CN119461234A - Vacuum microcavity interferometer chip, manufacturing method and low-drift optical pressure sensor - Google Patents

Abstract

The vacuum microcavity interferometer chip comprises a first substrate, a vacuum microcavity interferometer chip, a manufacturing method and a low-drift optical pressure sensor, wherein a film island structure is formed on the upper surface of the first substrate, the film island structure comprises a protruding part and a pressure sensitive film surrounding the protruding part, a first side wall part, a getter cavity, a second side wall part and a F-P interference cavity positioned at the center are sequentially arranged on the lower surface of the first substrate in the F-P interference cavity, a first reflecting surface is deposited on the lower surface of the first substrate in the F-P interference cavity, a second reflecting surface is deposited on the upper surface of the second substrate in the F-P interference cavity, a first optical antireflection film is deposited on the surface of the protruding part, and the first optical antireflection film, the protruding part, the pressure sensitive film, the first reflecting surface and the second reflecting surface have the same center, and further comprises a vent hole, and the vent hole is arranged on the second side wall part and used for communicating the getter cavity and the F-P interference cavity.

Description

Vacuum microcavity interferometer chip, manufacturing method and low-drift optical pressure sensor

Technical Field

The invention relates to a sensor in the photoelectric technical field, in particular to a wide-range vacuum microcavity interferometer chip based on a vacuum microcavity multi-beam interferometer principle, a manufacturing method and a low-drift optical pressure sensor, which are mainly used for measuring pressure signals of fluid media such as gas, liquid and the like, and also can be used for measuring and controlling flow, flow velocity, density, liquid level, altitude, contact acting force between objects and the like.

Background

The pressure sensor is a device or apparatus capable of sensing pressure signals of fluid media such as gas, liquid and the like and converting the pressure signals into usable output electric signals or optical signals according to a certain rule. The pressure sensor is the most commonly used sensor in industrial practice, is widely applied to various industrial self-control environments such as water conservancy and hydropower, railway traffic, intelligent building, production self-control, aerospace, military industry, petrochemical industry, oil well, electric power, ships, machine tools, pipelines and the like, and is increasingly widely applied to the consumer electronics fields such as medical equipment, robots, automobile electronics, smart phones, intelligent household appliances, wearable electronic products and the like.

The product selling price of the pressure sensor is mainly dependent on applicable use conditions and measurement accuracy that can be maintained for a long period of time. Industrial pressure sensors meeting 0.01% precision within the working temperature range of-55 ℃ to 85 ℃ and pressure sensors with temperature resistance exceeding 200 ℃ and full temperature area meeting 0.1% precision reach thousands yuan or even tens of thousands of primordial notes. Pressure sensors with wide temperature range, high accuracy, high reliability and low drift have great application requirements in various fields such as nuclear power, aerospace, rail transit, semiconductor equipment, process industry and the like. Pressure sensors may be categorized in terms of detection, such as electrically and optically detected pressure sensors. Among the pressure sensors for electrical detection, the resonant pressure sensor has a series of advantages of high temperature stability, high long-term stability, high comprehensive precision and the like, and is widely accepted by the market. However, the use of the optical fiber pressure sensor is limited in the occasions of high temperature, radiation, electromagnetic interference and the like, and the optical fiber pressure sensor can meet the use requirements of the occasions. The optical fiber sensing technology is a new technology which is rapidly developed in the late 70 th century and is the application of fiber optics in the non-communication field. The optical fiber sensing technology has the advantages of wide application range, high sensitivity, electromagnetic interference resistance, good insulativity, corrosion resistance, flexibility, small volume, low cost, good compatibility with optical fiber transmission lines and the like.

The optical fiber F-P (Fabry-Perot) pressure sensor is one of optical fiber pressure sensors, and a Fabry-Perot micro resonant cavity is generally formed by an optical fiber end face and a diaphragm end face, and when pressure acts on a pressure sensitive film, deformation is generated, so that the cavity length of the Fabry-Perot cavity is changed, and sensing measurement is realized. The optical fiber Fabry-Perot pressure sensor has a simple structure and is easy to realize, and is the interference type optical fiber pressure sensor most commonly used at present. The pressure sensitive film of some sensors is made by micro-electro-mechanical (MEMS) bulk silicon process and surface sacrificial layer process, and the pressure sensitive film of some sensors is made by optical fiber corrosion fusion process. In recent years, some design schemes, such as （Jie Zhou, Samhita Dasgupta, et al. Optically interrogated MEMS pressure sensors for propulsion applications, Optical Engineering, 2001, 40: 598-604.） of Cincinnati university in 2001, are adopted to manufacture an optical fiber Fabry-Perot pressure sensor by using a bulk silicon process, wherein a monocrystalline silicon film is used as a pressure sensitive film, a shallow thin cylindrical cavity is corroded on glass by using an HF buffer solution, the silicon film and the glass are tightly bonded together by using an electrostatic bonding process to form a Fabry-Perot cavity, finally, an optical fiber and a sensor chip are aligned and bonded by using epoxy resin, and the coupling angle between the optical fiber and the sensor chip is changed due to creep of the epoxy resin under the action of external environment, so that zero output of the sensor is drifted.

The MEMS optical fiber pressure sensor combines the advantages of microminiaturization, high reliability and high consistency of the MEMS technology and the advantages of the optical fiber signal reading technology, and greatly expands the application range of the high-precision pressure sensor. High precision MEMS fiber optic sensors typically use wavelength demodulation schemes, particularly F-P optical interferometric cavity (fabry-perot) interferometers. The working principle is that the pressure sensitive film is integrated with the optical F-P optical interference cavity, the external pressure causes the pressure sensitive film to generate translational displacement, the cavity length of the F-P optical interference cavity is synchronously changed, the interference wavelength is also changed, and the external pressure is measured through the change of the optical fiber reading wavelength. Specifically, the Chinese patent application CN201410728291.6 in the prior art discloses that the pressure is measured by utilizing an F-P optical interference cavity, the sensor is provided with a film island structure arranged in the F-P optical interference cavity, the inward arranged film island structure increases the volume of the F-P optical interference cavity, the arrangement area of a getter film is further increased, meanwhile, the inward arranged film island structure has limited height due to the limitation of the F-P optical interference cavity, so that an optical antireflection film arranged on the film island structure needs to have high transmittance, the cost of a vacuum microcavity interferometer chip is increased, and in addition, the inward arranged film island structure cannot be continuously processed after the sensitive chip is bonded and connected, and the parameters of the vacuum microcavity interferometer chip cannot be adjusted.

The dynamic detection resolution of the multi-beam F-P interferometer on the cavity length can reach 1 pm-10 pm, and the dynamic detection resolution of the dual-beam F-P interferometer on the cavity length can only reach the magnitude of 100 pm-1 nm, so that the sensitivity of the pressure sensor can be greatly improved by constructing the multi-beam F-P interferometer inside the vacuum microcavity interferometer chip. However, the optical reflectivity of two reflecting surfaces of the F-P interferometer is improved by depositing an optical film, and the parallelism and the cleanliness of the two reflecting surfaces are very high, so that laser signals entering the cavity can be maintained to form hundreds of reflections between the two reflecting surfaces, and the basic condition of multi-wavelength interference is met. The temperature-resistant range of 500-600 ℃ of the optical film is limited, and the reflective surface optical film of the multi-beam F-P interferometer in the MEMS chip can be kept intact only by adopting a silicon-glass bonding process in the temperature range of 300-400 ℃, but the vacuum degree of an interference cavity in the multi-beam F-P interferometer is reduced and an unstable refractive index is formed due to gas released by silicon-glass bonding, so that the low-voltage measurement range and zero stability of the MEMS pressure sensitive chip are affected, and the temperature coefficient is increased and the measurement repeatability is reduced. For high-precision pressure measurement, such sensors typically require that the interior of the F-P optical interferometric cavity be evacuated and that the vacuum be maintained stable. Typically, some residual gas remains in the chamber during the manufacturing process. Therefore, it is necessary to enclose a getter in the vacuum chamber and activate the getter during sensor fabrication to absorb residual gases in the F-P optical interference chamber, achieving a high vacuum inside the pressure sensor. Chinese patent application CN20121017590.0 discloses a MEMS chip package structure, in which a getter is usually deposited inside an F-P optical interference cavity by PVD (physical vapor deposition), and the getter occupies a large area to ensure that residual gas is absorbed cleanly. On the other hand, the getter is of a porous structure, the density of the getter is poor, the getter is heated or vibrated by the outside to generate particles, pollute an F-P optical interference cavity, potentially cause spectrum degradation, have larger influence on measurement of an optical sensor in particular, and seriously cause device failure. The Chinese patent application CN201410264998.6 relates to a mixed wafer level vacuum packaging method, wherein a getter cavity is arranged at the side part of a chip packaging cavity and communicated through a vent hole, and after the getter is fixed in the getter cavity, a fixed cover plate is used, so that the structure and the method have the potential of polluting an F-P optical interference cavity by the getter, and the getter cavity and the getter are overlapped after the chip is molded, so that the manufacturing process is complex; and there is a certain possibility that the getter particles enter the working cavity through the vent hole channel, and the getter particles have a certain insulation property and have little influence on the electric detection type sensor.

In addition, after the MEMS pressure sensitive chip and the optical fiber are coupled and packaged to form the MEMS optical pressure module, the MEMS pressure sensitive chip and the optical fiber are usually required to be secondarily packaged and fixed on the pressure sensor shell, so that the MEMS optical pressure sensor capable of being independently installed and used is realized from sealing pressure taking and module measurement to lead-out cable isolation protection. In the sensitive chip structure described in CN201410728291.6, in the secondary packaging process, no matter the external mechanical force received by the shell is conducted to the MEMS pressure sensitive chip or conducted to the welding packaging position of the MEMS pressure sensitive chip and the optical fiber, the multi-beam F-P interferometer is subjected to uneven stress, so that the interference spectrum is degraded, the measured value is abnormally changed, and the zero output of the sensor is also caused to drift.

In addition to high accuracy requirements, pressure sensors of industrial type are often required to have low drift characteristics, including long-term high stability of zero point and low temperature drift, due to difficult maintenance and calibration or high cost. Compared with the traditional voltage force sensor (such as piezoresistance type), the MEMS optical fiber sensor has higher zero point stability naturally due to no influence of resistance thermal noise and the like. According to the invention, the welding of the sensor chip and the shell is realized through the welding of the second substrate and the shell, so that the influence of residual stress and thermal expansion and cold contraction of the shell and solder on the pressure sensor sensitive film and the optical fiber collimator is greatly reduced, and the zero point stability of the pressure sensor can be effectively improved. The first and third substrates are substantially symmetrical with respect to the second substrate, and also substantially reduce sensor output variations due to temperature variations, i.e. low temperature drift. Under the condition of not adding additional temperature measuring elements for digital temperature compensation, the thermal drift output change of the full temperature area at-55 ℃ to 125 ℃ can reach less than 1% of the full range pressure output change of the sensor.

Disclosure of Invention

In order to overcome the technical defects of the optical fiber pressure sensor in the prior art, the invention provides a vacuum microcavity interferometer chip, a manufacturing method and a low-drift optical pressure sensor, wherein the vacuum microcavity interferometer chip comprises a first substrate, a second substrate and a third substrate, the first substrate and the third substrate can be silicon wafers or silicon nitride wafers and other substrates with similar functions, the second substrate can be glass sheets or sapphire and other substrates with similar functions, the three substrates are fixedly connected through silicon-glass-silicon bonding or bonding through corresponding dielectric layers such as BCB (binary coded block) glue, gold layers or glass paste and the like, a film island structure is formed on the upper surface of the first substrate, the film island structure comprises a bulge formed by utilizing a counter bore and a pressure sensitive film surrounding the bulge, and the lower surface of the first substrate is sequentially provided with a first side wall part, a second side wall part and a third side wall part in the radial direction, The optical fiber collimator comprises a getter cavity, a second side wall part, an F-P interference cavity positioned in the center, wherein a first reflecting surface is deposited on the lower surface of a first substrate in the F-P interference cavity, a second reflecting surface is deposited on the upper surface of a second substrate in the F-P interference cavity, a first optical antireflection film is deposited on the surface of a protruding part, the first optical antireflection film, the protruding part, the pressure sensitive film, the first reflecting surface and the second reflecting surface have the same center, a mounting hole of the optical fiber collimator is arranged in the center of a third substrate, at least one surface of the getter cavity is provided with the getter film, and the optical fiber collimator further comprises a vent hole which is arranged on the second side wall part and used for communicating the getter cavity with the F-P interference cavity. The upper surface of the first substrate is a pressure facing side, the thickness of the bulge can be increased through the film island structure facing the pressure facing side, the optical path is increased by utilizing the high refractive index of silicon of the bulge, the light passing through the first reflecting surface is attenuated, the process difficulty of depositing an optical antireflection film on the bulge surface and the transmittance of the optical antireflection film are reduced, the interference influence of multi-interface reflected light on an F-P interference cavity is better eliminated, the multi-beam F-P interference cavity has more excellent spectral characteristics, the pressure monitoring interference of a vacuum microcavity interferometer chip is reduced, the reflectivity of the first reflecting surface is non-total reflection, the reflectivity is less than 50%, the light which is more than 50% is transmitted into the bulge from the first reflecting surface, the partial transmission light is attenuated by the smaller bulge thickness, the first optical antireflection film with higher transmittance is required to be arranged, even the first optical antireflection film with higher transmittance of 99% is better, the optical film with higher transmittance is opposite to the first optical antireflection film, the island structure is required to be reduced, the total cost of the film is reduced, the total film is required to pass through the film with the pressure-reducing film on the pressure facing side, and the pressure-reducing side of the bulge is reduced, the total volume of the film is required to be reduced, and the total three-layer of the film is reduced, the total film is required to pass through the film is reduced, and the film is reduced after the film is required to be pressed, the total has the film is reduced and the total has the film is reduced, the required to be pressed, the film is reduced and has the film and has the required to be reduced and has the film and has the advantages, the geometric dimensions of the pressure sensitive film and the frame positioned outside the pressure sensitive film are selectively processed, so that the sensitivity of the vacuum microcavity interferometer chip is flexibly adjusted. Through the structure, the getter cavity is connected with the F-P interference cavity through the vent holes, and the getter cavity can be independently arranged, so that the getter cavity is ensured to have enough surface area to absorb residual gas in the F-P optical interference cavity, the area of the pressure sensitive film can be flexibly adjusted, and the pressure sensitive film can be reduced to the minimum area during wide-range pressure measurement.

In a preferred embodiment, the vent hole is arranged on the second side wall part, the second side wall part has a first height, the vent hole is preferably arranged at the middle height position of the second side wall part and is communicated with the getter cavity and the F-P interference cavity, the getter film generates a small amount of particles after activation, and the particles cannot pass through the vent hole to reach the F-P interference cavity along with vibration of the sensor by arranging the vent hole at the middle height position of the second side wall part, so that the optical film in the F-P interference cavity is prevented from being polluted to cause chip failure.

In a further preferred embodiment, the getter cavity is an annular cavity, thereby providing a maximum getter cavity area, increasing the area of the getter film.

In a further preferred embodiment, the vent hole is arranged at the bottom of the second side wall part, and the vent hole can be processed by etching, and can be formed in the same step with the getter cavity and the F-P interference cavity.

In a preferred embodiment, the first substrate protrusion is in a cylindrical structure, and the pressure sensitive film has a circular area, so that uniform stress is realized on fluid media such as gas, liquid and the like, the high pressure resistance of the chip is improved, and the interference spectrum stability between two reflecting surfaces of an F-P interference cavity in the vacuum microcavity interferometer chip under the action of pressure is improved.

In a preferred embodiment, the first substrate and the third substrate have the same diameter, and the first substrate and the third substrate have the same thickness, and the same thickness and diameter form a symmetrical structure about the second substrate, and because the first substrate and the third substrate are both silicon wafers, silicon nitride or other substrates, and have the same temperature coefficient, the three-layer substrate has good stress matching characteristics, so that the whole of the vacuum microcavity interferometer chip has extremely low temperature coefficient, bending deformation of the center of the vacuum microcavity interferometer chip is reduced to ensure that two reflecting surfaces of the F-P optical interference cavity are kept relatively parallel under the action of full range pressure, high zero point long-term stability (0.1% of full range can be kept through good stress matching) and low temperature drift characteristics (full temperature drift output change of minus 55 ℃ to 125 ℃ can be smaller than 1% of full range temperature measurement output change of a sensor under the condition of no additional digital temperature compensation of an additional element) are formed.

In a preferred embodiment, the second substrate is larger than the first substrate and the third substrate, so that when the sensor is manufactured by using the vacuum microcavity interferometer chip, the exposed surfaces formed by the second substrate and the third substrate are adhered or welded and fixed with the sensor shell by using the second substrate with larger external dimensions than the first substrate and the third substrate, so that the first substrate, the third substrate and the optical fiber collimator are not contacted with the sensor shell, the stress isolation between the film island structure of the vacuum microcavity interferometer chip and the optical fiber collimator on the third substrate and the sensor shell is realized, and the stress isolation is directly transmitted to the second substrate when the sensor shell is stressed or vibrated, and because the first substrate and the third substrate are arranged on two sides of the second substrate and have approximately symmetrical structures, the first substrate and the third substrate vibrate integrally, the stress is not applied to the film island structure and the optical fiber collimator on the third substrate, the zero point output is not changed before and after the field mechanical fastening or when the sensor shell is impacted by external force, and the high zero point long-term stability and low temperature drift characteristics are formed.

In a preferred embodiment, the getter film is deposited on the lower surface of the second substrate in the getter cavity and/or on the upper surface of the first substrate, a notch groove is provided in the first and second side wall parts, the notch groove being located at the position where the first and second side wall parts are bonded to the second substrate, and the notch groove communicates with the getter cavity, the notch groove being an annular groove, and when a small amount of particles are generated by the getter film after activation, the particles can be received in the notch groove when the sensor is tilted or vibrated. Free-moving particles within the getter chamber are further reduced, reducing the likelihood of particles entering the F-P interferometric chamber through the vent holes.

The application also relates to a low-drift optical pressure sensor, which comprises a sensor shell and a sensitive chip mounting seat arranged in the sensor shell, wherein the vacuum microcavity interferometer chip is in contact fixation with the sensitive chip mounting seat only through the second substrate. The structure can realize stress isolation among the film island structure of the vacuum microcavity interferometer chip, the optical fiber collimator on the third substrate and the sensor shell, and when the sensor shell is stressed or vibrated, the stress is directly transmitted to the second substrate, and because the first substrate and the third substrate are arranged on two sides of the second substrate and have approximately symmetrical structures, the first substrate and the third substrate vibrate integrally, stress can not be applied to the film island structure and the optical fiber collimator on the third substrate, and zero point output of the vacuum microcavity interferometer chip is ensured not to be changed before and after field mechanical fastening installation or when the vacuum microcavity interferometer chip is impacted by external force.

The application also relates to a manufacturing method of the MEMS vacuum microcavity interferometer chip, wherein the first substrate is selected as an SOI silicon wafer (top silicon-buried oxide layer-bottom silicon three-layer structure); S1, forming a getter cavity, a F-P interference cavity and a vent hole which is communicated with the getter cavity and the F-P interference cavity on one surface of a first substrate through etching and/or KOH etching, depositing a first reflecting surface on the surface of the F-P interference cavity, etching and/or KOH etching on the other surface of the first substrate to form a film island structure, wherein the surface of the protruding part is an original polished surface and has the same thickness as a frame, a first optical antireflection film is deposited on the protruding part, S2 the second substrate is a double-sided polished glass sheet, a second reflecting surface and a getter film are deposited on the surface of the second substrate at the position corresponding to the F-P interference cavity, the getter film and the second reflecting surface are positioned on the same side of the second substrate, a second optical antireflection film is deposited on the other surface of the second substrate at the position corresponding to the mounting hole, S3 is selected to be a super-flat double optical fiber, the collimator is deposited on the protruding part, the second substrate is normally bonded with the second substrate at the temperature of 300 ℃ at the surface of the second substrate, the second substrate is normally bonded with the second substrate at the temperature of 300 ℃ by thermal bonding, and the thermal bonding surface of the second substrate is normally prevented from being influenced by the thermal bonding surface of the second substrate, and the second substrate is subjected to 300 ℃, therefore, the getter film can be activated at the same time of bonding, the getter film does not need to be activated after the device is manufactured, the bonding temperature of silicon-glass-silicon is usually lower than 400 ℃ or the bonding temperature of a corresponding dielectric layer is lower than 400 ℃, and the optical film with the temperature resistance higher than 500 ℃ manufactured by adopting optical dielectric material deposition in the chip can be ensured not to be influenced.

Further preferred embodiments further comprise step S5, after the three-layer substrate is bonded, measuring the thickness of the single crystal silicon of each of the protrusion of the film island structure and the pressure sensitive thin film in real time and controlling the selective processing. The geometric dimensions of the protruding part of the membrane island structure, the pressure sensitive thin film and the frame positioned outside the pressure sensitive thin film are selectively processed, so that the sensitivity of the vacuum microcavity interferometer chip is flexibly adjusted.

The invention aims to provide a vacuum microcavity interferometer chip, a manufacturing method and a low-drift optical pressure sensor, wherein a multi-beam F-P interference cavity for pressure sensitivity and detection is separated from a getter cavity in the vacuum microcavity interferometer chip and connected with the getter cavity through a vent hole, the area of a pressure sensitive film and the area of the getter can be independently adjusted according to the requirement by the structure, and activated getter particles are prevented from entering the F-P interference cavity by the corresponding structure, so that the reliability of the vacuum microcavity interferometer chip is influenced; the second substrate of the MEMS vacuum microcavity interferometer chip has the external dimension larger than the exposed surface formed by the first substrate and the third substrate or is bonded or welded and fixed with the sensor shell through a glass protection tube, the first substrate, the third substrate and the optical fiber collimator are not connected with the sensor shell through solder or adhesive, the sensitive structure of the MEMS vacuum microcavity interferometer chip, the packaging part of the optical fiber collimator and the chip and the pressure sensor shell are isolated in stress, the chip adopts a three-layer bonding structure, various structures and materials such as a pressure sensitive film, an optical F-P optical interference cavity and a getter are integrated and miniaturized, the getter film is activated in the bonding process, the manufacturing process of the sensor is simplified, the energy consumption is not required to be consumed independently, the film island structure facing the pressure facing side is beneficial to reducing the thickness of the F-P interference cavity, the volume and the air in the film island structure are reduced, the area of the getter film is reduced, and after the three-layer bonding of the substrate is completed, the bump part of the film island structure is subjected to the bonding, the geometric dimensions of the pressure sensitive film and the frame positioned outside the pressure sensitive film are selectively processed, so that the sensitivity of the vacuum microcavity interferometer chip is flexibly adjusted.

Drawings

FIG. 1 is a schematic diagram of a MEMS vacuum microcavity interferometer chip of the present application;

FIG. 2 is a schematic top structure of a first substrate;

FIG. 3 is a schematic diagram of another embodiment;

FIG. 4 is a schematic view of the bottom structure of the first substrate in FIG. 3;

FIG. 5 is a schematic diagram of a pressure sensor;

fig. 6 is a schematic view of a portion of the structure in fig. 5.

Reference numerals illustrate:

1-a first substrate, 11-a bulge, 111-a first optical antireflection film, 112-a first reflection surface, 113-a second reflection surface, 114-a second optical antireflection film, 12-a pressure sensitive film, 13-a first side wall part, 14-a getter cavity, 141-a notch groove, 142-a vent hole, 15-a second side wall part, 16-F-P interference cavity, 2-a second substrate, 3-a third substrate, 31-an optical fiber collimator, 32-a mounting hole, a 4-sensor housing and 5-a sensitive chip mounting seat.

Detailed Description

In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

For the sake of simplicity of the drawing, the parts relevant to the present invention are shown only schematically in the figures, which do not represent the actual structure thereof as a product. Additionally, in order to simplify the drawing for ease of understanding, components having the same structure or function in some of the drawings are shown schematically with only one of them, or only one of them is labeled. Herein, "a" means not only "only this one" but also "more than one" case.

It should be further understood that the term "and/or" as used in the present specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.

In this context, unless explicitly stated or limited otherwise, the terms "mounted," "connected," "coupled," and "connected" are to be construed broadly, and may, for example, be fixedly connected, detachably connected, or integrally connected, mechanically connected, electrically connected, directly connected, indirectly connected via an intervening medium, or communicate between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

In order to overcome the technical defects of the optical fiber pressure sensor in the prior art, the invention provides a vacuum microcavity interferometer chip, a manufacturing method and a low-drift optical pressure sensor, the vacuum microcavity interferometer chip comprises a first substrate 1, a second substrate 2 and a third substrate 3, the first substrate 1 and the third substrate 3 are silicon wafers, the second substrate 2 is a glass sheet, the three substrates are connected through bonding, a film island structure is formed on the upper surface of the first substrate 1, as shown in fig. 1, the film island structure comprises a bulge 11 formed by utilizing a counter bore and a pressure sensitive film 12 surrounding the bulge 11, a first side wall part 13 is sequentially arranged on the lower surface of the first substrate 1 along the radial direction, The optical fiber collimator comprises a getter cavity 14, a second side wall part 15 and a centrally located F-P interference cavity 16, wherein a first reflecting surface 112 is deposited on the lower surface of a first substrate 1 in the F-P interference cavity 16, a second reflecting surface 113 is deposited on the upper surface of a second substrate 2 in the F-P interference cavity 16, a first optical antireflection film 111 is deposited on the surface of a convex part 11, the first optical antireflection film 111, the convex part 11, the pressure sensitive film 12, the first reflecting surface 112 and the second reflecting surface 113 have the same center, a mounting hole 32 of the optical fiber collimator 31 is arranged at the center of a third substrate 3, at least one surface of the getter cavity 14 is provided with a getter film, and a vent hole 142 is arranged on the second side wall part 15 and used for communicating the getter cavity 14 with the F-P interference cavity 16. The upper surface of the first substrate 1 is a pressure facing side, and through a film island structure facing the pressure facing side, the optical path can be increased by increasing the thickness of the protruding part 11 and utilizing the high refractive index of silicon of the protruding part 11 to attenuate the light passing through the first reflecting surface 112, so that the process difficulty of depositing an optical antireflection film on the surface of the protruding part 11 and the transmittance requirement of the optical antireflection film are reduced, the interference influence of multi-interface reflected light on the F-P interference cavity 16 is better eliminated, the multi-beam F-P interference cavity 16 has more excellent spectral characteristics, and the pressure monitoring sensitivity of the vacuum microcavity interferometer chip is improved; for example, when the half-reflection demodulation mode is adopted, the reflectivity of the first reflecting surface 112 is set to be non-total reflection, the half-reflection demodulation mode has the reflectivity less than 50%, more than 50% of light can be transmitted from the first reflecting surface 112 into the convex part 11, for example, at the thickness of the smaller convex part 11, the partial transmitted light is attenuated less, so that the first optical antireflection film 111 with higher light transmittance, even the first optical antireflection film 111 with 99% light transmittance, has high process and cost requirements on the first optical antireflection film 111, and meanwhile, the film island structure facing the pressure facing side is beneficial to reducing the thickness of the F-P interference cavity 16, thereby reducing the volume and air in the F-P interference cavity and reducing the area of a getter film, and after the three-layer substrate is bonded, the convex part of the film island structure is subjected to the following the steps of bonding, the geometry of the pressure sensitive membrane 12 and the rim on the outside of the pressure sensitive membrane 12 are selectively machined, see fig. 2, to flexibly adjust the sensitivity of the vacuum microcavity interferometer chip. Through the structure, the getter cavity 14 is connected with the F-P interference cavity 16 through the vent hole 142, and the getter cavity 14 can be independently arranged, so that the getter cavity 14 is ensured to have enough surface area to absorb residual gas in the F-P optical interference cavity, and the area of the pressure sensitive film 12 is ensured to be small enough during large pressure measurement, and the requirement of corresponding measurement sensitivity is met.

In a preferred embodiment, the at least one vent hole 142 is arranged on the second side wall 15, the second side wall 15 has a first height, preferably the vent hole 142 is arranged at the middle height position of the second side wall 15 and is communicated with the getter cavity 14 and the F-P interference cavity 16, the getter film generates a small amount of particles after activation, and the vent hole 142 is arranged at the middle height position of the second side wall 15, so that the particles cannot pass through the vent hole 142 to reach the F-P interference cavity 16 along with vibration of a sensor, thereby preventing the F-P interference cavity 16 from being influenced and resulting in inaccurate measurement.

In a further preferred embodiment, the vent hole 142 may be further provided at the bottom of the second sidewall 15, as shown in fig. 3 and 4, and the vent hole 142 may be processed by etching, and may be formed in the same processing step as the getter cavity and the F-P interference cavity 16 during processing, thereby improving the vent hole processing efficiency.

In a further preferred embodiment, the getter chamber 14 is an annular chamber, thereby providing a maximum getter chamber 14 volume area, increasing the getter film area.

In a preferred embodiment, the protrusion 11 is in a cylindrical structure, and the pressure sensitive film 12 has a circular area, which is beneficial to realizing uniform stress on a fluid medium such as gas, liquid and the like, improving the high pressure resistance of the chip and improving the interference spectrum stability between two reflecting surfaces of the F-P interference cavity 16 inside the vacuum microcavity interferometer chip under the action of pressure.

In a preferred embodiment, the first substrate 1 and the third substrate 3 have the same thickness, and the first substrate 1 and the third substrate 3 have the same diameter, and the same thickness and diameter form a substantially symmetrical structure about the second substrate 2, and since the first substrate 1 and the third substrate 3 are silicon wafers and have the same temperature coefficient, the three-layer substrate has good stress matching characteristics, so that the whole of the vacuum microcavity interferometer chip has extremely low temperature coefficient, bending deformation of the center of the vacuum microcavity interferometer chip is reduced, so that the two reflecting surfaces of the F-P optical interference cavity are kept relatively parallel under the action of full-scale pressure, and high stability of zero output of the vacuum microcavity interferometer chip is realized through good stress matching.

In a preferred embodiment, the dimensions of the second substrate 2 are larger than those of the first substrate 1 and the third substrate 3, and the dimensions can be parameters such as length or diameter, and the dimensions depend on the shape of the second substrate, so when the low-drift optical pressure sensor is manufactured by using the vacuum microcavity interferometer chip, the exposed surfaces formed by the second substrate 2 and the third substrate 3 are bonded or welded and fixed by using the external dimensions of the second substrate 2 larger than those of the first substrate 1 and the third substrate 3, so that the first substrate 1 and the third substrate 3 and the optical fiber collimator 31 are not contacted with the sensor housing, stress isolation between the film island structure of the vacuum microcavity interferometer chip and the optical fiber collimator 31 and the sensor housing on the third substrate 3 is realized, when the sensor housing is stressed or vibrated, the stress is directly transmitted to the second substrate 2, and the first substrate 1 and the third substrate 3 are integrally vibrated, and the stress on the film island structure and the third substrate 3 is not guaranteed to be changed after the micro-field impact is applied to the optical fiber collimator 31, and the mechanical shock is not generated when the micro-cavity is fastened or the micro-impact is applied to the sensor housing.

In a preferred embodiment, a lower surface of the second substrate 2 and/or an upper surface of the first substrate 1, on which the getter film is deposited in the getter chamber 14, is provided, and a notch groove 141 is provided in the first and second sidewall parts 13 and 15, the notch groove 141 being located at a position where the first and second sidewall parts 13 and 15 are bonded to the second substrate 2, and the notch groove 141 is in communication with the getter chamber 14, and when a small amount of particles are generated from the getter film after activation, the particles can be received in the notch groove 141 upon tilting or shaking of the sensor. Free-moving particles within the getter chamber 14 are further reduced, reducing the likelihood of particles entering the F-P interferometric cavity 16 through the vent holes 142.

The application also relates to a low-drift optical pressure sensor, comprising a sensor housing 4 and a sensitive chip mount 5 arranged in the sensor housing, as shown in fig. 4-5, see fig. 5 and 6, wherein the vacuum microcavity interferometer chip is only in contact fixation with the sensitive chip mount 5 via the second substrate 2. The structure can realize the stress isolation among the film island structure of the vacuum microcavity interferometer chip, the optical fiber collimator 31 on the third substrate 3 and the sensor shell, and when the sensor shell is stressed or vibrated, the stress is directly transmitted to the second substrate 2, and because the first substrate 1 and the third substrate 3 are arranged on two sides of the second substrate 2 and have approximately symmetrical structures, the first substrate 1 and the third substrate 3 vibrate integrally, the stress can not be applied to the film island structure and the optical fiber collimator 31 on the third substrate 3, and the zero output of the vacuum microcavity interferometer chip is ensured not to be changed before and after the installation of the vacuum microcavity interferometer chip is mechanically fastened on site or when the vacuum microcavity interferometer chip is impacted by external force.

The application also relates to a manufacturing method of the MEMS vacuum microcavity interferometer chip, wherein the first substrate 1 is selected as an SOI silicon wafer (top silicon-buried oxide layer-bottom silicon three-layer structure); S1, forming a getter cavity 14, an F-P interference cavity 16 and a vent hole 142 which is communicated with the getter cavity 14 and the F-P interference cavity 16 on one surface of a first substrate 1 through etching and/or KOH etching, depositing a first reflecting surface 112 on the surface of the F-P interference cavity 16, etching and/or KOH etching on the other surface of the first substrate 1 to form a film island structure, wherein the surface of the bulge 11 is an original polished surface and has the same thickness as a frame, depositing a first optical antireflection film 111 on the bulge 11, etching on the other surface of the first substrate to form a film island structure is not necessary, the step can be omitted, the step can be completed in the subsequent step, S2, the second substrate 2 is a double-sided polished glass sheet, a second reflecting surface 113 and a getter film are deposited on the surface of the second substrate 2 corresponding to the F-P interference cavity 16, the getter film 113 is positioned on the position corresponding to the getter cavity 14, the getter film and the second reflecting surface 113 are positioned on the same side as the second substrate 2, the second optical antireflection film is deposited on the second substrate 2 to form a second optical countersink film 32, the second optical countersink is arranged on the surface of the second substrate 2 corresponding to the second substrate 3, the second optical countersink film 32 is arranged on the surface of the second substrate 2, the second optical countersink film 32 is arranged on the surface of the second substrate 3, the second countersink film 32 is arranged on the surface of the second substrate is opposite to the surface of the second substrate 32, the bonding quality of the second substrate 2 and the third substrate 3 is prevented from being influenced by the second optical antireflection film 114, the bonding temperature of the first substrate 1, the second substrate 2 and the third substrate 3 is 300-400 ℃ through a three-layer bonding technology, the activation temperature is usually higher than 300 ℃ because the getter is usually required to be thermally activated after being deposited, the activation of the getter film can be completed at the same time of bonding, the getter film is not required to be activated after the device is manufactured, the bonding temperature of silicon-glass-silicon is usually lower than 400 ℃ or the bonding temperature of a corresponding medium layer is selected to be lower than 400 ℃, and the optical film with the temperature resistance higher than 500 ℃ manufactured by adopting the optical medium material deposition in the chip can be ensured not to be influenced.

Further preferred embodiments further comprise step S5 of measuring and selectively processing the thickness of the single crystal silicon of each of the protrusions 11 of the film island structure and the pressure sensitive thin film 12 in real time after the three-layer substrate is bonded. The geometric dimensions of the protruding part of the membrane island structure, the pressure sensitive film 12 and the frame positioned outside the pressure sensitive film 12 are selectively processed, so that the sensitivity of the vacuum microcavity interferometer chip is flexibly adjusted.

Claims (11)

1. The vacuum microcavity interferometer chip comprises a first substrate, a second substrate and a third substrate, and is characterized in that a film island structure is formed on the upper surface of the first substrate, the film island structure comprises a protruding portion and a pressure sensitive film surrounding the protruding portion, a first side wall portion, a getter cavity, a second side wall portion and a centrally located F-P interference cavity are sequentially arranged on the lower surface of the first substrate along the radial direction, a first reflecting surface is deposited on the lower surface of the first substrate in the F-P interference cavity, a second reflecting surface is deposited on the upper surface of the second substrate in the F-P interference cavity, a first optical antireflection film is deposited on the surface of the protruding portion, the same centers are arranged on the first optical antireflection film, the protruding portion, the pressure sensitive film, the first reflecting surface and the second reflecting surface, a mounting hole of an optical fiber collimator is arranged in the center of the third substrate, a getter film is arranged on at least one surface of the getter cavity, and at least one vent hole is formed in the center of the getter cavity, and the vent hole is formed in the F-P interference cavity and is used for communicating the second side wall with the getter cavity.

2. The vacuum microcavity interferometer chip of claim 1, wherein the vent is disposed on the second sidewall portion, the second sidewall portion having a first height, the vent being disposed intermediate the first height of the second sidewall portion.

3. The vacuum microcavity interferometer chip of claim 1 or 2, wherein the getter cavity is an annular cavity.

4. The vacuum microcavity interferometer chip of claim 1 or 2, wherein the vent is provided at the bottom of the second sidewall portion, and is formed in the same processing step as the getter cavity and the F-P interferometer cavity during processing.

5. The vacuum microcavity interferometer chip of claim 1 or 2, wherein the protrusion is of cylindrical configuration and the pressure sensitive film has a circular area.

6. The vacuum microcavity interferometer chip of claim 1 or 2, wherein the first substrate and the third substrate have the same diameter, and the first substrate and the third substrate have the same thickness and the same diameter so as to form a substantially symmetrical structure about the second substrate.

7. The vacuum microcavity interferometer chip of claim 1 or 2, wherein the second substrate has a diameter larger than the first substrate and the third substrate, and the exposed surfaces formed by the second substrate and the third substrate are bonded or welded to the sensor housing by using the second substrate having a larger outer dimension than the first substrate and the third substrate, so that the first substrate and the third substrate and the fiber collimator are not in contact with the sensor housing.

8. A vacuum microcavity interferometer chip as recited in claim 1 or 2, characterized in that a surface of a second substrate, i.e. a lower surface, and/or a surface of the first substrate, i.e. an upper surface, of the getter film deposited in the getter cavity is provided, and that a notch groove is provided in the first and second sidewall portions, which notch groove is located where the first and second sidewall portions are bonded to the second substrate, and which notch groove is in communication with the getter cavity.

9. A low drift optical pressure sensor comprising a sensor housing and a sensitive die mount disposed within the sensor housing, the vacuum microcavity interferometer die of any of claims 1 to 8 being secured in contact with the sensitive die mount only through the second substrate.

10. The method for manufacturing the vacuum microcavity interferometer chip according to any one of claims 1 to 8, comprising the steps of S1 forming a getter cavity, an F-P interference cavity and a vent hole communicating the getter cavity and the F-P interference cavity on one surface of a first substrate, depositing a first reflecting surface on the surface of the F-P interference cavity, S2 depositing a second reflecting surface on the surface of a second substrate corresponding to the position of the F-P interference cavity and a getter film on the position corresponding to the getter cavity, wherein the getter film and the second reflecting surface are located on the same side of the second substrate, depositing a second optical antireflection film on the other surface of the second substrate corresponding to the position of the mounting hole, S3 manufacturing a mounting hole of the optical fiber collimator on a third substrate, disposing a third reflecting surface on the surface of the third substrate facing the second substrate, wherein the area of the counterbore is larger than the area of the second optical antireflection film, and S4 bonding the substrates to be subjected to bonding at a temperature of 400 ℃ by means of bonding the first substrate, the third substrate and the third optical collimator.

11. The method of claim 10, further comprising the step S5 of measuring the thicknesses of the protrusions of the island structure and the pressure sensitive film in real time and selectively controlling the processing after bonding the three substrates.