Pulsed Power Plasma Cleaning for Electrostatic Chuck Protection
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Solution Overview
Problem
Conventional capacitively coupled plasma etching apparatuses face issues with erosion of the electrostatic chuck during plasma cleaning, leading to shortened lifespan and metal contamination due to ion sputtering, which complicates the cleaning process and requires expensive post-processing for deposition of protective films.
Innovation Solution
A plasma etching apparatus with a controller that modulates the high frequency power supply to alternate between plasma generation and non-generation states during plasma cleaning, reducing ion sputtering on the electrostatic chuck by pulsing the power at specific frequencies and duties, thereby preventing erosion and contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous high frequency power is supplied to generate plasma for cleaning, then cleaning performance is improved, but ion sputtering erodes the electrostatic chuck shortening its lifespan
Solution Approach 1:
The patent applies periodic pulsed power supply to the lower electrode, alternating between plasma generation mode (with cleaning gas flow) and plasma suppression mode (with reduced power). This periodic action allows cleaning to occur during plasma generation phases while reducing ion sputtering damage during low-power phases, thereby extending electrostatic chuck lifespan while maintaining cleaning effectiveness.
2Reliability
If high frequency power is continuously applied for plasma generation, then cleaning effectiveness is improved, but metal contamination from electrostatic chuck erosion increases
Solution Approach 1:
By periodically switching between high-power plasma generation mode and low-power plasma suppression mode, the system achieves effective cleaning during high-power phases while minimizing metal ion ejection and contamination during low-power phases. The pulsed operation reduces cumulative erosion and metal particle generation.
3Duration of action of stationary object
If high frequency power is modulated to reduce ion sputtering, then electrostatic chuck protection is improved, but plasma generation efficiency may be reduced
Solution Approach 1:
The control unit modulates high frequency power between two levels: a first level sufficient for plasma generation during cleaning phases, and a second level that suppresses plasma to protect the electrostatic chuck. This periodic modulation optimizes the balance between cleaning efficiency and chuck protection by timing power delivery to match process requirements.
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 method effectively suppresses ion sputtering on the electrostatic chuck, extending its lifespan and preventing metal contamination while maintaining the cleaning performance, allowing for efficient and cost-effective plasma cleaning without the need for additional protective film deposition.
Implementation Method 1
a high frequency voltage is applied between the upper and the lower electrode. Accordingly, an electric field is generated between the electrodes by the high frequency voltage to accelerate electrons and, thus, the impact ionization occurs between the accelerated electrons and a processing gas, thereby generating a plasma
Implementation Method 2
the electrostatic chuck includes a dielectric layer having a DC electrode therein which is provided on an upper surface (mounting surface) of the lower electrode and a preset DC voltage is applied to the DC electrode to attract a substrate by a Coulomb force generated between the substrate and the dielectric layer
Implementation Method 3
the substrate is indirectly cooled by supplying a coolant having an adjusted temperature from a chiller unit to a coolant path provided inside the lower electrode to be circulated and a heat transfer gas such as He gas to a backside of the substrate through the lower electrode
Implementation Method 4
a plasma cleaning performed by decomposing a cleaning gas by a plasma
Implementation Method 5
ion sputtering, which complicates the cleaning process and requires expensive post-processing for deposition of protective films
Data Source
AI summary
A plasma etching apparatus includes an electrostatic chuck and an etching gas supply unit for supplying an etching gas to a processing space between a first and a second electrode to perform a dry etching process on the target object. The apparatus further includes a cleaning gas supply unit for supplying a cleaning gas to a processing space; a first high frequency power supply unit for supplying a first high frequency power to the first electrode; and a controller for controlling the first high frequency power supply unit such that a first period during which the first high frequency power has a first amplitude that generates the plasma and a second period during which the first high frequency power has a second amplitude that generates substantially no plasma are alternately repeated at a specific cycle when the plasma cleaning is performed in the processing chamber without the target object.