Plasma Etching Bias Cycling for Sidewall Charge Neutralization
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Solution Overview
Problem
Current plasma processing techniques face challenges in controlling ion transport and minimizing defects due to net charge accumulation on high aspect ratio feature sidewalls during semiconductor manufacturing.
Innovation Solution
The method involves ramping a sheath voltage during the first phase of a plasma process to bias the substrate, followed by a second phase without substrate biasing to remove sidewall charge buildup, using varying source power cycles to manage ion energy and charge neutralization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If substrate biasing is applied during plasma etching to control ion transport, then etching precision is improved, but sidewall charge buildup occurs causing defects
Solution Approach 1:
The patent applies periodic pulsed biasing where the substrate bias is turned on during etching phases and turned off during charge neutralization phases. This periodic switching allows the system to achieve precise ion transport control when needed while eliminating sidewall charge buildup at other times, resolving the contradiction between etching precision and charge accumulation defects
Solution Approach 2:
The patent implements a preliminary charge neutralization step before etching begins, and periodically during the process. By proactively removing sidewall charges before they can cause defects like twisting and bowing, the system maintains etching precision without suffering from charge buildup harmful effects
2Productivity
If continuous substrate biasing is used to maintain ion acceleration, then etching rate is improved, but defect formation increases due to charge accumulation
Solution Approach 1:
The patent uses pulsed biasing with alternating etching phases and charge neutralization phases. During etching phases, substrate biasing is applied to maintain high ion acceleration and etching rate. During neutralization phases, biasing is removed to eliminate charge accumulation. This periodic approach maintains high productivity while preventing defect formation
Solution Approach 2:
The patent maintains continuous progress by alternating between productive etching phases with biasing and brief neutralization phases without biasing. The overall process continues without interruption, achieving both high etching rate and low defect formation through this continuous alternating action
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 enhances ion transport efficiency, reduces defects such as twisting, bowing, and notching, and allows for more precise etching of high aspect ratio features in semiconductor devices.
Implementation Method 1
A combination of source power (SP) applied to a coupling element and bias power (BP) applied to a substrate holder can be used to generate and direct charged species from plasma
Implementation Method 2
biasing a substrate by ramping a sheath voltage during a first phase of a plasma process
Implementation Method 3
bombarding a feature of a substrate with ions from a first plasma generated with a first source power cycle from a power source, the ions being accelerated towards the substrate by ramping up a DC voltage provided to a boundary electrode above the substrate
Data Source
AI summary
A method for plasma processing includes biasing a substrate by ramping a sheath voltage during a first phase of a plasma process and removing sidewall charge buildup on a feature of the substrate in an absence of substrate biasing during a second phase of the plasma process.