Four-State RF Pulsing for High Aspect Ratio Etch Control
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Solution Overview
Problem
Current high aspect ratio contact (HARC) etch processes face a trade-off between bow control, selectivity, and not-open margin, which becomes challenging as device sizes shrink and pitch sizes reduce, limiting further improvements in etch selectivity versus process margin trade-offs.
Innovation Solution
Implementing a four-state RF pulsing scheme with specific power levels and duty cycles for bias and source signals, allowing for enhanced flexibility in managing the trade-offs by incorporating a fourth state that addresses issues related to bowing, selectivity, and not-open margin in high aspect ratio structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If three-state RF pulsing is used, then the process can maintain basic etch functionality, but it cannot simultaneously optimize bow control, selectivity, and not-open margin as pitch shrinks
Solution Approach 1:
The RF pulsing cycle is segmented into four distinct states instead of three, with each state having specific bias and source power level combinations. This segmentation allows independent optimization of different etch aspects: state 1 for high etch rate, state 2 for bow control, state 3 for selectivity, and state 4 for not-open margin, thereby resolving the contradiction between adaptability and manufacturing precision.
Solution Approach 2:
The invention changes the parameter space by introducing a fourth state with specific bias and source power level combinations that are distinct from the traditional three states. The bias power levels (first bias power level, second bias power level, third bias power level, fourth bias power level) and source power levels are independently controlled, allowing fine-tuning of etch parameters to simultaneously achieve bow control, selectivity, and not-open margin optimization.
2Productivity
If high bias power is applied to achieve high etch rate, then productivity improves, but bow control deteriorates
Solution Approach 1:
The invention employs periodic RF pulsing with four distinct states where high bias power (state 1) is applied intermittently rather than continuously. This periodic application allows high etch rates during state 1 while subsequent states (particularly state 2 with lower bias power) provide bow control, thus resolving the contradiction between productivity and shape control through time-dependent parameter modulation.
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 four-state RF pulsing scheme enables simultaneous improvement in selectivity and etch profile, breaking the limitations of three-state pulsing, and allows for higher aspect ratio etching at lower pitch sizes with improved device yield.
Implementation Method 1
The plasma can be generated using specific reactant gases that will cause constituents of the plasma to interact with the material(s) to be removed/modified from the semiconductor wafer... The plasma is generated by using radiofrequency signals to energize the specific reactant gases.
Implementation Method 2
The plasma is generated by using radiofrequency signals to energize the specific reactant gases. These radiofrequency signals are transmitted through the plasma processing volume that contains the reactant gases
Data Source
AI summary
A method for performing an etch process on a substrate includes applying a bias signal and a source signal to an electrode of a plasma processing system. The bias signal and the source signal are pulsed RF signals that together define a repeated pulsed RF cycle, wherein each pulsed RF cycle sequentially includes a first state, a second state, a third state, and a fourth state. The power level of the bias signal in the first state is greater than in the third state, which is greater than in the second state, which is greater than in the fourth state. The power level of the source signal in the first state is greater than in the third state, which is greater than in the second state, which is greater than in the fourth state.