阅读说明：本技术 三氟化氮气体探测用红外滤光片及其制备方法 (Infrared filter for nitrogen trifluoride gas detection and preparation method thereof ) 是由 何虎 张�杰 许晴 于海洋 王爽 于 2021-08-05 设计创作，主要内容包括：本发明涉及一种三氟化氮气体探测用红外滤光片,所述的红外滤光片包括基底、主膜系结构和截止膜系结构；所述的主膜系结构为：Sub/HLHL2HLHLHLHL2HLH0.08M/Air；所述的截止膜系结构为：Sub/0.18(HL)^5 0.265(HL)^7 0.38(HL)^7 0.52(HL)^7 0.73(HL)^7 1.43(0.5LH0.5L)^7 0.1M/Air；所述的红外滤光片的中心波长为11050±100nm,带宽为380±60nm,峰值透射率大于等于78％,截止区2000～18000nm最大透射率小于1％。本发明还提供了相应的制备方法和红外气体传感器。(The invention relates to an infrared filter for nitrogen trifluoride gas detection, which comprises a substrate, a main membrane system structure and a cut-off membrane system structure; the main membrane system structure is as follows: Sub/HLHL2HLHLHLHL2HLH0.08M/Air; the structure of the cut-off film system is as follows: sub/0.18(HL) 50.265 (HL) 70.38 (HL) 70.52 (HL) 70.73 (HL) 71.43(0.5LH0.5L) 70.1M/Air; the central wavelength of the infrared filter is 11050 +/-100 nm, the bandwidth is 380 +/-60 nm, the peak transmittance is greater than or equal to 78%, and the maximum transmittance of a cut-off region of 2000-18000 nm is less than 1%. The invention also provides a corresponding preparation method and an infrared gas sensor.)

1. The infrared filter for detecting nitrogen trifluoride gas is characterized by 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 two sides of the substrate;

the main membrane system structure is as follows:

Sub/HLHL2HLHLHLHL2HLH0.08M/Air, where Sub represents the substrate, Air represents Air, H is a Ge film layer of quarter-wavelength optical thickness, L is a ZnS film layer of quarter-wavelength optical thickness, and M is YbF of quarter-wavelength optical thickness₃The number in the film system structure is the film thickness coefficient, and the design wavelength is 11050 nm;

the structure of the cut-off film system is as follows:

sub/0.18(HL) ^ 50.265 (HL) ^ 70.38 (HL) ^ 70.52 (HL) ^ 70.73 (HL) ^71.43(0.5LH0.5L) ^ 70.1M/Air, wherein Sub represents a substrate, Air represents Air, H is a Ge film layer of quarter-wavelength optical thickness, L is a ZnS film layer of quarter-wavelength optical thickness, M is a YbF film layer of quarter-wavelength optical thickness₃The film layers are the repetition times of the film stack, the numbers in front of the film stack are film thickness coefficients, and the design wavelength is 11050 nm;

the central wavelength of the infrared filter is 11050 +/-100 nm, the bandwidth is 380 +/-60 nm, the peak transmittance is greater than or equal to 78%, and the maximum transmittance of a cut-off region of 2000-18000 nm is less than 1%.

2. The infrared filter for nitrogen trifluoride gas detection according to claim 1, wherein said substrate is single-crystal silicon or single-crystal germanium having a thickness of 0.5mm and polished on both sides.

3. A method for producing the infrared filter for nitrogen trifluoride gas detection according to claim 1 or 2, characterized by comprising the steps of:

(1) putting the substrate into a fixture, placing the fixture into a vacuum chamber of a film coating machine, and vacuumizing;

(2) baking the substrate;

(3) ion bombardment of the substrate;

(4) coating a main film system structure on one side of the substrate layer by layer according to the film layer required by the main film system structure;

(5) turning over the substrate, repeating the steps (1) to (3), and plating a cut-off film system structure on the other side of the substrate layer by layer according to the film layer required by the cut-off film system structure;

(6) and (5) breaking the hollow part after the plating is finished, and taking the part.

4. The method for producing the infrared filter for nitrogen trifluoride gas detection according to claim 3, wherein the step (1) is specifically:

loading the substrate material of single crystal silicon wafer or germanium wafer with thickness of 0.5mm and smoothness satisfying 40/20 standard into fixture, placing in vacuum chamber of film plating machine, and pumping the background vacuum degree to 8 × 10^-4Pa；

The step (2) is specifically as follows:

baking the substrate material at 200-300 ℃, and keeping the constant temperature for more than 120 min;

the step (3) is specifically as follows:

bombarding the substrate material by using Hall ion source ions for 5-15 min, wherein the ion source uses high-purity argon, and the gas flow is 15-25 sccm;

the step (6) is specifically as follows:

and after the plating is finished, reducing the baking temperature to 20-40 ℃, and breaking and taking out the workpiece.

5. The method for producing the infrared filter for nitrogen trifluoride gas detection according to claim 3, wherein the step (4) is specifically:

coating the main film system structure layer by layer according to the film layer required by the main film system structure, and evaporating Ge film material and YbF by adopting an electron beam evaporation process₃The film material is formed by evaporating ZnS film material by adopting a resistance evaporation process, wherein the film coating rate of a Ge film is 0.4-0.6 nm/s, YbF₃The film coating rate of the film is 0.4-0.6 nm/s, the film coating rate of the ZnS film is 2.0-3.0 nm/s, and the thickness and the rate of the film are controlled by combining indirect light control and crystal control in the deposition process.

6. The method for producing the infrared filter for nitrogen trifluoride gas detection according to claim 3, wherein the step (5) is specifically:

reversing the substrate plated with the main film system structure, repeating the steps (1) to (3), plating a cut-off film system structure on the other side of the substrate layer by layer according to the film layer required by the cut-off film system structure, and evaporating the Ge film material and the YbF by adopting an electron beam evaporation process₃The film material has a Ge film coating rate of 0.4-0.6 nm/s and YbF₃The film coating rate of the film is 0.4-0.6 nm/s, the ZnS film material is evaporated by adopting a resistance evaporation process, the film coating rate of the ZnS film is 2.0-3.0 nm/s, and the thickness and the rate of the film are controlled by combining indirect light control and crystal control in the deposition process.

7. The method for manufacturing the infrared filter for nitrogen trifluoride gas detection according to claim 3, further comprising the steps of:

(7) placing the plated infrared filter into an annealing furnace for annealing, wherein the annealing temperature is 250-350 ℃, the constant temperature time is 7-9 hours, and the temperature rising/reducing speed is 1 ℃/min;

(8) the transmittance spectra at normal incidence of the filters were measured using a PE spectra two fourier transform infrared spectrometer.

8. An infrared temperature measuring sensor characterized in that the infrared thermometer is provided with the infrared filter for nitrogen trifluoride gas detection according to claim 1 or 2.

Technical Field

The invention relates to the technical field of infrared gas detectors, and relates to an infrared filter for detecting nitrogen trifluoride gas, and a preparation method and application thereof.

Background

Nitrogen trifluoride, formula NF₃The molecular weight is 71.002, and the product is colorless toxic gas at normal temperature, and has melting point of-206.8 deg.C and boiling point of-129 deg.C. Nitrogen trifluoride gas is a fluorine source for high-energy chemical lasers and is also a plasma etching gas in the microelectronics industryThe method has good selectivity and etching rate for the plasma etching of the silicon substrate. Particularly, with the development of the semiconductor industry in recent years, the consumption of nitrogen trifluoride gas is also rapidly increased. At the same time, however, nitrogen trifluoride gas and a mixed gas of water, hydrogen, ammonia, carbon monoxide, hydrogen sulfide or the like can explode violently in the event of a spark. Meanwhile, nitrogen trifluoride is easy to react with hemoglobin, and the danger is high after the nitrogen trifluoride is inhaled into a human body. Therefore, the problems of gas leakage need to be closely concerned in the production, preparation, storage and use processes of nitrogen trifluoride, otherwise, the problems are easy to cause serious safety accidents. While the infrared gas sensor using the NDIR technique is an important means for performing the nitrogen trifluoride gas monitoring, as shown in FIG. 1, according to the Lambert-beer law at an incident light intensity I₀(λ), gas absorption coefficient α (λ), and optical length L are constant, and the emergent light intensity I (λ) is I₀(λ)exp[-α(λ)CL]Only with respect to the gas concentration C. The function of the filter in the structure is to allow only the light in the infrared absorption region of nitrogen trifluoride to enter the detector, and the light in other wave bands is completely cut off. However, no specially designed infrared filter aiming at nitrogen trifluoride gas detection exists in the market at present, which influences the popularization and application of nitrogen trifluoride gas infrared sensors.

CN 109870408A, an optical filter for non-dispersive infrared detection of nitrogen trifluoride, application thereof and a detection method of nitrogen trifluoride, a sapphire optical filter is used for realizing a filtering effect with high transmittance in a wave band of 10-12 mu m, and the optical filter is inconsistent with optical common knowledge, so the optical filter provided by the patent cannot realize the effect. It is known that to achieve high transmission effect in a certain wavelength band, materials with no or low absorption in the wavelength band should be selected for design, and sapphire materials should be contraindicated in the 10-12 μm wavelength band. Since sapphire has strong optical absorption characteristics in this band, resulting in its complete absorption cutoff (i.e., opaque). Specifically, see fig. 2, which is a transmittance spectrum of sapphire with a thickness of 1mm, self-measured by the inventors; reference may also be made to the contents of the second edition of the rest of the book "infrared optical materials", page 68, fig. 2-30-2-33 and tables 2-8 in the textbook, it is also clear that after 7 microns, it is not useful; also, with reference to FIG. 3, is disclosed by CRYSTRAN, BritishTransmittance spectrum of sapphire, the figure being derived fromhttps://www.crystran.co.uk/optical-materials/sapphire-al2o3. Reference may also be made to the data relating to sapphire, published by the company schottky (schott) germany, which explicitly indicates that sapphire can be used in the transmission spectral range of 250-5000 nm. Therefore, based on the common knowledge of these optics, the filter disclosed in the patent has a transmission spectrum region with a thickness of 10-12 μm, and other spectral curves and lighttight cannot be realized. Secondly, in this patent, the effect of the band pass filter cannot be achieved by plating barium fluoride of 0.4 to 1mm on the silicon wafer, and fig. 8 is a transmission spectrum of the scheme simulated by using the film system design software. In addition, the barium fluoride film with the thickness of 0.4-1 mm plated on the silicon wafer is not consistent with the common technical knowledge, the thickness of the plated film layer is usually in the nanometer and micrometer range, and if the plated film layer with the millimeter range has higher cost, the barium fluoride thin sheet is generally directly used for replacing the film layer.

Disclosure of Invention

The invention mainly aims to solve the problems and provides an infrared filter for nitrogen trifluoride gas detection and a preparation method and application thereof.

In order to achieve the above object, the present invention adopts the following technical scheme of an infrared filter for nitrogen trifluoride gas detection:

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 two sides of the substrate;

the main membrane system structure is as follows:

Sub/HLHL2HLHLHLHL2HLH0.08M/Air, where Sub represents the substrate, Air represents Air, H is a Ge film layer of quarter-wavelength optical thickness, L is a ZnS film layer of quarter-wavelength optical thickness, and M is YbF of quarter-wavelength optical thickness₃The number in the film system structure is the film thickness coefficient, and the design wavelength is 11050 nm;

the structure of the cut-off film system is as follows:

sub/0.18(HL) SP 50.265 (HL) SP 70.38 (HL) SP 70.52 (HL) SP 70.73 (HL) SP 71.43(0.5LH0.5L) SP 70.1M/Air, where Sub represents the substrate, AirRepresenting air, H a Ge film layer of quarter-wavelength optical thickness, L a ZnS film layer of quarter-wavelength optical thickness, and M a YbF of quarter-wavelength optical thickness₃The film layers are the repetition times of the film stack, the numbers in front of the film stack are film thickness coefficients, and the design wavelength is 11050 nm;

the central wavelength of the infrared filter is 11050 +/-100 nm, the bandwidth is 380 +/-60 nm, the peak transmittance is greater than or equal to 78%, and the maximum transmittance of a cut-off region of 2000-18000 nm is less than 1%.

Preferably, the substrate is monocrystalline silicon or monocrystalline germanium with a thickness of 0.5mm and polished on two sides.

The present invention also provides a method for preparing the infrared filter for nitrogen trifluoride gas detection, the method comprising the steps of:

(1) putting the substrate into a fixture, placing the fixture into a vacuum chamber of a film coating machine, and vacuumizing;

(2) baking the substrate;

(3) ion bombardment of the substrate;

(4) coating a main film system structure on one side of the substrate layer by layer according to the film layer required by the main film system structure;

(5) turning over the substrate, repeating the steps (1) to (3), and plating a cut-off film system structure on the other side of the substrate layer by layer according to the film layer required by the cut-off film system structure;

(6) and (5) breaking the hollow part after the plating is finished, and taking the part.

Preferably, the step (1) is specifically:

loading the substrate material of single crystal silicon wafer or germanium wafer with thickness of 0.5mm and smoothness satisfying 40/20 standard into fixture, placing in vacuum chamber of film plating machine, and pumping the background vacuum degree to 8 × 10^-4Pa；

The step (2) is specifically as follows:

baking the substrate material at 200-300 ℃, and keeping the constant temperature for more than 120 min;

the step (3) is specifically as follows:

bombarding the substrate material by using Hall ion source ions for 5-15 min, wherein the ion source uses high-purity argon, and the gas flow is 15-25 sccm;

the step (6) is specifically as follows:

and after the plating is finished, reducing the baking temperature to 20-40 ℃, and breaking and taking out the workpiece.

Preferably, the step (4) is specifically:

coating the main film system structure layer by layer according to the film layer required by the main film system structure, and evaporating Ge film material and YbF by adopting an electron beam evaporation process₃The film material is formed by evaporating ZnS film material by adopting a resistance evaporation process, wherein the film coating rate of a Ge film is 0.4-0.6 nm/s, YbF₃The film coating rate of the film is 0.4-0.6 nm/s, the film coating rate of the ZnS film is 2.0-3.0 nm/s, and the thickness and the rate of the film are controlled by combining indirect light control and crystal control in the deposition process.

Preferably, the step (5) is specifically:

reversing the substrate plated with the main film system structure, repeating the steps (1) to (3), plating a cut-off film system structure on the other side of the substrate layer by layer according to the film layer required by the cut-off film system structure, and evaporating the Ge film material and the YbF by adopting an electron beam evaporation process₃The film material has a Ge film coating rate of 0.4-0.6 nm/s and YbF₃The film coating rate of the film is 0.4-0.6 nm/s, the ZnS film material is evaporated by adopting a resistance evaporation process, the film coating rate of the ZnS film is 2.0-3.0 nm/s, and the thickness and the rate of the film are controlled by combining indirect light control and crystal control in the deposition process.

Preferably, the method further comprises the steps of:

(7) placing the plated infrared filter into an annealing furnace for annealing, wherein the annealing temperature is 250-350 ℃, the constant temperature time is 7-9 hours, and the temperature rising/reducing speed is 1 ℃/min;

(8) the transmittance spectra at normal incidence of the filters were measured using a PE spectra two fourier transform infrared spectrometer.

The invention also provides an infrared temperature measurement sensor, and the infrared temperature measurement instrument is provided with the infrared optical filter for nitrogen trifluoride gas detection.

The infrared filter for nitrogen trifluoride gas detection, the preparation method and the application thereof are adopted, and a regular film system is used, so that the infrared filter for nitrogen trifluoride gas detection is beneficial to positioning and filtering by using a light control technologyThe center wavelength and the bandwidth of the pass band of the chip ensure the accuracy of a transmission peak, and simultaneously fluoride YbF is used as the outermost layer₃The film material can ensure the accurate spectrum and play a role in resisting nitrogen trifluoride reaction, and the service life of the optical filter is prolonged.

Drawings

FIG. 1 is a schematic diagram of a structure of an NDIR infrared sensor.

Fig. 2 is a transmittance spectrum of sapphire with a thickness of 1mm, which was self-measured by the inventors.

Fig. 3 is a transmittance spectrum of sapphire disclosed by CRYSTRAN corporation, uk.

FIG. 4 is a schematic view showing the structure of an infrared filter for nitrogen trifluoride gas detection according to the present invention.

FIG. 5 is a spectrum diagram of a narrow-band infrared filter with a central wavelength of 11000 nm.

FIG. 6 is a partial enlarged view of the spectrum of a 11000nm center wavelength narrow band infrared filter of the present invention.

Fig. 7 is a transmission spectrum of an infrared band of single crystal silicon.

Fig. 8 is a transmission spectrum of CN 109870408A solution simulated using film system design software.

Detailed Description

In order to clearly understand the technical contents of the present invention, the following examples are given in detail.

As shown in fig. 4, in order to solve the problem that no special filter dedicated for nitrogen trifluoride gas detection exists in the current market, the present invention provides an embodiment of an infrared filter for nitrogen trifluoride gas detection, wherein the infrared filter includes a substrate, a main film structure and a cut-off film structure, and the main film structure and the cut-off film structure are respectively disposed on two sides of the substrate. The main membrane system structure and the cut-off membrane system structure use alternately superposed Ge membrane layers and ZnS membrane layers, and ytterbium fluoride (YbF3) is used as the outermost layer, so that the accuracy of the spectrum is ensured, and the corrosion of nitrogen trifluoride is resisted.

Specifically, the main film system structure is as follows: Sub/HLHL2HLHLHLHL2HLH0.08M/Air, where Sub denotes substrate, Air denotes Air, and H is quarter-wave optical thicknessGe film, ZnS film with quarter-wavelength optical thickness L, YbF with quarter-wavelength optical thickness M₃The number in the film system structure is the film thickness coefficient, and the design wavelength is 11050 nm;

the structure of the cut-off film system is as follows: sub/0.18(HL) ^ 50.265 (HL) ^ 70.38 (HL) ^ 70.52 (HL) ^ 70.73 (HL) ^71.43(0.5LH0.5L) ^ 70.1M/Air, wherein Sub represents a substrate, Air represents Air, H is a Ge film layer of quarter-wavelength optical thickness, L is a ZnS film layer of quarter-wavelength optical thickness, M is a YbF film layer of quarter-wavelength optical thickness₃The film layers are the repetition times of the film stack, the numbers in front of the film stack are film thickness coefficients, and the design wavelength is 11050 nm;

according to the infrared absorption spectrogram of nitrogen trifluoride gas, a deep absorption peak is formed at the position of 11.05 +/-0.2 mu m, so that the high transmission region of the optical filter is arranged in the waveband, but the condition that the absorption saturation is easily generated under the same optical path condition because the absorption coefficient of the gas is larger as the bandwidth is wider is also considered, namely when alpha (lambda) is larger, the emergent light intensity I (lambda) approaches to zero and is not sensitive to the concentration change. As shown in FIG. 5 and FIG. 6, the center wavelength of the narrow-band infrared filter of the invention is 11050 +/-100 nm, the bandwidth is 380 +/-60 nm, the peak transmittance is more than or equal to 78%, and the maximum transmittance of the cut-off region of 2000-18000 nm (except the passband) is less than 1%. The transmission passband of the invention is 380nm, which is obviously different from the projection passband of 2000nm of CN 109870408A.

The substrate is monocrystalline silicon or monocrystalline germanium with the thickness of 0.5mm and double-side polishing. As shown in FIG. 7, the single crystal silicon is used as the transmission spectrum of the infrared band of the substrate material, and the material has the advantages of wide infrared transmission spectrum (2-18 μm transmission) and low cost. In addition, the monocrystalline germanium can also be used as a substrate material, but the monocrystalline germanium is expensive and is not suitable for mass production.

The present invention also provides an embodiment of a method for preparing the infrared filter for nitrogen trifluoride gas detection, the method comprising the steps of:

(1) loading the base material of monocrystalline silicon piece with thickness of 0.5mm, diameter of 100mm and fineness satisfying 40/20 standard into fixture, and placing into vacuum chamber of film coating machineIn the interior, the background vacuum degree is pumped to 8X 10^-4Pa; when the main film system structure is plated, the substrate is preferentially placed at a position with better film thickness uniformity, and the outermost circle station of the rotary substrate table is generally avoided.

(2) Baking the substrate material at 200-300 ℃, and keeping the constant temperature for more than 120 min; preferably, the baking temperature is 250 ℃;

(3) bombarding the substrate material by using Hall ion source ions for 5-15 min, wherein the ion source uses high-purity argon, and the gas flow is 15-25 sccm; the bombardment time is preferably 10 min;

(4) coating a main film system structure on one side of the substrate layer by layer according to the film layer required by the main film system structure, and evaporating Ge film material and YbF by adopting an electron beam evaporation process₃The film material is formed by evaporating ZnS film material by adopting a resistance evaporation process, wherein the film plating rate of the Ge film is preferably 0.5nm/s, YbF₃The film coating rate of the film is preferably 0.5nm/s, the film coating rate of the ZnS film is 2.5nm/s, and the thickness and the rate of the film are controlled by combining indirect light control and crystal control in the deposition process;

(5) reversing the substrate plated with the main film system structure, repeating the steps (1) to (3), plating a cut-off film system structure on the other side of the substrate layer by layer according to the film layer required by the cut-off film system structure, and evaporating the Ge film material and the YbF by adopting an electron beam evaporation process₃The film material and the Ge film have the film coating rate of 0.5nm/s and YbF₃The film coating rate of the film is preferably 0.5nm/s, a ZnS film material is evaporated by adopting a resistance evaporation process, the film coating rate of the ZnS film is 2.5nm/s, and the thickness and the rate of the film layer are controlled by combining indirect light control and crystal control in the deposition process;

(6) after the plating is finished, the baking temperature is reduced to 30 ℃, and the workpiece is broken and taken out.

(7) Placing the plated infrared filter into an annealing furnace for annealing, wherein the annealing temperature is preferably 300 ℃, the constant temperature time is preferably 8 hours, and the temperature rising/reducing speed is 1 ℃/min;

(8) the transmittance spectra at normal incidence of the filters were measured using a PE spectra two fourier transform infrared spectrometer.

The invention also provides an infrared temperature measurement sensor, and the infrared temperature measurement instrument is provided with the infrared optical filter for nitrogen trifluoride gas detection.

By adopting the infrared filter for nitrogen trifluoride gas detection and the preparation method and application thereof, the structured film system is used, the positioning of the center wavelength and the bandwidth of the passband of the filter by using the light control technology is facilitated, the accuracy of a transmission peak is ensured, and the fluoride YbF is used as the outermost layer₃The film material can ensure the accurate spectrum and play a role in resisting nitrogen trifluoride reaction, and the service life of the optical filter is prolonged.

In this specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.