Multi-layer Mask Etch Selectivity and Roughness Control
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Solution Overview
Problem
Conventional photolithography processes for controlling critical dimensions in integrated circuits face challenges in achieving precise etch selectivity and reducing over/under etching, pattern bridges, and line-width roughness, especially due to loading differences and wavy features in multi-layer masks.
Innovation Solution
A multi-layer mask structure is developed, comprising a bottom layer, a first middle layer with high Si—CH3 bond content silicon oxycarbide (SiOC) material, and a second middle layer with reduced Si—CH3 bond content, along with a UV treatment to enhance etch selectivity and mechanical strength, and a top layer for patterning, which improves etch rates and reduces loading effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional tri-layer mask is used for controlling critical dimensions, then the basic patterning function is achieved, but over/under etching, pattern bridges, and line-width roughness occur due to loading differences
Solution Approach 1:
The mask structure is segmented into multiple layers with different materials and functions. The patent uses a multi-layer mask comprising a first mask layer, a second mask layer, and a third mask layer, where each layer has specific etch selectivity characteristics. This segmentation allows different layers to handle different etching tasks, reducing loading effects and improving etch uniformity across the wafer.
Solution Approach 2:
The patent employs composite mask materials with different etch selectivities. Specifically, the mask structure includes layers made of different materials (such as silicon nitride, silicon oxide, and photoresist) that exhibit distinct etch rates when exposed to the same etchant. This composite approach enables precise control over etching depth and prevents over/under etching by allowing selective removal of mask layers.
2Manufacturing precision
If a multi-layer mask is used to improve etch selectivity, then pattern precision is enhanced, but the device complexity and process difficulty increase
Solution Approach 1:
Different regions of the mask structure are assigned different material compositions and thicknesses to achieve local optimization. The patent describes a mask where the first mask layer, second mask layer, and third mask layer have varying material properties and thicknesses tailored to specific etching requirements. This local quality approach allows precise control over etch selectivity in different mask regions without requiring a completely complex multi-layer structure throughout.
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
The solution effectively reduces over/under etching, pattern bridges, and line-width roughness, enhancing the formation of conductive interconnects with low RC delays and improved leakage performance, thereby increasing wafer yield and precision in semiconductor manufacturing.
Implementation Method 1
along with a UV treatment to enhance etch selectivity and mechanical strength
Implementation Method 2
The photoresist is exposed using a photolithography mask, which includes opaque patterns and transparent patterns
Data Source
AI summary
A method includes forming a multi-layer mask over a dielectric layer. Forming the multi-layer mask includes forming a bottom layer over the dielectric layer. A first middle layer is formed over the bottom layer. The first middle layer includes a first silicon-containing material. The first silicon-containing material has a first content of Si—CH3 bonds. A second middle layer is formed over the first middle layer. The second middle layer includes a second silicon-containing material. The second silicon-containing material has a second content of Si—CH3 bonds less than the first content of Si—CH3 bonds.