Photoelectric sensing inertial sensor and manufacturing method thereof

Abstract

The invention provides a photoelectric sensing inertial sensor and a manufacturing method thereof, and the sensor comprises a semiconductor substrate which is internally provided with an annular cavity; a light conduction device is arranged in a circle defined by the annular cavity and is used for transmitting light to the inner side wall of the circumference of the annular cavity along the radius; the light source is used for emitting light rays vertically emitted to the circumferential plane of the annular cavity; a modulation device is arranged in a vertical projection area of the light source to the plane where the light conduction device is located and used for modulating a light source beam to the radius direction of the annular cavity; the light receiving devices are uniformly arranged on the circumferential side wall of the outer side of the annular cavity; and the inertial body is located in the annular cavity and can rotate around the annular cavity, and when the inertial body rotates to the position of a certain light receiving device, the inertial body can shield the light receiving device to receive light beams. According to the invention, the miniaturization of the sensing device is realized, the manufacturing cost is greatly reduced, the comprehensive damping is small, the test error is low, and the impact resistance is higher.

Description

Technical Field

[0001] This application relates to the field of inertial sensors, and particularly to a photoelectric inertial sensor and its manufacturing method. Background Technology

[0002] Since the invention of the magnetic compass, humans have continuously searched for and invented various methods to sense orientation and rotation angles. This has been especially true with the creation of moving machines such as cars, airplanes, rockets, and spacecraft, which have had a series of unprecedented and fundamental impacts on human society and people's lives. However, to accurately grasp and control the state of these moving machines and to perform precise sensing, it is necessary to test information such as the machine's orientation and speed. This has led to the development of various devices, from traditional magnetic compasses to today's magnetic sensor chips, for sensing these machines. Among these, inertial sensors, especially inertial sensor chips designed and manufactured based on modern silicon-based semiconductor technology, are the most widely used. Silicon-based inertial sensor chips include accelerometers for sensing linear motion and angular velocity sensors (also known as gyroscopes) for sensing rotational motion, as well as three-axis and six-axis composite motion inertial sensors that combine linear and rotational motion. All of these inertial sensors utilize an inertial body and a semiconductor substrate contained within one or more cavities of the inertial body. Due to its own inertia, the semiconductor substrate experiences a small relative motion with the inertial body. Inertial sensors use electronic methods to sense and measure minute relative motions. The motion parameters of the inertial body are primarily acceleration and angular velocity. Unfortunately, to date, sensing minute relative motion depends on the relative motion between the inertial body and the semiconductor substrate. The resulting inductive signal and its changes constitute the working principle of the inertial sensor. Therefore, the inertial sensor, fixed to the substrate, must have electrical signal connections and specific components, also known as connecting keys. The position of these connecting keys must have a certain elastic reaction to restrict the free movement of the semiconductor substrate within the cavity, thus limiting the acquisition of velocity and angular signals. Consequently, multiple analyses are required to estimate the error, and the error increases with the number of analyses. Therefore, current gyroscopes all have some limitations or defects. Summary of the Invention

[0003] To address the aforementioned product performance issues, this invention provides a photoelectric inertial sensor and its manufacturing method.

[0004] This invention provides a photoelectric inertial sensor, comprising: A semiconductor substrate has an annular cavity inside; the circle enclosed by the annular cavity has a light transmission device inside for transmitting light along the radius to the inner circumference of the annular cavity; it also includes a light source, which is arranged perpendicular to the circumferential plane of the annular cavity along the central axis of the annular cavity, and has an internal light channel to emit light perpendicularly toward the circumferential plane of the annular cavity; a modulation device is provided in the vertical projection area of ​​the light source toward the plane where the light transmission device is located, for modulating the light beam of the light source to be along the radial direction of the annular cavity; The light receiving devices are evenly arranged on the outer circumferential sidewall of the annular cavity; An inertial body is located inside a circular cavity and can rotate around the circular cavity. When the inertial body rotates to the position of a certain optical receiving device, it can block the optical receiving device from receiving the light beam.

[0005] The method for manufacturing the photoelectric inertial sensor of the present invention includes the following steps: Provide a first substrate; A first semiconductor layer is formed on a first substrate; The first semiconductor layer is etched to form an annular trench and a light-conducting device that is connected to the annular trench and is arranged radially from the center axis to the circumference. A first sacrificial layer is formed, which completely covers the first semiconductor layer within the annular trench; A light-shielding layer is formed on the first sacrificial layer, and the light-shielding layer in a portion of the annular groove is etched to form an inertial body; Continue to form a capping layer covering the inertial body and the first sacrificial layer; Remove the first sacrificial layer to form an annular cavity; A light source is formed at the central axis position of the semiconductor substrate corresponding to the cap, which is used to provide a light beam signal to the light transmission device.

[0006] The photoelectric inertial sensor of this invention can accurately sense and measure rotational motion relative to an inertial body in the same plane, including parameters such as angle, velocity, and acceleration. The rotational inertia of this sensor depends on a freely rotating inertial body. A semiconductor substrate receives light signals incident into a circular cavity. By placing light receiving devices at different positions within the cavity, the rotational angular velocity, rotational angle, and velocity relative to the inertial body can be directly measured. This invention is applicable to the measurement of absolute angles in various rotational motions. Due to the use of photoelectric sensing technology and the fact that the compass is a suspended bare disc, it has the advantages of being direct, accurate, and unrestricted. It also possesses strong resistance to electromagnetic interference, is unaffected by factors such as algorithms, and compared to prior art, this invention achieves miniaturization of the sensing device, significantly reducing manufacturing costs, has low overall damping, low testing error, and higher impact resistance. Attached Figure Description

[0007] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0008] Figure 1 This is a top view of the first embodiment of the photoelectric inertial sensor of the present invention; Figure 2 This is a top view of a second embodiment of the photoelectric inertial sensor of the present invention; Figures 3-8 This is a cross-sectional schematic diagram of a manufacturing method of an embodiment of the photoelectric inertial sensor of the present invention.

[0009] For better explanation, the following is an explanation of the corresponding labels: Semiconductor substrate—110; Inertial body—120; Light source—130; Light receiving device—140; Light transmission device—150; Annular cavity—210; Central axis—220; Light transmission tube—230; Substrate—310; First semiconductor layer—320; First sacrificial layer—330; First semiconductor substrate—310; Annular trench—330; Light transmission tube trench—340; Photodiode—350; First sacrificial layer 331; Capping—332; Optical channel—131. Detailed Implementation

[0010] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0011] In this invention, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower parts of the device in its normal operating state, while "inner" and "outer" refer to the parts relative to the outline of the device. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Since this invention pertains to electrical devices, connection and interconnection both refer to conductive interconnections. Because the accompanying drawings describe the same device, the same reference numerals denote the same components.

[0012] The following detailed description of specific examples of the present invention is provided in conjunction with the accompanying drawings.

[0013] Figure 1This is a top view of the first embodiment of the photoelectric inertial sensor of the present invention. In the first embodiment, a semiconductor substrate 110 has an annular cavity 210 inside; the circle enclosed by the annular cavity 210 has a light transmission device 150 for transmitting light along the radius to the inner circumferential sidewall 210a of the annular cavity; it also includes a light source 130, which is arranged perpendicular to the circumferential plane of the annular cavity along the central axis 220 of the annular cavity, and has an internal light channel to emit light perpendicularly to the circumferential plane of the annular cavity; a modulation device (not shown) is provided in the vertical projection area of ​​the light source 130 onto the plane where the light transmission device 150 is located, for modulating the light beam of the light source to the direction along the radius of the annular cavity; a light receiving device 140 is uniformly arranged on the outer circumferential sidewall 210b of the annular cavity 210; an inertial body 120 is located inside the annular cavity 210 and can rotate around the annular cavity 210, and when the inertial body 120 rotates to the position of a certain light receiving device 140, it can block the light beam received by the light receiving device.

[0014] In one embodiment, the light transmission device 150 is a cylinder surrounded by an annular cavity 210 and is made of a light-transmitting material, such as silicon dioxide. In this embodiment, the light channel of the light source is perpendicular to the circumferential plane of the annular cavity. The modulation device includes a reflector disposed between the exit of the light channel and the entrance of the light transmission device to reflect the emitted light beam from the light source to the light transmission device. Since the light transmission device 150 is made of a light-transmitting material, the light beam exits from the light source and is directed towards the modulation device. Each reflector of the modulation device deflects the light beam by 90° along the radius of the circle, so that the light beam travels along the radius to the entire circumference and is received by the light receiving device disposed around the circumference. The light receiving device can be connected to a detection circuit to detect the light signal. When the inertial body rotates to the position of the corresponding light receiving device, it blocks the light beam, preventing the light receiving device from receiving the light beam, which is then detected by the detection circuit. The relative position, relative angle, and relative angular velocity of the inertial body can then be calculated.

[0015] In one embodiment, the light transmission device 150 is a cylindrical cavity surrounded by an annular cavity 210, with the height of the cylinder being less than the height of the annular cavity. This allows the inertial body to be stuck at the step formed by the annular cavity and the cylindrical cavity, preventing it from slipping out of the annular cavity. It also ensures that the light beam can be uniformly directed from the modulation device to each light receiving device on the entire circumference.

[0016] Figure 2This is a top view of a second embodiment of the photoelectric inertial sensor of the present invention. In this embodiment, it includes a semiconductor substrate 110, an inertial body 120, a light source 130, and a light receiving device 140. The semiconductor substrate 110 has an annular cavity 210. Within the annular cavity are several light-conducting tubes 230 uniformly arranged radially from a central axis 220. The outlets of the light-conducting tubes 230 communicate with the annular cavity 210, and their inlets communicate with the light source 130. The light source 130 is perpendicular to the circular cross-section along the central axis 220 of the cavity 210. The device is planar and has an internal optical channel that communicates with the inlet of the optical transmission tube 230. Several optical receiving devices 140 corresponding to the outlet of the optical transmission tube 230 are arranged on the side wall of the annular cavity 230 of the semiconductor substrate. An inertial body 120 is located inside the annular cavity 210 and can rotate around the central axis of the annular cavity. The size of the inertial body 120 is comparable to the outlet of the waveguide. When the inertial body 120 rotates to a certain position, it can block the light transmission from the optical transmission tube 230 at that position to the corresponding optical receiving device.

[0017] In one embodiment, the light transmission tubes 230 are arranged sequentially adjacent to each other, and the light receiving devices 140 are arranged sequentially adjacent to each other on the sidewall of the annular cavity 210.

[0018] In one embodiment, the inertial body 120 is any one of a circle, a cylinder, a segment of a ring, a cube variant, or a polyhedron, and its width or diameter along the circumferential direction of the circular cavity is greater than or equal to the opening width of the light transmission tube 230.

[0019] In one embodiment, the light receiving device 140 includes a photodiode and a transistor connected to the photodiode for switching or amplifying the photoelectronic signal generated by the photodiode.

[0020] In one embodiment, the materials of the inertial body 120 and the semiconductor substrate 110 are one or a combination of silicon compounds, metals, alloys, and organic materials. The material of the light source 130 is a silicon compound or a metal.

[0021] In one embodiment, the light channel of the light source 130 is perpendicular to the light transmission tube 230, and a reflector is provided between the light source 130 and the entrance of the light transmission tube 230 to reflect the emitted light beam from the light source back to the light transmission tube 230. For example, there is a 45-degree angle reflective surface between the light source and the entrance of the light transmission tube 230, and the light receiving device is disposed at the top or bottom of the cavity. A reflector is provided on the inner surface of the internal light channel of the light source to prevent light leakage and improve light utilization; the light source may be formed of semiconductor material and has a light source at the entrance end. In this embodiment, the wavelength of the emitted light beam from the light source is between 0.3 and 2.0 micrometers, and is a continuous or pulsed signal. In a specific embodiment, the reflector may be a continuous 45° ramp arranged along a circle.

[0022] Specifically, in this embodiment, one end of the light-conducting tube 230 is open at the beam incident position of the light source 130, and the other end is connected to the annular cavity 210. Since the light-conducting tube 230 is arranged along the radial direction, the light beam is emitted into the annular cavity 210 along the radial direction. The light receiving device 140 is arranged on the side wall of the annular cavity 210 at a position coplanar with the light-conducting tube 230. The light-conducting tube 230 can be an optical fiber, or a cavity conduit surrounded by a reflective material, or a transparent material conduit, such as a trench formed by depositing silicon dioxide, with a metal reflective layer formed on the side wall of the trench. In this embodiment, the light source 130 is cylindrical.

[0023] A reflector is disposed between the light source 130 and the light transmission tube 230 to reflect the incident light beam along the central axis 220 of the cavity to the transmission direction along the light transmission tube 230. For example, in this embodiment, the reflector is disposed between the light transmission tube 230 and the light source 130, specifically a metal reflective film layer, with the reflective surface at a 45° angle to the incident direction of the light beam from the light source 130, i.e., the central axis direction. This causes the light beam to be redirected by 90° and enter from the opening of the light transmission tube 230, transmit along the light transmission tube 230, and finally exit from the circumference into the annular cavity.

[0024] The light receiving device 140 includes at least one photodiode and a transistor connected to the photodiode. The transistor is used to switch or amplify the photoelectronic signal generated by the photodiode.

[0025] In this embodiment, in order to reduce resistance, the annular cavity 210 is filled with lubricating gas or liquid, or a gas-liquid mixture.

[0026] This invention utilizes photoelectric sensors to achieve contactless or conductive light-speed crossings between moving bodies, thereby obtaining direct relative position, angle, velocity, and angular velocity signals of relative motion. Since inertia can receive light-speed signals without any connecting links, it is free from artificial constraints, creating superior conditions for connecting continuous relative motions and overcoming the limitations of all motion sensors. In this scheme, the primary application device is a photoelectric inertial sensor specifically designed for sensing rotational angular velocity and estimating angular acceleration. When a light beam signal enters the semiconductor substrate from a light source, as the inertial body rotates relative to it, the light beam emitted from the corresponding angle of the light guide tube 230 is blocked by the inertial body, allowing the rotation angle of the inertial body relative to the semiconductor substrate to be obtained from the corresponding light receiving device. This method can directly measure the relative rotation angle without calculating acceleration and angular velocity, offering higher anti-interference capabilities and accuracy compared to MEMS gyroscope sensors, and without limitations on velocity and acceleration ranges. Furthermore, its rotation angle sensitivity can reach 1 / 10000, with room for further improvement. Compared to traditional fiber optic gyroscopes, photoelectric inertial sensors have greater potential for miniaturization and broader application prospects.

[0027] Figure 3 This is a top view of a third embodiment of the photoelectric inertial sensor of the present invention. In this third embodiment, the light-conducting tubes 230 are arranged sequentially adjacent to each other, and the light-receiving devices 140 are arranged sequentially adjacent to each other on the sidewall of the annular cavity. That is, the light-conducting tubes 230 do not need to be spaced apart; only a sidewall for isolating light is required. Correspondingly, the light-receiving devices 140 also do not need to be spaced apart; they can be arranged as adjacent as possible. For example, they can be adjacent photodiodes 350 formed on the same substrate of a chip. This can effectively improve the accuracy of the test.

[0028] In addition, the semiconductor substrate may integrate, but is not limited to, drive and detection signal processing modules. It may also be a fully functional system with interconnect pads.

[0029] Figures 4 to 8 This is a cross-sectional schematic diagram of a manufacturing method for an embodiment of the photoelectric inertial sensor of the present invention. The following is in conjunction with... Figures 4 to 8 The manufacturing method of the photoelectric inertial sensor of the present invention will be described in detail. The manufacturing method of the photoelectric inertial sensor of the present invention includes the following steps: First, such as Figure 4 As shown, a first semiconductor substrate 310 is provided; in this embodiment, the first semiconductor substrate 310 can be a silicon substrate or a substrate of other materials, such as a silicon wafer, in which a MOS device or other functional device with a detection circuit is pre-formed, and a first semiconductor layer 320 is formed on the first semiconductor substrate 310, such as a dielectric layer, silicon oxide, silicon nitride or other materials.

[0030] Next, as Figure 5 As shown, the first semiconductor layer 320 is etched to form an annular trench 330 and a light-conducting tube 230 trench 340 connected to the annular trench 330, which is arranged radially from the central axis 220 towards the circumference. In this step, a photodiode 350 can be formed on the sidewall of the annular cavity. In embodiments where the light-conducting device is a cylinder surrounded by an annular cavity and is made of a light-transmitting material, this step can also involve etching to form a 45° inclined surface for exposing the modulation device. In embodiments where the light-conducting device tube is a cylindrical cavity surrounded by an annular cavity, a cylindrical cavity can also be formed simultaneously, with varying etching depths, and the height of the cylindrical cavity is less than the height of the annular cavity.

[0031] In one embodiment, a reflective layer, such as a metal layer, can also be formed on the sidewalls and bottom of the annular trench 330 and the optical transducer 230 trench 340. Specifically, in this embodiment, a strip-shaped metal layer, such as Cu or Al, is first formed along the radial direction. Further, a reflective layer at a 45° angle to the metal layer is also formed at the position corresponding to the central axis 220. This reflective layer serves to form a mirror. Specifically, the reflective layer can be formed by etching the first semiconductor layer 320 before forming the metal layer, creating an angled shape, thus forming it simultaneously during the metal layer deposition process. Then, a transparent light-guiding medium is deposited on the surfaces of the metal layer and the reflective layer; then, the light-guiding medium is etched to form trenches distributed along both sides of the strip-shaped metal layer, and these trenches are filled with metal; then, a metal layer is formed on the surface of the transparent light-guiding medium, thereby forming an optical transducer 230 surrounded by metal layers on all four sides. Of course, in other embodiments, optical fibers can be directly laid to form the optical transducer 230. Alternatively, a silicon dioxide layer can be deposited on the metal layer, and due to the properties of silicon dioxide, an optical transducer 230 surrounded by a metal reflective layer is formed.

[0032] like Figure 5 As shown, a first sacrificial layer 331 is formed, which completely covers the first semiconductor layer 320 within the annular trench 330; A light-shielding layer is formed on the first sacrificial layer 331, and the light-shielding layer in a portion of the annular groove is etched to form an inertial body 120. like Figure 6 As shown, a cap 332 is formed to cover the inertial body 120 and the first sacrificial layer 331. In one embodiment, the cap 332 may be a wafer or bare die with a light source, directly bonded to the sidewall of the first semiconductor layer. In another embodiment, it may be a second semiconductor layer deposited on the sidewall of the first semiconductor layer and the first sacrificial layer 331.

[0033] like Figure 7As shown, the first sacrificial layer 331 is removed to form an annular cavity and a light transmission tube 230 is formed; specifically, the first sacrificial layer can be removed by using the through hole of the light channel 131 of the light source or by forming a through hole on the cover 332.

[0034] A light source 130 is formed at the position corresponding to the central axis 220 of the semiconductor substrate in the capping layer 332 or the second semiconductor layer, for providing a light beam signal to the light transmission tube 230. Specifically, the light source can be a cylindrical structure with sidewalls and a light channel, positioned perpendicular to the semiconductor substrate. For example, the light source can be a laser light source, and a chip containing laser pixels or an array of laser pixels can be bonded at the central axis 220 of the semiconductor substrate. This allows for the formation of a complete inertial sensor product during semiconductor processing.

[0035] In this embodiment, the annular cavity 210 is also filled with lubricating gas or liquid, or a gas-liquid mixture.

[0036] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, such as the combination of technical features between embodiments, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A photoelectric inertial sensor, characterized in that, include: A semiconductor substrate has an annular cavity inside; the circle enclosed by the annular cavity has a light transmission device inside for transmitting light along the radius to the inner circumference of the annular cavity; it also includes a light source, which is arranged perpendicular to the circumferential plane of the annular cavity along the central axis of the annular cavity, and has an internal light channel to emit light perpendicularly toward the circumferential plane of the annular cavity; a modulation device is provided in the vertical projection area of ​​the light source toward the plane where the light transmission device is located, for modulating the light beam of the light source to be along the radial direction of the annular cavity; The light receiving devices are evenly arranged on the outer circumferential sidewall of the annular cavity; An inertial body is located inside a circular cavity and can rotate around the circular cavity. When the inertial body rotates to the position of a certain optical receiving device, it can block the optical receiving device from receiving the light beam.

2. The photoelectric inertial sensor as described in claim 1, characterized in that, The light transmission device includes a plurality of light transmission tubes arranged radially from the central axis. The outlet of the light transmission tube is connected to the annular cavity, and the inlet is connected to the modulation device.

3. The photoelectric inertial sensor as described in claim 2, characterized in that, The light source's optical channel is perpendicular to the light transmission tube, and the modulation device includes a reflector disposed between the exit of the optical channel and the entrance of the light transmission tube for reflecting the emitted light beam from the light source to the light transmission tube.

4. The photoelectric inertial sensor as described in claim 2, characterized in that, The optical transmission tubes are arranged adjacent to each other in sequence, and the optical receiving devices are arranged adjacent to each other on the side wall of the annular cavity in sequence.

5. The photoelectric inertial sensor as described in claim 1, characterized in that, The light transmission device is a cylinder surrounded by an annular cavity and is made of a light-transmitting material.

6. The photoelectric inertial sensor as described in claim 1, characterized in that, The light transmission device tube is a cylindrical cavity surrounded by an annular cavity, and the height of the cylindrical cavity is less than the height of the annular cavity.

7. The photoelectric inertial sensor as described in claim 1, characterized in that, The inertial body is any one of a circle, a cylinder, a segment of a torus, a cube variant, or a polyhedron.

8. The photoelectric inertial sensor as described in claim 1, characterized in that, The optical receiving device includes a photodiode and a transistor connected to the photodiode, used to switch or amplify the photoelectronic signal generated by the photodiode.

9. The photoelectric inertial sensor as described in claim 1, characterized in that, The materials of the inertial body and the semiconductor substrate are one or a combination of silicon compounds, metals, alloys, and organic materials.

10. A method for manufacturing a photoelectric inertial sensor according to any one of claims 1-9, characterized in that, Including the following steps: Provide a first substrate; A first semiconductor layer is formed on a first substrate; The first semiconductor layer is etched to form an annular trench and a light-conducting device that is connected to the annular trench and is arranged from the center axis along the circumference and radial direction. A first sacrificial layer is formed, which completely covers the first semiconductor layer within the annular trench; A light-shielding layer is formed on the first sacrificial layer, and the light-shielding layer in a portion of the annular groove is etched to form an inertial body; Continue to form a capping layer covering the inertial body and the first sacrificial layer; Remove the first sacrificial layer to form an annular cavity; A light source is formed at the central axis position of the semiconductor substrate corresponding to the cap, which is used to provide a light beam signal to the light transmission device.

Images