Self-Aligned Fin Cut Isolation for Dense GAA Transistors
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Solution Overview
Problem
The challenge in integrated circuit fabrication lies in maintaining mobility improvement and short channel control as device dimensions scale below the 10 nanometer node, particularly in multi-gate transistors, where lithographic processes face constraints due to the trade-off between feature dimension and spacing, leading to over-dimensioned isolation gaps and reduced transistor density.
Innovation Solution
A fin cut isolation technique is implemented after gate patterning, allowing self-aligned isolation of non-planar transistors with gate electrodes, reducing the need for multiple dummy gates and enabling higher transistor density by aligning fin isolation dimensions perfectly with gate electrodes, thus maintaining strain and optimizing space utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multi-gate transistors are scaled down to sub-10nm dimensions, then transistor density and capacity are increased, but lithographic process constraints cause over-dimensioned isolation gaps and reduced manufacturing precision
Solution Approach 1:
The gate electrode is formed first as a self-aligned reference structure, and then the isolation gaps are defined by etching fins at locations precisely aligned to the gate electrode edges. This preliminary gate formation establishes the dimensional reference that eliminates the need for separate, imprecise isolation gap patterning steps.
Solution Approach 2:
The gate electrode serves a dual function: it acts as both the transistor control element and the alignment reference for defining isolation gaps. By using the gate electrode's own position to define isolation gap locations, the system eliminates the need for additional alignment references and achieves self-aligned precision.
2Reliability
If conventional isolation techniques are used with dummy gates, then isolation gaps can be formed, but multiple dummy gates are required leading to increased device complexity and reduced transistor density
Solution Approach 1:
The invention extracts and eliminates the dummy gate structures from the device architecture. Instead of using dummy gates to define isolation gaps, the method directly forms isolation gaps aligned to the actual gate electrodes, removing the unnecessary intermediate structures and simplifying the overall device design.
Solution Approach 2:
The function of defining isolation gaps is merged with the gate electrode formation process. The gate electrode serves simultaneously as the transistor control element and the alignment reference for isolation gaps, combining two functions into a single structural element and eliminating the need for separate dummy gates.
3Quantity of substance
If feature dimensions are reduced below 10nm, then increased device capacity is achieved, but short channel control and mobility improvement become difficult to maintain
Solution Approach 1:
The invention transitions from planar transistor geometry to three-dimensional multi-gate structures (tri-gate, gate-all-around). This dimensional change provides enhanced electrostatic control over the channel region, improving short channel control and mobility while maintaining scaled dimensions below 10nm.
Data Source
AI summary
Fin cuts in neighboring gate and source or drain regions for advanced integrated circuit structure fabrication is described. For example, an integrated circuit structure includes a horizontal stack of semiconductor nanowire portions. A dielectric gate spacer is vertically over the horizontal stack of semiconductor nanowire portions. A gate isolation structure is laterally adjacent to a first side of the horizontal stack of semiconductor nanowire portions. A source or drain isolation structure is laterally adjacent to a second side of the horizontal stack of semiconductor nanowire portions.