Preparation method of germanium dual-band antireflection film

Abstract

A preparation method of a germanium antireflection coating film system comprises the following steps: S1, cleaning the surface of a product and a plating piece, both of which are germanium and collectively referred to as a lens; S2, placing the lens into a tool clamp and hanging it into a cavity of a vacuum coating machine, and setting the temperature of the cavity to 150 DEG C; S3, starting vacuumizing of the vacuum coating machine and opening a Hall ion source of the vacuum coating machine for cleaning; S4, on a first surface of the lens, sequentially coating each film layer according to a nine-layer film system composed of ZnS, Ge, YbF3 and Y2O3, and each film layer is ion source assisted deposition, and each film layer is deposited at a cavity temperature of 150 DEG C; S5, after the first surface of the lens is coated with the film system, the cavity is naturally cooled to below 80 DEG C, and the tool clamp together with the lens is taken out; S7, repeating steps S1 to S6, and coating the same film system on a second surface of the lens. The average transmittance of the plating piece together with the film system on the two surfaces is less than 30% at 2-5 mu m and greater than 95% at 7.5-14 mu m.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of infrared coating, and more particularly to a preparation method of a germanium antireflection coating film system. BACKGROUND

[0002] In the field of infrared optical coating, germanium has good infrared transmittance and refractive index, and is therefore commonly used to manufacture infrared optical lenses, infrared cameras, infrared telescopes, infrared sensors, infrared detectors and other equipment.

[0003] In the 2-14 mu band range of infrared detection, different application ends have different requirements for transmittance and its range, and further in-depth development is needed. SUMMARY

[0004] In view of the problems in the background art, an object of the present disclosure is to provide a preparation method of a germanium antireflection coating film system, which has an average transmittance of less than 30% in the 2-5 mu band and an average transmittance of more than 95% in the 7.5-14 mu band.

[0005] Thus, a preparation method of a germanium antireflection coating film system includes the following steps: S1, cleaning the surface of a test piece and a product, wherein the test piece and the product are both germanium, and the test piece and the product are collectively referred to as a lens; S2, placing the cleaned lens into a tool clamp, and hanging the assembled lens into a vacuum coating machine cavity, with the temperature of the cavity being set to 150°C; S3, starting vacuum pumping of the vacuum coating machine, and when the vacuum degree reaches 1.5x10 -3Pa, turn on the Hall ion source of the vacuum coating machine for cleaning, and the cleaning time is 6 min. The parameters of the Hall ion source are as follows: anode voltage is 220 V, anode current is 1.2 A, neutralization current is 1.5 A, neutralization gas flow is 10 sccm, and argon flow ratio is 100%; S4, on the first surface of the lens, a nine-layer film system 149 nm ZnS / 175.6 nm Ge / 488.4 nm ZnS / 107.8 nm Ge / 120 nm ZnS / 1150 nm YbF3 / 182.5 nm ZnS / 100 nm YbF3 / 10 nm Y2O3 composed of ZnS, Ge, YbF3 and Y2O3 is sequentially coated, wherein the number with nm before ZnS, Ge, YbF3 and Y2O3 is the film thickness of the corresponding film layer, the ZnS and YbF3 film layers are evaporated by resistance heating, the Ge film layer and the Y2O3 film layer are evaporated by electron beam heating, the deposition rate of the ZnS film layer is 0.6 nm / s, the deposition rate of the Ge film layer is 0.4 nm / s, the deposition rate of the YbF3 film layer is 0.6 nm / s, and the deposition rate of the Y2O3 film layer is 0.6 nm / s, each film layer is deposited at a cavity temperature of 150°C; S5, after the film system is coated on the first surface of the lens, the cavity is naturally cooled to below 80°C, and the jig is taken out together with the lens; S7, repeat steps S1 to S6 to coat the same film system on the second surface of the lens.

[0006] The beneficial effects of the present disclosure are as follows: in the preparation method of the germanium anti-reflection film film system according to the present disclosure, through the repeated step S4 of step S4 and step S7, the same nine-layer film system (two-surface film system constitutes an anti-reflection film film system) composed of ZnS, Ge, YbF3 and Y2O3 four film materials is coated on both surfaces of the lens, and in combination with the repeated step S1 of step S1 and step S7, the repeated step S2 of step S2, the repeated step S3 of step S3, and the repeated step S5 of step S5, as verified by Example 1 of the test process described below, the average transmittance of the accompanying coating piece together with the film system on both surfaces is less than 30% (specifically 26%) at 2-5 μm, and the average transmittance is greater than 95% (specifically 95.2%) at 7.5-14 μm. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is a transmittance curve of the accompanying coating piece together with the film system coated on both surfaces of Example 1. DETAILED DESCRIPTION

[0008] It will be understood that the disclosed embodiments are only examples of the disclosure and that the disclosure can be embodied in various forms, therefore, the specific details disclosed herein should not be interpreted as limiting, but only as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to variously embody the present disclosure in various forms.

[0009] [Method for preparing germanium antireflection coating film system]

[0010] The method for preparing a germanium antireflection coating film system according to the present disclosure comprises the steps of:

[0011] S1, cleaning the surface of the accompanying plated piece and the product, wherein the accompanying plated piece and the product are both germanium, and the accompanying plated piece and the product are collectively referred to as a lens;

[0012] S2, placing the treated lens into a tool clamp, and hanging the lens after assembly into the cavity of a vacuum coating machine, and setting the temperature of the cavity to 150°C;

[0013] S3, starting vacuumizing of the vacuum coating machine, and when the vacuum degree reaches 1.5x10 -3 Pa, opening the Hall ion source of the vacuum coating machine for cleaning, and the cleaning time is 6min, and the parameters of the Hall ion source are: anode voltage 220V, anode current 1.2A, neutralizing current 1.5A, neutralizing gas flow 10sccm, and argon flow ratio 100%;

[0014] S4, on the first surface of the lens, depositing a nine-layer film system composed of ZnS, Ge, YbF3 and Y2O3 film materials in sequence,

[0015] 149nm ZnS / 175.6nm Ge / 488.4nm ZnS / 107.8nm Ge / 120nm ZnS / 1150nm YbF3 / 182.5nm ZnS / 100nm YbF3 / 10nm Y2O3, each film layer is deposited in sequence,

[0016] Wherein, the numbers with nm before ZnS, Ge, YbF3 and Y2O3 are the film thicknesses of the corresponding film layers, the ZnS and YbF3 film layers are deposited by resistance heating evaporation, the Ge film layer and the Y2O3 film layer are deposited by electron beam heating evaporation, the deposition rate of the ZnS film layer is 0.6nm / s, the deposition rate of the Ge film layer is 0.4nm / s, the deposition rate of the YbF3 film layer is 0.6nm / s, and the deposition rate of the Y2O3 film layer is 0.6nm / s, each film layer is deposited by ion source assisted deposition, and each film layer is deposited at a temperature of 150°C in the cavity;

[0017] S5, after depositing the film system on the first surface of the lens, naturally cooling the cavity to below 80°C, and taking out the tool clamp together with the lens;

[0018] S7, repeating steps S1 to S6 to coat the same film system on the second surface of the lens.

[0019] In the method of preparing the germanium antireflection coating film system according to the present disclosure, through the repeated step S4 of step S4, a nine-layer film system (two-surface film system constituting an antireflection coating film system) composed of ZnS, Ge, YbF3, and Y2O3 four film materials is coated on both surfaces of the lens, and in combination with step S1 and the repeated step S1 of step S7, the surface cleaning of step S2 and the repeated step S2 of step S7, the ion source cleaning of step S3 and the repeated step S3 of step S7, and the cooling of step S5 and the repeated step S5 of step S7, as verified by Example 1 of the test process described below, the average transmittance of the coated wafer together with the film system on both surfaces is less than 30% (specifically 26%) at 2-5 μm, and the average transmittance is greater than 95% (specifically 95.2%) at 7.5-14 μm.

[0020] The long-wave infrared 7.5-14 μm is an atmospheric window, and the atmosphere hardly absorbs the infrared energy emitted by the measured object in this waveband, so generally long-wave detectors set the spectrum at this frequency to better receive the infrared energy emitted by the measured object. Due to the absorption effect of the ground atmosphere, ground-based infrared telescopes (or detectors) can only observe from several atmospheric windows. 2-5 μm is the beginning of the thermal infrared band and is the region where the important L and M bands of ground-based observation are located. The product prepared by the method of preparing the germanium antireflection coating film system according to the present disclosure together with the film system on both surfaces can be suitable for ground-based infrared astronomical detection.

[0021] The surface cleaning of step S1 and the repeated step S1 of step S7 is beneficial to improve the surface state of each surface of the lens and helps to improve the bonding performance of the film system on each surface and the corresponding surface of the lens. For example, in step S1, the surface of the lens is cleaned by ultrasonic or hand rubbing. Further, for example, in step S1, the surface of the lens is cleaned by ultrasonic, followed by polishing with an alumina polishing liquid and then ultrasonic pure water cleaning. For example, the alumina polishing liquid is a 0.1 μm type polycrystalline diamond liquid from Nanjing Hengrui Precision Optics Co., Ltd.

[0022] In step S1, for example, the thickness of the coated wafer is 1 mm.

[0023] The temperature setting of the vacuum coating machine of step S2 heats the lens through the cavity of the coating machine, which helps the growth of the film layer from the lens and reduces the film layer growth stress.

[0024] Step S3 uses a Hall ion source for cleaning, which removes impurities and oil molecules adsorbed on the surface of each lens surface, significantly improving the interface state and helping to enhance the bonding performance between the film layer and the corresponding lens surface. Simultaneously, cleaning with the Hall ion source heats the corresponding lens surface, facilitating film growth and reducing film growth stress. For example, the vacuum coating machine is a Hall ion source equipped with a neutralizer, manufactured and sold by Chengdu West Work Vacuum Technology Co., Ltd. The Hall ion source equipped with a neutralizer was purchased from Boton Optoelectronics Technology Co., Ltd.

[0025] In one example, in step S4, the ion source adopts a Hall ion source, and the ion source parameters when depositing a ZnS film are: neutralization current of 0.5A, neutralization flow rate of 8sccm, anode voltage of 120V, anode current of 1.2A, and argon flow rate of 100%; when depositing a Ge film, the ion source parameters are: neutralization current of 0.5A, neutralization flow rate of 6-8sccm, anode voltage of 120V, anode current of 1A, and argon flow rate of 100%; When depositing the YbF3 film, the ion source parameters are: neutralization current 0.5A, neutralization flow rate 10sccm, anode voltage 110V, anode current 1.2A, argon flow rate 30%, and oxygen flow rate 70%; when depositing the Y2O3 film, the ion source parameters are: neutralization current 0.5A, neutralization flow rate 6-8sccm, anode voltage 120V, anode current 1.2A, argon flow rate 30%, and oxygen flow rate 70%.

[0026] In one example, in step S4, argon gas is introduced and vacuum is drawn to maintain a constant vacuum in the flow mode when depositing each film layer, and the constant vacuum is set to be no less than 5.0×10 -3 Pa; use the crystal oscillator method to monitor the film thickness using the corresponding crystal oscillator of the multiple crystal oscillators of the crystal controller. After the ion source is cleaned, the crystal controller controls the corresponding operation of the new crystal oscillator among the multiple crystal oscillators, and the crystal oscillator frequency is not less than 5.99MHz.

[0027] [test]

[0028] Example 1

[0029] The method for preparing the germanium antireflection film system of Example 1 adopts the following steps:

[0030] S1, using ultrasonic cleaning to clean the surface of the accompanying plating sheet and the product, wherein both the accompanying plating sheet and the product are made of germanium and are collectively referred to as lenses. The surface cleaning of the lenses using ultrasonic cleaning is performed by polishing with an aluminum oxide polishing liquid and then ultrasonically rinsing with pure water. The aluminum oxide polishing liquid is a 0.1 μm polycrystalline diamond liquid produced by Nanjing Henry Precision Optics Co., Ltd.;

[0031] S2, the processed lens is placed in a tool clamp, and the lens after assembly is hung in the cavity of a vacuum coating machine, and the temperature of the cavity is set to 150°C. The vacuum coating machine is a vacuum coating machine with a neutralizer Hall ion source manufactured and sold by Chengdu Xiwoker Vacuum Technology Co., Ltd., and the Hall ion source with a neutralizer is commercially available from Boton Optoelectronics Technology Co., Ltd.;

[0032] S3, the vacuum coating machine starts to pump, and the vacuum degree reaches 1.5x10 -3 Pa, open the Hall ion source of the vacuum coating machine for cleaning, the cleaning time is 6min, the parameters of the Hall ion source are: anode voltage is 220V, anode current is 1.2A, neutralizing current is 1.5A, neutralizing gas flow is 10sccm, and argon flow ratio is 100%;

[0033] S4, on the first surface of the lens, a nine-layer film system composed of ZnS, Ge, YbF3 and Y2O3 is coated according to the order of 149nm ZnS / 175.6nm Ge / 488.4nm ZnS / 107.8nm Ge / 120nm ZnS / 1150nm YbF3 / 182.5nm ZnS / 100nm YbF3 / 10nm Y2O3,

[0034] 149nm ZnS / 175.6nm Ge / 488.4nm ZnS / 107.8nm Ge / 120nm ZnS / 1150nm YbF3 / 182.5nm ZnS / 100nm YbF3 / 10nm Y2O3, each film layer is sequentially coated,

[0035] Wherein, the number with nm before ZnS, Ge, YbF3 and Y2O3 is the film thickness of the corresponding film layer, ZnS and YbF3 film layer is evaporated by resistance heating, Ge film layer and Y2O3 film layer are evaporated by electron beam heating, the deposition rate of ZnS film layer is 0.6nm / s, the deposition rate of Ge film layer is 0.4nm / s, the deposition rate of YbF3 film layer is 0.6nm / s, and the deposition rate of Y2O3 film layer is 0.6nm / s. Each film layer is deposited at a temperature of 150°C in the cavity.

[0036] In step S4,

[0037] The ion source is a Hall ion source,

[0038] When coating ZnS film layer, the ion source parameters are: neutralizing current is 0.5A, neutralizing flow is 8sccm, anode voltage is 120V, anode current is 1.2A, and argon flow ratio is 100%;

[0039] When coating Ge film layer, the ion source parameters are: neutralizing current is 0.5A, neutralizing flow is 7sccm, anode voltage is 120V, anode current is 1A, and argon flow ratio is 100%;

[0040] The ion source parameters when plating YbF3 film layer are: neutralization current is 0.5 A, neutralization flow is 10 sccm, anode voltage is 110 V, anode current is 1.2 A, argon flow proportion is 30%, and oxygen flow proportion is 70%;

[0041] The ion source parameters when plating Y2O3 film layer are: neutralization current is 0.5 A, neutralization flow is sccm, anode voltage is 120 V, anode current is 1.2 A, argon flow proportion is 30%, and oxygen flow proportion is 70%;

[0042] When plating each film layer, argon is introduced and vacuum is extracted to maintain the flow type constant vacuum, and the constant vacuum degree is set to 5.0*10 -3 Pa;

[0043] The crystal oscillator method is used to monitor the film thickness by using the corresponding crystal oscillator piece of the crystal controller, the new crystal oscillator piece in the plurality of crystal oscillator pieces is controlled to work after the ion source is cleaned, and the crystal oscillator frequency is 5.99 MHz;

[0044] S5, after plating the film system on the first surface of the lens, the cavity is naturally cooled to 80°C, and the lens is taken out together with the tool clamp;

[0045] S7, repeating steps S1 to S6, plating the same film system on the second surface of the lens.

[0046] Figure 1 The transmittance curve of the accompanying plating piece together with the film system plated on two surfaces of Example 1 is shown in the figure. Figure 1 It can be seen that the transmittance of the accompanying plating piece together with the film system on two surfaces is less than 30% (specifically 26%) on average in 2-5 μm, and greater than 95% (specifically 95.2%) on average in 7.5-14 μm.

[0047] The film system on the accompanying plating piece together with the film system on two surfaces is tested as follows.

[0048] Bubble test: the accompanying plating piece together with the film system on two surfaces prepared in Example 1 is subjected to a bubble test for 10 min with water taken from tap water, and no film system on each surface is found to fall off from the accompanying plating piece, nor is the film system on each surface found to be cracked.

[0049] Adhesion test: after the bubble test with water taken from tap water is completed, 3M adhesive tape paper is pasted on the film system on each surface of the product by hand, and the tape is pulled in the direction opposite to the pasting end, and the film system on each surface is not pulled up.

[0050] Through the bubble test and the adhesion test, it is shown that the adhesion of the film system on each surface of the accompanying plating piece is good.

[0051] The foregoing detailed description has set forth various exemplary embodiments of the systems and techniques via the use of a number of particular examples and urposes, but other embodiments of the systems and techniques herein disclosed can be employed in each particular case to embody the principles thereof, and this application is intended to be limited only by the claims, properly construed following full interpretation of this specification. Accordingly, unless otherwise indicated herein, the various features of the described embodiments can be combined in any suitable combination, only a portion of which can be used in a particular case.

Claims

1. A method for producing a germanium antireflection coating film system, characterized by comprising the steps of: Including steps: S1, cleaning the surface of a accompanying plated sheet and a product serving as a germanium substrate for a lens, wherein both the accompanying plated sheet and the product are made of germanium and are collectively referred to as a lens; S2, placing the processed lens into a fixture, and hanging the mounted lens into the vacuum coating machine cavity, and setting the cavity temperature to 150°C; S3, the vacuum coating machine starts to pump, the vacuum degree reaches 1.5x10 -3 Pa, open the Hall ion source of the vacuum coating machine for cleaning, the cleaning time is 6 min, the parameters of the Hall ion source are: anode voltage is 220 V, anode current is 1.2 A, neutralizing current is 1.5 A, neutralizing gas flow is 10 sccm, and argon flow ratio is 100%; S4, on the first side of the lens, a nine-layer film system consisting of four film materials: ZnS, Ge, YbF3 and Y2O3 149nmZnS / 175.6nmGe / 488.4nmZnS / 107.8nmGe / 120nmZnS / 1150nmYbF3 / 182.5nmZnS / 100nmYbF3 / 10nmY2O3, sequentially depositing each film layer, Among them, the numbers in nm before ZnS, Ge, YbF3, and Y2O3 are the film thicknesses of the corresponding film layers. The ZnS and YbF3 film layers were evaporated by resistance heating, and the Ge film layer and Y2O3 film layer were evaporated by electron beam heating. The deposition rate of the ZnS film layer was 0.6 nm / s, the deposition rate of the Ge film layer was 0.4 nm / s, the deposition rate of the YbF3 film layer was 0.6 nm / s, and the deposition rate of the Y2O3 film layer was 0.6 nm / s. Each film layer was deposited by ion source assisted deposition, and each film layer was deposited at a chamber temperature of 150°C. S5, after the coating system on the first side of the lens is completed, the cavity is naturally cooled to below 80°C, and the fixture and the lens are taken out; S7, repeating steps S1 to S6 to coat the same coating system on the second surface of the lens.

2. The method for preparing a germanium antireflection film system according to claim 1, wherein: In step S1, the surface of the lens is cleaned by ultrasonic wave or hand wiping.

3. The method for preparing a germanium antireflection film system according to claim 1, wherein: In step S1, the surface of the lens is cleaned by ultrasonic wave by polishing with aluminum oxide polishing liquid and then cleaning with ultrasonic pure water.

4. The method for preparing a germanium antireflection film system according to claim 3, wherein: In step S1 , the aluminum oxide polishing liquid uses a 0.1 μm polycrystalline diamond liquid.

5. The method for preparing a germanium antireflection film system according to claim 1, wherein: The thickness of the accompanying plating sheet is 1mm.

6. The method for preparing a germanium antireflection film system according to claim 1, wherein: In step S4, The ion source adopts Hall ion source. The ion source parameters for depositing the ZnS film are: neutralization current 0.5 A, neutralization flow rate 8 sccm, anode voltage 120 V, anode current 1.2 A, and argon flow rate 100%; When depositing the Ge film, the ion source parameters are: neutralization current 0.5A, neutralization flow rate 6-8sccm, anode voltage 120V, anode current 1A, and argon flow rate 100%; The ion source parameters when plating YbF3 film layer are: neutralization current is 0.5 A, neutralization flow is 10 sccm, anode voltage is 110 V, anode current is 1.2 A, argon flow proportion is 30%, and oxygen flow proportion is 70%; The ion source parameters when plating Y2O3 film layer are: neutralization current is 0.5 A, neutralization flow is 6-8 sccm, anode voltage is 120 V, anode current is 1.2 A, argon flow proportion is 30%, and oxygen flow proportion is 70%.

7. The method of claim 1, wherein the germanium anti-reflection coating is formed by a plurality of layers of germanium and silicon oxide. In step S4, When plating each film layer, argon is introduced and vacuum is extracted to maintain a flow-type constant vacuum, and the constant vacuum degree is set to be not less than 5.0 x 10 -3 Pa; The crystal oscillator method is used to monitor the film thickness by using the corresponding crystal oscillator piece of the plurality of crystal oscillator pieces of the crystal controller, and after the ion source is cleaned, the crystal controller controls the corresponding operation of the new crystal oscillator piece in the plurality of crystal oscillator pieces, and the crystal oscillator frequency is not less than 5.99 MHz.

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