Photoacoustic sensor and manufacturing method thereof

Abstract

The invention provides a photoacoustic sensor and a manufacturing method thereof, the photoacoustic sensor comprises a first substrate, a strip waveguide, a slab waveguide and a vibrating diaphragm, the first substrate comprises a base, a buried oxide layer, a top semiconductor layer and a dielectric layer which are stacked in sequence; the strip-shaped waveguide is located above the buried oxide layer and comprises an annular part and a strip-shaped part which are spaced by a first preset distance, the periphery of the strip-shaped waveguide is provided with a peripheral gap which exposes the buried oxide layer and isolates the top semiconductor layer from the strip-shaped waveguide, and an inner circle surrounding area of the annular part and a main body of the annular part form a cavity which exposes the buried oxide layer; the slab waveguide is located above the strip-shaped waveguide, and the lower surface of the slab waveguide and the upper surface of the strip-shaped waveguide are spaced by a second preset distance; the vibrating diaphragm is located above the annular part and covers the upper surface of the slab waveguide. According to the photoacoustic sensor and the manufacturing method thereof, the manufacturing process is compatible with the CMOS process, the manufacturing process is simplified, and the sensitivity of the photoacoustic sensor is improved.

Description

Technical Field

[0001] The present invention relates to the field of silicon-based optoelectronic technology, and in particular to a photoacoustic sensor and a manufacturing method thereof. Background Art

[0002] Microring photoacoustic sensors are increasingly used in biomedical diagnosis and photoacoustic imaging due to their high sensitivity and high resolution. Photoacoustic imaging can visualize the distribution of ultrasound excited by laser pulses in biological tissues, and such ultrasound sensors can also detect tissue information and reconstruct tissue images. The working principle of the ultrasound sensor is to use a sensor to receive ultrasound signals. When the ultrasound wave slightly deforms the film, the effective refractive index of light propagating in the microring changes, thereby changing the resonance peak of the optical resonant cavity. The movement of the resonance peak means a change in the intensity of the transmitted light at the same wavelength, and the optical signal is then converted into an electrical signal by a photodetector for reading and processing.

[0003] The existing micro-ring ultrasonic sensors use polymer or silicon materials to prepare the micro-ring structure on a vibrating membrane. The vibration of the membrane changes the effective refractive index of the waveguide, but such a structure has low sensitivity and cannot be miniaturized due to material reasons; or the vibration of the diaphragm changes the spacing with the waveguide micro-ring, changes the coupling efficiency, and then changes the output light intensity. The sensor is integrated on a single-mode optical fiber. The device size is large and the resonant frequency is low. At the same time, the sensitivity of the sensor is not high, and the process requirements are relatively strict. Therefore, designing a highly sensitive small ultrasonic sensor is of great significance for biomedical photoacoustic imaging.

[0004] In view of this, there is an urgent need for a photoacoustic sensor with high sensitivity, small size and simple process. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a photoacoustic sensor and a method for manufacturing the same, so as to solve the problems of low sensitivity, large size and complex manufacturing process of the photoacoustic sensor in the prior art.

[0006] To achieve the above objectives and other related objectives, the present invention provides a photoacoustic sensor, comprising:

[0007] The first substrate comprises a base, a buried oxide layer, a top semiconductor layer and a dielectric layer stacked in sequence;

[0008] A strip waveguide is located above the buried oxide layer, the strip waveguide comprises an annular portion and a strip portion separated by a first preset distance, a peripheral gap is provided around the strip waveguide to expose the buried oxide layer and isolate the top semiconductor layer from the strip waveguide, an inner circular surrounding area of ​​the annular portion and a main body of the annular portion form a cavity, and the bottom surface of the cavity exposes the buried oxide layer;

[0009] A slab waveguide is located above the strip waveguide, and a lower surface of the slab waveguide is spaced a preset distance from an upper surface of the strip waveguide;

[0010] The vibration membrane is located above the annular portion and covers the upper surface of the planar waveguide.

[0011] Optionally, the material of the planar waveguide includes silicon and silicon nitride; the material of the strip waveguide includes silicon, silicon nitride and polymer.

[0012] Optionally, a spacing distance between the lower surface of the planar waveguide and the upper surface of the strip waveguide ranges from 10 nm to 30 nm.

[0013] Optionally, the radius of the annular portion ranges from 5 μm to 8 μm.

[0014] Optionally, the material of the vibration membrane includes silicon dioxide.

[0015] Optionally, the shape of the vibration membrane includes a circle.

[0016] Optionally, the radius of the vibration membrane is in the range of 9 μm to 15 μm.

[0017] Optionally, the width of the strip-shaped portion ranges from 400 nm to 700 nm; the thickness of the strip-shaped portion ranges from 90 nm to 220 nm.

[0018] Optionally, the thickness of the slab waveguide ranges from 50 nm to 250 nm.

[0019] The present invention also provides a method for manufacturing a photoacoustic sensor, comprising the following steps:

[0020] Providing an SOI substrate, the SOI substrate comprising a base, a buried oxide layer, and a top semiconductor layer stacked in sequence, and forming a dielectric layer on the upper surface of the top semiconductor layer to obtain the first substrate;

[0021] A patterned first shielding layer is formed on the upper surface of the dielectric layer, and a strip waveguide is formed based on the patterned first shielding layer, and a peripheral gap that exposes the buried oxide layer and isolates the top semiconductor layer from the strip waveguide, wherein the strip waveguide includes an annular portion and a strip portion separated by a first preset distance, an inner circular surrounding area of ​​the annular portion and a main body of the annular portion form a cavity, and the bottom surface of the cavity exposes the buried oxide layer;

[0022] forming a second shielding layer that only exposes the dielectric layer above the strip waveguide, so as to remove the dielectric layer above the strip waveguide;

[0023] Providing a second substrate, and forming a vibration membrane and a planar waveguide stacked in sequence on the second substrate;

[0024] The strip waveguide is bonded to the dielectric layer, and the second substrate is removed. After bonding, the vibration membrane is located above the annular portion, and the lower surface of the strip waveguide is spaced a second preset distance from the upper surface of the strip waveguide.

[0025] As described above, the photoacoustic sensor and the manufacturing method thereof of the present invention have the following beneficial effects: by arranging the planar waveguide and the strip waveguide in the photoacoustic sensor, the strip waveguide includes the strip portion and the ring portion separated by a first preset distance, and the upper surface of the strip waveguide and the lower surface of the planar waveguide are separated by a second preset distance, the planar waveguide and the strip waveguide constitute an optical microring resonator, by combining the vibration membrane with the planar waveguide, when the waveguide is in a critical coupling state, the photoacoustic sensor receives an ultrasonic wave, and the distance between the upper surface of the strip waveguide and the lower surface of the planar waveguide will change slightly, thereby causing a large change in the effective refractive index of the waveguide, and then causing the resonance peak to shift, and the laser wavelength is fixed at the center of the rise or fall with a large slope of the resonance peak, and the light intensity will change significantly when the resonance peak is slightly shifted, thereby realizing the detection of deep ultrasonic signals. The photoacoustic sensor is improved in sensitivity by forming the dielectric layer on the SOI substrate, forming the strip waveguide based on the patterned first shielding layer above the dielectric layer, and removing the dielectric layer above the strip waveguide based on the second shielding layer, and then forming the vibration membrane and the planar waveguide stacked in sequence, bonding the dielectric layer to the planar waveguide to obtain the photoacoustic sensor in which the strip waveguide and the planar waveguide are spaced a second preset distance apart. The manufacturing process is compatible with the CMOS process, which simplifies the manufacturing process and reduces the process cost. By seeking the material and structural size of the photoacoustic sensor with excellent performance, the vibration frequency range of the photoacoustic sensor can be effectively adjusted, which satisfies the need to manufacture the photoacoustic sensor in a small size while also satisfying the need to improve the sensitivity of the photoacoustic sensor, thereby greatly expanding the application field of the photoacoustic sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Shown is a schematic diagram of a cross-sectional structure of the photoacoustic sensor of the present invention.

[0027] Figure 2 Another schematic diagram of the cross-sectional structure of the photoacoustic sensor of the present invention is shown.

[0028] Figure 3 It shows a third cross-sectional structure schematic diagram of the photoacoustic sensor of the present invention.

[0029] Figure 4The diagram shows the resonance displacement of the center of the vibrating membrane of the photoacoustic sensor of the present invention under different sound pressures.

[0030] Figure 5 The photoacoustic sensor of the present invention is shown as Plotted against waveguide transmission loss.

[0031] Figure 6 The graph shows the relationship between the ratio of the effective refractive index of the waveguide and the displacement at the center of the vibrating membrane under different waveguide widths and planar waveguide thicknesses of the photoacoustic sensor of the present invention.

[0032] Figure 7 Shown is a vibration curve diagram of the vibrating membrane of the photoacoustic sensor of the present invention.

[0033] Figure 8 Shown is a waveguide light field diagram of the photoacoustic sensor of the present invention.

[0034] Fig. 9 A schematic diagram showing the manufacturing process of a photoacoustic sensor according to the manufacturing method of the photoacoustic sensor of the present invention is shown.

[0035] Fig.10 It is a schematic diagram showing the structure after forming the dielectric layer in the method for manufacturing the photoacoustic sensor of the present invention.

[0036] Fig.11 It is a schematic diagram showing the structure after forming a strip waveguide in the method for manufacturing a photoacoustic sensor of the present invention.

[0037] Fig.12 It is a schematic diagram showing the structure of the photoacoustic sensor manufacturing method of the present invention after removing the dielectric layer above the strip waveguide.

[0038] Fig.13 It is a schematic diagram showing the structure after forming a planar waveguide in the method for manufacturing a photoacoustic sensor of the present invention.

[0039] Fig.14 It is a schematic structural diagram showing the bonding of a planar waveguide and a dielectric layer in the method for manufacturing a photoacoustic sensor of the present invention.

[0040] Component number description

[0041] 1. First substrate

[0042] 11 Buried Oxide Layer

[0043] 12 Top semiconductor layer

[0044] 13 Dielectric layer

[0045] 2 Strip waveguide

[0046] 21 Strip

[0047] 22 Ring

[0048] 3 Slab waveguide

[0049] 4. Diaphragm

[0050] 5 Peripheral clearance

[0051] 6. Gap

[0052] 7 Second substrate DETAILED DESCRIPTION

[0053] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0054] See also Figures 1 to 14 . It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings in this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0055] Embodiment 1

[0056] This embodiment provides a photoacoustic sensor, such as Figure 1-Figure 3, which are respectively a schematic diagram of a cross-sectional structure of the photoacoustic sensor, another schematic diagram of a cross-sectional structure of the photoacoustic sensor, and a third schematic diagram of a cross-sectional structure of the photoacoustic sensor, comprising: a first substrate 1, a strip waveguide 2, a planar waveguide 3, and a vibrating membrane 4, wherein the first substrate 1 comprises a base (not shown), a buried oxide layer 11, a top semiconductor layer 12, and a dielectric layer 13 stacked in sequence; the strip waveguide 2 is located above the buried oxide layer 11, and the strip waveguide 2 comprises an annular portion 22 and a strip portion spaced a first preset distance apart. 21, the strip waveguide 2 is surrounded by a peripheral gap 5 that exposes the buried oxide layer 11 and isolates the strip waveguide 2 from the top semiconductor layer 12, the inner circle surrounding area of ​​the annular portion 22 and the main body of the annular portion 22 form a cavity 6, and the bottom surface of the cavity 6 exposes the buried oxide layer 11; the slab waveguide 3 is located above the strip waveguide 2, and the lower surface of the slab waveguide 3 is spaced from the upper surface of the strip waveguide 2 by a second preset distance; the vibration membrane 4 is located above the annular portion 22 and covers the upper surface of the slab waveguide 3.

[0057] Specifically, the substrate (not shown) is made of silicon or other suitable materials.

[0058] Specifically, under the condition that the performance of the photoacoustic sensor is met, the size and shape of the substrate can be selected according to actual conditions and are not limited here.

[0059] Specifically, the buried oxide layer 11 is made of silicon dioxide or other suitable materials.

[0060] Specifically, under the condition that the performance of the photoacoustic sensor is met, the size and shape of the buried oxide layer 11 can be selected according to actual conditions and are not limited here.

[0061] Specifically, under the condition that the performance of the photoacoustic sensor is met, the material, size and shape of the top semiconductor layer 12 can be selected according to actual conditions and are not limited here.

[0062] As an example, the material of the strip waveguide 2 includes silicon, silicon nitride, polymer or other suitable materials. In this embodiment, the material of the strip waveguide 2 is silicon.

[0063] As an example, the spacing distance between the annular portion 22 and the strip portion 21 ranges from 200 nm to 600 nm.

[0064] Specifically, the spacing distance between the annular portion 22 and the strip portion 21 is changed according to different designs of the radius of the outer circle of the annular portion 22 of the micro-ring, so that the annular portion 22 and the strip portion 21 achieve critical coupling.

[0065] Specifically, the radius of the annular portion 22 ranges from 5 μm to 8 μm. In the present embodiment, the radius of the annular portion 22 is 6 μm. The radius here refers to the radius of a circle at the annular center axis of the annular portion 22 .

[0066] Specifically, the thickness of the annular portion 22 ranges from 90 nm to 220 nm, where the thickness refers to the vertical distance between the bottom surface and the top surface of the annular portion 22 .

[0067] As an example, the material of the strip-shaped portion 21 includes silicon, silicon nitride, polymer or other suitable materials. In this embodiment, the material of the strip-shaped portion 21 is silicon.

[0068] Specifically, the width of the strip-shaped portion 21 ranges from 400 nm to 700 nm; the thickness of the strip-shaped portion 21 ranges from 90 nm to 220 nm. In this embodiment, the width of the strip-shaped portion 21 is 550 nm, and the thickness is 150 nm.

[0069] Specifically, under the condition that the performance of the photoacoustic sensor is met, the size and shape of the cavity 6 can be selected according to actual conditions and are not limited here.

[0070] As an example, the material of the slab waveguide 3 includes silicon, silicon nitride or other suitable materials. In this embodiment, the material of the slab waveguide 3 is silicon nitride.

[0071] As an example, the thickness of the slab waveguide 3 ranges from 50 nm to 250 nm. In this embodiment, the thickness of the slab waveguide 3 ranges from 150 nm.

[0072] Specifically, under the condition that the performance of the photoacoustic sensor is met, the shape of the planar waveguide 3 can be selected according to actual conditions, and is not limited here.

[0073] As an example, the shape of the vibration membrane 4 includes a circle or other suitable shapes.

[0074] As an example, the radius of the vibration membrane 4 ranges from 9 μm to 15 μm. In this embodiment, the radius of the vibration membrane is 12 μm.

[0075] As an example, the material of the vibration membrane 4 includes silicon dioxide or other suitable materials. In this embodiment, the material of the vibration membrane 4 is silicon dioxide, and the silicon dioxide material with low tensile stress is used as the vibration membrane 4 to meet the yield of the photoacoustic sensor.

[0076] Specifically, the thickness of the vibration membrane 4 is in the range of 2 μm to 4 μm. In this embodiment, the thickness of the vibration membrane 4 is 3 μm.

[0077] Specifically, the center of the vibration membrane 4 coincides with the projection of the center of the annular portion 22 in the stacking direction of the first substrate 1 and the slab waveguide 3 .

[0078] Specifically, by adjusting the structural size and material of the photoacoustic sensor, the vibration frequency range of the photoacoustic sensor can be effectively adjusted, so that the photoacoustic sensor can be applied to different scenarios. For example, the size of the vibration membrane 4 can be designed according to the resolution required by the photoacoustic sensor. The higher the required lateral resolution, the higher the frequency, the thicker the vibration membrane 4, and the smaller the radius. When the thickness of the vibration membrane 4 is 2μm and a low tensile stress silica material is used as the vibration membrane 4, if the vibration frequency of the photoacoustic sensor is to reach above 30MHz, the radius of the vibration membrane 4 is less than 10μm. That is, by adjusting the thickness, radius and material of the vibration membrane 4, the vibration frequency and sensitivity of the photoacoustic sensor can be adjusted.

[0079] Specifically, the material of the dielectric layer 13 includes silicon dioxide or other suitable materials.

[0080] Specifically, the thickness of the dielectric layer 13 ranges from 10 nm to 30 nm. In this embodiment, the thickness of the dielectric layer 13 is 10 nm.

[0081] As an example, the distance between the lower surface of the slab waveguide 3 and the upper surface of the strip waveguide 2 is in the range of 10 nm to 30 nm. In this embodiment, the distance between the lower surface of the slab waveguide 3 and the upper surface of the strip waveguide 2 is 10 nm.

[0082] Specifically, the thickness of the dielectric layer 13 is consistent with the distance between the lower surface of the planar waveguide 3 and the upper surface of the strip waveguide 2 .

[0083] Specifically, the working principle of the photoacoustic sensor device is: the incident ultrasonic wave causes the vibration membrane to shift, and the resonance curve will shift, which means the change of the transmitted light intensity at the same wavelength, and then the optical signal is converted into an electrical signal through a photodetector for reading and processing.

[0084]

[0085] Specifically, the above formula defines the sensitivity of the photoacoustic sensor, where T is the transmittance of light, P is the sound pressure, and n e is the effective refractive index of the waveguide, g is the gap between the slab waveguide and the strip waveguide, and w r is the displacement of the vibrating membrane at the micro-ring, w 0 is the displacement at the center of the diaphragm, such as Figure 4-Figure 6As shown, they are respectively the resonance displacement diagram of the center of the vibration membrane 4 under different sound pressures of the photoacoustic sensor, The relationship diagram of the waveguide transmission loss and the ratio of the effective refractive index of the waveguide to the displacement at the center of the vibration membrane 4 under different waveguide widths and slab waveguide thicknesses, that is, when the material of the vibration membrane 4 is silicon dioxide material, the material of the slab waveguide 3 is silicon nitride material, the material of the strip waveguide 2 is silicon material, the spacing distance between the slab waveguide 3 and the strip waveguide 2 is 10nm, the waveguide microring formed by the slab waveguide 3 and the strip waveguide 2 is an optical ring resonator, a part of the waveguide microring is located on the vibration membrane 4, and the other part is located on the buried oxide layer 11. At this time, the displacement of the center of the membrane under different sound pressures When the micro-ring of the photoacoustic sensor is in a critical coupling state, when the planar waveguide is made of silicon nitride material, since the waveguide transmission loss of silicon nitride material is relatively low, it is assumed that silicon material is used as the strip waveguide and silicon nitride material is used as the planar waveguide. The transmission loss of the composite waveguide is 1 dB / cm. The strip portion 21 has a thickness of 150 nm and a width of 550 nm. When the thickness of the planar waveguide is 150 nm, the photoacoustic sensor has excellent performance.

[0086] Specifically, Figure 7-Figure 8 As shown, they are respectively a vibration curve diagram of the vibration membrane 4 of the photoacoustic sensor and a waveguide light field diagram of the photoacoustic sensor. When the thickness of the vibration membrane 4 of the photoacoustic sensor is defined as 3 μm, the radius of the vibration membrane 4 is 12 μm, the thickness of the planar waveguide 3 is 150 nm, the width of the strip portion 21 is 550 nm, the thickness is 150 nm, and the minimum straight-line distance between the center of the annular portion 22 and the top semiconductor layer 12 is 6 μm, the strip waveguide 3 and the planar waveguide 2 are in a critical coupling state. When the working wavelength of the photoacoustic sensor is 1570 nm, the distance between the lower surface of the planar waveguide 3 and the upper surface of the strip waveguide 2 is greatly affected by the process. When the distance is 10 nm, the sensitivity of the photoacoustic sensor is 3.67 kPa -1 The resonant frequency of the photoacoustic sensor is about 30 MHz, which has a high detection sensitivity, and the transverse cross-sectional size of the photoacoustic sensor is 24 μm, which is a small-sized photoacoustic sensor.

[0087] Specifically, by seeking the material and structural dimensions of the photoacoustic sensor with excellent performance, the vibration frequency range of the photoacoustic sensor can be effectively adjusted, which satisfies the requirement of reducing the size of the photoacoustic sensor while improving the sensitivity of the photoacoustic sensor, greatly expanding the application field of the photoacoustic sensor.

[0088] Specifically, by arranging the flat waveguide 3 under the vibration membrane 4, and the lower surface of the flat waveguide 3 is spaced from the upper surface of the strip waveguide 2 by a second preset distance, under the joint action of the flat waveguide 3 and the strip waveguide 2, part of the light field of the photoacoustic sensor when it is in action is distributed in the spacing distance between the flat waveguide 3 and the strip waveguide 2, and the electric field intensity of the waveguide mode is very high in the spacing distance between the flat waveguide 3 and the strip waveguide 2. A slight change in the spacing distance caused by ultrasonic waves leads to a large change in the effective refractive index of the photoacoustic sensor. When the laser wavelength is fixed at the center of the rise or fall of the resonant frequency peak when the photoacoustic sensor is working, due to the large slope of the resonant frequency peak here, the spacing distance between the flat waveguide 3 and the strip waveguide 2 is slightly displaced, and the light intensity changes greatly, resulting in a higher sensitivity of the photoacoustic sensor.

[0089] The photoacoustic sensor of the present embodiment is provided with the planar waveguide 3 and the strip waveguide 2 in the photoacoustic sensor, and the upper surface of the strip waveguide 3 and the lower surface of the planar waveguide 3 are spaced by a preset distance, and the planar waveguide 3 and the strip waveguide 2 constitute an optical microring resonator. By combining the vibration membrane 4 with the planar waveguide 3, and when the planar waveguide 3 and the strip waveguide 2 are in a critical coupling state, the photoacoustic sensor receives an ultrasonic wave, and the distance between the upper surface of the strip waveguide 3 and the lower surface of the planar waveguide 3 will change slightly, thereby causing a large change in the effective refractive index of the waveguide, and then causing the resonance peak to shift, and the laser wavelength is fixed at the center of the rise or fall with a larger slope of the resonance peak. A slight displacement of the resonance peak will cause a large change in light intensity, thereby realizing the detection of deep ultrasonic signals and improving the sensitivity of the photoacoustic sensor.

[0090] Embodiment 2

[0091] This embodiment provides a method for manufacturing a photoacoustic sensor. Fig. 9 FIG. 1 is a schematic diagram of the manufacturing process of the photoacoustic sensor, which includes the following steps:

[0092] S1: providing an SOI substrate, wherein the SOI substrate comprises a base, a buried oxide layer, and a top semiconductor layer stacked in sequence, and forming a dielectric layer on the upper surface of the top semiconductor layer to obtain the first substrate;

[0093] S2: forming a patterned first shielding layer on the upper surface of the dielectric layer, forming a strip waveguide based on the patterned first shielding layer and exposing the buried oxide layer and isolating the outer peripheral gap of the top semiconductor layer and the strip waveguide, wherein the strip waveguide comprises an annular portion and a strip portion separated by a first preset distance, an inner circular surrounding area of ​​the annular portion and a main body of the annular portion forming a cavity, and the bottom surface of the cavity exposing the buried oxide layer;

[0094] S3: forming a second shielding layer that only exposes the dielectric layer above the strip waveguide, so as to remove the dielectric layer above the strip waveguide;

[0095] S4: providing a second substrate, and forming a vibration membrane and a planar waveguide stacked in sequence on the second substrate;

[0096] S5: Bonding the planar waveguide to the dielectric layer and removing the second substrate, wherein after bonding, the vibration membrane is located above the annular portion, and the lower surface of the planar waveguide is spaced a second preset distance from the upper surface of the strip waveguide.

[0097] For details, please refer to Fig.10 , perform the step S1, provide an SOI substrate, the SOI substrate includes a base, a buried oxide layer 11, and a top semiconductor layer 12 stacked in sequence, and form a dielectric layer 13 on the upper surface of the top semiconductor layer 12 to obtain the first substrate 1.

[0098] Specifically, before forming the dielectric layer 13 , the method further includes thinning the top semiconductor layer 12 to a preset thickness of the dielectric layer 13 and the strip waveguide 2 .

[0099] Specifically, the method of thinning the top semiconductor layer 12 is a conventional technical means, which will not be described in detail here.

[0100] Specifically, Fig.10 , which is a schematic diagram of the structure after the dielectric layer 13 is formed, the method of forming the dielectric layer 13 on the upper surface of the top semiconductor layer 12 includes thermal oxidation or other suitable methods.

[0101] Specifically, the dielectric layer 13 is formed by a thermal oxidation method, so that the spacing distance between the strip waveguide 2 and the slab waveguide 3 can be precisely controlled.

[0102] For details, please refer to Fig.11, executing step S2, forming a patterned first shielding layer (not shown) on the upper surface of the dielectric layer 13, forming a strip waveguide 2 based on the patterned first shielding layer and exposing the buried oxide layer 11 and isolating the top semiconductor layer 12 from the outer peripheral gap of the strip waveguide 2, the strip waveguide 2 includes an annular portion 22 and a strip portion 21 separated by a first preset distance, the inner circular surrounding area of ​​the annular portion 22 and the main body of the annular portion 22 constitute a cavity, and the bottom surface of the cavity 6 exposes the buried oxide layer 11.

[0103] Specifically, forming the patterned first shielding layer is a conventional technical method, which will not be described in detail here.

[0104] Specifically, Fig.11 As shown, it is a schematic diagram of the structure after the strip waveguide 2 is formed, and the formation of the strip waveguide 2 includes the following steps: etching the dielectric layer 13 and the top semiconductor layer 12 based on the patterned first shielding layer until the buried oxide layer 12 is exposed to obtain the strip waveguide 2, and at the same time as the strip waveguide 2 is formed, the buried oxide layer 11 is exposed and the outer gap 5 isolating the top semiconductor layer 12 and the strip waveguide 2 is obtained.

[0105] Specifically, the method of etching the dielectric layer 13 includes dry etching, wet etching or other suitable etching methods.

[0106] Specifically, the method of etching the top semiconductor layer 12 includes wet etching, dry etching or other suitable methods.

[0107] For details, please refer to Fig.12 , performing the step S3 to form a second shielding layer that only exposes the dielectric layer 13 above the strip waveguide 2 to remove the dielectric layer 13 located above the strip waveguide 2.

[0108] Specifically, forming the second shielding layer (not shown) is a conventional technical means, which will not be described in detail here.

[0109] Specifically, Fig.12 , which is a schematic diagram of the structure after the dielectric layer 13 above the strip waveguide 2 is removed, and the method of removing the dielectric layer 13 above the strip waveguide 2 includes dry etching, wet etching or other suitable etching methods.

[0110] For details, please refer to Fig.13 , perform the step S4, provide a second substrate 7, and form a vibration membrane 4 and a planar waveguide 3 stacked in sequence on the second substrate 7.

[0111] Specifically, the material of the second substrate 7 includes silicon or other suitable materials.

[0112] Specifically, under the condition that the performance of the photoacoustic sensor is met, the size and shape of the second substrate 7 can be selected according to actual conditions, and are not limited here.

[0113] Specifically, the method of forming the vibration film 4 includes plasma enhanced chemical vapor deposition (PECVD) or other suitable methods.

[0114] Specifically, Fig.13 , which is a schematic diagram of the structure after the slab waveguide 3 is formed. The method of forming the slab waveguide 3 includes low pressure chemical vapor deposition (LPCVD) or other suitable methods.

[0115] Specifically, after forming the planar waveguide 3, a step of annealing the planar waveguide 3 is further included to reduce waveguide loss and improve the sensitivity of the photoacoustic sensor.

[0116] Specifically, after forming the slab waveguide 3 , the method further includes a step of polishing the exposed surface of the slab waveguide 3 .

[0117] Specifically, the method for polishing the exposed surface of the slab waveguide 3 includes chemical mechanical polishing (CMP) or other suitable methods.

[0118] Specifically, polishing the exposed surface of the slab waveguide 3 can reduce the roughness of the surface of the slab waveguide 3 , thereby facilitating subsequent bonding with the dielectric layer 13 .

[0119] For details, please refer to Fig.14 , which is a structural schematic diagram of bonding the slab waveguide 3 to the dielectric layer 13, executes the step S5, bonds the slab waveguide 3 to the dielectric layer 13, and removes the second substrate 7, and after bonding, the vibration membrane 4 is located above the annular portion, and the lower surface of the slab waveguide 3 is spaced from the upper surface of the strip waveguide 2 by a second preset distance.

[0120] Specifically, the method of removing the second substrate 7 includes wet etching or other suitable methods.

[0121] Specifically, the dielectric layer 13 is formed on the SOI substrate, and the shielding layer is formed on the dielectric layer 13. The dielectric layer 13 and the top semiconductor layer 12 are sequentially etched based on the patterned first shielding layer to obtain the strip waveguide 2 and the dielectric layer 13 located above the strip waveguide 2 is removed. Then, the vibration membrane 4 and the planar waveguide 3 are stacked in sequence, and the dielectric layer 13 and the planar waveguide 3 are bonded to obtain the photoacoustic sensor in which the upper surface of the strip waveguide 2 and the lower surface of the planar waveguide 3 are spaced a second preset distance apart. The manufacturing process is compatible with the CMOS process, which simplifies the process steps and reduces the process cost.

[0122] The manufacturing method of the photoacoustic sensor of the present embodiment is as follows: the dielectric layer 13 is formed on the SOI substrate, and the first shielding layer is formed on the dielectric layer 13; based on the patterned first shielding layer, the dielectric layer 13 and the top semiconductor layer 12 are sequentially etched to obtain the strip waveguide 2; and based on the second shielding layer, the dielectric layer 13 located above the strip waveguide 2 is removed; and then, the vibration membrane 4 and the planar waveguide 3 are stacked in sequence, and the dielectric layer 13 and the planar waveguide 3 are bonded to obtain the photoacoustic sensor with the strip waveguide 2 and the planar waveguide 3 spaced by the second preset distance. The manufacturing process is compatible with the CMOS process, which simplifies the process steps and reduces the process cost.

[0123] In summary, the photoacoustic sensor and the manufacturing method thereof of the present invention are provided with a planar waveguide and a strip waveguide in the photoacoustic sensor, wherein the strip waveguide includes a ring portion and a strip portion separated by a first preset distance, and the upper surface of the strip waveguide and the lower surface of the planar waveguide are separated by a second preset distance, and the planar waveguide and the strip waveguide constitute an optical microring resonator, and by combining the vibrating membrane with the planar waveguide, and the waveguide is in a critical coupling state, when the photoacoustic sensor receives ultrasonic waves, the distance between the upper surface of the strip waveguide and the lower surface of the planar waveguide will change, thereby causing a large change in the effective refractive index of the waveguide, and then causing the resonance peak to shift, and fixing the laser wavelength at the center of the rise or fall with a large slope of the resonance peak, a slight displacement of the resonance peak will cause a large change in light intensity, thereby realizing the detection of deep ultrasonic signals and improving the sensitivity of the photoacoustic sensor; In addition, by forming a dielectric layer on the SOI substrate and forming a first shielding layer on the dielectric layer, etching the dielectric layer and the top semiconductor layer based on the patterned first shielding layer to obtain a strip waveguide and removing the dielectric layer above the strip waveguide based on the second shielding layer, and then forming a vibration membrane and a flat waveguide stacked in sequence, bonding the dielectric layer and the flat waveguide to obtain a photoacoustic sensor with a preset distance between the upper surface of the strip waveguide and the lower surface of the flat waveguide, the manufacturing process is compatible with the CMOS process, the manufacturing process is simplified, the process cost is reduced, and by seeking the structural size and material of the photoacoustic sensor with excellent performance, the vibration frequency range of the photoacoustic sensor can be effectively adjusted, which satisfies the requirements of manufacturing a small-sized photoacoustic sensor while also satisfying the improvement of the sensitivity of the photoacoustic sensor, greatly expanding the application field of the photoacoustic sensor. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has great industrial utilization value.

[0124] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A photoacoustic sensor, characterized in that: include: The first substrate comprises a base, a buried oxide layer, a top semiconductor layer and a dielectric layer stacked in sequence; A strip waveguide is located above the buried oxide layer, the strip waveguide comprises an annular portion and a strip portion separated by a first preset distance, a peripheral gap is provided around the strip waveguide to expose the buried oxide layer and isolate the top semiconductor layer from the strip waveguide, an inner circular surrounding area of ​​the annular portion and a main body of the annular portion form a cavity, and the bottom surface of the cavity exposes the buried oxide layer; A slab waveguide is located above the strip waveguide, and a lower surface of the slab waveguide is spaced a second preset distance from an upper surface of the strip waveguide; The vibration membrane is located above the annular portion and covers the upper surface of the planar waveguide.

2. The photoacoustic sensor according to claim 1, characterized in that: The material of the planar waveguide includes silicon and silicon nitride; The material of the strip waveguide includes silicon, silicon nitride, and polymer.

3. The photoacoustic sensor according to claim 1, characterized in that: The spacing distance between the lower surface of the planar waveguide and the upper surface of the strip waveguide is in the range of 10 nm to 30 nm.

4. The photoacoustic sensor according to claim 1, characterized in that: The radius of the annular portion ranges from 5 μm to 8 μm.

5. The photoacoustic sensor according to claim 1, characterized in that: The material of the vibration membrane includes silicon dioxide.

6. The photoacoustic sensor according to claim 1, characterized in that: The shape of the vibration membrane includes a circle.

7. The photoacoustic sensor according to claim 6, characterized in that: The radius of the vibration membrane ranges from 9 μm to 15 μm.

8. The photoacoustic sensor according to claim 1, characterized in that: The width of the strip-shaped portion ranges from 400nm to 700nm; the thickness of the strip-shaped portion ranges from 90nm to 220nm.

9. The photoacoustic sensor according to claim 1, characterized in that: The thickness of the planar waveguide ranges from 50 nm to 250 nm.

10. A method for manufacturing a photoacoustic sensor, characterized in that: The following steps are involved: Providing an SOI substrate, the SOI substrate comprising a base, a buried oxide layer, and a top semiconductor layer stacked in sequence, and forming a dielectric layer on the upper surface of the top semiconductor layer to obtain the first substrate; A patterned first shielding layer is formed on the upper surface of the dielectric layer, and a strip waveguide is formed based on the patterned first shielding layer, and a peripheral gap that exposes the buried oxide layer and isolates the top semiconductor layer from the strip waveguide, wherein the strip waveguide includes an annular portion and a strip portion separated by a first preset distance, an inner circular surrounding area of ​​the annular portion and a main body of the annular portion form a cavity, and the bottom surface of the cavity exposes the buried oxide layer; forming a second shielding layer that only exposes the dielectric layer above the strip waveguide, so as to remove the dielectric layer above the strip waveguide; Providing a second substrate, and forming a vibration membrane and a planar waveguide stacked in sequence on the second substrate; The planar waveguide is bonded to the dielectric layer, and the second substrate is removed. After bonding, the vibration membrane is located above the annular portion, and the lower surface of the strip waveguide is spaced from the upper surface of the strip waveguide by a second preset distance.

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