MEMS device preparation method based on surface silicon process and MEMS device

Abstract

The invention is suitable for the technical field of semiconductor devices, and provides an MEMS device preparation method based on a surface silicon process and an MEMS device, and the device comprises the steps: growing an oxide layer on a silicon substrate; growing a polycrystalline silicon wiring layer on the oxide layer; growing a layer of first ALD thin film on the polycrystalline silicon wiring layer; growing a sacrificial layer on the first ALD thin film; preparing a polycrystalline silicon structure layer on the sacrificial layer; an aluminum electrode and a release hole are arranged on the polycrystalline silicon structure layer; and releasing the sacrificial layer through the release hole to form a movable structure, and integrally forming the sensitive structure of the MEMS device. The problem that the insulating oxide layer on the lower portion of the polycrystalline silicon wiring layer in the cavity of the movable MEMS structure is prone to being over-corroded by hydrofluoric acid steam can be solved, corrosion protection is carried out, and the insulation characteristic is improved.

Description

Technical Field

[0001] The present application belongs to the technical field of semiconductor devices, and in particular, relates to a method for preparing a MEMS device based on a surface silicon process and a MEMS device. Background Art

[0002] Generally speaking, semiconductor technology can be used to build various components, which are also called semiconductor components. Semiconductor components can have structures with dimensions in the micrometer range. If mechanical microstructures are combined with circuits, they are called micro-electro-mechanical systems (MEMS). MEMS components can integrate logic components and micromechanical structures on a single chip.

[0003] Surface silicon MEMS processing technology is to first deposit a layer of material called a sacrificial layer on the substrate, then deposit a structural layer on the sacrificial layer and process it into the required pattern. After the structure is processed and formed, the sacrificial layer is etched away by selective etching, so that the structural material is suspended above the substrate, forming two-dimensional or three-dimensional movable MEMS structures of various shapes.

[0004] In this case, HF (hydrogen fluoride) etching is generally used to remove the sacrificial layer to make the MEMS structure flexible. However, when hydrogen fluoride enters the component through the etching area and etches the sacrificial layer, the lower insulating oxide layer of the polysilicon wiring layer in the cavity of the movable MEMS structure is easily over-corroded by hydrofluoric acid vapor, resulting in reliability and insulation risks. Summary of the invention

[0005] In order to overcome the problems existing in the related art, the embodiments of the present application provide a MEMS device preparation method and a MEMS device based on surface silicon process, which can solve the problem that the lower insulating oxide layer of the polysilicon wiring layer in the cavity of the movable MEMS structure is easily corroded by hydrofluoric acid vapor, and perform corrosion protection and improve insulation properties.

[0006] This application is implemented through the following technical solutions: In a first aspect, an embodiment of the present application provides a method for preparing a MEMS device based on a surface silicon process, comprising: growing an oxide layer on a silicon substrate; growing a polysilicon wiring layer on the oxide layer; growing a first ALD film on the polysilicon wiring layer; growing a sacrificial layer on the first ALD film; A polysilicon structure layer is prepared on the sacrificial layer; an aluminum electrode and a release hole are arranged on the polysilicon structure layer; The sacrificial layer is released through the release hole to form a movable structure, and the whole structure forms a sensitive structure of the MEMS device.

[0007] In one embodiment, growing a first ALD film on a polysilicon wiring layer includes: Etching a first circuit pattern on the polysilicon wiring layer; the first circuit pattern is used to connect with the polysilicon structure layer; A first ALD film is grown on the polysilicon wiring layer in a single-atom stacking manner; the first ALD film has a first preset pattern, and the first preset pattern is used to cover the area of ​​the polysilicon wiring layer outside the first circuit pattern and to cover the position of the lower projection area of ​​the movable structure.

[0008] In one embodiment, the material of the first ALD film includes aluminum oxide or aluminum nitride.

[0009] In one embodiment, after growing a first ALD film on the polysilicon wiring layer, the method for preparing a MEMS device based on a surface silicon process further includes: A second ALD film is grown on the polysilicon wiring layer; the first ALD film is parallel to the horizontal plane of the polysilicon wiring layer; the second ALD film is perpendicular to the horizontal plane of the polysilicon wiring layer and is arranged on both sides of the first circuit pattern.

[0010] In one embodiment, a polysilicon structure layer is prepared on a sacrificial layer, comprising: growing an initial polysilicon structure layer on the sacrificial layer; Prepare aluminum electrodes on the initial polysilicon structure layer; A release hole is etched on the initial polysilicon structure layer to form an initial movable structure, thereby forming a polysilicon structure layer.

[0011] In one embodiment, releasing the sacrificial layer through the release hole to form a movable structure includes: Hydrofluoric acid vapor is released through the release hole, and the sacrificial layer is released by the hydrofluoric acid vapor to form a cavity under the initial movable structure, thereby forming a movable structure in the polysilicon structure layer.

[0012] In one embodiment, an etching ratio of the hydrofluoric acid vapor to the first ALD film and the sacrificial layer is less than or equal to 1:100.

[0013] In one embodiment, after the sensitive structure of the MEMS device is integrally formed, the method for preparing the MEMS device based on the surface silicon process further includes: preparing a cover plate adapted to the sensitive structure of the MEMS device; The MEMS sensitive structure is hermetically bonded to the cover plate to form a MEMS device.

[0014] In the second aspect, the present application provides a MEMS device based on surface silicon process, characterized in that it is prepared using the MEMS device preparation method based on surface silicon process as in the first aspect, and the MEMS device includes, from bottom to top, a silicon substrate, an oxide layer, a polysilicon wiring layer, a first ALD film, a sacrificial layer and a polysilicon structure layer; an aluminum electrode and a movable structure are arranged on the polysilicon structure layer.

[0015] In one embodiment, the MEMS device further includes a cover plate; the cover plate is disposed on the polysilicon structure layer and bonded to the polysilicon structure layer to hermetically encapsulate the sensitive structure of the MEMS device.

[0016] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: In the embodiment of the present application, in the process of preparing the MEMS device, after preparing the polysilicon wiring layer and before growing the sacrificial layer, an atomic layer deposition (ALD) film is used to conformally cover the wiring layer to prevent lateral corrosion, thereby solving the problem that the lower insulating oxide layer of the polysilicon wiring layer in the cavity of the movable MEMS structure is easily corroded by hydrofluoric acid vapor. At the same time, the insulation performance is good, which ensures the processability and improves the processing accuracy.

[0017] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 is a schematic diagram of an insulating layer being over-corroded by hydrofluoric acid vapor provided by an embodiment of the present application; Figure 2 It is a schematic flow chart of a method for preparing a MEMS device based on a surface silicon process provided in an embodiment of the present application; Figure 3 It is a schematic structural diagram of a MEMS device based on surface silicon technology provided in one embodiment of the present application; Figure 4 It is a structural schematic diagram of another MEMS device based on surface silicon process provided by an embodiment of the present application; Figure 5 is a schematic diagram of a structure for providing a second ALD film according to an embodiment of the present application; Figure 6 It is a schematic structural diagram of another MEMS device based on surface silicon process provided in one embodiment of the present application. DETAILED DESCRIPTION

[0020] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0021] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0022] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0023] As used in the specification and appended claims of this application, the term "if" can be interpreted as "when" or "uponce" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "uponce it is determined" or "in response to determining" or "uponce [described condition or event] is detected" or "in response to detecting [described condition or event]", depending on the context.

[0024] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0025] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0026] The signal line is usually under the movable structure, or is part of the upper and lower capacitors. Since the lower part of the wiring layer in the movable structure cavity is silicon oxide, when hydrofluoric acid releases the sacrificial layer, it is easy to corrode the wiring layer, or pass through the area not covered by the wiring layer to form an insulating oxide layer formed by silicon oxide, such as Figure 1 As shown. The sacrificial layer release process will definitely involve the wiring process. It can be seen that as the silicon oxide of the insulating oxide layer below is corroded, the wiring will be corroded regardless of whether it is a single-layer wiring or a double-layer wiring, and the insulating layers on both sides of the wiring will form lateral corrosion, forming a cavity where the wiring is suspended, which will reduce the reliability of the MEMS device and cause insulation risks.

[0027] In order to solve the above problems, whether it is a single-layer wiring or a double-layer wiring method, after preparing the polysilicon wiring layer and before growing the sacrificial layer, an ALD film is used to conformally cover the wiring layer to prevent lateral corrosion. This can solve the problem that the lower insulating oxide layer of the polysilicon wiring layer in the cavity of the movable MEMS structure is easily corroded by hydrofluoric acid vapor.

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0029] Figure 2 is a schematic flow chart of a method for preparing a MEMS device based on a surface silicon process according to an embodiment of the present application. Figure 3 is a schematic diagram of the structure of a MEMS device based on surface silicon technology provided by an embodiment of the present application; Figure 2 and Figure 3 , mainly for the preparation of MEMS multi-layer wiring or small line width signal lines, the preparation method of MEMS devices based on surface silicon process is described as follows: The present application provides a method for preparing a MEMS device based on a surface silicon process, comprising: Step 101, growing an oxide layer on a silicon substrate.

[0030] Step 102: growing a polysilicon wiring layer on the oxide layer.

[0031] Step 103: growing a first ALD film on the polysilicon wiring layer.

[0032] Step 104: growing a sacrificial layer on the first ALD film.

[0033] Step 105 , preparing a polysilicon structure layer on the sacrificial layer.

[0034] Wherein, aluminum electrodes and release holes are arranged on the polysilicon structure layer.

[0035] Step 106 , releasing the sacrificial layer through the release hole to form a movable structure, thereby forming a sensitive structure of the MEMS device as a whole.

[0036] In this embodiment, after preparing the polysilicon wiring layer and before growing the sacrificial layer, an ALD film is used to conformally cover the wiring layer to prevent lateral corrosion, thereby solving the problem that the lower insulating oxide layer of the polysilicon wiring layer in the cavity of the movable MEMS structure is easily corroded by hydrofluoric acid vapor. At the same time, the insulation performance is good, which ensures the processability and improves the processing accuracy.

[0037] In one embodiment, the implementation details of growing a first ALD film on the polysilicon wiring layer are specifically introduced, and step 103 includes: First, a first circuit pattern is etched on the polysilicon wiring layer, wherein the first circuit pattern is used to connect with the polysilicon structure layer.

[0038] Then, a first ALD film is grown on the polysilicon wiring layer in a single-atom stacking manner.

[0039] The first ALD film has a first preset pattern, which is used to cover the area of ​​the polysilicon wiring layer outside the first circuit pattern and to cover the position of the lower projection area of ​​the movable structure.

[0040] Due to the wiring mode of the first preset pattern, some parts will expose the underlying oxide layer. Therefore, when a first ALD film is grown on the polysilicon wiring layer, a first ALD film will also be formed on the upper surface of the exposed oxide layer.

[0041] For example, ALD films generally grow in a single-atom stacking manner, are very slow, very thin, have good filling and conformal properties, and have good corrosion resistance and insulation properties.

[0042] Exemplarily, the material of the first ALD film includes aluminum oxide or aluminum nitride.

[0043] In this embodiment, by arranging the area of ​​the polysilicon wiring layer outside the first circuit pattern of the ALD film to correspond to the lower projection area of ​​the movable structure, it is possible to protect the wiring layer and the oxide layer when etching the sacrificial layer through the release hole without affecting the circuit conduction.

[0044] In one embodiment, see Figure 4 During the etching process, due to the partial corrosion of the sacrificial layer, when the sacrificial layers on both sides of the polysilicon wiring layer are not completely corroded, there is no need to grow the second ALD film; if the distance between the polysilicon wiring layer and the movable structure is close, the sacrificial layers on both sides of the polysilicon wiring layer are completely corroded, which will affect the polysilicon wiring layer. Therefore, it is necessary to grow a second ALD film to protect the polysilicon wiring layer, such as Figure 4 Then, after step 103, a first ALD film is grown on the polysilicon wiring layer, and a second ALD film may be further grown. The method for preparing a MEMS device based on the surface silicon process also includes: A second ALD film is grown on the polysilicon wiring layer; the first ALD film is parallel to the horizontal plane of the polysilicon wiring layer; the second ALD film is perpendicular to the horizontal plane of the polysilicon wiring layer and is arranged on both sides of the first circuit pattern.

[0045] Exemplarily, if when the polysilicon structure layer and the polysilicon wiring layer are interconnected, the portion of the polysilicon structure layer corresponding to the first circuit pattern is provided with a protruding portion, or the polysilicon wiring layer is provided with a protruding portion, then the second ALD film is provided on both sides of the polysilicon structure layer corresponding to the first circuit pattern; or, a portion of the second ALD film is provided on both sides of the polysilicon structure layer corresponding to the first circuit pattern, and the other portion is provided on both sides of the first circuit pattern of the polysilicon wiring layer; or both the first ALD film and the second ALD film are provided on both sides of the polysilicon structure layer.

[0046] The material of the second ALD film includes aluminum oxide or aluminum nitride.

[0047] In this embodiment, a second ALD film is disposed in the vertical direction to further prevent lateral corrosion and improve insulation.

[0048] In one embodiment, a detailed process of preparing a polysilicon structure layer on a sacrificial layer is specifically introduced, and step 105 includes: An initial polysilicon structure layer is grown on the sacrificial layer.

[0049] Aluminum electrodes are prepared on the initial polysilicon structure layer.

[0050] A release hole is etched on the initial polysilicon structure layer to form an initial movable structure, thereby forming a polysilicon structure layer.

[0051] Exemplarily, after step 105, in step 106, releasing the sacrificial layer through the release hole to form a movable structure includes: Hydrofluoric acid vapor is released through the release hole, and the sacrificial layer is released by the hydrofluoric acid vapor to form a cavity under the initial movable structure, thereby forming a movable structure in the polysilicon structure layer.

[0052] Exemplarily, the etching ratio of the hydrofluoric acid vapor to the ALD film and the sacrificial layer is less than or equal to 1: 100. A suitable etching ratio is selected to achieve better etching selectivity.

[0053] Due to lateral corrosion, suspended films may be formed, such as Figure 1As shown, it is easy to break during use, there are reliability issues, and corrosion products are easily left, causing the insulation performance to deteriorate; further, the suspended distance is too large, and the design of wiring requires complex rules, and the density of wiring and movable structures cannot be improved. This embodiment is based on the ALD film set in the above embodiment, which blocks the lateral corrosion of hydrofluoric acid vapor. After improving the insulation, it can construct wiring with an accuracy of several microns, increase density, reduce volume, and improve design flexibility. It has good insulation performance itself, and there is no suspended film structure in the wiring layer, which improves reliability, is not easy to leave corrosion products, and has a consistent surface, which improves uniformity and effectively improves insulation performance.

[0054] In one embodiment, see Figure 6 After the sensitive structure of the MEMS device is formed as a whole, the method for preparing the MEMS device based on the surface silicon process further includes: A cover plate adapted to the sensitive structure of the MEMS device is prepared; the MEMS sensitive structure and the cover plate are airtightly bonded to form a MEMS device.

[0055] This embodiment integrates the multi-functions of the MEMS device into one through an adaptive cover and airtight packaging technology to form a complex microsystem. Through airtight packaging, the MEMS device can better resist adverse factors such as temperature changes and mechanical shocks in the external environment, thereby improving its working stability and life.

[0056] Exemplarily, the method for preparing a MEMS device based on the surface silicon process is mainly aimed at preparing MEMS multi-layer wiring or signal lines with small line width (less than 20 micrometers line width).

[0057] The method for preparing a MEMS device based on a surface silicon process in an embodiment of the present application, in the process of preparing the MEMS device, after preparing the polysilicon wiring layer and before growing the sacrificial layer, uses an ALD film to conformally cover the wiring layer to prevent lateral corrosion, thereby solving the problem that the lower insulating oxide layer of the polysilicon wiring layer in the cavity of the movable MEMS structure is easily corroded by hydrofluoric acid vapor. At the same time, the insulation performance is good, which ensures the processability while improving the processing accuracy.

[0058] Second, see Figures 3 to 6 The present application provides a MEMS device based on surface silicon process, which is prepared using the MEMS device preparation method based on surface silicon process as in the first aspect. The MEMS device includes, from bottom to top, a silicon substrate, an oxide layer, a polysilicon wiring layer, a first ALD film, a sacrificial layer and a polysilicon structure layer; an aluminum electrode and a movable structure are arranged on the polysilicon structure layer.

[0059] Exemplarily, the MEMS device further includes a cover plate; the cover plate is disposed on the polysilicon structure layer and bonded to the polysilicon structure layer to hermetically encapsulate the sensitive structure of the MEMS device.

[0060] For the beneficial effects of the embodiments of the present application, please refer to the beneficial effects of the method for preparing a MEMS device based on surface silicon technology.

[0061] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0062] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for preparing a MEMS device based on surface silicon technology, characterized in that: include: growing an oxide layer on a silicon substrate; growing a polysilicon wiring layer on the oxide layer; growing a first ALD film on the polysilicon wiring layer; growing a sacrificial layer on the first ALD film; A polysilicon structure layer is prepared on the sacrificial layer; an aluminum electrode and a release hole are arranged on the polysilicon structure layer; The sacrificial layer is released through the release hole to form a movable structure, and the whole structure forms a sensitive structure of the MEMS device.

2. The method for preparing a MEMS device based on surface silicon technology according to claim 1, characterized in that: The step of growing a first ALD film on the polysilicon wiring layer comprises: Etching a first circuit pattern on the polysilicon wiring layer; the first circuit pattern is used to connect with the polysilicon structure layer; A first ALD film is grown on the polysilicon wiring layer in a single-atom stacking manner; the first ALD film has a first preset pattern, and the first preset pattern is used to cover the area of ​​the polysilicon wiring layer outside the first circuit pattern and to cover the position of the lower projection area of ​​the movable structure.

3. The method for preparing a MEMS device based on surface silicon technology according to claim 1, characterized in that: The material of the first ALD film includes aluminum oxide or aluminum nitride.

4. The method for preparing a MEMS device based on surface silicon technology according to claim 2, characterized in that: After growing a first ALD film on the polysilicon wiring layer, the method for preparing a MEMS device based on a surface silicon process further includes: A second ALD film is grown on the polysilicon wiring layer; the first ALD film is parallel to the horizontal plane of the polysilicon wiring layer; the second ALD film is perpendicular to the horizontal plane of the polysilicon wiring layer and is arranged on both sides of the first circuit pattern.

5. The method for preparing a MEMS device based on surface silicon technology according to claim 1, characterized in that: The step of preparing a polysilicon structure layer on the sacrificial layer comprises: growing an initial polysilicon structure layer on the sacrificial layer; preparing an aluminum electrode on the initial polysilicon structure layer; A release hole is etched on the initial polysilicon structure layer to form an initial movable structure, thereby forming a polysilicon structure layer.

6. The method for preparing a MEMS device based on surface silicon technology according to claim 5, characterized in that: The step of releasing the sacrificial layer through the release hole to form a movable structure comprises: The hydrofluoric acid vapor is released through the release hole, and the sacrificial layer is released by the hydrofluoric acid vapor to form a cavity under the initial movable structure, thereby forming the movable structure in the polysilicon structure layer.

7. The method for preparing a MEMS device based on surface silicon technology according to claim 6, characterized in that: The etching ratio of the hydrofluoric acid vapor to the first ALD film and the sacrificial layer is less than or equal to 1:

100.

8. The method for preparing a MEMS device based on surface silicon technology according to any one of claims 1 to 7, characterized in that: After the sensitive structure of the MEMS device is formed as a whole, the method for preparing the MEMS device based on the surface silicon process further includes: Preparing a cover plate adapted to the sensitive structure of the MEMS device; The MEMS sensitive structure is airtightly bonded to the cover plate to form a MEMS device.

9. A MEMS device based on surface silicon technology, characterized in that: The MEMS device is prepared using the method for preparing a MEMS device based on a surface silicon process as described in any one of claims 1 to 8, wherein the MEMS device includes, from bottom to top, a silicon substrate, an oxide layer, a polysilicon wiring layer, a first ALD film, a sacrificial layer and a polysilicon structural layer; an aluminum electrode and a movable structure are arranged on the polysilicon structural layer.

10. The MEMS device based on surface silicon technology according to claim 9, characterized in that: It also includes a cover plate; the cover plate is arranged on the polysilicon structure layer and bonded to the polysilicon structure layer to hermetically encapsulate the sensitive structure of the MEMS device.

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