Two-Slope Contact Barrier Structure to Prevent Gate Shorts
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Solution Overview
Problem
Semiconductor devices are prone to electrical shorts due to conductive materials being directly connected or across thin insulating materials, leading to device failure during manufacturing and usage, especially when transient high voltages cause insulating materials to break down, increasing parasitic power consumption and contact resistance.
Innovation Solution
Implementing a two-slope contact structure with a lower sidewall slope of 85° to 89.5° and an upper sidewall slope of 45° to 85°, decoupling the contact from the gate structure through a barrier layer, which helps in reducing the likelihood of electrical shorts and improving contact filling, thereby reducing resistance and parasitic power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional contact structure with uniform slope is used, then the manufacturing process is simpler, but the separation distance between contact and gate structure is reduced, increasing the likelihood of electrical shorts
Solution Approach 1:
The contact structure is divided into two distinct segments: a lower portion with a first slope (85°-89.5°) and an upper portion with a second slope (45°-85°). This segmentation allows each portion to serve different functions - the lower portion provides close spacing for good electrical contact, while the upper portion provides larger separation for electrical isolation from the gate structure, thereby preventing shorts without excessive complexity
Solution Approach 2:
The contact structure employs asymmetric slopes rather than a uniform slope throughout. The lower portion has a steeper slope (85°-89.5°) optimized for electrical connection, while the upper portion has a gentler slope (45°-85°) optimized for electrical isolation. This asymmetry resolves the contradiction by allowing different geometric characteristics in different regions to simultaneously achieve both good contact and short prevention
2Area of stationary object
If the contact is placed closer to the gate structure, then the device area is reduced, but the insulating material thickness is decreased, leading to higher risk of electrical shorts
Solution Approach 1:
The solution moves the separation mechanism from a purely lateral (horizontal) dimension to include a vertical dimension through the two-slope configuration. The upper portion's gentler slope extends the contact structure upward, creating vertical separation distance from the gate structure while maintaining lateral proximity. This dimensional approach allows small device area while preserving electrical isolation through the vertical spacing provided by the sloped geometry
3Manufacturing precision
If a single slope contact structure is used, then the manufacturing process is simpler, but the contact filling is less effective, resulting in higher contact resistance
Solution Approach 1:
Different regions of the contact structure have different slope qualities optimized for their specific functions. The lower portion has a steeper slope (85°-89.5°) that promotes better material filling and lower contact resistance at the critical electrical connection point, while the upper portion has a gentler slope (45°-85°) that facilitates manufacturing. This local differentiation of geometric quality achieves superior contact filling without requiring the entire structure to be complex
Data Source
AI summary
A semiconductor device includes a gate structure on a substrate and a dielectric film stack over the gate structure and the substrate, where the dielectric film stack includes a first inter layer dielectric (ILD) over the substrate and the gate structure, a barrier layer over the first ILD, a second ILD over the barrier layer, and a contact extending through the dielectric film stack. An upper portion of a contact sidewall has a first slope, a lower portion of the contact sidewall has a second slope different from the first slope, and a transition from the first slope to the second slope occurs at a portion of the contact extending through the barrier layer.