Multi-State RF Pulsing for Mask Shape and Etch Selectivity
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Solution Overview
Problem
Current RF pulsing technologies struggle to balance etch selectivity versus process margin trade-offs, particularly in high aspect ratio etching, leading to issues such as mask faceting, bowing, and clogging, which are exacerbated by shrinking device sizes and reduced pitch sizes.
Innovation Solution
Implementing a multi-state RF pulsing regime with an intermediate state based on source power only, combined with traditional two-state on-off pulsing, to control mask shape and improve the selectivity versus process margin trade-off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional two-state RF pulsing is used, then etch rate is improved, but mask shape control deteriorates causing necking and faceting
Solution Approach 1:
The RF pulsing cycle is segmented into three distinct states: State1 (high bias/high source power for etching), State2 (zero bias/low source power for mask shape control), and State0 (low bias/low source power for passivation). This segmentation allows independent optimization of etching and mask shape control functions, resolving the contradiction between etch rate and mask shape control.
Solution Approach 2:
State2 acts as an intermediary state between the high-power etching state (State1) and the low-power passivation state (State0). This intermediate state with zero bias and low source power specifically targets mask shape control by removing excess polymer deposits without causing mask faceting, thereby mediating between the competing requirements of high etch rate and good mask shape control.
2Length of moving object
If high aspect ratio etching is pursued, then device scaling is enabled, but process margin deteriorates due to necking and clogging
Solution Approach 1:
State2 is introduced as a preliminary action between the high etching rate state (State1) and the passivation state (State0). By actively managing mask shape at the neck region before the passivation step, excess polymer deposits are removed in advance, preventing necking and clogging that would otherwise limit aspect ratio and reduce process margin.
Solution Approach 2:
The invention changes the RF power parameters dynamically through three distinct states. State2 specifically uses zero bias power and low source power to selectively remove polymer deposits from the mask neck region. This parameter modulation enables high aspect ratio etching by maintaining open necks throughout the etch process, thereby improving process margin and reliability.
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 enables improved etch profile control, maintaining adequate process margin while enhancing selectivity, reducing necking, and facilitating higher aspect ratio etching without device failure.
Implementation Method 1
applying source RF power to an electrode of the plasma processing system; and applying bias RF power to the electrode
Implementation Method 2
multi-state RF pulsing regime with an intermediate state based on source power only, combined with traditional two-state on-off pulsing
Implementation Method 3
the second state is configured to effect passivation of the feature on the surface of the substrate
Implementation Method 4
the first state is configured to effect etching of a feature on a surface of the substrate
Data Source
AI summary
A method for performing an etch process on a substrate in a plasma processing system, including: applying source RF power and bias RF power to an electrode; wherein the source RF power and the bias RF power are pulsed signals that together define a plurality of multi-state pulsed RF cycles, each cycle having a first state, second state, and third state; wherein the first state is defined by the source RF power having a first source RF power level and the bias RF power having a first bias RF power level; wherein the second state is defined by the source RF power and the bias RF power having substantially zero power levels; wherein the third state is defined by the source RF power having a second source RF power level less than the first source RF power level, and the bias RF power having a substantially zero power level.