Method and apparatus for preventing microcircuit thermo-mechanical damage during an ESD event

Abstract

A method and apparatus for preventing thermo-mechanical damage to an electrostatic discharge (ESD) protection device is disclosed. The method and apparatus of the invention use materials with superior thermo-mechanical properties, in particular, the Coefficient of Thermal Expansion (CTE), melting temperature, tensile strength and fracture toughness. The thermo-mechanical energy absorber materials are incorporated in, or replace, components of the ESD device that are susceptible to thermo-mechanical stress and cracking due to localized heating and thermal expansion.

1 . An integrated circuit incorporating an Electrostatic Discharge (ESD) protection device comprising: 
 a semiconductor substrate;    an electrical contact pad;    an ESD switch coupled to the pad and having an active device region formed in the semiconductor substrate; and    a thermo-mechanical reinforcement region formed in the semiconductor in thermal contact with said active device region made from a material substantially more resistant to thermo-mechanical damage than said active device region, whereby said ESD protection device becomes highly resistant to thermo-mechanical stress and damage resulting from thermal expansion.    
   
   
       2 . The integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 1 , wherein said material substantially more resistant to thermo-mechanical damage has a thermal expansion coefficient lower than approximately 5×10 −6 ° K −1 .  
   
   
       3 . The integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 1 , wherein said material substantially more resistant to thermo-mechanical damage has a melting temperature higher than approximately 2000° K.  
   
   
       4 . The integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 1 , wherein said material substantially more resistant to thermo-mechanical damage has a tensile strength higher than approximately 300 MPa (Mega Pascals).  
   
   
       5 . The integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 1 , wherein said material substantially more resistant to thermo-mechanical damage has a fracture toughness approximately higher than about 1.0 MPa m 1/2 .  
   
   
       6 . The integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 1 , wherein the ESD switch is a transistor.  
   
   
       7 . The integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 1 , wherein said thermo-mechanical reinforcement region is in direct contact with said active device region.  
   
   
       8 . The integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 6 , wherein the transistor is a MOSFET structure and wherein the active device region comprises: 
 a source region;    a drain region; and    a channel region between the source region and the drain region.    
   
   
       9 . The integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 1 , wherein the ESD switch is a diode.  
   
   
       10 . The integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 1 , wherein said material substantially more resistant to thermo-mechanical damage than the active device region is selected from the group consisting of diamond, boron nitride, silicon carbide or carbon.  
   
   
       11 . The integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 1 , wherein the ESD switch includes a resistor or a capacitor.  
   
   
       12 - 21 . (canceled)  
   
   
       22 . The integrated circuit incorporating an Electrostatic Discharge (ESD) protection device comprising: 
 a semiconductor substrate;    an electrical contact pad;    a connector electrically connected to the electrical contact pad; and    an ESD switch coupled to the pad, at least in part via the connector, said ESD switch having an active device region in the semiconductor substrate, and wherein said semiconductor substrate comprises a thermo-mechanical energy withstanding region fabricated from material resistant to thermo-mechanical damage, the material having physical properties including a low thermal expansion coefficient lower than approximately 5×10 −6 ° K −1 , whereby said ESD protection device becomes highly resistant to thermo-mechanical stress and damage resulting from thermal expansion.    
   
   
       23 . The integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 22 , wherein the material resistant to thermo-mechanical damage has physical properties further including a high melting temperature approximately higher than 2000° K.  
   
   
       24 . The integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 22 , wherein the material resistant to thermo-mechanical damage has physical properties further including a high fracture toughness higher than about 1.0 MPa m 1/2 .  
   
   
       25 . The integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 22 , wherein the material resistant to thermo-mechanical damage has physical properties further including a high tensile strength approximately higher than 300 MPa.  
   
   
       26 . The integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 22 , further comprising a grounded back contact electrically coupled to the semiconductor substrate, so that when an ESD event occurs producing an ESD current, the current is shunted from the ESD protection device through thermo-mechanical energy withstanding region and through the grounded back contact.  
   
   
       27 . An integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 22 , wherein said active device region comprises said thermo-mechanical energy withstanding region.  
   
   
       28 . An integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 22 , wherein said semiconductor substrate is fabricated from said material resistant to thermo-mechanical stress.  
   
   
       29 . An integrated circuit incorporating an Electrostatic Discharge (ESD) protection device according to  claim 22 , wherein said material resistant to thermo-mechanical damage is selected from a group consisting of diamond, hard carbon, silicon carbide or boron nitride.  
   
   
       30 . An integrated circuit, comprising: 
 a semiconductor substrate;    a core circuit comprising a plurality of devices having electrical connectors and active device regions formed in the semiconductor substrate and one or more electrical insulator regions; and    an ESD circuit comprising an active device having an active device region formed in a substrate material, one or more electrical connectors, and one or more electrical insulator regions, and one or more passive components wherein at least one of said substrate material, electrical connectors, active device region, passive circuit components or electrical insulator is composed in whole or in part of a material substantially more resistant to thermo-mechanical damage than the corresponding structure in said core circuit devices, whereby said ESD protection device becomes highly resistant to thermo-mechanical stress and damage resulting from thermal expansion.    
   
   
       31 . The integrated circuit of  claim 30 , wherein the passive component comprises a resistor or a capacitor.  
   
   
       32 . The integrated circuit of  claim 30 , wherein the ESD switch is spaced apart from the core circuitry by at least 10 microns.  
   
   
       33 . The integrated circuit of  claim 30 , wherein said material substantially more resistant to the thermo-mechanical damage comprises a material having a substantially lower coefficient of thermal expansion.  
   
   
       34 . The integrated circuit of  claim 30 , wherein at least one of the said electrical connectors of the ESD circuit comprises carbon.  
   
   
       35 . An integrated circuit, comprising: 
 a semiconductor substrate;    a core circuit comprising a plurality of devices having electrical connectors and active device regions formed in the semiconductor substrate and one or more electrical insulator regions; and    an ESD switch having means, integrated with the switch structure, having thermo-mechanical properties adapted for preventing thermo-mechanical damage due to an ESD event.    
   
   
       36 . A method of fabricating an ESD device on a semiconductor substrate, the method comprising: 
 fabricating an ESD switch from one or more connectors and one or more active device regions formed in the semiconductor substrate;    providing a region composed of a material resistant to thermo-mechanical damage, the region in thermal contact with said switch, wherein the material has physical properties including a low thermal expansion coefficient lower than approximately 5×10 −6 ° K −1 .    
   
   
       37 . The method of  claim 36 , wherein the material has physical properties further including a high melting temperature higher than approximately 2000° K.  
   
   
       38 . The method of  claim 36 , wherein the material has physical properties further including a high tensile strength higher than approximately 300 MPa (Mega Pascals).  
   
   
       39 . The method of  claim 36 , wherein the material has physical properties further including a high fracture toughness higher than approximately 1.0 MPa m 1/2 .