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Advances in Microelectronic Engineering (AIME) Volume 3, 2015 doi: 10.14355/aime.2015.03.002
Researches and Applications of Microelectronic Materials and their Devices in the high-frequency Ultrasonic Fields Li Quanlu *1 , Li Yuan *2 , Wu Jing 3 *1,3
School of Physics and Information Technology, Shaanxi Normal University, No. 199, Chang’an South Road, Xi’an, Shaanxi 710062, China
*2
Department of Political Theory, Humanities and Social Sciences, Third Military Medical University, Sha-ping-ba District, Chongqing City 400038, China
*1
Lql0314@snnu.edu.cn; *2 sophie224@sina.com; 3 wujing@snnu.edu.cn
Abstract This paper essay offers survey of the research and development of the applications of microelectronics in the high-frequency ultrasonic fields. Furthermore, it briefly gives microelectronics materials and processing, their high-frequency ultrasonic transducer, and amplifications of the high-frequency ultrasonics, etc. Finally, some problems of microelectronics in the high-frequency ultrasonic fields, especially piezoelectric semiconductor and its acoustoelectric effect which need further researches are pointed out. Keywords Microelectronic Material; Microelectronic Device; High-frequency Ultrasonic; Research; Application
Introduction The microelectronics studying in solid materials (main semiconductors) to constitute microminiaturization electrocircuit, circuits and its systems is a branch of the electronics, which researched the laws of movement and applications of electronics (or ions) and achieved the function of the signal processing. In microelectronics, the spatial size of the devices, components and electrocicuits in µ m(1µ m = 10−6 m) and nm(1nm = 10−9 m) as a unit generally. This paper researched microelectronics materials and processing, their high-frequency ultrasonic transducer and their applications etc. Microelectronics Materials and Processing The materials are the basic of the devices (e.g., ultrasonic transducer, etc.), components (such as substrate etc.) and micro-electrocicuits, etc. Microelectronics materials are different kinds of semiconductors materials. [1,2,3, 4] The Classification of Semiconductors Materials Microelectronics materials are used in the high-frequency ultrasonic fields that main is piezoelectric semiconductor materials which possess piezoelectric effects (including the element semiconductor, compound semiconductor, amorphous or glass semiconductor, organic semiconductor, etc.). In piezoelectric semiconductors, ultrasonic waves and free carriers (i.e. electronics and holes) interaction produce as amplification and attenuation of ultrasonic waves, large amplitude for the influence (including saturation of current, current oscillation, to produce acoustoelectric domain, etc.) of the characteristic of the voltage and the currents are collectively known as acoustoelectric effects. In recent years, the theory of acoustoelectric effect has been used to develop some new high-frequency ultrasonic devices. Some semiconductor materials as: Ge, Si, CdS, ZnO, GaAs, ZnTe, InTe, polydivinylbenzene, polypropylene resin, naphthaline, anthracene, etc all possess the effects. Here needs to be explained: the first, in piezoelectric semiconductors its piezoelectric effects result from ultrasonic waves and free carriers (i.e. electronics and holes) interaction; however, in non-piezoelectric semiconductors its interaction results
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from the coupling of the deformation potential. The second, even now, for piezoelectric semiconductor materials development and utilization related to scopes have very wide range: single crystal, ceramics, organic matters, complex and biofilm, etc, but, main present practical applications are crystal materials (including single crystal and multicrystal). In acoustoelectric effects, semiconductor more are applied Ⅱ～Ⅵ race compounds (such as CdS, ZnO, CdSe, CdTe, ZnTe), Ⅲ～Ⅴ race compounds (such as GaAs, CdSb, InSb, GaP, InAs) of the periodic table of chemical elements, ternary compounds, e.g., Ag3 AsS , CdGeAs, GaAs1− x Px , Ga1− x Alx As , TeCdHg etc, mixed BaTiO 3 and some piezoelectric ceramics. The Preparation Technologies of Semiconductors Materials 1)
The Preparation Methods of the Single Crystal of Piezoelectric Semiconductors
The preparation methods of the single crystal of piezoelectric semiconductors are Solution techniques, such as Crystal growth from solution by the temperature—drop method, Evaporation technique, Crystal growth from solution evaporation technique, Hydro—thermal method, Vertical pulling method, Czochalski, i.e. CZ method, Floating zone mothod—FZmethod, etc. The single crystal of piezoelectric semiconductors has: SiO 2 , LiNbO3 , Bi12 GeO20 , Bi12 SiO20 , etc. which have been prepared later, they could pass incision, grinding to make of 10 µm thickly acoustoelectric transducers which are pasted in acoustic transmission medium such as Al2 O3Ti 4 + Fe3+ , α − SiO2 , Ge or si, so the frequency of the transducer could achieve 500 MHz. 2)
The Preparation Methods of the Film of the Piezoelectric Semiconductors
Because piezoelectric semiconductors (including single crystal and ceramics) are applied in high-frequency acoustoelectric devices which mainly adopt thin-film technologies (i.e. cover “the thick film” is general less than 10 µ m , and “the thin film” is less than 1 µ m ) that are included physical and chemical methods. The vacuum evaporation, electron been evaporation, ion been evaporation, DC sputtering, HF sputtering, RF sputtering, ion—sputtering, co—sputtering, molecular been epitaxy, etc. belong to the physical methods. The chemical vapor—deposition, sol—gel method, liquid source misted chemical vapor deposition (LSMCD), metal organic chemical vapor deposition (MOCVD),[5] etc. belong to the chemical methods. Furthermore, laser deposition is a method combining physical and the chemical method. In general the physical methods need for substratum of the materials heating to about 700 °C . The BaTiO3 , Bi4Ti3O12 , and partial PZT at high-temperature are expected directly to obtain preferred orientation (usual is axial C), with sputtering method successful manufactured 0.75 µm ZnO film and CdS, ZnS, ZnO, AlN etc. acoustoelectric materials and their film transducer. The Developments and Applications of Microelectronic Devices Are Used in the High-Frequency Ultrasonic Fields In broad applications of microelectronics in high-frequency ultrasonic treatment and processing, generally microelectronic high-frequency ultrasonic equipment or instruments are must be used. The schematic diagram of the working principle of the ultrasonic treatment with microelectronic high-frequency ultrasonic equipment is illustrated in Fig. 1.
FIG. 1 THE SCHEMATIC DIAGRAM OF WORKING PRINCIPLE OF MICROELECTRONIC HIGH-FREQUENCY ULTRASONIC EQUIPMENT
The frequency of the ultrasonic transducer is particularly high so that it could be used in surface wave techniques. In the face of the metal spraying CDS film piezoelectric transducer and in the end socket of α − SiO2 glass stick
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Advances in Microelectronic Engineering (AIME) Volume 3, 2015
spraying Ni film magneto striction type ultrasonic transducer whose two faces of the transducers are must smooth and mutual parallel and their dimensions are less than the wavelength of the acoustic waves. The ultimate frequency of these transducers approximately is 100GHz (1011 Hz ) , the wavelength of the acoustic waves is less than
0.1µ m .
When the frequency of the transducers exceeds 100GHz (1011 Hz ) , it is used in the research and
development of the fields of the phonon and the quantum of the superconductors.[6] When the frequency of the film transducers are higher, the microsonics ( 1010 − 1012 Hz ) and the light-wave ultrasonics ( 1012 − 1014 Hz ) are used. The Microelectronics General Are Used Directly the Amplifications of the High-Frequency Ultrasonics The direct amplifications of the high-frequency ultrasonics are mean, in propagation process, high-frequency ultrasonic wave could absorb the energy from the microstructure of the acoustic transmission medium continually to increase self- amplitudes. This work researches the direct amplifications of the high-frequency ultrasonics as fellows: high-frequency ultrasonic wave propagates in piezoelectric semiconductors, because their carriers (i.e. electronics and holes) suffer from the drive of applied DC (direct current) electric field, with the acoustic wave in same direction move and their movement speeds have exceeded that of the velocity of high-frequency ultrasonics which absorb the energy from the carriers (i.e. electronics and holes) of the piezoelectric semiconductors that come out the amplifications of the velocity of high-frequency ultrasonics, which have two amplifying ways: body wave and surface wave. The principle of body wave amplifiers is as shown in Fig. 2.
FIG. 2 THE SCHEMATIC DIAGRAM OF THE PIEZOELECTRIC SEMICONDUCTOR ACOUSTIC WAVE AMPLIFIER
When high-frequency electric signals are inputted a transducer and changed into same frequency ultrasonic wave to propagate in piezoelectric semiconductors, due to piezoelectric effects on the moving ultrasonic wave which could excited longitudinal electric field travelling wave, at the same time, two ends of piezoelectric semiconductors are applied in DC (or impulse) drift electric field to cause the carriers (i.e. electronics and holes) of the piezoelectric semiconductors along with the ultrasonic wave which goes forward. Because in the time and in space, the longitudinal electric field travelling waves along with the ultrasonic wave does periodic transformation for the speeds of the drift carriers (i.e. electronics and holes) possessing modulating actions to cause the drift carriers (i.e. electronics and holes) in the time and in space formation density distribution. When the speed of the drift carriers (i.e. electronics and holes) are exceeded that of the velocity of ultrasonic wave, it will occur interaction of phonon—electronic, [7] and transfer the energy from carriers (i.e. electronics and holes) to the ultrasonic wave, resulting in the amplifications of the high-frequency ultrasonic waves which by the output transducer transformed the electric signal to output. This type of amplifiers has already been successfully applied in the oscillators, filters, delay lines, etc. of electronic and optical integration systems, and varied acousto-optic devices. The High-Frequency Ultrasonics Directly Applied in the Microelectronics In this work, we have adopted electroacoustic ultrasonic equipment, where there is a key device used as an electroacoustic transducer (for receiving waves from an electrical system and delivering waves to an acoustic system, or vice versa.). Applying an alternating electric field to a piezoelectric transducer normally generates ultrasonic waves, or a magnetic field to a magnetostrictive one.[8] These techniques are capable of producing coherent pulses of ultrasound over a very wide frequency range which are directly applied in microelectronic technologies to promote theirs development, such as ultrasonic packing, ultrasonic bonding, ultrasonic welding of
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the Ni—Ti superconducting wires, etc. [9,10,11,12,13] Conclusions The present age, in nanotechnology propelling the research and development of microelectronics materials is unimaginable. The authors consider the following points needing relevant researchers to pay attention to: 1. The relationship of low dimension microelectronics material structures and nanotechnology applications are extremely important; [14] 2. The applications and developments of acoustic wave amplifiers (that is used the principle of acoustoelectric effect) are completely dependent on microelectronics material; 3. When the preparation of microelectronics material films needs the right to control theirs thickness to accurate manufacturing high-frequency ultrasonic transducers. On the other hand, with control frequency and light signal to accurate control the thickness of the microelectronics material films; 4. In microelectronics materials for the interaction of the phonon—phonon, phonon—electronic, phonon—photon and phonon—carrier, and acoustoelectric domain, acoustoelectric current, phonon echo, etc. which are deeply researched could produce some newly devices of microelectronic, optoelectronics and microwave acoustics, etc. REFERENCES
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