Positive Substrate Biasing to Reduce Ion Damage in Plasma Processing
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Solution Overview
Problem
In CCP and ICP semiconductor processing, substrates are damaged by high-energy ions, and existing ion filters reduce both ions and radicals needed for processing, while pulsed DC bias with polarity switching increases ion damage.
Innovation Solution
A substrate processing system using a positively biased DC voltage with a triangular-pulsed DC signal, controlled by a controller to maintain a positive bias on the substrate, switching off the signal at its crest to prevent ion damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If ion filters are used to reduce ion damage, then ion damage is reduced, but radicals needed for processing are also reduced
Solution Approach 1:
The patent extracts only the harmful ions from the plasma by applying a positive DC bias to the substrate, while allowing beneficial radicals to reach the substrate surface. The positive bias creates an electric field that repels positive ions before they can bombard the substrate, but does not affect neutral radicals, thus selectively removing only the harmful component.
Solution Approach 2:
The positive DC bias voltage acts as an intermediary between the plasma and substrate, creating an electric field that mediates the interaction by repelling ions while permitting radicals to pass through to the substrate surface for processing.
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 system effectively reflects and deflects ions, reducing substrate damage while maintaining radical processing efficiency.
Implementation Method 1
The positive biased substrate (and the susceptor) may reflect and/or deflect the high energy ion bombardment to prevent any ion damage that may be inflicted on the surface of the substrate
Data Source
AI summary
A method to apply positively biased DC voltage to a substrate to reduce ion damage during substrate processing and a substrate processing system using the method is presented. For reducing ion damage from the ion bombardment, a substrate processing system may comprise a reaction chamber comprising a susceptor and a substrate process space, wherein the susceptor comprises a heater; and a direct current (DC) bias unit comprising a DC supply configured to generate a triangular-pulsed DC voltage signal and a switch disposed between the DC supply and the susceptor, the switch being configured to open or close a line from the DC supply to the susceptor, wherein the triangular-pulsed DC voltage signal has a first crest and a first frequency.