CN115787080A

CN115787080A - Preparation method of wafer-level self-supporting CdTe film

Info

Publication number: CN115787080A
Application number: CN202211500128.5A
Authority: CN
Inventors: 白伟; 曹贺淳; 唐晓东; 王旭东; 王建禄
Original assignee: Shanghai Institute of Technical Physics of CAS; East China Normal University
Current assignee: Shanghai Institute of Technical Physics of CAS; East China Normal University
Priority date: 2022-11-28
Filing date: 2022-11-28
Publication date: 2023-03-14

Abstract

The invention discloses a preparation method of a wafer-level self-supporting CdTe film, which comprises the following steps: providing a two-dimensional material/sapphire substrate; growing a CdTe thin film on the surface of the two-dimensional material/sapphire substrate; separating the CdTe/two-dimensional material from the surface of the sapphire substrate by a method of stripping the heat release adhesive tape; the high-quality self-supporting CdTe film can be obtained by heating to remove the viscosity of the heat release adhesive tape. The method utilizes the good lattice matching between the sapphire substrate and the CdTe film, utilizes a two-dimensional material as a transition layer, avoids bonding of a dangling bond on the surface of the sapphire and the CdTe film, grows the CdTe film through a molecular beam epitaxy system, then utilizes a heat release adhesive tape to strip the CdTe film from the substrate, and finally heats and removes the viscosity of the adhesive tape to obtain the self-supporting CdTe film. The self-supporting CdTe film prepared by the invention can be widely compatible with silicon-based electronic devices, and has a great application value in the aspects of flexible wearable electronic devices and the like.

Description

Preparation method of wafer-level self-supporting CdTe film

Technical Field

The invention relates to the field of photoelectric semiconductor film manufacturing, in particular to a preparation method of a wafer-level self-supporting CdTe film.

Background

CdTe is a semiconductor with cubic zincblende structure, and the CdTe film is prepared through epitaxial growth with conventional substrate material. The first is to epitaxially grow CdTe on cubic crystals with large mismatch such as silicon, germanium and gallium arsenide along the same crystal orientation, but because of huge lattice mismatch between the CdTe and the cubic crystals, the lattice distortion at the interface is serious, so that the CdTe thin films on the substrates have a large number of defects such as dislocation and stacking fault, and the quality of the thin film crystals is seriously influenced. The second is that CdTe grows epitaxially on the sapphire substrate in hexagonal system along the diagonal direction of the cubic crystal cell body, and the CdTe growing along the direction has in-plane lattice constant similar to that of the sapphire substrate, so that the grown CdTe film has relatively high quality. However, the CdTe film directly epitaxially grown on the sapphire substrate is difficult to be directly compatible with the current mainstream silicon-based integrated circuit process, and strong force exists between the substrate and the CdTe film, so that the CdTe film is difficult to be transferred and integrated into a silicon-based electronic device, which limits the application of the CdTe film in the field of semiconductors, and therefore, a new preparation method needs to be designed.

Disclosure of Invention

The purpose of the invention is: the method can utilize weak van der Waals acting force between the two-dimensional materials/sapphire substrates, and can freely transfer the self-supporting CdTe film to any substrate through a stripping-heat releasing method. The problem of poor compatibility of the high-quality CdTe thin film and a silicon-based electronic device is solved, and the CdTe thin film is widely suitable for other flexible electronic devices.

The specific technical scheme for realizing the purpose of the invention is as follows:

a preparation method of a wafer-level self-supporting CdTe film comprises the following steps: selecting a proper two-dimensional material/sapphire substrate, carrying out pretreatment to obtain a clean surface, assembling the treated substrates, conveying the assembled substrates to a molecular beam epitaxy system, and controlling a molecular beam epitaxy process to epitaxially grow a CdTe thin film on the two-dimensional material/sapphire substrate; the wafer-level self-supporting CdTe film is obtained in a stripping-heat release mode.

The two-dimensional material is one of graphene, molybdenum disulfide and molybdenum ditelluride; the two-dimensional material is a single layer structure.

The clean surface is obtained by cleaning a two-dimensional material/sapphire substrate with acetone, absolute ethyl alcohol and deionized water, and heating at 100 ℃ for 60min under the protection of nitrogen atmosphere.

The substrate assembly is to weld the two-dimensional material/sapphire substrate and the substrate heating bracket through molten metal, wherein: the molten metal is metallic indium or lead-tin alloy.

The CdTe film is prepared by molecular beam epitaxy, wherein: the beam source of molecular beam epitaxy adopts CdTe and Te sources with the purity of more than 7N grade, the beam equivalent pressure ratio is controlled to be CdTe: te = 1: 0.5 to 0.7, the temperature of a heating wire in a molecular beam epitaxy system is controlled to be 280 to 320 ℃, the growth time is controlled to be 10 to 90min, the thickness of the CdTe film grown by epitaxy is 50 to 500nm, the out-of-plane crystal orientation of the film is along the [111] direction, and the size of the film is 0.5cm multiplied by 0.5cm to 1cm multiplied by 1cm.

The stripping-heat release is to strip the CdTe film epitaxially grown from the two-dimensional material/sapphire substrate by the heat release adhesive tape, and then remove the heat release adhesive tape by heating to transfer the CdTe film to any substrate, so as to obtain the self-supporting CdTe film. Wherein: the thermal release adhesive tape is polydimethylsiloxane, the temperature for heating and removing the thermal release adhesive tape is set to be 90-110 ℃, and the heating time is 3-5 min.

The method for growing the CdTe thin film utilizes the lattice constant matched between the CdTe and the sapphire substrate to enable the CdTe to easily nucleate on the CdTe, utilizes weak van der Waals acting force on the surface of the two-dimensional material to isolate strong interaction force between the CdTe and the sapphire substrate, and finally obtains the high-quality continuous self-supporting CdTe thin film on the two-dimensional material/sapphire substrate, and the CdTe thin film can be transferred to any substrate in a stripping-heating release transfer mode.

Compared with the prior art, the CdTe thin film obtained by the method has the characteristics of high quality, large area and continuity, can be separated from the original substrate, is transferred to any other substrate, is suitable for a mainstream silicon-based integrated circuit, and solves the problems of large defect and poor quality of a heteroepitaxial CdTe thin film on a silicon substrate.

Drawings

FIG. 1 is a flow chart for preparing a self-supporting CdTe film provided by the invention;

FIG. 2 is a physical diagram of a wafer-level self-supporting CdTe film prepared by the present invention;

FIG. 3 is a scanning electron microscopy image of a wafer-level self-supporting CdTe film prepared in accordance with the present invention;

FIG. 4 is a high resolution X-ray diffraction pattern of a wafer-level self-supporting CdTe thin film prepared in the present invention on a sapphire substrate and transferred to the silicon substrate by exfoliation-heat release.

Detailed Description

In order to clarify the objects and technical advantages of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is understood that the described embodiments are only specific embodiments of the invention, and not all embodiments. Based on the embodiments of the present invention, other embodiments obtained by a person of ordinary skill in the art without making any creative effort belong to the protection scope of the present invention.

Examples

The embodiment of the invention provides a preparation method of a wafer-level self-supporting CdTe film, which is shown in the attached drawing 1 and comprises the following steps:

step 1: a two-dimensional material/sapphire substrate is provided and cleaned to obtain a clean surface. The specific operation is that acetone, absolute ethyl alcohol and deionized water are respectively used for fully washing the surface of the two-dimensional material 1/sapphire substrate 2, and then the two-dimensional material is heated in the atmosphere protected by nitrogen and baked for 60min at the temperature of 100 ℃ to remove surface water vapor.

Step 2: the two-dimensional material 1/sapphire substrate 2 and the substrate heating holder were assembled. The method comprises the following specific operations of heating a substrate heating support to about 180 ℃, then placing 0.2g of metal indium or lead-tin alloy on the surface of the substrate heating support, after the metal is completely melted, uniformly coating the molten metal by using a tungsten sheet, then horizontally moving the sapphire side of the substrate to the molten metal, repeatedly pushing and pulling to enable the substrate to be fully contacted with the molten metal, and closing the heating temperature of the plate, thus finishing the assembly.

And 3, step 3: and carrying out vacuum pretreatment on the two-dimensional material 1/sapphire substrate 2. Is specifically operated to transfer the assembled substrate and heated holder into a pre-treatment chamber of a molecular beam epitaxy system at a vacuum of 10 deg.C ^-9 Heating the substrate to 200 ℃ under the Torr condition, and heating for 120min to remove impurity molecules adsorbed on the surface during the substrate transmission process.

And 4, step 4: a self-supporting CdTe film 3 is epitaxially grown. Specifically, the substrate is conveyed to a growth chamber of a molecular beam epitaxy system and heated to 280-320 ℃, a mechanical motor is started to enable a substrate heating support to rotate at a constant speed of 0.1r/s, then crucibles containing CdTe and Te sources are heated respectively, the beam equivalent pressure ratio CdTe/Te = 1: 0.5-0.7 is controlled by controlling the heating temperature of the crucibles, after the state is stable, a molecular beam main baffle is opened, the CdTe film 3 starts to grow epitaxially, and the growth time is controlled, so that films with different thicknesses can be obtained.

And 5: lift-off-transfer wafer-level self-supporting CdTe films. Specifically, the CdTe film 3/two-dimensional material 1/sapphire substrate 2 is taken down from a heating bracket, polydimethylsiloxane is tightly attached to the surface of the CdTe film 4, the CdTe film and the substrate are soaked in deionized water for 24 hours, weak van der Waals effect between CdTe and the substrate is destroyed by water molecules, the CdTe film is separated from the substrate, the heat release tape 4 adhered with the CdTe film surface is adhered to the silicon substrate, and the heat release tape is heated at 90 to 100 ℃ for 3 to 5 minutes to destroy the viscosity of the heat release tape 4, so that the self-supporting CdTe film is obtained, wherein the self-supporting CdTe film is shown in figure 2, and the scanning electron microscope image is shown in figure 3.

Referring to fig. 4, the high resolution X-ray diffraction spectrum of the self-supporting CdTe thin film prepared by the present invention on the sapphire substrate and after the film is transferred to the silicon substrate by lift-off-heat release can be seen from the figure: the CdTe thin film 3 growing on the two-dimensional material 1/sapphire substrate 2 through a molecular beam epitaxy system is a single crystal thin film, and the growth direction of the crystal is along the [111] direction; the diffraction peak position of CdTe before and after transfer has no change, and the crystallography property after growth is maintained.

The wafer-level self-supporting CdTe thin film prepared by the embodiment is a single crystal thin film, the epitaxial direction is along the [111] crystal direction, the thin film is highly continuous, and the single crystal CdTe thin film is easily peeled from a native substrate due to weak van der Waals force of a two-dimensional material interface and can be transferred to any other substrate. Compatible with mainstream silicon-based electronic circuits and applicable to various flexible electronic equipment requirements.

The present embodiment is only an example for clearly illustrating the invention, and the person skilled in the art should understand that the scope of the present invention includes not limited to the above embodiment, and various changes made thereto in other forms without departing from the spirit or essential characteristics of the invention are included in the protection scope of the present invention.

Claims

1. A preparation method of a wafer-level self-supporting CdTe film is characterized by comprising the following steps:

selecting a two-dimensional material/sapphire substrate;

cleaning the surface of the two-dimensional material/sapphire substrate;

assembling a two-dimensional material/sapphire substrate and a substrate heating support by a molten metal material;

growing a CdTe thin film on a two-dimensional material/sapphire substrate through a molecular beam epitaxy system;

stripping the CdTe film/two-dimensional material by using a heat release adhesive tape;

removing the heat release adhesive tape by heating to obtain a self-supporting CdTe film; wherein:

the two-dimensional material is one of graphene, molybdenum disulfide and molybdenum ditelluride; the two-dimensional material is of a single-layer structure; growing a CdTe film on the single-layer two-dimensional material;

the method comprises the following steps of growing a CdTe thin film on a two-dimensional material/sapphire substrate through a molecular beam epitaxy system, and specifically comprises the following steps: adopting a beam source to be a CdTe and Te source with the purity of at least 7N grade, controlling the equivalent pressure ratio of the beam to the CdTe to the Te to be = 1: 0.5 to 0.7, controlling the temperature of a heating wire to be 280 to 300 ℃, controlling the growth time to be 10 to 90min and the thickness to be 50 to 500nm, and monitoring the growth state of the CdTe film in real time through a reflective high-energy electron diffractometer;

the self-supporting CdTe thin film is a single crystal thin film, the size of the thin film is 0.5cm multiplied by 0.5cm to 1cm multiplied by 1cm, and the out-of-plane crystal direction of the thin film grown by a molecular beam epitaxy system is along the [111] direction;

the CdTe film/two-dimensional material stripped by the heat release adhesive tape comprises the following components in percentage by weight: the heat release adhesive tape, namely polydimethylsiloxane, is tightly attached to the surface of the CdTe film; extruding bubbles between the thermal release adhesive tape and the CdTe film by using a cotton swab until the thermal release adhesive tape and the CdTe film are fully bonded;

the heat release adhesive tape is removed by heating, wherein the heating temperature is 90 to 110 ℃, and the heating time is 3 to 5min.

2. The method for preparing a wafer-level self-supporting CdTe film as claimed in claim 1, wherein the metallic material is metallic indium or lead-tin alloy.

3. The method for preparing self-supporting CdTe film at wafer level as claimed in claim 1, wherein the prepared self-supporting CdTe film can be transferred to any substrate material.