KR20210053152A - Lens structure configured to increase quantum efficiency of image sensor - Google Patents

Abstract

Various embodiments of the present invention relate to an image sensor. The image sensor has a substrate including a plurality of sidewalls which define a plurality of protrusions along a first side of the substrate. The substrate has a first index of refraction. A photodetector is disposed within the substrate and placed under the plurality of protrusions. A plurality of microlenses are placed on the first side of the substrate. The microlenses have a second index of refraction less than the first index of refraction. The microlenses are respectively disposed laterally between and in direct contact with an adjacent pair of protrusions in the plurality of protrusions. In addition, the microlenses have a convex upper surface.

Description

Lens structure constructed to increase the quantum efficiency of an image sensor {LENS STRUCTURE CONFIGURED TO INCREASE QUANTUM EFFICIENCY OF IMAGE SENSOR}

This application claims priority to U.S. Provisional Application No. 62/928,559 filed on October 31, 2019, the contents of which are incorporated herein by reference in their entirety.

Many modern electronic devices (eg, digital cameras, optical imaging devices, etc.) include image sensors. The image sensor converts an optical image into digital data that can be expressed as a digital image. The image sensor includes an array of pixel sensors, which are unit devices for conversion of optical images into digital data. Some types of pixel sensors include charge-coupled device (CCD) and complementary metal-oxide-semiconductor (CMOS) image sensors (CIS). Compared to CCD pixel sensors, CIS is preferred because of its low power consumption, small size, fast data processing, direct data output and low manufacturing cost.

In some embodiments, the present application provides an image sensor. The image sensor comprises: a substrate comprising a plurality of sidewalls defining a plurality of protrusions along a first side of the substrate, the substrate having a first refractive index; A photo detector placed under the plurality of protrusions and disposed within the substrate; And a plurality of micro lenses overlying the first side of the substrate. The microlens has a second refractive index smaller than the first refractive index, and the microlenses are disposed between adjacent pairs of protrusions in the plurality of protrusions in each lateral direction and directly contact the adjacent pair of protrusions, each of the microlenses It has a convex upper surface.

In some embodiments, the present application provides an integrated chip. The integrated chip comprises: a substrate comprising a plurality of first protrusions along a rear surface of the substrate, the substrate comprising a first material having a first index of refraction; An interconnect structure disposed along the front surface of the substrate; A photo detector placed under the plurality of first protrusions and disposed within the substrate; A passivation layer arranged between the plurality of first protrusions and on the plurality of first protrusions-the passivation layer includes a plurality of second protrusions along an upper surface of the passivation layer, the plurality of second protrusions Different from the plurality of first protrusions, the passivation layer comprising a second material having a second refractive index different from the first refractive index; And an optical filter overlying the passivation layer.

In some embodiments, the present application provides a method of forming an image sensor. A method of forming an image sensor includes: performing an ion implantation process to define a photo detector in a substrate; Etching the first side of the substrate to define a plurality of protrusions overlying the photo detector; Depositing a dielectric layer comprising a first material over the plurality of protrusions; Depositing an anti-reflection coating (ARC) layer over the dielectric layer, the ARC layer comprising a second material different from the first material; Performing a first patterning process on the ARC layer; And defining a plurality of microlenses each having a concave upper surface by performing a second patterning process on the dielectric layer and the ARC layer. The dielectric layer is etched at a first rate during the second patterning process and the ARC layer is etched at a second rate during the second patterning process, the first rate being greater than the second rate.

Aspects of the present disclosure are best understood from the detailed description below when read in conjunction with the accompanying drawings. It should be noted that, in accordance with the general practice of the industry, various features are not drawn to scale. Indeed, the dimensions of the various features can be arbitrarily increased or decreased for clarity of discussion.
1 shows a cross-sectional view of some embodiments of an image sensor including a substrate having a plurality of protrusions, and a plurality of microlenses disposed thereon and spaced laterally between the protrusions.
2 shows a cross-sectional view of some alternative embodiments of the image sensor of FIG. 1 with a plurality of semiconductor devices disposed on the front side of a substrate.
3A and 3B show cross-sectional views of some alternative embodiments of the image sensor of FIG. 2 with an optical filter overlying a plurality of micro lenses.
4-9 illustrate cross-sectional views of some embodiments of a method of forming an image sensor including a plurality of protrusions and a plurality of microlenses disposed over the plurality of protrusions and laterally spaced between the protrusions.
FIG. 10 shows a flow chart form of a method representing some embodiments of forming an image sensor including a substrate having a plurality of protrusions, and a plurality of microlenses disposed thereon and spaced laterally between the protrusions.

The present disclosure provides many different embodiments or examples for implementing the various features of the present disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. Of course, this is merely an example and is not intended to be limited to these. For example, in the following detailed description, the formation of a first feature on or on a second feature may include an embodiment in which the first and second features are formed by direct contact, and may also include the first and second features. 2 An embodiment may be included in which additional features may be formed between the first and second features so that the features may not be in direct contact. In addition, the present disclosure may repeat reference numbers and/or letters in various examples. This repetition is for the purpose of simplicity and clarity, and such repetition itself does not affect the relationship between the various embodiments and/or configurations disclosed.

In addition, "below", "bottom", "lower", "above", "above" to describe the relationship of another element(s) or feature(s) to one element or feature shown in the figures. Spatial relative terms such as "and the like may be used herein for ease of description. Spatial relative terms are intended to cover different orientations of a device in use or in operation in addition to the orientation shown in the figures. The device may be otherwise oriented (rotated 90° or rotated in another orientation), so the spatial relative descriptors used herein can be interpreted in the same way.

A CMOS image sensor (CIS) generally includes an array of pixel regions each having a photo detector positioned within a semiconductor substrate. An optical filter (eg, a color filter, an infrared (IR) filter, etc.) is positioned above the photo detector and is configured to filter incident light provided to different photo detectors in the CIS. The photo detector is configured to generate an electrical signal corresponding to the received light upon receiving the light. The electrical signal from the photo detector can be processed by the signal processing unit to determine the image captured by the CIS. Quantum efficiency (QE) is the ratio of the number of photons that contribute to the electrical signal generated by the photo detector within the pixel area to the number of photons incident on the pixel area. It was understood that the QE of CIS could be improved with on-chip absorption enhancing structures.

The absorption enhancing structure may include a plurality of protrusions arranged along the surface of the semiconductor substrate. The absorption enhancing structure can increase absorption by reducing the reflection of incident radiation. In addition, the passivation layer overlies the absorption enhancing structure and fills the recesses between the plurality of protrusions. While forming the passivation layer over the absorption enhancing structure, an anti-reflective coating (ARC) layer is formed over the passivation layer. Subsequently, the ARC layer and the passivation layer are etched at the same rate until the top surface of the protrusion is reached so that the passivation layer has a substantially flat top surface. However, incident radiation may be reflected from the sidewalls of the protrusions away from the photo detectors underneath as they advance through the substantially flat top surface of the passivation layer to the plurality of protrusions. This may be because the incident light travels along a path approximately perpendicular to the substantially flat top surface of the passivation layer and may not be focused toward the lower photo detector. The reflected radiation can be directed towards an adjacent underlying photo detector, causing crosstalk between the photo detectors and/or being reflected away from the pixel area. Further, the reflected radiation can be directed away from the semiconductor substrate, thereby reducing incident radiation disposed on the lower photo detector. This can partially reduce the QE of the lower photo detector.

Accordingly, some embodiments of the present disclosure relate to an image sensor. The image sensor includes a substrate having a plurality of protrusions, and a plurality of microlenses each having a convex upper surface and spaced apart between the protrusions in the lateral direction and overlying the protrusions. For example, during manufacture of the image sensor, a photo detector is formed in the substrate and a plurality of protrusions are formed along the rear surface of the substrate. A passivation layer is formed over the plurality of protrusions, so that the passivation layer fills a plurality of recesses disposed between the plurality of protrusions. An ARC layer is formed over the passivation layer and partial etching is performed on the ARC layer until it reaches the top surface of the passivation layer, leaving at least a portion of the ARC layer over the passivation layer. In addition, one or more highly selective etching processes are performed on the ARC layer and the passivation layer, so that the passivation layer is etched at a higher rate than the ARC layer. This in part defines a plurality of microlenses over the plurality of protrusions, such that the microlenses are disposed between each adjacent pair of protrusions and each microlens has a convex top surface. With the convex top surface, the microlens is configured to focus the incident radiation towards a focal point between each adjacent pair of protrusions, thereby reducing reflection of the incident radiation and increasing the incident radiation directed towards the photo detector. This in turn increases the QE of the image sensor.

1 is an image sensor 100 including a substrate 104 having a plurality of protrusions 110, and a plurality of micro lenses 112 disposed on the protrusions 110 and spaced between the protrusions in the lateral direction. ) Shows a cross-sectional view of some embodiments.

The image sensor 100 includes an interconnect structure 102 disposed along the front surface 104f of the substrate 104. In some embodiments, the substrate 104 comprises any semiconductor body (e.g., bulk silicon, epitaxial silicon, other suitable semiconductor material, or the like) and/or a first type of doping (e.g., , p-type doping). The photo detector 108 is disposed within the substrate 104 and is to convert incident electromagnetic radiation 114 (e.g., photons) into electrical signals (i.e., to generate electron-hole pairs from the incident electromagnetic radiation 114). ) Is composed. The photo detector 108 includes a second doping type (eg, n-type doping) opposite to the first doping type. In some embodiments, the first doping type may be n-type and the second doping type may be p-type, or vice versa. In further embodiments, the photo detector 108 may comprise and/or consist of a photo diode. The isolation structure 106 is disposed within the substrate 104 and extends from the front surface 104f of the substrate 104 to a point above the front surface 104f. In some embodiments, the isolation structure 106 may include a dielectric material (e.g., silicon dioxide, silicon nitride, silicon carbide, etc.) and/or a shallow trench isolation (STI) structure, a deep trench isolation (DTI) structure. , Or other suitable isolation structure.

The rear surface 104b of the substrate 104 is disposed opposite the front surface 104f of the substrate 104. The rear surface 104b of the substrate 104 includes a non-planar surface defining a plurality of protrusions 110 located in a periodic pattern. Accordingly, the protrusion 110 may be or include the same material (eg, silicon) as the substrate 104. The plurality of protrusions 110 are laterally separated from each other by recesses in the rear surface 104b of the substrate 104. Each of the plurality of protrusions 110 includes opposite angled sidewalls. The protrusion 110 of the substrate 104 is configured to increase the light-receiving surface area for incident electromagnetic radiation 114 disposed on the photo detector 108, for example. This, in part, increases the sensitivity and/or quantum efficiency (QE) of the image sensor 100.

In addition, a plurality of microlenses 112 are disposed in the recesses between the protrusions 110 in the lateral direction, so that one of the microlenses 112 is disposed between the pair of protrusions 110 corresponding in the lateral direction. Is placed in The micro lenses 112 may, for example, be or include a dielectric material (eg, silicon dioxide), respectively, and/or may have a first index of refraction. It will be appreciated that other materials for micro lenses 112 are also within the scope of the present disclosure. In a further embodiment, the substrate 104 includes a semiconductor material (eg, silicon) different from the dielectric material of the micro lenses 112 and/or has a second refractive index different from the first refractive index. It will be appreciated that other materials for substrate 104 are also within the scope of the present disclosure. In some embodiments, the second index of refraction is greater than the first index of refraction. In some embodiments, the micro lenses 112 each include micro lens protrusions 112p along sidewalls of the protrusions 110 and filling the recesses between the protrusions 110. In another embodiment, the micro lenses 112 directly contact the protrusions 110. Each of the micro lenses 112 includes a convex upper surface 112us that is rounded and/or curved outward in a direction away from the protrusion 110. 1, incident electromagnetic radiation 114 enters the microlens 112 through the convex upper surface 112us (as shown by the arrows). Due to the convex top surface 112us of each micro-lens 112, the incident electromagnetic radiation 114 is angled/or significantly bent toward the focal point 119 below the convex top surface 112us. All. The focal plane 119 is vertically separated from the upper surface 110ts of the protrusion 110 by a first height h1 and vertically separated from the lower surface 110bs of the protrusion 110 by a second height h2. ). In some embodiments, the first height h1 is greater than the second height h2. In this embodiment, this mitigates incident electromagnetic radiation 114 from being reflected off the sidewall of the protrusion 110 in a direction away from the photo detector 108. In another embodiment, since the second height h2 is smaller than the first height h1, the incident angle θ ₁ of the incident electromagnetic radiation 114 on the sidewall of the protrusion 110 is considerably small, so that the light is ) Is not reflected away from it. Other electromagnetic radiation (not shown) that is not parallel to the incident electromagnetic radiation 114 and enters the microlens 112 is refracted as described above and intersects another focal point along the focal plane 120.

Further, after the incident electromagnetic radiation 114 is angled towards the focal point 119 it may traverse the sidewall of the protrusion 110. In some embodiments, since the micro lens 112 has a first index of refraction that is less than the second index of refraction of the lower protrusion 110, the incident electromagnetic radiation 114 moves the photodetector 108 from the corresponding vertical axis 122. Will be refracted towards. In other words, the low refractive index of the microlens 112 with respect to the protrusion 110 causes the incident electromagnetic radiation 114 to have a refractive angle (θ _{2 ) smaller than the corresponding incident angle (θ 1} ), so that the incident electromagnetic radiation 114 Is focused toward the photo detector 108. This increases the absorption of the incident electromagnetic radiation 114 by the substrate 104 (eg, by reducing the reflection of the incident electromagnetic radiation 114 away from the protrusion 110 ). Increasing the absorption of the incident electromagnetic radiation 114 increases the QE of the photo detector 108 and improves the performance of the image sensor 100.

FIG. 2 shows a cross-sectional view of some embodiments of an image sensor 200 corresponding to an alternative embodiment of the image sensor 100 of FIG. 1.

In some embodiments, the image sensor 200 includes a substrate 104 overlying the interconnect structure 102. The image sensor 200 may be configured as a back-illuminated CMOS image sensor (BSI-CIS). A plurality of semiconductor devices 212 are disposed within the interconnect structure 102 and along the front surface 104f of the substrate 104. In some embodiments, the semiconductor device 212 may be configured as a pixel device capable of outputting and/or processing an electrical signal generated by the photo detector 108. The semiconductor device 212 may be configured as, for example, a transfer transistor, a source follower transistor, a row select transistor and/or a reset transistor. It will be appreciated that semiconductor device 212 configured as another semiconductor device is also within the scope of the present disclosure. Further, the semiconductor device 212 may include a gate structure 216 disposed along the front surface 104f of the substrate 104 and a sidewall spacer structure 214 disposed along a sidewall of the gate structure 216, respectively. . In another embodiment, the gate structure 216 includes a gate dielectric layer and a gate electrode, wherein the gate dielectric layer is disposed between the substrate 104 and the gate electrode.

The interconnect structure 102 may include an interconnect dielectric structure 206, a plurality of conductive wires 208, and a plurality of conductive vias 210. In some embodiments, interconnect dielectric structures 206 are each an oxide such as silicon dioxide, fluorosilicate glass, phosphate glass (e.g., borophosphate silicate glass), other suitable dielectric material, or any combination of the foregoing. And one or more interlayer dielectric (ILD) layers, which may include it. It will be appreciated that interconnect structures 206 including other suitable materials are also within the scope of the present disclosure. Conductive wires and vias 208 and 210 are disposed within interconnect dielectric structure 206 and configured to electrically connect devices disposed within image sensor 200 to each other and/or to other integrated chips (not shown). In some embodiments, the conductive wires and/or vias 208, 210 may be or include copper, aluminum, titanium nitride, tantalum nitride, tungsten, other conductive materials, or any combination of the foregoing, for example, respectively. . It will be appreciated that conductive wires and/or vias 208, 210 including other suitable materials are also within the scope of the present disclosure.

In some embodiments, the substrate 104 may be any semiconductor body (eg, bulk silicon, other suitable semiconductor material, etc.) and/or has a first type of doping (eg, p-type doping). The pixel regions 202a-b are laterally separated from each other by a plurality of isolation structures 106. In some embodiments, the plurality of isolation structures 106 may be comprised of an STI structure, a DTI structure, a backside deep trench isolation (BDTI) structure, other suitable isolation structure, or any combination of the foregoing. In other embodiments, the isolation structure 106 may be, or may include silicon dioxide, silicon nitride, silicon carbide, or the like. Further, the photo detector 108 is disposed within each pixel area 202a-b. The photo detector 108 may include, for example, a second doping type (eg, n-type doping) opposite to the first doping type. It will be appreciated that photo detector 108 and/or substrate 104 including other doping types are also within the scope of the present disclosure.

In some embodiments, the photo detector 108 may be configured to generate an electrical signal from near infrared (NIR) radiation, including electromagnetic radiation within a first range of wavelengths. For example, the first wavelength range can be in the range of about 850 to 940 nanometers. It will be appreciated that other values for the first range of wavelengths are also within the scope of this disclosure. The substrate 104 has a thickness Ts defined between the front surface 104f of the substrate 104 and the rear surface 104b of the substrate 104. In some embodiments, the thickness Ts is in the range of about 4 to 6 microns. It will be appreciated that other values for the thickness Ts are also within the scope of the present disclosure. The thickness Ts of the substrate 104 is selected to ensure a high QE for the first range of wavelengths. For example, if the thickness Ts of the substrate 104 is thin (e.g., less than about 4 micrometers), the photo detector 108 will have poor NIR light QE, which can reduce the phase detection capability. have. Further, if the thickness Ts of the substrate 104 is thick (e.g., greater than about 6 micrometers), the placement of the pixel device such as the contact area, the isolation structure and/or the transfer transistor is determined by, for example, the QE for near-infrared radiation. It can be adversely affected without increasing.

The rear surface 104b of the substrate 104 includes a plurality of protrusions 110, and a plurality of micro lenses 112 are disposed between a pair of adjacent protrusions 110. Each of the micro lenses 112 is configured to have a convex top surface 112 configured to direct incident radiation toward the lower photo detector 108 as shown and described in FIG. 1. This increases the QE of the photo detector 108, thereby increasing the performance of the image sensor 200.

In a further embodiment, the plurality of micro lenses 112 may be constructed and/or referred to as a passivation layer that extends continuously laterally across the back surface 104b of the substrate 104. In this embodiment, the passivation layer comprises a plurality of upper convex protrusions 112up overlying each protrusion 110 and spaced between a pair of laterally adjacent protrusions 110, and below the upper convex protrusion 112up. It includes a plurality of lower protrusions (112lp) disposed in the. The lower protrusion 112lp directly contacts the sidewall of the protrusion 110. Further, in some embodiments, the passivation layer may extend laterally continuously across the protrusion 110 along an unbroken path.

3A shows a cross-sectional view of some embodiments of an image sensor 300a corresponding to an alternative embodiment of the image sensor 200 of FIG. 2.

The image sensor 300a includes a micro lens 112 and an upper dielectric layer 302 overlying the rear surface 104b of the substrate 104. In some embodiments, the top dielectric layer 302 may be or include a plasma-enhanced oxide (PEOX) layer, silicon dioxide, or other suitable dielectric material, for example. It will be appreciated that other suitable materials for the upper dielectric layer 302 are also within the scope of the present disclosure. Further, a plurality of optical filters 304 (eg, color filters, infrared (IR) filters, etc.) overlies the upper dielectric layer 302. Each of the plurality of optical filters 304 is configured to transmit incident radiation of a specific wavelength. For example, a first optical filter may transmit radiation having a wavelength within a first range, while a second optical filter adjacent to the first optical filter transmits radiation having a wavelength within a second range different from the first range. I can make it. In another embodiment, the light filter 304 may be configured as, for example, a color filter, wherein the first light filter is configured to transmit a first color (eg, green light) and the adjacent second light filter is It is configured to transmit a second color (eg, blue light) different from the first color. In addition, the plurality of upper lenses 306 are disposed on the plurality of optical filters 304. Each of the upper lenses 306 is laterally aligned with the optical filter 304 and overlies the pixel regions 202a and 202b. The plurality of upper lenses 306 are configured to focus the incident electromagnetic radiation towards the photo detector 108, further increasing the QE of the photo detector and the performance of the image sensor 300a.

The photo detector 108 is configured to generate an electrical signal from electromagnetic radiation of a wavelength [lambda]. In some embodiments, the wavelength λ may include near-infrared (NIR) radiation, including electromagnetic radiation in the range of about 850 to 940 nanometers. It will be appreciated that other values for wavelength [lambda] are also within the scope of the present disclosure. In another embodiment, the height hp of the protrusion 110 may be greater than about λ/2.5, thereby increasing the light-receiving surface area for incident electromagnetic radiation disposed on the substrate 104. For example, the height (hp) may be greater than about 340 nanometers. It will be appreciated that other values for height hp are also within the scope of this disclosure. This in part increases the sensitivity and/or QE of the image sensor 300a. The distance d1 is defined between the top surfaces of two adjacent protrusions 110. In another embodiment, the distance d1 may be greater than about λ/2, thereby increasing the light-receiving surface area for incident electromagnetic radiation disposed on the substrate 104. The distance d1 may be greater than about 425 nanometers. It will be appreciated that other values for distance d1 are also within the scope of the present disclosure. This in part further increases the sensitivity and/or QE of the image sensor 300a. Since the height (hp) is greater than λ/2.5 and the distance (d1) is greater than about λ/2, absorption of incident radiation having a wavelength (λ) by the substrate 104 is increased, and incident radiation having a wavelength (λ) The reflection from the photo detector 108 of is reduced. In some embodiments, the distance d1 is greater than the height hp.

3B shows a cross-sectional view of some embodiments of the image sensor 300b corresponding to some alternative embodiments of the image sensor 300a of FIG. 3A, with the upper dielectric layer 302 omitted. In this embodiment, the plurality of optical filters 304 are in direct contact with the plurality of micro lenses 112.

4-9 are cross-sectional views 400-900 of some embodiments of a method of forming an image sensor comprising a substrate having a plurality of protrusions according to the present invention, and a plurality of microlenses spaced between the protrusions and disposed over the protrusions. ). Although the cross-sectional views 400-900 shown in FIGS. 4-9 are described with reference to the method, it will be understood that the structures shown in FIGS. 4-9 are not limited to the method and can be separated separately from the method. . In addition, although FIGS. 4 to 9 are described as a series of operations, in other embodiments, the order of operations may be changed, and in that the disclosed method is applicable to other structures, these operations are not limited. Will make sense. In other embodiments, some operations shown and/or described may be omitted in whole or in part.

As shown by cross-sectional view 400 of FIG. 4, a substrate 104 is provided and an isolation structure 106 is formed on the front surface 104f of the substrate 104. In some embodiments, the substrate 104 may be a bulk substrate (eg, a bulk silicon substrate), a silicon-on-insulator (SOI) substrate, or other suitable substrate. It will be appreciated that other materials for substrate 104 are also within the scope of the present disclosure. In some embodiments, prior to forming the isolation structure 106, a first implant process is performed to dope the substrate 104 with a first doping type (eg, p-type). In some embodiments, the process of forming the isolation structure 106 comprises: selectively selecting the substrate 104 to form a trench in the substrate 104 extending into the substrate 104 from the front surface 104f of the substrate 104. Etching; And trenches (e.g., by chemical vapor deposition (CVD), atomic layer deposition (ALD), physical vapor deposition (PVD), thermal oxidation, etc.) Filling with another suitable dielectric material, or any combination of the foregoing). In a further embodiment, the substrate 104 is applied to one or more etchants configured to form a masking layer (not shown) on the front surface 104f of the substrate 104 and then selectively remove the unmasked portion of the substrate. It is selectively etched by exposing the substrate 104.

Further, as shown in FIG. 4, the photo detector 108 is formed in the substrate 104. In some embodiments, the photo detector 108 includes a region of the substrate 104 that includes a second doping type (eg, n-type) as opposed to the first doping type. In some embodiments, the photo detector 108 may be formed by a selective ion implantation process that uses a masking layer (not shown) on the front surface 104f of the substrate 104 to selectively implant ions into the substrate. In another embodiment, the first doping type includes a p-type dopant, and the second doping type includes an n-type dopant, or vice versa. The photo detector 108 is configured to generate an electrical signal from electromagnetic radiation of a wavelength [lambda]. In some embodiments, the wavelength λ may include near-infrared (NIR) radiation, including electromagnetic radiation in the range of about 850 to 940 nanometers. It will be appreciated that other values for wavelength [lambda] are also within the scope of the present disclosure.

In addition, as shown in FIG. 4, after forming the photodetector 108, thinning on the rear surface 104b of the substrate 104 in order to reduce the initial thickness Ti of the substrate 104 to the thickness Ts. The processing is carried out. The thickness Ts is defined between the front surface 104f of the substrate 104 and the rear surface 104b of the substrate 104. In some embodiments, the thickness Ts is in the range of about 4 to 6 microns. It will be appreciated that other values for the thickness Ts are also within the scope of the present disclosure. In some embodiments, the thinning process may include performing a mechanical grinding process, a chemical mechanical planarization (CMP) process, another suitable thinning process, or any combination of the foregoing.

As shown by the cross-sectional view 500 of FIG. 5, the structure of FIG. 4 is patterned after being turned over to define a plurality of protrusions 110 along the rear surface 104b of the substrate 104. The rear surface 104b of the substrate 104 is opposite to the front surface 104f of the substrate 104. In some embodiments, the plurality of protrusions 110 are formed by performing one or more etching processes according to one or more masking layers (not shown). The one or more etching processes may include, for example, wet etching processes, dry etching processes, other suitable etching processes, or any combination of the foregoing. In addition, in some embodiments, the protrusion 110 is formed such that the height hp of the protrusion 110 is greater than about λ/2.5 and the distance d1 is greater than about λ/2, so that the protrusion 110 is formed on the substrate 104. Increase the area of the light-receiving surface for the incident electromagnetic radiation to be disposed. The distance d1 is defined between the top surfaces of two adjacent protrusions 110. In another embodiment, the height hp may be greater than about 340 nanometers and/or the distance d1 may be greater than about 425 nanometers. It will be appreciated that other values for height hp and/or distance d1 are also within the scope of the present disclosure.

As shown by cross-sectional view 600 of FIG. 6, an upper dielectric layer 602 is deposited over the protrusion 110. The upper surface of the upper dielectric layer 602 may correspond to the shape of the protrusion 110. In some embodiments, the top dielectric layer 602 is, for example, by CVD, ALD, PVD, thermal oxidation, plasma enhanced deposition process (e.g., plasma enhanced CVD (PECVD)), or other suitable deposition or growth process. Can be formed. Thus, the top dielectric layer 602 can be, for example, a plasma enhanced oxide, silicon dioxide, silicon oxycarbide (SiOC), other suitable dielectric material, or any combination of the foregoing and/or of about 3,000 to 5,000 angstroms. It can be formed to a thickness within a range. It will be appreciated that other values for the thickness of the upper dielectric layer 602 are also within the scope of the present disclosure. In another embodiment, a bottom anti-reflective coating (BARC) layer 604 is formed over the top dielectric layer 602. In some embodiments, the BARC layer 604 may be formed by, for example, CVD, ALD, PVD, or other suitable deposition or growth process. In another embodiment, the BARC layer 604 is, for example, a high-k dielectric material (e.g., a dielectric material having a dielectric constant greater than 3.9), another suitable dielectric material, or any combination of the foregoing, It may include, and/or be formed to a thickness in the range of about 4,000 to 6,000 angstroms. It will be appreciated that other values for the thickness of the BARC layer 604 are also within the scope of the present disclosure. Thus, in some embodiments, BARC layer 604 has a greater thickness than top dielectric layer 602.

As shown by cross-sectional view 700 of FIG. 7, a first patterning process is performed on the BARC layer 604 to reduce the initial thickness of the BARC layer 604. In some embodiments, the first patterning process comprises a dry etching process, a blanket dry etching process, or other suitable etching process. In a further embodiment, the first patterning process comprises adding the BARC layer 604 to _{one or more etchants such as oxygen (e.g., O 2} ), carbon monoxide (CO), another suitable etchant, or any combination of the foregoing. It may include the step of exposing. In yet another embodiment, the first patterning process does not etch the upper dielectric layer 602.

8A-8C show cross-sectional views 800a-c corresponding to some embodiments of forming micro lenses 112 by performing a second patterning process on upper dielectric layer 602 and BARC layer 604. The second patterning process is performed in such a manner that each of the micro lenses 112 has a convex upper surface 112 that is placed on the protrusion 110. 8A and 8B show cross-sectional views 800a and 800b corresponding to some embodiments of a first snapshot and a second snapshot of a second patterning process. 8C illustrates a cross-sectional view 800c corresponding to some embodiments of the microlens 112 after completing the second patterning process.

In some embodiments, the second patterning process includes performing a dry etching process, a blanket dry etching process, or other suitable etching process. In various embodiments, the second patterning process is performed only by a blanket dry etch process. In a further embodiment, the second patterning process comprises one or more etchants (e.g., polymer rich etchants, octafluoro cyclobutane (e.g. C ₄ F ₈ ), trifluoromethane (e.g., CHF ₃ )). , Other suitable etchant, or any combination of the foregoing). During the second patterning process, the upper dielectric layer 602 is etched at a first etch rate and the BARC layer 604 is etched at a second etch rate. In some embodiments, the first etch rate is at least ten times greater than the second etch rate. In this embodiment, the second patterning process is compared to the top dielectric layer 602 so that the top dielectric layer 602 is etched faster (e.g., at least 10 times more) than the BARC layer 604. ) Has low selectivity. This may be because one or more etchants remove the top dielectric layer 602 faster than the BARC layer 604. Since the first etch rate is at least 10 times higher than the second etch rate, each micro lens 112 has a convex top surface 112us. Thus, in some embodiments, the ratio of the first etch rate to the second etch rate is, for example, in the range of about 10:1 to about 20:1, for example about 10:1, about 11:1, about It is 12:1, or is greater than 10:1. It will be appreciated that other values for the ratio of the first etch rate to the second etch rate are also within the scope of the present disclosure. The convex top surface 112us of the microlens 112 is each configured to bend and/or angle the incident electromagnetic radiation toward a focal point below the corresponding convex top surface 112us. This increases the absorption of the incident electromagnetic radiation by the substrate 104 (eg, by reducing the reflection of the incident electromagnetic radiation away from the substrate 104). Increasing the absorption of incident electromagnetic radiation increases the QE of the photodetector 108.

Cross-sectional view 800a of FIG. 8A shows some embodiments of a first snapshot of a second patterning process taken at a first time, where the top dielectric layer 602 is removed faster than the BARC layer 604. Cross-sectional view 800b of FIG. 8B shows some embodiments of a second snapshot of a second patterning process taken at a second time, where the second snapshot is taken at some point after the first snapshot. As shown in FIG. 8B, the residue of the BARC layer 604 is disposed along the top surface of the upper dielectric layer 602, so that the upper dielectric layer 602 is spaced between a pair of laterally adjacent protrusions 110. ) And the top surface of the BARC layer 604 is outwardly rounded and/or curved (ie, convex) in a direction away from the protrusion 110. A cross-sectional view 800c of FIG. 8C shows some embodiments of the microlens 112 after performing a second patterning process on the upper dielectric layer 602 and the BARC layer 604. The convex top surface 112us of each of the micro lenses 112 corresponds to the curved top surface of the top dielectric layer 602 and BARC layer 604 shown in FIG. 8B.

As shown by the cross-sectional view 900 of FIG. 9, the optical filter 304 is formed over the micro lens 112. The optical filter 304 is formed of a material that allows transmission of incident electromagnetic radiation (eg, light) having a specific wavelength range, and blocks incident wavelengths having other wavelengths outside the specific range. In further embodiments, the optical filter 304 may be formed by CVD, PVD, ALD, sputtering, or the like, and/or may be planarized after formation (eg, through a chemical mechanical planarization (CMP) process). Further, the upper lens 306 is formed over the optical filter 304. In some embodiments, the upper lens 306 may be formed by depositing a lens material on the optical filter 304 (eg, by CVD, PVD, or the like). A lens template (not shown) with a curved top surface is patterned over the lens material. Thereafter, the upper lens 306 is formed by selectively etching the lens material according to the lens template.

10 illustrates a method 1000 of forming an image sensor including a substrate having a plurality of protrusions and a plurality of microlenses spaced apart between the plurality of protrusions and disposed over the plurality of protrusions according to some embodiments of the present disclosure. Shows. While method 1000 is shown and/or described as a series of actions or events, it will be appreciated that the method is not limited to the sequence or actions shown. Thus, in some embodiments, operations may be performed in a different order than shown and/or may be performed concurrently. Further, in some embodiments, the illustrated action or event may be subdivided into a number of actions or events, which may be performed at separate times or concurrently with other actions or sub-actions. In some embodiments, some of the illustrated operations or events may be omitted, and other operations or events not illustrated may be included.

In operation 1002, an isolation structure is formed over the front surface of the substrate. 4 shows a cross-sectional view 400 corresponding to some embodiments of operation 1002.

In operation 1004, a photo detector is formed in the substrate. 4 shows a cross-sectional view 400 corresponding to some embodiments of operation 1004.

In operation 1006, a plurality of protrusions are formed on the rear surface of the substrate. The protrusion rests on the photo detector. 5 shows a cross-sectional view 500 corresponding to some embodiments of operation 1006.

In operation 1008, an upper dielectric layer is deposited over the plurality of protrusions. In addition, a lower anti-reflective coating (BARC) layer is deposited over the upper dielectric layer. 6 shows a cross-sectional view 600 corresponding to some embodiments of operation 1008.

In operation 1010, a first patterning process is performed on the BARC layer. 7 shows a cross-sectional view 700 corresponding to some embodiments of operation 1010.

In operation 1012, a second patterning process is performed on the top dielectric layer and the BARC layer. The upper dielectric layer is etched faster than the BARC layer. In addition, the second patterning process defines a plurality of microlenses on the protrusions so that each microlens has a convex upper surface. 8A-8C illustrate cross-sectional views 800a-c corresponding to some embodiments of operation 1012.

In operation 1014, an optical filter is formed over the plurality of micro lenses. 9 shows a cross-sectional view 900 corresponding to some embodiments of operation 1014.

In operation 1016, an upper lens is formed over the optical filter. 9 shows a cross-sectional view 900 corresponding to some embodiments of operation 1014.

Thus, in some embodiments, the present invention relates to an image sensor comprising a substrate having a plurality of protrusions disposed along the rear surface of the substrate. Further, a plurality of microlenses are laterally spaced between the protrusions and are disposed over the protrusions. Each microlens includes a convex top surface configured to direct incident radiation to a focal point below the convex top surface.

1) An image sensor according to an embodiment of the present disclosure includes a substrate including a plurality of sidewalls defining a plurality of protrusions along a first side of the substrate, the substrate having a first refractive index; A photo detector placed under the plurality of protrusions and disposed within the substrate; And a plurality of micro lenses disposed on the first side of the substrate. The microlens has a second refractive index smaller than the first refractive index, and the microlenses are disposed between adjacent pairs of protrusions in the plurality of protrusions in each lateral direction and directly contact the adjacent pair of protrusions, each of the microlenses It can have a convex top surface.

2) In the image sensor according to the embodiment of the present disclosure, the plurality of protrusions are laterally separated from each other by a recess in the first side of the substrate, and each of the plurality of microlenses has a corresponding recess. It may include a filling lens protrusion.

3) In the image sensor according to the embodiment of the present disclosure, the substrate may include silicon and the microlens may include silicon dioxide.

4) In the image sensor according to the embodiment of the present disclosure, the height of the plurality of micro lenses may be greater than the height of the protrusion.

5) In the image sensor according to the embodiment of the present disclosure, the plurality of protrusions includes a first protrusion and a second protrusion disposed adjacent to each other in a lateral direction, and the first protrusion includes a first upper point, and The second protrusion may include a second upper point, and a height of the plurality of protrusions may be smaller than a lateral distance between the first upper point and the second upper point.

6) In the image sensor according to an embodiment of the present disclosure, the plurality of microlenses includes a first microlens disposed between the first protrusion and the second protrusion, and a convex upper surface of the first microlens May be spaced laterally between the first upper point of the first protrusion and the second upper point of the second protrusion.

7) In the image sensor according to an embodiment of the present disclosure, the first microlens is configured to direct incident electromagnetic radiation toward a focal point lying under the convex upper surface of the first microlens, and the focal point is side In a direction, the first protrusion and the second protrusion may be spaced apart from each other, and the focal point may be vertically spaced apart on a lower surface of the plurality of protrusions.

8) An integrated chip according to an embodiment of the present disclosure includes: a substrate comprising a plurality of first protrusions along a rear surface of the substrate, the substrate comprising a first material having a first refractive index; An interconnect structure disposed along the front surface of the substrate; A photo detector placed under the plurality of first protrusions and disposed within the substrate; A passivation layer arranged between the plurality of first protrusions and on the plurality of first protrusions-the passivation layer includes a plurality of second protrusions along an upper surface of the passivation layer, the plurality of second protrusions Different from the plurality of first protrusions, the passivation layer comprising a second material having a second refractive index different from the first refractive index; And an optical filter overlying the passivation layer.

9) In the integrated chip according to the embodiment of the present disclosure, each of the first protrusions may have a triangular shape and each of the second protrusions may have a semicircular shape.

10) In the integrated chip according to the embodiment of the present disclosure, the lower surface of the passivation layer is a plurality of third protrusions engagingly contacting a plurality of recesses spaced between the plurality of first protrusions of the substrate. It may include.

11) In the integrated chip according to the exemplary embodiment of the present disclosure, the first refractive index may be at least twice larger than the second refractive index.

12) In the integrated chip according to the embodiment of the present disclosure, the photo detector may be configured to generate an electric signal from near infrared (NIR) radiation.

13) In the integrated chip according to the embodiment of the present disclosure, the thickness of the substrate may be in the range of about 4 to 6 micrometers.

14) In the integrated chip according to the embodiment of the present disclosure, an upper lens disposed on the optical filter may be further included, and an upper surface of the upper lens may be convex.

15) In the integrated chip according to the embodiment of the present disclosure, the lower surface of the optical filter may directly contact the plurality of second protrusions.

16) A method of forming an image sensor according to an embodiment of the present disclosure includes: performing an ion implantation process to define a photo detector in a substrate; Etching the first side of the substrate to define a plurality of protrusions overlying the photo detector; Depositing a dielectric layer comprising a first material over the plurality of protrusions; Depositing an anti-reflection coating (ARC) layer over the dielectric layer, the ARC layer comprising a second material different from the first material; Performing a first patterning process on the ARC layer; And defining a plurality of microlenses each having a concave upper surface by performing a second patterning process on the dielectric layer and the ARC layer. The dielectric layer is etched at a first rate during the second patterning process and the ARC layer is etched at a second rate during the second patterning process, and the first rate may be greater than the second rate.

17) In the method of forming an image sensor according to an embodiment of the present disclosure, the second patterning process may include performing a blanket dry etching process.

18) In the method of forming an image sensor according to an exemplary embodiment of the present disclosure, the method may further include forming an optical filter on the plurality of microlenses so that the optical filter directly contacts the microlenses.

19) In the method of forming an image sensor according to an exemplary embodiment of the present disclosure, the method may further include forming an upper lens on the optical filter so that the upper lens has a curved upper surface.

20) In the method of forming an image sensor according to an embodiment of the present disclosure, the second patterning process includes exposing the dielectric layer and the ARC layer to one or more etchants, wherein the one or more etchants are octafluoro. Rocyclobutane and/or trifluoromethane.

Features of several embodiments have been outlined above so that aspects of the present disclosure may be better understood by those skilled in the art. Those skilled in the art should know that they can readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes of the embodiments introduced herein and/or achieving the same advantages. . Those skilled in the art also know that such an equivalent configuration does not depart from the spirit and scope of the present disclosure, and those skilled in the art can make various changes, alternatives, and modifications in the present invention without departing from the spirit and scope of the present disclosure. You have to be aware that there is.

Claims (10)

A substrate comprising a plurality of sidewalls defining a plurality of protrusions along a first side of the substrate, the substrate having a first refractive index;
A photo detector placed under the plurality of protrusions and disposed within the substrate; And
A plurality of micro lenses overlying the first side of the substrate
Including,
The microlens has a second refractive index less than the first refractive index, and the microlenses are disposed between adjacent pairs of protrusions in the plurality of protrusions in each lateral direction and directly contact the adjacent pair of protrusions, each of the microlenses An image sensor having a convex top surface. The method of claim 1,
The plurality of protrusions are laterally separated from each other by a recess in the first side of the substrate, and each of the plurality of micro lenses includes a lens protrusion filling a corresponding recess. The method of claim 1,
The image sensor, wherein the substrate comprises silicon and the microlens comprises silicon dioxide. The method of claim 1,
The image sensor, wherein the height of the plurality of micro lenses is greater than the height of the protrusion. The method of claim 1,
The plurality of protrusions includes a first protrusion and a second protrusion disposed adjacent to each other in a lateral direction, the first protrusion includes a first upper point, and the second protrusion includes a second upper point, and the The image sensor, wherein the height of the plurality of protrusions is less than a lateral distance between the first upper point and the second upper point. The method of claim 5,
The plurality of microlenses includes a first microlens disposed between the first protrusion and the second protrusion, and a convex upper surface of the first microlens is lateral to the first upper point of the first protrusion And the second upper point of the second protrusion. The method of claim 6,
The first microlens is configured to direct incident electromagnetic radiation toward a focal point placed under the convex upper surface of the first microlens, and the focal point is laterally spaced between the first protrusion and the second protrusion. And the focal point is vertically spaced apart on the lower surfaces of the plurality of protrusions. A substrate comprising a plurality of first protrusions along a rear surface of the substrate, the substrate comprising a first material having a first refractive index;
An interconnect structure disposed along the front surface of the substrate;
A photo detector placed under the plurality of first protrusions and disposed within the substrate;
A passivation layer arranged between the plurality of first protrusions and on the plurality of first protrusions-the passivation layer includes a plurality of second protrusions along an upper surface of the passivation layer, the plurality of second protrusions Different from the plurality of first protrusions, the passivation layer comprising a second material having a second refractive index different from the first refractive index; And
An optical filter overlying the passivation layer
Containing, integrated chip. The method of claim 8,
Each of the first protrusions has a triangular shape and each of the second protrusions has a semicircular shape. Performing an ion implantation process to define a photo detector in the substrate;
Etching the first side of the substrate to define a plurality of protrusions overlying the photo detector;
Depositing a dielectric layer comprising a first material over the plurality of protrusions;
Depositing an anti-reflection coating (ARC) layer over the dielectric layer, the ARC layer comprising a second material different from the first material;
Performing a first patterning process on the ARC layer; And
Defining a plurality of microlenses each having a concave upper surface by performing a second patterning process on the dielectric layer and the ARC layer
Including,
The dielectric layer is etched at a first rate during the second patterning process and the ARC layer is etched at a second rate during the second patterning process, and the first rate is greater than the second rate. Way.

Images