Multilayer Gate Isolation Structure for Leakage and Capacitance Control
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Solution Overview
Problem
Existing three-dimensional transistors, such as FinFET and GAA transistors, face challenges with undesirable leakage and parasitic capacitance due to the formation of gate structures, which affect device performance.
Innovation Solution
A semiconductor device structure is formed with a multilayer gate isolation structure that includes a first insulating feature with higher etch resistance and a second insulating feature with lower dielectric constant, separating the gate structures to reduce parasitic capacitance and enhance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-layer dielectric material is used to fill the gate structure space, then the fabrication process is simple, but leakage current and parasitic capacitance increase
Solution Approach 1:
The single-layer dielectric structure is divided into multiple layers with different materials (first dielectric layer with higher etch resistance, second dielectric layer with lower etch resistance). This segmentation allows each layer to perform specialized functions: the first layer provides structural support and leakage prevention, while the second layer reduces parasitic capacitance, thereby resolving the contradiction between fabrication simplicity and device reliability.
Solution Approach 2:
The patent employs composite dielectric structures combining materials with different properties (e.g., silicon nitride with silicon oxide, or different low-k materials). This composite approach enables simultaneous achievement of high etch resistance for structural integrity and low dielectric constant for reduced parasitic capacitance, while maintaining manageable fabrication processes through selective deposition techniques.
2Productivity
If dielectric material is filled in the gate structure space, then the transistor density increases, but undesirable leakage and parasitic capacitance affect device performance
Solution Approach 1:
Different regions of the gate structure are filled with dielectric materials having different properties. The first dielectric layer (with higher etch resistance) provides structural support and leakage prevention in critical areas, while the second dielectric layer (with lower etch resistance and potentially lower dielectric constant) is positioned to minimize parasitic capacitance effects. This local differentiation allows high transistor density while controlling harmful electrical effects.
Solution Approach 2:
The patent changes the dielectric constant parameter by using different materials for different layers. By selecting materials with appropriate dielectric constants (e.g., low-k materials for the second layer), the parasitic capacitance is reduced while maintaining the space-filling function for high transistor density. The etch resistance parameter is also optimized by assigning higher etch resistance materials to structural support layers.
3Reliability
If a multilayer gate isolation structure is used, then leakage and parasitic capacitance are reduced, but the fabrication process complexity increases
Solution Approach 1:
The multilayer dielectric structure is integrated into the fabrication process at an early stage, before final transistor formation. The first dielectric layer is deposited and patterned first, establishing the basic gate structure framework. Subsequent layers are then added in a systematic sequence, allowing each step to build upon the previous one. This preliminary action approach distributes the complexity across multiple manageable steps rather than requiring a single complex process.
Solution Approach 2:
The first dielectric layer with higher etch resistance serves multiple functions: it provides structural support during subsequent fabrication steps, acts as a barrier against leakage current, and serves as a template for the second dielectric layer. This multi-functionality reduces the need for additional specialized layers, thereby controlling fabrication complexity while achieving reliable leakage and parasitic capacitance control.
Data Source
AI summary
Structures and formation methods of a semiconductor device structure are provided. The semiconductor device structure includes first and second gate structures formed over a semiconductor substrate and a multilayer gate isolation structure separating the first gate structure from the second gate structure. The multilayer gate isolation structure includes a first insulating feature adjacent to upper portions of the first gate structure and the second gate structure, and a second insulating feature separating the semiconductor substrate from the first insulating feature. The material of the second insulating feature is different than that of the first insulating feature. The second insulating feature has a lower dielectric constant or lower etch resistance than the first insulating feature.