SENSOR PACKAGES HAVING SEMICONDUCTOR DIES OF DIFFERING SIZES
A sensor package comprises a composite structure in which the composite structure includes a first electronic component having first bond pads, the first electronic component exhibiting a first surface area. A mold material encapsulates the first electronic component to produce the composite structure, and the composite structure exhibits a second surface area that is greater than the first surface area. The sensor package further comprises a second electronic component having a top side and a bottom side opposing the top side. The top side includes second bond pads, and the bottom side is bonded to an outer surface of the composite structure to form a stacked structure. Electrical interconnects are attached between corresponding ones of the first bond pads and the second bond pads.
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The present invention relates generally to semiconductor packaging. More specifically, the present invention relates to wafer level semiconductor packaging for forming sensor packages in which semiconductor dies are of differing sizes.
BACKGROUND OF THE INVENTIONMicroelectronic device technology has achieved wide popularity in recent years, as it provides a way to make very small electronic and mechanical structures and integrate these structures on a single substrate using conventional batch semiconductor processing techniques. While such microelectronic devices are becoming mainstream technologies, cost effectively packaging them in semiconductor packages for manufacture and ease of use remains challenging. Indeed, packaging is one of the major cost drivers for such devices.
A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in connection with the Figures, wherein like reference numbers refer to similar items throughout the Figures, the Figures are not necessarily drawn to scale, and:
Semiconductor packages generally provide a set of related elements. These elements include, in some examples, one or more semiconductor devices to be packaged, interconnection from the devices to the package, a surrounding or containing structure to provide both mechanical support and electrical, chemical, and environmental protection, and a joining structure to attach the package to the board or system. The challenges faced by developers of semiconductor packaging processes result from, for example, the sensitivity of the semiconductor devices (e.g., microelectronics and microstructures) to high temperature processes, the need for suitable shielding, the requirement in some instances for a hermetic or near-hermetic seal to protect the devices from contaminants, and so forth. Due at least in part to these challenges, packaging is one of the major cost drivers for such devices.
One or more of the semiconductor devices in a semiconductor package may be a microelectronic sensor (e.g., a magnetometer), a microelectromechanical systems (MEMS) sensor (e.g., an accelerometer, gyroscope, pressure sensor), or some other miniaturized sensor. With regard to such sensors, proper packaging is important to ensure the integrity of the signals to and from the sensor devices. For example, angular misalignment of a sensor device or multiple sensor devices in a sensor package can lead to inaccuracies in the measured signals. As such, precise angular alignment of sensors in a sensor package is critical for receiving accurate measurements.
Angular alignment of sensors in traditional chip level packaging is currently limited to approximately plus or minus two degrees of accuracy. The angular alignment accuracy is limited by the tolerance of placement equipment utilized in die placement techniques. More precise angular alignment is being called for in the industry to improve the accuracy of measurements received from such sensors. As integrated circuit (IC) device geometries continue to decrease, the use of miniaturized sensor devices continues to rise, and the fabrication of semiconductor packages containing multiple microelectronic components continue to evolve, the need for low cost, accurate, reliable, high density packaging solutions increases.
Embodiments entail sensor packaging methodology and sensor packages produced in accordance with the packaging methodology. The packaging methodology involves a wafer-level packaging technique in lieu of traditional die-to-die placement techniques. Wafer-level packaging refers to packaging semiconductor devices at wafer level, and essentially extends the wafer fabrication process to include device interconnection and device protection processes. The wafer-level packaging process discussed herein provides high-throughput and precise placement packaging of sensors at relatively low cost. Additional advantages entail a chip-scale packaging technology that results in the sensor package being generally the same size as the die, stacking of sensors and microelectronic devices for size reduction, packaging of sensors and microelectronic devices of differing sizes, improved electrical performance, and so forth. The subsequent discussion pertains to the packaging of sensors. However, the packaging methodology discussed herein can be implemented to package various types of electronic components.
Referring now to
Sensor structure 22 includes a sensor die 26, a cap 28, and a sensor 30 formed on or in a substrate material 32 of sensor die 26. An inner surface 34 of cap 28 is coupled to an inner surface 36 of sensor die 26 with sensor 30 being interposed between sensor die 26 and cap 28. Thus, inner surface 34 of cap 28 is referred to hereinafter as inner cap surface 34 and inner surface 36 of sensor die 26 is referred to hereinafter as inner die surface 36. Sensor 30 may be a microelectromechanical systems (MEMS) sensor device such as an accelerometer, gyroscope, or some other sensor. However, sensor 30 need not be limited to a MEMS sensor configuration. Rather, sensor 30 may be an optical device, electro-magnetic device, chemical device, or some other sensor device that contains micron and/or sub-micron sized components. Additionally, although sensor 30 is mentioned in singular form, in alternative embodiments, sensor die 26 may include more than one sensor device formed on or in substrate material 32.
Cap 28 generally covers sensor die 26 so as to encapsulate sensor 30 and/or provide appropriate covering. In the embodiment shown, cap 28 may be attached to sensor die 26, for example, by a seal ring, so as to seal sensor 30 hermetically or near-hermetically within the encapsulated area. In some embodiments, cap 28 may include a cavity (not shown) extending inwardly from inner cap surface 34 so as to provide clearance for the moving elements of sensor 30, although such a configuration is not a limitation. In the illustrated embodiment shown in
Controller die 24 has a top side 44 and a bottom side 46 opposing top side 44. In
Sensor structure 22 includes an outer surface 52 which corresponds to the outer, or external, surface of cap 28. Thus, outer surface 52 is referred to hereinafter as outer cap surface 52 for clarity. Sensor structure 22 further includes an opposing outer surface 54 which corresponds to the outer, or external, surface of sensor die 26. Thus, outer surface 54 is referred to hereinafter as outer die surface 54 for clarity. In the illustrated embodiment, bottom side 46 of controller die 24 is attached to outer die surface 54 of sensor structure 22 to produce a stacked structure 55 having sensor die 26 positioned between cap 28 and controller die 24.
In sensor structure 22, bond pads 42 on inner cap surface 34 of substrate portion 40 of cap 28 face in the same direction (i.e., upwardly in
Controller die 24 further includes bump pads 58 formed on and distributed across top side 44. In an embodiment, conductive elements 60 are formed on bump pads 58 after controller die 24 is bonded to sensor structure 22. Conductive elements 60 are illustrated in
In some embodiments, an integral sensor 61 may be formed integrally with the passive and active elements of control circuitry 48 within controller die 24 in accordance with conventional and upcoming semiconductor manufacturing processes. In lieu of or in addition to integral sensor 61, sensor package 20 may include a sensor die 62 mounted on top side 44 of controller die 24. In an embodiment, integral sensor 61 or sensor die 62 may be a magnetometer for measuring the strength or direction of magnetic fields. However, integral sensor 61 and/or sensor die 62 may be some other sensor device in accordance with particular design criteria for sensor package 20.
A packaging material 64 is applied over top side 44 of controller die 24 to encapsulate control circuitry 48, bond wires 56, sensor die 62, and to at least partially encapsulate conductive elements 60 so that only a top side 66 of conductive elements 60 is exposed from packaging material 64. Packaging material 64 may be any conventional molding compound such as, for example, an epoxy resin material.
In the top view of
Accordingly, an embodiment described herein entails methodology that cost effectively addresses the problem of a mismatch in surface area 68 of controller die 24 and surface area 70 of sensor structure 22. Referring again to
As particularly illustrated in
Another distinguishing feature of sensor package 76, as also illustrated in
As discussed above, sensor package 20 (
Packaging process 90 will be discussed in connection with the packaging of a plurality of sensor packages 20 (
Packaging process 90 begins with an activity 92. At activity 92, a controller wafer is provided. The controller wafer may be provided from a device manufacturer and packaged in accordance with packaging process 90 at a separate packaging facility. Alternatively, the controller wafer may be fabricated and packaged within the same manufacturing facility.
Referring to
Controller wafer 94 may be manufactured utilizing conventional and upcoming integrated circuit (IC) fabrication techniques for forming control circuitry 48 in the active regions of controller wafer 94. The implementation of standard IC wafer fabrication techniques creates transistors, capacitors, resistors, diodes, and all other components of control circuitry 48 and, if present, integral sensor 61. In addition, these IC fabrication techniques may be implemented to form bond pads 50 and bumps pads 58 at top side 44 of controller wafer 94. These conventional process steps need not be described herein.
Top side 44 of controller wafer 94 is marked with dashed lines 96 along the generally planar top side 44 of controller wafer 94. Dashed lines 96 represent the locations at which controller wafer 94 will be sawn or diced. Additionally, in the illustrated embodiment, adjacent pairs 98 of vertically arranged dashed lines 96 denoted by a dash-dot sequence represent the locations at which material sections 100 (discussed below) of controller wafer 94 may be removed in order to access an underlying sensor wafer structure (discussed below). These adjacent pairs of lines are collectively referred to herein as saw-to-reveal lines 98. The remaining dashed lines 96 represent the locations at which controller wafer 94 will eventually be singulated (discussed below) concurrent with singulation of the sensor wafer structure. Dashed lines 96 are collectively referred to herein as saw lines 96.
Controller wafer 94 is illustrated as being generally disk-shaped. However, alternative embodiments of controller wafer 94 may be any suitable shape, such as rectangular shaped. Additionally, the quantity of controller dies 24 formed on a given controller wafer 94 varies depending upon the size of controller dies 24 and upon the size of controller wafer 94.
Referring back to
Referring to
Alternatively, the illustration of
Sensor structures 22 and 78 may include any of a plurality of sensor devices such as inertial sensors, gyroscopes, optical devices, pressure sensors, magnetic field sensors, switches, microphones, and so forth. However, in alternative embodiments, sensor structures 22 and 78 may include any other device in which it is desirable to individually protect, i.e., cap, sensitive features and additionally expose or reveal terminal elements, i.e., bond pads 42 (
Sensor wafer structures 104 and 106 may be manufactured utilizing conventional and upcoming bulk micromachining, surface micromachining, and/or high aspect ratio silicon micromachining techniques. Fabrication processes for a surface micromachining technique can generally include, for example, deposition, patterning, and etching of one or more sacrificial oxide layers, one or more structural polysilicon layers, and the like. For example, one or more sacrificial oxide layers may be deposited overlying the silicon-based wafer, and one or more structural layers may then be deposited over the sacrificial layers.
All elements on either of sensor wafer structures 104 or 106 may be identical, or either of sensor wafer structures 104 or 106 can contain a mixture of sensor elements. Dashed lines 108 represent borders delineating the various sensor structures 22 that make up sensor wafer structure 104, or alternatively, the various sensor structures 78 that make up sensor wafer structure 106. Dashed lines 108 can additionally represent the locations at which sensor wafer structure 104 may eventually be sawn, diced, etched, or otherwise singulated in one or more separate operations (discussed below). Thus, dashed lines 108 are referred to hereinafter as saw lines 108.
Sensor wafer structures 104 and 106 are illustrated as being generally disk-shaped. However, alternative embodiments of sensor wafer structures 104 and 106 may be any suitable shape, such as rectangular shaped. The quantity of sensor structures 22 or 78 that make up a given sensor wafer structure 104 or 106 varies depending upon the size of sensor structures 22 or 78 and upon the size of the wafers (discussed below) used to assemble sensor wafer structure 104 or 106.
Now referring to
In the illustrated embodiment, select pairs of 114 of lines denoted by a dash-dot sequence represent the locations at which portions (discussed below) of sensor wafer 110 will be removed in order to access bond pads 42 of cap wafer 112. These select pairs 114 are referred to hereinafter as saw-to-reveal lines 114. Therefore, a saw line 108 and an adjacent saw-to-reveal line 114 delineates a material section 116 of each controller die 26 on sensor wafer 110 to be removed in accordance with packaging process 90 (
Now referring to
In accordance with an embodiment, sensor wafer structure 106 includes seal members 119, of which only one is visible in
Referring back to
Following activity 102, packaging process 90 continues with an activity 120. At activity 120, the provided sensor wafer is diced or sawn to produce sensor elements. It should be recalled that surface area 70 (
Referring to
Sensor wafer structure 104 is diced, sawn, laser cut, or otherwise separated along saw lines 108 so that each sensor element 122 includes two sensor structures 22 whose corresponding bond pads 42 are arranged adjacent to one another. Note in
Returning back to
With reference to
Array 126 includes three columns of sensor elements 122 in this exemplary configuration. However, any quantity of sensor elements 122 may be present in array 126 in accordance with the quantity of controller dies 24 in controller wafer 94. In this illustration, sensor elements 122 are oriented with caps 28 facing upwardly so that adjacent outer cap surfaces 52 are visible. However, in alternative arrangements, caps 28 may be oriented downwardly so that outer die surfaces 54 (
With reference back to
Referring to
Returning back to packaging process 90 (
With reference to
Alignment of controller wafer 94 with sensor elements 122 of panel 130 may be achieved by utilizing mechanical or optical fiduciary marks, such as notches at the edges of controller wafer 94 and panel 130, pins, etchings, or holographic images, among others. Automatic process equipment for silicon wafer bonding, as well as the integration of suitable alignment techniques, can provide precision location keyed to specific features on the semiconductor elements within panel 130 and controller wafer 94. Thus, angular alignment of less than one tenth of a degree of accuracy for the sensors may be achieved. This alignment accuracy is in contrast with the angular alignment of sensors achieved in traditional chip level die packaging, which is typically limited to approximately plus or minus two degrees of accuracy.
Referring back to
Referring now to
Conductive elements 60 are formed on bump pads 58 of the bonded wafers of stacked wafer structure 136 as a wafer-level process to achieve improvements in rotational accuracy of sensor package 20 (
As further shown in
With reference back to
Referring to
Again referring back to
Referring now to
Referring back to
With reference to
Referring back to
With reference now to
Again referring back to
Following activity 156, an activity 166 is eventually performed. At activity 166, the fabricated stacked wafer structure 136 is singulated, i.e., cut, punched, or diced, in a conventional manner. Following activity 166, packaging process 90 ends.
Referring to
Packaging process 90 was described above as a wafer-to-wafer packaging process utilizing sensor wafer structure 104 (
In accordance with an alternative embodiment, packaging processes 90 is described below utilizing sensor wafer structure 106 (
Referring to
As mentioned previously, sensor wafer structure 106 includes seal members 119. Seal members 119 are advantageous in configurations in which singulated sensor structures 78 are to be utilized to form a new panel. Since seal members 119 bridge saw lines 108 (i.e., are wider than the width of the cut), a portion of each of seal members 119 remains in place extending between sensor wafer 110 (
Inclusion of seal members 119 may result in sensor wafer structure 106 being larger than a sensor wafer structure that does not have seal members 119 (e.g., sensor wafer structure 104 of
Array 168 includes six columns of sensor structures 78 in this exemplary configuration. However, any quantity of sensor structures 78 may be present in array 168 in accordance with the quantity of controller dies 24 in controller wafer 94 and the size of controller wafer 94. In this illustration, sensor structures 78 are oriented with sensor dies 26 facing upwardly so that outer die surfaces 54 are visible. However, in alternative arrangements, sensor dies 26 may be oriented downwardly so that outer cap surfaces 52 (see
Referring to
By implementing a technique in which singulated sensor structures 78 are used to form a panel commensurate in size with the controller wafer, greater disparities in die sizes between the sensor dies and the controller dies and bond pad locations may be accommodated. Sensor dies 26 may be probed and tested while still in wafer form, i.e., while still configured as sensor wafer 110 (
Embodiments described herein entail sensor packaging methodology and electronic component packages produced in accordance with the packaging methodology. The packaging methodology involves a wafer-level packaging technique in lieu of traditional die placement techniques. In accordance with the wafer-level packaging technique, a sensor wafer structure is diced into sensor elements, without exposing bond pads to contamination. The sensor elements are picked and placed in an array and encapsulated to form a panel. A controller wafer is subsequently bonded to this panel to form a stacked wafer structure with the active side of the controller wafer facing outwardly from the package. Thus, the package inputs and outputs can be formed on the controller wafer. A portion of the stacked wafer structure is sawn, etched, or otherwise cut to reveal the underlying bond pads of the sensor wafer structure and the corresponding bond pads for the controller dies on the controller wafer are wire bonded to the sensor bond pads in wafer format. The methodology is particularly useful when the sensor structures containing sensor dies are smaller than the controller dies within the stacked configuration.
The wafer-level packaging process is especially suitable for the packaging of miniaturized sensors where precise rotation and tilt accuracy of the sensors can be achieved at the wafer level, rather than at the die level. Moreover, the required angular accuracy can be assured without more costly and time consuming testing. Accordingly, the wafer-level packaging process discussed herein provides high-throughput and precise placement packaging of sensors at relatively low cost. Moreover, the wafer-level packaging process results in individual sensor packages that are generally the same size as the larger controller die, stacking of sensors and microelectronic devices for size reduction and improved package density, enhanced electrical performance, and so forth. Additionally, the wafer structure and corresponding methodology are cost-effective, readily implemented, and adaptable to existing assembly and packaging tools and techniques.
Although the preferred embodiments of the invention have been illustrated and described in detail, it will be readily apparent to those skilled in the art that various modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims. For example, the process operations following wafer bonding can be performed in a differing order then that which was presented.
Claims
1. A package comprising:
- a composite structure including: a first electronic component having first bond pads, said first electronic component exhibiting a first surface area; and a mold material encapsulating said first electronic component to produce said composite structure, said composite structure exhibiting a second surface area that is greater than said first surface area;
- a second electronic component having a top side and a bottom side opposing said top side, said top side including second bond pads, said bottom side being bonded to an outer surface of said composite structure to form a stacked structure; and
- electrical interconnects attached between corresponding ones of said first bond pads and said second bond pads.
2. The package of claim 1 wherein said bottom side of said second electronic component exhibits a third surface area that is approximately equivalent to said second surface area of said composite structure.
3. The package of claim 1 wherein said first electronic component comprises a sensor structure having a sensor die and a cap, a first inner surface of said cap is coupled to a second inner surface of said sensor die, one of said cap and said sensor die includes a substrate portion with said first bond pads being located on a corresponding one of said first and second inner surfaces, a material section of the other one of said cap and sensor die being absent, and said electrical interconnects extend through a region where said material section is absent.
4. The package of claim 3 wherein said outer surface of said composite structure is an outer die surface of said sensor die, and said bottom side of said second electronic component is attached to said outer die surface to produce said stacked structure having said sensor die positioned between said cap and said second electronic component.
5. A The package of claim 4 wherein said cap includes said substrate portion with said first bond pads located on said first inner surface, and said first bond pads face in the same direction as said top side of said second electronic component.
6. The package of claim 3 wherein said outer surface of said composite structure is an outer cap surface of said cap, and said bottom side of said second electronic component is attached to said outer cap surface to produce said stacked structure having said cap positioned between said sensor die and said second electronic component.
7. The package of claim 6 wherein said sensor die includes said substrate portion with said first bond pads located on said second inner surface, and said first bond pads face in the same direction as said top side of said second electronic component.
8. The package of claim 1 further comprising a third electronic component located at said top side of said second electronic component.
9. The package of claim 1 wherein said second electronic component includes bump pads formed on said top side of said second electronic component, and said package further comprises conductive elements formed on and extending above said bump pads.
10. The package of claim 9 further comprising a packaging material located over said top side of said second electronic component wherein each of said conductive elements has a top surface that is exposed from said packaging material.
11. The package of claim 1 further comprising a packaging material located over said top side of said second electronic component and encapsulating said electrical interconnects.
12. A package comprising:
- a composite structure including: a first electronic component having first bond pads, said first electronic component exhibiting a first surface area, wherein said first electronic component comprises a sensor structure having a sensor die and a cap, a first inner surface of said cap is coupled to a second inner surface of said sensor die, one of said cap and said sensor die includes a substrate portion with said first bond pads being located on a corresponding one of said first and second inner surfaces, a material section of the other one of said cap and sensor die being absent; and a mold material encapsulating said first electronic component to produce said composite structure, said composite structure exhibiting a second surface area that is greater than said first surface area;
- a second electronic component having a top side and a bottom side opposing said top side, said top side including second bond pads, said bottom side being bonded to an outer surface of said composite structure to form a stacked structure, wherein said bottom side of said second electronic component exhibits a third surface area that is approximately equivalent to said second surface area of said composite structure; and
- electrical interconnects attached between corresponding ones of said first bond pads and said second bond pads, said electrical interconnects extending through a region where said material section is absent.
13. The package of claim 12 wherein said outer surface of said composite structure is an outer die surface of said sensor die, and said bottom side of said second electronic component is attached to said outer die surface to produce said stacked structure having said sensor die positioned between said cap and said second electronic component.
14. A The package of claim 13 wherein said cap includes said substrate portion with said first bond pads located on said first inner surface, and said first bond pads face in the same direction as said top side of said second electronic component.
15. The package of claim 12 wherein said outer surface of said composite structure is an outer cap surface of said cap, and said bottom side of said second electronic component is attached to said outer cap surface to produce said stacked structure having said cap positioned between said sensor die and said second electronic component.
16. The package of claim 15 wherein said sensor die includes said substrate portion with said first bond pads located on said second inner surface, and said first bond pads face in the same direction as said top side of said second electronic component.
17. A package comprising:
- a composite structure including: a first electronic component having first bond pads, said first electronic component exhibiting a first surface area; and a mold material encapsulating said first electronic component to produce said composite structure, said composite structure exhibiting a second surface area that is greater than said first surface area;
- a second electronic component having a top side and a bottom side opposing said top side, said top side including second bond pads, said bottom side being bonded to an outer surface of said composite structure to form a stacked structure, wherein said bottom side of said second electronic component exhibits a third surface area that is approximately equivalent to said second surface area of said composite structure;
- electrical interconnects attached between corresponding ones of said first bond pads and said second bond pads; and
- a packaging material located over said top side of said second electronic component and encapsulating said electrical interconnects.
18. The package of claim 17 wherein said first electronic component comprises a sensor structure having a sensor die and a cap, a first inner surface of said cap is coupled to a second inner surface of said sensor die, one of said cap and said sensor die includes a substrate portion with said first bond pads being located on a corresponding one of said first and second inner surfaces, a material section of the other one of said cap and sensor die being absent, and said electrical interconnects extend through a region where said material section is absent.
19. The package of claim 17 wherein said second electronic component includes bump pads formed on said top side of said second electronic component, and said package further comprises conductive elements formed on and extending above said bump pads.
20. The package of claim 19 wherein each of said conductive elements has a top surface that is exposed from said packaging material.
Type: Application
Filed: Mar 5, 2014
Publication Date: Jul 3, 2014
Applicant: FREESCALE SEMICONDUCTOR, INC. (Austin, TX)
Inventor: Philip H. Bowles (Gilbert, AZ)
Application Number: 14/197,990
International Classification: H01L 23/522 (20060101); H01L 23/498 (20060101);