Patent Application
20120255357
This application claims the benefit under 35 U.S.C. §119(a) of Chinese Application Nos. 201110087554.6 and 201110087553.1 filed on Apr. 8, 2011, which are herein incorporated by reference in their entireties for all purposes.
The proliferation of consumer electronics, especially portable devices such as smartphones and pads has significantly increased the demand for different sensors to implement the functionality and applications provided in these devices. The need for these sensors, e.g., accelerometers and magnetometers for location and direction-based, i.e., compass applications, is has significantly increased and these are now found in even the most basic handheld devices.
Currently, each sensor device, however, has only one function, such as being a two or three axis magnetic sensor, being a three axis accelerometer, a single axis gyro, etc. Furthermore, these single-function sensors often come in larger package sizes, e.g., 3×3 mm. This leads to larger space requirements, and the associated increased costs, for mobile devices in order to accommodate multiple sensing functions.
Embodiments of the present invention address the shortcomings described above and are directed to a sensor package structure that integrates a three axis accelerometer, a three axis magnetic sensor and an ASIC to interface with these sensors.
In one embodiment,
In one embodiment the sensor package includes a first substrate having an accelerometer structure provided therein and magnetometer circuitry coupled to the first substrate. A second substrate is coupled to the first substrate to enclose the accelerometer structure.
In one embodiment, first circuitry is provided in the first substrate and electrically coupled to the accelerometer structure and the magnetometer circuitry. Further, the first substrate includes a first cavity and the accelerometer structure is provided in the first cavity. The second substrate includes a second cavity and the first and second cavities are in a sealed fluid connection with one another to define a single enclosing cavity.
In another embodiment, a sensor package includes a first substrate having a top surface with a first cavity and first circuitry provided in the first substrate. An accelerometer structure is provided in the first cavity and electrically coupled to the first circuitry and magnetometer circuitry is coupled to the first substrate and electrically coupled to the first circuitry. A second substrate includes a second cavity and the second substrate is coupled to the first substrate such that the first and second cavities are oriented with respect to one another to define a single enclosing cavity.
Various aspects of at least one embodiment of the present invention are discussed below with reference to the accompanying figures. It will be appreciated that for simplicity and clarity of illustration, elements shown in the drawings have not necessarily been drawn accurately or to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity or several physical components may be included in one functional block or element. Further, where considered appropriate, reference numerals may be repeated among the drawings to indicate corresponding or analogous elements. For purposes of clarity, not every component may be labeled in every drawing. The figures are provided for the purposes of illustration and explanation and are not intended as a definition of the limits of the invention. In the figures:
Chinese Application Nos. 201110087554.6 and 201110087553.1 filed on Apr. 8, 2011, are herein incorporated by reference in their entireties for all purposes.
In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present invention. It will be understood by those of ordinary skill in the art that these embodiments of the present invention may be practiced without some of these specific details. In other instances, well-known methods, procedures, components and structures may not have been described in detail so as not to obscure the embodiments of the present invention.
Prior to explaining at least one embodiment of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.
Referring now to
ASIC circuitry 108 is provided in the first wafer 100 by any of the processes known to those of ordinary skill in the art and receives signals from the accelerometer structure 105 through traces that have been placed in the wafer as is known. The ASIC circuitry 108 is configured to interface with the accelerometer structure 105 in the first cavity 104 in addition to a magnetic sensor, as will be described below. A plurality of metal pads 112 is provided on the upper surface of the first wafer 100 and couple to one or more of the ASIC circuitry 108, the accelerometer structure 105 and any other circuitry that may be provided. A cross-sectional view along the line A-A, as shown in
A second substrate or wafer 200, which may be referred to as the upper wafer 200, is made from a same, or different, material with respect to the first wafer 100 as shown in
In one embodiment of the present invention, the second wafer 200 is placed over, and is coupled to, the first wafer 100 such that the second cavity 204 covers the first cavity 104. As a result, a larger enclosure or sealed cavity 404 is created between the first and second wafers 100, 200. Depending on the relative sizes of the two cavities, in one embodiment the center of the second cavity 204 and center of the first cavity 104 are generally aligned with one another. An exploded view of a partially assembled sensor package 300 is shown in
The first and second wafers 100, 200 may be a glass wafer or a silicon wafer. Further, the wafers 100, 200 may be a CMOS wafer. The first and second wafers 100, 200 need not be made from the same material. It should be noted, however, that if two different materials are used, the respective coefficients of thermal expansion (CTE) of the two materials should not differ too much in order to avoid any warpage of the device after being bonded together.
Referring now to
In addition, when the accelerometer structure 105 is a thermo accelerometer, a heavy gas may be sealed in the large cavity 404. In this case, a heavy gas is one that has a large molecular weight such as, for example, SF6, HFC125, HFC227, C3F8, etc. The pressure of the heavy gas in the large cavity 404 should be in the range of 0.5-4.0 atmospheres. Advantageously, providing the second cavity 204 over the first cavity 104 allows for the provided gas to be around, i.e., on all sides of, the accelerometer structure 105. Bonding machines that also insert gas are known to those of ordinary skill in the art.
Metal traces 408 are provided to connect the metal pads 112 to a bottom surface of the first wafer 100, as shown in
A magnetic sensor 416 that senses a magnetic field in one or more axes of orientation includes a plurality of contact pads 418 as shown in
Ball Grid array (BGA) solder balls 420 are provided on respective metal traces 408 such that the entire assembly 400 may be solder mounted onto an appropriately configured Printed Circuit Board, as shown in
In an alternate embodiment, as shown in
In yet another embodiment of the present invention, magnetic sensor circuitry 602 may be provided in the first wafer 100, e.g., in the upper surface, as shown in
A process of manufacturing a sensor package in accordance with an embodiment of the present invention includes the following steps:
1. Prepare the first wafer 100 by implementing the ASIC circuitry 108 and accelerometer structure 105.
2. Etch the first wafer 100 to release portions of the accelerometer structure 105. The etching of the top surface of the first wafer 100 could be by dry etch or wet etch, to release accelerometer structure 105, and form cavity 104. Located the pads 112 on the first wafer 100 top surface but not in the first cavity area 104. The metal pads 112 are provided on the first wafer 100 top surface but not in the first cavity 104 area.
3. Prepare the second wafer 200 with the second cavity 204 which is a little larger than the is first cavity 104 in the first wafer 100. The processing method of forming the second cavity 204 can vary depending upon the material from which it is made. If the second wafer 200 is a glass wafer, then sand blasting, laser drilling or wet etching could be used. If the second wafer 200 is an Si wafer, then dry or wet etching could be used.
4. Bond the first wafer 100 and the second wafer 200 together such that the second cavity 204 in the second wafer 200 covers the first cavity 104 in the first wafer 100 to create the large cavity 404.
5. If the accelerometer structure 105 is a thermal accelerometer, seal a heavy gas in the large cavity 404 and maintain the pressure of the heavy gas in a range of 0.5 - 4.0 atm.
Furthermore, the thicknesses of the wafers 100, 200 could be adjusted by grinding after bonding if a thinner profile is necessary.
6. Lead the metal pads 112 on the first wafer 100 surface to the bottom side by metal traces 408 and use redistribution technology to reassign the locations for all pads. For example, the BGA pads could be arranged in a standard orientation to couple with pads on another device or substrate. Leading the metal pads to the bottom side could be by TSV, as described above.
7. A bumping process can be applied to the magnetic sensor 416, then using flip-chip technology, connect the magnetic sensor 416 to the bottom side of the first wafer 100. Furthermore, in different applications, the bumping process could be implemented by plating, screen printing or ball drop.
8. Form BGA balls on the first wafer 100 bottom side.
One of ordinary skill in the art will understand that the foregoing steps need not be performed in the specific order outlined above. There may be variations of the process where the order of the steps is changed, where some steps are omitted and where some steps are repeated.
Having thus described several features of at least one embodiment of the present invention, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the invention. Accordingly, the foregoing description and drawings are by way of example only, and the scope of the invention should be determined from proper construction of the appended claims, and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201110087553.1 | Apr 2011 | CN | national |
| 201110087554.6 | Apr 2011 | CN | national |
