Multi-State RF Pulsing for High Aspect Ratio Dielectric Etch
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Solution Overview
Problem
Current dielectric etch processes face challenges in achieving high aspect ratio etching with minimal bow and capping margin impact, particularly in maintaining vertical etch rates while reducing lateral etch and preventing mask facet clogging.
Innovation Solution
Implementing a multi-state pulsing method with mid-power RF pulsing during dielectric etch operations in a capacitively coupled plasma chamber, where a middle state with reduced RF power is applied to increase the critical dimension at the neck of the mask layer, and sputtering mask material downward to protect the substrate and balance mask redeposition versus neck removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high RF power is applied during dielectric etch to maintain vertical etch rate, then etch productivity is improved, but lateral etch increases causing bow in substrate layer
Solution Approach 1:
The patent applies periodic multi-state pulsing to the RF power during dielectric etch, alternating between high power states (for vertical etch rate) and low power states (for lateral etch control). This periodic modulation allows the system to achieve both high productivity and manufacturing precision by cycling through different power levels rather than maintaining a constant state.
2Productivity
If high RF power is applied to maintain etch rate, then productivity is improved, but mask material deposits excessively at neck causing clogging
Solution Approach 1:
The multi-state pulsing methodology periodically switches between high power states (which drive etch rate) and low power states (which reduce mask material deposition). This temporal separation prevents excessive mask material accumulation at the neck while maintaining overall etch productivity, resolving the contradiction between speed and clogging prevention.
3Manufacturing precision
If low RF power is applied to reduce lateral etch and bow, then manufacturing precision is improved, but vertical etch rate decreases
Solution Approach 1:
Rather than maintaining continuously low power, the system uses periodic pulsing where low power states are interspersed with high power states. The low power portions control lateral etch and bow, while the high power portions restore vertical etch rate, achieving both precision and productivity through temporal modulation.
4Productivity
If continuous high RF power is applied, then vertical etch rate is maintained, but mask selectivity deteriorates due to excessive mask material deposition
Solution Approach 1:
The periodic multi-state pulsing methodology maintains mask selectivity by introducing low power intervals that prevent excessive mask material deposition. These periodic reductions in power allow the mask to maintain its protective function while the high power intervals ensure adequate etch rate, preserving both reliability and productivity.
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 effectively minimizes lateral etch, maintains vertical etch rates, and reduces bow growth, thereby enhancing etch selectivity and aspect ratio dependent etch performance without compromising capping or causing mask facet clogging.
Implementation Method 1
a mask material that is deposited on the mask layer during the high state is sputtered towards a substrate layer of the substrate
Implementation Method 2
The RF signal passes through the components to change the RF signal. The changed RF signal is provided from the impedance match to the plasma chamber to process the wafer
Data Source
AI summary
Systems and methods for applying three or more states for achieving a high aspect ratio dielectric etch operation are described. In one of the methods, a middle state is introduced between a high state and a low state. The middle state is applied to both a source radio frequency (RF) generator and a bias radio frequency (RF) generator. During the middle state, RF power is maintained to be between a high amount of RF power associated with the high state and a low amount of RF power associated with the low state to achieve the high aspect ratio dielectric etch.