Infrared filter for detecting diethyl carbonate gas and preparation method thereof

Abstract

The invention relates to an infrared filter for detecting diethyl carbonate gas, comprising a substrate, a main film system structure and a cut-off film system structure, wherein the main film system structure and the cut-off film system structure are respectively arranged on both sides of the substrate; the main film system structure is: Si / 0.11L1.23H1.07H0.98H0.98L2.00H 0.99L0.98H1.02L1.09H1.01L0.99H0.98L1.99H0.99L0.83H0.44L / Air; the cut-off film system structure is: Si / 0.26L 0.32(0.5HL0.5H)^60.48(0.5HL0.5H)^6 0.70(0.5HL0.5H)^6 1.35(0.5LH0.5L)^5 1.7(0.5LH0.5L)^5 / Air, the design wavelength is 7900nm. The invention also provides a corresponding preparation method and an infrared gas sensor.

Description

Technical Field

[0001] The invention relates to the technical field of infrared gas detectors, and in particular to an infrared filter for detecting diethyl carbonate gas, a preparation method thereof and an application thereof. Background Art

[0002] In recent years, with the promotion of my country's new energy policy, the lithium-ion battery industry has experienced explosive growth. At the same time, the supporting diethyl carbonate (DEC) electrolyte industry has also achieved rapid development. However, DEC is a toxic, flammable and volatile colorless liquid, so the leakage of DEC should be strictly monitored during production, transportation and use.

[0003] Usually, the industry will choose PID sensors to monitor the gas concentration of DEC (liquid leakage and volatilization). Although this type of sensor has the advantages of low cost and sensitive response, it also has the disadvantages of being easily interfered by other organic matter and having a short service life. Among many gas detection technologies, non-dispersive infrared (NDIR) is increasingly favored by the market due to its characteristics of no poisoning, anti-interference and long life. Therefore, there is a need for an NDIR gas sensor that can be used to detect DEC gas.

[0004] Non-dispersive InfraRed (NDIR) is a method of using two or more different infrared bands to detect gas concentration. Its basic principle follows the Lambert-Beer law:

[0005] I = I0·exp(-μCL);

[0006] Among them, I0 represents the light intensity when there is no gas absorption, I represents the light intensity when there is gas absorption, μ is the gas molecule absorption coefficient (constant at room temperature and pressure), L represents the optical path (i.e. the length of the sensor optical path, which is a constant), and C is the concentration of the gas to be measured. The two filters of different bands represent the light intensity channel I0 (reference channel) without absorption and the light intensity channel I (measurement channel) with absorption, so the ratio of the two channels is only related to the gas concentration.

[0007] ln(I0 / I)=μCL;

[0008] That is, the gas concentration is proportional to the ratio of the signal strength of the reference channel and the measurement channel.

[0009] Usually the reference channel filter is easier to select (such as 3900nm / 90nm filter), and the measurement channel must be determined based on the specific absorption peaks of different gases.

[0010] In the Chinese invention patent application CN 114895395 A, a far-infrared filter and its preparation method, an infrared filter with a central wavelength of 7800nm ​​and a bandwidth of 160nm and a preparation method are proposed, which are suitable for detecting CF4 (refrigerant R14) gas. Among them, the filter (7800nm / 160nm) in CN 114895395 A cannot be used directly or simply improved to detect diethyl carbonate (DEC) gas, mainly because, based on this filter, the infrared absorption peak overlap is low and the bandwidth is too small, the signal-to-noise ratio obtained by the sensor is too low, and it cannot be used to detect diethyl carbonate; expensive single crystal germanium substrate material is used in the film system design, and the germanium substrate material is more brittle and not suitable for making large-area germanium sheets; three coating materials are used in the film system design, namely germanium, zinc selenide and zinc sulfide, which will bring the problem of using more than one coating material, and it is easy to mix materials during the preparation and production process (zinc sulfide is light yellow crystals, zinc selenide is orange crystals). Summary of the invention

[0011] The main purpose of the present invention is to provide an infrared filter for detecting diethyl carbonate gas and a preparation method thereof in view of the above problems.

[0012] In order to achieve the above object, the technical solution of the infrared filter for detecting diethyl carbonate gas adopted by the present invention is as follows:

[0013] The infrared filter comprises a substrate, a main film system structure and a cut-off film system structure, wherein the main film system structure and the cut-off film system structure are respectively arranged on both sides of the substrate;

[0014] The main film system structure is:

[0015] Si / 0.11L1.23H1.07H0.98H0.98L2.00H0.99L0.98H1.02L1.09H1.01L0.99H0.98L1.99H0.99L0.83H0.44L / Air;

[0016] The cut-off film system structure is:

[0017] Si / 0.26L 0.32(0.5HL0.5H)^6 0.48(0.5HL0.5H)^6 0.70(0.5HL0.5H)^6 1.35(0.5LH0.5L)^5 1.7(0.5LH0.5L)^5 / Air;

[0018] Among them, Si represents optical grade single crystal silicon substrate material, Air represents air, H is a Ge film layer with a quarter wavelength optical thickness, L is a ZnS film layer with a quarter wavelength optical thickness, ^5 and ^6 are the number of repetitions of the film stack, the number before the film stack is the film thickness coefficient, and the design wavelength is 7900nm.

[0019] Preferably, the central wavelength of the infrared filter is 7900±50nm, the bandwidth is 280±20nm, the peak transmittance is greater than 80%, and the transmittance in the cut-off range of 1500-7300nm and 8500-16000nm is less than 1%.

[0020] The present invention also provides a method for preparing the infrared filter for detecting diethyl carbonate gas, wherein the method comprises the steps of:

[0021] (1) Place the substrate into a fixture and place it in the vacuum chamber of the coating machine, and evacuate the chamber;

[0022] (2) baking the substrate;

[0023] (3) ion bombardment of substrate;

[0024] (4) On one side of the substrate, the main film system structure is plated layer by layer according to the film layers required by the main film system structure;

[0025] (5) turning the substrate over, repeating steps (1) to (3), and coating the cut-off film structure layer by layer on the other side of the substrate according to the film layers required by the cut-off film structure;

[0026] (6) After plating is completed, break the hole and take out the parts.

[0027] Preferably, the step (1) is specifically as follows:

[0028] The single crystal silicon wafer substrate material is loaded into the fixture and placed in the vacuum chamber of the coating machine. The background vacuum is pumped to 8×10 -4 Pa;

[0029] The step (2) is specifically as follows:

[0030] Bake the base material at 190°C to 210°C and keep the constant temperature for 100 to 120 minutes;

[0031] The step (3) is specifically as follows:

[0032] The substrate material is bombarded with ions using a Hall ion source for 6 to 10 minutes, wherein the ion source uses high-purity oxygen with a gas flow rate of 15 to 30 sccm;

[0033] The step (6) is specifically as follows:

[0034] After plating, the baking temperature is reduced to 20-40°C for breaking and taking out the parts.

[0035] Preferably, the step (4) is specifically as follows:

[0036] The main film system structure is plated layer by layer according to the film layers required by the main film system structure. The Ge film material is evaporated by electron beam evaporation process, and the ZnS film material is evaporated by resistance evaporation process. The coating rate of Ge film is 0.4-0.6nm / s, and the coating rate of ZnS film is 1.0-3.0nm / s. The deposition process uses light control to monitor the film thickness and stop, and crystal control is used to monitor the coating rate.

[0037] Preferably, the step (5) is specifically as follows:

[0038] The substrate coated with the main film structure is turned over and steps (1) to (3) are repeated. On the other side of the substrate, the cut-off film structure is coated layer by layer according to the film layer requirements of the cut-off film structure. The Ge film material is evaporated by electron beam evaporation process, and the coating rate of the Ge film is 0.4 to 0.6 nm / s. The ZnS film material is evaporated by resistance evaporation process, and the coating rate of the ZnS film is 1.0 to 3.0 nm / s. The deposition process uses light control to monitor the film thickness and stop, and crystal control is used to monitor the coating rate.

[0039] Preferably, the method further comprises the steps of:

[0040] (7) Use PE spectrum two Fourier transform infrared spectrometer to measure the transmittance spectrum of the filter at normal incidence.

[0041] The invention provides an infrared pyroelectric sensor, the main feature of which is that the infrared pyroelectric sensor is provided with the infrared filter for detecting diethyl carbonate gas.

[0042] The infrared filter for detecting diethyl carbonate gas and the preparation method thereof of the present invention can be well used for monitoring the gas concentration of DEC volatilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is the gas absorption spectrum of diethyl carbonate tested in the present invention.

[0044] Figure 2 Transmittance of 0.5mm thick silicon wafer.

[0045] Figure 3 Transmittance spectrum of the main film structure.

[0046] Figure 4 is the transmittance spectrum of the cut-off film structure.

[0047] Figure 5a and5b They are the global image and local magnified image of the infrared spectrum of the 7900NBP filter.

[0048] Figure 6 This is the measured signal response diagram of DEC gas. DETAILED DESCRIPTION

[0049] In order to more clearly understand the technical content of the present invention, the following embodiments are given in detail.

[0050] The infrared filter for detecting diethyl carbonate gas of the present invention comprises a substrate, a main film system structure and a cut-off film system structure, wherein the main film system structure and the cut-off film system structure are respectively arranged on both sides of the substrate;

[0051] The main film system structure is:

[0052] Si / 0.11L1.23H1.07H0.98H0.98L2.00H0.99L0.98H1.02L1.09H1.01L0.99H0.98L1.99H0.99L0.83H0.44L / Air;

[0053] The cut-off film system structure is:

[0054] Si / 0.26L 0.32(0.5HL0.5H)^6 0.48(0.5HL0.5H)^6 0.70(0.5HL0.5H)^6 1.35(0.5LH0.5L)^5 1.7(0.5LH0.5L)^5 / Air;

[0055] Among them, Si represents optical grade single crystal silicon substrate material, specifically optical grade direct-pull single crystal silicon substrate material, Air represents air, H is a Ge film layer with a quarter wavelength optical thickness, L is a ZnS film layer with a quarter wavelength optical thickness, ^5 and ^6 are the number of repetitions of the film stack, the number before the film stack is the film thickness coefficient, and the design wavelength is 7900nm.

[0056] like Figure 1 As shown in the figure, after testing, diethyl carbonate (DEC) gas has an obvious absorption peak at 7.9 μm and a large bandwidth (about 300 nm). Figure 3-5b As shown, after many tests, it was found that the spectral characteristics of the infrared filter are: central wavelength of 7900±50nm, bandwidth of 280±20nm, peak transmittance>80%, and the cut-off range is 1500-7300nm and 8500-16000nm band transmittance <1%, which best meets the use requirements.

[0057] In the infrared filter of the present invention, optical grade Czochralski single crystal silicon is used, and its transmittance is shown in Figure 2 , with lower cost (about one-tenth of germanium), and easier to process into large silicon wafers (such as 4 inches or 6 inches, etc.), large-area substrates have higher utilization rates for subsequent filter dicing. Using lower-cost single-crystal silicon as the substrate material improves the cost-effectiveness of the product

[0058] In the infrared filter of the present invention, both the main film system and the cut-off film system use irregular film system structures (the film layer thickness is not an integral multiple of a quarter wavelength), and fewer film layers can be used to obtain an ideal spectrum, reducing coating time and film material consumption.

[0059] The present invention provides a method for preparing the infrared filter for detecting diethyl carbonate gas, wherein the method comprises the steps of:

[0060] (1) Load the substrate into a fixture and place it in the vacuum chamber of the coating machine, and evacuate the chamber; specifically:

[0061] The double-sided polished single-crystal silicon wafer substrate material with a thickness of 0.5 mm and a diameter of 100 mm was cleaned: first, a cleaning agent (solvent ratio of ammonia water: hydrogen peroxide: pure water = 5:15:80) was used for ultrasonic cleaning for 10 minutes, and then the silicon wafer was placed in pure water for ultrasonic cleaning for 5 minutes, and finally, it was sprayed with pure water for 1 minute, and then dried with nitrogen, loaded into a fixture and placed in the vacuum chamber of the coating machine, and the background vacuum was pumped to 8×10 -4 Pa;

[0062] (2) Baking the substrate; specifically:

[0063] Bake the base material at 200±10℃ and keep the temperature constant for 100-120 minutes;

[0064] (3) Ion bombardment of the substrate; specifically:

[0065] The substrate material is bombarded with ions using a Hall ion source for 6 to 10 minutes, wherein the ion source uses high-purity oxygen (99.99%), the anode voltage is 150 to 200 V, and the gas flow rate is 15 to 30 sccm;

[0066] (4) On one side of the substrate, the main film system structure is plated layer by layer according to the film layers required by the main film system structure; specifically:

[0067] The main film system structure is plated layer by layer according to the film layers required by the main film system structure. The Ge film material is evaporated by electron beam evaporation process, and the ZnS film material is evaporated by resistance evaporation process. The coating rate of Ge film is 0.5nm / s, and the coating rate of ZnS film is 2.0nm / s. The deposition process uses light control to monitor the film thickness and stop, and crystal control is used to monitor the coating rate;

[0068] (5) Turning the substrate over, repeating steps (1) to (3), and coating the cut-off film structure layer by layer on the other side of the substrate according to the film layers required by the cut-off film structure; specifically:

[0069] The substrate coated with the main film structure is turned over, and steps (1) to (3) are repeated. On the other side of the substrate, the cut-off film structure is coated layer by layer according to the film layer required by the cut-off film structure. The Ge film material is evaporated by electron beam evaporation process, and the coating rate of the Ge film is 0.5nm / s. The ZnS film material is evaporated by resistance evaporation process, and the coating rate of the ZnS film is 2.0nm / s. The deposition process uses optical control to monitor the film thickness and stop, and crystal control is used to monitor the coating rate;

[0070] (6) After plating is completed, break the hole and take out the parts; specifically:

[0071] After plating, the baking temperature is reduced to 30°C, and the holes are broken and the parts are taken out;

[0072] (7) Use PE spectrum two Fourier transform infrared spectrometer to measure the transmittance spectrum of the filter at normal incidence.

[0073] In the method of the present invention, the use of an optical control system to monitor the optical thickness of the film layer improves the repeatability of batch production and has better process robustness.

[0074] Among them, the main film system structure and its light control parameters are shown in Table 1 below:

[0075] Table 1

[0076]

[0077] The cut-off film structure and its light control parameters are shown in Table 2:

[0078] Table 2

[0079]

[0080] The prepared filter is made into an infrared pyroelectric sensor through the following steps:

[0081] (8) Use a Disco dicing machine and a resin blade for dicing (spindle speed: 35000 rpm, cutting speed 8 mm / s). The size of the filter after dicing is 3×3 mm;

[0082] (9) Use a Musashi glue dispenser to seal the sliced ​​3900NBP and 7900NBP filters on the tube cap window;

[0083] (10) Using a capping machine in a high-purity nitrogen environment, the dual-element tube cap and the pyroelectric sensitive element are packaged into a pyroelectric detector.

[0084] The pyroelectric sensor can be assembled into an infrared sensor for diethyl carbonate (DEC) gas detection according to the method in patent CN 215066148 U.

[0085] like Figure 6 As shown, the infrared sensor for detecting diethyl carbonate gas of the present invention uses 7900NBP filter and 3900NBP filter, and can be well used for monitoring the gas concentration of DEC volatilization.

[0086] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it is apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the specification and drawings should be regarded as illustrative rather than restrictive.

Claims

1. An infrared filter for detecting diethyl carbonate gas, characterized in that: The infrared filter comprises a substrate, a main film system structure and a cut-off film system structure, wherein the main film system structure and the cut-off film system structure are respectively arranged on both sides of the substrate; The main film system structure is: Si / 0.11L1.23H1.07L0.98H0.98L2.00H0.99L0.98H1.02L1.09H1.01L0.99H0.98L1.99H0.99L0.83H0.44L / Air; The cut-off film system structure is: Si / 0.26L0.45H0.29L0.23H0.35L0.49H0.35L0.22H0.43L0.29H0.34L0.21H0.63L0.56H0 .43L0.49H0.24L0.53H0.57L0.54H0.35L0.62H0.32L0.71H0.7L0.6H0.7L0.76H0.64L0.76 H0.62L0.63H0.8L0.77H0.68L0.39H0.59L1.34H1.44L1.51H1.31L1.36H1.38L1.44H1.32 L1.41H1.53L1.55H1.89L1.87H1.79L1.81H1.76L1.64H1.77L2.04H1.96L1.3H0.87L / Air; Among them, Si represents optical grade single crystal silicon substrate material, Air represents air, H represents Ge film layer with a quarter wavelength optical thickness, L represents ZnS film layer with a quarter wavelength optical thickness, the number in front of the film stack is the film thickness coefficient, and the design wavelength is 7900nm.

2. The infrared filter for detecting diethyl carbonate gas according to claim 1, characterized in that: The central wavelength of the infrared filter is 7900±50nm, the bandwidth is 280±20nm, the peak transmittance is greater than 80%, and the transmittance in the cut-off intervals of 1500-7300nm and 8500-16000nm is less than 1%.

3. A method for preparing the infrared filter for detecting diethyl carbonate gas according to claim 1 or 2, characterized in that: The method comprises the steps of: (1) Place the substrate into a fixture and place it in the vacuum chamber of the coating machine, and evacuate the chamber; (2) baking the substrate; (3) ion bombardment of substrate; (4) On one side of the substrate, the main film system structure is plated layer by layer according to the film layers required by the main film system structure; (5) turning the substrate over, repeating steps (1) to (3), and coating the cut-off film structure layer by layer on the other side of the substrate according to the film layers required by the cut-off film structure; (6) After plating is completed, break the hole and take out the parts.

4. The method according to claim 3, characterized in that The step (1) is specifically as follows: The single crystal silicon wafer substrate material is loaded into the fixture and placed in the vacuum chamber of the coating machine. The background vacuum is pumped to 8×10 - 4 Pa; The step (2) is specifically as follows: Bake the base material at 190°C to 210°C and keep the constant temperature for 100 to 120 minutes; The step (3) is specifically as follows: The substrate material is bombarded with ions using a Hall ion source for 6 to 10 minutes, wherein the ion source uses high-purity oxygen with a gas flow rate of 15 to 30 sccm; The step (6) is specifically as follows: After plating, the baking temperature is reduced to 20-40°C for breaking and taking out the parts.

5. The method according to claim 3, characterized in that: The step (4) is specifically as follows: The main film system structure is plated layer by layer according to the film layers required by the main film system structure. The Ge film material is evaporated by electron beam evaporation process, and the ZnS film material is evaporated by resistance evaporation process. The coating rate of Ge film is 0.4-0.6nm / s, and the coating rate of ZnS film is 1.0-3.0nm / s. The deposition process uses light control to monitor the film thickness and stop, and crystal control is used to monitor the coating rate.

6. The method according to claim 3, characterized in that The step (5) is specifically as follows: The substrate coated with the main film structure is turned over and steps (1) to (3) are repeated. On the other side of the substrate, the cut-off film structure is coated layer by layer according to the film layer requirements of the cut-off film structure. The Ge film material is evaporated by electron beam evaporation process, and the coating rate of the Ge film is 0.4 to 0.6 nm / s. The ZnS film material is evaporated by resistance evaporation process, and the coating rate of the ZnS film is 1.0 to 3.0 nm / s. The deposition process uses light control to monitor the film thickness and stop, and crystal control is used to monitor the coating rate.

7. The method according to claim 3, characterized in that The method further comprises the steps of: (7) Use PE spectrum two Fourier transform infrared spectrometer to measure the transmittance spectrum of the filter at normal incidence.

8. An infrared pyroelectric sensor, characterized in that: The infrared pyroelectric sensor is provided with the infrared filter for detecting diethyl carbonate gas as claimed in claim 1 or 2.

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