The field of the disclosed subject matter relates to optical packages. In particular, the field of the disclosed subject matter relates to wafer level integrated optics in packaging, e.g., for imaging sensor applications and to methods of manufacturing the same.
One of the key challenging issues in commercialization of imaging sensors is the manufacturing cost. There are two major parts—packaging and optics—in imaging sensors that significantly contribute the total cost. High packaging cost is mainly due to the fact that high quality hermetic seal is often required for imaging sensors, in particular for thermal imaging sensors. In optics, mainly the-optical lens assembly, cost is driven by the high precision machining, special materials, as well as the discrete assembly processes. In the most instances, these two parts can be more than 60% of total cost, and sometime this can go as high as 80%.
The conventional optical lens assembly 100A is assembled discretely. That is, each sensor module 150A is individually made by packaging an individual optical sensor 110 within an individual capping window 160 and an individual ceramic packaging 170. The individually made sensor module 150A is assembled together with an individual lens 120 on the board 190 with the housings 180 to arrive at the optical lens assembly 100A. As indicated, such discrete assembly incurs high costs.
Also, the material for the capping window 160 can be costly. This is because the capping window 160 must often satisfy two requirements simultaneously. For the protection of the optical sensor 110, the capping window 160 should maintain high quality hermetic seal over a long period of time. For performance, the capping window 160 should allow maximum amount of light to pass through to reach the optical sensor 110. That is, the capping window 160 should have very low optical absorption. Materials satisfying both requirements can be expensive.
The conventional optical lens assembly 100B improves upon the conventional optical lens assembly 100A in the following ways. First, cost is reduced since the ceramic packaging 170 is removed. Second, multiple optical sensors 110 and multiple capping windows 160 can be formed together at a wafer level and then diced. Therefore, the cost of the sensor module 150B can be lower than that of the sensor module 150A.
Unfortunately, the conventional optical lens assembly 100B itself is still discretely assembled. That is, the individually diced sensor module 150B is assembled together with the individual lens 120 on the board 190 with the housings 180 to arrive at the assembly 100B. Thus, there is still high cost associated with the conventional lens assembly 100B. In addition, the capping material can impact on the performance unless very low optical absorption materials used, which can be expensive, especially for long wavelength inferred radiation sensors.
This summary identifies features of some example aspects, and is not an exclusive or exhaustive description of the disclosed subject matter. Whether features or aspects are included in, or omitted from this Summary is not intended as indicative of relative importance of such features. Additional features and aspects are described, and will become apparent to persons skilled in the art upon reading the following detailed description and viewing the drawings that form a part thereof.
An exemplary lens assembly is disclosed. The lens assembly may comprise an imaging sensor, left and right spacers on the imaging sensor, and a lens on the left and right spacers. The left and right spacers may be spaced apart from each other. The lens, the left and right spacers, and the imaging sensor may define an interior space. The interior space may be hermetically sealed.
An exemplary method is disclosed. The method may comprise forming a lens assembly array; and individualizing the lens assembly array into a plurality of individual lens assemblies. After individualizing the lens assembly array, each lens assembly may comprise an imaging sensor, left and right spacers on the imaging sensor, and a lens on the left and right spacers. The left and right spacers may be spaced apart from each other. The lens, the left and right spacers, and the imaging sensor may define an interior space. The interior space may be hermetically sealed.
An exemplary lens assembly is disclosed. The lens assembly may comprise means for radiation sensing, left and right means for spacing on the means for radiation sensing, and a lens on the left and right means for spacing. The left and right means for spacing may be spaced apart from each other. The lens, the left and right means for spacing, and the means for radiation sensing may define an interior space. The interior space may be hermetically sealed.
The accompanying drawings are presented to aid in the description of examples of one or more aspects of the disclosed subject matter and are provided solely for illustration of the examples and not limitation thereof
Aspects of the subject matter are provided in the following description and related drawings directed to specific examples of the disclosed subject matter. Alternates may be devised without departing from the scope of the disclosed subject matter. Additionally, well-known elements will not be described in detail or will be omitted so as not to obscure the relevant details.
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Likewise, the term “embodiments” does not require that all embodiments of the disclosed subject matter include the discussed feature, advantage or mode of operation.
The terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, integers, processes, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, processes, operations, elements, components, and/or groups thereof
Further, many examples are described in terms of sequences of actions to be performed by, for example, elements of a computing device. It will be recognized that various actions described herein can be performed by specific circuits (e.g., application specific integrated circuits (ASICs)), by program instructions being executed by one or more processors, or by a combination of both. Additionally, these sequence of actions described herein can be considered to be embodied entirely within any form of computer readable storage medium having stored therein a corresponding set of computer instructions that upon execution would cause an associated processor to perform the functionality described herein. Thus, the various aspects may be embodied in a number of different forms, all of which have been contemplated to be within the scope of the claimed subject matter. In addition, for each of the examples described herein, the corresponding form of any such examples may be described herein as, for example, “logic configured to” perform the described action.
As indicated above, one of the key challenging issues facing commercialization of imaging sensors, especially for thermal imaging sensors, is the manufacturing cost. Many efforts have been pursued to save costs in the manufacturing of imaging sensors. For example, wafer level lens fabrication processes have been proven to be cost effective compared to the discrete lens fabrication processes.
In a non-limiting aspect, a wafer level integrated optics in packaging (OiP) is proposed. Unlike the conventional lens assemblies 100A, 100B of
In this disclosure, terms such as “upper”, “lower”, “top”, “bottom”, “left”, “right” and so on are used. Such terms are used merely for convenience, i.e., they should not be interpreted to be limiting.
The imaging sensor 210 may be an optical sensor, a thermal sensor, or a sensor that is sensitive to spectrum other than the visible and the infrared (IR). The imaging sensor 210 may be an example of means for radiation sensing. While not specifically shown, the imaging sensor 210 may include a sensor portion (e.g., focal plane array (FPA)) and a circuit portion (e.g., readout integrated circuit (ROTC)). In some aspects, the imaging sensor 210 may incorporate a substrate (e.g., glass, PCB) with the sensor and circuit portions on the substrate. The left spacer 230-L and the right spacer 230-R may comprise portions of adjacent spacers 230 of the spacer array 230′. The heights of the left and right spacers 230-L, 230-R may correspond to the focal length of the lens 220. The spacers 230-L and 230-R may each be examples of means for spacing.
Unlike the conventional optical lens assemblies 100A, 100B of
In addition, recall that with the conventional assemblies 100A, 100B, one primary purpose of the capping window 160 is for the protection of the optical sensor 110. But in an aspect, the lens assembly 200 of
In an aspect, hermetic sealing is more than a simple vacuum packaging. Sensor packages are often sealed to protect the sensor for optimum performance. In most instances, this means isolating the sensor from the ambient operating environment by providing the sensor with a controlled environment (e.g., a vacuum). However, if the controlled environment cannot be maintained, the performance of the sensor, and therefore the performance of the assembly, will likely degrade over time. Thus, to enable a long product lifetime (e.g., greater than 5 years, greater than 20 years, etc.), a high quality hermetic sealing is proposed for the lens assembly 200. For example, a hermeticity level less than 10−14 cc/sec may be provided.
Over time, the controlled environment (e.g., vacuum) may not be maintained due to any combination of leaks, permeation and outgassing. As a result, the operational performance lens assembly 200 may degrade. Leaks may be viewed as flow of contaminants (e.g., ambient gas) into the interior space 240 through unintentional openings. Leaks can be minimized through high quality bonding between the different components of the lens assembly 200, e.g., between the lens 220 and the spacers 230-L, 230-R, and between the imaging sensor 210 and the spacers 230-L, 230-R. Bonding techniques include metal-to-metal, eutectic, anodic, direct and glass frit.
Permeation may be viewed as diffusion of contaminants through a material. For example, contaminants may diffuse through the lens 220 and/or the spacers 230-L, 230-R into the interior space 240. Permeation may be minimized through selection of the materials for the components of the lens assembly 200, e.g., through selection of the materials for the lens 220, the spacers 230-L, 230-R, and/or the imaging sensor 210. For example, glasses, metals and metal oxides have lower permeabilities than epoxies and fluorocarbons. Permeation may also be minimized through design, e.g., by increasing the thicknesses of the spacers 230-L, 230-R or coating metallic layer on the surfaces of spacers as diffusion (permeation) barriers.
Outgassing may be viewed as a release of materials from surfaces thereof. Note that a lower surface of the lens 220 and inner side surfaces of the spacers 230-L, 230-R are exposed to the interior space 240. Materials of the lens 220 and/or the spacers 230-L, 230-R may be released, i.e., outgassed, into the interior space 240 from these exposed surfaces. Like permeation, outgassing may be minimized through selection of materials and/or through incorporating materials with gettering properties (more on this below).
The lens assembly 220 may be formed in consideration of factors described above as well as others (such as cost, ease of manufacture, etc.). In an aspect, for optical sensing applications (e.g., visible wavelengths), the lens 220 may be formed from glass, which is relatively inexpensive and has relatively small permeability. For thermal sensing applications (infrared (IR) wavelengths), the lens 220 may molded from a chalcogenide material. Of course, the lens 220 may be formed from a variety of materials (glass, chalcogenide, Si based, Ge based, Zn based, fluoride based, etc.). It is recognized that different materials may be preferred for sensing different wavelengths. Satisfactory hermetic seal can be provided when the thickness of the lens ranges between 500 μm to 1 mm.
The spacers 230-L, 230-R may also be formed a variety of materials. In an aspect, the spacers 230-L, 230-R may be formed low permeability materials such as glass, silicon nitride, metal and/or metal oxides. Alternatively, the spacers 230-L, 230-R may be formed from relatively high permeability materials (e.g., fluorocarbons, organic polymers, epoxies) with the inner sides of the spacers 230-L, 230-R coated with low permeability materials.
As indicated above, outgassing may be reduced through the selection of the materials for the lens 220 and/or the spacers 230. Another way to minimize outgassing is through gettering. For example,
The first and second lenses 220, 420 may be shaped similarly or differently. For example, the first lens 220 may be shaped to diverge (e.g., concave) or to converge (e.g., convex) the incoming radiation. The second lens 420 may also be shaped to diverge or converge the incoming radiation. In addition, the heights of the first spacers 230-L, 230-R may be same or different from the heights of the second spacers 430-L, 430-R. Preferably, the shapes of the lens 220, 420 and the heights of the spacers 230, 430 are such that the incoming radiation is focused on the imaging sensor 210. The first and second lenses 220, 420 may be formed from same or different materials. Also, the first spacers 230-L, 230-R may be formed from same or different materials as the second spacers 430-L, 430-R.
Recall that hermetically sealing the first interior space 240 may be a significant consideration when choosing the materials for the first lens 220 and the first spacers 230-L, 230-R. However, hermetically sealing the second interior space 440 may be of significantly less concern. In such instances, the second lens 420 and/or the second spacers 430-L, 430-R may be formed from less costly materials relative to the first lens 220 and/or the first spacers 230-L, 230-R.
If the lens assembly array 200′ of
In block 810 of
If a single level of lenses is sufficient, then the method 800 may proceed to block 820 of
The following is a list (not necessarily exhaustive) of advantages of the proposed lens assemblies:
Those of skill in the art will appreciate that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.
Further, those of skill in the art will appreciate that the various illustrative logical blocks, modules, circuits, and algorithms described in connection with the examples disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and methods have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.
The methods, sequences and/or algorithms described in connection with the examples disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled with the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor.
Accordingly, an aspect can include a computer readable media embodying a method of forming a semiconductor device. Accordingly, the scope of the disclosed subject matter is not limited to illustrated examples and any means for performing the functionality described herein are included.
While the foregoing disclosure shows illustrative examples, it should be noted that various changes and modifications could be made herein without departing from the scope of the disclosed subject matter as defined by the appended claims. The functions, processes and/or actions of the method claims in accordance with the examples described herein need not be performed in any particular order. Furthermore, although elements of the disclosed subject matter may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.