A method for etching preparation of a strong weather-resistant DLC film on a chalcogenide glass surface

Abstract

The application belongs to the technical field of optical thin films, and discloses an etching preparation method of a chalcogenide glass surface strong weather-resistant DLC thin film, wherein the method is characterized in that: an infrared antireflection medium film system and a DLC-1 layer are sequentially coated on a chalcogenide glass substrate, and then a deposition-etching procedure is repeatedly executed for multiple times to prepare a DLC-2 layer; a single deposition-etching procedure comprises the following steps: a carbon-containing precursor gas is introduced to deposit a DLC film, and then the DLC film is subjected to plasma etching to remove part of the thickness; according to the application, the deposition-etching procedure is alternately and cyclically executed, that is, after a thin layer is deposited, plasma etching is performed once, so that loose defect layers are effectively removed, and the longitudinal continuity of penetrating pinholes is broken, thus fundamentally solving the problem of corrosion medium penetration failure; meanwhile, a double-layer structure design of the DLC-1 loose transition layer and the DLC-2 dense weather-resistant layer is adopted; the prepared thin film has an average reflectivity of less than 4.0% in the 8000-12000 nm wave band, and has excellent weather resistance and firmness after passing through 1000-hour salt spray test and other extreme environment tests.

Description

Technical Field

[0001] This invention belongs to the field of optical thin film technology, and particularly relates to an etching method for preparing a highly weather-resistant DLC thin film on the surface of chalcogenide glass. Background Technology

[0002] Chalcogenide glass, as a new generation of infrared optical materials, has significant advantages such as low thermal coefficient, good optical uniformity, easy molding and low cost, and is widely used in precision guidance, night vision equipment, security monitoring, automotive infrared and aerospace fields. However, chalcogenide glass itself has low hardness, poor strength and weak resistance to environmental corrosion. In engineering applications, it is necessary to coat the surface with a protective film to improve its reliability and service life.

[0003] Diamond-like carbon (DLC) films are metastable materials composed of amorphous carbon, diamond microcrystals, and graphite microcrystals. They possess high hardness, low coefficient of friction, excellent wear resistance and chemical inertness, and high transmittance in the infrared band, making them an ideal choice for antireflective protective films on chalcogenide glasses. They can significantly improve the surface hardness and wear resistance of components, enabling them to withstand harsh environments such as sand, rain, salt spray, and chemical corrosion.

[0004] However, existing technologies for preparing DLC ​​protective films on chalcogenide glasses still face bottlenecks: First, the coefficient of thermal expansion of chalcogenide glasses differs greatly from that of DLC films, making the film prone to cracking due to stress mismatch under alternating hot and cold environments; second, the growth mechanism of DLC films prepared by conventional chemical vapor deposition methods results in the presence of penetrating pinholes and micro-defects within the film, leading to poor density; in harsh environmental tests such as salt spray and humid heat, corrosive media can penetrate through these pinhole defects, forming damage points that gradually expand into film peeling and blistering, causing component failure. Summary of the Invention

[0005] This invention provides an etching method for preparing a highly weather-resistant DLC thin film on a chalcogenide glass surface, aiming to solve the above-mentioned problems.

[0006] This invention is achieved by an etching method for preparing a highly weather-resistant DLC thin film on a chalcogenide glass surface, comprising the following steps: Infrared antireflection dielectric films are sequentially deposited on a chalcogenide glass substrate; A DLC-1 layer was prepared on the dielectric film system using chemical vapor deposition. On the DLC-1 layer, the DLC-2 layer is prepared by repeatedly performing deposition-etching processes; The single deposition-etching process includes: Deposition process: A carbon-containing precursor gas is introduced to deposit a DLC film; Etching process: Plasma etching is performed on the deposited DLC film to remove part of the thickness of the DLC film.

[0007] Furthermore, the thickness of the DLC-1 film is 50~100nm, and the thickness of the DLC-2 film is greater than 1000nm. The DLC-1 layer has a loose structure and, as a stress transition layer, effectively buffers the huge thermal stress between the dielectric film system and the dense DLC-2 layer, preventing the film from cracking.

[0008] Furthermore, the infrared antireflective dielectric film system comprises alternating germanium layers and zinc sulfide layers, and the layers adjacent to the DLC-1 layer and the chalcogenide glass substrate are all germanium layers. The germanium layers exhibit good adhesion to both the DLC-1 layer and the chalcogenide glass substrate, significantly enhancing the bonding strength between the layers. The germanium layers are deposited using electron beam evaporation at a rate of 0.3–0.5 nm / s. The zinc sulfide layers are deposited using resistance evaporation supplemented by ion-assisted deposition at a rate of 0.8–1.5 nm / s. The ion-assisted parameters are: Hall ion source voltage 90–110 V and current 1.2–1.5 A. Electron beam evaporation ensures a uniform and dense germanium film, resistance evaporation precisely controls the evaporation rate of zinc sulfide, and ion assistance improves the density of the zinc sulfide film.

[0009] Preferably, the infrared antireflection medium film system comprises a first germanium layer, a first zinc sulfide layer, a second germanium layer, a second zinc sulfide layer, and a third germanium layer arranged sequentially; the thickness of each layer is optimized using professional film system design software such as TFCcalc or Macleod, which can achieve excellent antireflection effect in the 8000~12000nm wavelength band.

[0010] Furthermore, the deposition of the germanium layer adjacent to the chalcogenide glass substrate is divided into two stages: First, an underlayer of 10-20 nm thickness is deposited using electron beam evaporation supplemented by ion-assisted deposition technology. The ion-assisted parameters are: Hall ion source voltage 120-160 V, current 1.2-1.5 A; then, ion assistance is stopped, and the remaining thickness of the germanium layer is deposited using electron beam evaporation at a rate of 0.3-0.5 nm / s. The purpose of using ion-assisted deposition for the underlayer is that high-energy ion bombardment causes germanium atoms to form a diffusion layer on the substrate surface, which significantly improves the density of the germanium film and its adhesion to the chalcogenide glass substrate, solving the problem of poor surface adhesion and easy film detachment caused by the softness and large thermal expansion coefficient of chalcogenide glass.

[0011] Furthermore, before depositing the dielectric film, the process includes an ion beam cleaning step on the chalcogenide glass substrate. The ion beam cleaning parameters are: Hall ion source voltage 100~130V, current 1.0~1.2A. Ion beam cleaning can further improve the surface cleanliness of the substrate and form a diffusion layer on the surface, which is beneficial to improving the adhesion of the film.

[0012] Furthermore, the deposition process parameters for the DLC-1 layer are: RF power 780~820W, pressure 8~10Pa, and electrode spacing 17~21cm. The DLC-1 layer and the DLC-2 layer are deposited in the same CVD equipment, continuously prepared without breaking the vacuum, avoiding interface contamination and ensuring interlayer adhesion. Furthermore, in the single deposition-etching process, the thickness of the DLC film deposited in the deposition process is 100~150nm, and the thickness removed in the etching process is 50~75nm. By controlling the thickness ratio of deposition to etching, the net increase in thickness in each cycle is ensured to be moderate, which not only guarantees the preparation efficiency but also achieves sufficient defect removal.

[0013] Furthermore, the process parameters for the deposition process are: RF power 780~820W, pressure 8~10Pa, and electrode spacing 17~21cm; the process parameters for the etching process are: RF power 600~720W, pressure 8~10Pa, and electrode spacing 17~21cm.

[0014] Compared with the prior art, the embodiments of this application have the following main advantages: The etching preparation method for highly weather-resistant DLC thin films on chalcogenide glass surfaces provided by this invention employs an alternating deposition-etching cycle process. Each time a thin layer is deposited, plasma etching is performed, effectively removing loosely structured defect layers while simultaneously compacting the DLC film, making it more dense. This ensures that the final micron-sized DLC-2 film layer is free of any penetrating pinholes, fundamentally solving the problem of corrosion medium penetration failure and enabling the film layer to pass 1000 hours of extreme environmental testing such as salt spray.

[0015] The design employs a dual-layer DLC structure. The DLC-1 layer has a loose structure, which effectively buffers the huge thermal stress between the dielectric film system and the dense DLC-2 layer. The DLC-2 layer is dense and weather-resistant, providing high hardness and strong environmental resistance. The two layers work together to balance stress matching and environmental protection.

[0016] By employing a dual approach of ion beam cleaning and ion-assisted deposition of the first germanium film, the problem of easy film detachment is fundamentally solved. Ion beam cleaning improves the cleanliness of the substrate surface and forms a diffusion layer, while ion-assisted deposition further enhances the compactness and bonding strength of the first film. Attached Figure Description Figure 1This is a schematic diagram of the structure of the DLC film with strong weather resistance on the surface of chalcogenide glass provided by the present invention.

[0017] Figure 2 This is a flowchart of the etching preparation method for a highly weather-resistant DLC film on a chalcogenide glass surface provided by the present invention.

[0018] Figure 3 This is the reflectance test curve of the thin film prepared in Example 1 of the present invention in the 8000-12000 nm wavelength band; Figure 4 This is the reflectance test curve of the thin film prepared in Example 2 of the present invention in the 8000-12000nm wavelength band. Detailed Implementation

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0020] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0021] Example 1 This embodiment focuses on a chalcogenide glass substrate, IRG206. The film structure is as follows: Figure 1 As shown.

[0022] After optimization using professional membrane design software, the thicknesses of each membrane layer are as follows: The first germanium layer is 50 nm thick. The first zinc sulfide layer has a thickness of 528.57 nm; The second germanium layer has a thickness of 298.51 nm; The second zinc sulfide layer has a thickness of 231.3 nm; The third germanium layer has a thickness of 703.18 nm. DLC-1 layer, 80nm thick; The DLC-2 layer has a total thickness of 1054.7nm.

[0023] Membrane structures such as Figure 1 As shown, the reflectivity test results are as follows: Figure 3 As shown.

[0024] The preparation process steps are as follows: The IRG206 chalcogenide glass substrate was placed in an infrared vacuum coating machine and a vacuum was drawn; when the vacuum level was higher than 4.0 × 10⁻⁶... -3 At Pa, the Hall ion source was turned on to perform ion beam cleaning on the substrate, with the following parameters: voltage 120V and current 1.1A.

[0025] Continue evacuating to a vacuum level of 8.0 × 10⁻⁶. -4 Once the temperature reaches 100°C, turn on the baking switch and heat the base to 100°C, then maintain the temperature for 35 minutes.

[0026] First, the first germanium layer was deposited. The Hall ion source was turned on (voltage 140V, current 1.4A), and electron beam evaporation was used for ion-assisted deposition to a thickness of 15nm. Then the ion source was turned off, and the remaining 35nm germanium layer was deposited by electron beam evaporation at a rate of 0.4nm / s.

[0027] Zinc sulfide was evaporated using a resistance boat with ion source assistance (100V, 1.3A) at an evaporation rate of 1.0 nm / s. The designed thicknesses of the first zinc sulfide layer, second germanium layer, third zinc sulfide layer, and fourth germanium layer were deposited sequentially. The second and third germanium layers were deposited using electron beam evaporation at a rate of 0.4 nm / s.

[0028] The sample with the dielectric film system was transferred to a CVD carbon film coating machine; methane gas was introduced, and a DLC-1 layer with a thickness of 80nm was deposited under the conditions of RF power of 800W, pressure of 9Pa and spacing of 20cm.

[0029] Within the same chamber, without removing the sample, begin the preparation of the DLC-2 layer directly. Repeat the following steps cyclically: Deposition: Methane gas was introduced, and the radio frequency power was maintained at 800W, the pressure at 9Pa, and the spacing at 20cm to deposit a DLC film with a thickness of about 120nm. Etching: Turn off methane, introduce argon gas into the chamber (flow rate 50 sccm), adjust the RF power to 680W, keep the pressure and spacing unchanged, and perform plasma etching on the newly deposited film layer. The etching depth is about 60nm. Repeat the above deposition-etching cycle until the cumulative net increase in thickness of the DLC-2 layer reaches the design value of 1054.7 nm.

[0030] Once the plating is complete, remove the equipment after it has cooled down.

[0031] According to Fourier transform infrared spectroscopy, the average reflectance (coated surface reflectance) of the thin film prepared in this embodiment in the 8000~12000nm wavelength band is 3.3%.

[0032] Example 2 This embodiment is for chalcogenide glass substrate IRG201.

[0033] After software optimization, the thickness of each film layer is as follows: The first germanium layer has a thickness of 80 nm. The first zinc sulfide layer has a thickness of 701.52 nm; The second germanium layer has a thickness of 309.46 nm; The second zinc sulfide layer has a thickness of 237.28 nm; The third germanium layer has a thickness of 699.69 nm. DLC-1 layer, 70nm thick; The DLC-2 layer has a total thickness of 1080.28nm.

[0034] Membrane structures such as Figure 1 As shown, the reflectivity test results are as follows: Figure 4 As shown.

[0035] The preparation process steps in this embodiment are basically the same as those in Example 1. The main difference is that: in step 3, the ion-assisted deposition thickness of the first germanium layer is 20 nm, and the remaining thickness is 60 nm; in step 4, the auxiliary parameters of the zinc sulfide ion source are voltage 100 V and current 1.3 A; when preparing the DLC-2 layer, each deposition process deposits about 140 nm, and each etching process etches about 70 nm, and this process is repeated until the total thickness reaches 1080.28 nm.

[0036] Tests showed that the film has an average reflectivity of 3.2% in the 8000~12000nm wavelength range.

[0037] Environmental resistance performance verification All the coated samples prepared in the above embodiments were subjected to environmental tests under the following stringent conditions, and the results were all completely satisfactory: Salt spray test: without packaging, at 35℃±2℃, 5%±1% NaCl solution, pH 6.5~7.2, sedimentation rate 1~3mL / 80cm. 2 Under the condition of ·h, spray continuously for 1000h. After wiping the film surface clean, check for pitting, delamination, and blistering. Adhesion test: Use 3M tape with a peel strength of not less than 2.74N / cm to stick tightly to the film surface and quickly pull it up vertically. There is no delamination or peeling.

[0038] Solvent resistance test: Immersed in acetone and ethanol at 16~32℃ for 20 minutes each, no delamination, cracking or blistering was observed.

[0039] Friction test: Using a MIL-E-12397 standard eraser, maintain a vertical pressure of ≥9.8N and rub along the diagonal or diametrical direction of the surface 400 times. No delamination, peeling, or scratches should be observed.

[0040] Damp heat test: Maintain at 50℃±2℃ and relative humidity of 95%~100% for 48 hours, and then recover at normal temperature and humidity for 4 hours. No delamination, cracking or blistering should be observed.

[0041] It should be noted that, for the sake of simplicity, the foregoing embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0042] It should be understood that the disclosed apparatus can be implemented in other ways, as illustrated in the embodiments provided in this application. For example, the apparatus embodiments described above are merely illustrative; the division of units described above is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or communication connections shown or discussed may be through some interfaces; the indirect coupling or communication connections between devices or units may be telecommunications or other forms.

[0043] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0044] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still combine, add, delete, or otherwise adjust the features of the various embodiments of the present invention according to the circumstances without conflict or creative effort, thereby obtaining different technical solutions that do not fundamentally depart from the concept of the present invention. These technical solutions also fall within the scope of protection of the present invention.

Claims

1. A method for etching and preparing a highly weather-resistant DLC thin film on a chalcogenide glass surface, characterized in that, Includes the following steps: Infrared antireflection dielectric films are sequentially deposited on a chalcogenide glass substrate; A DLC-1 layer was prepared on the dielectric film system using chemical vapor deposition. On the DLC-1 layer, the DLC-2 layer is prepared by repeatedly performing deposition-etching processes; wherein a single deposition-etching process includes: Deposition process: A carbon-containing precursor gas is introduced to deposit a DLC film; Etching process: Plasma etching is performed on the deposited DLC film to remove part of the thickness of the DLC film.

2. The etching method for preparing a highly weather-resistant DLC thin film on a chalcogenide glass surface as described in claim 1, characterized in that, The thickness of the DLC-1 film is 50~100nm, and the thickness of the DLC-2 film is greater than 1000nm.

3. The etching method for preparing a highly weather-resistant DLC thin film on a chalcogenide glass surface as described in claim 1, characterized in that, The infrared antireflection dielectric film system comprises alternating germanium layers and zinc sulfide layers, wherein the layers adjacent to the DLC-1 layer and the layers adjacent to the chalcogenide glass substrate are both germanium layers; the germanium layers are deposited by electron beam evaporation at an evaporation rate of 0.3~0.5 nm / s; the zinc sulfide layers are deposited by resistive evaporation supplemented by ion-assisted deposition at an evaporation rate of 0.8~1.5 nm / s, and the ion-assisted parameters are: Hall ion source voltage 90~110V, current 1.2~1.5A.

4. The etching method for preparing a highly weather-resistant DLC thin film on a chalcogenide glass surface as described in claim 3, characterized in that, The infrared antireflective dielectric film system comprises a first germanium layer, a first zinc sulfide layer, a second germanium layer, a second zinc sulfide layer, and a third germanium layer arranged sequentially.

5. The etching method for preparing a highly weather-resistant DLC thin film on a chalcogenide glass surface as described in claim 3, characterized in that, The deposition of the germanium layer adjacent to the chalcogenide glass substrate is divided into two stages: First, an underlayer of 10-20 nm thickness is deposited using electron beam evaporation supplemented by ion-assisted deposition technology. The ion-assisted parameters are: Hall ion source voltage 120-160 V, current 1.2-1.5 A; then, ion assistance is stopped, and the remaining thickness of the germanium layer is deposited by electron beam evaporation at a rate of 0.3-0.5 nm / s.

6. The etching method for preparing a highly weather-resistant DLC thin film on a chalcogenide glass surface as described in claim 1, characterized in that, The deposition process parameters for the DLC-1 layer are: RF power 780~820W, pressure 8~10Pa, and electrode spacing 17~21cm.

7. The etching method for preparing a highly weather-resistant DLC thin film on a chalcogenide glass surface as described in claim 1, characterized in that, In the single deposition-etching process, the thickness of the DLC film deposited in the deposition process is 100~150nm, and the thickness removed in the etching process is 50~75nm.

8. The etching method for preparing a highly weather-resistant DLC thin film on a chalcogenide glass surface as described in claim 7, characterized in that, The process parameters for the deposition process are: RF power 780~820W, pressure 8~10Pa, and electrode spacing 17~21cm; the process parameters for the etching process are: RF power 600~720W, pressure 8~10Pa, and electrode spacing 17~21cm.

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