Dielectric constant

Product of relative permittivity and absolute permittivity in vacuum

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The dielectric constant is the main parameter reflecting the dielectric property or polarization property of piezoelectric materials under the action of electrostatic field, which is usually expressed by ε. Different piezoelectric elements have different requirements for the dielectric constant of piezoelectric materials. When the shape and size of the piezoelectric material are fixed, the dielectric constant ε is determined by measuring the inherent capacitance CP of the piezoelectric material.^[3]

The polarity of polymer materials can be judged according to the dielectric constant of the material. Generally, substances with a relative dielectric constant greater than 3.6 are polar substances; The materials with relative permittivity in the range of 2.8~3.6 are weakly polar materials; The material with relative dielectric constant less than 2.8 is non-polar.

Chinese name: Dielectric constant
Foreign name: permittivity
Applicable fields: electrical science

Discipline: electromagnetics 、 Dielectric Physics 、 electrodynamics 、 material science
Unit: C²/(N·M²)
Alias: Permittivity

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measuring method

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Relative permittivity ε r The electrostatic field can be used to measure the capacitance of the capacitor when there is a vacuum between the two plates C zero 。 Then, use the same distance between capacitive plates, but add dielectric between the plates to measure the capacitance C x 。 Then the relative dielectric constant can be calculated with the following formula:

ε r ＝ C x / C zero 。

Relative permittivity of dry air without carbon dioxide at standard atmospheric pressure ε r ＝1.00053。 Therefore, the capacitance of this electrode configuration in air C air Instead of C zero To measure the relative permittivity ε r It also has sufficient accuracy. (Refer to GB/T 1409-2006)

For time-varying electromagnetic field, dielectric constant of the material is related to frequency, which is usually called dielectric coefficient.^[1]

Common solvents

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The relative dielectric constant of common solvents is attached. The test frequency is 1KHz at room temperature.

Influence of temperature on dielectric constant

H two O (water) 78.5

HCOOH (formic acid) 58.5

HCON（CH three ） two (N, N-dimethylformamide) 36.7

CH three OH (methanol) 32.7

C two H five OH (ethanol) 24.5

CH three COCH three (Acetone) 20.7

n-C six H thirteen OH (n-hexanol) 13.3

CH three COOH (acetic acid or acetic acid) 6.15

C six H six (Benzene) 2.28

CCl four (carbon tetrachloride) 2.24

n-C six H fourteen (n-hexane) 1.88

n-C four H ten (No. 4 solvent) 1.78^[1]

dielectric

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Gas	Relative permittivity	solid	Relative permittivity
Water vapor Gaseous bromine helium hydrogen oxygen nitrogen argon Gaseous mercury atmosphere hydrogen sulfide vacuum Ether Liquid carbon dioxide methanol ethanol water Liquid ammonia Liquid helium Liquid hydrogen Liquid oxygen Liquid nitrogen Liquid chlorine kerosene turpentine benzene paint glycerol	one point zero zero seven eight five one point zero one two eight one point zero zero zero zero seven four one point zero zero zero two six four one point zero zero zero five one one point zero zero zero five eight one point zero zero zero five six one point zero zero zero seven four one point zero zero zero five eight five one point zero zero four one four point three three five one point five eight five thirty-three point seven twenty-five point seven eighty-one point five sixteen point two one point zero five eight one point two two one point four six five two point two eight one point nine 2~4 two point two two point two eight three three point five forty-five point eight	Solid ammonia Solid acetic acid paraffin wax polystyrene Radio porcelain UHF porcelain Barium dioxide rubber Ebonite paper Dry sand 15% wet sand (diamond) wood amber ice Shellac Celluloid Glass yellow phosphorus sulfur carbon mica Granite Marble salt Beryllium oxide polyvinyl chloride	4.01～4.1 2.0～2.3 2.4～2.6 6～6.5 7～8.5 one hundred and six 2~3 four point three two point five two point five About 2-8 two point eight two point eight 3~4 three point three 4~11 5~10 four point two 5.5～16.5 6~8 6~8 eight point three six point two seven point five nine 3.1~3.5

Relevant interpretation

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Explanation of "dielectric constant" in the reference book:

1. Also called permittivity or relative permittivity, it is an important data representing the electrical properties of dielectrics or insulating materials, commonly used ε express. It refers to the ratio of capacitance when the same substance is used as dielectric and vacuum in the same capacitor, indicating the relative ability of dielectric to store electrostatic energy in the electric field. Air and carbon disulfide Of ε The values are about 1.0006 and 2.6, respectively ε The value is larger, 83.83 at 10 ℃.

2. The dielectric constant is a measure of the capacity of a substance to increase the capacitance of a capacitor relative to vacuum. The dielectric constant increases with the increase of molecular dipole moment and polarizability. In chemistry, dielectric constant is an important property of solvent, which characterizes the ability of solvent to solvate solute molecules and isolate ions. Solvents with large dielectric constant have greater ability to separate ions, and also have strong solvation ability. For dielectric constant ε It indicates that the dielectric constants of some common solvents are shown in the following table:

Explanation of "dielectric constant" in academic literature:

1. The dielectric constant refers to the ability of the material to maintain the charge, and the loss factor refers to the size of the energy loss due to the dispersion of the material. The two parameters of an ideal substance are smaller.

Relationship between dielectric constant and frequency change

2. The dielectric constant has a complex form. The real part is called the dielectric constant, and the imaginary part is called the loss factor. Usually, the tangent value tan of the loss angle is used θ (the ratio of loss factor to dielectric constant). The larger the loss tangent, the stronger the coupling ability between the material and the microwave.

3. The dielectric constant refers to the ratio between the dielectric of a certain substance in the same capacitor and the capacitance of the capacitor in vacuum. The formula of signal propagation speed in high-frequency line is as follows: v ＝ k 。

4. For the sake of simplicity, the relative dielectric constant will be referred to as the dielectric constant later. The intensity of the reflected pulse signal is related to the wave reflection coefficient of the interface and the attenuation coefficient of the transmitted wave, and mainly depends on the conductivity and dielectric constant of the surrounding medium and reflector.^[2]

application

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Measurement Results of Mechanical Quality of Low Dielectric Constant Thin Films

In the past decade, the research on low dielectric constant materials in the semiconductor industry has increased day by day, and the types of materials are also varied. However, the application speed of these low dielectric constant materials in integrated circuit production process is far from what people think. The main reason is that many low dielectric constant materials can not meet the requirements of integrated circuit process applications. Figure 2 shows the prospect forecast of the application of low dielectric constant materials in the integrated circuit process predicted by the semiconductor industry in different periods.

As early as 1997, it was believed that in 2003, the dielectric constant (k value) of insulating materials to be used in integrated circuit technology would reach 1.5. However, as time goes by, this optimistic estimate is constantly updated. By 2003, the International Semiconductor Technology Plan (ITRS 2003 [7]) gave the application of low dielectric constant materials in integrated circuits in the next few years, and its dielectric constant range has become 2.7~3.1.

The reason why people's expectations are so different from reality is that in the integrated circuit process, low dielectric constant materials must meet many conditions, such as: sufficient mechanical strength to support the architecture of multi-layer wiring, high Young's modulus, high breakdown voltage>4MV/cm, and low leakage current<10 ^ (- 9) at 1MV/cm）、 High thermal stability>450oC, good adhesion strength, low moisture uptake, low film stress, high planarization, low coefficient of thermal expansion and compatibility with CMP process wait. Low dielectric constant materials that can meet the above characteristics are not easy to obtain. For example, the dielectric constant of thin films is often inversely proportional to the thermal conductivity. Therefore, the characteristics of low dielectric constant materials directly affect the difficulty of process integration.

Among the VLSI manufacturers, many companies such as TSMC, Motorola, AMD and NEC have selected Black Diamond from Applied Materials as the low dielectric constant material in order to develop the research of 90nm and below technologies. This material adopts PE-CVD technology [8], which is fully integrated with the existing integrated circuit production process, and introduces BLOK film as the isolation layer between low dielectric constant materials and metals, which has solved many of the problems mentioned above, and is one of the few low dielectric constant materials that have been used in the commercial production of integrated circuits.^[2]

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