Integrated reference vacuum pressure sensor with atomic layer deposition coated input port

Abstract

An integrated reference vacuum pressure sensor with an atomic layer deposition (ALD) coated input port comprises a housing with an port for a media to enter the housing; a substrate and stress isolation member in the housing; wherein a channel extends through the substrate and the stress isolation member, wherein a trace is embedded within the stress isolation member, wherein stress isolation member and substrate surfaces exposed to the channel are coated with an ALD; a sensor die bonded to the stress isolation member, the sensor die comprising a diaphragm having circuitry, wherein a side of the diaphragm is exposed to the channel and the circuitry is mounted to another side of the diaphragm; a via extending through the sensing die electrically connecting the circuitry to the trace; and a cover bonded to the stress isolation member, the cover having a recess, the sensor die in the recess.

What is claimed is: 
     
         1 . A method for fabricating a pressure sensor, the method comprising:
 forming a stress isolation member in contact with a substrate, wherein the stress isolation member and the substrate have a channel formed through the substrate and the stress isolation member;   fabricating a sensor die, wherein the sensor die comprises a diaphragm having sensing circuitry formed thereon;   mounting the sensor die to the stress isolation member, wherein a first side of the diaphragm is exposed to an opening of the channel;   securing the stress isolation member, the substrate, and the sensor die in a housing having an input port, wherein the channel is positioned in the housing such that a pressure media entering the input port also enters the channel;   coating surfaces of the stress isolation member and the substrate that are exposed to either the input port or the channel with an atomic layer deposition;   electrically connecting the sensing circuitry to an external system; and   sealing a second side of the sensor die within an environment having a known pressure, wherein the second side is hermetically isolated from the opening of the channel.   
     
     
         2 . The method of  claim 1 , wherein sealing the side of the sensor die within an environment having a known pressure comprises bonding a reference cover to the stress isolation member in the environment, the reference cover having a recess, wherein the sensor die is located within the recess. 
     
     
         3 . The method of  claim 2 , wherein the reference cover is fabricated from a material having the same coefficient of thermal expansion as the sensor die. 
     
     
         4 . The method of  claim 1 , wherein forming the stress isolation member on the substrate comprises forming embedded conductive traces within the stress isolation member, wherein the embedded conductive traces electrically connect to the sensing circuitry. 
     
     
         5 . The method of  claim 4 , wherein fabricating the sensor die comprises forming vias through the sensor die, wherein the vias electrically connect the embedded conductive trace to the sensing circuitry when the sensor die is mounted to the stress isolation member. 
     
     
         6 . The method of  claim 1 , wherein the stress isolation member is fabricated from a silicon coefficient of thermal expansion matching low temperature co-fired ceramic. 
     
     
         7 . The method of  claim 1 , wherein the stress isolation member comprises a pedestal, extending away from a surface of the substrate, wherein the channel extends longitudinally through the pedestal, the sensor die being mounted to the pedestal, wherein the opening of the channel exposed to the first side of the diaphragm is in a side of the pedestal that is farthest from the substrate. 
     
     
         8 . The method of  claim 1 , wherein the atomic layer deposition comprises a metal oxide. 
     
     
         9 . The method of  claim 1 , wherein electrically connecting the sensing circuitry to an external system comprises:
 electrically connecting the sensing circuitry to front end circuitry within the housing;   electrically connecting the front end circuitry to the external system through an external connector.   
     
     
         10 . The method of  claim 1 , wherein the substrate and the stress isolation member are secured within the housing with at least one of a braze and solder joint.