DESC:TECHNICAL FIELD
[0001] The present disclosure relates, in general, to fluorine ion (F-) doping and its activation schemes for 2D semiconductors, and more specifically, relates to the fabrication of high-performance MoS2 and other transition metal dichalcogenides (TMDs)-based field-effect transistors (FETs).

BACKGROUND
[0002] TMDs are two-dimensional materials, which offer enhanced electrostatic control compared to traditional silicon channels, particularly mitigating short-channel effects—a critical aspect for sub-5 nm transistor technology. However, for viable commercial utilization of these materials, several challenges need to be addressed. These challenges include issues such as the Schottky nature of metal/TMDs contact leading to high contact resistance (RC) and low drive current, and intrinsic defects like chalcogen vacancies leading to low carrier mobility.
[0003] Numerous attempts have been undertaken to address these challenges. However, these efforts often lead to trade-offs, impacting crucial parameters such as the ION/IOFF ratio, mobility, and other parameters of the FETs. For example, methods utilizing surface charge transfer doping (SCTD) technique using benzyl viologen and polyethyleneimine show improvement in on-current (ION); however, with a reduced ION/IOFF. Also, other SCTD techniques demonstrated using potassium iodide do not show stable improvements with time. Looking at the instability of wet chemistry-based methods like SCTD, dry methods using O2 plasma have been used to improve the performance of the MoS2 FETs. However, these plasma-based methods have been found to degrade mobility due to defects formed during plasma bombardment on the TMD surface. Other than these methods, many dry transfer techniques have been proposed to demonstrate improvement in contact resistance and overall performance of the MoS2 FETs. For example, MoS2/graphene-based Dirac-source FET (DSFET) disclosed to achieve a subthreshold swing of 37.9 mV/dec. Similarly, MoSe2 was used between Ti and MoS2 contact to reduce the Schottky barrier height (SBH) and improve the performance of the MoS2 FET. Even though these dry transfer-based methods provide an approach to enhance the performance of the TMD-based FETs, these are not scalable and are time-consuming.
[0004] Recognizing the challenges and limitations posed by the methods mentioned above, there arises a necessity for a stable and scalable technique to enhance the drive current, mobility, and overall performance of TMD-based FETs without deteriorating the other key parameters. The proposed methodology achieves these requirements by implanting the F- ions into MoS2 FET’s contacts and their subsequent cyclic electric field-assisted activation, leading to n-type doping in the contact and channel region of MoS2 FETs and further passivation of intrinsic sulfur (S) vacancy defects. This results in improved contact resistance, mobility, and drive current of MoS2 FETs without any degradation in ION/IOFF.

OBJECTS OF THE PRESENT DISCLOSURE
[0005] An object of the present disclosure is to provide a device with enhanced carrier mobility, allowing for more efficient charge transport in the MoS2 FET.
[0006] Another object of the present disclosure is to provide a device with reduced contact resistance, resulting in lower energy loss and improved electrical performance.
[0007] Another object of the present disclosure is to provide a device with improved drive current, enhancing the power output and overall functionality of the MoS2 FET.
[0008] Another object of the present disclosure is to provide a device with a decent ION/IOFF ratio of 7-8 orders, ensuring better switching performance and low power consumption.
[0009] Another object of the present disclosure is to provide a device that achieves these advantages by utilizing fluorine ion implantation and its cyclic electric field-assisted activation.
[0010] Another object of the present disclosure is to provide a device that is efficient, versatile, and suitable for various semiconductor applications.
[0011] Another object of the present disclosure is to provide a device that enhances the performance of MoS2 FETs, making them suitable for high-performance electronic devices.
[0012] Another object of the present disclosure is to provide a device that maintains stable electrical characteristics over time, ensuring long-term reliability.
[0013] Another object of the present disclosure is to provide a device that can be integrated into existing semiconductor manufacturing processes, facilitating ease of adoption.
[0014] Yet another object of the present disclosure is to provide a device that supports the development of advanced electronic applications, including flexible and wearable electronics.

SUMMARY
[0015] The present disclosure relates to fluorine ion (F-) doping and its activation schemes for 2D semiconductors, and more specifically, relates to the fabrication of high-performance contacts for MoS2 and other transition metal dichalcogenides (TMDs)-based field-effect transistors (FETs). The main objective of the present disclosure is to overcome the drawbacks, limitations, and shortcomings of the existing semiconductor device technology by providing an electronic device is disclosed, comprising a layer of transition metal dichalcogenide (TMD) material disposed on a substrate. The device includes a source contact region and a drain contact region patterned on the layer of TMD material. A fluorine-treated region is created by subjecting the layer of TMD material beneath the patterned source and drain contact regions to an ion implantation source, which implants fluorine ions into the source/drain contact regions. A metal layer is then deposited onto the fluorine-treated source/drain contact regions to form source/drain electrical contacts. A cyclic electric field is applied across the layer of TMD material using the source/drain electrical contacts, which activates and migrates the implanted fluorine ions into the layer of TMD material. This process results in the bonding of fluorine ions to chalcogen vacancies, leading to n-type doping in the layer of TMD material and passivation of chalcogen vacancies.
[0016] The n-type doping and passivation enhance the device's performance by reducing contact resistance and increasing mobility, which improves drive current and overall device performance. The ion implantation source may be selected from fluorine chemistry-based plasma, an accelerated source of fluorine ions, or any combination thereof. The layer of TMD material can be selected from molybdenum disulfide (MoS2), tungsten disulfide (WS2), tungsten diselenide (WSe2), or molybdenum diselenide (MoSe2), and may be in monolayer or multilayer form.
[0017] Further, the device may be configured in a top-gated, back-gated, or any other suitable field-effect transistor (FET) architecture. The cyclic electric field may be applied by applying cyclic rectangular voltage pulses across the source/drain electrical contacts or by placing the devices with fluorine-implanted source/drain electrical contacts at a wafer scale into a radio-frequency (RF) chamber with an oscillating electric field along the basal plane of the layer of TMD material. The substrate is a dielectric material selected from silicon dioxide (SiO2), aluminum oxide (Al2O3), hafnium oxide (HfO2), or any combination thereof. The metal layer deposited onto the fluorine-treated source/drain contact regions may include metals selected from nickel (Ni), gold (Au), titanium (Ti), chromium (Cr), aluminum (Al), palladium (Pd), or any combination thereof. The layer of TMD material is disposed on the substrate using chemical vapor deposition (CVD), exfoliation, or a combination thereof.
[0018] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The following drawings form part of the present specification and are included to further illustrate aspects of the present disclosure. The disclosure may be better understood by reference to the drawings in combination with the detailed description of the specific embodiments presented herein.
[0020] FIG. 1A presents a schematic representation of the MoS2 FET and its fabrication process, in accordance with an embodiment of the present disclosure.
[0021] FIG. 1B outlines the fabrication process flow of the MoS2 FET, in accordance with an embodiment of the present disclosure.
[0022] FIG. 1C demonstrates the density functional theory (DFT) calculated band structure of MoS2 containing a sulfur (S) vacancy, in accordance with an embodiment of the present disclosure.
[0023] FIG. 1D illustrates the band structure of MoS2 with a fluorine (F) atom bonded to the S vacancy, in accordance with an embodiment of the present disclosure.
[0024] FIG. 1E illustrates the transfer characteristics of the MoS2 FET, both with and without F-based plasma treatment in the contacts, used for F- ion implantation and doping in the contact region, in accordance with an embodiment of the present disclosure.
[0025] FIG. 2A illustrates a scanning electron microscopy (SEM) image showcasing the completed fabrication of the back-gated MoS2 field-effect transistor (FET), in accordance with an embodiment of the present disclosure.
[0026] FIG. 2B illustrates the lateral RF field chamber for implanted F- ion activation activation at the wafer scale, in accordance with an embodiment of the present disclosure.
[0027] FIG. 2C illustrates the schematic and biasing arrangement for cyclic electric field-assisted activation of implanted F ions by the application of pulses across source-drain contacts, in accordance with an embodiment of the present disclosure.
[0028] FIG. 3A illustrates the change in the transfer characteristics of the MoS2 FET with -10 V to 10 V cyclic electrical pulses applied across the S/D contacts for the exfoliated case, in accordance with an embodiment of the present disclosure.
[0029] FIG. 3B illustrates the change in the transfer characteristics of the MoS2 FET with -10 V to 10 V cyclic electrical pulses applied across the S/D contacts for chemical vapor deposition (CVD)-grown MoS2 case, in accordance with an embodiment of the present disclosure.
[0030] FIG. 3C illustrates the improvement in ION of exfoliated and CVD-grown MoS2 FETs with cyclic electrical pulses applied across S/D contacts, obtained from
FIG. 3A and FIG. 3B, respectively, in accordance with an embodiment of the present disclosure.
[0031] FIG. 3D and FIG. 3E illustrates the transfer characteristics of FIG. 3A and FIG. 3B, respectively, on a log scale, and shows that the improvement in ION is found without any deterioration in ION/IOFF, which remained in 7-8 orders, in accordance with an embodiment of the present disclosure.
[0032] FIG. 3F illustrates the X-ray photoelectron spectroscopy (XPS) spectra of the channel of the MoS2 FETs before and after cyclic electrical pulsing across S/D contacts, showing F- ion migration into the channel, in accordance with an embodiment of the present disclosure.
[0033] FIG. 4A and FIG. 4B illustrates the photoluminescence (PL) spectra of the MoS2 FET channel captured before and after the application of two hundred -10 V to 10 V pulses, respectively, in accordance with an embodiment of the present disclosure.
[0034] FIG. 4C illustrates the contact resistance extraction of MoS2 FETs before and after two hundred -10 V to 10 V pulses using the transfer length method (TLM) structure, in accordance with an embodiment of the present disclosure.
[0035] FIG. 5 illustrates a flow chart of a method for fabricating an electronic device, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0036] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.
[0037] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0038] The present disclosure relates, in general, to F- ion doping and its activation schemes for 2D semiconductors, and more specifically, relates to the fabrication of a high-performance MoS2 field-effect transistor (FET).
[0039] The present disclosure relates to a fabrication process of CVD-grown and exfoliated MoS2 FET. To start, pattern the source and drain (S/D) contact regions using e-beam lithography on the surface of CVD-grown or exfoliated MoS2. Develop and open the (S/D) contact areas utilizing a developer solution, comprising of Methyl Isobutyl Ketone (MIBK) and Isopropyl Alcohol (IPA). Subject the sample having developed contact regions to F-based plasma for a duration of 5 seconds. Deposit a layer of metal onto the sample for forming electrical contacts for the MoS2 device. Apply cyclic electric field across the S/D contacts to activate and migrate F- ions within the MoS2 material. The migrated F- ions bond with sulfur (S) vacancies within the MoS2 material, enhancing the properties of the device.
[0040] MoS2-based field-effect transistors (FETs), and in general, Transition Metal Dichalcogenide (TMD) channels are fundamentally limited by high contact resistance (RC) and intrinsic defects like chalcogen vacancies, which results in low drive current and lower carrier mobilities, respectively. The present disclosure solves the above limitations by using a unique fluorine ion implantation technique in the contact region of the MoS2 transistor, and its electric field-assisted activation using cyclic electrical pulses applied across the source-drain (S/D) contacts. The migrated F- ions bond with S vacancies and result in their passivation and n-type doping in the channel and near the S/D contacts.
[0041] The n-type doping near the contacts reduces RC by approximately 90%, and the passivation of S vacancies enhances mobility by around 150%. Additionally, the ON-current (ION) improves by around 90% and 480% for exfoliated and CVD-grown MoS¬2, respectively. These enhancements are achieved without any deterioration in the ION/IOFF, which can be found to be greater than 7-8 orders. The present disclosure opens pathways to physically dope the TMDs via ion implantation and address the contact resistance and defect passivation issues for wafer-scale processes using the proposed lateral RF field-based dopant activation approach. The description of terms and features related to the present disclosure shall be clear from the embodiments that are illustrated and described; however, the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents of the embodiments are possible within the scope of the present disclosure. Additionally, the invention can include other embodiments that are within the scope of the claims but are not described in detail with respect to the following description.
[0042] FIG. 1A presents a schematic representation of the MoS2 FET, FIG. 1B outlines the fabrication process flow of the MoS2 FET. Additionally, FIG. 1C demonstrates the density functional theory (DFT) calculated band structures of MoS2 containing a sulfur (S) vacancy, while FIG. 1D highlights the band structure with a fluorine (F) atom bonded to the S vacancy. Furthermore, FIG. 1E displays the transfer characteristics of the MoS2 FET, both with and without F-based plasma treatment in the contacts. The FET employed for these characteristics features a channel length of 1 µm.
[0043] FIG.1A illustrates a schematic representation of the MoS2 FET, in accordance with an embodiment of the present disclosure. The present disclosure employs a unique fluorine ion implantation technique in the contact region of MoS2 transistor ( also referred to as MoS2-based device, herein), and electric field-assisted activation and migration of F- ions using cyclic electric field applied across the source-drain (S/D) contacts.
[0044] The electronic device 100 (also referred to as transition metal dichalcogenides (TMD)-based devices 100) includes a layer of transition metal dichalcogenide (TMD) material 102 disposed on the substrate 110. The device includes a source contact region 104-1 and a drain contact region 104-2 patterned on the layer of TMD material 102. A fluorine-treated region 106 is created by subjecting the layer of TMD material beneath the patterned source and drain contact regions (104-1, 104-2) to an ion implantation source, which implants fluorine ions into the source/drain contact regions. A metal layer is then deposited onto the fluorine-treated source/drain contact regions (104-1, 104-2) to form source/drain electrical contacts 108. A cyclic electric field is applied across the layer of TMD material 102 using the source/drain electrical contacts 108, which activates and migrates the implanted fluorine ions into the layer of TMD material 102. This process results in the bonding of fluorine ions to chalcogen vacancies, leading to n-type doping in the layer of TMD material and passivation of chalcogen vacancies.
[0045] The n-type doping and passivation enhance the device's performance by reducing contact resistance and increasing mobility, which improves drive current and overall device performance. The ion implantation source may be selected from fluorine chemistry-based plasma, an accelerated source of fluorine ions, or any combination thereof. The layer of TMD material can be selected from molybdenum disulfide (MoS2), tungsten disulfide (WS2), tungsten diselenide (WSe2), or molybdenum diselenide (MoSe2), and may be in monolayer or multilayer form.
[0046] Further, the device 100 may be configured in a top-gated, back-gated, or any other suitable field-effect transistor (FET) architecture. The cyclic electric field may be applied by applying cyclic rectangular voltage pulses across the source/drain electrical contacts 108 or by placing the devices with fluorine-implanted source/drain electrical contacts 108 at a wafer scale into a radio-frequency (RF) chamber with an oscillating electric field along the basal plane of the layer of TMD material. The substrate 110 is a dielectric material selected from silicon dioxide (SiO2), aluminum oxide (Al2O3), hafnium oxide (HfO2), or any combination thereof. The metal layer deposited onto the fluorine-treated source/drain contact regions may include metals selected from nickel (Ni), gold (Au), titanium (Ti), chromium (Cr), aluminum (Al), palladium (Pd), or any combination thereof. The layer of TMD material is disposed on the substrate using chemical vapor deposition (CVD), exfoliation, or a combination thereof.
[0047] Referring to FIG. 1A, the MoS2 in the S/D contact regions 108 is exposed to F-based plasma resulting in the partial etching of MoS2, followed by metal deposition. To check any RC and ION improvement after treatment of F-based plasma plasma in the S/D contacts, on the same exfoliated MoS2 flake, two adjacent FETs with the same metal contact were made, with plasma treatment in only one of the FETs.
[0048] FIG. 1B outlines the fabrication process flow of the MoS2 FET, in accordance with an embodiment of the present disclosure. The fabrication process involves the following steps for both Chemical Vapor Deposition (CVD) and exfoliated TMDs. Consider CVD-grown or exfoliated TMDs on the SiO2/Si substrate. Pattern source and drain (S/D) contact by employing e-beam lithography to define the source and drain (S/D) contact regions on the MoS2 surface. Utilize a developer solution, such as Methyl Isobutyl Ketone (MIBK) and Isopropyl Alcohol (IPA), to develop and open the (S/D) contact areas. Subject the sample having opened contact regions to fluorine-based plasma for a duration of 5 seconds. Deposit a layer of metal onto the S/D region that has been exposed to fluorine-based plasma. These layers serve as the electrical contacts for the TMD device. Subsequently, apply a cyclic electrical field across the S/D contacts, where these cyclic electric fields assist in activating and migrating F- ions within the TMD material, which bond with sulfur (S) or chalcogen vacancies, leading to n-type doping and thereby improving the contact resistance and device’s performance. The present disclosure also discloses an RF plasma chamber to expose the channel to the said lateral RF field.

PRELIMINARY RESULTS
[0049] FIG. 1C demonstrates the density functional theory (DFT) calculated band structures of MoS2 containing a sulfur (S) vacancy, in accordance with an embodiment of the present disclosure. Sulfur vacancies are found in MoS2 as the intrinsic form of defects. These can be passivated using foreign atoms like fluorine, which are smaller in size compared to naturally existing sulfur. To understand the possible effects of fluorine bonding at sulfur vacancies, density functional theory (DFT) calculations were performed on an in-plane periodic 5 x 5 supercell of single-layer MoS2. For DFT calculations, three cases were considered, MoS2 (i) without any sulfur vacancy, (ii) with a single sulfur vacancy, and (iii) with a fluorine atom bonded to the sulfur vacancy. For pristine MoS2 with no sulfur vacancy, no defect states are present in the bandgap, and the fermi level (EF) lies in the mid of the bandgap. FIG. 1C shows that with a sulfur vacancy, although defect states come near the conduction band (CB) of MoS2, the EF shifts closer to the valence band (VB). However, when the fluorine atom bonds to sulfur vacancy, more defect states come near the CB, and EF also shifts closer to the CB, resulting in n-type doping in MoS2, as shown in FIG. 1D. Considering these preliminary observations, fluorine-based plasma could be used in the S/D contact region of MoS2 FETs to dope it n-type and improve ION by reducing RC.
[0050] However, in FIG. 1E, from the transfer characteristics of MoS2 FETs with exposure to fluorine-based plasma and without exposure to fluorine-based plasma in the S/D contacts, no improvement in ION is found, which is expected after plasma treatment in the contact region. This could be due to no bonding of F atoms at the S vacancies in the contact region, which is essential for n-type toping to happen. Based on the above observations, other methods are used that could activate the F atoms and lead to their bonding at S vacancies. In that row, cyclic electrical pulses of 1 kHz frequency and 50% duty cycle are applied across the S/D contacts of the MoS2 FETs under floating gate conditions, as shown in FIG. 2C. This process is repeated till 200 square pulses, where after every ten pulses applied across the S/D, transfer characteristic of the FET was observed. Here, the pulses applied were of 20 V amplitude with a base value of -10 V. These pulses may be referred to as -10 V to 10 V pulses. Here, the time duration of one pulse is defined as equal to the time period of the applied square wave.
[0051] FIG. 2A illustrates a scanning electron microscopy (SEM) image showcasing the completed fabrication of the back-gated MoS2 field-effect transistor (FET). FIG. 2B illustrates the lateral RF field chamber for fluorine dopant activation at the wafer scale. FIG. 2C illustrates the biasing arrangement while pulsing across the S/D contacts of MoS2 FET.
[0052] In FIG. 2B, an RF chamber is shown, which can be used to apply a lateral cyclic electric field along the basal plane of MoS2 at a wafer scale to activate the implanted F- ions, as was done in FIG. 2C for a single FET.
[0053] FIG. 2C illustrates the biasing arrangement and schematic configuration for the MoS2 FET while pulsing. The setup demonstrates the implementation of cyclic electrical pulsing across the source-drain (S/D) contacts under a floating gate condition. The pulses are applied at the drain with 20 V amplitude and a base value of -10 V, while the source remains grounded.

IMPROVEMENT IN MOS2 FET’S PERFORMANCE WITH CYCLIC PULSING
[0054] FIG. 3A and FIG. 3B illustrates the change in the transfer characteristics of the MoS2 FET with -10 V to 10 V cyclic pulsing for an exfoliated and CVD-grown MoS2 case.
[0055] FIG. 3A and FIG. 3B confirm the improvement in the performance of the exfoliated and CVD-grown MoS2 FETs after cyclic pulses are applied. After two hundred pulses, the ION for exfoliated MoS2 and CVD-grown MoS2 increases by ~89% and ~483%, respectively. The quantitative increase in ION (at VBG = 40 V, VDS = 3 V) with cyclic pulsing is shown in FIG.3C. For exfoliated and CVD-grown MoS2, after two hundred pulses, the field-effect mobility (µFE) increases by 54.55% and 156%, respectively.
[0056] For activating the F- ions by applying cyclic pulses along the basal plane of MoS2 at a wafer scale, where billions of transistors are there, FIG. 2B shows a proposed approach. In FIG. 2B, an RF chamber is shown, which can be used to apply a lateral cyclic electric field along the basal plane of MoS2 at a wafer scale to activate the implanted F- ions, as was done in FIG. 2C for a single FET. The RF field chamber can be used similarly to the reactive ion etching (RIE) tool, with the only difference being that no gases are used, and a high vacuum is maintained while applying the RF field.
[0057] FIG. 3C illustrates the improvement in ION with cyclic pulsing obtained from FIG. 3A and FIG. 3B, respectively. The channel length used here for all the FETs is 1 µm.
[0058] FIG. 3D and FIG. 3E illustrates transfer characteristics on the log scale of FIG. 3A and FIG. 3B, respectively. It shows that the improvement in ION is found without any deterioration in ION/IOFF, which remained in 7-8 orders.

F- ION MIGRATION INTO THE MOS2 CHANNEL
[0059] FIG. 3F illustrates XPS spectra of the MoS2 FETs before and after cyclic pulsing. To investigate the exact role F- ion implantation and cyclic electric field activation play in performance enhancement, XPS is done before and after pulsing the MoS2 FETs having contact treated with plasma. Before applying the cyclic electric field, no peak is observed in 670 eV to 700 eV of binding energy corresponding to F atoms, as shown in FIG. 3F. These fabricated FETs were then kept for cyclic electric field activation using 200 pulses of -10 V to 10 V, post which the XPS spectra were taken in the same area of fabricated FETs. This time, the peaks are observed in 670 eV to 700 eV of binding energy, which belongs to F 1s core electrons, and hence confirm the presence of F in the channel region after the application of the cyclic electric field. After deconvolution, the peaks at a higher binding energy of 685.9 eV and at a lower binding energy of 683.2 eV show that the F atoms in the channel are present in the covalently bonded and ionic form. Here, the F atoms are initially present in the S/D contact regions due to F-based plasma treatment, which, after pulsing, migrate into the channel (observed from XPS).

CONTACT AND CHANNEL DOPING
[0060] FIG. 4A and FIG. 4B illustrates the photoluminescence (PL) spectra of the MoS2 FET channel captured both before and after the application of two hundred -10 V to 10 V pulses. The increase in the trion-to-exciton ratio signifies an increase in n-type doping in the channel after pulsing.
[0061] To further explore the changes in the channel properties after cyclic pulsing, PL spectra of the channel region of the MoS2 FET were taken before and after pulsing, as shown in FIG. 4A and FIG. 4B, respectively. After the deconvolution of PL spectra, A and B exciton peaks and the negatively charged A- trion peak are obtained. Comparing the PL spectra before and after two hundred pulses, a red-shift in A peak from 679.12 nm to 682.03 nm, along with an increase in the trion-to-exciton ratio (A-/A) from 0.23 to 1.35 is observed.
[0062] An increase in (A-/A) here signifies an increase in n-type doping in the channel post-pulsing. To understand the reason for increased n-type doping, density functional theory (DFT) and molecular dynamics (MD) simulations are used, which show the F- ions migrate into the channel after cyclic pulsing and bond to S vacancies in the channel and near the S/D contacts, resulting in n-type doping, as observed in FIG. 1D. Further, the red shift in the A peak after pulsing should be due to the combined effect of the cyclic pulsing and migration of F- ions into the channel, resulting in an excess strain in the MoS2 lattice.
[0063] To study the reduction in RC as a possible reason for the improvement in ION and other parameters of the FET, MoS2 FETs are fabricated based on the transfer length method (TLM) structure, and RC is extracted from it.
[0064] FIG. 4C illustrates contact resistance extraction of MoS2 FETs before and after two hundred -10 V to 10 V pulses. FIG. 4C shows the variation in total resistance (RTOT) with the channel length (LCH) of the FETs. From FIG. 4C, it is observed that after 200 pulses, RC decreases from 12.55 KO-µm to 1.74 KO-µm, and sheet resistance (RS) decreases from 34.39 KO/sq to 17.01 KO/sq. The reduction in RC is due to the n-type doping near the S/D contacts and the narrowing of the Schottky barrier width at the metal-semiconductor junction. The combined effect of the decrease in RC and increase in mobility by passivation of the S vacancies from the migrated F- ions results in the performance enhancement of the MoS2 FETs. The phenomenon of F bonding at naturally existing S vacancies used in this work can be carried further to physically dope the contacts, passivate the defects, and improve the performance of MoS2 FETs at wafer scale processes using a proposed lateral RF field chamber for dopant activation.
[0065] FIG. 5 illustrates a flow chart of a method for fabricating an electronic device, in accordance with an embodiment of the present disclosure. The method 500 involves exfoliating/growing of a layer of TMD material on a dielectric substrate, as indicated in block 502. At block 504, source and drain (S/D) contact regions are patterned on the layer of TMD material. In block 506, a developer solution is employed to open the source and drain (S/D) contact regions. At block 508, the developed S/D contact regions are subjected to a fluorine-based plasma treatment. At block 510, fluorine ions are implanted into the S/D contact regions of the TMD material. At block 512, a metal layer is deposited onto the fluorine-based plasma-treated S/D contact regions to form electrical contacts. Finally, at block 514, a cyclic electric field is applied across the source-drain contacts to activate and migrate the F- ions into the FET’s channel, which leads to its bonding to sulfur vacancies in the TMD channel and near the S/D contacts. This results in n-type doping in both places. The n-typed doping near the S/D contacts leads to the narrowing of Schottky barrier width at the S/D contacts/TMD junction, reducing contact resistance of TMD-based FET.
[0066] Thus, the present invention of fluorine ion implantation in S/D contacts of TMD-based FETs and its cyclic electric field-assisted activation overcomes the drawbacks, shortcomings, and limitations associated with existing solutions, and collectively yields advantages such as enhanced carrier mobility, reduced contact resistance, improved drive current, and a decent ION/IOFF of 7-8 orders. These advantages collectively pave the way for the creation of high-performance TMD-based FETs with improved efficiency, versatility, and potential for various semiconductor applications.
[0067] It will be apparent to those skilled in the art that the method of the disclosure may be provided using some or all of the mentioned features and components without departing from the scope of the present disclosure. While various embodiments of the present disclosure have been illustrated and described herein, it will be clear that the disclosure is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the disclosure, as described in the claims.

ADVANTAGES OF THE PRESENT DISCLOSURE
[0068] The present disclosure provides a device with enhanced carrier mobility, allowing for more efficient charge transport in the MoS2 FET.
[0069] The present disclosure provides a device with reduced contact resistance, resulting in improved electrical performance.
[0070] The present disclosure provides a device with improved drive current, enhancing the overall functionality of the MoS2 FET.
[0071] The present disclosure provides a device with a decent ION/IOFF ratio of 7-8 orders, ensuring better-switching performance and low power consumption.
[0072] The present disclosure provides a device that achieves these advantages by utilizing fluorine ion implantation and their cyclic electric field-assisted activation.
[0073] The present disclosure provides a device that is efficient and versatile, suitable for various semiconductor applications.
[0074] The present disclosure provides a device that enhances the performance of MoS2 FETs, making them suitable for high-performance electronic devices.
[0075] The present disclosure provides a device that maintains stable electrical characteristics over time, ensuring long-term reliability.
[0076] The present disclosure provides a device that can be integrated into existing semiconductor manufacturing processes, facilitating ease of adoption.
[0077] The present disclosure provides a device that supports the development of advanced electronic applications, including flexible and wearable electronics.
,CLAIMS:1. An electronic device (100) comprising:
a layer of transition metal dichalcogenide (TMD) material (102) disposed on a substrate (110);
a source contact region (104-1) patterned on the layer of TMD material;
a drain contact region (104-2) patterned on the layer of TMD material;
a fluorine-treated region (106) formed by subjecting the layer of TMD material (102) under the patterned source (104-1) and drain contact (104-2) regions to an ion implantation source so as to implant fluorine ions into the source-drain (S/D) contact regions (104-1, 104-2); and
a metal layer deposited onto the fluorine-treated S/D contact regions to form S/D electrical contacts (108), wherein a cyclic electric field is applied across the layer of TMD material (102) using S/D electrical contacts (108) to activate and migrate the implanted fluorine ions into the layer of TMD material (102) leading to bonding of the fluorine ions to chalcogen vacancies resulting in n-type doping in the layer of TMD material (102) and passivation of chalcogen vacancies.
2. The device as claimed in claim 1, wherein the n-type doping in the layer of TMD material (102) and passivation of chalcogen vacancies results in reduction of contact resistance and increase in mobility of the device (100) leading to increase in drive current and performance of the device (100).
3. The device as claimed in claim 1, wherein the ion implantation source is selected from fluorine chemistry-based plasma, accelerated source of fluorine ions and any combination thereof.
4. The device as claimed in claim 1, wherein the layer of TMD material (102) is selected from molybdenum disulfide (MoS2), tungsten disulfide (WS2), tungsten diselenide (WSe2), or molybdenum diselenide (MoSe2), and wherein the layer of TMD material is any or a combination of monolayer or multilayer form.
5. The device as claimed in claim 1, wherein the device is configured in a top-gated, back-gated, or any other suitable field-effect transistor (FET) architecture.
6. The device as claimed in claim 1, wherein the cyclic electric field is applied across the layer of TMD material (102) by applying cyclic rectangular voltage pulses across the S/D electrical contacts (108), or by placing the devices with fluorine-implanted S/D electrical contacts (108) at a wafer scale into a radio-frequency (RF) chamber having an oscillating electric field along basal plane of the layer of TMD material (102).
7. The device as claimed in claim 1, wherein the substrate (110) is a dielectric material selected from silicon dioxide (SiO2), aluminum oxide (Al2O3), hafnium oxide (HfO2), or any combination thereof.
8. The device as claimed in claim 1, wherein the metal layer deposited onto the fluorine-treated S/D contact regions (104-1, 104-2) comprises a metal selected from the group consisting of nickel (Ni), gold (Au), titanium (Ti), chromium (Cr), aluminium (Al), and palladium (Pd) or any combination thereof.
9.The device as claimed in claim 1, wherein the layer of TMD material is disposed on the substrate (110) using chemical vapor deposition (CVD), exfoliation, or a combination thereof.
10.A method (500) for fabricating an electronic device, the method comprising:
transferring (502) a layer of TMD material on a substrate;
patterning (504) source and drain (S/D) contact regions on the layer of TMD material;
subjecting (506) the layer of TMD material under the patterned S/D contact regions to an ion implantation source so as to implant fluorine ions into the S/D contact regions of the TMD material;
depositing (508) a metal layer onto the fluorine-treated S/D contact regions to form S/D electrical contacts; and
applying (510) a cyclic electric field across the layer of TMD material (102) using the S/D electrical contacts (108) to activate and migrate the implanted fluorine ions into the TMD layer leading to the bonding of fluorine ions to chalcogen vacancies resulting in n-type doping in the layer of TMD material (102) and passivation of chalcogen vacancies.