Plasma Etching Bias Switching for Uniform Dense and Isolation Features
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Solution Overview
Problem
Existing plasma etching technologies face challenges in achieving comparable etch rates for both isolation and dense features within a substrate, with current methods either over-etching isolation features or under-etching dense features due to differences in feature geometry and passivation layers.
Innovation Solution
The method involves generating hot neutrals by applying low bias power and low transformer coupled plasma (TCP) power, which increases the etch rate of dense features, while high bias power and high TCP power are used to etch isolation features more effectively, with a pulsing technique to manage the TCP state and bias frequency to balance etch depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high bias frequency is applied to etch isolation features, then directional ion flux is improved, but hot neutral generation deteriorates
Solution Approach 1:
The patent periodically switches bias frequency between low and high states in synchronization with TCP power pulsing. High bias frequency phases (13-60 MHz) provide directional ion flux for isolation feature etching when TCP power is high. Low bias frequency phases (1-10 MHz) generate hot neutrals for dense feature etching when TCP power is low. This periodic switching resolves the contradiction by providing each frequency regime at the appropriate time.
Solution Approach 2:
The patent dynamically modulates bias frequency in real-time based on the TCP power phase. The frequency transitions between low and high states are synchronized with TCP power pulsing, creating a dynamic control scheme that optimizes both ion directionality and neutral generation at different moments in the etching cycle, resolving the contradiction between precision and productivity.
2Productivity
If low bias frequency is applied to generate hot neutrals, then etch rate of dense features is improved, but etch rate of isolation features deteriorates
Solution Approach 1:
The patent employs periodic pulsing where low bias frequency phases are synchronized with low TCP power phases to generate hot neutrals for dense feature etching. High bias frequency phases are synchronized with high TCP power phases to provide directional ions for isolation feature etching. This periodic action ensures both feature types achieve their required etching rates at appropriate intervals.
Solution Approach 2:
The patent coordinates changes in bias frequency with changes in TCP power level. Low bias frequency (1-10 MHz) is applied during low TCP power phases to maximize hot neutral generation for dense features. High bias frequency (13-60 MHz) is applied during high TCP power phases to maximize ion directionality for isolation features. This coordinated parameter change resolves the contradiction between productivity and manufacturing precision.
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 allows for etching both isolation and dense features to achieve substantially equal etch depths by compensating for the higher etch rate of isolation features with enhanced etching of dense features, reducing passivation layer impact and improving etching efficiency.
Implementation Method 1
the drop in the electron temperature produces electron attachment reactions to create a large number of negative ions
Implementation Method 2
Positive ions that bombard the substrate with energy have collisions with the negative ions in a pre-sheath region causing neutralization reactions and producing the hot neutrals
Implementation Method 3
Positive ions that bombard the substrate with energy have collisions with the negative ions
Implementation Method 4
ions to penetrate small openings of the dense features to enhance an etch rate of the dense features
Implementation Method 5
a radio frequency (RF) generator supplies power. The power is supplied to a plasma chamber. In the plasma chamber, a substrate is being processed. When the power is supplied, plasma is generated within the plasma chamber
Implementation Method 6
the low bias frequency is applied with low transformer coupled plasma (TCP) power
Data Source
AI summary
Systems and methods for etching different features in a substantially equal manner are described. One of the methods includes applying a low frequency bias signal during a low TCP state and applying a high frequency bias signal during a high TCP state. The application of the low frequency bias signal during the low TCP state facilitates generation of hot neutrals, which are used to increase an etch rate of etching dense features compared to an etch rate for etching isolation features. The application of the high frequency bias signal during the high TCP state facilitates generation of ions to increase an etch rate of etching the isolation features compared to an etch rate of etching the dense features. After applying the low frequency bias signal during the low TCP state and the high frequency bias signal during the high TCP state, the isolation and dense features are etched similarly.