A method for preparing a thick-film oxide film layer

Abstract

The application provides a thick-film oxide film layer preparation method, which comprises the following steps: preparing a deep groove and a hole on a substrate; depositing a first oxide film layer with a thickness of 20000 angstroms, a second oxide film layer with a thickness of 10000 angstroms, a third oxide film layer with a thickness of 10000 angstroms and a fourth oxide film layer with a thickness of 10000 angstroms on the substrate after the preparation of the deep groove and the hole; and placing the substrate containing the oxide film layers in an annealing device to perform annealing after the preparation of each oxide film layer. The annealing treatment is performed after the preparation of each oxide film layer, and the multiple annealings are helpful to gradually release the stress in the oxide film layers, so that the stress of the generated thick oxide film layer is within a receiving range. Through the multiple annealings and the deposition of multiple layers of thin films by using LPTEOS process and PETEOS process, the uniformity and compactness of the thin films are improved, and the performance of the final device is improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor integrated circuit manufacturing, and in particular to a method for preparing a thick oxide film layer. Background Technology

[0002] In the manufacturing process of MEMS products, the selection of sacrificial layer materials is crucial. These materials include polysilicon, silicon oxide, photoresist, metal thin films, and polyimide. They play a key role in the fabrication of MEMS devices. MEMS manufacturing first involves depositing a sacrificial layer on a substrate, followed by depositing a structural layer on its surface and processing it to form the desired pattern. Finally, the sacrificial layer is removed using a specific etching method, allowing the structural material to levitate above the substrate and construct various complex two-dimensional or three-dimensional structures. In other words, selective removal of the sacrificial layer releases and forms the desired three-dimensional structure. Choosing a suitable sacrificial layer material requires comprehensive consideration of factors such as etching rate, internal stress, compatibility with microstructure materials, and matching of thermal expansion coefficients. For example, polysilicon is easily deposited using chemical vapor deposition (CVD) technology and is highly compatible with other manufacturing steps, but its electrical and mechanical properties are relatively poor. In contrast, silicon oxide has excellent chemical stability and electrical insulation, but is not suitable as a structural material.

[0003] For loudspeakers manufactured using traditional non-semiconductor processes, diaphragms are typically made of materials such as paper cones, polypropylene, or carbon fiber. However, in the design of silicon-based MEMS loudspeakers, silicon is chosen as the diaphragm material due to its excellent material stiffness and the superior sound clarity and fidelity it provides. The manufacturing process of silicon diaphragms requires a flat sacrificial layer underneath to support the silicon deposition process. This sacrificial layer must withstand the high temperatures during polycrystalline silicon growth and must not damage the overlying metal structure during sacrificial layer removal. Based on these requirements, silicon oxide has become the optimal choice for the sacrificial layer in silicon-based MEMS loudspeakers.

[0004] To ensure sufficient vibration space for the silicon diaphragm, the thickness design of the sacrificial layer is crucial. However, the use of thick oxide films may affect the sealing effect of the speaker vias due to physical obstruction or filling difficulties. Furthermore, issues such as thermal stress and deposition stress can adversely affect the overall performance of MEMS devices. Therefore, a sacrificial layer generation method needs to be designed to ensure that the vibration requirements of the silicon diaphragm are met without causing other process problems.

[0005] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a thick oxide film layer, which utilizes multiple film growth and multiple annealing processes, and the mixed film formation technology can reduce stress during film growth and improve the sealing effect of through holes.

[0007] To address the aforementioned problems, a method for preparing a thick oxide film is provided below, comprising: preparing deep trenches and holes on a substrate; sequentially depositing a first oxide film layer with a thickness of 20,000 angstroms, a second oxide film layer with a thickness of 10,000 angstroms, a third oxide film layer with a thickness of 10,000 angstroms, and a fourth oxide film layer with a thickness of 10,000 angstroms on the substrate after preparing the deep trenches and holes; after each oxide film layer is prepared, placing the substrate containing the oxide film layer in an annealing apparatus for annealing.

[0008] The substrate is a silicon-based substrate.

[0009] The substrate is fully coated with photoresist and subjected to photolithography and development. The developed substrate is then etched to form deep trenches and holes.

[0010] After each oxide film layer is prepared, the substrate containing the oxide film layer is placed in an annealing equipment, and the annealing temperature is 600℃-1000℃, and the annealing time is 30min-60min.

[0011] After each oxide film layer is prepared, annealing is performed using gradient annealing, with the annealing temperature gradually increased and then gradually decreased to room temperature after annealing.

[0012] The depth of the etched grooves and holes ranges from 10um to 400um.

[0013] The first oxide film layer and the second oxide film layer are prepared in an LPTEOS apparatus, and the third oxide film layer and the fourth oxide film layer are prepared in a PETEOS apparatus.

[0014] The LPTEOS and PETEOS devices are used to prepare oxide films. The precursor gases are tetraethyl orthosilicate gas and oxygen, wherein the flow rate of tetraethyl orthosilicate gas is 50-200 sccm; the flow rate of oxygen is 500-1000 sccm; the plasma power of the PETEOS device is 100-500W; the heating system is turned on during the reaction, and the temperature of the reaction chamber of the LPTEOS device is maintained at 650℃-750℃, and the temperature of the reaction chamber of the PETEOS device is maintained at 300℃-400℃. The thickness of the oxide film is controlled by controlling the deposition time.

[0015] After the oxide film layer is prepared, it is allowed to cool naturally to room temperature or cooled to room temperature by passing nitrogen gas through it.

[0016] An atmosphere gas is introduced into the annealing equipment. The atmosphere gas is any one of nitrogen, argon, hydrogen, or a mixture of nitrogen and oxygen, wherein the mixture of nitrogen and oxygen is composed of 80% nitrogen and 20% oxygen.

[0017] Compared with the prior art, the beneficial effects of the present invention mainly include the following: 1. The present invention utilizes the characteristics of LPTEOS process (low-pressure tetraethoxysilane growth process) for growing oxide film layers, which has high stress, slow release rate and good sealing effect, and PETEOS process (plasma-enhanced tetraethoxysilane process) for growing silicon oxide, which has low stress, fast release rate and poor sealing effect. Two oxide film layers are first deposited on the silicon substrate using the LPTEOS process. The two oxide film layers deposited by the LPTEOS process have the advantage of good sealing effect, which can better seal deep trenches or holes after deep silicon etching. Then, two more oxide film layers are deposited on the two oxide film layers deposited by the LPTEOS process. Since the sealing of deep trenches or holes mainly relies on the oxide film layers deposited by the LPTEOS process, the two oxide film layers deposited by the PETEOS process have the advantage of fast deposition speed, which can accelerate the growth rate of oxide film layers on the silicon substrate surface. The present invention can improve the film growth rate while meeting the sealing requirements through hybrid film technology.

[0018] 2. In this invention, an annealing process is performed after each oxide film layer is formed. Multiple annealing processes help to gradually release the stress in the oxide film layer, so that the stress of the formed thick oxide film layer is within the acceptable range.

[0019] 3. Multiple annealing processes and the deposition of multilayer films using LPTEOS and PETEOS processes help improve the uniformity and density of the films, thereby enhancing the performance of the final devices. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The following are the steps for preparing the thick oxide film layer of the present invention. Detailed Implementation

[0022] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the accompanying drawings. The directional terms mentioned in the following embodiments, such as up, down, left, right, front, or back, are merely for reference to the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the present invention.

[0023] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0024] Example 1

[0025] This embodiment provides a method for preparing a thick oxide film layer. In order to solve the problem in the prior art that the sealing effect of the speaker through hole and the thermal stress deposition are affected by the physical obstruction or filling difficulties during the forming of the MEMS speaker sacrificial layer, this embodiment adopts the method of generating oxide film layer by layer and annealing after each oxide film layer is generated to release the stress in the oxide film layer.

[0026] The specific method for layer-by-layer oxide film generation in this embodiment involves preparing deep trenches and holes on a substrate. The depth of the holes and trenches needs to be determined according to the design. After preparing the deep trenches and holes, an oxide film layer is deposited on the substrate. The oxide film layer is deposited layer by layer, and the thickness of each layer is different. In this invention, four oxide film layers are deposited sequentially on the substrate, wherein the oxide film layer in contact with the substrate has a thickness of 20,000 angstroms, and the second, third, and fourth oxide film layers are each 10,000 angstroms thick. After each oxide film layer is deposited, it needs to be annealed sequentially. The substrate with deposited oxide film layers is placed in an annealing equipment to perform the annealing operation.

[0027] In this embodiment, a silicon-based substrate is used to fabricate a MEMS loudspeaker, and the oxide film layer on the silicon-based substrate material of the MEMS loudspeaker is a silicon dioxide layer.

[0028] In this embodiment, when forming the pattern required for the MEMS loudspeaker on the substrate, photoresist is first fully coated on the substrate. After photolithography and development, etching is performed. This etching can form deep trenches or hole structures. Through photolithography, development, and etching, the pattern required for the MEMS loudspeaker can finally be formed on the substrate. The etching can be performed using either wet etching or dry etching.

[0029] The depth of the etched trenches and holes ranges from 10um to 400um.

[0030] In this embodiment, to release stress and ensure the sealing effect of deep trenches or holes during oxide film deposition, a scheme combining layer-by-layer oxide film deposition with LPTEOS and PETEOS processes is adopted. Specifically, the first oxide film layer and the second oxide film layer are deposited on the substrate using the LPTEOS process (low-pressure tetraethoxysilane growth process). The third and fourth oxide film layers are deposited sequentially on top of the second oxide film layer using the PETEOS process (plasma-enhanced tetraethoxysilane process). More specifically, during the deposition of the first and second oxide film layers, the silicon substrate is placed in the LPTEOS equipment, and the precursor gases tetraethyl orthosilicate gas and oxygen are introduced. Auxiliary gases can also be introduced during preparation, such as diluent gases argon or nitrogen, reducing agents hydrogen, or water vapor to enhance oxidation. The specific auxiliary gases can be used and adjusted as needed. The gas flow rate of tetraethyl orthosilicate is 50-200 sccm; the oxygen flow rate is 500-1000 sccm; the reaction chamber temperature of the LPTEOS equipment is maintained at 650℃-750℃; and the thickness of the film growth can be controlled by controlling the film deposition time.

[0031] When preparing the third and fourth oxide films, the substrate with the second oxide film prepared is placed in the PETEOS apparatus, and the third and fourth oxide films are prepared sequentially. Tetraethyl orthosilicate gas and oxygen are introduced as precursor gases; auxiliary gases may also be introduced during preparation. The tetraethyl orthosilicate gas flow rate is 50-200 sccm; the oxygen flow rate is 500-1000 sccm; the plasma power of the PETEOS apparatus is 100-500 W; and the reaction chamber temperature is maintained at 300℃-400℃. The thickness of the oxide film is controlled by adjusting the deposition time.

[0032] In this embodiment, the first and second oxide films are prepared using an LPTEOS device. The first and second oxide films prepared by the LPTEOS process have high stress, slow release rate, and good sealing effect, which can effectively seal deep trenches or holes on the substrate. After depositing the first and second oxide films, the third and fourth oxide films are deposited using a PETEOS device. The third and fourth oxide films prepared by the PETEOS process have low silicon oxide growth stress and slow release rate, but poor sealing effect. Since the first and second oxide films are mainly used for sealing, while the outer layer mainly serves to reinforce and meet thickness requirements, using the PETEOS process to prepare the third and fourth oxide films can accelerate the process and reduce stress.

[0033] In this embodiment, after the oxide film layer is prepared, it can be naturally cooled to room temperature or cooled to room temperature by passing nitrogen gas through it.

[0034] In this embodiment, in order to reduce stress and avoid excessive stress affecting the oxide film structure, a method combining layer-by-layer oxide film deposition and successive annealing is adopted. Specifically, after each oxide film layer is deposited, the substrate with the deposited oxide film layer is placed in an annealing equipment for annealing treatment. The annealing equipment maintains an annealing temperature of 600℃-1000℃ for annealing for 30min-60min.

[0035] In this embodiment, an ambient gas can be introduced into the annealing equipment. The ambient gas can be any one of nitrogen, argon, hydrogen, or a mixture of nitrogen and oxygen, wherein the nitrogen-oxygen mixture is composed of 80% nitrogen and 20% oxygen. Annealing after film formation can significantly improve the film's performance, including density, purity, stress, electrical properties, and mechanical properties. For example, during annealing, nitrogen is introduced as an inert protective gas to prevent the film from reacting with other impurities in the air, maintaining the film's chemical composition and structural integrity. It also helps reduce film stress and improves the film's mechanical properties. In this embodiment, annealing is performed after each oxide film layer is formed. Multiple annealings help to gradually release the stress in the oxide film layer, ensuring that the stress of the formed thick oxide film layer is within acceptable limits. Furthermore, multiple annealings and the use of LPTEOS and PETEOS processes to deposit multilayer films help improve the film's uniformity and density, thereby enhancing the performance of the final device.

[0036] In this embodiment, the annealing temperature can be gradually increased during annealing. By gradually increasing the temperature, the internal stress in the film can be effectively reduced. Rapid heating will cause a large temperature gradient in the film, leading to the accumulation of internal stress. Gradient annealing, with its slow heating, can make the temperature distribution in the film more uniform and reduce the generation of internal stress. At the same time, gradient annealing helps to improve the interface quality between the film and the substrate. Gradual heating can make the bonding between the film and the substrate stronger and reduce defects and inhomogeneities at the interface. Taking a film annealing temperature of 600℃ and an annealing time of 60 minutes as an example, the process is as follows: In the initial heating stage, the temperature is slowly increased from room temperature to 300℃ over 15 minutes, while nitrogen is introduced as the atmosphere gas. In the intermediate heating stage, the temperature is increased from 300℃ to 450℃ over 15 minutes, while a nitrogen-oxygen mixture (80% nitrogen, 20% oxygen) is introduced. In the high-temperature annealing stage, the temperature is increased from 450℃ to 600℃ over 15 minutes, while nitrogen is introduced as the atmosphere gas. In the isothermal annealing stage, the temperature is maintained at 600℃ for 15 minutes, while nitrogen is introduced into the annealing equipment as the atmosphere gas. After the annealing process is completed, cooling is performed using a gradient cooling method. For example, the temperature is reduced from 600℃ to 300℃ over 15 minutes, and then from 300℃ to room temperature over another 15 minutes. Gradual cooling avoids internal stress and cracks caused by rapid cooling.

[0037] For substrate processing, please refer to [link / reference]. Figure 1 , Figure 1 In the diagram, 'a' is a schematic diagram of the structure after the substrate is etched. Multiple deep trenches and hole structures can be formed on the substrate by patterning through photolithography and etching. The depth of these deep trenches and hole structures is 10um-400um. Figure 1 Figure b is a schematic diagram of the structure after the first oxide film layer is deposited using the LPTEOS process. As can be seen from the figure, although the first oxide film layer deposited by the LPTEOS process is not easy to completely seal deep trenches and pores, it can achieve partial sealing. Figure 1 c in the diagram is a schematic diagram of the structure after the second oxide film layer is deposited using the LPTEOS process. The second oxide film layer deposited on the first oxide film layer using the LPTEOS process can achieve the sealing of deep trenches and pores. Figure 1 The diagrams d and e in the figure show the structural results after the deposition of the third and fourth oxide layers using the PETEOS process. The third and fourth oxide layers are deposited layer by layer to ensure that the oxide layer thickness on the substrate meets the design requirements of the sacrificial layer structure.

[0038] The common English terms or letters used in this invention for clarity of description are for illustrative purposes only and are not intended to be limiting or specific. They should not be used to limit the scope of protection of this invention based on their possible Chinese translations or specific letters.

[0039] It should also be noted that in this article, relational terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

Claims

1. A method for preparing a thick oxide film, characterized in that, This includes fabricating deep trenches and holes on a substrate, and then sequentially depositing a first oxide film layer with a thickness of 20,000 angstroms, a second oxide film layer with a thickness of 10,000 angstroms, a third oxide film layer with a thickness of 10,000 angstroms, and a fourth oxide film layer with a thickness of 10,000 angstroms on the substrate after fabricating the deep trenches and holes. After each oxide film layer is prepared, the substrate containing the oxide film layer is placed in an annealing apparatus for annealing.

2. The method for preparing a thick oxide film according to claim 1, characterized in that, The substrate is a silicon-based substrate.

3. The method for preparing a thick oxide film according to claim 1, characterized in that, The substrate is fully coated with photoresist and subjected to photolithography and development. The developed substrate is then etched to form deep trenches and holes.

4. The method for preparing a thick oxide film according to claim 1, characterized in that, After each oxide film layer is prepared, the substrate containing the oxide film layer is placed in an annealing equipment, and the annealing temperature is 600℃-1000℃, and the annealing time is 30min-60min.

5. The method for preparing a thick oxide film according to claim 4, characterized in that, After each oxide film layer is prepared, annealing is performed using gradient annealing, with the annealing temperature gradually increased and then gradually decreased to room temperature after annealing.

6. The method for preparing a thick oxide film according to claim 3, characterized in that, The depth of the etched grooves and holes ranges from 10um to 400um.

7. The method for preparing a thick oxide film according to claim 1, characterized in that, The first oxide film layer and the second oxide film layer are prepared in an LPTEOS apparatus, and the third oxide film layer and the fourth oxide film layer are prepared in a PETEOS apparatus.

8. The method for preparing a thick oxide film according to claim 7, characterized in that, The LPTEOS equipment and the PETEOS equipment are used to prepare oxide film layers. The precursor gases are tetraethyl orthosilicate gas and oxygen, wherein the flow rate of tetraethyl orthosilicate gas is 50 sccm-200 sccm. The oxygen flow rate is 500-1000 sccm; The plasma power of the PETEOS device is 100-500W; During the reaction, the heating system is turned on, and the reaction chamber temperature of the LPTEOS equipment is maintained at 650℃-750℃, while the reaction chamber temperature of the PETEOS equipment is maintained at 300℃-400℃. The thickness of the oxide film is controlled by controlling the deposition time of the oxide film.

9. The method for preparing a thick oxide film according to claim 8, characterized in that, After the oxide film layer is prepared, it is allowed to cool naturally to room temperature or cooled to room temperature by passing nitrogen gas through it.

10. The method for preparing a thick oxide film according to claim 1, characterized in that, An atmosphere gas is introduced into the annealing equipment. The atmosphere gas is any one of nitrogen, argon, hydrogen, or a mixture of nitrogen and oxygen, wherein the mixture of nitrogen and oxygen is composed of 80% nitrogen and 20% oxygen.

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