A method for preparing high-quality semiconductor thin films
By setting macropore structures in porous layers and performing precise control, the problems of lattice mismatch stress release and material defects in the epitaxial and transfer processes of high-quality semiconductor thin films were solved, realizing the transfer of high-quality layers and the improvement of epitaxial thin films.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI INST OF MICROSYSTEM & INFORMATION TECH CHINESE ACAD OF SCI
- Filing Date
- 2026-01-20
- Publication Date
- 2026-06-02
AI Technical Summary
Existing technologies for the epitaxy and transfer of high-quality semiconductor thin films suffer from problems such as limited lattice mismatch stress release capability, high material defect density, high process cost, and severe damage during the transfer process.
By setting macropore structures in a porous structure layer and retaining supporting structures around them, precise control of mechanical strength can be achieved. After epitaxial semiconductor thin films are formed on the substrate, they are bonded to the supporting substrate. The macropore structures are preferentially peeled off through fluid corrosion or crystallization stress, thus achieving the transfer of high-quality layers.
It improves the crystal quality of epitaxial films, reduces material defect density, and reduces process costs and damage through precise control of the peeling process.
Smart Images
Figure CN122138622A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor device technology, and specifically relates to a method for preparing high-quality semiconductor thin films. Background Technology
[0002] Semiconductor devices are typically fabricated on epitaxial material layers, which can have lower defect density, higher mobility, and higher breakdown voltage than substrate materials.
[0003] When performing material epitaxy, the following factors need to be considered:
[0004] (1) Reduce defects in the substrate material to extend into the epitaxial material layer;
[0005] (2) Reduce material defects and wafer warping caused by lattice mismatch and thermal stress mismatch between epitaxial material layer and substrate material.
[0006] To achieve the above objectives, a patterned epitaxial substrate can be used, with a convex-concave structure of a certain depth on its upper surface. During the epitaxial process, the epitaxial material along the convex portions will preferentially heal. As the epitaxial material along the convex portions heals, the epitaxial process along the concave portions gradually stops, forming a cavity within the healed structure. This cavity structure can release lattice mismatch stress, thermal stress, etc., thereby reducing material defects during the healing of the epitaxial material. However, using only a single-layer patterned structure has limited ability to release lattice mismatch stress and thermal stress, and the degree of reduction in material defect density is also limited.
[0007] In addition, after epitaxial high-quality semiconductor thin films, they often need to be transferred to other target substrates to meet device fabrication and integration requirements.
[0008] CEA-LETI of France invented a smart stripping technology: hydrogen ions are injected into a target substrate at a certain depth, and after annealing, the hydrogen ions agglomerate into plate-shaped bubbles, achieving targeted stripping of the material. This method has certain limitations: (1) not all materials can be transferred through smart stripping; (2) H ion implantation will cause a large number of damage defects, requiring secondary annealing for repair; (3) when stripping micron-thick films, an implantation energy of 100 keV or even MeV is required, which places high demands on the implantation equipment and increases the process cost.
[0009] Canon of Japan developed Eltran-SOI technology, such as... Figure 1 As shown: (1) Low-porosity porous silicon and high-porosity porous silicon are sequentially prepared on the surface of single-crystal silicon. Figure 2(1) The high porosity porous silicon layer is located below the low porosity porous silicon layer; (2) The low porosity porous silicon surface is hydrogen annealed to achieve surface smoothing and pore healing; (3) Single crystal silicon is epitaxially grown on the above substrate; (4) The epitaxial substrate is bonded to another support substrate; (5) The bonded substrate is cracked along the high porosity layer; (6) The high porosity layer and the low porosity layer are removed, and the epitaxial single crystal silicon layer is ground to the required thickness and roughness.
[0010] The drawback of Eltran-SOI technology is that, Figure 3 As shown: (1) The upper surface of the low porosity layer is a sponge-like rough structure, which cannot be directly used for high-quality thin film epitaxy. (2) The low porosity layer needs to be healed by hydrogen annealing. However, the hydrogen annealing process only has a healing and polishing effect on a few semiconductor materials, and the process conditions are harsh. (3) When preparing the second high porosity layer structure, it is necessary to simultaneously achieve: the mechanical strength of the second high porosity layer is lower than a certain threshold, and the secondary corrosion damage to the surface of the first low porosity layer is small when the second high porosity layer is etched. The control conditions are relatively harsh.
[0011] Therefore, it is essential to develop a technical solution that can simultaneously meet the requirements of high-quality semiconductor thin film epitaxy and high-quality transfer. Summary of the Invention
[0012] The technical problem to be solved by the present invention is to provide a method for preparing high-quality semiconductor thin films. This method can achieve precise control of the mechanical strength at the macropore structure by setting macropore structures in a porous structure layer while retaining a certain proportion of support structure around the macropore structure. The macropore structure can keep the substrate structurally intact during cleaning, epitaxy, bonding and other processes, and preferentially peel off from the location of the macropore structure during transfer and peeling, thereby achieving high-quality layer transfer.
[0013] This invention provides a method for preparing high-quality semiconductor thin films, comprising the following steps:
[0014] (1) Prepare the epitaxial substrate;
[0015] (2) A porous structure layer is prepared on the surface of the epitaxial substrate;
[0016] (3) A patterned macroporous structure is formed inside the porous structure layer;
[0017] (4) Epitaxially extending a target semiconductor thin film over the porous structure layer;
[0018] (5) Bond the semiconductor thin film to another supporting substrate to form a bonding substrate;
[0019] (6) The bonding substrate is cleaved along the porous structure layer to obtain a transfer substrate containing a semiconductor thin film;
[0020] (7) Remove the porous structure layer remaining on the transfer substrate.
[0021] Optionally, after preparing the epitaxial substrate in step (1), an etched structure layer containing several longitudinal etched structures is prepared on the surface of the epitaxial substrate.
[0022] The non-etched areas of the etched structure layer retain good lattice quality and low roughness, which helps to improve the quality of the epitaxial film. The porous structure layer is located below the etched structure layer and contains a rich network of pores. It has strong deformation capability and can better release lattice mismatch stress and thermal stress, meeting the process requirements of thicker epitaxial films, larger epitaxial wafers, and higher epitaxial quality.
[0023] Optionally, the etching depth of the non-etched area of the etched structural layer is ≤1 nm, and the increase in surface roughness compared to before the etching process is ≤1 nm; the depth of the etched structural layer is 10 nm to 10 μm. Furthermore, electrochemical etching can be used to prepare the etched structural layer. Since the chemical reaction barrier at material defects is usually lower than that in defect-free areas, under precise control of the electrochemical etching process parameters (controlling the bias voltage of the electrochemical etching interface below a certain value so that the corrosion rate of the reactive ions in the electrochemical etching solution at the defects is significantly higher than that at the non-defect areas), corrosion pits can be preferentially formed at the material defects. This prevents the defects from extending into the epitaxial layer in subsequent epitaxial processes, further improving the quality of the epitaxial film.
[0024] Optionally, the longitudinal etching structure in step (2) is a drill hole or a specific pattern structure.
[0025] Preferably, the diameter of the drilled hole is ≤1μm; the diameter of the hole-like structure in the specific pattern structure is ≤1μm, and the width of the line segment structure in the specific pattern structure is ≤1μm.
[0026] Preferably, the ratio of the diameter of the drilled hole to the etching depth is ≤4; the ratio of the diameter of the hole structure to the etching depth in the specific pattern structure is ≤4; and the ratio of the width of the line segment structure to the etching depth in the specific pattern structure is ≤4.
[0027] Preferably, in step (2), the porous structure layer is prepared by an electrochemical etching method, and the porous structure layer contains an inter-linked network of pores.
[0028] Before fabricating the porous structure layer, a patterned film structure can be formed on the surface of the epitaxial substrate. Then, an electrochemical etching process is performed on the substrate to etch the porous structure along the exposed area of the patterned film structure, and finally a porous structure layer is formed under the patterned film.
[0029] Preferably, the method for forming the patterned macroporous structure in step (3) includes one or more of the following:
[0030] (1) A patterned mask is formed on the surface of the porous structure layer, and the epitaxial substrate is electrochemically etched to form a patterned macropore structure at the bottom of the porous structure layer, and then the patterned mask is removed.
[0031] (2) A patterned film structure is formed on the surface of the epitaxial substrate, and a porous structure layer is formed below the patterned film structure, and a patterned macroporous structure is formed in the porous structure layer;
[0032] (3) Patterned illumination is performed on the surface of the porous structure layer and / or the back side of the epitaxial substrate, and electrochemical etching is performed on the epitaxial substrate to form a patterned macropore structure at the bottom of the porous structure layer.
[0033] Preferably, in step (3), the characteristic size of the macropore structure is ≥500 nm, and the thickness of the porous structure layer is ≥50 nm. The macropore structure can be an independent, closed macropore, or it can be an interconnected microchannel structure.
[0034] Preferably, in step (5), before the bonding process, a bonding buffer layer is deposited on at least one side of the bonding surface between the semiconductor thin film and the supporting substrate;
[0035] Alternatively, before the bonding process, a patterned groove structure can be prepared on at least one side of the bonding surface between the semiconductor thin film and the supporting substrate.
[0036] Alternatively, before the bonding process, a device process is performed on the surface of the semiconductor thin film to form an active device layer containing an electrical connection structure, and the active device layer is then bonded to the supporting substrate.
[0037] Preferably, the pyrolysis method in step (6) includes one or more of the following:
[0038] (1) One or more of the following methods are employed: fluid impact on the side of the porous structure layer, acoustic vibration on the bonding substrate, thermal stress introduced into the bonding substrate, stress introduced into the porous structure layer, oxidation of the side of the porous structure layer, and chemical etching of the side of the porous structure layer.
[0039] (2) Temporarily bond the two sides of the bonding substrate to an independent structural component, and cause the bonding substrate to crack along the porous structure layer by pulling the two independent structural components. Then perform a debonding process to obtain a transfer substrate containing an epitaxial semiconductor thin film.
[0040] (3) Introduce fluid into the macroporous structure and remove all or part of the supporting structure around the macroporous structure through the corrosion and oxidation of the fluid, thereby achieving the pyrolysis of the bonded substrate;
[0041] (4) Introduce fluid into the macroporous structure and crystallize the fluid by lowering the ambient temperature. The crystallization stress destroys the support structure of the macroporous structure, thereby achieving the pyrolysis of the bonded substrate.
[0042] Preferably, in step (6), the surface of the epitaxial substrate is polished after pyrolysis to achieve multiple reuses.
[0043] The present invention also provides a substrate obtained by the above-described high-quality semiconductor thin film preparation method.
[0044] Beneficial effects
[0045] (1) The thin film structure of the present invention is relatively stable and easy to peel off: By setting a large hole structure in the porous structure layer, while still retaining a certain proportion of support structure around the large hole structure, the mechanical strength at the large hole structure can be precisely controlled. By precisely controlling the characteristic size of the large hole structure, the substrate can maintain structural integrity during cleaning, epitaxy, bonding and other processes, and peel off preferentially from the location of the large hole structure during transfer and peeling, thus achieving high-quality layer transfer.
[0046] (2) By constructing a macroporous structure, the present invention can form a microchannel structure interconnected by the macroporous structure. Based on this, an external fluid can be introduced, and the supporting structure around the macroporous structure can be completely or partially removed through the corrosion effect of the fluid, thereby achieving the pyrolysis of the bonded substrate. Alternatively, the fluid can be introduced into the macroporous structure, and the fluid can be crystallized by lowering the ambient temperature. The crystallization stress can then destroy the supporting structure of the macroporous structure, thereby achieving the pyrolysis of the bonded substrate.
[0047] (3) This invention improves the surface structure quality of the porous structure layer and enhances the epitaxial quality: During the preparation of patterned macroporous structures, the use of patterned masks, patterned illumination, or other patterning measures limits electrochemical corrosion to specific areas, and the secondary damage to the top of the porous structure layer caused by electrochemical corrosion is limited and controllable. The area protected by the patterned structure is less affected by electrochemical corrosion and retains good single-crystal properties. The semiconductor thin film epitaxially grown on it has high crystal quality and can guide and improve the lattice quality of the surrounding material during the epitaxial process, thereby improving the overall epitaxial quality. Attached Figure Description
[0048] Figure 1 This is a schematic diagram of the Eltran-SOI technology process.
[0049] Figure 2 This is a schematic diagram of the cross-sections of the low-porosity layer and the high-porosity layer.
[0050] Figure 3 The images show electron microscope (EM) images of the low-porosity layer surface and the surface after hydrogen annealing.
[0051] Figure 4 This is a cross-sectional schematic diagram of the first process flow of the present invention.
[0052] Figure 5 This is a cross-sectional schematic diagram of the second process flow of the present invention.
[0053] Figure 6 This is a cross-sectional view of a high-quality semiconductor thin film obtained by the first process flow of the present invention.
[0054] Figure 7 This is a cross-sectional view of a high-quality semiconductor thin film obtained by the second process flow of the present invention.
[0055] Figure 8 This is a 3D structure diagram of a high-quality semiconductor thin film obtained by the process flow of this invention.
[0056] Figure 9 This is a physical image of the high-quality semiconductor thin film obtained by the process flow of this invention. Detailed Implementation
[0057] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.
[0058] Example 1
[0059] like Figure 4 As shown, this embodiment provides a method for preparing a high-quality semiconductor thin film, including the following steps:
[0060] (1) A porous structure layer is prepared on top of the initial substrate, and a patterned macroporous structure is prepared in the porous structure layer.
[0061] (2) Optionally, an epitaxial buffer layer is added above the etched structural layer. When adding the epitaxial buffer layer, a low-temperature epitaxial process or a high-quality epitaxial process such as MBE can be selected to promote defect healing, opening structure healing, and improve the lattice quality of the buffer layer. This avoids secondary damage to the etched structural layer and porous structural layer caused by temperature and specific process gases under high-temperature epitaxial processes.
[0062] (3) A high-quality epitaxial layer is prepared on the above substrate.
[0063] (4) Bond the above substrate to another support substrate.
[0064] (5) The above-mentioned bonding substrate is cleaved along the porous structure layer to obtain a new bonding substrate.
[0065] (6) Remove the residual etched structure layer on the epitaxial semiconductor film, and perform appropriate polishing, thinning, and morphology trimming on the epitaxial semiconductor film.
[0066] (2) An etched structure layer comprising several longitudinal etched structures is prepared on the surface of the epitaxial substrate;
[0067] like Figure 5 and Figure 6 As shown, before preparing the porous structure layer, an etched structure layer can be prepared on the top of the epitaxial substrate. The etched structure layer contains several vertical etched structures with a certain depth. Then, the etched structure is used as the starting point for electrochemical etching to form the porous structure layer below. The porous structure layer penetrates or partially penetrates the bottom of the etched structure layer in the horizontal direction.
[0068] When the etched structure is a drilled hole, the diameter of the hole is ≤1μm; when the etched structure is a specific pattern structure, the diameter of the hole-like structure in the specific pattern structure is ≤1μm in the horizontal direction, and the width of the line segment structure in the horizontal direction is ≤1μm. The ratio of the diameter of the drilled hole to the etching depth is ≤4; the ratio of the diameter of the hole-like structure in the specific pattern structure to the etching depth is ≤4; the ratio of the width of the line segment structure in the specific pattern structure to the etching depth is ≤4.
[0069] The aspect ratio of the etched structure needs to be ≥0.25 to avoid the low-quality epitaxial layer formed at the bottom of the etched structure from affecting the good healing of the buffer layer and the high-quality epitaxial layer.
[0070] Then proceed with Figure 1 A similar process flow.
[0071] like Figure 7As shown, before fabricating the porous structure layer, a patterned mask structure can be formed on top of it, and an electrochemical etching process is performed along the mask to form the porous structure layer. By adjusting one or more of the key parameters such as the electrochemical etching electric field, light field, solution composition and ratio, and temperature, the substrate under the patterned mask projection is made easier to be etched, and a patterned macropore structure is further formed in the porous structure layer. The macropores have a positional correspondence with the patterned mask structure.
[0072] Figure 8 Several examples of 3D structures of high-quality semiconductor thin films are shown.
[0073] Figure 9 This is a physical image of a high-quality semiconductor thin film, showing that a macroporous structure was fabricated beneath the porous structure layer.
Claims
1. A method for preparing a high-quality semiconductor thin film, characterized in that, Includes the following steps: (1) Prepare the epitaxial substrate; (2) A porous structure layer is prepared on the surface of the epitaxial substrate; (3) A patterned macroporous structure is formed inside the porous structure layer; (4) Epitaxially extending a target semiconductor thin film over the porous structure layer; (5) Bond the semiconductor thin film to another supporting substrate to form a bonding substrate; (6) The bonding substrate is cleaved along the porous structure layer to obtain a transfer substrate containing a semiconductor thin film; (7) Remove the porous structure layer remaining on the transfer substrate.
2. The method for preparing a high-quality semiconductor thin film according to claim 1, characterized in that, After preparing the epitaxial substrate in step (1), an etched structure layer containing several longitudinal etched structures is prepared on the surface of the epitaxial substrate.
3. The semiconductor thin film epitaxy method according to claim 2, characterized in that, The etching depth of the non-etched area material surface of the etched structure layer is ≤1nm, and the increase in surface roughness compared to before the etching process is ≤1nm; the depth of the etched structure layer is 10nm~10μm.
4. The semiconductor thin film epitaxy method according to claim 2, characterized in that, The longitudinal etching structure is a drilled hole or a specific pattern structure.
5. The method for preparing a high-quality semiconductor thin film according to claim 1, characterized in that, In step (2), the porous structure layer is prepared by electrochemical etching, and the porous structure layer contains an inter-linked network of pores.
6. The method for preparing a high-quality semiconductor thin film according to claim 1, characterized in that, The method for forming the patterned macroporous structure in step (3) includes one or more of the following: (1) A patterned mask is formed on the surface of the porous structure layer, and the epitaxial substrate is electrochemically etched to form a patterned macropore structure at the bottom of the porous structure layer, and then the patterned mask is removed. (2) A patterned film structure is formed on the surface of the epitaxial substrate, and a porous structure layer is formed below the patterned film structure, and a patterned macroporous structure is formed in the porous structure layer; (3) Patterned illumination is performed on the surface of the porous structure layer and / or the back side of the epitaxial substrate, and electrochemical etching is performed on the epitaxial substrate to form a patterned macropore structure at the bottom of the porous structure layer.
7. The method for preparing a high-quality semiconductor thin film according to claim 1, characterized in that, In step (5), before the bonding process, a bonding buffer layer is deposited on at least one side of the bonding surface between the semiconductor thin film and the supporting substrate. Alternatively, before the bonding process, a patterned groove structure can be prepared on at least one side of the bonding surface between the semiconductor thin film and the supporting substrate. Alternatively, before the bonding process, a device process is performed on the surface of the semiconductor thin film to form an active device layer containing an electrical connection structure, and the active device layer is then bonded to the supporting substrate.
8. The method for preparing a high-quality semiconductor thin film according to claim 1, characterized in that, The pyrolysis methods in step (6) include one or more of the following: (1) One or more of the following methods are employed: fluid impact on the side of the porous structure layer, acoustic vibration on the bonding substrate, thermal stress introduced into the bonding substrate, stress introduced into the porous structure layer, oxidation of the side of the porous structure layer, and chemical etching of the side of the porous structure layer. (2) Temporarily bond the two sides of the bonding substrate to an independent structural component, and transmit the tensile force or stress to the bonding substrate through the two independent structural components, so that the bonding substrate is cracked along the porous structure layer. Then, the debonding process of the temporary bonding surface is performed to obtain a transfer substrate containing an epitaxial semiconductor thin film. (3) Introduce fluid into the macroporous structure and remove all or part of the supporting structure around the macroporous structure through the corrosion and oxidation of the fluid, thereby achieving the pyrolysis of the bonded substrate; (4) Introduce fluid into the macroporous structure and crystallize the fluid by lowering the ambient temperature. The crystallization stress destroys the support structure of the macroporous structure, thereby achieving the pyrolysis of the bonded substrate.
9. The method for preparing a high-quality semiconductor thin film according to claim 1, characterized in that, In step (6), the surface of the epitaxial substrate is polished after pyrolysis to achieve multiple reuses.
10. A substrate obtained by the high-quality semiconductor thin film preparation method according to any one of claims 1 to 9.