Micro-electromechanical system sensor, manufacturing method thereof and electronic device

Abstract

Disclosed are a micro-electromechanical system sensor, a manufacturing method thereof, and an electronic device. The manufacturing method comprises: forming a device layer of the micro-electromechanical system sensor on a sacrificial layer on a device substrate, wherein the device layer comprises a mechanical layer located on the sacrificial layer and a sensing layer located on the mechanical layer, and a portion of the mechanical layer corresponding to a back hole to be formed in the device substrate is closed; forming a back hole in the device substrate and the sacrificial layer; and forming a connecting groove in the mechanical layer that is connected to the back hole.

Description

Technical Field

[0001] The present disclosure relates to the technical field of micro-electromechanical system (MEMS) sensors, and more specifically, to a method for manufacturing a micro-electromechanical system (MEMS) sensor, a micro-electromechanical system (MEMS) sensor, and an electronic device. Background Art

[0002] Micro-Electro-Mechanical System (MEMS) is also called micro-electro-mechanical system, microsystem, micro-machine, etc. The structure of MEMS is generally in the micron or even nanometer level. MEMS is developed on the basis of microelectronics technology (semiconductor manufacturing technology), integrating technologies such as lithography, corrosion, thin film, LIGA, silicon micromachining, non-silicon micromachining and precision machining.

[0003] MEMS sensors are new sensors manufactured using microelectronics and micromachining technology. Compared with traditional sensors, MEMS sensors are small in size, light in weight, low in cost, low in power consumption, and high in reliability. MEMS sensors are also suitable for mass production and easy to integrate.

[0004] As the size of MEMS sensors continues to decrease, the impact between different process steps during manufacturing becomes increasingly significant. Summary of the invention

[0005] One object of the present disclosure is to provide a new technical solution for micro-electromechanical system sensors.

[0006] According to a first aspect of the present disclosure, a method for manufacturing a micro-electromechanical system sensor is provided, comprising: forming a device layer of the micro-electromechanical system sensor on a sacrificial layer on a device substrate, wherein the device layer comprises a mechanical layer located on the sacrificial layer and a sensing layer located on the mechanical layer, and a portion of the mechanical layer corresponding to a back hole to be formed in the device substrate is closed; forming a back hole in the device substrate and the sacrificial layer; and forming a connecting groove in the mechanical layer that is connected to the back hole.

[0007] According to a second aspect of the present disclosure, a micro-electromechanical system sensor manufactured using the above manufacturing method is provided.

[0008] According to a third aspect of the present disclosure, an electronic device is provided, comprising the above-mentioned micro-electromechanical system sensor.

[0009] In the disclosed embodiments, the etchant used for the back holes can be prevented from damaging the structures on the mechanical layer.

[0010] Other features and advantages of the present disclosure will become apparent from the following detailed description of exemplary embodiments of the present disclosure with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0012] Figure 1 A schematic diagram of the structure of a MEMS sensor before release is shown.

[0013] Figure 2 A schematic diagram of the structure of a MEMS sensor after release is shown.

[0014] Figure 3-8 A schematic manufacturing process of a MEMS sensor according to one embodiment is shown.

[0015] Fig. 9 A schematic diagram of an electronic device according to an embodiment is shown.

[0016] Reference numerals:

[0017] 1. Device substrate; 2. Sacrificial layer; 3. Mechanical layer; 4. Passivation layer; 5. Pad and interconnect structure; 6. Protective layer; 7. Sensing layer; 8. Back hole; 9. Connecting groove; 10. Pad. DETAILED DESCRIPTION

[0018] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure unless otherwise specifically stated.

[0019] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses.

[0020] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0021] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0022] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0023] MEMS sensors are small in size. Therefore, slight differences in the manufacturing process will affect the quality of the final product. Due to the complex process of MEMS sensors, in most cases, it is difficult to determine which process step has a greater impact on the quality of the final product. The inventors found through a large number of experiments during research and development that the etchant used to form the back hole will affect the performance of the MEMS sensor. Especially when MEMS sensors are becoming smaller and smaller, the leakage of the etchant used to form the back hole has an increasingly greater impact on the performance of the MEMS sensor.

[0024] Figure 1 Figure 2 shows a schematic diagram of the structure of a MEMS sensor before release. Figure 1 As shown, a sacrificial layer 2 is formed on a device substrate 1. The device substrate 1 is, for example, a silicon substrate. The sacrificial layer 2 is made of, for example, silicon dioxide, which has high compressive resistance, for example, about 300 MPa. A device layer is formed on the sacrificial layer 2, and the device layer includes a mechanical layer 3 and a sensing layer 7. The material of the mechanical layer 3 is, for example, silicon or polysilicon. The sensing layer 7 is located above the mechanical layer 3. The mechanical layer 3 is located on the sacrificial layer 2. The mechanical layer 3 is located between the sacrificial layer 2 and the sensing layer 7. Figure 1 In FIG. 5 , the sensing layer 7 is shown as a magnetoresistive and magnetic source, but the sensing layer 7 may also be other types of sensing structures, such as a piezoelectric sensing structure, a capacitive sensing structure, etc.

[0025] The sensing layer 7 is a portion of the mechanical layer 3 for sensing, and it may occupy only a portion of the space above the mechanical layer 3. The sensing layer 7 includes a passivation layer 4 for protecting the sensing layer 7. In addition, the mechanical layer 3 is usually also covered with a passivation layer 4. A pad and an interconnection structure 5 are also arranged on the device layer. The material of the pad and the interconnection structure 5 may be Cr / Ni / Au, etc.

[0026] Before releasing the device layer, a back hole 8 and a connecting groove 9 in the device layer for connecting the back hole 8 have been formed. According to design requirements, the connecting groove 9 can be a gap or a through hole.

[0027] Usually, in order to protect the formed MEMS structure, a temporary protection layer 6 is formed above the device layer. The temporary protection layer 6 can be, for example, photoresist, tape, etc.

[0028] exist Figure 1 In the process, the various layers of the front-side MEMS are patterned on the unpatterned sacrificial layer 2, such as the mechanical layer to be released, the sensing layer, the pad and the interconnection structure, the passivation layer, etc. The silicon device substrate 1 is patterned and stopped at the sacrificial layer 2 by front-back alignment lithography and deep reactive ion etching (DRIE).

[0029] The temporary protection layer 6 is used to enhance the protection of the front-end structure. In many cases, this is an issue for low temperature deposited passivation layers due to process limitations after the formation of the sensing layer (eg, giant magnetoresistive GMR).

[0030] Figure 2 FIG. 6 shows a schematic diagram of the structure of the MEMS sensor after release. Generally, the temporary protection layer 6 is sufficient to protect the formed MEMS structure from damage by the hydrofluoric acid HF / buffered oxide etchant BOE from the front side. However, when removing the sacrificial layer 2, the etchant applied from the back hole 8 will leak in through the interface between the photoresist and the device layer, thereby damaging the passivation layer 4 and even the sensing layer 7. Figure 2 As shown, when removing the sacrificial layer 2, the etchant will leak into the interface between the temporary protection layer 6 and the MEMS structure through the position indicated by c, for example, Figure 2 The positions indicated by a and b in the figure are damaged, thereby damaging the MEMS sensor, for example, the passivation layer 5, or even the sensing components in the sensing layer 7. This can lead to serious yield loss, especially in the case of a low-temperature deposited passivation layer, which needs to be used due to processing issues after forming certain sensing layers such as GMR or TMR. For example, generally, the temperature requirement for chemical vapor deposition after forming magnetoresistance is less than 250 degrees, or 200 degrees.

[0031] Figure 3-8 A schematic manufacturing process of a MEMS sensor according to one embodiment is shown.

[0032] like Figure 3 As shown, a device layer of a MEMS sensor is formed on a sacrificial layer 12 on a device substrate 11. The device layer includes a mechanical layer 13 located on the sacrificial layer 12 and a sensing layer 14 located on the mechanical layer 13. Figure 3 In the embodiment, the portion of the mechanical layer 13 corresponding to the back hole 18 to be formed in the device substrate 11 is closed.

[0033] exist Figure 3 The device substrate 11 is an original substrate that has not been thinned. Its material is, for example, silicon, and its thickness is, for example, 380 microns to 750 microns. The material of the sacrificial layer 12 is, for example, silicon dioxide or buried oxide, and its thickness is, for example, 200 nanometers to 1000 nanometers. The mechanical layer 13 can be any material that can form a micromechanical structure, for example, silicon or polycrystalline silicon. The sensing layer 17 is located above the mechanical layer 13. The mechanical layer 13 is located on the sacrificial layer 12. The mechanical layer 13 is located between the sacrificial layer 12 and the sensing layer 17. Figure 3 In FIG. 1 , the sensing layer 17 is shown as a magnetoresistive and magnetic source, but the sensing layer 17 may also be other types of sensing structures, such as a piezoelectric sensing structure, a capacitive sensing structure, and the like.

[0034] A passivation layer 14 and a pad and interconnect structure 15 may also be disposed on the mechanical layer 13. The passivation layer 14 may be a low temperature deposited SiN x The material of the pad and the interconnection structure 15 may be Cr / Ni / Au or the like.

[0035] like Figure 3 As shown, a patterned hard mask layer 16 is formed on the closed device layers 13 and 17. For example, the material of the hard mask layer 17 is BCB material (benzocyclobutene), and its thickness ranges from 2 microns to 3 microns. Figure 3 In the embodiment, the pattern of the hard mask layer 17 is formed by lithography or patterned etching. For example, at the position where the connecting groove 19 is to be formed in the mechanical layer 13, the hard mask layer 17 includes a pattern 21. Figure 3 In the following process, the mechanical layer 13 is closed. In the subsequent process, the pattern 21 can be used to form a connecting groove 19 in the mechanical layer 13.

[0036] A resist protection layer 21 may be formed on the hard mask layer 16 to increase protection. For example, the material of the resist protection layer 21 is AZ4620 material, and its thickness ranges from 3 microns to 7 microns. The AZ4620 material has the characteristics of high contrast and high sensitivity. The 3 microns to 7 microns resist protection layer 8 can effectively protect the structure in the device layer from being corroded when the back hole 5 is formed, and it is also relatively simple in the removal process.

[0037] like Figure 4 and Figure 5 As shown, a back hole 18 is formed in the device substrate 11 and the sacrificial layer 12 .

[0038] exist Figure 4 In the process, the device substrate 11 is thinned by back grinding and / or polishing. The thickness of the device substrate 11 after thinning can be 150 microns to 350 microns. Then, patterning is performed on the device substrate 11 and deep reactive ion etching is performed to form a back hole 18 on the device substrate 11. At this time, the etching stops at the sacrificial layer 12.

[0039] Then, if Figure 5 As shown, the sacrificial layer portion corresponding to the back hole 18 is etched by wet etching. For example, the wet etching may be performed by using hydrofluoric acid HF or buffered oxide etchant BOE.

[0040] like Figure 5As shown, since the mechanical layer 13 is closed, the etchant used for the sacrificial layer 12 will not enter the upper part of the mechanical layer 13, nor will it leak into the interface between the resist and the micro-electromechanical system structure. Therefore, here, the possibility of the etchant used for the sacrificial layer 12 damaging the passivation layer and the sensing layer above the mechanical layer 13 is reduced. This is conducive to improving the yield of the product.

[0041] like Figures 6 to 8 As shown, a communication groove 19 communicating with the back hole 18 is formed in the mechanical layer 13 .

[0042] like Figure 6 As shown, the resist protection layer 21 is removed.

[0043] Here, for example, the stress of the hard mask layer 16 is close to the stress of the device layer, thereby providing strong protection. For example, the stress range of the hard mask layer 16 is 20MPa to 30MPa, which is close to the stress range of the device layer. For example, BCB material can be advantageously used for the hard mask layer 16. On the one hand, the stress range of the BCB material is 20MPa to 30MPa, which is close to the stress range of the MEMS device layer; on the other hand, the BCB material can be processed within a range of 200 degrees Celsius, which matches the structure after spin electronic processing and will not cause excessive impact on these structures. In addition, the hardness of the cured BCB material is large enough to effectively protect the device layer, such as the mechanical layer 13.

[0044] like Figure 7 As shown, the connecting trench 19 is formed by using the patterned hard mask layer 16 .

[0045] For example, the MEMS device layer (mechanical layer 13) can be released by reactive ion etching RIE, thereby forming a connecting groove 19 in the mechanical layer 13. Here, the hard mask layer 16 has sufficient etching selectivity for etching through the mechanical layer 13, for example, the etching selectivity is greater than 2:1, preferably, greater than 5:1.

[0046] like Figure 8 As shown, the hard mask layer 16 is removed. The hard mask layer 16 can be removed using O2 plasma, O2 reactive ion etching, and O2 / SF6 reactive ion etching.

[0047] As mentioned above, in Figure 8 In the MEMS sensor shown, since the MEMS device layer is released by dry etching after wet etching using hydrofluoric acid HF / buffered oxide etchant BOE, the MEMS device layer can well protect the structure above it. In this case, in the manufactured MEMS sensor, the structure above the mechanical layer 13 may not have traces of damage by the wet etchant. Therefore, the yield of the product can be effectively improved.

[0048] Fig. 9 Schematic diagram of an electronic device according to an embodiment disclosed herein is shown. Fig. 9 As shown, the electronic device 200 may include Figure 8 The micro-electromechanical system piezoelectric microphone 201 is shown. The electronic device 200 may be a mobile phone, a tablet computer, a wearable device, etc.

[0049] Although some specific embodiments of the present disclosure have been described in detail through examples, those skilled in the art should understand that the above examples are only for illustration rather than for limiting the scope of the disclosure herein.

Claims

1. A method for manufacturing a micro-electromechanical system sensor, comprising: forming a device layer of a MEMS sensor on a sacrificial layer on a device substrate, wherein the device layer comprises a mechanical layer on the sacrificial layer and a sensing layer on the mechanical layer, and a portion of the mechanical layer corresponding to a back hole to be formed in the device substrate is closed; forming a back hole in the device substrate and the sacrificial layer; and A communication groove communicating with the back hole is formed in the mechanical layer.

2. The manufacturing method according to claim 1, further comprising: forming a patterned hard mask layer on the enclosed device layer; as well as forming a resist protective layer on the hard mask layer, Wherein, forming a connecting groove in the mechanical layer to communicate with the back hole includes: removing the resist protective layer; Using the patterned hard mask layer, forming the connecting trench; and The hard mask layer is removed.

3. The manufacturing method according to claim 2, wherein: The material of the hard mask layer is BCB material, and its thickness ranges from 2 microns to 3 microns.

4. The manufacturing method according to claim 3, wherein: The material of the anti-etching protection layer is AZ4620 material, and its thickness ranges from 3 microns to 7 microns.

5. The manufacturing method according to claim 2, wherein: The stress range of the hard mask layer is 20 MPa to 30 MPa.

6. The manufacturing method according to claim 2, wherein: Removing the hard mask layer includes: The hard mask layer is removed using O2 plasma, O2 reactive ion etching, and O2 / SF6 reactive ion etching.

7. The manufacturing method according to claim 1, wherein: Forming a back hole in the device substrate and the sacrificial layer includes: Thinning the device substrate by back grinding and / or polishing; performing patterning on a device substrate; A back hole is formed in the device substrate by deep reactive ion etching; The sacrificial layer portion corresponding to the back hole is etched by wet etching.

8. The manufacturing method according to claim 7, wherein: The wet etching includes etching using hydrofluoric acid or a buffered oxide etchant.

9. A micro-electromechanical system sensor manufactured using the manufacturing method according to claim 1. 10 . An electronic device comprising the micro-electromechanical system sensor according to claim 9 .

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