Wire Trench Etch Prior to Via for Interconnect Profile Control
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Solution Overview
Problem
The conventional dual damascene process for forming via-wire conductive structures in integrated circuits faces challenges such as chamfer creation during trench etching, which can lead to shorts and increased time-dependent dielectric breakdown due to overlay errors and liner erosion, particularly near the wafer edge.
Innovation Solution
The method involves forming a hard mask with a wire trench pattern, etching a wire trench opening, creating a metal liner sidewall spacer, and then forming a via mask to etch via openings, resulting in a unitary via-wire conductive structure with a double layered sidewall spacer to prevent chamfering and ensure precise profile control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wire trench etching is performed after via etching in conventional dual damascene process, then via openings can be formed first, but chamfer is created during trench etching that can cause shorts and liner erosion
Solution Approach 1:
The patent inverts the conventional etching sequence by performing wire trench etching first, then via etching. This reversal prevents the chamfer formation problem because the trench etching is done when the via opening mask is still present, protecting the trench sidewalls. The via etching subsequently follows, creating via openings that align with the pre-formed trench structure, thereby eliminating the harmful chamfer effect and associated shorts.
Solution Approach 2:
The patent applies preliminary action by forming the wire trench structure and its protective sidewall spacers before performing via etching. The trench sidewall spacers are deposited and patterned in advance, creating a protective framework that prevents chamfer formation during the subsequent via etching process. This preliminary structuring ensures that when via openings are created, the trench boundaries remain intact and free from erosion.
2Manufacturing precision
If trench etching is performed to create wire trench opening, then wire can be formed, but enlarged chamfer can cause short of via to wire therebelow
Solution Approach 1:
The patent introduces trench sidewall spacers as intermediary protective structures during the via etching process. These spacers are deposited on the trench sidewalls before via etching and serve as a mediator that prevents the etching plasma from directly attacking the trench boundaries. The spacers absorb the erosive effect, preventing chamfer formation at the trench corners and eliminating the source of shorts between via structures and underlying wires.
Solution Approach 2:
The patent applies preliminary anti-action by depositing protective sidewall spacers on the trench structure before performing via etching. This preliminary protective layer counteracts the harmful chamfer-forming effect that would otherwise occur during via etching. The spacers are specifically designed to prevent etching attack at critical locations, thereby preemptively eliminating the chamfer defect before it can cause shorts.
3Productivity
If via etching is followed by wire trench etching, then via openings are formed first, but trench etching can erode metal liner and increase TDDB
Solution Approach 1:
The patent inverts the conventional process sequence by performing wire trench etching before via etching. This inversion fundamentally changes the protective dynamics: during trench etching, the via opening mask is still present, protecting the trench sidewalls from chamfer formation. Subsequently, via etching creates openings into the pre-formed trench structure. This reversed sequence eliminates the liner erosion problem because the trench boundaries are already protected by sidewall spacers before via etching begins, preventing the plasma from attacking and eroding the metal liner at trench corners.
Solution Approach 2:
The patent applies preliminary action by establishing the wire trench structure with protective sidewall spacers before performing via etching. The trench sidewall spacers are deposited and patterned in advance, creating a protective framework that prevents chamfer formation and subsequent liner erosion during the via etching process. This preliminary structuring ensures that when via openings are created, the trench boundaries remain intact and free from erosion that would lead to TDDB.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables chamferless via formation and improved dual damascene profile control, reducing the likelihood of shorts and enhancing reliability by protecting the etch stop layer and maintaining the integrity of the via structure.
Implementation Method 1
forming a metal liner sidewall spacer on sidewalls of the first wire trench opening
Implementation Method 2
depositing a barrier liner over the via-wire opening, the first metal liner sidewall spacer and the exposed upper surface of the conductive structures
Data Source
AI summary
Methods of forming an interconnect of an IC are disclosed. The methods etch a wire trench opening partially into an ILD layer using a hard mask, and form a metal liner sidewall spacer on sidewalls of the wire trench opening, prior to etching via openings that create a via-wire opening with the wire trench opening. The metal liner sidewall spacer protects against chamfering during the via etch and/or removal of an etch stop layer over conductive structures in an underlying ILD layer. In one embodiment, a barrier liner is deposited over the metal liner sidewall spacer, creating a double layered sidewall spacer on the sidewalls of the wire trench opening portion of the via-wire opening. A conductor is deposited to form a unitary via-wire conductive structure. An interconnect includes the double layered sidewall spacer on the sidewalls of a wire trench opening portion of the via-wire conductive structure.