Hydrocarbon Passivation for Partially Etched Contact Structures
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Solution Overview
Problem
Current semiconductor manufacturing techniques face challenges in accurately placing contacts between the first metal layer and silicon layers with gates and source/drains due to incomplete etching and electric leakage issues, primarily caused by the exposure of spacer material and inadequate passivation of cap layers during the etching process.
Innovation Solution
A method involving the in-situ deposition of a fluorine-free, non-conformal carbon-containing mask over the semiconductor wafer, which is selectively thicker on the nitride regions than on the oxide regions, allowing for precise etching and effective passivation without introducing fluorine-related etching issues, thereby minimizing critical dimension reduction and incomplete etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorocarbon-based passivation is used to protect cap layers during etching, then passivation coverage is improved, but fluorine release promotes cap etching and reduces passivation efficacy
Solution Approach 1:
The patent removes fluorine from the passivation layer composition entirely, using only carbon-containing materials (hydrocarbons) deposited via PECVD. This extraction of the harmful fluorine element eliminates the source of fluorine release that promotes cap etching, while maintaining passivation protection through carbon-based film formation.
Solution Approach 2:
The patent changes the chemical composition parameters of the passivation layer from fluorocarbon-based to pure hydrocarbon-based. By altering the precursor material from CF4 or C4F6 to hydrocarbon gases and adjusting deposition parameters, the passivation layer achieves different chemical properties that eliminate fluorine-related harmful effects while maintaining protective function.
2Ease of manufacture
If conventional photolithography placement is used for contact holes, then manufacturing simplicity is maintained, but contact placement accuracy deteriorates leading to electric leakage
Solution Approach 1:
The patent performs preliminary etching of contact holes through the mask layer before final photolithography patterning. This preliminary action creates initial contact openings that guide subsequent photolithography alignment, ensuring accurate contact placement relative to gates and S/D regions while maintaining manufacturing simplicity through a sequential process approach.
Solution Approach 2:
The patent segments the contact hole formation process into multiple stages: preliminary etching through mask, photolithography patterning, and completion etching. This segmentation allows each step to optimize for its specific function, with preliminary etching establishing geometric constraints that improve final placement accuracy without requiring advanced photolithography tools.
3Reliability
If passivation deposition is performed to protect cap layers, then cap protection is improved, but opening critical dimension reduces due to film deposition
Solution Approach 1:
The patent implements non-conformal passivation where the carbon-based film thickness varies spatially across the substrate. The passivation layer is thinner or absent in contact hole opening regions and thicker over cap layer regions, providing localized protection where needed while minimizing impact on opening critical dimensions. This is achieved through controlled PECVD deposition parameters and substrate positioning.
4Speed
If higher energy ions are used to activate passivation film during etch steps, then etch activation is improved, but fluorine unbinding increases and reacts with cap nitride
Solution Approach 1:
The patent converts the harmful effect of high-energy ion impact by changing the passivation material composition. Instead of using fluorocarbon-based passivation where ion impact releases harmful fluorine, the patent uses hydrocarbon-based passivation where ion impact does not release harmful elements. The high-energy ions still provide effective activation and etch enhancement without generating fluorine-related harmful reactions with cap nitride.
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 accurate and complete etching of small features with reduced electric leakage and improved contact resistance, maintaining a robust etch process while avoiding the tradeoffs associated with conventional fluorocarbon-based passivation methods.
Implementation Method 1
An in-situ a fluorine-free, non-conformal, carbon-containing mask is deposited over the first region and the second region, wherein the carbon-containing mask is selectively deposited on the second region at a second thickness with respect to the first region at a first thickness
Implementation Method 2
The first region is further etched in-situ to etch the at least one partial feature and wherein the carbon-containing mask acts as an etch mask for the second region
Implementation Method 3
The first region is selectively etched with respect to the second region to form at least one partial feature in the first region
Data Source
AI summary
A method for selectively etching at least one feature in a first region with respect to a second region of a stack is provided. The first region is selectively etched with respect to the second region to form at least one partial feature in the first region, the at least one partial feature having a depth with respect to a surface of the second region. An in-situ a fluorine-free, non-conformal, carbon-containing mask is deposited over the first region and the second region, wherein the carbon-containing mask is selectively deposited on the second region at a second thickness with respect to the first region at a first thickness, the second thickness being greater than the first thickness. The first region is further etched in-situ to etch the at least one partial feature and wherein the carbon-containing mask acts as an etch mask for the second region.