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EP-4390385-B1 - GRAPHENE DEVICE AND METHOD OF FABRICATION OF A GRAPHENE DEVICE

EP4390385B1EP 4390385 B1EP4390385 B1EP 4390385B1EP-4390385-B1

Inventors

  • TORRES ALONSO, Elías

Dates

Publication Date
20260506
Application Date
20221223

Claims (8)

  1. A method of fabricating a graphene-based solid-state device, the method comprising: disposing a layer of an electric conductive material (102) on a substrate (101); depositing a first layer of an insulating material (103) on the layer of an electric conductive material (102), the first layer of an insulating material (103) being made of a first oxide dielectric material or any of GaN, TaN or Si3N4; patterning the first layer of an insulating material (103) to expose at least a portion (104) of the layer of an electric conductive material (102); disposing a graphene layer (105) on the first layer of an insulating material (103); patterning the graphene layer (105) to define at least one channel region; applying a lithographic process to define at least two contact areas in the graphene layer (105); depositing one metallic contact (106) on each one of the at least two defined contact areas of the graphene layer (105); depositing a second layer of an insulating material (107) on the stacked structure, the second layer of an insulating material (107) being made of a second oxide dielectric material or any of GaN, TaN or Si3N4 different of the first oxide dielectric material or any of GaN, TaN or Si3N4 of which the first layer of an insulating material (103) is made; and wherein the selectivity to at least one etchant of the first oxide dielectric material or any of GaN, TaN or Si3N4 of which the first layer of an insulating material (103) is made is different from the selectivity to said at least one etchant of the second oxide dielectric material or any of GaN, TaN or Si3N4 of which the second layer of an insulating material (107) is made; selectively etching the second layer of an insulating material (107) to expose one or more portions of the graphene layer (105) and the at least one portion (104, 109) of the layer of an electric conductive material (102), while preserving the first layer of an insulating material (103).
  2. The method of claim 1, wherein the first oxide dielectric material is selected from the following group: SiO2, Al2O3, ZrO2, HfO2, HfSiO4, Ta2O5, La2O3, LaAlO3, Nb2O5, TiO2, BaTiO3, SrTiO3, CaCu3Ti4O12, ZrSiO4, Y2O3, CaO, MgO, BaO, WO3, MoO3, Sc2O3, Li2O and SrO.
  3. The method of any one of claims 1 or 2, wherein the second oxide dielectric material is selected from the following group: SiO2, Al2O3, ZrO2, HfO2, HfSiO4, Ta2O5, La2O3, LaAlO3, Nb2O5, TiO2, BaTiO3, SrTiO3, CaCu3Ti4O12, ZrSiO4, Y2O3, CaO, MgO, BaO, WO3, MoO3, Sc2O3, Li2O and SrO, provided that the second oxide dielectric material is different of the first oxide dielectric material and the selectivity to at least one etchant of the first oxide dielectric material is different from the selectivity to said at least one etchant of the second oxide dielectric material.
  4. The method of any one of claims 1-3, wherein prior to disposing the at least one graphene layer (105) on the first layer of an insulating material (103), the substrate (101) is cleaned to remove impurities and increase hydrophilicity.
  5. The method of any one of claims 1-4, wherein the layer of an electric conductive material (102) and/or the at least one metallic contact (106) are made of at least one of: Titanium (Ti), Nickel (Ni), Gold (Au), Palladium (Pd), Cobalt (Co), Chromium (Cr), Aluminum (Al), Tungsten (W), TaN, (Tantalum Nitride), TiN (Titanium Nitride), Silicon (Si), doped Silicon (doped Si), poly-silicon (poly-Si), Cobalt monosilicide (CoSi), Platinum (Pt), Copper (Cu), Silver (Ag), Lead (Pb), Iron (Fe), Co/Fe alloy, and combinations/alloys of these materials.
  6. A graphene-based solid-state device comprising a substrate (101), at least one graphene channel and at least three contacts (102, 106), the graphene-based solid-state device comprising: a layer of an electric conductive material (102) disposed on a substrate (101), the layer of electric conductive material defining a back electrical contact (); a first insulating material (103) covering the layer of electric conductive material (102) except on the area (109) defining the back electrical contact, the first insulating material (103) being made of a first oxide dielectric material or any of GaN, TaN or Si3N4; a graphene layer (105) disposed on the first insulating material (103), the graphene layer defining the graphene channel; at least two top electrical contacts (106) disposed on the graphene layer (105); a second layer of an insulating material (107) covering part of the graphene layer (105) while leaving part thereof (108) and at least one portion (104, 109) of the layer of an electroconductive material (102) exposed, and covering the first insulating material (103), the second insulating material (107) being made of a second oxide dielectric material or any of GaN, TaN or Si3N4 different of the first oxide dielectric material or any of GaN, TaN or Si3N4; and wherein the selectivity to at least one etchant of the first oxide dielectric material or any of GaN, TaN or Si3N4 of which the first insulating layer (103) is made is different from the selectivity to said at least one etchant of the second oxide dielectric material or any of GaN, TaN or Si3N4 of which the second insulating layer (107) is made.
  7. The device of claim 6, wherein the first oxide dielectric material is selected from the following group: SiO2, Al2O3, ZrO2, HfO2, HfSiO4, Ta2O5, La2O3, LaAlO3, Nb2O5, TiO2, BaTiO3, SrTiO3, CaCu3Ti4O12, ZrSiO4, Y2O3, CaO, MgO, BaO, WO3, MoO3, Sc2O3, Li2O and SrO.
  8. The device of any one of claims 6 or 7, wherein the second oxide dielectric material is selected from the following group: SiO2, Al2O3, ZrO2, HfO2, HfSiO4, Ta2O5, La2O3, LaAlO3, Nb2O5, TiO2, BaTiO3, SrTiO3, CaCu3Ti4O12, ZrSiO4, Y2O3, CaO, MgO, BaO, WO3, MoO3, Sc2O3, Li2O and SrO, provided that the second oxide dielectric material is different of the first oxide dielectric material and the selectivity to at least one etchant of the first oxide dielectric material is different from the selectivity to said at least one etchant of the second oxide dielectric material.

Description

TECHNICAL FIELD The present invention relates to the field of semiconductors and electronics industry and, in particular, to solid-state devices and associated methods. More particularly, it relates to solid-state devices comprising graphene, and associated methods. STATE OF THE ART Since its discovery at the beginning of the 21st century, graphene has attracted much attention due to its properties, such as high electronic mobility, extraordinary thermal conductivity, great strength, flexibility and transparency. Due to these properties, many diverse uses and applications have been researched, such as transparent conductive electrodes and photoactive layers in optoelectronics, Hall-effect sensors for low-magnetic field sensing, diodes, copper interconnects replacements in Very Large Scale Integration (VLSI) semiconductor processes and biosensing, biotechnology and healthcare, to name a few. In particular, the monolayer (atomically thin) structure of graphene allows it to be sensitive to electrostatic perturbations at its surface. The observation of this sensitivity has enabled the development of graphene-based chemical and biological sensors based on graphene solid-state devices, such as graphene field effect transistors (GFETs), whose operation is based on the change in electrical properties when exposed to a targeted chemical or biological agent. This ultra-sensitivity can be selective if the graphene is functionalized with the right molecules and bioconjugates, which act as recognition element and provide specificity to the biosensor, thus creating specific binding sites for the biomarkers of choice to be bond to. This way, when the biomarker interacts with the probe molecule, they bind, producing a change in the electronic state of the probe and linker molecule, if any. This produces a charge transfer into the graphene channel which changes its conductivity. This results in a change in the conductance of graphene and thus a change in the current flowing through the, for example, transistor, which is the output signal. Obtaining electrical readouts -versus chromatographic or optical ones- permits to benefit from well-known techniques for electrical analysis of signals. Thus, graphene sensors or graphene chips, such as chips having one or more graphene solid-state devices, have immense potential for disrupting the diagnosis -and thus healthcare- sector, among other sectors. HAN SHU-JEN et al: "Multifinger Embedded T-Shaped Gate Graphene RF Transistors With High fMAX/fT Ratio", IEEE Electron Device letters, vol. 34, n° 10, October 2013, discloses a graphene device structure having multiple-finger T-shaped gates embedded in the substrate, which provides certain advantages in the field of RF transistors. JP2018163146A discloses a graphene-based sensor provided with a back gate electrode. US 2018/0368743 A1 discloses a FET comprising substrate, gate electrode, and microfluidic channel including graphene, where channel is formed between drain and source electrodes. A passivation layer made from a thin polymer layer, e.g. parylene is provided. To manufacture GFETs for biosensing, source and drain contacts are usually passivated to insulate them from the liquid analyte. This prevents, among other things, large current leakage through the sample. Passivation is achieved by applying an insulating material on top of the contacts acting as source and drain. For this passivation, different materials may be used, such as oxide dielectric materials (from now on dielectrics) and polymeric materials. Biosensing is not the only application benefiting from this approach. Other applications in the field of photonics and optoelectronics can benefit therefrom. For instance, sensitized photodetectors with quantum dots, photosensitive polymers and perovskites, among others, can use this approach to insulate the active layer from the source and drain contacts, enhancing the photogain mechanism characteristic in these hybrid devices and thus improving responsivity of the photodetector. An example of sensor device having passivated contacts is disclosed in US2018/0321184A1, wherein a transparent sensor device is disclosed. This device implements gate, drain and source bottom contacts, each contact being performed in separate lithographic and metallization steps. Having different metallization steps adds complexity to the manufacturing process and involves a less accurate alignment between, for example, drain and source contacts. Therefore, there is a need to develop new methods of fabricating graphene-based devices which overcome the above-mentioned drawbacks. DESCRIPTION OF THE INVENTION The present invention provides a new graphene-based solid-state device as defined in claim 6 and a new method of fabricating a graphene-based solid-state device as defined in claim 1, which overcomes the drawbacks of conventional devices and methods of fabrication of these devices. The graphene-based solid-state device has at least two top contac