Laser etching method and system for two-dimensional materials

Abstract

The application provides a laser etching method and system for a two-dimensional material, wherein in-situ real-time monitoring of etching temperature in a single-point laser etching process is used to determine a step-shaped temperature drop characteristic in the single-point laser etching process, laser power required for layer-by-layer etching in a single-layer controllable etching range is obtained according to the step-shaped temperature drop characteristic, and controllable etching of a sample of a specific number of layers of the two-dimensional material is realized according to the laser power. The method and system according to the application can provide higher vertical direction layer-by-layer etching precision, a highly controllable and universal single-layer or layer-by-layer etching scheme, which can realize large-range layer-by-layer etching of two-dimensional materials, and the etching process is controllable and quantifiable, and has large-scale automatic production prospects.

Description

TECHNICAL FIELD

[0001] The present invention belongs to the field of laser etching system, and in particular, the present invention relates to a laser etching method and system for two-dimensional materials. BACKGROUND

[0002] Two-dimensional materials generally have significant quantum confinement effect, and new devices based on two-dimensional materials have wide application prospects and are currently a hot research topic. The thickness or layer number of two-dimensional materials is an important factor determining the performance of devices, and the control of the planar structure and thickness of two-dimensional materials is the key to the preparation of devices. At present, the planar structure of two-dimensional materials can be obtained by mask-chemical etching or laser direct writing etching, and the technology is relatively mature. However, the control of the thickness of two-dimensional materials, especially the precise distribution control of the thickness in the same device, is still in its initial stage. For example, through the control of MBE growth conditions, two-dimensional materials with specific thickness (single layer, double layer, or several layers) can be obtained, but the thickness or layer number is basically single or only a simple layer-by-layer structure limited by crystal growth on the wafer scale. Although mask-chemical etching can achieve a control accuracy of sub-micron or even tens of nanometers in the plane, it is difficult to achieve layer-by-layer control in terms of etching thickness, and the preparation process of layer-by-layer structure is complex. Laser direct writing etching is one of the possible ways to achieve controllable preparation of two-dimensional material devices. By adjusting the intensity and wavelength of the laser, the local temperature of the two-dimensional material can be controlled to excite chemical reactions or physical processes, thereby achieving point-by-point etching. It has been an important goal in the field to achieve higher vertical etching precision in the laser etching process and realize layer-by-layer etching of two-dimensional materials on a large scale. Recent studies have shown that under appropriate laser settings, two-dimensional materials can be etched layer by layer. However, the reported techniques still have various shortcomings, which limit their further application. The main problems are as follows: 1) Since the laser etching process is sensitive to material properties, thermal diffusion environment, and physicochemical reaction conditions, the time and laser power required to etch the material to a specific layer number can only be given empirically, and there is no effective etching strategy; 2) The range of layer-by-layer etching is small. For example, the maximum controllable etching range of layered molybdenum disulfide material achieved by laser etching technology in the reported studies is only three layers. SUMMARY

[0003] To solve the problems of the prior art, the first aspect of the present invention provides a laser etching method for a sample of two-dimensional material, the method comprising:

[0004] determining a stepwise temperature drop feature in the single-point laser etching process by in-situ real-time monitoring of the etching temperature in the process;

[0005] obtaining the etching laser power required for etching the sample within the single-layer controllable etching range according to the stepwise temperature drop feature;

[0006] The etching laser power is used to achieve the controllable etching of a specific layer of the sample.

[0007] Preferably, the single-layer controllable etching range of the sample to be etched comprises controlling the temperature distribution of the sample to decrease layer by layer from the surface layer inward by adjusting the etching environment, wherein the etching environment comprises: substrate thermal conductivity, substrate and sample contact thermal resistance, substrate and ambient temperature, etching environment gas atmosphere, control accuracy and stability of the etching laser power.

[0008] Preferably, the adjustment of the substrate thermal conductivity in the method comprises replacing the substrate material and replacing the substrate surface cover layer type and thickness.

[0009] Preferably, in the method, the determination of the stepwise temperature drop feature through the in-situ real-time monitoring comprises: determining the etching threshold temperature through the etching temperature evolution curve of the sample irradiation center and obtaining the stepwise temperature drop feature, wherein

[0010] Under the premise of no defocusing, the laser power is gradually increased until the temperature of the sample irradiation center is no longer rising synchronously and the inflection point appears, and then the laser power is kept unchanged and the defocusing is not allowed, and the temperature obtained after waiting for a sufficient time until the temperature of the sample irradiation center no longer changes is the etching threshold temperature.

[0011] Preferably, the temperature evolution curve in the method is obtained by real-time detection of Raman spectrum.

[0012] Preferably, the method further comprises:

[0013] Using the temperature evolution curve to determine whether the initial layer thickness of the sample is within the single-layer controllable etching range, if not, etching the sample until its initial layer thickness is within the single-layer controllable etching range, wherein if the etching laser power cannot make the temperature evolution curve appear single-step drop, or the temperature of the irradiation center first increases and then decreases stepwise relative to the etching threshold temperature, or the temperature of the irradiation center is stable at a specific temperature higher than the etching threshold temperature but the instrument detects that etching is still continuing, it can be determined that the initial layer thickness of the sample is not within the single-layer controllable etching range.

[0014] Preferably, the initial layer thickness of the sample in the method can be indirectly obtained by growth preparation conditions, or directly obtained by spectrum or atomic force microscope.

[0015] Preferably, in the method, the etching laser power required for etching the sample within the single-layer controllable etching range according to the stepwise temperature drop feature further comprises:

[0016] determining a specific etching laser power according to the temperature evolution curve, wherein the specific etching laser power corresponds to a single etching layer number of the sample equal to the step number of the stepwise temperature drop feature in the temperature evolution curve corresponding thereto.

[0017] Preferably, the step number of the stepwise temperature drop feature in the method is determined by: under the condition of no defocus, gradually increasing the etching laser power irradiated on the sample so that the irradiation center temperature of the sample gradually reaches and temporarily exceeds the etching threshold temperature, then keeping the laser power unchanged and observing the step number in the process of the irradiation center temperature of the sample returning to the etching threshold temperature.

[0018] Preferably, in the method, each point in the etching area of the sample is etched for a sufficient exposure time using the specific etching laser power, wherein each point is scanned for a single scan, and the single scan is sufficient in exposure time, wherein the sufficient exposure time refers to performing the etching under the condition of no defocus until the temperature of the irradiation center in the etching process is lower than the etching threshold temperature.

[0019] Preferably, in the method, each point is exposed for a single short-time exposure and scanned multiple times to accumulate sufficient total etching time to achieve the sufficient exposure time, instead of being scanned for a single scan.

[0020] A second aspect of the present application provides a two-dimensional material etching system, comprising a controllable power laser source, a temperature detector, a temperature control console, a displacement table and an etching gas atmosphere cavity, wherein

[0021] The controllable power laser source is used to provide etching laser with required power; the temperature detector is used to realize in-situ real-time monitoring of etching temperature; the temperature control console is used to control the temperature distribution of the sample to be within the single-layer controllable etching range; the displacement table is used to control the etching position of the sample; and the etching gas atmosphere cavity is used to form a gas atmosphere surrounding the sample to be etched; and the system is characterized in that

[0022] Further comprising a controller configured to implement the etching method of any one of the above first aspect.

[0023] Compared with the prior art, the layer-by-layer controllable laser etching method and system according to various embodiments of the present application have higher vertical direction layer-by-layer etching precision, realize large-range layer-by-layer etching of two-dimensional materials, and greatly reduce the limitations or requirements of the etching object and the etching environment, and the etching process is controllable and quantifiable, and has the prospect of large-scale automatic production. BRIEF DESCRIPTION OF DRAWINGS

[0024] The embodiments of the present application are further described below with reference to the accompanying drawings.

[0025] Figure 1 A brief flow chart of a layer-by-layer etching method according to one of the preferred embodiments of the present application is shown;

[0026] Figure 2 A brief schematic diagram of a layer-by-layer laser etching system according to one of the preferred embodiments of the present application is shown;

[0027] Figure 3 Evolution curves of the Raman characteristic peaks of molybdenum disulfide and silicon in an etched sample after Lorentz fitting according to one of the preferred embodiments of the present application are shown;

[0028] Figure 4 Optical and Raman imaging results of a sample before and after etching according to one of the preferred embodiments of the present application are shown. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to specific embodiments and the accompanying drawings. The structures, proportions, sizes, etc. shown in the description are merely used to cooperate with the content disclosed in the description for the understanding and reading of those skilled in the art, and do not constitute undue restrictions on the present application or have technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size, which does not affect the effects and purposes produced by the present application, should be included in the scope of the technical content disclosed by the present application.

[0030] The present application proposes a new layer-by-layer laser etching method for two-dimensional materials. The technology has high applicability to etching materials and etching environments, can obtain optimal etching parameters in situ according to etching environmental conditions, and can effectively realize layer-by-layer etching in a larger range. Taking molybdenum disulfide as an example, under a normal etching environment, the control range of layer-by-layer etching can be improved to more than ten layers only by the different adhesion of two-dimensional materials to the substrate, which expands the ability to control material properties through the number of layers.

[0031] Figure 1A brief flow chart of a layer-by-layer etching method according to one of the preferred embodiments of the present application is shown. In the flow, first, the etching structure needs to be designed and the etching path is planned. Specifically, the layer-by-layer etching technique described in the present application achieves the etching of the target remaining layer number of material under the condition of a specific laser power saturation time length by the temperature difference between the layers of the two-dimensional material. Its implementation relies on the interlayer temperature difference of the two-dimensional material targeted by the present application, which refers to the temperature field formed due to the heat transfer from the sample to the substrate under laser irradiation conditions for the two-dimensional material transferred or grown on a specific substrate. For example, the substrate with the sample can be in physical contact with a cold source to form a temperature field gradient distribution that monotonically decreases from the upper surface of the sample to the contact surface of the sample substrate. The two-dimensional material structure with this temperature gradient distribution characteristic is the etching structure desired in various embodiments of the present application. Advantageously, it is also necessary to adjust or maintain the temperature gradient distribution characteristic substantially unchanged during the etching process by a temperature control console or other means. When the surface layer of the sample does not have the above-mentioned interlayer temperature gradient that monotonically decreases from the upper surface of the sample to the contact surface of the sample substrate, for example, when the highest temperature layer of the sample under the condition of equal laser power irradiation is not at the surface layer or the temperature difference of the surface layers is very close (such as the temperature difference between adjacent layers is within ten degrees Celsius), the sample can be pre-etched to remove the unsuitable surface layer of the above example until a qualified sample for single-layer controllable etching is obtained. The sample pre-etching is to adjust the laser power to be higher than the etching threshold power of the surface layer, and then etch the sample for a sufficient time until the temperature at the center of laser irradiation decreases below the etching threshold temperature.

[0032] Secondly, the flow includes selecting the corresponding etching conditions according to the maximum number of layers of the etching material and structure. Specifically, the etching material of a specific layer number is usually arranged on a substrate, and the etching conditions include the presetting of the etching laser wavelength and the starting power, as well as the adjustment of the etching environment, wherein the etching environment includes the thermal conductivity of the substrate, the contact thermal resistance between the substrate and the multi-layer two-dimensional material, the temperature of the substrate and the environment, the gas atmosphere of the etching environment, the control accuracy and stability of the etching laser power; wherein the adjustment of the thermal conductivity of the substrate includes replacing the substrate material and replacing the kind and thickness of the substrate surface cover layer.

[0033] Then, the flow also includes transferring the sample to be etched corresponding to the maximum layer thickness of the target after etching to the selected substrate, or obtaining it by growing on it. Since the actual etching layer number after pre-etching is not easy to accurately determine, and the etching reaction rate is relatively slow, preferably, the layer number of the initial sample is controlled to be within the maximum layer number for layer-by-layer or single-layer controllable etching when the initial sample is prepared.

[0034] After obtaining the sample suitable for layer-by-layer or single-layer controllable etching, it is also necessary to determine the power range that meets the layer-by-layer laser etching, which can be obtained by analyzing the temperature evolution curve characteristics of the laser irradiation center on the sample to be etched. One preferred way is to obtain the temperature evolution curve by measuring the peak shift of the Raman characteristic peak of the material to be etched. However, the technical solution of the present application can also obtain the temperature evolution curve of the laser irradiation center on the sample to be etched according to other measurement techniques, which does not deviate from the inventive concept of the present application. This step specifically includes the following sub-steps:

[0035] (1) Obtain the temperature evolution curve by adjusting the laser power. One preferred process is as follows: use a pre-set etching laser of a specific wavelength (preferably 532 nm laser in this embodiment) to irradiate the sample, gradually increase the laser power under the condition of no defocus, and monitor the temperature of the laser spot center in real time using Raman peak shift. The temperature first increases with the increase of laser power, and then does not decrease with the increase of laser power after reaching a certain temperature. This phenomenon indicates that the material begins to etch at this laser power. Under this condition, the temperature of the sample irradiation center will have a stepwise temperature drop characteristic and the stepwise temperature drop trend will stabilize around a certain specific temperature. This specific temperature is the threshold temperature of laser etching under this condition.

[0036] (2) After determining the etching threshold temperature, the laser power range required for single-layer etching can be determined by more accurately measuring the temperature evolution curve. The process is as follows: under the condition of no defocus, gradually increase the laser power irradiating the sample to be etched so that the center temperature of the etching sample gradually reaches the etching threshold temperature, then further increase the laser power in steps so that the center temperature of the sample exceeds the threshold temperature for a short time, then keep the laser power unchanged and observe the number of stepwise decreases (temperature steps) in the process of the etching area temperature returning to the threshold temperature. If the number of temperature steps is 1, the laser power meets the single-layer etching condition of the material; if the number of temperature steps exceeds 1, the laser power is too large and does not meet the single-layer etching condition of the material, and the laser power value should be reduced. By multiple tests, the laser power range that meets the single-layer etching requirement can be obtained. Preferably, for molybdenum disulfide two-dimensional material, the adjustable range of laser power can be 0 to 20 milliwatts, and the actual laser power fluctuation and single adjustment accuracy are within 0.1 milliwatts.

[0037] (3) After obtaining the single-layer etching laser power range and selecting a fixed value of single-layer etching laser power, the region etching can be realized by sufficient exposure of the specific region. The etching completion is determined by ensuring that the etching temperature of each point in the region reaches or is below the etching threshold temperature. The sufficient exposure is preferably realized by long-time exposure of each point. The long-time exposure can also be obtained by accumulating the exposure time through repeated scanning of the etching region along the etching path. The repeated scanning of single-point short-time exposure is used to reduce the etching process time of single scanning, to weaken the defocusing effect of the etching system and to avoid the additional exposure time of the completed etching part due to the random fluctuation of the etching reaction process time. For the purpose of ensuring the signal quality of the Raman spectrum collection, the single-point collection time cannot be too short. Preferably, the single-point exposure time required for etching in the atmospheric environment is 2 s, so the single-point exposure time can be 0.1 s and the repeated scanning is 20 times.

[0038] The initial thickness or layer number of the sample can be obtained according to the spectral characteristics or the direct scanning detection height of the atomic force microscope.

[0039] The above process further includes that after realizing the single-layer controllable etching, the multi-layer controllable etching can also be realized by repeatedly performing single-layer etching on the new etching surface.

[0040] The above process further includes that after the layer-by-layer controllable etching is completed, the excess sample part except the target etching region is etched by the laser direct writing method to obtain the finished product.

[0041] In other preferred embodiments according to the present application, the temperature evolution curve can also be used to determine whether the sample to be etched is single-layer controllable. In the case of single-layer uncontrollable etching, the temperature evolution curve is characterized in that after adjusting the laser power to make the sample reach the etching threshold temperature, further increasing the laser power, the sample temperature will first further increase with the etching reaction and then decrease to the etching threshold temperature in a stepwise manner after the sample temperature is rapidly increased above the etching threshold temperature with the change of the laser power. Or, under the condition that the sample temperature is maintained above the etching threshold temperature without obvious change, it is determined that the etching is still in progress by other parameters such as the Raman signal intensity of the sample to be tested. Or, it is impossible to stably obtain a single-stage temperature ladder by adjusting the laser power.

[0042] In other preferred embodiments according to the present application, for the commonly used silicon substrate covered with silicon oxide, the thickness of the substrate silicon oxide can also be 2-20 nm. The temperature field can also be regulated by the substrate temperature or the chemical environment of the etching process. Taking the typical two-dimensional molybdenum disulfide etching as an example, the etching threshold temperature is about 350 degrees Celsius in the atmospheric environment, while in the inert gas atmosphere, the etching process changes from oxidation evaporation to direct evaporation, and the new etching requires a temperature of about 450 degrees Celsius, which is equivalent to a decrease of 100 degrees Celsius in the substrate temperature.

[0043] Figure 2 A schematic diagram of a layer-by-layer laser etching system according to a preferred embodiment of the present application is shown. The laser etching system 10 comprises a laser module 11, a computer control system 12, a temperature control platform 14 on which a substrate 13 is arranged, a displacement platform 15, and an etching gas atmosphere chamber 16. The laser module 11 comprises a laser source, a laser power controller, and a Raman spectrometer. The substrate 13 faces the top surface of the laser module 11 and is used to arrange the two-dimensional material to be etched. The computer control system 12 comprises at least an etching path planning module, an etching layer number judgment module, and an etching feedback module. The etching path planning module is used to automatically convert and generate a planning path for layer-by-layer structure etching according to a target structure. The etching layer number judgment module is used to automatically count the number of temperature steps in the temperature detection process of the center of the laser spot. The etching feedback module judges whether the etching is completed by monitoring whether the temperature of the laser irradiation point (or region) reaches or is below the etching threshold temperature.

[0044] The temperature control platform 14 is in direct thermal contact with the substrate and is used to regulate the temperature of the substrate during etching according to the needs of etching conditions. In a preferred embodiment, the temperature control platform 14 includes the following operations: when the etching laser power has reached the maximum value and still cannot complete the etching of the target layer, the substrate temperature is raised to facilitate the etching of the target layer, or when the controllable number of layers is insufficient under the etching environmental conditions, the substrate temperature is lowered to slow down or prevent the etching of the remaining layers.

[0045] The etching gas atmosphere chamber 16 can provide a gas environment with ideal airtightness and simple composition, which is used to change the gas atmosphere of the two-dimensional material, change the physicochemical reaction process of the material etching and the composition of the etching product, and further regulate the etching conditions of the two-dimensional material. Taking the etching of two-dimensional molybdenum disulfide as an example, when other etching environmental conditions cannot be changed, changing the gas atmosphere chamber from atmospheric atmosphere to inert gas atmosphere can reduce the substrate temperature by one hundred degrees Celsius, while inhibiting the molybdenum oxide part in the etching product residue, and achieving the purpose of increasing the controllable etching range of single layer.

[0046] The following is a more specific example to illustrate the etching process of the two-dimensional material according to the laser etching method of the present application.

[0047] Example 1:

[0048] Taking the etching of thirteen or fewer layers of molybdenum disulfide as an example, the specific etching process is as follows: Step 1, set the etching environmental conditions. This step specifically includes that the etching laser power fluctuates and the power control accuracy is about 0.1 milliwatt. Under the condition of atmospheric atmosphere at room temperature, in order to achieve single-layer controllable etching of molybdenum disulfide 13 layers or more, the required substrate can be a 2 to 20 nanometer silicon oxide covered silicon substrate.

[0049] Step 2: Arrange the sample to be etched. This step specifically includes transferring the mechanically stripped molybdenum disulfide layer onto a silicon substrate covered with, for example, 2 nm silicon oxide prepared in Step 1, and selecting a sample with a suitable layer thickness and area. AFM characterization shows that the selected sample region has a height of 8.5 nm, corresponding to a molybdenum disulfide thickness of thirteen layers, meeting the initial layer number requirement for the etched structure. If the actual thickness of the sample is too thick, such that the required etched layer thickness exceeds the maximum etching range of the layer-by-layer controllable etching, the sample can be pre-etched until it meets the etching range of the layer-by-layer controllable etching, and the thickness of the molybdenum disulfide layer can be retested.

[0050] Step 3: Obtain the threshold wavenumber corresponding to the controllable etching of the layer to be etched. This step specifically includes controlling the laser power on the sample to be etched, gradually increasing it without defocusing until the temperature at the irradiation center of the sample no longer rises synchronously and a reflection occurs, then stopping. Record the single-point temperature evolution curve of the irradiation center of the sample during this process, and determine the At of molybdenum disulfide using the evolution of the Raman characteristic peak position as the temperature criterion. 1g The threshold wavenumber for the characteristic peak etching reaction was determined to be 405.5 cm⁻¹ in this embodiment. -1 The temperature of the irradiation center of the sample can be obtained by directly measuring the temperature of the surface to be etched.

[0051] Figure 3 An example is shown illustrating the evolution curves of the molybdenum disulfide Raman characteristic peak and the silicon Raman characteristic peak in the etched sample after Lorentz fitting according to step 3, as a function of laser power. In this curve, the left side shows the evolution curve of the molybdenum disulfide Raman characteristic peak with time and power. Starting from time 0 on the horizontal axis and approaching approximately 50 seconds, the laser power was increased three times (i.e., the temperature in the target region of the sample was increased three times), causing the characteristic peak on the vertical axis to rise from its highest value (approximately 407 cm⁻¹). -1 At the point ( ), the Raman characteristic peak decreases in a three-step manner. After the sample's Raman characteristic peak decreases to near the etching threshold temperature (i.e., after the sample temperature rises to near the etching threshold temperature, see the horizontal axis in the figure for about 50 seconds), the Raman characteristic peak exhibits a clear step-like change trend. The wavenumber first decreases, and then increases in two steps until it reaches the threshold wavenumber of 405.5 cm⁻¹. -1 Near the same time, this process corresponds to the sample temperature first rising and then decreasing in two steps to near the etching threshold temperature, indicating that two layers on the sample surface are etched.

[0052] Step 4, determining the single-layer etching power range according to the obtained threshold wave number. This step specifically includes observing the displacement of the centroid of the MoS2 A1g characteristic peak in real time at a point on the non-target structure region of the sample to be etched, and further increasing the laser power after it approaches the threshold wave number, and controlling the power increase to ensure that only a single-stage appears in the temperature evolution curve of MoS2. Thus, the power range obtained by satisfying the above conditions is the power range of the single-layer etching power, and the value thereof is P1.

[0053] Step 5, verifying the test on another non-target etching region of the sample according to the obtained single-layer etching power. If two or more stages appear in the temperature evolution curve, repeat step 4.

[0054] Step 6, performing single-layer etching on the MoS2 sample according to the single-layer etching laser power determined in step 4. This step specifically includes setting the laser power to P1, and performing full-area etching on the target etching region of the first layer on the surface by continuous scanning according to the calculated path. The integration time of etching a single point is 0.1 seconds, the etching point spacing is 0.1 microns, and the etching line spacing is 0.1 microns. The etching completion degree is monitored in real time by etching temperature distribution or material Raman spectrum signal intensity uniformity until the etching is completed.

[0055] Step 7, continuing to perform layer-by-layer etching according to the foregoing steps 1 to 6 (this step is not necessary in other preferred embodiments where only single-layer etching is desired). This step includes taking the single-layer etching power P1 of the first layer on the surface as the initial power, and after the central temperature is stable, measuring the etching temperature evolution curve of the second layer to obtain the laser power P2 required for etching the second layer, and then completing the etching of the second layer etching region. Similarly, each subsequent layer can be etched in turn, and finally the target etching structure is obtained. Thereafter, the excess sample portion other than the target etching region is removed by laser direct writing to obtain the finished product. Figure 4 The optical and Raman imaging results of the sample before and after etching are shown by way of example.

[0056] The technical effects of the laser etching system and method according to various embodiments of the present application: the laser etching system and method according to various embodiments of the present application can obtain higher vertical etching precision in the laser etching process, realize large-scale layer-by-layer etching of two-dimensional materials, and better control the temperature field and other key factors of the material to be etched under single-layer etching conditions by adjusting the etching environment, accurately obtain whether the layer to be measured meets the single-sided etching condition by real-time monitoring of the temperature of the center of the etching laser spot, and accurately adjust the etching laser power to meet the optimal single-layer etching condition. Meanwhile, the present application aims to form a highly versatile etching strategy, accurately etch each layer by using the threshold temperature to determine the single-sided etching power of the etching method according to the present application during the etching process, and greatly reduce the limitations or requirements of the etching object and the etching environment, thus having a large-scale automatic production prospect.

[0057] Although the present application has been described by preferred embodiments, the present application is not limited to the embodiments described herein, and various changes and variations are included without departing from the scope of the present application.

Claims

1. A method for laser etching of a sample of two-dimensional material, the method comprising: controlling temperature distribution of the sample to decrease layer by layer along the surface inwardly to achieve a stepwise temperature decreasing feature by adjusting etching environment, wherein the etching environment comprises: substrate thermal conductivity, substrate and sample contact thermal resistance, substrate and ambient temperature, etching environment gas atmosphere, control precision and stability of etching laser power; determining the stepwise temperature decreasing feature in a single point laser etching process by in-situ real-time monitoring of etching temperature; obtaining etching laser power required for etching the sample within a single layer controllable etching range according to the stepwise temperature decreasing feature; achieving controllable etching of a specific number of layers of the sample according to the etching laser power. 2.The method of claim 1, wherein the adjustment of the substrate thermal conductivity comprises changing substrate material and changing substrate surface cover layer species and thickness.

3. The method of claim 1, wherein, determining the stepwise temperature decreasing feature by the in-situ real-time monitoring comprises determining etching threshold temperature by etching temperature evolution curve of sample irradiation center and obtaining the stepwise temperature decreasing feature, wherein controlling etching laser power to gradually increase under the premise of no defocus until the sample irradiation center temperature no longer increases synchronously and appears a reverse fold, then waiting for a sufficient time until the sample irradiation center temperature no longer changes under the premise of no defocus and constant etching laser power, the obtained temperature is the etching threshold temperature. 4.The method of claim 3, wherein the temperature evolution curve is obtained by real-time detection of Raman spectrum. 5.The method of claim 3, further comprising: judging whether the initial layer thickness of the sample is within the single layer controllable etching range by using the temperature evolution curve, if not, etching the sample until its initial layer thickness is within the single layer controllable etching range, wherein if the etching laser power cannot make the temperature evolution curve appear single stepwise decrease, or the temperature of the irradiation center first increases and then stepwise decreases relative to the etching threshold temperature, or the temperature of the irradiation center stabilizes at a specific temperature higher than the etching threshold temperature but etching is still detected by the instrument, it can be determined that the initial layer thickness of the sample is not within the single layer controllable etching range. 6.The method of claim 5, wherein the initial layer thickness of the sample can be indirectly obtained by growth preparation conditions, or directly obtained by spectral or atomic force microscope. 7.The method of claim 3, wherein obtaining etching laser power required for etching the sample within a single layer controllable etching range according to the stepwise temperature decreasing feature further comprises: setting a specific etching laser power according to the temperature evolution curve, wherein the specific etching laser power corresponds to the number of layers of the sample etched at a time, which is equal to the number of steps of the stepwise temperature decreasing feature in the temperature evolution curve corresponding thereto.

8. The method as claimed in claim 7, wherein determining the number of steps of the stepwise temperature profile comprises: the step number of the irradiation center temperature of the sample recovering to the etching threshold temperature is observed.

9. The method as recited in claim 7, wherein, each point of the etching region of the sample is exposed to the etching with the specific etching laser power for a sufficient exposure time, wherein each point is scanned for a single scan and the single scan is for a sufficient exposure time, wherein the sufficient exposure time refers to performing the etching under the condition of no defocus until the temperature of the irradiation center in the etching process is lower than the etching threshold temperature.

10. The method of claim 9, wherein each point is exposed to a single-point short-time exposure and multiple scans accumulate a sufficient total etching time to achieve the sufficient exposure time, instead of each point being scanned for a single scan.

11. A two-dimensional material etching system, comprising a controllable power laser source, a temperature detector, a temperature control console, a displacement table, and an etching gas atmosphere cavity, wherein the controllable power laser source is used to provide an etching laser with a required power; the temperature detector is used to realize in-situ real-time monitoring of etching temperature; the temperature control console is used to control the temperature distribution of the sample to be within a single-layer controllable etching range; the displacement table is used to control the etching position of the sample; and the etching gas atmosphere cavity is used to form a gas atmosphere surrounding the sample to be etched; characterized in that a controller is further included, and the controller is configured to implement the etching method of any one of claims 1 to 10.

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