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Bias brief introduction

Oct 26, 2018

Negative bias

Providing particle energy;

Heating effect on substrate;

Removing the gas and oil adsorbed on the substrate can improve the bonding strength of the film layer.

Activated matrix surface;

The Arc Ion Plating (Arc Ion Plating) the large particles have purification effect;

Classification of bias

According to the waveform, it can be divided into:

Dc bias

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Dc pulse bias

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Dc stack pulse bias

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Bipolarity pulse bias

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Switch the high voltage/low voltage when the power is used

Many biased power supplies need to switch between high and low voltage at work, high pressure gear is used for bombardment and cleaning, and low pressure gear is used for depositing film. The output coordinate chart of the two types of power supplies is described below:

Power output diagram of high voltage (HV) and low voltage (LV) needs to be switched

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No need to switch high - low gear stepless continuous adjustment output

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Adjustable parameter of bias power supply

Bias amplitude

Duty ratio

frequency

waveform

Important characteristics of a bias power supply

Number of arcing extinguishers per minute (in units of arcing extinguishers per minute)

Sensitivity to detect large arc (mJ/kW detectable arc energy)

Load characteristics of bias

The work load of bias is plasma. When dc bias is used, the plasma shows resistance. When the pulse bias is applied, the plasma exhibits resistance + capacity, which can be considered as series connection of resistance and capacitance. The nature of capacity generation is caused by the plasma sheath on the substrate surface.

Comparison of dc bias and pulse bias

Conventional arc ion plating is to control ion bombardment energy by applying dc negative bias on the substrate. This deposition process has the following disadvantages:

The high temperature of matrix is not conducive to the deposition of hard film on the substrate with low tempering temperature.

High-energy ion bombardment can not easily synthesize high-reactive threshold films by increasing the ion bombardment energy.

Dc bias arc ion plating process, in order to prevent the continuous bombardment by ion of the substrate surface caused by the substrate temperature is exorbitant, mainly to reduce the sedimentary power, shorten time, USES the method of intermittent deposition to reduce the deposition temperature, these measures can generally called energy control 'although this method can reduce the deposition temperature, but also make some performance of the film, but also reduces the production efficiency and the stability of the film quality, therefore, difficult to popularization and application.

Pulsed bias arc ion plating process, due to the ion bombardment substrate surface is discontinuous pulse way, so by adjusting the duty ratio of pulse bias, can change the matrix between the internal and surface temperature gradient, and then change the matrix between the internal and surface hot isostatic compensation effect, achieve the purpose of regulating the deposition temperature. In this way, the height of the biased pulse can be adjusted separately from the workpiece temperature (with little or no influence on each other), the high-energy ion bombardment effect can be obtained by high pressure pulse to improve the structure and performance of the film, and the total heating effect of ion bombardment can be reduced by reducing the duty ratio to reduce the deposition temperature.

The effect of bias on the membrane layer

Bias effects on membrane layer mechanism is very complicated, many companies and research institutions have done a lot of research, of different membrane layer and different equipment, affect the way and the results are quite different, the following is a list of some of the major impact, can be used according to their own process, observation, can quickly understand the effects of bias on membrane layer.

Membrane structure, crystalline structure orientation and tissue structure

Deposition rate

Large particle cleaning

Film hardness

Film density

Surface morphology

Internal stress


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