Sealing Method, Device and Medium of Wafer-Level Multistage Air Pressure Microcavity

Abstract

The present invention provides a sealing method, device and medium for a wafer-level multi-stage air-pressure micro-cavity, which relates to the technical field of microsystems and micro-nano devices. The method includes: by setting M types of sealing ring structures, M types of to-be-sealed micro-cavity structures corresponding to N to-be-sealed devices are formed on a pre-set wafer, and the height of each sealing ring structure is positively correlated with the sealing priority corresponding to the M types of to-be-sealed micro-cavity structures; according to the order of the sealing priorities corresponding to the M types of to-be-sealed micro-cavity structures from high to low, sealing operations are sequentially performed on the M types of to-be-sealed micro-cavity structures to form a multi-stage air-pressure micro-cavity including M types of sealing structures, and the air-pressure environment of the multi-stage air-pressure micro-cavity is the required air-pressure environment corresponding to the to-be-sealed devices in the M types of to-be-sealed micro-cavity structures pre-set. The present invention realizes the multi-stage sealing of devices with different required air-pressure environments.

Description

Technical Field

[0001] The present invention relates to the technical field of microsystems and micro-nano devices, and particularly to a sealing method, device and medium for a wafer-level multi-stage air pressure microcavity. Background Art

[0002] Hermetic sealing is a key processing step for micro-nano devices such as gyroscopes and thermal radiation detectors in micro-electro-mechanical systems (MEMS). Its purpose is to seal and maintain a microcavity environment with a specific air pressure, achieving the goals of improving the quality factor, reducing air heat conduction, and isolating oxygen. It directly determines whether the sealed MEMS device can work normally, persistently and reliably. Hermetic sealing technology has become a key factor restricting the processing yield and reliability of many MEMS devices, and is also the main process link with high costs (up to 50%-90%) in the production process of MEMS factories. Among them, wafer-level hermetic sealing can complete the one-time sealing of thousands of devices on a wafer. Compared with chip-level sealing, it has obvious advantages in efficiency and cost, and is also convenient for direct integration with complementary metal oxide semiconductor (CMOS) integrated circuit wafers. It is a key research field in academia and industry.

[0003] Currently, with the increasing demand for miniaturization and integration of MEMS devices in the upgrading of the microsystem industry, the traditional system-level sealing method of separately sealing independent devices and then integrating them shows disadvantages in terms of volume and cost. Achieving on-chip heterogeneous integration of multi-functional devices has become a trend. For example, a multi-functional sensing unit integrating MEMS accelerometers, gyroscopes, thermal radiation detectors, etc. If it is possible to complete one-time hermetic sealing of different devices at the wafer level, it will greatly enhance its integration and miniaturization, while reducing the overall processing cost, and further promoting the development of application fields such as micro and small unmanned aerial vehicles and portable electronic devices.

[0004] However, existing methods are only applicable to specific devices to achieve sealing in a single air pressure environment with unified requirements. However, different MEMS devices may have different requirements for the sealing air pressure. For example, MEMS accelerometers need to work in an air pressure environment of about dozens of kPa, while MEMS thermal radiation detectors need to work in a low air pressure environment of 10 -5 -10 -3 kPa. Existing methods are difficult to achieve wafer-level multi-stage sealing of MEMS devices with different sealing air pressure requirements, thus restricting the further development of on-chip heterogeneous integration of multiple devices. Summary of the Invention

[0005] The present invention provides a sealing method, device and medium for a wafer-level multi-stage pneumatic microcavity, aiming to solve the problem that it is difficult to achieve wafer-level multi-stage sealing of MEMS devices with different sealing air pressure requirements in the prior art.

[0006] The present invention provides a sealing method for a wafer-level multi-stage pneumatic microcavity, including:

[0007] By setting M kinds of sealing ring structures, M kinds of to-be-sealed microcavity structures corresponding to N to-be-sealed devices are formed on a pre-set wafer, where N is an integer greater than 1, and M is an integer greater than 1 and less than or equal to N; wherein, the height of each of the sealing ring structures is positively correlated with the sealing priority corresponding to the M kinds of to-be-sealed microcavity structures;

[0008] According to the order of the sealing priorities corresponding to the M kinds of to-be-sealed microcavity structures from high to low, sealing operations are sequentially performed on the M kinds of to-be-sealed microcavity structures to form a multi-stage pneumatic microcavity including M kinds of sealing structures, and the air pressure environment of the multi-stage pneumatic microcavity including M kinds of sealing structures is the required air pressure environment corresponding to the to-be-sealed devices in the pre-set M kinds of to-be-sealed microcavity structures;

[0009] Among them, for the current to-be-sealed microcavity structure among the M kinds of to-be-sealed microcavity structures that is currently performing the sealing operation, the sealing operation includes: based on the bonding pressure and bonding temperature corresponding to the current sealing ring structure of the current to-be-sealed microcavity structure, sealing the current to-be-sealed microcavity structure, and bonding occurs between the upper sealing ring structure and the lower sealing ring structure of the current sealing ring structure under the bonding pressure and bonding temperature.

[0010] According to the sealing method for a wafer-level multi-stage pneumatic microcavity provided by the present invention, for the current to-be-sealed microcavity structure, the sealing operation specifically includes:

[0011] Establish the required air pressure environment corresponding to the to-be-sealed device in the current to-be-sealed microcavity structure;

[0012] Under the required air pressure environment corresponding to the to-be-sealed device in the current to-be-sealed microcavity structure, seal the current to-be-sealed microcavity structure based on the bonding pressure and bonding temperature corresponding to the current sealing ring structure.

[0013] According to the sealing method for a wafer-level multi-stage pneumatic microcavity provided by the present invention, for the current to-be-sealed microcavity structure, the sealing operation specifically includes:

[0014] Set a getter in the current to-be-sealed microcavity structure; wherein, the getter is used to absorb gas when the temperature is greater than or equal to a pre-set threshold;

[0015] Under a preset current air pressure environment, based on the bonding pressure and bonding temperature corresponding to the current sealing ring structure, seal the current microcavity structure to be sealed to form a current sealing structure corresponding to the current microcavity structure to be sealed; wherein, the air pressure of the current air pressure environment is higher than the required air pressure environment corresponding to the device to be sealed in the current microcavity structure to be sealed.

[0016] Set a bonding temperature greater than or equal to the threshold for the current sealing structure to form a sealing structure corresponding to the required air pressure environment of the device to be sealed in the current microcavity structure to be sealed.

[0017] According to a method for sealing a wafer-level multi-stage air pressure microcavity provided by the present invention, the wafer includes a device wafer and a capping wafer, the N devices to be sealed are arranged on the device wafer, the upper sealing ring structure is arranged on the capping wafer, the lower sealing ring structure is arranged on the device wafer, and the upper sealing ring structure and the lower sealing ring structure are arranged corresponding to each other.

[0018] According to a method for sealing a wafer-level multi-stage air pressure microcavity provided by the present invention, the materials of the upper sealing ring structure and the lower sealing ring structure are the same or different.

[0019] According to a method for sealing a wafer-level multi-stage air pressure microcavity provided by the present invention, the height of each sealing ring structure is set in the range of 100 nm to 100 μm.

[0020] The present invention also provides a sealing device for a wafer-level multi-stage air pressure microcavity, including: a wafer, and N devices to be sealed and M types of sealing ring structures arranged on the wafer, the M types of sealing ring structures are used to form M types of microcavity structures to be sealed corresponding to the N devices to be sealed, the height of each sealing ring structure is positively correlated with the sealing priority corresponding to the M types of microcavity structures to be sealed, the upper sealing ring structure and the lower sealing ring structure among the M types of sealing ring structures are bonded under the bonding pressure and bonding temperature corresponding to the M types of sealing ring structures, so as to form a multi-stage air pressure microcavity including M types of sealing structures, and the air pressure environment of the multi-stage air pressure microcavity including M types of sealing structures is the required air pressure environment corresponding to the devices to be sealed in the M types of microcavity structures to be sealed preset, N is an integer greater than 1, and M is an integer greater than 1 and less than or equal to N.

[0021] According to a sealing device for a wafer-level multi-stage air pressure microcavity provided by the present invention, the wafer includes a device wafer and a capping wafer, the N devices to be sealed are arranged on the device wafer, the upper sealing ring structure is arranged on the capping wafer, the lower sealing ring structure is arranged on the device wafer, and the upper sealing ring structure and the lower sealing ring structure are arranged corresponding to each other.

[0022] A sealing device for wafer - level multi - stage pneumatic micro - cavities provided by the present invention, the M types of micro - cavity structures to be sealed perform sealing operations in sequence according to the order of the sealing priorities corresponding to the M types of micro - cavity structures from high to low;

[0023] Among them, for the current micro - cavity structure to be sealed that is currently performing the sealing operation among the M types of micro - cavity structures to be sealed, the execution of the sealing operation includes: based on the bonding pressure and bonding temperature corresponding to the current sealing ring structure of the current micro - cavity structure to be sealed, sealing the current micro - cavity structure to be sealed.

[0024] The present invention also provides a non - transitory computer - readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the sealing method of the wafer - level multi - stage pneumatic micro - cavity as described in any one of the above.

[0025] The sealing method, device and medium of the wafer - level multi - stage pneumatic micro - cavity provided by the present invention can determine different heights of the sealing ring structures corresponding to N devices to be sealed according to the order of the sealing priorities corresponding to the N devices to be sealed. Specifically, the height of each sealing ring structure is positively correlated with the sealing priorities corresponding to the N devices to be sealed, that is, the height of the sealing ring structure increases as the sealing priority of the device to be sealed increases, and vice versa. Then, M types of sealing ring structures with different heights are correspondingly arranged on the wafer to form M types of micro - cavity structures to be sealed corresponding to the N devices to be sealed; in the stage of multi - stage sealing, since the height of the sealing ring structure corresponding to the device to be sealed that is sealed earlier is higher, the corresponding upper sealing ring structure and lower sealing ring structure come into contact earlier, and can be bonded under the bonding pressure and bonding temperature to seal the micro - cavity structure to be sealed corresponding to the device to be sealed, and then seal the device to be sealed with the next sealing priority, and so on. The present invention can realize the wafer - level multi - stage pneumatic micro - cavity sealing of the devices to be packaged in different required air - pressure environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 is a flowchart of the sealing method of the wafer - level multi - stage pneumatic micro - cavity provided by the present invention;

[0028] Figure 2 is a schematic diagram of the setting of the sealing ring structure in the sealing method of the wafer - level multi - stage pneumatic micro - cavity provided by the present invention;

[0029] Figure 3 It is a schematic diagram of the first - stage sealing in the sealing method of the wafer - level multi - stage pneumatic micro - cavity provided by the present invention;

[0030] Figure 4 It is a schematic diagram of the second - stage sealing in the sealing method of the wafer - level multi - stage pneumatic micro - cavity provided by the present invention;

[0031] Figure 5 It is a schematic diagram of the third - stage sealing in the sealing method of the wafer - level multi - stage pneumatic micro - cavity provided by the present invention;

[0032] Figure 6 It is a schematic structural diagram of the sealing device of the wafer - level multi - stage pneumatic micro - cavity provided by the present invention. Detailed implementation manners

[0033] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative efforts based on the embodiments in the present invention belong to the scope of protection of the present invention.

[0034] The following describes the sealing method, device and medium of the wafer - level multi - stage pneumatic micro - cavity of the present invention with reference to the accompanying drawings.

[0035] Figure 1 It is a schematic flowchart of the sealing method of the wafer - level multi - stage pneumatic micro - cavity provided by the present invention. As Figure 1 shown, the sealing method of the wafer - level multi - stage pneumatic micro - cavity includes step S101 and step S102; where:

[0036] Step S101: By setting M kinds of seal - ring structures, M kinds of to - be - sealed micro - cavity structures corresponding to N to - be - sealed devices are formed on a pre - set wafer, N is an integer greater than 1, and M is an integer greater than 1 and less than or equal to N; wherein, the height of each of the seal - ring structures is positively correlated with the sealing priority corresponding to the M kinds of to - be - sealed micro - cavity structures;

[0037] Step S102: According to the order of the sealing priorities corresponding to the M kinds of to - be - sealed micro - cavity structures from high to low, sealing operations are sequentially performed on the M kinds of to - be - sealed micro - cavity structures to form a multi - stage pneumatic micro - cavity including M kinds of sealing structures, and the pneumatic environment of the multi - stage pneumatic micro - cavity including M kinds of sealing structures is the required pneumatic environment corresponding to the to - be - sealed devices in the M kinds of to - be - sealed micro - cavity structures pre - set.

[0038] Among them, for the current microcavity structure to be sealed in the M types of microcavity structures to be sealed, the sealing operation includes: based on the bonding pressure and bonding temperature corresponding to the current sealing ring structure of the current microcavity structure to be sealed, sealing the current microcavity structure to be sealed, and bonding occurs between the upper sealing ring structure and the lower sealing ring structure of the current sealing ring structure under the bonding pressure and bonding temperature.

[0039] In the related art, different MEMS devices may have different requirements for air pressure. For example, MEMS accelerometers need to work in an air pressure environment of about dozens of kPa, while MEMS thermal radiation detectors need to work in a low air pressure environment of 10 -5 ~10 -3 kPa. Therefore, it has become an urgent need to complete wafer-level multi-stage vacuum packaging for MEMS devices with different sealed air pressure requirements. However, existing methods usually only achieve sealing in a single air pressure environment with unified requirements for specific devices, which restricts the further development of heterogeneous integration of multiple devices on a chip.

[0040] In view of the above problems, the embodiments of the present invention provide the following technical concept: different microcavities to be sealed are sealed step by step in different air pressure environments through sealing ring structures arranged at different heights on the wafer, so as to encapsulate different air pressure environments in different microcavities to be sealed.

[0041] Specifically, first, by setting M types of sealing ring structures, M types of microcavity structures to be sealed corresponding to N devices to be sealed are formed on a pre-set wafer. Among them, the height of each sealing ring structure is positively correlated with the sealing priority corresponding to the N devices to be sealed. It can be understood that the height of the sealing ring structure increases as the sealing priority of the device to be sealed increases; the sealing ring structure can be divided into an upper sealing ring structure and a lower sealing ring structure. The height of the sealing ring structure can be understood as the total height of the upper sealing ring structure and the lower sealing ring structure. The higher the height of the sealing ring structure, the earlier the upper sealing ring structure and the lower sealing ring structure come into contact. Under appropriate bonding pressure and bonding temperature, bonding occurs between the upper sealing ring structure and the lower sealing ring structure, thereby realizing the sealing of the microcavity structure to be sealed;

[0042] Optionally, the height setting range of each of the sealing ring structures is 100 nm to 100 μm.

[0043] It should be noted that corresponding microcavity structures to be sealed can be formed for all N devices to be sealed. In this case, it is equivalent to forming N types of microcavity structures to be sealed in total; or for multiple devices to be sealed with the same required air pressure environment, the same type of microcavity structure to be sealed can be formed. In this case, M is less than N.

[0044] It should also be noted that the same type of sealing ring structure can be correspondingly arranged on the devices to be sealed with the same required air pressure environment to form the same type of microchamber structure to be sealed. When the same type of microchamber structure to be sealed is under the condition of establishing the same corresponding required air pressure environment, the sealing operation can be performed simultaneously;

[0045] Optionally, different types of sealing ring structures (corresponding to different sealing priorities) can be adopted for each sealing ring, or the same type of sealing ring structure (corresponding to the same sealing priority) can be adopted for multiple sealing rings.

[0046] Optionally, the heights of the same type of sealing ring structures are usually the same or similar.

[0047] After forming M types of microchambers to be sealed, based on the order of the sealing priorities corresponding to the M types of microchambers to be sealed, specifically, based on the order of the sealing priorities corresponding to the devices to be sealed in the M types of microchambers to be sealed, the required air pressure environments corresponding to N devices to be sealed are established in sequence, and under the required air pressure environments corresponding to the N devices to be sealed, based on the bonding pressures and bonding temperatures corresponding to each sealing ring structure, by bonding the upper sealing ring structure and the lower sealing ring structure of each sealing ring structure, multi-level sealing is performed on the M types of microchambers to be sealed corresponding to the N devices to be sealed;

[0048] Specifically, the sealing operation can be performed on the M types of microchambers to be sealed in sequence according to the order of the sealing priorities corresponding to the M types of microchambers to be sealed from high to low, to form a multi-level air pressure microchamber including M types of sealing structures, so that the air pressure environment of the multi-level air pressure microchamber including M types of sealing structures reaches the required air pressure environment corresponding to the devices to be sealed in the M types of microchambers to be sealed preset;

[0049] For the current microchamber to be sealed that is currently performing the sealing operation among the M types of microchambers to be sealed, the sealing operation includes the following steps: based on the bonding pressure and bonding temperature corresponding to the current sealing ring structure of the current microchamber to be sealed, the current microchamber to be sealed is sealed, and the upper sealing ring structure and the lower sealing ring structure of the current sealing ring structure are bonded under the bonding pressure and bonding temperature to achieve sealing.

[0050] For example, the microcavity structure to be sealed where the device to be sealed with the highest sealing priority (the first sealing priority) can be sealed first. Specifically, the required air pressure environment corresponding to the device to be sealed with the highest sealing priority can be established first, and then the microcavity structure to be sealed can be sealed under this required air pressure environment. Specifically, the existing wafer bonding process can be used, and the bonding pressure and bonding temperature corresponding to the sealing ring structure of the device to be sealed with the highest sealing priority can be adopted, so that the upper sealing ring structure and the lower sealing ring structure of the sealing ring structure are bonded under the bonding pressure and bonding temperature, thereby realizing the sealing of the microcavity structure to be sealed. Since the height of the sealing ring structure corresponding to the device to be sealed with the highest sealing priority is the highest, the upper sealing ring structure and the lower sealing ring structure of the sealing ring structure corresponding to the device to be sealed with the highest sealing priority come into contact and are bonded first, and when other sealing ring structures have not come into contact, the bonding between their upper sealing ring structure and lower sealing ring structure cannot occur;

[0051] When the microcavity structure to be sealed where the device to be sealed with the second sealing priority needs to be sealed, since the sealing ring structure corresponding to the device to be sealed with the first sealing priority has undergone plastic deformation, the above principle can be used to seal the device to be sealed with the second sealing priority, and so on, to realize the sealing of all microcavity structures to be sealed.

[0052] Optionally, the device to be sealed can be a micro-nano device, such as a MEMS switch, a MEMS accelerometer, a MEMS thermal radiation meter, etc.

[0053] In the sealing method of the wafer-level multi-stage air pressure microcavity provided in the embodiment of the present invention, the different heights of the sealing ring structures corresponding to the N devices to be sealed can be determined according to the order of the sealing priorities corresponding to the N devices to be sealed. Specifically, the height of each sealing ring structure is positively correlated with the sealing priorities corresponding to the N devices to be sealed, that is, the height of the sealing ring structure increases as the sealing priority of the device to be sealed increases, and vice versa. Then, M types of sealing ring structures with different heights are correspondingly arranged on the wafer to form M types of microcavity structures to be sealed corresponding to the N devices to be sealed; in the stage of multi-stage sealing, since the height of the sealing ring structure corresponding to the device to be sealed that is sealed first is the highest, its corresponding upper sealing ring structure and lower sealing ring structure come into contact first and can be bonded under the bonding pressure and bonding temperature to seal the microcavity structure to be sealed corresponding to the device to be sealed, and then the device to be sealed with the next sealing priority is sealed, and so on. The present invention can realize the wafer-level multi-stage air pressure microcavity sealing of the device to be packaged with different required air pressure environments.

[0054] Optionally, the wafer may include a device wafer and a capping wafer. The N devices to be sealed are disposed on the device wafer, the upper sealing ring structure is disposed on the capping wafer, the lower sealing ring structure is disposed on the device wafer, and the upper sealing ring structure and the lower sealing ring structure are correspondingly arranged.

[0055] Specifically, the wafer can be divided into a device wafer and a capping wafer. The N devices to be sealed are disposed on the device wafer. The upper sealing ring structure of the sealing ring structure is disposed on the capping wafer, and the lower sealing ring structure of the sealing ring structure is disposed on the device wafer. Moreover, the upper sealing ring structure and the lower sealing ring structure are correspondingly arranged, and a microcavity structure to be sealed can be formed.

[0056] Optionally, a wafer bonder can be used to establish a suitable required air pressure environment, set the bonding temperature, and apply a bonding pressure to the outer sides of the device wafer and the capping wafer to seal the microcavity structure to be sealed.

[0057] Optionally, for the current microcavity structure to be sealed, the sealing operation specifically may include:

[0058] Establish the required air pressure environment corresponding to the device to be sealed in the current microcavity structure to be sealed;

[0059] Under the required air pressure environment corresponding to the device to be sealed in the current microcavity structure to be sealed, seal the current microcavity structure to be sealed based on the bonding pressure and bonding temperature corresponding to the current sealing ring structure.

[0060] Specifically, for the sealing of each level of microcavity structure to be sealed, the required air pressure environment corresponding to the device to be sealed in the current microcavity structure to be sealed can be established first, and then the current microcavity structure to be sealed can be sealed under this required air pressure environment. Specifically, the wafer bonding process can be utilized to seal the current microcavity structure to be sealed based on the bonding pressure and bonding temperature corresponding to the current sealing ring structure.

[0061] Optionally, for the current microcavity structure to be sealed, the sealing operation specifically may include:

[0062] Set a getter in the current microcavity structure to be sealed; wherein, the getter is used to absorb gas when the temperature is greater than or equal to a preset threshold.

[0063] Under a preset current air pressure environment, seal the current microcavity structure to be sealed based on the bonding pressure and bonding temperature corresponding to the current sealing ring structure to form the current sealing structure corresponding to the current microcavity structure to be sealed; wherein, the air pressure of the current air pressure environment is higher than the required air pressure environment corresponding to the device to be sealed in the current microcavity structure to be sealed.

[0064] Set a bonding temperature greater than or equal to the threshold for the current sealing structure to form a sealing structure corresponding to the required air pressure environment for the device to be sealed in the current microcavity structure to be sealed.

[0065] Specifically, a getter can also be used to perform the sealing operation, so that the microcavity structure to be sealed reaches its corresponding required air pressure environment after being sealed;

[0066] For the sealing of the current microcavity structure to be sealed, a getter can be first set in the current microcavity structure to be sealed. The setting amount of the getter can be set by the operator based on the actual situation, and the setting position in the current microcavity structure to be sealed can also be set based on the actual situation. For example, the getter can be set on the capping wafer side of the current microcavity structure to be sealed;

[0067] After setting the getter, the current microcavity structure to be sealed can be sealed. Since the getter can further reduce the air pressure in the sealing structure by absorbing gas after being activated, the current microcavity structure to be sealed can be sealed under the current air pressure environment higher than the required air pressure environment. Specifically, the current microcavity structure to be sealed can be sealed based on the bonding pressure and bonding temperature corresponding to the current sealing ring structure to form the current sealing structure corresponding to the current microcavity structure to be sealed;

[0068] After sealing the current microcavity structure to be sealed to form the current sealing structure, a bonding temperature greater than or equal to the threshold can be set for the current sealing structure to activate the set getter, so that it further reduces the air pressure of the current sealing structure by absorbing gas to reach the required air pressure environment.

[0069] Optionally, when the required air pressure of some devices to be sealed is relatively low and it is difficult to directly establish the required air pressure environment, a getter can be set in the microcavity structure to be sealed corresponding to the device to be sealed. The getter can be set on the capping wafer side of the microcavity structure to be sealed, and the getter can be activated by a bonding temperature greater than or equal to the threshold after sealing to further reduce the air pressure.

[0070] Optionally, the getter can include titanium-based and vanadium-based getters.

[0071] Optionally, taking two-stage sealing as an example in the embodiments of the present invention, when N is 100 (the value is not limited to 100 when taking values, and it is sufficient to be greater than or equal to M), and M is 2, the N devices to be sealed include the first device to be sealed corresponding to the first sealing ring structure and the second device to be sealed corresponding to the second sealing ring structure. Assuming that the sealing priority of the first device to be sealed is higher than that of the second device to be sealed, the sealing method of the wafer-level multi-stage air pressure microcavity may include the following steps:

[0072] 1. Establish the first required air pressure environment corresponding to the first device to be sealed;

[0073] 2. Under the first required air pressure environment, use the first bonding pressure and the first bonding temperature corresponding to the sealing ring structure of the first device to be sealed to seal the microcavity structure to be sealed corresponding to the first device to be sealed (primary sealing);

[0074] 3. Establish the second required air pressure environment corresponding to the second device to be sealed;

[0075] 4. Under the second required air pressure environment, use the second bonding pressure and the second bonding temperature corresponding to the sealing ring structure of the second device to be sealed to seal the microcavity structure to be sealed corresponding to the second device to be sealed (secondary sealing).

[0076] Specifically, the N devices to be sealed include: the first device to be sealed with a higher sealing priority and the second device to be sealed with a lower sealing priority. Therefore, the height of the sealing ring structure set for the first device to be sealed is higher, and the height of the sealing ring structure set for the second device to be sealed is lower;

[0077] First, seal the first device to be sealed with a higher sealing priority. Specifically, establish the first required air pressure environment corresponding to the first device to be sealed, and under the first required air pressure environment, use the first bonding pressure and the first bonding temperature corresponding to the sealing ring structure of the first device to be sealed to seal the microcavity structure to be sealed corresponding to the first device to be sealed;

[0078] Since the height of the sealing ring structure set for the first device to be sealed is higher, after sealing the microcavity structure to be sealed corresponding to the first device to be sealed, the microcavity structure to be sealed corresponding to the second device to be sealed is not yet sealed. Then, seal the second device to be sealed with a lower sealing priority. Specifically, establish the second required air pressure environment corresponding to the second device to be sealed, and under the second required air pressure environment, use the second bonding pressure and the second bonding temperature corresponding to the sealing ring structure of the second device to be sealed to seal the microcavity structure to be sealed corresponding to the second device to be sealed. Since the sealing ring structure of the already sealed first device to be sealed has undergone plastic deformation, the second device to be sealed can be further sealed.

[0079] Optionally, the materials of the upper sealing ring structure and the lower sealing ring structure can be the same or different, as long as bonding can occur between the upper sealing ring structure and the lower sealing ring structure.

[0080] Optionally, the materials of the upper sealing ring structure and the lower sealing ring structure can both be copper or gold, or can be a multi-layer stacked metal, such as a copper-tin double-layer metal.

[0081] The following is an example to illustrate the sealing method of the wafer-level multi-stage air pressure microcavity provided by the embodiments of the present invention.

[0082] 1. Taking the sealing of a two - level air pressure environment as an example, the method includes the following steps:

[0083] Figure 2 It is a schematic diagram of the setting of the sealing ring structure in the sealing method of the wafer - level multi - stage air pressure micro - cavity provided by the present invention, as Figure 2 shown.

[0084] Step 1: Complete the preparation of the device wafer 101 and the capping wafer 201, and the preparation of the sealing ring structures 301 (lower sealing ring) and 302 (higher sealing ring) with different heights;

[0085] In the embodiment of the present invention, the device wafer 101 and the capping wafer 201 provided can both be silicon wafers. Among them, the device wafer contains the micro - nano devices (devices to be sealed) 102 and 103 to be sealed, and their required sealing air pressures are different. For example, in the embodiment of the present invention, the micro - nano device 102 is a MEMS switch, and the micro - nano device 103 is a MEMS accelerometer;

[0086] Optionally, the above - mentioned capping wafer 201 further includes the sealing micro - cavities (structures of micro - cavities to be sealed) 202 and 203 that provide packaging spaces for the micro - nano devices 102 and 103. The micro - processing process can first prepare a photoresist mask plate through photolithography, and then complete it through deep reactive ion etching of silicon;

[0087] In the embodiment of the present invention, the materials of the sealing ring structures 301 and 302 are copper and gold respectively, the shapes are both square, and the four vertices are designed as rounded corners. Among them, the width of the sealing ring structure 301 on the capping wafer 201 is 30μm, and the height is 1 - 4μm. The width of the sealing ring structure 302 is 50μm, and the height is 3 - 8μm. Their micro - processing processes can all be completed through the standard photolithography process combined with the electroplating process; the sealing ring structure 301 corresponding to the device wafer 101 is consistent with the structure on the capping wafer 201, and the thickness is 0.5 - 1μm. The corresponding sealing ring structure 302 is consistent with that on the capping wafer 201, and the thickness is 1 - 2μm. They can all be prepared through the standard photolithography process combined with the wet stripping process.

[0088] Figure 3 It is a schematic diagram of the first - level sealing in the sealing method of the wafer - level multi - stage air pressure micro - cavity provided by the present invention, as Figure 3 shown.

[0089] Step 2: Load the aligned device wafer 101 and capping wafer 201 into the wafer bonder 401. Then, evacuate the air pressure inside the wafer bonder cavity to the set first-stage air pressure P1, so that the air pressure environment is also established to the P1 level inside the sealed microcavity 203. In the embodiment of the present invention, P1 can be set to 10 kPa. Then, load the bonding pressure F1 and bonding temperature T1, so that the higher sealing ring structure 302 first completes contact, thermocompression bonding and sealing, and completes the encapsulation of the air pressure environment required for the device 103;

[0090] The bonding pressure F1 provided by the embodiment of the present invention can be finally determined according to the density of the sealing ring structure on the wafer, and its application effect needs to ensure that the sealing ring structure 302 completes reliable sealing, and at the same time undergoes a small-scale deformation to ensure that the sealing ring structure 301 has not yet come into contact;

[0091] The bonding temperature provided by the embodiment of the present invention is set to 250 °C.

[0092] Figure 4 It is a schematic diagram of the second-stage sealing in the sealing method of the wafer-level multi-stage air pressure microcavity provided by the present invention, as Figure 4 shown.

[0093] Step 3: On the basis of the above Steps 1 and 2, evacuate the air pressure inside the wafer bonder cavity to the set second-stage air pressure P2, so that the air pressure environment is also established to the P2 level inside the sealed microcavity 202. In this embodiment, P2 can be set to 0.01 kPa. Then, load the bonding pressure F2 and bonding temperature T2, so that the higher sealing ring structure 302 undergoes plastic deformation, so that the lower sealing ring structure 301 completes contact, thermocompression bonding and sealing, and completes the encapsulation of the air pressure environment required for the device 102;

[0094] The bonding pressure F2 provided by the embodiment of the present invention can be finally determined according to the density of the sealing ring structure on the wafer, and the bonding temperature is set to 250 °C.

[0095] Optionally, after the above Steps 1 to 3 are completed, a polymer material can be filled between the already bonded capping wafer and device wafer by means of capillary force, so as to enhance the bonding strength and reliability of the sealing ring.

[0096] Second, taking the sealing of a three-stage air pressure environment as an example, the method includes the following steps:

[0097] Steps 1 to 3 can refer to Steps 1 to 3 in the sealing of the two-stage air pressure environment;

[0098] Figure 5 It is a schematic diagram of the three-stage sealing in the sealing method of the wafer-level multi-stage air pressure microcavity provided by the present invention, as Figure 5As shown, the difference is that on the basis of the above solution, the embodiment of the present invention adds a sealing microcavity 204 required for encapsulating the third micro-nano device 104, and a getter 205 for low-pressure fine tuning. The required sealing ring structure is the same as that of Figure 2 the sealing ring structure 301 shown;

[0099] The micro-nano device 104 provided by the embodiment of the present invention can be a MEMS gyroscope, and the getter is a titanium-based and vanadium-based getter, which can be deposited by combining standard lithography process and sputtering process;

[0100] Step 4: On the basis of the above steps 1 to 3, further apply a bonding pressure F3 and a bonding temperature T3. The air pressure environment can be modulated to a conventional atmospheric pressure environment. Under the action of T3, the getter is activated, so that the air pressure in the sealing microcavity is further reduced to the P3 level on the basis of P2, that is, 10 -3 ~10 -5 kPa level, so as to meet the packaging requirements of the micro-nano device 104;

[0101] In the embodiment of the present invention, the bonding pressure F3 is only used to facilitate the application of the bonding temperature T3. Therefore, the bonding pressure F3 can be only about 1 kN, and the bonding temperature T3 and its holding time can be adjusted and determined according to the specific type of getter and the target air pressure.

[0102] The embodiment of the present invention can, on the basis of two-stage air pressure sealing, without changing the sealing ring structure and type, only by using a getter, partially arranged in a certain type of sealing ring structure on the capping wafer, and on the basis of the steps of the above sealing process, load the third-stage bonding temperature and bonding pressure, so that some of the sealed microcavities containing the getter reach a lower air pressure level, thereby realizing three-stage and above multi-stage air pressure sealing.

[0103] III. In the sealing method of the wafer-level multi-stage air pressure microcavity, the steps of wafer bonding and sealing are as follows:

[0104] S1: Prepare different sealing ring structures on the capping wafer and the device wafer respectively. The preparation method can be realized by a conventional lithography process in cooperation with a material deposition process, including standard microfabrication process steps such as evaporation, plasma sputtering, electroplating, etc. The device wafer contains a micro-nano device to be hermetically packaged and is placed in the structure of the microcavity to be sealed;

[0105] Optionally, the sealing microcavity can be completed on the capping wafer by processes such as plasma etching, so that the device wafer preparation process only needs to change the steps of preparing the sealing ring structure, thereby minimizing the impact on the standard device wafer preparation process.

[0106] S2: Align the capping wafer and the device wafer and load them into the wafer bonder. Establish the first-level air pressure environment, and load the first-level bonding pressure and bonding temperature, so that the higher sealing ring structure first contacts, bonds, and seals, thus completing the sealing of the first-level air pressure.

[0107] S3: Establish the second-level air pressure environment, and load the second-level bonding pressure and bonding temperature, so that the first-level sealing ring structure undergoes plastic deformation, so that the lower sealing ring structure contacts, bonds, and seals, completing the sealing of the second-level air pressure.

[0108] Optionally, for the above sealing method of the wafer-level multi-stage air pressure microcavity, sealing ring structures with two or more different heights and materials can be prepared to further realize the sealing of more than two-stage multi-stage air pressure, that is, steps such as S4 are added after S3.

[0109] The sealing method of the wafer-level multi-stage air pressure microcavity provided by the embodiment of the present invention has at least the following advantages compared with the prior art:

[0110] (1) By means of the sealing ring structures with different heights arranged on the wafer, through the wafer bonding process, control the sealing ring structures to sequentially complete contact, bonding, and sealing under different bonding temperature, pressure and other parameters, so as to realize the sequential sealing of microcavities with different air pressure environments, and realize large-span multi-stage air pressure sealing at the wafer level, overcoming the limitation that the previous methods can only realize single-type air pressure sealing, or can only be adjusted on the basis of low air pressure by using getters and cannot realize large-span air pressure packaging;

[0111] (2) The structure is simple, and standard microfabrication process flows and equipment are adopted, which is convenient for large-scale application, and the sealed microcavity can be independently prepared on the capping wafer, minimizing the impact on the existing preparation process of the device wafer;

[0112] (3) It has the outstanding advantage of realizing large-span air pressure sealing at the wafer level with a single-step bonding, and the process is flexible, and it can accurately and efficiently realize wafer-level integration and packaging for micro-nano devices with different packaging air pressure requirements, providing a new solution for future realization of multi-device wafer-level on-chip integration.

[0113] The sealing method of the wafer-level multi-stage air pressure microcavity proposed by the present invention can provide a key packaging technology solution for realizing wafer-level multi-functional, miniaturized, and low-cost on-chip integration of different MEMS / Nano-Electromechanical Systems (NEMS) devices, and is expected to promote the industrial upgrading of the packaging field in China.

[0114] The sealing device of the wafer-level multi-stage air-pressure micro-cavity provided by the present invention will be described below. The sealing device of the wafer-level multi-stage air-pressure micro-cavity described below can be referred to in correspondence with the sealing method of the wafer-level multi-stage air-pressure micro-cavity described above.

[0115] Figure 6 It is a schematic structural diagram of the sealing device of the wafer-level multi-stage air-pressure micro-cavity provided by the present invention. As Figure 6 shown, the sealing device 600 of the wafer-level multi-stage air-pressure micro-cavity includes:

[0116] a wafer 601, and N devices to be sealed 602 and M types of sealing ring structures 603 arranged on the wafer 601. The M types of sealing ring structures 603 are used to form M types of micro-cavity structures to be sealed 604 corresponding to the N devices to be sealed 602. The height of each sealing ring structure 603 is positively correlated with the sealing priority levels corresponding to the M types of micro-cavity structures to be sealed 604. The upper sealing ring structure and the lower sealing ring structure of the M types of sealing ring structures 603 are bonded at the bonding pressure and bonding temperature corresponding to the M types of sealing ring structures 603, so as to form a multi-stage air-pressure micro-cavity including M types of sealing structures. The air-pressure environment of the multi-stage air-pressure micro-cavity including M types of sealing structures is the required air-pressure environment corresponding to the device to be sealed 602 in the M types of micro-cavity structures to be sealed 604 set in advance. N is an integer greater than 1, and M is an integer greater than 1 and less than or equal to N.

[0117] In the sealing device of the wafer-level multi-stage air-pressure micro-cavity provided by the embodiment of the present invention, the different heights of the sealing ring structures corresponding to the N devices to be sealed can be determined according to the order of the sealing priority levels corresponding to the N devices to be sealed. Specifically, the height of each sealing ring structure is positively correlated with the sealing priority levels corresponding to the N devices to be sealed, that is, the height of the sealing ring structure increases as the sealing priority level of the device to be sealed increases, and vice versa. Then, the M types of sealing ring structures with different heights are correspondingly arranged on the wafer to form M types of micro-cavity structures to be sealed corresponding to the N devices to be sealed. In the stage of multi-stage sealing, since the height of the sealing ring structure corresponding to the device to be sealed that is sealed first is higher, the corresponding upper sealing ring structure and lower sealing ring structure will contact first, and can be bonded at the bonding pressure and bonding temperature to seal the micro-cavity structure to be sealed corresponding to the device to be sealed, and then seal the device to be sealed with the next sealing priority level, and so on. The present invention can realize the wafer-level multi-stage air-pressure micro-cavity sealing of the devices to be packaged with different required air-pressure environments.

[0118] Optionally, the wafer includes a device wafer and a capping wafer. The N devices to be sealed are disposed on the device wafer. The upper sealing ring structure is disposed on the capping wafer, and the lower sealing ring structure is disposed on the device wafer. The upper sealing ring structure and the lower sealing ring structure are correspondingly arranged.

[0119] Optionally, the M types of microcavity structures to be sealed are sealed in sequence according to the descending order of the sealing priorities corresponding to the M types of microcavity structures to be sealed.

[0120] Among them, for the current microcavity structure to be sealed that is currently being sealed among the M types of microcavity structures to be sealed, the sealing operation includes: based on the bonding pressure and bonding temperature corresponding to the current sealing ring structure of the current microcavity structure to be sealed, sealing the current microcavity structure to be sealed.

[0121] Optionally, the materials of the upper sealing ring structure and the lower sealing ring structure are the same or different.

[0122] Optionally, the height of each of the sealing ring structures is set in the range of 100 nm to 100 μm.

[0123] On the other hand, the present invention further provides a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the sealing method of the wafer-level multi-stage air pressure microcavity provided by the above-mentioned various methods. The method includes:

[0124] By setting M types of sealing ring structures, M types of microcavity structures corresponding to N devices to be sealed are formed on a pre-set wafer, where N is an integer greater than 1, and M is an integer greater than 1 and less than or equal to N; among them, the height of each of the sealing ring structures is positively correlated with the sealing priorities corresponding to the M types of microcavity structures to be sealed.

[0125] According to the descending order of the sealing priorities corresponding to the M types of microcavity structures to be sealed, the M types of microcavity structures to be sealed are sequentially sealed to form a multi-stage air pressure microcavity including M types of sealing structures. The air pressure environment of the multi-stage air pressure microcavity including M types of sealing structures is the required air pressure environment corresponding to the devices to be sealed among the M types of microcavity structures to be sealed that are pre-set.

[0126] Among them, for the current microcavity structure to be sealed that is currently being sealed among the M types of microcavity structures to be sealed, the sealing operation includes: based on the bonding pressure and bonding temperature corresponding to the current sealing ring structure of the current microcavity structure to be sealed, sealing the current microcavity structure to be sealed, and the upper sealing ring structure and the lower sealing ring structure of the current sealing ring structure are bonded under the bonding pressure and bonding temperature.

[0127] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. A person of ordinary skill in the art can understand and implement it without creative effort.

[0128] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the essence of the above technical solution, or the part that contributes to the prior art, can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sealing method for a wafer-level multi-stage pneumatic microcavity, characterized in that, Comprising: By setting M kinds of seal ring structures, M kinds of to-be-sealed microcavity structures corresponding to N to-be-sealed devices are formed on a pre-set wafer, where N is an integer greater than 1, and M is an integer greater than 1 and less than or equal to N; wherein, there is a positive correlation between the height of each of the seal ring structures and the sealing priority corresponding to the M kinds of to-be-sealed microcavity structures; According to the order of the sealing priorities corresponding to the M kinds of to-be-sealed microcavity structures from high to low, sealing operations are sequentially performed on the M kinds of to-be-sealed microcavity structures to form a multi-level air pressure microcavity including M kinds of sealing structures, and the air pressure environment of the multi-level air pressure microcavity including M kinds of sealing structures is the required air pressure environment corresponding to the to-be-sealed devices in the pre-set M kinds of to-be-sealed microcavity structures; Wherein, for the currently to-be-sealed microcavity structure among the M kinds of to-be-sealed microcavity structures that is currently undergoing the sealing operation, the sealing operation includes: based on the bonding pressure and bonding temperature corresponding to the current seal ring structure of the currently to-be-sealed microcavity structure, sealing the currently to-be-sealed microcavity structure, and bonding occurs between the upper seal ring structure and the lower seal ring structure of the current seal ring structure under the bonding pressure and bonding temperature.

2. The sealing method of the wafer-level multi-stage pneumatic microcavity according to claim 1, wherein For the currently to-be-sealed microcavity structure, the sealing operation specifically includes: Establishing the required air pressure environment corresponding to the to-be-sealed device in the currently to-be-sealed microcavity structure; Under the required air pressure environment corresponding to the to-be-sealed device in the currently to-be-sealed microcavity structure, sealing the currently to-be-sealed microcavity structure based on the bonding pressure and bonding temperature corresponding to the current seal ring structure.

3. The sealing method of the wafer-level multi-stage pneumatic microcavity according to claim 1, wherein For the currently to-be-sealed microcavity structure, the sealing operation specifically includes: Setting a getter in the currently to-be-sealed microcavity structure; wherein, the getter is used to absorb gas when the temperature is greater than or equal to a pre-set threshold; Under a pre-set current air pressure environment, sealing the currently to-be-sealed microcavity structure based on the bonding pressure and bonding temperature corresponding to the current seal ring structure to form the current sealing structure corresponding to the currently to-be-sealed microcavity structure; wherein, the air pressure of the current air pressure environment is higher than the required air pressure environment corresponding to the to-be-sealed device in the currently to-be-sealed microcavity structure; Setting a bonding temperature greater than or equal to the threshold for the current sealing structure to form a sealing structure corresponding to the required air pressure environment of the to-be-sealed device in the currently to-be-sealed microcavity structure.

4. The sealing method of the wafer-level multi-stage pneumatic microcavity according to any one of claims 1 to 3, characterized in that, The wafer includes a device wafer and a capping wafer, the N to-be-sealed devices are arranged on the device wafer, the upper seal ring structure is arranged on the capping wafer, the lower seal ring structure is arranged on the device wafer, and the upper seal ring structure and the lower seal ring structure are arranged corresponding to each other.

5. The sealing method of the wafer-level multi-stage pneumatic microcavity according to any one of claims 1 to 3, characterized in that, The materials of the upper seal ring structure and the lower seal ring structure are the same or different.

6. The sealing method of the wafer-level multi-stage pneumatic microcavity according to any one of claims 1 to 3, characterized in that, The setting range of the height of each of the seal ring structures is 100nm to 100um.

7. A sealing device for a wafer-level multi-stage pneumatic microcavity, characterized in that, Comprising: A wafer, N devices to be sealed, and M types of sealing ring structures disposed on the wafer. The M types of sealing ring structures are used to form M types of micro cavities to be sealed corresponding to the N devices to be sealed. There is a positive correlation between the height of each sealing ring structure and the sealing priority corresponding to the M types of micro cavities to be sealed. The upper sealing ring structure and the lower sealing ring structure among the M types of sealing ring structures are bonded at the bonding pressure and bonding temperature corresponding to the M types of sealing ring structures, so as to form a multi-level air pressure micro cavity including M types of sealing structures. The air pressure environment of the multi-level air pressure micro cavity including M types of sealing structures is the required air pressure environment corresponding to the device to be sealed in the M types of micro cavities to be sealed preset in advance. N is an integer greater than 1, and M is an integer greater than 1 and less than or equal to N.

8. The sealing device of the wafer-level multi-stage pneumatic microcavity according to claim 7, wherein The wafer includes a device wafer and a capping wafer. The N devices to be sealed are disposed on the device wafer. The upper sealing ring structure is disposed on the capping wafer, and the lower sealing ring structure is disposed on the device wafer. The upper sealing ring structure and the lower sealing ring structure are correspondingly arranged.

9. The sealing device for a wafer-level multi-stage pneumatic microcavity according to claim 7 or 8, characterized in that, The M types of micro cavities to be sealed are sealed in sequence according to the descending order of the sealing priorities corresponding to the M types of micro cavities to be sealed. Among them, for the current micro cavity to be sealed that is currently being sealed among the M types of micro cavities to be sealed, the sealing operation includes: based on the bonding pressure and bonding temperature corresponding to the current sealing ring structure of the current micro cavity to be sealed, sealing the current micro cavity to be sealed.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the sealing method of the wafer-level multi-level air pressure micro cavity according to any one of claims 1 to 6.

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