Microwell structures for chemically-sensitive sensor arrays

Abstract

Methods and apparatus relating to FET arrays for monitoring chemical and/or biological reactions such as nucleic acid sequencing-by-synthesis reactions. Some methods provided herein relate to improving signal (and also signal to noise ratio) from released hydrogen ions during nucleic acid sequencing reactions.

What is claimed is: 
     
         1 . A sensor, comprising:
 an array of chemically-sensitive field effect transistors (chemFETs), chemFETs in the array including floating gates having upper surfaces;   a microwell layer defining microwells over the floating gate structures of the chemFETs, the microwells having sidewalls; and   a sensing material between bottom surfaces of the microwells and the upper surfaces of the floating gate structures, wherein the sensing material is different from material of the microwell layer at the sidewalls.   
     
     
         2 . The sensor of  claim 1 , wherein the sensing material includes a metal oxide material. 
     
     
         3 . The sensor of  claim 1 , wherein the material of the microwell layer at the sidewalls includes a polymer. 
     
     
         4 . The sensor of  claim 1 , wherein the sensing material is an etch stop layer. 
     
     
         5 . The sensor of  claim 1 , wherein the sensing material is a metal oxide or metal nitride selected from one or more of the group of Al 2 O 3 , Ta 2 O 5 , HfO 3 , and WO 3  or mixtures thereof. 
     
     
         6 . The sensor of  claim 1 , wherein the chemFETs in the array provide outputs indicating an ion-concentration in an analyte solution within the microwells. 
     
     
         7 . The sensor of  claim 1 , including a micro fluidic structure in fluid flow communication with the array of microwells, and arranged to deliver analytes for sequencing. 
     
     
         8 . The sensor of  claim 1 , wherein the sensing material is a thin film material. 
     
     
         9 . The sensor of  claim 1 , wherein the sensing material has higher sensitivity to pH than that of the material of the microwell layer at the sidewalls of the microwells. 
     
     
         10 . The sensor of  claim 1 , wherein the material of the microwell layer at the sidewalls of the microwells has lower buffering capacity of ions than that of the sensing material.