Fin Active Region Cut with Residue-Free Hard Mask Etching
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Solution Overview
Problem
In semiconductor fabrication, the active region cut process for multi-gate devices often results in undesirable residues of hard mask layers, leading to defects such as gate-source/drain shorts and incomplete removal of the cut portion, which can cause over-etching or under-etching issues.
Innovation Solution
A method involving a patterned masking layer with a window portion and a mask portion is used, where a first etch process exposes the third hard mask layer, followed by a second etch process to expose the second hard mask layer, and a selective third etch process removes residual second hard mask layer residues using fluoromethane, sulfur dioxide, oxygen, argon, or helium, ensuring precise removal of the cut portion and maintaining segment integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single hard mask layer is used for active region cutting, then the process is simple, but residues of the hard mask layer remain on the cut portion leading to defects
Solution Approach 1:
The single hard mask layer is divided into multiple hard mask layers (first, second, and third hard mask layers) with different compositions. Each layer serves a specific function in the etch sequence, allowing complete removal of all mask materials without residues that would cause defects.
Solution Approach 2:
The patent changes the composition parameter of each hard mask layer (silicon oxide, silicon nitride, silicon oxynitride) to create etch selectivity. This enables sequential removal of each layer through specific etch processes, ensuring complete clearance without residues.
2Reliability
If multiple etch processes are used to remove hard mask layers, then residues are eliminated, but the process complexity increases
Solution Approach 1:
The patent performs preliminary actions by forming multiple hard mask layers with different compositions before the cutting etch process. This preliminary structuring enables subsequent selective removal of each layer through tailored etch processes, ensuring complete residue elimination.
Solution Approach 2:
By changing the composition parameters of the hard mask layers, the patent creates etch selectivity that allows each layer to be removed by a specific etch process. This parameter differentiation simplifies the control of each etch step despite the multiple processes required.
3Productivity
If the active region is cut without removing hard mask residues, then the process is faster, but over-etching or under-etching issues occur
Solution Approach 1:
The patent changes the composition of each hard mask layer to create distinct etch rates and selectivities. This allows each layer to be removed by a specific etch process with controlled parameters, ensuring precise cutting without over-etching or under-etching the underlying active region.
Solution Approach 2:
The multiple hard mask layers act as intermediaries that facilitate precise control of the etch process. Each layer serves as a temporary protective barrier that is selectively removed, enabling precise definition of the cut boundary without directly exposing the active region to uncontrolled etching.
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 removes residual hard mask layer residues, preventing over-etching and ensuring satisfactory division of the active region, thereby reducing defects and ensuring the integrity of the segmented fin-shaped structures.
Implementation Method 1
A third etch process is then performed to remove any residual second hard mask layer over the cut portion and to pull back the masking layer
Data Source
AI summary
A method of the present disclosure includes forming a fin-shaped structure including a plurality of semiconductor layers, a first hard mask layer, a second hard mask layer, and a third hard mask layer, forming a patterned masking layer having a mask portion and a window portion, wherein the third hard mask layer is exposed through the window portion, performing a first etch process to expose the second hard mask layer through the window portion, performing a second etch process to etch the exposed second hard mask layer and to leave behind second hard mask layer residues, performing a third etch process to remove the second hard mask layer residues, etching the plurality of semiconductor layers in the fin-shaped structure through the window portion to divide the fin-shaped structure into a first segment and a second segment, and forming an isolation feature around the first segment and the second segment.