Patent Application
20250230038
The present disclosure relates generally to micro-electro-mechanical system (MEMS) packages, and more particularly to a MEMS package including MEMS devices with different device layer thicknesses and different electrode gaps, and fabrication methods thereof.
Micro-electro-mechanical system (MEMS) devices are 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. These MEMS devices may require different device layer thicknesses to meet the requirements in sensitivity and performance. However, in the conventional MEMS packages, for MEMS devices requiring different device layer thicknesses, these MEMS devices are fabricated separately by using different device wafers and then co-packaged. Therefore, the whole fabricating process of the conventional MEMS packages is complicated, and the cost thereof is also increased.
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 includes different MEMS devices with different device layer thicknesses and different electrode gaps to meet the sensitivities and the performances of various MEMS devices. Moreover, these MEMS devices are fabricated simultaneously by using the same device wafer and packaged simultaneously on the same wafer having an interconnect layer and a raised electrode thereon. Therefore, the whole fabricating process of the MEMS package is simplified and the cost thereof is reduced 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, a first device layer, a second device layer, a raised electrode, a first cap substrate and a second cap substrate. The wafer has an interconnect layer disposed thereon. The first device layer includes a first MEMS device having a first thickness. The first device layer is disposed on the wafer and bonded to the interconnect layer. The second device layer includes a second MEMS device having a second thickness thinner than the first thickness. The second device layer is laterally spaced apart from the first device layer, disposed on the wafer and bonded to the interconnect layer. The raised electrode is disposed above the interconnect layer and directly below the second MEMS device. The first cap substrate with a first cavity is bonded to the first device layer, where the first MEMS device corresponds to the first cavity. The second cap substrate with a second cavity is laterally spaced apart from the first cap substrate and bonded to the second device layer, where the second MEMS device corresponds to the second cavity.
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 is provided, and a first cavity and a second cavity are formed in the cap wafer. A device wafer is provided and boned to the cap wafer, where the first cavity and the second cavity are covered by the device wafer. The device wafer is thinned and etched to form a recessed portion corresponding to the second cavity after the device wafer is bonded with the cap wafer and thinned. The device wafer is patterned to form a first MEMS device and a second MEMS device, where the first MEMS device has a first thickness and corresponds to the first cavity, the second MEMS device has a second thickness and corresponds to the second cavity, and the second thickness is thinner than the first thickness. A wafer with an interconnect layer formed thereon is provided. A raised electrode is formed above the interconnect layer. The device wafer is bonded to the interconnect layer on the wafer, where the raised electrode corresponds to the second MEMS device. In addition, a portion of the cap wafer and a portion of the device wafer at a scribe line are removed to form a first cap substrate with the first cavity, a second cap substrate with the second cavity, a first device layer with the first MEMS device, and a second device layer with the second MEMS device.
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 device layer thicknesses and different electrode gaps. In the MEMS package, a MEMS device requiring a relatively high vacuum has a device layer thickness that is thinner than the device layer thickness of another MEMS device requiring a low vacuum or atmospheric pressure. These MEMS devices are fabricated simultaneously by using the same device wafer and packaged simultaneously on the same wafer having an interconnect layer formed thereon. In addition, a raised electrode is disposed above the interconnect layer and corresponds to the MEMS device with a thinner device layer thickness. An electrode gap for the MEMS device with the thinner device layer thickness is smaller than the electrode gap for the MEMS device with a thicker device layer thickness. The whole fabricating process of the MEMS packages of the present disclosure is simplified. The cost and the time of fabricating the MEMS packages are also reduced. Moreover, the sensitivities and the performances of various MEMS devices are satisfied in the MEMS packages of the present disclosure.
In addition, the MEMS package 100 includes a raised electrode 145 disposed above the interconnect layer 132 and directly below the second MEMS device 122. A dielectric layer 141 is disposed between the raised electrode 145 and the interconnect layer 132. A via 143 is disposed to pass through the dielectric layer 141 and a passivation layer 138 and a top dielectric layer 136 of the interconnect layer 132 for electrically connecting the raised electrode 145 to a top metal layer 133 of the interconnect layer 132. In the first MEMS region 100A, a portion 133P of the top metal layer 133 is exposed through an opening of the passivation layer 138 and the top dielectric layer 136 and located directly below the first MEMS device 121.
There is a first gap G1 between the portion 133P of the top metal layer 133 and the bottom surface of the first MEMS device 121 in the Z-axis direction. There is a second gap G2 between the raised electrode 145 and the bottom surface of the second MEMS device 122 in the Z-axis direction. In some embodiments, an electrode (not shown) is formed in the first MEMS device 121, and another electrode (not shown) is formed in the second MEMS device 122. The electrode in the first MEMS device 121 may be electrically coupled to the interconnect layer 132 through the first device layer 120A and stand-off bumps formed at the bottom of the first device layer 120A. The electrode in the second MEMS device 122 may be electrically coupled to the interconnect layer 132 through the second device layer 120B and stand-off bumps formed at the bottom of the second device layer 120B. The entire first device layer 120A is highly conductive and thus the first device layer 120A may be regarded as an upper electrode that interacts with the portion 133P of the top metal layer 133. The entire second device layer 120B is highly conductive and thus the second device layer 120B may be regarded as another upper electrode that interacts with the raised electrode 145.
The portion 133P of the top metal layer 133 is a lower electrode interacting with the upper electrode in the first MEMS device 121, so that the first gap G1 may be referred to as an electrode gap for the first MEMS device 121. The raised electrode 145 is a lower electrode interacting with the upper electrode in the second MEMS device 122, so that the second gap G2 may be referred to as an electrode gap for the second MEMS device 122. In the MEMS package 100, the second gap G2 is smaller than the first gap G1, thereby improving the sensitivity of the second MEMS device 122 having the thinner device layer thickness. The first MEMS device 121 and the second MEMS device 122 have different electrode gaps to meet different requirements in the sensitivity and the performance of these MEMS devices. In some embodiments, the raised electrode 145 may be located directly below a proof mass of the second MEMS device 122 to further improve the sensitivity and the performance of the second MEMS device 122.
Moreover, the second gap G2 is variable and controlled by the thickness of the dielectric layer 141. The second gap G2 is smaller while the dielectric layer 141 is thicker. The thickness of the dielectric layer 141 is dependent on the difference between the first thickness T1 of the first MEMS device 121 and the second thickness T2 of the second MEMS device 122. In some embodiments, the difference between the first thickness T1 and the second thickness T2 is greater than the thickness of the dielectric layer 141. In some embodiments, the raised electrode 145 and the dielectric layer 141 may have the same pattern in a top view, for example, in the XY plane.
In the MEMS package 100, the first MEMS device 121 and the second MEMS device 122 require different vacuum levels. In some embodiments, the first MEMS device 121 may be an accelerometer requiring low vacuum or atmospheric pressure, and the second MEMS device 122 may be a gyroscope requiring high vacuum, but not limited thereto. The MEMS structures of the first MEMS device 121 and the second MEMS device 122 are different from each other. Each of the first MEMS device 121 and the second MEMS device 122 may include features such as standoff bumps, trenches, proof masses, etc., and the layout of these features in the first MEMS device 121 is different from that in the second MEMS device 122. In order to make the figure simple and easy to understand, the MEMS structures of the first MEMS device 121 and the second MEMS device 122 are simplified in
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In addition, the second device layer 120B has a recessed portion 124 facing towards the interconnect layer 132, and the raised electrode 145 is located in the recessed portion 124. In one embodiment, the sidewalls of the recessed portion 124 are vertically aligned with the inner sidewalls of the second bond seal ring 125B. In other embodiments, the sidewalls of the recessed portion 124 may retracted inward towards the second cavity 112 and not vertically aligned with the inner sidewalls of the second bond seal ring 125B.
Furthermore, in other embodiments, the MEMS package 100 may further include other MEMS devices requiring vacuum levels different from those of the first MEMS device 121 and the second MEMS device 122. For example, a third MEMS region (not shown) including a third MEMS device is disposed laterally spaced from the first MEMS region 100A and the second MEMS region 100B by the scribe line SL. A third device layer (not shown) including the third MEMS device is also packaged on the same wafer 130. The third MEMS device may have a device layer thickness different from the first thickness T1 and the second thickness T2. Moreover, the third MEMS device may have an electrode gap different from the first gap G1 and the second gap G2. Another raised electrode (not shown) may be disposed above the interconnect layer 132 and directly below the third MEMS device. Alternatively, another portion of the top metal layer 133 may be exposed through an opening of interconnect layer 132 and located directly below the third MEMS device. The MEMS structure of the third MEMS device may be different from those of the first MEMS device 121 and the second MEMS device 122. The MEMS packages of the present disclosure are suitable for 1-axis, 2-axis, 3-axis and 6-axis inertial measurement unit (IMU) and other MEMS devices requiring different device layer thicknesses and different electrode gaps.
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In step S125, the cap wafer 110 has a thickness T5, and the wafer 130 has a thickness T7. Then, referring to
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Afterwards, a portion of the cap wafer 110 and a portion 120P of the device wafer 120 at the scribe line SL between the pre-cut lines 129 are removed by a sawing process to complete the MEMS package 100 of
In some embodiments, the first MEMS device 121 with the first thickness T1 is, for example, an accelerometer, and the second MEMS device 122 with the second thickness T2 thinner than the first thickness T1 is, for example, a gyroscope, but not limited thereto. Moreover, the electrode gap for the second MEMS device 122, i.e., the second gap G2 between the raised electrode 145 and the bottom surface of the second MEMS device 122, is smaller than the electrode gap for the first MEMS device 121, i.e., the first gap G1 between the portion 133P of the top metal layer 133 and the bottom surface of the first MEMS device 121. The first MEMS device 121 and the second MEMS device 122 are fabricated by using the same device wafer 120 and packaged on the same wafer 130 to complete the MEMS package 100.
After the aforementioned steps S115, S117, S119, S121, S123, S125, S127 and S129 are performed, referring to
According to the embodiments of the present disclosure, the MEMS package includes different MEMS devices with different device layer thicknesses and different electrode gaps to meet the sensitivities and the performances of various MEMS devices. These MEMS devices are fabricated simultaneously by using the same device wafer and packaged simultaneously on the same wafer having the interconnect layer and the raised electrode formed thereon, thereby simplifying the whole fabricating process and reducing the cost of the MEMS packages.
Moreover, in the MEMS packages, the raised electrode is disposed above the interconnect layer and corresponds to the MEMS device with a thinner device layer thickness, thereby reducing the electrode gap and improving the sensitivity of the MEMS device. Furthermore, the dielectric layer is disposed between the raised electrode and the interconnect layer. Therefore, the electrode gap between the raised electrode and the bottom of the MEMS device is variable and controlled by the thickness of the dielectric layer to ensure the sensitivity of the MEMS device. Also, the fabrication of the raised electrode is compatible with the fabricating process of the CMOS wafer.
Furthermore, the device layer thicknesses of different MEMS devices are precisely controlled by thinning and etching the same device wafer without additional device wafer. Therefore, the sensitivities and the performances of the different MEMS devices are satisfied, and the cost and the time of fabricating the MEMS packages are reduced. In addition, the MEMS packages of the present disclosure do not require individual wire bonding, thereby reducing the parasitic effect. The MEMS packages of the present disclosure are suitable for 1-axis, 2-axis, 3-axis and 6-axis inertial measurement unit (IMU) and other MEMS devices requiring different device layer thicknesses and different electrode gaps.
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.
