Self-Aligned MOL Contacts Using Selective Dielectrics
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Solution Overview
Problem
Conventional methods for forming middle of the line (MOL) contacts in integrated circuits face challenges such as voids between BEOL metal levels and source/drain contacts, shorts between gate contacts and metal plugs, and shorts between source/drain contacts and the gate, particularly when scaling down device size.
Innovation Solution
The use of different dielectric materials for a dielectric cap, spacer, and layers in the IC structure allows for self-aligned MOL contacts, preventing opens and shorts by ensuring precise alignment and placement of contacts to the gate and metal plugs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional techniques are used to form MOL contacts, then the manufacturing process is simpler, but opens occur between the first BEOL metal level and the source/drain contacts and gate contact
Solution Approach 1:
The patent implements self-aligned contact formation where the gate contact and source/drain contact are automatically positioned relative to each other through the gate electrode structure itself. The gate contact is formed to extend over the gate electrode, and the source/drain contact is formed adjacent to the gate contact, using the gate electrode as a self-aligned reference that eliminates the need for separate alignment processes.
Solution Approach 2:
The gate electrode serves as an intermediary structure that mediates the alignment between the gate contact and source/drain contact. By forming the gate contact over the gate electrode and the source/drain contact adjacent to it, the gate electrode acts as a physical mediator that ensures proper spatial relationship and prevents opens between contacts and metal levels.
2Length of moving object
If the gate contact is formed on the gate above the active region to allow size scaling, then device size can be reduced, but shorts occur between the gate contact and metal plug
Solution Approach 1:
The patent resolves the shorting risk by transitioning to a three-dimensional contact arrangement where the gate contact extends vertically over the gate electrode in the active region, and the source/drain contact is positioned adjacent to it in a different lateral dimension. This spatial separation in multiple dimensions prevents shorting while enabling compact device scaling.
Solution Approach 2:
The contact structure is segmented into distinct gate contact and source/drain contact regions that are spatially separated and independently formed. The gate contact is positioned over the gate electrode while the source/drain contact is adjacent to it, creating segmented contact zones that prevent unintended electrical connection while maintaining compact dimensions.
3Ease of manufacture
If conventional contact formation is used, then the process is simpler, but shorts occur between source/drain contacts and the gate
Solution Approach 1:
The self-aligned contact formation process uses the gate electrode structure itself as a reference to automatically position the gate contact and source/drain contact with proper spacing. This self-service mechanism ensures reliable isolation between contacts and the gate while maintaining manufacturing simplicity through reduced alignment steps.
Data Source
AI summary
Disclosed are methods of forming an integrated circuit (IC) structure with self-aligned middle of the line (MOL) contacts and the resulting IC structure. In the methods, different, selectively etchable, dielectric materials are used above the gate level for: a dielectric cap above a gate; a dielectric spacer above a gate sidewall spacer and laterally surrounding the dielectric cap; and a stack of dielectric layer(s) that covers the dielectric cap, the dielectric spacer, and metal plugs positioned laterally adjacent to the dielectric spacer and above source/drain regions. Due to the different dielectric materials, subsequently formed gate and source/drain contacts are self-aligned in two dimensions to provide protection against the occurrence of opens between wires and/or vias in the first BEOL metal level and the contacts and to further provide protection against the occurrence of shorts between the gate contact and any metal plugs and between the source/drain contacts and the gate.