JP2010530063A - Nanostructured field effect sensor and method of forming and using the same - Google Patents

Abstract

A solid state field effect transistor sensor for detecting chemical and biological species and detecting radiation changes is disclosed. The device improves device sensitivity by including a porous or structured channel compartment. The device operates in full deplate mode so that a sensed biological, chemical or radiation change causes an exponential change in channel conductance. In one embodiment, further comprising a dielectric layer overlying the channel and a layer of material overlying the dielectric layer, wherein the layer of material comprises radioactive, chemical and biological species. Interacts with the target species detected from the group, the layer of material is either a continuous layer or a discrete island.

Description

(Field of Invention)
The present invention relates generally to solid state sensors. In particular, the present invention relates to a field effect sensor having a structured active region or a porous active region, and a method of making and using the sensor.

(Background of the Invention)
Solid state sensors can be used in a wide variety of applications. For example, chemical solid state sensors can be used for real-time analysis of chemical mixtures in both continuous and discrete sampling modes. Similarly, biological sensors can be used to detect biological agents and hazards, and radiation sensors can be used to detect the type and amount of radiation.

  Sensors can detect a single component in a complex mixture, such as toxic molecules in the atmosphere, or analyze multiple components in a composition, for example, by pattern recognition using an array-based sensor, It can be used to characterize complex mixtures and perform quality assessments, as used to characterize odors, tastes, aromas, and the like.

  A typical solid state sensor generally includes a detection or receptor element and signal conversion means. The receptor layer interacts with the target species (s) by, for example, physical absorption or physical adsorption, chemisorption, microencapsulation, and the like. The transducer converts the change at the receptor surface into a measurable electrical signal. The signal conversion or coupling of the signal between the acceptor and the transducer can be linear, non-linear, logarithmic or exponential in relation. The coupling relationship between the two elements generally determines the sensitivity of the device.

  Various signal transducer elements have been developed, such as potentiometric sensors, current measuring sensors, conductivity measuring sensors, field effect transistor (FET) based sensors, optical sensors, temperature sensors, gravity measuring sensors or piezoelectric sensors. FET devices may be particularly desirable. This is because FET devices are relatively fast and exhibit sensitive signal conversion, are relatively easy to use, and are relatively easy to integrate with other sensor components.

  In the case of FET devices, the metal gate of the field effect transistor device is replaced or covered with a sensitive thin film, insulator or film that acts as a signal sensing element. FET devices operate on the general principle of detecting local potential shifts due to device surface interactions. The FET device converts the detection event into an electrical signal through a change in conductance of the channel region that results in a change in drain current. An FET device can operate as a sensor by biasing the device with a constant gate voltage and measuring the change in current or detecting the change in gate voltage required to maintain a constant current .

  Metal oxide semiconductor FET (MOSFET) type sensors often operate in the inversion mode, and an inversion current is established in the semiconductor channel by biasing the metal gate of the MOSFET. In these devices, a change in target molecule or radiation level bound with a sensitive thin film modulates minority charge carrier density in the inversion channel. That is, the reversal current in the bulk p-type MOSFET decreases when negative charges are added to the device surface.

  While such devices and transducer elements have been shown to work for some sensing applications, non-FET devices are relatively bulky and expensive, and FET-based devices are comparable Unstable and may exhibit relatively low sensitivity. Accordingly, improved sensors and methods for making and using the sensors are desired.

(Summary of Invention)
The present invention provides a sensitive sensor suitable for detecting chemical, biological and / or radioactive chemical species. While the manner in which the present invention addresses various shortcomings of the prior art is discussed in greater detail below, in general, the present invention has structured channels or porous channels to improve device sensitivity. A field effect transistor (FET) is provided.

  In accordance with various embodiments of the present invention, a sensor includes a substrate, an insulator formed overlying the substrate, and a porous or structured layer formed overlying the insulator. Channel. According to various aspects of these embodiments, the upper surface of the channel layer acts as a receptor or sensitive layer that interacts with chemical, biological or radioactive species. According to an alternative aspect, the sensor further includes a sensitive layer overlying the channel layer.

  In accordance with additional embodiments of the present invention, the sensor further includes a dielectric layer overlying the channel region. In accordance with some aspects of the exemplary embodiment, the dielectric layer acts as a receptor or sensitive layer that interacts with chemical, biological or radioactive species.

  According to a still further embodiment, a sensor includes a sensitive layer formed overlying the dielectric layer.

  In accordance with various additional aspects, the channel thickness ranges from about 3 angstroms to about 1000 nm.

  In accordance with further various aspects, the sensor includes a negative charge added to the channel, sensitive layer, or dielectric layer causing an increase in conductance of an electron inversion channel to the n-channel FET device and to the n-channel FET. Adding a negative charge to the channel, sensitive layer, or dielectric layer of a p-channel device causes a decrease in conductance of the inversion channel, while The addition of a positive charge to the surface is then configured to operate in a full deplate mode so as to increase the conductance of the inversion channel.

  According to still further embodiments, the sensor includes an additional layer between the channel and the dielectric layer.

  According to a further embodiment, a sensor includes additional material that forms a heterostructure with the channel layer. The additional material may be in the form of one or more layers of one or more layers of material or discrete islands.

  According to various additional embodiments of the present invention, the sensor is a biological sensor.

  In addition, according to additional embodiments, the sensor is a chemical sensor.

  According to a still further embodiment, the sensor is a radiation sensor.

  In accordance with additional embodiments of the present invention, a method of forming a sensor includes providing a substrate (eg, a p-type SOI silicon wafer) and thinning a channel region layer (eg, a dry oxide seed layer). Using a wet oxidation followed by a doping mask over a portion of the SOI wafer (eg, a portion of the oxide layer formed using the wet oxidation step followed by a dry oxide seed layer). Forming (by etching), forming a doped region in the channel region, forming a mask for the source and drain regions, and forming the source and drain regions Removing any excess masking material as needed, and forming device isolation regions (e.g., photoresist Comprising the use of the patterning and plasma etching) and, forming a porous or structured channel region, and forming a contact in the substrate.

  In accordance with various aspects of these embodiments, the pores or structures of the channel pattern the channel region (e.g., using electron beam lithography) and the regions are formed to form the pores or the structure. It is formed by etching (for example, using SF6 in the REI apparatus). According to further aspects of these embodiments, a chemical, biological and / or radiation sensitive material is formed overlying the channel region. According to a still further aspect, a dielectric layer is formed overlying the channel region. According to a still further aspect, a sensitive layer is formed overlying the dielectric layer. And in accordance with still additional aspects of the present invention, one or more additional layers of material may be included in the sensor structure.

  A local oxidation of silicon (LOCOS) process, according to an alternative embodiment of the present invention, is used to achieve device isolation. In accordance with various aspects of these embodiments, the method provides an SOI wafer and selectively etches silicon in the channel region of the device to a predetermined depth (eg, using reactive ion etching). ), Forming pores or structures in the channel region, forming a diffusion mask layer, and forming a field oxide to consume silicon in the channel region (e.g., wet Using an oxidation process), doping a portion of the device, and forming a substrate contact. According to further aspects of these embodiments, a chemical, biological and / or radiation sensitive material is formed overlying the channel region. According to a still further aspect, a dielectric layer is formed overlying the channel region. According to a still further aspect, a sensitive layer is formed overlying the dielectric layer. And in accordance with still additional aspects of the present invention, one or more additional layers of material may be included in the sensor structure.

  According to still further embodiments, the sensor is formed using flexible sensor technology.

  In accordance with yet a further embodiment of the present invention, a chemical, biological or radioactive species uses a full-deplate exponential coupled FET having a structured or porous channel region. Perceived.

FIG. 1 illustrates a sensor according to various embodiments of the present invention. FIG. 2 illustrates a sensor according to an additional embodiment of the present invention. FIG. 3 illustrates a sensor according to a still further embodiment of the present invention. Figures 4a and 4b illustrate channel regions having pores and structures in accordance with various embodiments of the present invention. Figures 4a and 4b illustrate channel regions having pores and structures in accordance with various embodiments of the present invention. 5-6 illustrate the operation of the sensor illustrated in FIG. 5-6 illustrate the operation of the sensor illustrated in FIG. 7-15 illustrate a method of forming a sensor according to various embodiments of the present invention. 7-15 illustrate a method of forming a sensor according to various embodiments of the present invention. 7-15 illustrate a method of forming a sensor according to various embodiments of the present invention. 7-15 illustrate a method of forming a sensor according to various embodiments of the present invention. 7-15 illustrate a method of forming a sensor according to various embodiments of the present invention. 7-15 illustrate a method of forming a sensor according to various embodiments of the present invention. 7-15 illustrate a method of forming a sensor according to various embodiments of the present invention. 7-15 illustrate a method of forming a sensor according to various embodiments of the present invention. 7-15 illustrate a method of forming a sensor according to various embodiments of the present invention.

  Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. The dimensions of some of the elements in the figures can be exaggerated with respect to other elements to help facilitate an understanding of embodiments of the invention.

(Detailed explanation)
The present invention provides an improved solid state sensor for the detection of biological and chemical species and for the detection of radiation. In particular, the present invention provides a field effect transistor (FET) that includes a porous or structured channel region, the field effect transistor operating as a full-deplate, exponential coupled (FDEC) sensor. As discussed in greater detail below, the threshold voltage of a sensor or channel conductance is manipulated when a sensed biological, chemical or radioactive species is detected and is an exponential function of channel current. Cause change.

  The exponential change in channel current of the sensor of the present invention is in the opposite direction compared to that of a typical FET sensor, and n-channel type upon detection of a chemical species having excess electronic charge or negative charge. Increase in devices. Such an exponential response makes the sensor of the present invention more sensitive to qualitative and quantitative analysis.

  FIG. 1 illustrates a sensor 100 according to various embodiments of the present invention. Sensor 100 includes a base or substrate 102, an insulator layer 104, a channel region 106, a source 108, a drain 110, and contacts 112, 114. As will be discussed in more detail below, the channel region 106 is porous and / or structured in accordance with various aspects of exemplary embodiments of the invention.

  In operation, the sensor 100 operates in an inversion mode, and an inversion current is established in the channel region 106 by biasing the gate or base 102. When the target molecule binds to the surface of the sensor 100, the reversal threshold voltage is thought to be modulated by a secondary capacitive charge-coupling mechanism related to the interface defect level, which causes an exponential increase in device response. As a result. This unique exponential coupling of the device response to the surface charge provided by the target species on the sensor surface results in a full deplate exponential coupling (FDEC) sensor.

  In contrast to the present invention, in the prior art, the addition of negative charge to the n-channel FET surface causes a decrease in inversion channel conductance (ie, a decrease in drain current), and the addition of positive charge to the surface Increase the conductance of the inversion channel, and in p-channel FETs, the addition of negative charge to the device surface causes an increase in channel conductance (ie, an increase in drain current), resulting in a positive Teaches inversion-based FET devices applied to chemical sensing by changes in device structure in such a manner that the addition of charge causes a decrease in channel conductance. Such a response of the device structure is in the opposite direction for the device of the present invention. As noted above, according to various embodiments of the present invention, the addition of a negative charge to the surface of an n-channel inversion-based FET device according to the present invention increases the conductance of the inversion channel and the positive charge on the surface. The addition reduces the conductance of the inversion channel, while the addition of negative charge to the device surface of the p-channel inversion base reduces the conductance of the inversion channel, and the addition of positive charge to the surface reduces the conductance of the inversion channel. Increase.

  Still referring to FIG. 1, the base 102 acts as a gate during operation of the sensor 100. The base 102 can be formed from any suitable material. Examples include Ge, Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, La, Metals and metal nitrides such as Hf, Ta, W, Re, Os, Ir, Pt, Au, TaTi, Ru, HfN, TiN, etc., alloys, group IV (eg silicon), group III-IV Including any organic or inorganic material that operates as a semiconductor, metal semiconductor alloy, metalloid, or MOSFET gate, such as a group (eg, gallium arsenide) and a group II-VI (eg, cadmium selenide) However, it is not limited to these.

  The thickness of the base 102 can vary according to the material and application. The base 102 according to one example is substrate silicon in a silicon on insulator (SOI) wafer. In another example, the base 102 is a flexible substrate, for example an organic material such as Pentacene.

  Insulator layer 104 acts as a gate insulator or gate dielectric during operation of sensor 100. Layer 104 may be formed from any suitable material, such as any suitable organic or inorganic insulating material. Examples include silicon dioxide, silicon nitride, hafnium oxide, alumina, magnesium oxide, zirconium oxide, zirconium silicate, calcium oxide, tantalum oxide, lanthanum oxide, titanium oxide, yttrium oxide, titanium nitride, etc. It is not limited. One exemplary material suitable for layer 104 is an oxide layer embedded in an SOI wafer. The thickness of layer 104 may vary according to the material and application. As one specific example, layer 104 is silicon oxide having a thickness of about 1 nm to 100 microns, and layer 104 according to other aspects can be 1 mm or more.

The channel region 106 can be formed from a variety of materials, such as crystalline or amorphous inorganic semiconductor materials, as used in typical MOS technology. Examples include elemental semiconductors such as silicon, germanium, diamond, and tin; compound semiconductors such as silicon carbide, silicon germanium, diamond, and graphite; aluminum antimonide (AlSb), aluminum arsenide (AlAs), and aluminum nitride (AlN). ), Aluminum phosphide (AlP), boron nitride (BN), boron phosphide (BP), boron arsenide (BAs), gallium antimonide (GaSb), gallium arsenide (GaAs), gallium nitride (GaN), phosphorus Gallium phosphide (GaP), indium antimonide (InSb), indium arsenide (InAs), indium nitride (InN), indium phosphide (InP), cadmium selenide (CdSe), cadmium sulfide (CdS), cadmium telluride ( CdTe), zinc oxide ( nO), zinc selenide (ZnSe), zinc sulfide (ZnS), zinc telluride (ZnTe), cuprous chloride (CuCl), lead selenide (PbSe), lead sulfide (PbS), lead telluride (PbTe) , Tin sulfide (SnS), tin telluride (SnTe), bismuth telluride (Bi ₂ Te ₃ ), cadmium phosphide (Cd ₃ P ₂ ), cadmium arsenide (Cd ₃ As ₂ ), cadmium antimonide (Cd ₃ Binary materials such as Sb ₂ ), zinc phosphide (Zn ₃ P ₂ ), zinc arsenide (Zn ₃ As ₂ ), zinc antimonide (Zn ₃ Sb ₂ ), and lead (II) iodide (PbI ₂ ) , molybdenum disulfide _(MoS 2), gallium selenide (GaSe), tin sulfide (SnS), bismuth sulfide _{(Bi 2 S} 3), platinum silicide (PtSi), bismuth iodide (III _(BiI 3), mercury iodide (II) _(HgI 2), thallium bromide (I) (TlBr), semiconductor oxides such as zinc oxide, titanium dioxide _(TiO 2), copper oxide (I) (Cu ₂ Other binary materials such as O), copper (II) oxide (CuO), uranium dioxide (UO ₂ ), uranium trioxide (UO ₃ ), gallium aluminum arsenide (AlGaAs, AlxGa1-xAs), arsenic Indium gallium (InGaAs, InxGa1-xAs), indium aluminum arsenide (AlInAs), indium aluminum antimonide (AlInSb), gallium nitride arsenide (GaAsN), gallium arsenide phosphorus (GaAsP), gallium aluminum nitride (AlGaN), gallium phosphide Aluminum (AlGaP), Indium gallium nitride (InG N), indium arsenide antimonide (InAsSb), indium gallium antimonide (InGaSb), zinc cadmium telluride (CdZnTe, CZT), mercury cadmium telluride (HgCdTe), mercury zinc telluride (HgZnTe), mercury zinc selenide 6.1 liters or ternary materials such as (HgZnSe), lead tin telluride (PbSnTe), thallium tin telluride (Tl ₂ SnTe ₅ ), thallium germanium telluride (Tl ₂ GeTe ₅ ) and aluminum gallium indium phosphide (AlGaInP, InAlGaP, InGaAlP, AlInGaP), aluminum gallium arsenide phosphorus (AlGaAsP), indium gallium arsenide phosphorus (InGaAsP), aluminum indium arsenide phosphorus (AlIn quaternary materials such as sP), gallium aluminum arsenide (AlGaAsN), indium gallium arsenide (InGaAsN), indium aluminum arsenide (InAlAsN), copper indium gallium selenide (CIGS), or gallium nitride Including, but not limited to, quinary materials such as indium arsenide antimonide (GaInNAsSb).

  The channel region 106 can also be made from an organic semiconductor material. Examples of such materials include polyacetylene, polypyrrole, polyaniline, Rubrene, phthalocyanine, poly (3-hexylthiophene), poly (3-alkylthiophene), α-ω-hexathiophene, Pentacene, α-ω-di- Hexylhexathiophene, α-ω-dihexylhexathiophene, poly (3-hexylthiophene), bis (dithienothiophene), α-ω-dihexyl-tetrathiophene, dihexyl-anthradithiophene, n-decapentafluoroheptylmethylnaphthalene -1,4,5,8-tetracarboxyldiimide, α-ω-dihexyl-5-thiophene, N, N′-dioctyl3,4,9,10-perylenetetracarboxyl, CuPc, methanofullerene, [6,6] -Phenyl-C61-butyric acid Luster (PCBM), C60,3 ′, 4′-dibutyl-5-5bis (dicyanomethylene) -5,5′-dihydro-2,2 ′: 5 ′, 2 ″ terthiophene (DCMT), PTCDI— C5, P3HT, poly (3,3 ″ -dialkyl-terthiophene), C60-condensed N-methylpyrrolidine-meta-C12 phenyl (C60MC12), thieno [2,3-b] thiophene, PVT, QM3T, DFH— nT, DFHCO-4TCO, BBB, FTTTTTF, PPy, DPI-CN, NTCDI, F8T2-poly [9,9′dioctylfluorene-co-bithiophene], MDMO-PPV-poly [2-methoxy-5- (3, 7-dimethyloctyloxy)]-1,4-phenylene vinylene, P3HT-regioregular poly 3-hexylthiophene], PTAA, polytriarylamine, PVT-poly- [2,5-thienylene vinylene], DH-5T-α, ω-dihexylpentathiophene, DH-6T-α, ω-dihexyl hexathiophene , Phthalocyanine, [alpha] -6T- [alpha] -6-thiophene, NDI, naphthalenediimide, F16CuPc-perfluorocopper phthalocyanine, perylene, PTCDA-3,4,9,10-perylene-tetracarboxyl dianhydride and its derivatives, PDI-N, Including, but not limited to, N′-dimethyl3,4,9,10-perylenetetracarboxyldiimide.

  The thickness of region 106 may vary according to material and application. As one specific example, the region has a thickness of about 10 angstroms to about 10 millimeters.

  As described above, the channel region 106 includes pores and / or structures to increase device sensitivity, according to various embodiments of the present invention.

  Figures 4a and 4b show various examples of such structures and pores. The channel region 106 can include structures or pores throughout the thickness of the region, or the structures and / or pores can be formed on the upper surface 402 of the region 106. In accordance with various examples of the present invention, the upper surface 402 of the region 106 includes micropores, mesopores, nanopores or macropores 404, i.e., the size of the pore diameter is about 3Å to It can range from 100 microns, or from about 10 mm to about 10 mm. In accordance with additional embodiments of the present invention, channel region 106 includes structures 406-408, such as nanostructures or microstructures, and has dimensions ranging from about 3 cm to about 100 microns. The structure can include, for example, square, circular, triangular, hexagonal, nanoscale or microscale struts of any suitable cross section. The structure may also include a micropore or mesopore or nanopore structure superimposed on a nanopattern or micropattern in a relief or recess 410.

  As discussed in more detail below, the pores and / or structures may be formed by electron beam lithography, patterning, template-based selective etching, electrochemical etching, stain etching, silicon CVD deposition, molten state imprinting. Can be formed using a variety of techniques such as imprinting, laser etching, ion etching, particle etching, e-beam etching, chemical enhanced laser ablation, or any other structuring technique, thereby creating a cruciform pattern, line Forms a pattern, struts, any other pattern, or a porous structure or a porous structure that overlaps any of these patterns, which acts in a manner that increases the net surface area of the device surface The material of region 106 is In essentially continuous, and remains crystalline, therefore increasing the interaction of the interface state.

  During operation of sensor 100, an inversion channel 116 is formed at the channel region 106 / insulator layer 104 interface by controlling the voltage bias at the base 102. Alternatively, the inversion channel 116 can be formed in the channel region 106 without bias on the base 102, which means that the doping of the channel region 106, the thickness of the region 106, other such variables, and the channel 106 boundary. Depends on the fixed oxide film charge density and interface trap level density. The thickness of the channel region 106 can be from about 1 nm to about 10 microns, depending on the material and its doping density.

  When biasing the base 102 to obtain an inversion channel in the channel region 106, the thickness (t) of the channel region 106 is such that the channel before the inversion channel is formed at the interface between the channel region 106 and the insulator 104. The depletion width at inversion should be as illustrated by the following equation so that the entire thickness of region 106 is full deplate.

ここで、
ｋは、半導体の比誘電率であり、
ε_０は、自由空間の誘電率であり、
ｑは、電子電荷であり、
Ｎ_Ａ／Ｂは、ドナー／アクセプタの密度であり、
Φ_Ｆは、半導体内のフェルミ準位と真性準位との間の電位差である。

here,
k is the relative dielectric constant of the semiconductor,
ε ₀ is the permittivity of free space,
q is the electronic charge,
N _{A / B} is the density of the donor / acceptor,
Φ _F is a potential difference between the Fermi level and the intrinsic level in the semiconductor.

  In one case, the above equation defines the thickness (t) of the channel region 106, as appropriate in an example device of the present invention, and the thickness (t) of the channel region 106 is given by It is less than the full depletion width (w) of the semiconductor material.

  For example, in the case of a channel region 106 that is a silicon thin film, if the doping density is 1E17, the thickness of the channel region 106 should be less than about 200 nm. If the doping density is 1E14, the layer thickness is less than about 4 microns. Stated another way, the thickness of the inversion layer 116 is less than the width of the depletion layer for a given doping density in the channel region 106.

  Channel region 106 may be doped p-type or n-type, respectively, corresponding to n-channel devices and p-channel devices. The above equation corresponds to the case of a channel region 106 that does not have a special delta doping profile or that does not have other special steps similar to those used to modulate channel region conductance, inversion threshold, etc. is doing. In the case of using delta doping or the like in the channel region 106, the analysis and thickness of the channel region 106 vary depending on the situation.

  One exemplary channel region 106 includes a p-type silicon layer doped to 1E15 and having a thickness of about 100 nm. The inversion layer is formed at the interface between the silicon in the silicon thin film and the buried oxide film by biasing the base 102.

  Source doping region 108 and drain doping region 110 are formed on either side of channel region 106 using known doping techniques. According to one example, the source and drain regions are N ++ regions formed in p-type silicon doped with phosphorus at 1E19.

FIG. 2 illustrates another sensor 200 according to an additional exemplary embodiment of the present invention. Sensor 200 is similar to sensor 100 except that sensor 200 includes an additional dielectric layer 202. Exemplary materials suitable for the dielectric layer 202 include inorganic dielectric materials that act as gate dielectric materials. _{Examples, SiO 2, Si 3 N 4} , SiNx, Al2O 3, AlOx, La2O 3, Y2O 3, ZrO 2, Ta2O 5, HfO 2, HfSiO 4, HfOx, TiO 2, TiOx, a-LaAlO 3, SrTiO ₃ , Ta ₂ O ₅ , ZrSiO ₄ , BaO, CaO, MgO, SrO, BaTiO ₃ , Sc ₂ O ₃ , Pr ₂ O ₃ , Gd ₂ O ₃ , Lu ₂ O ₃ , TiN, CeO ₂ , BZT, BST, Or including, but not limited to, these stacked or mixed compositions and / or such other gate dielectric material (s).

The dielectric layer 202 may additionally or alternatively include an organic gate dielectric material. Examples of organic materials include PVP-poly (4-vinylphenol), PS-polystyrene, PMMA-polymethyl-methacrylate, PVA-polyvinyl alcohol, PVC-polyvinyl chloride, PVDF-polyvinylidene fluoride, PαMS-poly [α -Methylstyrene], CEYPL-cyano-ethyl pullulan, BCB-divinyltetramethyldisiloxane-bis (benzocyclobutene), CPVP-Cn, CPS-Cn, PVP-CL, PVP-CP, polynorb, GR, nano-TiO ₂ , OTS, Pho-OTS, these various self-assembled monolayers or multilayers, or laminated or mixed compositions thereof, and such other organic gate dielectric materials, It is not limited.

  The dielectric layer 202 can also be material from intrinsic semiconductor material or lightly doped semiconductor material, and is actually semi-insulating due to low density charge carriers and low carrier mobility.

In accordance with exemplary aspects of various embodiments of the present invention, the processing and fabrication of dielectric layer 202 may include interface state density levels at the interface between layer 202 and channel region 106 and other such defect levels. Is performed in a controlled manner such that is "optimized". For example, the use of the Si [111] -SiO2 interface creates a higher interface state density than the Si [100] -SiO2 interface. Trap optimization does not necessarily mean maximizing the interface state density level, but it can be used for interface state density applications at the interface to manipulate and maximize the resulting sensor signal. It means specific control. In one case, the material of the dielectric layer 202 is selected to be a material that simultaneously acts as both a dielectric layer and a chemical sensitive layer. This example is the use of yttrium oxide (Y2O ₃₎ as the gate dielectric, yttrium oxide may be used to sense the sulfur mustard gas. This is because Y ₂ O ₃ reacts with mustard gas.

  The thickness of layer 202 can vary depending on the application, and is generally between about 2 angstroms and 100 nm.

  FIG. 3 illustrates another sensor 300 in accordance with additional embodiments of the present invention. Sensor 300 is similar to sensor 200 except that sensor 300 includes an additional layer 302, which is sensitive to biological, chemical and / or radioactive materials.

  Layer 302 is designed to be sensitive to, for example, gas phase or liquid phase species in the environment. Layer 302 can also be selected to be sensitive to radiation and is applied as a radiation sensitive device.

  Layer 302 may actually be an organic material, an inorganic material, a conductive material, an insulating material, a semiconductor material, or a metallic material, and may include any suitable material. The thickness of layer 302 can generally be between about 1 angstrom and about 1000 nanometers. One exemplary material for layer 302 is a monolayer of zinc porphyrin molecules that can be used to detect amine molecules, piperidine.

  Layer 302 can be in the form of a continuous layer, particles of various sizes, discrete islands of material, a substantially continuous layer, a stack of layers of different materials, a combination of these structures, etc. It acts to selectively interact with biological, chemical and / or radioactive species. In accordance with additional embodiments of the present invention, the additional layers can be continuous, substantially continuous, discrete islands, or particles, and charge at the interface trap density at the interface between the channel region 106 and the dielectric layer 202. Can be added on layer 302 to increase the capacitive coupling of and to form inversion layer 116 in channel region 106.

  Specific exemplary materials suitable for layer 302 include:

  Antibodies: Antigens that bind specific organic or inorganic or biomolecules are sensitive and selective using devices coated with antibody (s) or antigen (s) biomolecules Can be detected. For example, a sensor that includes a biotin layer can be used to detect avidin and streptavidin molecules.

Explosive sensors: Explosives of peroxides such as TATP tend to dissociate in the presence of acidic groups in acidic peroxides, so sensor devices with an acidic group finish on the surface or Zn ²⁺ , In ³⁺ , Sb ³⁺ , Sc ³⁺ , Ti ^4+, etc. Nitro compound-based explosives can be detected using devices coated with various dielectric materials that selectively react with activated nitro groups.

  DNA sensor: A single helical structured DNA oligomer array of any length in base pairs can be attached to the surface of the device and used as layer 302. In this case, the device 300 can be used to detect a corresponding complementary DNA helix structure via DNA hybridization on the device surface. Device 300 covered by an array of such DNA helix structures (single or double helix structures, depending on the application) can identify target DNA or specific ions or organic molecules, biomolecules, viruses Or it can be used for detection of bacteria and the like. Large arrays of devices finished with a given array of DNA oligomers can be used for applications that determine the sequence of DNA.

  Neural agent sensor: A diazo group (eg, 3,5-dichlorophenyldiazomethane or its phenyl group derivative) can be used as layer 302 to detect the presence of methylphosphonic acid (MPA), and methylphosphonic acid is The product of the atmospheric hydrolysis of the active substance, and therefore the presence of the neuroactive substance in the environment can be detected in a selective manner. Alternatively, layer 302 can include a Cu ++ cation finish on organic molecules, and sensor 300 can be used for sensitive measurements of neural agents.

  Metalloporphyrin array sensors: Single and multi-layer selected arrays of given specific organic molecules (eg, metalloporphyrin) can also be used in organic vapors or solutions in various gases by changing sensitivity and selectivity. Can be used as layer 302 to detect the ions.

Mustard gas sensor: Layer 302 can sense sulfur mustard gas by including DNA oligomers finished with guanine. Alternatively, layer 302 can detect mustard gas by including Y ₂ O ₃ nanocrystals.

  Molecularly imprinted surface: layer 302 may comprise a “molecularly imprinted” molecule or monolayer or multilayer or thin film or polymer matrix, by binding to a specific predetermined target molecule, Realize highly selective sensors. By using an Epitome (a specific part of a large molecule such as a protein) based approach, a smaller microscopic molecular imprint within the monomer—a crosslinker matrix is used, and a larger molecule such as a protein. DNA, and other biomolecules are detected at the site of the micrograph by selected binding.

  Ion sensor: Layer 302 can include specific organic molecules or inorganic thin films that can be used to sense ions in solution with high selectivity and sensitivity. For example, a thin film of urea (N, N ″-(9,10-dihydro-9,10-dioxo-1,2-anthracenediyl) bis [N′-phenyl] (eg, up to about 3 simplex Multiple layers of layers) can be used to detect fluoride ions with high selectivity.

  Forming pores and / or structures within region 106 not only increases the surface area of the active region of the sensor, but also at the channel region 106-dielectric layer 202 interface to the surface group density or charge density on surface 402. Increase the ratio of interface state density. This concept is illustrated in FIG. When the analyte molecule M binds to the surface of the layer 302, the number of interface states 502 entering the potential / electric field affected by the target chemical species M is more flat when the surface is nanostructured. Greater than there are. This is done to optimize or maximize the modulation of the interface state occupancy and density at the channel region 106-dielectric layer 202 interface to changes in charge on the sensitive layer 302 surface or the dielectric layer 202 surface. .

  Modulation of the interface state occupancy at the channel region 106-dielectric layer 202 interface then changes the chemical potential of the channel region 106 at the channel region 106-insulator 104 interface, and in a fully deplated semiconductor channel, the channel This causes a change in the threshold voltage of the inversion channel formed in the channel 106 at the 106-insulator 104 interface. This indirect coupling by the electric field of this species M, which causes modulation of the interface trap occupancy at the channel 106-dielectric 202 interface and then changes the threshold voltage of the inversion channel formed in the channel 106, is Any sensor that is referred to as a plate-type exponential coupling (FDEC) effect and uses this effect as a principle of operation is referred to as an FDEC sensor.

  In another case of the device structure, the trap charge in the insulator 202 or in the channel 106, where the modulation of the conductance of the same inversion channel is not due to modulation of the interface state occupancy, but due to the binding of chemical components at the device surface Or it can be achieved by modulation of impurity doping and other similar charge center modulation.

  FIG. 6 illustrates the response of the device, where the addition of electrons that a chemical species (piperidine molecule) provides to layer 302 (eg, a monolayer of zinc porphyrin molecules) is applied to dielectric layer 202 (eg, natural oxidation). Causing an increase in the electronic charge at the surface of the silicon) and then increasing the conductance of the electron inversion channel in the channel 106 (eg, silicon) due to a decrease in the threshold voltage of the electron inversion channel 116 (ie, drain). Current increases). In the illustrated example, the increase in device drain current of the 500 nm device when the n-channel device is exposed to 0.6 PPB piperidine molecules (line 602) is simply a control experiment in which inert gas was introduced (line 602). 604), the device is established as a sensitive sensor.

  Referring now also to FIGS. 2-3, one or more layers may be introduced between the channel region 106 and the dielectric layer 202 in accordance with various additional embodiments of the present invention. The nature of these layers can be insulating, semi-insulating, semi-conducting or semi-metallic. An example of this is approximately between the channel region 106 and the dielectric layer 202, or alternatively between the channel region 106-dielectric layer 202 interface and the insulator 104-channel region 106 interface, The use of a thin layer of germanium having a thickness of 1 nm to about 100 nm. The stack in this example is Si (channel region 106), Ge (special layer) and oxide (dielectric layer 202), or Si (channel region 106), Ge (special layer), Si (another special layer). Layer) and an oxide film (dielectric layer 202). In the same manner, a stack of layers of different materials can be used between the channel region 106 and the dielectric layer 202. These extra layers can be desired to increase the efficiency of the sensor signal or for specific sensor applications. In all of these examples of stacked structures, the negative charge on the surface of an n-channel inversion-based FET device (electrons are carriers in the inversion channel), similar to the five-layer structure described above (illustrated in FIG. 3) P channel inversion-based device (holes are carriers in the inversion channel) surface, while the addition of increases the inversion channel conductance and the addition of positive charge to the surface decreases the inversion channel conductance The addition of negative charge to the surface reduces the conductance of the inversion channel, and the addition of positive charge to the surface increases the conductance of the inversion channel.

Specific example production:
Device fabrication, according to one embodiment of the present invention, is illustrated in FIGS. The illustrated process can be used to form the device 300 illustrated in FIG. 3 using a silicon-on-insulator (SOI) inversion mode FET device, where the base 102 is the substrate silicon of the SOI wafer. The insulator 104 is a buried oxide layer of the SOI wafer, the channel region 106 is porous or structured silicon on the insulator layer, and the dielectric layer 202 is a natural oxide layer. And the sensitive layer 302 is a chemical sensitive layer (here, a monolayer of zinc porphyrin molecules) that binds specific target molecules in the environment. An exemplary process flow is for an n-channel, p-type bulk, silicon-on-insulator wafer using standard nMOS process technology. It will be appreciated that fabrication can be done in a variety of ways, depending on the materials selected for the various device layers, the process technology steps selected to implement the sensor device, and the like. .

FIG. 7 illustrates a starting material structure 700 suitable for fabrication of the device 300. Structure 700 is a p-type SOI wafer with a boron doping (10 ¹⁵ cm ³ ) resistivity of about 20 ohm centimeters and is created using an implanted oxygen separation (SIMOX) process. Exemplary wafers can be obtained from IBIS technology Corporation. The initial thickness of the upper silicon thin film layer 702 is greater than about 100 nm, with a buried oxide (BOX) layer 704 implanted with ions and having a thickness of about 400 nm below. The top silicon thin film 702 is thinned to about 100 nm using a wet oxidation at about 1050 ° C. in a diffusion furnace for about 45 minutes, resulting in less than the Debye length of minority carrier electrons (layer illustrated in FIG. 802). Plasma enhanced chemical vapor deposition (PECVD) is further performed to increase the oxide (layer 804) thickness. As discussed below, oxide layer 804 is also used as an effective mask for N + phosphorus doping in subsequent processing. A positive photoresist OCG 825 is then spin-coated at about 4000 rpm for about 30 seconds to create a photoresist layer having a thickness of about 1000 mm. The resist is soft baked at about 80 ° C. for about 15 minutes. A UV mask aligner is used to expose the resist for about 20 seconds through an n-well mask designed to open a source, drain window for phosphorus doping. The exposed wafer is developed with OCG945 developer for about 30 seconds, followed by a DI water rinse. The resist is then hard baked at about 115 ° C. for about 15 minutes. The hard baked resist protects the substrate during buffered oxide etch (BOE) dissolution, which can be about 30 minutes long. A buffered oxide etch (BOE) is used to etch the top oxide for about 10 minutes, leaving a source doping window 902, with the oxide 906 remaining, as illustrated in FIG. Open the drain doping window 904. The photoresist is then removed using a Microstrip 2000 stripper solution at about 100 ° C. for about 20 minutes. Phosphorous doping of the exposed well region on silicon is performed in a solid source diffusion furnace at about 950 ° C. for about 30 minutes. Diffusion for about 30 minutes at about 950 ° C. results in an N + junction depth on the order of 1 micron with a phosphorus doping density of about 10 ¹⁹ cm ⁻³ and a resistivity of about 0.01 ohm centimeter. The masking oxide is then removed by immersing the wafer in BOE for about 15 minutes, resulting in a structure 1000 having doped regions 1002, 1004 and silicon regions 1006 illustrated in FIG.

  In this process flow, device separation is achieved by physical separation of the devices by plasma etching. On the other hand, LOCOS or other suitable processes can be used instead for device isolation.

Referring now to FIG. 11, selective etching of silicon is performed in a reactive ion etching (RIE) system using SF ₆ etch chemistry. The wafer or substrate is spin coated with an OCG825 photoresist and soft baked. The wafer is patterned with a reactive mask using the alignment mark as a guide, followed by photoresist development in OCG945 developer. The patterned photoresist is not hard baked against silicon plasma etching. Silicon is selectively etched using SF ₆ based gas chemistry (4 sccm SF ₆ gas flow at 20 mbar pressure) with 50 watts of RF power applied for about 1 minute. The etching rate of silicon under these conditions is about 2000 mm / min. The photoresist is then removed using a Microstrip 2000 stripper solution. This results in a structure 1100 that includes an isolated silicon mesa 1102 on a buried oxide 704 with a source region 1002 and a drain region 1004 on either side.

  The surface of the silicon mesa 1102 is then coated with a PMMA e-beam resist and by e-beam lithography to obtain a structure 1200 that includes structures 1202-1206 on the active areas of the device surface, as illustrated in FIG. Patterned. The source-drain region can be excluded from patterning depending on the situation. This is because it is not necessary if ohmic contact is formed with the source and drain. Alternatively, the source-drain region can be masked by metal contact, depending on the selected process step. The exposed pattern has a dimension as small as 10 nm (which can be as large as 100 nm or more), for example, a cruciform, straight line, strut pattern, or any other Designed to be acquired in a desired pattern. RIE etching of the patterned silicon structure is then performed to obtain depths of tens of nanometers (which can range up to hundreds of nanometers) to structure in three dimensions of any desired design To achieve (eg, nanostructured) patterns. This surface can be further processed, depending on the requirements of the application, with a diameter ranging from tens of nanometers to less than a few nanometers and a depth of up to tens or hundreds of nanometers Obtained pores (eg, nanopores). The same is also achieved by superimposing micro and meso pore structures on a macroporous structure.

  The surface of the active region 106 (excluding the source-drain region) of the device 300, according to various embodiments of the invention, is made porous or structured, even after processing. Maintains the crystallinity of the silicon across all of the silicon channels. This acts to increase the interface trap density per target molecule bond, thus resulting in charge modulation at the top interface and greater modulation of the inversion threshold voltage. A wide variety of oxidant-based wet etching conditions (eg, techniques using aqueous and organic solvent HF solutions) can be used in part with lighting techniques. Porosity, pore size, fabrication method, method of electrical contact formation for anodization, etc. are determined by the specific application of the sensor. The anodization of the upper silicon active region (after electrical contact formation) (tens of milliamperes per square centimeter with a 50% HF solution in ethanol for a period of minutes to tens of minutes) is performed with boron-doped silicon. Create an upper mesoporous structure. Similarly, microporous, nanoporous and macroporous silicon device surfaces can be achieved depending on the sensor application, such as by changing the etching conditions. Other known techniques for realizing pores and / or structures (eg, template-based selective etching, electrochemical etching, silicon CVD deposition, molten state imprinting, laser etching, ion etching, particle etching, e-beam etching Alternatively, chemically enhanced laser ablation) can be used instead.

  According to one embodiment of the invention, the silicon channel 1102 is not completely etched down to the buried oxide. This is done to provide better electrical and mechanical properties at the porous / structured channel-buried oxide interface and to obtain better turn-on characteristics of the field effect sensor. In this example, since the buried oxide film is formed by ion implantation, the silicon-buried oxide film junction may not be mechanically strong. Overetching the silicon channel can result in nanowire undercuts. Thus, a very thin layer of silicon (eg, about 25 nm to about 30 nm) can desirably remain overlying the insulator.

Contact to the substrate 706 is formed using sufficient etching through the buried oxide layer 704 to allow electrical contact with the substrate 706. This substrate contact makes it possible to facilitate bonding and probing. To form contacts, the wafer is spin coated with OCG 825 resist and patterned with an optical aligner to open contact holes. The resist is developed and hard baked at about 115 ° C. for about 15 minutes. The etching rate of the buried oxide film in the BOE is about 600 mm per minute. The 4000 nm buried oxide film is etched with BOE for 15 minutes in consideration of slight over-etching. The Si / SiO ₂ interface is because no gentle is sharp over-etching is performed, in order to make good electrical contact with the substrate, the structure is further etched in RIE using 1 min CF4 plasma. CF ₄ etches both the Si and SiO _2, thus allowing good contact of the metal with the silicon substrate. The RIE process recipe used is 50 sccm CF4 at 50 mbar pressure with 50 watts applied RF power. The photoresist is then removed with a Microstrip 2000 solution, resulting in a structure 1300 that includes a trench 1302.

  To form metal contacts, the wafer is spin coated with OCG 825 resist and soft baked at 80 ° C. The wafer is patterned with a metal mask using an optical aligner and developed. 2500 Å of gold is deposited on the exposed window to make ohmic contact with the source region 1402, drain region 1404 and contact 1406 to the substrate 706. AZ4330 resist is used to obtain a thicker gold metal layer. After gold deposition, removal is performed with 50 ° C. acetone for 30 minutes using an e-beam or a thermal evaporation tool. The device surface is then treated with a buffered oxide etch (BOE) for 15 seconds and a new 2 nm thick oxide is grown on the silicon surface by soaking in a hydrogen peroxide solution for 30 minutes. This can also be achieved by PECVD oxide deposition or wet oxide growth in specific conditions.

  Finally, the surface of the device is coated with a chemical sensitive layer (eg, layer 1502 illustrated in FIG. 15) that is predetermined to sense a specific target molecule. The surface coating of the chemical sensitive layer can be achieved by any process technique. An example of this is the coating of a device surface with a metalloporphyrin monolayer (by Langmuir Blodgett or covalent or contact imprinting or similar techniques) that is sensitive to the binding of amine molecules with a positively charged central metal atom. is there.

  Although the invention has been described herein in connection with the accompanying drawings, it should be recognized that the invention is not limited to the specific forms shown. For example, the structure of the sensor device has been described above for convenience in connection with a silicon substrate, while the present invention is not so limited. The structure of the present invention can be additionally or alternatively formed on alternative substrates. Furthermore, although only a portion of the device has been illustrated with certain layers, the devices and structures of the present invention may include additional layers not illustrated. Various other modifications, changes and improvements in the design and arrangement of the methods and apparatus described herein may be made without departing from the spirit and scope of the invention as set forth in the appended claims. obtain.

Claims (25)

A sensor for detecting a biological, chemical or radioactive chemical species comprising:
A substrate,
An insulator formed overlying a portion of the substrate;
A channel formed overlying the insulator, the channel surface comprising a channel that is nanostructured or includes pores;
The sensor is operated in a full deplate mode so that the sensed biological, chemical or radioactive species causes an exponential change in the conductance of the channel of the field effect sensor. It is configured,
Sensor.   The substrate, the insulator and the channel are sensors that detect biological, chemical or radioactive species formed from a silicon-on-insulator substrate.   2. The sensor for detecting biological, chemical or radioactive species according to claim 1, wherein the channel width ranges from about 10 angstroms to about 10 millimeters.   The sensor for detecting a biological, chemical or radioactive chemical species according to claim 1, wherein the channel comprises a plurality of structures.   The sensor for detecting a biological, chemical or radioactive chemical species according to claim 4, wherein the width of each of the plurality of structures varies from about 10 angstroms to 10 millimeters.   The sensor for detecting a biological, chemical or radioactive chemical species according to claim 4, wherein the plurality of structures have different widths.   The biological, chemical or chemical according to claim 1, further comprising a layer of dielectric material overlying the channel, the dielectric layer being either a continuous layer or a discrete island. A sensor that detects radioactive species. The dielectric _{material, SiO 2, Si 3 N 4} , SiNx, Al2O 3, AlOx, La2O 3, Y2O 3, ZrO 2, Ta2O 5, HfO 2, HfSiO 4, HfOx, TiO 2, TiOx, a-LaAlO 3 , SrTiO ₃ , Ta ₂ O ₅ , ZrSiO ₄ , BaO, CaO, MgO, SrO, BaTiO ₃ , Sc ₂ O ₃ , Pr ₂ O ₃ , Gd ₂ O ₃ , Lu ₂ O ₃ , TiN, CeO ₂ , BZT, BST, PVP-poly (4-vinylphenol), PS-polystyrene, PMMA-polymethyl-methacrylate, PVA-polyvinyl alcohol, PVC-polyvinyl chloride, PVDF-polyvinylidene fluoride, PαMS-poly [α-methylstyrene], CEYPL-cyano-ethyl pullulan, BCB-divinyl tet Disiloxane - bis (benzocyclobutene), CPVP-Cn, CPS- Cn, PVP-CL, PVP-CP, poly noRb, GR, nano _{TiO 2, OTS, Pho-OTS} , and from the group consisting of combinations thereof 8. A sensor for detecting biological, chemical or radioactive chemical species according to claim 7, comprising a selected material. It said dielectric material has a SiO _2, a sensor for detecting biological, chemical or radioactive species according to claim 8.   From the group consisting of antibody sensors, explosive material sensors, protein sensors, biomolecular sensors, DNA sensors, DNA mating sensors, poisonous gas sensors, neuroactive substance sensors, mustard gas sensors, molecularly imprinted surface sensors and ion sensors The sensor for detecting a biological, chemical or radioactive chemical species according to claim 1, further comprising a layer comprising a selected material.   A dielectric layer overlying the channel; and a layer of material overlying the dielectric layer, wherein the layer of material is detected from a group consisting of radioactive, chemical and biological species. Detecting a biological, chemical or radioactive species according to claim 1, wherein the layer of material is either a continuous layer or a discrete island. Sensor.   The biological, chemical, or radioactive chemistry of claim 1, wherein the channel is an n-channel structure and the addition of a negative charge to the channel surface causes an exponential increase in inversion channel conductance. A sensor that detects the species.   The biological, chemical or radioactive chemistry of claim 1, wherein the channel is an n-channel structure and the addition of a positive charge to the channel surface causes an exponential decrease in the conductance of the inversion channel. A sensor that detects the species.   The biological, chemical, or radioactive chemistry of claim 1, wherein the channel is a p-channel structure and the addition of a negative charge to the channel surface causes an exponential decrease in the conductance of the inversion channel. A sensor that detects the species.   The biological, chemical or radioactive chemistry of claim 1, wherein the channel is a p-channel structure and the addition of a positive charge to the channel surface causes an exponential increase in the conductance of the inversion channel. A sensor that detects the species. A method of operating a sensor, the method comprising:
A substrate,
An insulator formed overlying a portion of the substrate;
Providing a sensor comprising a nanostructured or porous channel formed overlying the insulator; and
Exposing the sensor to an atmosphere suspected of containing chemical, biological or radioactive species;
Measuring an exponential change in drain current upon detection of the chemical, biological or radioactive species. A method of forming a solid state sensor, the method comprising:
Providing a substrate;
Forming an insulator overlying the substrate;
Forming a porous channel region overlying the insulator.   The method of claim 17, further comprising forming a chemically, biologically or radioactively sensitive material overlying the porous channel region.   The method of claim 17, further comprising forming a dielectric layer overlying the porous channel region.   20. The method of claim 19, further comprising forming a chemically, biologically or radioactively sensitive material overlying the dielectric layer. A sensor for detecting a biological, chemical or radioactive chemical species comprising:
An insulator;
A channel formed overlying the insulator, the channel surface comprising a nanostructured or containing pores, and a sensor;
The sensor is operated in a full deplate mode so that the sensed biological, chemical or radioactive species causes an exponential change in the conductance of the channel of the field effect sensor. Configured,
The channel is fully deplated without any gate bias required.
Sensor.   8. The sensor for detecting biological, chemical or radioactive species according to claim 7, wherein the channel is fully deplated without substrate material and without any gate bias.   The sensor for detecting biological, chemical, or radioactive species according to claim 21, wherein the sensor further comprises a dielectric layer overlying the channel.   The sensor further comprises a dielectric layer overlying the channel and a layer of material overlying the dielectric layer, the layer of material comprising radioactive, chemical and biological species. The sensor for detecting a biological, chemical or radioactive chemical species according to claim 21, which interacts with a target chemical species detected from a group.   The sensor for detecting biological, chemical or radioactive species according to claim 1, wherein the substrate is made of a flexible material.

Images