Direct sensing bioFETs and methods of manufacture
The present disclosure provides a biological 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 plurality of micro wells having a sensing gate bottom and a number of stacked well portions. A bottom surface area of a well portion is different from a top surface area of a well portion directly below. The micro wells are formed by multiple etching operations through different materials, including a sacrificial plug, to expose the sensing gate without plasma induced damage.
1. A biological field-effect transistor (BioFET) device, comprising:
a substrate;
a plurality of BioFETs formed on the substrate, each BioFET comprising
a micro well structure having a top well portion and a bottom well portion, wherein a bottom surface area of the top well portion is different from a top surface area of the bottom well portion,
a source region adjacent a first side of the micro well structure and a drain region adjacent an opposite side of the micro well structure and a channel region extending below the micro well structure, and
a dielectric on the substrate at a bottom surface of the bottom well portion.
2. The BioFET device of claim 1 , wherein each micro well further has a middle well portion and wherein a top surface area of the middle well portion is different from the bottom surface area of the top well portion and a bottom surface area of the middle well portion is different from a top surface area of the bottom well portion.
3. The BioFET device of claim 1 , wherein the dielectric is selected from the group consisting of SiO 2 , Si 3 N 4 , Al 2 O 3 , TiO 2 , HfO 2 , Ta 2 O 5 , SnO, SnO 2 , BaxSr 1-x TiO 3 and combinations thereof.
4. The BioFET device of claim 1 , wherein each BioFET further comprises an electrode on the dielectric.
5. The BioFET device of claim 1 , further comprising:
a multi-layer interconnect (MLI) surrounding at least one micro well of the plurality of BioFETs, wherein the MLI has three or more metal layers.
6. The BioFET device of claim 1 , further comprising logic processors, control circuits, signal amplifiers and A/D converters formed on the substrate.
7. The BioFET device of claim 1 , further comprising:
a fluidic channel between respective ones of the plurality of BioFETs.
8. The BioFET device of claim 1 , wherein each BioFET further comprises:
a coating on sidewalls of the micro well.
9. The BioFET device of claim 1 , further comprising:
a plurality of second BioFETs, each second BioFET comprising
a micro well having a top well portion and a bottom well portion, wherein a bottom surface area of the top well portion is different from a top surface area of the bottom well portion, and
an electrode and a dielectric on the substrate at a bottom surface of the bottom well portion.
10. The BioFET device of claim 1 wherein the BioFET further comprises:
a gate electrode adjacent to the micro well.
11. A device, comprising:
a substrate having a biological field-effect transistor (BioFET) region and a complementary metal-oxide semiconductor field-effect transistor (C-MOSFET) region;
a plurality of BioFETs in the BioFET region, each BioFET comprising
a micro well having a plurality of stacked well portions and a ridge between adjacent well portions;
a gate dielectric on the substrate below a bottom surface of the micro well;
a plurality of C-MOSFETs in the C-MOSFET region and,
a multi-layer interconnect (MLI) comprising at least two vertically stacked layers of metal interconnects surrounding the micro well of the plurality of BioFETs.
12. The device of claim 11 , wherein each BioFET further comprises a gate electrode on the gate dielectric.
13. The device of claim 11 , wherein the gate dielectric is silicon nitride, hafnium oxide, or tantalum oxide.
14. The device of claim 11 , further comprising:
a coating on a bottom of the micro well.