阅读说明：本技术 一种像元级多光谱滤光片的制备方法 (Method for preparing pixel-level multispectral optical filter ) 是由 杨海贵 张建 王笑夷 杨飞 张卓 高劲松 于 2019-10-11 设计创作，主要内容包括：本发明提供了一种像元级多光谱滤光片的制备方法,包括：在基底上沉积具有良好光谱通带特性的较厚宽带通滤光膜堆；在带通滤光膜堆上制备图形化的金属薄膜；在图形化的金属薄膜上干法刻蚀带滤光膜堆,制备出一个陡峭的台阶状光谱通道单元；重复以上步骤制备出其它数个光谱通道单元；最后去掉所有光谱通道单元上的金属膜。本发明提供的像元级多光谱滤光片的制备方法,可以形成厚度为5-15微米较厚阵列式周期性排列的带通滤光膜堆,有利于提高像元级多光谱滤光片光谱通道的通带特性,利用了图形化的金属薄膜作为掩膜层和刻蚀停止层,阻止已形成的光谱通道单元免于刻蚀,降低制备过程中的阴影遮蔽效应以保证通道单元外形尺寸完整性。(The invention provides a method for preparing a pixel-level multispectral optical filter, which comprises the following steps: depositing a thicker wide-band-pass filter film stack with good spectral passband characteristics on a substrate; preparing a graphical metal film on the band-pass filtering film stack; dry etching the filter film stack on the patterned metal film to prepare a steep step-shaped spectrum channel unit; repeating the steps to prepare other spectrum channel units; and finally, removing the metal films on all the spectral channel units. The method for preparing the pixel-level multispectral optical filter can form the array-type periodically-arranged band-pass optical filter film stack with the thickness of 5-15 micrometers, is favorable for improving the passband characteristics of the spectral channel of the pixel-level multispectral optical filter, utilizes the patterned metal film as a mask layer and an etching stop layer, prevents the formed spectral channel unit from being etched, and reduces the shadow shielding effect in the preparation process so as to ensure the integrity of the appearance size of the channel unit.)

1. A method for preparing a pixel-level multispectral optical filter is characterized by comprising the following steps:

s1: the structure of the wide-band-pass filtering film stack is designed by using film system design software, the average transmittance of the designed pass band is better than 85 percent, and the average transmittance of the designed stop band is less than 5 percent;

s2: cleaning a substrate, and plating a first broadband pass filter film stack on the substrate;

s3: depositing a metal film on the first broadband pass filter film stack, and patterning the metal film, wherein the patterned metal film is a metal film unit structure which is arranged in an array type periodic manner, and the size of each metal film unit structure is 5-30 micrometers and corresponds to the pixels of the detector chip one by one;

s4: etching the first broadband-pass filter film stack outside the metal mask layer by using the patterned metal film as the mask layer and using a dry etching method to form a first array-type periodically-arranged spectrum channel unit;

s5: repeating the steps S1-S4, repeating the steps (N-1) times, plating a second broadband pass filter film stack and a third broadband pass filter film stack … N-th broadband pass filter film stack in the step S2, and correspondingly and sequentially forming a second and a third … N-th arrayed periodically-arranged spectral channel units;

s6: and removing the metal films on the surfaces of all the array-type periodically arranged spectral channel units to obtain the pixel-level multispectral optical filter.

2. The method for preparing a pixel-level multispectral optical filter according to claim 1, wherein the first and second … nth broadband pass filter stacks have correspondingly designed spectral characteristics, are composed of alternating high-refractive-index and low-refractive-index thin films, and have a thickness of 5-15 μm.

3. The method for preparing pixel-level multispectral optical filter according to claim 2, wherein the high-refractive-index thin film is made of TiO₂、Ta₂O₅、HfO₂Any one of Si, Ge and ZnSe; the low refractive index film is made of SiO₂、Al₂O₃、MgF₂、YF₃、YbF₃Any one of them.

4. The method for preparing a pixel-level multispectral optical filter according to claim 1, wherein the second broadband pass filter stack and the third broadband pass filter stack …, and the nth broadband pass filter stack are formed by any one of ion beam assisted electron beam evaporation, magnetron sputtering, ion beam sputtering, and plasma enhanced chemical vapor deposition in step S2.

5. The method for preparing a pixel-level multispectral optical filter as claimed in claim 1, wherein the thickness of the metal film deposited in step S3 is 300-1000 nm, and the material of the metal film is any one of aluminum, copper, chromium and nickel; the technology adopted by the graphical metal film is photoetching and dry etching technology, or Lift-off technology and film coating technology.

6. The method for preparing the pixel-level multispectral optical filter according to claim 1, wherein the dry etching method for etching the broadband pass filter stack except the metal mask layer in step S4 adopts inductively coupled plasma etching; the etching gas is CHF₃、C₃F₈、CF₄Or BCl₃、Cl₂Any one of the above; the etching rate is 50-300 nm/min.

7. The method for preparing a pixel-level multispectral optical filter according to claim 1, wherein the metal thin film on the surfaces of all the arrayed periodically arranged spectral channel units in step S6 is removed by wet etching or dry etching.

8. The method for manufacturing the pixel-level multispectral optical filter according to claim 7, wherein an acid or alkali etching solution is used as the etching solution in the wet etching.

9. The method for preparing the pixel-level multispectral optical filter according to claim 7, wherein the dry etching is inductively coupled plasma etching, and the etching gas is BCl₃、Cl₂At an etching rate of 50 to 100 nm/min.

10. The method for preparing a pixel-level multispectral optical filter according to claim 1, wherein the substrate is a K9 glass substrate.

Technical Field

The invention relates to the technical field of optical thin films, in particular to a method for preparing a pixel-level multispectral optical filter.

Background

The imaging spectrometer with the light splitting technology as the core combines the imaging technology and the spectrum technology together, not only can image a detection target, but also can acquire rich spectrum information of the detection target, and is widely and deeply applied in the fields of precision agriculture and forestry monitoring, environment monitoring, natural disaster assessment, mineral exploration, biomedical detection, security monitoring, military target early warning, identification and the like. At present, the imaging spectrometer usually carries out remote sensing work in the modes of aviation, spaceflight and unmanned aerial vehicle load, the size and the weight of the imaging spectrometer are very critical, and particularly as the spaceflight load, the size and the weight which are difficult to compress greatly increase the emission cost of the imaging spectrometer. Therefore, the miniaturization and light-weight research of the imaging spectrometer has very urgent needs.

The traditional light splitting methods include prism light splitting, grating light splitting and the like, but the light splitting methods cannot meet the requirements of miniaturization and light weight of an imaging spectrometer. The multispectral optical filter greatly optimizes the structure of a light splitting system of the imaging spectrometer, and the multispectral optical filter is used as a light splitting element in the imaging spectrometer, so that the imaging spectrometer can be miniaturized and lightened. The multispectral optical filter has two types, one type is a linear multispectral optical filter, the spectral channel of the multispectral optical filter can only change along one direction, the channel size is larger, the size precision is lower, the multispectral optical filter can be obtained by combining coating and splicing, and can also be obtained by coating and Lift-off photoetching technology, and the linear multispectral optical filter can only enable the imaging spectrometer to work in a push-scan imaging mode; the other is a pixel-level multispectral optical filter, the spectral channels of the multispectral optical filter are arrayed periodically and correspond to the pixels of the detector chip one by one, the channel size is in a micron order (5-30 microns), the size precision is very high, and the pixel-level multispectral optical filter enables the imaging spectrometer to work in a video imaging mode and can perform high-frame-frequency imaging on a fast moving target.

At present, two preparation methods are probably available for a pixel-level multispectral optical filter, one method is based on a Fabry-Perot cavity film system structure, a first reflecting film stack and a middle cavity layer are firstly plated on a substrate, then micron-level steps with different thicknesses are formed by selectively etching the middle cavity layer for multiple times so as to regulate and control the peak position of a spectrum, and finally a second reflecting film stack is plated so as to form an array-type pixel-level multispectral optical filter which is periodically arranged. The other film system structure based on the wide band pass is characterized in that a micron-order spectral channel unit is firstly patterned on a substrate by utilizing a Lift-off photoetching process, then a wide band pass film stack is plated, finally a spectral channel is formed by removing photoresist, and the steps are repeated to form the array type pixel-level multispectral optical filter which is periodically arranged.

Therefore, a method for preparing the pixel-level multispectral optical filter is urgently needed to be researched, the problems of the spectral passband of the pixel-level multispectral optical filter and the size of a channel unit are solved, the passband characteristics of the spectral channel of the pixel-level multispectral optical filter are improved, the shadow shielding effect in the preparation process is reduced, and the overall size integrity of the channel unit is ensured.

Disclosure of Invention

The invention aims to provide a method for preparing a pixel-level multispectral optical filter aiming at the defects in the prior art, solves the problems of spectral passband of the pixel-level multispectral optical filter and the size of a channel unit, improves the passband characteristics of a spectral channel of the pixel-level multispectral optical filter, reduces the shadow shielding effect in the preparation process, and ensures the integrity of the overall size of the channel unit.

The object of the invention can be achieved by the following technical measures:

the invention provides a method for preparing a pixel-level multispectral optical filter, which comprises the following steps:

s1: the structure of the wide-band-pass filtering film stack is designed by using film system design software, the average transmittance of the designed pass band is better than 85 percent, and the average transmittance of the designed stop band is less than 5 percent;

s2: cleaning a substrate, and plating a first broadband pass filter film stack on the substrate;

s3: depositing a metal film on the first broadband pass filter film stack, and patterning the metal film, wherein the patterned metal film is a metal film unit structure which is arranged in an array type periodic manner, and the size of each metal film unit structure is 5-30 micrometers and corresponds to the pixels of the detector chip one by one;

s4: etching the first broadband-pass filter film stack outside the metal mask layer by using the patterned metal film as the mask layer and using a dry etching method to form a first array-type periodically-arranged spectrum channel unit;

s5: repeating the steps S1-S4, repeating the steps (N-1) times, plating a second broadband pass filter film stack and a third broadband pass filter film stack … N-th broadband pass filter film stack in the step S2, and correspondingly and sequentially forming a second and a third … N-th arrayed periodically-arranged spectral channel units;

s6: and removing the metal films on the surfaces of all the array-type periodically arranged spectral channel units to obtain the pixel-level multispectral optical filter.

Furthermore, the first … Nth broadband pass filter film stack and the second … Nth broadband pass filter film stack have correspondingly designed spectral characteristics, are alternately composed of high-refractive-index and low-refractive-index films, and have the thickness of 5-15 micrometers.

Further, the high-refractive-index film is made of TiO₂、Ta₂O₅、HfO₂Any one of Si, Ge and ZnSe; the low refractive index film is made of SiO₂、Al₂O₃、MgF₂、YF₃、YbF₃Any ofOne kind of the medicine.

Further, in step S2, the second broadband pass filter film stack and the third broadband pass filter film stack …, the nth broadband pass filter film stack is formed by any one of ion beam assisted electron beam evaporation, magnetron sputtering, ion beam sputtering, and plasma enhanced chemical vapor deposition.

Further, the thickness of the metal film deposited in step S3 is 300-1000 nm, and the material of the metal film is any one of aluminum, copper, chromium, and nickel; the technology adopted by the graphical metal film is photoetching and dry etching technology, or Lift-off technology and film coating technology.

Further, in step S4, the dry etching method for etching the broadband pass filter stack other than the metal mask layer adopts inductively coupled plasma etching; the etching gas is CHF₃、C₃F₈、CF₄Or BCl₃、Cl₂Any one of the above; the etching rate is 50-300 nm/min.

Further, in step S6, the method for removing the metal thin film on the surface of all the array-type periodically arranged spectral channel units is wet etching or dry etching.

Further, the etching solution in the wet etching is an acid or alkali etching solution.

Further, the dry etching is inductively coupled plasma etching, and the etching gas is BCl₃、Cl₂At an etching rate of 50 to 100 nm/min.

Further, the substrate is a K9 glass substrate.

The method for preparing the pixel-level multispectral optical filter forms the array periodically-arranged broadband pass filter film stack with the thickness of 5-15 microns, and is favorable for improving the passband characteristics of the spectral channel of the pixel-level multispectral optical filter. In addition, the preparation method of the pixel-level multispectral optical filter also utilizes the graphical metal film as a mask layer and an etching stop layer, prevents the formed spectral channel unit from being etched, can reduce the shadow shielding effect in the preparation process, and effectively ensures the integrity of the overall dimension of the channel unit.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic flow chart of a process for preparing a visible near-infrared 4-channel pixel-level multispectral optical filter according to an embodiment of the present invention;

fig. 2 is a transmittance characteristic curve of the visible near-infrared 4-channel pixel-level multispectral filter prepared in fig. 1.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.

In order to make the description of the present disclosure more complete and complete, the following description is given for illustrative purposes with respect to the embodiments and examples of the present invention; it is not intended to be the only form in which the embodiments of the invention may be practiced or utilized. The embodiments are intended to cover the features of the various embodiments as well as the method steps and sequences for constructing and operating the embodiments. However, other embodiments may be utilized to achieve the same or equivalent functions and step sequences.

The invention provides a method for preparing a pixel-level multispectral optical filter, which comprises the following steps:

s1: the structure of the wide-band-pass filtering film stack is designed by using film system design software, the average transmittance of the designed pass band is better than 85 percent, and the average transmittance of the designed stop band is less than 5 percent;

s2: cleaning a substrate, and plating a first broadband pass filter film stack on the substrate;

s3: depositing a metal film on the first broadband pass filter film stack, and patterning the metal film, wherein the patterned metal film is a metal film unit structure which is arranged in an array type periodic manner, and the size of each metal film unit structure is 5-30 micrometers and corresponds to the pixels of the detector chip one by one;

s4: etching the first broadband-pass filter film stack outside the metal mask layer by using the patterned metal film as the mask layer and using a dry etching method to form a first array-type periodically-arranged spectrum channel unit;

s5: repeating the steps S1-S4, repeating the steps (N-1) times, plating a second broadband pass filter film stack and a third broadband pass filter film stack … N-th broadband pass filter film stack in the step S2, and correspondingly and sequentially forming a second and a third … N-th arrayed periodically-arranged spectral channel units;

s6: and removing the metal films on the surfaces of all the array-type periodically arranged spectral channel units to obtain the pixel-level multispectral optical filter.

The first … Nth broadband pass filter film stack and the second … Nth broadband pass filter film stack have correspondingly designed spectral characteristics, are composed of high-refractive-index and low-refractive-index films alternately, and are controlled to be 5-15 microns in thickness in order to ensure good spectral pass band characteristics. The high-refractive-index film can be made of TiO₂、Ta₂O₅、HfO₂Any one of Si, Ge, ZnSe, etc.; the low refractive index film can be made of SiO₂、Al₂O₃、MgF₂、YF₃、YbF₃And the like.

In step S2, the second broadband pass filter film stack and the third broadband pass filter film stack …, the nth broadband pass filter film stack are formed by ion beam assisted electron beam evaporation, magnetron sputtering, ion beam sputtering, plasma enhanced chemical vapor deposition, or the like.

Wherein, the thickness of the metal film deposited in step S3 is 300-1000 nm, and the material of the metal film is any one of aluminum, copper, chromium, nickel, etc.; the technology adopted by the graphical metal film is photoetching and dry etching technology, or Lift-off technology and film coating technology.

Preferably, in step S4, the dry etching method for etching the broadband pass filter film stack except for the metal mask layer is inductive coupling plasma etching; the etching gas is preferably CHF₃、C₃F₈、CF₄Any one of fluorine-based gases, or BCl₃、Cl₂Any one of chlorine-based gases; the etching rate is preferably 50 to 300 nm/min.

The method for removing the metal thin film on the surfaces of all the arrayed periodically arranged spectral channel units in step S6 is preferably wet etching or dry etching. The etching solution in the wet etching is preferably an acid or alkali etching solution. The dry etching is preferably inductively coupled plasma etching, and the etching gas is preferably BCl₃、Cl₂The etching rate of any one of the isochloro-based gases is preferably 50-100 nm/min.

In addition, the substrate is preferably a K9 glass substrate suitable for use in the manufacture of optical elements.