Optical pressure sensing chip, preparation method thereof and sensor
By providing the first and second waveguide layers on the front of the substrate of the optical pressure sensing chip to form a cantilever beam structure, the problem of fragility in the existing optical pressure sensing chip structure is solved, and the stability and reliability of the chip are improved.
Patent Information
- Application Number
- CN202411918589.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-24
- Publication Date
- 2025-04-11
AI Technical Summary
The existing optical pressure sensing chips have a relatively fragile structure, resulting in low reliability.
An optical pressure sensing chip is designed, which adopts an end-face coupling structure, including a substrate, a first waveguide layer and a second waveguide layer. The second waveguide layer forms a cantilever beam structure. By providing the first and second waveguide layers on the front of the substrate, the step of hollowing out on the back of the substrate is avoided, and the stability of the structure is enhanced.
This design improves the structural stability and reliability of the optical pressure sensing chip, avoiding the problem of structural fragility in traditional methods.
Smart Images
Figure CN119803740A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to the technical field of pressure sensors, and specifically provides an optical pressure sensor chip and a preparation method thereof, and a sensor. Background Art
[0002] A pressure sensor is a device or apparatus that can sense pressure signals and convert them into electrical signals according to certain rules. An optical pressure sensor is a type of pressure sensor, and its detection of pressure is mainly based on the relationship between pressure and optical signals, where the optical signal can be the intensity of light, the phase of light, the wavelength of light, etc. At present, optical pressure sensors are mainly divided into optical fiber pressure sensors and optical pressure sensors based on silicon planar technology. Optical fiber pressure sensors mainly detect pressure based on the relationship between film deformation and interference cavity length, but the overall device size is relatively large. As optical pressure sensors gradually develop towards miniaturization and integration, optical pressure sensors based on silicon planar technology have gradually become mainstream, especially optical pressure sensors based on MEMS (Micro-Electro-Mechanical Systems) structures have begun to emerge.
[0003] In existing optical pressure sensor chips based on silicon planar technology, the back side of the substrate is usually hollowed out to form a cavity, which makes the overall structure of the pressure sensor relatively fragile and has low reliability. Summary of the invention
[0004] The present disclosure aims to solve the above technical problem, that is, to solve the problem that the structure of the existing optical pressure sensor chip is relatively fragile.
[0005] In a first aspect, the present disclosure provides an optical pressure sensor chip, comprising an end surface coupling structure, wherein the end surface coupling structure comprises:
[0006] A substrate and a first cladding layer and a first waveguide layer sequentially stacked on the substrate;
[0007] a second cladding layer located on the first waveguide layer, the second cladding layer having a cavity, and a portion of the first waveguide layer is exposed at the bottom of the cavity;
[0008] A second waveguide layer is located on the second cladding layer, the second waveguide layer is exposed at the top of the cavity, and a part of the second waveguide layer and a part of the first waveguide layer form an interlayer coupling structure;
[0009] The third cladding is located on the second waveguide layer, the third cladding is fixedly connected to one end of the second waveguide layer, the third cladding has a first opening connected to the cavity, the first opening exposes the other end of the second waveguide layer, so that the second waveguide layer forms a cantilever beam structure.
[0010] In some embodiments, a portion of the cavity extends to an end surface of the optical pressure sensing chip to form a second opening.
[0011] In some embodiments, the end-face coupling structure satisfies at least one of the following conditions:
[0012] The distance between the end surface of one end of the second waveguide layer and the end surface of the optical pressure sensing chip is 1 μm to 5 μm;
[0013] The distance between the end surface of one end of the first waveguide layer and the end surface of the optical pressure sensing chip is 20 μm to 40 μm; and,
[0014] Along the thickness direction of the substrate, the spacing between the first waveguide layer and the second waveguide layer is 100 nm to 300 nm.
[0015] In some embodiments, along the waveguide extension direction, the length of the second waveguide layer exposed through the first opening is at most 3 / 4 of the total length of the second waveguide layer.
[0016] In some embodiments, the optical pressure sensor chip further includes at least one of a functional device for light transmission and light processing, an output device for outputting an optical signal, and a metal interconnect structure for outputting an electrical signal.
[0017] In a second aspect, the present disclosure provides a method for preparing an optical pressure sensor chip, comprising:
[0018] Providing a substrate, which includes a substrate, a material layer as a first cladding layer, and a first waveguide material layer stacked in sequence;
[0019] patterning the first waveguide material layer to form a first waveguide layer;
[0020] A first deposition layer, a first sacrificial layer, a second deposition layer, a second waveguide layer, a third deposition layer, a second sacrificial layer and a fourth deposition layer are sequentially formed, wherein: the first deposition layer covers the first waveguide layer and the exposed first cladding material layer, the second deposition layer covers the first sacrificial layer, and the third deposition layer covers the second waveguide layer;
[0021] patterning the fourth deposition layer to form a first opening, wherein the first opening exposes at least a portion of the second sacrificial layer;
[0022] Patterning the substrate, the first deposition layer, the second deposition layer, the third deposition layer and the fourth deposition layer to form a deep groove structure, wherein the deep groove structure exposes an end surface of one end of the first sacrificial layer;
[0023] removing the first sacrificial layer and the second sacrificial layer, and forming a first cavity and a second cavity at the positions of the first sacrificial layer and the second sacrificial layer, respectively;
[0024] A portion of the third deposition layer and a portion of the fourth deposition layer located above the second waveguide layer are removed, and the first deposition layer and the second deposition layer between the first waveguide layer and the second waveguide layer are removed, so that the first cavity and the second cavity are connected, and a cavity is formed between the first waveguide layer and the second waveguide layer, so that the second waveguide layer forms a cantilever beam structure.
[0025] In some embodiments, after forming the first cavity and the second cavity, the step of forming the cantilever beam structure includes:
[0026] forming a mask on the fourth deposition layer, wherein the mask has a window corresponding to the first opening;
[0027] Allowing the etching gas or the etching liquid to enter the second cavity from the first opening to etch the fourth deposition layer, the third deposition layer, the second deposition layer and the first deposition layer, so that the second cavity is connected with the first cavity, and removing the first deposition layer and the second deposition layer between the first waveguide layer and the second waveguide layer to form a cavity, so that the second waveguide layer is suspended on the first cladding layer to form a cantilever beam structure;
[0028] Remove the mask.
[0029] In some embodiments, the second waveguide layer has a first end and a second end opposite to each other along the waveguide extension direction, wherein the first end is close to an end of the substrate, the second waveguide layer has a first side and a second side along a direction perpendicular to the waveguide extension direction, and the second waveguide layer satisfies at least one of the following:
[0030] The orthographic projection of the first end of the second waveguide layer on the substrate falls within the orthographic projection range of the first sacrificial layer on the substrate; the orthographic projection of the second end of the second waveguide layer on the substrate exceeds the orthographic projection range of the first sacrificial layer on the substrate; and the orthographic projection of the first sacrificial layer on the substrate along a boundary perpendicular to the waveguide extension direction exceeds the orthographic projections of the first side and the second side of the second waveguide layer on the substrate.
[0031] In some embodiments, a distance between an orthographic projection of the first sacrificial layer on the substrate along a boundary perpendicular to the waveguide extension direction and an orthographic projection of the first side and / or the second side of the second waveguide layer on the substrate is greater than 1 μm.
[0032] In some embodiments, the second sacrificial layer has a first end and a second end relative to each other along the waveguide extension direction, the first end of the second sacrificial layer is close to the end of the substrate, the first opening exposes the second end and both sides of the second sacrificial layer and the third deposition layer located outside the second end and both side boundaries of the second sacrificial layer; or, the first opening completely exposes the second sacrificial layer.
[0033] In a third aspect, the present disclosure provides an optical pressure sensor, comprising the above-mentioned optical pressure sensing chip.
[0034] In some embodiments, the optical pressure sensor further includes: a shell, the interior of the shell is hollow, and a vent hole connected to the internal hollow structure is provided on the shell; a laser aligned with the end face coupling structure in the optical pressure sensor chip; and a detector for processing optical signals.
[0035] In some embodiments, the detector is independently disposed in the housing; or, the detector is integrated into the optical pressure sensing chip.
[0036] Compared with the prior art, the present invention has the following beneficial effects:
[0037] The optical pressure sensing chip provided by the present disclosure arranges a first waveguide layer and a second waveguide layer on the front side of a substrate to form an interlayer coupling structure, thereby eliminating the need for processing on the back side of the substrate and providing a high structural stability.
[0038] The preparation method of the optical pressure sensor chip provided by the present disclosure forms a first sacrificial layer between the first deposition layer and the second deposition layer, and forms a second sacrificial layer between the third deposition layer and the fourth deposition layer, so that after removing the sacrificial layer, a cavity can be formed accordingly, so that the second waveguide layer can form a cantilever beam structure by removing the redundant deposition layer through the first opening and connecting the two cavities. Therefore, the preparation method does not need to form a cavity on the back of the substrate, so that the obtained optical pressure sensor chip has a relatively stable and firm structure, and thus has high reliability. BRIEF DESCRIPTION OF THE DRAWINGS
[0039] The preferred embodiments of the present disclosure are described below in conjunction with the accompanying drawings, in which:
[0040] Figure 1 is a three-dimensional schematic diagram of the end face coupling structure in the optical pressure sensing chip provided by the present disclosure;
[0041] Figure 2 is a cross-sectional view of an end face coupling structure in an optical pressure sensing chip provided by the present disclosure;
[0042] Figure 3 is a schematic diagram of an optical pressure sensor provided by the present disclosure;
[0043] Figure 4 is a schematic diagram of another optical pressure sensor provided by the present disclosure;
[0044] Figure 5 is a flow chart of the method for preparing an optical pressure sensing chip provided by the present disclosure;
[0045] FIG. 6A to FIG. 6C , FIG. 6E to FIG. 6G and Figures 6K to 6N A cross-sectional view of the optical pressure sensor chip provided by the present disclosure during the preparation process;
[0046] Fig.6D for Figure 6C The corresponding top view;
[0047] Figure 6H for Fig. 6F The corresponding top view;
[0048] Fig.6I for Figure 6G The corresponding top view;
[0049] Figure 6J yes Figure 6K A top view of the structure shown before patterning.
[0050] Description of reference numerals:
[0051] 1. Base; 11. Substrate; 12. Dielectric layer; 13. First waveguide material layer; 2. First waveguide layer; 3. Second cladding; 31. Cavity; 311. Second opening; 32. First deposition layer; 33. Second deposition layer; 4. First sacrificial layer; 41. First cavity; 5. Second waveguide layer; 6. Third cladding; 61. First opening; 62. Third deposition layer; 63. Fourth deposition layer; 7. Second sacrificial layer; 71. Second cavity; 8. Mask; 10. Shell; 101. Vent; 20. Optical pressure sensor chip; 30. Detector; 40. First optical fiber; 50. Second optical fiber; 60. Laser; 70. Circuit board. DETAILED DESCRIPTION
[0052] The preferred embodiments of the present disclosure are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present disclosure and are not intended to limit the scope of protection of the present disclosure. The preferred embodiments of the present disclosure are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present disclosure and are not intended to limit the scope of protection of the present disclosure. It should also be noted that in the expressions of the present disclosure, "first", "second" and the like are only used for distinction and do not represent priority or quantity.
[0053] The present disclosure provides an optical pressure sensor chip, which includes a substrate, an end face coupling structure formed based on the substrate, and may also include at least one of a functional device, an output device and a metal interconnection structure located on the substrate. Among them, the end face coupling structure is used to transmit the optical signal between the integrated optical circuit and the optical fiber, the functional device is used for optical transmission and optical processing, the output device is used to output the optical signal, and the metal interconnection structure is used to output the electrical signal. The functional device can be a strip waveguide, a ridge waveguide, a microring resonator, a Y branch, an electro-optic modulator, a thermo-optic modulator, a germanium detector, etc., and the output device for the optical signal can be a grating coupler, an end face coupler, etc.
[0054] In some examples, the optical pressure sensor chip includes an end face coupling structure, a functional device and an output device, wherein the end face coupling structure is used to receive the optical signal of the optical fiber and transmit it to the functional device through an integrated optical circuit, the functional device performs optical transmission and optical processing, and the processed optical signal is output through the output device to an external detector for processing.
[0055] In other examples, the optical pressure sensor chip includes an end coupling structure, a functional device and a metal interconnection structure. Among them, the functional device includes at least a detector (such as a germanium detector), and may also include at least one of an electro-optic modulator and a thermo-optic modulator. The end coupling structure is used to receive the optical signal of the optical fiber, and transmit it to the functional device through an integrated optical path for optical transmission and optical processing, wherein the electro-optic modulator and / or the thermo-optic modulator is used to modulate the phase of the optical signal, and the detector is used to convert the optical signal into an electrical signal, and then output the electrical signal through the metal interconnection structure.
[0056] like Figure 1 and Figure 2 As shown, in some examples, the material of the substrate 11 is silicon, and a dielectric layer 12 and a first waveguide layer 2 are sequentially stacked on the substrate 11 , and a portion of the dielectric layer 12 corresponding to the first waveguide layer 2 serves as a lower cladding layer of the first waveguide layer 2 .
[0057] The end face coupling structure is located at the end of the optical pressure sensor chip 20, and includes a dielectric layer 12, a first waveguide layer 2, a second cladding layer 3, a second waveguide layer 5 and a third cladding layer 6 which are stacked in sequence, wherein the dielectric layer 12 serves as the lower cladding layer of the first waveguide layer 2; the second cladding layer 3 serves as both the upper cladding layer of the first waveguide layer 2 and the lower cladding layer of the second waveguide layer 5; and the third cladding layer 6 serves as the upper cladding layer of the second waveguide layer 5. The second cladding layer 3 has a cavity 31, a portion of the first waveguide layer 2 is exposed at the bottom of the cavity 31, and the second waveguide layer 5 is exposed at the top of the cavity 31. The first waveguide layer 2 and the second waveguide layer 5 form an interlayer coupling structure. The third cladding layer 6 is fixedly connected to one end of the second waveguide layer 5, and the third cladding layer 6 has a first opening 61 which is connected to the cavity 31, and the first opening 61 exposes the other end of the second waveguide layer 5 and the portion between the two ends, so that the second waveguide layer 5 forms a cantilever beam structure. The second waveguide layer 5 , except for the cantilever beam structure, is located below the third cladding layer 6 . The second waveguide layer 5 can be stably suspended above the cavity 31 by utilizing the bonding force between the third cladding layer 6 and one end of the second waveguide layer 5 .
[0058] When the external pressure changes, the cantilever beam structure of the second waveguide layer 5 will vibrate, causing the distance between the first waveguide layer 2 and the second waveguide layer 5 (the dimension along the thickness direction of the substrate 11, i.e., the Z direction in the figure) to change, thereby affecting the coupling efficiency of the end face coupling structure and causing a change in the output optical power. On this basis, the detector detects the value of the optical power in real time, and then the relationship between the output optical power and the distance between the two waveguide layers as above, as well as the relationship between the distance between the two waveguide layers and the external pressure can be established, so that the corresponding relationship between the pressure signal and the optical signal can be constructed, and the pressure state can be fed back in real time, thereby realizing pressure sensing.
[0059] It can be understood that the second waveguide layer 5 (i.e., the cantilever beam structure) exposed by the first opening 61 should have an appropriate length to take into account the overall reliability and sensitivity. Therefore, the length of the second waveguide layer 5 exposed by the first opening 61 is at most 3 / 4 of the total length of the second waveguide layer 5, and is usually 2 / 3 to 3 / 4 of the total length of the second waveguide layer 5, so that the second waveguide layer 5 and the third cladding layer 6 have sufficient bonding length and bonding strength to ensure the stability of the connection between the second waveguide layer 5 and the third cladding layer 6, and also ensure the vibration amplitude of the cantilever beam structure and the overall sensitivity of the optical pressure sensor chip.
[0060] In the example of the present disclosure, part of the cavity 31 may extend to the end face of the optical pressure sensing chip 20 to form a second opening 311. The spacing between the first waveguide layer 2 and the second waveguide layer 5 may be 100 nm to 300 nm. The spacing between the end face of the second waveguide layer 5 and the end face of the optical pressure sensing chip 20 (i.e., the dimension along the X direction in the figure) may be 1 μm to 5 μm. The spacing between the end face of the first waveguide layer 2 and the end face of the optical pressure sensing chip 20 (i.e., the dimension along the X direction in the figure) is 20 μm to 40 μm, that is, compared with the second waveguide layer 5, the first waveguide layer 2 is farther away from the end face of the optical pressure sensing chip 20.
[0061] In summary, the optical pressure sensing chip provided by the present disclosure has at least the following advantages:
[0062] (1) The first waveguide layer 2 and the second waveguide layer 5 are arranged on the front surface of the substrate 11, wherein the second waveguide layer 5 is suspended on the first waveguide layer 2 to form a cantilever beam structure, so that the first waveguide layer 2 and the second waveguide layer 5 do not need to be hollowed out from the back surface of the substrate 11, so that an interlayer coupling structure is formed between the first waveguide layer 2 and the second waveguide layer 5, thereby ensuring the structural stability of the chip while ensuring processing efficiency and processing cost;
[0063] (2) The second waveguide layer 5 can be formed by CMOS technology, and its thickness and width can be flexibly adjusted according to actual needs, so that the first waveguide layer 2 can achieve higher sensitivity as the external pressure changes, and the measurement accuracy of the optical pressure sensor chip is correspondingly higher.
[0064] like Figure 3 and Figure 4 As shown, the present disclosure also provides an optical pressure sensor, including a housing 10, a laser 60, a detector 30 and the above-mentioned optical pressure sensing chip 20. The housing 10 is hollow inside, and a vent hole 101 connected to the internal hollow structure is provided on the housing 10. The laser 60 is aligned with the end face coupling structure in the optical pressure sensing chip 20 through the first optical fiber 40, and the detector 30 is used to process the optical signal and convert it into an electrical signal. When the external air pressure changes, the airflow enters the hollow structure of the housing 10 through the vent hole 101, causing the cantilever beam structure of the second waveguide layer 5 in the optical pressure sensing chip 20 to vibrate, and the coupling efficiency of the interlayer coupling structure formed by the first waveguide layer 2 and the second waveguide layer 5 changes, resulting in a change in the output optical power, which is then detected by the detector 30. According to the parameter changes of the detector 30, the relationship between the spacing between the first waveguide layer 2 and the second waveguide layer 5 and the external pressure can be characterized, thereby realizing pressure sensing.
[0065] The detector 30 may be external to the optical pressure sensor chip 20, or may be integrated into the optical pressure sensor chip 20. In addition, the optical pressure sensor chip 20 may be an unpackaged die (ie, a bare chip) or a packaged chip.
[0066] like Figure 3 As shown, when the detector 30 is externally mounted on the optical pressure sensor chip 20, the optical pressure sensor chip 20 includes an output device for outputting optical signals and a functional device for optical transmission and optical processing. The functional device can receive and process the optical signal transmitted by the end face coupling structure, and the output device transmits the processed optical signal to the detector 30 through the second optical fiber 50 for further processing to convert the optical signal into an electrical signal.
[0067] like Figure 4As shown, when the detector 30 is integrated into the optical pressure sensor chip 20, the optical pressure sensor chip 20 includes a metal interconnect structure for outputting electrical signals and a functional device for optical transmission and optical processing. The housing 10 covers and is fixed on a circuit board 70 (such as a printed circuit board, a flexible circuit board, etc.), and the metal interconnect structure of the optical pressure sensor is electrically connected to the metal wiring on the circuit board 70. The detector 30 built into the optical pressure sensor chip 20 is one of the functional devices. In addition, the functional device may also include at least one of an electro-optic modulator and a thermo-optic modulator. The detector 30 may be a germanium detector. The end face coupling structure is used to receive the optical signal of the first optical fiber 40, and transmit it to the functional device through the integrated optical path for optical transmission and optical processing, wherein the electro-optic modulator and / or the thermo-optic modulator is used to modulate the phase of the optical signal, and the detector 30 is used to convert the optical signal into an electrical signal, and then output the electrical signal through the circuit board 70 through the metal interconnect structure.
[0068] like Figure 5 As shown, the present disclosure also provides a method for preparing an optical pressure sensor chip, comprising the following steps:
[0069] S100, providing a substrate, wherein the substrate comprises a substrate, a first cladding material layer, and a first waveguide material layer stacked in sequence;
[0070] S200, patterning the first waveguide material layer to form a first waveguide layer;
[0071] S300, sequentially forming a first deposition layer, a first sacrificial layer, a second deposition layer, a second waveguide layer, a third deposition layer, a second sacrificial layer, and a fourth deposition layer, wherein the first deposition layer covers the first waveguide layer and the exposed first cladding material layer, the second deposition layer covers the first sacrificial layer, and the third deposition layer covers the second waveguide layer;
[0072] S400, patterning the fourth deposition layer to form a first opening, wherein the first opening exposes at least a portion of the second sacrificial layer;
[0073] S500, patterning the substrate, the first deposition layer, the second deposition layer, the third deposition layer and the fourth deposition layer to form a deep groove structure, wherein the deep groove structure exposes an end surface of the first sacrificial layer;
[0074] S600, removing the first sacrificial layer and the second sacrificial layer, and forming a first cavity and a second cavity at the positions of the first sacrificial layer and the second sacrificial layer, respectively;
[0075] S700, removing part of the third deposition layer and part of the fourth deposition layer located above the second waveguide layer, and removing the first deposition layer and the second deposition layer between the first waveguide layer and the second waveguide layer, so that the first cavity and the second cavity are connected, and a cavity is formed between the first waveguide layer and the second waveguide layer, so that the second waveguide layer forms a cantilever beam structure.
[0076] The method for preparing the optical pressure sensor chip disclosed in the present invention is described below through specific examples.
[0077] S100, first provide a substrate 1. Fig. 6A As shown, the substrate 1 includes a substrate 11, a dielectric layer 12 as a first cladding material layer, and a first waveguide material layer 13, which are stacked in sequence, wherein the materials of the substrate 11 and the first waveguide material layer 13 can both be silicon, and the material of the dielectric layer is silicon dioxide or other materials that can be used as a waveguide cladding. In specific practice, a SOI (Silicon On Insulator) substrate that meets the requirements can be selected as the substrate 1, and the SOI substrate includes a single crystal silicon top layer, a silicon dioxide middle layer, and a thicker silicon substrate layer that are stacked in sequence, wherein the single crystal silicon top layer serves as the first waveguide material layer 13, the silicon dioxide middle layer serves as the dielectric layer 12, and the silicon substrate layer provides mechanical support for the two layers above. Alternatively, a substrate 1 that meets the requirements can be prepared by oneself or purchased commercially.
[0078] S200, forming a first waveguide layer 2. Figure 6B As shown, the first waveguide material layer 13 is patterned to form a first waveguide layer 2 at the edge of the substrate 1. Of course, the orthographic projection of the first waveguide layer 2 on the substrate 11 falls within the orthographic projection range of the dielectric layer 12 on the substrate 11.
[0079] Of course, in the process of forming the first waveguide layer 2, the first waveguide material layer 13 can also be processed simultaneously or successively, and other required structural layers can be formed and processed on this basis to form at least a partial film layer of any one of the functional devices, output devices and metal interconnection structures. Among them, the functional device can be a strip waveguide, a ridge waveguide, a microring resonator, a Y branch, an electro-optic modulator, a thermo-optic modulator, a germanium detector, etc., and the output device can be a grating coupler, an end coupler, etc. Figure 6B As shown in the figure, from left to right are the grating coupler, the ridge waveguide, the electro-optic modulator and at least part of the film layer of the end face coupling structure. Of course, it should be noted that Figure 6B The cross section of the cross-sectional view shown is not a plane, but an expanded view of a complex stepped cross section that can reflect the cross-sectional conditions of each functional device or output device.
[0080] The preparation method of the optical pressure sensor chip introduced in the present disclosure is mainly based on forming an end face coupling structure. The following figure also mainly reflects the formation process of the end face coupling structure, that is, Figure 6B The local structure on the right side of the middle is omitted Figure 6B Of course, the subsequent descriptions of the substrate or chip end are based on the end on the right side of the figure.
[0081] S300, sequentially forming a first deposition layer 32, a first sacrificial layer 4, a second deposition layer 33, a second waveguide layer 5, a third deposition layer 62, a second sacrificial layer 7 and a fourth deposition layer 63, wherein the first deposition layer 32 covers the first waveguide layer 2 and the exposed dielectric layer 12, the second deposition layer 33 covers the first sacrificial layer 4, and the third deposition layer 62 covers the second waveguide layer 5. It specifically includes the following steps:
[0082] S310, combined Figure 6C As shown, a first deposition layer 32 is formed on the substrate 1, and the first deposition layer 32 covers the first waveguide layer 2 and the exposed dielectric layer 12. Specifically, the first deposition layer 32 can be formed by PECVD (plasma enhanced chemical vapor deposition), and more specifically, HDP CVD (High-Density Plasma Chemical Vapor Deposition) can be used. The material of the first deposition layer 32 can be silicon dioxide or other materials that can be used as a cladding.
[0083] Afterwards, the first deposition layer 32 may be planarized according to actual conditions, for example, by using a CMP (Chemical Mechanical Polishing) process.
[0084] S320, continue to combine Figure 6C As shown, a first sacrificial layer 4 is formed on the first deposition layer 32, wherein a material layer forming the first deposition layer can be first deposited and then patterned using a composition process, wherein the composition process includes but is not limited to processes such as coating photoresist, exposure, development, and etching.
[0085] The orthographic projection range of the first sacrificial layer 4 on the substrate 11 at least partially overlaps with the orthographic projection range of the first waveguide layer 2 on the substrate 11. The first sacrificial layer 4 and the first waveguide layer 2 both have a first end and a second end along the waveguide extension direction (X direction in the figure), and the first ends of the first sacrificial layer 4 and the first waveguide layer 2 are both close to the substrate end, and the second ends are both far away from the substrate end. The orthographic projection of the first end of the first sacrificial layer 4 on the substrate 11 preferably exceeds the orthographic projection of the first end of the first waveguide layer 2 on the substrate 11, so as to expose the end face of the first end of the first sacrificial layer 4 in the subsequent process of forming the deep groove structure.
[0086] Of course, in some possible implementations, the first end of the first sacrificial layer 4 may not exceed the first end of the first waveguide layer 2, for example, the ends of the two are flush, as long as the first sacrificial layer 4 can be exposed and removed through the substrate end in subsequent processes.
[0087] The material of the first sacrificial layer 4 is different from the material of the first deposition layer 32, and preferably has a large etching selectivity ratio between the two, so as to avoid damaging the first deposition layer 32 as much as possible during the subsequent removal of the first sacrificial layer 4. For example, the material of the first deposition layer 32 is silicon dioxide, and the material of the first sacrificial layer 4 is silicon nitride.
[0088] S330, continue to combine Figure 6C As shown, a second deposition layer 33 is formed, and the second deposition layer 33 covers the first sacrificial layer 4 and the exposed first deposition layer 32. The materials of the first deposition layer 32 and the second deposition layer 33 can be the same, and the two are subsequently used to form a cladding layer.
[0089] After the second deposition layer 33 is formed, the second deposition layer 33 may be planarized according to actual conditions, such as by using a CMP process.
[0090] S340, continue to combine Figure 6C As shown, a second waveguide layer 5 is formed on the second deposition layer 33. For example, the distance between the second waveguide layer 5 and the first waveguide layer 2 (the dimension along the thickness direction of the substrate 11 in the figure, ie, the Z direction) is 100nm to 300nm.
[0091] Along the waveguide extension direction, the second waveguide layer 5 has a first end and a second end opposite to each other, the first end is close to the substrate end, and the second end is far away from the substrate end. The orthographic projection of the first end of the second waveguide layer 5 on the substrate 11 falls within the orthographic projection range of the first sacrificial layer 4 on the substrate 11, that is, compared with the first end of the first sacrificial layer 4, the first end of the second waveguide layer 5 is farther away from the adjacent substrate end, so that the second waveguide layer 5 will not be damaged when the end of the second sacrificial layer 7 is exposed in the subsequent process. In addition, the position of the second waveguide layer 5 will also affect the final bonding surface between it and the third cladding layer 6, so the relative position relationship between the second waveguide layer 5 and the second sacrificial layer 7 can be reasonably determined according to the overall size (weight) of the second waveguide layer 5.
[0092] Combination Fig.6D As shown, the second waveguide layer 5 has a first side and a second side along a direction perpendicular to the waveguide extension direction (specifically, the Y direction), and the orthographic projection of the boundary of the first sacrificial layer 4 along the direction perpendicular to the waveguide extension direction on the substrate 11 exceeds the orthographic projection of the first side and the second side of the second waveguide layer 5 on the substrate 11, and the exceeding distances are both greater than 1 μm, so as to fully remove the first deposition layer 32 and the second deposition layer 33 located between the first waveguide layer 2 and the second waveguide layer 5 in subsequent processes.
[0093] S350, combined Fig. 6EAs shown, a third deposition layer 62 is formed, and the third deposition layer 62 covers the second waveguide layer 5 and the exposed second deposition layer 33. The third deposition layer 62 can be made of a material that can be used as a cladding layer, such as the same material as the first deposition layer 32.
[0094] After the third deposition layer 62 is formed, the third deposition layer 62 may be planarized according to actual conditions, especially the flatness of the surface of the third deposition layer 62 , such as by using a CMP process.
[0095] S360, continue to combine Fig. 6E As shown, a second sacrificial layer 7 is formed on the third deposition layer 62. The material of the second sacrificial layer 7 can be the same as that of the first sacrificial layer 4, for example, both are made of silicon nitride.
[0096] The second sacrificial layer 7 has a first end and a second end opposite to each other along the waveguide extension direction, the first end is close to the substrate end, and the second end is far away from the substrate end. There is a certain distance between the first end of the second sacrificial layer 7 and the substrate end, and the first end of the second waveguide layer 5 exceeds the first end of the second sacrificial layer 7, that is, compared with the first end of the second waveguide layer 5, the first end of the second sacrificial layer 7 is farther away from the adjacent substrate end, so that in the subsequent process, a part of the deposited layer between the first end of the second sacrificial layer 7 and the first end of the second waveguide layer 5 is retained, so that the second waveguide layer 5 forms a cantilever beam structure. Of course, it can be understood that the distance between the first end of the second waveguide layer 5 and the first end of the second sacrificial layer 7 (the dimension along the X direction in the figure) can be determined according to the size of the second waveguide layer 5, so as to ensure that the second waveguide layer 5 can have sufficient bonding force with the remaining deposited layer.
[0097] S370, continue to combine Fig. 6E As shown, a fourth deposition layer 63 is formed, and the fourth deposition layer 63 covers the second sacrificial layer 7 and the exposed third deposition layer 62. The fourth deposition layer 63 and the third deposition layer 62 are subsequently used to form an upper cladding layer, so the materials of the two layers can be the same, and both can select materials commonly used for cladding layers.
[0098] After the fourth deposition layer 63 is formed, the fourth deposition layer 63 may be planarized according to actual conditions, such as by using a CMP process.
[0099] S400, such as Fig. 6F As shown, the fourth deposition layer 63 is patterned to form a first opening 61 , and the first opening 61 exposes at least a portion of the top surface of the second sacrificial layer 7 .
[0100] Specifically, Fig. 6F and Figure 6HAs shown, in some examples, the first opening 61 exposes the second end of the second sacrificial layer 7 in the X direction, both sides in the Y direction, and the third deposition layer 62 located outside the second end and both side boundaries of the second sacrificial layer 7, so as to facilitate better removal of the second sacrificial layer 7 in the subsequent process. That is, in a top view, the first opening 61 exposes the top surface at the second end of the second sacrificial layer 7, also exposes a part of the top surface of the third deposition layer 62, and the exposed top surface of the third deposition layer 62 is in a "匚" shape (or "U" shape), surrounding the second end of the second sacrificial layer 7.
[0101] As Figure 6G and Fig.6I shown, in other examples, the first opening 61 can also completely expose the second sacrificial layer 7, and even expose the third deposition layer 62 outside the boundary of the second sacrificial layer 7, so as to facilitate better removal of the second sacrificial layer 7 in the subsequent process. That is, in a top view, the first opening 61 exposes the entire top surface of the second sacrificial layer 7, also exposes a part of the top surface of the third deposition layer 62, and the exposed top surface of the third deposition layer 62 is in a "口" shape or "匚" shape, completely surrounding or partially surrounding the second sacrificial layer 7.
[0102] S500, in combination with Figure 6J and Figure 6K shown, the patterned substrate 1, the first deposition layer 32, the second deposition layer 33, the third deposition layer 62, and the fourth deposition layer 63 (hereinafter, the first to fourth deposition layers are collectively referred to as deposition layers) are patterned to form a deep trench structure at the edge of the chip, and at the same time, the first end of the first sacrificial layer 4 is exposed by the deep trench structure. Of course, Figure 6K only shows the structure near one end region of a chip (or die). In the specific implementation process, a deep trench structure can be formed at each die end, or a deep trench structure can be formed between two adjacent dies on the wafer, that is, two chips share one deep trench structure. The side walls of the deep trench structure expose the substrate 11 and part of the end faces of the deposition layers.
[0103] Specifically, the above deep trench structure can be formed by a deep trench etching process. In the specific implementation process, it can be divided into two steps. First, the deposition layers are etched with the substrate 11 as the etching stop layer; then the substrate 11 is etched, and the etching depth is lower than the thickness of the substrate 11, which can be specifically adjusted according to the actual product requirements. For example, the etching depth is between 100 μm and 200 μm.
[0104] As Figure 6JAs shown, the V102 area is the etching area, that is, the area where the substrate 1 and the first to fourth deposition layers need to be removed during the patterning process. In the example disclosed in the present invention, there is an overlapping area between the V102 area and the projection of the first sacrificial layer 4 on the substrate 11, and the overlapping area is specifically located at the first end of the first sacrificial layer 4. Therefore, in the process of patterning the deposition layer, the first end of the first sacrificial layer 4 is also removed to ensure that the end face of the first sacrificial layer 4 is fully exposed. The length of the patterned removal of the first sacrificial layer 4 (that is, the length L of the overlapping area between the V102 area and the projection of the first sacrificial layer 4 on the substrate 11) needs to be greater than the lithography overlay deviation, which is generally 6 times the standard deviation of the lithography overlay deviation.
[0105] S600, combined Figure 6L As shown, the first sacrificial layer 4 and the second sacrificial layer 7 (hereinafter collectively referred to as sacrificial layers) are removed. After the sacrificial layers are removed, a first cavity 41 and a second cavity 71 are formed at the positions of the first sacrificial layer 4 and the second sacrificial layer 7, respectively.
[0106] The sacrificial layer can be removed by a wet etching process, wherein the wet etching process has a large etching selectivity ratio between the sacrificial layer and the adjacent deposition layer, and reduces damage to the deposition layer as much as possible while etching away the sacrificial layer. In a specific example of the present disclosure, the material of the sacrificial layer is silicon nitride, the material of the deposition layer is silicon oxide, and the etching solution of the wet etching uses or contains hot phosphoric acid.
[0107] S700, removing the first deposition layer 32 and the second deposition layer 33 between the first waveguide layer 2 and the second waveguide layer 5 and part of the third deposition layer 62 and part of the fourth deposition layer 63 above the second waveguide layer 5, so that the first cavity 41 and the second cavity 71 are connected, thereby forming a cavity 31 between the first waveguide layer 2 and the second waveguide layer 5, and the second cavity 71 above the second waveguide layer 5 is expanded and connected with the cavity 31, so that the second waveguide layer 5 forms a cantilever beam structure. Specifically, it includes:
[0108] S710, such as Figure 6M As shown, a mask 8 is formed on the fourth deposition layer 63 , and the mask 8 has a window corresponding to the first opening 61 .
[0109] S720, combined Figure 6NAs shown, a hydrofluoric acid vapor etching process is adopted to allow hydrofluoric acid vapor to enter the second cavity 71 from the first opening 61. In the process, the fourth deposition layer 63, the third deposition layer 62, the second deposition layer 33 and the first deposition layer 32 are etched starting from the side wall and the bottom surface of the second cavity 71, so that the second cavity 71 is expanded and communicated with the first cavity 41, until the first deposition layer 32 and the second deposition layer 33 between the first waveguide layer 2 and the second waveguide layer 5 and part of the third deposition layer 62 and part of the fourth deposition layer 63 above the second waveguide layer 5 are removed, so that a cavity 31 is formed between the first waveguide layer 2 and the second waveguide layer 5 and the second waveguide layer 5 forms a cantilever beam structure.
[0110] After being etched by hydrofluoric acid vapor, the remaining first deposition layer 32 and the second deposition layer 33 constitute the second cladding 3, which serves as the upper cladding of the first waveguide layer 2 and the lower cladding of the second waveguide layer 5; the remaining third deposition layer 62 and the fourth deposition layer 63 constitute the third cladding 6, which serves as the upper cladding of the second waveguide layer 5. Figure 6N The dotted line portion shown is the original outline of the first cavity 41 and the second cavity 71. The outlines of the first cavity 41, the second cavity 71 and the first opening 61 are expanded after being etched, wherein the first cavity 41 is expanded to form a cavity 31, and the second cavity 71 and the first opening 61 are expanded and merged to form an expanded first opening 61, and the expanded first opening 61 is connected to the cavity 31 to expose the end face of the second end of the second waveguide layer 5.
[0111] In the hydrofluoric acid vapor etching process, the etching rates in all directions are approximately equal, but due to film quality and other reasons, there are still slight differences in the longitudinal and lateral etching rates. In order to ensure that the second waveguide layer 5 can form a cantilever beam structure, it is necessary to ensure that except for the connection between the second waveguide layer 5 and the third deposition layer 62 at the first end, there is no third deposition layer 62 at the rest of the second waveguide layer 5.
[0112] The vertical distance from the lower surface of the second sacrificial layer 7 to the upper surface of the first waveguide 2 is recorded as D1, and the horizontal distance from the end surface of the second sacrificial layer close to the substrate to the end surface of the second waveguide 5 close to the substrate is recorded as D2, and the two satisfy: D1<D2. In this way, it is ensured that the third deposition layer 62 can be corroded to the depth of the first cavity 41 in the longitudinal direction, so that the first cavity 41 and the second cavity 71 can be connected. The spacing D3 between the first waveguide layer 2 and the second waveguide layer 5 can be controlled to be 100nm to 300nm, and the spacing D4 between the first end of the second waveguide layer 5 and the end of the substrate can be 1μm to 5μm.
[0113] This embodiment is described by taking hydrofluoric acid vapor as an example. In other embodiments, other corrosive gases or even corrosive liquids may be selected as long as the above-mentioned effects can be achieved.
[0114] It is obvious that the positions of the first sacrificial layer 4 and the second sacrificial layer 7 determine the positions of the first cavity 41 and the second cavity 71, thereby affecting the performance of the end face coupling structure formed after the hydrofluoric acid vapor etching process. Among them, the position of the second end of the first sacrificial layer 4 can be flexibly designed according to the etching rate of the hydrofluoric acid vapor etching process. After the hydrofluoric acid vapor etching process is completed, no second deposition layer 33 remains on the lower surface of the second waveguide layer 5, and the dielectric layer below the end of the first waveguide layer 2 close to the substrate can be retained, so that the remaining dielectric layer can effectively support the first waveguide layer 2, ensuring that the first waveguide layer 2 does not vibrate. The positions of the first end and the second end of the second sacrificial layer 7 can be flexibly designed according to the etching rate of the hydrofluoric acid vapor etching process. After the hydrofluoric acid vapor etching process is completed, a certain distance needs to be maintained between the second waveguide layer 5 and the side wall of the cavity 31 formed by the etching to ensure that the cantilever beam structure of the second waveguide layer 5 has enough vibration space; at the same time, after the second cavity 71 is corroded and expanded, the remaining third deposition layer 62 is roughly aligned with the remaining fourth deposition layer 63, and there is sufficient adhesion between the remaining third deposition layer 62 and the second waveguide layer 5 to fix the end of the second waveguide layer 5. For example, the length of the second waveguide layer 5 connected to the third deposition layer 62 is preferably not less than 1 / 4 of the total length of the second waveguide layer 5.
[0115] S730, remove the mask 8, forming Figure 1 and Figure 2 The end-face coupling structure shown.
[0116] The above is only a specific implementation of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present disclosure should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.
Claims
1. An optical pressure sensor chip, characterized in that: The end surface coupling structure includes: A substrate (11) and a first cladding layer and a first waveguide layer (2) sequentially stacked on the substrate (11); a second cladding layer (3) located on the first waveguide layer (2), the second cladding layer (3) having a cavity (31), and a portion of the first waveguide layer (2) being exposed at the bottom of the cavity (31); a second waveguide layer (5) located on the second cladding layer (3), wherein the second waveguide layer (5) is exposed at the top of the cavity (31); A third cladding layer (6) is located on the second waveguide layer (5), the third cladding layer (6) is fixedly connected to one end of the second waveguide layer (5), the third cladding layer (6) has a first opening (61) connected to the cavity (31), the first opening (61) exposes the other end of the second waveguide layer (5), so that the second waveguide layer (5) forms a cantilever beam structure.
2. The optical pressure sensor chip according to claim 1, characterized in that: Part of the cavity (31) extends to the end surface of the optical pressure sensor chip to form a second opening (311).
3. The optical pressure sensor chip according to claim 2, characterized in that: The end face coupling structure satisfies at least one of the following: The distance between the end surface of one end of the second waveguide layer (5) and the end surface of the optical pressure sensing chip is 1 μm to 5 μm; The distance between the end surface of one end of the first waveguide layer (2) and the end surface of the optical pressure sensing chip is 20 μm to 40 μm; as well as, Along the thickness direction of the substrate (11), the distance between the first waveguide layer (2) and the second waveguide layer (5) is 100 nm to 300 nm.
4. The optical pressure sensor chip according to claim 1, characterized in that: Along the waveguide extension direction, the length of the second waveguide layer (5) exposed through the first opening (61) is at most 3 / 4 of the total length of the second waveguide layer (5).
5. The optical pressure sensor chip according to claim 1, characterized in that: The optical pressure sensor chip also includes at least one of a functional device for light transmission and light processing, an output device for outputting an optical signal, and a metal interconnection structure for outputting an electrical signal.
6. A method for preparing an optical pressure sensor chip, characterized in that: include: Providing a substrate, the substrate comprising a substrate (11), a first cladding material layer and a first waveguide material layer (13) stacked in sequence; patterning the first waveguide material layer (13) to form a first waveguide layer (2); A first deposition layer (32), a first sacrificial layer (4), a second deposition layer (33), a second waveguide layer (5), a third deposition layer (62), a second sacrificial layer (7) and a fourth deposition layer (63) are sequentially formed, wherein: the first deposition layer (32) covers the first waveguide layer (2) and the exposed first cladding material layer, the second deposition layer (33) covers the first sacrificial layer (4), and the third deposition layer (62) covers the second waveguide layer (5); Patterning the fourth deposition layer (63) to form a first opening (61), wherein the first opening (61) exposes at least a portion of the second sacrificial layer (7); Patterning the substrate (1), the first deposition layer (32), the second deposition layer (33), the third deposition layer (62) and the fourth deposition layer (63) to form a deep groove structure, wherein the deep groove structure exposes an end surface of one end of the first sacrificial layer (4); removing the first sacrificial layer (4) and the second sacrificial layer (7), and forming a first cavity (41) and a second cavity (71) at the positions of the first sacrificial layer (4) and the second sacrificial layer (7), respectively; A portion of the third deposition layer (62) and a portion of the fourth deposition layer (63) located above the second waveguide layer (5) are removed, and the first deposition layer (32) and the second deposition layer (33) between the first waveguide layer (2) and the second waveguide layer (5) are removed, so that the first cavity (41) and the second cavity (71) are connected, and a cavity (31) is formed between the first waveguide layer (2) and the second waveguide layer (5), so that the second waveguide layer (5) forms a cantilever beam structure.
7. The preparation method according to claim 6, characterized in that: After forming the first cavity (41) and the second cavity (71), the step of forming the cantilever beam structure comprises: forming a mask on the fourth deposition layer (63), the mask having a window corresponding to the first opening (61); Allowing a corrosive gas or a corrosive liquid to enter the second cavity (71) from the first opening (61) to corrode the fourth deposition layer (63), the third deposition layer (62), the second deposition layer (33) and the first deposition layer (32), so that the second cavity (71) is connected to the first cavity (41), and the first deposition layer (32) and the second deposition layer (33) located between the first waveguide layer (2) and the second waveguide layer (5) are removed to form the cavity (31), so that the second waveguide layer (5) is suspended on the first waveguide layer (2) to form a cantilever beam structure; The mask is removed.
8. The preparation method according to claim 6, characterized in that: The second waveguide layer (5) has a first end and a second end opposite to each other along the waveguide extension direction, wherein the first end is close to the end of the substrate (11), and the second waveguide layer (5) has a first side and a second side perpendicular to the waveguide extension direction, and the second waveguide layer (5) satisfies at least one of the following conditions: The orthographic projection of the first end of the second waveguide layer (5) on the substrate (11) falls within the orthographic projection range of the first sacrificial layer (4) on the substrate (11); The orthographic projection of the second end of the second waveguide layer (5) on the substrate (11) exceeds the orthographic projection range of the first sacrificial layer (4) on the substrate (11); and The orthographic projection of the first sacrificial layer (4) on the substrate (11) along a boundary perpendicular to the waveguide extension direction exceeds the orthographic projections of the first side and the second side of the second waveguide layer (5) on the substrate (11).
9. The preparation method according to claim 6, characterized in that: The second sacrificial layer (7) has a first end and a second end opposite to each other along the waveguide extension direction, the first end of the second sacrificial layer (7) is close to the end of the substrate, and the first opening (61) exposes the second end and both sides of the second sacrificial layer (7) and the third deposition layer (62) outside the second end and both sides of the second sacrificial layer (7); or, The first opening (61) completely exposes the second sacrificial layer (7).
10. An optical pressure sensor, characterized in that: The optical pressure sensing chip comprises the optical pressure sensing chip as claimed in any one of claims 1 to 5.
11. The optical pressure sensor according to claim 10, characterized in that: Also includes: A shell (10), the interior of the shell (10) is hollow, and the shell (10) is provided with a vent hole (101) communicating with the internal hollow structure; A laser (60) is aligned with an end face coupling structure in the optical pressure sensing chip (20); The detector (30) is used for processing the optical signal.