Multispectral transmission filter structure

Abstract

This invention discloses a method for manufacturing multiple filters with Fabry-Pérot (FP) cavity structures, comprising: setting a carrier; setting a first reflective layer on the carrier; setting a first optical pattern layer and a second optical pattern layer on the surface of the first reflective layer, the first optical pattern layer having multiple first nanostructures and the second optical pattern layer having multiple second nanostructures; reflowing the first and second optical pattern layers to form a first film layer and a second film layer, respectively; and coating a second reflective layer onto the first and second film layers. This invention also proposes a multispectral transmission filter structure produced by the above method.

Description

[Technical Field]

[0001] This invention relates to a divisional application of Taiwan Patent Application No. 114100207, the full contents of which are incorporated herein by reference as part of the patent specification. The present invention relates to a filter, and more particularly to a filter having a Fabry-Perot cavity structure. [Previous Technology]

[0002] In the prior art, image sensors are an integral part of today's electronic products, especially in digital cameras and mobile phones. Traditionally, charge-coupled device (CCD) and complementary metal-oxide-semiconductor (CMOS) image sensors have been used as silicon (Si) based image sensors, but CMOS image sensors are generally more advantageous than CCD image sensors due to their simplicity, cost-effectiveness and low power consumption.

[0003] To exhibit color sensitivity, image sensors typically use color filters equipped with photodiodes. These color filters are usually composed of organic dye filters. However, due to their lack of high-temperature durability, the costly manufacturing process is impractical for multispectral imaging that requires more than three primary colors.

[0004] Therefore, the Fabry-Pérot (FP) cavity structure, which includes an intermediate dielectric layer sandwiched between two metal reflectors, is a promising choice for multispectral transmission filters due to its excellent narrow-band full width at half maximum (FWHM). In the FP cavity structure, color can be adjusted by controlling the thickness of the intermediate dielectric layer. Therefore, the ability to control the thickness of the intermediate dielectric layer and the method of fabricating multispectral filters in a single wafer have become very important in related technical fields. [Summary of the Invention]

[0005] In view of the above-mentioned technical defects, the present invention provides a method for manufacturing multiple filters with Fabry-Perot (FP) cavity structures, a multispectral transmission filter array, and a multispectral transmission filter structure.

[0006] This invention provides a method for manufacturing a plurality of filters having a Fabry-Perot cavity structure, comprising: setting a carrier; setting a first reflective layer on the carrier; setting a first optical pattern layer and a second optical pattern layer on the surface of the first reflective layer, the first optical pattern layer having a plurality of first nanostructures and the second optical pattern layer having a plurality of second nanostructures; reflowing the first optical pattern layer and the second optical pattern layer to form a first film layer and a second film layer, respectively; coating a second reflective layer on the first film layer and the second film layer; and providing a multispectral transmission filter array and a multispectral transmission filter structure produced by the above method.

[0007] According to some embodiments, adjusting the thickness of the optical layer is equivalent to adjusting the thickness of the Fabry-Perot (FP) cavity structure, thereby modulating the peak wavelength of the filter. For example, the filter can span from visible light to near-infrared light.

[0008] To further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are for reference and illustration only and are not intended to limit the present invention.

Implementation Method

[0015] The following specific embodiments illustrate the implementation of the present invention regarding "a method for manufacturing a filter having a Fabry-Perot cavity structure, a multispectral transmission filter array, and a multispectral transmission filter structure." Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. Furthermore, the accompanying drawings of the present invention are for simple illustrative purposes only and are not depictions of actual dimensions; this is stated in advance. The following embodiments will further describe the relevant technical content of the present invention in detail, but the disclosed content is not intended to limit the scope of protection of the present invention.

[0016] It should be understood that although terms such as “first,” “second,” and “third” may be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are primarily used to distinguish one component from another, or one signal from another. In addition, the term “or” as used herein may include, as appropriate, any combination of any one or more of the associated listed items.

[0017] Please refer to Figures 1 to 5, which are schematic diagrams of a method for manufacturing multiple filters with Fabry-Pérot (FP) cavity structures according to an embodiment of the present invention. The manufacturing method includes step S11: setting a carrier 11, as shown in Figure 1. Step S12: setting a first reflective layer 12 on the carrier 11, as shown in Figure 2. Step S13: setting a first optical pattern layer 131 and a second optical pattern layer 132 on the surface of the first reflective layer 12, wherein the first optical pattern layer 131 has multiple first nanostructures 1311 and the second optical pattern layer 132 has multiple second nanostructures 1321, as shown in Figure 3. Step S14: reflowing the first optical pattern layer 131 and the second optical pattern layer 132 to form a first film layer 133 and a second film layer 134, respectively, as shown in Figure 4. Step S15: coating a second reflective layer 15 on the first film layer 133 and the second film layer 134, as shown in Figure 5.

[0018] As shown in Figure 3, a first spacing P1 is formed between two adjacent island-shaped first nanostructures 1311, and a second spacing P2 is formed between two adjacent island-shaped second nanostructures 1321. The first spacing P1 and the second spacing P2 are the same; however, the width (or diameter) of the first nanostructure 1311 is different from that of the second nanostructure 1321. Furthermore, according to some embodiments, at least one of the plurality of first nanostructures 1311 and the plurality of second nanostructures 1321 differs in shape, size, or number. According to some embodiments, the first spacing P1 and the second spacing P2 are not the same. In other words, the overall surface contours / patterns of two adjacent first optical patterning layers 131 and second optical patterning layers 132 are not identical.

[0019] As shown in Figure 4, the thicknesses of the first film layer 133 and the second film layer 134 can be precisely controlled through patterning and reflow processes, for example, a first optical pattern layer 131 and a second optical pattern layer 132 are generated after patterning. On the other hand, referring to Table 1 below, the thicknesses of the first film layer 133 and the second film layer 134 are preferably in the range of 92 to 228 nm, corresponding to the transmittance of visible light and near-infrared wavelengths.

[0020] In addition, according to some embodiments, the carrier 11 is a silicon carrier 11 or a silicon-containing carrier 11. The first reflective layer 12 and the second reflective layer 15 are made of silver (Ag) or are Bragg mirrors. According to some embodiments, the first optical pattern layer 131 and the second optical pattern layer 132 are dielectric layers made of polymethyl methacrylate (PMMA). Therefore, through the design of the above structure, an Ag-PMMA-Ag structure is formed on a single crystal wafer (quartz), realizing a multispectral filter structure.

[0021] Please refer to Figures 6 to 8 to illustrate a method using Simple-step-binary-lithography (SSBL) in one embodiment of the present invention. Step S13 may further include steps S131 and S132. Step S131: Coating an optical layer 13 onto the first reflective layer 12. The optical layer 13 is an intermediate dielectric layer, made of materials such as PMMA. Step S132: Patterning the optical layer 13 using electron beam lithography to form a first optical pattern layer 131 and a second optical pattern layer 132. Therefore, multiple nano-patterned structures (pore-like structures) are formed in multiple patterned optical regions corresponding to the first optical pattern layer 131 and the second optical pattern layer 132. Then, a reflow process (step S14) is performed to form a first film layer 133 and a second film layer 134.

[0022] Furthermore, according to some embodiments, step S132 further includes: forming an internal boundary 135 between the first optical pattern layer 131 and the second optical pattern layer 132. The internal boundary 135 is integrally connected by the first sidewall 1312 and the second sidewall 1322. According to some embodiments, during the reflow step, the internal boundary 135 is not affected by the reflow, as shown in FIG8. According to some other embodiments, step S132 may also include: forming a frame boundary 136 around the first film layer 133 and the second film layer 134. The frame boundary 136 may also be integrally connected by the first sidewall 1312 and the second sidewall 1322, as shown in FIG3 and FIG4. The present invention does not limit the presence or absence of the frame boundary 136.

[0023] Please refer to Figures 9A to 9C, which are schematic diagrams of patterned processing according to an embodiment of the present invention. According to these embodiments, the range of the first spacing P1 or the second spacing P2 is 0.5 to 1 μm. The nanostructures (including the first nanostructure 1311 or the second nanostructure 1321) are similar to pores or islands. According to Figure 9A, nanostructure 1313 forms a 0.6 μm × 0.6 μm square hole (i.e., region A1). According to Figure 9B, region A2 formed by nanostructure 1313 exhibits a channel shape. According to the embodiment of Figure 9C, nanostructure 1313 is formed in region A3, with a spacing of 0.6 μm between two adjacent regions A3.

[0024] According to some embodiments, the first film layer 133 and the second film layer 134 have different predetermined thicknesses to produce pixels of different colors.

[0025] Referring again to FIG5, the present invention also provides an embodiment of a multispectral transmission filter array. The multispectral transmission filter array includes: a carrier 11, a first reflective layer 12, an optical layer 13, and a second reflective layer 15. The optical layer 13 forms a first color pixel 133 and a second color pixel 134 with different thicknesses, and a pixel boundary 135 therebetween.

[0026] According to one embodiment, the thickness of the pixel boundary 135 is greater than the thickness of the first color pixel 133 and the second color pixel 134. Furthermore, the optical layer 13 also includes a frame boundary 136 surrounding the first color pixel 133 and the second color pixel 134. The thickness of the frame boundary 136 is greater than the thickness of the first color pixel 133 and the second color pixel 134.

[0027] Please refer to Figure 10, which is a schematic diagram showing the relationship between the thickness of the optical film layer and the number of nanostructures (pores) in one embodiment of the present invention. The thickness of the film layer (first film layer 133 and second film layer 134) is inversely proportional to the number of nanostructures (corresponding to the first color pixel 133 or the second color pixel 134). In other words, the more nanostructures there are, the thinner the film layer (first film layer 133 and second film layer 134) will be. Furthermore, in other embodiments, the thickness of the first color pixel 133 and the second color pixel 134 is inversely proportional to the wavelength. For example, the thickness of the first film layer 133 corresponding to the first color pixel and the second film layer 134 corresponding to the second color pixel is in the range of 92 nm to 228 nm. The color filtering range of the multispectral transmission filter array is from 450 to 850 nm.

[0028] Please refer to Figure 11, which is a schematic diagram showing the relationship between the thickness, transmittance, and wavelength of multiple reflective layers in one embodiment of the present invention. A silver layer is used as an example of a reflective layer. As the thickness of the silver layer increases by 18-28 nm, the transmission band narrows, and the transmission peak decreases from 80% to 50%. According to one embodiment, using a 24 nm thick silver layer as a metal reflector in an FP cavity structure results in a narrow-band transmission with a preferred transmission peak of 70%. Furthermore, in these embodiments, the first reflective layer 12 and the second reflective layer 15 preferably have the same thickness. At the same wavelength, the smaller the thickness of the reflective layer, the higher the transmittance.

[0029] According to some embodiments, the material of the optical layer 13 is selected from PMMA or silicon dioxide (SiO2), and the material of the carrier 11 is selected from silicon dioxide or silicon nitride (Si3N4).

[0030] Taking PMMA as the material of optical layer 13 as an example, please refer to Table 1 below: Film thickness (nm) 92 102~109 119~131 143 154~160 171~177 188~194 206~211 223~228 Wave peak wavelength (nm) 450 480~500 530~564 600 632~650 682~700 732~750 784~800 833~850 Table 1

[0031] Taking silicon dioxide as the material of optical layer 13 as an example, please refer to Table 2 below: Film thickness (nm) SiO2 thickness 102 119 131 143 154 171 188 Wave peak wavelength (nm) peak nm 460~475 512-521 546-565 580-590 610-623 662-670 710-715 Table 2

[0032] It should be noted that when different carrier materials are used, the filtering range will shift. Taking silicon nitride as a carrier as an example, there is a significant blue shift in the blue and green light wavelength range, and the FWHM also widens, that is, the transmission band widens by about 40%, preferably 50% to 60%, and the transmission peak increases from 60% to 75%.

[0033] Please refer to Figure 12, and also to Figures 7 and 8. Figure 12 is a schematic diagram of a multispectral transmission filter structure according to an embodiment of the present invention. This embodiment provides a multispectral transmission filter structure Z, which includes: a carrier 11, a first transmission filter 100, and a second transmission filter 200. The carrier 11 has a first sensing region R1 and a second sensing region R2. The first transmission filter 100 includes a first bottom reflective layer 21, a first optical structure 22, and a first top reflective layer 23. The first bottom reflective layer 21 is disposed on the first sensing region R1. The first optical structure 22 includes a first groove with a first depth. The first top reflective layer 23 is disposed on the first optical structure 22. The second transmission filter 200 is adjacent to the first transmission filter 100, and the second transmission filter 200 includes a second bottom reflective layer 31, a second optical structure 32, and a second top reflective layer 33. The second bottom reflective layer 31 is disposed on the second sensing region R2. The second optical structure 32 includes a second groove with a second depth. A second top reflective layer 33 is disposed on the second optical structure 32. The first depth is different from the second depth.

[0034] Furthermore, the first optical structure 22 and the second optical structure 32 are connected to each other and formed as a wall 235 surrounding the first transmission filter 100 and the second transmission filter 200.

[0035] Furthermore, the first optical structure 22 receives a first wavelength, and the second optical structure 32 receives a second wavelength, wherein the first wavelength is greater than the second wavelength. The second depth is deeper than the first depth.

[0036] In addition, the thickness of multiple pixels is in the range of 92nm to 228nm, and the filtering range of the multispectral transmission filter structure Z is between 450nm and 850nm.

[0037] Furthermore, the materials of the first optical structure 22 and the second optical structure 32 are selected from PMMA or silicon dioxide (SiO2); the material of the carrier 11 is selected from silicon dioxide or silicon nitride (Si3N4); the materials of the first top reflective layer 23, the first bottom reflective layer 21, the second top reflective layer 33, and the second bottom reflective layer 31 are selected from DBR (Drawbridge mirror) or silver. According to some embodiments, multilayer combinations such as Ag-PMMA-Ag-SiO2 structures or Ag-PMMA-DBR-Si3N4 structures can be considered as FP cavity structures, and the multispectral transmission filter structure filters light across the range of visible to infrared wavelengths.

[0038] Therefore, the multispectral transmission filter array and multispectral transmission filter structure provided by the present invention can be applied to a wafer by means of "optical film layers disposed on a carrier, wherein the first pixel and the second pixel are formed by film layers of different thicknesses and an internal boundary is formed between the pixels".

[0039] In addition, adjusting the thickness of the optical film is equivalent to adjusting the thickness of the Fabry-Perot (FP) cavity structure, thereby modulating the peak wavelength of the filter. For example, a multispectral transmission filter can span the wavelength range from visible light to near-infrared light.

[0040] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention specification and drawings are included in the scope of the patent application of the present invention. [Simplified Explanation of the Diagram]

[0009] Figures 1-5 are schematic diagrams of a manufacturing method corresponding to an embodiment of the present invention.

[0010] Figures 6-8 are schematic diagrams corresponding to the patterning steps in one embodiment of the present invention.

[0011] Figures 9A-9C are schematic diagrams of the patterned processing in one embodiment of the present invention.

[0012] Figure 10 is a schematic diagram showing the relationship between the thickness of the optical film and the number of nanostructures in one embodiment of the present invention.

[0013] Figure 11 is a schematic diagram showing the relationship between the thickness, transmittance and wavelength of multiple reflective layers in one embodiment of the present invention.

[0014] Figure 12 is a schematic diagram of a multispectral transmission filter structure according to an embodiment of the present invention.

Claims

1. A multispectral transmission filter structure, comprising: A carrier having a first sensing area and a second sensing area; A first transmission filter includes: a first bottom reflective layer disposed in a first sensing region; a first optical structure including a first groove having a first depth; and a first top reflective layer disposed on the first optical structure; and a second transmission filter adjacent to the first transmission filter, the second transmission filter including: a second bottom reflective layer disposed in the second sensing region; a second optical structure including a second groove having a second depth; and a second top reflective layer disposed on the second optical structure; wherein the first depth and the second depth are different.

2. The multispectral transmission filter structure as described in claim 1, wherein, The first optical structure is connected to the second optical structure and forms a wall that surrounds the first transmission filter and the second transmission filter.

3. The multispectral transmission filter structure as described in claim 1, wherein, The first optical structure receives a first wavelength, and the second optical structure receives a second wavelength, wherein the first wavelength is greater than the second wavelength.

4. The multispectral transmission filter structure as described in claim 1, wherein, The second depth is greater than the first depth.

5. The multispectral transmission filter structure as described in claim 1, wherein, The filtering range of the multispectral transmission filter structure is 450-850 nm.

6. The multispectral transmission filter structure as described in claim 3, wherein, The thicknesses of the first top reflective layer, the first bottom reflective layer, the second top reflective layer, and the second bottom reflective layer range from 18 to 24 nm.

7. The multispectral transmission filter structure as described in claim 1, wherein, The materials of the first optical structure and the second optical structure are selected from PMMA or silicon dioxide.

8. The multispectral transmission filter structure as described in claim 1, wherein, The carrier material is selected from silicon dioxide or silicon nitride.

9. The multispectral transmission filter structure as described in claim 1, wherein, The materials of the first top reflective layer, the first bottom reflective layer, the second top reflective layer, and the second bottom reflective layer are selected from DBR (Bragg reflector) or silver.

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