Manufacturating method of back side illumination image sensor

Abstract

A back side illumination image sensor including a substrate, a photosensitive device and a filling layer is provided. The substrate includes a first surface and a second surface opposite to each other, wherein the second surface includes a first recess, a second recess and a third recess, a maximum depth of the second recess is greater than a maximum depth of the first recess, and a maximum depth of the third recess is greater than a maximum depth of the second recess. The photosensitive device is disposed in the substrate and adjacent to the first surface of the substrate, wherein the photosensitive device includes a first photosensitive device, a second photosensitive device and a third photosensitive device, and the first photosensitive device, the second photosensitive device and the third photosensitive device are respectively corresponding to the first recess, the second recess and the third recess. The filling layer is disposed on the second surface of the substrate and fills the first recess, the second recess and the third recess. A wavelength of the light sensed by the first photosensitive device is greater than a wavelength of the light sensed by the second photosensitive device, and a wavelength of the light sensed by the second photosensitive device is greater than a wavelength of the light sensed by the third photosensitive device.

Description

[Technical Field]

[0001] This disclosure relates to an image sensor and a method of manufacturing the same, and more particularly to a back-illuminated image sensor and a method of manufacturing the same. [Previous Technology]

[0002] Back-illuminated image sensors are widely used in many electronic devices. Currently, an inverted pyramid array (IPA) structure is formed on the surface of the substrate of the back-illuminated image sensor to reduce the possibility of the light to be sensed being reflected and / or scattered by the substrate. However, for light with relatively short wavelengths (e.g., blue light), it will be converted into electrons relatively quickly in the substrate. These electrons may not be sensed by the photosensitive element and / or may be attenuated in the substrate, which makes the quantum efficiency of the back-illuminated image sensor lower when sensing light with relatively short wavelengths.

[0003] Based on this, further improving the quantum efficiency of back-illuminated image sensors is the current goal of continuous efforts. [Summary of the Invention]

[0004] This disclosure provides a back-illuminated image sensor with relatively good quantum efficiency.

[0005] The back-illuminated image sensor disclosed herein includes a substrate, a photosensitive element, and a filling layer. The substrate includes a first surface and a second surface opposite to each other, wherein the second surface includes a first recess, a second recess, and a third recess, the maximum depth of the second recess being greater than the maximum depth of the first recess, and the maximum depth of the third recess being greater than the maximum depth of the second recess. The photosensitive element is disposed in the substrate and adjacent to the first surface of the substrate, wherein the photosensitive element includes a first photosensitive element, a second photosensitive element, and a third photosensitive element, and each of the first, second, and third photosensitive elements is respectively disposed corresponding to the first, second, and third recesses. The filling layer is disposed on the second surface of the substrate and fills the first, second, and third recesses. The wavelength of light sensed by the first photosensitive element is greater than the wavelength of light sensed by the second photosensitive element, and the wavelength of light sensed by the second photosensitive element is greater than the wavelength of light sensed by the third photosensitive element.

[0006] This disclosure provides a method for manufacturing a back-illuminated image sensor, which produces a back-illuminated image sensor with relatively good quantum efficiency.

[0007] The method for manufacturing a back-illuminated image sensor disclosed herein includes the following steps. First, a substrate including photosensitive elements is provided, wherein the photosensitive elements are adjacent to a first surface of the substrate and include a first photosensitive element, a second photosensitive element, and a third photosensitive element. Next, a first opening, a second opening, and a third opening are formed on a second surface of the substrate, wherein the second surface is opposite to the first surface, and the first, second, and third photosensitive elements are respectively disposed corresponding to the first, second, and third openings, respectively. The wavelength of light sensed by the first photosensitive element is greater than the wavelength of light sensed by the second photosensitive element, and the wavelength of light sensed by the second photosensitive element is greater than the wavelength of light sensed by the third photosensitive element. Then, the first opening, the second opening, and the third opening of the substrate are etched to form a first recess, a second recess, and a third recess, respectively, wherein the maximum depth of the second recess is greater than the maximum depth of the first recess, and the maximum depth of the third recess is greater than the maximum depth of the second recess. Afterward, a filler layer is filled into the first recess, the second recess, and the third recess of the substrate.

[0008] Based on the above, in the back-illuminated image sensor provided in this disclosure, the recess corresponding to the photosensitive element that senses light with a relatively short wavelength has a relatively large maximum depth, which can shorten the path of the light with a relatively short wavelength in the substrate, thereby reducing the possibility that the light is not sensed by the photosensitive element after being converted into electrons in the substrate and / or the signal (electron) is attenuated, thereby improving the quantum efficiency of the back-illuminated image sensor disclosed in this disclosure.

Implementation Method

[0009] Examples are listed below in conjunction with the accompanying drawings to describe this disclosure in detail, but the examples provided are not intended to limit the scope of this disclosure. Furthermore, the accompanying drawings are for illustrative purposes only, and certain elements in the drawings are not drawn to scale. For ease of understanding, the same elements will be identified using the same symbols in the following description.

[0010] Figures 1A to 1F are partial cross-sectional schematic diagrams of a method for manufacturing a back-illuminated image sensor according to an embodiment of the present disclosure.

[0011] Referring to Figures 1A to 1F, in this embodiment, the back-illuminated image sensor 10 can be formed by performing the following steps, but this disclosure is not limited thereto.

[0012] Step (1): Provide a substrate SB including a photosensitive element PS.

[0013] The substrate SB may be, for example, a semiconductor substrate. In some embodiments, the substrate material may include silicon, doped silicon, germanium, silicon-germanium, semiconductor compounds, other suitable semiconductor materials, or combinations thereof. In this embodiment, the substrate SB is an epitaxial silicon substrate, but this disclosure is not limited thereto. In addition, the substrate SB has a first surface S1 and a second surface S2 opposite thereto.

[0014] Referring to FIG1A, in this embodiment, a photosensitive element PS has been formed in the substrate SB, but this disclosure is not limited thereto. The photosensitive element PS can be formed, for example, by performing an ion implantation process. In this embodiment, the photosensitive element PS is adjacent to the first surface S1 of the substrate SB. In some embodiments, the photosensitive element PS can be a photodiode, but this disclosure is not limited thereto. In this embodiment, the photosensitive element PS includes a first photosensitive element PS1, a second photosensitive element PS2, and a third photosensitive element PS3, wherein the first photosensitive element PS1 can sense red light, the second photosensitive element PS2 can sense green light, and the third photosensitive element PS3 can sense blue light, but this disclosure is not limited thereto.

[0015] Additionally, in some embodiments, an element layer (not shown) may be formed on the first surface S1 of the substrate SB. In some embodiments, the element layer may include, for example, elements electrically connected to the photosensitive element PS, such as driving elements and / or traces, and this disclosure is not limited thereto.

[0016] Proceed to step (2): Form the first opening OP1 in the substrate SB.

[0017] Please continue to refer to FIG1A. In this embodiment, the first opening OP1 can be formed by performing the following steps, but this disclosure is not limited thereto.

[0018] Step (2a): A hard mask layer HM is formed on the second surface S2 of the substrate SB.

[0019] The hard mask layer HM can be formed, for example, by performing a suitable deposition process, and this disclosure is not limited thereto. In some embodiments, the material of the hard mask layer HM may include silicon nitride.

[0020] Step (2b): Patterning process is performed on the rigid mask layer HM and the substrate SB.

[0021] In this embodiment, a portion of the hard mask layer HM and a portion of the substrate SB can be removed by first forming a photoresist layer PR on the hard mask layer HM, and then using the photoresist layer PR to perform an etching process on the hard mask layer HM and the substrate SB. However, this disclosure is not limited thereto. The photoresist layer PR can be formed, for example, by performing a suitable coating process and / or lithography process. This disclosure is not limited thereto.

[0022] It is worth noting that after patterning the hard mask layer HM and the substrate SB, the photoresist layer PR is removed. The photoresist layer PR can be removed, for example, by performing a suitable stripping process, and this disclosure is not limited thereto.

[0023] In this embodiment, the first opening OP1 corresponds to the first photosensitive element PS1 in the Z direction.

[0024] Refer to Figure 1B and perform step (3): fill the first protective layer PL1 into the first opening OP1 of the substrate SB.

[0025] The first protective layer PL1 may be formed, for example, by performing a suitable deposition process, and this disclosure is not limited thereto. In some embodiments, the material of the first protective layer PL1 may include silicon oxide.

[0026] Please continue to refer to Figure 1B. It is worth noting that after the above deposition process, a planarization process can be performed on the first protective layer PL1 to remove the first protective layer PL1 located outside the first opening OP1, but this disclosure is not limited thereto.

[0027] In some embodiments, the first protective layer PL1 may be used to reduce the possibility that the first opening OP1 will be affected in subsequent processes, but this disclosure is not limited thereto.

[0028] Refer to Figure 1C and perform step (4): form a second opening OP2 in the substrate SB.

[0029] In this embodiment, the method for forming the second opening OP2 is similar to the method for forming the first opening OP1. In other words, the method for forming the second opening OP2 can refer to step (2) above, and will not be repeated here.

[0030] Please continue to refer to Figure 1C. In this embodiment, the depth D2 of the second opening OP2 in the Z direction is greater than the depth D1 of the first opening OP1 in the Z direction. In addition, in this embodiment, the second opening OP2 corresponds to the second photosensitive element PS2 in the Z direction.

[0031] Please continue to refer to Figure 1C and proceed to step (5): fill the second protective layer PL2 into the second opening OP2 of the substrate SB.

[0032] In this embodiment, the method for forming the second protective layer PL2 is similar to the method for forming the first protective layer PL1. In other words, the method for forming the second protective layer PL2 can refer to step (3) above, and will not be repeated here.

[0033] Refer to Figure 1D and perform step (6): form a third opening OP3 in the substrate SB.

[0034] In this embodiment, the method for forming the third opening OP3 is similar to the method for forming the first opening OP1. In other words, the method for forming the third opening OP3 can refer to step (2) above, and will not be repeated here.

[0035] In this embodiment, the depth D3 of the third opening OP3 in the Z direction is greater than the depth D2 of the second opening OP2 in the Z direction. Furthermore, in this embodiment, the third opening OP3 corresponds to the third photosensitive element PS3 in the Z direction.

[0036] Proceed to step (7): Fill the third protective layer PL3 into the third opening OP3 of the substrate SB.

[0037] In this embodiment, the method for forming the third protective layer PL3 is similar to the method for forming the first protective layer PL1. In other words, the method for forming the third protective layer PL3 can refer to step (3) above, and will not be repeated here.

[0038] Refer to Figure 1E and perform step (8): remove the first protective layer PL1, the second protective layer PL2 and the third protective layer PL3.

[0039] The first protective layer PL1, the second protective layer PL2, and the third protective layer PL3 can be removed, for example, by performing a suitable etching process, and this disclosure is not limited thereto. In this embodiment, after removing the first protective layer PL1, the second protective layer PL2, and the third protective layer PL3, the first opening OP1, the second opening OP2, and the third opening OP3 are exposed.

[0040] Please continue to refer to FIG1E and perform step (9): use the patterned hard mask layer HM as a mask to perform an etching process on the substrate SB to form the first recess IP1, the second recess IP2 and the third recess IP3.

[0041] In detail, in this embodiment, a wet etching process can be performed on the first opening OP1, the second opening OP2, and the third opening OP3 of the substrate SB by using a patterned hard mask layer HM as a mask, so as to form a first recess IP1, a second recess IP2, and a third recess IP3, respectively. In some embodiments, the etching solution used in the above-described wet etching process may be tetramethylammonium hydroxide (TMAH), but this disclosure is not limited thereto.

[0042] In this embodiment, the first recess IP1, the second recess IP2, and the third recess IP3 may each have inclined sidewalls, and the bottom of the first recess IP1, the second recess IP2, and the third recess IP3 may each have a tip t1, a tip t2, and a tip t3. In other words, the first recess IP1, the second recess IP2, and the third recess IP3 may each have an inverted pyramid array (IPA) structure.

[0043] In this embodiment, the maximum depth MD3 of the third recess IP3 in the Z direction is greater than the maximum depth MD2 of the second recess IP2 in the Z direction, and the maximum depth MD2 of the second recess IP2 in the Z direction is greater than the maximum depth MD1 of the first recess IP1 in the Z direction. It is worth noting that the maximum depth MD3 is measured by measuring the distance between the tip t3 of the third recess IP3 and the second surface S2 of the substrate SB in the Z direction, the maximum depth MD2 is measured by measuring the distance between the tip t2 of the second recess IP2 and the second surface S2 of the substrate SB in the Z direction, and the maximum depth MD1 is measured by measuring the distance between the tip t1 of the first recess IP1 and the second surface S2 of the substrate SB in the Z direction.

[0044] In this embodiment, after forming the first recess IP1, the second recess IP2 and the third recess IP3, the patterned hard mask layer HM is removed.

[0045] Refer to Figure 1F and perform step (10): fill the first recess IP1, the second recess IP2 and the third recess IP3 of the substrate SB with a filling layer FL.

[0046] The filler layer FL may be formed, for example, by performing a suitable deposition process, and this disclosure is not limited thereto. In some embodiments, the material of the filler layer FL may include silicon oxide.

[0047] It is worth noting that a planarization process can be performed on the filling layer FL after the above deposition process, but this disclosure is not limited to this.

[0048] Step (11): A color filter layer (not shown) is formed on the second surface S2 of the substrate SB.

[0049] Although not shown in the figures, in this embodiment, after forming the filling layer FL, a color filter layer can be formed on the second surface S2 of the substrate SB, but this disclosure is not limited thereto. In some embodiments, the color filter layer is formed on the filling layer FL. The color filter layer may include, for example, a red filter layer, a green filter layer, and a blue filter layer, wherein the red filter layer is disposed corresponding to the first photosensitive element PS1 in the Z direction, the green filter layer is disposed corresponding to the second photosensitive element PS2 in the Z direction, and the blue filter layer is disposed corresponding to the third photosensitive element PS3 in the Z direction. From another perspective, the red filter layer is disposed corresponding to the first recess IP1 in the Z direction, the green filter layer is disposed corresponding to the second recess IP2 in the Z direction, and the blue filter layer is disposed corresponding to the third recess IP3 in the Z direction.

[0050] Additionally, although not shown in the figures, in this embodiment, after forming the color filter layer, a microlens may be formed on the second surface S2 of the substrate SB, but this disclosure is not limited thereto. In some embodiments, the microlens is formed on the color filter layer. The microlens may, for example, be used to focus light rays entering the photosensitive element PS from the outside through the second surface S2 of the substrate SB, but this disclosure is not limited thereto.

[0051] Thus, the fabrication of the back-illuminated image sensor 10 is completed. Although the manufacturing method of the back-illuminated image sensor 10 in this embodiment is described using the above method as an example, the manufacturing method of the back-illuminated image sensor disclosed herein is not limited thereto.

[0052] In the manufacturing method of the back-illuminated image sensor 10 provided in this embodiment, by increasing the maximum depth of the recess corresponding to the photosensitive element that senses light with a relatively short wavelength, the path of the light with a relatively short wavelength in the substrate can be shortened, thereby reducing the possibility that the light is converted into electrons in the substrate and not sensed by the photosensitive element, thereby improving the quantum efficiency of the back-illuminated image sensor 10 in this embodiment.

[0053] The structure of the back-illuminated image sensor 10 of this embodiment will be briefly described below with reference to FIG1F, but this disclosure is not limited thereto.

[0054] In this embodiment, the back-illuminated image sensor 10 includes a substrate SB, a photosensitive element PS, and a filling layer FL.

[0055] The substrate SB includes, for example, a first surface S1 and a second surface S2 opposite to each other. In this embodiment, the second surface S2 of the substrate SB includes a first recess IP1, a second recess IP2, and a third recess IP3. The first recess IP1, the second recess IP2, and the third recess IP3 each have, for example, an inverted pyramid structure. In this embodiment, the maximum depth MD3 of the third recess IP3 in the Z direction is greater than the maximum depth MD2 of the second recess IP2 in the Z direction, and the maximum depth MD2 of the second recess IP2 in the Z direction is greater than the maximum depth MD1 of the first recess IP1 in the Z direction. Further descriptions of the substrate SB can be found in the foregoing embodiments and will not be repeated here.

[0056] A photosensitive element PS is disposed, for example, in a substrate SB, and is, for example, adjacent to a first surface S1 of the substrate SB. In this embodiment, the photosensitive element PS includes a first photosensitive element PS1, a second photosensitive element PS2, and a third photosensitive element PS3, wherein the first photosensitive element PS1 can sense red light, the second photosensitive element PS2 can sense green light, and the third photosensitive element PS3 can sense blue light. From another perspective, the wavelength of the light sensed by the first photosensitive element PS1 is greater than the wavelength of the light sensed by the second photosensitive element PS2, and the wavelength of the light sensed by the second photosensitive element PS2 is greater than the wavelength of the light sensed by the third photosensitive element PS3.

[0057] In this embodiment, the first photosensitive element PS1 is disposed corresponding to the first recess IP1 of the substrate SB in the Z direction, the second photosensitive element PS2 is disposed corresponding to the second recess IP2 of the substrate SB in the Z direction, and the third photosensitive element PS3 is disposed corresponding to the third recess IP3 of the substrate SB in the Z direction. Based on this, the path of light sensed by the third photosensitive element PS3 in the substrate SB can be shorter than the path of light sensed by the second photosensitive element PS2 in the substrate SB, and the path of light sensed by the second photosensitive element PS2 in the substrate SB can be shorter than the path of light sensed by the first photosensitive element PS1 in the substrate SB.

[0058] The remaining description of the photosensitive element PS can be found in the foregoing embodiments, and will not be repeated here.

[0059] The filler layer FL is disposed, for example, on the second surface S2 of the substrate SB, and fills, for example, the first recess IP1, the second recess IP2, and the third recess IP3. Further details regarding the filler layer FL can be found in the foregoing embodiments and will not be repeated here.

[0060] In some embodiments, the back-illuminated image sensor 10 may further include an element layer (not shown), a color filter layer (not shown), and microlenses (not shown). The element layer is disposed, for example, on a first surface S1 of the substrate SB. In some embodiments, the element layer may include a plurality of active elements and / or a plurality of signal lines, wherein the active elements and / or the signal lines may be electrically connected to a photosensitive element PS. The color filter layer is disposed, for example, on a filler layer FL. In some embodiments, the color filter layer may include a red filter layer, a green filter layer, and a blue filter layer, wherein the red filter layer is disposed corresponding to the first photosensitive element PS1 in the Z direction, the green filter layer is disposed corresponding to the second photosensitive element PS2 in the Z direction, and the blue filter layer is disposed corresponding to the third photosensitive element PS3 in the Z direction. Microlenses are disposed, for example, on the color filter layer. Further descriptions of the color filter layer and microlenses can be found in the foregoing embodiments and will not be repeated here.

[0061] In summary, in the back-illuminated image sensor disclosed herein, the recess corresponding to the photosensitive element that senses light with a relatively short wavelength has a relatively large maximum depth, which can shorten the path of the light with a relatively short wavelength in the substrate, thereby reducing the possibility that the light with a relatively short wavelength is converted into electrons in the substrate and is not sensed by the photosensitive element and / or the signal (electron) is attenuated, thereby improving the quantum efficiency of the back-illuminated image sensor disclosed herein. [Simplified Explanation of the Diagram]

[0062] Figures 1A to 1F are partial cross-sectional schematic diagrams of a method for manufacturing a back-side illumination image sensor according to an embodiment of the present disclosure.

Claims

1. A method for manufacturing a back-illuminated image sensor, comprising: A substrate including a photosensitive element is provided, wherein the photosensitive element is adjacent to a first surface of the substrate and includes a first photosensitive element, a second photosensitive element, and a third photosensitive element; A first opening, a second opening, and a third opening are formed on a second surface of the substrate, wherein the second surface is opposite to the first surface, and the first photosensitive element, the second photosensitive element, and the third photosensitive element are each correspondingly disposed with respect to the first opening, the second opening, and the third opening; an etching process is performed on the first opening, the second opening, and the third opening of the substrate to form a first recess, a second recess, and a third recess, respectively, wherein the maximum depth of the second recess is greater than the maximum depth of the first recess, and the maximum depth of the third recess is greater than the maximum depth of the second recess; and a filling layer is filled into the first recess, the second recess, and the third recess of the substrate, wherein the wavelength of light sensed by the first photosensitive element is greater than the wavelength of light sensed by the second photosensitive element, and the wavelength of light sensed by the second photosensitive element is greater than the wavelength of light sensed by the third photosensitive element, wherein before performing the etching process on the first opening, the second opening, and the third opening of the substrate, a first protective layer, a second protective layer, and a third protective layer are each filled into the first opening, the second opening, and the third opening.

2. A method of manufacturing a back-illuminated image sensor as claimed in claim 1, wherein the first recess and the second recess have an inverted pyramid structure.

3. A method for manufacturing a back-illuminated image sensor as claimed in claim 1, wherein the third recess has an inverted pyramid structure.

4. A method of manufacturing a back-illuminated image sensor as claimed in claim 1, wherein the etching process performed on the first opening, the second opening, and the third opening of the substrate includes a wet etching process.

5. A method for manufacturing a back-illuminated image sensor as claimed in claim 1, wherein the step of forming the first opening, the second opening, and the third opening on the second surface of the substrate comprises: A rigid mask layer is formed on the second surface of the substrate; A patterned photoresist layer is formed on the rigid mask layer; And the patterning process is used to pattern the rigid mask layer and the substrate using the patterned photoresist layer.

6. A method of manufacturing a back-illuminated image sensor as claimed in claim 5, wherein the first opening is formed prior to the second opening.

7. The method of manufacturing a back-illuminated image sensor as claimed in claim 1, wherein after filling the filler layer into the first recess, the second recess, and the third recess of the substrate, the method further comprises: A color filter layer is formed on the filler layer; And microlenses are formed on the color filter layer.

8. A method for manufacturing a back-illuminated image sensor as claimed in claim 7, wherein the color filter layer includes a first filter layer, a second filter layer, and a third filter layer, wherein the first filter layer is disposed corresponding to the first photosensitive element, the second filter layer is disposed corresponding to the second photosensitive element, and the third filter layer is disposed corresponding to the third photosensitive element.

Images