High Power Plasma Generation for Sputtering Adhesion
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Solution Overview
Problem
Existing sputter coating processes face challenges in achieving high adhesion of films and preventing target poisoning during reactive sputtering, while also limiting the simultaneous use of power supply for etching due to the need for high power discharge pulses and low voltage initial ionization steps.
Innovation Solution
A method to generate a highly ionized plasma by applying a high energy, high power pulse of short duration (less than 500µs) directly from a neutral gas, without going through low ionized or arc discharge stages, using a magnetically enhanced sputtering apparatus with a high energy pulse power source to create a plasma volume cross section increase with constant current density and ionization degree, ensuring efficient sputter deposition and etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a high power discharge pulse is applied to ionize the gas rapidly, then the ionization speed is improved, but the adhesion of the film deteriorates and target poisoning occurs
Solution Approach 1:
The ionization process is divided into two distinct phases: a first period with low voltage (below breakdown voltage) for gradual ionization and adhesion improvement, followed by a second period with high voltage for rapid ionization. This segmentation allows each phase to optimize its function without compromising the other.
Solution Approach 2:
During the first period, a low voltage is applied to perform preliminary ionization of the gas before the high power discharge. This preliminary action creates a foundation of ionized particles that enables the subsequent high power pulse to achieve full ionization without causing target poisoning or poor adhesion.
2Reliability
If a low voltage is applied during the first period for initial ionization, then the film adhesion is improved, but the power supply cannot be used for etching simultaneously
Solution Approach 1:
The power supply operates in periodic cycles, alternating between a first period for deposition (low voltage) and a second period for etching (high voltage). This periodic action allows the system to achieve both good film adhesion during deposition and effective etching during the high power phase, maximizing overall power supply utilization.
Solution Approach 2:
The system dynamically switches between different voltage modes based on the process requirements. The power supply adapts its output characteristics between deposition and etching modes, allowing simultaneous optimization of both functions that would be impossible with a static voltage setting.
3Quantity of substance
If a high power discharge pulse is used to create highly ionized plasma, then the plasma ionization is improved, but arc discharge is generated which damages the target
Solution Approach 1:
A low voltage is applied during the first period to perform preliminary ionization of the gas, creating a population of ionized particles before the high power pulse. This preliminary action reduces the likelihood of arc discharge during the subsequent high power phase by ensuring more uniform plasma distribution.
Solution Approach 2:
The ionization process continues uninterrupted across both periods, with the first period establishing a foundation of ionized particles that carries through into the second period. This continuous action ensures smooth transition to high ionization without abrupt changes that could trigger arc discharge.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in improved adhesion of deposited coatings, enhanced target utilization, and prevention of electrode poisoning, making the process suitable for both sputter deposition and etching without the drawbacks of arc or low ionized plasma stages.
Implementation Method 1
accelerating free electrons to ionize atoms of the neutral gas and to generate secondary electrons
Implementation Method 2
deviate the direction of flow of accelerated electrons by a magnetic field
Implementation Method 3
accelerating ionized gas atoms towards the cathode thereby building a first ionization wave, sputtering target material from a target in electrical connection with the cathode
Data Source
Figure 1~2
Figure 3a~3b
Figure 4a~4b
AI summary
A method of generating a highly ionized plasma in a plasma chamber (2), comprises the steps of: a. providing a neutral gas to be ionized in the plasma chamber (2) at pressure below 50 Pa; b. supplying at least one high energy high power electrical pulse with power equal or larger than 100 kW and energy equal or larger than 10 J, to at least one magnetron cathode in connection with a target in the plasma chamber (2) c. producing a highly ionized plasma from the neutral gas in a plasma volume such that the plasma volume cross section increases during a current rise period, d. sputtering atoms from the target with the highly ionized plasma, e. ionizing at least part of the sputtered atoms.