Method for fabricating semiconductor device on basis of van der waals contact, and device

Abstract

Disclosed are a method for fabricating a semiconductor device on the basis of a van der Waals contact, and a device fabricated thereby. The method comprises: forming an ice layer on the surface of a semiconductor substrate in a low-temperature vacuum environment, and depositing a metallic film on the surface of the ice layer; and finally, sublimating the ice layer, so that the metallic film settles onto the surface of the semiconductor substrate to form a van der Waals contact, thereby obtaining a metal-semiconductor device. The method for fabricating a semiconductor device of the present invention has a simpler process, does not require high-temperature conditions, eliminates the need for organic solvents, and is environmentally friendly, thereby avoiding the influence of solvents or high-temperature treatment conditions on the device, and achieving rapid and efficient processing for temperature-sensitive semiconductor substrates; moreover, the resulting semiconductor device has more excellent performance, and the resulting field effect transistor has both high on-off ratio and high mobility and shows no hysteresis.

Description

A method for preparing a semiconductor device based on van der Waals contact and a device Technical Field

[0001] The present invention belongs to the field of optoelectronic device manufacturing, and in particular relates to a method for preparing a semiconductor device based on van der Waals contact and a device. Background Art

[0002] Van der Waals (vdW) integration between semiconductors and metal electrodes with pristine interfaces is crucial for unlocking novel device functionalities, advancing fundamental materials research, and achieving unprecedented performance. However, the practical realization of vdW contacts in fragile material systems faces significant challenges. These challenges are particularly pronounced for two-dimensional semiconductor materials, which have atomically thin bodies and flat surfaces with arbitrarily stacked layered structures. Metallization of two-dimensional semiconductors has traditionally been achieved via high-energy metal deposition methods such as electron beam / thermal evaporation and sputtering, which inevitably introduce defects, strain, and metal diffusion, leading to interfacial chemical disorder and Fermi level pinning. The challenges of establishing reliable, high-quality vdW contacts to semiconductors highlight the importance of addressing these obstacles and realizing the full potential of next-generation semiconductor technologies.

[0003] In order to make two-dimensional semiconductors have high-quality vdW contacts after metallization, researchers proposed and used physical transfer technology to demonstrate field-effect transistors made of transition metal disulfide thin films. In particular, MoS2 transistors with transferred electrodes showed 10 6 ~10 9 The excellent on / off ratio highlights the enormous potential of two-dimensional semiconductors. High-quality metal-semiconductor contacts rely on pre-deposition, physical exfoliation, and transfer to the two-dimensional semiconductor via a flexible substrate. As a result, the intrinsic physicochemical properties of the two-dimensional semiconductor are well preserved, forming an ideal vdW contact. In addition, researchers have proposed a graphene-assisted metal transfer printing technique for transferring arbitrary metal electrodes.

[0004] Recently, wafer-scale universal vdW integration has been achieved using a thermally decomposable polymer (poly(propylene carbonate)) as a buffer layer between a metal and a two-dimensional semiconductor. The polymer layer is dry-decomposed into a gas at 300°C, resulting in the precipitation of a clean and sharp semiconductor-metal interface on the two-dimensional semiconductor. These methods have demonstrated the ability to transfer arbitrary metal electrodes onto two-dimensional semiconductors to achieve vdW contacts. However, the specific operation process has severely limited their application to bulk semiconductors (such as the widely used organic-inorganic halide perovskites, which cannot withstand temperatures as high as 300°C). The reactivity of organic-inorganic halide perovskites greatly hinders the formation of reliable perovskite contacts. Therefore, it is necessary to develop a universal vdW integration technology that is not limited to two-dimensional semiconductors but can be well extended to bulk or perovskite brittle materials including peritectics.

[0005] Summarizing existing technologies, there are still some difficulties in preparing metal-van der Waals contact interfaces, such as undesirable structural damage, fragmentation, wrinkles, and the formation of interface bubbles. In addition, the release process of the electrode window requires the removal of the stamping support, which usually requires the use of chemical solutions and / or heat treatment. This process inevitably produces chemical residues that may reduce and change the performance of the device. In addition, it also limits the applicability of this technology to specific material systems. For example, the widely used organic-inorganic halide perovskites cannot withstand temperatures as high as 300°C, which constitutes a key limitation. Therefore, it is necessary to develop a universal vdW integration technology that is not limited to two-dimensional semiconductors, but can be well extended to bulk or brittle materials including perovskites.

[0006] Summary of the Invention

[0007] This invention describes a solvent-free, chemically residue-free method for forming van der Waals contacts between metals and semiconductors. It also provides a method for fabricating semiconductor devices based on van der Waals contacts, overcoming technical challenges associated with traditional manufacturing methods, such as residual solvents and the need for high-temperature processing.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0009] A method for preparing a semiconductor device based on van der Waals contact comprises: forming an ice layer on the surface of a semiconductor substrate in a low-temperature vacuum environment, and depositing a metal film on the surface of the ice layer; finally, the ice layer sublimates, and the metal film settles onto the surface of the semiconductor substrate, forming a van der Waals contact between the metal electrode and the semiconductor, and obtaining a metal-semiconductor device.

[0010] This invention uses an ice layer as a buffer to prevent high-energy metal clusters from directly bombarding the substrate sample. As the ice sublimates, the metal electrode naturally settles onto the semiconductor. Unlike typical wafer-to-wafer physical transfer processes, we employ a simpler, more efficient in-situ transfer process that eliminates contamination and damage and is suitable for large-scale production.

[0011] A method for preparing a semiconductor device based on van der Waals contact specifically comprises the following steps:

[0012] (1) placing a semiconductor substrate in a vacuum chamber and cooling it to below 130K to form an ice layer on the surface of the semiconductor substrate;

[0013] (2) transferring the entire sample with the ice film formed thereon to a low-temperature coating chamber under a vacuum environment;

[0014] (3) depositing a metal thin film in a coating chamber;

[0015] (4) After the metal deposition is completed, the entire sample is returned to room temperature in a vacuum environment, and the ice layer sublimates. At this point, the construction of the ice-assisted metal-semiconductor van der Waals contact and the processing of the semiconductor device are completed.

[0016] Optionally, before step (1), a mask is pre-covered on the semiconductor substrate, and the mask is removed simultaneously in step (4) to obtain a semiconductor device with a specific pattern structure.

[0017] Preferably, the metal film material is one or more of Au, Ag, Al, Ti, Cr, Ni, Cu, Co or Pd.

[0018] Preferably, the semiconductor substrate material is one or more of MoS2, WS2, MoTe2, Si, Ge, GaAs, IGZO or perovskite.

[0019] As a preference, the low temperature vacuum environment is: vacuum degree 1~10*10 -7 mbar; the temperature is below 130K. Further, in step (1), the vacuum degree of the vacuum chamber is 3*10 -7 mbar or above; more preferably (5 to 7)*10 -7 mbar; more preferably the vacuum degree is 6*10 -7 mbar. In step (2), the vacuum degree of the vacuum environment is 2*10 -5 Pa or above; further (4-6)*10 -5 Pa.

[0020] Preferably, the total thickness of the ice layer is 100 nm-200 nm.

[0021] Preferably, the metal film deposition thickness is 30nm-100nm.

[0022] Preferably, after the ice layer is formed and before the metal film is deposited, a hard mask plate may be optionally covered on the ice layer; after the metal film is deposited, the hard mask plate is removed.

[0023] A semiconductor device is prepared by the method described in any one of the above technical solutions.

[0024] Preferably, the device is a field effect transistor.

[0025] As an example, the on-off ratio of the field effect tube is 10 9 and above; migration rate is 70cm 2 V -1 s -1 above.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The method for preparing a semiconductor device of the present invention has a simpler process, does not require high temperature conditions, does not require the use of organic solvents, is environmentally friendly, and avoids the influence of solvents or high temperature processing conditions on the device. At the same time, it can also achieve fast and efficient processing for temperature-sensitive semiconductor substrates, and the performance of the obtained semiconductor device is better. The on-off ratio and mobility of the obtained field-effect transistor are both very high, and there is no hysteresis phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 shows a process of covering a substrate with a metal hard mask (this process is optional).

[0029] FIG2 is a schematic diagram of ice growth after the entire substrate is cooled;

[0030] FIG3 shows the deposition of evaporated metal on a substrate sample after ice growth;

[0031] FIG4 is a schematic diagram showing the final formation of a van der Waals contact after the entire sample is restored to room temperature and the mask (if any) is removed;

[0032] Figure 5: Metal-semiconductor van der Waals contact interface characterized by transmission electron microscopy (MoS2-Au as an example);

[0033] Figure 6 shows the electrical characteristics of a van der Waals contact field effect transistor prepared using an ice-assisted process (taking MoS2-Au as an example). DETAILED DESCRIPTION

[0034] A method for preparing a semiconductor device based on van der Waals contact, the process steps comprising:

[0035] 1. If the metal layer needs to be patterned, a metal hard mask plate 1 (thickness 100μm, usually made of stainless steel, copper, nickel, etc.) can be used to cover the target substrate 2. The target substrate can be a two-dimensional material, a semiconductor such as perovskite.

[0036] 2. Place the entire sample and metal hard mask plate (if any) into a vacuum chamber (vacuum degree 6*10 -7 mbar), and cool the sample stage carrying the sample to below 130K.

[0037] 3. Deposit ice layer 3. The deposition rate and thickness of ice layer 3 are controlled by a micro-leak valve with an accuracy of 20 nm. The total thickness of the ice layer can be controlled to 100 nm-200 nm.

[0038] 4. After the ice layer 3 is deposited, the entire sample is placed in a vacuum environment (5*10 -5 Pa) is transferred to the low-temperature coating chamber.

[0039] 5. Deposit a metal thin film 4 on the sample using conventional thermal deposition or electron beam deposition technology. The deposition thickness can be within the range of 30nm-100nm.

[0040] 6. After metal deposition, the entire sample is returned to room temperature under vacuum, the ice layer sublimes, and the metal hard mask (if present) is removed. This completes the ice-assisted metal-semiconductor van der Waals contact. Evidence of the van der Waals contact is demonstrated using transmission electron microscopy (Figure 5).

[0041] Figure 5 shows a transmission electron microscopy (TEM) image of the Au-MoS2 van der Waals contact interface (i.e., the target substrate is the two-dimensional material MoS2; the metal film 4 is a 50nm thick Au layer). The upper half of the image shows the Au layer, and the lower half shows the MoS2 layer. The TEM image demonstrates a very clean, sharp interface between the Au and MoS2 layers. Furthermore, Au atoms do not penetrate into the MoS2 material, demonstrating that ice-assisted metal integration achieves a good van der Waals contact between the metal and the two-dimensional material.

[0042] Figure 6 shows the output and transfer curves of a van der Waals contact field-effect transistor fabricated using an ice-assisted process. The substrate material of the field-effect transistor is a single-layer MoS2 mechanically exfoliated on SiO2 / Si, with a SiO2 thickness of 280nm. The electrode is Au with a thickness of 50nm. The channel width of the field-effect transistor is 80μm and the channel length is 15μm. Using our technology, the MoS2-based field-effect transistor we fabricated achieved a high-resolution CMOS process with a CMOS performance of up to 6.3*10 9 On / off ratio, very low hysteresis, and high mobility (70(cm 2 V -1 s-1 ))'s outstanding performance.

[0043] It can be seen that the field effect transistor obtained by using the ice layer-assisted method to achieve metal-van der Waals contact has a 10 10 Ultra-high on-off ratio, high mobility and extremely low hysteresis performance.

Claims

1. A method for preparing a semiconductor device based on van der Waals contact, characterized in that: include: In a low-temperature vacuum environment, an ice layer is formed on the surface of the semiconductor substrate, and a metal film is deposited on the surface of the ice layer; finally, the ice layer sublimates, and the metal film settles to the surface of the semiconductor substrate, forming a van der Waals contact and obtaining a metal-semiconductor device.

2. The method for preparing a semiconductor device based on van der Waals contact according to claim 1, characterized in that: The metal is one or more of Au, Ag, Al, Ti, Cr, Ni, Cu, Co or Pd.

3. The method for preparing a semiconductor device based on van der Waals contact according to claim 1, characterized in that: The semiconductor substrate material is one or more of MoS2, WS2, MoTe2, Si, Ge, GaAs, IGZO or perovskite.

4. The method for preparing a semiconductor device based on van der Waals contact according to claim 1, characterized in that: Low temperature vacuum environment: vacuum degree 1~10*10 -7 mbar; temperature is below 130K.

5. The method for preparing a semiconductor device based on van der Waals contact according to claim 1, characterized in that: The total thickness of the ice layer is 100nm-200nm.

6. The method for preparing a semiconductor device based on van der Waals contact according to claim 1, characterized in that: The thickness of the metal film deposition is 30nm-100nm.

7. The method for preparing a semiconductor device based on van der Waals contact according to claim 1, characterized in that: After forming the ice layer and before depositing the metal film, a hard mask plate can be optionally covered on the ice layer; after depositing the metal film, the hard mask plate is removed.

8. A semiconductor device, characterized in that: The invention is prepared by the method according to any one of claims 1 to 7.

9. The semiconductor device according to claim 8, wherein The device is a field effect tube.

10. The semiconductor device according to claim 8, wherein The on-off ratio of the field effect tube is 10 9 and above; migration rate is 70cm 2 V -1 s -1 above.

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