Semiconductor heterojunction based on MSi2N4 mediated interface regulation and manufacturing method

Abstract

The invention relates to the field of research, development and application of novel semiconductor devices, in particular to a semiconductor heterojunction based on MSi2N4 mediated interface regulation and a manufacturing method, and M is a metal element such as Mo, W and the like. The heterojunction is composed of a top metal electrode, an MSi2N4 thin film insertion layer, a germanium substrate and a bottom metal electrode from top to bottom, wherein the top metal electrode serves as a Schottky contact electrode or an ohmic contact electrode. A silicon-nitrogen compound semiconductor is formed by adjusting metal element components in MSi2N4, a Fermi level pinning effect at a p-type germanium interface is relieved by inserting a single-layer two-dimensional semiconductor film MSi2N4 mediated interface for regulation and control, a unique Si-N atomic structure is beneficial to reduction of an interstitial state generated by induction of a metal electrode, and the performance of the device is improved. And the insertion layer has an atomic-scale thickness without introducing an obvious extra resistor, and is matched with different work function electrodes to realize Schottky contact and ohmic contact of p-type germanium, so that the stability and the overall performance of the device are improved.

Description

Technical Field

[0001] The present invention relates to the research and development and application field of novel semiconductor devices, specifically to a semiconductor heterojunction based on MSi2N4 mediated interface regulation and a manufacturing method thereof. Background Art

[0002] As the size of transistors continues to shrink to the atomic scale, Moore's Law is gradually approaching its physical limit, making it difficult for silicon-based chips to further improve integration and reduce power consumption. Germanium (Ge) is considered to be one of the most promising semiconductor materials in the post-Moore era because it has higher hole mobility than silicon and has good compatibility with silicon-based heterogeneous integration processes. Therefore, the contact characteristics between metal and germanium play a vital role in the design of high-performance germanium-based transistors, which determines the carrier transmission efficiency, stability and reliability during operation. However, the metal / germanium contact interface and performance are usually limited by the Fermi level pinning (FLP) effect, in which the Fermi level of germanium at the interface is almost completely fixed near the valence band edge, resulting in the metal / germanium contact barrier being uncontrollable. In general, Fermi level pinning mainly originates from the gap state effect induced by metal atoms or defects, which significantly reduces the intrinsic performance of materials and devices. In order to improve the performance and application of germanium-based integrated circuits, it is necessary to reduce FLP to form a good and stable metal / germanium contact and achieve high-performance Ohmic and Schottky contact behavior in a specific device structure.

[0003] It is reported that inserting an ultra-thin layer at the interface between metal and germanium helps to improve the contact performance. By selecting the appropriate intercalation material, the band structure can be adjusted, the carrier transport can be optimized, and the contact stability can be improved, thereby achieving an overall enhancement of the device performance. Due to its inherent insulating properties, traditional ultra-thin insulating intercalation materials usually introduce tunneling resistance and series resistance, resulting in an increase in the total resistance. At the same time, the interface defects of the insulating layer may also cause additional FLP effects. In contrast, the emerging two-dimensional transition metal silicon nitride compound semiconductor thin film material MSi2N4 (such as MoSi2N4, WSi2N4) has a unique atomic and electronic structure, and has both sub-nanometer thickness and an ideal surface state without dangling bonds. With the rapid development of material preparation technology, it can effectively reduce resistance as an intercalation-mediated interface, and is expected to alleviate the Fermi level pinning effect caused by the gap state, providing a new idea for optimizing the metal / germanium contact performance. Summary of the invention

[0004] The purpose of the present invention is to provide a semiconductor heterojunction based on MSi2N4 mediated interface regulation and a manufacturing method thereof, by inserting a single-layer two-dimensional semiconductor MSi2N4 layer (wherein M is a metal element such as Mo, W, etc.) between the metal and p-type Ge, the ohmic contact and Schottky contact characteristics of lightly doped germanium are respectively realized according to metals with different work functions, thereby effectively weakening the Fermi level pinning of p-type germanium.

[0005] The technical solution of the present invention is: A semiconductor heterojunction based on MSi2N4-mediated interface regulation is composed from top to bottom of a top metal electrode, an MSi2N4 thin film insertion layer, a germanium substrate, and a bottom metal electrode. The top metal electrode is arranged uniformly and stably on the top of the germanium substrate as a Schottky contact electrode or an ohmic contact electrode; wherein the Schottky contact electrode is an aluminum / titanium / gold stacked composite structure from bottom to top, and the ohmic contact electrode is a gold / titanium / gold stacked composite structure from bottom to top.

[0006] The semiconductor heterojunction based on MSi2N4-mediated interface regulation is characterized in that the MSi2N4 thin film insertion layer in contact with the germanium substrate is a MSi2N4 semiconductor thin film with a thickness of 1 to 2 nanometers, wherein M is a metal element Mo or W, and the MSi2N4 thin film used is grown by chemical vapor deposition; the heterojunction inserts a single-layer two-dimensional semiconductor MSi2N4 thin film insertion layer between the top metal electrode and the germanium substrate, and forms a silicon-nitride compound semiconductor MoSi2N4 or WSi2N4 by adjusting the metal element composition in the MSi2N4.

[0007] The semiconductor heterojunction based on MSi2N4 mediated interface regulation has a p-type lightly doped germanium substrate, a bottom metal electrode is arranged at the bottom of the germanium substrate as an ohmic contact electrode, and a titanium / gold laminated composite structure is formed from top to bottom.

[0008] The method for manufacturing a semiconductor heterojunction based on MSi2N4 mediated interface regulation comprises the following steps: (1) A lightly doped p-type germanium substrate was used, which was sequentially immersed in acetone and isopropanol for ultrasonic cleaning to remove surface impurities, and then diluted hydrofluoric acid and deionized water were used to wash to remove surface oxides; (2) Forming a good titanium / gold bottom metal electrode contact on the back of the germanium substrate through vacuum electron beam evaporation technology; (3) A single-layer MSi2N4 thin film is obtained by chemical vapor deposition and transferred to a treated germanium substrate by chemical etching to form a MSi2N4 / Ge structure; (4) Through a simplified hard mask process, the metal hard mask is tightly attached to the MSi2N4 film of the MSi2N4 / Ge structure, exposing the area in contact with the top metal electrode; (5) Using vacuum electron beam evaporation technology, a top metal electrode composite structure in contact with the MSi2N4 film is prepared.

[0009] In the method for preparing a semiconductor heterojunction based on MSi2N4 mediated interface regulation, in step (1), the hydrofluoric acid used is obtained by diluting the original concentration hydrofluoric acid with deionized water in a volume ratio of 1:8, the concentration of the original hydrofluoric acid is 40wt%, and the washing time in the hydrofluoric acid and deionized water is 1 min.

[0010] In the method for manufacturing a semiconductor heterojunction based on MSi2N4-mediated interface regulation, in step (2), a diamond cutter is first used to scratch the back of the germanium substrate to produce a large number of defects, and then a vacuum electron beam evaporation is used to sequentially evaporate a Ti layer with a thickness of 5 to 6 nm and an Au layer with a thickness of 50 to 51 nm in the bottom metal electrode to form a good ohmic contact with the germanium substrate at the bottom.

[0011] The method for preparing a semiconductor heterojunction based on MSi2N4-mediated interface regulation, in step (3), a single-layer MSi2N4 film is obtained by chemical vapor deposition as a single-layer two-dimensional film grown on a copper / molybdenum substrate, and then polymethyl methacrylate is spin-coated to cover the MSi2N4 film; a 0.1-0.3 mol / L (NH4)2S2O8 aqueous solution is used to etch the Cu substrate, and the MSi2N4 film is separated from the copper / molybdenum substrate and floated flat on the surface of the solution at 60-80°C for 20-40 min, and then a germanium substrate is clamped and immersed in the (NH4)2S2O8 aqueous solution from the side, and the germanium substrate is moved to the bottom of the MSi2N4 film, and one side of the MSi2N4 film is attached to the upper surface of the germanium substrate, and then lifted to the liquid surface to ensure that there are no wrinkles when combined with the germanium substrate, and the MSi2N4 film does not overlap, until the MSi2N4 film structure is completely removed from the solution to complete the transfer.

[0012] In the method for manufacturing a semiconductor heterojunction based on MSi2N4-mediated interface regulation, in step (4), after the metal hard mask is bonded to the germanium substrate, the exposed pattern is a square area with a side length of 70-72 μm.

[0013] The method for manufacturing a semiconductor heterojunction based on MSi2N4 mediated interface regulation, in step (4), vacuum electron beam evaporation is used to sequentially evaporate the Au layer in the top metal electrode to a thickness of 50-51 nm, the Ti layer to a thickness of 5-6 nm, and the Au layer to a thickness of 50-51 nm, so as to form a good ohmic contact on the top; vacuum electron beam evaporation is used to sequentially evaporate the Al layer in the top metal electrode to a thickness of 50-51 nm, the Ti layer to a thickness of 5-6 nm, and the Au layer to a thickness of 50-51 nm, so as to form a good Schottky contact on the top.

[0014] The design idea of ​​the present invention is: The Fermi level pinning effect of semiconductor germanium seriously affects the contact performance of germanium-based devices, thus greatly limiting the development of germanium-based integrated circuits. Through in-depth research on efficient contact regulation methods, exploring the mechanism of Fermi level pinning, and continuously optimizing the metal-germanium contact structure and process, it is an important factor in promoting the development of germanium-based semiconductor integrated circuits. Inserting an intermediate layer at the metal and germanium contact interface plays an important role in improving the contact performance. By selecting a suitable intermediate layer material, the band structure can be regulated, the carrier transport can be optimized, and the contact stability can be improved, thereby achieving device performance improvement. The emerging two-dimensional semiconductor thin film material has an ideal surface state with sub-nanometer atomic thickness and no dangling bonds, and the preparation technology has developed rapidly and gradually matured in recent years. As an insertion layer material, it can not only effectively reduce resistance, but also is expected to alleviate the Fermi level pinning effect caused by the gap state, providing a new idea for optimizing the metal / germanium contact performance.

[0015] Here, we designed a mediated interface based on low-dimensional semiconductor MSi2N4 film, used MSi2N4 as an insertion layer of the metal / p-type germanium contact interface, constructed a mixed-dimensional heterostructure and regulated the interface contact characteristics. The two-dimensional transition metal silicon nitride compound MSi2N4 represented by MoSi2N4 has a unique Si-N atomic structure. The use of inserted single-layer two-dimensional semiconductor film MSi2N4 to mediate interface regulation helps to reduce the gap state induced by the metal electrode and alleviate the Fermi level pinning effect at the p-type germanium interface. The insertion layer has an atomic thickness without introducing significant additional resistance, so that efficient Schottky contact and ohmic contact of p-type germanium can be achieved with electrodes of different work functions. Based on the special structural advantages of two-dimensional materials, it is expected to obtain a weakly pinned or pin-free semiconductor contact interface, realize the regulation of the band structure in the mixed-dimensional heterostructure, and then optimize the contact performance and stability of germanium-based devices, providing strong support for promoting the application expansion of germanium-based integrated circuits and the continuous development of advanced semiconductor technology.

[0016] The advantages and beneficial effects of the present invention are: 1. The semiconductor heterojunction and manufacturing method based on MSi2N4 mediated interface regulation involved in the present invention do not involve complicated micro-nano preparation processes, but only use a simplified hard mask process to ensure the quality of the single-layer film and avoid the doping of the two-dimensional semiconductor material by the photolithography process. At the same time, the performance of the prepared device is uniform and repeatable, and the process conditions are stable and reliable.

[0017] 2. The semiconductor heterojunction and manufacturing method based on MSi2N4-mediated interface regulation involved in the present invention adopts MSi2N4 thin film material with mature preparation process as the insertion layer, and transfers the MSi2N4 thin film by chemical etching process. The transfer process is simple and effective and can achieve clean and lossless transfer, thus reducing process costs and realizing large-scale preparation of germanium heterojunctions. At the same time, there is almost no pollution and damage to the surface of the germanium substrate, thus ensuring device performance.

[0018] 3. The semiconductor heterojunction and manufacturing method based on MSi2N4-mediated interface regulation involved in the present invention effectively weaken the p-type germanium Fermi level pinning effect, realize the flexible and controllable transformation of metal / p-type germanium ohmic contact and Schottky contact, obtain linear ohmic contact with high on-current and Schottky contact with high rectification ratio, and the stable two-dimensional semiconductor intercalation contact process ensures uniformity and reliability. By changing the metal work function of the contact electrode to regulate the contact characteristics, a p-type germanium Schottky contact with low leakage current is realized by using a low work function aluminum electrode, and a p-type germanium ohmic contact is realized by using a high work function gold electrode.

[0019] 4. The present invention relates to a metal / germanium Schottky contact process based on MSi2N4 thin film intercalation. The electrical performance is statistically evaluated under -1 V ~ +1 V conditions. The on-current is greater than 10 2 mA / cm 2 The Schottky barrier height is greater than 0.5 eV, achieving the lowest closed-state current value based on lightly doped p-type germanium contact and more than 5×10 3 The rectification ratio.

[0020] 5. The present invention uses the low-dimensional material MSi2N4 intercalation technology to fully utilize the unique atomic structure and electronic structure advantages of two-dimensional transition metal silicon nitrogen compounds such as MoSi2N4, deeply studies the mechanism of the Fermi level pinning effect of low-dimensional materials and bulk materials, explores effective pinning regulation methods, and continuously optimizes the structure and process of metal semiconductor contact, thereby further improving the performance and stability of the device, providing a feasible idea for the future development of mixed-dimensional devices and integrated circuits, and providing strong support for promoting the sustainable development of semiconductor technology in the post-Moore era. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The schematic diagram of the planar structure of the semiconductor heterojunction based on the MoSi2N4 film mediated interface of the present invention is shown in the figure, 1-germanium substrate, 2-MoSi2N4 film insertion layer (molybdenum silicon nitrogen compound layer), 3-top electrode (Topelectrode), 4-bottom electrode (Bottom electrode).

[0022] Figure 2This is an atomic force microscope (AFM) image of the microscopic morphology of the MoSi2N4 film involved in the present invention.

[0023] Figure 3 This is a Raman spectrum image of a single-layer MoSi2N4 film (Monolayer MoSi2N4on Ge) transferred onto germanium involved in the present invention. The horizontal axis Raman Shift represents the Raman frequency shift (cm -1 ), the vertical axis Intensity represents the relative intensity of scattered light (au).

[0024] Figure 4 This is an optical microscope photograph of the heterojunction prepared by the hard mask process.

[0025] Figure 5 This is a transmission electron microscope (TEM) image of the Al / MoSi2N4 / Ge structure based on the MoSi2N4 thin film insertion layer involved in the present invention.

[0026] Figure 6 For the TEM image ( Figure 5 ) corresponding X-ray energy spectrum element analysis image.

[0027] Figure 7 When the top metal electrode is grounded, the current-voltage ( IV ) characteristic comparison. Among them, the horizontal axis Voltage represents the voltage between the probes V (V), the vertical axis Current represents the current between the probes I (A).

[0028] Figure 8 The current-voltage characteristic curves of repeated measurements of multiple Al / MoSi2N4 / p-Ge heterojunctions, where the horizontal axis Voltage represents the voltage (V) and the vertical axis Current represents the current (A).

[0029] Fig. 9 This is a comparison of the germanium Schottky contact current using MoSi2N4 thin film insertion layer and other insertion layers. I on / I off Represents the Schottky rectification ratio, the ordinate I off represents the closed-state current density (A / cm 2 ), the specific insertion layer materials in the figure are as follows: BP is black phosphorus, Ge3N4 is germanium nitride, HfN X / GeON is a stacked structure of hafnium nitride / germanium oxynitride, SiN is silicon nitride, GeO X It is germanium oxide. Our work MoSi2N4 is the MoSi2N4 film used in the present invention.

[0030] Fig.10 The current-voltage characteristic curve of Al / MoSi2N4 / p-Ge heterojunction under different temperature conditions. The horizontal axis Voltage represents the voltage between the probes. V (V), the vertical axis Current represents the current between the probes I (A), the temperature range is between 232 and 285 K.

[0031] Fig.11 :(a) is a comparison of the electrical properties of Al / p-Ge and Au / p-Ge heterojunctions formed by direct contact of low work function electrode metal Al and high work function metal Au with p-type germanium, respectively. The work function of Al is about 4.28 eV, and the work function of Au is about 5.10 eV. Among them, the horizontal axis Voltage represents the voltage between the probes V (V), the vertical axis Current represents the current between the probes I (A). (b) is the band structure diagram of the Fermi level pinning state corresponding to the direct contact between metal and p-type germanium. Metal represents the band structure on the metal side, and p-Ge represents the band structure on the semiconductor germanium side. E c represents the conduction band position of germanium, E V represents the valence band position of germanium, E F Represents the position of the Fermi level in the equilibrium state after germanium contacts with metal.

[0032] Fig.12 :(a) is a comparison of the electrical characteristics of the Al / MoSi2N4 / p-Ge and Au / MoSi2N4 / p-Ge heterojunctions formed by the metal electrodes Al and Au contacting p-type germanium respectively after the MoSi2N4 thin film insertion layer is used. Among them, the horizontal axis Voltage represents the voltage between the probes V (V), the vertical axis Current represents the current between the probes I (A). (b) is a band structure diagram of the use of MoSi2N4 thin film insertion layer to alleviate the Fermi level pinning effect of the metal contact with p-type germanium. Al represents low work function metal, Au represents high work function metal, and p-Ge represents the band structure on the semiconductor germanium side. E c represents the conduction band position of germanium, E V represents the valence band position of germanium,E F It represents the Fermi level position in the equilibrium state after germanium contacts with metal. The upper and lower horizontal dotted lines represent the difference in the Fermi level position in the equilibrium state caused by the change of work function. DETAILED DESCRIPTION

[0033] In the specific implementation process, the present invention relates to a semiconductor heterojunction and a manufacturing method based on MSi2N4-mediated interface regulation, which effectively weakens the Fermi level pinning effect of the p-type germanium substrate to achieve a flexible and controllable transition between ohmic contact and Schottky contact, thereby promoting the expanded application of germanium-based devices. Aiming at the MSi2N4 material family of transition metal silicon nitrogen compounds whose preparation process is becoming increasingly mature, the present invention uses MoSi2N4 thin film material obtained by chemical vapor deposition as a mediating insertion layer, and adopts a chemical etching process for transfer. The process is simple, the cost is low, the conditions are stable and reliable, and the large-scale preparation of germanium heterojunctions can be achieved, while there is almost no pollution and damage to the surface of the germanium substrate. The present invention adopts a simple hard mask process, and the contact problem between the metal and p-type germanium is weakened by inserting a MoSi2N4 thin film, so as to achieve stable regulation of the metal / p-type germanium ohmic contact and Schottky contact, and obtain a linear ohmic contact with a high on-current and a Schottky contact with a high rectification ratio, and the device performance has uniformity and reliability. In the present invention, other silicon-nitrogen compounds with similar properties (such as WSi2N4) can be formed by adjusting the metal element composition in MoSi2N4, which is expected to mediate the precise adjustment of the p-type germanium interface barrier and contact properties, thereby further optimizing the carrier injection efficiency and improving the stability and overall performance of the device.

[0034] The present invention requires optimization of the substrate pretreatment process, the thin film transfer process, and the heterostructure construction process to ensure stable and efficient electrical contact performance. The manufacturing method includes the following steps: (1) Using a lightly doped p-type germanium substrate, ultrasonic cleaning was performed with acetone and isopropanol to remove surface impurities, and then washing with diluted hydrofluoric acid and deionized water to remove surface oxides; In step (1), the hydrofluoric acid used is obtained by diluting the original concentration hydrofluoric acid and deionized water in a volume ratio of 1:8, the concentration of the original hydrofluoric acid is 40wt%, and the washing time in the hydrofluoric acid and deionized water is 1min.

[0035] (2) Forming a good titanium / gold bottom metal electrode contact on the back of the germanium substrate through vacuum electron beam evaporation technology; (3) Using a chemical etching process, the MoSi2N4 thin film grown by chemical vapor deposition is transferred to the target substrate; (4) A simplified hard mask process was used to prepare the required insertion layer pattern using a hard mask layer. The metal hard mask was tightly attached to the Ge substrate with a MoSi2N4 film. The hard mask was a square opening area with a size of 70 μm × 70 μm, and the area on the target germanium substrate that was in contact with the top metal electrode was obtained. (5) A top metal electrode composite structure in contact with the MoSi2N4 film was prepared by vacuum electron beam evaporation technology.

[0036] The present invention is further described in detail below through examples and drawings.

[0037] Example:

[0038] In this embodiment, the semiconductor heterojunction based on MSi2N4 mediated interface regulation and the manufacturing method are as follows: The pretreatment process of the germanium substrate was optimized, and the resistivity was about 1~10 Ω·cm and the doping concentration was about 9×10 14 cm -3 Lightly doped p-type germanium is used as the substrate, and a diamond knife is used to scratch the back of the germanium substrate to form a large number of scratch defects, and the Ti / Au bottom metal electrode of the ohmic contact is directly formed by electron beam evaporation.

[0039] The front side of the substrate was cleaned by ultrasonic cleaning with acetone and isopropanol for 5 min each to remove surface impurities, and then soaked in a diluted hydrofluoric acid aqueous solution for 1 min and cleaned with deionized water for 1 min to remove the natural oxide on the germanium surface. The diluted hydrofluoric acid aqueous solution used was obtained by diluting the original concentration of hydrofluoric acid and deionized water in a volume ratio of 1:8, and the concentration of the original concentration of hydrofluoric acid was 40 wt%.

[0040] MoSi2N4 thin film from the MSi2N4 material family of transition metal silicon nitride compounds was prepared by chemical vapor deposition process, and high-purity Cu foil (99.95 wt%) and high-purity Mo foil (99.95 wt%) were used as the substrate for the growth of MoSi2N4 thin film. The Cu / Mo stack was placed in the center of the quartz tube, and a quartz or pure silicon plate was placed upstream. Before heating, the quartz tube was purged with high-purity argon (99.999% by volume purity), and then switched to hydrogen purge for 5 minutes. The quartz tube cavity was heated to 1090 °C within 45 minutes, maintained for 1 minute to melt Cu on the Mo surface, and then cooled to 1080 °C to solidify. Subsequently, NH3 with a volume purity of 99.0% was used as the nitrogen source to grow MoSi2N4 thin film for 4 hours. After the reaction was completed, the sample was quickly taken out and cooled to keep the atmosphere unchanged. After cooling to room temperature, argon gas was introduced to exhaust the gas in the quartz tube and then the sample was taken out. The MoSi2N4 film grown on the Cu / Mo substrate was transferred to the substrate through a chemical etching process.

[0041] The non-destructive transfer process of MoSi2N4 film was optimized. Polymethyl methacrylate (PMMA) was evenly spin-coated on the Cu / Mo substrate using a coating machine, and then placed on a 120 ℃ hot plate for baking. The PMMA-covered MoSi2N4 film was immersed in a 0.2 mol / L (NH4)2S2O8 aqueous solution to etch the Cu substrate. The PMMA-coated MoSi2N4 film was separated from the Cu / Mo substrate by soaking at 70 ℃ for 30 min, and the PMMA-coated MoSi2N4 composite film was flatly floated on the surface of the (NH4)2S2O8 aqueous solution. The surface residue was removed by repeated washing with deionized water several times. A corner of the target substrate (germanium substrate) was clamped and slowly immersed in the solution from the side to avoid large fluctuations in the liquid level. The germanium substrate was moved directly below the film, and one side of the film was attached to it, and it was slowly lifted to the liquid surface to ensure that there were no wrinkles when combined with the germanium substrate, and the film did not overlap until the composite film structure was completely fished out from the solution. The film was dried at 100 °C to remove moisture from the film and make it fit tightly to the germanium substrate. It was then immersed in hot acetone at 55 °C to remove the PMMA layer. Finally, the film and the germanium substrate were repeatedly cleaned with isopropanol, and the germanium substrate was quickly dried with high-purity nitrogen (volume purity 99.999%) to obtain the MoSi2N4 film transferred to the target substrate.

[0042] For the design and optimization of the heterostructure construction process, after completing the pretreatment of the germanium wafer and the film transfer, in order to form a cleaner contact interface, we adopted a simplified hard mask process preparation process to ensure the quality of the single-layer film and avoid the doping of the two-dimensional semiconductor material by the photolithography process. The hard mask plate is a square opening area with a size of 70 μm×70 μm. The metal hard mask plate is tightly attached to the Ge substrate, and the metal electrode composite structure is prepared by electron beam evaporation. The ohmic contact electrode is Au / Ti / Au (50 nm / 5 nm / 50 nm) composite structure from bottom to top, and the Schottky contact electrode is Al / Ti / Au (50 nm / 5 nm / 50 nm) composite structure from bottom to top. The bottom metal Au or Al is used as the contact layer metal, the middle layer Ti is used as the bonding layer, and the top metal Au forms a good contact with the probe.

[0043] According to the above process flow, the Figure 1 The heterojunction structure shown. Figure 1 The preparation process is shown in Figure 1. Electron beam evaporation was used to prepare metal electrodes of different types and thicknesses in this experiment. The equipment model was ULVACei-501z from Japan’s ULVAC Co., Ltd. In the experiment, the evaporation chamber temperature was maintained below 60 °C and below 3×10 -4In a vacuum environment of 1.377 Pa, Ti, Au, Al metal electrodes and their composite metal structures are evaporated at a rate of 0.2 nm / sec. The evaporation rate and film thickness are precisely controlled by the crystal oscillator. The film purity is high, and high-quality metal electrodes are prepared. The heterojunction is composed of a top metal electrode 3, a MoSi2N4 film insertion layer 2, a germanium substrate 1, and a bottom metal electrode 4 from top to bottom. The MoSi2N4 film insertion layer 2 and the top metal electrode 3 are sequentially arranged on the top of the germanium substrate 1. The top metal electrode 3 is a Schottky contact electrode of a bottom-up laminated composite structure of aluminum / titanium / gold or an ohmic contact electrode of a bottom-up laminated composite structure of gold / titanium / gold. The top metal electrode 3 is evenly and stably arranged on the top of the germanium substrate 1. The MoSi2N4 film insertion layer 2 is a MoSi2N4 film with a thickness of 1.17 nanometers, and the MoSi2N4 film used is grown by chemical vapor deposition. The germanium substrate 1 is a p-type lightly doped germanium sheet (p-Ge). A bottom metal electrode 4 is arranged at the bottom of the germanium substrate 1. The bottom metal electrode 4 in contact with the germanium substrate 1 is a titanium / gold top-down laminated composite structure. The bottom metal electrode 4 in contact with the germanium substrate 1 serves as an ohmic contact electrode. The top metal Ti of the bottom metal electrode 4 has a thickness of 5 nm and serves as a contact layer and an adhesive layer. The bottom metal Au of the bottom metal electrode 4 has a thickness of 50 nm and can form a good contact with the probe.

[0044] like Figure 2 As shown in the figure, the morphology and size of the MoSi2N4 film on the germanium substrate were further characterized by atomic force microscopy (AFM). The actual thickness of the MoSi2N4 film on the germanium substrate was measured to be about 1.17 nm. If the interference of impurities on the substrate surface is excluded, the MoSi2N4 film is considered to be sufficiently flat and stable, with good cleanliness and roughness. In this experiment, the atomic force microscope model used is the Dimension Icon AFM of Bruker, Germany.

[0045] like Figure 3 As shown in the figure, Raman spectroscopy is used to obtain the characteristic peaks of two-dimensional materials to characterize the phase and quality of the transferred single-layer MoSi2N4 film. The Raman laser power is 5 mW and the wavelength is 532 nm. In addition to the 300 cm peaks on the Ge substrate, the -1 In addition to the characteristic peak (Ge peak), the experiment also measured several significant characteristic peaks of MoSi2N4 material, namely 348 cm -1 、589 cm -1 、633 cm -1 、693 cm -1 、928 cm -1 and 1051 cm -1The Raman peaks correspond to the three vibration modes of Mo-N, Si-N, and Mo-Si-N in the MoSi2N4 crystal material, indicating that the transferred MoSi2N4 film maintains a high quality. The equipment model used in this experiment is LabRAM HR800 from Horiba, Japan, using a 532 nm laser light source, with the optical power kept below 15 mW and the laser diameter of about 1 μm.

[0046] like Figure 4 As shown, according to Figure 1 The basic structure of the heterojunction is shown in the figure. A large area of ​​heterojunction arrays was prepared. The images were characterized under a low-power optical microscope. The square area of ​​a single heterojunction is the effective area of ​​the junction area. The square area is the top metal electrode (Top electrode) based on the hard mask process, with a side length of 70~72 μm. Multiple top metal electrodes are arranged uniformly and stably over a large area. The basic structure from top to bottom is top metal electrode-MoSi2N4 film-germanium substrate-bottom ohmic electrode. The device edge and surface are flat, indicating that the device preparation process is simple and controllable. The optical microscope used in this experiment is a Nikon LV100ND from Japan, which consists of a lens barrel, a stage, a condenser, an objective lens and an eyepiece. The objective lens magnifications are 2.5 times, 5 times, 20 times, 50 times and 100 times respectively. When used with an eyepiece, it can be magnified up to 1000 times, and the field of view accuracy can reach the sub-micron level.

[0047] like Figure 5 As shown in the figure, the interfaces of various materials in the Al / MoSi2N4 / Ge heterostructure were characterized by transmission electron microscopy. By analyzing and comparing the boundaries with different contrasts in the TEM image, we can clearly observe the clear interface morphology between the layers of materials. The different contrasts indicate that there are obvious interfaces between the materials (scale bar: 20 nm). There is an obvious sub-nanometer thick MoSi2N4 intermediate layer between the contact interface of the Al electrode and the Ge substrate. Figure 6 The X-ray energy spectrum element analysis image corresponding to this position is analyzed. The element enrichment represented by each area fully demonstrates the stability of the interface between the materials in the Al-MoSi2N4-Ge contact structure and proves Figure 6 The atomic thickness of the MoSi2N4 film within the range marked by the middle dashed line, and the Mo-Si-N element enrichment area has been marked within the dashed line (scale: 20 nm). The TEM equipment used in this experiment is FEI Titan Cubed Themis G2 300, which has ultra-high resolution and is used to observe the interface morphology and structural characteristics in the mixed-dimensional device. At the same time, the energy dispersive X-ray spectrum analysis technology equipped with the TEM equipment is used to determine the types and contents of elements contained in the sample, which provides an important basis for the performance optimization and mechanism analysis of the intercalation device.

[0048] Figure 7-Figure 12 The electrical performance test and result analysis of the heterojunction. During the room temperature electrical performance measurement process, the prepared device is placed on the probe station stage, the device structure is magnified through a microscope, the distance between the probe and the object to be tested is clearly observed under a low-power microscope, the probe is accurately moved close to the sample using the probe station, and then switched to a high-power microscope to make it directly contact the device electrode, forming an electrical path, and outputting the electrical signal and transmitting it to the semiconductor analyzer. The corresponding electrical test results are identified and presented in the form of images, characterizing the DC electrical behavior of the heterojunction and measuring the diode switching ratio. The B1500A semiconductor device analyzer from Agilent Technologies of the United States was used in this experiment, the conventional probe station model is the Cascade M150 from the United States, and the optical microscope used is the SZX7 from Olympus of Japan.

[0049] In the process of low-temperature electrical performance measurement, the low-temperature probe station is specially used to test the performance of semiconductor samples under low-temperature conditions, with the help of molecular pumps to reach 10 -3 The high vacuum state of Pa is achieved by the temperature controller under high vacuum conditions to achieve precise control in the temperature range of 232~285 K to achieve a stable temperature environment and avoid oxidation of germanium-based devices, ensuring the accuracy and reliability of device performance results. The test environment temperature is changed by this device, thereby changing the contact electrical characteristics of metal / germanium, and the current-voltage curves at different temperatures are tested, and based on this, the metal / germanium semiconductor Schottky barrier height in this experimental system is calculated. The low-temperature probe station model used in this experiment is the Lake Shore TTPX from the United States, and the temperature controller model is the Lake Shore Model 336.

[0050] In this example, the above characterization method confirmed the stability of the Al / MoSi2N4 / Ge heterostructure. Then, the electrical performance of the heterostructure was measured by the semiconductor analyzer B1500A at room temperature and compared with the Al / Ge heterostructure without intercalation structure. The top metal electrode was grounded and the bias voltage range was -1V~+1V. The measurement results are shown in Figure 1. Figure 7 As shown, the Al / p-Ge device with direct contact between the metal electrode and the semiconductor exhibits symmetrical IV The electrical properties of the device are good, and the current value is large, showing the characteristics of ohmic contact, which proves that p-Ge has a strong Fermi level pinning effect. However, after inserting MoSi2N4 film between Al and p-Ge, the Al / MoSi2N4 / p-Ge device has obvious on-state and off-state currents, among which the on-state current is maintained at a high level, and the on-off ratio exceeds 10 3 .

[0051] In this embodiment, we randomly sampled and collected a large number of test results through electrical testing to confirm that the device has stable and uniform IV Characteristics. The repeatability of the electrical performance of the Al / MoSi2N4 / p-Ge device is as follows Figure 8 As shown in the figure, 20 devices were randomly measured on the same substrate, and the test conditions were -1 V~+1 V. The device performance was uniform and stable over a large range, showing significant Schottky rectification characteristics, indicating the existence of a large hole barrier. Compared with the Al / p-Ge ohmic contact characteristics under non-intercalation conditions, this result shows that MoSi2N4 effectively alleviates the Fermi level pinning effect between metal and p-type Ge, and realizes the regulation from ohmic to Schottky contact.

[0052] like Fig. 9 As shown in the figure, compared with the control performance of other insertion layer materials, we have achieved the lowest closed-state current value and more than 5×10 3 The maximum on / off ratio.

[0053] In this embodiment, the typical current-temperature test is further used to extract the Schottky barrier height. The Al / MoSi2N4 / p-Ge heterojunction is measured in the temperature range of 232~285K. IV Characteristics, results such as Fig.10 As shown in Figure 2, the device electrical behavior exhibits a significant temperature dependence, which is consistent with the Schottky barrier leakage current characteristics of the thermal electron emission model. The Al / MoSi2N4 / p-Ge heterojunction has a significant effective Schottky barrier height (Φ B ), which fully proves that the MoSi2N4 thin film insertion layer effectively alleviates the original Fermi level pinning effect.

[0054] In order to verify the regulation effect of the p-type germanium Fermi level pinning effect, we replaced the high work function metal electrode Au and used the same process to prepare Au / Ge and Au / MoSi2N4 / Ge heterojunctions. Under the same test conditions, we obtained their electrical properties and compared them with Al / Ge and Al / MoSi2N4 / Ge heterojunctions.

[0055] like Fig.11 As shown in (a), in the device without MoSi2N4 thin film insertion layer, Al / Ge and Au / Ge both produce the same IV The characteristics of the metal / p-type germanium interface are good ohmic contacts, and the charge transfer effect of the low work function electrode Al and the high work function electrode Au is consistent, indicating that there is indeed a serious Fermi level pinning effect at the metal / p-type germanium interface. The corresponding band structure is shown in Fig.11 As shown in (b), the pinning site is close to the top of the germanium valence band, and contact with various metals results in barrier-free transport of holes.

[0056] like Fig.12 As shown in (a), in the device with MoSi2N4 thin film insertion layer, Al / MoSi2N4 / Ge and Au / MoSi2N4 / Ge heterojunctions show different IV Characteristics, Al / MoSi2N4 / Ge device has obvious rectification characteristics and small leakage current, while Au / MoSi2N4 / Ge heterojunction still shows approximately ohmic contact characteristics and large leakage current. This is because the band structure changes at this time, such as Fig.12 As shown in (b), MoSi2N4 as an intermediate layer effectively weakens the interfacial Fermi level pinning. When the Al electrode with a lower work function contacts MoSi2N4 / Ge, the depinning Fermi level rises significantly from the original position (top of the valence band) to close to the bottom of the germanium conduction band, thereby generating a significant hole barrier and causing a smaller leakage current. However, due to the high work function of the Au electrode itself, when it contacts MoSi2N4 / Ge, the depinning Fermi level at the interface tends to decrease. After the overall Fermi level reaches equilibrium, it is still located near the germanium valence band, so the hole barrier generated is smaller, resulting in a larger leakage current.

[0057] Through the above method, the semiconductor heterojunction based on MSi2N4 mediated interface regulation proposed in the present invention was successfully prepared. This work uses transition metal silicon nitride compound MSi2N4 material as a medium and molybdenum silicon nitride compound MoSi2N4 film as an example to propose a general and scalable interface engineering regulation strategy, which provides a new way to modulate and understand Fermi level pinning, and helps to give full play to the intrinsic characteristics of new semiconductor materials and improve device performance, so as to achieve application in high-performance electronic and optoelectronic devices, and provide a new technical approach for the design and manufacture of next-generation semiconductor devices.

[0058] The results of the embodiments show that the present invention proposes a semiconductor heterojunction and a manufacturing method based on MSi2N4-mediated interface regulation, uses a single-layer two-dimensional semiconductor material as an insertion layer to improve the germanium contact, and ensures the quality of the single-layer film through a simplified hard mask process, effectively weakening the p-type germanium Fermi level pinning effect. With different electrodes, the flexible and controllable transformation of metal / p-type germanium ohmic contact and Schottky contact is achieved, and a linear ohmic contact with high on-current and a Schottky contact with a high rectification ratio are obtained. The process conditions are stable and reliable, clean and lossless, and can realize the large-scale preparation of germanium heterojunctions. The electrical properties are uniform and repeatable, and have high practical application value. The present invention optimizes the structure and process of metal-semiconductor contact, thereby further improving the performance and stability of traditional devices. The method involved is simple, efficient, and low-cost, and is compatible with the increasingly mature mainstream semiconductor process. It has great application potential and provides a feasible idea for the future development of mixed-dimensional devices and integrated circuits. At the same time, it also provides strong support for promoting the sustainable development of semiconductor technology in the post-Moore era.

Claims

1. A semiconductor heterojunction based on MSi2N4 mediated interface regulation, characterized in that: The heterojunction consists of a top metal electrode, an MSi2N4 thin film insertion layer, a germanium substrate, and a bottom metal electrode from top to bottom. The top metal electrode is evenly and stably arranged on the top of the germanium substrate as a Schottky contact electrode or an ohmic contact electrode; among them, the Schottky contact electrode is an aluminum / titanium / gold stacked composite structure from bottom to top, and the ohmic contact electrode is a gold / titanium / gold stacked composite structure from bottom to top.

2. The semiconductor heterojunction based on MSi2N4 mediated interface regulation according to claim 1, characterized in that: The MSi2N4 thin film insertion layer in contact with the germanium substrate is a MSi2N4 semiconductor thin film with a thickness of 1 to 2 nanometers, wherein M is a metal element Mo or W, and the MSi2N4 thin film used is grown by chemical vapor deposition; the heterojunction inserts a single-layer two-dimensional semiconductor MSi2N4 thin film insertion layer between the top metal electrode and the germanium substrate, and forms a silicon-nitride compound semiconductor MoSi2N4 or WSi2N4 by adjusting the metal element composition in the MSi2N4.

3. The semiconductor heterojunction based on MSi2N4 mediated interface regulation according to claim 1, characterized in that: The germanium substrate is a p-type lightly doped germanium sheet. A bottom metal electrode is arranged at the bottom of the germanium substrate as an ohmic contact electrode, and a titanium / gold stacked composite structure is formed from top to bottom.

4. A method for manufacturing a semiconductor heterojunction based on MSi2N4 mediated interface regulation according to any one of claims 1 to 3, characterized in that: The steps include: (1) A lightly doped p-type germanium substrate was used, which was sequentially immersed in acetone and isopropanol for ultrasonic cleaning to remove surface impurities, and then diluted hydrofluoric acid and deionized water were used to wash to remove surface oxides; (2) Forming a good titanium / gold bottom metal electrode contact on the back of the germanium substrate through vacuum electron beam evaporation technology; (3) A single-layer MSi2N4 thin film is obtained by chemical vapor deposition and transferred to a treated germanium substrate by chemical etching to form a MSi2N4 / Ge structure; (4) Through a simplified hard mask process, the metal hard mask is tightly attached to the MSi2N4 film of the MSi2N4 / Ge structure, exposing the area in contact with the top metal electrode; (5) Using vacuum electron beam evaporation technology, a top metal electrode composite structure in contact with the MSi2N4 film is prepared.

5. The method for manufacturing a semiconductor heterojunction based on MSi2N4 mediated interface regulation according to claim 4, characterized in that: In step (1), the hydrofluoric acid used is obtained by diluting the original concentration hydrofluoric acid with deionized water in a volume ratio of 1:8, the concentration of the original hydrofluoric acid is 40wt%, and the washing time in the hydrofluoric acid and deionized water is 1 min.

6. The method for manufacturing a semiconductor heterojunction based on MSi2N4 mediated interface regulation according to claim 4, characterized in that: In step (2), a diamond cutter is first used to scratch the back of the germanium substrate to produce a large number of defects, and then a vacuum electron beam evaporation is used to sequentially evaporate a Ti layer with a thickness of 5-6 nm and an Au layer with a thickness of 50-51 nm in the bottom metal electrode to form a good ohmic contact with the germanium substrate at the bottom.

7. The method for manufacturing a semiconductor heterojunction based on MSi2N4 mediated interface regulation according to claim 4, characterized in that: In step (3), the single-layer MSi2N4 film obtained by chemical vapor deposition is a single-layer two-dimensional film grown on a copper / molybdenum substrate, and then polymethyl methacrylate is spin-coated to cover the MSi2N4 film; the Cu substrate is etched using a 0.1-0.3 mol / L (NH4)2S2O8 aqueous solution, and the MSi2N4 film is separated from the copper / molybdenum substrate and floated flat on the surface of the solution at 60-80 °C for 20-40 min, and then the germanium substrate is clamped and immersed in the (NH4)2S2O8 aqueous solution from the side, and the germanium substrate is moved to the bottom of the MSi2N4 film, and one side of the MSi2N4 film is attached to the upper surface of the germanium substrate, and then lifted to the liquid surface to ensure that there are no wrinkles when combined with the germanium substrate, and the MSi2N4 film does not overlap, until the MSi2N4 film structure is completely removed from the solution to complete the transfer.

8. The method for manufacturing a semiconductor heterojunction based on MSi2N4 mediated interface regulation according to claim 4, characterized in that: In step (4), after the metal hard mask is bonded to the germanium substrate, the exposed pattern is a square area with a side length of 70-72 μm.

9. The method for manufacturing a semiconductor heterojunction based on MSi2N4 mediated interface regulation according to claim 4, characterized in that: In step (4), vacuum electron beam evaporation is used to sequentially deposit the Au layer with a thickness of 50-51 nm, the Ti layer with a thickness of 5-6 nm, and the Au layer with a thickness of 50-51 nm in the top metal electrode to form a good ohmic contact on the top; vacuum electron beam evaporation is used to sequentially deposit the Al layer with a thickness of 50-51 nm, the Ti layer with a thickness of 5-6 nm, and the Au layer with a thickness of 50-51 nm in the top metal electrode to form a good Schottky contact on the top.

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