JP2007054831A - Ultrasonic sound source and ultrasonic sensor - Google Patents

Ultrasonic sound source and ultrasonic sensor Download PDF

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JP2007054831A
JP2007054831A JP2006223380A JP2006223380A JP2007054831A JP 2007054831 A JP2007054831 A JP 2007054831A JP 2006223380 A JP2006223380 A JP 2006223380A JP 2006223380 A JP2006223380 A JP 2006223380A JP 2007054831 A JP2007054831 A JP 2007054831A
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ultrasonic
sound source
thickness
silicon layer
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Nobuyoshi Koshida
信義 越田
Kenji Tsubaki
健治 椿
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Tokyo University of Agriculture and Technology NUC
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<P>PROBLEM TO BE SOLVED: To provide a novel ultrasonic sound source, which is useful as an ultrasonic sound source, a speaker sound source, an actuator, or the like and particularly useful as an ultrasonic sensor sound source, possesses high power-proof property, and can enlarge the maximum generation sound pressure and to provide an ultrasonic sensor using such ultrasonic sound source. <P>SOLUTION: The ultrasonic sound source (1) is provided with a thermally conductive substrate (2), a heat insulation single layer (3) made of a nano crystal silicon layer formed on one surface of the substrate (2), and a heating thin film (4) formed on the heat insulation layer (3) and made of a metal film. The heating thin film (4) is electrically driven by application of a current including an AC component. In the ultrasonic sound source (1), the thickness of the nano crystal silicon layer of the heat insulation layer (3) is a thickness not smaller than a heat diffusion length defined by the frequency of ultrasonic wave to be transmitted and not larger than a thickness obtained by adding 5 μm to the heat diffusion length. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

この出願の発明は、超音波音源および超音波センサに関するものである。さらに詳しくは、この出願の発明は、空気に熱を与えることで空気の粗密を作り、超音波を発生する装置であって、超音波音源、スピーカー音源、アクチュエータ等に有用で、とくに超音波センサ音源として有用な新しい超音波音源さらにその超音波音源を用いた超音波センサに関するものである。   The invention of this application relates to an ultrasonic sound source and an ultrasonic sensor. More specifically, the invention of this application is a device that generates air waves by applying heat to air and generates ultrasonic waves, and is useful for ultrasonic sound sources, speaker sound sources, actuators, etc., particularly ultrasonic sensors. The present invention relates to a new ultrasonic sound source useful as a sound source and an ultrasonic sensor using the ultrasonic sound source.

従来より各種の超音波発生装置が知られており、これらの従来の超音波発生装置は、電気火花や流体振動などを用いる特殊なものを除いて、すべて何らかの機械振動を空気の振動へと変換するものである。このような機械振動を用いる方法には動電型・コンデンサ型などもあるが、超音波領域では圧電素子を利用したものが主流である。例えば、圧電材料であるチタン酸バリウムの両面に電極を形成し、電極間に超音波電気信号を印加することで、機械振動を発生させ、空気などの媒質にその振動を伝達して超音波を発生するようにしている。だが、このような機械振動を利用した超音波発生装置では、固有の共振周波数を有するために周波数帯域が狭い、周囲の環境（温度、振動）等の影響を受けやすい、微細・アレイ化が困難と言った問題があった。   Various types of ultrasonic generators have been known, and these conventional ultrasonic generators convert all mechanical vibrations into air vibrations, except for special ones that use electric sparks and fluid vibrations. To do. Such a method using mechanical vibration includes an electrodynamic type and a capacitor type, but in the ultrasonic region, a method using a piezoelectric element is mainly used. For example, electrodes are formed on both sides of a piezoelectric material, barium titanate, and an ultrasonic electric signal is applied between the electrodes, thereby generating mechanical vibrations and transmitting the vibrations to a medium such as air. It is trying to occur. However, such an ultrasonic generator using mechanical vibration has a unique resonance frequency, so the frequency band is narrow, it is easily affected by the surrounding environment (temperature, vibration), etc. There was a problem that said.

一方、機械振動を全く行わない新しい発生原理の圧力発生装置が提案されている（たとえば特許文献１および非特許文献１参照）。この提案では、基板と基板上に設けられた熱絶縁層（断熱層）と、熱絶縁層上に設けられて電気的に駆動される発熱体薄膜から構成されており、発熱体薄膜から発生した熱が熱伝導率のきわめて小さい多孔質層や高分子層などの熱絶縁層を設けることで、発熱体薄膜表面の空気層の温度変化が大きくなるようにして、超音波を発生するようにしている。この提案されたデバイスは機械振動を伴わないので、周波数帯域が広く、周囲環境の影響を受けにくく、微細・アレイ化も比較的容易であるなどの特徴を有している。このような熱励起による圧力発生装置の発生原理について考えてみると、電気的に駆動される発熱体薄膜に交流電流を印加した場合の発熱体薄膜表面温度の変化Ｔ（ω）は、熱絶縁層の熱伝導率をα、体積あたりの熱容量をＣ、発信する超音波の角周波数（周波数の２π倍）をωとして、単位面積当たりのエネルギーの出入りｑ（ω）〔Ｗ／ｃｍ2〕があったとき、次式（１）で与えられる。 On the other hand, a pressure generating device based on a new generation principle that does not perform mechanical vibration at all has been proposed (see, for example, Patent Document 1 and Non-Patent Document 1). This proposal consists of a substrate, a thermal insulation layer (heat insulation layer) provided on the substrate, and a heating element thin film provided on the thermal insulation layer and electrically driven. By providing a heat insulating layer such as a porous layer or a polymer layer whose heat conductivity is extremely small, the temperature change of the air layer on the surface of the heating element thin film is increased, so that ultrasonic waves are generated. Yes. Since the proposed device is not accompanied by mechanical vibration, it has characteristics such as a wide frequency band, being hardly affected by the surrounding environment, and being relatively fine and arrayable. Considering the generation principle of the pressure generator by such thermal excitation, the change T (ω) in the surface temperature of the heating element thin film when an AC current is applied to the electrically driven heating element thin film is the thermal insulation. When the thermal conductivity of the layer is α, the heat capacity per volume is C, and the angular frequency of the transmitted ultrasonic wave (2π times the frequency) is ω, the energy input / output q (ω) [W / cm 2 ] per unit area is When there is, it is given by the following formula (1).

Figure 2007054831
また、そのとき発生する音圧Ｐ（ω）は、次式（２）で与えられる。
Figure 2007054831
 The sound pressure P (ω) generated at that time is given by the following equation (2).

Figure 2007054831
すなわち、図４に示すように超音波周波数の信号を発生する信号源から供給された周波数ｆの電流（図４−ａ）によって、発熱体薄膜から発生する熱（図４−ｂ）が周囲の媒体である空気との熱交換により、空気の温度変化が起こる（図４−ｃ）。これは空気の疎密波を生み出し、周波数２ｆの音波を発生する（図４−ｄ）。
Figure 2007054831
 That is, as shown in FIG. 4, the heat (FIG. 4-b) generated from the heating element thin film is caused by the current of the frequency f (FIG. 4-a) supplied from a signal source that generates an ultrasonic frequency signal. Due to heat exchange with air as a medium, a temperature change of the air occurs (FIG. 4-c). This creates a dense wave of air and generates a sound wave of frequency 2f (FIG. 4-d).

ここで、前記（２）式より、発生する音圧Ｐ（ω）は、単位面積当たりのエネルギーの出入りｑ（ω）、すなわち、入力電力に比例する、熱絶縁層の熱伝導率α、体積当たりの熱容量Ｃが小さいほど大きくなることがわかる。さらに、熱絶縁層と基板の熱的コントラストが重要な役割をする。すなわち、熱伝導率α、体積当たりの熱容量Ｃをもつ熱絶縁層の厚さをＬとし、その下にα、Ｃとも十分に大きな熱伝導性の基板がある場合、次式（３）   Here, from the above equation (2), the generated sound pressure P (ω) is the input / output q (ω) of energy per unit area, that is, the thermal conductivity α and volume of the thermal insulating layer proportional to the input power. It can be seen that the smaller the per-heat capacity C, the larger. Furthermore, the thermal contrast between the thermal insulation layer and the substrate plays an important role. That is, when the thickness of a thermal insulation layer having a thermal conductivity α and a heat capacity C per volume is L, and there is a substrate having sufficiently large thermal conductivity under both α and C, the following formula (3)

Figure 2007054831
程度の厚み（交流成分の熱拡散長）をとると、発熱の交流成分は断熱し、発熱体の熱容量のため発生する直流成分の熱は、大きな熱伝導性の基板へ効率良く逃がすことができる。
特開平１１−３００２７４号公報 Nature 400 (1999) 835-855
Figure 2007054831
 If the thickness (the thermal diffusion length of the AC component) is taken, the AC component of the heat generation is insulated, and the heat of the DC component generated due to the heat capacity of the heating element can be efficiently released to the large heat conductive substrate. .
Japanese Patent Laid-Open No. 11-3000274 Nature 400 (1999) 835-855

しかしながら、先の従来の圧電素子を用いた場合、３０ｃｍ位置で２０Ｐａ程度の音圧しか得られなかったため、超音波センサとして長い距離のセンシングを行うことは困難であった。   However, when the conventional piezoelectric element is used, only a sound pressure of about 20 Pa is obtained at the 30 cm position, and it is difficult to perform long distance sensing as an ultrasonic sensor.

一方、特許文献１に記載の超音波音源を用いた場合、発生音圧は印加電力密度に比例するが、印加電力が大きくなると金属膜からなる発熱体薄膜にクラックが発生し断線してしまい、十分な音圧を発生することができなかった。そのため最大印加電力を大きくすることが望まれていた。   On the other hand, when the ultrasonic sound source described in Patent Document 1 is used, the generated sound pressure is proportional to the applied power density, but when the applied power is increased, the heating element thin film made of the metal film is cracked and disconnected. Sufficient sound pressure could not be generated. Therefore, it has been desired to increase the maximum applied power.

そこでこの出願の発明は、上記のとおりの問題点を解消し、最大印加電力の向上、すなわち耐電力特性を向上させ、最大発生音圧を大きくすることができる、新しい超音波音源およびその超音波音源を用いた超音波センサを提供することを課題としている。   Therefore, the invention of this application solves the problems as described above, improves the maximum applied power, that is, improves the power withstand characteristics, and increases the maximum generated sound pressure, and the ultrasonic wave and its ultrasonic wave. It is an object to provide an ultrasonic sensor using a sound source.

この出願の発明は、上記の課題を解決するものとして、まず第１には、熱伝導性の基板と、基板上の一方の面に形成されたナノ結晶シリコン層からなる単層の断熱層と、断熱層上に形成され、交流成分を含む電流が印加されて電気的に駆動される金属膜からなる発熱体薄膜と、を備えた超音波音源であって、断熱層のナノ結晶シリコン層の厚みが、発信する超音波の周波数で規定される熱拡散長以上でかつ熱拡散長に５μｍ加えた厚み以下であることを特徴とする超音波音源を提供する。   In order to solve the above problems, the invention of this application firstly includes a thermally conductive substrate and a single heat insulating layer formed of a nanocrystalline silicon layer formed on one surface of the substrate. An ultrasonic sound source comprising a heating element thin film formed on a heat insulating layer and made of a metal film that is electrically driven by applying an electric current containing an alternating current component. Provided is an ultrasonic sound source characterized in that the thickness is not less than the thermal diffusion length specified by the frequency of the transmitted ultrasonic wave and not more than the thickness obtained by adding 5 μm to the thermal diffusion length.

第２には、第１の発明の超音波音源にパルス信号を印加し超音波を発生させ、物体からの反射波を受信させることを特徴とする超音波センサをも提供する。   Second, there is also provided an ultrasonic sensor characterized in that a pulse signal is applied to the ultrasonic sound source of the first invention to generate an ultrasonic wave and receive a reflected wave from an object.

この出願の発明の超音波音源によれば、ナノ結晶シリコン層からなる断熱層の厚みを薄く形成することで、耐電力特性が向上し、最大発生音圧を大きくすることが可能となる。   According to the ultrasonic sound source of the invention of this application, by forming the thickness of the heat insulating layer made of the nanocrystalline silicon layer thin, it is possible to improve the power durability and increase the maximum generated sound pressure.

この出願の発明は上記のとおりの特徴をもつものであるが、以下にその実施の形態について説明する。   The invention of this application has the features as described above, and an embodiment thereof will be described below.

図１は、この出願の発明の超音波音源の一実施形態を例示した断面図である。この図１の例における超音波音源（１）は、熱伝導性の基板（２）と、基板（２）上の一方の面に形成されたナノ結晶シリコン層からなる単層の断熱層（３）と、断熱層（３）上に形成され、交流成分を含む電流が印加されて電気的に駆動される金属膜からなる発熱体薄膜（４）とで構成されており、発熱体薄膜（４）が超音波周波数の信号を発生する信号源（５）と配線接続されており、その発熱体薄膜（４）の表面より超音波（６）が発生するが、この超音波音源（１）は、とくに断熱層（３）のナノ結晶シリコン層の厚みが、発信する超音波の周波数で規定される熱拡散長以上でかつ熱拡散長に５μｍ加えた厚み以下であることを大きな特徴としている。   FIG. 1 is a cross-sectional view illustrating an embodiment of an ultrasonic sound source of the invention of this application. The ultrasonic sound source (1) in the example of FIG. 1 includes a heat conductive substrate (2) and a single heat insulation layer (3) composed of a nanocrystalline silicon layer formed on one surface of the substrate (2). ) And a heating element thin film (4) made of a metal film which is formed on the heat insulation layer (3) and is electrically driven by applying an electric current containing an alternating current component. ) Is connected to a signal source (5) for generating an ultrasonic frequency signal, and an ultrasonic wave (6) is generated from the surface of the heating element thin film (4). This ultrasonic sound source (1) In particular, the feature is that the thickness of the nanocrystalline silicon layer of the heat insulating layer (3) is not less than the thermal diffusion length defined by the frequency of the transmitted ultrasonic wave and not more than the thickness obtained by adding 5 μm to the thermal diffusion length.

まず、断熱層（３）に関して以下詳細に述べる。断熱層（３）はナノ結晶シリコン層からなり、ナノ結晶シリコン層は、多孔質材料でありかつナノオーダのシリコンの量子効果（フォノン閉じ込め効果）により、単結晶シリコンに比べて、熱伝導率、熱容量とも非常に小さい値を示す。多孔度が６０％程度のナノ結晶シリコンの具体的な数値を表１に示す。   First, the heat insulating layer (3) will be described in detail below. The heat insulation layer (3) is composed of a nanocrystalline silicon layer. The nanocrystalline silicon layer is a porous material and has a quantum effect (phonon confinement effect) of nano-order silicon. Both values are very small. Table 1 shows specific numerical values of nanocrystalline silicon having a porosity of about 60%.

Figure 2007054831
金属電極（発熱体薄膜（４））にクラックが発生し断線する場合、金属電極の下地の断熱層（３）であるナノ結晶シリコン層の状態が強く影響し、特にその厚みをできるだけ薄くすること、機械的強度を上げることが有効であることが種々の検討から明らかになった。しかしながら、音圧の発生効率は前述の（２）式からも分かるように断熱層（３）のナノ結晶シリコン層のαＣが小さいほど良い。αＣが小さいということは、ナノ結晶シリコン層の多孔度を大きくすることであり、それによりその機械的強度は小さくなる傾向にある。またその厚みに関しても、広い周波数帯域で音波を発生させる場合は１０μｍ以上の厚みが必要となる。これらのことを考慮してナノ結晶シリコン層の厚みを音圧発生効率に影響を及ぼさない最低限の厚みとすることで、発生音圧を下げないで耐電力特性を向上させることができる。以下、このことに関して詳細を記載する。
Figure 2007054831
 When the metal electrode (heating element thin film (4)) is cracked and disconnected, the state of the nanocrystalline silicon layer, which is the heat insulating layer (3) underlying the metal electrode, strongly influences the thickness of the metal electrode, especially as much as possible. Various studies have revealed that it is effective to increase the mechanical strength. However, the sound pressure generation efficiency is better as the αC of the nanocrystalline silicon layer of the heat insulating layer (3) is smaller, as can be seen from the above-described equation (2). A small αC means an increase in the porosity of the nanocrystalline silicon layer, which tends to reduce its mechanical strength. Further, regarding the thickness, when generating sound waves in a wide frequency band, a thickness of 10 μm or more is required. Considering these points, the power-saving characteristics can be improved without lowering the generated sound pressure by setting the thickness of the nanocrystalline silicon layer to a minimum thickness that does not affect the sound pressure generation efficiency. Details will be described below in this regard.

前述の（３）式から、ナノ結晶シリコン層のα、Ｃが一定であれば、交流成分の熱拡散長Ｌは発信する超音波の周波数の関数である。αＣ＝０．７（×１０6）、αＣ＝０．０７（×１０6）の場合の発信する超音波の周波数（ｋＨｚ）と熱拡散長（μｍ）の関係を図２に示す。この熱拡散長以上の厚みのナノ結晶シリコン層を設ければ、効率良く超音波を放出することが可能となる。可聴域レベルの音波を放出しようとした場合、１０μｍ程度以上の比較的厚いナノ結晶シリコン層が必要であるが、超音波域においては、αＣ値が小さければ数μｍの厚みで十分であることがわかる。 From the above equation (3), if α and C of the nanocrystalline silicon layer are constant, the thermal diffusion length L of the AC component is a function of the frequency of the transmitted ultrasonic wave. FIG. 2 shows the relationship between the ultrasonic wave frequency (kHz) and thermal diffusion length (μm) transmitted when αC = 0.7 (× 10 6 ) and αC = 0.07 (× 10 6 ). If a nanocrystalline silicon layer having a thickness equal to or greater than the thermal diffusion length is provided, it is possible to emit ultrasonic waves efficiently. When attempting to emit sound waves in the audible range, a relatively thick nanocrystalline silicon layer of about 10 μm or more is necessary. However, in the ultrasonic range, a thickness of several μm may be sufficient if the αC value is small. Recognize.

このように断熱層（３）のナノ結晶シリコン層の厚みとしては、発信する超音波の周波数で規定される熱拡散長以上でかつ熱拡散長に５μｍ加えた厚み以下とすることで、発生音圧を下げないで耐電力特性を向上させることができる。ナノ結晶シリコン層の厚みが薄いほど耐電力特性は優れているが、前述の熱拡散長で決めたナノ結晶シリコン層の厚みは理論的な最低限の厚みであり、音圧発生効率の点からは、面内の膜厚のばらつきなどを考慮すると、熱拡散長に５μｍ加えた厚み以下とした厚みの範囲に設定する必要がある。なおこれ以上の厚みとした場合には耐電力特性は向上しない。   As described above, the thickness of the nanocrystalline silicon layer of the heat insulating layer (3) is not less than the thermal diffusion length specified by the frequency of the transmitted ultrasonic wave and not more than the thickness obtained by adding 5 μm to the thermal diffusion length. The power durability characteristics can be improved without reducing the pressure. The thinner the nanocrystalline silicon layer is, the better the power handling characteristics are. However, the thickness of the nanocrystalline silicon layer determined by the thermal diffusion length described above is the theoretical minimum thickness. In consideration of variations in the in-plane film thickness, it is necessary to set the thickness within the range of 5 μm or less added to the thermal diffusion length. When the thickness is larger than this, the power durability is not improved.

また、耐電力特性の向上のためには、ナノ結晶シリコン層の機械的強度を大きくすることが有効である。実用上多孔度の調整は、用いる単結晶シリコン基板の種類、抵抗、陽極酸化条件（電流密度、溶液組成）などで調整可能であり、その方法は特に限定されない。   In order to improve the power durability, it is effective to increase the mechanical strength of the nanocrystalline silicon layer. Practically, the porosity can be adjusted depending on the type of single crystal silicon substrate used, resistance, anodizing conditions (current density, solution composition), etc., and the method is not particularly limited.

次に熱伝導性の基板（２）としては、直流成分の熱を逃すために熱伝導率αの大きな材料を用いることが好ましく、単結晶シリコンやポリシリコンなどの半導体基板を好適に用いることができる。基板（２）の形状としては、放熱効率を良くするために放熱フィンを裏面に形成していても良い。   Next, as the thermally conductive substrate (2), it is preferable to use a material having a large thermal conductivity α in order to release the heat of the DC component, and it is preferable to use a semiconductor substrate such as single crystal silicon or polysilicon. it can. As for the shape of the substrate (2), heat radiation fins may be formed on the back surface in order to improve heat radiation efficiency.

次に発熱体薄膜（４）としては、金属膜であれば材質は特に限定されない。たとえばＷ，Ｍｏ，Ｉｒ，Ａｕ，Ａｌ，Ｎｉ，Ｔｉ，Ｐｔなどの金属単体やそれらの積層構造などを用いることができ、真空蒸着、スパッタなどで成膜することができる。また膜厚は、熱容量を小さくするためにできるだけ薄くするのが好ましいが、適当な抵抗とするために１０ｎｍ〜１００ｎｍの範囲で選択することができる。   Next, the material of the heating element thin film (4) is not particularly limited as long as it is a metal film. For example, single metals such as W, Mo, Ir, Au, Al, Ni, Ti, and Pt, or a laminated structure thereof can be used, and the film can be formed by vacuum deposition, sputtering, or the like. The film thickness is preferably as thin as possible in order to reduce the heat capacity, but can be selected in the range of 10 nm to 100 nm in order to obtain an appropriate resistance.

このようにして作製したこの出願の発明にかかる超音波音源は、パルス状の高いピーク電力を投入することが可能となり、空気中において３０ｃｍ以上の比較的長い距離のセンシングが可能な超音波センサとして特に有効である。   The ultrasonic sound source according to the invention of the present application produced as described above is capable of applying high pulsed peak power, and is an ultrasonic sensor capable of sensing a relatively long distance of 30 cm or more in the air. It is particularly effective.

以下、添付した図面に沿って実施例を示し、この出願の発明の実施の形態についてさらに詳しく説明する。もちろん、この発明は以下の例に限定されるものではなく、細部については様々な態様が可能であることは言うまでもない。   Embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Of course, the present invention is not limited to the following examples, and it goes without saying that various aspects are possible in detail.

＜実施例１＞
Ｐ型（１００）単結晶シリコン基板（８０−１２０Ωｃｍ）の裏面に陽極酸化処理時のコンタクト電極として、Ａｌを真空蒸着として３００ｎｍ成膜した。その後、この基板をＨＦ（５５％）：ＥｔＯＨ＝１：１の溶液中で白金を対極として電流密度１００ｍＡ／ｃｍ2で２０秒間陽極酸化処理を行い、厚み２μｍのナノ結晶シリコン層よりなる断熱層を形成した。次にナノ結晶シリコン層上に発熱体薄膜としてタングステンをスパッタ法で５０ｎｍの厚みで形成し、５ｍｍ□の面積の超音波音源を作製した。
＜実施例２＞
陽極酸化処理を５０秒間行い、厚み５μｍのナノ結晶シリコン層を形成したこと以外、実施例１と同様にして超音波音源を作製した。
＜比較例１＞
陽極酸化処理を４８０秒間行い、厚み５０μｍのナノ結晶シリコン層を形成したこと以外、実施例１と同様にして超音波音源を作製した。
＜比較例２＞
陽極酸化処理を２００秒間行い、厚み２０μｍのナノ結晶シリコン層を形成したこと以外、実施例１と同様にして超音波音源を作製した。 <Example 1>
On the back surface of a P-type (100) single crystal silicon substrate (80-120 Ωcm), as a contact electrode at the time of anodizing, Al was vacuum-deposited to a thickness of 300 nm. Thereafter, this substrate was anodized in a solution of HF (55%): EtOH = 1: 1 with platinum as a counter electrode at a current density of 100 mA / cm 2 for 20 seconds, and a heat insulating layer comprising a nanocrystalline silicon layer having a thickness of 2 μm. Formed. Next, tungsten was formed as a heating element thin film with a thickness of 50 nm on the nanocrystalline silicon layer by sputtering to produce an ultrasonic sound source having an area of 5 mm □.
<Example 2>
An ultrasonic sound source was produced in the same manner as in Example 1 except that the anodizing treatment was performed for 50 seconds to form a nanocrystalline silicon layer having a thickness of 5 μm.
<Comparative Example 1>
An ultrasonic sound source was produced in the same manner as in Example 1 except that the anodization treatment was performed for 480 seconds to form a nanocrystalline silicon layer having a thickness of 50 μm.
<Comparative example 2>
An ultrasonic sound source was produced in the same manner as in Example 1 except that the anodization treatment was performed for 200 seconds and a nanocrystalline silicon layer having a thickness of 20 μm was formed.

以上の実施例１、２、比較例１、２の各々において得られた超音波音源の発熱体薄膜にパルス幅１６μｓ（周波数６０ｋＨｚ）、周期１ｓの単パルス信号を印加し、発熱体薄膜が断線するまで印加電力を上げていき、３０ｃｍ位置での最大音圧をマイクで測定した。なお、実施例１、２、比較例１、２で電流密度１００ｍＡ／ｃｍ2で形成したナノ結晶シリコン層のαＣはαＣ＝０．０７であり、６０ｋＨｚでの熱拡散長は約１．５μｍであった。 A single pulse signal having a pulse width of 16 μs (frequency of 60 kHz) and a period of 1 s was applied to the heating element thin film of the ultrasonic sound source obtained in each of Examples 1 and 2 and Comparative Examples 1 and 2, and the heating element thin film was disconnected. The applied power was increased until the maximum sound pressure at the 30 cm position was measured with a microphone. The αC of the nanocrystalline silicon layer formed at a current density of 100 mA / cm 2 in Examples 1 and 2 and Comparative Examples 1 and 2 is αC = 0.07, and the thermal diffusion length at 60 kHz is about 1.5 μm. there were.

表２にその測定結果を示す。   Table 2 shows the measurement results.

Figure 2007054831

表２より明らかなように、実施例１、２の超音波音源は、比較例１、２の超音波音源に比べて最大印加電力が増加し、その結果最大音圧を大きくすることができることがわかる。
Figure 2007054831
As is clear from Table 2, the ultrasonic sound sources of Examples 1 and 2 have the maximum applied power increased as compared with the ultrasonic sound sources of Comparative Examples 1 and 2, and as a result, the maximum sound pressure can be increased. Recognize.

以上詳しく説明したとおり、この出願の発明によれば、ナノ結晶シリコン層の厚みを薄く形成することで、耐電力特性が向上し、最大発生音圧を大きくすることができる超音波音源および超音波センサが提供される。   As described above in detail, according to the invention of this application, an ultrasonic sound source and an ultrasonic wave capable of improving power durability and increasing a maximum generated sound pressure by forming a thin nanocrystalline silicon layer. A sensor is provided.

この出願の発明の超音波音源の一実施形態を例示した断面図である。It is sectional drawing which illustrated one Embodiment of the ultrasonic sound source of invention of this application. この出願の発明の発信する超音波の周波数（ｋＨｚ）と熱拡散長（μｍ）の 関係を例示したグラフである。3 is a graph illustrating the relationship between the frequency (kHz) of ultrasonic waves transmitted by the invention of this application and the thermal diffusion length (μm). この出願の発明の超音波音源の原理を示したグラフである。It is the graph which showed the principle of the ultrasonic sound source of the invention of this application.

符号の説明Explanation of symbols

１ 超音波音源
２ 基板
３ 断熱層
４ 発熱体薄膜
５ 信号源
６ 超音波 DESCRIPTION OF SYMBOLS 1 Ultrasonic sound source 2 Board | substrate 3 Heat insulation layer 4 Heat generating body thin film 5 Signal source 6 Ultrasonic wave

Claims (2)

熱伝導性の基板と、基板上の一方の面に形成されたナノ結晶シリコン層からなる単層の断熱層と、断熱層上に形成され、交流成分を含む電流が印加されて電気的に駆動される金属膜からなる発熱体薄膜と、を備えた超音波音源であって、断熱層のナノ結晶シリコン層の厚みが、発信する超音波の周波数で規定される熱拡散長以上でかつ熱拡散長に５μｍ加えた厚み以下であることを特徴とする超音波音源。   A thermally conductive substrate, a single heat insulating layer composed of a nanocrystalline silicon layer formed on one surface of the substrate, and an electric drive including an alternating current component formed on the heat insulating layer. A heat source thin film made of a metal film, and the thickness of the nanocrystalline silicon layer of the heat insulating layer is equal to or greater than the thermal diffusion length specified by the frequency of the transmitted ultrasonic wave An ultrasonic sound source characterized by having a thickness of 5 μm or less in length. 請求項１に記載の超音波音源にパルス信号を印加し超音波を発生させ、物体からの反射波を受信させることを特徴とする超音波センサ。   An ultrasonic sensor characterized by applying a pulse signal to the ultrasonic sound source according to claim 1 to generate an ultrasonic wave and receiving a reflected wave from an object.
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US7397167B2 (en) * 2006-01-30 2008-07-08 Denso Corporation Ultrasonic wave generating device
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US8225501B2 (en) 2009-08-07 2012-07-24 Tsinghua University Method for making thermoacoustic device
US8238586B2 (en) 2008-12-30 2012-08-07 Beijing Funate Innovation Technology Co., Ltd. Thermoacoustic device
US8249279B2 (en) 2008-04-28 2012-08-21 Beijing Funate Innovation Technology Co., Ltd. Thermoacoustic device
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US8905320B2 (en) 2009-06-09 2014-12-09 Tsinghua University Room heating device capable of simultaneously producing sound waves
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7397167B2 (en) * 2006-01-30 2008-07-08 Denso Corporation Ultrasonic wave generating device
US8249279B2 (en) 2008-04-28 2012-08-21 Beijing Funate Innovation Technology Co., Ltd. Thermoacoustic device
US8259966B2 (en) 2008-04-28 2012-09-04 Beijing Funate Innovation Technology Co., Ltd. Acoustic system
JP2010141894A (en) * 2008-12-12 2010-06-24 Qinghua Univ Ultrasonic acoustic device
US8238586B2 (en) 2008-12-30 2012-08-07 Beijing Funate Innovation Technology Co., Ltd. Thermoacoustic device
JP2010220313A (en) * 2009-03-13 2010-09-30 Tokyo Electron Ltd Sample injection device
US8905320B2 (en) 2009-06-09 2014-12-09 Tsinghua University Room heating device capable of simultaneously producing sound waves
US8225501B2 (en) 2009-08-07 2012-07-24 Tsinghua University Method for making thermoacoustic device
JP2011059108A (en) * 2009-09-11 2011-03-24 Qinghua Univ Active sonar system
CN103567136A (en) * 2012-08-02 2014-02-12 纳米新能源（唐山）有限责任公司 Nanometer ultrasonic generating device, method for manufacturing same and ion induction device
CN103567136B (en) * 2012-08-02 2016-03-23 纳米新能源（唐山）有限责任公司 Nanometer ultrasonic generator and preparation method thereof and electro-ionic osmosis device
RU2545312C1 (en) * 2013-12-03 2015-03-27 Виталий Николаевич Максимов Thermoacoustic radiator
CN109154521A (en) * 2016-04-08 2019-01-04 流线公司 Ultrasonic liquid level sensor with reflector
CN115815776A (en) * 2023-02-15 2023-03-21 中北大学 Ultrasonic-electric field assisted vacuum hot-pressing heterogeneous interface diffusion forming device and process
CN115815776B (en) * 2023-02-15 2023-05-16 中北大学 Ultrasonic-electric field assisted vacuum hot-pressing heterogeneous interface diffusion forming device and process

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