Light-blocking layer for an image sensor device

Abstract

Image sensor (200), including: a semiconductor layer (202) having a top surface and a bottom surface, wherein the semiconductor layer (202) comprises one or more detection areas (204) designed to detect radiation (800, 802) entering the semiconductor layer (202) from the top surface; a grid structure (216) with one or more cells (218) each aligned with the one or more detection areas (204), wherein each of the one or more cells (218) of the grid structure (216) comprises a color filter (220), wherein each of the one or more cells (218) of the grid structure (216) accommodates the color filter (220) within side walls of the one or more cells (218); a transparent material layer (228) arranged over the grid structure (216), wherein the transparent material layer (228) forms a microlens (230) over each of the one or more cells (218); and a light-blocking material layer (500) arranged on the transparent material layer (228) between microlenses (230).

Description

STATE OF THE ART

[0001] Semiconductor image sensors are used to detect visible and invisible radiation, such as visible light, infrared light, etc. Complementary metal-oxide-semiconductor (CMOS) image sensors (CIS sensors) and charge-coupled device sensors (CCD sensors) are used in various applications, such as digital cameras, mobile phones, tablets, eyeglasses, etc. Arrays of pixels found in CMOS and CIS devices can detect incident radiation projected onto the sensor and convert it into electrical signals.

[0002] US 2013 / 0001724A1 describes a solid-state image sensor in which two lens layers consisting of in-layer lenses and microlenses are arranged on a semiconductor layer. A color filter layer is located between the in-layer lenses and the microlenses, in which the color filters are positioned adjacent to one another. Furthermore, a light blocker is formed at the interfaces between the adjacent microlenses, each of which is positioned above a corresponding color filter. In addition, the microlenses are each aligned with corresponding light-receiving portions in the semiconductor layer.

[0003] Further prior art relating to the subject matter of the invention can be found in publications US 2016 / 0 276 394 A1, US 2014 / 0 077 323 A1 and US 2015 / 0 243 805 A1. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Aspects of the present disclosure are best understood from the detailed description below, when read together with the accompanying figures. It should be noted that, in accordance with standard industry practice, various features are not drawn to scale. Rather, the dimensions of the various features may have been enlarged or reduced as appropriate for clarity of illustration and discussion. Fig. Figure 1 is a flowchart of a method for forming an image sensor device according to some embodiments of the present disclosure. Fig. Figure 2 is a cross-sectional view of a back-illuminated image sensor device according to some embodiments of the present disclosure. Fig. Figure 3 is a top view of a composite grid structure designed to accommodate color filters, according to some embodiments of the present disclosure. Fig. Figure 4 is a cross-sectional view of an enlarged upper section of a back-illuminated image sensor device according to some embodiments of the present disclosure. Fig. Figure 5 is a cross-sectional view of a back-illuminated image sensor device after the deposition of a light-blocking material layer, according to some embodiments of the present disclosure. Fig. Figure 6 is a cross-sectional view of an enlarged upper section of a back-illumination image sensor device after the deposition of a light-blocking material layer, according to some embodiments of the present disclosure. Fig. Figure 7 is a cross-sectional view of an enlarged upper section of a back-illuminated image sensor device after etching a light-blocking material layer, according to some embodiments of the present disclosure. Fig. Figure 8 is a cross-sectional view of a back-illuminated image sensor device after etching a light-blocking material layer, according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0005] The following disclosure provides many different embodiments, or examples, for implementing various features of the present subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, forming a first feature over a second feature in the description below may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features are not in direct contact.

[0006] Furthermore, terms relating to spatial relativity, such as "below," "under," "lower," "above," "upper," and the like, may be used herein for the convenience of discussion to describe the relationship of one element or feature to another element or feature (or other elements or features), as illustrated in the figures. The terms relating to spatial relativity are intended to encompass various orientations of the apparatus used or operated in addition to the orientation illustrated in the figures. The apparatus may be oriented in a different way (rotated by 90 degrees or otherwise), and the terms relating to spatial relativity used herein may likewise be interpreted accordingly.

[0007] As used here, the term "approximately" indicates the value of a given quantity, which may vary based on a specific technology node associated with the object semiconductor device. Based on that specific technology node, the term "approximately" can indicate a value of a given quantity that varies, for example, within 10 to 30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0008] As used here, the term “essentially” indicates that the value of a given quantity varies by ±1% to ±5% of the value.

[0009] In a back-illuminated image sensor device, color filters and microlenses are arranged on the back of a substrate (e.g., on the side of the substrate opposite the circuitry) so that the image sensor device can collect light with minimal or no obstruction. Consequently, back-illuminated image sensors are designed to capture light from the back of the substrate, rather than from the front, where the image sensor device's color filters and microlenses are located between the substrate's circuitry and the pixels. Compared to front-illuminated image sensors, back-illuminated image sensors exhibit improved low-light performance and higher quantum efficiency (QE) (e.g., photon-to-electron conversion percentage).

[0010] Image sensor devices use color filters to detect color information from incident light rays. For example, by using color filters, image sensor devices can detect the red, green, and blue (RGB) regions of the visible light spectrum. A composite grid structure, which can be filled with a color filter material, can be used to arrange the color filter material over the pixels of the image sensor device. The composite grid structure can, for example, comprise an oxide or any other dielectric material that is transparent to visible light.

[0011] During normal operation, incident natural light enters the color filter of the image sensor device from various directions. For example, incident light rays can have angles of incidence ranging from a normal angle (e.g., 90°) to approximately 0° (grazing angle) with respect to a horizontal top surface of the color filter. "Scattered" light rays, which strike the color filter at grazing angles of incidence between approximately 0° and approximately 45°, artificially increase the amount of light collected by the color filter, resulting in an artificial increase in the pixel's quantum efficiency (QE). This artificial increase in the pixel's QE due to scattered light rays is called "crosstalk" and is an undesirable phenomenon. The composite grating structure containing the color filter is transparent to visible light and cannot be used to block scattered light rays.

[0012] Various embodiments according to the present disclosure provide a method for forming a light-blocking material layer (or structure) that can prevent light rays from entering the color filter at grazing angles of incidence. Light rays entering the color filter at grazing angles of incidence can also be referred to as "scattered" light rays. In some embodiments of the present disclosure, the light-blocking material layer can reflect the incident light. Alternatively, the light-blocking material layer can absorb the incident light. In some embodiments of the present disclosure, the light-blocking material layer is formed using a self-adjusting process such that the light-blocking material layer is selectively formed in areas where light rays at grazing angles of incidence can enter the color filter.Such regions can, for example, be areas of the composite lattice structure between the microlenses. In some embodiments of the present disclosure, the light-blocking material layer is a metal—such as tungsten, aluminum, or copper—or a metal alloy. In other embodiments of the present disclosure, the light-blocking material layer can be a dielectric, such as silicon oxide, silicon oxynitride, or silicon carbide. Alternatively, the light-blocking material layer can comprise an infrared (IR) color filter material that can absorb visible light and allow IR to pass through. According to some embodiments of the present disclosure, the light-blocking material layer improves the light-guiding capacity of the composite lattice structure.

[0013] According to some embodiments of the present disclosure, Fig. 1. A method 100 for forming a light-blocking layer that can prevent stray light rays from entering the color filters of an image sensor device. The formation of the light-blocking layer can therefore prevent or minimize crosstalk in the image sensor device (e.g., a back-illuminated image sensor device). For illustrative purposes, method 100 is described in the context of a back-illuminated image sensor device. However, method 100 may not be limited to back-illuminated image sensor devices and can be applied to other types of image sensor devices (e.g., front-illuminated image sensor devices) that utilize similar material layers and / or geometries. These other types of image sensor devices are within the scope of the invention and the present disclosure.

[0014] With reference to Fig. 1. Procedure 100 begins with process 102, in which a light-blocking material layer is deposited over a transparent material layer that forms microlenses on a composite grid structure of an image sensor device. Fig. Figure 2 is a simplified cross-sectional view of a back-illumination image sensor device 200 according to some embodiments of the present disclosure. The back-illumination image sensor device 200 comprises a semiconductor layer 202 with radiation detection areas 204. By way of example, and not as a limitation, the semiconductor layer 202 comprises silicon material doped with a p-type dopant, such as boron. Alternatively, the semiconductor layer 202 may comprise silicon doped with an n-type dopant, such as phosphorus or arsenic. The semiconductor layer 202 may also comprise other elemental semiconductors, such as germanium or diamond. The semiconductor layer 202 may optionally comprise a compound semiconductor and / or an alloy semiconductor. Furthermore, the semiconductor layer 202 may include an epitaxial layer that can be strained to improve performance.The semiconductor layer 202 can comprise an SOI (silicon on an insulator) structure.

[0015] The semiconductor layer 202 has a front (also referred to as a bottom surface) 206 and a back (also referred to as a top surface) 208. The semiconductor layer 202 has a thickness that can range from approximately 100 µm to approximately 3000 µm.

[0016] Radiation detection areas or pixels 204 are formed in the semiconductor layer 202. As disclosed herein, the terms "radiation detection areas" and "pixels" may be used interchangeably. The pixels 204 are designed to detect radiation, such as incident light rays striking the semiconductor layer 202 from the rear side 208. According to some embodiments of the present disclosure, each of the radiation detection areas or pixels 204 may include a photodiode capable of converting photons into electrical charge. In some embodiments of the present disclosure, the pixels 204 may include photodiodes, transistors, amplifiers, other similar devices, or combinations thereof. The pixels 204 may also be referred to herein as "radiation detection devices" or "light sensors."

[0017] For simplicity's sake, two pixels are 204 in Fig. Figure 2 shows that additional pixels 204 can be implemented in semiconductor layer 202. As an example, and not as a limitation, pixels 204 can be formed on semiconductor layer 202 from the front face 206 using an ion implantation process. Pixels 204 can also be formed by a dopant diffusion process.

[0018] Pixels 204 are electrically isolated from each other by STO structures 210 (shallow trench isolation) and DTI structures 211 (deep trench isolation). The STI structures 210 and the DTI structures 211 are trenches etched into the semiconductor layer 202 and filled with a dielectric material, such as silicon oxide, silicon nitride, silicon oxynitride, fluorine-doped silicate glass (FSG), a low-k dielectric material (e.g., a material with a k-value lower than 3.9), and / or a suitable insulating material. According to some embodiments of the present disclosure, the DTI structures 211 have an antireflection coating (ARC) 212 on the back side 208 of the semiconductor layer 202. The ARC 212 is a liner layer that prevents incident light rays from being reflected away from the radiation detection areas / pixels 204. The ARC 212 can be a high-k material (e.g., a material with a k-value lower than 3.9), such as...B. hafnium oxide (HfO2), tantalum pentoxide (Ta2O5), zirconium dioxide (ZrO2), aluminum oxide (Al2O3), or any other high-k material. ARC 212 can be deposited using sputtering, a chemical vapor deposition (CVD) process, an atomic layer deposition (ALD) process, or any other suitable deposition process or method. In some embodiments of the present disclosure, the thickness of ARC 212 can be in the range of approximately 1 nm to approximately 50 nm.

[0019] The back-illuminating image sensor device 200 can also include a cover layer 214 formed over the semiconductor layer 202, such as over the ARC 212, as shown in Fig. Figure 2 is shown. In some embodiments of the present disclosure, the cover layer 214 can provide a flat surface on which additional layers of the back-illumination image sensor device 200 can be formed. The cover layer 214 can comprise a dielectric material, such as silicon oxide (SiO2), silicon nitride (Si3N4), silicon oxynitride (SiON), or any other suitable dielectric material. Furthermore, the cover layer 214 can be deposited using CVD or any other suitable cover layer. In some embodiments of the present disclosure, the thickness of the cover layer 214 can be in a range between approximately 50 nm and approximately 200 nm.

[0020] Furthermore, the back-illuminating image sensor device 200 comprises a composite grid structure 216 formed above the cover layer 214. According to some embodiments of the present disclosure, the composite grid structure 216 comprises cells 218 arranged in columns and rows, each cell 218 being directed towards a respective radiation detection area 204. As mentioned above, the cells 218 can accommodate a red, a green, or a blue color filter 220.

[0021] Fig. Figure 3 is a top view of a composite grid structure 216 according to some embodiments of the present disclosure. Each cell 218 of the composite grid structure 216 comprises a color filter 220 (e.g., is filled with it). As an example, a red, a green, or a blue color filter can occupy more than one cell 218. For example, in Fig. 3 four cells (e.g., adjacent cells) 218 ​​the same color filter 220 (e.g., are filled with it). For example, in Fig. 3. Four cells 218 are filled with a black shading, four cells 218 are filled with a gray shading, and four cells 218 are filled with a hatched shading, etc., where each shading can correspond to a different color filter 220. The number of cells 218 that comprise the same color filter 220, as in Fig. Figure 3 is an example and not a limitation. Therefore, the group of cells 218 that include the same color filter 220 can be larger or smaller (e.g., two, six, etc.).

[0022] With reference to Fig. 2. Cells 218 of the composite lattice structure 216 can be formed by depositing a lower layer 222 and an upper dielectric layer 224 and selectively etching away sections of the metal layer and the dielectric layer to form cells 218. As an example, and not as a limitation, the composite lattice structure 216 can be formed as follows: the lower layer 222 and the upper dielectric layer 224 can be deposited over the entire surface of the cover layer 214. One or more photolithographic and etching operations can be used to pattern the lower layer 222 and the upper dielectric layer 224 to form the sidewalls of the cells 218. The photolithographic and etching processes can be carried out such that each cell 218 of the composite lattice structure 216 is aligned with respective pixels 204 of the semiconductor layer 202.In some embodiments, the sidewall height of each cell 188 of the composite lattice structure 216 can be in a range of approximately 200 nm to approximately 1000 nm.

[0023] The lower layer 222 of the cell 218 can comprise titanium, tungsten, aluminum, or copper. However, the lower layer 222 of the cells 218 need not be limited to metals and can comprise other suitable materials or stacks of materials that can reflect and direct incident visible light to the radiation detection areas 204. In some embodiments of the present disclosure, the lower layer 222 of the cells 218 is formed using a sputtering process, a plating process, an evaporation process, or any other suitable deposition method. According to some embodiments of the present disclosure, the thickness of the lower layer 222 of each cell 218 can be in a range of approximately 10 nm to approximately 300 nm.

[0024] The upper dielectric layer 224 can comprise one or more dielectric layers. In some embodiments of the present disclosure, the upper dielectric layer 224 can protect previously formed layers of the back-illumination image sensor device 200 (e.g., the lower layer 222 and the cover layer 214). The upper dielectric layer 224 can allow incident light to pass through and reach the radiation-sensitive areas (or pixels) 204. The upper dielectric layer 224 can comprise a transparent material or materials. In some embodiments of the present disclosure, the upper dielectric layer 224 can comprise SiO2, Si3N4, SiON, or any other suitable transparent dielectric material.According to some embodiments of the present disclosure, the upper dielectric layer 224 can be deposited using a CVD or an ALD and can have a deposited thickness in a range of approximately 100 nm to approximately 300 nm.

[0025] The cells 218 can also include a passivation layer 226 arranged between the color filters 220 and the sidewalls of the cells 218 (e.g., the lower layer 222 and the upper dielectric layer 224). In some embodiments of the present disclosure, the passivation layer 226 can be conformally deposited using a CVD-based or ALD-based deposition technique in a thickness range between approximately 5 nm and approximately 300 nm. The passivation layer 226 can be formed from a dielectric material such as SiO2, Si3N4, or SiON.

[0026] According to some embodiments of the present disclosure, the upper surface of the color filters 220 can be aligned with the upper surface of the passivation layer 226 on the upper dielectric layer 224. Alternatively, the color filters 220 can be formed above the upper surface of the passivation layer 226 on the upper dielectric layer 224. For illustrative and explanatory purposes, the upper surface of the color filters 220 is described as being aligned with the upper surface of the passivation layer 226 on the upper dielectric layer 224.

[0027] After the cells 218 of the composite grid structure 216 have received their respective color filters 220, it can be determined with reference to Fig. 2. A transparent material layer 228 is formed over the composite grid structure 216 and the color filters 220. The transparent material layer 228 can be in contact with the passivation layer 226 if the upper surface of the color filters 220 is aligned with the upper surface of the passivation layer 226 above the upper dielectric layer 224. Alternatively, the transparent material layer 228 may not be in contact with the passivation layer 226 if the upper surface of the color filters 220 is located over the upper surface of the passivation layer 226 above the upper dielectric layer 224. In some examples, the transparent material layer 228 forms a microlens 230 over each cell 218 of the composite grid structure 216. The microlenses 230 are aligned with respective radiation detection areas 204 and are configured such that they reflect the upper surface of the color filters 220 within the boundaries of the cell 218 (e.g.,within the side walls of each cell (218).

[0028] The microlenses 230 are thicker than other areas of the transparent material layer 228 due to their curvature (e.g., areas between the microlenses 230 above the upper dielectric layer 224). For example, the transparent material layer 228 is thicker above the color filter 220 (e.g., where the microlens 230 is formed) and thinner in areas between the microlenses 230 (e.g., above the upper dielectric layer 224). With reference to Fig. 4, which shows an enlarged view of an upper section of the back-illuminated image sensor device 200 of Fig. In section 2, the transparent material layer 228 above the color filter 220 (e.g., where the microlens 230 is formed) is thicker and thinner in areas between the microlenses 230 (e.g., above the upper dielectric layer 224). The transparent material layer 228 has a thickness T1 in the area of ​​the microlenses 230 above the color filter 220 and a thickness T2 between adjacent microlenses 230 above the upper dielectric layer 224.

[0029] With reference to Fig. 2 The back-illuminating image sensor device 200 can also include an interconnection structure 232. The interconnection structure 232 can comprise several structured dielectric layers and conductive layers that provide connections (e.g., wiring) between the pixels 204 and other components located in Fig. 1 not shown, form the back-illumination image sensor device 200. The interconnect structure 232 can, for example, be one or more MLI structures 234 (multilayer interconnect) embedded in a dielectric intermediate layer (ILD) 236. According to some embodiments of the present disclosure, the MLI structures 234 can comprise contacts / vias and metal conductors. For illustrative purposes, several conductive conductors 238 and vias / contacts 240 are shown in Fig. 2 shown. The position and design of the conductive lines 238 and the vias / contacts 240 can vary depending on design requirements and are not limited to the illustration of Fig. 2 limited. Furthermore, the interconnection structure 232 can include detection devices 242. The detection devices 242 can, for example, be an array of field-effect transistors (FETs) and / or memory cells electrically connected to respective radiation detection areas (or pixels) 204 and designed to read the electrical signal generated in those areas as a result of a light-landing conversion process.

[0030] In some embodiments of the present disclosure, the interconnect structure 232 can be an upper layer of a partially fabricated integrated circuit (IC) or a fully fabricated IC, which may comprise several layers of interconnects, resistors, transistors, or other semiconductor devices. Furthermore, the interconnect structure 232 can be protected by a buffer layer (in Fig. 2 not shown) on a support substrate (in Fig. (1 not shown) are attached, which can provide support for the structures fabricated on it (e.g., the interconnect layer 232, the semiconductor layer 202, etc.). The support substrate can be, for example, a silicon wafer, a glass substrate, or another suitable material.

[0031] In some embodiments of the present disclosure, a method for fabricating the back-illuminating image sensor device 200 may include forming a semiconductor layer 202 on a silicon substrate (e.g., a silicon wafer) and subsequently forming the interconnect structure 232 over the front face 206 of the semiconductor layer 202. The interconnect structure 232 may, before being completed, be subjected to several photolithographic etching, deposition, and planarization operations. After the interconnect structure 232 has been formed, a support substrate, as discussed above, may be applied to the top of the interconnect structure 232. For example, a buffer layer may act as an adhesive between the support substrate and the interconnect structure 232. The silicon substrate may be flipped over and mechanically ground and polished until the back face 208 of the semiconductor layer 202 is exposed.The DTI structures 211 on the back side 208 of the semiconductor layer 202 can subsequently be formed, according to some embodiments, to further electrically isolate the radiation detection areas or pixels 204. The cover layer 214 together with the composite grid structure 216 can be formed on the back side 208 of the semiconductor layer 202.

[0032] The composite lattice structure 216 can be configured such that each of its cells 218 is aligned with respective radiation detection areas or pixels 204. The alignment of the composite lattice structure 216 and the radiation detection areas or pixels 204 can be achieved using photolithographic operations, for example, based on alignment marks present on the back side 208 of the semiconductor layer 202. The formation of the composite lattice structure 216 can involve the deposition and subsequent patterning of the lower layer 222 and the upper dielectric layer 224 using photolithographic and etching operations to form the cells 218. The passivation layer 226 is then deposited over the exposed surfaces of the lower layer 222 and the upper dielectric layer 224.The color filters 220 can fill the cells 218, and the transparent material layer 228 can be deposited on them to form the microlenses 230. The fabrication of the back-illuminated image sensor device 200 is not limited to the operations described above, and additional or alternative operations can be performed.

[0033] With reference to Fig. 2. The transparent material layer 228 of the back-illumination image sensor device 200 can be the transparent material layer described in Process 102; and the composite lattice structure 216 of the back-illumination image sensor device 200 can be the composite lattice structure of Process 102. As discussed above, the transparent material layer 228 can form the microlenses 230, which are aligned with the respective color filters 220 of the back-illumination image sensor device 200. In some embodiments of the present disclosure, the microlenses 230 are configured to focus incident light rays and direct them through the color filters 220 to the respective pixel or radiation-sensitive areas 204.

[0034] Fig. Figure 5 shows the back-illuminating image sensor device 200 after the deposition of a light-blocking material layer 500 according to process 102. According to some embodiments of the present disclosure, the light-blocking material layer 500 is deposited over the entire area of ​​the transparent material layer 228. In some embodiments of the present disclosure, the light-blocking material layer 500 covers the entire area of ​​the transparent material layer 228 – including areas where the microlenses 230 are formed and areas in between (e.g., above the upper dielectric layer 224 of the composite lattice structure 216 between the cells 218). Furthermore, the light-blocking material layer 500 can comprise an infrared (IR) color filter material that can absorb visible light. According to some embodiments of the present disclosure, the light-blocking material layer 500 can comprise a dielectric, such as…The light-blocking material layer 500 may comprise silicon nitride, silicon oxynitride, silicon carbide, or any other suitable material. Alternatively, it may comprise a reflective material such as tungsten, copper, aluminum, a metal alloy, or any other suitable material.

[0035] The deposition of the light-blocking material layer 500 can be carried out using physical vapor deposition (PVD), CVD, ALD, plasma-assisted CVD, plasma-assisted ALD, evaporation, focused ion beam induced deposition, electron beam-assisted deposition, a spin coating process, or any other suitable deposition technique. In some embodiments of the present disclosure, after deposition of the light-blocking material layer 500, an optional chemical-mechanical planarization (CMP) process can be used to planarize and smooth the top surface of the light-blocking material layer 500.

[0036] With reference to Fig. 6, which shows an enlarged top view of Fig. 5, the unprocessed deposited (or planarized) light-blocking material layer 500 has a thickness T3 that is greater than the thickness T4 of the microlenses 230 above the height of the transparent material layer 228. If T3 is smaller than T4 (e.g., T3 <T4), kann der CMP-Prozess die Fläche der Lichtblockiermaterialschicht 500 nicht auf eine geeignete Weise planarisieren, ohne die Mikrolinsen 230 zu beschädigen, und / oder ein anschließender Ätzschritt ist nicht in der Lage, die Lichtblockiermaterialschicht 500 auf eine gewünschte Weise auszusparen. In einigen Ausführungsformen ist das Verhältnis von T3 zu T4 größer gleich eins (z.B. T3 / T1 ≥ 1).

[0037] With reference to Fig. In steps 1 and 104, an etching process is used to remove / embed the light-blocking material layer 500 from a section of the upper surface of the microlenses 130. The etching process can be stopped when the etched / embedded blocking material layer 500 is limited to sections of the transparent material layer 128 between the microlenses 130. Fig. Figure 7 shows the recessed blocking material layer 500 on the transparent material layer 128 after the etching process of operation 404. According to some embodiments of the present disclosure, the resulting thickness T5 of the light-blocking material layer 500 can be in a range of approximately 5% to approximately 50% of the thickness T1 of the microlenses 130. In other words, the thickness ratio between T5 and T1 can be in a range of approximately 0.05 to approximately 0.5 (e.g., 0.05 ≤ T5 / T1 ≤ 0.5). If the T5 / T1 ratio is less than 0.05, the blocking material layer 500 does not effectively block light rays entering the microlenses 230 at grazing angles (e.g., between 0° and approximately 45°). On the other hand, if the T5 / T1 ratio is greater than approximately 0.5, the blocking material layer blocks 500 light rays entering the microlenses 230 at angles greater than approximately 45°, resulting in fewer light rays entering the sensor device.According to some embodiments of the present disclosure, the thickness ratio T5 / T1 is determined based on the thickness T1 of the microlenses 130 and the type of material of the light-blocking material layer 500. For example, the light-blocking material layer 500 can be made of a dielectric (e.g., silicon nitride, silicon oxide nitride, silicon carbide, or any other suitable material) and can have a different recessed thickness T5 than a light-blocking material layer 500 made of a metal (e.g., tungsten, copper, aluminum, or any other suitable material) or than a light-blocking material layer 500 made of a light-absorbing material comprising an IR color filter.Alternatively, in some embodiments of the present disclosure, the selection of the light-blocking material layer 500 can be made on the basis of geometric characteristics of the back-illumination image sensor device 100, such as the thickness T4 of the microlenses 130 and the desired recessed thickness T5 of the light-blocking material layer 500.

[0038] According to some embodiments of the present disclosure, the etching process is an anisotropic etching. For example, an etching process that is direction-dependent, with a high etch rate in a single direction. Furthermore, the etching process exhibits high selectivity with respect to the light-blocking material layer 500. For example, the etch selectivity ratio between the light-blocking material layer 500 and the transparent material layer 228 can be greater than 5:1 (e.g., 10:1). The etching process can be a dry etching or a wet etching with a suitable selectivity (e.g., greater than 5:1). In addition, the etching process can be time-controlled—for example, the etching process can be triggered after a certain time period, which is determined by the unprocessed deposited thickness T3 (in Fig. 6 shown) and based on the type of light-blocking material layer 500, are completed.

[0039] As described above, the method 100 does not include any operations that do not require a photolithographic mask or photolithographic operations to form the light-blocking material layer 500 between the microlenses 230. For example, the recessed light-blocking material layer 500 can be self-aligning with sections of the transparent material layer 228 between the microlenses 230. Therefore, the recessed thickness T4 can be adjusted depending on (i) the type of material of the light-blocking material layer 500 and (ii) the thickness T1 of the microlenses 230.

[0040] Fig. Figure 8 is a cross-sectional view of the back-illumination image sensor device 200 after etching a light-blocking material layer 500, according to some embodiments of the present disclosure. For example, a light beam 800—which strikes the back-illumination image sensor device 200 at a grazing angle θ—is reflected by the light-blocking material layer 500 according to some embodiments of the present disclosure. In some embodiments of the present disclosure, the incident beam 800 is absorbed by the light-blocking material layer 500. In contrast to the light beam 800, a light beam 802—which strikes the back-illumination image sensor device 200 at a normal angle—is allowed to enter the color filter 220. Therefore, the light-blocking material layer 500 can mitigate crosstalk from light beams that strike at grazing angles of incidence.

[0041] The present disclosure relates to an exemplary manufacturing process that can be used to form a self-aligning light-blocking material layer on a back-illumination image sensor device. The light-blocking material layer can block or absorb light rays incident on the back-illumination image sensor device at grazing angles of incidence. In some embodiments of the present disclosure, the light-blocking material layer can be formed using a self-aligning process that does not require the use of a photolithographic mask or photolithographic operations. For example, the light-blocking material layer can be formed over an image sensor device and subsequently etched so that the light-blocking material layer remains in areas where light rays incident at grazing angles of incidence enter the color filter.In other words, the etching process utilizes the local topography of the microlenses to form a self-aligning light-blocking layer on the areas between adjacent microlenses. Such areas can, for example, be regions of the composite lattice structure between the microlenses (between cells 218 of ). Fig.2) In some embodiments of the present disclosure, the light-blocking material layer can be a metal—such as tungsten, aluminum, or copper—or a metal alloy. In other embodiments of the present disclosure, the light-blocking material layer can be a dielectric, such as silicon oxide, silicon oxynitride, or silicon carbide. Alternatively, the light-blocking material layer can comprise an IR color filter material that allows IR to pass through. An IR color filter material can, for example, be a polymer. Consequently, the light-blocking material layer can improve the light-guiding capability of the back-illumination image sensor device.

[0042] In some embodiments of the present disclosure, an image sensor comprises a semiconductor layer with a top surface and a bottom surface, wherein the semiconductor layer comprises one or more detection areas configured to detect radiation entering the semiconductor layer from the top surface. The image sensor further comprises a grid structure with one or more cells, each of which is oriented towards the one or more detection areas, each of which or comprising a color filter in the multiple cells of the grid structure, wherein each of the one or multiple cells of the grid structure accommodates the color filter within side walls of the one or multiple cells; a transparent material layer arranged over the grid structure, wherein the transparent material layer forms a microlens over each of the one or multiple cells; and a light-blocking material layer arranged on the transparent material layer between the microlenses.

[0043] In some embodiments of the present disclosure, a semiconductor image sensor comprises a grid structure with one or more cells arranged over a semiconductor layer designed to detect radiation received by the grid structure, the semiconductor layer being arranged on a multilayer interconnect structure. The semiconductor image sensor further comprises a color filter in each of the one or more cells, each of the one or more cells of the grid structure accommodating the color filter within sidewalls of the one or more cells; microlenses formed over the one or more cells of the grid structure; and a light-blocking layer arranged between the microlenses. The light-blocking layer is also thinner than the microlenses.

[0044] In some embodiments of the present disclosure, a method for manufacturing a semiconductor image sensor comprises forming a semiconductor layer over a multilayer interconnect structure, wherein the semiconductor layer comprises one or more detection areas configured to detect radiation received by the semiconductor layer. The method further comprises forming, on the semiconductor layer, a lattice structure with one or more cells, each oriented towards one or more of the detection areas, each of the one or more cells of the lattice structure accommodating a color filter within sidewalls of the one or more cells; arranging a transparent layer over the lattice structure to form a microlens oriented towards each of the one or more cells; and forming a light-blocking layer between adjacent microlenses.Furthermore, the formation of the light-blocking layer involves depositing the light-blocking layer over the transparent layer and etching the light-blocking layer to remove the light-blocking layer over the microlens.

Claims

[1] Image sensor (200), comprising: a semiconductor layer (202) having a top surface and a bottom surface, wherein the semiconductor layer (202) comprises one or more detection areas (204) designed to detect radiation (800, 802) entering the semiconductor layer (202) from the top surface; a grid structure (216) with one or more cells (218) each aligned with the one or more detection areas (204), wherein each of the one or more cells (218) of the grid structure (216) comprises a color filter (220), wherein each of the one or more cells (218) of the grid structure (216) accommodates the color filter (220) within side walls of the one or more cells (218); a transparent material layer (228) arranged over the grid structure (216), wherein the transparent material layer (228) forms a microlens (230) over each of the one or more cells (218); and a light-blocking material layer (500) arranged on the transparent material layer (228) between microlenses (230). [2] Image sensor (200) according to claim 1, further comprising a connection structure (232) arranged below the lower surface of the semiconductor layer (202). [3] Image sensor (200) according to claim 1 or 2, wherein the light-blocking material layer (500) has a thickness (T5) that is 0.05 to 0.5 times smaller than a thickness (T1) of the microlens (230). [4] Image sensor (200) according to one of the preceding claims, wherein the grid structure (216) is arranged above the upper surface of the semiconductor layer (202). [5] Image sensor (200) according to any of the preceding claims, wherein the light-blocking material layer (500) comprises tungsten, aluminium, copper or a metal alloy. [6] Image sensor (200) according to one of the preceding claims, wherein the light-blocking material layer (500) comprises an infrared color filter material. [7] Image sensor (200) according to any of the preceding claims, wherein the light-blocking material layer (500) comprises silicon nitride, silicon oxynitride or silicon carbide. [8] Semiconductor image sensor (200), comprising: a lattice structure (216) with one or more cells (218) arranged over a semiconductor layer (202), wherein the semiconductor layer (500) is arranged on a multilayer interconnect structure (234) and is designed to detect radiation (800, 802) received by the lattice structure (220); a color filter (220) in each of the one or more cells (218), wherein each of the one or more cells (218) of the grid structure (216) accommodates the color filter (220) within side walls of the one or more cells; Microlenses (230) formed above one or more cells (218) of the lattice structure (216); and a light-blocking layer (500) arranged between the microlenses (230), wherein the light-blocking layer (500) is thinner than the microlenses (230). [9] Semiconductor image sensor (200) according to claim 8, wherein the semiconductor layer (202) comprises one or more detection areas (204) which are each aligned with the one or more cells (218) of the grid structure (216). [10] Semiconductor image sensor (200) according to claim 8, wherein the microlenses (230) comprise a transparent material. [11] Semiconductor image sensor (200) according to any one of the preceding claims 8 to 10, wherein the ratio between the thickness (T5) of the light-blocking layer (500) and the thickness (T1) of the microlenses (230) is in a range of 0.05 to 0.

5. [12] Semiconductor image sensor (200) according to any one of the preceding claims 8 to 11, wherein the light-blocking material layer (500) comprises tungsten, aluminium, copper or a metal alloy. [13] Semiconductor image sensor (200) according to any one of the preceding claims 8 to 12, wherein the light-blocking layer (500) comprises an infrared color filter material. [14] Semiconductor image sensor (200) according to any one of the preceding claims 8 to 13, wherein the light-blocking layer (500) comprises silicon nitride, silicon oxynitride or silicon carbide. [15] Method for manufacturing a semiconductor image sensor (200), the method comprising: Forming a semiconductor layer (202) with a first side (206) and an opposing second side (208) and with a multilayer interconnect structure (234) coupled to the first side (206) of the semiconductor layer (202); Forming, on the second side (208) of the semiconductor layer (202), a lattice structure (216) with one or more cells (218), wherein each of the one or more cells (218) of the lattice structure (216) accommodates a color filter (220) within side walls of the one or more cells (218); Arranging a transparent layer (228) over the grid structure (216) to form a microlens (230) that is directed towards each of the one or more cells (218); and Forming a light-blocking layer (500) between adjacent microlenses (230), wherein the formation of the light-blocking layer (500) comprises: Deposition of the light-blocking layer (500) over the transparent layer (228); and Etching the light-blocking layer (500) to remove the light-blocking layer (500) over the microlens (228). [16] Method according to claim 15, wherein the deposition of the light-blocking layer (500) comprises the deposition of the light-blocking layer (500) using a physical vapor deposition (PVD) process, a chemical vapor deposition (CVD) process, an atomic layer deposition (ALD) process, a plasma-assisted CVD process, a plasma-assisted ALD process, an evaporation process, a focused ion beam induced deposition process, an electron beam-assisted deposition process or a rotational coating process. [17] Method according to claim 15 or 16, wherein the etching of the light-blocking layer (500) comprises etching the light-blocking layer (500) using dry etching or wet etching. [18] Method according to any one of the preceding claims 15 to 17, wherein the light-blocking material layer (500) comprises tungsten, aluminium, copper, a metal alloy, silicon nitride, silicon oxynitride or silicon carbon. [19] Method according to any one of the preceding claims 15 to 18, wherein the light-blocking material layer (500) comprises an infrared color filter material.

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