Amorphous Carbon Hard Mask with Oxide Buffer for Contact Holes
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Solution Overview
Problem
The existing methods for forming self-aligned contact holes in semiconductor devices using amorphous carbon as a hard mask face challenges such as polymer generation during etching, which can damage the amorphous carbon layer and disrupt the hard mask, leading to defects and incomplete processes.
Innovation Solution
A method involving the use of an oxide-based material as a top hard mask over the amorphous carbon layer, which reduces damage and prevents lifting of the hard mask during etching by forming a buffering oxide layer beneath the amorphous carbon, allowing for smoother and more effective contact hole formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If amorphous carbon is used as a hard mask material, then low deposition temperature and low-k value are achieved, but polymer generation during etching causes damage to the hard mask and device defects
Solution Approach 1:
A silicon oxynitride (SiON) layer is introduced as an intermediary protective layer between the amorphous carbon hard mask and the etching environment. This SiON layer acts as a buffer that prevents direct interaction between etching polymers and the amorphous carbon, thereby protecting the hard mask from damage while allowing the low-temperature deposition benefits of amorphous carbon to be retained.
Solution Approach 2:
The hard mask structure is transformed from a single-material amorphous carbon layer to a composite structure consisting of amorphous carbon combined with a silicon oxynitride (SiON) layer. This composite structure combines the low-k and low-temperature deposition advantages of amorphous carbon with the protective properties of SiON, preventing polymer-induced damage during etching.
2Reliability
If SiON layer is used as top hard mask over amorphous carbon, then etching protection is provided, but the SiON layer remains after etching processes causing device defects
Solution Approach 1:
The etching parameters are optimized to selectively remove the silicon oxynitride (SiON) protective layer after it has served its protective function during the main etching process. By adjusting etching conditions, the SiON layer is completely removed while the amorphous carbon hard mask remains intact, eliminating residual layer defects without compromising the protective function during etching.
3Reliability
If multiple layers (amorphous carbon, SiON, anti-reflective coating) are deposited, then comprehensive protection is achieved, but process complexity increases
Solution Approach 1:
The silicon oxynitride (SiON) protective layer and the anti-reflective coating layer are merged into a single deposition step, eliminating the need for separate deposition processes. This integration maintains the protective function of the SiON layer while reducing process complexity by combining two layers that can be formed 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 minimizes damage to the amorphous carbon layer and reduces defects by preventing polymer-induced lifting, enabling more reliable and efficient self-aligned contact hole formation.
Implementation Method 1
forming a buffering oxide layer beneath the amorphous carbon, allowing for smoother and more effective contact hole formation
Implementation Method 2
selectively etching the amorphous carbon layer and the oxide layer to form a mask pattern
Data Source
AI summary
A method for forming a contact hole of a semiconductor is provided. Conductive patterns are formed over a substrate. An insulation layer is formed over the substrate to bury the conductive patterns. A hard mask including an amorphous carbon layer and an oxide based layer are formed in sequential order over the insulation layer and the conductive pattern. The amorphous carbon layer and the oxide layer are selectively etched to form a mask pattern. The insulation layer is etched using the mask pattern as a mask to form a contact hole.