CN100385268C - Micro-integrated narrow-band filter array and its preparation method - Google Patents

Abstract

The invention discloses a micro-integrated narrow-band optical filter array and a preparation method thereof. The optical filter array includes: a substrate, and a plurality of channel miniature narrow-band optical filter film layers firmly combined with the substrate are placed on one side of the substrate , the other side of the substrate is plated with a public truncation peak film layer, which is characterized in that: there is an interval between the micro-narrow-band filter film layers of each channel, and an opaque metal layer for preventing optical crosstalk is built in the interval, the metal The layer extends from the interval to the side of the filter film layer, that is, the side of each channel filter film layer is covered with a metal layer, which completely solves the light string between each channel. The feature of the preparation method is that in the preparation process of the optical filter, a measurement coating window is added, and the corresponding channel is plated at the same time, which solves the difficulty of measuring the single-channel film system in the preparation process; the metal mask is used to effectively It solves the problem that the photoresist cannot withstand high temperature, and the deformation and edge effect caused by the mechanical mask, and solves the problem of channel pattern refinement.

Description

Micro-integrated narrow-band filter array and its preparation method

technical field

The invention relates to an optical film and an optical filter, in particular to a multi-channel micro-integrated narrow-band filter array for focal plane devices.

Background technique

With the development of the focal plane detector, it provides the basis for the miniaturization and modularization of the instrument. In order to get more information, multi-channel detection is needed. There are many ways to obtain multi-channel detection, such as grating splitting, filter splitting, prism splitting, etc. The combination of multi-channel filter array and detector array can greatly simplify the optical system and reduce the volume and weight of the instrument. Therefore, the research of micro-integrated narrow-band filter array is of great significance to the development of space remote sensing technology. In recent years, optical thin film technology has developed by leaps and bounds. From the maturity of coating methods such as electron guns, ion sources, and magnetron sputtering to the continuous enrichment of monitoring methods, the reliability and stability of coatings have been greatly developed. The control accuracy has also been greatly improved, and ideal optical filters can be obtained. The conditions for developing micro-integrated narrow-band optical filter arrays are ripe. Combining the filter array and the detector array into one component, as a multi-channel focal plane detector array, can greatly reduce the volume and weight of the optical system, which is of great significance to space instruments. At the same time, since the detector and the optical filter become a component, the detection system can be modularized and miniaturized, and the flexibility of the satellite system and the utilization efficiency of the payload can be improved.

At present, there are mainly the following ways to realize the integration of optical filters:

1. Glue integration

After the narrow-band filters of each channel are prepared by the method of optical coating PVD, after cutting into the required size, these narrow-band filters with different spectral channels are glued together on the common support. There are no special requirements for the plating of narrowband filters, but the combination is difficult, and it is difficult to precisely combine them into one. The size of the filter is limited, and it is difficult to make it small, which is not conducive to miniaturization and integration. Moreover, the cross-winding between channels is relatively large, which has a great influence on the optical transfer function.

2. Tunable filters

This structure is relatively simple, and the narrow-band filter is mostly designed with the structure of F-P interferometer, and the thickness or refractive index of the resonant cavity layer in the structure is controlled by means of electricity, sound, heat, etc., so as to achieve the wavelength selection. effect. This kind of filter structure can be made very small, but the corresponding control mechanism is relatively complicated, and the tunable range is very narrow, generally only about 30nm, and this method cannot simultaneously obtain spectral information of different wavelengths.

3. Integrated narrowband filter

This kind of filter is based on the principle of F-P interference, and the thickness of different resonant cavity film layers is obtained at different positions through semiconductor etching technology, so as to control the central wavelength of the bandpass of the narrowband filter, thereby realizing narrowband filtering of different transmission wavelengths. The light sheets are integrated on the same substrate. The channel wavelength range of this filter is very small, and it is only suitable for the preparation of a filter with a small spectral range, and the form factor is poor and the transmittance is low. Waveforms that cannot be applied to a wide spectral range require the use of a filter array with high transmittance.

4. Gradient filter array

A micro-integrated narrow-band filter capable of rapidly detecting different wavelength bands simultaneously. It adopts the shielding plate method and is made by vacuum coating. One end of the substrate only transmits the short-wavelength spectrum, and the other end only transmits the long-wavelength spectrum; in the middle of the substrate, only a specific wavelength spectrum in the two wavelength ranges is transmitted, and the spectral resolution reaches 0.2μm. And the transmitted light wavelength and its corresponding transmission position change linearly from one end of the substrate to the other end. Its disadvantage is that the spectrum is continuous, and the specified spectrum cannot be obtained at the specified position, and the spectral performance and transmittance of a single channel become worse due to linear gradients.

5. Micro-integrated filter array

One of the most promising optical filter integration methods, it is a sub-area plating mask separation method combined with the semiconductor device manufacturing process and the basic PVD method, and the optical filters with different spectral characteristics can be integrated to the same substrate, and can be made to the micron level as needed. See "Cheng Shiping, Yan Yixun, Zhang Fengshan, Xu Buyun, Zhu Cuiyuan, "Journal of Infrared and Millimeter Waves" 13, 401 (1994); Cheng Shiping, Zhang Fengshan, Yan Yixun, "Journal of Infrared and Millimeter Waves" 13, 110 (1994)". Due to the complex process steps of this integration method, the yield of the filter will drop by half for each additional channel, and the filters of each channel are very small, so it is difficult to measure a single-channel filter during the preparation process. to filter. In addition, there is still crosstalk between the channels of this integration method at present.

Contents of the invention

Based on the various problems existing in the above-mentioned existing integrated optical filter arrays, the purpose of the present invention is to propose a micro-integrated narrow-band optical filter array that can prevent crosstalk between the optical filter channels and save costs and its preparation method .

The micro-integrated narrow-band filter array of the present invention comprises a substrate 1, a plurality of channel miniature narrow-band filter film layers 2 firmly combined with the substrate are placed on one side of the substrate, and the other side of the substrate is plated with common The truncation peak film layer 3 is characterized in that: there is an interval between the micro narrow-band filter film layers of each channel, and an opaque metal layer 4 to prevent optical crosstalk is built in the interval, and the metal layer extends from the interval to the filter film The side of the layer, that is, the side of each channel filter film layer is covered with a metal layer, which completely solves the light string between each channel.

The preparation method of the micro-integrated narrow-band filter array of the present invention is a mask separation method combined with a semiconductor device manufacturing process and a basic PVD method, and its specific preparation method steps are as follows:

A. Firstly, the lithographic alignment mark 5 and the multi-channel aperture 7 are prepared on the substrate by photolithography and coating process for the coating system of each channel. The number of channels is determined according to the requirements of the focal plane detector. The aperture It is an opaque metal line between the filter layers of the micro-integrated narrow-band filter to prevent optical crosstalk, and the coating window of the single-channel filter layer is between the two metal lines;

B. Use the photolithography process to cold-plate metal masks, leaving only the first channel as the coating window, and opening the corresponding measurement coating window 6 next to the multi-channel aperture. According to the design of the main film system of the first channel, the The coating window of the first channel and the measurement coating window are simultaneously coated with the vacuum main film system. After the main film system is coated, measure the single channel film system formed by the measurement coating window to see if it meets the design requirements;

C. If the design requirements are met, peel off the mask and dielectric film layer outside the channel by chemical etching, and repeat step B to obtain the second channel narrow-band filter. Repeating this many times can get the required channel number array;

D. Then cold-plate the metal layer on the side of the channel through the photolithography process, and coat the side of each channel film layer with a metal layer;

E. Finally, a common truncation peak film layer is vacuum-plated on the back of the substrate to complete the preparation of the micro-integrated narrow-band filter array.

The advantage of the micro-integrated narrow-band filter array of the present invention is:

1. There is an opaque metal layer isolation between the channels and a metal layer coating on the side of each channel film layer, which can effectively eliminate the cross-winding of light between channels and improve the transfer function of the optical system;

2. The metal mask is used to effectively solve the problem that the photoresist cannot withstand high temperature, and the deformation and edge effect caused by the mechanical mask, and solve the problem of channel pattern refinement;

3. The metal mask is used to effectively improve the consistency of the substrate temperature and greatly improve the uniformity of the coating;

4. The mask is made by photolithography technology, which greatly improves the alignment accuracy of the channel;

5. The bandwidth and transmittance of the multi-channel filter can be well controlled, and the band can be set according to needs;

6. The multi-channel main film system is plated on one surface, and the common truncation peak film system is plated on the other side of the substrate, which greatly reduces the difficulty of filter design and plating;

7. The setting of the measurement coating window reduces the cost and improves the measurement accuracy, yield and efficiency.

Instructions attached

Fig. 1 is a schematic diagram of a cross-sectional structure of a seven-channel filter.

Figure 2 is the anti-light series metal diaphragm of the seven-channel filter.

Figure 3 shows seven seven-channel optical filters plated on a large piece and the corresponding measurement windows.

Figure 4 is the measured curve of the common truncation peak film system of the seven-channel filter.

Fig. 5 (a) is the measured curve of the first channel 412nm;

Fig. 5 (b) is the measured curve of the second channel 443nm;

Fig. 5 (c) is the measured curve of the third channel 470nm;

Fig. 5 (d) is the measured curve of the fourth channel 490nm;

Fig. 5 (e) is the measured curve of the fifth channel 520nm;

Fig. 5 (f) is the measured curve of the sixth channel 550nm;

Figure 5(g) is the measured curve of the seventh channel at 565nm.

Detailed ways

Taking the seven-channel micro-integrated filter array of visible light as an example, the specific implementation of the present invention will be described in detail in conjunction with the accompanying drawings. Table 1 shows the design requirements of the central wavelength, bandwidth and transmittance of the seven-channel filter. The sub-peak cut-off range is from 400nm to 1100nm, and the transmittance in the cut-off area is less than 1%. Since it is very difficult to plate a narrow-band filter with seven channels on a substrate, the film system design uses a public truncation peak film system for the sub-peaks from 600nm to 1100nm, so that the range of the truncation peak film system of each channel It is greatly reduced to 400-600nm, and the difficulty of designing and plating the main peak film system is greatly reduced. The film system of the present invention can be designed with a regular film system or an irregular film system. Generally, the irregular film system design is adopted, the film thickness can be reduced, and the yield of the coating film and the firmness of the film layer can be improved.

The seven-channel irregular film system is as follows:

The first channel 412nm film system:

1.033L.879H.824H.875L 2.211H 1.001L.99H.897L.97H 1.07H 1.07H 1.089L 1.846H1.215L.936H.773L.977h 1.121L 1.219L 1.296L 1.333H 1.257L 1.257L 1.257L 1.257L 1.2577. 1.248H 1.275L 1.67H 1.549L 1.22H 1.238L 1.316H 1.373L 1.506H 1.359L 1.495H 1.451L 1.51H 2.415L λ=412nm H—Nb ₂ O ₅ , L—SiO ₂ .

The second channel 443nm film system:

1L.964H.991L.976H 4.018L 1.007L 1.007L 1H.999L.989H 1.001L.999H 3.986L 1.011H1.01L 1.016H 1.006L 1.005H 1.001L.972H 1.013H 1.059L 1.05L 1.05L 1.966H. 1.087L1.435H 1.356L 1.44H 1.13L 1.299H 1.195L 1.487H 1.321L _{1.454H 1.192L} 1.492H 1.337L 1.312H1.114L 1.547H.562LλO5＝443nm H-Nb2O _.

The third channel 470nm film system:

.999L.974H.741L.396H.841L2.802H.834L.763H.88L.958H.862L.37H.679L.985H 1.032L1.003H 1.047L 1.016H 1.849L1.101H1.0852L 1.0159L7L 1.0159L 1.0159L 1.0159L 1.0159L 1.0159L 1.303H 1.157L 1.131H 1.158L 1.206H 1.271L 1.57H 1.173L 1.19H 1.059L λ=470nm H—Nb2O5, L—SiO ₂ .

The fourth channel 490nm film system:

1.052L 2.004H 2.057L 1.097H 1.393L 1.093H 1.27L 1.005H 1.523L 1.025H 1.303L 1.226H1.012L.979H 1.019L.98H 1.457L 1.107H.95L 1.909H.99L.871H1.004L.99H.969L .757H.809L.68H.915L.905H.938L.644H.496L1.057H.843L 1.067H2.726L.22H.598L

λ=490nm H-Nb2O5, L- _SiO2 .

Fifth channel 520nm film system:

1.24L2.533H 1.296L 1.266H.958L 1.568H 1.365L.755H 1.451L 1.094H 1.073H.99L1.031H 1.587L.73511L2.964L 1.0175L1.219H.95L.95L.95L.95L.95L.95L.95L.95L.95L.95L.95L.95L.95L.95L.95L.95L.95L.95L.95L.95L. .888H.84L.683H.668L.727H.857L.885H.913L.911H.926L.931H.927L 2.48H.732L.628H 1.962Lλ=520nm H-Nb2O5, L- _SiO2 .

Sixth channel 550nm film system:

2.112L.699H.664L.641H.749L.791H.831L.877H.842L.75H.81L.743H.802L.79H.815L.766H.824L.773H.874L 1.268H 3.1L.126H.748L.861H.958L 1.299H 1.002L.732H 1.676L 1.295H1.277L 1.15H.971L 1.237H 1.04L 1.288H 1.833L 2.482H 1.371L.799H 1.269H 1.394L1.344H 1.663H λ 1.663H λ -Nb2O5, L- _SiO2 .

Seventh channel 565nm film system:

918L 1.006H 1.067L.826H.671L 2.294H.995L.988H.99L.992H 1.006L 1.014H.978L.961H1.012L 2.101H.987L.848H.924L1.041H.977L.946H.973 λ=565nm H-Nb2O5, L- _SiO2 .

Public truncation film system:

1.214L 1.103H.989L 1.071H.891L 1.1H.795L 1.213H.493L 1.205H.83L 1.074H.859L1.034H.93L.972H 1.006L.921H 1.067L.976H 1.186LH 1.1.9 .978H 1.137L1.144H 1.377L 1.369H 1.393L 1.319H 1.384L 1.397H 1.478L 1.442H 1.494L 1.454H 1.465L 1.416H1.357O1.14H.566L2nm-Nb0, λH＝70

The substrate is made of transparent quartz or K9 material within the operating band.

The opaque metal used to prevent optical crosstalk in the present invention may be metal black chromium, or other metal materials, as long as it can shield light and resist corrosion.

The metal mask referred to in this embodiment is composed of three layers of metal film. The first layer is metal aluminum with a thickness of 0.5 microns, the second layer is metal copper with a thickness of 1.0 microns, and the third layer is also metal layer of aluminum with a thickness of 0.5 microns.

Six seven-channel optical filters were simultaneously prepared on a large substrate according to the above-mentioned preparation steps, and the measured performance curves of the seven-channel optical filters are shown in solid lines in Fig. 5 (a-g). It can be seen that the method of the present invention has reached the expected purpose.

Table 1

channel number Central wavelength (nm) Bandwidth (nm) Transmittance (%) 1 412 20 75 2 443 20 75 3 470 50 75 4 490 20 75 5 520 20 75 6 550 50 75 7 565 20 75

Claims (2)

1. a micro-integrated narrow-band filter array comprises substrate (1), is coated with a plurality of Channel Micro narrow-band-filter retes (2) with the substrate strong bonded in the one side of substrate, has been coated with public section secondary peak rete (3) at the another side of substrate, it is characterized in that:

Have one between each Channel Micro narrow-band-filter rete at interval, be built-in with the lighttight metal level (4) that prevents optical crosstalk at interval, this metal level extends to the side of filter membranous layer in the interval, and promptly each passage filter membranous layer side all has metal level to coat.

2. the preparation method of a micro-integrated narrow-band filter array is characterized in that concrete preparation process is as follows:

A. at first on substrate, utilize photoetching and coating process to be prepared as follow-up each passage and be coated with photoetching alignment mark that film is a usefulness (5) and hyperchannel diaphragm (7), port number requires to decide according to focus planardetector, this diaphragm is exactly the lighttight metal wire that prevents optical crosstalk between each filter membranous layer of micro-integrated narrow-band filter, is the plated film window of single channel filter membranous layer between two metal wires;

B. utilize the cold plating mask of photoetching process, only stay first passage as the plated film window, and the measurement plated film window (6) of leaving correspondence on hyperchannel diaphragm next door, design according to first passage master film system, to the plated film window of first passage and measure the plated film window and carry out vacuum master film system simultaneously and be coated with, main film is after being coated with, and the single channel film system of measuring the formation of plated film window is measured, and sees whether it adheres to specification;

C. as adhering to specification, peel off passage outer mask and media coating by the method for chemical corrosion again, repeat the B step, obtain second passage narrow band pass filter; So repeated multiple times can obtain access desired and count array;

D. again by photoetching process to the cold metal cladding in passage side, each passage rete side is coated with metal level;

E. at last be coated with public section secondary peak rete, finish the preparation of micro-integrated narrow-band filter array in the back side of substrate vacuum.

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