Air tightness monitoring structure for use inside vacuum cavities of microelectronic devices

Abstract

This invention provides an airtightness monitoring structure for the interior of a vacuum cavity in a microelectronic device, comprising: a first substrate and a second substrate, the second substrate including: a first main surface and a second main surface opposite to each other, a cavity for accommodating the microelectronic device formed on the surface of the first main surface of the second substrate, the first main surface of the second substrate being bonded to the first substrate to form an airtight cavity with the cavity on the first main surface of the first substrate; and a sealed chamber, the sealed chamber being airtightly isolated from the surrounding environment by a film layer disposed on the second main surface of the second substrate, the film layer being configured to bulge or indent according to the pressure difference between the sealed chamber and the surrounding environment, the pressure inside the sealed chamber being positively correlated with the pressure inside the airtight cavity. The airtightness monitoring structure of this invention can solve the problem of low reliability of MEMS in vacuum cavities in the prior art, has a higher utilization rate of the sealed substrate, and allows for more flexible overall design of the MEMS device structure.

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 and its fabrication method for the vacuum cavity of 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 an airtightness monitoring structure for the interior of a vacuum cavity of a microelectronic device, characterized in that it comprises: a first substrate; a second substrate, the second substrate comprising: a first main surface and a second main surface opposite to each other, a cavity for accommodating the microelectronic device being formed on the surface of the first main surface of the second substrate, the first main surface of the second substrate being bonded to the first main surface of the first substrate such that the cavity and the first main surface of the first substrate form an airtight cavity; a sealing chamber, the sealing chamber being airtightly isolated from the surrounding environment by a film layer disposed on the second main surface of the second substrate, the film layer being configured to bulge or dent according to the pressure difference between the sealing chamber and the surrounding environment, the sealing chamber being defined between the film layer and the first substrate, and the air pressure inside the sealing chamber being positively correlated with the air pressure inside the airtight cavity.

[0006] Optionally, the main body of the microelectronic device is formed on the first main surface of the first substrate.

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

[0008] 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.

[0009] Optionally, the film layer is integrally formed with the second substrate.

[0010] 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.

[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 an Al-Ge eutectic bonding layer.

[0012] Optionally, the film is formed in a circular shape and has a thickness of 1 micrometer to 20 micrometers.

[0013] 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.

[0014] As described above, the airtightness monitoring structure for the vacuum cavity of microelectronic devices and its fabrication method of the present invention have the following beneficial effects:

[0015] 1) This invention provides a gas tightness monitoring structure for the vacuum cavity of a microelectronic device. The gas tightness monitoring structure may include a gas tightness cavity and a sealed chamber disposed on the same substrate, which can realize a vacuum-encapsulated MEMS device. At the same time, the internal vacuum degree change of the tiny space is measured in real time by characterizing the deformation degree of the thin film used for gas tightness, which can improve the reliability of the device.

[0016] 2) The airtightness monitoring structure provided by the present invention adopts a structure in which both the airtightness cavity and the sealed chamber are set on the sealed substrate, making the overall design of the MEMS device more flexible and the structure more compact. Attached Figure Description

[0017] Figure 1 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.

[0018] Figure 2 The diagram shown is a schematic of an airtightness monitoring structure for a vacuum cavity in a microelectronic device, according to Embodiment 1 of the present invention.

[0019] Figures 3A-3B The diagram shows a real-time monitoring operation of the airtightness monitoring structure inside the vacuum cavity of a microelectronic device according to the present invention.

[0020] Component designation explanation

[0021] 100 First substrate

[0022] 100a First Main Face

[0023] 100b Second Main Face

[0024] 104 Microelectromechanical devices

[0025] 200 Second substrate

[0026] 200a First Main Face

[0027] 200b Second Main Face

[0028] 202 Airtight Cavity

[0029] 205 concavity

[0030] 206 Through Hole

[0031] 208 Sealed Chamber

[0032] 300 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 and a second substrate. The second substrate includes opposing first and second main surfaces. A cavity for accommodating the microelectronic device is formed on the surface of the first main surface of the second substrate. 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. A sealing chamber is also included. The sealing chamber is airtightly isolated from the surrounding environment by a film layer disposed on the second main surface of the second substrate. The film layer is configured to bulge or indent based on the pressure difference between the sealing chamber and the surrounding environment. The sealing chamber is defined between the film layer and the first substrate. The pressure within the sealing chamber is positively correlated with the pressure within the airtight cavity.

[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 minute spaces. This enhances the reliability of MEMS devices in vacuum environments and extends their lifespan. Furthermore, the airtightness monitoring structure of this invention features a cavity formed on the sealed substrate to accommodate the MEMS, eliminating the need for a large cavity on the MEMS substrate. This allows for greater design flexibility and a more compact structure for the overall MEMS device, resulting in a wider range of applications.

[0043] See afterward Figure 1 Figure 3 illustrates the specific details of the airtightness monitoring structure inside the vacuum cavity of a microelectronic device according to the present invention.

[0044] Example 1

[0045] Figure 1This 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 has a first main surface 100a and a second main surface 100b. The second substrate 200 includes opposing first main surfaces 200a and 200b. A cavity for accommodating a microelectronic device is formed on the surface of the first main surface. The first main surface 200a of the second substrate is bonded to the first main surface 100a of the first substrate to form a bonding layer 400 between the first and second substrates. Simultaneously, the cavity and the second substrate 200 form a gas tightness cavity 202, within which a microelectronic device, such as a microelectromechanical device (MEMS) 204, is accommodated. 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. In this embodiment, a microelectromechanical device (MEMS) 204 is disposed within the hermetically sealed cavity 202, and the main body of the MEMS 204 is disposed on the first main surface of the first substrate. As an example, the MEMS 204 may include 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 further includes a sealed chamber 208, which is airtightly isolated from the surrounding environment by a membrane layer 300 disposed on the second main surface 200b of the second substrate. See also Figure 1 The film layer 300 is in airtight contact with the second main surface 200b of the second substrate, and the film layer, the first substrate 100, and the through hole 206 located on the second substrate together define the sealing chamber 208. Alternatively, the film layer and the second substrate can be integrally formed, for example, by selectively etching a recess 205 into a block substrate. Figure 2 As shown, a suspended film layer 2051 is formed above the recess. See also Figure 1 In this embodiment, the sealing chamber is disposed in the through hole 206 of the second substrate, that is, both the sealing chamber 208 and the airtight cavity 102 are located on the second substrate 200, which makes the utilization rate of the sealing substrate higher and the airtightness monitoring structure more reasonable.

[0047] As an example, film layer 300 may be grown from the second main surface 200b of the second substrate and cover the through-hole 206 on the second substrate. The film layer may be made of the same material as the second substrate or a different material. Film layer 300 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.

[0048] See Figures 3A-3B A membrane layer 300 is suspended above the sealed chamber 208, and is configured to airtightly isolate the sealed chamber from the surrounding environment. The internal air pressure of the sealed chamber is positively correlated with the internal air pressure of the airtight cavity 202. The membrane layer 300 can be configured to bulge or indent based on 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, when the internal air pressure P of the sealed 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 3A 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 3B 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.

[0049] 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 substratec 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.

[0050] 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 200; 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.

[0051] 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.

[0052] As mentioned above, the airtightness monitoring structure inside the vacuum cavity for microelectronic devices provided in this embodiment can be formed while packaging microelectronic devices (e.g., MEMS). The fabrication method has advantages such as simple fabrication and low cost.

[0053] As described above, the airtightness monitoring structure for the vacuum cavity of microelectronic devices of the present invention has the following beneficial effects:

[0054] 1) This invention provides a gas tightness monitoring structure for the vacuum cavity of a microelectronic device. The gas tightness monitoring structure may include a gas tightness cavity and a sealed chamber disposed on the same substrate, which can realize a vacuum-encapsulated MEMS device. At the same time, the internal vacuum degree change of the tiny space is measured in real time by characterizing the deformation degree of the thin film used for gas tightness, which can improve the reliability of the device.

[0055] 2) The airtightness monitoring structure provided by the present invention adopts a structure in which both the airtightness cavity and the sealing chamber are set in the sealing substrate, which removes the additional limitation of forming a large cavity on the MEMS substrate, is applicable to various MEMS, and gives the overall design of MEMS devices more flexibility, a more compact structure, and a wider range of applications.

[0056] Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0057] 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 hermeticity monitoring structure for use inside a vacuum cavity of a microelectronic device, characterized by, Comprising: a first substrate; a second substrate comprising: opposite first and second main faces, a cavity for accommodating a microelectronic device formed on a surface of the first main face of the second substrate, the first main face of the second substrate being bonded to the first main face of the first substrate to form a hermetic cavity with the cavity; a sealed chamber hermetically blocked from ambient environment by a membrane layer disposed on the second main face of the second substrate, the membrane layer being configured to be deformed in bulge or in sag according to a pressure difference between the sealed chamber and the ambient environment, the sealed chamber being defined between the membrane layer and the first substrate, a pressure in the sealed chamber being positively correlated with a pressure in the hermetic cavity; the membrane layer, the first substrate and a through hole on the second substrate constitute the sealed chamber, the membrane layer being in hermetic contact with the second main face of the second substrate.

2. The air barrier monitoring structure of claim 1, wherein: a main body of the microelectronic device is formed on the first main face of the first substrate.

3. The air barrier monitoring structure of claim 1, wherein: the membrane layer and the second substrate have different materials, the membrane layer being a single layer composed of one material selected from polycrystalline silicon, silicon oxide and silicon nitride, or a composite layer of the above.

4. The air barrier monitoring structure of claim 1, wherein: the membrane layer is integrally formed with the second substrate.

5. The air barrier monitoring structure of claim 1, wherein: the hermetic monitoring structure further comprises a bonding layer disposed between the first substrate and the second substrate, the bonding layer being formed by direct bonding between the interface of the first substrate and the second substrate.

6. The air barrier monitoring structure of claim 1, wherein, the hermetic monitoring structure further comprises a bonding layer disposed between the first substrate and the second substrate, the bonding layer being an Al-Ge eutectic bonding layer.

7. The air barrier monitoring structure of claim 1, wherein: the membrane layer is formed in a circular shape and has a thickness of 1-20 microns.

8. The air barrier monitoring structure of claim 1, wherein: the microelectronic device comprises one or more of an infrared sensor device, a MEMS gyroscope, a MEMS accelerometer, a MEMS vacuum gauge, a MEMS micromirror and a MEMS pressure sensor.

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