Biofet with increased sensing area

Abstract

The present disclosure provides a bio-field effect transistor (BioFET) and a method of fabricating a BioFET device. The method includes forming a BioFET using one or more process steps compatible with or typical to a complementary metal-oxide-semiconductor (CMOS) process. The BioFET device includes a substrate, a transistor structure, an isolation layer, an interface layer in an opening of the isolation layer, and a metal crown structure over the interface layer. The interface layer and the metal crown structure are disposed on opposite side of the transistor from a gate structure.

What is claimed is: 
     
         1 . A biological field-effect transistors (BioFET) device, comprising:
 a substrate;   a transistor structure in the substrate having a gate structure over a source region, a drain region, and a channel region;   an isolation layer on a side of the substrate opposite from the gate structure, said isolation layer having an opening at the channel region of the transistor structure;   an interface layer in the opening; and,   a metal crown structure over the interface layer and at least partially covering sidewalls of the opening.   
     
     
         2 . The BioFET device of  claim 1 , wherein the metal crown structure comprises tantalum, tantalum nitride, niobium, tungsten nitride, ruthenium oxide, or combinations of these. 
     
     
         3 . The BioFET device of  claim 1 , wherein the metal crown structure completely covers the sidewalls of the opening. 
     
     
         4 . The BioFET device of  claim 1 , wherein a portion of the metal crown structure covers a portion of the isolation layer. 
     
     
         5 . The BioFET device of  claim 1 , wherein the interface layer comprises a high-k dielectric. 
     
     
         6 . The BioFET device of  claim 1 , wherein the interface layer comprises aluminum oxide, titanium oxide, hafnium oxide, tantalum oxide, or tin oxide. 
     
     
         7 . The BioFET device of  claim 1 , further comprising:
 a fluidic channel disposed on the isolation layer.   
     
     
         8 . The BioFET device of  claim 1 , further comprising:
 a multi-layer interconnect (MLI) disposed in the substrate on a side of the substrate that is same as the gate structure.   
     
     
         9 . The BioFET device of  claim 8 , wherein a carrier substrate is bonded to the substrate via a passivation layer over the MLI. 
     
     
         10 . The BioFET device of  claim 1 , wherein a surface area of the metal crown structure is at least twice of the interface layer. 
     
     
         11 . A method of making a biological field-effect transistors (BioFET) device, comprising:
 forming a transistor on a semiconductor substrate, wherein the transistor includes a gate structure formed on a front side of the semiconductor substrate and a channel region between a source region and a drain region;   etching an opening in an isolation layer disposed on a back side of the semiconductor substrate, wherein the opening exposes the channel region of the transistor;   depositing an interface material on the channel region in the opening;   depositing a metal layer on the interface material; and   patterning the metal layer to form a metal crown structure.   
     
     
         12 . The method of  claim 11 , further comprising forming a multi-layer interconnect (MLI) on the front side of the substrate. 
     
     
         13 . The method of  claim 11 , wherein the isolation layer is an insulator of a silicon-on-insulator (SOI) substrate. 
     
     
         14 . The method of  claim 11 , further comprising:
 thinning the semiconductor substrate; and   depositing an isolation layer on the back side of the semiconductor substrate.   
     
     
         15 . The method of  claim 14 , wherein the semiconductor substrate is an SOI substrate and the thinning removes a buried oxide layer. 
     
     
         16 . The method of  claim 11 , further comprising:
 binding a receptor on the metal crown structure, wherein the receptor is selected from the group consisting of enzymes, antibodies, ligands, receptors, peptides, nucleotides, cells of organs, organisms and pieces of tissue.   
     
     
         17 . A device, comprising:
 a first biological field-effect transistors (BioFET) device, including:
 a gate structure formed on a substrate; 
 a source region and a drain region formed in the substrate adjacent the gate structure; 
 a channel region interposing the source and drain regions and underlying the gate structure; 
 an interface layer disposed on the channel region, wherein the interface is disposed on a first side of the channel region and the gate structure is disposed on an opposing, second side of the channel region; and 
 a metal crown structure over the interface layer, the metal crown structure having a larger surface area than the interface layer; and 
   a sense amplifier coupled to the first BioFET device.   
     
     
         18 . The device of  claim 17 , wherein the metal crown structure comprises multiple layers. 
     
     
         19 . The device of  claim 17 , further comprising:
 a plurality of BioFETs, wherein the plurality of BioFETs are configured in an array.   
     
     
         20 . The device of  claim 19 , wherein at least one of the plurality of BioFETs has a different material in the metal crown structure from at least another one of the plurality of BioFETs.