Image sensing device

Abstract

Various embodiments of the utility model relate to an image sensing device. The image sensing device comprises a germanium sensor in a semiconductor main body and a super lens formed in the back side of the semiconductor main body. The superlens is configured to focus infrared light on the germanium sensor and may have a lower profile than an equivalent microlens. Optionally, the superlens is combined with the microlens to obtain the desired focal length. The superlens or a combination of the superlens and the microlens overcomes the limitation of the manufacturing process on the focal length of the microlens, thus eliminating the need for a spacer between the microlens and the germanium sensor, or reducing the thickness of the spacer. Eliminating the spacer or reducing the thickness thereof can improve the angle response of the image sensing device.

Description

Technical Field

[0001] The embodiment of the utility model relates to an image sensing device. Background Art

[0002] Integrated circuits (ICs) containing image sensors are widely used in modern electronic devices such as cameras and mobile phones. Complementary metal oxide semiconductor (CMOS) image sensors (CIS) have become popular. Compared with charge-coupled devices (CCDs), CISs are becoming more and more popular due to their low power consumption, small pixel size, fast data processing speed, and low manufacturing cost. As pixel size becomes smaller, manufacturing becomes more and more difficult, and it becomes more and more difficult to limit crosstalk between pixels. Utility Model Content

[0003] An embodiment of the utility model relates to an image sensing device, which includes: a semiconductor body having a first side and a second side; a light detection area including a photosensitive structure within the semiconductor body; and a superlens configured on or at the second side, wherein the superlens is configured to focus electromagnetic radiation on the photosensitive structure.

[0004] An embodiment of the utility model relates to an image sensing device, which includes: a semiconductor body, including a first side and a second side, wherein the semiconductor body has a first refractive index; an optical material, configured on the second side, wherein the optical material has a second refractive index different from the first refractive index; a light detection area, including a photosensitive structure configured in the semiconductor body; and a super lens, formed by the optical material and the semiconductor body, wherein the super lens is constructed to focus near-infrared light on the photosensitive structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] When read in conjunction with the accompanying drawings, various aspects of the present invention can be best understood from the following detailed description. It should be noted that, in accordance with industry standard practice, various features are not drawn to scale. In fact, for the sake of clarity of discussion, the size of various features can be increased or reduced at will.

[0006] Figure 1 A cross-sectional view of an image sensing device according to some embodiments is shown.

[0007] Figure 2 A plan view of an image sensing device according to some embodiments is shown and may correspond to Figure 1 image sensing device.

[0008] Figure 3 A plan view of an image sensing device according to some other embodiments is shown and may correspond to Figure 1image sensing device.

[0009] Figure 4 FIG. 4 shows a plan view of an image sensing device according to some other embodiments.

[0010] Figure 5-8 Cross-sectional views of image sensing devices according to various other embodiments are shown.

[0011] Figure 9-22 is a series of cross-sectional views of methods of forming an image sensing device according to some example embodiments.

[0012] Fig.23 A flow chart is provided that illustrates a method of forming an image sensing device according to some embodiments. DETAILED DESCRIPTION

[0013] The utility model provides many different embodiments or examples for realizing different features of the utility model. Specific examples of components and configurations are described below to simplify the utility model. Of course, these are merely examples and are not intended to be limiting. For example, forming a first feature on or above a second feature in the following description may include an embodiment in which the first and second features are formed in direct contact, and may also include an embodiment in which additional features may be formed between the first and second features, so that the first and second features may not be in direct contact. In addition, the utility model may repeat reference numerals and / or letters in various examples. This repetition is for the purpose of simplicity and clarity, and does not itself dictate the relationship between the various embodiments and / or configurations discussed.

[0014] Additionally, for ease of description, spatially relative terms such as "below," "beneath," "lower," "above," "upper," etc. may be used herein to describe the relationship of one component or feature to another component or feature as illustrated in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein should likewise be interpreted accordingly.

[0015] Manufacturing process constraints limit the focal length of the type of microlenses used to focus electromagnetic radiation on the photosensitive structure in CMOS image sensing devices. Spacers or similar structures inserted between the microlenses and the photosensitive structure can increase the optical path length so that the incident electromagnetic radiation can be reduced from the spot size of the microlens to the spot size of the photosensitive structure within the focal length constraints. The disadvantage of this approach is that increasing the optical path length deteriorates the angular response. The angular response is related to the range of incident angles within which the incident electromagnetic radiation is effectively captured by the photosensitive structure.

[0016] Some aspects of the present invention relate to an image sensing device in which a metalens is interposed between a microlens and a photosensitive structure. The metalens is combined with the microlens to shorten the focal length, thereby reducing the spacer height or eliminating the spacer entirely. The metalens has an array of nanostructures that are smaller than the wavelength of the electromagnetic radiation being focused. The pattern of the nanostructures is organized to systematically vary in one or more of width, shape, spacing, and height around the center of the metalens. Light passing through the metalens is delayed by the nanostructures. The delay varies as the nanostructures vary, thereby creating a lens effect and focusing the incident electromagnetic radiation on the photosensitive structure. In some embodiments, the variation occurs in a pattern that repeats from the center to the edge of the metalens.

[0017] Some aspects of the present invention relate to an image sensing device having a metalens positioned to focus electromagnetic radiation on a photosensitive structure. The metalens can be used in combination with or in place of a microlens. In some embodiments, the metalens is effective for wavelengths in the near infrared range. In some embodiments, the photosensitive structure is within a semiconductor body and the nanostructure is formed from the surface of the semiconductor body. In some embodiments, the semiconductor body is silicon. In some embodiments, the photosensitive structure is a germanium sensor including a germanium structure within the semiconductor body. The germanium structure provides a photosensitive structure for the germanium sensor. In some embodiments, the image sensing device is designed for illumination from the back side of the semiconductor body, has a germanium structure near the front side of the semiconductor body, and the metalens is effective for focusing electromagnetic radiation having a wavelength in the near infrared range on the germanium structure.

[0018] In some embodiments, the nanostructures of the metalens are formed of a first optical material and a second optical material is filled in and around the nanostructures. The first optical material may be a semiconductor body. The first optical material and the second optical material have different refractive indices. In some embodiments, the second optical material has a refractive index of at least 2.0. The large difference between the refractive index of the first material and the refractive index of the second material increases the effectiveness of the metalens. A smaller difference between the refractive index of the first material and the refractive index of the second material may allow for reduced reflections.

[0019] In some embodiments, the nanostructures are pillars of a first optical material. In some embodiments, the nanostructures are holes in a first optical material that are filled with pillars of a second optical material. In some embodiments, the nanostructures are rings of a first optical material interlaced with rings of a second optical material. Holes, pillars, annular ridges, and annular grooves are structures suitable for small-scale manufacturing.

[0020] Some aspects of the utility model relate to an image sensing device having a lens formed in a semiconductor body including a photosensitive structure. In some embodiments, the lens is formed in the backside surface of the semiconductor body and illuminates the photosensitive structure from the backside. The lens can be shallower than a spherical lens of equivalent focal length. In some embodiments, the backside surface of the lens is neither a pure convex surface nor a pure concave surface, but has a plurality of nanostructures so that the surface has peaks and valleys. In some embodiments, the lens includes nanostructures that vary in a pattern of a periodic function on the surface of the lens. In some embodiments, the pattern is repeated on the lens. The nanostructures are subwavelength structures relative to the wavelength of near infrared light. In some embodiments, the lens is a super lens. In some embodiments, the photosensitive structure is configured in the semiconductor body near its front side. In some embodiments, the semiconductor body is silicon and the photosensitive structure is germanium configured in the semiconductor body.

[0021] Some aspects of the utility model relate to a method for forming an image sensing device. The method includes forming a light detection area in the front side of a semiconductor body. In some embodiments, forming the light detection area includes etching a hole in the semiconductor body and epitaxially growing a second semiconductor in the hole. In some embodiments, the semiconductor body is silicon and the second semiconductor is germanium. The semiconductor body is flipped over and the semiconductor body is thinned. The back side of the semiconductor body is patterned to define a nanostructure of a superlens, which is positioned to focus electromagnetic radiation from the back side onto the second semiconductor. An optical material layer is deposited on the nanostructure and fills the inside and around the nanostructure. In some embodiments, an anti-reflective coating is formed above the optical material layer. In some embodiments, a spacer is formed above the optical material layer. In some embodiments, a microlens is formed above the superlens. In some embodiments, a second superlens is formed above the superlens.

[0022] Some other aspects of the present invention relate to a variation of the aforementioned method. In this variation, a first optical material layer located above the back side of the semiconductor body is patterned to form a nanostructure. A second optical material layer having a different refractive index than the first optical material layer is deposited above the first optical material layer to complete the formation of the metalens.

[0023] Figure 1A cross-sectional view of an image sensing device 100 according to some aspects of the present invention is shown. Image sensing device 100 includes a photodetecting region 122 within a semiconductor body 119. Semiconductor body 119 has a front side 135 and a back side 137. Photodetecting region 122 includes a photosensitive structure 121 within semiconductor body 119 near front side 135. Metalens 113A is formed in back side 137. Metal interconnect 133 can be configured on front side 135.

[0024] The light detection region 122 may be a pixel in the array. Isolation structures such as the backside deep trench isolation structure 115 and the shallow trench isolation structure 123 may provide electrical isolation that suppresses crosstalk between adjacent pixels. The photosensitive structure 121 may have a relatively high infrared light absorption rate, while the semiconductor body 119 may have a relatively low infrared light absorption rate. The light detection region 122 may include a PN diode (not shown). In some embodiments, the PN diode is configured within the photosensitive structure 121. In some embodiments, the PN diode is formed between the photosensitive structure 121 and the semiconductor body 119. The photodetector may include transistors and other additional structures (not shown), such as a floating diffusion region, a selection gate, a transfer gate, a reset gate, etc. These structures may be formed in or on the semiconductor body 119. Optionally, some of these structures are configured on a second substrate (not shown) and connected to the light detection region 122 through a metal line 131 and a via 129 of a metal interconnect 133.

[0025] Incoming electromagnetic radiation 103 incident on the superlens 113A is focused by the superlens 113A into converging electromagnetic radiation 117. The converging electromagnetic radiation 117 is converged onto the photosensitive structure 121. The converging electromagnetic radiation 117 generates electron-hole pairs within the photosensitive structure 121. The electric field generated by the PN diode or the like separates the electrons and holes before they recombine so that the generated charges can be accumulated and detected. The reflector 125 can reflect some of the converging electromagnetic radiation 117 that passes through or passes through the photosensitive structure 121 back to the photosensitive structure 121 to increase the efficiency of the light detection area 122.

[0026] The metalens 113A includes nanostructures 109A provided by the back side 137 of the semiconductor body 119. The nanostructures 109A have a spacing S1 that varies relative to the distance of the center 102. The center 102 is the center of the photosensitive structure 121 and the metalens 113A. In some embodiments, the variation includes a monotonically increasing or decreasing sequence. In some embodiments, the sequence repeats. In some embodiments, the nanostructures 109A are symmetrical about the center 102. In some embodiments, except that the nanostructures 109A are on the center 102, the nanostructures 109A each have a width W1.

[0027] In some embodiments, the width W1 of the nanostructure 109A is less than about 1000 nm. In some embodiments, the width W1 of the nanostructure 109A is in the range of about 10 nm to about 500 nm. In some embodiments, the spacing S1 between adjacent nanostructures 109A is less than about 1000 nm. In some embodiments, the spacing S1 is in the range of about 10 nm to about 500 nm. In some embodiments, a string of nanostructures 109A (a group of nanostructures 109A arranged in a row along a line segment) has three or more different spacings in a monotonically increasing or decreasing order. In some embodiments, a string of nanostructures 109A has five or more different spacings in a monotonically increasing or decreasing order. In some embodiments, a string of nanostructures 109A has a sequence of monotonically increasing or decreasing spacings S1 that repeats two or more times between the center 102 and the edge of the super lens 113A. In some embodiments, a string of nanostructures 109A has a sequence of monotonically increasing or decreasing spacings S1 that repeats three or more times between the center 102 and the edge of the super lens 113A.

[0028] An optical material layer 111 is disposed over the back side 137 and fills the gaps between adjacent nanostructures 109A. The optical material layer 111 can be any transparent material with a refractive index that is different from the refractive index of the semiconductor body 119. In some embodiments, the refractive index of the optical material layer 111 is less than the refractive index of the semiconductor body 119. In some embodiments, the difference in refractive index is in a range of about 0.3 to about 2. In some embodiments, the difference in refractive index is in a range of about 1.0 to about 1.5. Increasing the difference in refractive index shortens the focal length, but may also increase reflection. In some embodiments, the optical material layer 111 is an oxide, such as silicon dioxide (SiO 2) , tantalum oxide (Ta2O5), etc. Additional dielectric layers (not shown) may be configured over the optical material layer 111 to reduce reflection, improve electrical isolation, provide wavelength filtering, or provide packaging.

[0029] Metalens 113A provides an example of a metalens according to the present invention. More generally, a metalens according to the present invention includes nanostructures that vary in distance relative to center 102. The variation can be any of the size, spacing, shape, or depth of the nanostructures. The variation in the nanostructures is related to the variation in the effective refractive index experienced by electromagnetic radiation passing through the metalens. A composite medium including nanostructures and any medium filling the gaps between the nanostructures provides an effective refractive index that varies in a position-dependent manner, such that the overall variation produces the focusing effect of the lens. The variation in the effective refractive index is associated with a variation in the phase shift. These variations are structures such that the phase shift is associated with the following formula:

[0030]

[0031] in is the phase shift, x is the distance from the center 102, λ is the wavelength of the focused electromagnetic radiation, and f is the focal length. In some embodiments, the metalens provides a desired focal length f for wavelengths in the near infrared range. The near infrared range is about 800 nm to about 2,500 nm. The desired focal length f can be achieved for a wavelength of, for example, about 1000 nm.

[0032] refer to Figure 1 , the focal length f is related to the width W2 of the superlens 113A, the width W3 of the photosensitive structure 121, and the distance D1 from the superlens 113A to the photosensitive structure 121. In order for the superlens 113A to reduce the spot size of the incident electromagnetic radiation to the spot size of the photosensitive structure 121, the focal length should be approximately:

[0033]

[0034] In some embodiments, D1 is in a range of about 1 μm to about 5 μm. In some embodiments, D1 is in a range of about 2 μm to about 3 μm. In some embodiments, the ratio of W3 to W2 is in a range of about 0.2 to about 0.8. In some embodiments, the ratio of W3 to W2 is in a range of about 0.4 to about 0.6, such as about 0.5. The initial design of the metalens based on the mathematical formula can be refined by computer simulation.

[0035] Figure 2 A plan view 200 is shown which illustrates a Figure 1 The metalens 113B of the metalens 113A is a metalens 113B. The metalens 113B has a ring-shaped nanostructure 109B. The optical material layer 111 fills the space between the ring-shaped nanostructures 109B to complete the metalens 113B. The ring-shaped nanostructures 109B are provided by ridges on the back side 137 of the semiconductor body 119 (see Figure 1). The spacing between the annular nanostructures 109B gradually decreases through a series of four annular nanostructures 109B. The pattern begins to repeat at the center and edge of the metalens 113B. It should be understood that there may be more annular nanostructures 109B per light detection region 122 in the array than shown in the figure. For ease of illustration, the figure shows a smaller number of nanostructures.

[0036] Figure 3 A plan view 300 is shown showing a metalens 113C, which may correspond to Figure 1 The super lens 113C has a column-shaped nanostructure 109C formed of a semiconductor body 119 (see Figure 1 ). The columnar nanostructure 109C may have a diameter equal to the width W1. The columnar nanostructures 109C are arranged in concentric rings centered on the center 102. The concentric rings have a spacing S1 that undergoes periodic changes. The columnar nanostructure 109C protrudes into the optical material layer 111. The metalens according to an alternative embodiment includes a hole (not shown) in the semiconductor body 119. In the alternative embodiment, the column of the optical material layer 111 protrudes into the hole. More generally, for each nanostructure shape shown in the utility model, there is an inverse nanostructure shape that can be used to provide an alternative embodiment.

[0037] Figure 4 A plan view 400 of a metalens 113D is shown. The metalens 113D may be used to replace Figure 1 109D. The superlens 113D has a columnar nanostructure 109D. The width W1 of the columnar nanostructure 109D varies relative to the distance of the center 102 to provide a focusing effect of the superlens 113D. In some embodiments, the columnar nanostructures 109D are evenly spaced as shown. In some embodiments, the columnar nanostructures 109D have variable spacing that contributes to the focusing effect. For example, the columnar nanostructures 109D can become more widely spaced as they become narrower.

[0038] Figure 5 FIG. 5 shows a cross-sectional view of an image sensing device 500 according to another embodiment. Figure 1 The image sensing device 100 of the present invention is shown in FIG. 5 , except that the image sensing device 500 has a metalens 113E. The metalens 113E has a nanostructure 109E provided by a hole or annular groove in the back side 137. The nanostructure 109E has a depth variation, which enables the metalens 113E to effectively focus the incoming electromagnetic radiation 103, redirecting it to the focused electromagnetic radiation 117 focused on the photosensitive structure 121.

[0039] Figure 6 FIG. 4 is a cross-sectional view of an image sensing device 600 according to another embodiment. Figure 1 The image sensing device 100 includes the image sensing device 600 having a super lens 113F. The super lens 113F has a similar Figure 1 109F, except that nanostructures 109F are formed in a layer 601 disposed above back side 137. Layer 601 is an optical material having a different refractive index than optical material layer 111. Layer 601 can have a greater or lesser refractive index than optical material layer 111. Alternatively, optical material layer 111 is completely eliminated so that the contrast medium is air. If layer 601 is above optical material layer 111 instead of below, the pattern of nanostructures 109F can be reversed, for example, from spacing that decreases with distance from center 102 to spacing that increases with distance from center 102.

[0040] Figure 7 FIG. 4 is a cross-sectional view of an image sensing device 700 according to another embodiment. Figure 1 The image sensing device 100 of the present invention is shown in FIG. 7 , except that the image sensing device 700 has a microlens 101 disposed above the superlens 113A. The microlens 101 and the superlens 113A are combined to provide a desired focal length. An optical material spacer 105 can be disposed between the microlens 101 and the superlens 113A. In some embodiments, the spacer 105 is a wavelength filter. In some embodiments, the spacer 105 is formed integrally with the optical material layer 111 that fills the gap between the nanostructures 109A of the superlens 113A.

[0041] Figure 8 FIG. 8 is a cross-sectional view of an image sensing device 800 according to another embodiment. Figure 1 The image sensing device 100 of the present invention is different in that the image sensing device 800 has a second super lens 113G connected in series with the super lens 113A. The super lens 113A and the second super lens 113G are combined to provide a desired focal length. The second super lens 113G can have a nanostructure 109G formed in the upper surface of the optical material layer 111. In some embodiments, the nanostructure 109G is formed in a separate layer configured above the optical material layer 111. The nanostructure 109G can have the same pattern as the nanostructure 109A or a different pattern.

[0042] Figures 9 to 22 A cross-sectional view of an exemplary method of forming an image sensing device according to the present invention is shown. Figures 9 to 22 , but it should be understood that Figures 9 to 22The structure shown in is not limited to the method, but can be independent of the method. Figures 9 to 22 Described as a series of actions. The order of these actions may be changed in other embodiments. Figures 9 to 22 A particular set of actions is shown and described, but some actions may be omitted in other embodiments. In addition, actions not shown and / or described may be included in other embodiments.

[0043] like Fig. 9 As shown in the cross-sectional view 900 of , the method may start by forming a shallow trench isolation structure 123 in the semiconductor body 119. The semiconductor body may be a bulk semiconductor substrate or an upper layer of a semiconductor-on-insulator substrate, etc. The semiconductor body 119 may be silicon (Si), etc., or some other semiconductor. The shallow trench isolation structure 123 may be formed by etching a trench in the semiconductor body 119 and filling the trench with a dielectric such as silicon dioxide (SiO2), etc., or some other semiconductor. The shallow trench isolation structure 123 is a portion of a structure for creating isolation between adjacent light detection regions 122. Any suitable isolation strategy may be used. Therefore, the shallow trench isolation structure 123 is optional.

[0044] like Fig.10 As shown in the cross-sectional view 1000 of FIG. 1 , a mask 1001 may be formed and used to etch a trench 1003 in the semiconductor body 119. After etching, the mask 1001 may be stripped. Fig.11 As shown in the cross-sectional view 1100 of FIG. 1 , the trench 1003 may be filled with a second semiconductor to form a photosensitive structure 121. The composition of the second semiconductor is different from that of the semiconductor body 119. In some embodiments, the second semiconductor is germanium (Ge), etc. The trench 1003 may be filled with the second semiconductor by epitaxial growth, etc. or some other suitable process. Excess semiconductor may be removed by a planarization process such as chemical mechanical polishing (CMP), etc.

[0045] Additional processing (not shown) may be performed to form the light detection region 122 including the light sensing structure 121. Such additional processing may include masking, doping, deposition, and patterning of the gate stack. The additional processing may form structures such as floating diffusion regions, transfer gates, PN diodes, and other structures related to the functionality of the light detection region 122. In some embodiments, the additional processing includes forming a PN diode (not shown) within the light sensing structure 121. The PN diode may also be formed within the semiconductor body 119. At this point, it should be understood that the light sensing structure 121 may be a light sensing region of any type of light detector.

[0046] like Fig.12As shown in the cross-sectional view 1200 of , a metal interconnect 133 can be formed above the semiconductor body 119. The metal interconnect 133 includes a metal line 131 and a via 129 that can form an electrical connection to the light detection region 122. The metal line 131 and the via 129 can be a metal, etc., or any other suitable conductive material. The metal line 131 and the via 129 can be surrounded by an interlevel dielectric 127. The reflector 125 can also be formed within the metal interconnect 133. The interlevel dielectric 127 can be silicon dioxide (SiO2), a low-k dielectric, etc., or any other suitable dielectric material. The metal interconnect 133 can be formed by a series of damascene or dual damascene processes, etc., or by any other suitable method.

[0047] like Fig.13 As shown in the cross-sectional view 1300 of FIG. 1 , a bonding structure 1301 may be formed over the metal interconnect 133 . The bonding structure 1301 may include a bonding pad 1303 electrically coupled to the metal line 131 .

[0048] like Fig.14 As shown in the cross-sectional view 1400, the second substrate 1405 can be Fig.13 The structure shown in the cross-sectional view 1300 of FIG. 1404 can be aligned. Metal interconnects 1403 and bonding structures 1401 can be formed over a second substrate 1405. Transistors 1407 and other such structures can be formed in the second substrate 1405. These transistors can provide select gates, erase gates, etc. and other such structures that enable the light detection region 122 to operate in an image sensing device. The bonding structure 1401 can include a bonding pad 1409.

[0049] like Fig.15 As shown in the cross-sectional view 1500 of FIG. 1 , the semiconductor body 119 can be connected to the second substrate 1405 by a bonding process. The bonding process can be oxide-to-oxide bonding, metal bonding, a combination thereof, or any other suitable bonding process. An electrical connection can be formed between the bonding pad 1303 and the bonding pad 1409.

[0050] like Fig.16 As shown in the cross-sectional view 1600, Fig.15 The structure shown in the cross-sectional view 1500 is flipped, and the semiconductor body 119 can be thinned. The thinning process can be CMP, etc., or any other suitable process.

[0051] like Fig.17 As shown in the cross-sectional view 1700 of FIG. 1 , a mask 1701 may be formed and used to etch a trench 1703 in the semiconductor body 119. After etching, the mask 1701 may be stripped. Fig.18As shown in the cross-sectional view 1800 of FIG. 1703 , the trench 1703 may be filled with a dielectric material to form a backside deep trench isolation structure 115. The dielectric material may include one or more layer dielectrics, such as hafnium oxide (HfO), aluminum oxide (AlO), tantalum oxide (Ta2O3), silicon oxide (SiO2), etc., or any other suitable material. The dielectric may be deposited by chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), etc., or any other suitable process. Excess dielectric may be removed by a planarization process such as chemical mechanical polishing (CMP).

[0052] like Fig.19 As shown in the cross-sectional view 1900 of FIG. 1 , a mask 1901 can be formed and used to etch trenches 1903 in the back side 137 of the semiconductor body 119. The etching process forms the nanostructures 109 in the back side 137. The mask 1901 can be a photoresist, a hard mask, or any other suitable type of mask. The mask 1901 can be patterned by photolithography, electron beam lithography, etc., or any other type of patterning process. The etching process can be dry etching, wet etching, etc. The dry etching process can be plasma etching, etc. In some embodiments, the etching conditions are selected so that the trenches 1903 all have approximately equal depths. After etching, the mask 1901 can be stripped.

[0053] like Fig. 20 As shown in the cross-sectional view 2000 of FIG. 1 , an optical material layer 111 may be deposited over the back side 137 so as to fill the space between the grooves 1903 between the nanostructures 109. The optical material layer 111 may be deposited by CVD, PVD, ALD, etc., or any other suitable process. Optionally, the deposition is followed by a planarization process, such as CMP, etc., or any other suitable process. The nanostructures 109 and the optical material layer 111 form a superlens 113. The planarization of the optical material layer 111 may be used to improve the focusing of the superlens 113.

[0054] like Fig.21 As shown in the cross-sectional view 2100 of FIG. 1 , a back side metal grid 2101 may be formed over the optical material layer 111. The back side metal grid 2101 may reduce crosstalk between adjacent light detection regions 122. The back side metal grid 2101 may be formed by depositing a layer of metal or other suitable material, then forming a mask and etching to pattern the layer.

[0055] like Fig. 22As shown in the cross-sectional view 2200 of , the spacer 105 and the microlens 101 can be formed above the optical material layer 111. The spacer 105 can be deposited by CVD, PVD, ALD, etc. or any other suitable process. The microlens 101 can be formed of a dielectric, a polymer, etc. or any other suitable material, and can be formed by any suitable process. The process of forming the microlens may include, for example, deposition of the lens material, followed by etching to define the lens shape. In some embodiments, the formation process includes a thermal reflow process, etc.

[0056] Fig.23 A flow chart of a process 2300 that may be used to form an image sensing device according to the present invention is presented. Fig.23 The process 2300 is illustrated and described herein as a series of actions or events, but it should be understood that the illustrated order of these actions or events should not be interpreted as limiting. For example, some actions may occur in a different order and / or occur simultaneously with other actions or events other than those shown and / or described herein. In addition, not all of the actions shown are required to implement one or more aspects or embodiments described herein, and one or more of the actions described herein may be performed in one or more separate actions and / or stages.

[0057] Process 2300 may begin with activity 2301, forming a photosensitive structure in a semiconductor body. The photosensitive structure may be any type of photosensitive structure. In some embodiments, the photosensitive structure is germanium (Ge) and provides a germanium sensor. Figure 9-11 An example is provided by cross-sectional views 900-1100.

[0058] The process 2300 may continue with act 2303 by forming metal and bonding layers over the semiconductor body. Figure 12-13 The cross-sectional views 1200-1300 of the present invention provide an example. The metalens according to the present invention can be used in an image sensing device with front side or back side illumination. In some embodiments, the image sensing device is of the type using back side illumination. Forming the bonding layer and attaching to the second substrate are steps in the process of forming a device using back side illumination.

[0059] Act 2305 bonds the semiconductor body to a second substrate via a bonding layer. Figure 14-15 An example is provided by cross-sectional views 1400-1500 of Act 2307 thins the semiconductor body from the back side. Fig.16 An example is provided by cross-sectional view 1600 of FIG. Thinning the semiconductor body can bring the backside within a few microns of the frontside, such as within about 4 to about 10 microns.

[0060] Action 2309 etches the back side to define the nanostructure of the metalens. Fig.19An example is provided by the cross-sectional view 1900 of FIG. 19. In an alternative embodiment, a second layer of optical material is deposited over the back side and the nanostructures of the metalens are formed in said layer.

[0061] Action 2311 is an optional action of depositing a layer of optical material on the nanostructures. Fig. 20 An example is provided in cross-sectional view 2000 of . The optical material layer fills the gaps between the nanostructures and may serve other functions, such as reducing reflections and providing electrical isolation for the semiconductor body.

[0062] Action 2313 is another optional action of forming a spacer layer on the nanostructure. In some embodiments, the spacer layer includes a wavelength filter. If a spacer layer is used, it may be thinner than a spacer layer used without a metalens.

[0063] Action 2315 is another optional action of forming microlenses on the spacer layer. Fig.21 An example is provided by cross-sectional view 2100 of . Microlenses and metalenses together can provide a shorter focal length than either type of lens can provide by itself.

[0064] Some aspects of the present invention relate to an image sensing device including a photosensitive structure within a semiconductor body. A superlens that focuses electromagnetic radiation on the photosensitive structure is located on the back side of the semiconductor body. In some embodiments, the superlens includes a nanostructure formed in the back side. In some embodiments, the nanostructure is a concentric ring. In some embodiments, the nanostructure protrudes into a film of optical material on the back side. In some embodiments, the nanostructure has a spacing that varies with the distance from the center of the photosensitive structure. In some embodiments, the superlens includes a configuration of optical material columns protruding into the semiconductor body. In some embodiments, the superlens includes a nanostructure whose height varies systematically with the distance from the center of the photosensitive structure. In some embodiments, the superlens includes a nanostructure that achieves a focusing effect by varying two or more of depth, spacing, or size. In some embodiments, there is a microlens above the superlens. In some embodiments, the superlens at least doubles the concentration of infrared light on the photosensitive structure relative to infrared light incident vertically on the back side. In some embodiments, the superlens includes a nanostructure having a varying pattern that repeats at least twice over the length of increasing distance from the center of the superlens.

[0065] Some aspects of the utility model relate to an image sensing device, which includes a semiconductor body, the semiconductor body including a front side and a back side. The semiconductor body has a first refractive index. An optical material is arranged on the back side. The optical material has a second refractive index different from the first refractive index. A light detection area including a photosensitive structure is arranged in the semiconductor body. A superlens formed by the optical material and the semiconductor body focuses near-infrared light on the photosensitive structure. In some embodiments, the photosensitive structure includes a second semiconductor having a composition different from that of the semiconductor body. In some embodiments, the semiconductor body is silicon and the photosensitive structure is germanium.

[0066] Some aspects of the utility model relate to a method for manufacturing an image sensing device. The method includes providing a semiconductor body, forming a photosensitive structure in the semiconductor body, and patterning the back side of the semiconductor body to form a nanostructure containing a superlens. The nanostructure is configured so that the superlens focuses electromagnetic radiation with a wavelength in the infrared range on the photosensitive structure. In some embodiments, forming the photosensitive structure in the semiconductor body includes etching a groove in the semiconductor body and filling the groove with a second semiconductor. In some embodiments, the method also includes depositing an optical material on the nanostructure. The optical material fills the space between the nanostructures. In some embodiments, the method includes forming a microlens above the superlens. In some embodiments, the photosensitive structure is a germanium sensor including a germanium structure, and the superlens focuses electromagnetic radiation with a wavelength in the infrared range on the germanium structure.

[0067] The foregoing summarizes the features of several embodiments so that those skilled in the art can better understand the various aspects of the present invention. Those skilled in the art should understand that they can easily use the present invention as a basis for designing or modifying other processes and structures to achieve the same purpose and / or achieve the same advantages as the embodiments described herein. Those skilled in the art should also recognize that such equivalent constructions do not depart from the spirit and scope of the present invention, and they can make various changes, substitutions and modifications without departing from the spirit and scope of the present invention.

Claims

1. An image sensing device, characterized in that: include: a semiconductor body having a first side and a second side; a light detection region including a light-sensitive structure within the semiconductor body; as well as A metalens is disposed on or at the second side, wherein the metalens is configured to focus electromagnetic radiation on the photosensitive structure.

2. The image sensing device according to claim 1, wherein: The metalens includes a nanostructure formed in the second side of the semiconductor body.

3. The image sensing device according to claim 2, wherein: The nanostructures are concentric rings.

4. The image sensing device according to claim 2, wherein: The nanostructures protrude into the film of optical material on the second side.

5. The image sensing device according to claim 2, wherein: The nanostructures have a spacing that varies relative to a center of the photosensitive structure.

6. The image sensing device according to claim 1, wherein: The metalens includes an arrangement of columns of optical material protruding from the second side into the semiconductor body.

7. The image sensing device according to claim 1, wherein: The metalens includes nanostructures whose height varies systematically with distance from the center of the photosensitive structure.

8. The image sensing device according to claim 1, wherein: The metalens includes nanostructures that achieve a focusing effect through variations in two or more of depth, spacing, or size.

9. The image sensing device according to claim 1, wherein: Also included is a microlens on the metalens.

10. An image sensing device, characterized in that: include: a semiconductor body comprising a first side and a second side, wherein the semiconductor body has a first refractive index; an optical material disposed on the second side, wherein the optical material has a second refractive index different from the first refractive index; a light detection region, comprising a light-sensitive structure disposed within the semiconductor body; as well as A superlens is formed by the optical material and the semiconductor body, wherein the superlens is configured to focus near infrared light onto the photosensitive structure.

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