WO2020119469A1

WO2020119469A1 - Processing device and processing method for toroidal gratings

Info

Publication number: WO2020119469A1
Application number: PCT/CN2019/121596
Authority: WO
Inventors: 林慧; 陈垚鑫; 赖厚湖; 马翠; 余明; 陈世祈
Original assignee: 深圳先进技术研究院
Priority date: 2018-12-12
Filing date: 2019-11-28
Publication date: 2020-06-18
Also published as: CN109709636A

Abstract

Disclosed are a processing device and processing method for toroidal gratings. The method comprises the following steps: manufacturing a PDMS soft template, arranging the soft template in a coining cavity (2), precisely controlling the air pressure of the upper and lower separate cavities (3,4) of the PDMS soft template, using the pressure difference between the upper and lower separate cavities to coin the PDMS soft template to form toroidal gratings, and using the method of regulating multiple process parameters such as the pressure difference, the distance between template substrates, and the substrate tilt angle to realize a high efficient and precise manufacture of toroidal gratings.

Description

Processing device and processing method for curved grating

Technical field

The invention relates to a grating processing device and a processing method, in particular to a curved surface grating processing device and a processing method.

Background technique

Gratings are the core components of spectroscopic instruments. According to the surface type classification of the grating substrate, it can be divided into planar gratings and curved gratings. Typical curved gratings include concave gratings, convex gratings and cylindrical gratings. Compared with ordinary planar gratings, curved gratings integrate the spectral characteristics of gratings and the focusing characteristics of curved optical components. Replacing the optical path combination of the planar grating and the curved lens/reflector with a curved grating can reduce the number of components in the spectroscopic instrument, thereby simplifying the optical path and improving the integration and stability of the instrument. Therefore, curved gratings play an indispensable role in miniature spectrometers and imaging spectrometers.

Traditional planar gratings are all equidistant, and their manufacturing process is quite mature. For curved gratings, the pitch of the grating lines often needs to be changed according to certain rules, so as to achieve the purpose of aberration correction, but this also increases the difficulty of making curved gratings.

For the manufacturing process of curved gratings, the main existing methods are mechanical scribing, direct writing and holographic methods, but these methods have the disadvantages of low efficiency and high cost.

The mechanical scribing method is to use a diamond tool to process grating lines on the substrate under the control of a precision machine tool. The mechanical scribing method relies on high-precision equipment and harsh working environment. The processing efficiency is very low and the cost is high. It is only suitable for processing master gratings. The processing of variable pitch gratings on curved substrates undoubtedly puts forward higher requirements for the motion control system of the scribing machine.

The direct writing technology includes laser direct writing, electron beam direct writing, focused ion beam direct writing, etc., that is, scanning and exposing the corresponding resist with a laser beam, an electron beam, or an ion beam, thereby obtaining a grating micro-nano structure. By increasing the number of degrees of freedom of the substrate worktable, the production of curved gratings can be achieved. The direct writing technology can achieve high preparation accuracy, but requires complicated and expensive equipment, and has low processing efficiency. Generally, it can only be used for the preparation of high-precision grating masks and the like, and it is difficult to apply it to batch processing and production.

The holographic method uses two beams of coherent light to form an interference field in the photoresist on the curved substrate. After exposure and development, a photoresist grating can be obtained, and then the grating structure can be transferred to the curved substrate by ion beam etching. The exposure and development process of the holographic method is more convenient and efficient. It is easy to realize the variable pitch by adjusting the interference field, but the etching process is still relatively time-consuming and expensive.

The prior art CN101221358A discloses a method for processing a multi-phase micro-optical element on a curved substrate based on a flexible ultraviolet stamper. This solution proposes a method of transferring a micro-nano pattern to a curved substrate using a flexible template. The advantage of low cost. However, this plan is only a rough conceptual plan, and it does not elaborate on the production of curved variable pitch gratings, nor does it carry out comprehensive analysis and in-depth exploration from the perspectives of device design, process control, and processing equipment, and truly solve the core of curved grating production. technical problem.

Summary of the invention

The purpose of the present invention is to provide a manufacturing apparatus and manufacturing method of a curved surface grating, which solves the problems in the existing manufacturing method of curved surface gratings that the manufacturing process is complicated, the processing cycle is long, and the processing equipment is expensive. The invention utilizes ultraviolet nanoimprint technology, adopts polydimethylsiloxane soft template (PDMS), and realizes high-efficiency and low-cost production of curved gratings with the aid of air pressure assisted pressure technology.

To achieve the above objectives, the present invention adopts the following technical solutions:

A curved grating processing device includes an imprinting cavity, a control gas path and an ultraviolet light source, a PDMS soft template is provided in the middle of the imprinting cavity, and the PDMS soft template divides the imprinting cavity into two upper and lower compartments. The gas path is respectively connected to the upper and lower compartments and precisely controls the air pressure in the two compartments. The bottom of the lower compartment is provided with a base fixture. The curved substrate used for processing the curved grating is set on the upper surface of the base fixture and the base fixture The height of the surface and its angle of inclination to the horizontal are adjustable.

The middle of the imprinting cavity is provided with a PDMS soft template installation position, and the PDMS soft template is sealingly arranged on the PDMS soft template installation position.

The control gas circuit includes an air pipe communicating with the upper and lower compartments, a vacuum pump, a solenoid valve and a barometer arranged on the gas pipe, and the air pressure in the upper and lower compartments is accurately controlled by the solenoid valve and the barometer.

The ultraviolet light source is arranged in the upper center of the upper compartment, and the imprinting cavity is arranged in an ultraviolet protection box.

A method for processing a curved grating using the above device is characterized in that it includes the following steps:

1) Preparation of PDMS soft template;

2) PDMS soft template installation and pretreatment;

3) Embossing;

4) Demoulding.

Furthermore, the preparation of the PDMS soft template includes the following steps:

1a) Embed a commercial flat equidistant grating in a grating fixture as a copy template;

1b) The mixture of PDMS prepolymer and cross-linking agent is spin-coated on the replication template multiple times, and a thin round iron ring is embedded on the edge, and the PDMS soft template is obtained after curing.

Furthermore, the installation and pretreatment of the PDMS soft template means that the PDMS soft template is installed in the imprinting cavity in the curved grating processing device described above, and at the same time, the curved substrate is spin-coated and pre-cured by ultraviolet curing glue, and the substrate fixture is adjusted The height of the upper surface and its inclination with the horizontal plane to the set value.

Furthermore, the imprinting includes the following steps:

3a) Vacuuming the upper and lower compartments;

3b) After the upper and lower compartments reach the set air pressure, keep the air pressure in the upper compartment unchanged and reduce the air pressure in the lower compartment. The pressure difference between the upper and lower compartments causes the PDMS flexible membrane to bend and deform downward, and then contact the curved base The UV curable adhesive on the surface of the curved substrate is filled into the voids of the micro-nano structure of the PDMS soft template under the action of imprinting force and capillary force, and the ultraviolet light source is turned on for curing.

The demolding means that when the preset imprint time is reached, the air pressure of the upper cavity is reduced until the PDMS soft template rebounds to its original position, completing the entire imprint process.

Furthermore, before the preparation of the PDMS soft template, a step of curved grating design is included.

The uniqueness of the present invention:

1) The process idea of the plane equally spaced grating to the curved surface variable space grating: firstly, the micro-nano structure of the plane equally spaced grating is transferred to the PDMS soft template through the replication technology, and then the soft template is used by the ultraviolet nanoimprint technology Controllable deformation can realize the controlled change of the spacing, and complete the production of the curved surface variable pitch grating. Soft template preparation and nano-imprinting are one-time molding, the process is simple and efficient; the entire process does not need to rely on expensive equipment, and the planar equal-spaced grating as the mother board can directly use mature commercial products with low process cost;

2) The imprinting device provides the imprinting force required for imprinting based on gas-assisted pressure application, ensuring the uniformity of the imprinting force. Compared with the conventional atmospheric pressure imprinting device, the air pressure of the upper and lower compartments of the processing device of this solution can be independently and accurately controlled, which ensures the accuracy of the imprinting force and does not cause deviations due to atmospheric fluctuations; The body is isolated from the external environment, plus the vacuum treatment before the imprinting starts, the small particles of impurities that may remain in the cavity are discharged, providing a clean imprinting environment, ensuring the final imprinting quality .

3) The grating parameters are optimized by adjusting the embossing force (the pressure difference between the upper and lower compartments), the distance between the PDMS soft template and the curved substrate, and the inclination angle of the curved substrate. Precise control.

4) Flexible selection of grating groove shape can be realized. The groove shape of the grating depends on the groove shape of the plane grating master. Therefore, different plane grating masters can be selected according to the application requirements, and various grating groove shapes can be flexibly produced. Common ones are zigzag, rectangle, sine, etc.

BRIEF DESCRIPTION

The present invention is further described below with reference to the drawings:

1 is a schematic structural diagram of a curved grating processing device according to the present invention;

2 is a schematic diagram of the installation of a PDMS soft template in the method for processing a curved grating according to the present invention;

3 is a schematic view of the state of the surface grating processing method of the present invention when vacuuming is performed;

4 is a schematic view of the state when imprinting is performed in the curved grating processing method of the present invention;

FIG. 5 is a schematic diagram of the state when demolding is performed in the curved grating processing method of the present invention; FIG.

6 is a schematic diagram of the structure of a curved grating;

7 is a schematic diagram of the structure of a commercial planar equidistant grating used in the preparation of a PDMS soft template;

FIG. 8 is a schematic diagram of the appearance of the completed PDMS soft template.

detailed description

The present invention will be further described in detail below through specific examples, but the embodiments of the present invention are not limited thereto.

The invention provides a processing device for a curved grating, whose structure is shown in FIG. 1 and includes an imprinting cavity 2, a control gas path and an ultraviolet light source 9, and a PDMS (polydimethyl silicon) is provided in the middle of the imprinting cavity 2 Oxygen) soft template installation position 5, PDMS soft template installation position 5 is used to install PDMS soft template 6, PDMS soft template 6 is installed on PDMS soft template installation position 5, the imprinting cavity 2 is divided into upper compartment 3 and The two compartments of the lower compartment 4 are sealed between the PDMS soft template 6 and the PDMS soft template installation position 5, so that the upper compartment 3 and the lower compartment 4 are two independent sealed cavities, the upper compartment 3 and the lower compartment 4 are respectively communicated with the control air circuit, the control air circuit includes an air pipe communicating with the upper and lower compartments and a vacuum pump 31, a solenoid valve 32 and a barometer 33 provided on the air pipe, the vacuum pump 31 can be separated by the air pipe The chamber 3 and the lower compartment 4 are evacuated, and the solenoid valve 32 and the barometer 33 provided on the trachea can realize real-time monitoring and precise control of the air pressure in the upper compartment 3 and the lower compartment 4.

A base clamp 8 is provided in the center of the bottom of the lower compartment 4. The height of the upper surface of the base clamp 8 and the angle of inclination relative to the horizontal plane are adjustable. On the upper surface of the base clamp 8 is a curved substrate 7 for processing curved gratings.

The entire imprinting cavity 2 is set in the ultraviolet protection box 1, and the ultraviolet light source 4 is installed in the center of the top of the ultraviolet protection box 1. The UV protection box protects the experimenter from ultraviolet light during the experiment.

The invention also provides a method for processing a curved surface grating. The method uses the above-mentioned curved surface grating processing device, and specifically includes the following steps:

The first step is to design curved gratings: for curved gratings with aberration correction, it is necessary to design the grating line distribution according to the conditions of use. Specifically, as shown in FIG. 6, the grating pitch d changes regularly along the Y direction (perpendicular to the grating line direction), namely

d=d ₀ +d ₁ y+d ₂ y ² +…+d _n y ⁿ

Where d ₀ is the grid line spacing in the center of the substrate, and the following items are variable spacing items. The higher the aberration correction requirement, the more variable pitch terms to consider. In general applications, a good aberration correction effect can be obtained by controlling the first-order term, that is, d=d ₀ +d ₁ y.

The second step is to prepare the PDMS soft template: as shown in FIG. 7, firstly, the commercial flat equidistant grating 21 is embedded in the grating fixture 22 as a copy template. Considering the deformation characteristics of the flexible template, the grid line spacing of the flat grating master must be less than D _{0 of the} surface grating. Then, the mixture of PDMS prepolymer and crosslinking agent is spin-coated on the template multiple times, and a thin round iron ring is embedded on the edge. The main purpose of this is to increase the rigidity of the edge of the soft template, and finally cured A PDMS soft template with equidistant micro-nano structures as shown in FIG. 8 is obtained.

The third step is to use the curved grating processing device for the imprinting operation, which has the following steps:

1) As shown in Fig. 2, install the fabricated PDMS soft template with equipitch micro-nano structure to the middle of the imprinting cavity, and spin-coat UV on the curved substrate 7 (the concave glass substrate in the figure) The adhesive 11 is cured and pre-cured, and then the curved substrate 7 is installed on the substrate jig 8 at the bottom of the lower compartment 4, and the curved substrate 7 is set by adjusting the height of the upper surface of the substrate jig 8 and its inclined angle with the horizontal plane The height (ie, the distance between the PDMS soft template 6 and the curved substrate 7) and the inclination angle;

2) Vacuuming: As shown in Figure 3, the upper compartment 3 and the lower compartment 4 are evacuated at the same time by controlling the air path until the air pressure of the two chambers reaches the preset value, the purpose is to separate the lower compartment Impurities of small particles in the cavity 4 are discharged to ensure a clean imprinting environment, so as not to cause defects on the imprinting surface and affect the quality of imprinting;

3) Embossing: as shown in Fig. 4, keep the air pressure of the upper compartment 3 unchanged, and continue to reduce the air pressure of the lower compartment 4, so that the PDMS soft template 6 will be deformed under the action of the pressure difference, and then with the curved base 7 Contacting and bonding, the ultraviolet curing adhesive 11 on the surface of the curved substrate 7 is filled into the micro-nano structure gap of the PDMS soft template 6 under the action of imprinting force and capillary force, and the ultraviolet light source 9 is turned on for curing at the same time;

4) Demoulding: As shown in FIG. 5, when the preset imprint time is reached, the air pressure of the upper compartment 3 is reduced until the PDMS soft template 6 rebounds to its original position, completing the entire imprint process. In order to ensure the effect of imprinting, avoid contact between the PDMS flexible membrane 6 and the curved substrate 7 during vacuuming and final demolding, and always ensure that the air pressure of the upper compartment 3 is slightly less than or equal to the lower compartment during these two processes 4 barometric pressure.

Since the height of the base fixture 8 and its inclination angle with the horizontal plane are adjustable, by controlling these two parameters and the pressure difference between the upper and lower compartments, the precise adjustment of the grating pitch change can be achieved.

The groove shape of the grating (that is, the shape in the Z direction shown in FIG. 6) depends on the groove shape of the planar grating master. Therefore, different planar grating masters can be selected according to the application requirements, and various grating grooves can be flexibly produced. Common ones are zigzag (shown in the picture), rectangular, sinusoidal, etc.

Through the processing device and processing method of the present invention, a concave variable pitch grating sample has been successfully manufactured. After microscopic morphology testing, the concave grating maintains the sawtooth groove shape of the master plane grating and realizes the regular change of the spacing; its spectral resolution is tested, and the resolution in the visible light band is better than 1.5nm, which verifies its image Difference correction function.

It should be noted that the above-mentioned embodiments are only a part of the preferred embodiments of the present invention, but not all the embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Claims

A curved grating processing device includes an imprinting cavity, a control gas path and an ultraviolet light source, characterized in that a PDMS soft template is provided in the middle of the imprinting cavity, and the PDMS soft template divides the imprinting cavity into two upper and lower parts The compartment, the control air path is respectively connected to the upper and lower compartments and precisely controls the air pressure in the two compartments. The bottom center is provided with a base fixture at the bottom center, and the curved substrate used for processing the curved grating is set on the upper surface of the base fixture The height of the upper surface of the base fixture and its tilt angle with the horizontal plane can be adjusted.
The curved grating processing device according to claim 1, wherein a PDMS soft template mounting position is provided in the middle of the imprinting cavity, and the PDMS soft template sealing is provided on the PDMS soft template mounting position.
The curved grating processing device according to claim 1, wherein the control gas path includes an air pipe communicating with the upper and lower compartments, and a vacuum pump, an electromagnetic valve and a barometer provided on the air pipe. Precisely control the air pressure in the upper and lower compartments.
The curved grating processing device according to claim 1, wherein the ultraviolet light source is disposed in the upper center of the upper compartment, and the imprinting cavity is disposed in an ultraviolet protection box.
A method for processing a curved grating using the device according to claim 1, characterized in that it includes the following steps:

1) Preparation of PDMS soft template;

2) PDMS soft template installation and pretreatment;

3) Embossing;

4) Demoulding.
The method according to claim 5, wherein the preparation of the PDMS soft template includes the following steps:

1a) Embed a commercial flat equidistant grating in a grating fixture as a copy template;

1b) The mixture of PDMS prepolymer and cross-linking agent is spin-coated on the replication template multiple times, and a thin round iron ring is embedded on the edge, and the PDMS soft template is obtained after curing.
The method according to claim 5, characterized in that the installation and pretreatment of the PDMS soft template refers to the installation of the PDMS soft template in the imprinting cavity in the curved grating processing device of claim 1, while aligning the curved substrate Carry out spin coating and pre-curing of the ultraviolet curing adhesive, and adjust the height of the upper surface of the base fixture and its inclination angle with the horizontal plane to the set value.
The method of claim 5, wherein the imprinting includes the following steps:

3a) Vacuuming the upper and lower compartments;

3b) After the upper and lower compartments reach the set air pressure, keep the air pressure in the upper compartment unchanged and reduce the air pressure in the lower compartment. The pressure difference between the upper and lower compartments causes the PDMS soft template to bend and deform downward, and then contact and fit with the curved substrate Under the action of embossing force and capillary force, the ultraviolet curing adhesive on the surface of the curved substrate is filled into the micro-nano structure gap of the PDMS soft template, and the ultraviolet light source is turned on for curing.
The method according to claim 5, wherein the demolding means that when the preset imprint time is reached, the air pressure in the upper cavity is reduced until the PDMS soft template rebounds to its original position, completing the entire press印process.
The method according to claim 5, characterized in that before the preparation of the PDMS soft template, a step of curved grating design is further included.