Large-area monolithic integrated planarized multi-channel filter array and preparation method

Abstract

The present invention discloses a planarized multi-channel filter array with large-area single-chip integration and a preparation method thereof. It sequentially includes a substrate, a lower reflective film, a dielectric layer, an upper reflective film, and an upper cladding layer from bottom to top; the substrate, the lower reflective film, the dielectric layer, and the upper reflective film form an FP cavity structure; an upper cladding layer is coated on the FP cavity structure to planarize the filter array; the dielectric layer is in a stepped shape. This filter array can support a transmission or reflection mode, and its upper and lower surfaces are flat, which is very suitable for integration with other devices. The device proposed by the present invention can achieve large-area single-chip integration of different filters through a single exposure process, which can greatly simplify the process flow, reduce production costs, and through the planarization technology, the surface of the filter is flat, durable, and convenient for integration with other devices.

Description

Technical Field

[0001] The present invention relates to a planarized multi-channel filter array with large-area monolithic integration and a preparation method thereof, which is applicable to fields such as display, spectral imaging, anti-counterfeiting, holographic imaging, data storage, 3D printing, sensing, etc. Background Art

[0002] Interference filters are very common filter devices and are widely used in fields such as display imaging, spectral measurement, laser protection, etc. due to their advantages such as adjustable central wavelength, bandwidth, and cut-off depth.

[0003] Multilayer interference filters can achieve narrow-band filtering in a transmissive or reflective manner, and their basic structure is composed of alternating combinations of multiple periods of high and low refractive index dielectric films. Among them, the thickness of a single layer film is about 1 / 4 of the central wavelength. By changing the thickness or refractive index of the multilayer film, the filtering wavelength of the filter can be adjusted. In order to achieve a better filtering effect, the number of layers of the multilayer film is usually up to dozens of layers, which means that dozens of deposition processes are required to realize the multilayer interference filter. In addition, the existing processes generally can only achieve the filtering function of a single color on a single substrate. The monolithic integration of different color filters often involves multiple patterning processes using techniques such as lithography, which will greatly increase the process complexity. At the same time, the integration of different filters needs to be achieved by combining multiple deposition processes, which greatly limits the practical application of such filters. Therefore, commercially available filters are basically single-color filters. Filters based on the metal-dielectric-metal Fabry-Perot (FP) cavity structure are another common type of interference filter. By changing the thickness of the dielectric layer, the central wavelength of the filter can be accurately adjusted. Similar to the multilayer film structure filter, since the central wavelength is determined by the thickness of the dielectric layer, patterning using processes such as lithography is required to achieve the integration of different color filters. Summary of the Invention

[0004] In order to overcome the problems in the prior art, the object of the present invention is to propose a planarized multi-channel filter array with large-area monolithic integration and a preparation method thereof.

[0005] The technical solution of the present invention is as follows:

[0006] A preparation method of a planarized multi-channel filter array with large-area monolithic integration, wherein the multi-channel filter array sequentially includes a substrate, a lower reflective film, a dielectric layer, an upper reflective film, and an upper cladding layer from bottom to top;

[0007] 1) Grow the lower reflective film on the substrate through a sputtering or evaporation film growth process;

[0008] 2) Coat a dielectric layer on the lower reflective film, expose the dielectric layer using a grayscale exposure process, and control the thickness of the dielectric layer by controlling the exposure power, exposure time, and exposure dose to achieve a stepped dielectric layer;

[0009] 3) Fabricate the upper reflective film on the dielectric layer to complete the FP cavity structure;

[0010] 4) Coat an upper cladding on the FP cavity structure and perform planarization on the filter array.

[0011] The dielectric layer is composed of SU8 polymer and is prepared by spin coating or roll coating. The thickness of the dielectric layer in different filter channels is different, and the filters are distributed in a mosaic pattern.

[0012] The FP cavity structure selects the transmission or reflection mode; in the transmission mode, the thickness of both the upper and lower reflective films does not exceed 30 nm, so that light can be transmitted; in the reflection mode, the thickness of the lower reflective film needs to be greater than or equal to 100 nm to achieve total reflection.

[0013] The reflective film of the FP cavity structure is selected from metallic materials including gold, silver, aluminum, or from semiconductor materials including silicon, germanium, titanium dioxide, and silicon nitride.

[0014] The substrate uses a substrate material suitable for the infrared / ultraviolet band and the upper and lower reflective films. The substrate materials include silicon nitride, aluminum oxide, and calcium fluoride, so as to achieve monolithic integration of multi-channel filters in the infrared / ultraviolet band.

[0015] The substrate uses a commercial CCD or CMOS imaging chip. During the manufacturing process, the multi-channel filter array is directly integrated on the imaging chip; or through an alignment process, the fabricated multi-channel filter array is bonded to the CCD or CMOS imaging chip.

[0016] A large-area monolithic integrated planarized multi-channel filter array includes a substrate, a lower reflective film, a dielectric layer, an upper reflective film, and an upper cladding from bottom to top in sequence; the substrate, the lower reflective film, the dielectric layer, and the upper reflective film constitute the FP cavity structure; an upper cladding is coated on the FP cavity structure to planarize the filter array;

[0017] The dielectric layer is stepped.

[0018] The FP cavity structure selects the transmission or reflection mode; in the transmission mode, the thickness of both the upper and lower reflective films does not exceed 30 nm, so that light can be transmitted; in the reflection mode, the thickness of the lower reflective film needs to be greater than or equal to 100 nm to achieve total reflection.

[0019] The substrate described above uses a substrate material suitable for the infrared / ultraviolet band and upper and lower layer reflection films, thereby realizing the monolithic integration of a multi-channel filter in the infrared / ultraviolet band.

[0020] The substrate described above uses commercial CCD and CMOS imaging chips. During the manufacturing process, the multi-channel filter array is directly integrated onto the imaging chip; or through an alignment process, the fabricated multi-channel filter array is bonded to the CCD and CMOS imaging chips.

[0021] The beneficial effects of the present invention are as follows:

[0022] 1) By precisely controlling the thickness of the dielectric layer in the FP cavity, the central wavelength of the filter can be precisely regulated, thereby realizing filters of different transmission / reflection types.

[0023] 2) Only a single gray-scale exposure process is required to realize the integration and fabrication of a large-area multi-channel filter array.

[0024] 3) By using a planarization technique, the surface of the structure can be made flat, making it easier to integrate with other structures. Description of the Drawings

[0025] Figure 1 is a schematic structural diagram of a large-area monolithic integrated reflective planarized multi-channel filter array related to the present invention.

[0026] Figure 2 is the reflection spectrum of a reflective filter array with different dielectric layer thicknesses obtained by simulation.

[0027] Figure 3 is a schematic diagram of a large-area monolithic integrated transmissive planarized multi-channel filter array related to the present invention.

[0028] Figure 4 is the reflection spectrum of a transmissive filter array with different dielectric layer thicknesses obtained by simulation.

[0029] Description of the reference numerals: Substrate 1, Lower layer reflection film 2, Dielectric layer 3, Upper layer reflection film 4, Upper cladding layer 5. Detailed Embodiments

[0030] Next, the invention will be further described in detail with reference to the drawings and embodiments. Embodiment 1

[0031] As Figure 1 shown, it is a reflective monolithic integrated multi-channel filter array of a specific implementation scheme of the present invention. Referring to Figure 1 , the incident light enters the upper cladding layer 5 from top to bottom, passes through different filters, is reflected by the lower layer reflection film 2, and finally exits from the upper cladding layer 5. The specific manufacturing process is as follows:

[0032] Reference Figure 1 Figure 1 , on a clean substrate 1, a lower reflective film 2 is grown. The lower reflective film 2 can be composed of highly reflective materials such as gold, silver, and aluminum. The thickness needs to reach above the penetration depth to achieve the purpose of blocking light, and the typical thickness is 100 nm.

[0033] A dielectric layer 3 is coated on the lower reflective film 2. The dielectric layer 3 is composed of SU8 polymer and can be prepared by spin coating or roll coating.

[0034] Using the grayscale exposure process, the required structure is exposed on the dielectric layer 3. The exposure dose, exposure time, exposure power, etc. directly affect the final thickness of the dielectric layer 3, and the thickness of the dielectric layer 3 determines the central wavelength of the filter. By methods such as development, the excess dielectric is removed, leaving the required dielectric structure, thus forming a stepped dielectric layer 3.

[0035] On the patterned dielectric layer 3, an upper reflective film 4 is grown. The upper reflective film 4 can be made of common high-loss metal materials such as titanium, aluminum, chromium, iron, copper, tungsten, etc., and its typical thickness is 10 - 20 nm; it can also be replaced by common semiconductor materials such as silicon, germanium, titanium nitride, titanium dioxide, etc., and its typical thickness is 10 - 20 nm.

[0036] An upper cladding 5 is coated on the upper reflective film 4. A stable dielectric film such as silica or alumina can be prepared by deposition, sputtering, evaporation, etc., or a stable polymer material such as BCB film or polyimide film can be made by spin coating and other processes to make the surface flat and also play a role in protecting the filter.

[0037] Figure 2 The filter reflection spectra of different thickness intermediate dielectric layers obtained by simulation. The upper reflective film is metal Ti and the lower reflective film is metal silver. Example 2

[0038] As Figure 3 shown, it is a transmissive monolithic integrated multi-channel filter array of a specific implementation scheme of the present invention.

[0039] Reference Figure 3 Figure 3 , the incident light enters from above into the upper cladding 5, passes through different filters, and exits from the substrate 1. The specific manufacturing process is as follows:

[0040] On a clean substrate 1, a lower reflective film 2 is grown. The lower reflective film 2 can be composed of common metals such as gold, silver, and aluminum, or can be made of semiconductor materials such as silicon, germanium, titanium nitride, and titanium dioxide. The typical thickness is 10 - 20 nm to achieve the purpose of partial light transmission.

[0041] A dielectric layer 3 is coated on the lower reflective film 2. The dielectric layer 3 is composed of SU8 polymer and can be prepared by spin coating or roll coating.

[0042] Using the gray-scale exposure process, the required structure is exposed on the dielectric layer 3. The exposure dose, exposure time, exposure power, etc. directly affect the final thickness of the dielectric layer 3, and the thickness of the dielectric layer 3 determines the central wavelength of the filter. By methods such as development, the excess dielectric is removed, leaving the required dielectric structure, thus forming a stepped dielectric layer 3.

[0043] On the patterned dielectric layer 3, an upper reflective film 4 is grown. The upper reflective film 4 can be made of common metal materials such as gold, silver, aluminum, etc., or can be replaced by common semiconductor materials such as silicon, germanium, titanium nitride, titanium dioxide, etc. Its typical thickness is 10 - 20 nm.

[0044] A cladding layer 5 is coated on the upper reflective film 4. A stable dielectric film such as silicon dioxide, aluminum oxide, etc. can be prepared by deposition, sputtering, evaporation, etc., or a stable polymer material such as BCB, polyimide, etc. can be made by spin coating and other processes to make the surface flat and also play a role in protecting the filter.

[0045] Figure 4 The transmission spectra of filters with different thicknesses of the middle dielectric layer obtained by simulation. The upper reflective film is made of silicon material and the lower reflective film is made of metallic silver.

[0046] The present invention discloses a large-area monolithic integrated planarized multi-channel filter array device. Adopting the FP cavity structure, by adjusting the materials and thicknesses of the dielectric layer and the upper and lower reflective films, transmissive and reflective filter arrays can be realized respectively. Using the single-time gray-scale exposure process, filter arrays with different thicknesses and different filtering performances can be prepared simultaneously on the same substrate. This method has a simple process, abandons the redundant deposition and lithography processes required in traditional interference multi-color filter arrays, and theoretically can realize the preparation of multi-channel filter arrays of wafer size; in addition, by coating a cladding dielectric layer on the filter, the planarization of the filter array can be achieved, making the integration of this filter with other devices possible.

[0047] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A preparation method of a planarized multi-channel filter array with large-area single-chip integration, characterized in that: The multi-channel filter array described above sequentially includes a substrate, a lower reflective film, a dielectric layer, an upper reflective film, and an upper cladding layer from bottom to top; 1) Grow the lower reflective film on the substrate through a sputtering or evaporation film growth process; 2) Coat a dielectric layer on the lower reflective film, expose the dielectric layer using a grayscale exposure process, and control the thickness of the dielectric layer by controlling the exposure power, exposure time, and exposure dose to achieve a stepped dielectric layer; 3) Fabricate the upper reflective film on the dielectric layer to complete the FP cavity structure; 4) Coat an upper cladding layer on the FP cavity structure and perform planarization processing on the filter array; The dielectric layer is composed of SU8 polymer and is prepared by spin coating or roll coating. The thicknesses of the dielectric layers in different filter channels are different, and the filters are distributed in a mosaic pattern; The reflective film of the FP cavity structure is selected from metal materials or semiconductor materials. The metal materials include gold, silver, and aluminum, and the semiconductor materials include silicon, germanium, titanium dioxide, and silicon nitride.

2. The preparation method according to claim 1, characterized in that: The FP cavity structure selects a transmission or reflection mode; in the transmission mode, the thicknesses of both the upper and lower reflective films do not exceed 30 nm, allowing light to transmit through; in the reflection mode, the thickness of the lower reflective film needs to be greater than or equal to 100 nm to achieve total reflection.

3. The preparation method according to claim 1, characterized in that: The substrate uses a substrate material suitable for the infrared / ultraviolet band and upper and lower reflective films. The substrate materials include silicon nitride, aluminum oxide, and calcium fluoride, thereby achieving monolithic integration of multi-channel filters in the infrared / ultraviolet band.

4. The preparation method according to claim 1, wherein: The substrate uses a commercial CCD or CMOS imaging chip. During the manufacturing process, the multi-channel filter array is directly integrated on the imaging chip; or through an alignment process, the fabricated multi-channel filter array is bonded to the CCD or CMOS imaging chip.

5. A planarized multi-channel filter array with large-area monolithic integration prepared by the preparation method according to claim 1, characterized in that: Sequentially includes a substrate, a lower reflective film, a dielectric layer, an upper reflective film, and an upper cladding layer from bottom to top; the substrate, lower reflective film, dielectric layer, and upper reflective film constitute an FP cavity structure; an upper cladding layer is coated on the FP cavity structure to planarize the filter array; the dielectric layer is stepped.

6. The multi-channel filter array according to claim 5, characterized in that: The FP cavity structure selects a transmission or reflection mode; in the transmission mode, the thicknesses of both the upper and lower reflective films do not exceed 30 nm, allowing light to transmit through; in the reflection mode, the thickness of the lower reflective film needs to be greater than or equal to 100 nm to achieve total reflection.

7. The multi-channel filter array according to claim 5, characterized in that: The substrate uses a substrate material suitable for the infrared / ultraviolet band and upper and lower reflective films, thereby achieving monolithic integration of multi-channel filters in the infrared / ultraviolet band.

8. The multi-channel filter array according to claim 5, wherein: The substrate uses a commercial CCD or CMOS imaging chip. During the manufacturing process, the multi-channel filter array is directly integrated on the imaging chip; or through an alignment process, the fabricated multi-channel filter array is bonded to the CCD or CMOS imaging chip.

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