Semiconductor Gate Stack Etching Using Ammonium Hydroxide
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional word line etching processes in semiconductor device fabrication face challenges due to uneven topography, leading to bridge problems, shorting, and device leakage, resulting in high defect density and unreliability.
Innovation Solution
A method involving sequential formation of insulating, conductive, and silicide layers, followed by precise etching steps using a patterned hard masking layer and etchants like ammonium hydroxide to form a gate stack, which includes partial removal of layers to prevent shorting and leakage, and a third etching step to form a silicide neck.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional WL etching processes are used on uneven topography, then etching can be completed, but bridge problems occur with WL to WL shorting due to under-etching and device leakage due to over-etching
Solution Approach 1:
The etching process is divided into multiple sequential steps: a first etching step to perform the main etching, followed by a second etching step using ammonium hydroxide to remove residue. This segmentation allows each step to be optimized independently, preventing both under-etching and over-etching while maintaining reliability.
Solution Approach 2:
A patterned hard masking layer is introduced as an intermediary element between the etching tools and the underlying layers. This masking layer provides a precise etch stop and protects critical areas, enabling accurate etching even on uneven topography and preventing bridge formation and shorting.
2Ease of manufacture
If conventional WL etching processes are used, then etching can be performed, but device defect density increases due to bridge problems and shorting
Solution Approach 1:
The patterned hard masking layer serves as a mediator that simplifies the overall manufacturing process by providing a robust etch stop and protection mechanism. While it adds a layer to the process, it eliminates the need for complex process adjustments and reduces defect density through consistent, controlled etching.
Solution Approach 2:
The invention changes the etching parameters by using ammonium hydroxide in the second etching step. This chemical parameter change enables selective removal of residue material with high precision, significantly reducing device defect density while maintaining ease of manufacture through a well-defined chemical process.
3Productivity
If conventional WL etching processes are used on uneven topography, then etching can be completed, but device leakage and failure problems occur due to over-etching
Solution Approach 1:
The etching process is segmented into a first main etching step and a second residue removal step using ammonium hydroxide. This segmentation allows the first step to maintain high productivity by removing the majority of material, while the second step ensures reliability by precisely removing residue without causing over-etching and device failure.
Solution Approach 2:
The patterned hard masking layer acts as an intermediary that protects underlying structures during etching. It provides a reliable etch stop that prevents over-etching and device failure, while allowing the etching process to proceed efficiently through the unprotected areas.
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 reduces device defects, enhances reliability, and improves performance by preventing shorting and leakage, ensuring accurate etching and reducing critical dimension loss.
Implementation Method 1
a second etching step is performed to remove residue of any remaining conductive layer not covered by the hard masking layer after the first etching step. The second etching step is performed with an etchant comprising ammonium hydroxide.
Data Source
AI summary
A method of fabricating a semiconductor device is provided. The method of fabricating the semiconductor device comprises providing a substrate. Next, an insulating layer, a conductive layer and a silicide layer are formed on the substrate in sequence. Next, a hard masking layer is formed on the silicide layer exposing a portion of the silicide layer. A first etching step is performed to remove the silicide layer and the underlying conductive layer which are not covered by the hard masking layer, thereby forming a gate stack. And next, a second etching step is performed to remove any remaining conductive layer not covered by the hard masking layer after the first etching step. The second etching step is performed with an etchant comprising ammonium hydroxide.