Planting process and manufacturing process for semiconductor device thereby, and plating apparatus

Abstract

An objective of this invention is to reliably form a plating film. The following two steps are sequentially conducted: step 101 of connecting a film-formation surface of a wafer 109 to a cathode electrode 107 , making the film-formation surface inclined from the surface of a plating solution 103 and immersing the wafer 109 into the plating solution 103 with applying a first current between the cathode electrode 107 and an Cu anode electrode 105 disposed in the plating solution 103 , and step 103 of, after immersing the film-formation surface in the plating solution 103 , applying a second current between the cathode electrode 107 and the Cu anode electrode 105 to form a metal film on the film-formation surface by electrolytic plating. In step 101 , the first current is controlled on the basis of an inclination angle between the liquid surface and the film-formation surface.

1 . A plating process comprising 
 a first step of connecting a film-formation surface of a wafer to a cathode electrode, inclining the wafer to the surface of a plating solution and immersing the wafer into the plating solution with applying a first current between the cathode electrode and an anode electrode placed in the plating solution, and    a second step of, after immersing the film-formation surface in the plating solution, applying a second current between the cathode electrode and the anode electrode to form a metal film on the film-formation surface by electrolytic plating,    wherein in the first step, the first current is controlled on the basis of an inclination angle between the liquid surface and the film-formation surface.    
     
     
         2 . The plating process as claimed in  claim 1 , wherein in the first step, a liquid-contact area in the wafer is a function of an inclination angle as a variable and the first current varies depending on the liquid-contact area.  
     
     
         3 . The plating process as claimed in  claim 2 , wherein in the first step, the first current is varied in proportion to the liquid-contact area.  
     
     
         4 . The plating process as claimed in  claim 1 , wherein the first current is represented by the following equation (1):  
           I=I   0 (φ−cos φ sin φ)/π  (1)  wherein I 0  is an intensity of the second current and 2φ is an angle made by straight lines passing through the wafer center and intersections of outer edge of the wafer with the surface of the plating solution.    
     
     
         5 . The plating process as claimed in  claim 1 , wherein the first current is represented by the following equation (2):  
           I=I   0   t/t   0   (2)  wherein I 0  is an intensity of the second current and to is a time of completion of the first step.    
     
     
         6 . The plating process as claimed in  claim 1 , wherein in the first step, the inclination angle is substantially constant.  
     
     
         7 . The plating process as claimed in  claim 6 , wherein the wafer is immersed into the plating solution at a substantially constant speed.  
     
     
         8 . The plating process as claimed in  claim 7 , wherein the first current is represented by the following equation (1):  
           I=I   0 (φ−cos φ sin φ)/π  (1)  wherein I 0  is an intensity of the second current; 2φ is an angle made by straight lines passing through the wafer center and intersections of outer edge of the wafer with the surface of the plating solution; φ meets the condition: cos φ=(r−vt/sin θ)/r; r is a radius of the wafer; θ is the inclination angle; v is a moving speed of the wafer in the direction of the normal line in the liquid surface; and 0≦t≦2r sin θ/v.    
     
     
         9 . The plating process as claimed in  claim 7 , wherein the first current is represented by the following equation (3):  
           I=vI   0   t/ 2 r  sin θ  (3)  wherein I 0  is an intensity of the second current; r is a radius of the wafer; θ is the inclination angle; v is a moving speed of the wafer in the direction of the normal line of the liquid surface; and 0≦t≦2r sin θ/v.    
     
     
         10 . The plating process as claimed in  claim 1 , wherein in the first step, immersion of the wafer is initiated with applying a given voltage between the anode electrode and the cathode electrode.  
     
     
         11 . The plating process as claimed in  claim 1 , wherein in the second step, the second current is substantially constant.  
     
     
         12 . The plating process as claimed in  claim 1 , wherein the metal film is a copper-containing metal film.  
     
     
         13 . A process for manufacturing a semiconductor device having a metal film, comprising forming the metal film on a wafer by the plating process as claimed in  claim 1 .  
     
     
         14 . The process for manufacturing a semiconductor device as claimed in  claim 13 , 
 comprising preparing the wafer in which a transistor is formed on a silicon wafer,    wherein said forming a metal film is included in a process for forming a conductive pattern made of the metal film over the transistor.    
     
     
         15 . A plating apparatus, comprising: 
 a plating bath to be filled with a plating solution,    a wafer holding unit whereby a film-formation surface of a wafer is held at an angle to the surface of the plating solution,    a wafer moving unit whereby the wafer held by the wafer holding unit is immersed into the plating solution,    a cathode electrode feeding a current to the wafer when it comes into contact with the wafer,    an anode electrode placed in the plating bath such that it faces the wafer holding unit,    a power source for applying a current between the anode electrode and the cathode electrode, and    a controller controlling a current intensity applied between the anode electrode and the cathode electrode on the basis of an inclination angle of the film-formation surface from the liquid surface.    
     
     
         16 . The plating apparatus as claimed in  claim 15 , further comprising a current adjusting unit which adjusts a current intensity applied from the power source and then applies the current between the anode electrode and the cathode electrode, 
 wherein the controller controls the current adjusting unit on the basis of the inclination angle.    
     
     
         17 . The plating apparatus as claimed in  claim 15 , wherein a liquid-contact area in the wafer is a function of the inclination angle as a variable and the controller varies the first current depending on the liquid-contact area.  
     
     
         18 . The plating apparatus as claimed in  claim 15 , wherein the controller has a wafer position controller which controls the inclination angle and a lowering speed of the wafer.