Method for processing diffraction optical element by controlling thickness of residual adhesive layer through templateTechnical Field
The invention relates to the technical field of nanoimprint, in particular to a method for processing a diffraction optical element by controlling thickness of a residual adhesive layer through a template.
Background
The diffractive optical element (Diffractive Optical Elements, DOE) can accurately control the light intensity distribution while maintaining higher diffraction efficiency, has strong flexibility and customizable due to the more diversified light field regulation and control, can realize smaller and lighter design, has better optical performance, and therefore has special advantages in the fields of AR, HUD, 3D sensing, planar imaging and the like. Referring to fig. 1, the conventional diffractive optical element is generally processed by a nano imprinting technology, and because the structural layer of the DOE is an imprinting glue (organic polymer), compared with inorganic materials such as quartz, glass, silicon, and the like, the DOE has defects of poor hardness, easy scratching, easy structural damage during cleaning, unavoidable phenomena such as yellowing and cracking due to accumulation of high temperature or long-term illumination, and the weather resistance and hardness cannot meet the requirements of future products, so that imprinting and etching become the processing mode most likely to realize batch production due to consideration of cost and consistency.
Referring to fig. 2, in the conventional imprinting-transfer etching process, it is difficult to remove the groove structure layer under the condition that the structure is identical to the original structure due to the difference of different duty ratios of the structures in the process of etching and removing the residual glue layer by using different diffraction grating structures. Therefore, the groove residual glue can be completely etched only through excessive etching, and the next etching can be performed only after the groove residual glue is completely etched, so that the pattern of the stamping glue is transferred to the glass/quartz substrate. In the process of over etching, the situation that the target structure is affected due to the fact that the area of residual glue is etched in advance, the duty ratio and the height are changed, or the stamping glue structure of part of the structural area is completely consumed, pattern transfer cannot be continued, and improvement is needed.
Disclosure of Invention
The invention aims to solve the problems in the prior art by providing a diffraction optical element processing method for controlling the thickness of a residual adhesive layer through a template, which compensates the residual adhesive layer structure through controlling the template, solves the problem that the residual adhesive layer is inconsistent in processing by the conventional imprinting-rotating etching method, realizes the effect of simultaneously etching the residual adhesive layer in different areas without changing the line width of a structural area, has high processing reliability, and is suitable for industrialized application.
The above object of the present invention is achieved by the following technical solutions:
a method for processing a diffraction optical element by controlling the thickness of a residual adhesive layer through a template comprises the following steps,
s1, establishing a structural compensation relation between a template and a diffraction optical element, determining the etching rate of a residual adhesive layer and the pattern size of the surface of the template according to the diffraction grating sizes of different areas of the diffraction optical element, and forming the template;
；
w1 ：wn =v1 ：vn ；
wherein t is etching time of the residual adhesive layer, d is thickness of the residual adhesive layer on the minimum duty ratio partition, and w1 、h1 、v1 Diffraction grating line width, template pattern depth and residual glue layer etching rate on minimum duty ratio partition in sequence, wn 、hn 、vn The etching rate of the residual glue layer, which is the line width of the diffraction grating, the depth of the template pattern and the etching rate of the residual glue layer on other subareas, is more than or equal to 2;
s2, imprinting the pattern into the imprintable medium by using the template obtained in the S1, pressing the inorganic medium substrate on the surface of the imprintable medium, solidifying the imprintable medium in an imprinting way, demolding, and detecting the thickness d of the residual adhesive layer on the partition with the minimum duty ratio;
and S3, synchronously etching the imprintable medium obtained in the step S2 in a partition mode according to the etching time and the etching rate obtained in the step S1 so as to simultaneously etch the residual adhesive layer.
Specifically, in a typical hot stamping process, the imprintable medium may be, for example, a resin, without limitation, such as spin-coating and baking onto an inorganic medium substrate surface, when a thermosetting polymer resin is used, the resin is heated to a temperature such that when in contact with the template, the resin is sufficiently flowable to flow into a pattern defined on the template, then the temperature of the resin is raised to thermally cure (crosslink) the resin such that its cure does not irreversibly form the desired pattern, then the template is removed, the patterned resin is cooled, in hot stamping lithography employing a thermoplastic polymer resin layer, the thermoplastic resin is heated such that the thermoplastic resin is in a free-flowing state just prior to stamping with the template, it may be necessary to heat the thermoplastic resin to a temperature well above the glass transition temperature of the resin, the template is pressed into the flowable resin, then cooled below its glass transition temperature with the template in place, to cure the pattern, then the template is removed, the pattern will be formed by the raised features in the remaining layer of the imprintable medium, and then the pattern can be removed by the thermal stamping process of a suitable thermal stamping process (e.g., poly (methacrylate), poly (e), poly (methacrylate), poly (meth) or poly (acrylate).
Alternatively, in a typical UV-curable imprinting process, which includes the use of a transparent or translucent template that is transmissive to UV radiation and a UV-curable liquid as the imprintable medium (the term "UV" is used herein for convenience, but should be understood to include any suitable actinic radiation for curing the imprintable medium), the viscosity of the UV-curable liquid is generally less than the high of the thermosetting and thermoplastic resins used in hot imprint lithography, and as a result can be moved faster to fill the template pattern features, the template can be used with the resin applied to the UV-curable resin, the photoresist, however, instead of curing the pattern by curing the imprintable medium with UV radiation applied to the imprintable medium through the template as in hot imprint, the imprintable medium is etched after removal of the template.
In addition, a combination of the above-described hot stamping and uv curing stamping techniques is also possible.
Further, in the step S1, controlling the etching rate v of the residual adhesive layer on the minimum duty ratio zone1 1.0 to 7.0nm/s.
Further, in the step S1, the inorganic medium of the inorganic medium substrate and the template material of the template are each independently selected from quartz, silica, glass, YAG, caF2 Or sapphire.
Further, in the step S2, the thickness d of the residual glue layer on the minimum duty ratio partition is controlled to be 10-100 nm, and the imprintable medium is a Delo OM6113 photoresist or a Delo OM614 photoresist.
Further, in the step S2, the steps of,
s21, placing the template and an evaporation pan with 0.5-1.5 mL of release agent into a vacuum drying oven, and vacuumizing to 10-4 Stopping pumping air after Pa, and covering the surface of the template by evaporating a release agent after maintaining for 25-35 min;
s22, firstly placing the template obtained in the S21 on a spin coater, vacuum adsorbing and fixing, then dripping 1-6 mL of imprintable medium on the pattern of the template, then spin-coating at a low speed of 400-600 rpm for 4-6S, spin-coating at a high speed of 2000-600 rpm for 50-70S, and baking at 100-180 ℃ for 1-3 min after spin-coating is completed;
s23, firstly placing the inorganic medium substrate on a spin coater, carrying out vacuum adsorption and fixation, then dripping 1-2 mL of tackifier on the surface of the inorganic medium substrate, then carrying out low-speed spin coating for 4-6S at 400-600 rpm, then carrying out high-speed spin coating for 50-70S at 2000-600 rpm, and after spin coating is completed, baking for 1-3 min at 100-180 ℃;
s24, firstly mounting the template obtained in the S22 on an embossing machine, then mounting the inorganic medium substrate obtained in the S23 on an embossable medium, then applying 100-1000N pressure on the embossing machine, and performing 365nm UV light curing under the protection of nitrogen, wherein the curing energy is 300-600 mJ/cm2 Demolding along the gap between the template and the inorganic medium substrate after ultraviolet curing is completed, so that the imprintable medium is transferred onto the inorganic medium substrate;
s25, detecting the thickness of the residual adhesive at the bottom of the non-structural area of the imprintable medium or the thinnest groove on the longitudinal section by using an ellipsometer, and obtaining the thickness d of the residual adhesive on the minimum duty ratio partition.
Most further, in the step S2, the release agent is 1H, 2H-perfluorooctyl trichlorosilane, and the tackifier is AP3000 tackifier.
Further, in the step S3, the etching condition is controlled to be CHF3 10~40sccm，SF6 0~20sccm O2 0~100sccm，ICP Power 100~300W，Bias Power 0~100W。
Further, in the step S3, further etching the inorganic dielectric substrate after etching the resist layer to form a diffraction grating on the surface of the inorganic dielectric substrate.
And most further, in the step S3, the following steps are included,
s31, etching the imprintable medium and the inorganic medium substrate obtained in the S2 synchronously and in a partition mode by using ICP etching equipment, and etching the imprintable medium integrally downwards to a certain depth by using oxygen to expose the inorganic medium substrate at the bottom of the groove, so that the next pattern transfer etching is facilitated, and the etching conditions are ICP Power 200W, bias 0, O2 60sccm；
S32, continuing to etch the surface of the inorganic medium substrate to form a diffraction grating on the surface of the inorganic medium substrate, wherein the etching rate of the inorganic medium is 5.4nm/S, and the etching condition is CHF3 40sccm，SF6 10sccm O2 0sccm，ICP Power 300W，Bias Power 150W；
S33, etching the residual adhesive completely by using a plasma etching machine under the etching condition of O2 80sccm，Power 300W，10min。
In summary, the beneficial technical effects of the invention are as follows:
1. the problem of inconsistent thickness of residual glue caused by glue swallowing amount causes the follow-up residual glue removing and etching process to become extremely complex, so the invention solves the problem of inconsistent thickness of residual glue in the process of the traditional imprinting, rotating and etching by a method of compensating a template structure based on the defects of the traditional nanometer imprinting, diffracting and optical element and imprinting, and can control the thickness of the residual glue layer of all areas to be consistent;
2. according to the invention, according to different duty ratios of different structural areas of the target diffraction optical element and different groove volume ratios of different structural areas, the grating height is lower in the area with small duty ratio and the grating height is higher in the area with large duty ratio by keeping the glue-swallowing amount of all the raised areas of the template consistent, so that the grating height of the corresponding area of the template is compensated by the speed of etching the residual glue layer, each partition can be etched with the residual glue layer in the etching process of removing the residual glue layer, the line width of the structural area is not changed, the target structure of the target diffraction optical element is ensured to be transferred onto the glass or quartz substrate, and the method can be used as an effective industrialized scheme of the diffraction optical element with high reliability and reliable process route.
Drawings
Fig. 1 is a flowchart of a related art nanoimprint method of the background of the invention.
Fig. 2 is a flow chart of a prior art imprint-transfer etching process method of the background of the invention.
Fig. 3 is a flow chart of the processing method of example 1 of the present invention.
Fig. 4 is a schematic diagram of the structure of a diffraction optical element imprint template of embodiment 2 of the present invention.
FIG. 5 is an electron microscopic image of the diffraction optical element produced by the processing method of example 6 of the present invention.
Detailed Description
The invention will be further described with reference to the drawings and detailed description in order to make the technical means, the creation characteristics, the achievement of the objects and the functions of the invention more clear and easy to understand.
Example 1: referring to fig. 3, a method for manufacturing a diffractive optical element for controlling a thickness of a stub film by a template according to the present invention includes the steps of,
s1, establishing a structural compensation relation between a template and a diffraction optical element, determining the etching rate of a residual adhesive layer and the pattern size of the surface of the template according to the diffraction grating sizes of different areas of the diffraction optical element, and forming the template;
；
w1 ：wn =v1 ：vn ；
wherein t is etching time of the residual adhesive layer, d is thickness of the residual adhesive layer on the minimum duty ratio partition, and w1 、h1 、v1 Diffraction grating line width, template pattern depth and residual glue layer etching rate on minimum duty ratio partition in sequence, wn 、hn 、vn The etching rate of the residual glue layer, which is the line width of the diffraction grating, the depth of the template pattern and the etching rate of the residual glue layer on other subareas, is more than or equal to 2;
s2, imprinting the pattern into the imprintable medium by using the template obtained in the S1, pressing the inorganic medium substrate on the surface of the imprintable medium, solidifying the imprintable medium in an imprinting way, demolding, and detecting the thickness d of the residual adhesive layer on the partition with the minimum duty ratio;
and S3, synchronously etching the imprintable medium obtained in the step S2 in a partition mode according to the etching time and the etching rate obtained in the step S1 so as to simultaneously etch the residual adhesive layer.
Example 2: referring to FIG. 4, a method for manufacturing a diffraction optical element by controlling thickness of a stub film using a template according to the present invention is different from that of example 1 in that it is necessary to manufacture a quartz-based diffraction optical element having three different duty ratios, a period of 400nm, a depth of 200nm, and a line width w1~3 200nm, 150nm and 70nm, respectively. And (3) calculating the volume of the groove, designing and processing a correspondingly compensated silicon substrate template, and performing imprinting-to-etching processing by a method of controlling the thickness consistency of the residual adhesive mask layer through compensation.
Specifically, in S1, the following steps are included,
s11 is based on the line width w of the diffraction grating of the diffraction optical element1~3 And height h1~3 Dividing the diffraction gratings into 3 subareas (A-C areas), and determining the embossing convex line width of the imprintable medium by combining the period of the diffraction optical element, so as to determine that the pattern line width of the surface of the embossing template is 200nm, 250nm and 330nm;
s12, controlling the etching rate v of the residual adhesive layer on the minimum duty ratio partition1~3 The thickness d of the residual adhesive layer on the minimum duty ratio zone is 50nm at 2.5nm/s, 5.5nm/s and 7.4nm/s, thereby obtaining the depth h of the template pattern1~3 150nm, 200nm,428nm;
and S13, patterning by using an electron beam exposure or ultraviolet lithography machine or laser direct writing equipment, transferring the pattern onto a silica substrate by using ion beam etching, and finally removing the electron beam exposure glue or ultraviolet lithography glue to obtain the imprinting template.
Example 3: the method for processing a diffraction optical element by controlling the thickness of a stub film through a template according to the present invention is different from embodiment 2 in that, in S2, it includes the steps of,
s21, placing the imprinting template and an evaporation dish with 1.0mL of 1H, 2H-perfluorooctyl trichlorosilane into a vacuum drying oven, and vacuumizing to 10-4 Stopping pumping air after Pa, and covering the surface of the imprinting template by evaporating the release agent after maintaining for 30 min;
s22, firstly placing the imprinting template obtained in the S21 on a spin coater, vacuum adsorbing and fixing, then dripping 4mL of imprintable medium on the pattern of the imprinting template, then spin-coating at a low speed at 500rpm for 5S, spin-coating at a high speed at 4000rpm for 60S, and baking at 120 ℃ for 2min after spin-coating is completed;
s23, firstly placing an inorganic medium substrate on a spin coater, vacuum adsorbing and fixing, then dripping 1mL of AP3000 tackifier on the surface of the inorganic medium substrate, then spin-coating at a low speed at 500rpm for 5S, spin-coating at a high speed at 4000rpm for 60S, and baking at 120 ℃ for 2min after spin-coating is completed;
s24, firstly mounting the stamping template obtained in the S22 on a stamping machine, then mounting the inorganic medium substrate obtained in the S23 on a stamping medium, then applying 100-1000N pressure on the stamping machine, and performing 365nm UV light curing under the protection of nitrogen, wherein the curing energy is 400mJ/cm2 Demolding along a gap between the imprinting template and the inorganic medium substrate after ultraviolet curing is completed, so that the imprintable medium is transferred to the inorganic medium substrate;
s25, detecting the thickness of the residual adhesive at the bottom of the non-structural area or the longitudinal section of the imprintable medium by using an ellipsometer, and obtaining the thickness d of the residual adhesive on the minimum duty ratio partition.
Example 4: the method for processing a diffraction optical element by controlling the thickness of a stub film through a template according to the present invention is different from embodiment 3 in that, in S2, it includes the steps of,
s21, placing the imprinting template and an evaporation dish with 0.5mL of 1H, 2H-perfluorooctyl trichlorosilane into a vacuum drying oven, and vacuumizing to 10-4 Stopping pumping air after Pa, and covering the surface of the imprinting template by evaporating the release agent after maintaining for 25 min;
s22, firstly placing the imprinting template obtained in the S21 on a spin coater, vacuum adsorbing and fixing, then dripping 1mL of imprintable medium on the pattern of the imprinting template, then spin-coating for 4S at a low speed at 400rpm, spin-coating for 50S at a high speed at 2000rpm, and baking for 1min at 100 ℃ after spin-coating is completed;
s23, firstly placing an inorganic medium substrate on a spin coater, vacuum adsorbing and fixing, then dripping 1mL of AP3000 tackifier on the surface of the inorganic medium substrate, then spin-coating for 4S at a low speed at 400rpm, spin-coating for 50S at a high speed at 2000rpm, and baking for 1min at 100 ℃ after spin-coating is completed;
s24, firstly mounting the stamping template obtained in the S22 on a stamping machine, then mounting the inorganic medium substrate obtained in the S23 on a stamping medium, then applying 100-1000N pressure on the stamping machine, and performing 365nm UV light curing under the protection of nitrogen, wherein the curing energy is 300mJ/cm2 Demolding along a gap between the imprinting template and the inorganic medium substrate after ultraviolet curing is completed, so that the imprintable medium is transferred to the inorganic medium substrate;
s25, detecting the thickness of the residual adhesive at the bottom of the non-structural area or the longitudinal section of the imprintable medium by using an ellipsometer, and obtaining the thickness d of the residual adhesive on the minimum duty ratio partition.
Example 5: the method for processing a diffraction optical element by controlling the thickness of a stub film through a template according to the present invention is different from embodiment 3 in that, in S2, it includes the steps of,
s21 will imprint template and 1H with 1.5mLThe evaporating dish of 1H, 2H-perfluoro octyl trichlorosilane is placed into a vacuum drying box and vacuumized to 10-4 Stopping pumping air after Pa, and covering the surface of the imprinting template by evaporating the release agent after maintaining for 35 min;
s22, firstly placing the imprinting template obtained in the S21 on a spin coater, vacuum adsorbing and fixing, then dripping 6mL of imprintable medium on the pattern of the imprinting template, then spin-coating at a low speed at 600rpm for 6S, spin-coating at a high speed at 6000rpm for 70S, and baking at 180 ℃ for 3min after spin-coating is completed;
s23, firstly placing an inorganic medium substrate on a spin coater, vacuum adsorbing and fixing, then dripping 2mL of AP3000 tackifier on the surface of the inorganic medium substrate, then spin-coating at a low speed at 600rpm for 6S, then spin-coating at a high speed at 6000rpm for 70S, and baking at 180 ℃ for 3min after spin-coating is completed;
s24, firstly mounting the stamping template obtained in S22 on a stamping machine, then mounting the inorganic medium substrate obtained in S23 on a stamping medium, then applying 1000N pressure on the stamping machine, and performing 365nm UV light curing under the protection of nitrogen, wherein the curing energy is 600mJ/cm2 Demolding along a gap between the imprinting template and the inorganic medium substrate after ultraviolet curing is completed, so that the imprintable medium is transferred to the inorganic medium substrate;
s25, detecting the thickness of the residual adhesive at the bottom of the non-structural area or the longitudinal section of the imprintable medium by using an ellipsometer, and obtaining the thickness d of the residual adhesive on the minimum duty ratio partition.
Example 6: the method for processing a diffraction optical element by controlling the thickness of a stub film through a template according to the present invention is different from embodiment 3 in that, in S3, it includes the steps of,
s31, etching the imprintable medium and the inorganic medium substrate obtained in the S2 synchronously and in a partition mode by using ICP etching equipment, and etching the imprintable medium integrally downwards to a certain depth by using oxygen to expose the inorganic medium substrate at the bottom of the groove, so that the next pattern transfer etching is facilitated, and the etching conditions are ICP Power 200W, bias 0, O2 60sccm；
S32 continuing to etch the surface of the inorganic dielectric substrate to form a diffraction grating on the surface of the inorganic dielectric substrate,the etching rate of the inorganic medium is 5.4nm/s, and the etching condition is CHF3 40sccm，SF6 10sccm O2 0sccm，ICP Power 300W，Bias Power 150W；
S33, etching the residual adhesive completely by using a plasma etching machine under the etching condition of O2 80sccm，Power 300W，10min；
S34, structural information is tested by using detection equipment such as SEM (scanning electron microscope) or confocal lens, and the consistency with the target structure is confirmed to be very good as shown in FIG. 5.
Finally, it is noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the technical solution of the present invention, which is intended to be covered by the scope of the claims of the present invention.