WF6 Plasma Etching with Protective Metal Deposition on Masks
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Solution Overview
Problem
The challenge in semiconductor manufacturing is the decreased selectivity to metal-containing masks during etching processes, particularly as feature sizes become finer, leading to reduced etch rates and increased feature failures.
Innovation Solution
An etching method involving a substrate with a silicon-containing layer and a metal-containing mask, where a process gas including a metal-containing gas such as WF6 is used to generate plasma, allowing for the formation of a protective metal layer on the mask, thereby improving selectivity by preferentially depositing on the mask rather than the etching target layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal-containing gas (WF6) is added to the etching gas to form a conductive layer on the mask, then selectivity to the metal-containing mask is improved, but the process complexity increases due to additional gas supply requirements
Solution Approach 1:
The patent applies preliminary action by forming a protective layer on the mask surface before the main etching process begins. The metal-containing gas (WF6) is supplied during an initial phase to deposit a conductive protective layer on the mask, which prevents mask etching during subsequent etching of the insulating film. This preliminary protective action ensures mask integrity throughout the etching process.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the composition and flow rate of the process gas. Specifically, WF6 gas is added to the etching gas mixture at controlled flow rates (e.g., 5-50 sccm) to modify the plasma chemistry. This parameter adjustment enables selective deposition of metal on the mask surface while maintaining etching capability on the insulating film, thereby improving mask selectivity.
2Manufacturing precision
If the etching process is optimized for finer features, then manufacturing precision is improved, but selectivity to the metal-containing mask decreases leading to feature failures
Solution Approach 1:
The patent introduces an intermediary substance (metal-containing protective layer) that mediates between the etching plasma and the mask. This protective layer acts as a buffer that protects the mask from direct plasma exposure during etching of fine features. The intermediary layer prevents harmful interactions between the high-energy plasma and the mask, thereby preventing feature failures while maintaining precision.
Solution Approach 2:
The patent applies beforehand cushioning by depositing a protective metal layer on the mask prior to and during the etching process. This protective layer serves as a cushion that absorbs the impact of plasma ions and prevents direct damage to the mask structure. The cushioning effect is particularly important for fine features where mask damage would lead to feature failures.
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 method significantly enhances the selectivity to metal-containing masks, improving the etch rate and reducing feature failures by forming a thicker protective layer on the mask, thus addressing the selectivity issues in finer feature semiconductor processes.
Implementation Method 1
etching, with plasma generated from the process gas, the etching target layer through the opening
Implementation Method 2
forming a protective layer comprising a metal on a top of the mask and on the side wall of the mask
Data Source
AI summary
An etching method includes providing a substrate including an etching target layer including a silicon-containing layer, and a mask located on the etching target layer, comprising a metal, and having an opening defined by a side wall of the mask, supplying a process gas including a metal-containing gas, and etching, with plasma generated from the process gas, the etching target layer through the opening while forming a protective layer comprising a metal on a top of the mask and on the side wall of the mask.