A heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression properties and its preparation method

Abstract

This invention discloses a heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics and its fabrication method. The substrate is prepared by continuously growing lattice-coherent stress-relieving, compositional equilibrium, and pre-stress compensation sections on a single-crystal silicon support substrate using vapor phase epitaxy. Through the synergistic effect of a step-decreasing germanium composition and a pulsed fluctuating carbon composition, an asymmetric strain field is constructed in-situ within the single-crystal lattice. Cyclic thermal annealing during fabrication enables deep pinning of penetrating dislocations and precise arrangement of the micro-strain trap array. This invention not only solves the inherent lattice constant mismatch problem in heteroepitaxial growth but also ensures extremely high single-crystal quality and structural integrity of the top epitaxial layer through in-situ strain engineering, achieving dynamic stress balance within the material system over a wide temperature range.

Description

Technical Field

[0001] This application relates to the technical field of crystal growth, and mainly to a heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics and its preparation method. Background Technology

[0002] In the field of heteroepitaxial single crystal growth, the fabrication of heteroepitaxial composite substrates is fundamental to realizing high-performance devices. However, during vapor phase epitaxial growth, due to the inherent mismatch in lattice constants and thermal expansion coefficients between the substrate and the epitaxial layer, high-density dislocations and residual stresses are easily accumulated during the growth and cooling stages, leading to a decrease in the crystal quality of the epitaxial layer, an increase in interface defects, and even macroscopic warping and cracking.

[0003] Existing technologies mainly employ the following methods to alleviate the above problems: structural parameter optimization (such as increasing the thickness of the buffer layer), external stress compensation layer method, heteroepitaxial relaxation method (SiGe gradient buffer layer), and patterned stress release method. However, these methods are essentially "passive relaxation" or "post-compensation," and cannot establish an active stress balance mechanism from the source during crystal growth, making it difficult to achieve high-quality, large-area, and wide-temperature-range stable heteroepitaxial growth.

[0004] Therefore, there is an urgent need to develop a heteroepitaxial growth method that can pre-set internal stress in situ during epitaxial growth and actively suppress thermo-mechanical coupling, as well as the resulting composite substrate, to solve the above-mentioned technical problems from the source of crystal growth. Summary of the Invention

[0005] To address the aforementioned technical problems in the prior art, this application proposes a heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics and its preparation method. By constructing an asymmetric stress locking system during the in-situ epitaxial growth process of reduced pressure chemical vapor deposition (RPCVD), active stress control is achieved during the growth of heteroepitaxial single crystals, thus solving the defects and warping problems caused by thermo-mechanical coupling from the source of crystal growth.

[0006] According to one aspect of the present invention, a heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics is proposed. The main structure of the substrate is continuously grown by vapor phase epitaxy and, from bottom to top, includes a substrate single-crystal layer, an in-situ asymmetric stress-locking system, an intermediate interface layer, and a top single-crystal epitaxial layer; the substrate single-crystal layer is... 100 High-resistivity single-crystal silicon with crystal orientation; the in-situ asymmetric stress-locking system includes a stress release section, a composition balance section, and a pre-stress compensation section, which are continuously grown from bottom to top and maintain lattice coherence; the lattice constant of the pre-stress compensation section is set to be opposite to the lattice strain trend of the top single-crystal epitaxial layer at a preset operating temperature by the heteroatomic composition gradient, so that the composite substrate can withstand changes in operating temperature. When satisfied: ,in, This refers to the net residual stress between the top single-crystal epitaxial layer and the bottom layer of the substrate in its final operating state. This represents the internal stress generated by the in-situ asymmetric stress-locking system. This represents the difference in the coefficients of thermal expansion between different material layers. An asymmetric stress-locking system actively counteracts thermal mismatch stress at its source, fundamentally suppressing structural warping.

[0007] In a specific embodiment, the stress relief section is Si. 1-x Ge x The layer contains a germanium composition x that increases linearly with thickness, with an increase slope of 5% / μm to 15% / μm; the composition equilibrium section is Si with a constant germanium composition. 1-x Ge x Layer; the prestressed compensation section is Si 1-x-y Ge x C y The ternary alloy layer features a germanium component (x) decreasing in a stepwise manner and a carbon component (y) exhibiting a pulsed, fluctuating distribution. The three-segment SiGe / SiGeC structure creates a controllable internal stress field, providing both stress release and pre-compensation functions.

[0008] In a specific embodiment, the germanium component x in the prestress compensation section decreases by 0.05 to 0.15 every 50 to 200 nm in a stepwise manner, while the carbon component y exhibits a pulsed fluctuation frequency with a peak value of 0.2 at.% to 1.0 at.% periodically every 10 to 30 nm. The pulsed fluctuation of the carbon component y, in conjunction with the stepwise decrease of the germanium component in the prestress compensation section, forms a controllable tensile stress field. Through the synergy of pulsed carbon fluctuations and the stepwise decrease of germanium, a precisely controllable tensile stress field is generated, improving the accuracy of stress regulation.

[0009] In a specific embodiment, an in-situ grown interface anchoring layer is further included between the prestress compensation section and the intermediate interface layer. The interface anchoring layer contains a periodically arranged array of micro-strain traps. The period of the micro-strain trap array matches the pulse fluctuation frequency of the carbon component γ in the prestress compensation section. The interface anchoring layer is a carbon-rich single-crystal silicon layer, and its carbon content distribution coincides with the geometric center of the micro-strain trap array. The periodic micro-strain trap array actively confines dislocations within the locking system. The carbon content of the interface anchoring layer coincides with the trap center, further preventing dislocations from extending upwards and improving the mechanical fatigue strength of the diaphragm.

[0010] In a specific embodiment, the intrinsic stress state of the prestressed compensation section at room temperature is tensile stress, and its coefficient of thermal expansion is... The coefficient of thermal expansion of the top single-crystal epitaxial layer satisfy The intrinsic stress is taken from the range of 100 MPa to 350 MPa. This setting ensures that the internal stress and the lattice mismatch stress are precisely complementary.

[0011] In a specific embodiment, the thickness of the stress relief section is 300~800nm, the thickness of the composition equilibrium section is 100~300nm, the thickness of the prestress compensation section is 200~500nm, the thickness of the interface anchoring layer is 10~30nm, and the thickness of the intermediate interface layer is 0.5~3μm. This thickness range ensures lattice coherence and stress transmission blocking effect, meeting the requirements for industrial-scale fabrication.

[0012] In a specific embodiment, the thickness of the prestressed compensation section With respect to the thickness of the top single-crystal epitaxial layer Satisfying stiffness matching relationship: ,in, These represent the Young's modulus of the corresponding layers. This configuration maintains the flatness of the diaphragm and achieves macroscopic mechanical equilibrium.

[0013] According to a second aspect of the present invention, a method for preparing a heteroepitaxial composite substrate having in-situ thermo-mechanical coupling suppression characteristics as described above is provided, comprising the following steps: S1: Provides a single-crystal substrate layer for in-situ high-temperature hydrogen baking; S2: A reduced-pressure chemical vapor deposition process is adopted, with SiH4 as the silicon source and GeH4 as the germanium source. The stress relief section and the composition balance section are grown by linearly increasing the GeH4 flow rate. S3: A pulsed precursor switching process is adopted, with GeH4 and CH4 alternately introduced to grow the prestress compensation section, and cyclic hot annealing is applied simultaneously to freeze the tensile stress field. S4: An interface anchoring layer is grown in situ on the surface of the prestressed compensation section, followed by the preparation of an intermediate interface layer and a top single-crystal epitaxial layer; Among them, the synchronous coupling of pulse switching and cyclic thermal annealing ensures that the periodic arrangement of the micro-strain trap array matches the fluctuation of carbon composition.

[0014] In a specific embodiment, the reaction chamber pressure in S2 is controlled at 10~50 Torr, the growth temperature is 750~900℃, and the flow ratio of GeH4 to SiH4 increases linearly with time, with the ratio increasing by 0.005~0.02 per minute.

[0015] In a specific embodiment, the growth temperature in S3 is controlled at 700~800℃, and the CH4 pulse introduction frequency is set to switch to 1~5s every 10~30nm of thickness growth; the cyclic thermal annealing process adopts a heating and cooling rate of 50~150℃, and in-situ heat preservation at 650~750℃ is performed every 50~100nm of thickness growth.

[0016] This invention constructs an asymmetric stress-locking system (stress release section, composition equilibrium section, and pre-stress compensation section using germanium step reduction and carbon pulse fluctuation) in situ during RPCVD in-situ epitaxial growth. This precisely sets the lattice constant to be opposite to the thermal deformation trend of the top single-crystal epitaxial layer. Combined with an intermediate interface layer acting as a stress transfer circuit breaker and stiffness matching relationship, the total stress during heteroepitaxial growth and subsequent temperature changes is approximately zero, actively offsetting thermal mismatch stress from the crystal growth source. Simultaneously, a periodic micro-strain trap array effectively confines dislocations within the locking system, significantly improving the quality and integrity of the epitaxial single crystal. This allows the composite substrate to maintain extremely low warpage and excellent mechanical properties over a wide temperature range. The fabrication process employs RPCVD in-situ continuous growth combined with pulsed precursor switching and synchronous cyclic thermal annealing. The steps are simple, parameters are controllable, and it is compatible with existing epitaxial equipment. It boasts significant advantages such as low cost, high repeatability, and ease of industrial mass production, providing a novel technical path for high-quality heteroepitaxial single crystal growth. Attached Figure Description

[0017] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and, together with the description, serve to explain the principles of the invention. Other embodiments and many anticipated advantages of the embodiments will be readily recognized as they become better understood through reference to the following detailed description. Elements in the drawings are not necessarily to scale. The same reference numerals refer to corresponding similar parts.

[0018] Figure 1 A schematic cross-sectional view of a heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics is shown according to an embodiment of the present invention. Figure 2 A schematic diagram of the depth composition distribution of germanium and carbon atoms in a heteroepitaxial composite substrate according to a specific embodiment of the present invention is shown; Figure 3 The figure shows a comparison curve of the residual stress of the top single crystal of the present invention and a conventional heteroepitaxial single crystal structure at different operating temperatures, according to a specific embodiment of the present invention. Figure 4 A flowchart illustrating a method for preparing a heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics according to an embodiment of the present invention is shown.

[0019] The meanings of the numbers in the figure are as follows: 1-Top single crystal epitaxial layer, 2-Intermediate interface layer, 3-Interface anchoring layer, 4-Prestress compensation section, 5-Composition balance section, 6-Stress release section, 7-Substrate single crystal layer. Detailed Implementation

[0020] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] Figure 1 A schematic cross-sectional view of a heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics according to an embodiment of the present invention is shown, as follows. Figure 1 As shown, the present invention provides a heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics, comprising, from bottom to top (i.e., along the epitaxial growth direction): a substrate single-crystal layer 7, an in-situ asymmetric stress locking system (composed of a stress release section 6, a compositional equilibrium section 5, and a prestress compensation section 4), an interface anchoring layer 3, an intermediate interface layer 2, and a top single-crystal epitaxial layer 1. The substrate single-crystal layer 7 is selected from... 100 The high-resistivity single-crystal silicon has a specific crystal orientation; this layer serves as the physical carrier for the entire composite substrate, providing an atomically flat starting surface for subsequent heteroepitaxial growth. The in-situ asymmetric stress-locking system on top of the single-crystal substrate layer 7 is the core of this invention. This system maintains lattice coherence between its layers, ensuring the continuity and stability of stress transmission. Specifically, the bottom layer of this system is the stress-relieving section 6, made of Si. 1-x Ge x In this layer, the germanium composition x increases linearly with increasing thickness, with the thickness controlled between 300 and 800 nm and the increase slope set between 5% / μm and 15% / μm. This gradient is designed to guide mismatched dislocations to slip and annihilate within the layer through the slow evolution of the lattice constant, thereby obtaining a high-quality virtual substrate before subsequent growth. The adjacent composition equilibrium segment 5 is Si with a constant germanium composition. 1-x Ge x The layer, with a thickness of 100-300 nm, serves as a mechanical relay and stabilizes the strain state; the top of the system is the prestress compensation section 4, which is the key to achieving active thermal compensation in this invention. This section uses Si 1-x-y Ge x C yThe ternary alloy material has a thickness controlled between 200 and 500 nm. Within this range, the germanium component x does not maintain its previous constant state but exhibits a step-like decreasing distribution, specifically decreasing by 0.05 to 0.15 nm every 50 to 200 nm. Coordinated with this is the pulsed fluctuation distribution of the carbon component y, with the pulse frequency set to periodically peak every 10 to 30 nm of growth, and the peak concentration controlled between 0.2 at.% and 1.0 at.%. From a microscopic bond energy perspective, the Si-C and Si-Ge bonds in the prestress compensation section 4 exhibit an alternating and enhanced distribution. Furthermore, at the interface where the periodic pulses occur, the lattice distortion energy is highly concentrated around the carbon atom clusters, thus forming a stress-barrier interface perpendicular to the growth direction. This atomic arrangement allows the layer to lock in intrinsic tensile stresses ranging from 100 MPa to 350 MPa at room temperature.

[0023] In a specific embodiment, to further stabilize this locking system, an interface anchoring layer 3 with a thickness of 10-30 nm is grown in situ between the prestress compensation section 4 and the intermediate interface layer 2 (thickness 0.5~3 μm). This layer is a carbon-rich single-crystal silicon layer, in which a periodically arranged array of micro-strain traps is distributed. The period of this array is strictly matched with the pulse fluctuation frequency of the underlying carbon component y, so that the center of carbon content distribution coincides with the geometric center of the strain traps, thereby actively confining any possible residual dislocations within the stress locking system.

[0024] In a specific embodiment, the intrinsic tensile stress is pre-set by the prestressing compensation section 4. The intermediate interface layer 2 and the top single-crystal epitaxial layer 1 change with the operating temperature. The resulting lattice mismatch stress is offset at its source. In this embodiment, the thermal expansion coefficient of the prestress compensation section 4 is controlled. The coefficient of thermal expansion of the top single-crystal epitaxial layer 1 satisfy The proportional relationship, and ensure the thickness of the two layers (the thickness of the prestressed compensation section) With respect to the thickness of the top single-crystal epitaxial layer and Young's modulus ( The Young's moduli of the corresponding layers satisfy the stiffness matching relationship: This ensures that the composite substrate meets the requirements under actual temperature variations. The physical model states that the total stress equals the sum of the internal stress generated by the in-situ asymmetric stress-locking system and the lattice mismatch stress caused by temperature changes, and this total stress is approximately zero. This refers to the net residual stress between the top single-crystal epitaxial layer and the bottom layer of the substrate in its final operating state. This represents the internal stress generated by the in-situ asymmetric stress-locking system. This represents the difference in thermal expansion coefficients between different material layers. Within the operating temperature range, it represents the absolute value of the residual net stress between the top single-crystal epitaxial layer 1 and the bottom layer. It can be stably controlled within 50MPa.

[0025] Figure 2 A schematic diagram of the depth composition distribution of germanium and carbon atoms in a heteroepitaxial composite substrate according to a specific embodiment of the present invention is shown, as follows: Figure 2 As shown, within a depth range of 0 nm to 400 nm from the surface of the supporting substrate, i.e., stress relief section 6, the Ge composition exhibits a stable linear increase, gradually rising from 0 to a peak of approximately 15 at.%. This linear gradient design aims to guide mismatched dislocations generated in the early stages of heteroepitaxial growth to slip and cancel each other out within the layer through a slow change in the lattice constant, thereby effectively suppressing dislocation penetration into the functional layer. Subsequently, within a depth range of 400 nm to 600 nm, the Ge composition enters the composition equilibrium section 5, maintaining a constant high concentration level. This design serves as a mechanical buffer platform, aiming to stabilize lattice quality and provide a uniform strain reference for subsequent stress locking. The core feature of this invention is embodied in the prestress compensation section 4 region from 600 nm to 1000 nm. In this range, the Ge composition breaks away from the conventional continuous gradual change pattern, instead exhibiting a distinct step-like decline characteristic. Each time a specific thickness is grown, the Ge composition undergoes a step-like jump downwards. Simultaneously, the C composition appears rhythmically in the same region in a pulsed form, with the peak of each pulse locked at approximately 1.0 at.%. By coupling the stepwise decrease of the Ge component with the periodic pulses of the C component, a dense distorted field is created in the material's microstructure to convert and lock the contractile force generated by the small atomic radius of carbon atoms into intrinsic tensile stress. Through precise atomic ratio control, this structure can store internal stresses ranging from 100 MPa to 350 MPa in situ, providing a basis for subsequent performance requirements. The physical model provides structural guarantees.

[0026] To further verify the technical effectiveness of the in-situ asymmetric stress locking system described in this invention, this embodiment obtains results through multiphysics coupling simulation analysis. Figure 3 The stress performance curves shown are as follows. Figure 3 The figure shows a comparison curve of the residual stress of the top single crystal of the present invention and a conventional heteroepitaxial single crystal structure at different operating temperatures, according to a specific embodiment of the present invention. Figure 3As shown, due to the inherent thermal expansion coefficient mismatch between silicon and silicon dioxide at the interface layer in traditional heteroepitaxial single-crystal structures, the residual stress of the top single crystal exhibits a drastic linear shift with temperature. Far from the 25°C reference temperature, the stress value increases or decreases rapidly, quickly exceeding the tolerance range (±50MPa) shown in the shaded area. This drastic stress fluctuation is the physical root cause of zero-point temperature drift and nonlinear errors in traditional MEMS devices. In contrast, the solution of this invention, shown by the solid line in the figure, demonstrates significant in-situ decoupling characteristics: throughout the entire operating temperature cycle, the residual stress curve of the composite substrate of this invention is extremely stable, consistently maintaining slight fluctuations near the 0MPa reference line, and its maximum fluctuation amplitude is completely locked within the target tolerance range of ±50MPa. This simulation data intuitively demonstrates the effectiveness of the in-situ asymmetric stress locking system described in this invention, namely, the intrinsic tensile stress pre-set by the pre-stress compensation section 4. This invention can generate a compensating force in real time, opposite in direction and equal in magnitude to the lattice mismatch stress term, in response to temperature changes, thereby achieving dynamic stress cancellation at the source. This indicates that the composite substrate provided by this invention not only exhibits good mechanical properties at room temperature but also provides a near-zero stress stable operating background for epitaxial films under complex thermal cycling environments, ensuring high reliability and signal accuracy of single-crystal materials from the material's fundamental level.

[0027] Figure 4 A flowchart illustrating a method for fabricating a heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics according to an embodiment of the present invention is shown, as follows: Figure 4 As shown, the preparation method includes the following steps: S1: Provides a single-crystal substrate for in-situ high-temperature hydrogen baking.

[0028] In this step, the selected 100 A single-crystal layer of a high-resistivity single-crystal silicon substrate is placed in a reduced-pressure chemical vapor deposition reaction chamber. Subsequently, under a pure hydrogen atmosphere controlled at 10–100 Torr, the reaction chamber is heated to 1050–1150 °C and maintained for 3–5 minutes. This process not only effectively removes the native oxide layer and residual impurities from the silicon substrate surface, but more importantly, it utilizes the surface migration characteristics of silicon atoms at high temperatures to form a highly ordered two-atom step structure on the surface of the substrate single-crystal layer. This in-situ pretreatment provides a low-defect-density starting template for subsequent heteroepitaxial layers, suppressing the anti-phase domain defects that easily arise at polar / non-polar interfaces from the source.

[0029] S2: A reduced-pressure chemical vapor deposition process is adopted, using SiH4 as the silicon source and GeH4 as the germanium source. The stress relief section and the composition balance section are grown by adjusting the GeH4 flow rate linearly.

[0030] After entering the epitaxial growth stage, the reaction chamber pressure is controlled at 10~50 Torr, and the growth temperature is stabilized between 750~900℃. During the stress release stage, the SiH4 flow rate is kept constant, and the GeH4 inlet flow rate is adjusted by a mass flow controller to linearly increase at a rate of 5~15 sccm / min, ensuring that the flow ratio of GeH4 to SiH4 increases by 0.005~0.02 per minute. Through precise ratio control, the germanium composition x achieves a smooth gradient within a thickness range of 300~800 nm, thereby driving lattice mismatch dislocations to undergo lateral slip and mutual annihilation. After the germanium composition reaches the preset peak value (e.g., 15 at.%), the growth enters the composition equilibrium stage. By maintaining a constant gas flow ratio, a strain-stabilized layer with a thickness of 100~300 nm is grown, providing a mechanical reference surface for subsequent stress locking.

[0031] S3: A pulsed precursor switching process is adopted, with GeH4 and CH4 alternately introduced to grow the prestress compensation section, and cyclic hot annealing is applied simultaneously to freeze the tensile stress field.

[0032] This step is the core process for achieving in-situ stress locking in this invention. At a growth temperature of 700-800℃, a pulse-based switching mode is used to control the introduction of CH4. Specifically, a CH4 pulse with a width of 1-5 seconds is introduced every 10-30 nm of ternary alloy layer growth. Simultaneously, whenever the cumulative growth thickness reaches 50-100 nm, the system automatically triggers an in-situ cyclic thermal annealing, switching the temperature rise and fall rate at 50-150℃ / min to 650-750℃ for a short-term holding period. This synchronous coupling mechanism of "growth-pulse-annealing" forces small-radius carbon atoms to occupy substitution sites and induces strong local lattice contraction, effectively freezing the lattice stress generated by heteroatoms within the step-decreasing SiGe framework. Through this step, a stable intrinsic tensile stress field of up to 100MPa-350MPa is formed within the prestress compensation section.

[0033] S4: An interface anchoring layer is grown in situ on the surface of the prestressed compensation section, followed by the preparation of an intermediate interface layer and a top single-crystal epitaxial layer.

[0034] Without disrupting the vacuum, a mixed precursor of SiH4 and CH4 was used to grow a carbon-rich interface anchoring layer with a thickness of 10–30 nm at 650–700 °C. During this process, the residual effect of the pulsed switching combined with the residual thermal field from cyclic annealing ensured that the micro-strain trap array at the interface and the fluctuations in the underlying carbon composition were highly coincident at their geometric centers, thus achieving end-pinning of dislocations. Subsequently, an intermediate interface layer 2 with a thickness of 0.5–3 μm was prepared by in-situ plasma-assisted chemical vapor deposition or high-temperature oxidation, and finally, a top single-crystal epitaxial layer was formed through bonding thinning or epitaxial growth.

[0035] To further verify the technical effectiveness of the heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics described in this invention, this embodiment uses multiphysics coupling simulation software to evaluate the performance of the composite substrate under different process parameters and compares it with traditional techniques. As shown in the table below, the experiment included two embodiments of this invention and two control groups (comparative examples).

[0036]

[0037] As can be seen from the data in Examples 1 and 2, this invention can successfully construct an efficient prestress field inside the substrate by precisely controlling the Ge gradient slope (10.0~12.5% / μm) in the stress relief section and the C pulse peak value (0.8~1.2 at.%) in the prestress compensation section. Especially when the stiffness matching ratio (E1h1) 3 / E2h2 3When the stress ratio is controlled within the optimized range of 0.85 to 1.05, the composite substrate exhibits excellent thermo-mechanical stability. Simulation results show that, in the embodiment of the present invention, the maximum stress fluctuation of the top single-crystal epitaxial layer is only 12 to 18 MPa within the full temperature range of -40℃ to 125℃, which is far below the design tolerance of ±50 MPa; at the same time, the warpage of the epitaxial film is strictly limited to 0.8 to 1.2 μm, ensuring extremely high physical flatness. In contrast, the traditional heteroepitaxial single-crystal structure represented by Comparative Example 1, due to the lack of an in-situ stress compensation mechanism, has a maximum stress fluctuation of up to 145 MPa and a warpage of 12.5 μm across the entire temperature range. This drastic deformation will cause severe zero-point temperature drift in high-precision sensors. Although Comparative Example 2 retains the Ge gradient structure, it removes the C pulse fluctuation distribution (C pulse peak value is 0), and the stiffness matching ratio (0.60) also deviates from the optimized range of the present invention. The results show that although the stress fluctuation in Comparative Example 2 is lower than that of the traditional heteroepitaxial single-crystal structure, it is still as high as 88 MPa, and the warpage is 6.4 μm, which still cannot meet the requirements of high-performance devices for thermo-mechanical decoupling. In summary, the data indicate that only under the synergistic effect of the Ge / C composition distribution pattern and stiffness matching ratio defined in this invention can the composite substrate effectively suppress lattice mismatch stress at its source.

[0038] The specific embodiments of this application have been described above, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0039] In the description of this application, it should be understood that the terms "upper," "lower," "inner," "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and for simplification, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The simple fact that certain measures are recited in mutually different dependent claims does not indicate that combinations of these measures cannot be used for improvement. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics, characterized in that, The substrate's main structure is continuously grown using vapor phase epitaxy, and from bottom to top comprises a base single-crystal layer, an in-situ asymmetric stress-locking system, an intermediate interface layer, and a top single-crystal epitaxial layer; the base single-crystal layer is... 100 The high-resistivity single-crystal silicon has a specific crystal orientation; the in-situ asymmetric stress-locking system includes a stress-relieving section, a compositional equilibrium section, and a pre-stress compensation section, all grown continuously from bottom to top while maintaining lattice coherence; the lattice constant of the pre-stress compensation section is set to be opposite to the lattice strain trend of the top single-crystal epitaxial layer at a preset operating temperature through a heteroatomic composition gradient, thereby allowing the composite substrate to adapt to temperature changes. When satisfied: ,in, This refers to the net residual stress between the top single-crystal epitaxial layer and the bottom layer of the substrate in its final operating state. This represents the internal stress generated by the in-situ asymmetric stress-locking system. This represents the difference in the coefficients of thermal expansion between different material layers; the stress relief section is Si. 1-x Ge x The layer contains a germanium composition x that increases linearly with increasing thickness, with an increase slope of 5% / μm to 15% / μm; the composition equilibrium section is a Si layer with a constant germanium composition. 1-x Ge x Layer; the prestressed compensation section is Si 1-x-y Ge x C y The ternary alloy layer has a germanium component x that decreases in a stepwise manner and a carbon component y that exhibits a pulsed fluctuation distribution.

2. The heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics according to claim 1, characterized in that, In the prestress compensation section, the germanium component x decreases in a stepwise manner by 0.05 to 0.15 every 50 to 200 nm, and the carbon component y exhibits a pulsed fluctuation frequency with a peak value of 0.2 at.% to 1.0 at.% periodically every 10 to 30 nm. The pulsed fluctuation of the carbon component y and the stepwise decrease of the germanium component in the prestress compensation section work together to form a controllable tensile stress field.

3. The heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics according to claim 1, characterized in that, Between the prestress compensation section and the intermediate interface layer, there is also an in-situ grown interface anchoring layer, in which a periodically arranged array of micro-strain traps is distributed; the period of the micro-strain trap array matches the pulse fluctuation frequency of the carbon component y in the prestress compensation section; the interface anchoring layer is a carbon-rich single-crystal silicon layer, and its carbon content distribution coincides with the geometric center of the micro-strain trap array.

4. The heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics according to claim 1, characterized in that, The intrinsic stress state of the prestressed compensation section at room temperature is tensile stress, and its coefficient of thermal expansion is... The coefficient of thermal expansion of the top single-crystal epitaxial layer satisfy The intrinsic stress is taken from the range of 100MPa to 350MPa.

5. The heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics according to claim 3, characterized in that, The stress relief section has a thickness of 300~800nm, the component balance section has a thickness of 100~300nm, the prestress compensation section has a thickness of 200~500nm, the interface anchoring layer has a thickness of 10~30nm, and the intermediate interface layer has a thickness of 0.5~3μm.

6. The heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics according to claim 1 or 5, characterized in that, The thickness of the prestressed compensation section With respect to the thickness of the top single-crystal epitaxial layer Satisfying stiffness matching relationship: ,in, These are the Young's moduli of the corresponding layers.

7. A method for preparing a heteroepitaxial composite substrate with in-situ thermo-mechanical coupling suppression characteristics as described in any one of claims 1-6, characterized in that, Includes the following steps: S1: Provides a single-crystal substrate layer for in-situ high-temperature hydrogen baking; S2: The stress relief section and the composition balance section are grown by using a reduced pressure chemical vapor deposition process, with SiH4 as the silicon source and GeH4 as the germanium source, and by adjusting the GeH4 flow rate linearly increasing. S3: A pulsed precursor switching process is adopted to alternately introduce GeH4 and CH4 to grow the prestress compensation section, and cyclic hot annealing is applied simultaneously to freeze the tensile stress field. S4: An interface anchoring layer is grown in situ on the surface of the prestressed compensation section, followed by the preparation of an intermediate interface layer and a top single-crystal epitaxial layer; Among them, the synchronous coupling of pulse switching and cyclic thermal annealing ensures that the periodic arrangement of the micro-strain trap array matches the fluctuation of carbon composition.

8. The preparation method according to claim 7, characterized in that, In S2, the pressure in the reaction chamber is controlled at 10~50 Torr, the growth temperature is 750~900℃, and the flow ratio of GeH4 to SiH4 increases linearly with time, with the ratio increasing by 0.005~0.02 per minute.

9. The preparation method according to claim 7, characterized in that, In S3, the growth temperature is controlled at 700~800℃, and the CH4 pulse introduction frequency is set to switch to 1~5s every 10~30nm of thickness growth; the cyclic thermal annealing process adopts a heating and cooling rate of 50~150℃, and in-situ heat preservation at 650~750℃ is performed every 50~100nm of thickness growth.

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