Electrostatic Chuck Voltage Control for Wafer Stability
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Solution Overview
Problem
Plasma processing apparatuses face issues with wafer peeling due to insufficient chuck force, wafer cracking from excessive chuck force, uneven plasma processing, abnormal electric discharge, and power loss caused by excessive supply voltage, as well as concerns related to dielectric strength and costs.
Innovation Solution
A plasma processing apparatus with a control unit that adjusts the electrostatic chuck power supply output voltage based on calculated self-bias voltage, using either VESC+ or VESC- to maintain stable electrostatic chuck force while preventing abnormal electric discharge, and stopping gas supply during step transitions to avoid wafer peeling or flying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high electrostatic chuck voltage is applied to ensure sufficient chuck force, then wafer peeling is prevented, but wafer cracking occurs due to excessive force
Solution Approach 1:
The patent applies dynamic control of electrostatic chuck voltage by switching between VESC+ and VESC- based on real-time monitoring of plasma potential and self-bias voltage. This dynamic adjustment ensures the chuck force remains within safe limits while preventing wafer peeling, resolving the contradiction between holding stability and structural integrity.
Solution Approach 2:
The system incorporates feedback mechanisms that monitor plasma potential, self-bias voltage, and chuck force in real-time. Based on this feedback, the control unit dynamically adjusts the electrostatic chuck voltage to maintain optimal holding force without exceeding wafer strength limits, thus preventing both peeling and cracking.
2Reliability
If high electrostatic chuck voltage is applied to prevent wafer peeling, then wafer holding stability improves, but power consumption increases
Solution Approach 1:
The patent implements dynamic voltage adjustment by switching between VESC+ and VESC- modes based on plasma conditions. This dynamic control reduces power consumption by applying only the necessary chuck force required to prevent peeling, rather than continuously applying high voltage.
Solution Approach 2:
The system changes the electrostatic chuck voltage parameter dynamically based on plasma potential and self-bias voltage conditions. By adjusting this parameter to match actual process requirements, the system maintains wafer holding stability while minimizing power consumption.
3Power
If positive ESC voltage is used for plasma generation, then plasma generation is effective, but abnormal electric discharge occurs due to plasma potential rise
Solution Approach 1:
The patent dynamically switches between VESC+ and VESC- modes based on real-time monitoring of plasma potential and self-bias voltage. This dynamic control prevents abnormal electric discharge by avoiding conditions that lead to excessive plasma potential rise, while maintaining effective plasma generation through appropriate voltage selection.
Solution Approach 2:
The system uses feedback from plasma potential and self-bias voltage measurements to control the ESC voltage. When plasma potential rises to dangerous levels, the feedback mechanism triggers a switch to VESC- mode, preventing abnormal electric discharge while maintaining plasma generation efficiency.
4Force
If VESC+ is used for electrostatic chuck, then chuck force is sufficient, but plasma potential rises causing abnormal discharge
Solution Approach 1:
The patent implements dynamic switching between VESC+ and VESC- based on plasma potential conditions. This dynamic control allows the system to use VESC+ when it provides sufficient chuck force without causing harmful discharge, and switch to VESC- when plasma potential becomes dangerous, thus resolving the contradiction between chuck force and discharge prevention.
Solution Approach 2:
The feedback mechanism monitors plasma potential and self-bias voltage to determine when to switch between VESC+ and VESC-. This feedback control ensures that VESC+ is used only when it provides adequate chuck force without causing abnormal discharge, and VESC- is used when plasma potential becomes excessive.
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
Achieves stable electrostatic chuck force without wasting power, preventing wafer peeling, cracking, and abnormal electric discharge, while ensuring dielectric strength and cost-effectiveness by dynamically controlling the electrostatic chuck voltage and gas supply.
Implementation Method 1
a method called 'electrostatic chuck' or 'electrostatic attraction' is widely used for holding a wafer in the processing chamber. The electrostatic chuck (electrostatic attraction) is a method of holding a wafer on an electrode (sample stage) by electrostatic force which is caused by the potential difference between the wafer and the electrode.
Implementation Method 2
Average electric potential of the wafer 113 caused by application of output of a biasing high-frequency power supply 110 to the electrode 108 via a capacitor will hereinafter be referred to as 'self-bias voltage' (Vdc).
Implementation Method 3
a plasma processing apparatus including a processing chamber in which a sample is processed by plasma generated therein, a first radio-frequency power supply which supplies a first radio-frequency electric power for generating the plasma in the processing chamber
Data Source
AI summary
A plasma processing apparatus includes a plasma-generation high-frequency power supply which generates plasma in a processing chamber, a biasing high-frequency power supply which applies high-frequency bias electric power to an electrode on which a sample is placed, a monitor which monitors a peak-to-peak value of the high-frequency bias electric power applied to the electrode, an electrostatic chuck power supply which makes the electrode electrostatically attract the sample, a self-bias voltage calculating unit which calculates self-bias voltage of the sample by monitoring the peak-to-peak value of the high-frequency bias electric power applied to the electrode, and an output voltage control unit which controls output voltage of the electrostatic chuck power supply based on the calculated self-bias voltage.