Multistep immersion of wafer into liquid bath

Abstract

A holder-wafer conjugate, including a wafer in a wafer holder, is tilted so that the planar wafer surface makes a small angle with a plane parallel to the liquid surface of a liquid bath. Then, the holder-wafer conjugate is moved downward and a leading edge of the holder-wafer conjugate makes initial contact with the liquid surface of a liquid bath at a slow piercing speed to minimize generation of shock waves and bubbles. After a small portion of the holder-wafer conjugate is immersed in the liquid bath at a first pause location, the downward movement is stopped for a first pause time. After the first pause time, downward movement of the holder-wafer conjugate is resumed at a faster post-piercing speed until the wafer is fully immersed.

1 . A method of immersing a wafer substrate into a liquid bath, comprising processes of:
 positioning a wafer substrate above a horizontal liquid surface of a liquid bath, said wafer substrate having a planar surface;   combining said wafer substrate and a wafer holder to form a holder-wafer conjugate;   positioning said wafer holder so that said planar surface of said wafer substrate is tilted at an angle to a plane parallel to said horizontal liquid surface;   while said planar surface is tilted, moving said holder-wafer conjugate at a piercing speed downward toward said horizontal liquid surface so that an outer edge of said holder-wafer conjugate pierces said horizontal liquid surface;   then substantially stopping said holder-wafer conjugate for a first pause time at a first pause location at which a first portion of said holder-wafer conjugate is immersed in said liquid bath to a depth in a range of about from 1 mm to 5 mm below said horizontal liquid surface;   after said first pause time, resuming moving said holder-wafer conjugate downward; and   continuing moving said holder-wafer conjugate downward at a final post-piercing speed until said wafer substrate is fully immersed in said liquid bath.   
     
     
         2 . A method of immersing a wafer substrate as in  claim 1 , further comprising:
 substantially stopping said holder-wafer conjugate for an intermediate pause time at an intermediate pause location before said wafer substrate is fully immersed in said liquid bath.   
     
     
         3 . A method of immersing a wafer substrate as in  claim 1  wherein:
 said first pause time comprises a time period in a range of about from 0.1 seconds to five seconds.   
     
     
         4 . A method of immersing a wafer substrate as in  claim 1 , further comprising processes of:
 rotating said wafer substrate about an axis normal to said planar surface prior to said first pause time.   
     
     
         5 . A method of immersing a wafer substrate as in  claim 4  wherein:
 said rotating is conducted in a range of about from 1 rpm to 10 rpm.   
     
     
         6 . A method of immersing a wafer substrate as in  claim 1 , further comprising:
 rotating said wafer substrate about an axis normal to said planar surface during said first pause time.   
     
     
         7 . A method of immersing a wafer substrate as in  claim 6  wherein:
 said rotating during said first pause time is conducted in a range of about from 1 rpm to 10 rpm.   
     
     
         8 . A method of immersing a wafer substrate as in  claim 1 , further comprising:
 rotating said wafer substrate about an axis normal to said planar surface after resuming moving said holder-wafer conjugate downward after said first pause time.   
     
     
         9 . A method of immersing a wafer substrate as in  claim 8  wherein:
 said rotating is conducted in a range of about from 1 rpm to 100 rpm.   
     
     
         10 . A method of immersing a wafer substrate as in  claim 9  wherein:
 said rotating is conducted at about 30 rpm.   
     
     
         11 . A method of immersing a wafer substrate as in  claim 1 , further comprising:
 rotating said wafer about an axis normal to said planar surface after said wafer substrate is fully immersed.   
     
     
         12 . A method of immersing a wafer substrate as in  claim 11  wherein:
 said rotating after said wafer substrate is fully immersed is conducted in a range of about from 30 rpm to 150 rpm.   
     
     
         13 . A method of immersing a wafer substrate as in  claim 12  wherein:
 said rotating after said wafer substrate is fully immersed is conducted at about 100 rpm.   
     
     
         14 . A method of immersing a wafer substrate as in  claim 1  wherein:
 moving said holder-wafer conjugate toward said horizontal liquid surface is conducted along a trajectory substantially normal to said horizontal liquid surface.   
     
     
         15 . A method of immersing a wafer substrate as in  claim 1  wherein:
 said piercing speed is slower than said final post-piercing speed.   
     
     
         16 . A method of immersing a wafer substrate as in  claim 1  wherein:
 said moving downward at said piercing speed is conducted at a speed in a range of about from 0.1 mm per second to 15 mm per second.   
     
     
         17 . A method of immersing a wafer substrate as in  claim 16  wherein:
 said moving downward at said piercing speed is conducted at a speed in a range of about from 3 mm per second to 8 mm per second.   
     
     
         18 . A method of immersing a wafer substrate as in  claim 1  wherein:
 said moving downward at said final post-piercing speed is conducted at a speed in a range of about from 25 mm per second to 150 mm per second.   
     
     
         19 . A method of immersing a wafer substrate as in  claim 18  wherein:
 said moving downward at said final post-piercing speed is conducted at about 100 mm per second.   
     
     
         20 . A method of immersing a wafer substrate as in  claim 1  wherein said liquid bath comprises a plating solution. 
     
     
         21 . A method of immersing a wafer substrate as in  claim 20  wherein said plating solution comprises an electroless plating solution. 
     
     
         22 . A method of immersing a wafer substrate as in  claim 20  wherein said liquid bath comprises an electrolytic plating solution. 
     
     
         23 . A method of immersing a wafer substrate as in  claim 22  wherein said electrolytic plating solution comprises copper ions. 
     
     
         24 . In an apparatus comprising a wafer holder for moving a wafer downward into a liquid bath so that a planar surface of said wafer forms an angle with a plane parallel to a liquid surface of the liquid bath, the improvement characterized in that:
 said wafer holder is stopable at a selected pause location for a selected pause time; and   said wafer holder is startable at said pause location for moving until a wafer in the wafer holder is fully immersed.