Plasma Processing Apparatus DC Bias Control
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Solution Overview
Problem
Current plasma etching technologies face challenges in achieving high selectivity etching for Low-k films, particularly with SiC layers, and struggle with maintaining plasma resistance properties of resist layers and preventing electrode deposition, while also dealing with non-uniform plasma density and etching rate issues.
Innovation Solution
A plasma processing apparatus and method that utilize a power supply to apply DC or AC voltage to electrodes, controlling self-bias voltage and plasma sheath length to enhance plasma density and uniformity, and include a control unit to manage application voltage, current, and power for optimal etching conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If RF power for plasma generation is increased to improve etching rate, then productivity increases, but electrode deposition increases and process stability deteriorates
Solution Approach 1:
The invention changes the electrical parameter by applying DC voltage to the upper electrode in addition to RF power, creating a biased plasma environment. This parameter change allows independent control of plasma generation (via RF) and ion acceleration (via DC bias), resolving the contradiction by enabling high etching rates without the harmful deposition effects of excessive RF power alone
2Manufacturing precision
If DC voltage is applied to increase plasma density, then etching selectivity improves, but device complexity increases
Solution Approach 1:
The upper electrode serves multiple functions: it generates plasma via RF power and simultaneously accelerates ions via DC voltage. This multi-functionality achieves improved etching selectivity without requiring separate dedicated electrodes or complex additional components, thereby limiting the increase in device complexity
3Manufacturing precision
If photo-resist thickness is reduced to achieve smaller patterns, then manufacturing precision improves, but plasma resistance decreases causing surface roughness
Solution Approach 1:
The invention creates a non-uniform plasma environment with higher ion energy near the substrate surface through DC bias. This local quality change in plasma distribution provides gentler, more controlled etching at the resist-mask interface, protecting thin photo-resist layers from damage while maintaining precise pattern formation
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
The solution achieves high selectivity etching for Low-k films, maintains plasma resistance of resist layers, prevents electrode deposition, and ensures uniform etching rates by controlling plasma density and potential, thereby improving micro-fabrication precision and reducing surface roughness.
Implementation Method 1
generate plasma of the process gas between the first electrode and second electrode
Implementation Method 2
apply a DC voltage or AC voltage to the first electrode or second electrode
Implementation Method 3
an RF (radio frequency) is applied to one of the electrodes to form an electric field between the electrodes. The process gas is turned into plasma by the RF electric field
Implementation Method 4
cause an absolute value of a self-bias voltage Vdc on a surface of an application electrode to be large enough to obtain a predetermined sputtering effect on the surface
Data Source
AI summary
A plasma etching apparatus includes an upper electrode and a lower electrode, between which plasma of a process gas is generated to perform plasma etching on a wafer W. The apparatus further comprises a cooling ring disposed around the wafer, a correction ring disposed around the cooling ring, and a variable DC power supply directly connected to the correction ring, the DC voltage being preset to provide the correction ring with a negative bias, relative to ground potential, for attracting ions in the plasma and to increase temperature of the correction ring to compensate for a decrease in temperature of a space near the edge of the target substrate due to the cooling ring.