Amplified dual-gate bio field effect transistor
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 may include a substrate; a gate structure disposed on a first surface of the substrate and an interface layer formed on the second surface of the substrate. The interface layer may allow for a receptor to be placed on the interface layer to detect the presence of a biomolecule or bio-entity. An amplification factor of the BioFET device may be provided by a difference in capacitances associated with the gate structure on the first surface and with the interface layer formed on the second surface.
1. A method of fabricating a semiconductor device, the method comprising:
forming a first gate structure on a front surface of a substrate, the first gate structure comprising a conductive layer and a dielectric layer;
doping a region of the substrate to form a channel region beneath the first gate structure and to form a first source/drain region and a second source/drain region aligned relative to the first gate structure;
removing material over a back side of the substrate to expose a back surface of the substrate, wherein the exposed back surface comprises at least a portion of the channel region;
depositing an isolation layer after removing the material, and forming an opening through the isolation layer to expose at least a portion of the channel region; and
forming a second gate structure on the back surface of the substrate, wherein the second gate structure comprises an interface layer configured to bind to biomolecules, and wherein the interface layer is patterned such that at least a portion of the interface layer remains over the exposed portion of the channel region.
2. The method of claim 1 , further comprising immobilizing receptors on the interface layer.
3. The method of claim 2 , wherein the receptors are chosen from the group consisting of enzymes, antibodies, ligands, peptides, nucleotides, cells, organisms, and tissue.
4. The method of claim 1 , further comprising disposing a fluidic channel over the patterned interface layer.
5. The method of claim 1 , wherein a thickness of the dielectric layer is less than a thickness of the interface layer.
6. The method of claim 1 , wherein the first gate structure, second gate structure, channel region, first source/drain region, and second source/drain region form a FET, and wherein the method further comprises arranging a plurality of FETs in an array.
7. The method of claim 1 , wherein the source region, the channel region, and the drain region extend an entire thickness of the substrate measured from the front surface to the back surface.
8. A method of fabricating a semiconductor device, the method comprising:
forming a first gate structure on a front surface of a substrate, the first gate structure comprising a conductive layer and a dielectric layer;
doping a region of the substrate to form a channel region beneath the first gate structure and to form a first source/drain region and a second source/drain region aligned relative to the first gate structure;
removing material over a back side of the substrate to expose a back surface of the substrate, wherein the exposed back surface comprises the channel region, the first source/drain region, and the second source/drain region;
depositing an isolation layer on the back surface of the substrate, the isolation layer being over at least the channel region, the first source/drain region, and the second source/drain region;
forming an opening through the isolation layer to expose at least a portion of the channel region; and
forming a second gate structure on the back surface of the substrate, wherein the second gate structure comprises an interface layer configured to bind to biomolecules, and wherein the interface layer is patterned such that at least a portion of the interface layer remains over the exposed portion of the channel region.
9. The method of claim 8 , further comprising binding receptors to the interface layer.
10. The method of claim 9 , wherein the receptors are chosen from the group consisting of enzymes, antibodies, ligands, peptides, nucleotides, cells, organisms, and tissue.
11. The method of claim 8 , further comprising disposing a fluidic channel over the patterned interface layer.
12. The method of claim 8 , wherein a sub-threshold swing associated with the interface layer is less than a sub-threshold swing associated with the dielectric layer.
13. The method of claim 8 , wherein a thickness of the dielectric layer is less than a thickness of the interface layer.
14. The method of claim 8 , wherein the first gate structure, second gate structure, channel region, first source/drain region, and second source/drain region form a FET, and wherein the method further comprises arranging a plurality of FETs in an array.
15. A method of using a BioFET sensor to detect target molecules, the method comprising:
disposing a solution containing the target molecules over the BioFET sensor, wherein the BioFET sensor includes an interface layer on a backside of a substrate, the interface layer having receptors immobilized thereon that are exposed to the solution, and wherein the BioFET sensor further includes a gate structure pattered on a front side of the substrate, the interface layer being aligned with the gate structure, wherein the gate structure comprises a conductive layer and a dielectric layer, and wherein a thickness of the dielectric layer is less than a thickness of the interface layer;
binding the target molecules to the receptors;
changing a threshold voltage of the BioFET sensor based on the binding of the target molecules; and
detecting a presence of the target molecules based on the change of the threshold voltage.
16. The method of claim 15 , wherein the receptors are chosen from the group consisting of enzymes, antibodies, ligands, peptides, nucleotides, cells, organisms, and tissue.
17. The method of claim 15 , wherein the disposing comprises disposing the solution over a plurality of BioFET sensors arranged in an array.
18. The method of claim 15 , wherein the target molecules include single-stranded DNA (ssDNA) and the receptors include complementary ssDNA.
19. The method of claim 15 , wherein the disposing comprises disposing the solution in a microfluidic channel over the interface layer.
20. The method of claim 15 , wherein the receptors include monoclonal antibodies and the target molecules include tumor markers.