Via Anchor Profile Control with Cyclic Passivation Etching
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Solution Overview
Problem
The formation of via anchors in semiconductor devices is compromised due to grain boundaries in metal materials like cobalt, leading to structural failures and malformation, especially when subjected to vertical strain.
Innovation Solution
A multi-cycle process of alternating passivation and etching operations is employed to control via anchor profiles, preventing etchants from dispersing along grain boundaries and ensuring a desirable shape with sufficient lateral undercut, thereby maintaining structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching operations are used to form via anchors, then the via anchor formation process is simple and fast, but the via anchors become malformed and structurally compromised due to etchant dispersion along grain boundaries in metal materials like cobalt
Solution Approach 1:
The patent applies periodic action by implementing alternating cycles of passivation and etching operations. The process repeatedly switches between passivating the metal surface to prevent etchant penetration along grain boundaries, and then etching to form the via anchor profile. This periodic switching continues for multiple cycles to achieve the desired via anchor shape with proper lateral undercut while preventing structural compromise.
Solution Approach 2:
The patent applies preliminary action by performing passivation operations before each etching step. The metal surface is pre-treated with a passivation layer that prevents etchant from penetrating along grain boundaries before the etching process begins. This preliminary protective action ensures that subsequent etching operations do not cause harmful etchant dispersion along grain boundaries.
2Productivity
If the etching process is accelerated to improve productivity, then manufacturing throughput increases, but via anchor structural integrity deteriorates due to increased etchant penetration along grain boundaries
Solution Approach 1:
The periodic alternation between passivation and etching allows the process to maintain higher overall productivity while ensuring structural integrity. During etching cycles, the via anchor profile is formed efficiently, and during passivation cycles, the metal surface is protected from harmful etchant penetration. This rhythmic process ensures that even at accelerated speeds, the via anchors maintain proper structural integrity with adequate lateral undercut.
Solution Approach 2:
The patent maintains continuous useful action by ensuring that passivation and etching operations are seamlessly alternated without interruption. The passivation layer is continuously renewed before each etching step, and the etching process continuously progresses the via anchor formation. This continuous cyclic action prevents idle time while ensuring that every etching operation is preceded by protective passivation, maintaining both productivity and reliability.
3Manufacturing precision
If passivation and etching operations are alternated in multiple cycles, then via anchor profile precision and structural integrity are improved, but the manufacturing process time increases
Solution Approach 1:
The patent applies partial action by implementing a limited number of passivation-etching cycles rather than continuous indefinite cycling. The process performs just enough cycles to achieve the required via anchor profile precision and structural integrity, avoiding unnecessary additional cycles that would only increase process time without providing proportional benefits. The number of cycles is optimized to meet minimum specification requirements.
Solution Approach 2:
The patent applies parameter changes by adjusting the duration and intensity of passivation and etching operations within each cycle. By optimizing parameters such as passivation time, etching time, temperature, and chemical concentrations, the process achieves high via anchor profile precision with reduced cycle times. Parameter optimization allows each cycle to be more efficient, reducing the total number of cycles needed.
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 method improves the reliability of interconnect structures by ensuring via anchors remain securely anchored, reducing defects and enhancing the mechanical stability of vias.
Implementation Method 1
a passivation operation to prevent dispersal of the etchants along the grain boundaries
Implementation Method 2
an etching operation to achieve the desired shape of the via anchor opening
Data Source
AI summary
Improved control of via anchor profiles in metals at a contact layer can be achieved by slowing down an anchor etching process and by introducing a passivation operation. By first passivating a metallic surface, etchants can be prevented from dispersing along grain boundaries, thereby distorting the shape of the via anchor. An iterative scheme that involves multiple cycles of alternating passivation and etching operations can control the formation of optimal via anchor profiles. When a desirable anchor shape is achieved, the anchor maintains structural integrity of the vias, thereby improving reliability of the interconnect structure.