Method of forming bumps on a wafer utilizing a post-heating operation, and an apparatus therefore

Abstract

A bump forming apparatus which carries out a temperature control of a type different from the conventional art in forming bumps to a semiconductor wafer, and a bump formation method executed by the bump forming apparatus are provided. A bonding stage, a load and transfer device and a control device are provided. A wafer, after having bumps formed thereon, is held by the load and transfer device and arranged above the bonding stage through control by the control device, so that a temperature drop of the wafer is controlled. Accordingly, generation of troubles such as a crack because of thermal stress and the like can be prevented to even compound semiconductor wafers sensitive to a temperature change.

1 . A bump forming apparatus comprising:
 a bonding stage for supporting a semiconductor wafer and for heating the semiconductor wafer to a temperature for forming bumps on electrodes on a circuit of the semiconductor wafer;   a bump forming head for forming the bumps on the electrodes of the semiconductor wafer;   a load and transfer device for placing the semiconductor wafer on and removing the semiconductor wafer from said bonding stage; and   a controller for operating said bonding stage and said load and transfer device so as to perform a post-heating operation on the semiconductor wafer after the bumps are formed on the semiconductor wafer to thereby control a temperature drop of the semiconductor wafer, said controller being operable to control the post-heating operation on the semiconductor wafer by controlling said load and transfer device and said bonding stage so as to change at least one of a gap size between said bonding stage and the semiconductor wafer opposite the bonding stage by said load and transfer device when the semiconductor wafer is positioned in the cooling position by said load and transfer device, and a period of time during which the semiconductor wafer is positioned at the cooling position above the bonding stage by said load and transfer device while said bonding stage is heated to the temperature for forming the bumps such that the semiconductor wafer does not contact said bonding stage when in the cooling position.   
   
   
       2 . The bump forming apparatus of  claim 1 , wherein said controller is operable to control the post-heating operation on the semiconductor wafer by controlling said load and transfer device and said bonding stage so as to change at least one of the gap size and the period of time multiple times. 
   
   
       3 . The bump forming apparatus of  claim 1 , wherein said controller is operable to control the post-heating operation in accordance with a preliminarily set program for post-heating. 
   
   
       4 . The bump forming apparatus of  claim 1 , further comprising a temperature measuring device for measuring a temperature of the semiconductor wafer subjected to the post-heating operation, said controller being operable to control the post-heating operation based on the temperature of the semiconductor wafer measured by said temperature measuring device. 
   
   
       5 . The bump forming apparatus of  claim 1 , wherein said controller is operable to control the post-heating operation based on at least one of a material of the semiconductor wafer and a thickness of the semiconductor wafer. 
   
   
       6 . The bump forming apparatus of  claim 1 , wherein said load and transfer device includes clamp mechanisms spaced equally apart to prevent a dynamic stress and a thermal temperature gradient on the semiconductor wafer. 
   
   
       7 . The bump forming apparatus of  claim 1 , wherein said controller comprises a first controller, further comprising a second controller for operating said bonding stage and said load and transfer device so as to perform a preheating operation on the semiconductor wafer before the semiconductor wafer is placed on said bonding stage and heated to the temperature for forming bumps, said second controller being operable to control the preheating operation on the semiconductor wafer by controlling said load and transfer device and said bonding stage so that the semiconductor wafer is positioned by said load and transfer device at a preheating position above said bonding stage while said bonding stage is heated to the temperature for forming the bumps such that the semiconductor wafer does not contact said bonding stage when in the preheating position. 
   
   
       8 . The bump forming apparatus of  claim 7 , wherein said second controller is operable to control the preheating operation on the semiconductor wafer by controlling said load and transfer device and said bonding stage so as to change at least one of a gap size between said bonding stage and the semiconductor wafer when the semiconductor wafer is positioned in the preheating position by said load and transfer device, and a period of time during which the semiconductor wafer is positioned at the preheating position above the bonding stage by said load and transfer device. 
   
   
       9 . The bump forming apparatus of  claim 8 , wherein said second controller is operable to control the preheating operation on the semiconductor wafer by controlling said load and transfer device and said bonding stage so as to change at least one of the gap size and the period of time multiple times. 
   
   
       10 . The bump forming apparatus of  claim 7 , wherein said second controller is operable to control the preheating operation in accordance with a preliminarily set program for preheating. 
   
   
       11 . The bump forming apparatus of  claim 7 , further comprising a temperature measuring device for measuring a temperature of the semiconductor wafer subjected to the preheating operation, said second controller being operable to control the preheating operation based on the temperature of the semiconductor wafer measured by said temperature measuring device. 
   
   
       12 . The bump forming apparatus of  claim 7 , wherein said second controller is operable to control the preheating operation based on at least one of a material of the semiconductor wafer and a thickness of the semiconductor wafer.