Control of dissolved gas concentration in electroplating baths

Abstract

A concentration of a dissolved gas can be controlled by following an electroplating solution through a contactor, controlling a pressure within the contactor, and thereby maintaining the concentration of the dissolved gas in the electroplating solution within a first concentration range. The first concentration range is non-zero and sub-saturation.

What is claimed is: 
     
         1 . A method of controlling a concentration of a dissolved gas in an electroplating solution of an electroplating system having one or more electroplating cells, a contactor having a membrane with a shell side and a lumen side, and being fluidically connected to the one or more electroplating cells, a vacuum source connected to the contactor and configured to apply a vacuum to the contactor, the method comprising:
 flowing the electroplating solution through the contactor; and   controlling a pressure within the contactor and thereby maintaining the concentration of the dissolved gas in the electroplating solution within a first concentration range that is non-zero and sub-saturation.   
     
     
         2 . The method of  claim 1 , wherein:
 the controlling includes increasing the pressure in the contactor and thereby increasing the concentration, and   the controlling includes decreasing the pressure in the contactor and thereby decreasing the concentration.   
     
     
         3 . The method of  claim 2 , wherein:
 the electroplating system further includes a valve that is interposed between the vacuum source and the contactor, configured to stop the applying of the vacuum to the contactor when closed, and configured to enable application of the vacuum to the contactor when open,   the increasing the pressure further includes closing the valve to stop applying the vacuum to the contactor, and   the decreasing the pressure further includes opening the valve to apply the vacuum to the contactor.   
     
     
         4 . The method of  claim 3 , further comprising detecting the pressure within the contactor using a pressure sensor, wherein:
 the controlling further includes opening the valve, in response to detecting a first pressure in the contactor, and thereby decreasing the pressure within the contactor, and   the controlling further includes closing the valve, in response to detecting a second pressure in the contactor lower than the first pressure, and thereby increasing the pressure within the contactor.   
     
     
         5 . The method of  claim 3 , further comprising detecting a gas concentration of the electroplating solution using a gas sensor, wherein:
 the controlling further includes opening the valve, in response to detecting a first gas concentration, and thereby decreasing the pressure within the contactor, and   the controlling further includes closing the valve, in response to detecting a second gas concentration lower than the first gas concentration, and thereby increasing the pressure within the contactor.   
     
     
         6 . The method of  claim 5 , wherein:
 the dissolved gas is oxygen, and   the gas sensor is an oxygen sensor.   
     
     
         7 . The method of  claim 3 , wherein the controlling further includes:
 opening and closing the valve at a first frequency when one or more of the electroplating cells have a wafer positioned therein, and   opening and closing the valve at a second frequency greater than the first frequency when one or more of the electroplating cells do not have a wafer positioned therein.   
     
     
         8 . The method of  claim 3 , wherein the controlling further includes:
 opening and closing the valve at a first frequency when electroplating is being performed on a wafer one of the electroplating cells, and   opening and closing the valve at a second frequency different than the first frequency when one or more of the electroplating is not being performed in one of the electroplating cells.   
     
     
         9 . The method of  claim 1 , wherein the concentration of the electroplating solution has a substantially positive correlation to the pressure in the contactor. 
     
     
         10 . The method of  claim 1 , wherein:
 the controlling further includes repeatedly increasing and decreasing the pressure within the contactor and thereby maintaining the pressure within a first pressure range, and   the first pressure range corresponds with the first concentration range.   
     
     
         11 . The method of  claim 1 , wherein:
 the electroplating system further includes a pressure regulator connected to the contactor,   the controlling further includes maintaining the pressure within a first pressure range that corresponds with the first concentration range.   
     
     
         12 . The method of  claim 1 , wherein the first concentration range is between about 2 ppm and about 8 ppm. 
     
     
         13 . The method of  claim 1 , wherein the controlling includes maintaining the pressure within a first pressure range between about 0.2 atmosphere and about 1 atmosphere. 
     
     
         14 . The method of  claim 1 , wherein the dissolved gas is oxygen. 
     
     
         15 . The method of  claim 1 , wherein the controlling further includes:
 maintaining, when one or more of the electroplating cells have a wafer positioned therein, the pressure within the contactor to a first pressure range and thereby causing the concentration to be maintained within the first concentration range, and   maintaining, when one or more of the electroplating cells do not have a wafer positioned therein, the pressure within the contactor to a second pressure range and thereby causing the concentration to be maintained within a second concentration range that is non-zero, sub-saturation, and different than the first concentration range.   
     
     
         16 . The method of  claim 1 , wherein the controlling further includes:
 maintaining, when electroplating is being performed on a wafer in one of electroplating cells, the pressure within the contactor to a first pressure range and thereby causing the concentration to be maintained within the first concentration range, and   maintaining, when electroplating is being performed on a wafer in one of electroplating cells, the pressure within the contactor to a second pressure range and thereby causing the concentration to be maintained within a second concentration range that is non-zero, sub-saturation, and different than the first concentration range.   
     
     
         17 . An electroplating system comprising:
 one or more electroplating cells;   a contactor having a membrane with a shell side and a lumen side, and being fluidically connected to the one or more electroplating cells;   an electroplating solution having a concentration of dissolved gas;   a pump configured to pump the electroplating solution between the one or more electroplating cells and the contactor;   a vacuum source connected to the contactor and configured to apply a vacuum to the contactor; and   a controller with instructions that are configured to:
 cause the electroplating solution to flow through the contactor; and 
 control a pressure within the contactor and thereby maintain the concentration of dissolved gas in the electroplating solution within a first concentration range that is non-zero and sub-saturation. 
   
     
     
         18 . The electroplating system of  claim 17 , wherein the control of the pressure further includes:
 increasing the pressure in the contactor and thereby increasing the concentration, and decreasing the pressure in the contactor and thereby decreasing the concentration.   
     
     
         19 . The electroplating system of  claim 17 , further comprising: a valve that is:
 interposed between the vacuum source and the contactor,   configured to stop an application of the vacuum to the contactor when closed, and   configured to enable the application of the vacuum to the contactor when open, wherein the control of the pressure further includes:
 closing the valve to stop the application of the vacuum to the contactor and thereby increase the pressure in the contactor, and 
 opening the valve to apply the vacuum to the contactor and thereby decrease the pressure in the contactor. 
   
     
     
         20 . The electroplating system of  claim 19 , further comprising a pressure sensor configured to detect the pressure within the contactor, wherein the controller further includes instructions configured to:
 detect a first pressure in the contactor,   detect a second pressure in the contactor lower than the first pressure, and   the control further includes:
 opening the valve, in response to detecting the first pressure, and thereby decrease the pressure within the contactor, and 
 closing the valve, in response to detecting the second pressure, and thereby increase the pressure within the contactor. 
   
     
     
         21 . The electroplating system of  claim 19 , further comprising a gas sensor configured to detect a gas concentration of the electroplating solution, wherein the controller further includes instructions configured to:
 detect a first concentration of the electroplating solution,   detect a second concentration of the electroplating solution lower than the first concentration, and   the control further includes:
 opening the valve, in response to detecting the first concentration, and thereby decrease the pressure within the contactor, and 
 closing the valve, in response to detecting the second concentration, and thereby increase the pressure within the contactor. 
   
     
     
         22 . The electroplating system of  claim 21 , wherein the gas sensor is positioned in one or more of: one of the electroplating cells, the contactor, or a reservoir of the electroplating system. 
     
     
         23 . An electroplating system comprising:
 one or more electroplating cells;   a contactor having a membrane with a shell side and a lumen side, and being fluidically connected to the one or more electroplating cells;   an electroplating solution having a concentration of dissolved gas;   a pump configured to pump the electroplating solution between the one or more electroplating cells and the contactor;   a vacuum source connected to the contactor and configured to apply a vacuum to the contactor; and   a pressure regulator connected to the contactor and configured to maintain a first pressure range that corresponds with a first concentration range of dissolved gas in the electroplating solution that is non-zero and sub-saturation.   
     
     
         24 . An electroplating system comprising:
 one or more electroplating cells;   an electroplating solution having a concentration of dissolved gas;   a plating cell flow loop configured to flow electroplating solution within the electroplating system;   a contactor having a membrane with a shell side and a lumen side, and being fluidically connected in parallel with the plating cell flow loop such that electroplating solution can simultaneously flow in the plating cell flow loop and the contactor;   a pump configured to pump the electroplating solution within the plating cell flow loop and to the contactor;   a vacuum source connected to the contactor and configured to apply a vacuum to the contactor; and   a controller with instructions that are configured to:
 cause the electroplating solution to flow simultaneously through the plating cell flow loop and contactor, and 
 apply the vacuum source to the contactor and thereby maintain a first dissolved gas removal rate in the contactor.