专利汇可以提供FLEXIBLE CAPACITIVE MICROMACHINED ULTRASONIC TRANSDUCER ARRAY WITH INCREASED EFFECTIVE CAPACITANCE专利检索,专利查询,专利分析的服务。并且A Capacitive Micromachined Ultrasonic Transducer (CMUT) having a membrane operatively connected to a top electrode and having a bottom electrode having a concave void. When a DC bias voltage is applied, the membrane is deflected towards the bottom electrode such that a peripheral edge region of the membrane is brought into close proximity with the bottom electrode and an electrostatic force proximal to the peripheral edge region of the membrane is increased.,下面是FLEXIBLE CAPACITIVE MICROMACHINED ULTRASONIC TRANSDUCER ARRAY WITH INCREASED EFFECTIVE CAPACITANCE专利的具体信息内容。
What is claimed is:
1. Field of the Invention
The invention relates to an improved a Capacitive Micromachined Ultrasonic Transducer (CMUT) and method for manufacturing the CMUT.
2. Description of the Background Art
Referring to
In
To increase the sensitivity, the DC bias voltage is applied to load up the capacitor with charges, which can also pull the membrane 120 closer to the bottom electrode 140 to get a higher capacitance. The maximum sensitivity can be achieved when the membrane 120 is closest to the bottom electrode 140 without collapsing to the bottom electrode 140.
As the DC bias voltage increases, deflection of the membrane 120 also increases. However, when the DC bias voltage is increased above a certain voltage, electrostatic forces pressure the membrane 120 to collapse on the bottom electrode 140.
Referring to
Referring to
The capacitance in the air cavity between the bottom of the deflected membrane with radius Rb and the flat bottom electrode is calculated as follows.
C2=(The parallel plate capacitance between the flat bottom electrode and the virtual flat plate (dashed line))−(The capacitance between the spherical shell with radius Rb and the virtual flat plate).
It is therefore an object of the present invention to provide a Capacitive Micromachined Ultrasonic Transducer (CMUT), that includes a membrane operatively connected to a top electrode; and a bottom electrode having a concave void. Whereby, when a DC bias voltage is applied, the membrane is deflected towards the bottom electrode such that a peripheral edge region of the membrane is brought into close proximity with the bottom electrode and an electrostatic force proximal to the peripheral edge region of the membrane is increased.
When the DC bias voltage is applied, the distance between the peripheral edge region of the membrane and the bottom electrode may be less than the distance between a central region of the membrane and the bottom electrode.
When the DC bias voltage applied is above a predetermined amount to collapse the membrane to the bottom electrode, contact between the membrane and the bottom electrode may be minimised to a central region of the membrane.
About 25% of the membrane is in contact with the bottom electrode when the membrane is collapsed to the bottom membrane.
The top electrode may have the same diameter as the void of the bottom electrode.
The membrane may be flat or deflected.
The size of the membrane may be from about 500 μm to 5 μm with a frequency range from 100 kHz up to 100 MHz in air.
The thickness of the membrane may be from about 0.1 μm to 10 μm.
The CMUT may have an array of membranes where each top electrode fills the entire area of each membrane leaving only small voids for anchoring each membrane.
In another embodiment, a method for manufacturing a Capacitive Micromachined Ultrasonic Transducer (CMUT) is provided, whereby the method includes the features of sputtering a layer of Cr/Au as a seed layer on a silicon substrate that includes a layer of silicon nitride to form a CMUT membrane; coating a patterned photoresist to define the active area of a CMUT cell; melting the patterned photoresist to form a spherical profile by surface tension; and electroplating of nickel with the seed layer to form the bottom electrode by over-plating to cover the patterned photoresist.
The Young's modulus of the silicon nitride may be around 200 GPa.
The method may further include sealing released holes caused by the electroplating using a silicone-based polydimethylsiloxane (PDMS) with air trapped in CMUT cavities.
The method may further include coating parylene C in a vacuum chamber.
The method may further include removing the silicon substrate by single-side potassium hydroxide (KOH) etching that stops at the silicon nitride membrane.
The method may further include patterning the PDMS to define a membrane area and array elements.
The method may further include wire bonding to front-end electronics.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:
Referring to
Turning to
If the bottom electrode 240 is defined with a concave shape or curved profile, and when the membrane 220 is deflected, the membrane 220 can fully comply and conform to the top surface of the bottom electrode 240, especially around the outer edge 270 of the membrane 220 above the air cavity 230. This can increase the electrostatic force around the edge 270 of the membrane 220 to pull down the membrane 220 so a smaller DC bias voltage can be used. Using a smaller DC bias voltage is essential when inserting the transducer probe into the human body for an intravascular application. The bandwidth of the CMUT 200 can also be improved since most of the membrane 220 is under the electrostatic force from the DC bias voltage, which can increase the tensile stress on the membrane 220 to reduce the ringing tail.
Turning to
A CMUT can also operate at the collapsed mode to have an increased sensitivity and bandwidth. The sensitivity is increased from the increased capacitance at the minimum gap distance around the contacting area. The bandwidth can be improved because the movement of the membrane 220 can be damped by the bottom electrode 240 to reduce the ringing tail. When implementing the concave shaped bottom electrode 240 to operate CMUTs 200 at the collapsed mode, the whole membrane 220 is barely touching the bottom electrode 240 to increase the bandwidth and sensitivity. In particular, around the central area of the membrane 220 is damped by the bottom electrode 240. Thus, the CMUT 200 can increase effective capacitance to improve fill factor, output pressure, bandwidth, and sensitivity of the transducer.
The resonant frequency of the CMUT depends on the size and thickness of the membrane. The size of the membrane can range from 500 μm to 5 μm with a frequency range from 100 kHz up to 100 MHz in air. The thickness of the membrane can range from 0.1 μm to 10 μm. Since each membrane of the CMUT is very small, it requires an array of membranes for the CMUT to fill the area of a single transducer element.
The capacitance of a parallel plate capacitor can be determined from the area of the effective capacitance A and the distance between the top and bottom electrodes d, which is expressed as follows:
for series capacitor
Based on the geometry of the CMUT, the capacitance of the CMUT can be calculated as follows, where the electrode diameter is much greater than the cavity depth (2c>2b>>d2) and the capacitance C2 is assumed to be a parallel-plate capacitor.
Referring to
Referring to
C2=(The capacitance between the bottom electrode and the virtual flat plate (dashed line))−(The capacitance between the spherical shell with radius Rb and the virtual flat plate).
For output pressure, since the electrostatic force is inversely proportional to the square of the cavity depth, which means shorten the cavity depth can estimate to have two orders of magnitude increase on the output pressure when the capacitance increase is one order of magnitude.
Finally, in step S606, the released holes are first sealed by silicone-based polydimethylsiloxane (PDMS) with air trapped in CMUT cavities. This is followed by a coating of parylene C in a vacuum chamber. The vacuum chamber sucks the trapped air out through the gas permeable PDMS for vacuum sealed cavities since parylene is not gas permeable. The silicon substrate is then removed by single-side potassium hydroxide (KOH) etching that stops at the silicon nitride membrane. This eliminates the membrane stiction problem because the cavity remains dry during the wet etching with the protection of the PDMS and parylene coating. The PDMS now serves as the flexible substrate with silicon nitride membrane ready to be deposited with the metal for the top electrode. The PDMS is then patterned to define the membrane area and array elements. After wire bonding to front-end electronics, the CMUT array is ready to be used.
It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the scope or spirit of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects illustrative and not restrictive.
标题 | 发布/更新时间 | 阅读量 |
---|---|---|
声波探针用组合物、声波探针用硅酮树脂、声波探针及超声波探针以及相关装置 | 2020-05-08 | 415 |
微图案化碳-碳纳米管复合材料电极微加工工艺及应用 | 2020-05-17 | 98 |
直肠检查装置的探头及直肠检查装置 | 2020-05-12 | 284 |
Ultrasonic Sensor Microarray and Method of Manufacturing Same | 2020-05-21 | 67 |
Capacitive Micromachined Ultrasound Transducers with Pressurized Cavities | 2020-05-24 | 229 |
Method of varying the flow rate of fluid from a medical pump and hybrid sensor system performing the same | 2020-05-23 | 846 |
ULTRASONIC TRANSDUCER DEVICE WITH THROUGH-SUBSTRATE VIA | 2020-05-15 | 504 |
MULTI-MODE CAPACITIVE MICROMACHINED ULTRASOUND TRANSDUCER AND ASSOCIATED DEVICES, SYSTEMS, AND METHODS | 2020-05-16 | 839 |
ULTRASONIC SENSOR MICROARRAY AND METHOD OF MANUFACTURING SAME | 2020-05-25 | 833 |
ULTRASONIC SENSOR MICROARRAY AND ITS METHOD OF MANUFACTURE | 2020-05-21 | 528 |
高效检索全球专利专利汇是专利免费检索,专利查询,专利分析-国家发明专利查询检索分析平台,是提供专利分析,专利查询,专利检索等数据服务功能的知识产权数据服务商。
我们的产品包含105个国家的1.26亿组数据,免费查、免费专利分析。
专利汇分析报告产品可以对行业情报数据进行梳理分析,涉及维度包括行业专利基本状况分析、地域分析、技术分析、发明人分析、申请人分析、专利权人分析、失效分析、核心专利分析、法律分析、研发重点分析、企业专利处境分析、技术处境分析、专利寿命分析、企业定位分析、引证分析等超过60个分析角度,系统通过AI智能系统对图表进行解读,只需1分钟,一键生成行业专利分析报告。