Pulsed Plasma Etching With Gas Replenishment
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Solution Overview
Problem
Plasma etch processes face limitations in etching semiconductor structures with variable spacing, leading to micro-loading issues where etch rates vary with pattern density, resulting in over-etching and detrimental undercutting, especially at small dimensions and high aspect ratios.
Innovation Solution
A pulsed plasma etch process with pulsed reaction gas replenishment is employed, where the reaction gas is replenished during the OFF state of the plasma cycle, maintaining a homogeneous plasma and reducing etch by-product interference, thereby achieving consistent etch rates across different density regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous plasma etching is used, then high productivity is achieved, but micro-loading effects cause non-uniform etch rates across different density regions
Solution Approach 1:
The patent applies periodic pulsed plasma etching cycles with alternating high-power and low-power phases. During high-power phases, aggressive etching occurs to maintain productivity, while low-power phases allow reaction gas replenishment and byproduct removal to equalize etch rates across different density regions, eliminating micro-loading effects
Solution Approach 2:
The patent dynamically changes plasma parameters by adjusting radio frequency power between high and low states, and by pulsing reaction gas flow rates. These parameter variations enable the system to achieve both high etch rates during high-power phases and uniform etching across density regions during low-power phases with gas replenishment
2Manufacturing precision
If over-etch is applied to complete etching in high density regions, then all structures are fully etched, but detrimental undercutting occurs in low density regions
Solution Approach 1:
The pulsed etching process with alternating high and low power phases prevents undercutting by removing reaction byproducts during low-power phases. This periodic action ensures that etching proceeds uniformly across all density regions without the need for excessive over-etch, as the low-power phases allow volatile byproducts to evacuate and reaction gas to replenish, maintaining clean etch fronts
Solution Approach 2:
The patent converts the potentially harmful accumulation of reaction byproducts into a beneficial control mechanism. By intentionally introducing low-power phases where byproduct accumulation is minimized and gas replenishment occurs, the system uses the presence of byproducts as an indicator to trigger corrective action (gas pulsing), transforming the harmful effect into a self-regulating mechanism that prevents undercutting
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 significantly reduces micro-loading effects, ensuring that all regions of a semiconductor stack are etched simultaneously, minimizing over-etching and undercutting, and maintaining a consistent etch rate regardless of structure density.
Implementation Method 1
a lithography/etch process is typically employed. State-of-the-art etch processes include etching a semiconductor stack with a system comprising an ionized gas, i.e. a plasma
Implementation Method 2
A pulsed plasma process is then applied to remove a second portion of the semiconductor layer. The pulsed plasma process comprises a plurality of duty cycles, wherein each duty cycle represents the combination of an ON state and an OFF state of the plasma
Data Source
AI summary
A pulsed plasma system with pulsed reaction gas replenish for etching semiconductor structures is described. In an embodiment, a portion of a sample is removed by applying a pulsed plasma etch process. The pulsed plasma etch process comprises a plurality of duty cycles, wherein each duty cycle represents the combination of an ON state and an OFF state of a plasma. The plasma is generated from a reaction gas, wherein the reaction gas is replenished during the OFF state of the plasma, but not during the ON state. In another embodiment, a first portion of a sample is removed by applying a continuous plasma etch process. The continuous plasma etch process is then terminated and a second portion of the sample is removed by applying a pulsed plasma etch process having pulsed reaction gas replenish.