Method for manufacturing a vacuum chamber internal airtightness monitoring structure of a microelectronic device

Abstract

The application provides a manufacturing method of a vacuum cavity internal airtightness monitoring structure for a microelectronic device, which comprises the following steps: providing a first substrate; providing a second substrate, and then forming a film layer on a second main surface of the second substrate; forming a recess on a first main surface of the second substrate, the recess exposes a part of the film layer, and a cavity for accommodating a microelectronic device is also formed on the second main surface of the second substrate; bonding the first main surface of the second substrate with the first substrate, so that the cavity and the first substrate form an airtight cavity, and the recess is airtightly blocked by the film layer and the surrounding environment, and the film layer is configured to be deformed in bulging or concave according to the air pressure difference between the sealed chamber and the surrounding environment. Through the manufacturing method, the airtightness monitoring structure can be formed while the microelectronic device is bonded and packaged, and the problems such as low reliability of the MEMS device in the vacuum cavity in the prior art can be solved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method for fabricating a vacuum cavity internal pressure monitoring structure for microelectronic devices. Background Technology

[0002] Micro-Electro-Mechanical Systems (MEMS) technology, developed from microelectronics, is an emerging, multidisciplinary, high-tech field. To protect the internal MEMS devices, MEMS packaging is generally required to be hermetically sealed. This is especially true for MEMS devices such as MEMS gyroscopes and pressure gauges, which require vacuum packaging to achieve their desired performance in a vacuum environment. Similarly, MEMS devices such as infrared sensors also need to encapsulate their sensitive components in a relatively stable vacuum.

[0003] MEMS devices are extremely sensitive to their packaging environment, and certain key parameters can cause them to fail. However, MEMS applications require long-term hermeticity, but in practice, the internal vacuum level of the tiny space encapsulating the MEMS device often decreases over time. This frequently leads to performance degradation of these devices; that is, as the internal vacuum level of the tiny space encapsulating the MEMS device changes, the output values ​​of these devices will change, making the measurement results unable to accurately reflect the measured physical quantity. In other words, the lifespan of these devices is often limited by the degradation of the internal vacuum level of the tiny space encapsulating them. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for fabricating a vacuum cavity internal airtightness monitoring structure for microelectronic devices, in order to solve the problems in the prior art such as the difficulty in maintaining the internal vacuum level of the tiny space used to package microelectromechanical systems, the low reliability of MEMS devices in the vacuum cavity, and the lifespan of the devices.

[0005] To achieve the above and other related objectives, the present invention provides a method for fabricating an airtightness monitoring structure for a vacuum cavity of a microelectronic device. The method includes: providing a first substrate; providing a second substrate, the second substrate including opposing first and second main surfaces, and then forming a film layer on the second main surface of the second substrate; forming a recess on the first main surface of the second substrate, the bottom of which exposes a portion of the film layer, and further forming a cavity for accommodating the microelectronic device on the second main surface of the second substrate; bonding the first main surface of the second substrate to the first substrate so that the cavity and the first substrate form an airtight cavity, while the recess is airtightly isolated from the surrounding environment by the film layer, wherein the film layer is configured to bulge or indent according to the pressure difference between the sealed chamber and the surrounding environment.

[0006] Optionally, the film layer is integrally formed with the second substrate, and the recess is formed on the surface of the first main surface of the second substrate by photolithography and etching processes.

[0007] Optionally, before forming the film layer on the second main surface of the second substrate, a through hole is formed on the second substrate by photolithography and etching processes, and the through hole and a portion of the film layer constitute the recess.

[0008] Optionally, the film layer has a different material from the second substrate, wherein the film layer is a single layer or a composite layer of materials selected from the following materials deposited by a low-pressure chemical vapor deposition process: polycrystalline silicon, silicon oxide, and silicon nitride.

[0009] Optionally, the film is formed in a circular shape and has a thickness of 1 micrometer to 20 micrometers.

[0010] Optionally, the manufacturing method further includes: forming a first material layer on a first main surface of the second substrate; and forming the first material layer into a first patterned layer by photolithography and etching processes.

[0011] Optionally, before the step of bonding the first main surface of the second substrate to the first substrate, the fabrication method further includes: forming a second material layer on the first main surface of the first substrate; forming the second material layer into a second patterned layer by photolithography and etching processes, wherein the first patterned layer and the second patterned layer are aligned and bonded one by one to form a bonding layer, wherein the bonding layer is an Al-Ge eutectic bonding layer.

[0012] Optionally, the bonding layer is formed by direct bonding between the interface of the first substrate and the second substrate.

[0013] Optionally, the main body of the microelectronic device is disposed on the first main surface of the first substrate.

[0014] As described above, the method for fabricating the airtightness monitoring structure inside the vacuum cavity of a microelectronic device according to the present invention has the following beneficial effects:

[0015] 1) This invention provides a method for fabricating a gas tightness monitoring structure inside a vacuum cavity for microelectronic devices. The fabrication method can form the gas tightness monitoring structure while bonding and packaging the microelectronic devices, and is simple to fabricate and cost-effective.

[0016] 2) In the airtightness monitoring structure provided by the fabrication method, the vacuum cavity and the sealing chamber used to accommodate the microelectronic device are both located on the sealing substrate. The sealing substrate has a high utilization rate, which makes the overall design of the MEMS device more flexible and the structure is compact. Attached Figure Description

[0017] Figures 1-5 The diagram shows the structural schematic of each step in the vacuum cavity airtightness monitoring structure for microelectronic devices according to Embodiment 1 of the present invention; wherein... Figure 2A and Figure 2B The diagram shows a structure in which a recess is formed on the first main surface of the second substrate according to step 3).

[0018] Figure 6A and Figure 6B The diagram shows a real-time detection operation of a gas tightness monitoring structure for the vacuum cavity of a microelectronic device, as shown in Embodiment 1 of the present invention.

[0019] Component designation explanation

[0020] 100 First substrate

[0021] 100a First Main Face

[0022] 100b Second Main Face

[0023] 104 Microelectromechanical devices

[0024] 200 Second substrate

[0025] 200a First Main Face

[0026] 200b Second Main Face

[0027] 202 Airtight Cavity

[0028] 205 First recess

[0029] 206 Through Hole

[0030] 208 Sealed Chamber

[0031] 2051, 300 film layers

[0032] 400 bonded layers

[0033] 410 First Graphical Layer

[0034] 420 Second Graphics Layer Detailed Implementation

[0035] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0036] In the detailed description of embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged and not to scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0037] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the drawings for devices in use or operation. Furthermore, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or there may be one or more layers in between.

[0038] In the context of this application, the structure described above the first feature may include embodiments in which the first and second features are formed in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0039] In this invention, the term "substrate" may refer to substrates commonly used in the semiconductor manufacturing field.

[0040] As used herein, although the terms “first,” “second,” “third,” etc., may describe various elements, components, areas, layers, and / or segments, none of them are limited by these terms. These terms are used only to distinguish one element, component, area, material, layer, or segment from another. Therefore, without departing from the teachings herein, “first element,” “first component,” “first area,” “first material,” “first layer,” or “first segment” discussed below may be referred to as a second element, second component, second area, second material, second layer, or second segment.

[0041] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0042] To address the challenge of maintaining a consistently high vacuum level within the small space occupied by MEMS devices in a vacuum environment, which negatively impacts device reliability, this invention provides a method for fabricating an airtightness monitoring structure for a vacuum cavity of a microelectronic device. The method includes at least: providing a first substrate; providing a second substrate, the second substrate comprising opposing first and second main surfaces, and forming a film layer on the second main surface of the second substrate; forming a recess on the first main surface of the second substrate, the bottom of which exposes a portion of the film layer; and further forming a cavity on the second main surface of the second substrate for accommodating the microelectronic device; bonding the first main surface of the second substrate to the first substrate to form an airtight cavity with the first substrate, while simultaneously ensuring the recess is airtightly isolated from the surrounding environment by the film layer. The film layer is configured to bulge or indent based on the pressure difference between the sealed chamber and the surrounding environment.

[0043] See afterward Figures 1 to 5 The specific details of the fabrication method of the airtightness monitoring structure inside the vacuum cavity of microelectronic devices described in this invention are described in detail.

[0044] Example 1

[0045] like Figures 1-5 As shown, this embodiment provides a method for fabricating a gas tightness monitoring structure inside a vacuum cavity for microelectronic devices. The fabrication method specifically includes the following steps:

[0046] First, see Figure 1 In step 1), a first substrate 100 is provided, the first substrate having a first main surface 100a and a second main surface 100b. Preferably, the first substrate 100 may be a silicon substrate.

[0047] Then, in step 2), a second substrate 200 is provided, the second substrate including opposing first main surfaces 200a and second main surfaces 200b, and a film layer is then formed on the second main surface 200b of the second substrate. Figure 2A As shown, a cavity is formed on the surface of the first main surface 200a of the second substrate. The cavity is used to accommodate a microelectronic device, such as a microelectromechanical device 104. As an example, the main body of the microelectronic device can be disposed on the first surface of the first substrate. Preferably, the second substrate 200 can be a silicon substrate, SOI substrate, germanium-silicon substrate, germanium substrate, gallium nitride substrate, SiC substrate, etc., or it can be an insulating substrate such as quartz, sapphire, or glass.

[0048] Before forming the film layer at step 2), the fabrication method includes forming a through hole 206 on the second substrate 200. See also... Figure 2A The film layer 300 forms an hermetically tight contact with the first main surface 200a of the second substrate and covers the through-hole 206 on the second substrate. The through-hole and a portion of the film layer constitute the recess. As an example, the through-hole 206 can be formed on the second substrate using photolithography and etching processes. In other examples, the through-hole 206 can be formed on the second substrate 200 in step 3-1) after step 2). The film layer 300 can have the same material as the second substrate or a different material. In this embodiment, the film layer is a single layer or a composite layer of materials selected from polysilicon, silicon oxide, and silicon nitride. For example, the film layer can be a single layer of polysilicon or a composite layer of silicon oxide and silicon nitride. As an example, the film layer can be grown from the second substrate 200 using a low-pressure chemical vapor deposition (LPCVD) process. The film layer can be deposited as a polysilicon thin film with a thickness of 5 micrometers.

[0049] As an alternative, see Figure 2B At step 2), while forming the film layer, a recess 205 is formed on the first main surface 200a of the second substrate; that is, the film layer 2051 is integrally formed with the second substrate, and the recess is formed on the surface of the first main surface of the second substrate by photolithography and etching processes.

[0050] Optionally, step 3) further includes: forming a first material layer on the first main surface 200a of the second substrate; and then forming the first material layer into a first patterned layer 410 by photolithography and etching processes. In an example where the first material layer is an aluminum layer, an Al layer can be formed on the first main surface 200a of the second substrate by physical vapor deposition (PVD), and then the Al layer can be etched into a patterned Al layer by photolithography and etching processes. In this embodiment, the shape and thickness of the first patterned layer can be determined according to the bonding requirements between the first substrate and the second substrate.

[0051] Next, step 4) is performed, bonding the first main surface 200a of the second substrate to the first main surface 100a of the first substrate to form a bonding layer 400 between the first substrate and the second substrate. By bonding the first main surface 200a of the second substrate to the first main surface 100a of the first substrate, the cavity on the first main surface of the second substrate and the first substrate are formed into an airtight cavity 202, while the recess is airtightly isolated from the surrounding environment by a film layer disposed on the second main surface 200b of the second substrate. Figure 2A As shown, the first main surface 100a of the first substrate 100, the film layer 300, and the through hole 206 located on the second substrate together define the sealing chamber 208. The sealing chamber is airtightly isolated from the surrounding environment by the film layer 300 disposed on the second main surface 200b of the second substrate.

[0052] Optionally, see Figure 3 Step 4) further includes: 4-1) forming a second material layer on the first main surface 100a of the first substrate, and forming the second material layer into a second patterning layer 420 by photolithography and etching processes, such as... Figure 3 As shown. Specifically, in this embodiment, at step 4-2, the first patterned layer 410 and the second patterned layer 420 are aligned and bonded region by region to form a bonding layer 400. This bonding layer can be formed as a eutectic bonding layer, thereby obtaining the airtightness monitoring structure, as shown. Figure 4 and Figure 5 As shown.

[0053] See Figures 6A-6B Since the hermetic cavity 202 formed on the surface of the first main surface 200a of the second substrate and the sealed chamber are formed simultaneously on the same chip under the same conditions, the performance of the MEMS device in the vacuum cavity and the internal air pressure P of the sealed chamber can be determined according to the predetermined performance of the MEMS device in the vacuum cavity and the internal air pressure P of the sealed chamber. inThe membrane layer 300 is suspended above the sealing chamber. Furthermore, the membrane layer is configured to bulge or indent according to the pressure difference between the sealing chamber and the surrounding environment. The airtightness of the airtight cavity is reflected by monitoring the direction and degree of deformation of the membrane layer. Specifically, when the internal air pressure P of the sealing chamber 208... in The external atmospheric pressure P of the chip out When differences occur, the film layer 300 will deform by protrusion or depression. For example... Figure 6A As shown, when the internal air pressure P of the sealed chamber 208 in The external atmospheric pressure P is greater than that of the chip. out At this time, the membrane layer 300 will bulge and deform towards the environment, that is, the membrane layer will dent and deform towards the interior of the sealing chamber. For example... Figure 6B As shown, when the internal air pressure P of the sealed chamber 208 in The external atmospheric pressure P is less than that of the chip. out At this time, the membrane layer 300 will bulge and deform inward toward the sealing chamber 208. The thickness and size of the membrane layer can be designed according to the air pressure range that needs to be monitored. As an example, the size, geometry, and other physical parameters of the membrane layer can be designed based on simulation calculations. In particular, the membrane layer can be circular, polygonal, or other shapes adapted to the substrate. For example, in an example where the membrane layer has a circular shape, the membrane layer has a diameter of 1 mm to 10 mm and a thickness of 10 micrometers (μm) to 20 μm.

[0054] The deformation mode and amount of the film layer 300 can be precisely measured using methods such as laser morphology monitoring microscopy and probe-type profilometer. By measuring the deformation of the film layer and comparing the measurement results with predetermined parameters such as the film layer's size and geometry, the difference P between the internal air pressure of the sealed chamber and the external air pressure of the chip can be determined. d =P out -P in Due to the external ambient air pressure P out The internal air pressure P of the sealed chamber can be easily measured. in =P out -P d The hermetic cavity 202 formed on the surface of the first main surface 200a of the second substrate and the sealed chamber are formed simultaneously on the same chip under the same conditions, and the internal air pressure P of the sealed chamber is... in The internal air pressure P of the vacuum cavity on the first substrate c They are strongly correlated; in some cases, the internal air pressure P of both is similar. in With P cThey can be equal. Therefore, by pre-determining the performance of the microelectronic devices (e.g., MEMS) within the vacuum cavity and the internal gas pressure P of the sealed chamber... in Based on the relationship between the measured physical quantity and the output of the microelectronic device in the vacuum cavity, the true value of the measured physical quantity can be accurately obtained.

[0055] As an example, the second patterned layer 420 can be a patterned Ge layer, such that the bonding layer 400 between the first substrate 100 and the second substrate 200 can be an Al-Ge eutectic bonding layer. Forming a patterned Ge layer on the first main surface 100a of the first substrate includes at least: forming the Ge layer on the first main surface 100a of the first substrate using a physical vapor deposition (PVD) process, followed by etching the Ge layer into a patterned Ge layer using photolithography and etching processes. Although the formation steps of the bonding layer are described above using an Al-Ge eutectic bonding layer as an example, the type of bonding layer in this invention is not limited to this, and also includes other binary eutectic bonding layers, such as gold-tin eutectic bonding layers and gold-silicon eutectic bonding layers. The conditions for eutectic bonding between the first patterned layer 410 and the second patterned layer 420 can be designed according to actual bonding precision, vacuum requirements, etc.

[0056] As an alternative, the first substrate 100 and the second substrate 200 can be directly bonded; that is, the bonding layer 400 is formed by the mutual diffusion of materials between the first substrate 100 and the second substrate 200 at the bonding interface, without forming the first patterned layer 410 and the second patterned layer 420 composed of materials other than the substrate material.

[0057] Thus, by using the air pressure monitoring structure described in this invention, the deformation degree of the suspended film layer can be measured, and the air pressure inside the vacuum cavity where the MEMS is located can be easily monitored in real time. This allows for accurate acquisition of the true value of the measured physical quantity, thereby improving the reliability of the MEMS device. Moreover, even when the air pressure inside the MEMS vacuum cavity changes to a certain extent, the reliability of its performance can still be guaranteed, which is equivalent to extending the service life of the MEMS device.

[0058] As described above, the method for fabricating the airtightness monitoring structure inside the vacuum cavity of a microelectronic device according to the present invention has the following beneficial effects:

[0059] 1) This invention provides a method for fabricating a gas tightness monitoring structure inside a vacuum cavity for microelectronic devices. The fabrication method can form the gas tightness monitoring structure while bonding and packaging the microelectronic devices, and is simple to fabricate and cost-effective.

[0060] 2) In the airtightness monitoring structure provided by the fabrication method, the vacuum cavity and the sealing chamber used to accommodate the microelectronic device are both located on the sealing substrate. The sealing substrate has a high utilization rate, which makes the overall design of the MEMS device more flexible and the structure is compact.

[0061] Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0062] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for fabricating a vacuum cavity internal airtightness monitoring structure for microelectronic devices, characterized in that, The manufacturing method includes: Provide a first substrate; A second substrate is provided, the second substrate including opposing first and second main surfaces, and then a film layer is formed on the second main surface of the second substrate; A recess is formed on the first main surface of the second substrate, the bottom of which exposes a portion of the film layer, and a cavity for accommodating microelectronic devices is also formed on the second main surface of the second substrate. The first main surface of the second substrate is bonded to the first substrate so that the cavity and the first substrate form an airtight cavity, while the recess is airtightly isolated from the surrounding environment by the film layer. The film layer is configured to bulge or dent according to the air pressure difference between the recess and the surrounding environment. The air pressure of the airtight cavity is equal to that of the sealed recess.

2. The method for manufacturing the airtightness monitoring structure according to claim 1, characterized in that: The film layer is integrally formed with the second substrate, and the recess is formed on the surface of the first main surface of the second substrate by photolithography and etching processes.

3. The method for manufacturing the airtightness monitoring structure according to claim 1, characterized in that: Before the step of forming the film layer on the second main surface of the second substrate, a through hole is formed on the second substrate by photolithography and etching processes, and the through hole and a portion of the film layer constitute the recess.

4. The method for manufacturing the airtightness monitoring structure according to claim 3, characterized in that: The film layer is made of a different material from the second substrate, wherein the film layer is a single layer or a composite layer of materials selected from the following materials deposited by a low-pressure chemical vapor deposition process: polysilicon, silicon oxide and silicon nitride.

5. The method for manufacturing the airtightness monitoring structure according to claim 2 or 3, characterized in that: The film is formed in a circular shape and has a diameter of 1 mm to 10 mm and a thickness of 1 micrometer to 20 micrometers.

6. The method for manufacturing the airtightness monitoring structure according to claim 2 or 3, characterized in that, The manufacturing method further includes: A first material layer is formed on the first main surface of the second substrate; The first material layer is formed into a first patterned layer through photolithography and etching processes.

7. The method for manufacturing the airtightness monitoring structure according to claim 6, characterized in that, Prior to the step of bonding the first main surface of the second substrate to the first substrate, the fabrication method further includes: A second material layer is formed on the first main surface of the first substrate; The second material layer is formed into a second patterned layer by photolithography and etching processes. The first patterned layer and the second patterned layer are aligned and bonded one by one to form a bonding layer, wherein the bonding layer is an Al-Ge eutectic bonding layer.

8. The method for manufacturing the airtightness monitoring structure according to claim 1, characterized in that: A bonding layer is formed by direct bonding between the interface of the first substrate and the second substrate.

9. The method for manufacturing the airtightness monitoring structure according to claim 1, characterized in that: The main body of the microelectronic device is disposed on the first main surface of the first substrate.

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