Selective Hardmask Rework via CMP and Wet Etching
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Solution Overview
Problem
In semiconductor fabrication, reworking patterned stacks that are dimensionally out of specification is challenging due to the difficulty in selectively removing patterned films from stacks with similar dielectric materials, as conventional methods like plasma etching and chemical mechanical polishing (CMP) often damage the underlying interlevel dielectric (ILD) layer.
Innovation Solution
A method involving sequential removal of hardmask layers using chemical mechanical polishing (CMP) and selective wet etching to expose and preserve the ILD layer, allowing for the reformation of a reworked pattern stack without damaging the underlying dielectric materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional plasma etching or CMP is used to remove patterned layers, then layer removal is achieved, but the underlying ILD layer is damaged
Solution Approach 1:
The removal process is segmented into multiple selective steps: first removing the top dielectric hardmask layer, then the metal hardmask layer, and finally the bottom dielectric hardmask layer. Each step uses a different removal method (CMP or wet etching) optimized for that specific layer, preventing damage to the ILD layer by stopping before reaching it.
Solution Approach 2:
The invention changes the removal parameters by using selective wet etching chemistry that etches metal hardmask layers at different rates than dielectric layers, and using CMP with controlled selectivity to remove dielectric hardmask layers without etching the ILD. This parameter control enables selective removal while protecting the ILD.
2Manufacturing precision
If selective wet etching is used to remove metal hardmask layers, then selective removal is achieved, but similar dielectric materials may be damaged
Solution Approach 1:
The invention uses wet etching chemistry with carefully controlled parameters (etchant composition, temperature, time) that creates high selectivity between metal hardmask layers and dielectric layers. The etching parameters are optimized to etch metal at a much higher rate than dielectric materials, enabling selective removal while minimizing dielectric damage.
3Productivity
If all layers are removed by CMP, then complete pattern removal is achieved, but resource waste and cost increase
Solution Approach 1:
Instead of using CMP to remove all layers uniformly, the invention segments the removal process by layer type, using selective wet etching for metal layers and CMP only for dielectric hardmask layers when necessary. This selective approach removes only the required layers with appropriate methods, reducing unnecessary material removal and associated costs.
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 successful rework of semiconductor devices with minimal damage to the underlying layers, reducing resource waste and costs, and ensuring the integrity of the ILD layer for further processing.
Implementation Method 1
polishing the pattern stack to remove a top hardmask layer of the pattern stack
Implementation Method 2
Each hardmask layer of the pattern stack is selectively wet etched to remaining layers of the pattern stack and the ILD layer
Data Source
AI summary
A method for reworking a semiconductor device includes, in a pattern stack formed on an interlevel dielectric (ILD) layer, polishing the pattern stack to remove a top hardmask layer of the pattern stack. Each hardmask layer of the pattern stack is selectively wet etched to remaining layers of the pattern stack and the ILD layer. A reworked pattern stack is reformed on the ILD layer.