Epitaxial structure and preparation method thereof
By forming a SiON layer stack between the silicon substrate and the AlN nucleation layer, the problem of Al-Si alloy forming a leakage path during AlN growth is solved, and the performance of the epitaxial structure and radio frequency devices is improved.
Patent Information
- Application Number
- CN202510880322.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-27
- Publication Date
- 2025-09-19
AI Technical Summary
During the growth of AlN on a silicon-based substrate, Al reacts chemically with the Si of the substrate to form an Al-Si alloy, which creates a leakage path, leads to substrate loss, and affects the performance and gain of RF devices.
A high-resistance transition layer consisting of a single SiON layer or multiple SiON layers with different atomic ratios is formed between the silicon substrate and the AlN nucleation layer. The SiON layer combines the advantages of low stress, stable chemical properties, and good insulation performance of the SiO2 film with the advantages of stable chemical properties and high lattice constant matching of SiN, reducing or even eliminating stress and reducing leakage paths.
It effectively suppresses the loss of silicon-based substrates, improves the performance of epitaxial structures, enhances the efficiency of RF devices, and solves the chemical reaction problem caused by direct contact between the AlN nucleation layer and the silicon-based substrate.
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Figure CN120676670A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of radio frequency device preparation, and in particular to an epitaxial structure and a preparation method thereof. Background Art
[0002] In traditional silicon-based gallium nitride (GaN) epitaxial structures, AlN is usually selected as the nucleation layer to achieve lattice matching and prevent high-density dislocations and melt-back etching effects (melt-back effect) caused by direct growth of GaN on silicon substrates.
[0003] RF devices require that signals (current) not flow through the substrate to avoid affecting device performance and gain. However, during the AlN growth process, the Al reacts chemically with the Si in the substrate to form an Al-Si alloy. This alloy creates a leakage path, causing substrate loss and affecting device performance and gain. Summary of the Invention
[0004] In view of the shortcomings of the prior art described above, the object of the present invention is to provide an epitaxial structure and a preparation method thereof, which are used to solve the problem that in the process of growing AlN on a silicon-based substrate in the prior art, Al reacts chemically with the Si of the substrate to generate an Al-Si alloy, forming a leakage path, causing substrate loss, and affecting the performance and gain of the RF device.
[0005] To achieve the above-mentioned and other related purposes, the present invention provides an epitaxial structure, which comprises, from bottom to top, the following:
[0006] Silicon-based substrate;
[0007] a transition layer comprising a single SiON layer or a stack of multiple SiON layers having different atomic ratios;
[0008] AlN nucleation layer.
[0009] Optionally, the transition layer is a stack of multiple SiON layers with different atomic ratios, and the atomic ratio of O in the SiON layer gradually decreases from the silicon-based substrate toward the AlN nucleation layer.
[0010] Optionally, the stack of multiple SiON layers with different atomic ratios includes 10 to 50 pairs of stacking unit layers, wherein the stacking unit layers are stacks consisting of SiO2 layers / SiN layers.
[0011] Furthermore, the thickness of the stacked unit layer is 6 nm to 10 nm.
[0012] Optionally, the transition layer is a single SiON layer, and the thickness of the transition layer is less than 100 nm.
[0013] Optionally, in the SiON layer, the atomic ratio of Si, O and N is 1:(0-2):(0-1.3), wherein the atomic ratio of O and N does not include an endpoint value of 0.
[0014] Optionally, the refractive index of the SiON layer material is 1.45-2.2.
[0015] Optionally, the silicon-based substrate is a high-resistance silicon substrate, and the epitaxial structure further includes a radio frequency device channel layer and a barrier layer located on the AlN nucleation layer, the material of the channel layer includes GaN, and the material of the barrier layer includes AlGaN.
[0016] The present invention also provides a method for preparing an epitaxial structure, the method comprising:
[0017] providing a silicon-based substrate;
[0018] forming a transition layer on the silicon-based substrate, wherein the transition layer comprises a single SiON layer or a stack of multiple SiON layers with different atomic ratios;
[0019] An AlN nucleation layer is formed on the transition layer.
[0020] Optionally, the transition layer is formed by a CVD process, the growth temperature of the CVD process is 300° C. to 450° C., and the precursor gas of the CVD process includes SiH 4 , NH 3 and NO 2 .
[0021] As described above, the epitaxial structure and preparation method of the present invention have the following beneficial effects: by forming a high-resistance transition layer composed of a single SiON layer or a multi-layer SiON layer with different atomic ratios between the silicon-based substrate and the AlN nucleation layer, the SiON layer has the advantages of low stress, stable chemical properties, and good insulation performance of the SiO2 film, and stable chemical properties, good insulation, and high lattice constant matching of SiN. It not only ensures lattice matching under the premise of insulation, but also reduces or even eliminates stress, reduces or even avoids the formation of leakage paths in the silicon-based substrate, and suppresses the loss of the silicon-based substrate, thereby improving the performance of the epitaxial structure and enhancing the performance of the RF device. It effectively solves the problem in the existing epitaxial structure that due to the direct contact between the AlN nucleation layer and the silicon-based substrate, Al reacts chemically with Si of the silicon-based substrate to form Al-Si alloy during the growth of AlN, forming a leakage path, causing substrate loss, and affecting the performance and gain of the RF device. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 Shown is a schematic cross-sectional structural diagram of the epitaxial structure of the present invention.
[0023] Figure 2The schematic diagram shows a cross-sectional structure of an epitaxial structure in which the transition layer is a stack of multiple SiON layers with different atomic ratios according to an example of the present invention.
[0024] Figure 3 The transition layer shown as another example of the present invention is a stack of multiple SiON layers with different atomic ratios, and the stack of multiple SiON layers with different atomic ratios includes a cross-sectional structural diagram of an epitaxial structure of 10 to 50 pairs of stacked unit layers.
[0025] Figure 4 It is a schematic flow chart of the method for preparing an epitaxial structure of the present invention.
[0026] Figures 5 to 8 Shown are schematic cross-sectional structures of various steps in the method for preparing an epitaxial structure of the present invention.
[0027] Component number description
[0028] 10 Silicon-based substrate
[0029] 11 Transition Layer
[0030] 110 SiON layer
[0031] 111 SiO2 layer
[0032] 112 SiN layer
[0033] 113 stacked unit layers
[0034] 12 AlN nucleation layer
[0035] 13 Channel layer
[0036] 14 and barrier layer
[0037] Steps S1 to S3 DETAILED DESCRIPTION
[0038] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.
[0039] See also Figures 1 to 8 It should be noted that the diagrams provided in this embodiment are merely schematic illustrations of the basic concept of the present invention. Therefore, the diagrams only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.
[0040] This embodiment provides an epitaxial structure, such as Figure 1 As shown, the epitaxial structure includes, from bottom to top:
[0041] Silicon-based substrate 10;
[0042] The transition layer 11 includes a single SiON layer or a stack of multiple SiON layers with different atomic ratios;
[0043] Aluminum nitride (AlN) nucleation layer 12 .
[0044] The epitaxial structure of this embodiment forms a high-resistance transition layer between the silicon-based substrate and the AlN nucleation layer, which is formed by a single SiON layer or a multi-layer SiON layer stacked with different atomic ratios. The SiON layer combines the advantages of low stress, stable chemical properties, and good insulation performance of the SiO2 film with the advantages of stable chemical properties, good insulation, and high lattice constant matching of SiN. It not only ensures lattice matching under the premise of insulation, but also reduces or even eliminates stress, reduces or even avoids the formation of leakage paths in the silicon-based substrate, and suppresses the loss of the silicon-based substrate, thereby improving the performance of the epitaxial structure and enhancing the efficiency of the RF device. It effectively solves the problem in the existing epitaxial structure that due to the direct contact between the AlN nucleation layer and the silicon-based substrate, Al reacts chemically with Si in the silicon-based substrate to form Al-Si alloy during the growth of AlN, forming a leakage path, causing substrate loss, and affecting the performance and gain of the RF device.
[0045] As an example, Figure 1 As shown, the epitaxial structure further includes an RF device channel layer 13 and a barrier layer 14 located on the AlN nucleation layer 12. The channel layer 13 and the barrier layer 14 are made of different materials, and a two-dimensional electron gas is formed at the interface between the channel layer 13 and the barrier layer 14. The two-dimensional electron gas serves as the channel of the RF device, providing a conductive channel between the source and drain of the device.
[0046] Furthermore, the material of the channel layer 13 includes GaN, and the material of the barrier layer 14 includes aluminum gallium nitride (AlGaN). The materials of the channel layer 13 and the barrier layer 14 can be selected from other materials as needed, and are not overly limited here.
[0047] As a preferred example, the silicon-based substrate 10 is a high-resistance silicon substrate, and the signal (current) is not easy to flow through the substrate, which reduces leakage current, thereby significantly reducing substrate loss and improving signal transmission and device efficiency of RF devices.
[0048] As an example, in the SiON layer, the atomic ratio of Si, O and N is 1:(0~2):(0~1.3). It should be noted here that (0~2) and (0~1.3) do not include the endpoint value of "0", that is, the atomic ratio of O and N does not include the endpoint value 0. Under the premise of ensuring insulation, lattice matching is guaranteed and stress is reduced or even eliminated, and the advantages of both SiO2 and SiN are combined.
[0049] As an example, the refractive index of the SiON layer material is 1.45 to 2.2, so that the transition layer 11 formed has the advantages of low stress, stable chemical properties, and good insulation performance of SiO2 film, as well as stable chemical properties, good insulation, and high lattice constant matching of SiN.
[0050] The transition layer 11 may be a single SiON layer or a stack of multiple SiON layers with different atomic ratios.
[0051] As an example, the transition layer 11 is a single-layer SiON layer. In this case, the thickness of the transition layer 11 is less than 100 nm to achieve a more concentrated and efficient stress buffering effect. The thin layer can effectively reduce the stress accumulation caused by the thickness difference while maintaining good contact with the upper and lower layer materials, while reducing the defect density at the interface, further improving the quality and performance of the epitaxial structure. The thickness of the transition layer 11 is not limited to this and can be adjusted according to needs.
[0052] As another preferred example, the transition layer 11 is a stack of multiple SiON layers with different atomic ratios. Specifically, the SiON layer 110 in the stack of multiple SiON layers with different atomic ratios is as follows: Figure 2 As shown, the atomic ratio of O in the SiON layer 110 gradually decreases from the silicon-based substrate 10 toward the AlN nucleation layer 12, so as to form an O-rich form on the side close to the silicon-based substrate 10 and a N-rich form on the side close to the AlN nucleation layer 12, that is, the atomic ratio on the side close to the silicon-based substrate 10 is closer to that of SiO2, and the SiO2 film has low stress, stable chemical properties, and good insulation performance, so as to reduce or even avoid the formation of leakage paths in the silicon-based substrate 10, thereby achieving the beneficial effect of suppressing the loss of the silicon-based substrate 10; the atomic ratio on the side close to the AlN nucleation layer 12 is closer to that of SiN, and the advantage of high lattice constant matching of SiN is utilized to ensure lattice matching, reduce or even eliminate stress, thereby improving the performance of the epitaxial structure and enhancing the performance of the RF device.
[0053] As another example, Figure 3As shown, the multi-layer stack of SiON layers with different atomic ratios may include 10 to 50 pairs of stacking unit layers 113, for example, 10 pairs, 20 pairs, 30 pairs, 40 pairs or 50 pairs, wherein the stacking unit layer 113 is a stack composed of SiO2 layer 111 / SiN layer 112, the thickness of a single-layer film (the SiO2 layer 111 or the SiN layer 112) is 3nm to 5nm, and the thickness of the stacking unit layer 113 is 6nm to 10nm. The number of layers of the stacking unit layer 113 and the thickness of the single-layer film in the multi-layer stack of SiON layers with different atomic ratios are not limited thereto and can be adjusted according to demand.
[0054] This embodiment also provides a method for preparing an epitaxial structure, which is used to prepare the above-mentioned epitaxial structure, but is not limited thereto. Other suitable preparation methods are also possible. The above content can be quoted here in its entirety, and will not be described in detail below for the purpose of brevity. Figure 4 As shown, the preparation method includes:
[0055] S1, providing a silicon-based substrate;
[0056] S2, forming a transition layer on the silicon-based substrate, wherein the transition layer includes a single SiON layer or a stack of multiple SiON layers with different atomic ratios;
[0057] S3, forming an AlN nucleation layer on the transition layer.
[0058] The preparation method of the epitaxial structure of this embodiment forms a high-resistance transition layer between the silicon-based substrate and the AlN nucleation layer, which is formed by a single SiON layer or a stack of multiple SiON layers with different atomic ratios. The SiON layer has the advantages of low stress, stable chemical properties, and good insulation performance of the SiO2 film, and stable chemical properties, good insulation, and high lattice constant matching of SiN. It not only ensures lattice matching under the premise of insulation, but also reduces or even eliminates stress, reduces or even avoids the formation of leakage paths in the silicon-based substrate, and suppresses the loss of the silicon-based substrate, thereby improving the performance of the epitaxial structure and enhancing the efficiency of the RF device. It effectively solves the problem in the existing epitaxial structure that due to the direct contact between the AlN nucleation layer and the silicon-based substrate, Al reacts chemically with Si in the silicon-based substrate to form Al-Si alloy during the growth of AlN, forming a leakage path, causing substrate loss, and affecting the performance and gain of the RF device.
[0059] The method for preparing the epitaxial structure of this embodiment will be described in detail below with reference to the specific drawings.
[0060] like Figure 5 As shown, step S1 is first performed to provide a silicon-based substrate 10 .
[0061] like Figure 6As shown, step S2 is then performed to form a transition layer 11 on the silicon-based substrate 10. The transition layer 11 includes a single SiON layer or a stack of multiple SiON layers with different atomic ratios.
[0062] As an example, the transition layer 11 may be formed by a chemical vapor deposition (CVD) process.
[0063] Furthermore, as an example, the growth temperature of the CVD process is 300°C to 450°C, and the precursor gas of the CVD process includes SiH4, NH3 and NO2. In the SiON layer of the transition layer 11 formed, the atomic ratio of Si, O and N is 1:(0~2):(0~1.3). On the premise of ensuring insulation, lattice matching is guaranteed and stress is reduced or even eliminated, and the advantages of both SiO2 and SiN are combined. The specific preparation process can also be adjusted according to actual needs, and no excessive restrictions are made here.
[0064] like Figure 7 As shown, step S3 is then performed to form an AlN nucleation layer 12 on the transition layer 11 .
[0065] like Figure 7 and Figure 8 As shown, after forming the AlN nucleation layer 12, the process also includes sequentially epitaxially forming a radio frequency device channel layer 13 and a barrier layer 14 on the AlN nucleation layer 12, which is compatible with existing fabrication processes and ensures seamless integration. Regarding the fabrication methods of the channel layer 13 and the barrier layer 14, commonly used methods in the art can be selected based on actual needs and are not overly limited herein.
[0066] In summary, the epitaxial structure and preparation method of the present invention form a high-resistance transition layer between the silicon-based substrate and the AlN nucleation layer, which is formed by a single SiON layer or a multi-layer SiON layer stacked with different atomic ratios. The SiON layer combines the advantages of low stress, stable chemical properties, and good insulation performance of the SiO2 film, and the stable chemical properties, good insulation, and high lattice constant matching of SiN. It not only ensures lattice matching under the premise of insulation, but also reduces or even eliminates stress, reduces or even avoids the formation of leakage paths in the silicon-based substrate, and suppresses the loss of the silicon-based substrate, thereby improving the performance of the epitaxial structure and enhancing the efficiency of the RF device. It effectively solves the problem in the existing epitaxial structure that due to the direct contact between the AlN nucleation layer and the silicon-based substrate, Al reacts with Si in the silicon-based substrate to form Al-Si alloy during the growth of AlN, forming leakage paths, causing substrate loss, and affecting the performance and gain of the RF device. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has high industrial utilization value.
[0067] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.
Claims
1. An epitaxial structure, characterized in that The epitaxial structure includes, from bottom to top, the following: Silicon-based substrate; a transition layer comprising a single SiON layer or a stack of multiple SiON layers having different atomic ratios; AlN nucleation layer.
2. The epitaxial structure according to claim 1, wherein: The transition layer is a stack of multiple SiON layers with different atomic ratios, and the atomic ratio of O in the SiON layer gradually decreases from the silicon-based substrate toward the AlN nucleation layer.
3. The epitaxial structure according to claim 1, wherein: The stack of multiple SiON layers with different atomic ratios includes 10 to 50 pairs of stacking unit layers, wherein the stacking unit layers are stacked layers consisting of SiO2 layers / SiN layers.
4. The epitaxial structure according to claim 3, wherein: The thickness of the stacking unit layer is 6nm to 10nm.
5. The epitaxial structure according to claim 1, wherein: The transition layer is a single SiON layer, and the thickness of the transition layer is less than 100 nm.
6. The epitaxial structure according to claim 1, wherein: In the SiON layer, the atomic ratio of Si, O, and N is 1:(0-2):(0-1.3), wherein the atomic ratio of O and N does not include an endpoint value of 0.
7. The epitaxial structure according to claim 1, wherein: The refractive index of the SiON layer material is 1.45-2.
2.
8. The epitaxial structure according to claim 1, wherein: The silicon-based substrate is a high-resistance silicon substrate. The epitaxial structure further includes a radio frequency device channel layer and a barrier layer located on the AlN nucleation layer. The material of the channel layer includes GaN, and the material of the barrier layer includes AlGaN.
9. A method for preparing an epitaxial structure, characterized in that: The preparation method comprises: providing a silicon-based substrate; forming a transition layer on the silicon-based substrate, wherein the transition layer comprises a single SiON layer or a stack of multiple SiON layers with different atomic ratios; An AlN nucleation layer is formed on the transition layer.
10. The method for preparing an epitaxial structure according to claim 9, wherein: The transition layer is formed by a CVD process, the growth temperature of the CVD process is 300° C. to 450° C., and the precursor gas of the CVD process includes SiH 4 , NH 3 and NO 2 .