An ultrasonic transducer and a method of manufacturing the same

Abstract

This application relates to the field of ultrasonic transducers and discloses an ultrasonic transducer and its fabrication method. The ultrasonic transducer in this application includes: a chip, a piezoelectric unit formed on the chip, and a fuse; the chip includes: a substrate, and a first circuit structure formed on the substrate, wherein the first circuit structure is insulated from the substrate; the fuse connects the substrate and the first circuit structure; during the piezoelectric unit polarization process, the substrate is grounded, and the accumulated charge in the first circuit structure during the polarization process is discharged through the fuse and the substrate, avoiding damage to the chip from high voltage during polarization and improving product yield. Simultaneously, after polarization, the subsequent fuse-breaking process is simple and easy to operate, facilitating fuse-breaking to ensure normal operation of the ultrasonic transducer, and minimizing the impact of the short-circuit circuit generated by the fuse on the complexity of the ultrasonic transducer fabrication process.

Description

Technical Field

[0001] This application relates to the field of ultrasonic transducers, and in particular to an ultrasonic transducer and its fabrication method. Background Technology

[0002] In the process of manufacturing ultrasonic transducers, the piezoelectric unit needs to be polarized. During the polarization process, a high voltage needs to be applied to the piezoelectric unit. The accumulation of a large amount of polarization charge will cause the chip circuit below the piezoelectric unit to be at risk of breakdown, which will affect the product yield of the ultrasonic transducer. Summary of the Invention

[0003] The purpose of this application is to provide an ultrasonic transducer and its fabrication method. A fuse is used to short-circuit a first circuit structure in the chip that is insulated from the substrate and easily accumulates charge during polarization to the substrate. This short-circuit allows the accumulated charge during polarization to be discharged, preventing the chip from being damaged by high voltage during polarization and thus improving product yield. Furthermore, the subsequent fuse-breaking process is simple and easy to operate, minimizing the impact of the short-circuit circuit created by the fuse on the complexity of the ultrasonic transducer fabrication process.

[0004] To address the aforementioned technical problems, this application provides an ultrasonic transducer, comprising: a chip, a piezoelectric unit formed on the chip, and a fuse; the chip includes: a substrate, and a first circuit structure formed above the substrate, wherein the first circuit structure is insulated from the substrate; the fuse is connected between the substrate and the first circuit structure; during the polarization process of the piezoelectric unit, the substrate is grounded, and the charge accumulated in the first circuit structure during the polarization process is discharged via the fuse and the substrate.

[0005] This application also provides a method for fabricating an ultrasonic transducer, applied to the ultrasonic transducer described above. The method includes: polarizing the piezoelectric unit of the ultrasonic transducer; wherein, during the polarization process, the accumulated charge of the first circuit structure is discharged through a fuse and a substrate; after the polarization process, a preset current is applied to the fuse until the fuse is disconnected.

[0006] Compared to related technologies, this application involves forming a first circuit structure on the chip, which is insulated from the substrate, above the substrate using a fuse to short-circuit it. A piezoelectric unit is formed on the substrate, and the substrate is grounded. When the piezoelectric unit is polarized, the high-voltage charge generated on the first circuit structure of the chip during polarization is transferred to the substrate through the fuse and discharged from ground, thereby protecting the ultrasonic transducer. After polarization, the subsequent fuse-breaking process is simple and easy to operate, avoiding the short-circuit circuit from affecting the normal operation of the ultrasonic transducer, and minimizing the impact of the short-circuit circuit generated by the fuse on the complexity of the ultrasonic transducer fabrication process.

[0007] In addition, the fuse includes a fusing region; the fusing region is arranged parallel to the substrate surface, or the fusing region is arranged perpendicular to the substrate surface.

[0008] Additionally, the chip includes: a second circuit structure formed above a substrate; wherein, at least at a target time, the voltage of the second circuit structure is greater than a preset threshold; the chip also includes: multiple metal layers located between the second circuit structure and the substrate, and a resistor of a preset resistance value connected in series with each of the metal layers, wherein the resistor is connected to the substrate or the resistor is grounded.

[0009] In addition, the projection of the second circuit structure toward the metal layer falls on the metal layer.

[0010] In addition, each of the aforementioned metal layers constitutes a ring-shaped pressure-dividing structure.

[0011] Alternatively, the second circuit structure is the same as the first circuit structure; or, the piezoelectric unit includes a top electrode; the second circuit structure is electrically connected to the top electrode.

[0012] In addition, the preset resistance value is greater than or equal to 100kΩ.

[0013] In addition, after polarizing the piezoelectric unit of the ultrasonic transducer, the method further includes: electrically connecting the top electrode of the piezoelectric unit to the second circuit structure; applying a preset voltage to the top electrode to break down the oxide layer between the top electrode and the second circuit structure.

[0014] In addition, when the first circuit structure and the second circuit structure are the same, the step of applying a preset current to the fuse until the fuse breaks specifically means: after the oxide layer is broken down, the preset voltage is continuously applied to the top electrode until the fuse breaks.

[0015] In addition, the preset voltage range is 3V to 10V. Attached Figure Description

[0016] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0017] Figure 1 This is a schematic diagram of the structure of an ultrasonic transducer according to the first embodiment of this application; Figure 2 This is a schematic diagram of the fuse structure in an ultrasonic transducer according to the first embodiment of this application; Figure 3 This is a schematic diagram of another structure of the fuse in an ultrasonic transducer according to the first embodiment of this application; Figure 4 This is a schematic diagram of the structure of an ultrasonic transducer according to the second embodiment of this application; Figure 5 This is a schematic diagram of the equivalent circuit structure of the metal layer in an ultrasonic transducer according to the second embodiment of this application; Figure 6 This is a cross-sectional structural diagram of the metal layer of an ultrasonic transducer according to the second embodiment of this application; Figure 7 This is a schematic diagram of the structure of a single-layer metal layer of an ultrasonic transducer according to the second embodiment of this application; Figure 8 This is a schematic diagram of the structure of an ultrasonic transducer according to the third embodiment of this application; Figure 9 This is a schematic diagram of another structure of an ultrasonic transducer according to the third embodiment of this application; Figure 10 This is a schematic diagram of the structure of an ultrasonic transducer under the condition of applying a preset current in a method for preparing an ultrasonic transducer according to the fourth embodiment of this application; Figure 11 This is a schematic diagram of the structure of an ultrasonic transducer under the condition of applying a preset voltage in a method for preparing an ultrasonic transducer according to the fourth embodiment of this application.

[0018] Figure label: 10 - Chip; 11 - Substrate; 121 - First circuit structure; 122 - Second circuit structure; 20 - Piezoelectric element; 21 - Top electrode; 30 - Fuse wire; 31 - Fuse break zone; 4-Oxide layer; 5-Metallic layer; 6-Resistance. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the various embodiments of this application will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been presented in the various embodiments of this application to enable readers to better understand this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0020] The division of the following embodiments is for ease of description and should not constitute any limitation on the specific implementation of this application. The various embodiments can be combined with and referenced by each other without contradiction.

[0021] In the fabrication of ultrasonic transducers, the piezoelectric unit undergoes polarization treatment. To prevent the accumulation of polarization charge during polarization treatment from causing breakdown of the chip circuit below the piezoelectric unit, the area of ​​the chip that is easily damaged during polarization treatment needs to be short-circuited to ground, thereby dissipating the accumulated charge. After polarization treatment, the grounding line also needs to be disconnected by cutting or removing the short-circuit line to prevent the grounding line from affecting the normal operation of the piezoelectric unit.

[0022] However, cutting or removing the circuit requires manual operation. Furthermore, due to the complexity of the circuitry in ultrasonic transducers, cutting or removing specific circuits requires precision to avoid damaging the original circuitry of the ultrasonic transducer. Therefore, cutting or removing the grounding circuit is a complex operation that affects the manufacturing efficiency of ultrasonic transducers.

[0023] To simplify the fabrication process of ultrasonic transducers, the first embodiment of this application proposes an improved ultrasonic transducer, such as... Figure 1 As shown, the ultrasonic transducer includes: a chip 10, a piezoelectric unit 20 formed on the chip 10, and a fuse 30; the chip 10 includes: a substrate 11, and a first circuit structure 121 formed on the substrate 11, wherein the first circuit structure 121 is insulated from the substrate 11; the fuse 30 is connected between the substrate 11 and the first circuit structure 121; during the polarization process of the piezoelectric unit 20, the substrate 11 is grounded, and the charge accumulated in the first circuit structure 121 during the polarization process is discharged through the fuse 30 and the substrate 11.

[0024] Compared to related technologies, the first embodiment of this application forms a first circuit structure on the chip that is insulated from the substrate and short-circuited to the substrate using a fuse. A piezoelectric unit is formed on the substrate, and the substrate is grounded. When the piezoelectric unit is polarized, the high-voltage charge generated on the first circuit structure of the chip during the polarization process is transferred to the substrate through the fuse and discharged from the ground, thereby protecting the ultrasonic transducer. After the polarization process, the subsequent fuse-breaking process is simple and easy to operate, avoiding the short-circuit circuit from affecting the normal operation of the ultrasonic transducer, and minimizing the impact of the short-circuit circuit generated by the fuse on the complexity of the ultrasonic transducer manufacturing process.

[0025] Regarding the specific structure of the fuse, as follows: Figures 2 to 3 As shown, the fuse includes: a fusing zone 31. (As indicated...) Figure 2 As shown, the fusion break area is arranged perpendicular to the substrate surface, or as... Figure 3 As shown, the fusing region is arranged parallel to the substrate surface. When the fusing region is arranged perpendicular to the substrate surface, a low-melting-point metal structure inside the chip can be used as the fusing region of the fuse.

[0026] In addition to being connected to the substrate, the fuse can also be directly grounded. When implementing the fuse circuit connection, the bottom metal of the fuse can be used to connect the first circuit structure to the substrate or ground.

[0027] The second embodiment of this application relates to an ultrasonic transducer. Compared with the first embodiment, the second embodiment provides a metal layer for voltage division below the second circuit structure in the chip, which is prone to high voltage. The metal layer releases the charge on the second circuit structure, thereby preventing the chip from being damaged by high voltage.

[0028] The second circuit structure in a chip that is prone to high voltage can be a circuit structure electrically connected to the top electrode of the piezoelectric unit. The condition for high voltage is determined by the voltage of the second circuit structure being greater than a preset threshold at at least a target time. The target time can be understood as a specific moment during chip fabrication, such as a moment during the polarization process when the voltage on the chip exceeds the preset threshold; this is the second circuit structure. Alternatively, the target time can be understood as a specific moment during chip operation, such as a moment during the impulse response process when the voltage on the chip exceeds the preset threshold, and so on. Figure 4 As shown, the chip includes: a second circuit structure 122 formed above a substrate; a piezoelectric unit including: a top electrode 21; the second circuit structure 122 is electrically connected to the top electrode 21. The chip also includes: multiple metal layers 5 located between the second circuit structure 122 and the substrate 11, and resistors 6 with preset resistance values ​​connected in series with each metal layer 5, the resistors 6 being connected to the substrate 11 or grounded. Since a potential difference needs to be generated between the top and bottom electrodes of the piezoelectric unit during ultrasonic transducer operation, the driving voltage applied to the top electrode is relatively high. Therefore, the second circuit structure electrically connected to the top electrode is prone to breakdown damage, leading to chip damage. The multiple metal layers below the second circuit structure can divide the voltage transmitted from the top electrode to the second circuit structure, and the multi-layer metal structure can also control the interlayer voltage of the chip to be below the breakdown threshold.

[0029] The voltage division principle of multilayer metal layers is as follows: Figure 5 As shown, assuming the voltage in the second circuit structure is 20V and the frequency is from several megahertz to tens of megahertz, the voltage is divided by the four metal layers below. Each metal layer is equivalent to a capacitor structure, and the voltage drop of each metal layer is 4V, which is far lower than the interlayer breakdown voltage. The above principle description uses a four-metal-layer configuration as an example. In practical applications, other numbers of metal layers can be used, such as 1, 3, 5, 8, etc. The preset resistance value of the resistor 6 connected in series with the metal layers is usually greater than or equal to 100kΩ. The resistor achieves a discharge effect, thereby ensuring the voltage division effect of the metal layers.

[0030] In addition, the second circuit structure can also be the same as the first circuit structure in the first embodiment. In this case, the metal layer can divide the voltage on the first circuit structure during polarization treatment, further reducing the probability of the first circuit structure being damaged.

[0031] The second circuit structure applicable to any of the above situations has the metal layer configured as follows: Figure 6 and Figure 7 As shown, the projection of the second circuit structure toward the metal layer falls onto the metal layer. Additionally, as... Figure 7 As shown, each metal layer constitutes a ring-shaped pressure-dividing structure.

[0032] In addition to the pressure-dividing effect mentioned above, the metal layer also improves product yield, increases the metal density in local areas of the ultrasonic transducer, thereby ensuring the stability of that local area and preventing defects.

[0033] The third embodiment of this application relates to an ultrasonic transducer. Compared to the first and second embodiments, the third embodiment describes two connection methods for the resistors. For example... Figure 8 As shown, the resistors connected in series with each metal layer are connected in parallel. Or, as... Figure 9 As shown, the resistors connected in series with each metal layer are interconnected and can all achieve the voltage dividing effect of the metal layers.

[0034] In addition, such as Figure 8 and Figure 9 As shown, the conductive silver paste connecting the top electrode 21 and the second circuit structure 122 may form an oxide layer 4 due to oxidation. The presence of the oxide layer 4 will affect the electrical signal transmission between the top electrode and the second circuit structure. The oxide layer 4 can be broken down by applying a preset voltage between the top electrode and the substrate, thus achieving circuit conduction. When the first circuit structure and the second circuit structure are the same structure, Figure 8 and Figure 9 The second circuit structure shown is also short-circuited to the fuse. To prevent the short-circuited circuit from affecting the normal operation of the ultrasonic transducer, a preset voltage can be continuously applied after the oxide layer 4 is broken down until the fuse blows. By continuously applying the preset voltage, both the oxide layer can be removed and the fuse can be blown, reducing the number of processing steps.

[0035] In practical applications, a fuse can be used alone in the high-voltage circuit structure area of ​​the chip to achieve charge discharge, or multiple metal layers can be used alone to achieve voltage division, or both fuses and metal layers can be used simultaneously. Furthermore, when both the oxide layer and the fuse exist between the top electrode and the substrate, the oxide layer can be broken down and the fuse can be blown simultaneously by applying a preset voltage. When only the oxide layer exists between the top electrode and the chip, the oxide layer can be broken down by applying a preset voltage between the top electrode and the chip. When only the fuse exists between the chip and the substrate, the fuse can be blown by continuously applying a preset voltage at a suitable location between the chip and the substrate. The location where the preset voltage is applied can be adjusted to a suitable position according to the actual situation.

[0036] The fourth embodiment of this application relates to a method for fabricating an ultrasonic transducer, applied to the ultrasonic transducers mentioned in the first to third embodiments above. The method includes: polarizing the piezoelectric unit of the ultrasonic transducer; wherein, during the polarization process, the accumulated charge in the first circuit structure is discharged through a fuse and a substrate; after the polarization process, a preset current is applied to the fuse until the fuse is disconnected.

[0037] like Figure 10 As shown, when the fuse is blown, a preset current can be applied between the first circuit structure and the substrate for a preset duration until the fuse melts, breaking the short circuit and completing the fabrication of the ultrasonic transducer. This method of breaking the fuse is simpler and easier to operate than cutting or removing the short circuit.

[0038] The preset current applied can be 10mA.

[0039] The fifth embodiment of this application relates to a method for fabricating an ultrasonic transducer, applied to the aforementioned ultrasonic transducer having a second circuit structure. The method includes: after polarizing the piezoelectric unit of the ultrasonic transducer, electrically connecting the top electrode of the piezoelectric unit to the second circuit structure; applying a preset voltage to the top electrode to break down the oxide layer between the top electrode and the second circuit structure.

[0040] In addition, such as Figure 11 As shown, when the first circuit structure and the second circuit structure are the same, a preset current is applied to the fuse until the fuse breaks. Specifically, after the oxide layer is broken down, a preset voltage is continuously applied to the top electrode until the fuse breaks.

[0041] The preset voltage ranges from 3V to 10V, with a typical value of 5.5V. When applying the preset voltage between the top electrode and the substrate, current limiting is required to prevent damage to the circuit between the top electrode and the substrate. The current limiting current can be 10mA.

[0042] Finally, the overall fabrication process of the ultrasonic transducer is described to facilitate a clearer understanding of the above embodiments. The overall fabrication process of the ultrasonic transducer is as follows: A circuit structure is formed on a substrate, the circuit structure including at least a bottom electrode and a piezoelectric layer. The first circuit structure, which is insulated from the substrate, is connected to the substrate via a fuse. The piezoelectric layer is polarized, and the accumulated charge generated by the polarization process on the first circuit structure of the chip is discharged by the fuse, thus protecting the chip.

[0043] After polarization treatment, a top electrode is formed on the piezoelectric layer using conductive silver paste. The conductive silver paste electrically connects the top electrode to the circuit structure of the chip. The circuit structure electrically connected to the top electrode is the second circuit structure, which is the same circuit structure as the first circuit structure described above.

[0044] If the conductive silver paste connecting the top electrode and the second circuit structure forms an oxide layer, the oxide layer is broken down by applying a preset voltage. If an oxide layer exists and the second circuit structure is the same as the first circuit structure, i.e., the second circuit structure is short-circuited by a fuse, then after the oxide layer is broken down, the preset voltage is continuously applied until the fuse blows.

[0045] If the first circuit structure is an independent structure, a preset current can be continuously applied between the first circuit structure and the substrate until the fuse blows and the short-circuit circuit is broken.

[0046] Both the first and second circuit structures mentioned above satisfy the condition that the voltage on them is higher than the threshold at a specific time, which can easily cause damage to the chip circuit due to high voltage. In order to divide the voltage between the first and second circuit structures, multiple metal layers can be added below the first and second circuit structures. The metal layers are connected to the substrate or ground through resistors, and voltage division is achieved through resistor discharge.

[0047] The steps of the various methods described above are only for clarity. In practice, they can be combined into one step or some steps can be split into multiple steps. As long as they include the same logical relationship, they are all within the scope of protection of this application. Adding insignificant modifications or introducing insignificant designs to the algorithm or process, but without changing the core design of the algorithm and process, are also within the scope of protection of this application.

[0048] It is not difficult to see that the above method embodiments correspond to the device embodiments, and the method embodiments can be implemented in conjunction with the device embodiments. The relevant technical details mentioned in the method embodiments remain valid in the device embodiments, and will not be repeated here to avoid repetition. Correspondingly, the relevant technical details mentioned in the device embodiments can also be applied to the method embodiments.

[0049] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing this application, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of this application.

Claims

1. An ultrasonic transducer, characterized in that, include: Chip, piezoelectric unit formed on the chip, fuse; The chip includes: a substrate, and a first circuit structure formed on the substrate, wherein the first circuit structure is insulated from the substrate; The fuse is connected between the substrate and the first circuit structure; During the polarization process of the piezoelectric unit, the substrate is grounded, and the charge accumulated in the first circuit structure during the polarization process is discharged via the fuse and the substrate.

2. The ultrasonic transducer according to claim 1, characterized in that, The fuse includes: a fusing zone; The melting zone is arranged parallel to the surface of the substrate. Alternatively, the melting zone may be arranged perpendicularly to the substrate surface.

3. The ultrasonic transducer according to claim 1, characterized in that, The chip includes: a second circuit structure formed above a substrate; wherein, at least at a target time, the voltage of the second circuit structure is greater than a preset threshold. The chip further includes: multiple metal layers located between the second circuit structure and the substrate, and a resistor of a preset resistance value connected in series with each of the metal layers, wherein the resistor is connected to the substrate or the resistor is grounded.

4. The ultrasonic transducer according to claim 3, characterized in that, The projection of the second circuit structure toward the metal layer falls on the metal layer.

5. The ultrasonic transducer according to claim 3 or 4, characterized in that, The second circuit structure is the same as the first circuit structure; Alternatively, the piezoelectric unit includes a top electrode; the second circuit structure is electrically connected to the top electrode.

6. The ultrasonic transducer according to claim 3, characterized in that, The preset resistance value is greater than or equal to 100kΩ.

7. A method for manufacturing an ultrasonic transducer, characterized in that, The method, applied to an ultrasonic transducer as described in any one of claims 1 to 6, comprises: The piezoelectric unit of the ultrasonic transducer is polarized; wherein, during the polarization process, the accumulated charge in the first circuit structure is discharged through the fuse and the substrate. After the polarization process, a preset current is applied to the fuse until the fuse is disconnected.

8. The method for preparing an ultrasonic transducer according to claim 7, characterized in that, Applied to the ultrasonic transducer as described in any one of claims 3 to 6, after the piezoelectric unit of the ultrasonic transducer is polarized, it further includes: The top electrode of the piezoelectric unit is electrically connected to the second circuit structure; A preset voltage is applied to the top electrode to break down the oxide layer between the top electrode and the second circuit structure.

9. The method for preparing an ultrasonic transducer according to claim 8, characterized in that, When the first circuit structure and the second circuit structure are the same, applying a preset current to the fuse until the fuse disconnects specifically means: After the oxide layer is broken down, the preset voltage is continuously applied to the top electrode until the fuse is broken.

10. The method for preparing an ultrasonic transducer according to claim 8 or 9, characterized in that, The preset voltage range is 3V to 10V.

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