MEMS heat pumps for integrated circuit heat dissipation

Abstract

A cooling mechanism within an integrated circuit includes an internal pump for circulating thermally conductive fluid within closed loop channels. The cooling channels are embedded within an integrated circuit die, such as in interlevel dielectric layers between metal levels. The channels are formed by engineering deposition of a layer to line trenches and form continuous voids along the trenches. Exemplary heat pumps comprise cavities, formed in communication with the channels, covered by piezoelectric actuators. Preferably, the actuators are wired to act in sequence as a peristaltic pump, circulating the fluid within the channels. The channels are positioned to carry heat from active devices within the integrated circuit, and a heat sink carries heat from the die.

1 . A method for forming a pump actuator within an integrated circuit die, comprising: 
 forming a cavity within a structural layer of the integrated circuit die, said cavity being in fluid communication with channels within the integrated circuit die; and    forming a piezoelectric actuator over the cavity.    
   
   
       2 . The method of  claim 1 , wherein forming the piezoelectric actuator comprises forming a first conductive layer, a piezoelectric layer over the first conductive layer, and a second conductive layer over the piezoelectric layer.  
   
   
       3 . The method of  claim 2 , further comprising forming a layer of a flexible material below the first conductive layer and above the cavity.  
   
   
       4 . The method of  claim 3 , further comprising forming an insulating layer between the layer of the flexible material and the first conductive layer.  
   
   
       5 . The method of  claim 2 , further comprising forming a passivation layer over the second conductive layer.  
   
   
       6 . The method of  claim 1 , further comprising forming a closed loop of the channels.  
   
   
       7 . The method of  claim 6 , further comprising filling the channels with a thermally conductive fluid.  
   
   
       8 . The method of  claim 7 , wherein filling comprises introducing the fluid into the channels under pressure while sealing the fluid within the channels.  
   
   
       9 . The method of  claim 1 , wherein forming the piezoelectric actuator comprises laminating a preformed actuator over the cavity.  
   
   
       10 . The method of  claim 1 , further comprising laminating a heat sink to the integrated circuit die.  
   
   
       11 . The method of  claim 1 , wherein the structural layer is deposited integrally over a portion of a semiconductor substrate at least partially defining the integrated circuit die.  
   
   
       12 . A method for cooling an integrated circuit die, comprising: 
 providing a pump embedded within the integrated circuit die;    providing channels embedded within the integrated circuit die, the channels being in fluid communication with one or more cavities formed within a structural layer of the integrated circuit die; and    circulating fluid through the channels with the pump,    
   
   
       13 . The method of  claim 12 , wherein providing a pump comprises providing an electromechanical pump in communication with the channels.  
   
   
       14 . The method of  claim 13 , wherein circulating fluid comprises actuating the electromechanical pump.  
   
   
       15 . The method of  claim 14 , wherein actuating the electromechanical pump comprises activating a piezoelectric actuator formed over the cavity.  
   
   
       16 . The method of  claim 15 , further comprising actuating a plurality of piezoelectric actuators in sequence to collectively serve as a peristaltic pump.  
   
   
       17 . The method of  claim 12 , wherein providing channels comprises providing a closed loop of channels.