Polarizers for image sensor devices

Abstract

Semiconductor image sensor device (100) with: a semiconductor layer (102) with one or more sensor areas (104) configured to detect radiation; a lattice structure (116) above the semiconductor layer (102), wherein the lattice structure (116) has one or more cells (118) which are each oriented towards the one or more sensor areas (104); and a polarization grating structure (610) in one or more cells of the grating structure (116), wherein the polarization grating structure (610) is configured to polarize light entering the semiconductor image sensor, wherein the polarization grating structure (610) comprises grating elements (600) with an upper antireflective layer arranged over a lower metal layer.

Description

Background of the invention

[0001] Semiconductor image sensors are used to scan or detect radiation, such as light. CMOS image sensors (CISs) (CMOS: complementary metal-oxide semiconductor) and CCD sensors (CCD: charge-coupled device) are used in various applications, such as digital cameras or camera applications in mobile phones. These devices use a matrix of pixels (which may include photodiodes, transistors, and other components) in a substrate to absorb (e.g., scan) radiation projected onto the substrate and to convert the scanned radiation into electrical signals. A back-illuminated image sensor device is a type of image sensor device that can detect light from the back.

[0002] WO 2016 / 199 594 A1 discloses a semiconductor image sensor device with polarization filters. Brief description of the drawings

[0003] Aspects of the present invention are best understood with reference to the detailed description below in conjunction with the accompanying drawings. It should be noted that, in accordance with common industry practice, various elements are not drawn to scale. Rather, for the sake of clarity of discussion, the dimensions of the various elements may be arbitrarily enlarged or reduced. Fig. Figure 1 is a sectional view of a back-illuminated image sensor device, according to some embodiments. Fig. Figure 2 is a top view of a composite grid structure with color filters, according to some embodiments. Fig. Figure 3 is a flowchart of a method for producing a polarization grating structure in a composite grating structure of a back-illuminated image sensor device, according to some embodiments. The Fig. 4, Fig. 5 to Fig. Figure 6 shows sectional views of a partially manufactured, back-illuminated image sensor device during the manufacture of a polarization grating structure, according to some embodiments. The Fig. Figures 7A to 7D are top views of polarization grating structures with grating elements oriented at different polarization angles, according to some embodiments. Fig. Figure 8 is a sectional view of a partially manufactured, back-illuminated image sensor device after deposition of a passivation layer, according to some embodiments. Fig. Figure 9 is a sectional view of a back-illuminated image sensor device with a polarization grating structure, according to some embodiments. The Fig. 10, Fig. 11, Fig. 12 to Fig. Figure 13 are top views of composite grating structures with polarization grating structures in different arrangements, according to some embodiments. Detailed description

[0004] Improved semiconductor image sensors and a method for their fabrication are provided according to the independent claims. The following description provides many different embodiments or examples for implementing various features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present invention. For example, the fabrication of a first element above or on top of a second element in the following description may include embodiments in which the first and second elements are fabricated in direct contact, and it may also include embodiments in which additional elements can be fabricated between the first and second elements such that the first and second elements are not in direct contact.

[0005] Furthermore, spatially relative terms, such as "located below," "under," "lower," "located above," "upper," and the like, can be used here to simply describe the relationship of an element or structure to one or more other elements or structures depicted in the figures. These spatially relative terms are intended to encompass orientations of the component in use or operation beyond the orientation shown in the figures. The component may be oriented differently (rotated by 90 degrees or in a different orientation), and the spatially relative descriptors used here can be interpreted accordingly.

[0006] The term "nominal" as used here refers to a desired or target value of a property or parameter for a component or process step, which is defined during the design phase for a product or process, along with a range of values ​​above and / or below the target value. This range of values ​​results from minor variations in manufacturing processes or tolerances.

[0007] The term “essentially” used here indicates that the value of a given quantity varies by ±5% of the value.

[0008] The term "approximately" used here indicates the value of a given quantity, which can vary due to a specific technology node associated with the semiconductor device in question. Based on this specific technology node, the term "approximately" can indicate a value of a given quantity that can vary within, for example, 10 to 30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0009] Semiconductor image sensor devices are used to detect electromagnetic radiation, such as light (e.g., visible light). CMOS image sensors (CISs) (CMOS: complementary metal-oxide semiconductor) and CCD sensors (CCD: charge-coupled device) are used in various applications, such as digital cameras or camera phones. These devices use a matrix of pixels (which may include photodiodes, transistors, and other components) embedded in a substrate to absorb (e.g., scan) radiation projected onto the substrate. The absorbed radiation can be converted by photodiodes (within the pixel) into electrical signals, such as charge or current, which can then be further analyzed and / or processed by other modules of the image sensor device.

[0010] One type of image sensor device is a back-illuminated image sensor device. In a back-illuminated image sensor device, color filters and microlenses are located on the back side of a substrate (e.g., on one side of the substrate facing the circuitry), allowing the image sensor device to collect light with minimal or no interference. This means back-illuminated image sensors are configured to detect light from the back of the substrate rather than from a front side, with the image sensor device's color filters and microlenses positioned between the substrate's circuitry and the photodiodes. Compared to front-illuminated image sensors, back-illuminated image sensors offer better performance at lower light levels and a higher quantum efficiency (QE) (i.e., the percentage of photons converted to electrons).

[0011] Image sensor devices use color filters to capture color information from incident light rays. For example, image sensor devices can detect the red, green, and blue regions (RGB regions) of the visible light spectrum by using color filters. A composite grid structure, which may be filled with a color filter material, can be used to position the color filter material over the photodiodes of the image sensor device. The composite grid structure may consist partially of an oxide or other dielectric material that is transparent to visible light.

[0012] Furthermore, the image sensor can be equipped with external polarizers to collect polarization information from incident light. This polarization information can be used in applications such as photography and videography. However, because the polarizers are external and not integrated into the composite grating structure, the distance between the polarizers and the image sensor can be considerable, for example, in relation to the size of the back-illuminated image sensor device. This configuration can affect the size of the final product and may limit efforts to reduce its size. To obtain information under different polarization conditions, the external polarizer can be rotated, which can affect the acquisition time for the polarization data.

[0013] In various embodiments according to the present invention, a method for integrating one or more polarizers into a composite grating structure of a back-illuminated image sensor device is provided. In some embodiments, the polarizers are integrated into the composite grating structure by replacing one or more color filters of the composite grating structure with a polarizing grating structure (grid polarizer) within the composite grating structure. In some examples, the polarizing grating structure can provide polarization information for incident light with the following polarization angles: 0°, 45°, 90°, and / or 135°. However, these directions are not limiting, and other polarization angles are also possible. In some embodiments, the grid spacing between the elements (grid elements) of the polarizing grating structure can be approximately 100 nm to approximately 500 nm (e.g.,The wavelength of each grating element can range from 100 nm to 500 nm, and the width of each grating element can range from approximately 20 nm to approximately 300 nm (e.g., 20 nm to 300 nm). These ranges have been optimized based on the wavelength of the incident light. In some embodiments, the grating elements of the polarizing grating structure are made of the same material as the composite grating structure. In other embodiments, the grating elements of the polarizing grating structure are made of a different material than the composite grating structure.

[0014] Fig. Figure 1 is a simplified sectional view of a back-illuminated image sensor device 100 according to some embodiments of the present invention. The back-illuminated image sensor device 100 has a semiconductor layer 102 with radiation sensor areas 104. The semiconductor layer 102 can comprise silicon doped with an n-doped element, such as phosphorus or arsenic. The semiconductor layer 102 can also comprise other elemental semiconductors, such as germanium or diamond. The semiconductor layer 102 can optionally comprise a compound semiconductor and / or an alloy semiconductor. Furthermore, the semiconductor layer 102 can comprise an epitaxial layer, which may be strained to improve performance. The semiconductor layer 102 can have a silicon-on-insulator (SOI) structure.

[0015] The semiconductor layer 102 has a front side (also referred to here as a "bottom") 106 and a back side (also referred to here as a "top") 108. The semiconductor layer 102 has a thickness of approximately 100 µm to approximately 3000 µm (e.g., 100 µm to 3000 µm).

[0016] The radiation sensor areas 104 are fabricated in the semiconductor layer 102. The radiation sensor areas 104 are configured to detect radiation, such as incident light rays striking the semiconductor layer 102 from the back side 108. In some embodiments of the present invention, each radiation sensor area 104 includes a photodiode capable of converting photons into charge. In some embodiments of the present invention, the radiation sensor areas 104 may include photodiodes, transistors, amplifiers, other similar components, or combinations thereof. The radiation sensor areas 104 may also be referred to here as "radiation detection elements" or "light sensors."

[0017] For the sake of simplicity, in Fig. Figure 1 shows two radiation sensor areas 104, but further radiation sensor areas 104 can be implemented in the semiconductor layer 102. By way of example and without limitation, the radiation sensor areas 104 can be fabricated on the semiconductor layer 102 from the front face 106 using an ion implantation process. The radiation sensor areas 104 can also be fabricated using a dopant diffusion process.

[0018] The radiation sensor areas 104 are electrically separated from each other by separating structures 110. The separating structures 110 can be trenches etched into the semiconductor layer 102 and filled with a dielectric material, such as silicon oxide, silicon nitride, silicon oxide nitride, fluorosilicate glass (FSG), a low-k dielectric material (e.g., a material with a k-value lower than 3.9), and / or another suitable insulating material. In some embodiments of the present invention, the separating structures 110 have an antireflective coating (ARC) 112 on the back side 108 of the semiconductor layer 102. The ARC 112 is a cover layer that can prevent incident light rays from being reflected away from the radiation sensor areas / pixels 104. The ARC 112 can be a high-k material (e.g.,The ARC 112 comprises a material with a k-value of less than 3.9, such as hafnium oxide (HfO2), tantalum pentoxide (Ta2O5), zirconium dioxide (ZrO2), or aluminum oxide (Al2O3), or another high-k material. The ARC 112 can be deposited by sputtering, by CVD-based processes (CVD: chemical vapor deposition), ALD-based processes (ALD: atomic layer deposition), or by any other suitable deposition method. In some embodiments of the present invention, the thickness of the ARC 112 can be approximately 1 nm to approximately 50 nm (e.g., 1 nm to 50 nm).

[0019] The back-illuminated image sensor device 100 also has a capping layer 114 which is produced over the semiconductor layer 102, such as over the ARC 112, as shown in Fig. Figure 1 shows the following. In some embodiments of the present invention, the capping layer 114 can have a planar surface on which further layers of the back-illuminated image sensor device 100 can be produced. The capping layer 114 can comprise a dielectric material, such as silicon dioxide (SiO2), silicon nitride (Si3N4), silicon oxide nitride (SiON), or another suitable dielectric material. The capping layer 114 can be deposited by CVD or by another suitable deposition method. In some embodiments of the present invention, the thickness of the capping layer 114 can be approximately 50 nm to approximately 200 nm (e.g., 50 nm to 200 nm).

[0020] The back-illuminated image sensor device 100 also has a composite grid structure 116, which is produced over the capping layer 114. In some embodiments of the present invention, the composite grid structure 116 has cells 118 arranged in columns and rows, each cell 118 being oriented towards a respective radiation sensor area 104. As explained above, the cells 118 can accommodate a red, green, or blue color filter 120.

[0021] Fig. Figure 2 is a top view of the composite lattice structure 116 according to some embodiments. The arrangement of the color filters 120 in the composite lattice structure 116 can be based on a Bayer structure. For example, the composite lattice structure 116 can have 50% green color filters, 25% red color filters, and 25% blue color filters, with every second cell 118 of the composite lattice structure 116 being filled with a different color filter 120. However, this is not limiting, and adjacent cells 118 can be filled with a color filter of the same color.

[0022] In Fig. 2. The cells 118 of the composite lattice structure 116 can be fabricated by depositing a lower layer 122 and an upper dielectric layer 124, and subsequently etching away portions of the lower layer and the upper dielectric layer to form the cells 118. By way of example, and not as a limitation, the composite lattice structure 116 can be fabricated as follows: the lower layer 122 and the upper dielectric layer 124 can be deposited by protective deposition on the capping layer 114, and the lower layer 122 and the upper dielectric layer 124 can be structured by one or more photolithographic and etching steps to fabricate sidewalls of the cells 118. The photolithographic and etching steps can be performed such that each cell 118 of the composite lattice structure 116 is aligned with respective radiation sensor areas 104 of the semiconductor layer 102.In some embodiments, the height of the side wall of each cell 118 of the composite lattice structure 116 can be approximately 200 nm to approximately 1000 nm (e.g. 200 to 1000 nm).

[0023] The lower layer 122 of the cell 118 can be made of titanium, tungsten, aluminum, or copper. However, the lower layer 122 of the cells 118 is not limited to metals and can comprise other suitable materials or stacks of materials that can reflect and direct incident visible light to the radiation sensor areas 104. In some embodiments of the present invention, the lower layer 122 of the cells 118 is produced by structuring, plating, vapor deposition, or another suitable deposition process. In some embodiments of the present invention, the thickness of the lower layer 122 of each cell 118 can be from about 10 nm to about 300 nm (e.g., 10 nm to 300 nm).

[0024] The upper dielectric layer 124 can comprise one or more dielectric layers. In some embodiments, the upper dielectric layer 124 can protect previously fabricated layers of the back-illuminated image sensor device 100 (e.g., the lower layer 122 and the capping layer 114). The upper dielectric layer 124 can transmit incident light so that it can reach the radiation sensor areas 104. The upper dielectric layer 124 can consist of one or more transparent materials. In some embodiments of the present invention, the upper dielectric layer 124 can comprise SiO2, Si3N4, SiON, or another suitable transparent dielectric material. In some embodiments, the upper dielectric layer 124 can be deposited by CVD or ALD with a thickness of about 100 nm to about 300 nm (e.g., 100 nm to 300 nm).In some embodiments, the composite lattice structure 116 has more than two layers, such as a first layer of tungsten, a second layer of plasma-enhanced oxide (PEOX) over the first layer, and a third layer of silicon oxide nitride over the second layer.

[0025] The cells 118 also feature a passivation layer 126, which is layered between the color filter 120 and the sidewall materials of the cells 118 (e.g., the lower layer 122 and the upper dielectric layer 124). By way of example, and not as a limitation, the passivation layer 126 can be conformally deposited using a CVD-based or an ALD-based deposition method. The passivation layer 126 can consist of a dielectric material, such as SiO2, Si3N4, or SiON, and can have a thickness of approximately 5 nm to approximately 300 nm (e.g., 5 nm to 300 nm).

[0026] In some embodiments, the top surface of the color filters 120 can be aligned with the top surface of the passivation layer 126 on the upper dielectric layer 124. Alternatively, the color filters 120 can be located above the top surface of the passivation layer 126 on the upper dielectric layer 124. For illustrative purposes, the top surface of the color filters 120 is shown aligned with the top surface of the passivation layer 126 on the upper dielectric layer 124.

[0027] After the cells 118 of the composite lattice structure 116 have received their respective color filters 120, a transparent material layer 128 can be produced over the composite lattice structure 116 and the color filters 120. In some embodiments, the transparent material layer 128 can be in contact with the passivation layer 126 if the top surface of the color filters 120 is oriented towards the top surface of the passivation layer 126 above the upper dielectric layer 124. Alternatively, in some embodiments, the transparent material layer 128 can be out of contact with the passivation layer 126 if the top surface of the color filters 120 is located above the top surface of the passivation layer 126 above the upper dielectric layer 124. In some examples, the transparent material layer 128 forms a microlens 130 over each cell 118 of the composite lattice structure 116.The microlenses 130 are aligned to the respective radiation sensor areas 104 and are manufactured to cover the top of the color filters 120 within the boundaries of the cell 118 (e.g., within the side walls of each cell 118).

[0028] Due to their curvature, the microlenses 130 are thicker than other areas of the transparent material layer 128 (e.g., than the areas between the microlenses 130 above the upper dielectric layer 124). For example, the transparent material layer 128 is thicker above the color filter 120 (e.g., where the microlenses 130 are manufactured), and it is thinner in areas between the microlenses 130 (e.g., above the upper dielectric layer 124).

[0029] In Fig. 1. The back-illuminated image sensor device 100 can also have a connection structure 132. The connection structure 132 can have structured dielectric layers and conductive layers that provide intermediate connections (e.g., wiring) between the radiation sensor areas 104 and other components (in Fig. (1 not shown). The interconnect structure 132 can, for example, comprise one or more multilayer interconnect structures (MLI structures) 134 embedded in an interlayer dielectric layer (ILD layer) 136. In some embodiments of the present invention, the MLI structures 134 can comprise contacts / vias and metal conductors. For illustration, several conductive conductors 138 and vias / contacts 140 are shown in Fig. Figure 1 shows the positions and configurations of the conductive lines 138 and the vias / contacts 140, which may depend on the design and are not shown in Figure 1. Fig. 1 limited. The interconnection structure 132 can further include sensor elements 142. The sensor elements 142 can, for example, be a matrix of field-effect transistors (FETs) and / or memory cells that are electrically connected to respective radiation sensor areas (or pixels) 104 and are configured to read an electrical signal that is generated as a result of a light-to-charge conversion process in these areas.

[0030] In some embodiments of the present invention, the interconnect structure 132 can be an upper layer of a partially fabricated integrated circuit (IC) or a fully fabricated IC, which may have multiple layers of interconnects, resistors, transistors, and / or other semiconductor devices. Thus, the interconnect structure 132 can comprise FEOL (front end of line) and MEOL (middle end of line) layers. Furthermore, the interconnect structure 132 can be protected by a buffer layer (in Fig. 1 not shown) on a support substrate (in Fig. (1 not shown) is attached to a substrate that can support the structures produced on it (e.g., the interconnect structure 132, the semiconductor layer 102, etc.). The substrate can be, for example, a silicon wafer, a glass substrate, or another suitable material.

[0031] In some embodiments of the present invention, the fabrication of the back-illuminated image sensor device 100 may comprise the fabrication of the semiconductor layer 102 on a silicon substrate (e.g., a silicon wafer) and the subsequent fabrication of the interconnect structure 132 over the front surface 106 of the semiconductor layer 102. The interconnect structure 132 may undergo several photolithographic, etching, deposition, and planarization steps before it is completed. After the interconnect structure 132 has been fabricated, a support substrate (discussed above) may be attached to the top surface of the interconnect structure 132. A buffer layer may, for example, act as an adhesive between the support substrate and the interconnect structure 132. The silicon substrate may be turned over and mechanically ground and polished until the back surface 108 of the semiconductor layer 102 is exposed.Subsequently, separating structures can be fabricated on the back side 108 of the semiconductor layer 102 to further electrically isolate the radiation sensor areas or pixels 104. The capping layer 114, together with the composite lattice structure 116, can be fabricated on the back side 108 of the semiconductor layer 102.

[0032] The composite lattice structure 116 can be fabricated such that each of the cells 118 is aligned to the respective radiation sensor areas or pixels 104. The alignment of the composite lattice structure 116 and the radiation sensor areas or pixels 104 can be achieved using photolithographic steps, for example, by means of alignment marks located on the back side 108 of the semiconductor layer 102. The fabrication of the composite lattice structure 116 can involve the deposition and subsequent patterning of the lower layer 122 and the upper dielectric layer 124 using photolithographic and etching steps to fabricate the cells 118. Subsequently, the passivation layer 126 is deposited over the exposed surfaces of the lower layer 122 and the upper dielectric layer 124.The color filters 120 can fill the cells 118, and the transparent material layer 128 can be deposited onto them to produce the microlenses 130. The fabrication of the back-illuminated image sensor device 100 is not limited to the steps described above, and further or alternative steps can be carried out.

[0033] Fig. Figure 3 is a flowchart of a method 300 for producing one or more polarization grating structures (grid polarizers) in the composite grating structure of the image sensor, according to some embodiments. The method 300 is described by way of example in connection with the back-illuminated image sensor device 100. Fig. 1 described. The polarization grating structure can have one of the following polarization directions: 0°, 45°, 90°, or 135°. However, these directions are not limiting, and other polarization directions are also possible. Method 300 is not limited to back-illuminated image sensor devices and can also extend to other types of image sensor devices, such as front-illuminated image sensor devices that use similar material layers and / or geometries. These other types of image sensor devices are within the basic concept and scope of protection of the present invention.

[0034] In some embodiments, Method 300 can produce lattice elements in the cells 118 of the composite lattice structure 116. The lattice elements can be aligned to a polarization angle ranging from 0° to 135° in 45° increments (e.g., 0°, 45°, 90°, and 135°). However, Method 300 is not limited to the steps described below. Additional manufacturing steps can be performed between the various steps of Method 300, which are omitted for clarity.

[0035] In Fig. In step 302, process 300 begins with the fabrication of a layer stack over a semiconductor layer. In some examples, the layer stack may comprise more than two layers. Fig. Figure 4 shows a partially manufactured image sensor, such as the back-illuminated image sensor device 100 from Fig. 1, according to procedure 300. In Fig. 4 and according to step 302, a layer stack 400 is fabricated above the semiconductor layer 102, comprising the lower layer 122 and the upper dielectric layer 124. As stated above, the lower layer 122 may comprise titanium, tungsten, aluminum, or copper. However, the lower layer 122 is not limited to metals and may comprise other suitable materials or stacks of materials capable of reflecting and conducting incident visible light to the radiation sensing regions 104 of the semiconductor layer 102. By way of example, and without limitation, the lower layer 122 may be fabricated by sputtering, plating, evaporation, chemical vapor deposition (CVD), atomic layer deposition (ALD), or by any other suitable deposition process. The thickness of the lower layer 122 may be approximately 10 nm to approximately 300 nm (e.g., 10 nm to 300 nm). The lower layer 122 is not deposited directly onto the semiconductor layer 102.In some embodiments, the lower layer 122 is deposited above the capping layer 114. In some embodiments, the lower layer 122 can be deposited on an adhesive / barrier layer arranged between the lower layer 122 and the capping layer 114. For simplicity, the adhesive / barrier layer is in . Fig. 4 not shown.

[0036] In step 302 and in Fig. 4. The upper dielectric layer 124 of the layer stack 400 can be deposited over the lower layer 122. In some embodiments, the upper dielectric layer 124 can be a stack of one or more dielectric layers. In some embodiments, the upper dielectric layer 124 can transmit incident visible light. In other words, the upper dielectric layer 124 consists of one or more transparent materials that act as an antireflective material. In some embodiments, the upper dielectric layer 124 consists of SiO2, Si3N4, SiON, SiC, a polymer, or one or more other suitable transparent dielectric materials. The upper dielectric layer 124 can be deposited by CVD or ALD with a thickness (after deposition) of about 100 nm to about 300 nm (e.g., 100 nm to 300 nm).Alternatively, the upper dielectric layer 124 can be spin-deposited onto the lower layer 122.

[0037] In Fig. In step 304, the process 300 continues, in which one or more polarization grating structures are produced with grating elements in a composite grating structure, such as the composite grating structure 116. In some embodiments, the production of the one or more polarization grating structures is carried out simultaneously with the production of the composite grating structure, such as the composite grating structure 116. Fig. For example, a photoresist layer (PR layer) or a hard mask layer (HM layer) can be deposited over the layer stack 400. The PR or HM layer is then patterned to create patterned structures 402 and 404 over the layer stack 400. The patterned structures 402 can have a spacing P1 of approximately 100 nm to approximately 500 nm (e.g., 100 nm to 500 nm) and can be used to fabricate the lattice elements of the polarization grating structures. The spacing range P1 ensures that the width of each lattice element can be approximately 20 nm to approximately 300 nm (e.g., 20 nm to 300 nm), as explained above. The structured structures 404 can have a distance P2 that is greater than the distance P1 (i.e. P2 > P1), and they can be used to make side walls of the cells 118 of the compound lattice structure 116.Four structured structures 402 and 404 are examples and not exhaustive. Fig. Figure 4 shows that in some embodiments, further structured structures 402 and 404 are possible in the layer stack 400. Furthermore, the structured structures 402 required for the fabrication of the lattice elements of the polarization grating structures can be fabricated lengthwise at an angle to the structured structures 404 required for the fabrication of the cells 118 in the composite grating structure 116. In some embodiments, the angle between the structured structures 402 and 404 corresponds to a polarization angle of visible light. In some embodiments, the polarization angle can range from 0° to 135° in 45° increments.

[0038] The production of lattice elements with structured structures 402, which are parallel to the structured structures 404 (i.e., lattice elements with a polarization angle of 0° are produced), is described as an example. As explained above, other orientation angles can also be implemented. These orientation angles are within the basic concept and scope of protection of the present invention.

[0039] The structured structures 402 and 404 are used as a mask layer, so that in a subsequent etching process the layer stack 400 between the structured structures 402 and 404 can be selectively removed to produce the composite lattice structure 116. In some embodiments, different etching chemicals can be used for the upper dielectric layer 124 and the lower layer 122 in the etching process. In some embodiments, the etching process has an endpoint and can, for example, be automatically terminated when the capping layer 114 is exposed. Furthermore, the etching process can be time-definite or a combination of time-definite and endpoint etching. In some examples, the etching process is anisotropic, so that the etched structural elements nominally have vertical sidewalls.Furthermore, the etching process can exhibit high selectivity for the upper dielectric layer 124 and the lower layer 122. Fig. Figure 5 shows an exemplary structure of Fig. 4 after the etching process of step 304 described above.

[0040] Once the etching process is complete, the structured elements 402 and 404 can be removed using a wet etching chemical. The resulting etched structures, e.g., lattice elements 600 and the side walls of cells 118, are in Fig. Figure 6 shows. In some embodiments, the height of the lattice elements 600 is approximately 200 nm to approximately 1000 nm (e.g., 200 nm to 1000 nm), their width is approximately 20 nm to approximately 300 nm (e.g., 20 to 300 nm), and their spacing is approximately 100 nm to approximately 500 nm (e.g., 100 to 500 nm). In the example of Fig. 6 The lattice elements 600 of a polarization grating structure 610 are aligned parallel (e.g. with a polarization angle of 0°) to the side walls of the cells 118 of the composite grating structure 116, as for example in Fig. Figure 7A shows a top view of the polarization grating structure 610 in a cell 118 at a polarization angle of 0°. Fig. 6. The polarization grating structure 610 can be part of the composite grating structure 116. In other words, the polarization grating structure 610 can be manufactured in a cell 118 of the composite grating structure 116. As explained above, the grating elements 600 can be oriented at different angles to the side walls of the cells 118, so that the polarization grating structure 610 can detect light with further polarization angles. By way of example and without limitation are the following: Fig. Figures 7A to 7D show top views of exemplary polarization grating structures 610 with grating elements 600 oriented at different angles (e.g., 0°, 45°, 90°, or 135°) to the side walls of the cells 118. As explained above, these angles can correspond to the respective polarization angles of the incident light.

[0041] Furthermore, the cells 118 of the composite lattice structure 116 and the polarization lattice structure 610 are essentially aligned with the radiation sensor areas 104 of the semiconductor layer 102. Additional polarization lattice structures are also possible within the composite lattice structure 116.

[0042] In Fig. 8. After the fabrication of the grid elements 600 and the cells 118, the passivation layer 126 is conformally deposited over the side walls of the cells 118 and the grid elements 600. By way of example, and without limitation, the passivation layer 126 can be conformally deposited using a CVD-based or an ALD-based deposition process. The passivation layer 126 can consist of a dielectric material, such as SiO2, Si3N4, or SiON, and can have a thickness of approximately 5 nm to approximately 300 nm (e.g., 5 nm to 300 nm).

[0043] In Fig. In step 306, the process 300 continues with a gap between the grating elements 600 of the polarization grating structure 610, in which a gap is filled with a color filter, air, a dielectric material, or a combination thereof. In some embodiments, the dielectric material is a transparent antireflective material consisting of SiO2, Si3N4, SiON, SiC, or a polymer.

[0044] In step 308, the cells 118 of the composite grid structure 116 are filled with one or more color filters 120, as shown in Fig. Figure 9 is shown. In some embodiments, the color filters 120 can be red, green, or blue. In the example of Fig. 9. The gap between the grid elements 600 is filled with air. Fig. 10, Fig. 11, Fig. 12 to Fig. Figure 13 shows exemplary arrangements of the color filters 120 and the polarization grating structures 610, with different polarization angles, in the composite grating structure 116, according to some embodiments. The examples of Fig. 10, Fig. 11, Fig. 12 to Fig. However, the provisions of paragraph 13 are not limiting, and further arrangements are possible and fall within the basic concept and scope of protection of the present invention. For example, in a Bayer structure in which the composite grating structure 116 can comprise 50% green color filters, 25% red color filters, and 25% blue color filters, some of the green color filters can be replaced by polarization grating structures.

[0045] In Fig. 9 A microlens 130 can be fabricated above each cell 118 and the polarization grating structure 610. The microlens 130 focuses the light rays entering the respective cells 118 of the composite grating structure 116 onto the radiation sensor areas 104 of the semiconductor layer 102.

[0046] The present invention relates to a method that describes the fabrication of a polarizing grating structure (e.g., a polarizer) as part of a composite grating structure of a back-illuminated image sensor device. In some embodiments, the polarizing grating structure can be integrated into the composite grating structure by replacing one or more color filters of the composite grating structure with the polarizing grating structure (grid polarizer). In some embodiments, the polarizing grating structure can provide polarization information of the incident light along the following polarization directions: 0°, 45°, 90°, and / or 135°. However, the aforementioned polarization directions are not limiting, and other polarization directions are also possible. In some embodiments, the spacing between the grating elements of the polarizing grating structure can be approximately 100 nm to approximately 500 nm (e.g., 100 nm).The polarizer angles (e.g., 100 nm to 500 nm) and the width of each grid element can be approximately 20 nm to approximately 300 nm (e.g., 20 nm to 300 nm). The grid elements of the polarization grating structure can be made of the same material as the composite grating structure. Integrating the polarizers into the composite grating structure of a sensor element can offer several advantages, such as a compact design for the image sensor, no moving parts, and faster acquisition of light polarization information (e.g., polarization information for all polarization angles is collected simultaneously).

[0047] In some embodiments, a semiconductor image sensor device comprises: a semiconductor layer with one or more sensor areas configured to detect radiation; a grid structure over the semiconductor layer, the grid structure having one or more cells, each oriented toward the one or more sensor areas; and a polarization grid structure within the one or more cells of the grid structure, the polarization grid structure being configured to polarize light entering the semiconductor image sensor. The polarization grid structure includes grid elements with an upper antireflective layer arranged over a lower metal layer.

[0048] In some embodiments, a semiconductor image sensor comprises: one or more polarization grating structures with grating elements aligned to a light polarization angle, wherein the one or more polarization grating structures are arranged in cells defined by a grating structure; a semiconductor layer with sensor areas configured to detect radiation entering the semiconductor layer from the grating structure, wherein the semiconductor layer is positioned beneath the grating structure such that each cell of the grating structure is aligned to a sensor area of ​​the semiconductor layer; and a microlens above each cell of the grating structure. Each of the one or more polarization grating structures includes an antireflective layer mounted on a metal layer.

[0049] In some embodiments, a method for manufacturing an image sensor comprises the deposition of a layer stack over a semiconductor layer with radiation sensor areas, wherein the layer stack comprises a bottom layer and an upper antireflective layer. The method further comprises structuring the layer stack to produce a grid structure with cells and a polarization grid structure within a cell, wherein the polarization grid structure has grid elements oriented at a light polarization angle. The method also comprises filling the grid structure between the grid elements with air or a dielectric material and filling the cells that do not contain a polarization grid structure with a color filter.

Claims

[1] Semiconductor image sensor device (100) comprising: a semiconductor layer (102) with one or more sensor areas (104) configured to detect radiation; a lattice structure (116) above the semiconductor layer (102), wherein the lattice structure (116) has one or more cells (118) which are each oriented towards the one or more sensor areas (104); and a polarization grating structure (610) in one or more cells of the grating structure (116), wherein the polarization grating structure (610) is configured to polarize light entering the semiconductor image sensor, wherein the polarization grating structure (610) comprises grating elements (600) with an upper antireflective layer arranged over a lower metal layer. [2] Semiconductor image sensor device (100) according to claim 1, wherein a polarization angle of the polarization grating structure (610) is 0°, 45°, 90° or 135°. [3] Semiconductor image sensor device (100) according to claim 1 or 2, wherein the polarization grating structure (610) comprises grating elements (600) with a grid spacing of 100 nm to 500 nm. [4] Semiconductor image sensor device (100) according to one of the preceding claims, wherein the polarization grating structure (610) comprises grating elements (600) with a height of 200 nm to 1000 nm. [5] Semiconductor image sensor device (100) according to one of the preceding claims, wherein the polarization grating structure (610) comprises grating elements (600) with a width of 20 nm to 300 nm. [6] Semiconductor image sensor device (100) according to one of the preceding claims, wherein the polarization grating structure (610) comprises air, a color filter (120) or a dielectric material which is transparent to light. [7] Semiconductor image sensor device (100) according to one of the preceding claims, wherein the polarization grating structure (610) comprises grating elements (600) made of tungsten, silicon oxide nitride, silicon nitride, silicon carbide, silicon oxide or a polymer. [8] Semiconductor image sensor device (100) according to any one of the preceding claims, further comprising: a color filter (120) arranged in one or more cells; a microlens (130) over each of the one or more cells; and a connection structure (132) beneath the semiconductor layer (102), wherein the connection structure (132) is configured to establish electrical connections with the one or more sensor areas (104) of the semiconductor layer (102). [9] Semiconductor image sensor (100) with: one or more polarization grating structures (610) with grating elements (600) aligned to a light polarization angle, wherein the one or more polarization grating structures (610) are arranged in cells (118) defined by a grating structure (116), each of the one or more polarization grating structures (610) comprising an antireflection layer arranged on a metal layer; a semiconductor layer (102) with sensor areas (104) configured to detect radiation entering the semiconductor layer (102) from the grid structure (116), the semiconductor layer (102) being arranged below the grid structure (116) such that each of the cells (118) of the grid structure (116) is aligned with a sensor area (104) of the semiconductor layer (102); and a microlens (130) above each cell (118) of the lattice structure (116). [10] Semiconductor image sensor (100) according to claim 9, wherein the one or more polarization grating structures (610) are arranged in adjacent cells (118) in the grating structure (116). [11] Semiconductor image sensor (100) according to claim 9, wherein the one or more polarization grating structures (610) are arranged in non-adjacent cells (118) in the grating structure (116). [12] Semiconductor image sensor (100) according to claim 9, wherein the one or more polarization grating structures (610) occupy each cell (118) in the grating structure (116). [13] Semiconductor image sensor (100) according to one of claims 9 to 12, wherein a sensor area under a polarization grating structure (610) is configured to receive polarized light with a polarization angle that matches the light polarization angle of the grating elements (600) in the one or more polarization grating structures (610). [14] Semiconductor image sensor (100) according to one of claims 9 to 13, wherein each of the one or more polarization grating structures (610) is arranged between a microlens (130) and a sensor area (104) of the semiconductor layer (102). [15] Semiconductor image sensor (100) according to one of claims 9 to 14, further comprising a connection structure (132) arranged on a side of the semiconductor layer (102) opposite the grid structure (116). [16] Method for manufacturing an image sensor (100) by the following steps: Deposition of a layer stack (400) over a semiconductor layer (102) with radiation sensor areas (104), wherein the layer stack (400) comprises a lower metal layer and an upper antireflective layer; Structuring the layer stack (400) to produce a lattice structure (116) with cells (118) and a polarization lattice structure (610) in a cell (118), wherein the polarization lattice structure (610) has lattice elements (600) that are aligned to a light polarization angle; Filling the lattice structure (116) between the lattice elements (600) with air or a dielectric material; and Filling the cells (118) that do not contain a polarization grating structure (610) with a color filter (120). [17] Method according to claim 16, further comprising producing a microlens (130) over each cell (118) of the grid structure (116). [18] Method according to claim 16 or 17, wherein structuring the layer stack (400) comprises: Arranging a photoresist layer or a hard mask layer over the layer stack (400); Structuring the photoresist layer or the hard mask layer to create first structured structures and second structured structures, wherein the first structured structures have a different grid spacing than the second structured structures; Etching the layer stack (400) through the first structured structures to produce the cells (118) of the lattice structure (116); and Etching of the layer stack (400) through the second structured structures to produce the lattice elements (600) of the polarization lattice structure (610). [19] Method according to any one of claims 16 to 18, wherein the grid elements (600) have a grid spacing of 100 nm to 500 nm and a height of 200 to 1000 nm. [20] Method according to one of claims 16 to 19, wherein light entering the image sensor (100) is polarized according to the light polarization angle of the grating elements (600) in the polarization grating structure (610).

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