Trench Edge Rounding for Void-Free Copper Fill
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Solution Overview
Problem
The challenge in forming metallization layers in integrated circuits with copper is the inefficient deposition and patterning of copper, leading to voids in trenches and vias due to the high aspect ratios and reduced mechanical strength of low-k dielectric materials, which affects the reliability and conductivity of the metal-filled structures.
Innovation Solution
A technique that involves forming a dielectric layer stack with a low-k dielectric material and a capping layer, where the upper portion of the opening is rounded or tapered through an additional etch process, improving the deposition kinetics during electrochemical metal filling and reducing void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional anisotropic etching is used to form high aspect ratio trenches in low-k dielectric, then the trench depth and aspect ratio are improved for higher packing density, but void formation occurs during electrochemical deposition due to poor deposition kinetics
Solution Approach 1:
The patent applies preliminary corner rounding to the trench openings before electrochemical deposition. This is achieved by exposing the trench to a plasma treatment or chemical etch that rounds the sharp corners and creates a tapered profile. This preliminary geometric modification enables subsequent uniform copper deposition by eliminating the corner effects that cause void formation, thus resolving the contradiction between achieving high aspect ratios and maintaining good fill quality.
2Productivity
If copper is deposited by electrochemical techniques in high aspect ratio trenches, then the deposition efficiency is improved, but voids form due to the trench geometry and poor deposition kinetics
Solution Approach 1:
The patent modifies the geometric parameters of the trench by rounding the corners and creating a tapered profile. This parameter change in the trench geometry fundamentally alters the deposition kinetics during electrochemical filling, enabling uniform copper deposition throughout the high aspect ratio trench without void formation. The rounded corners improve current distribution and deposition uniformity, thus maintaining both high deposition efficiency and metal line reliability.
3Quantity of substance
If the number of stacked metallization layers is increased to accommodate more circuit elements, then the packing density is improved, but the mechanical and electrical reliability of the stacked layers deteriorates
Solution Approach 1:
The patent applies local quality modification by rounding only the corner regions of the trenches while maintaining the overall trench geometry. This localized geometric modification at the critical corner areas improves deposition uniformity and eliminates voids, thereby enhancing the reliability of individual metal lines. When applied across multiple stacked layers, this approach maintains overall system reliability while allowing increased packing density through additional metallization layers.
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 enhances the reliability of metal-filled openings by reducing voids and improving conductivity, allowing for more reliable and efficient formation of metal lines in advanced semiconductor devices, thereby addressing the limitations of conventional anisotropic etching and enhancing the mechanical integrity of low-k dielectric materials.
Implementation Method 1
a metal is filled into the opening having the tapered portion by an electrochemical deposition process
Implementation Method 2
performing a first etch process to form an opening in the dielectric layer stack and performing a second etch process to form a tapered portion at an upper portion of the opening
Data Source
AI summary
During the formation of a metal line in a low-k dielectric material, an upper portion of a trench formed in a capping layer and the low-k dielectric material is treated to provide enlarged tapering or corner rounding, thereby significantly improving the fill capabilities of subsequent metal deposition processes. In one particular embodiment, an additional etch process is performed after etching through the capping layer and the low-k dielectric layer and after resist removal.