Hybrid Cut Feature for Dense Source-Drain Contacts
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Solution Overview
Problem
Existing semiconductor fabrication processes face challenges in achieving desired density and performance due to limitations in photolithography resolution, particularly in reducing the spacing between adjacent source/drain contacts, which hinders the increase in transistor density.
Innovation Solution
A method involving the formation of a hybrid cut feature with a conformal dielectric liner and filler, where a portion of the dielectric liner is selectively removed to reduce the dimension of the cut feature, thereby reducing the spacing between source/drain contacts, allowing for more densely packed transistors without compromising electrical isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If photolithography processes are used to form contact features, then manufacturing capability is maintained, but spacing between adjacent contact features cannot be sufficiently reduced
Solution Approach 1:
The patent divides the formation process of contact features into multiple sequential steps: first forming mandrels at desired spacing, then forming dielectric layers and recesses, and finally forming contact features. This segmentation allows the final contact spacing to be determined by the mandrel spacing rather than being limited by photolithography resolution, effectively resolving the contradiction between achieving small spacing and maintaining manufacturing precision.
2Productivity
If spacing between contact features is reduced to increase density, then transistor density improves, but electrical isolation between adjacent contacts deteriorates
Solution Approach 1:
The patent applies different material properties to different regions: dielectric material with appropriate breakdown strength is deposited in recesses between contact features to provide electrical isolation, while allowing minimal spacing. This local application of insulating material ensures that even when contacts are densely packed, adequate electrical isolation is maintained through the strategically placed dielectric regions.
3Length of moving object
If dimension of cut features is reduced to enable denser contacts, then contact density improves, but photolithography process capability is exceeded
Solution Approach 1:
The patent performs preliminary actions by first forming mandrels at the desired final contact spacing using standard photolithography processes. Subsequent steps (forming dielectric layers, creating recesses, and forming contact features) are then performed to achieve the final dense contact structure. This preliminary positioning of mandrels allows the final contact dimensions and spacing to be determined by the pre-established mandrel pattern rather than being constrained by photolithography resolution limits.
Data Source
AI summary
Semiconductor structures and methods are provided. An exemplary method according to the present disclosure includes forming a first source/drain feature, a second source/drain feature and an interlayer dielectric (ILD) layer over the first and second source/drain features. The method also includes removing a portion of the ILD layer to form a cut feature opening and forming a hybrid cut feature therein to divide a to-be-formed metal layer into multiple pieces as source/drain contacts. The hybrid cut feature includes a conformal dielectric liner over the cut feature opening and a dielectric filler over the dielectric liner. During the formation of a source/drain contact opening, at least a portion of the dielectric liner extending along a sidewall of the dielectric filler is partially and selectively removed, leading to a dimension-reduced hybrid cut feature and thus a reduced spacing between two adjacent source/drain contacts.