Boron-Based Dielectric Etch Stop for ULSI BEOL Interconnects
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Solution Overview
Problem
The continuous shrinking of electronic devices in ULSI circuits increases resistance and capacitance, necessitating low dielectric constant insulators with high thermal and chemical stability, particularly for BEOL interconnect structures, where existing SiCOH materials face issues with etch selectivity, chemical mechanical polishing, and thermal stability.
Innovation Solution
Development of dense composite alloy materials comprising boron or phosphorus combined with other elements, such as carbon, nitrogen, hydrogen, silicon, germanium, and fluorine, which are amorphous, thermally and chemically stable, and used as etch stops, cap materials, or CMP stop layers in ULSI BEOL interconnect structures, fabricated using PECVD and remote plasma CVD methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If SiCOH materials are used as interlayer dielectric, then dielectric constant is reduced, but etch selectivity deteriorates
Solution Approach 1:
A boron-containing dielectric material is introduced as an intermediary layer between the SiCOH interlayer dielectric and the underlying etch stop layer. This intermediate boron-containing layer provides the necessary etch selectivity difference, allowing the SiCOH material to be etched selectively while the boron-containing layer remains resistant to the etch chemistry, thus resolving the etch selectivity problem while maintaining low dielectric constant requirements.
Solution Approach 2:
The patent employs composite material structures combining SiCOH dielectric with boron-containing dielectric layers. The composite structure leverages the low dielectric constant of SiCOH while incorporating boron-containing materials that provide etch resistance, achieving both low capacitance and good etch selectivity through material composition optimization.
2Quantity of substance
If porous SiCOH dielectric is used, then dielectric constant is reduced, but chemical mechanical polishing resistance deteriorates
Solution Approach 1:
The boron-containing dielectric material serves as a mediator that provides CMP stop functionality. When a CMP process is applied to planarize the structure, the boron-containing layer acts as a stop layer that protects the underlying SiCOH dielectric from over-polishing, while still allowing the SiCOH material to maintain its low dielectric constant properties.
3Ease of manufacture
If conventional etch stop layer is used, then manufacturing is simplified, but thermal stability deteriorates
Solution Approach 1:
The boron-containing dielectric material is deposited using PECVD at controlled temperatures and pressures to achieve optimal thermal stability. By adjusting deposition parameters such as substrate temperature, pressure, and gas flow rates, the material achieves enhanced thermal stability compared to conventional etch stop layers, while maintaining manufacturing feasibility through standard semiconductor fabrication equipment.
4Loss of time
If dielectric layer thickness is increased, then signal delay is reduced, but crack propagation increases
Solution Approach 1:
The patent uses composite dielectric structures with boron-containing layers interspersed with SiCOH layers. This composite architecture allows the overall dielectric thickness to be increased for signal delay reduction while the boron-containing layers act as crack-arresting barriers, preventing crack propagation through the entire thickness and maintaining structural reliability.
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
These materials provide improved etch selectivity, thermal stability, and resistance to chemical mechanical polishing, reducing signal delays and enhancing the reliability of ULSI circuits by maintaining structural integrity during processing and use.
Implementation Method 1
fabricated using PECVD and remote plasma CVD methods
Implementation Method 2
fabricated using PECVD and remote plasma CVD methods
Data Source
AI summary
A dense boron-based or phosphorus-based dielectric material is provided. Specifically, the present invention provides a dense boron-based dielectric material comprised of boron and at least one of carbon, nitrogen, and hydrogen or a dense phosphorus-based dielectric comprised of phosphorus and nitrogen. The present invention also provides electronic structures containing the dense boron-based or phosphorus-based dielectric as an etch stop, a dielectric Cu capping material, a CMP stop layer, and/or a reactive ion etching mask in a ULSI back-end-of-the-line (BEOL) interconnect structure. A method of forming the inventive boron-based or phosphorus-based dielectric as well as the electronic structure containing the same are also described in the present invention.