from d 1  to d 2  (d 1 ≠d 2 ), the power intensity map changes from brightest to darkest; herein d 2 −d 1  is quarter wave length of the megasonic wave. It discloses the standing wave formation in the immersion bath is different when the distance of said space between the ultra/mega sonic device and the reflection plate varying.  FIG. 10B  shows power intensity of a fixed point within the space between the ultra/mega sonic device and the reflection plate in an exemplary apparatus while the distance of the space changing. The results are obtained by an acoustic sensor and the measurement is performed in an immersion bath with a megasonic source while the distance of the space decreasing from do to dm. It discloses the power intensity changing periodically while the distance of the space between the ultra/mega sonic device and the reflection plate changing. The peak power intensity is achieved when the immersion bath meet the condition of standing wave formation when the distance of the space is the integral times of wave length, wherein the energy is maintained between the space with minimum energy lost. 
         [0049]      FIGS. 11A and 11B  illustrate the dynamic motions of the substrate and the reflection plate during the process of plating. The power intensity distribution map of the space between the ultra/mega sonic device and its reflection plate is measured by an acoustic testing station, wherein the dark area indicates low power intensity and bright area indicates high power intensity. The alternative dark and bright lines along the Z axis in the power intensity distribution map discloses the formation of the standing wave, wherein the node at darkest line and anti-node at brightest line. The dark strips along X′ axis in the power intensity distribution map discloses a not uniform power intensity distribution across the megasonic device length. To oscillate the substrate along Z axis with the amplitude of 
         [0000]    
       
         
           
             
               
                 Δ 
                  
                 
                     
                 
                  
                 Z 
               
               = 
               
                 
                   N 
                   · 
                   
                     λ 
                     4 
                   
                 
                 
                   sin 
                    
                   
                       
                   
                    
                   θ 
                 
               
             
             , 
             
               N 
               = 
               1 
             
             , 
             2 
             , 
             
               3 
                
               
                   
               
                
               … 
             
           
         
       
     
         [0050]    where λ is the wavelength of the ultra/mega sonic wave and N is integers, the lateral component movement along Z′ axis, an angle θ (0&lt;θ&lt;45) tilted from Z axis, leads the each point on the substrate passing through the strips, and the lateral component movement along to X′ axis, an angle θ (0&lt;θ&lt;45) tilted from X axis, leads the each point on the substrate passing through node and anti-node of the standing wave in each oscillation cycle. Meanwhile, the reflection plate oscillates along X′ axis with the amplitude of integral times of half wave length, so as to ensuring the total power intensity between the space in each oscillation cycle the same. Herein the oscillation speed of the reflection plate is faster than the oscillation speed of the substrate. This is a solution for the difficulty in the parallelism adjustment of the reflection plate to meet the best standing wave condition. It also make the immersion bath acoustic wave field stable between each oscillating period, if the condition of the immersion bath is unstable by time. 
         [0051]      FIGS. 12A to 12C  show an exemplary apparatus for substrate metallization from electrolyte by using ultra/mega sonic, standing wave in particular, according to an embodiment of the present invention. The apparatus includes an immersion bath  12021  containing at least one metal salt electrolyte  12020 , two sets of electrodes  12002   a  and  12002   b  connecting to the corresponding power supplies  12024   a  and  12024   b , an electricity conducting substrate holder  12003  holding two substrates  12001   a  and  12001   b  to expose the conductive sides of the substrates  12001   a  and  12001   b  to face the electrodes  12002   a  and  12002   b , an ultra/mega sonic device  12004  and a coupling reflection plate  12005  parallel to the ultra/mega sonic device  12004 , a vertical oscillating actuator  12013  named as first actuator for moving the substrate holder  12003  passing through the ultra/mega sonic area and non ultra/mega sonic area, and an oscillating actuator  12006  connecting to the reflection plate  12005 . The oscillating actuator  12006  is mounted with the reflection plate  12005  from its backside with a bellow component  12007  for flexible sealing, oscillating the reflection plating  12005  back and forth along X′ axis, wave propagation direction, so as to change the distance of the space between ultra/mega sonic device  12004  and reflection plate  12005 . The oscillating actuator  12006  has a frequency operated from 1 to 10 Hz and amplitude equaling to N time of half wave length of ultra/mega sonic wave, N is an integer number from 1 to 10. The oscillating actuator  12006  works while said first oscillating actuator  12013  moving the substrates  12001   a  and  12001   b  passing through entire acoustic zone B with different power intensity, from zone B to zone A then back to zone B, from zone B to zone C then back to zone B. Herein the oscillation speed of the oscillating actuator  12006  is faster than the oscillation speed of the first oscillating actuator  12013 . 
         [0052]      FIG. 13  shows an exemplary apparatus for substrate metallization from electrolyte by using ultra/mega sonic, standing wave in particular, according to an embodiment of the present invention. An oscillating actuator  13006  is mounted with the ultra/mega sonic device  13004  from its backside with a bellow component  13007  for flexible sealing, oscillating the ultra/mega sonic device  13004  back and forth along its axis, wave propagation direction, so as to change the distance of the space between ultra/mega sonic device  13004  and reflection plate  13005 . The oscillating actuator  13006  has a frequency operated from 1 to 10 Hz and amplitude equaling to N time of half wave length of ultra/mega sonic wave, N is a integer number from 1 to 10. 
         [0053]      FIG. 14  shows one exemplary of reflection plate in the apparatus according to an embodiment of the present invention. The reflection plate  14005  is made of one or multiple layers of solid plates  14050  and  14052 . An air gap of  14051  is provided between two solid plates  14050  and  14052  for increasing the reflection rate of the reflection plate  14005  and minimizing the acoustic energy lost. A seal ring  14053  is provided between the two solid plates  14051  and  14052  to prevent the electrolytes leakage to the air gap  14051 . In one embodiment, the solid plate  14050  of the reflection plate  14005  is made of thin quartz material with thickness of n time of half wavelength of ultra/mega sonic wave; n is integer number from 1 to 100. 
         [0054]      FIG. 15  shows an exemplary apparatus for substrate metallization from electroless electrolyte by using ultra/mega sonic according to an embodiment of the present invention. The apparatus includes an immersion bath  15021  containing at least one metal salt electrolyte  15020 , a substrate holder  15003  holding two substrates  15001   a  and  15001   b  with the plated sides exposed into the electrolyte  15020 , an ultra/mega sonic device  15004 , an oscillating actuator  15013 , named as first actuator, for moving the substrate holder  15003  passing through the ultra/mega sonic area and non ultra/mega sonic area. The substrate holder  15003  is available for arraying multiple substrates to be processed in the immersion bath  15021  at the same time. The first oscillating actuator  15013  oscillates the substrate holder  15003  along Z axis which is perpendicular to the bottom plane of immersion bath  15021  during process. It oscillates the substrates to ensure each point on the substrates passing through entire acoustic zone B with different power intensity, so as to resulting in an uniformed power intensity distribution across the substrates held by the substrate holder  15003  in an accumulated time. When the substrates  15001   a  and  15001   b  are oscillated to the non-acoustic zone of zone A and zone C, they are rotated 180 degree to further uniform the sonic energy through the substrates surfaces. 
         [0055]    In another embodiment of an apparatus for substrate metallization from electroless electrolyte, a reflection plate is placed parallel to the ultra/mega sonic device  15004  to generating standing wave in the immersion bath. The apparatus includes an immersion bath containing metal salt electrolyte, at least one ultra/mega sonic device coupled with said reflection plate, a first oscillating actuator oscillating the substrate holder along its axis, through the entire standing wave area with different ultra/mega sonic power intensity, so as to resulting in an uniformed power intensity distribution across the substrate in an accumulated time. The distance of the space between the ultra/mega sonic device and reflection plate is controlled for standing wave formation and distribution. 
         [0056]    One method applied to the metallization apparatus with an ultra/mega sonic device can be set as follows: 
         [0057]    Process Sequence 
         [0058]    Step 1: introduce a metal salt electrolyte into said apparatus, wherein the metal salt electrolyte contains at least one cationic form of the following metals: Cu, Au, Ag, Pt, Ni, Sn, Co, Pd, Zn. 
         [0059]    Step 2: transfer a substrate to one side of substrate holder or two substrates to both sides of substrate holder and the conductive side of the substrate is exposed to face electrode, the substrate holder is electricity conducting. 
         [0060]    Step 3: apply a small bias voltage up to 10V to the substrate; 
         [0061]    Step 4: bring the substrate into electrolyte, and the conductive side of the substrate are in full contact with the electrolyte. 
         [0062]    Step 5: apply electrical current to each electrode; the power supplies connected to electrodes switch from voltage mode to current mode at desired times; 
         [0063]    Step 6: maintain constant electrical current on electrode with the electrical current range from 0.1 A to 100 A and turn on ultra/mega sonic device; the power intensity of ultra/mega sonic device is in the range of 0.01 to 3 W/cm 2 ; the frequency of ultra/mega sonic device is set between 20 KHz to 10 MHz; in another embodiment, the applying electrical current is operable pulse reverse mode with pulse period from 5 ms to 2 s; 
         [0064]    Step 7: oscillate the substrate passing through entire acoustic zone B with different power intensity, from zone B to zone A then back to zone B, from zone B to zone C then back to zone B; the substrate holder oscillation amplitude range is from 1 mm to 300 mm and its frequency is 0.001 to 0.5 Hz; 
         [0065]    Step 8: turn off ultra/mega sonic device and stop oscillation of the substrate holder; 
         [0066]    Step 9: switch power supply to a small bias voltage mode from 0.1V to 0.5V, and apply it on the substrate; 
         [0067]    Step 10: bring the substrate out of the electrolyte; 
         [0068]    Step 11: stop power supply and clean off the residue electrolyte on a surface of the substrate. 
         [0069]    The above method is applied for metallization in the deep cavities on the substrate with dimensions of 0.5 to 50 μm in width and 5 to 500 μm in depth. 
         [0070]    In another embodiment, the substrate flips at 180 degree while it oscillating to zone A and zone C in step 7. 
         [0071]    Another method applied to the metallization apparatus with an ultra/mega sonic device can be set as follows: 
         [0072]    Process Sequence 
         [0073]    Step 1: introduce a metal salt electrolyte into said apparatus, wherein the metal salt electrolyte contains at least one cationic form of the following metals: Cu, Au, Ag, Pt, Ni, Sn, Co, Pd, Zn. 
         [0074]    Step 2: transfer a substrate to one side of substrate holder or two substrates to both sides of substrate holder with electrical conduction path to substrate conductive layer that is to be exposed to the electrolyte, the substrate holder is electricity conducting; 
         [0075]    Step 3: apply a small bias voltage up to 10V to substrate; 
         [0076]    Step 4: bring substrates into electrolyte, and the front surfaces of the substrates are in full contact with the electrolyte; 
         [0077]    Step 5: apply electrical current to each electrode; the power supplies connected to electrodes switch from voltage mode to current mode at desired times; 
         [0078]    Step 6: maintain constant electrical current on electrode with the electrical current range from 0.1 A to 100 A and turn on ultra/mega sonic device; the power intensity of ultra/mega sonic device is in the range of 0.01 to 3 W/cm 2 ; the frequency of ultra/mega sonic device is set between 20 KHz to 10 MHz; in another embodiment, the applying electrical current is operable pulse reverse mode with pulse period from 5 ms to 2 s; 
         [0079]    Step 7: oscillating substrate passing through entire acoustic zone B with different power intensity, from zone B to zone A then back to zone B, from zone B to zone C then back to zone B; the substrate holder oscillation amplitude range is from 1 mm to 300 mm and its frequency is 0.001 to 0.5 Hz; meanwhile, periodically changing the distance of space between the surfaces of ultra/mega sonic device and reflection plate; changing length of the distance of space between the ultra/mega sonic and reflection plate equals to 
         [0000]    
       
         
           
             
               N 
               · 
               
                 λ 
                 2 
               
             
             , 
           
         
       
     
         [0000]    where λ is the wavelength of the ultra/mega sonic wave and N is a integer number from 1 to 10, and changing frequency is in range of 1 to 10 HZ; 
         [0080]    Step 8: turn off ultra/mega sonic device and oscillation of the substrate holder and periodically changing of said space distance; 
         [0081]    Step 9: switch power supply to a small bias voltage mode from 0.1V to 0.5V, and apply it on the substrate; 
         [0082]    Step 10: bring the substrate out of the electrolyte; 
         [0083]    Step 11: stop power supply and clean off the residue electrolyte on a surface of the substrate. 
         [0084]    The above method is applied for metallization in the deep cavities on the substrate with dimensions of 0.5 to 50 μm in width and 5 to 500 μm in depth. 
         [0085]    In another embodiment of step 7, the amplitude of the substrate oscillation up and down equals to 
         [0000]    
       
         
           
             
               
                 N 
                 · 
                 
                   λ 
                   4 
                 
               
               
                 sin 
                  
                 
                     
                 
                  
                 θ 
               
             
             , 
           
         
       
     
         [0000]    N=1, 2, 3 . . . where λ is the wavelength of the ultra/mega sonic wave and N is integers, θ is the angle of ultra/mega sonic device to the bath side wall. 
         [0086]    In step 7, the frequency of the space distance periodically changing is larger than the frequency of the substrate oscillation. According to the motions of substrate oscillating and space distance periodically changing, each point of the substrate passing through the area of different power intensity within the space between ultra/mega sonic device and reflection plate, so that the sonic energy dose on substrate is uniform over the course of process. 
         [0087]    In another embodiment, the substrate is oscillated horizontally along the wave propagating direction while it oscillating vertically passing through the acoustic area with different power intensity in step 7. The amplitude is controlled as integral times of a quarter wave length of ultra/mega sonic wave. 
         [0088]    In another embodiment, the substrate flips at 180 degree while it oscillating in step 7. 
         [0089]    In another embodiment, the substrate oscillating up and down with an angle θ, in range of 0 to 45, tilted to the ultra/mega sonic device and its reflection plate in step 7. And the amplitude of the oscillation equals to 
         [0000]    
       
         
           
             
               
                 N 
                 · 
                 
                   λ 
                   4 
                 
               
               
                 sin 
                  
                 
                     
                 
                  
                 θ 
               
             
             , 
           
         
       
     
         [0000]    N=1, 2, 3 . . . where λ is the wavelength of the ultra/mega sonic wave and N is integers. 
         [0090]    In another embodiment, the substrate rotates with the speed in range of 10 rpm to 300 rpm while the substrate oscillating up and down in step 7. 
         [0091]    Another method applied to the metallization apparatus with an ultra/mega sonic device, metallization of substrate from an electroless electrolyte in particular, can be set as follows: 
         [0092]    Process Sequence 
         [0093]    Step 1: flowing metal salt electrolyte into an immersion bath, wherein the metal is selected from a group of metals consisting of Cu, Au, Ag, Pt, Ni, Sn, Co, Pd, Zn; 
         [0094]    Step 2: transferring at least one substrate to a substrate holder; 
         [0095]    Step 3: turning on ultra/mega sonic device; the power intensity of the ultra/mega sonic device is in the range of 0.01 to 3 W/cm 2 ; the frequency of the ultra/mega sonic device is set between 20 KHz to 10 MHz; 
         [0096]    Step 4: oscillating the substrate holder passing through entire acoustic zone B with different power intensity, from zone B to zone A then back to zone B, from zone B to zone C then back to zone B; the substrate holder oscillation amplitude range is from 1 mm to 300 mm and its frequency is 0.001 to 0.5 Hz; 
         [0097]    Step 5: stopping applying the ultra/mega sonic and stopping oscillation of the substrate holder; 
         [0098]    Step 6: bringing the substrate out of the metal salt electrolyte. 
         [0099]    Another method applied to the metallization apparatus with an ultra/mega sonic device, metallization of substrate from an electroless electrolyte in particular, can be set as follows: 
         [0100]    Process Sequence 
         [0101]    Step 1: flowing metal salt electrolyte into an immersion bath, wherein the metal is selected from a group of metals consisting of Cu, Au, Ag, Pt, Ni, Sn, Co, Pd, Zn; 
         [0102]    Step 2: transferring at least one substrate to a substrate holder; 
         [0103]    Step 3: turning on ultra/mega sonic device; the power intensity of the ultra/mega sonic device is in the range of 0.01 to 3 W/cm 2 ; the frequency of ultra/mega sonic device is set between 20 KHz to 10 MHz; 
         [0104]    Step 4: oscillating the substrate holder passing through entire acoustic zone B with different power intensity, from zone B to zone A then back to zone B, from zone B to zone C then back to zone B; the substrate holder oscillation amplitude range is from 1 mm to 300 mm and its frequency is 0.001 to 0.5 Hz; meanwhile, periodically changing the distance of space between the surfaces of ultra/mega sonic device and reflection plate; changing length of the distance of space between the ultra/mega sonic device and reflection plate equals to 
         [0000]    
       
         
           
             
               N 
               · 
               
                 λ 
                 2 
               
             
             , 
           
         
       
     
         [0000]    where λ is the wavelength of the ultra/mega sonic wave and N is a integer number from 1 to 10, and changing frequency is in range of 1 to 10 HZ; 
         [0105]    Step 5: stopping applying the ultra/mega sonic and stopping oscillation of the substrate holder and periodically changing of said space distance; 
         [0106]    Step 6: bringing the substrate out of the metal salt electrolyte. 
         [0107]    Although the present invention has been described with respect to certain embodiments, examples, and applications, it will be apparent to those skilled in the art that various modifications and changes may be made without departing from the invention.