Semiconductor material based on laser-assisted lateral epitaxy and method for producing same

Abstract

The application provides a semiconductor material based on laser-assisted lateral epitaxy and a preparation method thereof, and the preparation method comprises the following steps: selecting a substrate, and preparing a multilayer buffer layer with patterned and periodic recesses on the substrate based on interference laser, and the periodic recesses are suitable for growing adjacent buffer layers by a lateral epitaxy method. The preparation method of the laser-assisted buffer layer provided by the application can reduce the dislocation and defect density of the epitaxial material, has low cost, can be mass-produced, and has an important application prospect in the field of semiconductor materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of epitaxial semiconductor thin film growth, in particular to a semiconductor material based on laser-assisted lateral epitaxy and a preparation method thereof. BACKGROUND

[0002] The performance of a semiconductor device is closely related to the quality of the material used, and high-quality semiconductor substrates and epitaxial materials are the basis for preparing high-performance devices. Currently, metal organic chemical vapor deposition, molecular beam epitaxy and other preparation methods have become the preferred way to prepare high-quality layered semiconductor materials due to their controllable atomic deposition rate and nearly layer-by-layer deposition advantages. However, the above preparation methods have the following disadvantages: the above preparation methods often need to be heated during the preparation of layered semiconductor materials, so the preparation process of layered semiconductor materials has a high temperature. When the temperature of the prepared layered semiconductor material decreases to the ambient temperature, due to the influence of factors such as thermal mismatch, lattice mismatch and polarity difference between the layers, a high defect density will be generated, such as the high lattice mismatch of up to 17% on the top surface of the hexagonal crystal system of silicon and gallium nitride. This high lattice mismatch will bring a defect density of up to 10 to the power of 10, making it difficult to grow and prepare materials in a large area.

[0003] Therefore, it is of practical significance and good application prospect to develop a low-cost and high-efficiency method for preparing semiconductor materials. SUMMARY

[0004] Therefore, the main purpose of the present application is to provide a semiconductor material based on laser-assisted lateral epitaxy and a preparation method thereof to solve the above problems in the prior art.

[0005] In order to achieve the above-mentioned purpose, the present application provides a preparation method of a semiconductor material based on laser-assisted lateral epitaxy, comprising: selecting a substrate; preparing a plurality of patterned buffer layers on the substrate based on interference laser; the patterned buffer layer has periodically arranged recesses, and the periodically arranged recesses are suitable for growing an adjacent layer of buffer layer by a lateral epitaxy method. Wherein, the patterned buffer layer has periodically arranged recesses, and the periodically arranged recesses are suitable for growing an adjacent layer of buffer layer by a lateral epitaxy method.

[0006] In the embodiments of the present application, the preparation method of each patterned buffer layer comprises:

[0007] The grown buffer layer or the buffer layer in the growth process is treated by interference laser to obtain a patterned buffer layer.

[0008] In the embodiment of the present application, the interference laser is a first interference laser, and the method for preparing the multi-layer patterned buffer layer on the substrate comprises: preparing a buffer layer on the substrate; patterning the buffer layer by using the first interference laser to obtain a patterned buffer layer; repeating the steps of preparing a buffer layer and patterning to obtain the multi-layer patterned buffer layer.

[0009] In the embodiment of the present application, the first interference laser is a plurality of single-pulse lasers, and the plurality of single-pulse lasers are emitted to the buffer layer to increase the depth of the interference pattern recess.

[0010] In the embodiment of the present application, after the buffer layer is prepared on the substrate, the substrate and the buffer layer are subjected to a first in-situ annealing treatment.

[0011] In the embodiment of the present application, after the patterned buffer layer is obtained, the substrate and the patterned buffer layer are subjected to a second in-situ annealing treatment.

[0012] In the embodiment of the present application, the interference laser is a second interference laser, and the method for preparing the multi-layer patterned buffer layer on the substrate comprises: irradiating a second interference laser to the surface of the substrate; depositing a patterned buffer layer on the surface of the substrate under the action of the second interference laser, wherein the action of the interference laser comprises inhibiting the deposition of the buffer layer in the irradiation area; repeating the steps of irradiating the second interference laser to the surface of the substrate and depositing a patterned buffer layer on the surface of the substrate to obtain the multi-layer patterned buffer layer.

[0013] In the embodiment of the present application, any two adjacent patterned buffer layers are arranged in a staggered manner in the vertical direction.

[0014] In the embodiment of the present application, the substrate comprises an oxide layer, and before the multi-layer patterned buffer layer is prepared on the substrate, a third interference laser is used to remove part of the oxide layer on the substrate, and the area of the substrate where the oxide layer is removed is arranged periodically; the material of the buffer layer is deposited on the area of the substrate where the oxide layer is removed; and the substrate on which the buffer layer is deposited is heated to completely remove the oxide layer of the substrate.

[0015] In the embodiment of the present application, the substrate comprises an oxide layer, and before the multi-layer patterned buffer layer is prepared on the substrate, the method further comprises:

[0016] removing the oxide layer of the substrate;

[0017] patterning the substrate on which the oxide layer is removed by using the first interference laser to obtain a patterned substrate.

[0018] In the embodiment of the present application, the distance between any two adjacent recesses in the patterned buffer layer is greater than the thermal migration length of atoms of the material of the buffer layer; and the first interference laser is a plurality of single-pulse lasers.

[0019] In the embodiment of the present application, the energy density of the first interference laser is greater than that of the second interference laser, and the pulse width of the first interference laser is smaller than that of the second interference laser; and the method for preparing the multi-layer patterned buffer layer is to use an in-situ preparation method.

[0020] As another aspect of the present application, a semiconductor material prepared by the above method is provided.

[0021] From the above technical solution, the semiconductor material based on laser-assisted lateral epitaxy and the preparation method thereof provided by the present application have at least one or part of the following beneficial effects:

[0022] (1) By preparing the periodically arranged recesses in each buffer layer, the defect density can be gradually reduced from the substrate to the uppermost buffer layer, and finally the defects in the uppermost buffer layer are annihilated.

[0023] (2) By using the interference laser for patterning operation, the buffer layer can be in-situ patterned during the preparation of the buffer layer, so as to avoid the pollution of the buffer layer material by using the non-in-situ patterning photolithography method, and the cleanliness can be effectively improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] The present application will be further described in detail below with reference to the accompanying drawings.

[0025] Figure 1 is a flow chart of the preparation method of the semiconductor material based on laser-assisted lateral epitaxy provided by the embodiment of the present application;

[0026] Figure 2 is a sectional view of the epitaxial gallium arsenide buffer layer structure on the silicon substrate provided by the embodiment of the present application;

[0027] Figure 3 is a partial enlarged view of Figure 2 ;

[0028] Figure 4 is a flow chart of the preparation method of the semiconductor material based on laser-assisted lateral epitaxy provided by another embodiment of the present application;

[0029] Figure 5 is a flow chart of the preparation method of the semiconductor material based on laser-assisted lateral epitaxy provided by another embodiment of the present application;

[0030] Figure 6 is the change of the pattern on the buffer layer before and after annealing of the embodiment of the present application;

[0031] Figure 7This is a cross-sectional view of a gallium arsenide buffer layer fabricated on a gallium arsenide substrate including an oxide film, according to an embodiment of the present invention. Detailed Implementation

[0032] In the process of realizing this invention, it was discovered that defects can be reduced by preparing multiple patterned buffer layers on a substrate.

[0033] Photolithography is used to pattern the buffer layer in related technologies. However, the chemical etching method employed in photolithography cannot avoid leaving contaminants, which can further lead to defects. To minimize material defects, laser-assisted metal-organic chemical vapor deposition (MOCVD) has been introduced to pattern material surfaces. This method requires the introduction of a metal-organic source into the reaction chamber at high temperatures after the laser interaction with the material surface to clean the patterned substrate. Atomic-scale defects or contaminants can be introduced through multiple processing steps, making the surface unsuitable for subsequent epitaxial growth. This limits the applicable material systems and makes it unsuitable for ultra-high vacuum and low-temperature fabrication equipment. In nanoseconds, atoms in the laser-interacted region can only be rapidly vaporized and removed when the temperature of the laser-interacted region is much higher than that of the material's internal region. Since MOCVD preparation temperatures are generally around 900 degrees Celsius, insufficient temperature difference leads to the migration and aggregation of numerous atoms on the material surface, forming droplets such as gallium droplets. These gallium droplets need to be removed during subsequent fabrication processes. Alternatively, by controlling the formation of droplets, patterned areas can be etched onto the material surface. However, during the droplet etching process, due to atomic aggregation, the droplet volume will further increase, creating a surface tension difference and resulting in the Marangoni effect. This causes island-like morphologies with concave edges and convex centers to form within the patterned areas, requiring more time for in-situ annealing to smooth the material surface. In other words, the patterning methods used in related technologies easily introduce processing contaminants, leading to defects and damage in the material, and also have high manufacturing costs and low processing throughput.

[0034] To achieve low-cost and efficient fabrication of high-quality semiconductor materials, combining lateral patterning and epitaxy at low temperatures to maintain atomic smoothness and absolute cleanliness of the sample surface is highly beneficial. Future development and application directions include laser-assisted growth of gallium arsenide buffer layers on silicon-based materials.

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0036] Figure 1 This is a flowchart of a method for preparing semiconductor materials based on laser-assisted lateral epitaxy provided in an embodiment of the present invention.

[0037] As shown in Figure 1 The preparation method of semiconductor material based on laser-assisted lateral epitaxy includes operation S101-operation S102.

[0038] Operation S101, selecting a substrate.

[0039] Operation S102, preparing a multi-layer patterned buffer layer on the substrate based on interference laser.

[0040] The patterned buffer layer has a periodic arrangement of recesses, and the periodic arrangement of recesses is suitable for growing an adjacent layer of buffer layer by a method of lateral epitaxy.

[0041] According to an embodiment of the present application, the substrate can be a substrate composed of a single material layer as generally understood, or a substrate composed of multiple material layers, for example, the single material substrate can be a silicon substrate, and the substrate composed of multiple material layers can be a structure in which at least one material layer is grown on a silicon substrate. The buffer layer can be at least one functional layer grown on the substrate.

[0042] In an embodiment of the present application, the pattern on the buffer layer can be an array arrangement or a groove structure, and the pattern recess region is wide and has a certain depth, so as to avoid defects extending to the next layer of material in the subsequent growth process under the action of lateral epitaxy.

[0043] Figure 2 is a sectional view of the multi-layer patterned buffer layer prepared on the substrate according to an embodiment of the present application.

[0044] As shown in Figure 2 The substrate can be a silicon substrate, and the buffer layer can be a gallium arsenide buffer layer, Figure 2 The curve in the figure represents the extension direction of the ordinary threading dislocation, the arrowed curve schematically shows the deflection of the dislocation under the action of lateral epitaxy, and the density of the line reflects the defect density, from Figure 2 It can be seen that the defect density decreases layer by layer from the bottom layer upwards.

[0045] Figure 3 is a sectional view of the multi-layer patterned buffer layer prepared on the substrate according to an embodiment of the present application. Figure 2 is a partial enlarged view of

[0046] On the silicon substrate, a certain thickness of gallium arsenide buffer layer is grown and the surface of the gallium arsenide is patterned by laser interference in turn and repeatedly. After each time the surface of the material is patterned by laser interference, a certain thickness of buffer layer is grown. During the growth of the new layer of buffer layer, when the thickness does not exceed the patterning depth, as shown in Figure 3As shown, due to the lateral epitaxial mechanism, the deposition is more stable in the relatively flat patterned area. At the lower end of the sidewall of the convex area, especially at the two vertical sidewalls, it is more difficult for newly deposited atoms to be adsorbed, resulting in the deposition area at both ends of the sidewall gradually decreasing in inclination angle and the deposition in the center of the concave area gradually increasing with the increase of the deposition depth. Under the surface energy balance or surface tension balance mechanism, the deposition area on both sides of the concave area gradually becomes smooth and smaller.

[0047] However, due to the lattice mismatch, the orientation of the deposited atom layer in the center of the concave area is inconsistent with that of the deposited atom layer on both sides. The surface force of the deposited atoms in the center of the concave area is greater than that on both sides, causing the junction line between the deposited atoms in the center of the concave area and the deposited atoms on both sides to gradually change from pointing to the center line of the patterned concave to away from the center line of the patterned concave until pointing to the patterned convex. When the buffer layer thickness is deposited to a certain thickness, especially when the buffer layer thickness exceeds the pattern depth, this change in orientation will cause most of the dislocations from the bottom layer to start extending to the current growth area, and the direction of dislocation extension is almost perpendicular to the substrate surface, resulting in a nearly right-angle change.

[0048] Under the action of this lateral epitaxial mechanism, the deposition process in the patterned concave area is mainly diffusion deposition from the center to both sides. During the contact between the patterned concave sidewall and the patterned bottom area, a large lattice stress exists in each layer of the buffer layer, which is much larger than the defect extension force. Especially near the patterned area, the initial stage dislocation is parallel to the re-growth area, but with the extension, the change in this curve accompanied by stress will force the extension to bend 90° towards the patterned convex area, and then the extension of the dislocation forms a plane. Around a patterned convex area, the dislocations will eventually be parallel to each other and parallel to the substrate surface, especially the vertical screw defects, achieving defect annihilation. These defects will not subsequently propagate to the surface of the overgrown buffer layer, while the defects around the patterned concave area will continue to propagate in a direction perpendicular to the substrate surface, i.e. screw dislocations, threading dislocations and other defects will be bent by the strain field and propagate laterally, eventually disappearing on the surface of the patterned area, thus eliminating some defects.

[0049] This defect annihilation method will focus on a region about 5 microns above the substrate, so under a fixed pulse duration, as the thermal modulation depth increases with the increase of the interference period, in the future, a higher thermal modulation depth will be achieved at a given interference period, and a shorter laser pulse can be used to perform multiple times to effectively achieve patterning, avoid the appearance of droplets or introduce other gaseous or solid sources for cleaning, and also to a certain extent, stably eliminate defects and achieve higher quality material preparation.

[0050] In the embodiment of the present application, the interference laser is patterned to form more hot spots at the interference position, and the thermal transient is used to locally control the adsorption and desorption of atoms on the surface, thereby desorbing the contaminants on the surface. Meanwhile, the lateral epitaxy method can gradually reduce the dislocations from the substrate to the uppermost buffer layer, and finally eliminate the surface layer in the patterned area, thereby maintaining the smoothness and absolute cleanliness of the surface of the uppermost buffer layer. The method has low cost and high efficiency, and has important application prospects in the field of preparing high-quality semiconductor material systems. In the embodiment of the present application, the interference laser is patterned to realize in-situ patterning of the buffer layer during the preparation of the buffer layer, that is, the substrate does not need to be removed from the growth chamber, thereby avoiding the pollution of the buffer layer material by the non-in-situ patterning photolithography method, and effectively improving the cleanliness.

[0051] In the embodiment of the present application, since the laser pulse duration is a key parameter for forming a sub-micron resolution fine periodic structure, the highest possible spatial resolution of the ultra-fine laser interference ablation is determined by thermal diffusion. In order to fully illustrate the embodiment, a system for growing a gallium arsenide buffer layer on a silicon substrate is described.

[0052] The buffer layer preparation growth chamber in the embodiment adopts a molecular beam epitaxy growth chamber, and the laser source for generating interference laser is an Nd:YAG laser source or a flash lamp pumped light source. The laser source is set to work in a TEMOO spatial mode, that is, a Gaussian intensity distribution by default. The third harmonic wavelength, that is, the output wavelength is 355 nm, the pulse width is 7 ns, the repetition frequency is 5 Hz, the Gaussian beam diameter is 5 mm, and the pulse energy can be adjusted in the range of 10-200 mJ. The light path is controlled by configuring an attenuator, a half-wave plate and a laser polarizer on the path of each laser beam to control the energy and polarization direction of the four laser beams. Since single-pulse laser cannot cause significant thermal desorption, three 50:50 beam splitters are used to divide the laser beam into four sub-beams with the same intensity and the same light path. Then, four anti-reflection fused silica photonic windows with an azimuth angle of 0°, 90°, 180° and 270° are used to reflect the four sub-beams, and a mirror is used to guide the output laser beam upward into the growth chamber, and then gathered in the center of the substrate to be grown. Since the polarization state of the laser beam can change the distribution pattern, it also affects the contrast of the pattern, and the degree of polarization of the laser beam can determine the intensity distribution of the interference pattern, which also leads to different spatial periodicity in the four-beam interference.

[0053] The polarization states of the 4 beams of light are set to TM mode, the pulses are extracted from the 5Hz laser repetition signal by timing aperture based on the laser Pockels cell trigger signal with an external shutter, the femtosecond level laser is obtained, then the laser is recombined at the center of the substrate at a certain incident angle according to the angle between the growth chamber window and the substrate, when the low repulsion of coherent radiation is generated in the plane and space, an interference patterning is generated, which can be used to improve the periodic structure of the material surface, and because the beams are transmitted at a large incident angle, the vertical area of the four laser beams is reduced to 3mm in diameter, the pattern periodicity with a pitch range of about 100nm to 300nm is obtained, and the configuration can realize the patterning and sample growth process simultaneously. And the pulse duration of the femtosecond level laser is very short, so the peak power is very high, which is more conducive to the implementation of the patterning.

[0054] In the embodiment of the present application, due to the problems of laser power supply stability, optical path structure stability, substrate heater sensitivity and laser source energy density stability, the energy distribution of the laser acting area spot is too uneven. For example, in the process of implementing the patterning of the gallium arsenide buffer layer by laser interference, gallium residues appear in the patterned pits, which can be removed by increasing the laser duration and transient laser power density, so that the material gallium droplet is continuously heated, under the action of a certain arsenic bias, gradually interacts with arsenic, gradually diffuses around the patterned groove area, forms new gallium arsenide, and realizes the removal of the existing droplet. The above operation avoids the introduction of metal organic source to cause the new impurities to be left on the material surface.

[0055] In the embodiment of the present application, the preparation method of each layer of the patterned buffer layer comprises: treating the completed growth buffer layer or the buffer layer in the growth process by using the interference laser to obtain the patterned buffer layer.

[0056] In the embodiment of the present application, the interference laser in step S2 can be the first interference laser, and the preparation of the multiple layers of the patterned buffer layer on the substrate comprises: preparing a layer of buffer layer on the substrate; patterning the buffer layer by using the first interference laser to obtain the patterned buffer layer; repeating the steps of preparing a layer of buffer layer and patterning to obtain multiple layers of patterned buffer layer.

[0057] In the embodiment of the present application, the first interference laser is a high-energy-density, low-pulse-width interference laser, and is irradiated on the surface of the buffer layer at periodic interference sites, each interference site has a large diameter, and the buffer layer is completed by the first interference laser patterning operation in femtosecond level time through laser shutter operation. Based on the interference of the laser beam, the energy transferred to the material is converted into heat energy under the formation and interaction of the laser beam with the material. Local heat is generated on the buffer layer, forming a thermal transient distribution, which can make the atoms of the buffer layer evaporate instantaneously. The atomic movement generated by this evaporation is irregular, so there will be no traces left on the surface of the substrate.

[0058] In the embodiment of the present application, the first interference laser is a plurality of single-pulse lasers, and the depth of the interference pattern recess is increased by emitting a plurality of single-pulse lasers on the buffer layer. In the embodiment of the present application, after the buffer layer is prepared on the substrate in the first interference laser patterning processing step, the substrate and the buffer layer are subjected to a first in-situ annealing treatment.

[0059] In the embodiment of the present application, after the patterned buffer layer is obtained, the substrate and the patterned buffer layer are subjected to a second in-situ annealing treatment.

[0060] According to the embodiment of the present application, before the multi-layer patterned buffer layer is prepared on the substrate, it also includes: removing the oxide layer of the substrate; and patterning the substrate by using the first interference laser to obtain a patterned substrate.

[0061] In the embodiment of the present application, taking a silicon substrate as an example, the silicon substrate after the above operation is deoxidized and is subjected to patterning, which can also reduce the generation of defects and alleviate the stress of the material surface to a certain extent. Since the melting point of silicon is relatively high, the growth of a gallium arsenide buffer layer is generally not realized at the same time as the patterning of the silicon substrate. A laser with a relatively wide pulse time is used, and the laser interference interval is increased and acts on the surface of the silicon substrate for a long time. Since the action time is long enough, the heat of the silicon substrate surface can be fully transferred, so that the silicon atoms at the interference points have enough kinetic energy to migrate. The surface tension of the molten silicon is low at the interference maximum value and high at the interference minimum value. Due to the high surface tension, the silicon atoms migrate from the interference maximum value region to the interference minimum value region. Within a time span of tens of nanoseconds, the silicon will change before solidification, thereby leaving a nano-pit in the material without evaporation, and realizing the patterning operation of the silicon surface.

[0062] Figure 4 is a flowchart of a method for preparing a semiconductor material based on laser-assisted lateral epitaxy according to another embodiment of the present application.

[0063] As shown in Figure 4 , taking the growth of a gallium arsenide buffer layer on a silicon substrate as an example, the method includes operations 401-408.

[0064] In operation 401, a silicon substrate is selected;

[0065] In operation 402, deoxidation of the silicon substrate is completed;

[0066] In operation 403, the silicon substrate is patterned by using a first interference laser, so as to realize the patterning of the surface of the silicon substrate;

[0067] In operation 404, a buffer layer is grown;

[0068] In operation 405, the buffer layer is patterned by using the first interference laser;

[0069] In operation 406, a second in-situ annealing is performed;

[0070] In operation 407, operations 404-406 are repeated for a predetermined number of times.

[0071] In an embodiment of the present application, when the growth parameters fluctuate greatly or the source furnace is unstable, the droplets on the surface of the patterned buffer layer are removed after operation 405. Any two adjacent patterned buffer layers are staggered in the vertical direction. Since the material defects are distributed in a bulk density, and the area of the interference laser action region is limited, the optimization effect of the same region on the material defects is limited. In each execution of the operation of patterning the surface of the gallium arsenide by using the laser interference, the interference action region is changed to a certain extent, so that the defect density can be reduced by multiple orders of magnitude. At the same time, since it is a patterning operation, the stress problem of each buffer layer growth can be alleviated, thereby expanding the temperature window of the growth adaptation. With the increase of the patterning area, the problem of excessive deformation of the substrate edge caused by the existing patterning operation (photolithography) and the resulting utilization reduction can be overcome, and a substrate with higher quality and higher utilization can be prepared.

[0072] In an embodiment of the present application, the preparation of the multi-layer patterned buffer layer on the substrate comprises: irradiating a second interference laser on the surface of the substrate; depositing a layer of patterned buffer layer on the surface of the substrate under the action of the second interference laser, wherein the action of the second interference laser comprises inhibiting the deposition of the buffer layer in the irradiation area; repeating the steps of irradiating the second interference laser on the surface of the substrate and depositing a layer of patterned buffer layer on the surface of the substrate to obtain a multi-layer patterned buffer layer.

[0073] In an embodiment of the present application, the second interference laser is used to inhibit the deposition amount in the patterned area during the growth process, so as to increase the deposition amount in the patterned protruding area, and increase the depth of the patterned recessed area.

[0074] According to the embodiment of the present application, the deposition of the second interference laser inhibition buffer layer in the irradiation area is inhibited, the second interference laser duration is increased and the instantaneous laser power density is increased to remove the surface residual droplets, and in-situ annealing is used to improve the material surface quality. The second interference laser is a low energy density and high pulse width interference laser. Taking the conventional buffer layer material gallium arsenide as an example, during the growth of the gallium arsenide buffer layer, the substrate is grown at a constant temperature, the pulse width is appropriately increased and the energy density is reduced, so that the area temperature, i.e. the area hot spot, formed by the laser interference on the material surface is slightly higher than the temperature of the area not affected by the laser interference. Therefore, during the growth of the gallium arsenide material, the gallium arsenide in the area affected by the laser interference is easy to desorb due to the unstable energy of the material surface and the limited adsorption capacity of arsenic atoms and gallium atoms, so that the deposition amount of the gallium arsenide is greatly reduced, while the gallium arsenide in the area not affected by the laser interference is stable, so that the thickness of the gallium arsenide layer in this area gradually increases to form a certain thickness deposition and thus the patterning depth is increased. After the laser interference is stopped, the gallium arsenide buffer layer is continuously grown after the temperature is stabilized. In this way, the thickness of the gallium arsenide buffer layer can be fully utilized to reduce the defect density in a shorter operation period.

[0075] In the embodiment of the present application, each layer of the multi-layer patterned buffer layer can be formed by using the first interference laser or the second interference laser.

[0076] In the embodiment of the present application, before the multi-layer patterned buffer layer is prepared on the substrate, the method further comprises removing part of the oxide layer on the substrate by using a third interference laser, the area on the substrate where the oxide layer is removed is periodically arranged; the material of the buffer layer is deposited on the area on the substrate where the oxide layer is removed; and the substrate on which the buffer layer is deposited is heated to completely remove the oxide layer on the substrate.

[0077] Figure 5 is a flow chart of the method for preparing semiconductor material based on laser-assisted lateral epitaxy provided by another embodiment of the present application.

[0078] As shown in Figure 5 , taking the growth of the gallium arsenide buffer layer on the silicon substrate as an example, the method comprises operations 501-511.

[0079] In operation 501, a silicon substrate is selected;

[0080] In operation 502, part of the oxide layer is removed by using a third interference laser;

[0081] In operation 503, a certain thickness of gallium arsenide is grown on the area on the substrate where the oxide layer is removed by using a second interference laser;

[0082] In operation 504, the substrate containing the gallium arsenide is heated to completely remove the oxide layer;

[0083] In operation 505, a gallium arsenide buffer layer of a certain thickness is grown;

[0084] In operation 506, a first in-situ annealing is performed;

[0085] In operation 507, a first laser is used to pattern the surface of the gallium arsenide buffer layer;

[0086] In operation 508, a gallium arsenide buffer layer of a certain thickness is grown;

[0087] In operation 509, a first interference laser is used to remove residual droplets on the surface of the upper gallium arsenide buffer layer;

[0088] In operation 510, a second in-situ annealing is performed;

[0089] In operation 511, operations 508-510 are repeated a predetermined number of times.

[0090] Figure 6 is the change in the pattern on the buffer layer before and after annealing according to an embodiment of the present application.

[0091] As Figure 6 shown, when the patterned area appears as a deep inverted triangular shape, the lateral epitaxy effect is weakened. By performing an in-situ annealing operation, especially during a suitable long annealing process, the atomic movement in the patterned area is intensified, and the atoms on both sides of the deep inverted triangular tip quickly contact and fuse, gradually forming a flat surface, so that the triangular tip is gradually rounded, improving the atomic distribution in the patterned area, and ultimately forming a relatively shallow and certain width inverted trapezoidal pattern. Taking gallium arsenide, a commonly used buffer layer material, as an example, performing the above process under the protection of a stable arsenic bias, can also cause the surface residual gallium droplets to react with arsenic, forming new gallium arsenide combined with the substrate material, creating a cleaner pattern surface, and preparing for lateral epitaxy.

[0092] In the embodiments of the present application, due to the influence of the processing technology, the substrate surface is inevitably covered with a thin film of transparent oxide layer with a thickness of about 1 nm to 20 nm, complex composition, and uneven thickness distribution. At the same time, the substrate material generally placed in the environment will form an oxide layer material with a thickness from a few atomic layers to several hundred nanometers, and the oxide layer can be rapidly desorbed at high temperature, which is often performed in the growth chamber. Taking a silicon substrate as an example, in order to fully utilize the oxide layer on the surface of the material substrate, the silicon substrate placed in the growth chamber is subjected to long-term action of the third interference laser on the surface to leave a patterned groove. Due to the high laser energy and the long action time, the oxide layer in the third interference laser interference area can be effectively removed. Subsequently, laser interference is used in the patterned convex area, i.e. the oxide layer area, and under the inhibition of laser, gallium arsenide continues to grow on the surface of the material. When the gallium arsenide grows to a certain thickness, about 100 nm or even thicker, the action of the third interference laser is stopped, and the substrate is heated to remove the surface oxide layer, thereby leaving a patterned array of gallium arsenide protrusions, and then the gallium arsenide buffer layer continues to grow on the basis of this operation, which can greatly eliminate the defect propagation between gallium arsenide and the surface of the silicon substrate and improve the material quality. In addition, when the oxide layer thickness is removed while growing a thick gallium arsenide buffer layer, when the interference period is much smaller than the growth thickness, the gallium arsenide buffer layer can be directly derived from the patterned gallium arsenide protrusions to both sides, i.e. leaving a cavity in the middle area of the patterned protrusions, which can greatly reduce the defect density of the material. The above-mentioned third interference laser patterning operation is applicable to other materials that have been interrupted in growth and have left the growth chamber or vacuum environment, and is also applicable to applications that need to regrow a gallium arsenide buffer layer, which can improve the material utilization rate and reduce the material preparation cost. In the embodiments of the present application, in the homoepitaxy system, after the action of the interference laser, the patterned buffer layer is formed, and the patterned shape and the substrate are combined better, so that the substrate can better serve as the first buffer layer, reducing the number of patterned repetitions. For heteroepitaxy, compared with the normal operation steps, one more patterning operation is added, so that the defect density can be lower and the material quality is improved. Figure 7 A cross-sectional view of preparing a gallium arsenide buffer layer on a gallium arsenide substrate including an oxide layer thin film is schematically shown.

[0093] As Figure 7 shown in the embodiments of the present application, the pattern of the buffer layer adopts a Figure 7 semicircular shape of the protruding part shown in the middle. The pattern of the buffer layer adopts a Figure 2 sawtooth shape or other shapes.

[0094] In the embodiments of the present application, the distance between any two adjacent recesses in the patterned buffer layer is generally greater than the thermal migration length of atoms of the buffer layer material. The occurrence of an aperiodic melting surface is avoided, so that the patterned topography is greatly changed.

[0095] In the embodiments of the present application, the energy density of the first interference laser is greater than the energy density of the second interference laser, and the pulse width of the first interference laser is less than the pulse width of the second interference laser; and the method for preparing the multi-layer patterned buffer layer is prepared by using an in-situ preparation method.

[0096] According to the embodiments of the present application, the present application also provides a semiconductor material prepared by the above method.

[0097] The technical solutions of the present application are described in detail below by citing specific embodiments.

[0098] First, a silicon substrate is selected and transferred to a growth chamber, and a stable arsenic bias protection is continuously provided in the growth chamber. The protection gas is not easy to react with the silicon or gallium arsenide substrate, and needs to be at a suitable temperature and in the presence of a group III element to start deposition on the substrate surface in large quantities. Then a stable gallium bias is provided, so that the arsenic bias and the gallium bias start to extend on the material surface. After a period of time, a certain thickness of gallium arsenide buffer layer is epitaxially grown on the surface of the silicon substrate, and the gallium bias and the arsenic bias are turned off in turn.

[0099] Then, the laser generating device described above is used to form an interference pattern at low power and irradiate on the surface of the sample, to determine the shape to be acted on by laser on the surface of the gallium arsenide buffer layer. During the switching process of the external shutter, it is switched to a high energy density and low pulse width state, and the shutter is opened to quickly complete the patterning operation of the gallium arsenide buffer layer in femtosecond level time. Based on the interference of the laser beam, the coherent laser beam forms a periodic modulation laser intensity pattern that interacts with the material. In this interaction, the energy transferred to the material is then converted into heat, thereby causing the burning of the irradiated material. Due to the strong surface absorption of ultraviolet laser energy, local heat is generated on the gallium arsenide substrate. Therefore, after 7 ns pulse exposure, the surface temperature at the interference maximum value rises rapidly, and the surface presents a two-dimensional periodic thermal gradient distribution, forming a thermal transient distribution.

[0100] Because the adopted molecular beam epitaxy system growth temperature is low, generally 400 degrees Celsius, the heat of the material surface cannot be timely transmitted and diffused in a very short action time, and many hot spots are formed at the interference positions, and the temperature of these hot spots is much higher than 400 degrees Celsius, even as high as 1200 degrees Celsius. And gallium already has a relatively low vapor pressure at 700 degrees Celsius, and the vapor pressure has increased by many orders of magnitude at 900 degrees Celsius, so that it can realize rapid evaporation away from the material surface. Arsenic is the same, and it also has a certain vapor pressure at 150 degrees Celsius, and the vapor pressure has also increased by many orders of magnitude at 400 degrees Celsius, so that it can also realize rapid evaporation away from the material surface, that is, the temperature has exceeded the full evaporation temperature of gallium arsenide. By using this thermal transient to locally control the surface adsorption atom dynamics, the interference pattern produces a transient photothermal gradient on the nanoscale of the growth surface, forming a nanoscale surface patterning trace. Then immediately open the arsenic bias, wait for the growth chamber to stabilize, because the molecular beam epitaxy system provides the arsenic bias and the gallium bias source furnace, only directional evaporation can realize the growth on the substrate surface, and during the laser patterning process, the movement of arsenic atoms and gallium atoms removed by evaporation is irregular, so no trace is left on the substrate surface.

[0101] Compared with the prior art, the prior art mainly adopts a relatively wide pulse width, and the energy density is limited. When the laser fluence is not enough to raise the surface temperature to a temperature at which arsenic atoms and gallium atoms can be simultaneously evaporated and removed, the surface migration of the material dominates, that is, due to the absorption of the incident ultraviolet pulse, heat is generated in the near-surface of the wafer, and the temperature interference maximum rapidly rises in the nanosecond time scale, producing a lateral gradient of heat, which is the driving force for the migration of atoms from the interference maximum to the interference minimum, causing the material surface atoms to gather and migrate, leaving a migration trace. In a fixed laser interference modulation period, the thermal modulation depth decreases with the increase of the laser pulse duration. If the duration is longer, the heat travels a longer distance, and a high thermal modulation depth is reached in a given pulse duration. On the one hand, this will result in a deeper surface pattern, so that the corresponding gallium arsenide buffer layer thickness also increases. On the other hand, the entire surface is prone to reach a temperature higher than the melting point, so that the surface patterning effect is weakened, only arsenic atoms are desorbed, and gallium atoms are left on the surface, which gather to form droplets. This droplet needs to introduce a metal organic source into the reaction chamber to clean the substrate patterning, but the method described in the present application does not form a large number of gallium droplets on the material surface to change the material surface topography, avoids the introduction of an organic gaseous source, and avoids the cost in the process of processing the gallium droplets.

[0102] In the description of the present application, it is to be understood that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inner", "front", "central", "both ends" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0103] In addition, the terms "first", "second", "third", "fourth" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated, so that the features with "first", "second", "third", "fourth" can explicitly or implicitly include at least one of the features.

[0104] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "setting", "connecting", "fixing", "screwed" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited, the above-mentioned terms in the present application can be understood according to the specific meaning in the present application by the person skilled in the art according to the specific circumstances.

[0105] The above specific embodiments further illustrate the purpose, technical scheme and beneficial effects of the present application, it should be understood that the above description is only for the specific embodiments of the present application and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1.A method for preparing semiconductor material based on laser-assisted lateral epitaxy, comprising: selecting a substrate; preparing a plurality of patterned buffer layers on the substrate based on an interference laser; wherein the interference laser is a first interference laser, and the preparing a plurality of patterned buffer layers on the substrate based on the first interference laser comprises: preparing a buffer layer on the substrate; and patterning the buffer layer using the first interference laser to obtain the patterned buffer layer; or repeating the steps of preparing a buffer layer and patterning to obtain a plurality of patterned buffer layers; or the interference laser is a second interference laser, and the preparing a plurality of patterned buffer layers on the substrate based on the second interference laser comprises: irradiating the second interference laser to a surface of the substrate; and depositing a patterned buffer layer on the surface of the substrate under the action of the second interference laser, wherein the action of the interference laser comprises inhibiting the deposition of the buffer layer in the irradiation area; and repeating the steps of irradiating the second interference laser to the surface of the substrate and depositing a patterned buffer layer on the surface of the substrate to obtain a plurality of patterned buffer layers; wherein the patterned buffer layers have periodically arranged recesses, and the periodically arranged recesses are suitable for growing an adjacent buffer layer using a lateral epitaxy method; and any two adjacent patterned buffer layers are arranged in a staggered manner in a vertical direction. The method for preparing each patterned buffer layer comprises: processing a completed buffer layer or a buffer layer in a growth process using the interference laser to obtain the patterned buffer layer. After preparing a buffer layer on the substrate, the method further comprises: performing a first in-situ annealing process on the substrate and the buffer layer; and after obtaining the patterned buffer layer, the method further comprises: performing a second in-situ annealing process on the substrate and the patterned buffer layer. The substrate comprises an oxide layer, and before preparing a plurality of patterned buffer layers on the substrate, the method further comprises: removing part of the oxide layer on the substrate using a third interference laser, wherein the area on the substrate where the oxide layer is removed is periodically arranged; depositing a material of the buffer layer on the area on the substrate where the oxide layer is removed; and heating the substrate on which the buffer layer is deposited to completely remove the oxide layer on the substrate. The substrate comprises an oxide layer, and before preparing a plurality of patterned buffer layers on the substrate, the method further comprises: removing the oxide layer on the substrate; and patterning the substrate on which the oxide layer is removed using the first interference laser to obtain a patterned substrate. A distance between any two adjacent recesses in the patterned buffer layer is greater than a thermal migration length of an atom of the buffer layer material. The first interference laser is a plurality of single-pulse lasers. An energy density of the first interference laser is greater than an energy density of the second interference laser, and a pulse width of the first interference laser is less than a pulse width of the second interference laser. The plurality of patterned buffer layers are prepared using an in-situ preparation method. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2. The method of claim 1, wherein, ​ ​ 3. The method of claim 1, wherein, ​ ​ 4. The method of claim 1, wherein, ​ ​ ​ ​ 5. The method of claim 1, wherein, ​ ​ ​ 6. The method of claim 1, wherein, ​ ​ ​ ​ 7. A semiconductor material produced by the method of any one of claims 1-6.

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