CN110596929A - Silicon-based liquid crystal device, manufacturing method thereof and wavelength selection switch - Google Patents
Silicon-based liquid crystal device, manufacturing method thereof and wavelength selection switch Download PDFInfo
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- CN110596929A CN110596929A CN201910810341.8A CN201910810341A CN110596929A CN 110596929 A CN110596929 A CN 110596929A CN 201910810341 A CN201910810341 A CN 201910810341A CN 110596929 A CN110596929 A CN 110596929A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29302—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means based on birefringence or polarisation, e.g. wavelength dependent birefringence, polarisation interferometers
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1343—Electrodes
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/133357—Planarisation layers
Abstract
The invention provides a silicon-based liquid crystal device, a manufacturing method thereof and a wavelength selection switch. The manufacturing method of the silicon-based liquid crystal device comprises the steps of forming a planarization material film covering a plurality of bottom electrodes and intervals between adjacent bottom electrodes on a silicon wafer, polishing the planarization material film for multiple times to thin the planarization material film, etching the thinned planarization material film to remove the parts, located on the plurality of bottom electrodes, of the thinned planarization material film, forming filling parts located between the adjacent bottom electrodes, enabling the thickness of the parts, located on the bottom electrodes, of the thinned planarization material film to be extremely thin through polishing for multiple times, enabling the surface flatness of the filling parts formed after etching to be high, enabling the surface flatness of the whole areas, where the intervals between the plurality of bottom electrodes and the adjacent bottom electrodes are located, to be high, and improving the quality of products such as wavelength selective switches.
Description
Technical Field
The invention relates to the technical field of optical equipment, in particular to a silicon-based liquid crystal device, a manufacturing method thereof and a wavelength selective switch.
Background
A Wavelength Selective Switch (WSS) is a core optoelectronic device of a Reconfigurable Optical Add-Drop Multiplexer (ROADM), can realize switching, attenuation or blocking of Optical signals at any port with any Wavelength or any Wavelength combination, and is one of key products in the current Optical communication industry.
The wavelength selective switch generally comprises an optical fiber array, a shaping lens, a diffraction grating, a converging lens and a control chip, wherein optical signals input by the optical fiber array are collimated by the shaping lens, light spots are shaped and then pass through the diffraction grating, so that the optical signals with different wavelengths are separated along different angles in space, the converging lens focuses the optical signals with different wavelengths on the control chip, and the control chip outputs the optical signals with different wavelengths along different directions, so that the switching, attenuation or blocking of the optical signals are realized.
In the prior art, a Liquid Crystal ON Silicon (Liquid Crystal ON Silicon) device is commonly used as a control chip in a wavelength selective switch. The silicon-based liquid crystal device comprises a silicon wafer and a top plate which are oppositely arranged, a liquid crystal layer arranged between the silicon wafer and the top plate, a plurality of reflective bottom electrodes arranged at intervals on one side of the silicon wafer close to the top plate, and a transparent top electrode arranged on one side of the top plate close to the silicon wafer, wherein the deflection angle of liquid crystal in the liquid crystal layer can be controlled by controlling the voltage applied to the bottom electrodes and the top electrode. When the silicon-based liquid crystal device is used as a control chip in the wavelength selection switch, an optical signal is injected into the silicon-based liquid crystal device from one side of the top plate and is reflected by the bottom electrode and then is emitted, and the optical signals with different wavelengths can be output along different directions by adjusting the deflection angle of the liquid crystal, so that the switching of the optical signals is realized. At present, in order to improve the reflectivity of a bottom electrode of a liquid crystal on silicon device, a dielectric layer for enhancing the reflection effect is usually formed on the bottom electrode arranged at intervals, however, because the bottom electrodes are arranged at intervals, the surface flatness of the whole area where the intervals are formed between a plurality of bottom electrodes and adjacent bottom electrodes is poor, the dielectric layer is directly formed on the bottom electrodes, the flatness of the dielectric layer is poor, the thickness is difficult to control, and the reflection enhancing effect is greatly reduced. In order to solve the problem, the prior art forms a layer of silicon dioxide coating film on the bottom electrodes arranged at intervals, then, the silicon dioxide coating is thinned by carrying out a Chemical Mechanical Polishing (CMP) treatment, then, the residual silicon dioxide film is etched by plasma to expose the bottom electrodes, silicon dioxide is remained between the adjacent bottom electrodes to improve the surface flatness of the whole area where the plurality of bottom electrodes and the intervals between the adjacent bottom electrodes are positioned, since the chemical mechanical polishing treatment is performed only once, the thickness of the silicon dioxide plating film remaining after the chemical mechanical polishing treatment is thick, in order to fully expose the bottom electrode, the plasma etching is usually performed by over-etching, which finally results in a larger recess on the surface of the silicon dioxide remaining between the adjacent bottom electrodes, the effect of improving the surface flatness of the entire region where the plurality of bottom electrodes and the adjacent bottom electrodes are spaced is very limited.
Disclosure of Invention
The invention aims to provide a manufacturing method of a silicon-based liquid crystal device, which can improve the surface flatness of a plurality of bottom electrodes and the whole area where the intervals between the adjacent bottom electrodes are positioned, and improve the quality of products.
Another object of the present invention is to provide a liquid crystal on silicon device, which has a high surface flatness of the entire region where the plurality of bottom electrodes and the spaces between the adjacent bottom electrodes are located, and a high product quality.
It is another object of the present invention to provide a wavelength selective switch, which has a high surface flatness and a high product quality in the entire region where a plurality of bottom electrodes of a liquid crystal on silicon device and spaces between adjacent bottom electrodes are located.
In order to achieve the above object, the present invention first provides a method for manufacturing a liquid crystal on silicon device, comprising the following steps:
step S1, providing a silicon wafer;
step S2, forming a plurality of reflective bottom electrodes on the silicon wafer at intervals;
step S3, forming a planarization material film on the silicon wafer to cover the bottom electrodes and the gaps between the adjacent bottom electrodes;
step S4, polishing the planarization material film for multiple times to thin the planarization material film;
step S5 of performing an etching process on the thinned planarization material film to remove portions of the thinned planarization material film on the plurality of bottom electrodes, thereby forming filling portions between the adjacent bottom electrodes;
step S6, forming a dielectric layer on the bottom electrodes and the filling parts;
step S7, providing a top plate, and forming a light-transmitting top electrode on the top plate;
and step S8, arranging the side of the silicon wafer with the bottom electrode opposite to the side of the top plate with the top electrode, and forming a liquid crystal layer between the silicon wafer and the top plate to obtain the silicon-based liquid crystal device.
The dielectric layers comprise a plurality of sub-dielectric layers which are arranged in a stacked mode, the materials of two adjacent sub-dielectric layers are respectively a first material and a second material, the material of the sub-dielectric layer closest to the bottom electrode is the first material, and the refractive index of the first material is larger than that of the second material.
The dielectric constants of the first material and the second material are both larger than 10; the difference between the refractive index of the first material and the refractive index of the second material is greater than 0.5.
The material of the planarization material film is silicon dioxide;
the bottom electrode is made of aluminum;
in step S5, the thinned planarization material film is subjected to plasma etching treatment using chlorine as an etching gas.
In step S4, a plurality of chemical mechanical polishing processes are performed on the planarization material film.
In the step S4, the number of times the planarization material film is subjected to the chemical mechanical polishing process is 3 to 8 times.
In step S4, in addition to the first cmp processing, before each cmp processing, the thickness of the planarization material film is measured and the process parameters of the cmp processing are adjusted according to the thickness of the planarization material film, so that the thickness of the portion of the planarization material film on the bottom electrode after the cmp processing is performed is one-half of the thickness of the portion of the planarization material film on the bottom electrode before the cmp processing is performed.
The thickness of the part of the planarization material film formed in the step S3, which is positioned on the bottom electrode, is 0.5-1.5 μm; in step S4, after the first chemical mechanical polishing process, the thickness of the portion of the planarization material film on the bottom electrode is 0.2 to 0.5 μm.
The invention also provides a silicon-based liquid crystal device which is manufactured by the manufacturing method of the silicon-based liquid crystal device.
The invention also provides a wavelength selective switch which comprises the silicon-based liquid crystal device.
The invention has the beneficial effects that: the manufacturing method of the silicon-based liquid crystal device comprises the steps of forming a planarization material film covering a plurality of bottom electrodes and intervals between adjacent bottom electrodes on a silicon wafer, polishing the planarization material film for multiple times to thin the planarization material film, etching the thinned planarization material film to remove the parts of the thinned planarization material film on the bottom electrodes to form filling parts between the adjacent bottom electrodes, and polishing for multiple times to enable the thickness of the parts of the thinned planarization material film on the bottom electrodes to be extremely thin, so that the surface flatness of the filling parts formed after an etching process is high, the surface flatness of the whole areas where the intervals between the bottom electrodes and the adjacent bottom electrodes are located is high, and the quality of products is improved. The silicon-based liquid crystal device has the advantages that the surface flatness of the whole area where the plurality of bottom electrodes and the intervals between the adjacent bottom electrodes are located is high, and the product quality is good. The silicon-based liquid crystal device of the wavelength selection switch has the advantages that the surface flatness of the whole area where the plurality of bottom electrodes and the intervals between the adjacent bottom electrodes are located is high, and the product quality is good.
Drawings
For a better understanding of the nature and technical aspects of the present invention, reference should be made to the following detailed description of the invention, taken in conjunction with the accompanying drawings, which are provided for purposes of illustration and description and are not intended to limit the invention.
In the drawings, there is shown in the drawings,
FIG. 1 is a flow chart of a method of fabricating a liquid crystal on silicon device of the present invention;
FIG. 2 is a schematic diagram of steps S1 and S2 of the method for fabricating a liquid crystal on silicon device according to the present invention;
FIG. 3 is a schematic diagram of step S3 of the method for fabricating a liquid crystal on silicon device according to the present invention;
FIGS. 4 to 6 are schematic diagrams of step S4 of the method for fabricating a liquid crystal on silicon device according to the present invention;
FIG. 7 is a diagram illustrating step S5 of the method for fabricating a liquid crystal on silicon device according to the present invention;
FIG. 8 is a diagram illustrating step S6 of the method for fabricating a liquid crystal on silicon device according to the present invention;
FIG. 9 is a diagram illustrating step S7 of the method for fabricating a liquid crystal on silicon device according to the present invention;
FIG. 10 is a schematic diagram of step S8 of the method for fabricating a LCOS device according to the present invention and a schematic diagram of the structure of the LCOS device according to the present invention.
Detailed Description
To further illustrate the technical means and effects of the present invention, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.
Referring to fig. 1 to 10, the present invention provides a method for fabricating a liquid crystal on silicon device, comprising the following steps:
in step S1, please refer to fig. 2, a silicon wafer 10 is provided.
Specifically, the silicon chip 10 includes a bottom circuit 11 and an insulating layer 12 disposed on the bottom circuit 11, and the insulating layer 12 is provided with a plurality of via holes 121 disposed at intervals.
In step S2, referring to fig. 2, a plurality of reflective bottom electrodes 20 are formed on the silicon wafer 10 at intervals.
Specifically, a plurality of bottom electrodes 20 are formed on the insulating layer 12, and each bottom electrode 20 is connected to the bottom layer circuit 11 through a corresponding via 121.
Specifically, the material of the bottom electrode 20 is aluminum.
Preferably, the width of the space between the adjacent bottom electrodes 20 is 0.25 μm.
In step S3, referring to fig. 3, a planarization material film 30 is formed on the silicon wafer 10 to cover the bottom electrodes 20 and the gaps between the adjacent bottom electrodes 20.
Specifically, the material of the planarization material film 30 is silicon dioxide (SiO 2).
Specifically, the thickness of the portion of the planarization material film 30 formed in step S3, which is located on the bottom electrode 20, is 0.5-1.5 μm, preferably 1 μm.
In step S4, please refer to fig. 4 to 6, the planarization material film 30 is polished for a plurality of times to thin the planarization material film 30.
Specifically, in the step S4, the planarization material film 30 is subjected to the chemical mechanical polishing process a plurality of times.
Preferably, in the step S4, the number of times the planarization material film 30 is subjected to the chemical mechanical polishing process is 3 to 8 times.
Specifically, in step S4, in addition to the first cmp processing, before each cmp processing, the process parameters of the cmp processing are adjusted by measuring the thickness of the planarization material film 30 and according to the thickness of the planarization material film 30, so that the thickness of the portion of the planarization material film 30 on the bottom electrode 20 after the cmp processing is performed is one-half of the thickness of the portion of the planarization material film 30 on the bottom electrode 20 before the cmp processing is performed.
Further, the process parameters of the chemical mechanical polishing process include a process time.
Specifically, in step S4, after the first cmp process, the thickness of the portion of the planarization material film 30 on the bottom electrode 20 is 0.2 to 0.5 μm, preferably 0.35 μm.
Specifically, in a preferred embodiment of the present invention, the thickness of the portion of the planarization material film 30 formed in step S3, which is located on the bottom electrode 20, is 1 μm, in step S4, referring to fig. 4, a first chemical mechanical polishing process is performed to make the thickness of the portion of the planarization material film 30, which is located on the bottom electrode 20, 0.35 μm, then the thickness of the planarization material film 30 after the first chemical mechanical polishing process is measured and the process parameters of a second chemical mechanical polishing process are adjusted according to the measurement result, referring to fig. 5, a second chemical mechanical polishing process is performed to make the thickness of the portion of the planarization material film 30, which is located on the bottom electrode 20, halved to 0.175 μm, then the thickness of the planarization material film 30 after the second chemical mechanical polishing process is measured and the process parameters of a third chemical mechanical polishing process are adjusted according to the measurement result, then, referring to fig. 6, a third cmp process is performed to reduce the thickness of the portion of the planarization material film 30 on the bottom electrode 20 to 0.088 μm, and the planarization material film 30 is thinned by the third cmp process, but in other embodiments of the present invention, in order to further thin the thickness of the planarization material film 30, the cmp processes may be performed for a fourth time, a fifth time, a sixth time, and more times, so that the thickness of the portion of the planarization material film 30 on the bottom electrode 20 is further thinned to 0.044 μm, 0.022 μm, 0.011 μm, and thinner, and the specific number of cmp processes may be adjusted according to actual product requirements.
In step S5, referring to fig. 7, the thinned planarization material film 30 is etched to remove the portions of the thinned planarization material film 30 on the bottom electrodes 20, thereby forming the filling portions 31 between the adjacent bottom electrodes 20. Since the portions of the finally thinned planarization material film 30 on the bottom electrodes 20 are extremely thin after the polishing process is performed a plurality of times, the surface flatness of the filler 31 formed by removing the portions of the thinned planarization material film 30 on the bottom electrodes 20 by the etching process is extremely high, and the surface flatness of the entire region where the spaces between the bottom electrodes 20 and the adjacent bottom electrodes 20 are located is high.
Specifically, in step S5, the thinned planarization material film 30 is subjected to plasma etching processing in which the etching gas is chlorine gas (Cl 2).
In step S6, referring to fig. 8, a dielectric layer 40 is formed on the bottom electrodes 20 and the filling portions 31.
Specifically, the dielectric layer 40 includes a plurality of sub-dielectric layers 41 stacked, two adjacent sub-dielectric layers 41 are made of a first material and a second material, respectively, the sub-dielectric layer 41 closest to the bottom electrode 20 is made of the first material, and a refractive index of the first material is greater than a refractive index of the second material.
Further, the dielectric constants of the first material and the second material are both greater than 10. The difference between the refractive index of the first material and the refractive index of the second material is greater than 0.5.
Preferably, the first material is silicon and the second material is titanium oxide.
Specifically, in the first embodiment of the present invention, the dielectric layer 40 includes five sub-dielectric layers 41, the materials of the first, third and fifth sub-dielectric layers 41 are silicon, the materials of the second and fourth sub-dielectric layers 41 are titanium dioxide, the film thicknesses are sequentially 1000A, 1700A, 1000A, 1700A and 2000A, and as analyzed in the first embodiment, the voltage drops of the sub-dielectric layers 41 in the first embodiment are respectively 34.9mV, 8.7mV, 34.9mV, 8.7mV and 69.8mV, the total voltage drop is 157mV, and the reflectances of the pixel array and the plane are respectively 91.23% and 98.17%. In the second embodiment of the present invention, the dielectric layer 40 includes three sub-dielectric layers 41, the first sub-dielectric layer 41 is made of silicon, the second sub-dielectric layer 41 is made of titanium dioxide, the third sub-dielectric layer 41 is made of silicon, the three sub-dielectric layers have film thicknesses of 1000A, 1700A, and 2000A, respectively, and it is determined by analysis of the second embodiment that voltage drops of the sub-dielectric layers 41 of the second embodiment are 33.4mV, 8.3mV, and 66.8mV, a total voltage drop is 109mV, a pixel array reflectivity is 90.42%, and a planar reflectivity is 97.35%. In the third embodiment of the present invention, the dielectric layer 40 includes seven sub-dielectric layers 41, the first, third, fifth and seventh sub-dielectric layers 41 are made of silicon, the second, fourth and sixth sub-dielectric layers 41 are made of silicon dioxide, the film thicknesses are sequentially 1000A, 1700A, 1000A, 1700A and 2000A, the voltage drops of the sub-dielectric layers 41 in the third embodiment are sequentially 36.6mV, 9.1mV, 36.6mV, 9.1mV and 73.1mV, the total voltage drop is 210mV, and the reflectivities of the pixel array and the plane are 91.57% and 99.26% respectively. In the fourth embodiment of the present invention, the dielectric layer 40 includes five sub-dielectric layers 41, the materials of the first, third and fifth sub-dielectric layers 41 are titanium dioxide, the materials of the second and fourth sub-dielectric layers 41 are aluminum oxide, the film thicknesses are 1700A, 2400A, 1700A, 2400A and 3000A, the voltage drops are 63mV, 13mV, 63mV, 13mV and 111.2mV in sequence, the total voltage drop is 263mV, and the reflectivities of the pixel array and the plane are 90.58% and 96.34% respectively. Comparing the first to fourth embodiments, it is known that the reflectivity of the second and third embodiments is similar, the voltage drop of the third embodiment is slightly higher than that of the second embodiment, if the available number of layers is increased, the reflectivity can be improved, but the total voltage drop is also increased, and the cost is increased, so the second embodiment is the optimal number of layers and materials of the film, and this is only for the conventional case, and the first, third and fourth embodiments can be selected according to the needs.
Specifically, in the present invention, because the surface flatness of the filler 31 is extremely high, the surface flatness of the entire region where the gaps between the bottom electrodes 20 and the adjacent bottom electrodes 20 are located is high, so that the flatness of the dielectric layer 40 formed on the bottom electrodes 20 and the filler 31 is high, the film thickness of the sub-dielectric layer 41 in the dielectric layer 40 is easily controlled, and the effect of the dielectric layer 40 in enhancing the reflectivity of the device can be ensured.
Step S7, please refer to fig. 9, in which the top plate 50 is provided, and the transparent top electrode 60 is formed on the top plate 50.
Step S8, referring to fig. 10, the side of the silicon wafer 10 where the bottom electrode 20 is formed is opposite to the side of the top plate 50 where the top electrode 60 is formed, and the liquid crystal layer 70 is formed between the silicon wafer 10 and the top plate 50, thereby obtaining the liquid crystal on silicon device. Since the surface flatness of the filler 31 is extremely high, the surface flatness of the entire region where the plurality of bottom electrodes 20 and the gaps between the adjacent bottom electrodes 20 are located is high, and thus the liquid crystal molecules in the liquid crystal layer 70 can be continuously arranged, and uniform liquid crystal characteristics can be obtained.
It should be noted that, in the method for manufacturing a liquid crystal on silicon device of the present invention, after the planarization material film 30 covering the bottom electrodes 20 and the gaps between the adjacent bottom electrodes 20 is formed on the silicon wafer 10, the planarization material film 30 is polished for a plurality of times to thin the planarization material film 30, and then the thinned planarization material film 30 is etched to remove the portions of the thinned planarization material film 30 on the bottom electrodes 20, so as to form the filling portions 31 between the adjacent bottom electrodes 20, and the thickness of the portions of the thinned planarization material film 30 on the bottom electrodes 20 can be made extremely thin by performing the polishing for a plurality of times, so that the surface flatness of the filling portions 31 formed after the etching process is high, the surface flatness of the entire region where the gaps between the bottom electrodes 20 and the adjacent bottom electrodes 20 are high, and the flatness of the dielectric layer 40 to be manufactured later can be improved, the effect of the dielectric layer 40 for enhancing the reflectivity of the device can be ensured, liquid crystal molecules in the liquid crystal layer 70 can be continuously arranged, uniform liquid crystal characteristics can be obtained, and the quality of products can be improved.
Based on the same inventive concept, please refer to fig. 10, the invention further provides a liquid crystal on silicon device manufactured by the method for manufacturing the liquid crystal on silicon device. The liquid crystal on silicon device comprises a silicon wafer 10 and a top plate 50 which are oppositely arranged, a liquid crystal layer 70 arranged between the silicon wafer 10 and the top plate 50, a plurality of reflective bottom electrodes 20 arranged at intervals on one side of the silicon wafer 10 close to the top plate 50, filling parts 31 arranged between the adjacent bottom electrodes 20, dielectric layers 40 arranged on the bottom electrodes 20 and the filling parts 31, and a transparent top electrode 60 arranged on one side of the top plate 50 close to the silicon wafer 10.
Specifically, the silicon chip 10 includes a bottom layer circuit 11 and an insulating layer 12 disposed on the bottom layer circuit 11, a plurality of via holes 121 are disposed on the insulating layer 12 at intervals, a plurality of bottom electrodes 20 are formed on the insulating layer 12, and each bottom electrode 20 is correspondingly connected to the bottom layer circuit 11 through one via hole 121.
Specifically, the dielectric layer 40 includes a plurality of sub-dielectric layers 41 stacked, two adjacent sub-dielectric layers 41 are made of a first material and a second material, respectively, the sub-dielectric layer 41 closest to the bottom electrode 20 is made of the first material, and a refractive index of the first material is greater than a refractive index of the second material.
Further, the dielectric constants of the first material and the second material are both greater than 10. The difference between the refractive index of the first material and the refractive index of the second material is greater than 0.5.
Preferably, the first material is silicon and the second material is titanium oxide.
It should be noted that the liquid crystal on silicon device of the present invention is manufactured by the above-mentioned method for manufacturing a liquid crystal on silicon device, specifically, after the planarization material film 30 covering the bottom electrodes 20 and the gaps between the adjacent bottom electrodes 20 is formed on the silicon wafer 10, the planarization material film 30 is polished for a plurality of times to thin the planarization material film 30, then the thinned planarization material film 30 is etched to remove the portions of the thinned planarization material film 30 on the bottom electrodes 20, thereby forming the filling portions 31 between the adjacent bottom electrodes 20, the thickness of the portions of the thinned planarization material film 30 on the bottom electrodes 20 can be made extremely thin by performing the polishing for a plurality of times, so that the surface flatness of the filling portions 31 formed after the etching process is high, and the surface flatness of the entire region where the gaps between the bottom electrodes 20 and the adjacent bottom electrodes 20 are high, the flatness of the dielectric layer 40 can be improved, the effect of the dielectric layer 40 on enhancing the reflectivity of the device can be ensured, liquid crystal molecules in the liquid crystal layer 70 can be continuously arranged, uniform liquid crystal characteristics can be obtained, and the product quality can be improved.
Based on the same inventive concept, the invention also provides a wavelength selective switch, which comprises the silicon-based liquid crystal device, and the structure of the silicon-based liquid crystal device is not repeatedly described.
It should be noted that the liquid crystal on silicon device in the wavelength selective switch of the present invention is manufactured by the above-mentioned method for manufacturing a liquid crystal on silicon device, specifically, after the planarization material film 30 covering the plurality of bottom electrodes 20 and the space between the adjacent bottom electrodes 20 is formed on the silicon wafer 10, the planarization material film 30 is polished for a plurality of times to thin the planarization material film 30, then the thinned planarization material film 30 is etched to remove the portion of the thinned planarization material film 30 on the plurality of bottom electrodes 20, thereby forming the filling portion 31 between the adjacent bottom electrodes 20, the thickness of the portion of the thinned planarization material film 30 on the bottom electrodes 20 can be made extremely thin by performing the polishing for a plurality of times, so that the surface flatness of the filling portion 31 formed after the etching process is high, and the surface flatness of the entire region where the space between the plurality of bottom electrodes 20 and the adjacent bottom electrodes 20 is high, the flatness of the dielectric layer 40 can be improved, the effect of the dielectric layer 40 on enhancing the reflectivity of the device can be ensured, liquid crystal molecules in the liquid crystal layer 70 can be continuously arranged, uniform liquid crystal characteristics can be obtained, and the product quality can be improved.
In summary, the method for fabricating a liquid crystal on silicon device of the present invention forms a planarization material film on a silicon wafer to cover a plurality of bottom electrodes and spaces between adjacent bottom electrodes, performs a plurality of polishing processes on the planarization material film to thin the planarization material film, and then performs an etching process on the thinned planarization material film to remove portions of the thinned planarization material film on the plurality of bottom electrodes to form filling portions between the adjacent bottom electrodes. The silicon-based liquid crystal device has the advantages that the surface flatness of the whole area where the plurality of bottom electrodes and the intervals between the adjacent bottom electrodes are located is high, and the product quality is good. The silicon-based liquid crystal device of the wavelength selection switch has the advantages that the surface flatness of the whole area where the plurality of bottom electrodes and the intervals between the adjacent bottom electrodes are located is high, and the product quality is good.
As described above, it will be apparent to those skilled in the art that other various changes and modifications may be made based on the technical solution and concept of the present invention, and all such changes and modifications are intended to fall within the scope of the appended claims.
Claims (10)
1. A manufacturing method of a silicon-based liquid crystal device is characterized by comprising the following steps:
step S1, providing a silicon wafer (10);
step S2, forming a plurality of reflective bottom electrodes (20) arranged at intervals on a silicon wafer (10);
step S3, forming a planarization material film (30) on the silicon wafer (10) to cover the plurality of bottom electrodes (20) and the spaces between the adjacent bottom electrodes (20);
step S4, polishing the planarization material film (30) for multiple times to thin the planarization material film (30);
step S5, etching the thinned planarization material film (30), removing the part of the thinned planarization material film (30) on the bottom electrodes (20), and forming a filling part (31) between the adjacent bottom electrodes (20);
step S6, forming a dielectric layer (40) on the plurality of bottom electrodes (20) and the filling parts (31);
step S7, providing a top plate (50), and forming a light-transmitting top electrode (60) on the top plate (50);
in step S8, the side of the silicon wafer (10) on which the bottom electrode (20) is formed is arranged to face the side of the top plate (50) on which the top electrode (60) is formed, and a liquid crystal layer (70) is formed between the silicon wafer (10) and the top plate (50), thereby obtaining a liquid crystal on silicon device.
2. The method of claim 1, wherein the dielectric layer (40) comprises a plurality of sub-dielectric layers (41) stacked one on another, two adjacent sub-dielectric layers (41) are made of a first material and a second material, respectively, and a sub-dielectric layer (41) closest to the bottom electrode (20) is made of the first material, and the refractive index of the first material is greater than that of the second material.
3. The method of claim 2, wherein the first material and the second material each have a dielectric constant greater than 10; the difference between the refractive index of the first material and the refractive index of the second material is greater than 0.5.
4. A method for fabricating a liquid crystal on silicon device according to claim 1 wherein the material of said planarization material film (30) is silicon dioxide;
the bottom electrode (20) is made of aluminum;
in step S5, the thinned planarization material film (30) is subjected to plasma etching treatment using chlorine as an etching gas.
5. The method of fabricating a liquid crystal on silicon device as set forth in claim 1, wherein in said step S4, the planarization material film (30) is subjected to a plurality of chemical mechanical polishing processes.
6. The method of fabricating a liquid crystal on silicon device as set forth in claim 5, wherein the planarization material film (30) is subjected to the chemical mechanical polishing process 3 to 8 times in the step S4.
7. The method of claim 5, wherein in step S4, in addition to the first CMP process, the thickness of the planarization material film (30) is measured and the process parameters of the CMP process are adjusted according to the thickness of the planarization material film (30) before each CMP process is performed, such that the thickness of the portion of the planarization material film (30) on the bottom electrode (20) after the CMP process is performed is one-half of the thickness of the portion of the planarization material film (30) on the bottom electrode (20) before the CMP process is performed.
8. The method of claim 5, wherein the thickness of the portion of the planarization material film (30) formed in step S3, which is located on the bottom electrode (20), is 0.5-1.5 μm; in step S4, after the first CMP process, the thickness of the planarization material film (30) on the bottom electrode (20) is 0.2-0.5 μm.
9. A liquid crystal on silicon device, characterized by being produced by the method for producing a liquid crystal on silicon device according to any one of claims 1 to 8.
10. A wavelength selective switch comprising the liquid crystal on silicon device of claim 9.
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