Transmitting-receiving monomer integrated on-chip infrared light waveguide gas sensor chip and preparation method thereof

Abstract

The invention discloses a transmitting-receiving monomer integrated on-chip infrared waveguide gas sensor chip and a preparation method thereof. The on-chip infrared waveguide gas sensor chip comprises a substrate, a laser diode, a first coupler, an optical waveguide, a second coupler and a photodiode, wherein the laser diode, the first coupler, the optical waveguide, the second coupler and the photodiode are positioned on the substrate; wherein the laser diode is used for emitting infrared light; the first coupler is used for coupling the infrared light to the input end of the optical waveguide; the optical waveguide is a development type optical waveguide and is used for constraining and transmitting infrared light and enabling gas to be expanded into the optical waveguide; the second coupler is used for coupling the infrared light to the photodiode through the output end of the optical waveguide; and the photodiode is used for converting the infrared light into an electric signal so as to identify and quantify the gas. The gas sensor chip is high in integration level and small in size, meets the requirements of low-cost mobile application, and keeps the characteristics of high selectivity, low drift and long-term stability of an infrared light waveguide gas detection method.

Description

Technical Field

[0001] The present invention belongs to the technical field of MEMS gas sensors, and in particular relates to an on-chip infrared optical waveguide gas sensor chip with integrated transceiver units and a preparation method thereof. Background Art

[0002] Gas sensors are mainly used to detect the concentration of specific gases in the environment, which is of great significance for preventing environmental pollution, industrial accidents and disease diagnosis. Although traditional gas detection methods, such as metal oxide semiconductor sensors, are low-cost, they have problems such as poor selectivity, susceptibility to environmental factors, and short service life. With the advancement of microelectronics and optoelectronics technology, infrared optical waveguide gas sensors have emerged. They use the characteristics of gas absorption of specific infrared spectra to achieve high selectivity, high stability, and long life gas detection.

[0003] The infrared waveguide gas sensing system is based on open infrared waveguide technology. By integrating components such as light source, open waveguide and light detector, a complete gas sensing platform is constructed. When specific gas molecules absorb infrared light, the intensity of the light will decay. By measuring this attenuation, the concentration of the gas can be accurately determined. In addition, by designing different spectral absorption windows, the system can detect multiple gases at the same time, thereby improving the versatility of the sensor.

[0004] The invention patent application with publication number CN115639650A discloses a light emitting receiving assembly (BOSA) laser and an optical module. The BOSA laser includes a tube shell configured to be divided into a first chamber and a second chamber by an isolation block; a laser for generating a laser beam, which is emitted to a gas reaction chamber through a light output channel of the first chamber so as to interact with the gas to be measured in the gas reaction chamber; a plurality of optical elements are arranged in the tube shell, and are used to reflect the laser beam returned after interacting with the gas to be measured through a light input channel of the second chamber to a photoelectric detection unit; a photoelectric detection unit, which is used to generate an electrical signal based on the laser beam reflected to the photoelectric detection unit; and a transimpedance amplifier unit, which is used to generate a gas detection signal to be measured for indicating the state of the gas to be measured based on the electrical signal generated by the photoelectric detection unit. However, the system disclosed in the patent is large in size and has limited application space.

[0005] At present, mainstream infrared waveguide gas sensing systems usually require a larger size to accommodate components such as light sources, detectors and waveguides, which limits their use in space-constrained and mobile application scenarios. In addition, the light sources and detectors of traditional infrared waveguide gas sensors usually require higher electrical power and may consume a lot of electricity when running for a long time, which is a limitation for battery-powered applications. Another challenge is that traditional infrared waveguide gas sensors involve complex optical and electronic components and have high manufacturing costs, which leads to their generally high prices and are not suitable for some cost-sensitive application scenarios. Summary of the invention

[0006] The present invention provides an on-chip infrared optical waveguide gas sensor chip with integrated transceiver units. The gas sensor chip has high integration and small size, meeting the needs of low-cost mobile applications, while maintaining the high selectivity, low drift and long-term stability of the infrared optical waveguide gas detection method.

[0007] The present invention provides an on-chip infrared optical waveguide gas sensor chip with integrated transceiver units, comprising a substrate and a laser diode, a first coupler, an optical waveguide, a second coupler and a photodiode located on the substrate;

[0008] Wherein, the laser diode is used to emit infrared light;

[0009] The first coupler is used to couple infrared light to the input end of the optical waveguide;

[0010] The optical waveguide is an open-type optical waveguide, which is used to bind and transmit infrared light, and at the same time allows the gas to expand into the optical waveguide;

[0011] The second coupler is used to couple the infrared light from the output end of the optical waveguide to the photodiode;

[0012] The photodiode is used to convert infrared light into an electrical signal to identify and quantify the gas.

[0013] The open optical waveguide provided by the present invention is the core of the sensor, which confines the infrared light to propagate inside it. At the same time, the open structure allows the gas to expand into the optical waveguide so that it interacts with the infrared light. When the gas molecules absorb light, the light intensity decreases, and this change is captured by the photodetector and converted into an electrical signal. By analyzing the changes in light intensity at different wavelengths, the sensor can identify and quantify a variety of gases, achieving highly selective and highly sensitive detection.

[0014] The coupler provided by the present invention is used to realize the optical path coupling connection between the optical waveguide and the light source and the detector. It can adjust the angle and direction of the light and improve the transmission efficiency of infrared light between devices.

[0015] The wavelength of the infrared light emitted by the laser diode provided by the present invention corresponds to the absorption spectrum of the target gas, so that the target gas can absorb the infrared light, thereby achieving the purpose of changing the light intensity of the infrared light.

[0016] Preferably, a transition layer is provided between the substrate and the laser diode, and the laser diode with the transition layer provided on the surface is bonded to the substrate by flip-chip method.

[0017] The present invention utilizes a flip-chip method to bond a laser diode with a transition layer on the surface to a substrate. Compared with directly preparing the transition layer and the laser diode in sequence on the substrate, the present invention avoids the overly complicated process from affecting the performance of other devices on the substrate. Directly bonding the prepared laser diode with a transition layer on the surface to the substrate can be more accurately aligned with the first coupler, thereby ensuring coupling efficiency.

[0018] Further preferably, the material of the transition layer is p-InP. The present invention enables the laser diode to be better bonded to the substrate through the transition layer, avoiding defects caused by lattice mismatch.

[0019] Preferably, the first coupler, the optical waveguide and the second coupler are directly formed on the substrate by photolithography and etching.

[0020] Preferably, the photodiode is manufactured on a substrate by epitaxy, doping, photolithography, metallization, etc. Since the material of the photodiode is closer to the lattice of the substrate material, it can be manufactured directly on the substrate, and the impact of the manufacturing process steps on other components is within a controllable range.

[0021] Preferably, the photodiode is flip-chip bonded on the substrate. By flip-chip bonding the photodiode, the process of preparing the photodiode can avoid affecting other components.

[0022] Preferably, the material of the substrate is silicon (Si), germanium (Ge), silicon on insulator (SOI), lithium niobate on insulator (LNOI), lithium tantalate on insulator (LTOI) or the like.

[0023] Preferably, the material of the laser diode is a III-V semiconductor material, and the III-V semiconductor material is gallium arsenide (GaAs), aluminum gallium arsenide (AlGaAs), indium phosphide (InP), indium gallium arsenic phosphide (InGaAsP), gallium nitride (GaN) or indium gallium nitride (InGaN).

[0024] Preferably, the photodiode is germanium (Ge), silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), zinc oxide (ZnO) or the like.

[0025] Preferably, the single-piece integrated on-chip infrared optical waveguide gas sensor chip is packaged in a housing provided with a gas permeable window.

[0026] On the other hand, the present invention also provides a method for preparing an on-chip infrared optical waveguide gas sensor chip with integrated transceiver units, comprising:

[0027] (1) obtaining an SOI substrate and an InP-based substrate;

[0028] (2) forming a first coupler, an optical waveguide, and a second coupler on the SOI substrate by photolithography and etching, and forming a photodiode on the SOI substrate by epitaxy, photolithography, ion implantation, annealing, and thin film deposition;

[0029] (3) forming a laser diode on an InP-based substrate by photolithography, etching, and thin film epitaxy techniques, and depositing a transition layer on the surface of the laser diode;

[0030] (4) The laser diode with the transition layer deposited on the surface is bonded to the SOI substrate by flip-chip method and aligned with the first coupler, and then the InP-based substrate is etched away to obtain an on-chip infrared optical waveguide gas sensor chip with integrated transceiver units.

[0031] Preferably, the flip-chip method of step (4) includes chip-level flip-chip and wafer-level flip-chip;

[0032] The wafer-level flip-chip preparation method comprises first dicing the chip obtained in step (2) and the chip obtained in step (3) respectively, and then flipping them;

[0033] The wafer-level flip-chip preparation method comprises wafer-level bonding the chip obtained in step (2) and the chip obtained in step (3), and then dicing.

[0034] The wafer-level flip-chip is suitable for designs in which the sizes of the laser chip and the optical waveguide chip are close.

[0035] Preferably, the photodiode can be integrally processed with the optical waveguide chip on the same wafer, or can be separately processed using an independent substrate and then connected to the coupler at the output end of the optical waveguide by chip-level flip-chip bonding.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] Compared with the gas sensors disclosed in the prior art, in which the active laser and each passive optoelectronic device are usually independently processed and manufactured and then assembled and produced by off-chip coupling, the present invention integrates the active laser diode and each passive device in a chip-type manner, reduces their cost and makes them into a device-level sensor, so as to improve the integration of the infrared optical waveguide gas sensor, reduce the size of the sensor to meet the application requirements of mobile terminals, and at the same time reduce power consumption and improve stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic diagram of the structure of a single-chip integrated on-chip infrared optical waveguide gas sensor chip provided by a specific embodiment of the present invention;

[0039] Figure 2 A schematic diagram of different coupling types of the on-chip infrared optical waveguide gas sensor chip integrated in a single body according to a specific embodiment of the present invention;

[0040] Figure 3 A schematic diagram of the structure of laser couplers of different structures of a single-piece integrated on-chip infrared optical waveguide gas sensor chip provided by a specific embodiment of the present invention;

[0041] Figure 4 Schematic diagram of different optical waveguide structures of a monomer-integrated on-chip infrared optical waveguide gas sensor chip provided by a specific embodiment of the present invention;

[0042] Figure 5 A schematic diagram of a single-piece integrated on-chip infrared optical waveguide gas sensor chip packaging structure provided by a specific embodiment of the present invention;

[0043] Figure 6 A schematic diagram of the structure of a laser diode provided in a specific embodiment of the present invention.

[0044] Description of reference numerals:

[0045] 1: substrate; 2: laser diode; 21: metal bonding / transition layer; 22: p-side electrode; 23: p-ohmic contact layer; 24: cladding layer; 25: separation confinement heterojunction; 26: InGaAsP quantum well layer; 27: p-ohmic contact layer; 28: n-ohmic contact layer; 29: n-side electrode; 3: coupler; 4: optical waveguide; 5: coupler; 6: photodiode, 7: tube shell, 8: cover; DETAILED DESCRIPTION

[0046] The present invention is further described in detail below in conjunction with the embodiments and drawings. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.

[0047] In order to realize a small-sized and highly integrated on-chip infrared optical waveguide gas sensor chip, the specific embodiment of the present invention directly integrates the laser diode, the first coupler, the optical waveguide, the second coupler and the photodiode on the chip. Due to its small size, small power consumption, small light loss during transmission, and high stability.

[0048] The specific embodiment of the present invention provides a single integrated on-chip infrared optical waveguide gas sensor chip, such as Figure 1 As shown, the device comprises a substrate 1 and a laser diode 2 , a first coupler 3 , an optical waveguide 4 , a second coupler 5 and a photodiode 6 located on the substrate 1 .

[0049] The substrate 1 provided in the specific embodiment of the present invention only plays a supporting role, and the laser diode 2 on the substrate 1 is used to generate infrared light corresponding to the absorption spectrum of the target gas.

[0050] The first coupler 3 provided in the specific embodiment of the present invention is used to couple the infrared light to the input end of the optical waveguide 4. By adjusting the angle and direction of the first coupler 3, the transmission efficiency of the infrared light between devices is improved.

[0051] like Figure 2 As shown, the coupling mode between the first coupler 3 and the laser diode 2 provided in the specific embodiment of the present invention includes vertical coupling and edge coupling. Figure 3 As shown, the first coupler 3 may include an end face coupler, a grating coupler and an interlayer coupler. Different types of couplers may be selected according to different designs to achieve an optimal coupling effect.

[0052] The optical waveguide 4 provided in the specific embodiment of the present invention is an open optical waveguide. The open optical waveguide is the core of the sensor, which confines the infrared light to propagate inside it. At the same time, the open structure allows the gas to expand into the optical waveguide so that it interacts with the infrared light. When the gas molecules absorb light, the light intensity decreases, and this change is captured by the photodetector and converted into an electrical signal. By analyzing the changes in light intensity at different wavelengths, the sensor can identify and quantify a variety of gases, achieving highly selective and highly sensitive detection.

[0053] like Figure 4 As shown, the optical waveguide 4 provided in the specific embodiment of the present invention includes a straight waveguide, a double-slot waveguide, a ring waveguide or a grating waveguide. Different optical waveguides can be used to realize light propagation in different directions on the chip as needed.

[0054] The second coupler 5 provided in the specific embodiment of the present invention is used to couple the infrared light with changed light intensity after being absorbed by the target gas to the photodiode 6, and the infrared light signal with changed light intensity is converted into an electrical signal through the photodiode 6. By analyzing the changes in light intensity at different wavelengths, the sensor can identify and quantify multiple gases and achieve highly selective and highly sensitive detection.

[0055] like Figure 5 As shown, the monomer-integrated on-chip infrared waveguide gas sensor chip provided by a specific embodiment of the present invention is located inside a frame provided with a window, the frame includes a tube shell 7 and a tube cap 8, the monomer-integrated on-chip infrared waveguide gas sensor chip is located inside the tube shell 7, the target gas enters the frame through the tube cap 8, and reacts with the infrared light of the monomer-integrated on-chip infrared waveguide gas sensor chip.

[0056] Example 1

[0057] This embodiment provides an on-chip infrared optical waveguide gas sensor chip with integrated transceiver units, the laser diode type of the light-emitting end of which is a vertical cavity surface emitting laser (VCSEL), and the light-emitting surface is perpendicular to the cross section of the optical waveguide. The manufacturing process is as follows:

[0058] Step 1: Prepare two wafers, SOI and InP as the substrate materials for the optical waveguide and laser

[0059] Step 2: Prepare the optical waveguide structure and the coupler structure at its input and output ends on the SOI wafer through photolithography, etching and other processes.

[0060] Step 3: On the SOI wafer, prepare the photodiode PN junction through epitaxy, lithography, ion implantation, annealing, thin film deposition and other processes, prepare the external electrical connection PAD between the photodiode and the laser diode and the internal bonding PAD with the laser through lithography, electron beam evaporation, stripping and other processes.

[0061] Step 4: Prepare III-V VCSEL lasers on the 100 crystal phase of the InP substrate using lithography, etching, and thin film epitaxy techniques. It should be noted that because the laser needs to be bonded to the SOI substrate, the laser structure needs to be optimized, and a bonding transition layer should be left on the top of the laser to facilitate flip-chip bonding with the SOI substrate.

[0062] Step 5: Bond the VCSEL laser wafer and the patterned SOI wafer by flip-chip bonding. It should be noted that the alignment accuracy during the bonding process is very important. The relative position of the grating coupler on the light-emitting surface of the VCSEL laser must be guaranteed to ensure sufficient coupling efficiency and etch away the InP-based substrate.

[0063] Step 6: Slice the chip and package it into a permeable package lithography, fix the optical waveguide sensor chip and the tube shell by BCB gluing, and connect the optical waveguide gas connection PAD and the tube shell PAD by wire bonding.

[0064] The above steps can complete the manufacture of the on-chip infrared optical waveguide gas sensor chip with integrated transceiver units of the present invention.

[0065] This process can also be used to manufacture integrated infrared optical waveguide gas sensor chips with integrated edge-emitting lasers (EELs).

[0066] Furthermore, the wafer-level bonding method is preferentially suitable for designs in which the chip size of VCSEL and EEL is consistent with the waveguide size, making full use of the area of ​​the laser wafer, increasing the laser emission power to enhance the overall signal-to-noise ratio of the system, and improving the detection sensitivity.

[0067] Example 2

[0068] This embodiment provides an on-chip infrared optical waveguide gas sensor chip with integrated transceiver units, whose light-emitting end adopts an edge-emitting laser, and whose light-emitting surface is parallel to the optical waveguide cross section. Its manufacturing process is as follows:

[0069] Step 1: Prepare three wafers, SOI and InP as the substrate materials for the optical waveguide and laser

[0070] Step 2: Prepare the optical waveguide structure and the coupler structure at its input and output ends on the SOI wafer through photolithography, etching and other processes.

[0071] Step 3: On the SOI wafer, prepare the photodiode PN junction through epitaxy, photolithography, ion implantation, annealing, thin film deposition and other processes, prepare the external electrical connection PAD between the photodiode and the laser diode and the internal bonding PAD with the laser through photolithography, electron beam evaporation, stripping and other processes to obtain the optical waveguide chip.

[0072] Step 4: Use MOCVD epitaxial technology to sequentially grow functional layers such as ohmic contact layer, cladding layer, independent cladding heterostructure, quantum well layer and bonding interface layer based on III-V semiconductor material conductor material on P-InP substrate. Among them, the quantum well layer contains multiple pairs of InGaAsP quantum well layers with nanometer thickness and barrier layers with a thickness of several nanometers.

[0073] Step 5: Through a series of photolithography and etching processes, a ridge waveguide structure is made. A p-type electrode is made on the surface of the ridge waveguide. An n-type electrode is made by photolithography and thin film etching technology to form a complete laser diode. The structure of the laser diode is as follows: Figure 6The InP wafer is diced to form independent laser diode chips, and the light-emitting surface is coated to improve its light-emitting efficiency, thereby obtaining a laser chip.

[0074] Step 5: Bond the laser chip to the coupler at the input end of the optical waveguide chip by flip-chip bonding to form a complete optical path, and at the same time realize the internal electrical connection between the laser and the optical waveguide substrate, and etch away the InP-based substrate.

[0075] Step 6: Slice the bonded sensor chip and package it into a breathable packaging tube shell, fix the optical waveguide sensor chip and the tube shell by BCB gluing, and connect the optical waveguide gas connection PAD and the tube shell PAD by wire bonding.

[0076] The above steps can also complete the manufacture of an on-chip infrared optical waveguide gas sensor chip with integrated transceiver units of the present invention.

[0077] Furthermore, the chip bonding method is preferably suitable for designs with larger waveguide size requirements. This method can effectively utilize the length of the optical waveguide, increase the absorption distance, and improve the detection sensitivity. Separately manufacturing the laser chip can avoid the waste of laser wafer area and reduce its manufacturing cost.

Claims

1. An on-chip infrared optical waveguide gas sensor chip with integrated transceiver unit, characterized in that: The invention comprises a substrate and a laser diode, a first coupler, an optical waveguide, a second coupler and a photodiode located on the substrate; Wherein, the laser diode is used to emit infrared light; The first coupler is used to couple infrared light to the input end of the optical waveguide; The optical waveguide is an open-type optical waveguide, which is used to bind and transmit infrared light, and at the same time allows the gas to expand into the optical waveguide; The second coupler is used to couple the infrared light from the output end of the optical waveguide to the photodiode; The photodiode is used to convert infrared light into an electrical signal to identify and quantify the gas.

2. The on-chip infrared optical waveguide gas sensor chip with integrated transceiver unit according to claim 1, characterized in that: A transition layer is also provided between the substrate and the laser diode, and the laser diode with the transition layer provided on the surface is bonded to the substrate in a flip-chip manner.

3. The on-chip infrared optical waveguide gas sensor chip with integrated transceiver unit according to claim 1, characterized in that: The first coupler, the optical waveguide and the second coupler are directly formed on the substrate by photolithography and etching.

4. The on-chip infrared optical waveguide gas sensor chip with integrated transceiver unit according to claim 1, characterized in that: The photodiode is manufactured through processes such as epitaxy, doping, photolithography, and metallization on a substrate.

5. The on-chip infrared optical waveguide gas sensor chip with integrated transceiver unit according to claim 1, characterized in that: The photodiode is flip-chip bonded on the substrate.

6. The on-chip infrared optical waveguide gas sensor chip with integrated transceiver unit according to claim 1, characterized in that: The material of the substrate is silicon, germanium, silicon on insulator, lithium niobate on insulator or lithium tantalate on insulator.

7. The on-chip infrared optical waveguide gas sensor chip with integrated transceiver unit according to claim 1, characterized in that: The material of the laser diode is a III-V semiconductor material, and the III-V semiconductor material is gallium arsenide, aluminum gallium arsenide, indium phosphide, indium gallium arsenic phosphide, gallium nitride or indium gallium nitrogen.

8. The on-chip infrared optical waveguide gas sensor chip with integrated transceiver unit according to claim 1, characterized in that: The photodiode material is germanium, silicon, gallium arsenide, gallium nitride or zinc oxide.

9. The on-chip infrared optical waveguide gas sensor chip with integrated transceiver unit according to claim 1, characterized in that: The monomer-integrated on-chip infrared optical waveguide gas sensor chip is packaged in a housing provided with a gas permeable window.

10. A method for preparing an on-chip infrared optical waveguide gas sensor chip with integrated transceiver units according to any one of claims 1 to 9, characterized in that: include: (1) obtaining an SOI substrate and an InP-based substrate; (2) forming a first coupler, an optical waveguide, and a second coupler on the SOI substrate by photolithography and etching, and forming a photodiode on the SOI substrate by epitaxy, photolithography, ion implantation, annealing, and thin film deposition; (3) forming a laser diode on an InP-based substrate by photolithography, etching, and thin film epitaxy techniques, and depositing a transition layer on the surface of the laser diode; (4) The laser diode with the transition layer deposited on the surface is bonded to the SOI substrate by flip-chip method and aligned with the first coupler, and then the InP-based substrate is etched away to obtain an on-chip infrared optical waveguide gas sensor chip with integrated transceiver units.

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