Substrate with embedded cavity and preparation method thereof

Abstract

The invention relates to a substrate with an embedded cavity and a preparation method thereof. The preparation method of the substrate with the pre-buried cavity comprises the following steps that a supporting substrate is formed, a cavity is formed in the supporting substrate, the supporting substrate comprises a top face and a bottom face which are oppositely distributed in the first direction, and the cavity extends from the top face of the supporting substrate to the interior of the supporting substrate; a top structure is formed, the top structure comprises a top material layer, and a stripping layer is arranged in the top material layer; bonding the supporting substrate and the top structure; and peeling off a part of the top material layer along the peeling layer to form a substrate comprising the remaining top material layer and the supporting substrate. According to the invention, the manufacturing of the ultrathin top material layer can be realized, the preparation cost is low, and the preparation process is simple.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a substrate with a pre-buried cavity and a preparation method thereof. Background Art

[0002] A substrate with a pre-buried cavity, such as a SOI (Cavity SOI, C-SOI) substrate with a pre-buried cavity, is an advanced technology that further innovates on the basis of traditional SOI (Silicon-On-Insulator). Its core feature is the integration of a pre-etched cavity structure in the supporting substrate wafer. The application of the substrate technology with a pre-buried cavity in the manufacture of MEMS devices (such as pressure sensor devices) brings significant advantages: by directly integrating the required buried cavity structure in the substrate manufacturing process, it not only simplifies the manufacturing process, but also avoids the complex substrate cavity etching steps in the traditional process, providing a new solution for prefabricating complex cavities. However, the substrate technology with a pre-buried cavity faces a key challenge in the implementation process - the preparation of a thin top material layer. Due to the presence of a cavity structure in the supporting substrate wafer, the top material layer is partially suspended. This structural characteristic makes the thickness of the top material layer positively correlated with its mechanical strength, that is, the thinner the thickness of the top material layer, the more likely it is to have a fragmentation failure problem later.

[0003] With the rapid development of the semiconductor industry and the continuous deepening of related technical research, the semiconductor market has increasingly stringent requirements on the thickness of the top material layer in the substrate with a pre-buried cavity, especially the increasing demand for ultra-thin top material layers. However, the traditional preparation method is not only costly and complex in process, but also difficult to ensure the uniformity of the thickness of the top material layer, and it is difficult to obtain an ultra-thin top material layer.

[0004] Therefore, how to reduce the thickness of the top material layer while reducing the difficulty of the preparation process of the substrate with the embedded cavity, reduce the manufacturing cost of the substrate with the embedded cavity, and improve the uniformity of the thickness of the top material layer, thereby improving the performance and manufacturing yield of the substrate with the embedded cavity, is a technical problem that needs to be solved urgently. Summary of the invention

[0005] The present invention provides a substrate with a pre-embedded cavity and a preparation method thereof, which are used to reduce the difficulty of the preparation process of the substrate with the pre-embedded cavity while reducing the thickness of the top material layer, reduce the manufacturing cost of the substrate with the pre-embedded cavity, and improve the uniformity of the thickness of the top material layer, thereby improving the performance and manufacturing yield of the substrate with the pre-embedded cavity.

[0006] According to some embodiments, the present invention provides a method for preparing a substrate having a pre-buried cavity, comprising the following steps:

[0007] Form a support substrate having a cavity therein. The support substrate includes a top surface and a bottom surface that are oppositely distributed in a first direction, and the cavity extends from the top surface of the support substrate into the interior of the support substrate;

[0008] Form a top structure including a top material layer with a release layer therein;

[0009] Bond the support substrate and the top structure;

[0010] Remove a portion of the top material layer along the release layer to form a substrate including the remaining top material layer and the support substrate.

[0011] In some embodiments, the specific steps of forming the support substrate include:

[0012] Provide a bottom material layer made of silicon, silicon carbide, silicon nitride, or aluminum oxide, and use the bottom material layer as the support substrate;

[0013] Etch the bottom material layer from the top surface of the bottom material layer in the first direction to form a plurality of cavities spaced apart in a second direction, and the second direction is parallel to the top surface of the support substrate.

[0014] In some embodiments, the specific steps of forming the top structure include:

[0015] Provide an initial top material layer;

[0016] Oxidize the surface of the initial top material layer to form a buried oxide layer, and use the remaining initial top material layer below the buried oxide layer as the top material layer;

[0017] Inject doping ions into the interior of the top material layer to form the release layer. The release layer divides the top material layer into a first part and a second part arranged in the first direction, and the buried oxide layer covers the surface of the first part.

[0018] In some embodiments, the doping ions are any one of hydrogen ions and helium ions or a combination of the two.

[0019] In some embodiments, the specific steps of injecting doping ions into the interior of the top material layer to form the release layer include:

[0020] Inject the doping ions into the interior of the top material layer from the surface of the buried oxide layer in the first direction to form the release layer.

[0021] In some embodiments, the specific steps of bonding the support substrate and the top structure include:

[0022] Bond the support substrate and the top structure along the direction of the buried oxide layer towards the top surface of the bottom material layer.

[0023] In some embodiments, the specific steps of forming the support substrate include:

[0024] Provide an initial bottom material layer, the material of the initial bottom material layer being silicon;

[0025] Form a buried oxide layer and a plurality of cavities on the surface of the initial bottom material layer, the cavities being arranged at intervals along a second direction and at least located inside the buried oxide layer, and use the remaining initial bottom material layer below the buried oxide layer as the bottom material layer to form the support substrate including the bottom material layer and the buried oxide layer, the second direction being parallel to the top surface of the support substrate.

[0026] In some embodiments, the material of the top material layer is silicon, silicon carbide, silicon nitride, aluminum oxide or silicon dioxide; the specific steps of bonding the support substrate and the top structure include:

[0027] Bond the support substrate and the top structure along the direction of the top material layer towards the buried oxide layer.

[0028] In some embodiments, after partially peeling off the top material layer along the peeling layer, the thickness of the remaining top material layer above the support substrate is less than 1.5 μm.

[0029] According to some other embodiments, the present invention further provides a substrate with pre-embedded cavities, which is formed by using the preparation method of the substrate with pre-embedded cavities described in any one of the above.

[0030] The present invention provides a substrate with a pre-embedded cavity and a method for preparing the same. After forming a support substrate with a cavity, a release layer is formed inside the top material layer. After bonding and connecting the top structure and the support substrate through a bonding process, a part of the top material layer is peeled off through a peeling process to form a substrate including the remaining top material layer and the support substrate. Since the top material layer is thinned by a peeling process rather than a grinding process after bonding, the problem that the top material layer is easily broken and fails when the top material layer suspended above the cavity is ground subsequently is avoided, and the manufacturing yield of the substrate with a pre-embedded cavity having a thinner top material layer is improved. Moreover, by thinning the top material layer through a peeling process, the present invention can realize the manufacture of an ultra-thin top material layer and improve the thickness uniformity of the top material layer in the formed substrate. In addition, the present invention does not need to use a double-layer wafer to prepare a substrate with a pre-embedded cavity, has a low preparation cost, and a simple preparation process, thereby improving the manufacturing efficiency of the semiconductor structure. The top material layer peeled off by the peeling process in the present invention can also be recycled, thereby further reducing the semiconductor production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flowchart of a method for preparing a substrate with a pre-embedded cavity in a specific embodiment of the present invention;

[0032] Figure 2 is a schematic structural diagram of an initial top material layer in a specific embodiment of the present invention;

[0033] Figure 3 is a schematic structural diagram after forming a buried oxide layer and a top material layer in a specific embodiment of the present invention;

[0034] Figure 4 is a schematic structural diagram after forming a release layer in a specific embodiment of the present invention;

[0035] Figure 5 is a schematic structural diagram of a formed bottom material layer in a specific embodiment of the present invention;

[0036] Figure 6 is a schematic structural diagram after bonding a top structure and a support substrate in a specific embodiment of the present invention;

[0037] Figure 7 is a schematic structural diagram after peeling off a part of the top material layer along the release layer in a specific embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The following detailed description will be made on the specific embodiments of the substrate with a pre-embedded cavity and the method for preparing the same provided by the present invention in conjunction with the accompanying drawings.

[0039] This specific embodiment provides a method for manufacturing a substrate with a pre-embedded cavity. Figure 1 It is a flowchart of the method for manufacturing a substrate with a pre-embedded cavity in the specific embodiment of the present invention. As Figure 1 shown, the method for manufacturing a substrate with a pre-embedded cavity includes the following steps:

[0040] Step S11, forming a support substrate, the support substrate having a cavity inside, the support substrate including a top surface and a bottom surface distributed opposite to each other in a first direction, the cavity extending from the top surface of the support substrate into the interior of the support substrate;

[0041] Step S12, forming a top structure, the top structure including a top material layer, the interior of the top material layer having a release layer;

[0042] Step S13, bonding the support substrate and the top structure;

[0043] Step S14, peeling off a part of the top material layer along the release layer to form a substrate including the remaining top material layer and the support substrate.

[0044] Figure 5 It is a schematic structural diagram of the bottom material layer formed in the specific embodiment of the present invention. In some embodiments, as Figure 5 shown, the specific steps of forming the support substrate include:

[0045] Providing a bottom material layer 50, the material of the bottom material layer being silicon (Si), silicon carbide (SiC), silicon nitride (SiN), or aluminum oxide (Al2O3), and using the bottom material layer as the support substrate;

[0046] Etching the bottom material layer 50 from the top surface of the bottom material layer 50 along the first direction D1 to form a plurality of cavities 51 spaced apart along a second direction D2, the second direction D2 being parallel to the top surface of the support substrate.

[0047] Specifically, a dry etching process can be used to etch the bottom material layer 50 from the top surface of the bottom material layer 50 along the first direction D1 to form a plurality of cavities 51 spaced apart along the second direction D2, and each cavity 51 does not penetrate the bottom material layer 50 along the first direction D1. The cavity 51 serves as the pre-embedded cavity in the substrate with a pre-embedded cavity. In one example, the depth to which the cavity 51 extends into the bottom material layer 50 can be adjusted by controlling factors such as the etching time and the amount of dry etchant of the dry etching process, thereby further improving the flexibility of the manufacturing process of the substrate with a pre-embedded cavity to meet the requirements of different process manufacturing. The plurality mentioned in this specific embodiment means two or more.

[0048] Figure 2 is a schematic diagram of the structure of the initial top material layer in a specific embodiment of the present invention, Figure 3 is a schematic diagram of the structure after the buried oxide layer and the top material layer are formed in a specific embodiment of the present invention, Figure 4 Schematic diagram of the structure after the peeling layer is formed in a specific embodiment of the present invention. In some embodiments, the material of the top material layer is silicon; the specific steps of forming the top structure include:

[0049] Providing an initial top material layer 20, such as Figure 2 As shown;

[0050] The surface of the initial top material layer 20 is oxidized to form a buried oxide layer 30, and the remaining initial top material layer 20 below the buried oxide layer 30 is used as the top material layer 31. Figure 3 As shown;

[0051] Doping ions are implanted into the top material layer 31 to form the peeling layer 40. The peeling layer 40 separates the top material layer 31 into a first portion and a second portion arranged along the first direction D1. The buried oxide layer 30 covers the surface of the first portion. Figure 4 shown.

[0052] Specifically, the initial top material layer 20 is provided, and the initial top material layer 20 includes a first surface and a second surface that are relatively distributed along the first direction D1. The material of the initial top material layer 20 is silicon. The first surface of the initial top material layer 20 is oxidized by a thermal oxidation process to form the buried oxide layer 30 whose material is silicon dioxide, and the remaining unoxidized initial top material layer 20 serves as the top material layer 31. The surface of the top material layer 31 facing the buried oxide layer 30 serves as the front side of the top material layer 31, and the surface of the top material layer 31 away from the buried oxide layer 30 serves as the back side of the top material layer 31. During the implementation of the thermal oxidation process, the quality and thickness of the generated buried oxide layer 30 are adjusted by adjusting the parameters of the thermal oxidation process, such as any one or a combination of two or more of the thermal oxidation temperature, the thermal oxidation time, and the gas environment.

[0053] After forming the buried oxide layer 30, doping ions are implanted into the interior of the top material layer 31 to form the stripping layer 40. The stripping layer 40 separates the top material layer 31 into a first portion and a second portion arranged along the first direction D1. The buried oxide layer 30 covers the surface of the first portion. Figure 4As shown. By adjusting the implantation energy when implanting the doped ions, the depth of the stripping layer 40 can be adjusted, thereby adjusting the relative thickness of the first part and the second part. In one example, the thickness of the first part along the first direction D1 is less than the thickness of the second part along the first direction D1.

[0054] In some embodiments, the doped ions are any one of hydrogen ions and helium ions or a combination of both.

[0055] For example, the hydrogen ions are protium (1H), deuterium (2H), or tritium (3H). Using hydrogen ions or helium ions as the doped ions to implant into the top material layer 31, on the one hand, since the masses of hydrogen ions and helium ions are relatively light, therefore, the damage to the top material layer 31 during the ion implantation process can be reduced, thereby reducing the defects generated in the top material layer 31 due to ion implantation, and thus improving the quality of the subsequent formed substrate; on the other hand, the hydrogen ions and helium ions in the stripping layer 40 are prone to expand when heated, which not only simplifies the operation of stripping the second part from the top material layer 31, but also reduces the impurity residue on the surface of the first part after the stripping process.

[0056] In some embodiments, the specific steps of implanting doped ions into the top material layer 31 to form the stripping layer 40 include:

[0057] Implanting the doped ions from the surface of the buried oxide layer 30 along the first direction D1 into the top material layer 31 to form the stripping layer 40.

[0058] In other embodiments, the specific steps of implanting doped ions into the top material layer 31 to form the stripping layer 40 include:

[0059] Obliquely implanting the doped ions from the surface of the buried oxide layer 30 into the top material layer 31 to form the stripping layer 40. The oblique implantation means that the direction of implanting the doped ions intersects obliquely with the surface of the top material layer 31 facing the buried oxide layer 30 (i.e., the front surface of the top material layer 31), thereby reducing the influence of channeling effect during the doped ion implantation process.

[0060] Figure 6 It is a schematic structural diagram after bonding the top structure and the support substrate in the specific embodiment of the present invention. In some embodiments, the specific steps of bonding the support substrate and the top structure include:

[0061] Bonding the support substrate and the top structure along the direction of the top surface of the buried oxide layer 30 facing the bottom material layer 50, as Figure 6 shown.

[0062] Figure 7 It is a schematic structural diagram after the top material layer along the peeling layer in the specific implementation manner of the present invention is peeled off. After bonding the support substrate and the top structure, heat treatment is performed on the top material layer 31 bonded to the support substrate, so that hydrogen ions or helium ions in the peeling layer 40 expand due to heat to form bubbles. The formation of the bubbles will cause stress concentration in the top material layer 31, so that the top material layer 31 peels off at the position of the peeling layer 40, and the bubbles escape from the top material layer 31 during the peeling process. Using the heat treatment process to peel off the second part at the position of the peeling layer 40, as Figure 7 shown, it not only helps to improve the preparation efficiency of the substrate, but also can ensure the integrity of the remaining second part after peeling, so that the second part can be used again to form the substrate subsequently, effectively reducing the semiconductor manufacturing cost.

[0063] In some other embodiments, the specific steps of forming the support substrate include:

[0064] Providing an initial bottom material layer, the material of the initial bottom material layer is silicon;

[0065] Forming a buried oxide layer and a plurality of cavities arranged at intervals along a second direction and at least located inside the buried oxide layer on the surface of the initial bottom material layer, and using the remaining initial bottom material layer below the buried oxide layer as the bottom material layer to form the support substrate including the bottom material layer and the buried oxide layer, the second direction is parallel to the top surface of the support substrate.

[0066] In one example, the surface of the initial bottom material layer can be oxidized first to form a buried oxide layer, and the remaining initial bottom material layer below the buried oxide layer can be used as the bottom material layer to form the support substrate including the bottom material layer and the buried oxide layer. Then, at least the buried oxide layer is etched to form a plurality of cavities arranged at intervals along the second direction and at least located inside the buried oxide layer.

[0067] In another example, the initial bottom material layer can be etched first to form a plurality of cavities arranged at intervals along the second direction. Then, the surface of the initial bottom material layer is oxidized to form a buried oxide layer, and the remaining initial bottom material layer below the buried oxide layer is used as the bottom material layer to form the support substrate including the bottom material layer and the buried oxide layer, and the cavities are at least located inside the buried oxide layer.

[0068] Among them, the cavity may be only located within the buried oxide layer. In another example, the cavity penetrates the buried oxide layer along the first direction and extends into the bottom material layer, and the cavity does not penetrate the bottom material layer.

[0069] In some other embodiments, the material of the top material layer is silicon, silicon carbide, silicon nitride, aluminum oxide, or silicon dioxide; the specific steps of bonding the support substrate and the top structure include:

[0070] Bond the support substrate and the top structure along the direction of the top material layer towards the buried oxide layer.

[0071] For example, the buried oxide layer can also be formed in the initial substrate, so that there is no need to form the buried oxide layer in the top structure again, enabling the cavity to penetrate the buried oxide layer along the first direction D1 and extend into the interior of the bottom material layer to meet the setting requirements of different cavities.

[0072] In some embodiments, after partially stripping the top material layer 31 along the stripping layer 40, the thickness of the remaining top material layer 31 above the bottom material layer 50 is less than 1.5 μm. By using the stripping process to thin the top material layer 31, not only can the thickness of the top material layer 31 in the formed substrate be less than 1.5 μm, but also the flatness of the top material layer 31 in the finally formed substrate can be improved, ensuring the uniformity of the thickness of the top material layer 31 (e.g., the thickness along the first direction D1) in the finally formed substrate with a pre-embedded cavity. For example, the thickness uniformity of the top material layer 31 reaches ±10 nm, thereby further improving the quality of the prepared substrate with a pre-embedded cavity. This specific embodiment performs the stripping process after bonding the top structure and the support substrate, avoiding problems such as increased process complexity and easy generation of fragments caused by transferring and bonding a thinner top material layer. At the same time, the top material layer 31 (i.e., the second part) peeled off by the stripping layer 40 can form the next substrate by adopting steps S11 - S14, realizing the recycling of the initial top material layer, thereby effectively reducing the semiconductor production cost.

[0073] This specific embodiment also provides a substrate with a pre-embedded cavity, which is formed by using the preparation method of the substrate with a pre-embedded cavity described in any one of the above, see Figures 1-7 .

[0074] The substrate with a pre-embedded cavity and its manufacturing method provided by this specific embodiment, after forming a support substrate with a cavity, by forming a peeling layer inside the top material layer, after bonding and connecting the top structure and the support substrate through a bonding process, a part of the top material layer is peeled off through a peeling process to form a substrate including the remaining top material layer and the support substrate. Since the top material layer is thinned by a peeling process rather than a grinding process after bonding, the problem that the top material layer is easily broken and fails when grinding the top material layer suspended above the cavity is avoided, and the manufacturing yield of the substrate with a pre-embedded cavity having a thinner top material layer is improved. Moreover, by thinning the top material layer through a peeling process in this specific embodiment, the manufacturing of an ultra-thin top material layer can be realized, and the thickness uniformity of the top material layer in the formed substrate can be improved. In addition, this specific embodiment does not need to use a double-layer SOI wafer for preparation, the preparation cost is low, and the preparation process is simple, thereby improving the manufacturing efficiency of the semiconductor structure. The top material layer peeled off through the peeling process in this specific embodiment can also be recycled, thereby further reducing the semiconductor production cost.

[0075] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and retouches can still be made, and these improvements and retouches should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a substrate with a pre-buried cavity, characterized in that: The steps include: forming a support substrate, wherein the support substrate has a cavity therein, the support substrate comprising a top surface and a bottom surface that are relatively distributed along a first direction, and the cavity extends from the top surface of the support substrate to the interior of the support substrate; forming a top structure, the top structure comprising a top material layer, the top material layer having a peeling layer inside; bonding the support substrate and the top structure; A portion of the top material layer is peeled off along the peeling layer to form a substrate including the remaining top material layer and the supporting substrate.

2. The method for preparing a substrate with a pre-buried cavity according to claim 1, characterized in that: The specific steps of forming the support substrate include: Providing a bottom material layer, wherein the material of the bottom material layer is silicon, silicon carbide, silicon nitride or aluminum oxide, and using the bottom material layer as the supporting substrate; The bottom material layer is etched from the top surface of the bottom material layer along the first direction to form a plurality of the cavities spaced apart along a second direction, wherein the second direction is parallel to the top surface of the support substrate.

3. The method for preparing a substrate with a pre-buried cavity according to claim 2, characterized in that: The material of the top material layer is silicon; The specific steps to form the top structure include: providing an initial top material layer; Oxidizing the surface of the initial top material layer to form a buried oxide layer, and using the remaining initial top material layer below the buried oxide layer as the top material layer; Doping ions are implanted into the interior of the top material layer to form the stripping layer, wherein the stripping layer separates the top material layer into a first portion and a second portion arranged along the first direction, and the buried oxide layer covers the surface of the first portion.

4. The method for preparing a substrate with a pre-buried cavity according to claim 3, characterized in that: The doping ions are any one of hydrogen ions and helium ions or a combination of the two.

5. The method for preparing a substrate with a pre-buried cavity according to claim 3, characterized in that: The specific steps of injecting doping ions into the interior of the top material layer to form the peeling layer include: The doping ions are implanted from the surface of the buried oxide layer into the interior of the top material layer along the first direction to form the lift-off layer.

6. The method for preparing a substrate with a pre-buried cavity according to claim 3, characterized in that: The specific steps of bonding the support substrate and the top structure include: The support substrate and the top structure are bonded along a direction from the buried oxide layer toward a top surface of the bottom material layer.

7. The method for preparing a substrate with a pre-buried cavity according to claim 1, characterized in that: The specific steps of forming the support substrate include: Providing an initial bottom material layer, wherein the material of the initial bottom material layer is silicon; A buried oxide layer and a plurality of cavities arranged at intervals along a second direction and at least located inside the buried oxide layer are formed on the surface of the initial bottom material layer, and the initial bottom material layer remaining below the buried oxide layer is used as the bottom material layer to form the supporting substrate including the bottom material layer and the buried oxide layer, wherein the second direction is parallel to the top surface of the supporting substrate.

8. The method for preparing a substrate with a pre-buried cavity according to claim 7, characterized in that: The material of the top material layer is silicon, silicon carbide, silicon nitride, aluminum oxide or silicon dioxide; the specific steps of bonding the support substrate and the top structure include: The support substrate and the top structure are bonded along a direction from the top material layer toward the buried oxide layer.

9. The method for preparing a substrate with a pre-buried cavity according to claim 1, characterized in that: After a portion of the top material layer is peeled off along the peeling layer, the thickness of the top material layer remaining above the supporting substrate is less than 1.5 μm.

10. A substrate with a pre-buried cavity, characterized in that: The substrate is formed by the method for preparing a substrate with a pre-buried cavity as described in any one of claims 1 to 9.

Images