CN115657181A - Blazed grating and preparation method and application thereof - Google Patents
Blazed grating and preparation method and application thereof Download PDFInfo
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- CN115657181A CN115657181A CN202211326093.8A CN202211326093A CN115657181A CN 115657181 A CN115657181 A CN 115657181A CN 202211326093 A CN202211326093 A CN 202211326093A CN 115657181 A CN115657181 A CN 115657181A
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Abstract
The invention relates to the technical field of grating production, and discloses a blazed grating and a preparation method and application thereof, wherein S1, a silicon wafer is selected: selecting a silicon wafer with higher quality to process to obtain a silicon wafer, S2, oxidizing: placing the silicon wafer obtained in the step (S1) in an oxygen, water vapor or mixed atmosphere of the oxygen and the water vapor at a high temperature (over 900 ℃) for heating through a thermal oxidation technology, enabling oxygen molecules or water molecules to enter an interface between silicon dioxide and the silicon wafer through thermal diffusion, reacting with the silicon wafer to generate the silicon dioxide, and performing photoresist ashing (S3): processing the photoresist of the silicon wafer by adopting a photoresist ashing technology, and transferring the photoresist pattern: the method adopts the wet etching pattern transfer to transfer the pattern of the photoresist grating to the oxide layer, and the novel scheme can successfully manufacture the blazed grating which is close to an ideal sawtooth groove shape by using the oxide layer as a mask for silicon anisotropic etching.
Description
Technical Field
The invention belongs to the technical field of grating production, and particularly relates to a blazed grating and a preparation method and application thereof.
Background
When the grating is carved into the sawtooth-shaped groove section, the light energy of the grating is concentrated on a preset direction, namely a certain spectrum level, when the grating is detected from the direction, the intensity of the spectrum is maximum, the phenomenon is called blaze, the grating is called blazed grating, in the blazed grating carved in the way, the groove surface with the diffraction function is a smooth plane, and an included angle is formed between the groove surface and the surface of the grating, the wavelength corresponding to the maximum light intensity of the blazed angle is called blazed wavelength, and the grating can be suitable for a certain level spectrum of a certain specific wave band through the design of the blazed angle.
Most of existing blazed gratings are etched by a method of depositing a metal layer and then adopting a dry etching technology, the produced grating lines are thick, the requirement on a machine is high, and the steps are troublesome.
Disclosure of Invention
Aiming at the situation, in order to overcome the defects of the prior art, the invention provides the blazed grating and the preparation method and the application thereof, and effectively solves the problems that the existing blazed grating mostly adopts a method of depositing a metal layer and then adopting a dry etching technology to carry out etching, the produced grating lines are thick, the requirement on a machine is high, and the steps are troublesome.
In order to achieve the purpose, the invention provides the following technical scheme: a blazed grating and a preparation method and application thereof comprise the following steps:
s1, selecting a silicon wafer: selecting a high-quality (100) oriented p-doped silicon wafer grown by using a CZ with the resistivity of 1-100 omega-cm as a substrate;
s2, oxide: placing the silicon wafer obtained in the step S1 in an oxygen, water vapor or mixed atmosphere of the oxygen and the water vapor at a high temperature (over 900 ℃) for heating by a thermal oxidation technology, so that oxygen molecules or water molecules enter an interface between silicon dioxide and the silicon wafer through thermal diffusion and react with the silicon wafer to generate the silicon dioxide;
s3, photoresist ashing: processing the photoresist of the silicon wafer by adopting a photoresist ashing technology;
s4, transferring a photoresist pattern: transferring the pattern of the photoresist grating to the oxide layer by wet etching pattern transfer;
s5, anisotropic wet etching: and obtaining a blazed grating groove shape by adopting anisotropic wet etching.
Preferably, the processing of the silicon wafer comprises accurate cutting, silicon wafer polishing, first silicon wafer cleaning, first detection (detection items comprise length, weight, resistivity uniformity, defect, scratch, crack and damage), chamfering, second cleaning, second detection (detection of chamfer radius), lapping, cleaning, chemical corrosion and cleaning spin-drying.
Preferably, the wet etching pattern transfer uses 6 parts of 40% ammonium fluoride aqueous solution of BHF solution formula (volume ratio) 1 part of 49% hydrofluoric acid to soak for 8-12S, and the BHF solution is applied to SiO at room temperature of 22 DEG C 2 The etching rate of (2) is 120nm/min, the time required for etching is determined according to the thickness of the oxide layer, and whether the oxide layer is etched or not is judged.
Preferably, the photoresist ashing method is carried out on a plasma cleaning machine, the photoresist on the substrate is treated by electrons in a high-speed motion state, neutral atoms, molecules and atomic groups (free radicals) in an activated state, ionized atoms and molecules, unreacted molecules and atoms and the like, so as to avoid etching the substrate, the working pressure is 2X 10-2Pa, the time is 20min, and the transverse (aspect ratio) change and the longitudinal change of the groove shape of the photoresist before and after ashing are respectively observed by an optical microscope and a scanning electron microscope.
Preferably, the silicon wafer needs to be cleaned well before thermal oxidation to remove pollutants on the surface, and if cleaning is not performed well, impurities and water stains are left on the surface of the silicon wafer, so that black spots on the surface of the oxidation layer are formed.
Preferably, the anisotropic wet etching method comprises: the anisotropic etching was carried out at 60 ℃ in NC-200TMAH in pure and added concentrations (10, 20 and 25 wt.% TMAH) and the surfactant was added at a concentration of 0.1% of the total volume of the resulting etchant (0.1% v/v).
Before the S5 step anisotropic wet etching, it was necessary to immerse the wafer in a 5% hydrofluoric acid solution to ensure no native oxide left on the silicon surface, this step was followed by a thorough rinse in deionized water, a round container made of polytetrafluoroethylene was used for the etching experiments, which was equipped with a reflux condenser to maintain the etching concentration, and the anisotropic etching was carried out at 60 ℃ in NC-200TMAH at pure and added different concentrations (10, 20 and 25 wt% TMAH), with a surfactant added at a concentration of 0.1% (0.1 v/v) of the total volume of the resulting etchant.
Compared with the prior art, the invention has the beneficial effects that:
1. the method successfully manufactures the blazed grating which is close to an ideal sawtooth groove shape by using the oxide layer as a mask for silicon anisotropic etching, the blazed angle is 5 degrees, the linear density is 1200 lines/mm, the root mean square roughness of the blazed surface is about 0.2nm, and the blazed wavelength is about 140nm, the method has low requirement on equipment, the steps are relatively simple, and for manufacturing the blazed grating of a vacuum ultraviolet wave band or an extreme ultraviolet and soft X-ray wave band, the method using a natural oxide film as a wet etching mask is easy to manufacture the blazed grating with high groove shape efficiency and a smooth blazed surface;
2. the accurate grating profile of the actual grating is measured by AFM of the grating produced by the invention, the absolute efficiency and the groove shape efficiency of the-1 diffraction order of the grating sample S27 are calculated by utilizing PC-Grate2000 (MLT), the calculated absolute efficiency is well matched with the measured data, the absolute efficiency measured at the wavelength of 135nm is 53.7 percent, and the corresponding groove shape efficiency is 83.2 percent.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.
In the drawings:
FIG. 1 is a production flow chart of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments; all other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, a blazed grating, a method for manufacturing the blazed grating, and an application of the blazed grating include the following steps:
s1, selecting a silicon wafer: selecting a high-quality (100) oriented p-doped silicon wafer grown by using a CZ with the resistivity of 1-100 omega-cm as a substrate;
s2, oxide: placing the silicon wafer obtained in the step (S1) in an oxygen, water vapor or mixed atmosphere of the oxygen and the water vapor at a high temperature (over 900 ℃) for heating through a thermal oxidation technology, so that oxygen molecules or water molecules enter an interface between silicon dioxide and the silicon wafer through thermal diffusion and react with the silicon wafer to generate the silicon dioxide;
s3, photoresist ashing: processing the photoresist of the silicon wafer by adopting a photoresist ashing technology;
s4, transferring a photoresist pattern: transferring the pattern of the photoresist grating to the oxide layer by wet etching pattern transfer;
s5, anisotropic wet etching: and obtaining a blazed grating groove shape by adopting anisotropic wet etching.
Preferably, the processing of the silicon wafer comprises accurate cutting, silicon wafer polishing, first silicon wafer cleaning, first detection (detection items comprise length, weight, resistivity uniformity, defect, scratch, crack and damage), chamfering, second cleaning, second detection (detection of chamfer radius), lapping, cleaning, chemical corrosion and cleaning spin-drying.
Preferably, the wet etching pattern transfer is carried out by using 6 parts of 40% ammonium fluoride aqueous solution (volume ratio) 1 part of 49% hydrofluoric acid in the BHF solution formula, soaking for 8-12S, and reacting the BHF solution with SiO at room temperature of 22 DEG C 2 The etching rate of (2) is 120nm/min, the time required for etching is determined according to the thickness of the oxide layer, and whether the oxide layer is etched or not is judged.
Preferably, the photoresist ashing method is carried out on a plasma cleaning machine, the photoresist on the substrate is treated by electrons in a high-speed motion state, neutral atoms, molecules and atomic groups (free radicals) in an activated state, ionized atoms and molecules, unreacted molecules and atoms and the like so as to avoid etching the substrate, the working pressure is 2 x 10 < -2 > Pa, the time is 20min, and the transverse (aspect ratio) change and the longitudinal change of the groove shape of the photoresist before and after ashing are respectively observed by an optical microscope and a scanning electron microscope.
Preferably, the silicon wafer needs to be well cleaned before thermal oxidation to remove pollutants on the surface, and if cleaning is not well performed, impurities and water stains are left on the surface of the silicon wafer, so that black spots on the surface of the oxidation layer are formed.
Preferably, the anisotropic wet etching method comprises: the anisotropic etching was carried out at 60 ℃ in NC-200TMAH in pure form and with different concentrations added (10, 20 and 25% by weight of TMAH), with the surfactant added at a concentration of 0.1% of the total volume of the resulting etchant (0.1% v/v).
Before the anisotropic wet etching in the S5 step, it was necessary to immerse the wafer in a 5% hydrofluoric acid solution to ensure no native oxide remained on the silicon surface, this step was followed by a thorough rinsing in deionized water, a round container made of polytetrafluoroethylene was used for the etching experiments, which was equipped with a reflux condenser to maintain the etching concentration, and the anisotropic etching was carried out at 60 ℃ in NC-200TMAH in pure and added concentrations (10, 20 and 25 wt%) with a surfactant added at a concentration of 0.1% (0.1 v/v) of the total volume of the resultant etchant.
The silicon dioxide layer grown by the thermal oxidation method has high compactness, and the density of the silicon dioxide grown by the dry oxidation method is 2.24-2.27g/cm 3 The density of the silicon dioxide grown by the wet oxygen method is 2.18-2.21g/cm 3 The density of the silicon dioxide grown by the water vapor method is 2.00-2.20g/cm 3 Meanwhile, if a thinner silicon dioxide layer is to be grown, a dry oxygen method with a slower oxidation rate is generally adopted, while a thicker silicon dioxide film is mainly based on a wet oxygen method or a water vapor method, and the oxidation rates of the two methods are much faster than that of the dry oxygen method because the diffusion rate of water molecules or silanol in the oxide layer is much larger than that of oxygen atoms in the oxide layer
The photoresist ashing technology is to treat the photoresist by oxygen reactive ion etching, and the mechanism is that the photoresist is a photosensitive high molecular polymer composed of C, H, O and other elements, when the photoresist is etched by oxygen plasma, the oxygen plasma and the photoresist are subjected to chemical reaction to generate gas volatile matters which are pumped away by a vacuum pump, so that the photoresist is continuously etched, and the etching rate of a protruding part in the atmosphere of the oxygen plasma is relatively high, so that small defects at the edge of the photoresist line and residual photoresist between the lines can be smoothly removed, the lines tend to be smooth, the bottom of a grating groove is clean, and in addition, as the etching of the photoresist is basically isotropic, the lateral direction of the photoresist line is also etched while the thickness of the photoresist line is reduced.
The conditions, such as temperature, stirring mode and the like, of wet etching need to be strictly controlled when the wet etching is used, so that the rate of the wet etching is accurately grasped, the photoresist can be isotropically etched through the photoresist ashing technology, on the basis of solving the problem of residual photoresist between photoresist lines, a high-quality photoresist mask with a small aspect ratio can be obtained, the smaller the thickness of the silicon dioxide mask layer is, the better the silicon dioxide mask layer is, and considering that the surface of a silicon wafer has a natural oxide layer with the thickness of about 1-2nm, the oxide layer has the possibility of being used as a silicon wet etching mask.
When wet etching is used for transferring the photoresist pattern, the isotropy of chemical etching is utilized. Due to the extremely high selectivity of wet etching to the process material (e.g., hydrofluoric acid to silicon dioxide and silicon wafer), the etch can stop precisely at the interface of the mask material and the process material, which is the best heat for wet etching compared to dry etching.
Dry etching is a technique of performing thin film etching using plasma. When the gas is present in the form of a plasma, it has two characteristics: on one hand, the chemical activity of the gases in the plasma is much stronger than that of the gases in a normal state, and the gases can react with the materials more quickly by selecting proper gases according to the difference of the etched materials, so that the aim of etching removal is fulfilled; on the other hand, the electric field can be used for guiding and accelerating the plasma, so that the plasma has certain energy, and when the plasma bombards the surface of the etched object, atoms of the etched object material can be knocked out, thereby achieving the purpose of etching by utilizing physical energy transfer. Thus, dry etching is a result of a balance of both physical and chemical processes on the wafer surface.
The method successfully manufactures the blazed grating which is close to an ideal sawtooth groove shape by using the oxide layer as a mask for silicon anisotropic etching, the blazed angle is 5 degrees, the linear density is 1200 lines/mm, the root mean square roughness of the blazed surface is about 0.2nm, and the blazed wavelength is about 140 nm.
The etching agent for dry etching is plasma, and is a process for forming volatile substances by utilizing the reaction of the plasma and a surface film or directly bombarding the surface of the film to enable the film to be etched.
The method is characterized in that: anisotropic etching can be realized, so that the fidelity of the fine pattern after transfer is ensured.
The disadvantages are as follows: the manufacturing cost is high.
Wet etching is a method of stripping an etched substance by a chemical reaction between a chemical etching liquid and the etched substance. Most wet etches are isotropic etches that are not easily controlled.
The method is characterized in that: the method has the advantages of strong adaptability, good surface uniformity and little damage to the silicon wafer, and is almost suitable for all materials such as metal, glass, plastics and the like.
The accurate grating profile of the actual grating was measured by AFM, and the absolute efficiency of the-1 diffraction order and the groove efficiency of the grating sample S27 were calculated using PC-grace 2000 (MLT), the calculated absolute efficiency agreed well with the measured data, the absolute efficiency measured at 135nm wavelength was 53.7%, and the corresponding groove efficiency was 83.2%.
It should be noted that, in this document, relational terms such as first and second, and the like are only used for distinguishing one entity or operation from another entity or operation without necessarily requiring or implying any actual such relationship or order between such entities or operations, and the terms "comprise", "include", or any other variation thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but also other elements not expressly listed or inherent to such process, method, article, or apparatus, and the terms "mount", "connect", or "connect" should be broadly construed, for example, as being fixedly connected, detachably connected, or integrally connected unless expressly specified or limited otherwise; can be mechanically or electrically connected; the two elements may be directly connected or indirectly connected through an intermediate medium, and the two elements may be communicated with each other, and the specific meaning of the above terms in the present invention will be understood by those skilled in the art through specific situations.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (7)
1. A blazed grating and a preparation method and application thereof are characterized in that: the method comprises the following steps:
s1, selecting a silicon wafer: selecting a high-quality (100) oriented p-doped silicon wafer grown by using a CZ with the resistivity of 1-100 omega-cm as a substrate;
s2, oxide: placing the silicon wafer obtained in the step (S1) in an oxygen, water vapor or mixed atmosphere of the oxygen and the water vapor at a high temperature (over 900 ℃) for heating through a thermal oxidation technology, so that oxygen molecules or water molecules enter an interface between silicon dioxide and the silicon wafer through thermal diffusion and react with the silicon wafer to generate the silicon dioxide;
s3, photoresist ashing: processing the photoresist of the silicon wafer by adopting a photoresist ashing technology;
s4, transferring a photoresist pattern: transferring the pattern of the photoresist grating to the oxide layer by wet etching pattern transfer;
s5, anisotropic wet etching: and obtaining a blazed grating groove shape by adopting anisotropic wet etching.
2. A blazed grating, a method for its production and use according to claim 1, characterized in that: the processing of the silicon wafer comprises accurate cutting, silicon wafer polishing, first silicon wafer cleaning, first detection (detection items comprise length, weight, resistivity and resistivity uniformity, defects, scratches, cracks and damages), chamfering, second cleaning, second detection (detection of chamfer radius), grinding, cleaning, chemical corrosion and cleaning spin-drying.
3. A blazed grating and methods of making and using the same as claimed in claim 1, wherein: the wet etching pattern transfer uses 6 parts of BHF solution formula, 40% ammonium fluoride aqueous solution ratio (volume ratio) 1 part of 49% hydrofluoric acid, soaking for 8-12S, and BHF solution to SiO at room temperature of 22 DEG C 2 The etching rate of (2) is 120nm/min, the time required for etching is determined according to the thickness of the oxide layer, and whether the oxide layer is etched or not is judged.
4. A blazed grating and methods of making and using the same as claimed in claim 1, wherein: the photoresist ashing method is carried out on a plasma cleaning machine, the photoresist of a substrate is treated by electrons in a high-speed motion state, neutral atoms, molecules and atomic groups (free radicals) in an activated state, ionized atoms and molecules, unreacted molecules and atoms and the like so as to avoid etching the substrate, the working pressure is 2 multiplied by 10 < -2 > Pa, the time is 20min, and the transverse (aspect ratio) change and the longitudinal change of the groove shape of the photoresist before and after ashing are respectively observed by an optical microscope and a scanning electron microscope.
5. A blazed grating and methods of making and using the same as claimed in claim 1, wherein: the silicon wafer needs to be cleaned well before thermal oxidation to remove pollutants on the surface, and if cleaning is not carried out well, impurities and water stains can be left on the surface of the silicon wafer, so that black spots on the surface of the oxidation layer can be formed.
6. A blazed grating and methods of making and using the same as claimed in claim 1, wherein: the anisotropic wet etching method comprises the following steps: the anisotropic etching was carried out at 60 ℃ in NC-200TMAH in pure form and with different concentrations added (10, 20 and 25% by weight of TMAH), with the surfactant added at a concentration of 0.1% of the total volume of the resulting etchant (0.1% v/v).
7. A blazed grating and methods of making and using the same as claimed in claim 1, wherein: before the S5 step anisotropic wet etching, it was necessary to immerse the wafer in a 5% hydrofluoric acid solution to ensure no native oxide left on the silicon surface, this step was followed by a thorough rinse in deionized water, a round container made of polytetrafluoroethylene was used for the etching experiments, which was equipped with a reflux condenser to maintain the etching concentration, and the anisotropic etching was carried out at 60 ℃ in NC-200TMAH at pure and added different concentrations (10, 20 and 25 wt% TMAH), with a surfactant added at a concentration of 0.1% (0.1 v/v) of the total volume of the resulting etchant.
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