Additive Core Subtractive Liner for Metal Cut Etch
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Solution Overview
Problem
In semiconductor device manufacturing, the existing methods for forming contacts and gate structures face challenges such as shorting due to dielectric loss and complex processing steps, particularly in scaling integrated circuits, where aggressive contact spacing and residual silicon issues lead to increased leakage and resistance.
Innovation Solution
The additive core subtractive liner (ACSL) method involves forming a metal liner between source/drain regions, cutting it to create a tapered trench, filling with a dielectric, and using an additive core conductor to maintain contact area while increasing separation, thereby minimizing shorting and erosion of dielectric caps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional subtractive methods are used to form contacts, then mask requirements are reduced, but dielectric cap erosion occurs and contact area is lost
Solution Approach 1:
The patent inverts the conventional approach by using an additive process instead of a subtractive process. Rather than etching away material to form contacts, the method deposits conductive material additively to build contacts, thereby preserving the dielectric cap and maintaining contact area while still achieving the desired contact formation.
Solution Approach 2:
The patent performs preliminary actions by first forming a mandrel structure and depositing conductive material before final contact formation. This preliminary deposition ensures that the contact area is established early in the process, preventing subsequent erosion or loss of contact area during later processing steps.
2Productivity
If aggressive contact spacing is used to increase device density, then productivity is improved, but shorting occurs due to dielectric loss
Solution Approach 1:
The patent applies local quality by preserving the dielectric cap material specifically in the regions between contacts through the additive process. This localized preservation of dielectric material maintains electrical isolation between closely spaced contacts, enabling aggressive contact spacing without causing shorting.
3Manufacturing precision
If conventional etching methods are used, then manufacturing precision is maintained, but dielectric cap erosion increases
Solution Approach 1:
The patent converts the potential harm of material loss by using an additive process that adds material rather than removing it. This approach eliminates the erosion problem entirely while still achieving precise contact formation through controlled deposition and mandrel removal, turning the constraint of material preservation into a benefit.
4Manufacturing precision
If chemical mechanical planarization is used to achieve flat surfaces, then manufacturing precision is improved, but processing complexity increases
Solution Approach 1:
The patent extracts or removes the chemical mechanical planarization step from the processing sequence by using an additive process that naturally forms flat contact surfaces through controlled deposition. This eliminates the need for subsequent planarization steps, reducing processing complexity while maintaining surface flatness.
Data Source
AI summary
An additive core subtractive liner method is described for forming electrically conductive contacts. The method can include forming a first trench in an first dielectric layer to expose a first portion of a metal liner, and filling said first trench with a second dielectric layer. A metal cut trench is formed in the second dielectric layer. A portion of the metal liner exposed by the metal cut trench is removed with a subtractive method. The method continues with filling the metal cut trench with a dielectric fill, and replacing the remaining portions of the second dielectric layer with an additive core conductor to provide contacts to remaining portions of the metal liner.