A method for manufacturing microstructures

Abstract

This application provides a method for manufacturing a microstructure, comprising: forming a first sacrificial layer on the upper surface of a substrate; forming an isolation layer on the upper surface of the first sacrificial layer; forming a pattern of a first suspended structure on the upper surface of the isolation layer; forming a second sacrificial layer on the upper surface of the isolation layer, the second sacrificial layer covering the pattern of the first suspended structure; forming a pattern of a second suspended structure on the upper surface of the second sacrificial layer; and at least partially removing the first sacrificial layer, the second sacrificial layer, and the isolation layer, such that the first suspended structure and the second suspended structure are at least partially suspended. This application forms an isolation layer between two sacrificial layers, avoiding sacrificial layer peeling caused by direct contact between the two sacrificial layers, thereby improving product yield and reducing manufacturing costs.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and more particularly to a method for manufacturing microstructures. Background Technology

[0002] In Micro-Electro-Mechanical Systems (MEMS) devices, it is often necessary to form suspended microstructures (hereinafter referred to as suspended structures) on a semiconductor substrate. Sometimes, these suspended structures are used to allow the microstructure to move relative to the substrate, such as through high-speed vibration or displacement. This vibration or displacement can be used to detect surrounding physical quantities, such as acceleration, sound waves, and angular velocity. Such vibration or displacement can also allow suspended structures with reflective layers to control the direction of light propagation; for example, micromirrors used for projection can be flipped at a certain angle or scan at high speed due to their suspension. Sometimes, these suspended structures are used to provide excellent thermal insulation to the substrate, thereby effectively converting absorbed heat into physical quantities such as voltage. For example, infrared sensors and vacuum sensors utilizing the Pirani principle require the sensing part to be suspended.

[0003] In MEMS manufacturing, the aforementioned suspended structures are often formed using sacrificial layer technology. Sacrificial layer technology can generally define the gap size between the suspended structure and the substrate with relatively high precision. Forming a suspended structure using sacrificial layer technology requires first forming a sacrificial layer pattern on the substrate, and then forming the suspended structure pattern, creating a gap of the sacrificial layer thickness between the suspended structure pattern and the substrate. After the necessary processing is completed, the sacrificial layer is removed, leaving the suspended structure pattern suspended, thus forming the suspended structure.

[0004] The material of the sacrificial layer must have sufficient process tolerance. For example, it should not undergo excessive deformation due to heating and cooling during the fabrication of other structures in the MEMS device, nor should it be damaged by the processing techniques of other structures. Simultaneously, the sacrificial layer material must be easily removable. In other words, after the fabrication of other structures in the MEMS device is complete, the sacrificial layer must be selectively removed. That is, the removal process of the sacrificial layer should not cause significant damage to other structures in the MEMS device. This greatly limits the choice of sacrificial layer material. Polyimide (PI) is often used as a sacrificial layer material for manufacturing suspended structures in MEMS devices. This is because PI is liquid before curing, easily forming a good cover on uneven substrate surfaces and is relatively easy to planarize; after curing, PI is not easily deformed, has strong process adaptability, and hardly deforms, especially at process temperatures below 350°C; moreover, it is relatively easy to form a thick sacrificial layer using PI, and PI can be easily removed through ashing after other processes are completed.

[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] Some MEMS devices have a double-layered suspended structure, which requires the use of double sacrificial layers during the manufacturing process. The inventors of this application have discovered that when using double sacrificial layers, if both sacrificial layers are made of PI material, delamination can easily occur at the contact points between the two PI material layers, leading to structural damage and even making the entire manufacturing process difficult to complete.

[0007] This application provides a method for manufacturing a microstructure by forming an isolation layer between two sacrificial layers to avoid sacrificial layer peeling caused by direct contact between the two sacrificial layers, thereby improving product yield and reducing manufacturing costs.

[0008] According to one aspect of the embodiments of this application, a method for manufacturing a microstructure is provided, comprising:

[0009] A first sacrificial layer is formed on the upper surface of the substrate;

[0010] An isolation layer is formed on the upper surface of the first sacrificial layer;

[0011] A pattern of a first suspended structure is formed on the upper surface of the isolation layer;

[0012] A second sacrificial layer is formed on the upper surface of the isolation layer, and the second sacrificial layer covers the pattern of the first suspension structure;

[0013] A pattern of a second suspension structure is formed on the upper surface of the second sacrificial layer; and

[0014] At least partially remove the first sacrificial layer, the second sacrificial layer, and the isolation layer, so that the first suspension structure and the second suspension structure are at least partially suspended.

[0015] According to another aspect of the embodiments of this application, the first sacrificial layer and the second sacrificial layer are made of different materials.

[0016] According to another aspect of the embodiments of this application, the first sacrificial layer and the second sacrificial layer are made of the same material.

[0017] According to another aspect of the embodiments of this application, the first sacrificial layer and / or the second sacrificial layer are formed of a resin material.

[0018] According to another aspect of the embodiments of this application, the resin material includes polyimide.

[0019] According to another aspect of the embodiments of this application, the isolation layer is formed of a silicon compound.

[0020] According to another aspect of the embodiments of this application, oxygen plasma etching is used to remove the first sacrificial layer and / or the second sacrificial layer.

[0021] According to another aspect of the embodiments of this application, the method further includes:

[0022] Before forming the pattern of the first suspended structure, a first through-hole is formed in the isolation layer and the first sacrificial layer, and the upper surface of the substrate or the surface of an existing structure on the upper surface of the substrate is exposed through the first through-hole.

[0023] When forming the pattern of the first suspended structure, the pattern of the first suspended structure is connected to the upper surface of the substrate or the existing structure through the first through hole.

[0024] According to another aspect of the embodiments of this application, the method further includes:

[0025] Before forming the pattern of the second suspension structure, a second through-hole is formed in the second sacrificial layer, and the surface of the pattern of the first suspension structure is exposed through the second through-hole.

[0026] When forming the pattern of the second suspension structure, the pattern of the second suspension structure is connected to the surface of the pattern of the first suspension structure through the second through hole.

[0027] The beneficial effects of this application are: forming an isolation layer between two sacrificial layers, avoiding sacrificial layer peeling caused by direct contact between the two sacrificial layers, thereby improving product yield and reducing manufacturing costs.

[0028] Specific embodiments of this application are disclosed in detail with reference to the following description and accompanying drawings, indicating how the principles of this application can be adopted. It should be understood that the embodiments of this application are not limited in scope. Within the spirit and scope of the appended claims, embodiments of this application include many changes, modifications, and equivalents.

[0029] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0030] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, or components. Attached Figure Description

[0031] The accompanying drawings, which form part of the specification, are used to provide a further understanding of the embodiments of this application and illustrate the implementation methods of this application, together with the textual description, to explain the principles of this application. Obviously, the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any creative effort. In the drawings:

[0032] Figure 1 This is a schematic diagram of an example of a method for manufacturing a microstructure according to Embodiment 1 of this application;

[0033] Figure 2 This is a schematic diagram of the manufacturing method of the microstructure in Example 1. Detailed Implementation

[0034] Referring to the accompanying drawings, the foregoing and other features of this application will become apparent from the following description. Specific embodiments of this application are specifically disclosed in the description and drawings, illustrating partial implementations in which the principles of this application may be employed. It should be understood that this application is not limited to the described embodiments; rather, it includes all modifications, variations, and equivalents falling within the scope of the appended claims.

[0035] Example 1

[0036] Embodiment 1 of this application provides a method for manufacturing microstructures.

[0037] Figure 2 This is a schematic diagram of the manufacturing method of the microstructure in Example 1, as shown. Figure 2 As shown, the manufacturing method of the microstructure includes:

[0038] 201. A first sacrificial layer is formed on the upper surface of the substrate;

[0039] 202. An isolation layer is formed on the upper surface of the first sacrificial layer;

[0040] 203. A pattern of the first suspension structure is formed on the upper surface of the isolation layer;

[0041] 204. A second sacrificial layer is formed on the upper surface of the isolation layer, the second sacrificial layer covering the pattern of the first suspension structure;

[0042] 205. A pattern of a second suspension structure is formed on the upper surface of the second sacrificial layer; and

[0043] 206. At least partially remove the first sacrificial layer, the second sacrificial layer, and the isolation layer, such that the first suspension structure and the second suspension structure are at least partially suspended.

[0044] According to Embodiment 1 of this application, an isolation layer is formed between two sacrificial layers to avoid sacrificial layer peeling caused by direct contact between the two sacrificial layers, thereby improving product yield and reducing manufacturing costs.

[0045] In this embodiment, the materials of the first sacrificial layer and the second sacrificial layer can be the same or different. For example, the first sacrificial layer and / or the second sacrificial layer can be formed of a resin material, such as polyimide (PI).

[0046] In operation 206, the first sacrificial layer and / or the second sacrificial layer can be removed using an oxygen plasma etching method.

[0047] In this embodiment, the isolation layer may be formed from a silicon compound.

[0048] like Figure 2 As shown, the method also includes:

[0049] 207. Before forming the pattern of the first suspended structure (i.e., between operation 202 and operation 203), a first through hole is formed in the isolation layer and the first sacrificial layer, and the surface of the upper surface of the substrate or the surface of an existing structure on the upper surface of the substrate is exposed through the first through hole.

[0050] Therefore, in operation 203, when forming the pattern of the first floating structure, the pattern of the first floating structure can be connected to the upper surface of the substrate or the upper surface of the existing structure through the first through hole, so that the upper surface of the substrate or the upper surface of the existing structure can support at least a part of the first floating structure.

[0051] like Figure 2 As shown, the method also includes:

[0052] 208. Before forming the pattern of the second suspension structure (i.e., between operation 204 and operation 205), a second through hole is formed in the second sacrificial layer, and the surface of the first suspension structure pattern is exposed through the second through hole.

[0053] Therefore, in operation 205, when forming the pattern of the second suspension structure, the pattern of the second suspension structure can be connected to the surface of the first suspension structure pattern through the second through hole, so that the surface of the first suspension structure pattern can provide support for at least a part of the second suspension structure.

[0054] The manufacturing method of the microstructure in this embodiment will be further described below with reference to the accompanying drawings.

[0055] Figure 1 This is a schematic diagram illustrating an example of a method for manufacturing a microstructure according to Embodiment 1 of this application. Figure 1 The schematic diagram only includes the most basic elements reflecting the inventive concept of this application.

[0056] like Figure 1 As shown in a), substrate 1 is prepared first. Substrate 1 can be a wafer commonly used in the semiconductor manufacturing field, such as a silicon wafer, silicon-on-insulator (SOI) wafer, germanium-silicon wafer, germanium wafer, gallium nitride wafer, SiC wafer, etc., or it can be an insulating wafer such as quartz, sapphire, or glass. Alternatively, substrate 1 can also be a wafer commonly used in the semiconductor manufacturing field, with various thin films and structures required for semiconductor devices or MEMS devices further formed on the wafer surface. Substrate 1 can also contain a semiconductor integrated circuit, which is used to control or detect changes in physical quantities (including temperature, humidity, resistance, mass, displacement, and deflection) of the MEMS device further formed on the semiconductor substrate 1. As a special case, substrate 1 is a silicon substrate containing an application-specific integrated circuit (ASIC), with a thickness of approximately 725 micrometers and a diameter of approximately 200 millimeters. Substrate 1 has two parallel main surfaces 1a and 1b, with the ASIC formed on main surface 1a.

[0057] Then, as Figure 1As shown in b), if necessary, microfabrication can be performed on the main surface 1a of substrate 1 to form the protrusions or depressions represented by 2 and 3. The structures of 2 and 3 can be formed using standard semiconductor processing techniques, including photolithography, film elongation, etching, etc.

[0058] Then, as Figure 1 As shown in c), a first sacrificial layer 4 is formed on the main surface 1a of the substrate 1. The thickness of the first sacrificial layer 4 is determined according to the structural design of the MEMS device. The material and formation method of the first sacrificial layer 4 are rationally selected according to the overall process flow of MEMS device manufacturing. As an example, the first sacrificial layer 4 is made of polyimide (PI) and formed by spin coating, with a thickness of 3 micrometers after spin coating and heat curing. The thickness of PI refers to the thickness of the PI layer formed on the flat surface below it (the same applies below). As an example, the curing temperature of the PI used is 350°C. This means that the PI used can withstand process temperatures below 350°C. Generally speaking, during the curing process, the PI will undergo a volume shrinkage of about 30-60% compared to after spin coating. This point must be fully considered in the process design.

[0059] Then, as Figure 1 As shown in d), the first sacrificial layer 4 is planarized. Due to the presence of protrusions 2 or depressions 3 on its underlying surface, in Figure 1 c) The surface of the first sacrificial layer 4 formed during the process shown is not smooth enough. To facilitate the formation of a flat and uniformly thick subsequent structure, in Figure 1 During process d), the first sacrificial layer 4 is planarized, and its thickness is adjusted accordingly. Planarization of the first sacrificial layer 4 can be achieved using chemical mechanical polishing (CMP) or an etch-back method. For example, if the first sacrificial layer 4 is composed of polyimide (PI), after planarization, the thickness of the PI is 2 micrometers. This thickness will determine the gap height between the first suspended structure and the structure below it, as described later.

[0060] Then, as Figure 1 As shown in e), an isolation layer 5 is formed on the surface of the first sacrificial layer 4. The isolation layer 5 can be made of silicon-based materials commonly used in MEMS processes, such as silicon oxide or silicon nitride. The isolation layer 5 can be a single layer or a composite thin film formed by stacking multiple materials. The isolation layer 5 can be formed using commonly used MEMS processes. The thickness of the first sacrificial layer 4 can be between 5 nm and 500 nm. For example, the isolation layer 5 is a silicon oxide, formed by chemical vapor deposition (CVD). The formation temperature of the isolation layer 5 is lower than the curing temperature of the PI.

[0061] Then, as Figure 1 As shown in f), the isolation layer 5 is processed to form a window 5a, exposing the surface of the underlying first sacrificial layer 4, as needed. This step can be omitted if not required. The window 5a can be processed using photolithography and reactive ion etching (RIE) methods commonly used in semiconductor processes.

[0062] Then, as Figure 1 As shown in g), the first sacrificial layer 4 exposed through window 5a is processed as needed to form window 4a, thereby exposing the pattern 2 formed on the surface of substrate 1. The processing of window 4a can be performed using photolithography and RIE methods commonly used in semiconductor processes. Figure 1 f) and Figure 1 The steps shown in g) can be performed as a single step.

[0063] Then, as Figure 1 As shown in h), patterns 6 and 7 (i.e., the patterns of the first suspended structure) are formed, wherein pattern 6 is connected to pattern 2. Patterns 6 and 7 can be made of the same material or different materials. Patterns 6 and 7 can be formed simultaneously or by different processes. The processing of patterns 6 and 7 can be carried out using thin film growth, photolithography, and RIE methods commonly used in semiconductor processes.

[0064] like Figure 1 As shown in i), a second sacrificial layer 8 is formed on the isolation layer 5 and patterns 6 and 7. The thickness of the second sacrificial layer 8 is determined according to the structural design of the MEMS device. The formation of the second sacrificial layer 8 can be roughly the same as that of the first sacrificial layer 4 in terms of material and formation method. In one special case, the second sacrificial layer 8 is made of the same material as the first sacrificial layer 4, namely, PI. Since the second sacrificial layer 8 is formed on the isolation layer 5 and not directly on the first sacrificial layer 4, even if the second sacrificial layer 8 and the first sacrificial layer 4 are made of the same material (e.g., both are PI), the first sacrificial layer 4 will not be damaged due to deformation or other phenomena during the formation of the second sacrificial layer 8, nor will peeling occur between the two. For example, there is no through area on the surface of the isolation layer 5, so the second sacrificial layer 8 does not contact the first sacrificial layer 7, that is, the second sacrificial layer 8 and the first sacrificial layer 7 are completely isolated by the isolation layer 5, patterns 6 and 7.

[0065] Then, as Figure 1 As shown in j), the second sacrificial layer 8 is planarized. The planarization of the second sacrificial layer 8 can be performed in a manner largely similar to that of the first sacrificial layer 4. For example, after planarization, the thickness of PI is 3 micrometers. This thickness will determine the gap height between the second suspension structure and the structure below it, as described later.

[0066] Then, as Figure 1 As shown in k), patterns 9 and 10 (i.e., patterns of the second suspension structure) are formed on the second sacrificial layer 8, wherein pattern 9 is connected to pattern 6. Such a structure can be formed as follows. First, using... Figure 1 The method shown in g) opens a window on the second sacrificial layer 8, and then uses... Figure 1 Figures 9 and 10 are formed by the method shown in k). Figures 9 and 10 may be made of the same material or different materials. Figures 9 and 10 may be formed simultaneously or by different processes.

[0067] Then, as Figure 1 As shown in l), at least part of the second sacrificial layer 8 is removed, leaving patterns 9 and 10 at least partially suspended, forming a second suspension structure 10. The second suspension structure 10 is kept suspended above the substrate 1 by a cantilever beam. Pattern 9 can be part of the cantilever beam or part of an electrically connected electrode. The removal of the second sacrificial layer 8 can be performed using selective etching methods in semiconductor processing. For example, when the second sacrificial layer 8 is composed of organic materials such as PI, other resins, and photoresists, the removal of the second sacrificial layer 8 can be performed using oxygen plasma etching (also known as ashing).

[0068] Then, as Figure 1 As shown in m), at least part of the isolation layer 5 is removed, exposing the surface of the first sacrificial layer 4 to be removed. The isolation layer 5 can be removed using selective etching methods in semiconductor processing. For example, if the isolation layer 5 is composed of silicon oxide, it can be removed using a solution or gas containing hydrofluoric acid (HF). Alternatively, if the isolation layer 5 is composed of silicon nitride, it can be removed using a solution containing phosphoric acid.

[0069] Then, as Figure 1 As shown in n), at least part of the first sacrificial layer 4 is removed, causing patterns 9 and 7 to be at least partially suspended, forming a first suspension structure 7. The first suspension structure 7 is kept suspended above the substrate 1 by a cantilever beam. The removal of the first sacrificial layer 4 can be performed using selective etching methods in semiconductor processing. For example, when the first sacrificial layer 4 is composed of organic materials such as PI, other resins, and photoresists, the removal of the first sacrificial layer 4 can be performed using oxygen plasma etching.

[0070] pass Figure 1 The second sacrificial layer 8, the isolation layer 5, and the first sacrificial layer 4 are removed sequentially (also known as the release process), forming a microstructure including the second suspension structure 10 and the first suspension structure 7. The portions of the second sacrificial layer 8, the isolation layer 5, and the first sacrificial layer 4 that do not need to be removed serve as part of the MEMS device structure, providing support and fixation.

[0071] According to this embodiment, an isolation layer is formed between the two sacrificial layers to avoid sacrificial layer peeling caused by direct contact between the two sacrificial layers, thereby improving product yield and reducing manufacturing costs.

[0072] The present application has been described above with reference to specific embodiments. However, those skilled in the art should understand that these descriptions are exemplary and not intended to limit the scope of protection of the present application. Those skilled in the art can make various modifications and variations to the present application based on its spirit and principles, and these modifications and variations are also within the scope of the present application.

Claims

1. A method for manufacturing a microstructure, comprising: A first sacrificial layer is formed on the upper surface of the substrate; An isolation layer is formed on the upper surface of the first sacrificial layer; A pattern of a first suspended structure is formed on the upper surface of the isolation layer; A second sacrificial layer is formed on the upper surface of the isolation layer, and the second sacrificial layer covers the pattern of the first suspension structure; A pattern of a second suspension structure is formed on the upper surface of the second sacrificial layer; as well as At least partially remove the first sacrificial layer, the second sacrificial layer, and the isolation layer, so that the first levitation structure and the second levitation structure are at least partially suspended. The method further includes: Before forming the pattern of the first suspended structure, a first through-hole is formed in the isolation layer and the first sacrificial layer, and the upper surface of the substrate or the surface of an existing structure on the upper surface of the substrate is exposed through the first through-hole. When forming the pattern of the first suspended structure, the pattern of the first suspended structure is connected to the upper surface of the substrate or the existing structure through the first through hole.

2. The method for manufacturing microstructures as described in claim 1, wherein, The first sacrificial layer and the second sacrificial layer are made of different materials.

3. The method for manufacturing microstructures as described in claim 1, wherein, The first sacrificial layer and the second sacrificial layer are made of the same material.

4. The method for manufacturing microstructures as described in claim 1, wherein, The first sacrificial layer and / or the second sacrificial layer are formed of resin material.

5. The method for manufacturing microstructures as described in claim 4, wherein, The resin material includes polyimide.

6. The method for manufacturing microstructures as described in claim 1, wherein, The isolation layer is formed from a silicon compound.

7. The method for manufacturing microstructures as described in claim 1, wherein, Oxygen plasma etching was used to remove the first sacrificial layer and / or the second sacrificial layer.

8. The method for manufacturing microstructures as described in claim 1, wherein, The method further includes: Before forming the pattern of the second suspension structure, a second through-hole is formed in the second sacrificial layer, and the surface of the pattern of the first suspension structure is exposed through the second through-hole. When forming the pattern of the second suspension structure, the pattern of the second suspension structure is connected to the surface of the pattern of the first suspension structure through the second through hole.

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