Image sensor structure and method of forming the same

Abstract

In some embodiments, the present disclosure relates to an image sensor structure. The image sensor structure includes a substrate. The substrate includes a first side and a second side opposite the first side. A photodetector extends into the first side of the substrate. An isolation structure includes a first isolation segment and a second isolation segment extending through the substrate. The first isolation segment and the second isolation segment are respectively located on opposite sides of the photodetector and comprise a dielectric. A first metal line is located on the first side of the substrate. A dummy contact structure includes a first dummy segment and a second dummy segment. Both the first dummy segment and the second dummy segment comprise metal and extend from the first metal line to the first isolation segment and the second isolation segment respectively.

Description

Technical Field

[0001] An embodiment of the present invention relates to an image sensor structure and a method for forming the same. Background Art

[0002] Integrated circuits (ICs) with image sensors are used in various modern electronic devices (e.g., cameras and mobile phones). In recent years, complementary metal-oxide-semiconductor (CMOS) image sensors have begun to be widely used, greatly replacing charge-coupled device (CCD) image sensors. Compared with CCD image sensors, CMOS image sensors are favored for their low power consumption, small size, fast data processing, direct data output, and low manufacturing cost. Some types of CMOS image sensors include front-side illuminated (FSI) image sensors and back-side illuminated (BSI) image sensors. Summary of the Invention

[0003] An embodiment of the present invention provides an image sensor structure, including: a substrate, a photodetector, an isolation structure, a first metal line, and a dummy contact structure. The substrate includes a first side and a second side opposite to the first side. The photodetector extends into the first side of the substrate. The isolation structure includes a first isolation segment and a second isolation segment extending through the substrate. The first isolation segment and the second isolation segment are respectively located on opposite sides of the photodetector and contain a dielectric. The first metal line is located on the first side of the substrate. The dummy contact structure includes a first dummy segment and a second dummy segment. Both the first dummy segment and the second dummy segment contain metal and extend from the first metal line to the first isolation segment and the second isolation segment respectively.

[0004] An embodiment of the present invention provides an image sensor structure, including: a substrate, a pixel, a substrate isolation structure, a metal reflector, and a dummy contact structure. The substrate includes an upper surface and a lower surface. The pixel includes a photodetector along the lower surface of the substrate. The substrate isolation structure contains a first dielectric material. The substrate isolation structure extends vertically through the substrate from the upper surface of the substrate to the lower surface of the substrate. The substrate isolation structure extends laterally along the boundary of the pixel in a first closed path. The metal reflector is located under the photodetector. The dummy contact structure contains a first metal material extending from the metal reflector to the substrate isolation structure. The dummy contact structure extends laterally along the boundary of the pixel in a first closed path.

[0005] An embodiment of the present invention provides a method for forming an image sensor structure, including: forming a photodetector in a first side of a substrate; forming a first dielectric layer on the first side of the substrate; patterning the first dielectric layer to form a first opening, the first opening having a pair of first opening segments exposing the first side of the substrate, wherein the first opening segments respectively abut the photodetector on opposite sides of the photodetector; forming a dummy contact structure in the first opening, and the dummy contact structure includes a first dummy segment and a second dummy segment respectively located in the first opening segments; forming a metal reflector directly contacting the first dummy segment and the second dummy segment on the first side of the substrate; patterning a second side of the substrate opposite to the first side to form a second opening, the second opening having a pair of second opening segments, and the pair of second opening segments respectively align with the first dummy segment and the second dummy segment; and forming a substrate isolation structure in the second opening, and the substrate isolation structure includes a first isolation segment and a second isolation segment respectively located in the second opening segments. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Various aspects of the present disclosure will be best understood by reading the following detailed description in conjunction with the accompanying drawings. It should be noted that, in accordance with standard practice in the industry, the various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0007] Figure 1 A cross-sectional view showing some embodiments of an image sensor including a pixel isolation structure, the pixel isolation structure including a dummy contact structure.

[0008] Figure 2 Shows Figure 1 A top view of some embodiments of the shown image sensor.

[0009] Figures 3 to 5 A cross-sectional view showing some additional embodiments of an image sensor including a pixel isolation structure, the pixel isolation structure including a dummy contact structure.

[0010] Figure 6 A cross-sectional view showing some embodiments of a backside illuminated (BSI) image sensor including a pixel isolation structure, the pixel isolation structure including a dummy contact structure.

[0011] Figure 7 A cross-sectional view showing some embodiments of a front side illuminated (FSI) image sensor including a pixel isolation structure, the pixel isolation structure including a dummy contact structure.

[0012] Figure 8 A cross-sectional view showing some additional embodiments of an image sensor including a plurality of pixels and a pixel isolation structure, the pixel isolation structure including a dummy contact structure.

[0013] Figure 9 ShowsFigure 8 Top view of some embodiments of the illustrated image sensor.

[0014] Figures 10 to 29 A series of cross-sectional views showing some embodiments of a method of forming a BSI image sensor including a pixel isolation structure, the pixel isolation structure including a dummy contact structure.

[0015] Figure 30 A flowchart showing some embodiments of a method of forming a BSI image sensor including a pixel isolation structure, the pixel isolation structure including a dummy contact structure.

[0016] Figures 31 to 44 A series of cross-sectional views showing some embodiments of a method of forming an FSI image sensor including a pixel isolation structure, the pixel isolation structure including a dummy contact structure.

[0017] Figure 45 A flowchart showing some embodiments of a method of forming an FSI image sensor including a pixel isolation structure, the pixel isolation structure including a dummy contact structure. DETAILED DESCRIPTION

[0018] The following disclosure provides many different embodiments or examples for implementing different features of the provided subject matter. Specific examples of components and arrangements are set forth below to simplify the disclosure. Of course, these are merely examples and are not intended to be limiting. For example, in the following description, forming a first feature "on" or "above" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features such that the first and second features are not in direct contact. Additionally, the present disclosure may repeat reference numerals and / or letters in various instances. This repetition is for the purpose of simplicity and clarity and does not in itself indicate a relationship between the various embodiments and / or configurations discussed.

[0019] In addition, for ease of explanation, spatially relative terms such as "beneath", "below", "lower", "above", "upper", etc. may be used herein to describe the relationship of one element or feature shown in the figures to another (other) element or feature. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may have other orientations (rotated 90 degrees or at other orientations), and the spatially relative descriptive terms used herein may be interpreted accordingly.

[0020] Many modern integrated chips include image sensors. The image sensor may include a semiconductor substrate and a metal interconnect structure disposed on a front side of the substrate. In addition, the image sensor may include a plurality of pixels. Each pixel includes a photodetector located in the semiconductor substrate. Further, the pixels are separated from each other by a shallow trench isolation (STI) structure disposed in the front side of the substrate and a deep trench isolation (DTI) structure disposed in a back side of the substrate opposite to the front side. The DTI structure and the STI structure may be arranged along a common vertical axis. In addition, the DTI structure and the STI structure may extend vertically through the substrate together at a boundary of the pixels to separate the pixels. Accordingly, photons entering a portion of the substrate corresponding to a pixel may be confined to that portion and prevented from entering other portions of the substrate corresponding to adjacent pixels.

[0021] A challenge with image sensors is that, although the DTI structure and the STI structure may separate pixels at the substrate, the DTI structure and the STI structure cannot separate pixels at the interconnect structure. For example, a first dielectric layer of an interconnect structure disposed along the substrate may not be isolated at a boundary between pixels. Accordingly, some photons may travel between adjacent pixels through the non-isolated first dielectric layer. Thus, the STI structure and the DTI structure, which are intended to isolate adjacent pixels from each other, may not prevent some photons from traveling between adjacent pixels. Subsequently, this may result in high crosstalk between pixels and may reduce the performance of the image sensor (e.g., quantum efficiency (QE)).

[0022] Various embodiments of the present disclosure relate to an image sensor including a pixel isolation structure that includes a dummy contact structure for improving pixel isolation and reducing crosstalk between pixels. The image sensor may include a semiconductor substrate and a plurality of pixels along the substrate. The pixels among the plurality of pixels may include photodetectors located in the substrate. The pixel isolation structure may include a substrate isolation structure disposed in the substrate and a dummy contact structure disposed in a first dielectric layer. The substrate isolation structure and the dummy contact structure extend vertically through the substrate and through the first dielectric layer together along a boundary of the pixels to separate a first region of the substrate and a first region of the first dielectric layer associated with a pixel from an adjacent region of the substrate and an adjacent region of the first dielectric layer associated with an adjacent pixel. Accordingly, isolation between a pixel and an adjacent pixel may be improved. Thus, the pixel isolation structure may reduce the likelihood that photons entering a pixel leave the pixel and enter an adjacent pixel. Subsequently, less crosstalk may occur between adjacent pixels, thereby improving the performance of the image sensor (e.g., QE).

[0023] Figure 1Cross-sectional view 100 showing some embodiments of an image sensor including a pixel isolation structure 120, the pixel isolation structure 120 including a dummy contact structure 123. Cross-sectional view 100 may be taken, for example, along Figure 2 the line A-A' shown in

[0024] The image sensor includes pixels 111. The image sensor further includes a substrate 102, a photodetector 105 located in the substrate 102, a first etch stop layer 112 along the lower surface of the substrate 102, a first dielectric layer 114 along the lower surface of the first etch stop layer 112, a second etch stop layer 124 along the lower surface of the first dielectric layer 114, a second dielectric layer 126 along the lower surface of the second etch stop layer 124, and a first metal line 132 disposed within the second dielectric layer 126. In some embodiments, the first metal line 132 can be used as a metal reflector. In some embodiments, the image sensor may further include an interconnect structure (not labeled) located below the substrate 102. For example, the interconnect structure may include the first dielectric layer 114, the dummy contact structure 123, and / or the first metal line 132, and may further include a plurality of other metal lines or vias (not shown).

[0025] The pixel isolation structure 120 includes a substrate isolation structure 150 and a dummy contact structure 123. The substrate isolation structure 150 includes a first isolation segment 150a and a second isolation segment 150b that extend vertically through the substrate along the boundaries of the pixels 111. Thus, the first isolation segment 150a and the second isolation segment 150b laterally separate a first region 102a of the substrate from an adjacent region 102n of the substrate (and thus separate the photodetector 105 from an adjacent photodetector (not shown) located in the adjacent region 102n of the substrate). Additionally, the sidewalls of the first isolation segment 150a and the second isolation segment 150b define a first region 102a of the substrate that includes the photodetector 105. Further, the substrate isolation structure 150 can be a grid structure or an annular structure, as Figure 2 shown in. Additionally, the substrate isolation structure 150 extends vertically from a top surface above the substrate 102 to a bottom surface below the top of the substrate 102. For example, the substrate isolation structure 150 includes a front cover 150f that extends above the top surface of the substrate 102 between the first isolation segment 150a and the second isolation segment 150b. Photons 170 can enter the substrate 102 through the front cover 150f.

[0026] The dummy contact structure 123 includes a first dummy segment 123a and a second dummy segment 123b extending from the first metal line 132 to the first isolation segment 150a and the second isolation segment 150b, respectively. Accordingly, the first dummy segment 123a and the second dummy segment 123b laterally separate a first region 114a of the first dielectric layer from an adjacent region 114n of the first dielectric layer. In some embodiments, the pixel isolation structure 120 and the first metal line 132 completely surround a first region 102a of the substrate and a first region 114a of the first dielectric layer.

[0027] The pixel isolation structure 120 can reduce the likelihood that photons 170 entering the pixel 111 leave the pixel 111 and enter an adjacent pixel. The substrate isolation structure 150 reduces the likelihood that photons 170 enter an adjacent pixel at the substrate 102. In addition, the dummy contact structure 123 reduces the likelihood that photons 170 enter an adjacent pixel at the first dielectric layer 114. Additionally, the dummy contact structure 123 can isolate the pixels at the interconnect structure (not labeled) together with the first metal line 132, thereby reducing the likelihood that photons 170 enter an adjacent pixel at the interconnect structure. Accordingly, the pixel isolation structure 120 can improve the isolation between the pixel 111 and adjacent pixels. Subsequently, less crosstalk can occur between the pixel 111 and adjacent pixels, thereby improving the QE and other performance metrics of the image sensor.

[0028] In some embodiments, the substrate isolation structure 150 comprises one or more isolation materials. The one or more isolation materials can include, for example, silicon dioxide, silicon nitride, low dielectric constant (low k) dielectrics, hafnium oxide, aluminum oxide, high dielectric constant dielectrics, tungsten, aluminum, another suitable material, or any combination of the foregoing materials. In some embodiments, the substrate isolation structure 150 has a refractive index smaller than that of the substrate 102 to provide optical isolation by total internal reflection.

[0029] In some embodiments, the first isolation segment 150a, the second isolation segment 150b, and the front top cover 150f can be integrally formed using the same material (such as an oxide (e.g., silicon dioxide), tetraethyl orthosilicate (TEOS), etc.). Additionally, an anti-reflection layer (not shown) can be disposed over the substrate 102 and between the substrate 102 and the front top cover 150f. The anti-reflection layer can also be disposed along the sidewalls of the first isolation segment 150a and the second isolation segment 150b such that the anti-reflection layer is between the first isolation segment 150a and the substrate 102 and also between the second isolation segment 150b and the substrate 102. In some embodiments, the front top cover 150f can have curved surfaces disposed over the photodetector 105 and intersecting each other.

[0030] In some other embodiments, the first isolation segment 150a and the second isolation segment 150b may be formed using a material different from that of the front top cover 150f. For example, reflective materials such as the following may be provided within the first isolation segment 150a and the second isolation segment 150b: aluminum (Al), rhodium (Rh), ruthenium (Ru), copper (Cu), silver (Ag), gold (Au), tungsten (W), cobalt (Co), iron (Fe), molybdenum (Mo), titanium (Ti), chromium (Cr), or any combination of the above materials.

[0031] In some embodiments, the dummy contact structure 123 comprises a first metal material. The first metal material may for example include tungsten, copper, titanium, another suitable metal, or any combination of the above materials. The dummy contact structure 123 may have a width greater than that of the substrate isolation structure 150 at the interface between the dummy contact structure 123 and the substrate isolation structure 150 (i.e., along the top surface of the dummy contact structure 123). In addition, the dummy contact structure 123 may have a height smaller than that of the substrate isolation structure 150. In addition, the dummy contact structure 123 may have some other surface geometries (e.g., a polyhedral shape or a spherical shape).

[0032] In some embodiments, the image sensor is a CMOS image sensor or the like. In some embodiments, the substrate 102 may for example comprise a semiconductor material such as silicon or the like.

[0033] In some embodiments, the first dielectric layer 114 and the second dielectric layer 126 may for example comprise silicon dioxide, silicon nitride, a low dielectric constant dielectric, another suitable dielectric material, or any combination of the above materials. Additionally, the first etch stop layer 112 and the second etch stop layer 124 may for example comprise silicon nitride, silicon carbide, silicon carbonitride, another suitable dielectric, or any combination of the above materials.

[0034] In some embodiments, the first metal line 132 comprises a second metal material. The second metal material may for example include copper, aluminum copper, tungsten, another suitable metal, or any combination of the above materials.

[0035] Figure 2 Shown Figure 1 A top view 200 of some embodiments of the image sensor shown. A portion of the substrate isolation structure 150 in the substrate 102 may have an annular top layout. The annular portion of the substrate isolation structure 150 may extend along the boundary of the pixel 111 in a first closed path. The dummy contact structure 123 may be directly disposed below the annular portion of the substrate isolation structure 150 and may have the same top layout as the annular portion (i.e., the dummy contact structure 123 may be annular, may extend along the boundary of the pixel 111, and may extend along the first closed path).

[0036] In some embodiments, the first metal line 132, the dummy contact structure 123, and the substrate isolation structure 150 define a composite structure (not labeled) that vertically extends around the photodetector 105 in a second closed path (e.g., see Figure 1 ).

[0037] Figure 3 A cross-sectional view 300 of some additional embodiments of the image sensor is shown, where the substrate isolation structure 150 is not on top of and does not extend along the top of the substrate 102 between the first isolation segment 150a and the second isolation segment 150b. Instead, the top surface of the substrate isolation structure 150 is flush or approximately flush with the top surface of the substrate 102.

[0038] Figure 4 A cross-sectional view 400 of some additional embodiments of the image sensor is shown, where the substrate isolation structure 150 is divided into a DTI structure and an STI structure. The first isolation segment 150a and the second isolation segment 150b respectively include a first DTI segment 151a and a second DTI segment 151b, and the first DTI segment 151a and the second DTI segment 151b extend into the upper side of the substrate 102 to a first depth 148 and define the DTI structure. In addition, the first isolation segment 150a and the second isolation segment 150b respectively include a first STI segment 153a and a second STI segment 153b, and the first STI segment 153a and the second STI segment 153b extend into the lower side of the substrate 102 to a second depth 149 and define the STI structure, and the second depth 149 is less than the first depth 148.

[0039] The first STI segment 153a and the second STI segment 153b can be directly disposed below the first DTI segment 151a and the second DTI segment 151b, respectively. Additionally, the first dummy segment 123a and the second dummy segment 123b can be directly disposed below the first STI segment 153a and the second STI segment 153b, respectively, such that the first DTI segment 151a, the first STI segment 153a, and the first dummy segment 123a are disposed along a first common vertical axis 164a, and such that the second DTI segment 151b, the second STI segment 153b, and the second dummy segment 123b are disposed along a second common vertical axis 164b. Accordingly, the first STI segment 153a and the second STI segment 153b can separate the first DTI segment 151a from the first dummy segment 123a and the second DTI segment 151b from the second dummy segment 123b in the vertical direction, respectively. Further, the first DTI segment 151a can directly contact the first STI segment 153a, and the first STI segment 153a can directly contact the first dummy segment 123a. Additionally, the second DTI segment 151b can directly contact the second STI segment 153b, and the second STI segment 153b can directly contact the second dummy segment 123b. In some embodiments, any one of the DTI segments and the STI segments can include, for example, one or more isolation materials.

[0040] Figure 5 A cross-sectional view 500 showing some additional embodiments of an image sensor, in which a first isolation segment 150a and a second isolation segment 150b are defined by a first isolation layer 145 and a second isolation layer 147 including different materials. For example, the first isolation layer 145 can be or can include a dielectric, and the second isolation layer 147 can be or can include a metal. The first isolation layer 145 can be disposed along an outer sidewall and a lower surface of the second isolation layer 147 such that the first isolation layer 145 surrounds the second isolation layer 147 and laterally separates the second isolation layer 147 from the substrate 102.

[0041] In some embodiments, the first isolation layer 145 can include, for example, hafnium oxide, aluminum oxide, a high-k dielectric, another suitable dielectric material, or any combination of the foregoing materials. Additionally, the second isolation layer 147 can include, for example, silicon dioxide, silicon nitride, tungsten, another suitable material, or any combination of the foregoing materials.

[0042] Figure 6 A cross-sectional view 600 showing some embodiments of a backside illumination (BSI) image sensor including a pixel isolation structure. The BSI image sensor includes a photodetector 105 located in the substrate 102 along a front side 102fs of the substrate 102. The photodetector can include a first doped semiconductor region 108 and a surrounding region of the substrate 102. The first doped semiconductor region 108 can form a p-n junction with the surrounding region of the substrate 102.

[0043] In addition, the pixel transistor 104 including the gate 110 may be disposed along the front side 102fs of the substrate 102, and the floating diffusion (FD) region 106 may be disposed in the substrate 102 along the front side 102fs of the substrate. The first contact 122 may extend through the first dielectric layer 114 to the first metal line 132 and may electrically couple the pixel transistor 104 and / or the FD region 106 to the first metal line 132 or some other suitable metal line. The buffer layer 152 may be disposed on the back side 102bs of the substrate and may extend over the photodetector 105.

[0044] Additionally, a color filter 160 may be disposed on the back side 102bs of the substrate 102 and over the photodetector 105. A composite metal grid (CMG) 155 may be disposed on the back side 102bs of the substrate 102 and over isolation segments (e.g., 150a, 150b) and dummy segments (e.g., 123a, 123b) along the boundaries of the pixels 111. The CMG 155 may include a metal grid layer 154 and a dielectric grid layer 156 disposed over the metal grid layer 154. The color filter 160 may be disposed between the sidewalls of the CMG 155. A microlens 162 may be disposed on the back side 102bs of the substrate 102 and over the color filter 160, and thus the microlens 162 may be disposed over the photodetector 105. Photons 170 may enter the BSI image sensor through the microlens 162. Accordingly, the photons 170 may enter the substrate 102 through the back side 102bs of the substrate 102, rendering the image sensor a "back-side illuminated" type.

[0045] In some embodiments, the pixel transistor 104 may include, for example, a transfer transistor, a source-follower transistor, a row-select transistor, a reset transistor, some other pixel transistor, or another transistor.

[0046] In some embodiments, the FD region 106 and the first doped semiconductor region 108 may include, for example, doped silicon or the like.

[0047] In some embodiments, the first contact 122 may include, for example, tungsten, copper, titanium, some other suitable metal, or any combination of the above materials.

[0048] In some embodiments, the buffer layer 152 may include, for example, silicon dioxide, silicon nitride, some other suitable dielectric, or any combination of the above materials.

[0049] In some embodiments, the metal grid layer 154 may include, for example, tungsten, copper, another suitable metal, or any combination of the foregoing materials. In some embodiments, the dielectric grid layer 156 may include, for example, silicon dioxide, silicon nitride, another suitable dielectric, or any combination of the foregoing materials.

[0050] Figure 7 A cross-sectional view 700 showing some embodiments of a front-side illumination (FSI) image sensor including a pixel isolation structure is shown. The FSI image sensor includes a photodetector 105 located in a substrate 102 along a front side 102fs of the substrate 102. A first metal wire 133 may not extend over or beyond the boundary of the photodetector 105 so that radiation can be transmitted from the front side 102fs of the substrate 102 to the photodetector 105. One or more additional metal wires and vias (e.g., 138, 140) may be formed over the first metal wire 133, and the one or more additional metal wires and vias (e.g., 138, 140) may not extend over or beyond the boundary of the photodetector 105.

[0051] Additionally, a color filter 160 may be disposed on the front side 102fs of the substrate 102 and over the photodetector 105. A CMG 155 may be disposed on the front side 102fs of the substrate 102 and over isolation segments (e.g., 150a, 150b) and dummy segments (e.g., 123a, 123b) along the boundary of a pixel 111. The color filter 160 may be disposed between sidewalls of the CMG 155. A microlens 162 may be disposed on the front side 102fs of the substrate 102 and over the color filter 160, and thus the microlens 162 may be disposed over the photodetector 105. Photons 170 may enter the FSI image sensor through the microlens 162. Accordingly, the photons 170 may enter the substrate 102 through the front side 102fs of the substrate 102, rendering the image sensor "front-side illuminated".

[0052] Figure 8 A cross-sectional view 800 showing some additional embodiments of an image sensor including a plurality of pixels and a pixel isolation structure, the pixel isolation structure including a dummy contact structure 123, is shown. The cross-sectional view 800 may be along, for example, Figure 9Intercepted along line B-B' shown in. The first pixel 111a including the first photodetector 105a may be laterally adjacent to the second pixel 111b including the second photodetector 105b. The second isolation section 150b may separate the substrate 102 along the boundary between the first pixel 111a and the second pixel 111b, such that the substrate 102 includes a first substrate region 102a and a separated second substrate region 102b. In addition, a third isolation section 150c may be provided along the boundary of the second pixel 111b. Additionally, the second dummy section 123b may further separate the first pixel 111a and the second pixel 111b along the boundary between the pixels. In addition, a third dummy section 123c may be provided along the boundary of the second pixel 111b.

[0053] The second isolation section 150b and the second dummy section 123b may together isolate the first pixel 111a and the second pixel 111b. In this way, the first photon 170a entering the first pixel 111a may not leave the first pixel 111a and enter the second pixel 111b. In addition, the second photon 170b entering the second pixel 111b may not leave the second pixel 111b and enter the first pixel 111a. Therefore, crosstalk between the first pixel 111a and the second pixel 111b can be reduced, thereby improving the performance of the image sensor.

[0054] Figure 9 Shown Figure 8 A top view 900 of some embodiments of the image sensor shown. The image sensor may include a pixel array including a plurality of pixels. For example, the first pixel 111a, the second pixel 111b, the third pixel 111c, and the fourth pixel 111d may be arranged in a four-by-four array along the substrate 102. The substrate isolation structure 150 may laterally separate the first pixel 111a, the second pixel 111b, the third pixel 111c, and the fourth pixel 111d from each other along the boundaries of the foregoing pixels (i.e., the substrate isolation structure 150 may continuously and separately surround the first pixel 111a, the second pixel 111b, the third pixel 111c, and the fourth pixel 111d in a closed path along the boundaries of the foregoing pixels). Therefore, the substrate 102 may be divided into four or more substrate regions (not shown), and the substrate regions are laterally separated from each other by the substrate isolation structure 150. Additionally, the dummy contact structure 123 may be directly disposed below the substrate isolation structure 150. Therefore, the first dielectric layer 114 may be divided into four or more dielectric regions (e.g., 114a, 114b, 114c, 114d), and the dielectric regions are laterally separated from each other by the dummy contact structure 123.

[0055] In some embodiments, the dummy contact structure 123 and the substrate isolation structure 150 extend laterally along the boundary of the first pixel 111a in a first closed path and along the boundary of the second pixel 111b in a second closed path. In such embodiments, the second closed path overlaps with the first closed path partially but not completely (e.g., located between the first pixel 111a and the second pixel 111b).

[0056] Figures 10 to 29 Cross-sectional views 1000 to 2900 showing some embodiments of a method of forming a BSI image sensor including a pixel isolation structure, the pixel isolation structure including a dummy contact structure 123. Although described with respect to one method Figures 10 to 29 , it should be understood that Figures 10 to 29 the structures disclosed in

[0057] are not limited to such method only, but may exist independently as structures independent of the method. Figure 10 As shown in cross-sectional view 1000 of

[0058] , a photodetector 105 may be formed in the front side 102fs of the substrate 102. The photodetector 105 may include a first doped semiconductor region 108. The doping type of the first doped semiconductor region 108 may be opposite to the doping type of the substrate 102, such that the first doped semiconductor region 108 and the substrate 102 together form a p-n junction (i.e., a photodiode). A floating diffusion (FD) region 106 may also be formed in the front side 102fs of the substrate 102. Additionally, pixel transistors 104 may be formed along the front side 102fs of the substrate 102. In some embodiments, the first doped semiconductor region 108 and the FD region 106 may be formed in the substrate 102 by ion implantation or another suitable process. Figure 11 As shown in cross-sectional view 1100 of

[0059] , a first etch stop layer 112 and a first dielectric layer 114 may be formed on the front side of the substrate, such that the first etch stop layer 112 separates the first dielectric layer 114 from the substrate 102 in the vertical direction. The first dielectric layer 114 may cover the pixel transistors 104. The first etch stop layer 112 and the first dielectric layer 114 may be formed, for example, by chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), spin-on process, another suitable deposition process, or any combination of the above processes. Figure 12As shown in the cross-sectional view 1200, a first photoresist mask 116 can be formed over the first dielectric layer 114. The first dielectric layer 114 and the first etch stop layer 112 can be patterned with the first photoresist mask 116 in place to form a plurality of contact openings in the first dielectric layer 114 and the first etch stop layer 112. For example, the plurality of contact openings can include a first contact opening 118 and a pair of dummy contact openings 118d. The pair of dummy contact openings 118d can expose a portion of the front side 102fs of the substrate 102. Patterning can include, for example, wet etching, dry etching, or some other suitable etching.

[0060] In some embodiments, the first contact opening 118 can be formed over the FD region 106. Additionally, the pair of dummy contact openings 118d can be formed, for example, on opposite sides of the photodetector 105. In some embodiments, the dummy contact openings 118d correspond to segments of an annular opening that has the same layout as the Figure 2 dummy contact structure in. However, other suitable top layouts are also feasible. The plurality of contact openings can extend through the first dielectric layer 114 and the first etch stop layer 112 to the front side 102fs of the substrate 102.

[0061] As Figure 13 shown in the cross-sectional view 1300, a first contact 122 and a dummy contact structure 123 including a first dummy segment 123a and a second dummy segment 123b can be formed in the first contact opening 118 and the pair of dummy contact openings 118d, respectively, by depositing a first metal material in the foregoing openings. After depositing the first metal material, the first metal material can overlie the top of the first dielectric layer 114. Depositing the first metal material can include, for example, a sputtering process, an electroplating process, another suitable deposition process, or any combination of the foregoing processes.

[0062] As Figure 14 shown in the cross-sectional view 1400, a planarization process can be performed to remove the first metal material from the top of the first dielectric layer 114 such that the top of the first contact 122, the top of the first dummy segment 123a, and the top of the second dummy segment 123b are flush with the top of the first dielectric layer 114. In some embodiments, the first dummy segment 123a and the second dummy segment 123b correspond to segments of an annular dummy contact structure that has the same layout as the Figure 2 dummy contact structure in. The planarization process can include, for example, chemical mechanical polish (CMP) or some other suitable planarization process.

[0063] As Figure 15As shown in the cross-sectional view 1500, a second etch stop layer 124 and a second dielectric layer 126 can be formed over the first dielectric layer 114 and on top of the first contact 122, the first dummy segment 123a, and the second dummy segment 123b. The second etch stop layer 124 and the second dielectric layer 126 can be formed, for example, by CVD, PVD, ALD, spin coating process, another suitable deposition process, or any combination of the above processes.

[0064] As Figure 16 shown in the cross-sectional view 1600, a second photoresist mask 128 can be formed over the second dielectric layer 126. The second dielectric layer 126 and the second etch stop layer 124 can be patterned with the second photoresist mask 128 in place to form a first trench opening 130 in the second dielectric layer 126 and the second etch stop layer 124. The first trench opening 130 can extend over the photodetector 105 and can further extend from above the top of the first dummy segment 123a to above the top of the second dummy segment 123b (i.e., extend between the first dummy segment 123a and the second dummy segment 123b). The patterning can include, for example, wet etching, dry etching, or some other suitable etching.

[0065] As Figure 17 shown in the cross-sectional view 1700, a first metal wire 132 can be formed in the first trench opening 130 by depositing a second metal material in the first trench opening 130. After depositing the second metal material, the second metal material can overlie the top of the second dielectric layer 126 and can continuously extend from above the top of the first dummy segment 123a to above the top of the second dummy segment 123b. Depositing the second metal material can include, for example, a sputtering process, an electroplating process, another suitable deposition process, or any combination of the above processes.

[0066] As Figure 18 shown in the cross-sectional view 1800, a planarization process can be performed to remove the second metal material from the top of the second dielectric layer 126 such that the top of the first metal wire 132 can be flush with the top of the second dielectric layer 126. The polishing or planarization process can include, for example, CMP or some other suitable planarization process.

[0067] As Figure 19As shown in the cross-sectional view 1900, one or more dielectric layers and one or more etch stop layers may be formed over the first metal line 132. For example, a third etch stop layer 134 may be formed over the first metal line 132 and the second dielectric layer 126, a third dielectric layer 136 may be formed over the third etch stop layer 134, a fourth etch stop layer 135 may be formed over the third dielectric layer 136, and a fourth dielectric layer 137 may be formed over the fourth etch stop layer 135. Any of the foregoing layers may be formed, for example, by CVD, PVD, ALD, spin coating processes, another suitable deposition process, or any combination of the foregoing processes.

[0068] As Figure 20 As shown in the cross-sectional view 2000, one or more metal lines and one or more vias may be formed over the first metal line 132. For example, a first via 138 may be formed within the third dielectric layer 136 and over the first metal line 132. The first via 138 may directly contact the first metal line 132. Additionally, a second metal line 140 may be formed within the fourth dielectric layer 137 and over the first via 138. The second metal line 140 may directly contact the first via 138. Any of the foregoing metal lines and vias may be formed, for example, by sputtering, electroplating processes, another suitable deposition process, or any combination of the foregoing processes.

[0069] As Figure 21 As shown in the cross-sectional view 2100, additional internal connections 142 may be formed over the second metal line 140. The additional internal connections 142 may include additional metal lines and additional vias. The additional internal connections 142 may be formed, for example, by sputtering, electroplating processes, another suitable deposition process, or any combination of the foregoing processes.

[0070] As Figure 22 As shown in the cross-sectional view 2200, the image sensor may be rotated such that the rear side 102bs of the substrate 102 is overlaid on the front side 102fs of the substrate 102.

[0071] As Figure 23As shown in the cross-sectional view 2300, a third photoresist mask 144 may be formed over the back side 102bs of the substrate 102. The back side 102bs of the substrate 102 may be patterned with the third photoresist mask 144 in place to form a pair of isolation openings 146 in the back side 102bs of the substrate 102. The pair of isolation openings 146 may extend through the substrate from the back side 102bs to the front side 102fs on opposite sides of the photodetector 105. In addition, the pair of isolation openings 146 may be formed over the first dummy segment 123a and the second dummy segment 123b (i.e., the pair of isolation openings 146 may be aligned with the first dummy segment 123a and the second dummy segment 123b, respectively). In some embodiments, the isolation openings 146 correspond to multiple segments of an annular opening that has the same layout as the Figure 2 substrate isolation structure in. However, other suitable layouts are also possible. The patterning may include, for example, wet etching, dry etching, or some other suitable etching.

[0072] As Figure 24 shown in the cross-sectional view 2400, a substrate isolation structure 150 may be formed over the back side 102bs of the substrate 102 and the substrate isolation structure 150 may be formed in the pair of isolation openings 146 to define a first isolation segment 150a and a second isolation segment 150b. In some embodiments, the substrate isolation structure 150 is annular as shown in Figure 2 , and the first isolation segment 150a and the second isolation segment 150b correspond to multiple segments of the annulus. However, other suitable layouts are also possible. The substrate isolation structure 150 may be formed by depositing a first isolation material over the back side 102bs of the substrate 102 and in the pair of isolation openings 146. Depositing the first isolation material may include, for example, CVD, PVD, ALD, spin coating processes, another suitable deposition process, or any combination of the above processes. Additionally, it should be understood that forming the substrate isolation structure 150 may further include depositing a second isolation material over the first isolation material such that the substrate isolation structure 150 includes a first isolation layer 145 and a second isolation layer 147 surrounded by the first isolation layer 145, as shown in Figure 5 .

[0073] As Figure 25 shown in the cross-sectional view 2500, a planarization process may be performed to reduce the thickness of the substrate isolation structure 150. After the planarization process, the substrate isolation structure 150 may extend over the photodetector 105 (i.e., after the planarization process, the substrate isolation structure 150 may cover the back side 102bs of the substrate 102), as shown in Figure 25As shown. However, it should be understood that in some alternative embodiments, after the polishing or planarization process, the substrate isolation structure 150 may not extend over the photodetector 105 (i.e., after the polishing or planarization process, the substrate isolation structure 150 may not cover the back side 102bs of the substrate 102). The planarization process may include, for example, CMP or some other suitable planarization process.

[0074] As Figure 26 As shown in the cross-sectional view 2600 of, a buffer layer 152 may be formed over the back side 102bs of the substrate 102 and over the top of the substrate isolation structure 150. The buffer layer 152 may be formed, for example, by CVD, PVD, ALD, spin coating process, another suitable deposition process, or any combination of the above processes.

[0075] As Figure 27 As shown in the cross-sectional view 2700 of, a metal grid layer 154 may be formed over the buffer layer 152, and a dielectric grid layer 156 may be formed over the metal grid layer 154. The metal grid layer 154 may be formed, for example, by depositing a metal material over the buffer layer 152 using a sputtering process, an electroplating process, another suitable deposition process, or any combination of the above processes. The dielectric grid layer 156 may be formed, for example, by CVD, PVD, ALD, spin coating process, another suitable deposition process, or any combination of the above processes over the metal grid layer 154.

[0076] As Figure 28 As shown in the cross-sectional view 2800 of, a fourth photoresist mask 158 may be formed over the dielectric grid layer 156. The dielectric grid layer 156 and the metal grid layer 154 may be patterned with the fourth photoresist mask 158 in place to form a CMG 155 over the back side 102bs of the substrate 102. The CMG 155 may be formed directly over the first isolation segment 150a and the second isolation segment 150b. The patterning may include, for example, wet etching, dry etching, or some other suitable etching.

[0077] As Figure 29 As shown in the cross-sectional view 2900 of, one or more color filters may be formed over the buffer layer 152 and laterally adjacent to the CMG 155. Additionally, one or more microlenses may be formed over the one or more color filters, respectively. For example, a color filter 160 may be formed over the buffer layer 152 and between the CMG 155, and a microlens 162 may be formed directly over the color filter.

[0078] By forming a dummy contact structure 123 in the first dielectric layer 114 along the boundary of the pixel 111, a first region of the first dielectric layer 114 can be isolated from an adjacent region of the first dielectric layer 114 corresponding to an adjacent pixel. In addition, by forming a substrate isolation structure 150 directly over the dummy contact structure 123, a first region of the substrate 102 can also be isolated from an adjacent region of the substrate 102 corresponding to an adjacent pixel. Further, by forming a first metal such that a first metal line extends continuously between a first dummy segment 123a and a second dummy segment 123b, the pixel 111 can be further isolated from adjacent pixels at the interconnect level. Accordingly, the likelihood that photons leave the pixel 111 and enter an adjacent pixel at the first dielectric layer 114 and / or the substrate 102 can be reduced. Accordingly, the performance of the image sensor can be improved.

[0079] Figure 30 A flowchart showing some embodiments of a method 3000 of forming a BSI image sensor including a pixel isolation structure, the pixel isolation structure including a dummy contact structure.

[0080] Although the method 3000 is shown and described below as a series of acts or events, it should be understood that the order of such acts or events shown is not to be construed in a limiting sense. For example, some acts may occur in a different order and / or be synchronized with other acts or events other than those shown and / or described herein. Additionally, it may not be necessary to perform all of the acts shown to implement one or more aspects or embodiments of the description herein. Further, one or more of the acts depicted herein may be implemented in one or more separate acts and / or phases.

[0081] At 3002, a photodetector may be formed in the front side of a substrate, and a first dielectric layer may be formed on the front side of the substrate. Figure 10 And Figure 11 Cross-sectional views 1000 and 1100 showing some embodiments corresponding to act 3002.

[0082] At 3004, the first dielectric layer may then be patterned to form dummy contact openings in the first dielectric layer and on opposite sides of the photodetector. Figure 12 Cross-sectional view 1200 showing some embodiments corresponding to act 3004.

[0083] At 3006, a first metal material may be deposited in the dummy contact openings to form dummy contact structures in the dummy contact openings. Figure 13 Cross-sectional view 1300 showing some embodiments corresponding to act 3006.

[0084] At 3008, a second dielectric layer may be formed over the first dielectric layer and on top of the dummy contact structures. Figure 15Cross-sectional view 1500 showing some embodiments corresponding to operation 3008.

[0085] At 3010, the second dielectric layer may be patterned to form a first trench opening in the second dielectric layer. The first trench opening may extend over the photodetector and may further extend from the top of the first dummy segment of the dummy contact structure to above the top of the second dummy segment. Figure 16 Cross-sectional view 1600 showing some embodiments corresponding to operation 3010.

[0086] At 3012, a second metal material may be deposited in the first trench opening to form a first metal line in the first trench opening. Figure 17 Cross-sectional view 1700 showing some embodiments corresponding to operation 3012.

[0087] At 3014, one or more dielectric layers, one or more metal lines, and one or more vias may be formed over the first metal line. Figure 19 and Figure 20 Cross-sectional views 1900 and 2000 showing some embodiments corresponding to operation 3014.

[0088] At 3016, the substrate may be rotated such that the back side of the substrate overlays the front side of the substrate. Figure 22 Cross-sectional view 2200 showing some embodiments corresponding to operation 3016.

[0089] At 3018, the back side of the substrate may be patterned to form an isolation opening in the back side of the substrate. The isolation opening may extend through the substrate from the back side to the front side on opposite sides of the photodetector. Additionally, the isolation opening may be formed over the first dummy segment and the second dummy segment. Figure 23 Cross-sectional view 2300 showing some embodiments corresponding to operation 3018.

[0090] At 3020, a first isolation material may be deposited over the back side of the substrate and in the isolation opening to form a substrate isolation structure. Figure 24 Cross-sectional view 2400 showing some embodiments corresponding to operation 3020.

[0091] At 3022, a planarization process may be performed on the first isolation material. Figure 25 Cross-sectional view 2500 showing some embodiments corresponding to operation 3022.

[0092] At 3024, a buffer layer may be formed over the back side of the substrate and over the top of the substrate isolation structure. Figure 26 Cross-sectional view 2600 showing some embodiments corresponding to operation 3024.

[0093] At 3026, a composite metal grid may be formed over the back side of the substrate. Figure 27 And Figure 28 Cross-sectional views 2700 and 2800 showing some embodiments corresponding to operation 3026 are shown.

[0094] At 3028, one or more color filters may be formed over the buffer layer and laterally adjacent to the CMG. Additionally, one or more microlenses may be formed over the one or more color filters, respectively. Figure 29 Cross-sectional view 2900 showing some embodiments corresponding to operation 3028 is shown.

[0095] Figures 31 to 44 Cross-sectional views 3100 to 4400 showing some embodiments of a method of forming an FSI image sensor including a pixel isolation structure are shown, the pixel isolation structure including a dummy contact structure 123. Although described with respect to one method Figures 31 to 44 , it should be understood that Figures 31 to 44 the structures disclosed herein are not limited to such a method, but may exist separately as structures independent of the method.

[0096] Figures 31 to 40 Showing a process similar to the process shown in Figures 10 to 25 . However, in the method of forming an FSI image sensor, the metal lines may be restricted to the sides of the photodetector 105 so as not to block the photodetector 105 from receiving radiation from the front side 102fs of the substrate 102. In this way, one or more metal lines (e.g., 133, 140, etc.) may not be formed over the photodetector 105, and thus the first metal line 133 may not extend from the top of the first dummy segment 123a to the top of the second dummy segment 123b, as Figure 36 shown.

[0097] As Figure 41 shown in cross-sectional view 4100 of

[0098] As Figure 42 shown in cross-sectional view 4200 of

[0099] As Figure 43As shown in cross-sectional view 4300, a fourth photoresist mask 158 may be formed over the dielectric grid layer 156. The dielectric grid layer 156 and the metal grid layer 154 may be patterned with the fourth photoresist mask 158 in place to form the CMG 155 over the front side 102fs of the substrate 102. The patterning may include, for example, wet etching, dry etching, or some other suitable etching.

[0100] As Figure 44 As shown in cross-sectional view 4400, one or more color filters may be formed over the front side 102fs of the substrate 102 and adjacent to the CMG 155. Additionally, one or more microlenses may be formed over the one or more color filters, respectively. For example, a color filter 160 may be formed between the front side 102fs of the substrate 102 and the CMG 155, and a microlens 162 may be formed directly over the color filter.

[0101] Similarly, by forming dummy contact structures 123 in the first dielectric layer 114 along the boundaries of the pixels and by forming a substrate isolation structure 150 directly over the dummy contact structures 123, the pixels 111 may be isolated from adjacent pixels. Accordingly, the likelihood that photons leave the pixel 111 and enter adjacent pixels at the first dielectric layer 114 and / or the substrate 102 may be reduced. Accordingly, the performance of the image sensor may be improved.

[0102] Figure 45 A flowchart showing some embodiments of a method 4500 of forming an FSI image sensor including a pixel isolation structure, the pixel isolation structure including dummy contact structures.

[0103] Although the method 4500 is shown and described below as a series of acts or events, it should be understood that the illustrated order of such acts or events should not be construed in a limiting sense. For example, some acts may occur in a different order and / or be synchronized with other acts or events other than those shown and / or described herein. Additionally, it may not be necessary to perform all of the illustrated acts to implement one or more aspects or embodiments of the description herein. Further, one or more of the acts illustrated herein may be performed in one or more separate acts and / or phases.

[0104] At 4502, a photodetector may be formed in the front side of the substrate, and a first dielectric layer may be formed over the front side of the substrate. Figure 31 and Figure 32 Cross-sectional views 3100 and 3200 showing some embodiments corresponding to act 4502.

[0105] At 4504, the first dielectric layer may then be patterned to form dummy contact openings in the first dielectric layer and on opposite sides of the photodetector.Figure 33 Cross-sectional view 3300 showing some embodiments corresponding to operation 4504.

[0106] At 4506, a first metal material may be deposited in the dummy contact opening to form a dummy contact structure in the dummy contact opening. Figure 34 Cross-sectional view 3400 showing some embodiments corresponding to operation 4506.

[0107] At 4508, one or more dielectric layers, one or more metal lines, and one or more vias may be formed over the dummy contact structure. Figure 36 Cross-sectional view 3600 showing some embodiments corresponding to operation 4508.

[0108] At 4510, the substrate may be rotated such that the back side of the substrate overlies the front side of the substrate. Figure 37 Cross-sectional view 3700 showing some embodiments corresponding to operation 4510.

[0109] At 4512, the back side of the substrate may be patterned to form isolation openings in the back side of the substrate. The isolation openings may extend through the substrate from the back side to the front side on opposite sides of the photodetector. Additionally, the isolation openings may be formed over the first dummy segment and the second dummy segment. Figure 38 Cross-sectional view 3800 showing some embodiments corresponding to operation 4512.

[0110] At 4514, a first isolation material may be deposited over the back side of the substrate and in the isolation openings to form a substrate isolation structure. Figure 39 Cross-sectional view 3900 showing some embodiments corresponding to operation 4514.

[0111] At 4516, a planarization process may be performed on the first isolation material. Figure 40 Cross-sectional view 4000 showing some embodiments corresponding to operation 4516.

[0112] At 4518, the substrate may be rotated again such that the front side of the substrate overlies the back side of the substrate. Figure 41 Cross-sectional view 4100 showing some embodiments corresponding to operation 4518.

[0113] At 4520, a composite metal grid may be formed over the front side of the substrate. Figure 42 And Figure 43 Cross-sectional views 4200 and 4300 showing some embodiments corresponding to operation 4520.

[0114] At 4522, one or more color filters may be formed over the front side of the substrate and laterally adjacent to the CMG. Additionally, one or more microlenses may be formed over the one or more color filters, respectively.Figure 44 A cross-sectional view 4400 showing some embodiments corresponding to operation 4522 is illustrated.

[0115] Accordingly, the present disclosure relates to an image sensor including a pixel isolation structure and a method of forming an image sensor, the pixel isolation structure including a dummy contact structure for improving pixel isolation to reduce crosstalk between pixels.

[0116] Accordingly, in some embodiments, the present disclosure relates to an image sensor structure. The image sensor structure includes a substrate. The substrate includes a first side and a second side opposite the first side. A photodetector extends into the first side of the substrate. An isolation structure includes a first isolation segment and a second isolation segment extending through the substrate. The first isolation segment and the second isolation segment are respectively located on opposite sides of the photodetector and include a dielectric. A first metal line is located on the first side of the substrate. A dummy contact structure includes a first dummy segment and a second dummy segment. Both the first dummy segment and the second dummy segment include metal and extend from the first metal line to the first isolation segment and the second isolation segment respectively.

[0117] In some embodiments, the image sensor structure further includes: a dielectric layer covering the substrate on the second side of the substrate, wherein the dielectric layer defines the first isolation section and the second isolation section. In some embodiments, the isolation structure includes a deep trench isolation (DTI) structure extending into the second side of the substrate to a first depth, and further includes a shallow trench isolation (STI) structure extending into the first side of the substrate to a second depth, the second depth being less than the first depth, and wherein the deep trench isolation structure is in direct contact with the shallow trench isolation structure. In some embodiments, the dummy contact structure includes an annular top layout that extends in a closed path laterally around the boundary of the photodetector. In some embodiments, the isolation structure directly overlies and is in direct contact with the dummy contact structure, and also extends in a closed path laterally around the boundary of the photodetector. In some embodiments, the isolation structure includes a first isolation layer and a second isolation layer, wherein the first isolation layer wraps around the lower side of the second isolation layer, and the first isolation layer separates the second isolation layer from the substrate at each of the first isolation section and the second isolation section, and wherein the first isolation layer contains the dielectric and the second isolation layer contains metal. In some embodiments, the image sensor structure further includes: an adjacent photodetector disposed in the first side of the substrate, wherein the second isolation section and the second dummy section laterally separate the photodetector from the adjacent photodetector. In some embodiments, the first metal line is reflective and extends continuously between the first dummy section and the second dummy section, and wherein the image sensor structure further includes a microlens located above the photodetector and on the second side of the substrate. In some embodiments, the image sensor structure further includes: a composite metal grid located on the first side of the substrate and directly above the isolation structure at both the first isolation section and the second isolation section; and a microlens located on the first side of the substrate and disposed above the photodetector.

[0118] In other embodiments, the present disclosure relates to an image sensor structure. The image sensor structure includes a substrate. The substrate includes an upper surface and a lower surface. Pixels include photodetectors along the lower surface of the substrate. A substrate isolation structure includes a first dielectric material. The substrate isolation structure extends vertically through the substrate from the upper surface of the substrate to the lower surface of the substrate. The substrate isolation structure extends laterally along the boundary of the pixel in a first closed path. A metal reflector is located under the photodetector. A dummy contact structure includes a first metal material extending from the metal reflector to the substrate isolation structure. The dummy contact structure also extends laterally along the boundary of the pixel in the first closed path.

[0119] In some embodiments, the image sensor structure further includes: a second pixel adjacent to the pixel, wherein the dummy contact structure and the substrate isolation structure extend laterally along the boundary of the second pixel in a second closed path, and wherein the second closed path partially but not completely overlaps with the first closed path. In some embodiments, the metal reflector, the dummy contact structure, and the substrate isolation structure define a composite structure that surrounds the photodetector and extends vertically in a second closed path. In some embodiments, the first closed path is confined to the boundary of the pixel. In some embodiments, the substrate isolation structure includes a deep trench isolation (DTI) structure and a shallow trench isolation (STI) structure, and wherein the dummy contact structure is vertically separated from the deep trench isolation structure by the shallow trench isolation structure. In some embodiments, the dummy contact structure has a first segment and a second segment located on opposite sides of the pixel, and wherein the metal reflector extends from the bottom of the first segment to the bottom of the second segment. In some embodiments, the substrate isolation structure is defined by a metal layer and a dielectric layer surrounding the metal layer, such that the dielectric layer separates the metal layer from the substrate.

[0120] In still some other embodiments, the present disclosure relates to a method of forming an image sensor structure. The method includes forming a photodetector in a first side of a substrate and forming a first dielectric layer on the first side of the substrate. The first dielectric layer is patterned to form a first opening having a pair of first opening segments exposing the first side of the substrate. The first opening segments respectively abut the photodetector on opposite sides of the photodetector. A dummy contact structure is formed in the first opening, and the dummy contact structure includes a first dummy segment and a second dummy segment respectively located in the first opening segments. A metal reflector directly contacting the first dummy segment and the second dummy segment is formed on the first side of the substrate. A second side of the substrate opposite the first side is patterned to form a second opening having a pair of second opening segments respectively aligned with the first dummy segment and the second dummy segment. A substrate isolation structure is formed in the second opening, and the substrate isolation structure includes a first isolation segment and a second isolation segment respectively located in the second opening segments.

[0121] In some embodiments, the method further includes performing a planarization process on the substrate isolation structure to reduce the thickness of the substrate isolation structure. In some embodiments, forming the substrate isolation structure includes depositing a second dielectric layer lining the second opening and partially filling the second opening; and depositing a metal layer on the second dielectric layer to fill the remaining portion of the second opening such that the second dielectric layer separates the metal layer from the substrate. In some embodiments, forming the substrate isolation structure includes forming a shallow trench isolation (STI) structure in the first side of the substrate; and forming a deep trench isolation (DTI) structure in the second opening and directly on the shallow trench isolation structure.

[0122] The features of several embodiments are outlined above so that those skilled in the art may better understand various aspects of the present disclosure. Those skilled in the art should understand that they can readily use the present disclosure as a basis for designing or modifying other processes and structures to achieve the same purposes and / or realize the same advantages as the embodiments described herein. Those skilled in the art should also recognize that these equivalent structures do not depart from the spirit and scope of the present disclosure, and that they can make various changes, substitutions, and alterations to this document without departing from the spirit and scope of the present disclosure.

Claims

1. An image sensor structure, comprising: A substrate, including a first side and a second side opposite to the first side; A photodetector extending into the first side of the substrate; An isolation structure including a first isolation segment and a second isolation segment extending through the substrate, wherein the first isolation segment and the second isolation segment are respectively located on opposite sides of the photodetector and contain a dielectric; A first metal line located on the first side of the substrate; And A dummy contact structure including a first dummy segment and a second dummy segment, wherein both the first dummy segment and the second dummy segment contain metal and extend from the first metal line to the first isolation segment and the second isolation segment respectively, Wherein the first metal line extends laterally directly below the photodetector to connect the first dummy segment and the second dummy segment, and the projected area of the photodetector on the first side of the substrate falls within the projected area of the first metal line on the first side of the substrate.

2. The image sensor structure according to claim 1, further comprising: A dielectric layer covering the substrate on the second side of the substrate, wherein the dielectric layer defines the first isolation segment and the second isolation segment.

3. The image sensor structure according to claim 1, wherein the isolation structure includes a deep trench isolation structure extending into the second side of the substrate to a first depth, and further includes a shallow trench isolation structure extending into the first side of the substrate to a second depth, the second depth being less than the first depth, and wherein the deep trench isolation structure is in direct contact with the shallow trench isolation structure.

4. The image sensor structure according to claim 1, wherein the dummy contact structure includes an annular top layout that extends in a closed path laterally around the boundary of the photodetector.

5. The image sensor structure according to claim 4, wherein the isolation structure directly overlies and is in direct contact with the dummy contact structure, and also extends in a closed path laterally around the boundary of the photodetector.

6. The image sensor structure according to claim 1, wherein the isolation structure includes a first isolation layer and a second isolation layer, wherein the first isolation layer surrounds the lower side of the second isolation layer, and the first isolation layer separates the second isolation layer from the substrate at each of the first isolation segment and the second isolation segment, and wherein the first isolation layer contains the dielectric and the second isolation layer contains metal.

7. The image sensor structure according to claim 1, further comprising: An adjacent photodetector disposed in the first side of the substrate, wherein the second isolation segment and the second dummy segment laterally separate the photodetector from the adjacent photodetector.

8. The image sensor structure according to claim 1, wherein the first metal line is reflective and extends continuously between the first dummy segment and the second dummy segment, and wherein the image sensor structure further includes a microlens located above the photodetector and on the second side of the substrate.

9. The image sensor structure according to claim 1, further comprising: a composite metal grid located on the first side of the substrate and directly above the isolation structure at both the first isolation segment and the second isolation segment; and a microlens located on the first side of the substrate and disposed above the photodetector.

10. An image sensor structure, comprising: a substrate including an upper surface and a lower surface; a pixel including a photodetector along the lower surface of the substrate; a substrate isolation structure containing a first dielectric material, wherein the substrate isolation structure extends vertically through the substrate from the upper surface of the substrate to the lower surface of the substrate, and wherein the substrate isolation structure extends laterally along the boundary of the pixel in a first closed path; a metal reflector located below the photodetector; and a dummy contact structure containing a first metal material extending from the metal reflector to the substrate isolation structure, wherein the dummy contact structure extends laterally along the boundary of the pixel in the first closed path, wherein the dummy contact structure has a first segment and a second segment located on opposite sides of the pixel, respectively, and the metal reflector extends from the bottom of the first segment to the bottom of the second segment, wherein the metal reflector extends laterally directly below the photodetector to connect the first segment and the second segment, and the projected area of the photodetector on the lower surface of the substrate falls within the projected area of the metal reflector on the lower surface of the substrate.

11. The image sensor structure according to claim 10, further comprising: a second pixel adjacent to the pixel, wherein the dummy contact structure and the substrate isolation structure extend laterally along the boundary of the second pixel in a second closed path, and wherein the second closed path partially but not completely overlaps with the first closed path.

12. The image sensor structure according to claim 10, wherein the metal reflector, the dummy contact structure, and the substrate isolation structure define a composite structure surrounding the photodetector and extending vertically in a second closed path.

13. The image sensor structure according to claim 10, wherein the first closed path is confined to the boundary of the pixel.

14. The image sensor structure according to claim 10, wherein the substrate isolation structure includes a deep trench isolation structure and a shallow trench isolation structure, and wherein the dummy contact structure is vertically separated from the deep trench isolation structure by the shallow trench isolation structure.

15. The image sensor structure according to claim 10, wherein the substrate isolation structure is defined by a metal layer and a dielectric layer surrounding the metal layer, such that the dielectric layer separates the metal layer from the substrate.

16. A method of forming an image sensor structure, the method comprising: forming a photodetector in a first side of a substrate; forming a first dielectric layer on the first side of the substrate; patterning the first dielectric layer to form a first opening having a pair of first opening segments exposing the first side of the substrate, wherein the first opening segments respectively abut the photodetector on opposite sides of the photodetector; forming a dummy contact structure in the first opening, and the dummy contact structure includes a first dummy segment and a second dummy segment respectively located in the first opening segments; forming a metal reflector directly contacting the first dummy segment and the second dummy segment on the first side of the substrate, wherein the metal reflector laterally extends directly below the photodetector to connect the first dummy segment and the second dummy segment, and a projection area of the photodetector projected on the first side of the substrate falls within a projection area of the metal reflector projected on the first side of the substrate; patterning a second side of the substrate opposite to the first side to form a second opening having a pair of second opening segments respectively aligned with the first dummy segment and the second dummy segment; and forming a substrate isolation structure in the second opening, and the substrate isolation structure includes a first isolation segment and a second isolation segment respectively located in the second opening segments.

17. The method according to claim 16, further comprising: performing a planarization process on the substrate isolation structure to reduce a thickness of the substrate isolation structure.

18. The method according to claim 16, wherein forming the substrate isolation structure includes: depositing a second dielectric layer lining the second opening and partially filling the second opening; and depositing a metal layer on the second dielectric layer to fill the remaining portion of the second opening, such that the second dielectric layer separates the metal layer from the substrate.

19. The method according to claim 16, wherein forming the substrate isolation structure includes: forming a shallow trench isolation structure in the first side of the substrate; and forming a deep trench isolation structure in the second opening and directly above the shallow trench isolation structure.

Images