Interconnect Structure With Raised Via Base for Overlay Margin
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Solution Overview
Problem
The challenge in semiconductor device fabrication is to improve the via-to-line overlay window and via critical dimension (CD) window of the photolithography process, as the minimum distance between vias and neighboring metal lines becomes shorter, leading to potential leakage and reduced reliability and performance due to the scaling of semiconductor devices.
Innovation Solution
The method involves etching metal lines in a way that the intermetal dielectric layer protrudes between them, allowing the via's first portion to exceed the edge of the metal line, thereby increasing the distance and improving the overlay and CD windows, which relaxes the strict control limits of the photolithography process and reduces leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the minimum distance between vias and neighboring metal lines is reduced to increase device density, then device density is improved, but leakage increases and reliability deteriorates
Solution Approach 1:
The patent introduces a vertical dimension to solve the horizontal leakage problem. By forming the via with a raised first portion that extends upward from the metal line level, the solution moves the critical dimension control from the horizontal plane (via diameter and line width) to the vertical plane (height of raised portion and lateral offset). This dimensional transformation allows maintaining electrical isolation while enabling smaller horizontal pitch for higher density.
Solution Approach 2:
The raised first portion of the via acts as an intermediary structure between the via and the metal line. Instead of directly controlling the horizontal distance between via and line, the patent uses this vertical protrusion as a mediator that provides lateral offset protection. The raised portion creates a physical barrier that prevents leakage paths while allowing the via to be positioned closer to the metal line, thus enabling higher density without sacrificing reliability.
2Length of moving object
If the via-to-line overlay window is reduced due to scaling, then device size is reduced, but manufacturing precision requirements become more stringent
Solution Approach 1:
The patent shifts the overlay control challenge from the horizontal dimension to the vertical dimension. Instead of requiring precise horizontal alignment between via and metal line, the raised first portion provides a vertical reference that creates lateral offset. This allows the via to be formed with relaxed horizontal overlay specifications while still achieving the necessary lateral separation to prevent leakage, thus reducing manufacturing precision requirements.
3Length of moving object
If the via critical dimension window is reduced, then via size is reduced, but photolithography process control becomes more difficult
Solution Approach 1:
The patent addresses via CD control by introducing a vertical component (the raised first portion) that provides functional separation. The critical dimension for leakage prevention is no longer solely dependent on the horizontal via diameter, but also on the vertical height of the raised portion and its lateral offset from the metal line. This allows using larger via CDs with relaxed photolithography control while achieving the same leakage prevention effect through the combined vertical-horizontal geometry.
Data Source
AI summary
A method for forming an interconnect structure is provided. The method for forming the interconnect structure includes forming a first dielectric layer over a substrate, forming a first conductive feature through the first dielectric layer, etching the first conductive feature to form a recess over the first conductive feature, forming a second dielectric layer over the first dielectric layer and filling the recess, etching the second dielectric layer to form an opening exposing an upper surface of the first conductive feature, and forming a second conductive feature in the opening.