Hermeticity monitoring structure for vacuum cavity interior of microelectronic device

Abstract

The application provides a hermeticity monitoring structure for a vacuum cavity inside a microelectronic device, which comprises a first substrate, a second substrate comprising opposite first and second main surfaces, the first main surface of the second substrate being bonded to the first main surface of the first substrate to form a hermetic cavity with the second substrate on the first main surface of the first substrate, the microelectronic device being located in the hermetic cavity, and a sealed chamber being hermetically blocked from the ambient environment by a film layer arranged on the second substrate, the air pressure in the sealed chamber being positively correlated with the air pressure in the hermetic cavity, the film layer being configured to be deformed in bulging or concave according to the air pressure difference between the sealed chamber and the ambient environment. The application can solve the problem of low reliability of MEMS devices in a vacuum cavity, and the hermeticity monitoring structure is simple, and the measurement process is simple and feasible, thus having practical value.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a pressure monitoring structure for use inside a vacuum cavity of a microelectronic device. 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 gas tightness monitoring structure for the vacuum cavity of microelectronic devices, which solves the problems of difficulty in maintaining the internal vacuum level of the tiny space used to package microelectromechanical systems, low reliability of MEMS devices in the vacuum cavity, and device lifespan in the prior art.

[0005] To achieve the above and other related objectives, the present invention provides an airtightness monitoring structure for the interior of a vacuum cavity of a microelectronic device, comprising: a first substrate, wherein a cavity for accommodating the microelectronic device is formed on the surface of a first main surface of the first substrate; a second substrate, the second substrate including opposing first and second main surfaces, wherein the first main surface of the second substrate is bonded to the first main surface of the first substrate to form an airtight cavity with the cavity, the microelectronic device being located in the airtight cavity; and a sealing chamber, wherein the sealing chamber is airtightly isolated from the surrounding environment by a film layer disposed on the second substrate, the air pressure inside the sealing chamber being positively correlated with the air pressure inside the airtight cavity, and the film layer being configured to bulge or dent according to the air pressure difference between the sealing chamber and the surrounding environment.

[0006] Optionally, the film layer is disposed on the first main surface of the second substrate, and the film layer and the recess disposed on the first main surface of the first substrate constitute the sealing chamber, and the film layer is in airtight contact with the first main surface of the second substrate.

[0007] Optionally, the film layer is disposed on the second main surface of the second substrate, and the film layer, the first substrate, and the through hole located on the second substrate constitute the sealing chamber, and the film layer and the second main surface of the second substrate form an airtight contact.

[0008] Optionally, the film layer is integrally formed with the second substrate.

[0009] Optionally, the film layer has a different material from the second substrate. The film layer is a single layer made of a material selected from polycrystalline silicon, silicon oxide, and silicon nitride, or a composite layer thereof.

[0010] Optionally, the airtightness monitoring structure further includes a through hole disposed on the second substrate, the through hole being aligned with the center of the sealing chamber and the membrane layer being suspended between the through hole and the sealing chamber.

[0011] Optionally, the airtightness monitoring structure further includes a bonding layer disposed between the first substrate and the second substrate, wherein the bonding layer is formed by direct bonding between the interfaces of the first substrate and the second substrate.

[0012] Optionally, the airtightness monitoring structure further includes a bonding layer disposed between the first substrate and the second substrate, wherein the bonding layer is an Al-Ge eutectic bonding layer.

[0013] Optionally, the film is formed in a circular shape and has a thickness of 1 micrometer to 20 micrometers.

[0014] Optionally, the microelectronic device includes one or more of the following: infrared sensor, MEMS gyroscope, MEMS accelerometer, MEMS vacuum gauge, MEMS micromirror, and MEMS pressure sensor.

[0015] As described above, the airtightness monitoring structure for the vacuum cavity of microelectronic devices of the present invention has the following beneficial effects: it can encapsulate microelectronic devices while measuring the internal vacuum level of a tiny space in real time by characterizing the degree of thin film deformation, thereby calibrating the microelectronic devices contained in the vacuum cavity. This not only improves the reliability of the devices but also extends their service life. Attached Figure Description

[0016] Figure 1A and Figure 1B The diagram shown is a schematic of an airtightness monitoring structure for the interior of a vacuum cavity in a microelectronic device, according to Embodiment 1 of the present invention.

[0017] Figure 2A and Figure 2B The diagram shown is a schematic of an airtightness monitoring structure for a vacuum cavity in a microelectronic device, according to Embodiment 2 of the present invention.

[0018] Figure 3A and Figure 3B The diagram shows the working operation of the airtightness monitoring structure inside the vacuum cavity of a microelectronic device according to the present invention, which performs real-time monitoring.

[0019] Component designation explanation

[0020] 100 First substrate

[0021] 100a First Main Face

[0022] 100b Second Main Face

[0023] 102 Airtight Cavity

[0024] 104 Microelectromechanical devices

[0025] 105 First recess

[0026] 106, 206 Sealed Chambers

[0027] 200 Second substrate

[0028] 200a First Main Face

[0029] 200b Second Main Face

[0030] 202 Through Hole

[0031] 204 Second recess

[0032] 300a and 300b film layers

[0033] 400 bonded layers Detailed Implementation

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] In this invention, the term "substrate" may refer to substrates commonly used in the semiconductor manufacturing field.

[0039] 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.

[0040] 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.

[0041] 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 an airtightness monitoring structure for the interior of a vacuum cavity in a microelectronic device. The airtightness monitoring structure includes at least: a first substrate, on the surface of a first main surface of which a cavity for accommodating the microelectronic device is formed; a second substrate, comprising opposing first and second main surfaces, wherein the first main surface of the second substrate is bonded to the first main surface of the first substrate to form an airtight cavity with the cavity, and the microelectronic device is located within the airtight cavity; and a sealing chamber, which is airtightly isolated from the surrounding environment by a film layer disposed on the second substrate. The air pressure within the sealing chamber is positively correlated with the air pressure within the airtight cavity, and the film layer is configured to bulge or indent based on the pressure difference between the sealing chamber and the surrounding environment.

[0042] The aforementioned airtightness monitoring structure allows for the pre-measurement of MEMS device characteristics under different vacuum levels and real-time monitoring of the internal vacuum level of its tiny spaces. This enhances the reliability of MEMS devices in vacuum environments and extends their lifespan. Furthermore, the airtightness monitoring structure is simple in design, easy to operate, and possesses practical value.

[0043] The specific details of the airtightness monitoring structure for the vacuum cavity of microelectronic devices described in this invention will then be described in detail with reference to Figures 1 to 3.

[0044] Example 1

[0045] Figure 1AThis diagram illustrates a gas tightness monitoring structure for a vacuum cavity of a microelectronic device according to Embodiment 1 of the present invention. The gas tightness monitoring structure includes a first substrate 100 and a second substrate 200. The first substrate 100 has a first main surface 100a and a second main surface 100b, and a cavity for accommodating the microelectronic device is formed on the surface of the first main surface. The second substrate 200 includes opposing first main surfaces 200a and 200b. The first main surface of the second substrate is bonded to the first main surface 100a of the first substrate so that the cavity and the second substrate 200 form a gas tightness cavity 102, within which a microelectronic device, such as a microelectromechanical device (MEMS) 104, is accommodated. Depending on the situation, necessary portions of the MEMS located in the gas tightness cavity 102 are suspended. Preferably, the first substrate 100 can be a silicon substrate, and the second substrate 200 can be a silicon substrate, a silicon-on-insulator (SOI) substrate, a germanium-silicon substrate, a germanium substrate, a gallium nitride substrate, a SiC substrate, or an insulating substrate such as quartz, sapphire, or glass. As an example, the microelectromechanical device 104 includes one or more of the following: an infrared sensor, a MEMS gyroscope, a MEMS accelerometer, a MEMS vacuum gauge, a MEMS micromirror, and a MEMS pressure sensor.

[0046] The airtightness monitoring structure also includes a sealed chamber 106, which is airtightly isolated from the surrounding environment by a membrane layer 300a disposed on the second substrate 200. See also Figure 1A-Figure 1B In this embodiment, the sealing chamber is disposed on the surface of the first main surface 100a of the first substrate, that is, the sealing chamber 106 is located on the same side as the airtight cavity 102. The sealing chamber 106 is airtightly isolated from the surrounding environment by a film layer 300a disposed on the second substrate 200. Specifically, the film layer 300a and the first recess 105 disposed on the first main surface 100a of the first substrate constitute the sealing chamber, and the film layer is in airtight contact with the first main surface 200a of the second substrate. The film layer 300a may have the same material as the second substrate 200, or it may have a different material than the second substrate. In one example, the film layer 300a may be a single layer made of a material selected from polycrystalline silicon, silicon oxide, and silicon nitride, or a composite layer as described above. Figure 1A As shown, the film layer 300a can be grown from the second substrate 200 and cover the through hole 202 on the second substrate. The through hole is aligned with the center of the sealing chamber 106 on the first main surface 100a of the first substrate, and the film layer 300a is suspended between the sealing chamber and the through hole on the second substrate. Alternatively, the film layer and the second substrate can be integrally formed, for example, by selectively etching a block substrate to form a second recess 204, such as... Figure 1BAs shown, the second recess is aligned with the center of the sealing chamber on the first main surface 100a of the first substrate.

[0047] See Figure 1A-Figure 1B The membrane layer 300a is configured to airtightly isolate the sealed chamber 106 from the surrounding environment and is configured to bulge or indent based on the pressure difference between the sealed chamber and the surrounding environment. The internal pressure of the sealed chamber 106 is positively correlated with the internal pressure of the airtight cavity 102. The airtightness of the airtight cavity can be monitored in real time based on the pressure change of the sealed chamber, and the vacuum level of the tiny space where the MEMS is located can be easily measured in real time, thereby ensuring the reliability of the output values ​​of the microelectronic devices in the vacuum cavity. The measurement method for real-time monitoring of the internal vacuum level of this tiny space will be described in detail in conjunction with Embodiment 2 below.

[0048] As an example, a bonding layer 400 is formed between the first main surface 100a of the first substrate and the first main surface 200a of the second substrate. The bonding layer may be formed by direct bonding between the interface of the first substrate 100 and the second substrate 200a; or the bonding layer may be a film or thin layer formed of other materials, for example, an Al-Ge eutectic bonding layer formed by Al layer and Ge layer.

[0049] As an example, the microelectromechanical device 104 includes one or more of the following: an infrared sensor, a MEMS gyroscope, a MEMS accelerometer, a MEMS vacuum gauge, a MEMS micromirror, and a MEMS pressure sensor.

[0050] Example 2

[0051] See Figures 2A-2B This diagram illustrates a gas tightness monitoring structure for a vacuum cavity inside a microelectronic device according to Embodiment 2 of the present invention. The gas tightness monitoring structure includes a first substrate 100 and a second substrate 200. The first substrate 100 has a first main surface 100a and a second main surface 100b, and a cavity for accommodating a microelectronic device is formed on the surface of the first main surface. The second substrate 200 includes opposing first main surfaces 200a and 200b. The first main surface of the second substrate is bonded to the first main surface 100a of the first substrate so that the cavity and the second substrate 200 form a gas tightness cavity 102, within which a microelectronic device, such as a microelectromechanical device 104, is accommodated.

[0052] The first substrate 100 of this embodiment may be provided with the same airtight cavity 102 as the first substrate described in Embodiment 1, the difference being that: in this embodiment, the sealing chamber is disposed on the first main surface 200a of the second substrate 200. See also Figures 2A-2BThe airtightness monitoring structure further includes a sealed chamber 206, which is airtightly isolated from the surrounding environment by a film layer 300b disposed on the second substrate 200. Specifically, the sealed chamber 206 is located on the opposite side of the airtight cavity 102 relative to the bonding layer 400 between the first substrate 100 and the second substrate 200. The film layer 300b is disposed on the second main surface 200b of the second substrate 200, and the film layer is in airtight contact with the second main surface 200b of the second substrate. The film layer 300b may have the same material as the second substrate 200, or it may have a different material. In one example, the film layer 300b may be grown from the second substrate 200 and cover the through-hole 202 on the second substrate. The grown film layer may be a single layer composed of a material selected from polysilicon, silicon oxide, and silicon nitride, or a composite layer as described above. Figure 2A As shown. As an alternative, such as Figure 2B As shown, the film layer 300b is integrally formed with the second substrate, for example, by selectively etching a block substrate to form a second recess 204.

[0053] See Figures 2A-2B A membrane layer 300b is suspended above the sealed chamber 206, and is configured to airtightly isolate the sealed chamber 206 from the surrounding environment. The internal air pressure of the sealed chamber is positively correlated with the internal air pressure of the airtight cavity 102. The membrane layer 300b can be configured to bulge or indent according to the pressure difference between the sealed chamber and the surrounding environment, and the airtightness of the airtight cavity can be reflected by monitoring the direction and degree of deformation of the membrane layer. Specifically, as... Figures 3A-3B As shown, when the internal air pressure P of the sealed chamber 206 in The external atmospheric pressure P of the chip out When differences occur, film layer 300b will deform by protrusion or depression. For example... Figure 3A As shown, when the internal air pressure P of the sealed chamber 206 in The external atmospheric pressure P is greater than that of the chip. out At this time, the membrane layer 300b 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 3B As shown, when the internal air pressure P of the sealed chamber 206 in The external atmospheric pressure P is less than that of the chip. outAt this time, the membrane layer 300b will bulge and deform inward toward the sealing chamber 206. The thickness and size of the membrane layer can be designed according to the gas pressure range to be monitored. 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 300b 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 102 formed on the surface of the first main surface 100a of the first 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 c They 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] 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.

[0056] As described above, the airtightness monitoring structure for the vacuum cavity of microelectronic devices of the present invention has the following beneficial effects:

[0057] This invention provides an airtightness monitoring structure for the vacuum cavity of microelectronic devices. The airtightness monitoring structure can measure the internal vacuum level of a tiny space in real time by measuring the degree of thin film deformation, which not only improves the reliability of the device but also extends its service life. The airtightness monitoring structure is simple and the measurement process is easy and feasible, thus having practical value.

[0058] Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0059] 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 gas tightness monitoring structure for use inside a vacuum cavity of a microelectronic device, characterized in that, include: A first substrate has a cavity for accommodating a microelectronic device formed on the surface of a first main surface of the first substrate. The second substrate includes a first main surface and a second main surface opposite to each other. The first main surface of the second substrate is bonded to the first main surface of the first substrate so that the cavity and the second substrate form an airtight cavity, and the microelectronic device is located in the airtight cavity. A sealed chamber, wherein the sealed chamber is airtightly isolated from the surrounding environment by a membrane layer disposed on the second substrate, the air pressure inside the sealed chamber is positively correlated with the air pressure inside the airtight cavity, and the membrane layer is configured to bulge or dent according to the air pressure difference between the sealed chamber and the surrounding environment. The film layer is disposed on the first main surface of the second substrate. The film layer and the recess disposed on the first main surface of the first substrate constitute the sealing chamber. The film layer is in airtight contact with the first main surface of the second substrate. The airtightness monitoring structure also includes a through hole disposed on the second substrate. The through hole is aligned with the center of the sealing chamber and the film layer is suspended between the through hole and the sealing chamber. or: The film layer is disposed on the second main surface of the second substrate. The film layer, the first substrate, and the through hole located on the second substrate constitute the sealing chamber. The film layer and the second main surface of the second substrate form an airtight contact.

2. The airtightness monitoring structure according to claim 1, characterized in that: The film layer is integrally formed with the second substrate.

3. The airtightness monitoring structure according to claim 1, characterized in that: The film layer is made of a different material from the second substrate. The film layer is a single layer made of a material selected from polycrystalline silicon, silicon oxide and silicon nitride, or a composite layer thereof.

4. The airtightness monitoring structure according to claim 1, characterized in that, The airtightness monitoring structure further includes a bonding layer disposed between the first substrate and the second substrate, which is formed by direct bonding between the interfaces of the first substrate and the second substrate.

5. The airtightness monitoring structure according to claim 1, characterized in that, The airtightness monitoring structure further includes a bonding layer disposed between the first substrate and the second substrate, wherein the bonding layer is an Al-Ge eutectic bonding layer.

6. The airtightness monitoring structure according to claim 1, characterized in that: The film is formed in a circular shape and has a thickness of 1 micrometer to 20 micrometers.

7. The airtightness monitoring structure according to claim 1, characterized in that: The microelectronic devices include one or more of the following: infrared sensors, MEMS gyroscopes, MEMS accelerometers, MEMS vacuum gauges, MEMS micromirrors, and MEMS pressure sensors.

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