Position phase mask lithography prepares the method for the adjustable nanometer periodic optical grating of dutycycleTechnical field
The present invention relates to the preparing technical field of different duty nanometer periodic optical grating.Preparation method based on the photoetching of ± 1 grade of phase-only pupil filter deep UV lithography, photoresist layer thickness and exposure dose synergic adjustment, two-way cover deposit, the technical method such as reactive ion etching.
Background technology
Nanometer periodic optical grating (comprising fiber grating) and technology of preparing thereof obtain in recent years and apply more and more widely in integrated photonic device, optical fiber communication, Fibre Optical Sensor and optical information processing field, the technology of preparing of various advanced person and method also develop gradually and should use, and wherein phase-only pupil filter method obtains the favor of people with the advantage of its uniqueness.The stability requirement of position phase mask method to environment is lower, simultaneously also lower to the coherence requirement of light source, and likely in several parallel optical fiber, write grating in write-once process simultaneously, therefore the cost compare preparing grating is in this way cheap, process stabilizing is reliable, and is easy to industrially produce in enormous quantities.
Possess the nanometer grating of application function, its main physical parameter comprises the profile and grating material etc. of screen periods, grating depth, grating dutycycle, grating, and these parameters are all to performance and the embody rule important thereof of grating.Novel advanced person and the technology of preparing of the reliable and stable nanometer periodic optical grating be made up of various types of materials and process, and under cycle one stable condition, regulate the dutycycle of grating or line thickness for the optimization of grating performance and New function exploitation, to explore its potential using value be all an extremely important and conscientiously possible approach.
Summary of the invention
The object of the present invention is to provide a kind of phase mask lithography to prepare the method for the adjustable nanometer periodic optical grating of dutycycle, dutycycle and the line thickness of grating can be regulated easily.
The concrete technical scheme that the present invention adopts is as follows:
Position phase mask lithography prepares the method for the adjustable nanometer periodic optical grating of dutycycle, comprises the steps:
(1) at the certain thickness deep ultraviolet light-sensitive lacquer of substrate surface even spin coating one deck, then through preliminary drying process;
(2) the surface relief formula quartz grating choosing some cycles is as photoetching phase-only pupil filter used, and the dutycycle of quartz grating is 1:1, is highly 266nm;
(3) utilize wavelength 266nm ultraviolet source as exposure light source, the sample surfaces that in exposure process, phase mask plate and surface are coated with photoresist adopts uniform contact mode, not only the two fits tightly but also is unlikely to make in the structural embeddedness sample glue-line of mask plate, under stabilized lasers output power condition, according to different photoresist layer thickness, by the control of time shutter, accurately control exposure dose, thus control width and the dutycycle of grating lines;
(4), by wet development process, soak certain hour in certain developer solution after, obtain the nanometer grating structure of photoresist, in this grating structural parameter, the cycle should be 1/2 of mask screen periods;
(5) utilize reactive ion etching process, etched substrate material, obtain the grating sample of corresponding construction.
The thickness of described photoresist is 10 ~ 1000nm, and the cycle of quartz grating is 400-2000nm; The range of adjustment of exposure dose is between 10 × 40 ~ 200 × 40mW ﹒ s; The width of grating lines is 10 ~ 1980nm.
Further, after the nanometer grating structure that above-mentioned steps (4) obtains photoresist, according to the size of required grating line thickness and dutycycle, continuation following steps are revised:
A) utilize mask deposition techniques, by regulating inclined deposition angle: 10 ° ~ 89 °, at the photoresist layer upper surface of exposure imaging, with different angle of deposit respectively hydatogenesis metal (as Cr, Au etc.) or oxide (as SiO2, Si3n4deng) as anti-etching barrier film material; Then choose suitable etching parameters, adopt reactive ion etching method to etch not protected photoresist layer and primer respectively, obtain the nanometer grating structure of different line thickness and dutycycle;
B) O is utilized2plasma reaction etching is not coated with the photoresist layer of film mask, must arrive the photoresist layer optical grating construction that top is coated with the sidewall of mask layer;
C) reactive ion etching method is utilized, at the etching gas set (as CHF3deng) with under etching condition, to not etching by the backing material of above-mentioned photoresist layer protection;
D) select certain formula solution, the etch-resistant layer on above-mentioned sample is lifted off, finally obtain required grating sample.
The present invention proposes two kinds of technical schemes for regulating the dutycycle of prepared grating, one is regulate grating dutycycle by changing exposure dose and bondline thickness, and two is by regulating the angle of deposit covering sedimentary deposit as etching mask and association reaction ion etching technology regulates grating dutycycle.By the adjustment of above-mentioned technology factor, the grating of different duty and line thickness can be obtained, thus the different performance nanometer period grat-ing structure different from the dutycycle of application can be obtained.The invention is not restricted to grating material therefor and embody rule scope thereof, and this technical method is simple, reliable and stable, in the production in enormous quantities field of high-performance nano grating, there is outstanding technical advantage.
Accompanying drawing explanation
Fig. 1 is ± 1 order diffraction light position phase mask contact deep UV lithography process schematic representation;
Fig. 2 is photoresist exposure imaging binary model;
Fig. 3 is the process chart of embodiment 2;
Fig. 4 is exposure dose grating Electronic Speculum figure prepared when being 75*40mW*s.
Embodiment
Nanometer periodic optical grating preparation method in the present invention utilizes ± 1 order diffraction light position phase mask contact deep UV (ultraviolet light) lithography to carry out, and makes the effect that reduces by half with mask screen periods; Next combines exposure dose and bondline thickness coordinated regulation, and the mask deposition techniques of applied metal or oxide etch-resistant layer and reactive ion etching method, for regulating line thickness and the dutycycle of nanometer grating.Here ± 1 level phase mask means is the sculptured quartz grating phase-only pupil filter utilizing ultraviolet; and take normal incidence mode; guaranteeing substantially to suppress zero level with under the prerequisite of more senior diffraction light; make two the isocandela degree only deposited ± 1 order diffraction light carries out interference lithography exposure on photoresist layer, thus the cycle that obtains on photoresist layer reduces the grating pattern of half compared with mask plate.Typical exposure light source wavelength is 266nm, and for suppressing zero level and more senior diffraction light, the grating height of quartz grating mask used must meet d=λ/(2(n-1)), wherein λ is exposure light source wavelength, and n is the refractive index of mask material.For quartz mask, n=1.5, therefore this mask grating height is d=λ=266nm, and at this moment zero level can be inhibited preferably with more senior secondary diffraction light.This technology adopts contact exposure mode, and exposure process as shown in Figure 1.
Utilize the deep ultraviolet light sources such as wavelength 266nm, cycle 400-2000nm, the sculptured quartz grating of dutycycle 1:1 is as mask, and pass through ± 1 order diffraction light position phase mask lithography technology and contact exposure method, manufacturing cycle is the nanometer periodic optical grating of mask screen periods 1/2.The sample surfaces that in exposure process, mask plate and surface are coated with photoresist has good laminating type, not only make the two comparatively fit tightly but also be unlikely to make in the structural embeddedness sample glue-line of mask plate, reasonablely can meet ± the conditions of exposure of 1 level phase mask lithography.
On this basis, the line thickness of nanometer grating prepared by regulating and control and the technical scheme of dutycycle have two kinds: (1) is according to concrete photoresist, utilize its exposure dose, threshold exposure and and photoresist layer thickness between mutual relationship, by coordinated regulation process, prepare the nanometer grating of different line thickness and dutycycle; (2) using the metal of anti-reactive ion etching or oxidation as etch resistant material, application mask deposition techniques, under different angle of deposit, prepare the anti-etching thin layer of local on photoresist layer surface, association reaction ion etching technology, prepares the nanometer grating of different line thickness and dutycycle.
Embodiment 1
According to photoresist exposure imaging binary model (as shown in Figure 2), by the adjustment to exposure dose in certain limit in exposure process, make different-thickness photoresist layer after exposure and development, the line thickness of the grating obtained is different from dutycycle.The adjustment of exposure dose and bondline thickness all will control in certain scope, not so probably can not get the grating pattern that the cycle reduces half.Wherein exposure dose range of adjustment is between 10 × 40 ~ 200 × 40mW ﹒ s, and photoresist layer thickness range of adjustment is between 10 ~ 1000nm; Prepared screen periods is 1/2 of mask screen periods, and grating line thickness is between 10 ~ 1980nm.
Concrete technology step is as follows:
(1) at the certain thickness deep ultraviolet light-sensitive lacquer of substrate surface even spin coating one deck, then through preliminary drying process.
(2) the surface relief formula quartz grating choosing some cycles is as photoetching phase-only pupil filter used.
(3) adopt uniform contact mode to expose with 266nm coherent source, under stabilized lasers output power condition, by the control of time shutter, accurately control exposure dose.
(4) when different photoresist layer thickness, control the different time shutter, namely control different exposure doses.
(5), by wet development process, soak certain hour in certain developer solution after, the nanometer grating structure of photoresist is obtained.In this grating structural parameter, the cycle should be 1/2 of mask screen periods, and grating lines and dutycycle are determined by above-mentioned technological factor.
(6) utilize reactive ion etching process, etched substrate material, obtain the grating sample of corresponding construction.
At the AZ1500 photoresist that the even spin coating a layer thickness of silicon chip surface is 240nm, with 110 DEG C of bakings 1 minute; Utilize the cycle to be 550nm, the degree of depth is about 266nm quartz grating as phase mask plate, by contact exposure mode, utilize the deep ultraviolet laser bundle that wavelength is 266nm, its stable output power is 40mW, exposes photoresist, and the time shutter is 75 seconds; Then develop 6 seconds, obtain the optical grating construction of photoresist as shown in Figure 4, its cycle is about about 260nm.As seen from the figure, after exposure dose increases gradually, the dutycycle of grating reduces gradually, therefore achieves and utilizes the change of exposure dose to regulate the target of dutycycle.And if increase exposure dose within the scope of this, by a 550nm periodic optical grating more opening of dividing of the grating in two 275nm cycles that obtains out.
Embodiment 2
Utilize mask deposition techniques, by regulating inclined deposition angle, at the photoresist layer upper surface of exposure imaging, with different angle of deposit vapor deposition techniques metal or sull respectively; Then choose suitable etching parameters, adopt reactive ion etching method etching respectively not by photoresist layer and the primer of etch-resistant layer protection, obtain the nanometer grating structure of different line thickness and dutycycle.Inclined deposition angle: between 10 ° ~ 89 °, controls the deposition region of sedimentary deposit on film surface, for regulating and controlling width and the dutycycle thereof of grating lines after etching; For different photoresist layers and primer kind, select suitable metal or oxide as deposited layer material, and its thicknesses of layers is depending on bondline thickness to be etched or bottom grating height.
Concrete technical scheme and processing step following (process chart is as shown in Figure 3):
(1) at the certain thickness deep ultraviolet light-sensitive lacquer of substrate surface even spin coating one deck, then through preliminary drying process.
(2) the surface relief formula quartz grating choosing some cycles is as photoetching phase-only pupil filter used.
(3) adopt uniform contact mode to expose with 266nm coherent source, under stabilized lasers output power condition, by the control of time shutter, accurately control exposure dose.
(4), by wet development process, soak certain hour in certain developer solution after, the nanometer period grat-ing structure of photoresist layer is obtained.
(5) selected inclined deposition angle, utilizes the electron beam evaporation method certain thickness anti-etching film of twice evaporation deposition respectively.
(6) O is applied2plasma reaction etching by the photoresist layer of above-mentioned etch-resistant layer protection, does not obtain required photoresist layer optical grating construction.
(7) utilize reactive ion etching process, reactive ion etching is carried out to the backing material do not protected by above-mentioned etch-resistant layer and photoresist, obtain the nanometer grating sample of corresponding desired structure parameter.
(8) lift off technological process by glue-line, remove the etch-resistant layer on photoresist and surface thereof.