MEMS device with integral packaging

Abstract

A MEMS device and method of making same is disclosed. In one embodiment, a micro-switch includes a base assembly comprising a movable structure bearing a contact pad. The base assembly is wafer-scale bonded to a lid assembly comprising an activator and a signal path. The movable structure moves within a sealed cavity formed during the bonding process. The signal path includes an input line and an output line separated by a gap, which prevents signals from propagating through the micro-switch when the switch is deactivated. In operation, a signal is launched into the signal path. When the micro-switch is activated, a force is established by the actuator, which pulls a portion of the movable structure upwards towards the gap in the signal path, until the contact pad bridges the gap between the input line and output line, allowing the signal to propagate through the micro-switch. Prior to bonding, the MEMS structures are annealed on a first wafer and the conductive traces and other metals are annealed on a second wafer to allow each wafer to be processed separately using different processes, e.g., different annealing temperatures.

What is claimed is:  
     
         1 . A micro-switch, comprising: 
 a first substrate having a signal path, the signal path including a gap portion for preventing signal propagation; and    a second substrate bonded to the first substrate to form a sealed cavity, the sealed cavity adapted to house a movable structure, the movable structure having a contact pad for bridging the gap portion of the signal path when the movable structure is pulled toward the first substrate in response to a force provided by an actuator.    
     
     
         2 . The micro-switch of  claim 1 , further including: 
 a seal ring, forming a seal around the movable structure.    
     
     
         3 . The micro-switch of  claim 1 , further including: 
 an insulation ring disposed on the first substrate; and    a metal seal ring substantially aligned with and overlying the insulation ring, the metal seal ring forming a seal around the movable structure, the insulating ring electrically insulating the metal seal ring from the signal path.    
     
     
         4 . The micro-switch of  claim 1 , wherein the movable structure is made of polysilicon.  
     
     
         5 . The micro-switch of  claim 1 , wherein the movable structure is a cantilever beam.  
     
     
         6 . The micro-switch of  claim 1 , further comprising: 
 a passive element disposed on one of the first and second substrates and coupled to the signal path.    
     
     
         7 . The micro-switch of  claim 1 , further comprising: 
 an active element disposed on one of the first and second substrates and coupled to the signal path.    
     
     
         8 . The micro-switch in  claim 1 , further comprising: 
 a plurality of spacers formed in an insulating layer disposed between the contact pad and the movable structure.    
     
     
         9 . The micro-switch of  claim 1 , further comprising: 
 a passive element disposed on the first substrate and electrically coupled to the signal path.    
     
     
         10 . The micro-switch of  claim 1 , wherein at least one of the first and second substrates includes a mechanical stop.  
     
     
         11 . The micro-switch of  claim 1 , further including an isolation pad disposed between the contact pad and the movable structure.  
     
     
         12 . The micro-switch of  claim 11 , wherein the isolation pad is made of silicon nitride.  
     
     
         13 . The micro-switch of  claim 2 , wherein the seal ring is made of a deformable metal.  
     
     
         14 . The micro-switch of  claim 2 , wherein the deformable metal comprises gold.  
     
     
         15 . The micro-switch of  claim 2 , further comprising: 
 a seal-landing ring disposed on the second substrate, the seal-landing ring for mating with the metal seal ring to form a hermetic seal.    
     
     
         16 . The micro-switch of  claim 2 , wherein the signal path runs under the insulation ring to connect to an external contact point outside the insulation ring.  
     
     
         17 . The micro-switch of  claim 2 , wherein the contact point is a wire bond pad.  
     
     
         18 . A lid assembly for a micro-switch having a lid assembly and a base assembly, comprising: 
 a substrate;    a first insulating layer formed on the substrate;    a first conductive layer formed on the first insulating layer;    a signal path formed in the conductive layer and having a gap for preventing signals from propagating on the signal path;    an actuator formed in the first conductive layer for providing a force on a movable structure in the base assembly when the actuator is activated;    a second insulting layer formed on the first conductive layer;    an insulating ring formed in the second insulting layer;    a second conductive layer formed on the second insulating layer; and    a conductive ring formed in the second conductive layer, the conductive ring substantially aligned with and overlying the insulating ring, the conductive ring forming a seal around the movable structure when the lid assembly is bonded to the base assembly.    
     
     
         19 . A base assembly for a micro-switch having a lid assembly and a base assembly, comprising: 
 a substrate;    a sacrificial layer formed on the substrate;    a structural layer formed on the sacrificial layer;    an insulating layer formed on the structural layer;    an insulating pad formed in the insulating layer;    a movable structure formed in the structural layer and the sacrificial layer, the movable structure bearing the insulating pad; and    a contact pad formed on the insulating pad, the contact pad for bridging a gap in a signal path on the lid assembly, when the movable structure is pulled towards the lid assembly in response to a force provided by an actuator in the lid assembly.    
     
     
         20 . A method of making a lid assembly for a micro-switch having a lid assembly and a base assembly, the method comprising: 
 forming a first insulating layer on a substrate;    forming a first conductive layer on the first insulating layer;    forming a signal path and an actuator in the first conductive layer;    the signal path having a gap for preventing signals from propagating on the signal path, the actuator for providing a force on a movable structure in the base assembly when the actuator is activated;    forming a second insulating layer on the first conductive layer;    forming an insulating ring in the second insulating layer;    forming a second conductive layer on the second insulating layer; and    forming a conductive ring in the second conductive layer, the conductive ring substantially aligned with and overlying the insulating ring, the conductive ring for making a seal between the lid assembly and the base assembly.    
     
     
         21 . A method of making a base assembly for a micro-switch having a lid assembly and a base assembly, the method comprising: 
 forming a sacrificial layer on a substrate;    forming a structural layer on the sacrificial layer;    forming an insulating layer on the structural layer;    forming an insulating pad in the insulating layer;    forming an intermediate movable structure in the structural layer and the sacrificial layer;    forming a conductive layer on the structural layer and sacrificial layer;    forming a contact pad on the conductive layer, wherein the contact pad overlies the intermediate structure; and    removing a portion of the intermediate structure to form a movable structure, the movable structure bearing the contact pad, the contact pad for bridging a gap in a signal path in the lid assembly when the movable structure is pulled towards the lid assembly in response to a force provided by an actuator in the lid assembly.    
     
     
         22 . The lid assembly in  claim 18 , wherein the signal path extends under the insulation ring to connect with a contact point external to the insulation ring.