Self-Aligned Direct Pattern Contacts for Semiconductor Scaling
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Solution Overview
Problem
Advanced technology nodes in semiconductor manufacturing face challenges such as contact shorting between drain/source regions and gate structures due to overlay or misalignment issues, and scaling problems that lead to increased parasitic capacitance and resistance, particularly with the integration of super via structures.
Innovation Solution
The implementation of self-aligned direct pattern contacts with re-entrant profiles and metal to via negative enclosures, which allow for single metal layer contact planes, enabling super via-like structure integration without compromising resistance or capacitance, and relaxing tip-to-tip requirements, thus avoiding extra wire runs and improving yield and scaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional patterning processes are used with overlay or misalignment issues, then manufacturing is simpler, but contact shorting between drain/source regions and gate structures occurs
Solution Approach 1:
The contact structure uses self-aligned formation where the contact opening is automatically positioned relative to the gate structure through the spacer formation process. The spacer material is deposited conformally on the gate structure sidewalls, and the contact opening is formed by etching through the spacer, ensuring automatic alignment without requiring additional overlay precision in subsequent patterning steps.
Solution Approach 2:
The spacer structure is formed beforehand on the gate structure sidewalls before contact opening formation. This preliminary spacer formation establishes the contact position and prevents misalignment, as the contact opening is subsequently formed by etching through the pre-positioned spacer material rather than requiring precise alignment in a later patterning step.
2Ease of manufacture
If etching processes are used for forming interconnect contacts, then contact formation is achieved, but sidewall corrosion of gate structures occurs exposing metallization
Solution Approach 1:
The spacer structure serves as an intermediary protective layer between the etching process and the gate structure sidewalls. The spacer material is selectively etched to form the contact opening, while the gate structure metallization is protected from direct etching exposure. This intermediary spacer layer prevents etchant contact with the gate metallization, avoiding sidewall corrosion and exposing no unwanted metallization.
3Length of moving object
If tip-to-tip configurations are used at contact space equivalent to one contacted poly pitch, then scaling is achieved, but metal extensions are required adding parasitic capacitance
Solution Approach 1:
The contact structure extends vertically in the third dimension by forming a re-entrant profile that goes down into the interlevel dielectric layer. This vertical extension allows the contact to reach the underlying conductive layer directly beneath the gate structure, eliminating the need for lateral metal extensions. The contact space can be minimized to one contacted poly pitch while avoiding additional parasitic capacitance from extra wire runs.
4Adaptability or versatility
If super via structure integration is attempted, then alternative contact formation is achieved, but extra fabrication processes are required hurting scaling
Solution Approach 1:
The contact structure formation is merged with the existing spacer formation and etching processes. The same spacer deposition and etching steps used for other structures in the process flow are utilized to form the contact opening. This integration allows super via-like structure formation without requiring separate dedicated fabrication processes, maintaining process simplicity and supporting scaling.
5Reliability
If large cross-section vias are used for super via structure, then metal fill is ensured without airgaps, but parasitic capacitance and resistance increase due to extra metal material
Solution Approach 1:
The contact structure uses a re-entrant profile parameter change, where the opening cross-section varies with depth. The opening is wider at the top for easy access and narrower at the bottom where it contacts the underlying layer. This parameter change allows adequate metal fill without requiring excessive metal material, as the re-entrant profile provides sufficient metal volume for reliable filling while minimizing the overall metal quantity and associated parasitic capacitance and resistance.
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to middle of the line self-aligned direct pattern contacts and methods of manufacture. The structures described herein include: at least one gate structure with a metallization and source/drain regions; a source/drain contact in electrical connection with the source/drain regions, respectively; and a contact structure with a re-entrant profile in electrical connection with the source/drain contact and the metallization of the at least one gate structure, respectively.