Rounded Mask Structures for Recess Fill in Semiconductor Devices
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Solution Overview
Problem
As semiconductor process nodes shrink, the decreased processing window complicates the formation of integrated circuit components, such as conductive features, due to increased complexity in fabricating smaller structures.
Innovation Solution
The method involves forming a half-inverse mask over a dielectric layer, followed by a conformal mask layer, and then etching to create a full-rounded mask with rounded surfaces, which allows for the formation of recesses in the dielectric layer without pinch-off effects, enabling better fill properties for conductive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional masking processes are used at small process nodes, then manufacturing complexity increases, but recess fill properties deteriorate due to pinch-off effects
Solution Approach 1:
The masking process is divided into multiple stages: forming a first mask layer with initial pattern, depositing a second mask layer conformally, and performing selective etching to create the final rounded mask. This segmentation allows each stage to optimize for its specific function, avoiding pinch-off while maintaining manufacturability at small nodes
Solution Approach 2:
The patent employs rounded mask features with curved surfaces instead of sharp corners. The conformal deposition and selective etching processes create masks with rounded top surfaces and sidewalls, which prevent pinch-off effects during subsequent recess formation, thereby improving recess fill properties for conductive materials
2Area of moving object
If process node is shrunk to increase integration density, then integration density improves, but processing window decreases
Solution Approach 1:
The patent changes key process parameters including mask layer materials (e.g., mandrel layer, conformal mask layer), deposition thicknesses, and etching conditions to optimize the processing window for small process nodes. These parameter adjustments enable precise control over mask formation and recess etching, maintaining manufacturing precision despite node shrinkage
Solution Approach 2:
The conformal mask layer is deposited and patterned before the actual recess formation. This preliminary masking structure with rounded features is prepared in advance to prevent pinch-off during the subsequent conductive material fill process, ensuring proper recess fill properties are achieved from the outset
3Area of moving object
If tight pitches and high aspect ratios are used to increase integration density, then integration density improves, but recess fill properties worsen due to pinch-off effects
Solution Approach 1:
Rounded mask features with curved surfaces are created through conformal deposition and selective etching. These rounded features prevent pinch-off effects during recess formation, ensuring proper fill properties even when tight pitches and high aspect ratios are employed to achieve high integration density
Solution Approach 2:
The mask structure is designed with different local geometries: rounded top surfaces and curved sidewalls in critical areas to prevent pinch-off, while maintaining tight pitch dimensions elsewhere to achieve high integration density. This local optimization of geometry allows both goals to be achieved simultaneously
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 enhances recess fill properties, particularly in small technologies with tight pitches and high aspect ratios, by providing a greater spacing at the recess bottom, preventing pinch-off and improving conductivity.
Implementation Method 1
simultaneously etching the inverse mask and vertical portions of the mask layer. The etching the inverse mask is at a greater rate than the etching the vertical portions of the mask layer
Implementation Method 2
forming a mask layer conformally over the inverse mask
Data Source
AI summary
A method, e.g., of forming and using a mask, includes forming an inverse mask over a dielectric layer; forming a mask layer conformally over the inverse mask; removing horizontal portions of the mask layer; and after removing the horizontal portions, simultaneously etching the inverse mask and vertical portions of the mask layer. The etching the inverse mask is at a greater rate than the etching the vertical portions of the mask layer. The etching the inverse mask removes the inverse mask, and the etching the vertical portions of the mask layer forms a mask comprising rounded surfaces distal from the dielectric layer. Recesses are formed in the dielectric layer using the mask. Locations of the inverse mask correspond to fewer than all locations of the recesses.