EBB 443:
Mon: 11:00am-13:00pm BSK2
Wed: 11:00am-13:00pm BSK2
Topics:
Types of electroceramics
Dielectric ceramics
Piezoelectric ceramics
Ferroelectrics
Magnetic ceramics
Photonic ceramics
Processing, testing and application of electroceramics
The term Electroceramic is used to describe ceramic materials that have been specially formulated for specific electrical, magnetic, or optical properties. Their properties can be tailored to operation as insulators, ferroelectric materials, highly conductive ceramics, electrodes as well as sensors and actuators.
The applications of ceramics in the electronics industry can be divided into two groups:
- for interconnection and packaging of semiconductor circuits
- in circuit components such as capacitors and sensors.
1 comment:
NAME: HOR PAI HOOI
MATRIX NO.:87719
2. Most ceramic materials are insulator (high resistivity). However, it can be changed to semiconductor or conductor. Explain briefly!
ANSWER Question 2:
Ceramic is compound between metallic and nonmetallic elements for which the interatomic bonds are either totally ionic or predominantly ionic but having some covalent character but mostly they are insulator which has high resistivity. The ceramic which acts as semiconductor are neither good electrical conductors nor good electrical insulators. Semiconductor or ceramic that exist as insulator material has a large band gap where the band gap is the difference between the valence and conduction bands. Therefore it only allows few electrons to excite from the valence band into the conduction band. However, a ceramic can be a better conductor of electricity than metal. The ceramic can be changed to conductor or semiconductor due to the ionic conduction phenomenon. The movement of some negatively or positively charged ions which “hop” from lattice site to lattice site under the influence of an electric field causing the ionic conduction. The ceramics contain a density, n of mobile charge carriers, each carrying charge Q, is situated in an electric field E, the charge carriers experience a force causing them to accelerate but, because of the interaction with the lattice owing to thermal motion of the atoms or to defects, they quickly reach a terminal velocity, referred to as drift velocity v. They must have sufficient energy to pass over an “energy barrier” so that ions can move through a crystalline solid. Therefore the ceramic insulator can be change to semiconductor or conductor after the ions pass over the energy barrier. Besides due to elevated temperature the electrons gain enough energy to jump from valance into the conduction band. Thus the ceramic can be changed to semiconductor or conductor
6. What high dielectric constant (high-k) ceramics? Explain briefly the advantages these materials
ANSWER Question 6:
Dielectric constant is relative electrical permittivity of a material as compared to a perfect vacuum. It indicates the ability of a material to store electrical energy when a voltage is applied to it. The high dielectric constant (high-k) ceramic has high electrical permittivity which can store more electrical energy when voltage is applied to it. They are use as the multilayer capacitance and can produces capacitor with small size and large capacitance.
The high dielectric constant (high-K) ceramic has a dielectric constant greater than about 5. A conductive layer is formed over the high K dielectric material layer. Silicon dioxide has been used as a gate oxide material for decades. As transistors have decreased in size, the thickness of the silicon dioxide gate dielectric has steadily decreased to increase the gate capacitance and thereby drive current and device performance. Replacing the silicon dioxide gate dielectric with a high-K material allows increased gate capacitance without the concomitant leakage effects.
The advantages of high dielectric constant (high-k) ceramic are capable having a sustained high insulation resistance under high temperature operating conditions. Besides it has high crystallization onset temperature and posses a very good electric behavior with more desirable threshold voltages and it posses high interface quality. The high dielectric constant ceramic can be easily integrated into a manufacturing process. Furthermore the high dielectric constant (high-K) band alignment to silicon can alter leakage current, film morphology, thermal stability, maintenance of a high mobility of charge carriers in the channel and minimization of electrical defects in the film or interface. The high dielectric constant ceramic arises from the joint contribution of low-frequency modes with a small dipole (related to the movement of oxygen atoms against the metal ones) and of high frequency polar modes (issued from the movement of the oxygen atom cage) and reliability characteristics can be improved.
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