HK1212511B - Image sensor having a gapless microlenses - Google Patents

Abstract

The subject application is related to an image sensor having a gapless microlenses. An image sensor includes a plurality of photosensitive devices arranged in a semiconductor substrate. A planar layer is disposed over the plurality of photosensitive devices in the semiconductor substrate. A plurality of first microlenses comprised of a lens material is arranged in first lens regions on the planar layer. A plurality of lens barriers comprised of the lens material is arranged on the planar layer to provide boundaries that define second lens regions on the planar layer. A plurality of second microlenses comprised of the lens material is formed within the boundaries provided by the plurality of lens barriers that define the second lens regions on the planar layer. The plurality of lens barriers are integrated with respective second microlenses after a reflow process of the plurality of second microlenses.

Description

Image sensor with gapless micro-lenses

Technical Field

The present invention relates generally to imaging, and more specifically, the present invention is directed to a high dynamic range image sensor with gapless microlenses.

Background

Image sensors have become ubiquitous. Image sensors are widely used in digital still cameras, cellular phones, surveillance cameras, as well as medical, automotive and other applications. Technology for manufacturing image sensors, such as Complementary Metal Oxide Semiconductor (CMOS) image sensors (CIS), continues to progress substantially. For example, the demand for higher resolution and lower power consumption has encouraged further miniaturization and integration of these image sensors.

High Dynamic Range (HDR) image sensors have become useful for many applications. In general, common image sensors, including, for example, Charge Coupled Devices (CCDs) and CMOS image sensors, have a dynamic range of about 70dB dynamic range. In contrast, the human eye has a dynamic range of up to about 100 dB. There are a number of situations in which an image sensor with increased dynamic range is beneficial. For example, image sensors with dynamic ranges greater than 100dB dynamic range are needed in the automotive industry to handle different driving conditions, such as driving from a dark tunnel into bright sunlight. Indeed, many applications may require an image sensor with a dynamic range of at least 90dB or higher to accommodate various lighting conditions ranging from low-light conditions to bright-light conditions.

One of the challenges in providing miniaturized higher resolution image sensors is that the gap distance between the microlenses in known image sensors limits the density of the microlenses in the image sensor. Indeed, as the gap between lenses becomes smaller, the risk of adjacent microlenses merging together during the reflow process increases, which reduces yield. Thus, maintaining a minimum gap distance between microlenses has resulted in reduced fill factors and lower quantum efficiencies in known image sensors.

Disclosure of Invention

According to one aspect, an image sensor includes: a plurality of photosensitive devices arranged in a semiconductor substrate; a planar layer disposed over the plurality of photosensitive devices in the semiconductor substrate; a plurality of first microlenses composed of a lens material and arranged in first lens regions on the planar layer; a plurality of lens barriers comprised of the lens material and arranged on the planar layer to provide a boundary defining a second lens region on the planar layer; and a plurality of second microlenses composed of the lens material and formed within the boundaries provided by the plurality of lens barriers defining the second lens regions on the planar layer, wherein the plurality of lens barriers are integrated within the respective second microlenses after a reflow process of the plurality of second microlenses.

According to another aspect, an imaging system includes: a pixel array including a plurality of photosensitive devices arranged in a semiconductor substrate; a planar layer disposed over the plurality of photosensitive devices in the semiconductor substrate; a plurality of first microlenses composed of a lens material and arranged in first lens regions on the planar layer; a plurality of lens barriers comprised of the lens material and arranged on the planar layer to provide a boundary defining a second lens region on the planar layer; a plurality of second microlenses composed of the lens material and formed within the boundaries provided by the plurality of lens barriers defining the second lens regions on the planar layer, wherein the plurality of lens barriers are integrated within the respective second microlenses after a reflow process of the plurality of second microlenses; control circuitry coupled to the pixel array to control operation of the pixel array; and readout circuitry coupled to the pixel array to readout image data from the pixel array.

Drawings

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.

Figure 1 is a diagram illustrating one example of an imaging system including an example HDR image sensor with gapless microlenses, according to the teachings of this disclosure.

FIG. 2 is a schematic diagram illustrating one example of an HDR pixel circuit of an image sensor including multiple photosensitive devices according to the teachings of this disclosure.

Figure 3A illustrates a top view of one example of a plurality of first microlenses and a plurality of lens barriers patterned in an example image sensor, according to the teachings of this disclosure.

Figure 3B illustrates a cross-sectional view of an example of a plurality of lens barriers patterned in an example image sensor, according to the teachings of this disclosure.

FIG. 3C illustrates a top view of an example of a plurality of first microlenses and a plurality of lens stops after a first reflow process of an example image sensor, according to teachings of the disclosure.

Figure 3D illustrates a cross-sectional view of an example of a plurality of lens barriers after a first reflow process of an example image sensor, according to teachings of the disclosure.

Figure 3E illustrates a top view of an example of a plurality of second microlenses patterned in an example image sensor after the first plurality of microlenses and the plurality of lens barriers have been reflowed, according to the teachings of this disclosure.

Figure 3F illustrates a cross-sectional view of an example of a plurality of second microlenses and a plurality of lens barriers patterned in an example image sensor, according to the teachings of this disclosure.

Figure 3G illustrates a top view of an example of a plurality of second microlenses and a plurality of lens stops after a second reflow process of an example image sensor, according to teachings of this disclosure.

Figure 3H illustrates a cross-sectional view of an example of a plurality of second microlenses and a plurality of lens stops after a second reflow process of an example image sensor, according to teachings of this disclosure.

Figure 4A illustrates a top view of another example of a plurality of first microlenses and a plurality of lens barriers patterned in an example image sensor, according to the teachings of this disclosure.

Figure 4B illustrates a cross-sectional view of an example of a plurality of lens barriers patterned in an example image sensor, according to teachings of this disclosure.

FIG. 4C illustrates a top view of an example of a plurality of first microlenses and a plurality of lens stops after a first reflow process of an example image sensor, according to teachings of the disclosure.

Figure 4D illustrates a cross-sectional view of an example of a plurality of lens barriers after a first reflow process of an example image sensor, according to teachings of the disclosure.

Figure 4E illustrates a top view of another example of a plurality of second microlenses patterned in an example image sensor after the first plurality of microlenses and the plurality of lens stops have been reflowed, according to the teachings of this disclosure.

Figure 4F illustrates a cross-sectional view of an example of a plurality of second microlenses and a plurality of lens barriers patterned in an example image sensor, according to the teachings of this disclosure.

Figure 4G illustrates a top view of an example of a plurality of second microlenses and a plurality of lens stops after a second reflow process of an example image sensor, according to teachings of this disclosure.

Figure 4H illustrates a cross-sectional view of an example of a plurality of second microlenses and a plurality of lens stops after a second reflow process of an example image sensor, according to teachings of this disclosure.

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 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.

Detailed Description

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the specific details 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," "in one example," or "in 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 combination and/or sub-combination in one or more embodiments or examples. The particular features, structures, or characteristics may be included in integrated circuits, electronic circuits, combinational logic circuits, or other suitable components that provide the described functionality. Further, it should be understood that the drawings provided herein are for explanation purposes to persons of ordinary skill in the art and that the drawings are not necessarily drawn to scale.

An embodiment in accordance with the teachings of this disclosure describes an image sensor having a plurality of gapless microlenses. Using gapless microlenses provided in accordance with the teachings of the present disclosure, the fill factor is increased and improved quantum efficiency is provided to example image sensors in accordance with the teachings of the present disclosure. In various examples provided for purposes of explanation, the image sensor is an HDR image sensor that includes a first plurality of microlenses optically coupled to a short integrated photosensitive device of the image sensor and a second plurality of microlenses optically coupled to a long integrated photosensitive device of the image sensor. As will be described in various examples, a plurality of lens barriers made of lens material are arranged on a planar layer of an image sensor to provide a boundary that defines a second lens region on the planar layer, providing a gapless microlens, in accordance with the teachings of this disclosure.

To illustrate, FIG. 1 is a diagram showing generally one example of an HDR imaging system 100 including an example pixel array 102 having pixels 110 in accordance with the teachings of this disclosure. In one example, the pixel 110 may be an HDR pixel including at least a short integrated photosensitive device and a long integrated photosensitive device. In one example, a short integrated photosensitive device per pixel has a smaller exposure area and a higher total doping concentration than a long integrated photosensitive device of the pixel. Accordingly, in the depicted example, the first plurality of microlenses optically coupled to the short integrated photosensitive devices has a smaller area than the second plurality of microlenses optically coupled to the long integrated photosensitive devices, in accordance with the teachings of this disclosure.

In one example, a plurality of lens barriers made of the same lens material as the first and second plurality of microlenses are also arranged on the planar layer of the image sensor to provide a boundary defining a second lens region on the planar layer to provide gapless microlenses in accordance with the teachings of this disclosure. As shown in the depicted example, the HDR imaging system 100 includes a pixel array 102 coupled to control circuitry 108 and readout circuitry 104, the readout circuitry 104 coupled to functional logic 106.

In one example, pixel array 102 is a two-dimensional (2D) array of imaging sensors or pixels 110 (e.g., pixels P1, P2 …, Pn). In one example, each pixel 110 is a CMOS imaging pixel that includes at least a short integrated photosensitive device and a long integrated photosensitive device. As illustrated, each pixel 110 is arranged in rows (e.g., rows R1-Ry) and columns (e.g., columns C1-Cx) to obtain image data of a person, place, object, etc., which may be used to present an image of the person, place, object, etc.

In one example, after each pixel 110 has obtained its image data or image charge, the image data is read out by readout circuitry 104 through readout column 112 and then transferred to functional logic 106. In various examples, the readout circuitry 104 may include amplification circuitry, analog-to-digital (ADC) conversion circuitry, or other circuitry. Function logic 106 may simply store the image data or even manipulate the image data by applying post-image effects (e.g., crop, rotate, remove red-eye, adjust brightness, adjust contrast, or otherwise). In one example, readout circuitry 104 can readout a row of image data at a time along readout column lines (shown) or can readout the image data using a variety of other techniques (not shown), such as a serial readout or a full parallel readout of all pixels simultaneously.

In one example, control circuitry 108 is coupled to pixel array 102 to control operating characteristics of pixel array 102. For example, the control circuitry 108 may generate a shutter signal for controlling image acquisition. In one example, the shutter signal is a global shutter signal for simultaneously enabling all pixels within the pixel array 102 to simultaneously capture their respective image data during a single acquisition window. In another example, the shutter signal is a rolling shutter signal such that each row, column, or group of pixels is successively enabled during successive acquisition windows.

FIG. 2 is a schematic illustrating one example of a pixel 210 according to the teachings of this disclosure. In one example, it should be appreciated that the pixel 210 may be one of the plurality of pixels 110 included in the example pixel array 102 of the HDR image sensor 100 illustrated in fig. 1 above. It should be appreciated that the pixels 210 are provided for purposes of explanation and thus represent only one possible architecture for implementing each pixel within the pixel array 102 of fig. 1, and that examples in accordance with the teachings of this disclosure are not limited to a particular pixel architecture. Indeed, persons of ordinary skill in the art having benefit of the present disclosure will appreciate that the present teachings are applicable to 3T, 4T, 5T designs, as well as various other suitable pixel architectures in accordance with the teachings of the present disclosure.

As shown in the example depicted in FIG. 2, pixel 210 includes a short integrated photosensitive device PD_S216 and long integrated photosensitive device PD_L214. In one example, a long integrated Photosensitive Device (PD)_L214 has a larger than short integrated photosensitive device PD_S216, of the exposure area. Thus, optically coupled to a long integrated photosensitive device PD_LThe microlens of 214 correspondingly has an area greater than the area of the microlens optically coupled to the short integrated photosensitive device. In the example, a long integrated photosensitive device PD_L214 have a higher sensitivity to incident light and are therefore used for lower light intensity sensing. On the other hand, because of the short integration of the photosensitive device PD_S216 have less exposure area, so it is integrated with long photosensitive device PD_L214 are less sensitive to light than they are to and therefore are used for higher light intensity sensing. By utilizing long integrated photosensitive devices PD in the pixels 210_L214 and short integration photosensitive device PD_SHDR imaging sensing is achieved 216.

Continuing with the example depicted in FIG. 2, accumulation is on a long integrated photosensitive device PD_L214 in response to the control signal TX_LThrough transfer transistor T1_L218 is switched to the floating drain FD228 and accumulates in the short integrated photosensitive device PD_S216 in response to the control signal TX_SThrough transfer transistor T1_S220 to floating drain FD 228.

As shown in the example, pixel 210 also includes an amplifier transistor T3224 having a gate terminal coupled to floating drain FD 228. Thus, in the illustrated example, the PD is from a long integrated photosensitive device_L214 and short integration photosensitive device PD_S216 are individually switched to the floating drain FD228 coupled to the amplifier transistor T3224. In one example, the amplifier transistor T3224 is coupled in a source follower configuration as shown, which thus amplifies an input signal at the gate terminal of the amplifier transistor T3224 to an output signal at the source terminal of the amplifier transistor T3224. As shown, a row select transistor T4226 is coupled to the source terminal of the amplifier transistor T3224 to selectively switch the output of the amplifier transistor T3224 to the read-out column 212 in response to a control signal SEL. As shown in the example, pixel 210 also includes a reset transistor 241 coupled to floating drain FD228, a long integrated photosensitive device PD_L214 and short integration photosensitive device PD_S216, the reset transistor 214 may be used to reset the charge accumulated in the pixel 210 in response to a reset signal RST. In one example, long integrated photosensitive device PD accumulated at floating drain FD228 in accordance with the teachings of this disclosure_L214 and short integrated photosensitive devicesPD_S216 may be reset during an initialization period of pixel 210 or, for example, each time after charge information has been read out of pixel 210 and is present in long integrated photosensitive device PD_L214 and short integration photosensitive device PD_S216 to be reset before accumulating charge to acquire a new HDR image.

Figure 3A illustrates a top view of one example of a plurality of first microlenses 330 and a plurality of lens barriers 332 patterned in an example image sensor 300, according to the teachings of this disclosure. In the depicted example, it should be noted that the pixel array 302 of the image sensor 300 is arranged in a Bayer (Bayer) pattern. As shown, the bayer pattern uses a checkerboard pattern with alternating rows of color filters. The bayer pattern has twice as many green (G) pixels as red (R) or blue (B) pixels, and is arranged in alternating rows of red (R) sandwiched between green (G) and alternating rows of blue (B) sandwiched between green (G). This pattern takes advantage of the preference of the human eye to consider green brightness as the strongest contributor in defining sharpness. Furthermore, the bayer pattern produces the same image regardless of how you hold the camera (in either a landscape mode or a portrait mode).

As shown in the example depicted in fig. 3A, the first plurality of microlenses 330 is arranged in a first lens region on a planar layer of the image sensor 330. In the example, each of the plurality of microlenses 330 is optically coupled through an underlying planar layer to a corresponding photosensitive device disposed in an underlying semiconductor substrate of the image sensor 300. The example depicted in fig. 3A also illustrates that there are also a plurality of lens barriers 332 arranged on a planar layer, as shown. In the example, the plurality of lens barriers 332 are made of the same lens material having the same index of refraction as the first plurality of microlenses 330. In one example, the first plurality of microlenses 330 and the plurality of lens barriers 332 have a different index of refraction than the planar layer on which they are patterned. As will be discussed, in accordance with the teachings of this disclosure, a plurality of lens barriers 332 are arranged on the planar layer to provide a boundary that defines a second lens region on the planar layer. In various examples, the lens material used in the image sensor 300 may be formed of a polymer-based material or the like. As shown in the example illustrated in fig. 3A, a plurality of lens barriers 332 are arranged proximate to a boundary defined between two second lens regions on the planar layer.

For example, fig. 3A shows a plurality of lens barriers 332 arranged within a green (G) second lens region proximate to boundaries with adjacent red (R) and blue (B) second lens regions. Of course, it should be understood that the example illustrated in fig. 3A is provided for illustration purposes and that the plurality of lens barriers 332 may be arranged in the red (R) and blue (B) second lens regions proximate their respective boundaries with the green (G) second lens regions in accordance with the teachings of this disclosure.

FIG. 3B is a cross-sectional view of the example image sensor 300 illustrated in FIG. 3A along dashed line A-A'. Thus, similarly named and numbered elements mentioned below are coupled and function similarly to those described above. As shown in the cross-sectional example depicted in fig. 3B, a plurality of lens barriers 332 are arranged and patterned as shown on a planar layer 334 according to the teachings of the present disclosure. As shown, a planar layer 334 is disposed on a semiconductor substrate 336 in which a plurality of photosensitive devices 314 are arranged. In such an example, photosensitive device 314 may be an example of a photosensitive device included in pixel 110 or 210 discussed above in fig. 1-2. Continuing with the example shown in fig. 3B, a plurality of lens barriers 332 are arranged on a planar layer 334 to provide boundaries defining a second lens region on the planar layer in accordance with the teachings of this disclosure.

In various examples, it should be appreciated that planar layer 334 may include one or more layers of image sensor 300. For example, in one example, planar layer 334 may include one or more spacer layers and color filter layers having various combinations of red, green, blue, cyan, magenta, yellow, pure, or other suitable filters in accordance with the teachings of this disclosure.

FIG. 3C is a top view of the example image sensor 300 illustrated in FIGS. 3A-3B after a first reflow process according to the teachings of this disclosure. Thus, similarly named and numbered elements mentioned below are coupled and function similarly to those described above. As shown in the depicted example, the first reflow process allows surface tension in the first plurality of microlenses 330 and the plurality of lens barriers 332 to cause individual pieces of lens material of the first plurality of microlenses 330 and the plurality of lens barriers 332 to dome-shape and form curves.

To illustrate, FIG. 3D illustrates a cross-sectional view of the example image sensor 300 as illustrated in FIG. 3C along dashed line A-A' after a first reflow process. Thus, similarly named and numbered elements mentioned below are coupled and function similarly to those described above. As shown in the example depicted in fig. 3D, the first reflow process allows surface tension in the plurality of lens barriers 332 to cause individual pieces of lens material of the plurality of lens barriers 332 to dome-shape and form a curvature.

Figure 3E illustrates a top view of one example of a plurality of second microlenses 338 patterned in an example image sensor 300 after the first plurality of microlenses 330 and the plurality of lens barriers 332 have been reflowed as illustrated above in figures 3C-3D, according to the teachings of this disclosure. Thus, similarly named and numbered elements mentioned below are coupled and function similarly to those described above. As shown in the example depicted in fig. 3E, the second plurality of microlenses 338 is arranged in a second lens region defined by the boundary provided by the plurality of lens boundaries 332 on the planar layer 334 of the image sensor 300. In the example, each of the second plurality of microlenses 338 is optically coupled to a corresponding photosensitive device 314 disposed in an underlying semiconductor substrate 336 of the image sensor 330 through an underlying planar layer 334. In the example, the second plurality of microlenses 338 are made of the same lens material having the same index of refraction as the first plurality of microlenses 330 and the plurality of lens barriers 332. In one example, the second plurality of microlenses 338 thus also have a different index of refraction than the planarization layer 334 on which the second plurality of microlenses 338 are patterned. In the example illustrated in fig. 3E, the second plurality of microlenses 338 arranged in the green (G) second lens region are in contact with their respective lens barriers 332, while the second plurality of microlenses 338 arranged in the red (R) and blue (B) second lens regions are not in contact with the lens barriers 332, the lens barriers 332 being green (G) second lens regions in the example shown in fig. 3E.

FIG. 3F illustrates a cross-sectional view of the example image sensor 300 illustrated in FIG. 3E along dashed line A-A'. Thus, similarly named and numbered elements mentioned below are coupled and function similarly to those described above. As shown in the cross-sectional example depicted in fig. 3F, a plurality of second microlenses 338 are arranged on the planar layer 334 in second lens regions proximate to the plurality of lens barriers 332 as shown according to the teachings of the present disclosure. As shown, a planar layer 334 is disposed on a semiconductor substrate 336 in which a plurality of photosensitive devices 314 are arranged. In the example, each of the plurality of second microlenses 338 is also optically coupled to a corresponding one of the photosensitive devices 314 in the semiconductor substrate 336 through the planarization layer 334.

Figure 3G illustrates a top view of the example image sensor 300 illustrated in figures 3A-3F after a second reflow process (which occurs after the first reflow process) according to the teachings of this disclosure. Thus, similarly named and numbered elements mentioned below are coupled and function similarly to those described above. In the illustrated example, as shown, the second plurality of microlenses 338 are reflowed during a second reflow process. As shown in the example depicted in fig. 3G, the second reflow process allows surface tension in the second plurality of microlenses 338 to cause individual lens material in the second plurality of microlenses 338 to dome-shape and form curves. As shown in the example in figure 3G, each of the plurality of lens barriers 332 is arranged proximate to a respective boundary defined between two of the second plurality of microlenses 338 on the planar layer 334, in accordance with the teachings of this disclosure.

To illustrate, FIG. 3H illustrates a cross-sectional view of the example image sensor 300 as illustrated in FIG. 3G along dashed line A-A' after the second reflow process. Thus, similarly named and numbered elements mentioned below are coupled and function similarly to those described above. As shown in the example depicted in fig. 3H, the second reflow process allows surface tension in the lens material of the second plurality of microlenses 338 to dome-shape and form a curve. In the example, as shown, each of the lens barriers 332 is integrated with its respective microlens 338. Indeed, as discussed in one example, according to the teachings of this disclosure, the lens barriers 332 and the microlenses are made of the same lens material and have the same refractive index, such that the lens barriers 332 are fully integrated within their respective microlenses 338 after the second reflow process.

As shown, the plurality of lens barriers 332, which in the example depicted in fig. 3H are arranged within the green (G) second lens region proximate to the boundaries with the adjacent red (R) and blue (B) second lens regions, provide a boundary such that when the second plurality of microlenses 338 are reflowed in response to the second reflow process, the plurality of lens barriers 332 prevent lens material from adjacent microlenses 338 from merging with one another. Thus, because the use of the plurality of lens barriers 332 prevents the lens material of the microlenses 338 from merging together, the previously desired minimum gap distance between the second plurality of microlenses 338 is no longer necessary. Thus, an image sensor 300 having microlenses with no or little gaps is provided according to the teachings of this disclosure. According to the teachings of this disclosure, using gapless or nearly gapless microlenses as shown in the depicted examples increases the fill factor of image sensor 300, which also improves the quantum efficiency of image sensor 300.

Figure 4A illustrates a top view of another example of a plurality of first microlenses 430 and a plurality of lens barriers 432 patterned in an example image sensor 400, according to the teachings of this disclosure. In the depicted example, it should be noted that pixel array 402 of image sensor 400 is arranged in a bayer pattern. As can be observed, it should be noted that the image sensor 400 shown in fig. 4A shares many similarities with the image sensor 300 described above in fig. 3A-3H. Thus, similarly named and numbered elements mentioned below are coupled and function similarly to those described above. One difference between the image sensor 400 of fig. 4A and the image sensor 300 of fig. 3A to 3H is: a plurality of lens barriers 432 are arranged in pairs as shown on a planar layer of the image sensor 400 and will be discussed in further detail below.

Continuing with the example depicted in fig. 4A, a first plurality of microlenses 430 is arranged in a first lens region on a planar layer of the image sensor 400. In the example, each of the plurality of microlenses 430 is optically coupled through an underlying planar layer to a corresponding photosensitive device disposed in an underlying semiconductor substrate of the image sensor 400. The example depicted in fig. 4A also illustrates a plurality of lens barriers 432 disposed in pairs on a planar layer as shown. In the example, the plurality of lens barriers 432 are made of the same lens material having the same index of refraction as the first plurality of microlenses 430. In one example, the first plurality of microlenses 430 and the plurality of lens barriers 432 have a different index of refraction than the planar layer on which they are patterned. As will be discussed, in accordance with the teachings of this disclosure, a plurality of lens barriers 432 are arranged in pairs on a planar layer to provide a boundary that defines a second lens region on the planar layer. In various embodiments, the lens material used in image sensor 400 may be formed from a polymer-based material or similar materials. As shown in the example illustrated in fig. 4A, a plurality of lens barriers 432 are arranged proximate to a boundary between two lens regions defined on a planar layer.

FIG. 4B illustrates a cross-sectional view of the example image sensor 400 illustrated in FIG. 4A along dashed line B-B'. Thus, similarly named and numbered elements mentioned below are coupled and function similarly to those described above. As shown in the cross-sectional example depicted in fig. 4B, a plurality of lens boundaries 432 are arranged and patterned in pairs on a planar layer 434 as shown in accordance with the teachings of this disclosure. As shown, the planarization layer 434 is disposed in a semiconductor substrate 436 in which a plurality of photosensitive devices 414 are disposed. In such an example, photosensitive device 414 may be an example of a photosensitive device included in pixel 110 or 210 discussed above in fig. 1-2. Continuing with the example shown in figure 4B, each of the plurality of lens barriers 432 is arranged in pairs on the planar layer 434 to provide boundaries defining a second lens region on the planar layer in accordance with the teachings of this disclosure.

In various examples, it should be appreciated that planar layer 434 may include one or more layers of image sensor 400. For example, in one example, the planar layer 434 may include one or more spacer layers and color filter layers having various combinations of red, green, blue, cyan, magenta, yellow, pure, or other suitable filters in accordance with the teachings of this disclosure.

FIG. 4C illustrates a top view of the example image sensor 400 illustrated in FIGS. 4A-4B after a first reflow process according to the teachings of this disclosure. Thus, similarly named and numbered elements mentioned below are coupled and function similarly to those described above. As shown in the depicted example, the first reflow process allows surface tension in the first plurality of microlenses 430 and the plurality of lens barriers 432 to cause individual lens materials in the first plurality of microlenses 430 and the plurality of lens barriers 432 to dome-shape and form a curvature.

To illustrate, FIG. 4D illustrates a cross-sectional view of the example image sensor 400 as illustrated in FIG. 4C along dashed line B-B' after the first reflow process. Thus, similarly named and numbered elements mentioned below are coupled and function similarly to those described above. As shown in the example depicted in fig. 4D, the first reflow process allows surface tension in the plurality of lens barriers 432 to cause individual lens materials of the plurality of lens barriers 432 to dome-shape and form a curvature.

Figure 4E illustrates a top view of one example of a plurality of second microlenses 438 patterned in an example image sensor 400 after the first plurality of microlenses 430 and the plurality of lens barriers 432 have been reflowed as illustrated above in figures 4C-4D, according to the teachings of this disclosure. Thus, similarly named and numbered elements mentioned below are coupled and function similarly to those described above. As shown in the example depicted in fig. 4E, a second plurality of microlenses 438 is arranged in a second lens region defined by the boundary provided by the plurality of lens boundaries 432 on the planar layer 434 of the image sensor 400. In the example, each of the second plurality of microlenses 438 is optically coupled to a corresponding photosensitive device 414 disposed in an underlying semiconductor substrate 436 of the image sensor 400 through an underlying planarization layer 434. In the example, the second plurality of microlenses 438 is made of the same lens material having the same index of refraction as the first plurality of microlenses 430 and the plurality of lens barriers 432. In one example, the second plurality of microlenses 438 have a different index of refraction than the planarization layer 434 on which the second plurality of microlenses 438 is patterned. As shown in the example illustrated in fig. 4E, each of the second plurality of microlenses 438 is in contact with its respective lens barrier 432 within its respective second lens region.

FIG. 4F illustrates a cross-sectional view of the example image sensor 400 illustrated in FIG. 4E along dashed line B-B'. Thus, similarly named and numbered elements mentioned below are coupled and function similarly to those described above. As shown in the cross-sectional example depicted in fig. 4F, a plurality of second microlenses 438 are arranged as shown on planar layer 334 in a second lens region proximate to a plurality of lens barriers 432 according to the teachings of the present disclosure. As shown, the planarization layer 434 is disposed on a semiconductor substrate 436 in which a plurality of photosensitive devices 414 are disposed. In the example, each of the plurality of second microlenses 4338 is also optically coupled to a corresponding one of the photosensitive devices 414 in the semiconductor substrate 436 through the planarization layer 434.

Figure 4G illustrates a top view of the example image sensor 400 illustrated in figures 4A-4F after a second reflow process (which occurs after the first reflow process) according to the teachings of this disclosure. Thus, similarly named and numbered elements mentioned below are coupled and function similarly to those described above. In the illustrated example, as shown, the second plurality of microlenses 438 is reflowed during a second reflow process. As shown in the example depicted in fig. 4G, the second reflow process allows surface tension in the second plurality of microlenses 438 to cause individual lens material in the second plurality of microlenses 438 to dome-shape and form a curve. As shown in the example in figure 4G, each of the plurality of lens barriers 432 is arranged in pairs proximate to a defined boundary on the planar layer 434, such that each of the pair of lens barriers 432 provides a corresponding boundary that defines a portion of a respective second lens region on the planar layer 434, in accordance with the teachings of this disclosure.

To illustrate, FIG. 4H illustrates a cross-sectional view of the example image sensor 400 as illustrated in FIG. 4G along dashed line B-B' after the second reflow process. Thus, similarly named and numbered elements mentioned below are coupled and function similarly to those described above. As shown in the example depicted in fig. 4H, the second reflow process allows surface tension in the lens material of the second plurality of microlenses 438 to dome-shape and form a curve. In the example, as shown, each of the pair of lens barriers 432 is integrated with its respective microlens 438. Indeed, as discussed in one example, according to the teachings of the present disclosure, the lens barriers 432 are made of the same lens material and have the same index of refraction, such that the lens barriers 432 become fully integrated with their respective microlenses 438 after the second reflow process.

As shown in the example, according to the teachings of this disclosure, the pair of lens barriers 432 each provide a corresponding portion of the boundary such that when the second plurality of microlenses 438 is reflowed in response to the second reflow process, the plurality of lens barriers 432 prevent the lens material of the corresponding microlens 438 from merging with the lens material of the adjacent microlens 438. Thus, because the lens material of the microlenses 438 is prevented from merging together by the plurality of lens barriers 432, the previously desired minimum gap distance between the second plurality of microlenses 438 is no longer necessary. Thus, an image sensor 400 having micro-lenses with no or almost no gaps is provided in accordance with the teachings of the present invention. According to the teachings of this disclosure, using gapless or nearly gapless microlenses as shown in the depicted examples increases the fill factor of the image sensor 400, which also improves the quantum efficiency of the image sensor 400.

The above description of illustrated examples of the invention, including what is described in the abstract of the specification, is not intended to be exhaustive or to be limited 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 invention.

These modifications can be made to the 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 specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Drawing translation

FIG. 1 shows a schematic view of a

102 array of pixels

104 readout circuit

106 functional logic

108 control circuit

112 read out column

FIG. 2

212 read out column

Claims (19)

1. An image sensor, comprising:

a plurality of photosensitive devices arranged in a semiconductor substrate;

a planar layer disposed over the plurality of photosensitive devices in the semiconductor substrate;

a plurality of first microlenses composed of a lens material and arranged in first lens regions on the planar layer;

a plurality of lens barriers comprised of the lens material and arranged on the planar layer to provide a boundary defining a second lens region on the planar layer; and

a plurality of second microlenses composed of the lens material and formed within the boundaries provided by the plurality of lens barriers defining the second lens regions on the planar layer, wherein the plurality of lens barriers are integrated within the respective second microlenses after a reflow process of the plurality of second microlenses, wherein the second microlenses include green second lens regions, red second lens regions, and blue second lens regions.

2. The image sensor of claim 1, wherein the lens materials of the plurality of first microlenses, the plurality of lens barriers, and the plurality of second microlenses are the same lens material and have the same refractive index.

3. The image sensor of claim 1, wherein the lens material has a different index of refraction than the planar layer.

4. The image sensor of claim 1, wherein each of the plurality of first microlenses and each of the plurality of second microlenses is optically coupled to a corresponding one of the plurality of photosensitive devices through the planarization layer.

5. The image sensor of claim 1, wherein each of the plurality of first microlenses and each of the plurality of lens barriers includes a respective dome having a respective curvature formed during a first reflow process.

6. The image sensor of claim 5, wherein each of the plurality of second microlenses includes a respective dome having a respective curvature formed during a second reflow process that occurs after the first reflow process, wherein the reflow process of the plurality of second microlenses occurs during the second reflow process.

7. The image sensor of claim 1, wherein the plurality of lens barriers are arranged proximate to a boundary defined between two second lens regions on the planar layer.

8. The image sensor of claim 7, wherein the plurality of lens barriers are arranged within a second lens region of a first color on the planar layer.

9. The image sensor of claim 7, wherein the plurality of lens barriers are arranged in pairs on the planar layer, wherein each of the pair of lens barriers provides a corresponding boundary proximate to a portion of a respective second lens region on the planar layer.

10. An imaging system, comprising:

a pixel array including a plurality of photosensitive devices disposed in a semiconductor substrate;

a planar layer disposed over the plurality of photosensitive devices in the semiconductor substrate;

a plurality of first microlenses composed of a lens material and arranged in first lens regions on the planar layer;

a plurality of lens barriers comprised of the lens material and arranged on the planar layer to provide a boundary defining a second lens region on the planar layer;

a plurality of second microlenses composed of the lens material and formed within the boundaries provided by the plurality of lens barriers defining the second lens regions on the planar layer, wherein the plurality of lens barriers are integrated within the respective second microlenses after a reflow process of the plurality of second microlenses, wherein the second microlenses include green second lens regions, red second lens regions, and blue second lens regions;

control circuitry coupled to the pixel array to control operation of the pixel array; and

readout circuitry coupled to the pixel array to readout image data from the pixel array.

11. The imaging system of claim 10, further comprising functional logic coupled to the readout circuitry to store the image data read out of the pixel array.

12. The imaging system of claim 10, wherein the lens materials of the plurality of first microlenses, the plurality of lens barriers, and the plurality of second microlenses are the same lens material and have the same refractive index.

13. The imaging system of claim 10, wherein the lens material has a different index of refraction than the planar layer.

14. The imaging system of claim 10, wherein each of the plurality of first microlenses and each of the plurality of second microlenses is optically coupled to a corresponding one of the plurality of photosensitive devices through the planarization layer.

15. The imaging system of claim 10, wherein each of the plurality of first microlenses and each of the plurality of lens barriers includes a respective dome having a respective curvature formed during a first reflow process.

16. The imaging system of claim 15, wherein each of the plurality of second microlenses includes a respective dome having a respective curvature formed during a second reflow process that occurs after the first reflow process, wherein the reflow process of the plurality of second microlenses occurs during the second reflow process.

17. The imaging system of claim 10, wherein the plurality of lens barriers are arranged proximate to a boundary defined between two second lens regions on the planar layer.

18. The imaging system of claim 17, wherein the plurality of lens barriers are arranged within a second lens region of a first color on the planar layer.

19. The imaging system of claim 17, wherein the plurality of lens barriers are arranged in pairs on the planar layer, wherein each of the pair of lens barriers provides a corresponding boundary proximate to a portion of a respective second lens region on the planar layer.