Chemically-sensitive field effect transistors, systems, and methods for manufacturing and using the same
An apparatus includes a biosensor integrated circuit (IC) chip with sensing zones and/or well structures configured to receive a liquid with biological analytes. The chip includes passivation and etch stop layers with an opening over a channel layer and an array of liquid gated field effect transistors with a 2D channel disposed on a dielectric oxide layer. A conductive drain and a conductive source form edge and/or top side contacts with opposite ends of the 2D channel. The chip further includes reference electrodes formed in a metal layer, configured to contact the liquid, and disposed at a horizontal distance apart from the graphene channels. The transistors are operable to enable a set of measurements to sense parameters of the biological analytes based on changes in a shape of Id-Vgs transconductance curves. A system and a method have similar structures and perform the functions of the apparatus.
1. An apparatus comprising:
a biosensor integrated circuit (“IC”) chip with one or more sensing zones within one or more well structures configured to receive a liquid comprising one or more biological analytes, the biosensor IC chip further comprising:
a two-dimensional (“2D”) nanomaterial layer disposed on a dielectric oxide layer on a wafer to form a 2D channel for a liquid gated field effect transistor in an array of liquid gated field effect transistors;
an etch stop layer deposited over the 2D nanomaterial layer;
a passivation layer deposited over the etch stop layer;
one or more openings or trenches etched through the passivation layer and the etch stop layer to expose a portion of a top side and/or an edge of the 2D nanomaterial;
a drain electrode formed in electrode material so as to form one or more of an edge side contact or a top side contact with an exposed portion of the 2D nanomaterial at a first end of the 2D channel; and
a source electrode formed in electrode material so as to form one or more of an edge side contact or a top-side contact with an exposed portion of the 2D nanomaterial at a second end of the 2D channel,
wherein a liquid gate for the field effect transistor is formed above a top surface of the 2D channel upon receiving the liquid.
2. The apparatus of claim 1 , wherein the passivation layer provides an insulating layer between liquid and regions at which the source electrode and the drain electrode connect to the 2D channels of the one or more liquid gated field effect transistors.
3. The apparatus of claim 1 , wherein the passivation layer comprises one or more passivation materials selected from a silicon oxide, a silicon nitride, a metal oxide, and a metal nitride.
4. The apparatus of claim 1 , wherein:
the biosensor IC chip further comprises one or more reference electrodes formed in a metal layer of the biosensor IC chip and configured to contact the liquid, the one or more reference electrodes disposed at a horizontal distance apart from the 2D channels of the liquid gated field effect transistors in the array;
at least one of the one or more reference electrodes is configured to apply a liquid gate voltage to the liquid; and
at least one of the one or more reference electrodes is configured to measure a liquid gate voltage of the liquid.
5. The apparatus of claim 1 , wherein at least a portion of source electrodes and drain electrodes of the liquid gated field effect transistors in the array are interdigitated, curved, or both interdigitated and curved.
6. The apparatus of claim 4 , wherein the liquid gated field effect transistors in the array and the one or more reference electrodes are operable to enable a set of measurements to be made to sense one or more parameters of a biological analyte in the liquid based on changes in shape of a chemical sensing I d -V gs curve relative to a reference I d -V gs , in response to presence of the biological analyte in the liquid on or over the 2D channels of the one or more liquid gated field effect transistors.
7. The apparatus of claim 6 , wherein the changes in shape of the chemical sensing I d -V gs curve relative to a reference I d -V gs curves include transconductance slope changes.
8. The apparatus of claim 7 , wherein the transconductance slope changes include changes to transconductance slope in both a p-type region and an n-type region of the chemical sensing I d -V gs curve.
9. The apparatus of claim 8 , wherein the one or more liquid gated field effect transistors are configured to enable sensing of one or more parameters of the one or more biological analytes in the liquid based on shifts of a chemical sensing I d -V gs curve relative to a reference I d -V gs .
10. The apparatus of claim 9 , wherein the shifts of the chemical sensing I d -V gs curve relative to a reference I d -V gs are selected from horizontal shifts, vertical shifts, or combinations thereof.
11. The apparatus of claim 9 , wherein the shifts of the chemical sensing I d -V gs curve relative to a reference I d -V gs include shifts in parameters selected from on current (“I on” ) in the p-type region, Dirac voltage (“V Dirac” ), on current (“I on” ) in the n-type region, and combinations thereof.
12. The apparatus of claim 1 , further comprising one or more capture regions on or over the 2D channels of the one or more liquid gated field effect transistors, the capture regions configured respectively to accommodate attachment of biomolecule to a top surface of the 2D channel, the biomolecule selected to detect a biological analyte of the one or more biological analytes in the liquid.
13. The apparatus of claim 12 , wherein the biomolecule in respective capture regions of the one or more capture regions are selected to detect analytes selected from ions associated with biomolecules, nucleic acids, antigens, polysaccharides, proteins, peptides, small molecules, and combinations thereof.
14. A method for forming a biosensor integrated circuit (“IC”) chip, the method comprising:
depositing a dielectric oxide layer on a wafer;
disposing a two-dimensional (“2D”) nanomaterial layer on the dielectric oxide layer to form a 2D channel for a liquid gated field effect transistor in an array of liquid gated field effect transistors;
depositing an etch stop layer over the 2D nanomaterial layer;
depositing a passivation layer over the etch stop layer;
etching one or more openings through the passivation layer and the etch stop layer to expose a top side or an edge of the 2D nanomaterial;
depositing a metal layer comprising electrode material in the one or more openings to form:
a drain electrode that forms an edge contact and/or a top contact at a first end of the 2D channel; and
a source electrode that forms an edge contact and/or a top contact at a second end of the 2D channel;
wherein a liquid gate for the field effect transistor is formed above a top surface of the 2D channel upon receiving the liquid.
15. The method of claim 14 , wherein the passivation layer provides an insulating layer between liquid and regions at which the source electrode and the drain electrode connect to the 2D channels of the one or more liquid gated field effect transistors.
16. The method of claim 14 , wherein the passivation layer comprises one or more passivation materials selected from a silicon oxide, a silicon nitride, a metal oxide, and a metal nitride.
17. The method of claim 14 , further comprising forming one or more reference electrodes for contacting the liquid, the one or more reference electrodes disposed at a horizontal distance apart from the 2D channels of the liquid gated field effect transistors in the array, wherein:
at least one of the one or more reference electrodes is configured to apply a liquid gate voltage to the liquid; and
at least one of the one or more reference electrodes is configured to measure a liquid gate voltage of the liquid.
18. The method of claim 14 , wherein at least a portion of source electrodes and drain electrodes of the liquid gated field effect transistors in the array are interdigitated, curved, or both interdigitated and curved.
19. A system comprising:
a biosensor integrated circuit (“IC”) chip with one or more sensing zones within one or more well structures configured to receive a liquid comprising one or more biological analytes, the biosensor IC chip further comprising:
a two-dimensional (“2D”) nanomaterial layer disposed on a dielectric oxide layer on a wafer to form a 2D channel for a liquid gated field effect transistor in an array of liquid gated field effect transistors;
an etch stop layer deposited over the 2D nanomaterial layer;
a passivation layer deposited over the etch stop layer;
one or more openings or trenches etched through the passivation layer and the etch stop layer to expose a portion of a top side and/or an edge of the 2D nanomaterial;
a drain electrode formed in electrode material so as to form one or more of an edge side contact or a top-side contact with an exposed portion of the 2D nanomaterial at a first end of the 2D channel; and
a source electrode formed in electrode material so as to form one or more of an edge side contact or a top-side contact with an exposed portion of the 2D nanomaterial at a second end of the 2D channel,
wherein a liquid gate for the field effect transistor is formed above a top surface of the 2D channel upon receiving the liquid; and
a processor configured to read digitized signals from liquid gated field effect transistors in the array to make a set of measurements to sense one or more parameters of a biological analyte in the liquid based on changes in shape of a chemical sensing Id-Vgs curve relative to a reference Id-Vgs, in response to presence of the biological analyte in the liquid on or over the 2D channels of the one or more liquid gated field effect transistors.
20. The system of claim 19 , wherein the wafer on which the 2D nanomaterial layer is disposed is a CMOS ROIC wafer that comprises the processor.