TW200813406A - An underwater acoustic micro-sensor - Google Patents

Abstract

This invention discloses a MEMS type underwater acoustic sensor using 6'' single-crystalline silicon wafer. At resonant frequent of the membrane structure, a high signal-to-noise ratio is expected. By chemical vapor deposition thin layers of silicon nitride and poly-silicon, the sensing membrane and piezo-resistive material are patterned and etched using lithography and dry etching process, respectively. After the gold wire is patterned, the entire back side of the sensing membrane is etched in order to create the cavity. The waterproof of the hydrophone is completed by deposition a thin layer of Parylene polymer material. Moreover the controlled etching process can create the sensing membrane without difficulties and have successfully made the acoustic sensor.

Description

200813406 IX. Description of the invention: w [Technical field to which the invention pertains] The present invention relates to an apparatus for an underwater acoustic micro-sensor, which is fabricated using a surface processing technique of a microelectromechanical process. The sensing film structure of the sensor receives a sound wave of a specific frequency range close to the natural frequency of the structure, and the sensor output signal has a high signal-to-noise ratio characteristic, thereby receiving the signal transmitted by the underwater sound wave. content. [Prior Art] The research department of MEMS is a combination of traditional knowledge in the fields of electronics, motors, mechanics, biomedicine, and control, and micro-sensory and actuator systems developed by semiconductor manufacturing technology. For applications in various fields, the miniaturization of the sensing system has the advantages of reducing the load, reducing the occupied area, and lowering the overall energy loss. Therefore, the application of MEMS to the sensing crying, not only the volume sensor is smaller and more sensitive, its accuracy ^ can be followed by * and the energy consumed is also lower; in addition, and can be coordinated Semiconductor technology produces an array of sensors. 'But Although it is different from the industry, the scope of its application is quite wide: the research and development of micro-sensors related to Zhai is quite lacking. t疋, in view of the underwater technology, in this case, the inventor of this case accumulated the test, carefully studied, research and development of the P industry development of the nine development of a use of benefits, based on the traditional house force sensor The sound of the sound of the range and the technology of the acoustics of the mosquitoes combined with the micro-electromechanical sensor. This underwater measurement

CKU-P060054-TW 200813406 The combination of technology 'believes that it will bring breakthroughs in underwater measurement technology 【Abstract】 The main purpose of the month is to provide a kind of water that combines MEMS and underwater acoustic technology. Under the sound, the micro-sensing sound is slightly sensitive. _ ^ South, accurate, low-energy underwater For the above purposes, the sensor structure of the present invention is shown in Figure 1, Γί, - group conductor circuit, - insulating material, harsh sleep and a waterproof film. Among them, the piezoresistive group is transmitted by the guest to make the piezoresistive characteristic (4) t and ion-distributed ions, and the middle sentence person: the resistance group is a group of four piezoresistors, and its value is fixed piezoresistive. And _ is not set on the film structure to block the livestock road group, the gold is the wire material 'connected to the four piezoresistive group detectors, and the other pair is the sense of the guide = material, is nitrided ♦ For the material, it is located in the resistance and the gold 2 square '(4) resists the conductive single (four) substrate to avoid short circuit. The material ^m film is directly used as a base single crystal stone wafer, and the surface is first completed on the side of the film outer groove, and then the crystal is further

CKU-P060054-TW 200813406 With the precise control of the rate and depth of the record, the structure of the German and the field. The outer shape of the film is a slender type of structure, which can make it vibrate... narrow, m bucket and #扣4, two early and the width of the left and right sides of the film is thinner than the outer groove of the tooth, with To reduce the structural stiffness and natural vibration frequency. The waterproof film is deposited on the outer layer of the device, wherein the waterproof film is a parylene | to prevent moisture from entering the sensor to conform to the underwater operating environment. When designing the reticle, the limitation of the wafer space and the power of the sensor should be taken into consideration. Therefore, when designing the sensor on the wafer, except for the single sense, the device is placed in a single test wafer, as shown in the figure. As shown in the second, it is additionally designed to simultaneously configure two or four sensors on a single test wafer. In addition to increasing the number of sensors and reducing unit cost, test wafers with four sensors design four sensing films of different lengths, giving them different resonant frequencies to enhance the performance of the sensing wafer. [Embodiment] In order to facilitate the examination committee to further understand, understand and understand the structure, use and characteristics of the present invention, the inventors cite several preferred embodiments, with detailed drawings The description is as follows: The main manufacturing method and structure of the present invention are described in detail in FIG. 3 and FIG. The following is illustrated as follows: Figure 3 is a process flow diagram of the micro-sensor of the present invention, wherein the sensing

8 CKU-P060054-TW 200813406 The device is based on a six-inch single crystal germanium wafer. Figure 3 (The quality of the phantom deposited film, the present invention uses low pressure chemical vapor deposition (LPCVD) to deposit a thickness of 0. 3μπι nitride as an insulating layer. Figure 3 (8) using lpcVD deposited a thick layer on the tantalum nitride film ·3μπ1 polycrystalline germanium film as piezoresistive

Material. Due to the high resistance value of polycrystalline germanium, ion implantation of boron ions is required to reduce the resistivity, and the implantation concentration is lxl〇2GNA [cm-3]. This concentration is set so that the temperature coefficient of resistance of the multi-turn is reduced to zero to reduce the sensitivity of the piezoresistance to temperature, and finally the ions are evenly distributed through the annealing process. Figure 3 (c) is to ensure the accuracy of the piezoresistive shape, so the deep reactive ion etching machine (DRIE) is used to engrave the polysilicon film to produce a piezoresistive profile. The sensing terminal pressure resistance 11 and the piezoresistive resistor 13 are disposed on both sides of the film structure, and the resistance changes according to the deformation of the film structure; and the two piezoresistors which are not disposed on the film structure and have a fixed resistance = 12 and piezoresistive four 14, the position is far from the structure of the film to avoid excessive etching of the back hole to cause the piezoresistive suspension, causing the piezoresistive resistance to change with the vibration of the acoustic wave. Figure 3 (d) The system of gold (Au) / chromium (9) wire material is evaporated by electron beam evaporation machine, in which chromium is used as an adhesive layer to increase the adhesion of gold. The thickness of chromium evaporation is l5. 〇A, the thickness of gold evaporation is _人·, and the gold paste and chrome engraving solution are soaked in wet magnetic (four) way, so that the wire metal, wire 21, metal wire 22, metal wire 3 B and metal wire Four 24 and external wire connection points - buckle, external guide wire connection = two 212, external wire connection point three 213 and external wire connection point four 214 forming 'connect four pressure resistance to form the Wheatstone bridge circuit. The electric ΓΓΓ point is divided into a series, and the pair is connected to the external wire, and the external wire connection point is used as the input terminal of the applied voltage.

CKU-P060054-TW 200813406 Ground terminal, an external wire connection point 212, external wire connection point 4 2i4 is the output of the sensor voltage signal. Figure 3 (e) first repeats the para-protective piezoresistance of the first mask, and then etches excess tantalum nitride by a reactive ion etching machine (RIE), leaving only the area under the piezoresistive and the underlying conductor as the insulating layer 5 In order to avoid the excessive stress and cracking of the three materials. Next, aluminum is used as an etching mask, and a single crystal etched wafer is etched out of the upper half of the sensing thin raft 3 by an inductively coupled plasma ion etching system (icp), and the trench 4 is used for the sensing film 3 The outer lower half groove 42 shapes the sensing film 3 JL. Figure 3 (〇 铭 铭 做 彳 , , , , , , , , , 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭 铭Too deep 'causes the weed phenomenon and the curvature of the side bottom surface is too large. In addition, because it is a six-pair single crystal stone wafer, there is no money to resist the layer, and the depth of the sensing film 3 required to be engraved is extremely deep. , almost up to the bottom of the wafer, due to the depth of smoke and the rapid development of the film to obtain a film structure of appropriate thickness. Figure 3 (g) finally deposited on the outer layer of the wafer - waterproof layer 7 to meet the underwater operating environment, where the waterproof The layer 7 is a parylene film. The most critical process of the sensible sensing 11 is the #back side process, special = detailed description. On the back _ process, in addition to the side of the gambling structure Outside the hole 6 'gj should be behind the fine film material, in order to avoid the water column when cutting the pair _ injury can not be made to cut. Therefore, in the back of the money mask, more convenient diamond knife manually separate the sensor wafer The process of cutting the part by 8° is shown in Figure 4: Figure 4 (8) is the front film knot.

CKU-P060054-TW 10 200813406

External shape etching; Figure 4 (b) etched to the thickness of the wafer half, Figure 4 (C) to avoid inductively coupled plasma ion etching system cavity "Needle:: When the wafer is removed, the wafer is broken due to the etched path being too deep Before proceeding to the film structure, the photoresist is coated to protect the film. Figure 4 (4) follows the pattern of the film, and the control of the depth of the instrument is very important. When the outer groove 4 is required, the single off time must be reduced to -minute, and the next time, the sensing film structure 3 is finally produced. According to the above manufacturing process, the figure 5 and FIG. 6 are completed. The example diagram of the figure is shown in Fig. 5 and Fig. 6 respectively for the reticle pattern and the back side of the process behind the above process. The picture is the sensory micro-example diagram of the test. ^ After the completion of the process II external wire connection point -211, external wire connection potential two m, external wire connection point three 213 and external wire connection point four 214 wire ^ junction to the junction of the package, as shown in the figure. Finally, the seal U is connected to the test pedestal (4). The results of the test in Figure 9 are The azole is controlled by the 鼗 _ _ 〗 〖 in the second rolling by the knowledge frequency 耘 type control, the frequency is between the plus + pressure box _1G ghz _ wave, the sensor talks: the results from the receiving end can be known With the increase of frequency, the better the second degree is. This test result is consistent with the trend that the sensor is closer to the natural frequency. In the underwater test of the sensor, the control can generate a higher resolution wave. Therefore, the sweep frequency slot ^1 is too much to 1QOkIiz interval 1kHz sound wave: received by the sensor of 曰★明. The test result output signal is as shown in the figure

CKU-P060054-TW 11 200813406 Ten's ordinate is the vibration of the sensing ϋ output signal. When the frequency is less than 50 shame, the vibration of the sensor is not ^^^ when the sensor has obvious Resonance is ^^^ U This pushes its resonant frequency to be about 6 〇 kHz. Second, the micro-sensor of the present invention can be used for hydrological detection, t-bone source development, underwater communication of underwater unmanned vehicles and underwater sound recordings. The money is in the air

It can be used in the micro-sounding sensation of processing machinery. The invention has been disclosed in the preferred embodiments as described above, but it is not intended to limit the invention, and anyone skilled in the art can make various changes without departing from the essence of the invention. With modifications. As explained above, 3 can be used to modify and change various types without deteriorating the scope of the invention. The scope of protection of the present invention is defined by the scope of the appended claims.

CKU-P060054-TW 12 200813406 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a sensor of the present invention. FIG. 2 is a schematic diagram of a configuration of a sensing wafer of the present invention. FIG. 3 is a schematic diagram of a process of the sensor of the present invention. FIG. 5 is a schematic diagram of the etching process of the back surface of the present invention. FIG. 5 is an illustration of the etching mask behind the present invention. FIG. 6 is an example of etching behind the present invention. FIG. 7 is an example of a sensor of the present invention. 8: An example of the sensor of the present invention is disposed in a package. FIG. 9 is a power spectrum value of each frequency tested in the sensor air of the present invention. FIG. 10 is a sensor underwater test of the frequency of the present invention. Peak of output signal

13 CKU-P060054-TW 200813406 [Description of main components] I- Piezoresistive II- Piezoresistive 12- Piezoresistive 2-13- Piezoresistive Tri- 14- Piezoresistive 4-2 Metal Wire 21-Metal Wire-211-External Wire Connection point one• 22-metal wire two 212-external wire connection point two 23·metal wire three 213-external wire connection point three 24-metal wire four 214·external wire connection point four 3- sensing film 4-sensing film Outer groove 41 - sensing film profile upper half groove 42 - sensing film profile lower half groove 5 - insulation layer 6 - back etching hole 7 - waterproof layer 8 - cutting track.

14 CKU-P060054-TW

Claims (1)

200813406 X. Patent application scope: The sound micro-sensor used in the underwater environment is characterized by a set of piezoresistive resistance, which is characterized by multiple piezoresistive properties, using crystal crucible as material and ion implantation to make four The piezoresistive resistance is a group, ·, ,, ▼, urinary pen road, which is connected to the four piezoresistives to form a Wheatstone bridge, the circuit, which includes four contacts; An insulating material is disposed under the piezoresistive and metal wires to block the electrically conductive single crystal germanium substrate; - the sensing film is a single crystal germanium wafer as a substrate, and the outer shape is an elongated structure And a waterproof film deposited on the outer layer of the sensor. 2. The sensor of claim 3, wherein the pressure I and the two of the sensing end pressure resistances on both sides of the film structure are changed by the Φ 1 resistance mosquito film deformation; and A piezoresistance with a fixed resistance value on the film structure is not provided. 3. The sensor of claim 1, wherein the wire is connected to four piezoresistives to form a Wheatstone bridge circuit, the circuit comprising four contacts, which are divided into two pairs, one for The input terminal and the ground terminal of the applied voltage, and the other pair is the input end of the sensor voltage signal 〇CKU-P060054-TW 15 200813406. The sensor of claim 1, wherein the sensing film The outer shape of the structure is slender, the width of the left and right sides is relatively narrow, and the outer surface of the film is etched through. 5. The sensor of claim 1, wherein the pressure group is implanted with boron ions. 6. The sensor of claim 1, wherein the wire circuit is made of gold. 7. The sensor of claim 1, wherein the insulating material is a tantalum nitride compound. 8. The sensor of claim 1, wherein the film is made of a parylene material. A sensor as claimed in claim 2, wherein the pressure is known or "formed" by an inductively coupled plasma ion etching system (ICP). Measure the sensor described in the first item of the range, in which the sensation = 臈 system uses the back-engraving method to make a thin, appropriate structure, so that the vibration mode is simplistic. The sensor of claim </ RTI> wherein the etched region of the sensing film comprises a scribe line for separating the etched opening of the film structure from the convenient wafer. 12. The sensor of claim 1, wherein the method of engraving is to cover the scribe line with a photoresist when the thickness of the sensing film is half of the thickness of the sensing film, to avoid the sensing. The film broke due to insufficient film strength. 13·—A kind of acoustic micro-sensor for underwater environment, the structure of which includes: a set of piezoresistives, which are grouped by four piezoresistors; a set of wire circuits connected with four piezoresistors to form Wheatstone Bridge circuit; • an insulating material under the piezoresistive and metal wires to block the conductive single crystal germanium substrate; a sensing film, which is a single crystal germanium wafer directly used as a substrate, a slender structure; and a waterproof film deposited on the outer layer of the sensor; wherein 'the film is accurately engraved to a certain thickness in a manner behind the left', the thickness of the sensing film is received close When the sound wave in the natural frequency range is 'sound', it can output a high signal ratio signal. CKU-P060054-TW 200813406 14· A method for manufacturing an acoustic micro-sensor for use in an underwater environment, the method comprising: depositing tantalum nitride on a single crystal germanium substrate; depositing polycrystalline stone on the tantalum nitride Layered, and implanted ions into a pressure group material, the polycrystalline silicon film is engraved to form the piezoresistive shape; gold is deposited and etched into a gold wire on the polysilicon film to connect the piezoresistive to form a Wheatstone bridge circuit Removing excess tantalum nitride by reactive ion etching (RIE); engraving the monocrystalline front surface film trench; forming a film structure of appropriate thickness by back etching; and depositing a parylene Parylene waterproof layer. 15. The method of manufacture as described in claim 14 of the scope of the patent application. Before the post-etching step, a step of grinding the surface of the film is further included to avoid the weed phenomenon caused by the deep etching behind and the curvature of the underside of the etching. CKU-P060054-TW 18