High Sensitivity Silicon Piezoresistor Force Sensor

Abstract

Embodiments relate to systems and methods for sensing a force using a sense die. A sense die may comprise a chip comprising a slab; an actuation element configured to contact the slab at or near the center of the slab, and configured to apply a force to the slab; and one or more sense elements supported by the slab, wherein the ratio of the width of the slab to the distance between the one or more sense elements is at least 2/1. A method may comprise providing a sense die comprising a chip having a slab formed thereon; applying a force to the slab of the sense die; and determining the magnitude of the force applied to the slab via one or more sense elements attached to the slab, wherein the ratio of the width of the slab to the distance between the sense elements is greater than 2/1.

What is claimed is: 
     
         1 . A sense die comprising:
 a chip comprising a slab;   one or more sense elements supported by the slab, wherein the ratio of the width of the slab to the distance between the one or more sense elements is at least approximately 2/1;   one or more bond pads supported by a first side of the chip, each of the one or more bond pads electrically coupled to at least one of the one or more sense elements;   a structural frame disposed on the first side of the chip, wherein the structural frame is disposed at least partially about the slab; and   one or more electrical contacts extending through the structural frame, wherein the one or more electrical contacts are electrically coupled to the one or more bond pads.   
     
     
         2 . The sense die of  claim 1 , wherein the sense elements comprise piezoresistive elements. 
     
     
         3 . The sense die of  claim 1 , further comprising an actuation element configured to contact the slab at or near the center of the slab. 
     
     
         4 . The sense die of  claim 3 , wherein the distance between the sense elements is centered on the contact point between the slab and the actuation element. 
     
     
         5 . The sense die of  claim 1 , wherein the ratio of the width of the slab to the distance between the one or more sense elements is greater than approximately 5/1. 
     
     
         6 . The sense die of  claim 1 , wherein the ratio of the width of the slab to the distance between the one or more sense elements is greater than approximately 10/1. 
     
     
         7 . The sense die of  claim 1 , wherein the locations of the one or more sense elements are determined by mapping the force on the slab applied by the actuation element, and identifying one or more hotspots on the slab where the force is higher than the surrounding areas. 
     
     
         8 . The sense die of  claim 1 , wherein the locations of the one or more sense elements are determined by determining a correlation between the estimated force that will be applied to the slab and the desired location for sense elements on the slab. 
     
     
         9 . A method of sensing a force using a sense die, the method comprising:
 providing a sense die comprising a chip having a slab formed thereon;   applying a force to the slab of the sense die; and   determining the magnitude of the force applied to the slab via one or more sense elements attached to the slab, wherein the ratio of the width of the slab to the distance between the one or more sense elements is greater than approximately 2/1.   
     
     
         10 . The method of  claim 9 , further comprising determining a correlation between the estimated force that will be applied to the slab and the desired location for sense elements on the slab. 
     
     
         11 . The method of  claim 10 , wherein as the estimated force increases, the desired location for the sense elements increases in distance from the center of the slab. 
     
     
         12 . The method of  claim 9 , wherein applying a force comprises contacting the slab with an actuation element. 
     
     
         13 . The method of  claim 12 , wherein the distance between the sense elements is centered on the contact point between the slab and the actuation element. 
     
     
         14 . The method of  claim 9 , wherein the ratio of the width of the slab to the distance between the one or more sense elements is greater than approximately 5/1. 
     
     
         15 . The method of  claim 9 , further comprising:
 mapping the force on the slab applied by the actuation element;   identifying one or more hotspots on the slab where the force is higher than the surrounding areas; and   determining the location for a piezoresistive element to be located on the slab based on the location of the hotspots.   
     
     
         16 . A sense die comprising:
 a chip comprising a slab;   an actuation element configured to contact the slab at or near the center of the slab, and configured to apply a force to the slab; and   one or more sense elements supported by the slab, wherein the ratio of the width of the slab to the distance between the one or more sense elements is greater than approximately 2/1, and wherein the distance between the sense elements is centered on the contact point between the actuation element and the slab.   
     
     
         17 . The sense die of  claim 16 , wherein the sense elements comprise piezoresistive elements. 
     
     
         18 . The sense die of  claim 16 , wherein the ratio of the width of the slab to the distance between the one or more sense elements is greater than approximately 5/1. 
     
     
         19 . The sense die of  claim 16 , wherein the ratio of the width of the slab to the distance between the one or more sense elements is less than approximately 20/1. 
     
     
         20 . The sense die of  claim 16 , wherein the sense elements are located at or near hotspots identified on the surface of the slab by force mapping.