Chamferless Via Structures in BEOL Interconnects
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Solution Overview
Problem
Technology scaling in integrated circuits leads to challenges such as excessive non-self-aligned via chamfering, resulting in poor yields and jagged surfaces due to difficult control over trench formation in BEOL interconnect structures.
Innovation Solution
A method involving the formation of self-aligned vias within dielectric material, plugging them with selective material, and using a protective sacrificial mask to prevent damage during trench formation, allowing for the creation of chamferless wiring vias by filling the vias and trenches with conductive material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If non-self-aligned via chamfering is performed during trench formation, then via alignment flexibility is improved, but manufacturing precision deteriorates due to excessive chamfering and jagged surfaces
Solution Approach 1:
A protective sacrificial mask is introduced as an intermediary layer deposited over the via plug material before trench formation. This mask protects the via structure during etching, preventing excessive chamfering and jagged surfaces while allowing flexible via alignment. The mask is subsequently removed to reveal the protected via structure.
Solution Approach 2:
The protective sacrificial mask is formed in advance before the trench etching process. This preliminary action ensures that the via plug material is protected during the subsequent trench formation, preventing manufacturing defects such as excessive chamfering and surface jaggedness that would otherwise occur during the etching process.
2Reliability
If protective sacrificial mask is used during trench formation, then via structure protection is improved, but process complexity increases
Solution Approach 1:
The protective sacrificial mask serves as a temporary intermediary that simplifies the overall process by enabling standard trench etching without direct contact with the via plug material. Although it adds one deposition and removal step, it eliminates the need for complex etching parameter control and reduces defects, thereby improving reliability.
Solution Approach 2:
The protective sacrificial mask is a temporary, disposable layer that is deposited, used for protection during etching, and then removed. This approach is cost-effective and simple compared to developing complex etching processes that could achieve the same protection without the mask.
3Stability of the object's composition
If etch stop layer is removed to achieve continuous dielectric material, then dielectric continuity is improved, but via critical dimension control becomes more difficult
Solution Approach 1:
The protective sacrificial mask acts as an intermediary that protects the via plug material during trench etching even when no etch stop layer is present. This enables the formation of continuous dielectric material without compromising via critical dimension control, as the mask prevents over-etching and chamfering that would otherwise occur in the absence of an etch stop layer.
Data Source
AI summary
Chamferless via structures and methods of manufacture are provided. The method includes: forming at least one self-aligned via within at least dielectric material; plugging the at least one self-aligned via with material; forming a protective sacrificial mask over the material which plugs the at least one self-aligned via, after a recessing process; forming at least one trench within the dielectric material, with the protective sacrificial mask protecting the material during the trench formation; removing the protective sacrificial mask and the material within the at least one self-aligned via to form a wiring via; and filling the wiring via and the at least one trench with conductive material.