Integrated inductive circuits

Abstract

An integrated inductive element may be formed over a substrate. A trench may be defined in a variety of shapes in the substrate beneath the integrated inductive element in order to reduce eddy current losses arising from magnetic coupling between integrated inductors associated with the same integrated circuit.

What is claimed is:  
     
         1 . An integrated circuit comprising: 
 a substrate;    a spiral inductive element formed over said substrate; and    a trench formed in said substrate beneath said inductive element.    
     
     
         2 . The circuit of  claim 1  wherein said circuit is a complementary metal oxide semiconductor circuit  
     
     
         3 . The circuit of  claim 3  wherein said trench is formed in a x-shape.  
     
     
         4 . The circuit of  claim 3  wherein said trench includes a plurality of arms which radiate outwardly from a center.  
     
     
         5 . The circuit of  claim 4  including at least three arms.  
     
     
         6 . The circuit of  claim 1  including a triple well formed in said substrate, under said inductive element.  
     
     
         7 . The circuit of  claim 6  wherein said triple well includes an N-well with a P-well formed in said N-well and wherein said substrate is a P-type substrate.  
     
     
         8 . The circuit of  claim 7  wherein said N-well is a deep N-well.  
     
     
         9 . The circuit of  claim 8  wherein said inductive element is formed over said P-well.  
     
     
         10 . The circuit of  claim 9  wherein said trench extends completely across said P-well.  
     
     
         11 . The circuit of  claim 1  including a memory formed in said substrate.  
     
     
         12 . The circuit of  claim 11  wherein said memory is flash memory.  
     
     
         13 . The circuit of  claim 1  wherein said circuit is a radio frequency device.  
     
     
         14 . The circuit of  claim 13  wherein said radio frequency device is a cellular telephone.  
     
     
         15 . The circuit of  claim 1  wherein said circuit is a wireless network transceiver.  
     
     
         16 . The circuit of  claim 15  wherein said circuit is a Bluetooth transceiver.  
     
     
         17 . The circuit of  claim 1  including logic circuits formed in said substrate.  
     
     
         18 . The circuit of  claim 17  including memory formed with logic circuits in said substrate.  
     
     
         19 . The circuit of  claim 6  wherein said triple well forms a reverse biased diode between the substrate and said inductive element.  
     
     
         20 . A method comprising: 
 forming an inductive element over a substrate; and    forming a trench in said substrate beneath said inductive element.    
     
     
         21 . The method of  claim 20  including operating a cellular telephone.  
     
     
         22 . The method of  claim 20  including operating a radio frequency transceiver.  
     
     
         23 . The method of  claim 20  including operating a wireless network transceiver.  
     
     
         24 . The method of  claim 23  including operating a Bluetooth transceiver.  
     
     
         25 . The method of  claim 20  including filling said trench with an insulator.  
     
     
         26 . The method of  claim 20  wherein forming said trench includes forming said trench in a x-shape.  
     
     
         27 . The method of  claim 20  including forming a reverse biased diode between said inductive element and a substrate to isolate said inductive element from noise in said substrate.  
     
     
         28 . The method of  claim 27  including forming said inductive element over a triple well including a P-well formed in a N-well.  
     
     
         29 . The method of  claim 28  including forming a trench that extends completely across said P-well.  
     
     
         30 . The method of  claim 29  wherein said trench extends completely across said P-well in two different directions.