Bi-layer Mask CD Control via COS Plasma Etching
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Solution Overview
Problem
The challenge in semiconductor device production is to control the critical dimension (CD) of etch features with improved resolution, precision, and accuracy, especially as feature size is reduced to increase density, which existing methods struggle to achieve effectively.
Innovation Solution
A method involving a stack of mask layers, including a functionalized organic mask layer and an intermediate mask layer, where the intermediate mask layer is opened using a plasma process with carbonyl sulfide (COS) gas, and the etch layer is etched using a plasma processing chamber with controlled gas flow and RF power, allowing for precise control of CD features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If feature size is reduced to increase density, then manufacturing precision and resolution are improved, but etch selectivity and process control become more difficult
Solution Approach 1:
The mask structure is divided into multiple functional layers: a first mask layer for initial patterning, a second mask layer for CD control during etching, and a third mask layer for final pattern definition. This segmentation allows each layer to perform its specific function independently, enabling precise CD control while managing the complexity of small feature fabrication.
Solution Approach 2:
The solution transitions from controlling CD through single-layer mask parameters to controlling CD through the vertical stacking of multiple mask layers. By adding the dimension of layer stacking, the patent achieves precise CD control during etching while maintaining manageable process complexity through selective etching of individual layers.
2Measurement precision
If feature size is reduced to increase density, then resolution is improved, but etch selectivity deteriorates
Solution Approach 1:
Different mask layers are assigned different material compositions and etch selectivity characteristics tailored to their specific functions. The second mask layer uses materials with high etch selectivity relative to the underlying layer, while the first and third layers use materials optimized for their respective patterning needs. This local optimization of material properties maintains high etch selectivity even as feature sizes are reduced.
Solution Approach 2:
The mask stack employs composite material structures where each layer is made of different materials with complementary properties. This composite approach allows the system to achieve both high resolution for small features and maintained etch selectivity through the combined properties of the layered material structure.
3Manufacturing precision
If feature size is reduced to increase density, then accuracy is improved, but process control becomes more difficult
Solution Approach 1:
The first mask layer is used to pre-pattern and define the basic feature locations before the main etching process. The second mask layer is then applied and selectively removed to control the final CD during etching. This preliminary action of pre-patterning simplifies the overall process control by separating the pattern definition step from the CD control step, making each individually more manageable.
Solution Approach 2:
The second mask layer acts as an intermediary between the first and third mask layers during the etching process. It mediates the CD control function by being selectively etched away to expose precise amounts of the underlying layer, thereby controlling the final feature dimensions without requiring direct manipulation of the other mask layers.
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 enables precise control of CD features, enhancing resolution and accuracy, and allows for the shrinking of feature sizes while maintaining or improving etch selectivity, effectively addressing the need for increased density in semiconductor devices.
Implementation Method 1
The intermediate mask layer is opened by selectively etching the intermediate mask layer with respect to the patterned photoresist mask
Implementation Method 2
flowing an open gas comprising COS, forming a plasma
Implementation Method 3
The functionalized organic mask is opened. The functionalized organic mask layer opening comprises flowing an open gas comprising COS, forming a plasma
Implementation Method 4
flowing an etching gas comprising COS, forming a plasma and stopping the flowing of the etching gas
Implementation Method 5
The etch layer is etched
Implementation Method 6
at least one electrode for providing power to the plasma processing chamber enclosure for sustaining a plasma
Data Source
AI summary
A method for controlling critical dimension (CD) of etch features in an etch layer disposed below a functionalized organic mask layer disposed below an intermediate mask layer, disposed below a patterned photoresist mask, which forms a stack is provided. The intermediate mask layer is opened by selectively etching the intermediate mask layer with respect to the patterned photoresist mask. The functionalized organic mask layer is opened. The functionalized organic mask layer opening comprises flowing an open gas comprising COS, forming a plasma, and stopping the flowing of the open gas. The etch layer is etched.