1. Field of the Disclosure
The present invention is generally related to photodiodes, and more specifically, the present invention is directed to photodiodes utilized in photon sensors.
2. Background
An image capture device includes an image sensor and an imaging lens. The imaging lens focuses light onto the image sensor to form an image, and the image sensor converts the light into electric signals. The electric signals are output from the image capture device to other components of a host electronic system. The electronic system may be, for example, a mobile phone, a computer, a digital camera or a medical device.
There is a continuing demand to reduce the size of image sensors, which results in the smaller pixel cells for an image sensor with the same resolution. One type of photodetector that may be used in an image sensor or in a light detector is a single photon avalanche diode (SPAD). A SPAD normally needs a guard ring or isolation to overcome the problem of premature edge breakdown and interference between adjacent pixels. Known designs to create the guard ring or isolation increase the area of each pixel cell and sacrifices fill factor. Furthermore, as image sensors are miniaturized, the pixel cells contained therein suffer from increased dark current rates.
Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one having ordinary skill in the art that the specific detail need not be employed to practice the present invention. In other instances, well-known materials or methods have not been described in detail in order to avoid obscuring the present invention.
Reference throughout this specification to “one embodiment”, “an embodiment”, “one example” or “an example” means that a particular feature, structure or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment”, “in an embodiment”, “one example” or “an example” in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures or characteristics may be combined in any suitable combinations and/or subcombinations in one or more embodiments or examples. Particular features, structures or characteristics may be included in an integrated circuit, an electronic circuit, a combinational logic circuit, or other suitable components that provide the described functionality. In addition, it is appreciated that the figures provided herewith are for explanation purposes to persons ordinarily skilled in the art and that the drawings are not necessarily drawn to scale.
Examples in accordance with the teaching of the present invention describe a photon sensor including enhanced photon detection devices with biased deep trench isolation in accordance with the teachings of the present invention. In one example, the biased deep trench isolation structures are capacitive type isolation structures. As will be shown, in various examples, photon detection devices in accordance with the teachings of the present invention utilize a P enhanced single photon avalanche diode (SPAD) structure with no guard ring required. In addition, in various examples, a biased deep trench isolation (DTI) structure is included to provide isolation using much less area when compared with known isolation techniques, which allows pixels to be placed much closer together in a photon sensor in accordance with the teachings of the present invention. In one example, the DTI is formed with polysilicon and may be biased to reduce dark current in a photo collection area the SPAD in accordance with the teachings of the present invention. Furthermore, the utilization of a biased DTI in accordance with the teachings of the present invention allows a SPAD to be separated from its quenching circuit and allows the wells of the SPAD and the quenching circuit to be biased at different voltages.
To illustrate,
In one example, each pixel 110 converts a photon event into a digital signal pulse. In various examples, photon data from each pixel 110 may be read out by readout circuitry 104 through readout columns 112 as shown. In various examples, readout circuitry 104 includes counter circuitry 105 coupled to receive photon data to count the photon events, which are indicated in the digital signal pulses received from each pixel 110. In various examples, readout circuitry 104 may also include, time to digital converter (TDC) circuitry 107 coupled to counter circuitry 105 to record photon timing information associated with the photon events in the photon data received from each pixel 110. In one example, the photon data, which in one example includes the count and timing information, is then transferred to function logic 106. Function logic 106 may simply store the photon data or may even manipulate the photon data by performing post processing and/or analysis. In one example, readout circuitry 104 may read out a row of photon data at a time along readout column lines (illustrated) or may read out the photon data using a variety of other techniques (not illustrated), such as a serial read out or a full parallel read out of all pixels simultaneously.
In one example, control circuitry 108 is coupled to pixel array 102 to control operational characteristics of pixel array 102. For example, control circuitry 108 may generate a shutter signal for controlling photon data acquisition. In one example, the shutter signal is a global shutter signal for simultaneously enabling all pixels within pixel array 102 to simultaneously capture their respective photon data during a single acquisition window.
As shown in the illustrated example, photon detection device 210 also includes one or more deep trench isolation (DTI) structures 222A, 222B and 222C disposed in the semiconductor material 216. As shown
In addition, each DTI structure 222A, 222B and 222C is filled with lightly doped semiconductor material. For instance, example
The example depicted in
In operation, it is appreciated that the biased DTI structures 222A, 222B and 222C provide isolation between the regions of the semiconductor material 216 on opposite sides of the respective biased DTI structure. To illustrate, biased DTI structure 222B isolates the first region 216A of semiconductor material 216, which is located on the left hand side of biased DTI structure 222B in
As shown in the depicted example, photodiode 214 is adapted to be illuminated with light 220 that is directed through the back side 228 of semiconductor material 216. In another example (not shown), it is appreciated that photodiode 214 may be adapted to be illuminated with light 220 that is directed through the front side of semiconductor material 216. In the example depicted in
In the example depicted in
It is appreciated that another feature of the enhanced photon detection device 210 shown in
As shown in the depicted example, photon sensor 302 also includes a biased DTI structure 322, which is substantially similar to biased DTI structures 222A, 222B and 222C of
Another feature included in photon sensor 302 as illustrated in the example depicted in
Therefore, it is appreciated that example P enhanced SPAD photodiodes 314A, 314B, 314C and 314D of
The above description of illustrated examples of the present invention, including what is described in the Abstract, are not intended to be exhaustive or to be limitation to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible without departing from the broader spirit and scope of the present invention.
These modifications can be made to examples of the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims. Rather, the scope is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation. The present specification and figures are accordingly to be regarded as illustrative rather than restrictive.
Number | Name | Date | Kind |
---|---|---|---|
7838956 | McCarten et al. | Nov 2010 | B2 |
8188563 | Finkelstein et al. | May 2012 | B2 |
8445992 | Hsin et al. | May 2013 | B2 |
8723100 | Sanfilippo et al. | May 2014 | B2 |
8994138 | Roy et al. | Mar 2015 | B2 |
20050184353 | Mouli | Aug 2005 | A1 |
20080265348 | Maas et al. | Oct 2008 | A1 |
20090184384 | Sanfilippo et al. | Jul 2009 | A1 |
20100148040 | Sanfilippo et al. | Jun 2010 | A1 |
20100163925 | Ishibashi et al. | Jul 2010 | A1 |
20110272561 | Sanfilippo et al. | Nov 2011 | A1 |
20120153423 | Lee | Jun 2012 | A1 |
20120261730 | Chen et al. | Oct 2012 | A1 |
Number | Date | Country |
---|---|---|
H 05-211321 | Aug 1993 | JP |
2005-101864 | Apr 2005 | JP |
2007-005697 | Jan 2007 | JP |
200519697 | Mar 2007 | TW |
WO 2012032353 | Mar 2012 | WO |
Entry |
---|
Karami, M. A., “Deep-submicron CMOS Single Photon Detectors and Quantum Effects,” Technische Universiteit Delft, Netherlands, 2011 (121 pages). |
EP 14162895.8—Extended European Search Report, issued Jun. 23, 2014 (6 pages). |
JP Patent Application No. 2014-071001—Japanese Office Action and Search Report, with English Translation, issued Apr. 13, 2015 (6 pages). |
TW Patent Application No. 102139380—Taiwanese Office Action and Search Report, with English Translation, issued Apr. 10, 2015 (29 pages). |
KR Patent Application No. 2014-0037936—Korean Office Action, with English Translation, issued Apr. 29, 2015 (15 pages). |
Number | Date | Country | |
---|---|---|---|
20140291481 A1 | Oct 2014 | US |