|Número de publicación||US7920343 B2|
|Tipo de publicación||Concesión|
|Número de solicitud||US 12/353,807|
|Fecha de publicación||5 Abr 2011|
|Fecha de prioridad||14 Ene 2009|
|También publicado como||US20100177408|
|Número de publicación||12353807, 353807, US 7920343 B2, US 7920343B2, US-B2-7920343, US7920343 B2, US7920343B2|
|Inventores||Rick Lake, Ulrich Boettiger, Shashikant Hegde, Jacques Duparre|
|Cesionario original||Aptina Imaging Corporation|
|Exportar cita||BiBTeX, EndNote, RefMan|
|Citas de patentes (12), Citada por (2), Clasificaciones (12), Eventos legales (2)|
|Enlaces externos: USPTO, Cesión de USPTO, Espacenet|
Embodiments described herein relate generally to processes of forming lens wafers for use in imaging devices, and more particularly to processes of forming lenses on structures incorporating micro-electrical-mechanical systems (MEMS) technology.
Microelectronic imaging devices are used in a multitude of electronic devices. As microelectronic imaging devices have decreased in size and improvements have been made with respect to image quality and resolution, they are now commonly found in electronic devices including mobile telephones and personal digital assistants (PDAs) in addition to their traditional uses in digital cameras.
Microelectronic imaging devices include image sensors that typically are charged coupled device (CCD) systems or complementary metal-oxide semiconductor (CMOS) systems, as well as other imaging technologies. The lenses for these microelectronic imaging devices may require mobility for operations such as automatic focus or zoom features. To meet the increased need for smaller lenses with retained mobility, MEMS structures have been incorporated into lens stacks. For example, MEMS wafers may be integrated with lenses to be used as, e.g., an automatic focus (autofocus) or zoom system by accurately changing the relative distance of the lenses with respect to each other and/or a pixel array.
MEMS is a relatively new technology that exploits the existing microelectronics infrastructure to create complex machines with micron feature sizes. MEMS structures have been created for lens movement and may be integrated with lenses. Some examples of MEMS structures which my be used for lens movement may be found in U.S. Pat. Nos. 6,636,653, 7,242,541 and 7,280,290.
Lens replication for imaging devices may be carried out on a glass wafer using an ultra-violet (UV) curable optical polymer and a compression stamp or mold. Processes for manufacturing imaging devices which include lens structures and MEMS structures for moving the lens structures can be expensive because the MEMS structures and lenses are created in separated processes, and then attached together in a subsequent process. Bulky mechanical packaging is another problem experienced with the lens/MEMS structure combination. There is a need for a more efficient, less bulky and less expensive method of forming lenses which are integrated with MEMS structures.
In the following description, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustrations specific embodiments that may be practiced. It should be understood that like reference numerals represent like elements throughout the drawings. These example embodiments are described in sufficient detail to enable those skilled in the art to practice them. It is to be understood that other embodiments may be utilized, and that structural, material and electrical changes may be made, only some of which are discussed in detail below, without departing from the spirit and scope of the invention.
Embodiments described herein relate to a method of forming a lens wafer by forming lenses on the wafer and attaching them in aligned fashion to a wafer containing MEMS structures which eliminates the need for bulky mechanical packaging. The combined lenses/MEMS structure can then in turn be integrated with an imager wafer to form an imaging device. The embodiments described herein provide arrays of lenses that can be attached to arrays of movable MEMS structures for autofocus and/or zoom applications, and a means to transfer and attach the lens array to the MEMS structure array.
Surface micromachining is accomplished by three basic techniques: deposition of thin films; wet chemical etching; and dry etching techniques. The most common form of dry etching for micromachining applications is reactive ion etching (RIE). Ions are accelerated towards the material to be etched, and the etching reaction is enhanced in the direction of travel of the ion. RIE is an anisotropic etching technique. Trenches and pits many microns deep of arbitrary shape and with vertical sidewalls can be etched by prior art techniques in a variety of materials, including silicon, oxide, and nitride. RIE is not limited by the crystal planes of polysilicon. Dry etching techniques can be combined with wet etching to form various micro devices. “V” shaped grooves or pits with tapered sidewalls can be formed in silicon by anisotropic etching with KOH etchant. Another etching technique, with roots in semiconductor processing, utilizes plasma etching.
As shown in
While the lenses 130 shown in the embodiments of
Another example embodiment of a method of forming the lenses 130 comprises embossing a depression 137 into the temporary carrier 120 using a lens stamp 147 (
Once the lenses 130 are formed, for example as shown in
As illustrated in
Thus, similarly, once the
As illustrated in
Another alternative temporary carrier embodiment would be for both temporary carriers (upper and lower molds) 110, 120, 220 to be soluble, but not with the same solute. For example, carrier 110 could be dissolved with water (e.g., polycarbonate, polyvinyl alcohol, etc.) while carrier 120 is not water soluble, but solvent soluble (e.g., polynorborene) instead. Also, some materials such as soluble waxes can be used that are soluble in warm water, but not in cool water that is below a certain temperature. In this embodiment, both temporary carriers 110, 120 can be water soluble, however, one (e.g., temporary carrier 110) can be formed of a material capable of being dissolved with cool water (e.g., PVA), which will not affect the other carrier (e.g., temporary carrier 120). Then, when the lower mold is ready for removal, it can be dissolved using hot water (e.g., wax), leaving the lenses 130 in place on the MEMS structure 150. Another approach is to use a UV releasable material in the temporary carrier 120. Using this approach, the temporary carrier 120 will release from the lenses 130 when exposed to UV radiation.
It should be appreciated that the MEMS structures 150, 250 shown in
As shown in
Alternatively, as shown in
It should also be appreciated, as shown in
Signals from the imaging device 400 are typically read out a row at a time using a column parallel readout architecture. The timing and control circuit 432 selects a particular row of pixels in the pixel array 406 by controlling the operation of a row addressing circuit 434 and row drivers 440. Signals stored in the selected row of pixels are provided to a readout circuit 442. The signals are read from each of the columns of the array sequentially or in parallel using a column addressing circuit 444. The pixel signals, which include a pixel reset signal Vrst and image pixel signal Vsig, are provided as outputs of the readout circuit 442, and are typically subtracted in a differential amplifier 460 with the result digitized by an analog-to-digital (AID) converter 464 to provide digital pixel signals. The digital pixel signals represent an image captured by an example pixel array 406 and are processed in an image processing circuit 468 to provide an output image.
System 500, e.g., a digital still or video camera system, generally comprises a central processing unit (CPU) 502, such as a control circuit or microprocessor for conducting camera functions that communicates with one or more input/output (I/O) devices 506 over a bus 504 and for controlling the MEMS structures that adjust the distance of the lens from the pixel array. Imaging device 400 also communicates with the CPU 502 over the bus 504. The processor system 500 also includes random access memory (RAM) 510, and can include removable memory 515, such as flash memory, which also communicates with the CPU 502 over the bus 504. The imaging device 400 may be combined with the CPU processor with or without memory storage on a single integrated circuit or on a different chip than the CPU processor. In a camera system, a MEMS wafer 200, 300 according to various embodiments described herein may be used to focus image light onto the pixel array 406 of the imaging device 400 and an image is captured when a shutter release button 522 is pressed.
While embodiments have been described in detail in connection with the embodiments known at the time, it should be readily understood that the claimed invention is not limited to the disclosed embodiments. Rather, the embodiments can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described. For example, while some embodiments are described in connection with a CMOS pixel imaging device, they can be practiced with any other type of imaging device (e.g., CCD, etc.) employing a pixel array or a camera using film instead of a pixel array. Also, although the embodiments depicted herein show multiple MEMS and lenses arranged on each substrate, it should be understood that in practice either many MEMS and lenses (tens, hundreds, or thousands) may be formed at the same time on each substrate, or a single MEMS and lens may be formed at the same time on each substrate. Accordingly, the claimed invention is not limited by the embodiments described herein but is only limited by the scope of the appended claims.
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|Patente citante||Fecha de presentación||Fecha de publicación||Solicitante||Título|
|US8885272 *||3 May 2011||11 Nov 2014||Omnivision Technologies, Inc.||Flexible membrane and lens assembly and associated method of lens replication|
|US9001257 *||23 Dic 2009||7 Abr 2015||DigitalOptics Corporation MEMS||Wafer scale optics|
|Clasificación de EE.UU.||359/819, 359/619|
|Clasificación cooperativa||G02B26/0875, G02B7/08, G02B3/0075, G02B3/0031, Y10T156/1039|
|Clasificación europea||G02B26/08R, G02B3/00A1R, G02B7/08, G02B3/00A5|
|14 Ene 2009||AS||Assignment|
Owner name: APTINA IMAGING CORPORATION, CAYMAN ISLANDS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:LAKE, RICK;BOETTIGER, ULRICH;HEDGE, SHASHIKANT;AND OTHERS;SIGNING DATES FROM 20081203 TO 20090112;REEL/FRAME:022107/0979
|22 Sep 2014||FPAY||Fee payment|
Year of fee payment: 4