Patent Application
20250145452
The present disclosure relates generally to micro-electro-mechanical system (MEMS) packages, and more particularly to a MEMS package including MEMS devices with different pressures in respective cavities, and fabrication methods thereof.
Micro-electro-mechanical system devices are (MEMS) microscopic devices that integrate mechanical and electrical components to sense physical quantities and/or to interact with the surrounding environment. MEMS devices, such as accelerometers, gyroscopes, pressure sensors and microphones, have found widespread use in many modern electronic products. For example, inertial measurement units (IMU) composed of accelerometers and/or gyroscopes are commonly used in tablet computers, automobiles, or smartphones. For some applications, various MEMS devices need to be integrated into one MEMS package. However, for MEMS devices requiring different pressures, these MEMS devices need to be fabricated separately at different ambient pressure and then co-packaged. Therefore, the whole fabricating process of the conventional MEMS packages is complicated and the conventional MEMS packages have large footprint.
In view of this, the present disclosure provides micro-electro-mechanical system (MEMS) packages and fabrication methods thereof to overcome the drawbacks of the conventional MEMS packages. The MEMS package of the present disclosure includes a getter disposed on an interconnect structure formed on a wafer and directly under a MEMS device requiring a relatively high vacuum, thereby reducing the pressure in a cavity directly above the MEMS device. The MEMS package includes MEMS devices with different pressures in respective cavities, and the MEMS devices with different pressures are fabricated and packaged simultaneously on the same wafer. Therefore, the whole fabricating process of the MEMS package is simplified and the footprint of the MEMS package is small compared with those of the conventional MEMS packages.
According to one embodiment of the present disclosure, a MEMS package is provided and includes a wafer, an interconnect structure, a passivation layer, a first device substrate, a second device substrate, a first cap substrate, a second cap substrate and a getter. The interconnect structure is disposed on the wafer, and the passivation layer is disposed on the interconnect structure. The first device substrate including a first MEMS device is disposed on the wafer and bonded to the interconnect structure. The second device substrate including a second MEMS device is laterally spaced apart from the first device substrate, disposed on the wafer and bonded to the interconnect structure. The first cap substrate with a first cavity is bonded to the first device substrate. The second cap substrate with a second cavity is bonded to the second device substrate. The getter is disposed on the interconnect structure, in an opening of the passivation layer and directly under the second MEMS device. In addition, the first cavity has a first pressure, and the second cavity has a second pressure lower than the first pressure.
According to one embodiment of the present disclosure, a method of fabricating a MEMS package is provided and includes the following steps. A cap wafer with a first cavity and a second cavity formed therein is provided. A device wafer is provided and bonded to the cap wafer. The device wafer is patterned to form a first MEMS device and a second MEMS device laterally spaced apart from each other, where the first cavity corresponds to the first MEMS device, and the second cavity corresponds to the second MEMS device. A wafer with an interconnect structure formed thereon is provided. A getter is formed on the interconnect structure. The device wafer is bonded to the interconnect structure on the wafer at a first pressure, where both the first cavity and the second cavity have the first pressure, and the getter is located directly under the second MEMS device. In addition, the getter is activated to reduce the first pressure in the second cavity to a second pressure, where the first cavity has the first pressure, and the second cavity has the second pressure lower than the first pressure.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features may not be drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
The following disclosure provides many different embodiments, or examples, for implementing different features of the disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Further, spatially relative terms, such as “beneath”, “below”, “lower”, “under”, “on”, “over”, “above”, “upper”, “bottom”, “top” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” and/or “under” other elements or features would then be oriented “above” and/or “over” the other elements or features. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
It is understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer and/or section from another region, layer and/or section. Terms such as “first”, “second”, and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer and/or section discussed below could be termed a second element, component, region, layer and/or section without departing from the teachings of the embodiments.
As disclosed herein, the term “about” or “substantial” generally means within 20%, 10%, 5%, 3%, 2%, 1%, or 0.5% of a given value or range. Unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages disclosed herein should be understood as modified in all instances by the term “about” or “substantial”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the present disclosure and attached claims are approximations that may vary as desired.
Furthermore, as disclosed herein, the terms “coupled to” and “electrically connected to” include any directly and indirectly electrical connecting means. Therefore, if it is described in this document that a first component is coupled or electrically connected to a second component, it means that the first component may be directly connected to the second component, or may be indirectly connected to the second component through other components or other connecting means.
Although the disclosure is described with respect to specific embodiments, the principles of the disclosure, as defined by the claims appended herein, can obviously be applied beyond the specifically described embodiments of the disclosure described herein. Moreover, in the description of the present disclosure, certain details have been left out in order to not obscure the inventive aspects of the disclosure. The details left out are within the knowledge of a person having ordinary skill in the art.
The present disclosure is directed to MEMS packages and fabrication methods thereof. The MEMS package includes different MEMS devices with different pressures in respective cavities, and these MEMS devices are fabricated and packaged simultaneously on the same wafer. In the MEMS package, a getter is disposed on an interconnect structure of a wafer and directly under a MEMS device requiring a relatively high vacuum, thereby reducing the pressure in a cavity directly above the MEMS device. In some embodiments, the MEMS package includes an inertial measurement unit (IMU) including of an accelerometer with a low vacuum or atmospheric pressure, and a gyroscope with a high vacuum. The whole fabricating process of the MEMS packages of the present disclosure is simplified and the footprint of the MEMS packages is smaller compared with those of the conventional MEMS packages.
In the MEMS package 100, the first MEMS device 122 and the second MEMS device 124 require different vacuum levels. The MEMS structures of the first MEMS device 122 and the second MEMS device 124 are different from each other. Each of the first MEMS device 122 and the second MEMS device 124 may include features such as standoff bumps, trenches, proof masses, etc., and the layout of these features in the first MEMS device 122 is different from that in the second MEMS device 124. In order to make the figure simple and easy to understand, the MEMS structures of the first MEMS device 122 and the second MEMS device 124 are simplified in
Moreover, a first bond seal ring 126A is disposed on the bottom surface of the first device substrate 120A, and a second bond seal ring 126B is disposed on the bottom surface the second device substrate 120B. The first bond seal ring 126A and the second bond seal ring 126B are bonded to the interconnect structure 132 through a bonding material 128, thereby bonding the first device substrate 120A and the second device substrate 120B with the wafer 130. In some embodiments, the first bond seal ring 126A and the first device substrate 120A may be an integral structure and have the same composition such as silicon. The second bond seal ring 126B and the second device substrate 120B may also be an integral structure and have the same composition such as silicon. The composition of the bonding material 128 is for example germanium (Ge) for eutectic bonding with the top electrode layer 131 of the interconnect structure 132. The first bond seal ring 126A, the second bond seal ring 126B and the bonding material 128 are disposed in the bond areas of the interconnect structure 132.
In addition, the MEMS package 100 includes a first cap substrate 110A with a first cavity 112 located directly above the first MEMS device 122, and a second cap substrate 110B with a second cavity 114 located directly above the second MEMS device 124. The first cap substrate 110A and the second cap substrate 110B may have the same composition such as silicon. The first cap substrate 110A is bonded to the first device substrate 120A through a bonding layer 111. The second cap substrate 110B is bonded to the second device substrate 120B through another bonding layer 111. The bonding layer 111 is disposed between the first device substrate 120A and the first cap substrate 110A. The bonding layer 111 is also disposed between the second device substrate 120B and the second cap substrate 110B. In some embodiments, the bonding layer 111 is further extended into the first cavity 112 and the second cavity 114 to be conformally disposed on the sidewalls and the bottom surfaces of the first cavity 112 and the second cavity 114. The composition of the bonding layer 111 may be silicon oxide. In some embodiments, a conductive layer 117 may be disposed on surfaces of the first cap substrate 110A and the second cap substrate 110B. The conductive layer 117 may be a patterned conductive layer electrically coupled to the first MEMS device 122, the second MEMS device 124 and the interconnect structure 132. The composition of the conductive layer 117 may be aluminum (Al).
In some embodiments, the MEMS package 100 includes a getter 140B disposed on the interconnect structure 132 and directly under the second MEMS device 124. The getter 140B is activated to absorb gases such as H2, N2, CO, CO2 or H2O in the second cavity 114, thereby reducing the pressure in the second cavity 114. As a result, the first cavity 112 has a first pressure P1, and the second cavity 114 has a second pressure P2 lower than the first pressure P1. For example, the first pressure P1 is a low vacuum or atmospheric pressure required for the first MEMS device 122 such as an accelerometer, and the second pressure P2 is a high vacuum required for the second MEMS device 124 such as a gyroscope. The getter 140B is activated by a thermal process while the first device substrate 120A and the second device substrate 120B are bonded to the interconnect structure 132. The getter 140B may be activated at about 150° C. to about 450° C. In some embodiments, the composition of the getter 140B may be Ti, a Ti based alloy, a Zr based alloy, a Zr-V based alloy, a Zr-Co based alloy or other suitable material for absorbing gases in a cavity of the MEMS package. The Ti based alloy is for example Ti-Zr, Ti-Mo or Ti-Zr-V. The Zr based alloy is for example Zr-Al, Zr-C or Zr-Fe. The Zr-V based alloy is for example Zr-V-Fe or Zr-V-Mn. The Zr-Co based alloy is for example Zr-Co, Zr-Co-Ce or Zr-Co-La. The getter 140B may be a thin film with a thickness of about 1 μm to about 10 μm, or the getter 140B may be a thick film with a thickness of about 10 μm to about 1000 μm. Moreover, the getter 140B may have a pattern corresponding to the layout of the trenches 125 of the second MEMS device 124.
In one embodiment, the getter 140B is disposed in an opening of the passivation layer 134 and in contact with the top surface of the top electrode layer 131. The getter 140B is electrically connected to the interconnect structure 132 through the top electrode layer 131. In another embodiment, the getter 140B is disposed on the same level with the top electrode layer 131 and in contact with the top surface of the top dielectric layer 133. The getter 140B is electrically connected to the interconnect structure 132 through the vias in the top dielectric layer 133 or some portions of the top electrode layer 131 connected to the getter 140B. In some embodiments, the getter 140B is configured as a conductive stopper for the second MEMS device 124. The location of the getter 140B may correspond to the proof masses of the second MEMS device 124. Moreover, the vertical projection area of the getter 140B is overlapped with the vertical projection area of the second cavity 114. In some embodiments, the vertical projection area of the getter 140B is greater than or the same as the vertical projection area of the second cavity 114, thereby efficiently absorbing the gases in the second cavity 114 to provide a high vacuum for the second MEMS device 124. In other embodiments, the vertical projection area of the getter 140B may be smaller than the vertical projection area of the second cavity 114 while the second MEMS device 124 requires a medium vacuum.
Moreover, a third bond seal ring 126C is disposed on the bottom surface of the third device substrate 120C. The third bond seal ring 126C is also bonded to the interconnect structure 132 through the bonding material 128. The third bond seal ring 126C and the third device substrate 120C may be an integral structure and have the same composition such as silicon. In addition, the MEMS package 100 includes a third cap substrate 110C with a third cavity 116 directly above the third MEMS device 126. The composition of the third cap substrate 110C may be silicon. The third cap substrate 110C is bonded to the third device substrate 120C through the bonding layer 111. The bonding layer 111 is disposed between the third device substrate 120C and the third cap substrate 110C. Moreover, the bonding layer 111 may be further extended into the third cavity 116 to be conformally disposed on the sidewalls and the bottom surface of the third cavity 116. Furthermore, the conductive layer 117 may be also disposed on the surface of the third cap substrate 110C. The conductive layer 117 may be a patterned conductive layer electrically coupled to the third MEMS device 126.
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In some other embodiments, the MEMS package 100 may include the first MEMS region 100A, the second MEMS region 100B and the third
MEMS region 100C separated from each other by the scribe lines SL. The first cavity 112 directly above the first MEMS device 122 has the first pressure P1. The second cavity 114 directly above the second MEMS device 124 has the second pressure P2. The third cavity 116 directly above the third MEMS device 126 has the third pressure P3. The third pressure P3 is different from the second pressure P2 and is lower than the first pressure P1. According to the embodiments of the present disclosure, the MEMS package includes different MEMS devices with different pressures in respective cavities and packaged simultaneously on the same wafer through the getters.
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In the step S301, the cap wafer 110 has a thickness T1, and the bonding layer 111 is conformally formed on the cap wafer 110 and in the first cavity 112 and the second cavity 114 to wrap around the cap wafer 110. Then, still referring to
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In some embodiments, the MEMS package 100 of
According to the embodiments of the present disclosure, the MEMS package includes different MEMS devices with different pressures in respective cavities, and these MEMS devices are fabricated and packaged simultaneously on the same wafer. Therefore, the whole fabricating process of the MEMS packages of the present disclosure is simplified and the footprint of the MEMS packages is smaller compared with those of the conventional MEMS packages. The MEMS packages of the present disclosure do not require individual wire bonding, thereby reducing the parasitic effect.
In addition, the MEMS package includes the getter disposed on the interconnect structure formed on the CMOS wafer and directly under the MEMS device requiring high vacuum. The getter is activated to reduce the pressure in the cavity directly above the MEMS device requiring high vacuum. The process of forming the getter is compatible with the process of the CMOS wafer fabrication. The activation of the getter is compatible with the bonding process of the MEMS package fabrication. Therefore, the cost and the time of fabricating the MEMS packages are reduced. Moreover, the MEMS packages of the present disclosure are suitable for 1-axis, 2-axis, 3-axis and 6-axis inertial measurement unit (IMU) and MEMS devices.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
