CN101165514A - Process for preparing high density inorganic material grating - Google Patents

Abstract

The method comprises: in the first, using sensitization sol-gel method to prepare the sensitization film; using laser interference method to prepare the high density grating, and combining the heat treatment technique to get the inorganic film grating; using chemical etching method to improve the depth-width ratio; finally making surface-gilding process for the grating.

Description

A kind of preparation method of high-density inorganic material grating

technical field

The invention belongs to the field of optical technology, and relates to a preparation method of a high-density inorganic material grating, in particular to a preparation method of an inorganic material grating combined with a laser interference method and a chemical etching method.

Background technique

High-density grating is an important optical component in micro-optics. It can be widely used in spectroscopy, metrology, integrated optics, information processing and optical communication. It plays an important role in improving the resolution and integration of optical components. significance.

At present, there are many methods for preparing high-density gratings. Traditional methods include mechanical scribing and chemical etching. These methods generally have low precision and are difficult to prepare sub-micron high-density gratings. With the development of new organic photosensitive materials, combined with laser interference technology, great progress has been made in the preparation of submicron gratings. However, organic gratings are limited in terms of corrosion resistance, radiation resistance, and aging resistance, and there are still some problems to be solved in practical applications. Compared with organic materials, inorganic material gratings have obvious advantages in terms of corrosion resistance, radiation resistance, and stability.

At present, inorganic material gratings can be successfully prepared by ion etching or femtosecond laser etching, but these methods themselves are technically difficult, costly, and the process lasts for a long time, and the prepared gratings have poor edge regularity.

In order to reduce costs, some scholars have researched and developed some microfabrication methods based on sol-gel technology, such as nano-imprint lithography and softlithography. Or capillary phenomenon combined with heat treatment process to prepare sub-micron inorganic grating, the prepared grating area is small, and it is easy to cause deformation and distortion of the pattern during the demoulding process.

The photosensitive sol-gel method is another microfabrication method based on the sol-gel process. This method synthesizes organic-inorganic composite photosensitive materials by adding some diketone photosensitizers during the preparation process of the sol, and combines laser interference technology The submicron-scale inorganic grating that is difficult to obtain by traditional methods can be prepared, which greatly improves the lifespan and application range of the grating. However, the current problem of this method is that the groove depth of the prepared grating is very small, resulting in a small aspect ratio, so the diffraction efficiency of the prepared grating is very low, and it is difficult to meet the practical requirements.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a high-density inorganic material grating. Based on the photosensitive sol-gel method, the laser interference method and the chemical etching method are combined to prepare a high-density inorganic material grating with high diffraction efficiency.

The technical solution adopted in the present invention is that a preparation method of a high-density inorganic material grating is carried out according to the following steps,

a. Preparation of photosensitive film by photosensitive sol-gel method

Using metal compounds, ketones or diketones as raw materials, a sol-gel method is used to prepare a gel film containing a metal chelate with UV sensitivity, and the gel film is coated by pulling, spin coating, etc. on a silicon substrate;

b. Prepare high-density gratings by laser interferometry and convert them into inorganic material gratings

Using an ultraviolet laser as a light source, two beams of parallel light that meet the interference conditions are irradiated on the surface of the photosensitive gel film obtained in step a at the same angle to produce interference fringes. After interference exposure, the gel film and the substrate are immersed in an organic solvent In , the non-illuminated area is completely dissolved in the organic solvent, and the illuminated area is retained, thereby obtaining a gel film grating;

Further, in the atmospheric environment, heat-treat the gel film grating to convert it into an inorganic material grating;

c. Chemical etching of inorganic material grating

Prepare an anisotropic chemical etchant for silicon, stir until clear, immerse the inorganic material grating obtained in the previous step into the etchant, and etch in ultrasonic waves to obtain a silicon groove grating whose surface is covered by an inorganic material film;

d. The surface of the grating etched in the previous step is gold-plated to complete the preparation process.

Based on the photosensitive sol-gel method, the present invention combines the laser interference method and the chemical etching method. First, the laser interference method is used to prepare a high-density inorganic grating, and then the chemical etching is carried out by using the etching rate difference between the grating material and the substrate. Etching to increase the groove thickness of the grating and improve its diffraction efficiency. The invention combines the advantages of the laser interference method and the chemical etching method, can prepare inorganic material gratings with high density and high diffraction efficiency, has simple process and low cost, and is of great significance for the practical application of high-density gratings.

Description of drawings

Fig. 1 is the schematic diagram of the process of preparing high-density grating by the method of the present invention;

Fig. 2 is a schematic flow chart of preparing a high-density grating by laser interferometry;

Fig. 3 is an atomic force (AFM) scanning photo of high-density inorganic thin film grating etching, wherein a is an AFM three-dimensional scanning photo, and b is a cross-sectional profile scanning photo along the line ab drawn in a.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

The invention relates to a method for preparing a high-density inorganic material grating. Firstly, a photosensitive sol-gel method is used to prepare a photosensitive film, and then a laser interference method is used to prepare a high-density grating. Combined with a heat treatment process, an inorganic thin film grating is obtained, and then a chemical etching method is used to improve The aspect ratio of the grating, and finally the surface of the grating is gold-plated. As shown in Figure 1, the specific steps are as follows:

a. Preparation of photosensitive film by photosensitive sol-gel method

Using metal compounds as starting materials, adding ketones or diketones such as phenylacetone, using the sol-gel method to prepare a gel film containing metal chelates with UV sensitivity, by pulling, spin coating and other methods Spread the gel film on the silicon substrate.

b. Preparation of high-density gratings by laser interferometry

As shown in Figure 2, the ultraviolet laser is used as the light source, and the ultraviolet light emitted by the laser is reflected, beam-splitting, beam-expanding, parallel and other optical path designs, so that two beams of parallel light that meet the interference conditions are irradiated at the same angle to the photosensitizer obtained in step a. The surface of the gel film to produce interference fringes, after interference exposure, the gel film and the substrate are immersed in an organic solvent, the unirradiated area is completely dissolved in ethanol, and the illuminated area is retained, thereby obtaining the gel film grating;

Further, the gel thin film grating is heat-treated at a certain temperature for 10 minutes to 30 minutes in an atmospheric environment to transform it into an inorganic material grating.

c. Chemical etching of inorganic material grating

Prepare an anisotropic chemical etchant for silicon, such as iodine-saturated KOH aqueous solution, tetramethylammonium hydroxide, etc., stir until clear, immerse the inorganic material grating obtained in the previous step in the etchant, and etch in ultrasonic waves , to obtain a silicon groove grating whose surface is covered by a thin film of inorganic material, as shown in Fig. 3a, b. The groove thickness of the grating is increased, and the aspect ratio of the grating is improved.

d. The surface of the grating etched in the previous step is gold-plated to improve the reflectivity and smoothness of the grating surface, thereby effectively improving the diffraction efficiency of the grating.

Example 1

In a glove box with a relative humidity of less than 30%, dissolve zirconium tetrabutoxide (Zr(OC ₄ H ₉ ) ₄ , ZiroconiumTetra-n-Butoxide: Zr(O-nBu) ₄ into absolute ethanol (C ₂ H ₅ OH :EtOH), then add chemical modifier benzoylacetone (C ₆ H ₅ COCH ₂ COCH ₃ , Benzoylacetone: BzAc), after sealing, fully stir on a magnetic stirrer to make BzAc and Zr(O-nBu) ₄ chelate react to form a sol with a zirconium-containing chelate, and the molar ratio of each effectively added raw material in the solution is Zr(O-nBu) ₄ :BzAc:EtOH=1:1:40.

The (100) silicon substrate is pretreated in a certain HF solution to remove the oxide layer on the surface. Then, using the sol prepared by the above method, a gel film is prepared on the substrate by dipping and pulling method.

The obtained gel film is subjected to ultraviolet laser interference irradiation, that is, the ultraviolet light emitted by the laser is reflected, beam-splittered, beam-expanded, and parallelized to make two beams of coherent light incident on the sample surface at a certain angle (9.352°). and interfere. The sample after interference exposure was immersed in absolute ethanol for about 1 min, and the part that was not exposed to light was dissolved in ethanol, while the part that was exposed to light remained, forming a gel film grating with a period of 1 μm. Further, heat treatment at 600° C. for 20 minutes in the air environment, the organic matter volatilized, and the thin film crystallized to obtain a ZrO ₂ ceramic thin film grating with an aspect ratio of 0.04, and the diffraction efficiency of the grating was about 0.80%.

Using KOH as raw material and deionized water as solvent, a 35% KOH solution is prepared. Add _I2 and KI at a molar ratio of 1:2 so that the solubility of _I2 in 35% KOH solution is 0.0002 mol/ml. Stir the prepared KOH etchant until it becomes clear, and heat it to 70°C in an ultrasonic wave. The heat-treated inorganic ZrO ₂ grating was immersed in the etchant, and etched by ultrasonic vibration for 2 min. After etching, a ZrO ₂ /Si composite grating with a trench depth of 400 nm and an aspect ratio of 0.4 was obtained, and the diffraction efficiency of the grating was 7.50%. The surface of the grating is then plated with gold, and when the thickness of the gold layer reaches 640nm, the diffraction efficiency of the grating increases to 44.55%.

Example 2

Prepare a photosensitive film and a gel film grating according to the steps in Example 1; heat-treat the gel film grating at a temperature of 500° C. for 30 minutes to convert it into an inorganic material grating; immerse the inorganic material grating into the etchant configured in Example 1 In the process, it is heated to 100°C in ultrasonic waves and etched to obtain a silicon groove grating whose surface is covered by a thin film of inorganic materials. Finally, the etched grating is treated with gold, and the diffraction efficiency of the grating is increased to 45%.

Example 3

Prepare a photosensitive film and a gel film grating according to the steps in Example 1; heat-treat the gel film grating at a temperature of 800° C. for 10 minutes to convert it into an inorganic material grating; immerse the inorganic material grating into the etchant configured in Example 1 In the process, it is heated to 50°C in ultrasonic waves and etched to obtain a silicon groove grating whose surface is covered by a thin film of inorganic materials. Finally, the etched grating is treated with gold, and the diffraction efficiency of the grating is increased to 44%.

Example 4

Dissolve aluminum n-butoxide (Al(O-sec-Bu) ₃ : Aluminum sec-Butoxide) in isopropanol ((CH ₃ ) ₂ CHOH:i-PrOH) in a glove box with a relative humidity of less than 30%. , then add chemical modifier benzoylacetone (C ₆ H ₅ COCH ₂ COCH ₃ , Benzoylacetone: BzAc), after sealing, fully stir on a magnetic stirrer to make BzAc and Al(O-sec-Bu) ₃ chelate reaction , forming a sol with an aluminum-containing chelate, and the molar ratio of each effectively added raw material in the solution is Al(O-sec-Bu) ₃ :BzAc:i-PrOH=1:0.5:30.

The sol prepared by the above method was used to prepare the gel film on the (100) silicon substrate pretreated by HF solution by dipping and pulling method.

The obtained gel film is subjected to ultraviolet laser interference irradiation, that is, the ultraviolet light emitted by the laser is reflected, beam-splittered, beam-expanded, and parallelized to make two beams of coherent light incident on the sample surface at a certain angle (9.352°). and interfere. The sample after interference exposure was immersed in absolute ethanol for about 1 min, and the part that was not exposed to light was dissolved in ethanol, while the part that was exposed to light remained, forming a gel film grating with a period of 1 μm. Further, heat treatment at 500° C. for 20 minutes in the air environment, the organic matter volatilized, the thin film crystallized, and the Al ₂ O ₃ ceramic thin film grating was obtained.

Using KOH as raw material and deionized water as solvent, a 35% KOH solution is prepared. Add _I2 and KI at a molar ratio of 1:2 so that the solubility of _I2 in 35% KOH solution is 0.0002 mol/ml. Stir the prepared KOH etchant until it becomes clear, and heat it to 70°C in an ultrasonic wave. The heat-treated inorganic Al ₂ O ₃ grating was immersed in the etchant, and ultrasonically oscillatingly etched for 2 minutes to obtain the Al ₂ O ₃ /Si composite grating after etching. The surface of the grating is gold-plated, and its diffraction efficiency can reach 45%.

Example 5

Dissolve zirconium oxychloride (ZrOCl ₂ ·8H ₂ O Ziroconium Oxychloride) in absolute ethanol (C ₂ H ₅ OH:EtOH), then add chemical modifier benzoylacetone (C ₆ H ₅ COCH ₂ COCH ₃ , Benzoylacetone : BzAc), fully stirred on a magnetic stirrer after sealing, so that BzAc and ZrOCl ₂ 8H ₂ O undergo a chelation reaction to form a sol with a zirconium-containing chelate, and the molar ratio of each effectively added raw material in the solution is ZrOCl ₂ · 8H ₂ O:BzAc:EtOH=1:1:40.

The (100) silicon substrate is pretreated in a certain HF solution to remove the oxide layer on the surface. Then, using the sol prepared by the above method, a gel film is prepared on the substrate by dipping and pulling method.

The obtained gel film is subjected to ultraviolet laser interference irradiation, that is, the ultraviolet light emitted by the laser is reflected, beam-splittered, beam-expanded, and parallelized to make two beams of coherent light incident on the sample surface at a certain angle (9.352°). and interfere. The sample after interference exposure was immersed in absolute ethanol for about 1 min, and the part that was not exposed to light was dissolved in ethanol, while the part that was exposed to light remained, forming a gel film grating with a period of 1 μm. Further, heat treatment at 600° C. for 20 minutes in the atmosphere environment, the organic matter volatilizes, and the thin film crystallizes to obtain a ZrO ₂ ceramic thin film grating, and the diffraction efficiency of the grating is about 0.80%.

Using KOH as raw material and deionized water as solvent, a 35% KOH solution is prepared. Add _I2 and KI at a molar ratio of 1:2 so that the solubility of _I2 in 35% KOH solution is 0.0002 mol/ml. Stir the prepared KOH etchant until it becomes clear, and heat it to 70°C in an ultrasonic wave. The heat-treated inorganic ZrO ₂ grating is immersed in the etchant, and ultrasonically oscillated for 2 minutes to obtain a ZrO ₂ /Si composite grating. The surface of the grating is then gold-plated, and the diffraction efficiency of the grating is increased to 44%.

Example 6

In a glove box with a relative humidity of less than 30%, dissolve zirconium tetrabutoxide (Zr(OC ₄ H ₉ ) ₄ , ZiroconiumTetra-n-Butoxide: Zr(O-nBu) ₄ into absolute ethanol (C ₂ H ₅ OH : EtOH), then add chemical modifier acetylacetone (CH ₃ COCH ₂ COCH ₃ , Acetylacetone: AcAc), after sealing, fully stir on a magnetic stirrer, so that AzAc and Zr (OC ₄ H ₉ ) ₄ chelation reaction, A sol with a zirconium-containing chelate is formed, and the molar ratio of each effectively added raw material in the solution is Zr(OC ₄ H ₉ ) ₄ :AzAc:EtOH=1:1:40.

The sol prepared by the above method was used to prepare the gel film on the (100) silicon substrate pretreated by HF solution by dipping and pulling method.

The obtained gel film is subjected to ultraviolet laser interference irradiation, that is, the ultraviolet light emitted by the laser is reflected, beam-splittered, beam-expanded, and parallelized to make two beams of coherent light incident on the sample surface at a certain angle (9.352°). and interfere. The sample after interference exposure was immersed in absolute ethanol for about 1 min, and the part that was not exposed to light was dissolved in ethanol, while the part that was exposed to light remained, forming a gel film grating with a period of 1 μm. Further, heat treatment at 600° C. for 20 minutes in the air environment, the organic matter volatilizes, the thin film crystallizes, and a ZrO ₂ ceramic thin film grating is obtained.

Using KOH as raw material and deionized water as solvent, a 35% KOH solution is prepared. Add _I2 and KI at a molar ratio of 1:2 so that the solubility of _I2 in 35% KOH solution is 0.0002 mol/ml. Stir the prepared KOH etchant until it becomes clear, and heat it to 70°C in an ultrasonic wave. The heat-treated inorganic ZrO ₂ grid is immersed in the etchant, etched by ultrasonic vibration for 2 minutes, and the ZrO ₂ /Si composite grating is obtained after etching. The surface of the grating is gold-plated, and its diffraction efficiency can reach 45%.

Example 7

In a glove box with a relative humidity of less than 30%, dissolve zirconium tetrabutoxide (Zr(OC ₄ H ₉ ) ₄ , ZiroconiumTetra-n-Butoxide: Zr(O-nBu) ₄ into absolute ethanol (C ₂ H ₅ OH :EtOH), then add chemical modifier benzoylacetone (C ₆ H ₅ COCH ₂ COCH ₃ , Benzoylacetone: BzAc), after sealing, fully stir on a magnetic stirrer to make BzAc and Zr(O-nBu) ₄ chelate react to form a sol with a zirconium-containing chelate, and the molar ratio of each effectively added raw material in the solution is Zr(O-nBu) ₄ :BzAc:EtOH=1:1:40.

The (100) silicon substrate is pretreated in a certain HF solution to remove the oxide layer on the surface. Then, using the sol prepared by the above method, a gel film is prepared on the substrate by dipping and pulling method.

The obtained gel film is subjected to ultraviolet laser interference irradiation, that is, the ultraviolet light emitted by the laser is reflected, beam-splittered, beam-expanded, and parallelized to make two beams of coherent light incident on the sample surface at a certain angle (9.352°). and interfere. The sample after interference exposure was immersed in absolute ethanol for about 1 min, and the part that was not exposed to light was dissolved in ethanol, while the part that was exposed to light remained, forming a gel film grating with a period of 1 μm. Further, the grating was heat-treated at 400° C. for 20 minutes in an atmospheric environment.

Using tetramethylammonium hydroxide as raw material and deionized water as solvent, prepare 7% THAM solution. Stir the prepared TMAH etchant until it becomes clear, and heat it to 80°C in an ultrasonic wave. The heat-treated ZrO ₂ grating was immersed in the etchant and etched by ultrasonic vibration for 5 min. The ZrO ₂ /Si composite grating is obtained after etching, and the surface of the grating is plated with gold, so that the diffraction efficiency of the grating is increased to 44%.

The method of the present invention is based on the photosensitive sol-gel method, effectively combines the laser interference method and the chemical etching method, and uses the anisotropic etchant of silicon to perform wet chemical etching on the inorganic grating, thereby increasing the aspect ratio of the grating , so that the diffraction efficiency of the grating is effectively improved, and an inorganic material grating with high diffraction efficiency is obtained by performing gold-plating treatment on the surface of the etched grating. The method can obtain a high-performance inorganic material grating, has simple process and low cost, and has great significance for realizing the practical application of the inorganic material grating.

Claims (1)

1. a preparation method of high-density inorganic material grating, is characterized in that, the method is carried out according to the following steps, a. Preparation of photosensitive film by photosensitive sol-gel method Using metal compounds, ketones or diketones as raw materials, a sol-gel method is used to prepare a gel film containing a metal chelate with UV sensitivity, and the gel film is coated by pulling, spin coating, etc. on a silicon substrate; b. Prepare high-density gratings by laser interferometry and convert them into inorganic material gratings Using an ultraviolet laser as a light source, two beams of parallel light that meet the interference conditions are irradiated on the surface of the photosensitive gel film obtained in step a at the same angle to produce interference fringes. After interference exposure, the gel film and the substrate are immersed in an organic solvent In , the non-illuminated area is completely dissolved in the organic solvent, and the illuminated area is retained, thereby obtaining a gel film grating; Further, in the atmospheric environment, heat-treat the gel film grating to convert it into an inorganic material grating; c. Chemical etching of inorganic material grating Prepare an anisotropic chemical etchant for silicon, stir until clear, immerse the inorganic material grating obtained in the previous step into the etchant, and etch in ultrasonic waves to obtain a silicon groove grating whose surface is covered by an inorganic material film; d. The surface of the grating etched in the previous step is gold-plated to complete the preparation process.

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