WO2020224513A1

WO2020224513A1 - Method for manufacturing micro electro mechanical system device

Info

Publication number: WO2020224513A1
Application number: PCT/CN2020/087987
Authority: WO
Inventors: 胡永刚; 周国平; 夏长奉
Original assignee: 无锡华润上华科技有限公司
Priority date: 2019-05-09
Filing date: 2020-04-30
Publication date: 2020-11-12
Also published as: CN111908420A; CN111908420B

Abstract

A method for manufacturing a micro electro mechanical system (MEMS) device, comprising: providing a substrate (100), forming a first sacrificial layer (200) on a front surface of the substrate (100), and forming a functional structure (300) on the first sacrificial layer (200); etching a back surface of the substrate (100) to form grooves (110), wherein the etching stops at the first sacrificial layer (200), the grooves (110) communicate with each other and form a closed pattern, and the part of the substrate (100) surrounded by the grooves (110) is used as a support structure (120); and etching the first sacrificial layer (200), wherein the support structure (120) falls off as the first sacrificial layer (200) in contact with the support structure (120) is etched off, thus forming a back cavity (130). Supported by the support structure, the film layer above the grooves has a strong ability to bear the stress, ensuring that the film layer will not be deformed or broken during subsequent processes such as conveying and cleaning, and improving product yield. A small area of the grooves may help save the etching cost and etching time, a conveying device is facilitated to clamp devices conveniently, and automatic equipment can be used, thereby improving the production efficiency.

Description

MEMS device preparation method

Related application

This application claims the priority of the Chinese patent application filed with the Chinese Patent Office on May 9, 2019, with the application number 201910383273.1 and the application name "Micro-electromechanical system device preparation method", the entire content of which is incorporated into this application by reference .

Technical field

This application relates to the field of Micro-Electro-Mechanical System (MEMS), and in particular to a method for manufacturing a micro-electro-mechanical system device.

Background technique

In the preparation process of forming a MEMS device on a semiconductor substrate, a thin film structure is usually formed on the front side of the semiconductor substrate and a back cavity is etched on the back side of the semiconductor substrate so that the thin film structure covers the back cavity, such as a MEMS microphone And MEMS pressure sensor, etc. need to form the above structure. After the back cavity is etched, the device needs to be cleaned and dried. Because the thickness of the thin film structure is very thin, usually only a few microns, its ability to withstand stress is poor, and it is easy in the subsequent transfer and processing processes. Technical problems of deformation and even cracking.

Take the manufacturing process of a MEMS microphone as an example. First, a first film layer and a second film layer are formed on the front surface of the semiconductor substrate as the back plate and the diaphragm, respectively, and then the back surface of the semiconductor substrate is etched to form a back cavity. The cavity occupies a large area, and the structure above the back cavity is very fragile due to its thin thickness. In the subsequent process, on the one hand, the structure above the back cavity is easy to crack, on the other hand, a large area of the back cavity is formed on the back of the semiconductor substrate, because the device can only be clamped outside the back cavity of the semiconductor substrate when transferring devices. , The area of the back cavity is too large, which is not conducive to the operation of the device by the automated equipment, therefore, the production efficiency of the MEMS device is limited.

Summary of the invention

According to various embodiments of the present application, a method for manufacturing a microelectromechanical system device is provided, including:

Providing a substrate, forming a first sacrificial layer on the front surface of the substrate, and forming a functional structure on the first sacrificial layer;

The back of the substrate is etched to form a trench, the etching stops at the first sacrificial layer, the trenches communicate with each other and surround a closed pattern, and the substrate is surrounded by the trench Partly as a supporting structure; and

The first sacrificial layer is etched, and the support structure falls off as the first sacrificial layer in contact with the support structure is etched away, forming a back cavity.

The details of one or more embodiments of the application are set forth in the following drawings and description. Other features, purposes and advantages of this application will become apparent from the description, drawings and claims.

Description of the drawings

In order to better describe and illustrate the embodiments and/or examples of those applications disclosed herein, one or more drawings may be referred to. The additional details or examples used to describe the drawings should not be considered as limiting the scope of any one of the disclosed applications, the currently described embodiments and/or examples, and the best mode of these applications currently understood.

FIG. 1 is a flow chart of the steps of a method for manufacturing a MEMS device in an embodiment of the application;

2a to 2d are structural diagrams corresponding to the relevant steps of the MEMS device manufacturing method in an embodiment of the application;

3a to 3d are structural diagrams corresponding to related steps of a method for manufacturing a MEMS device in another embodiment of the application;

Figure 4a is a top view of a trench in an embodiment of the application;

Figure 4b is a top view of the trench in another embodiment of the application.

Detailed ways

In order to facilitate the understanding of the application, the application will be described in a more comprehensive manner with reference to the relevant drawings. The preferred embodiment of the application is shown in the accompanying drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of this application more thorough and comprehensive.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of this application. The terms used in the description of the application herein are only for the purpose of describing specific embodiments, and are not intended to limit the application. The term "and/or" as used herein includes any and all combinations of one or more related listed items.

In order to thoroughly understand this application, detailed steps and structures will be proposed in the following description to explain the technical solution proposed by this application. The preferred embodiments of the present application are described in detail as follows. However, in addition to these detailed descriptions, the present application may also have other embodiments.

Fig. 1 is a flow chart showing the steps of a method for manufacturing a microelectromechanical system device in an embodiment of the application. The manufacturing method includes the following steps:

Step S100: providing a substrate, forming a first sacrificial layer on the front surface of the substrate, and forming a functional structure on the first sacrificial layer.

As shown in FIG. 2a, a substrate 100 is provided. The substrate 100 is a semiconductor substrate. The substrate 100 has a front surface and a back surface. A first sacrificial layer 200 is formed on the front surface of the substrate 100, and a functional structure is formed on the first sacrificial layer 200. 300. The functional structure 300 is the functional unit of the MEMS device, and the functional structure 300 is stacked on the first sacrificial layer 200.

2a, in a specific embodiment, the functional structure 300 includes a first conductive layer 310, a second sacrificial layer 320, and a second conductive layer 330, and the steps of forming the functional structure 300 on the first sacrificial layer 200 are detailed Including: forming a first conductive layer 310 on the first sacrificial layer 200, forming a second sacrificial layer 320 on the first conductive layer 310, and forming a second conductive layer 330 on the second sacrificial layer 320, wherein the first sacrificial layer Both the second sacrificial layer 200 and the second sacrificial layer 320 are dielectric layers, and the first conductive layer 310 and the second conductive layer 330 are separated by the second sacrificial layer 320. In an embodiment, one of the first conductive layer 310 and the second conductive layer 330 is a semiconductor conductive layer, or the first conductive layer 310 and the second conductive layer 330 are both semiconductor conductive layers, and may be specifically doped. Polysilicon layer. In some integrated circuits manufactured on the same silicon wafer, when other devices have metal layers and the metal layers of other devices are located on the same layer as the first conductive layer or the second conductive layer of the MEMS device, they are located on the same layer as the metal layers of other devices. The level of the first conductive layer 310 or the second conductive layer 320 may also be a metal layer, so as to form the metal layer of other devices and the conductive layer of the MEMS device at one time in the manufacturing process.

In an embodiment, the substrate 100 is specifically a silicon substrate, and the first sacrificial layer 200 is silicon oxide. The formation of the first sacrificial layer 200 on the front side of the substrate 100 is specifically grown on the front side of the substrate 100 through a thermal oxidation process. A layer of silicon oxide. In one embodiment, the first conductive layer 310 is a polysilicon layer, and forming the first conductive layer 310 on the first sacrificial layer 200 specifically involves depositing a polysilicon layer on the first sacrificial layer 200 through a deposition process and applying the same The polysilicon layer is doped to adjust the conductivity of the first conductive layer 310, and then the polysilicon layer is patterned to form the first conductive layer 310. In one embodiment, the second sacrificial layer 320 is a silicon oxide layer, and forming the second sacrificial layer 320 on the first conductive layer 310 specifically involves depositing a silicon oxide layer on the first conductive layer 310 through a deposition process. In one embodiment, the second conductive layer 330 is a polysilicon layer, and forming the second conductive layer 330 on the second sacrificial layer 320 specifically involves depositing a polysilicon layer on the second sacrificial layer 320 through a deposition process and applying the same The polysilicon is doped to adjust the conductivity of the second conductive layer 330, and then the polysilicon layer is patterned to form the second conductive layer 330. In an embodiment, when the first conductive layer 310 and the second conductive layer 320 are semiconductor layers, after the second conductive layer 330 is formed on the second sacrificial layer 320, an annealing process is performed immediately, and the annealing temperature range may be 900°C-1100°C, the annealing time range may be 60min-150min, so as to adjust the stress of the first conductive layer 310 and the second conductive layer 330, and activate the ions implanted in the first conductive layer 310 and the second conductive layer 330.

In an embodiment, the above functional structure 300 further includes lead electrodes, and step S100 further includes forming a first metal electrode 341 and a second metal electrode 342, specifically including: etching the second conductive layer 330 and the second sacrificial layer 320 , Forming a contact hole penetrating through the second conductive layer 330 and the second sacrificial layer 320, exposing the first conductive layer 310 through the contact hole and forming a first metal electrode 341 on the first conductive layer 310, and at the same time in the second conductive layer 330 A second metal electrode 342 is formed thereon.

In one embodiment, the MEMS device is a MEMS microphone. As shown in FIG. 2a, the first conductive layer 310 is the diaphragm of the MEMS microphone, the second conductive layer 330 is the back plate of the MEMS microphone, and the second conductive layer 330 is provided with There are through holes as the sound holes of the MEMS microphone. In another embodiment, as shown in FIG. 3a, the first conductive layer 310 is the back plate of the MEMS microphone, the second conductive layer 330 is the diaphragm of the MEMS microphone, and the first conductive layer 310 is provided with a through hole as the MEMS microphone. The sound hole of the microphone.

Step S200: etching the back surface of the substrate to form a trench, the etching stops at the first sacrificial layer, the trenches communicate with each other and surround a closed pattern, and the part of the substrate surrounded by the trenches serves as a support structure.

As shown in FIGS. 2b and 3b, the backside of the substrate 100 is etched to form a trench 110, and the etching stops at the first sacrificial layer 200, that is, the trench 110 penetrates the substrate 100, exposing part of the first sacrificial layer 200 Outside, the trenches 110 communicate with each other and form a closed pattern, and the portion of the substrate 100 surrounded by the trenches 110 is the support structure 120. In one embodiment, as shown in FIG. 4 a, the orthographic projection of the groove 110 surrounds a circle, and the support structure 120 is surrounded by the groove 110. Fig. 2b is a cross-sectional view of an orthographic projection corresponding to the groove 110 surrounding a circle in an embodiment. In other embodiments, the orthographic projection of the groove 110 can also be enclosed in other shapes, such as a polygon, which needs to be determined according to the shape of the opening of the back cavity. In one embodiment, as shown in FIG. 4b, the orthographic projection of the groove 110 encloses a grid type, and FIG. 3b is a cross-sectional view corresponding to the orthographic projection of the groove 110 enclose a grid type in an embodiment. When the trenches are enclosed in a grid type, the first sacrificial layer exposes more areas, and the etching speed is faster during the etching process. Therefore, when the back cavity opening size is large, the grid-like trenches can be formed .

In one embodiment, before the back surface of the substrate 100 is etched to form the trench 110, the back surface of the substrate 100 is first thinned, which may be thinned by a chemical mechanical polishing process, so that the thickness of the substrate 100 is reduced. The substrate can be etched after the thickness is as thin as 250 μm-450 μm. Specifically, the substrate can be etched after the thickness is reduced to 400 μm. Generally, the above-mentioned MEMS devices are prepared with a wafer as a substrate, and the thickness of the wafer is relatively thick. If the wafer is directly etched to open trenches, more etching reagents are required and the etching process is longer, and the resulting trench shape The morphology is poor. In this embodiment, the substrate is first thinned to a certain degree and then the substrate is etched, which can reduce the etching difficulty, the etching time is short, and the morphology of the trench is easy to control.

Step S300: the first sacrificial layer is etched, and the support structure falls off as the first sacrificial layer in contact with the support structure is etched away, forming a back cavity.

The above structure is etched. As shown in FIG. 2c and FIG. 3c, the etching reagent contacts the first sacrificial layer 200 through the trench 110 and gradually etches the first sacrificial layer 200. The first sacrificial layer 200 is covered by the trench 110. The enclosed part is released during etching. As shown in FIG. 2d and FIG. 3d, when the first sacrificial layer 200 in contact with the support structure 120 is etched away, the support structure 120 also falls off to form the back cavity 130. In one embodiment, the functional structure includes a second sacrificial layer 320, and part of the second sacrificial layer 320 is etched away during the etching process to form between the first conductive layer 310 and the second conductive layer 330 Cavity. In one embodiment, the above-mentioned etching is wet etching, and the etching reagent used in the wet etching is Buffered Oxide Etch (BOE). In another embodiment, the above-mentioned etching may be dry etching, and the etching reagent for the dry etching includes vapor-phase hydrofluoric acid.

In one embodiment, a silicon nitride layer (not shown in the figure) is provided between the first conductive layer 310 and the second sacrificial layer 320, and a nitrogen layer is also provided between the second conductive layer 330 and the second sacrificial layer 320. A silicon layer (not shown in the figure). All the aforementioned silicon nitride layers are located in the orthographic projection area of the second sacrificial layer 320 after etching. Since the effective area where the first conductive layer 310 and the second conductive layer 320 deform is the area covering the opening of the cavity 321, the capacitor formed by the conductive layer in this area is an inductive capacitor, and the capacitor formed by the conductive layer outside the area is required The avoided parasitic capacitance, that is, the capacitance formed by the conductive layer located in the orthographic projection area of the second sacrificial layer 320 is a parasitic capacitance. In this embodiment, by providing a silicon nitride layer, the parasitic capacitance in this area can be reduced.

The traditional preparation method of MEMS devices usually directly etch a large area of the back cavity. After etching the substrate, it is generally necessary to transfer the device to a cleaning device for cleaning or to a detection device for testing before performing the release of the sacrificial layer. Craft. During the device transfer or cleaning process, due to the large area of the back cavity, the film on the back cavity has a weak stress bearing capacity, which is easy to deform or even break during these processes, causing the device to be scrapped. During the transfer process, it is also not conducive to the transfer equipment to clamp the substrate, which limits the automation of the transfer, resulting in low production efficiency.

In the present application, after etching the back surface of the substrate, only a small area of the trench is formed, and the trenches communicate with each other to form a closed pattern, and the part of the substrate surrounded by the trenches serves as a supporting structure. After the substrate is etched, the formed structure needs to be cleaned or inspected. Since the etched area on the back of the substrate is small, under the support of the support structure, the film layer above the trench has a strong ability to withstand stress, ensuring that it will not be deformed or broken during subsequent processes such as conveying and cleaning, thereby improving the product Yield rate. At the same time, due to the small groove area, it is conducive to the conveying equipment to clamp the device, and automatic equipment can be used, thereby improving production efficiency. Moreover, since only a small area of the trench needs to be etched, compared to the traditional etching of a large area of the back cavity, the present application can save etching costs and etching time. After the transfer and cleaning are completed, the process of releasing the sacrificial layer is performed. In the process of releasing the sacrificial layer, after releasing the sacrificial layer surrounded by the trench, the supporting structure will naturally fall off.

The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, All should be considered as the scope of this specification.

The above-mentioned embodiments only express a few implementation modes of the present application, and their description is relatively specific and detailed, but they should not be understood as a limitation on the scope of the patent application. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can be made, and these all fall within the protection scope of this application. Therefore, the scope of protection of the patent of this application shall be subject to the appended claims.

Claims

A method for preparing a microelectromechanical system device includes:

Providing a substrate, forming a first sacrificial layer on the front surface of the substrate, and forming a functional structure on the first sacrificial layer;

The back of the substrate is etched to form a trench, the etching stops at the first sacrificial layer, the trenches communicate with each other and surround a closed pattern, and the substrate is surrounded by the trench Partly as a supporting structure; and

The first sacrificial layer is etched, and the support structure falls off as the first sacrificial layer in contact with the support structure is etched away, forming a back cavity.
8. The preparation method according to claim 1, wherein the orthographic projection of the grooves surrounds any one of a circle, a polygon, and a grid.
8. The manufacturing method of claim 1, wherein before the step of etching the back surface of the substrate to form a trench, the method further comprises:

The back surface of the substrate is thinned, and the thickness of the thinned substrate ranges from 250 μm to 450 μm.
The manufacturing method of claim 1, wherein the step of forming a functional structure on the first sacrificial layer specifically comprises: sequentially forming a stacked first conductive layer, a second conductive layer on the first sacrificial layer A sacrificial layer and a second conductive layer, the first sacrificial layer and the second sacrificial layer are dielectric layers, and the first conductive layer and the second conductive layer are separated by the second sacrificial layer;

The second sacrificial layer is etched while the first sacrificial layer is etched to form a cavity between the first conductive layer and the second conductive layer.
The preparation method according to claim 4, wherein after the second conductive layer is formed on the front surface of the substrate, an annealing process is performed, and the annealing temperature may range from 900°C to 1100°C, and the annealing time range It can be 60min～150min.
8. The manufacturing method of claim 4, wherein, before the step of etching the back surface of the substrate to form a trench, the method further comprises:

Etching the second conductive layer and the second sacrificial layer to form contact holes penetrating the second conductive layer and the second sacrificial layer, and forming a second metal electrode on the second conductive layer, And forming a first metal electrode on the first conductive layer through the contact hole.
8. The manufacturing method of claim 4, wherein the first sacrificial layer and the second sacrificial layer are both silicon oxide.
8. The manufacturing method of claim 4, wherein the first conductive layer and the second conductive layer are doped polysilicon layers or metal layers.
The preparation method of claim 4, wherein a silicon nitride layer is provided between the first conductive layer and the second sacrificial layer, and a silicon nitride layer is provided between the second conductive layer and the second sacrificial layer. There is a silicon nitride layer, and all the silicon nitride layers are located in the orthographic projection area of the second sacrificial layer after etching.
The manufacturing method of claim 4, wherein the microelectromechanical system device is a MEMS microphone.
10. The manufacturing method of claim 10, wherein one of the first conductive layer and the second conductive layer is a diaphragm, and the other is a back plate, and the back plate is provided with a through hole.
8. The preparation method of claim 1, wherein the etching process for etching the first sacrificial layer is wet etching, and the etching reagent for the wet etching includes a buffered oxide etching solution.
8. The preparation method of claim 1, wherein the etching process for etching the first sacrificial layer is dry etching, and the etching reagent for the dry etching includes vapor-phase hydrofluoric acid.
The preparation method of claim 1, wherein forming a first sacrificial layer on the front surface of the substrate includes growing a silicon oxide layer on the front surface of the substrate as the first sacrificial layer through a thermal oxidation process Floor.
The preparation method of claim 4, wherein the first conductive layer is a polysilicon layer, and the method for forming the first conductive layer comprises: depositing a polysilicon layer on the first sacrificial layer and doping it To adjust the conductivity of the first conductive layer; the second conductive layer is a polysilicon layer, and the method for forming the second conductive layer includes: depositing a polysilicon layer on the second sacrificial layer and doping To adjust the conductivity of the second conductive layer.