CN113735055A

CN113735055A - MEMS device manufacturing method and MEMS device

Info

Publication number: CN113735055A
Application number: CN202110822242.9A
Authority: CN
Inventors: 王新龙
Original assignee: Semiconductor Manufacturing Electronics Shaoxing Corp SMEC
Current assignee: Semiconductor Manufacturing Electronics Shaoxing Corp SMEC
Priority date: 2021-07-21
Filing date: 2021-07-21
Publication date: 2021-12-03
Anticipated expiration: 2041-07-21
Also published as: CN113735055B

Abstract

The invention relates to a MEMS device manufacturing method and MEMS device, select SOI silicon-on-insulator slice as the substrate, carry on silicon-silicon bonding through SOI top silicon and silicon wafer as structural layer, make the whole manufacturing process compatible VHF craft; before the hydrophobic organic film is formed, a layer of sacrificial layer silicon dioxide is deposited in a region where the hydrophobic organic film needs to be removed, after the hydrophobic organic film is formed, the silicon dioxide sacrificial layers on the bonding region and the electrode region can be etched by means of a VHF (very high frequency) process, the hydrophobic organic films on the bonding region and the electrode region are removed completely while the silicon dioxide is removed, and the hydrophobic organic films needing to be reserved in other regions cannot be influenced. The manufacturing method disclosed by the invention has the advantages of simple process and strong practicability, can simultaneously and cleanly remove the hydrophobic organic films on the bonding region and the electrode region, and cannot damage the hydrophobic organic films reserved in other regions.

Description

MEMS device manufacturing method and MEMS device

Technical Field

The invention relates to the technical field of semiconductor manufacturing, in particular to a manufacturing method of an MEMS (micro-electromechanical system) device and the MEMS device.

Background

MEMS refers to a micro-electromechanical system that integrates a micro-sensor, an actuator, a signal processing and control circuit, an interface circuit, and a communication and power supply. The microsensor, the micro actuator, the micro component, the micro mechanical optical device, the vacuum microelectronic device, the power electronic device and the like manufactured by adopting the MEMS technology have very wide application prospects in the fields of aerospace, automobiles, biomedicine, environmental monitoring, military and the like. Common MEMS devices on the market today include pressure sensors, magnetic sensors, microphones, accelerometers, gyroscopes, infrared sensors, etc.

MEMS devices have a large surface-to-volume ratio, and such structures are prone to wear/adhesion between the structural layers during use, for example, between the movable comb teeth of a capacitive accelerometer and gyroscope. The oxide layer is a material commonly used for manufacturing the MEMS device, the oxide layer has hydrophilicity, and when the MEMS device is used in a humid environment, the surface of the oxide layer can be covered with a layer of water molecules, so that a strong capillary force is generated, and an adhesion phenomenon is caused. The adhesion problem has become a main factor influencing the performance and reliability of the MEMS device, and the surface modification of the material is an effective solution for solving the adhesion problem.

The common ways of solving the adhesion problem in the prior art are: the surface of the silicon structure is subjected to hydrophobic modification by using a self-assembled film (SAM) mode and using silane-based long carbon chain macromolecules, for example, the surface is subjected to hydrophobic property by using a perfluorodecyl trichlorosilane (FDTS) coating, so that the adhesion phenomenon is reduced. The hydrophobic self-assembled monolayer is generally formed by deposition in a molecular vapor deposition manner, and the monolayer is coated on the whole surface of a wafer in the manufacturing process of the MEMS device, and the monolayer coated on the bonding layer and the electrode layer of the MEMS device affects the wafer-level bonding reliability and the electrode layer routing reliability, so that the monolayer on the bonding layer and the electrode layer needs to be removed, and the monolayer on the structural layer is remained. In general, since the monomolecular film has the characteristics of acid resistance, alkali resistance and high temperature resistance, it is difficult to pattern by a conventional semiconductor process.

The invention patent with publication number CN112897454A discloses a MEMS device and a method for manufacturing the same, in which the method for removing hydrophobic organic films on the bonding layer and the electrode layer utilizes the difference in etching rates of different metal materials, and removes the metal protective layer deposited on the bonding layer, removes the metal protective layer and simultaneously removes the organic films thereon, and then etches the organic film on the electrode layer, and the organic films deposited on the surface of the bonding layer and the electrode layer are destroyed by high temperature heating before etching, so as to change the hydrophobicity into hydrophilicity. The processing technology for patterning the organic film needs to be completed in two steps, the technological links are relatively complex and the working procedures are multiple, the organic film on the surface of the electrode layer needs to be removed through a wet etching technology, a window needs to be formed through photoetching, the etching effect is difficult to guarantee, and the organic film in other reserved areas is difficult to guarantee not to be damaged.

Disclosure of Invention

The invention firstly discloses a manufacturing method of an MEMS device, which can synchronously remove hydrophobic organic films deposited on a bonding layer and an electrode layer, can not damage the hydrophobic organic films reserved in other areas, simplifies the whole process link and has good etching effect of the hydrophobic organic films.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a MEMS device manufacturing method, comprising:

selecting an SOI wafer as a substrate, and etching a top layer silicon of the SOI wafer to form a concave cavity and an insulating groove, wherein the insulating groove is etched from the bottom of the concave cavity to the buried oxide layer;

one surface of a silicon wafer is connected with the top silicon surface of the SOI wafer in a silicon-silicon bonding mode, a metal bonding region and an electrode region are formed on the other opposite surface of the silicon wafer, and sacrificial layers are formed on the surfaces of the metal bonding region and the electrode region;

etching a movable mass block on a silicon wafer;

forming a hydrophobic organic film, wherein the hydrophobic organic film covers the metal bonding region and the sacrificial layer on the surface of the electrode region, the surface and the side face of the movable mass block and the inner surface of the cavity;

and removing the sacrificial layer on the surface of the metal bonding region and the electrode region by adopting a VHF (very high frequency) vapor etching process, and bonding and connecting the cover wafer with the metal bonding region on the surface of the silicon wafer.

The invention selects SOI silicon-on-insulator as substrate, and silicon-silicon bonding is carried out through SOI top layer silicon and silicon wafer as structural layer, so that the whole manufacturing process can be compatible with VHF process; before the hydrophobic organic film is formed, a layer of sacrificial layer silicon dioxide is deposited in a region where the hydrophobic organic film needs to be removed, after the hydrophobic organic film is formed, the silicon dioxide sacrificial layers on the bonding region and the electrode region can be etched by means of a gas-phase hydrogen fluoride (VHF) process, the hydrophobic organic films on the bonding region and the electrode region can be removed completely while the silicon dioxide is removed, and the hydrophobic organic films which need to be reserved in other regions cannot be influenced. Compared with the method adopted by the patent mentioned in the background technology, the hydrophobic organic films on the bonding region and the electrode region can be removed synchronously, the whole process link is simplified, the removing effect is clean, the operability is strong, and the manufacturing cost is reduced.

Moreover, compared with the patents mentioned in the background art, the metal materials deposited in the bonding region and the electrode region can be the same and can be formed in one process, and the metal materials of the two regions of the patents mentioned in the background art need to be different, so that the number of process links is increased, the process is complicated, and the operability is not strong. The method comprises the steps of depositing a metal layer on the surface of a silicon wafer, forming a sacrificial layer on the surface of the metal layer, removing part of the sacrificial layer and the metal layer covered by the sacrificial layer through etching, using the remaining metal layer positioned at the edge as an electrode area, and using the remaining metal layer as a metal bonding area.

The invention uses the silicon wafer as a structural layer to form a movable mass block, after a metal bonding region and an electrode region covered by a sacrificial layer are formed, the surface of the silicon wafer is coated with photoresist, the photoresist covers the exposed surface of the silicon wafer and the sacrificial layer, a plurality of etching windows distributed at intervals are formed by photoetching, silicon at the etching windows is etched to form through holes, the through holes are communicated with the concave cavity, and then the photoresist is removed. Then, the exposed silicon surface is modified, namely a hydrophobic organic monomolecular film is formed on the surface of the silicon wafer by a molecular vapor deposition method, and the monomolecular film is used for solving the problem of adhesion in use. The hydrophobic organic film can be made of any one or a combination of more of perfluorooctyl trichlorosilane, tetrahydrooctyl methyl dichlorosilane, perfluorooctyl dimethylchlorosilane, tridecafluorooctyltriethoxysilane, perfluorododecyl trichlorosilane, octadecyl trichlorosilane and ethyl dichlorosilane.

Drawings

FIGS. 1 through 11 are cross-sectional structural views of MEMS devices at various stages of fabrication by a fabrication method according to an embodiment of the present invention;

FIG. 12 is a flow chart of a method of manufacture according to an embodiment of the invention;

fig. 13 is a block diagram of a MEMS device in the prior art.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

The embodiment discloses an MEMS device and an MEMS device manufacturing method, mainly solves the technical problem that a hydrophobic organic film for eliminating adhesion phenomena is difficult to remove on the surfaces of a bonding region and an electrode region through adjusting the structure and the process method of the existing MEMS device, optimally designs the graphical mode of the existing hydrophobic organic film, aims to simplify process links, is easier to implement technically, reduces manufacturing cost, ensures that the method can completely remove the hydrophobic organic film on the surfaces of the bonding region and the electrode region, and improves bonding reliability and electrode lead routing reliability.

The MEMS device structure in the prior art often adopts the structure shown in fig. 13, that is: selecting a single-polished silicon wafer 1 as a substrate, depositing a bottom electrode 7 on the surface of the substrate, depositing an insulating oxide layer 2 on the bottom electrode 7, etching a cavity on the oxide layer 2, carrying out silicon-oxygen bonding on the other silicon wafer 3 and the upper surface of the oxide layer 2, etching the silicon wafer 3 corresponding to the cavity to form a movable mass block 4, depositing a bonding layer 5 and a top electrode 6 on the upper surface of the silicon wafer 3, connecting the top electrode 6 and the bottom electrode 7 through a through-hole tungsten lead 8 of a TSV (through-silicon-via process), and finally bonding the other cover wafer (not shown in figure 13) and the bonding layer 5. When the MEMS device with the structure solves the adhesion problem in use, a layer of hydrophobic organic monomolecular film is formed on the surface of a silicon wafer before the MEMS device is bonded with a cover wafer, and then the hydrophobic organic monomolecular film deposited on the surfaces of the bonding layer 5 and the top electrode 6 is removed through an etching process. However, the hydrophobic organic monomolecular film usually has the characteristics of acid resistance, alkali resistance and high temperature resistance, and the hydrophobic organic monomolecular film in other areas is difficult to remove cleanly by adopting the traditional wet etching or dry etching technology without damaging the hydrophobic organic monomolecular film. The VHF gas phase etching technology is an etching process commonly used in the manufacturing process of MEMS devices, and is more controllable compared with the traditional wet etching. However, if the hydrophobic organic monomolecular film deposited on the surfaces of the bonding layer 5 and the top electrode 6 is removed by using the VHF etching technique, the above-mentioned MEMS device structure in the prior art is not compatible with the VHF process, and therefore, it is necessary to adjust the structure and process of the existing MEMS device comprehensively.

The MEMS device structure disclosed in this embodiment is shown in fig. 11, and the manufacturing method for forming the device structure is shown in fig. 12, and the whole manufacturing method and the device cross-sectional structure formed at each stage will be described with reference to fig. 1 to 12. First, the present invention selects the SOI wafer 100 as shown in fig. 1 as a substrate, and the SOI wafer 100 is generally called a silicon-on-insulator wafer and is composed of a silicon substrate 101 having a relatively thick bottom layer, a silicon dioxide buried oxide layer 102 having a relatively thin middle layer, and a single crystal top layer silicon 103. As shown in fig. 2, a cavity 104 is formed in the top silicon 103 by an etching process, and the depth of the cavity 104 is smaller than the thickness of the top silicon 103. An insulating trench 105 (as shown in fig. 3) is formed on each of the two sides of the bottom of the cavity 104 by an etching process, and the etching depth of the insulating trench 105 is required to ensure that the surface of the buried oxide layer 102 is exposed. Then, the bottom surface of a silicon wafer 200 and the upper surface of the top layer silicon 103 are bonded by silicon-silicon bonding (as shown in fig. 4), and the silicon wafer 200 is used as a structural layer for forming the MEMS device. Next, as shown in fig. 5, a metal layer 201 is deposited on the upper surface of the silicon wafer 200, and then a sacrificial layer 202 is formed on the surface of the metal layer 201, wherein the sacrificial layer 202 is used to isolate the hydrophobic organic film deposited subsequently from the metal layer 201, so that the hydrophobic organic film covered on the sacrificial layer 202 can be taken away together when the sacrificial layer 202 is removed. The method for removing the sacrificial layer 202 is selected to be a VHF vapor phase etching technology, and the silicon dioxide is etched by adopting vapor phase hydrogen fluoride without influencing the characteristics of the silicon surface, so that the sacrificial layer 202 in the embodiment is made of the silicon dioxide.

After the above steps are completed, part of the sacrificial layer 202 and the metal layer 201 covered by the sacrificial layer 202 are removed by photolithography and etching processes, and the remaining parts are respectively used as a metal bonding region 203 and an electrode region 204 (as shown in fig. 6), wherein the electrode region 204 is located at the edge. The surfaces of both the metallic bonding region 203 and the electrode region 204 are now also covered with sacrificial silicon dioxide. Next, a plurality of movable masses 206 are formed on the silicon wafer 200 corresponding to the cavities 104, that is: firstly, a layer of photoresist 205 is coated on the surface of the silicon wafer 200, the photoresist 205 covers the exposed surface of the silicon wafer 200 and the remaining sacrificial layer 202, then, photolithography is performed through a mask to form a plurality of etching windows arranged at intervals, silicon at the etching windows is etched to form through holes penetrating through the cavity 104 (as shown in fig. 7), and then, the remaining photoresist 205 is removed to form a plurality of movable mass blocks 206 (as shown in fig. 8). Next, a hydrophobic self-assembled monolayer 207 (hereinafter referred to as "hydrophobic organic film") is formed on the surface of the silicon wafer 200 by molecular vapor deposition, wherein the hydrophobic organic film is used for modifying the exposed silicon surface from hydrophilic to hydrophobic, thereby preventing adhesion during use. The hydrophobic organic film, which is shown as the wavy curve in fig. 9 and 10, is deposited so as to cover not only the sacrificial layer 202 on the surface of the metal bonding region 203 and the electrode region 204, but also the surface and the side surfaces of the movable mass 206 and the inner surface of the cavity 104, but all the covered regions are not shown in fig. 9 and 10 for simplicity. The material of the hydrophobic organic film can be selected from materials which can be modified into a hydrophobic surface in the prior art, such as: can be formed by one or a plurality of combinations of perfluorooctyl trichlorosilane, tetrahydrooctyl methyl dichlorosilane, perfluorooctyl dimethyl chlorosilane, tridecafluorooctyltriethoxysilane, perfluorododecyl trichlorosilane, octadecyl trichlorosilane and ethyl dichlorosilane.

After the hydrophobic organic film is deposited, the hydrophobic organic film on the metal bonding region 203 and the electrode region 204 needs to be etched clean, otherwise, the reliability of the bonding quality with the cover wafer 300 and the reliability of the wire bonding on the electrode region 204 are affected. The invention adopts VHF gas phase etching process to remove the sacrificial layer 202 on the surface of the metal bonding region 203 and the electrode region 204, along with the etching of the silicon dioxide sacrificial layer 202 by the gas phase hydrogen fluoride, the hydrophobic organic film covering the sacrificial layer is also removed completely, while the hydrophobic organic film covering other regions can not be damaged, and the structure after removal is shown as figure 10. Finally, the cap wafer 300 and the metal bonding region 203 on the surface of the silicon wafer 200 are bonded together by controlling the temperature and pressure (as shown in fig. 11, a MEMS device structure is formed).

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A method of manufacturing a MEMS device, comprising: the content comprises the following steps:

etching a movable mass block on a silicon wafer;

2. A MEMS device manufacturing method according to claim 1, wherein: the metal bonding region and the electrode region are formed in the following mode: depositing a metal layer on the surface of a silicon wafer, forming a sacrificial layer on the surface of the metal layer, removing part of the sacrificial layer and the metal layer covered by the sacrificial layer by etching, using the remaining metal layer positioned at the edge as an electrode area, and using the remaining metal layer as a metal bonding area.

3. A MEMS device manufacturing method according to claim 1, wherein: the sacrificial layer is a silicon oxide layer.

4. A MEMS device manufacturing method according to claim 1, wherein: the hydrophobic organic film is a monomolecular film and is formed in a molecular vapor deposition mode.

5. A MEMS device manufacturing method according to claim 4, characterized in that: the hydrophobic organic membrane is made of one or a combination of more of perfluorooctyl trichlorosilane, tetrahydrooctyl methyl dichlorosilane, perfluorooctyl dimethylchlorosilane, tridecafluorooctyltriethoxysilane, perfluorododecyl trichlorosilane, octadecyl trichlorosilane and ethyl dichlorosilane.

6. A MEMS device manufacturing method according to claim 1, wherein: the movable mass block is formed in the following manner: after the metal bonding region and the electrode region covered by the sacrificial layer are formed, photoresist is coated on the surface of the silicon wafer, the photoresist covers the exposed surface of the silicon wafer and the sacrificial layer, a plurality of etching windows distributed at intervals are formed through photoetching, silicon at the etching windows is etched cleanly to form through holes, the through holes are communicated with the concave cavity, and then the photoresist is removed.

7. A MEMS device manufacturing method according to claim 3, wherein: and etching the silicon oxide layers on the surfaces of the metal bonding region and the electrode region completely by adopting a gas-phase hydrogen fluoride process.

8. A MEMS device, characterized by: manufactured by the manufacturing method as claimed in any one of claims 1 to 7.

9. A MEMS device, characterized by: the silicon-on-insulator (SOI) wafer substrate comprises an SOI wafer substrate, a silicon wafer and a cover wafer, wherein a concave cavity is formed on top silicon of the SOI wafer substrate, an insulating groove is formed at the bottom of the concave cavity, and a buried oxide layer of the SOI wafer substrate is exposed at the bottom of the insulating groove; the lower surface of the silicon wafer is bonded with the upper surface of the top silicon of the SOI wafer substrate, a movable mass block is formed on the silicon wafer on the upper part of the concave cavity, and a metal bonding area and an electrode area are formed on the upper surface of the silicon wafer; and forming a hydrophobic organic film on the surface and the side surface of the movable mass block and the inner surface of the cavity, wherein one surface of the cover wafer is in bonding connection with the bonding region on the silicon wafer.

10. A MEMS device according to claim 9, wherein: the metal bonding region and the electrode region are made of the same metal material.