BCl3-Based Dry Etching of Hafnium Dioxide High-k Dielectrics
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Solution Overview
Problem
Conventional etching processes for hafnium containing high-k layers, such as HfO2, often damage poly-Si and SiO2 layers due to inadequate selectivity, as seen in HBr/Cl2-based chemistries, which fail to effectively differentiate between HfO2 and these materials during semiconductor manufacturing.
Innovation Solution
A dry plasma etching method using a process composition comprising BCl3 and an additive gas, such as an oxygen-containing, nitrogen-containing, or hydrocarbon gas, is employed to improve etch selectivity between HfO2 and poly-Si and SiO2 layers, minimizing damage to the gate structure during pattern transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If HBr/Cl2-based etching chemistry is used, then etching of HfO2 layer is achieved, but selectivity between HfO2 and poly-Si/SiO2 layers deteriorates causing damage to gate structure
Solution Approach 1:
The patent changes the chemical parameters of the etching process by replacing HBr/Cl2-based chemistry with BCl3-based chemistry combined with specific additive gases (CF4, C4F8, or O2). This parameter change fundamentally alters the etching mechanism to achieve superior selectivity between HfO2 and poly-Si/SiO2 layers, preventing gate structure damage while maintaining effective HfO2 removal.
Solution Approach 2:
The patent introduces additive gases (CF4, C4F8, or O2) as intermediaries that work synergistically with BCl3 to enhance etch selectivity. These intermediary substances modify the plasma chemistry to selectively etch HfO2 while protecting poly-Si and SiO2 layers, thereby resolving the selectivity issue without requiring complete process redesign.
2Productivity
If conventional etching processes are used, then pattern transfer is achieved, but damage to underlying layers increases
Solution Approach 1:
The patent modifies the etching process parameters by using BCl3 as the primary gas with specific additives and controlling substrate temperature above 30°C. These parameter changes enable effective pattern transfer while minimizing damage to underlying poly-Si and SiO2 layers through improved chemical selectivity and reduced ion bombardment damage.
Solution Approach 2:
The patent converts the potentially harmful effect of plasma exposure into a beneficial selective etching process. By using BCl3-based chemistry with additives, the plasma that would normally cause non-selective damage is transformed into a highly selective etching tool that removes HfO2 precisely while leaving underlying layers intact, thus converting a harmful process into a beneficial one.
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 method achieves enhanced etch selectivity between HfO2 and poly-Si and SiO2, allowing for precise pattern etching of high-k dielectric layers while preserving the integrity of underlying layers, thereby reducing damage and improving semiconductor device fabrication outcomes.
Implementation Method 1
forming a plasma from the process composition in the plasma processing system
Data Source
AI summary
A method and system for etching a hafnium containing material using a boron tri-chloride (BCl3) based process chemistry is described. A substrate having a hafnium containing layer, such as a layer of hafnium dioxide (HfO2) is subjected a dry etching process comprising BCl3 and an additive gas including: an oxygen-containing gas, such as O2; or a nitrogen-containing gas, such as N2; or a hydrocarbon gas (CxHy), such as CH4; or a combination of two or more thereof.