SiCN Etch Stop Adhesion via In Situ SiN Layer
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Solution Overview
Problem
The use of silicon carbide (SiCN) as an etch stop layer in semiconductor devices leads to poor adhesion with overlying dielectric materials, resulting in blistering and reduced device reliability and yield, due to its low bonding capabilities with materials like organosilicate glass (OSG) or fluorosilicate glass (FSG).
Innovation Solution
A method involving the in situ formation of a thin silicon nitride (SiN) layer on top of the SiCN layer within a deposition chamber, using a carbon-containing gas and silane/nitrogen flow, or converting a portion of the SiCN layer to SiN using an oxygen plasma, to create an adhesion layer that enhances bonding with the dielectric layers, while maintaining a low dielectric constant to reduce parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If silicon carbide (SiCN) is used as an etch stop layer to reduce parasitic capacitance, then parasitic capacitance is reduced, but adhesion to dielectric materials deteriorates causing blistering
Solution Approach 1:
A thin adhesion layer (5-20 nm) of silicon nitride (SiN) or silicon oxynitride (SiOxNy) is inserted between the SiCN etch stop layer and the dielectric layer (OSG or FSG). This intermediary layer serves as a bonding bridge that adheres to both the SiCN below and the dielectric above, eliminating blistering while preserving the low parasitic capacitance of the SiCN layer.
Solution Approach 2:
The structure employs a composite material system consisting of SiCN etch stop layer + thin SiN/SiOxNy adhesion layer + dielectric layer. This composite structure combines the low dielectric constant of SiCN with the excellent adhesion properties of silicon nitride/oxynitride, achieving both low parasitic capacitance and reliable bonding to dielectric materials.
2Reliability
If a thick adhesion layer is formed to improve bonding, then adhesion is improved, but parasitic capacitance increases
Solution Approach 1:
The adhesion layer is applied locally and selectively only where needed at the interface between SiCN and dielectric, with a precisely controlled thin thickness of 5-20 nm. This localized thin layer provides sufficient adhesion improvement while minimizing its contribution to parasitic capacitance, unlike a thick uniform layer would.
Solution Approach 2:
The thickness parameter of the adhesion layer is optimized to 5-20 nm, which is sufficiently thick to provide adhesion bridging but thin enough to maintain low parasitic capacitance. The dielectric constant of the adhesion layer material is also selected (SiN: ~7, SiOxNy: ~4-6) to balance adhesion performance with capacitance contribution.
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 approach effectively improves adhesion between the SiCN and dielectric layers, reducing blistering and maintaining low parasitic capacitance, thereby enhancing device reliability and yield by achieving a thin, uniform adhesion layer that controls the bulk dielectric constant.
Implementation Method 1
using an oxygen plasma to convert a portion of the SiCN layer to SiN
Implementation Method 2
A silicon nitride (SiN) layer is formed in situ on the SiCN layer, within the deposition chamber
Data Source
AI summary
One aspect of the invention provides a method of forming a semiconductor device (100). One aspect includes forming transistors (120, 125) on a semiconductor substrate (105), forming a first interlevel dielectric layer (165) over the transistors (120, 125), and forming metal interconnects (170, 175) within the first interlevel dielectric layer (165). A carbon-containing gas is used to form a silicon carbon nitride (SiCN) layer (180) over the metal interconnects (170, 175) and the first interlevel dielectric layer (165) within a deposition tool. An adhesion layer (185) is formed on the SiCN layer (180), within the deposition tool, by discontinuing a flow of the carbon-containing gas within the deposition chamber. A second interlevel dielectric layer (190) is formed over the adhesion layer (185).