Contact Plug Bottom-Up Metal Growth for Void-Free Backside Filling
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Solution Overview
Problem
The formation of metal contact plugs on the backside of semiconductor wafers with high aspect ratios often results in voids and seams due to incomplete filling, leading to high electrical resistance.
Innovation Solution
A method involving bottom-up metal growth is employed, where a silicide layer is formed on the silicon-containing feature, followed by a metal seed layer and a metal contact layer, with a protective metal nitride layer to prevent oxidation, ensuring complete filling and reducing electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If metal layer is deposited to fill high aspect ratio contact holes, then contact plug formation is achieved, but voids and seams form due to incomplete filling
Solution Approach 1:
The patent inverts the conventional top-down filling approach by using bottom-up metal growth. Instead of depositing metal from the top of the contact hole downward, the process grows metal from the bottom upward, allowing complete filling of high aspect ratio contact holes without voids and seams, thereby improving both filling completeness and electrical resistance.
2Length of moving object
If contact hole depth is increased to achieve backside connectivity, then electrical connection is established, but aspect ratio increases leading to incomplete metal filling
Solution Approach 1:
The patent reverses the filling direction to grow metal from the bottom of the contact hole upward. This bottom-up approach enables complete filling of deeper contact holes with higher aspect ratios, as the metal growth proceeds from the base where it can properly nucleate and fill the entire depth without creating voids.
3Ease of manufacture
If metal seed layer is formed to enable bottom-up growth, then controlled metal deposition is achieved, but oxidation of metal layers occurs
Solution Approach 1:
The patent introduces a protective metal nitride layer as an intermediary between the metal seed layer and the environment. This nitride layer prevents oxidation of the metal layers during the bottom-up growth process, allowing controlled metal deposition to proceed while protecting against harmful oxidative effects.
Solution Approach 2:
The formation of a metal nitride layer creates an inert protective environment around the metal seed layer and growing metal contact layer. This nitride atmosphere prevents oxygen from reaching and oxidizing the metal layers, enabling the bottom-up growth process to occur without oxidation damage.
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 prevents the formation of voids and seams, resulting in a contact plug with low electrical resistance and improved connectivity.
Implementation Method 1
a silicide layer is formed on the silicon-containing feature
Implementation Method 2
a metal contact layer is deposited over the metal seed layer to form the contact plug in the contact hole
Implementation Method 3
a metal contact layer is deposited over the metal seed layer to form the contact plug in the contact hole
Implementation Method 4
a protective metal nitride layer to prevent oxidation
Data Source
AI summary
A method is provided for forming a contact plug by bottom-up metal growth. In one step, a substrate is etched to form a contact hole that exposes a silicon-containing feature in the substrate. In one step, a silicide layer is formed on the silicon-containing feature. In one step, a metal seed layer is formed over the silicide layer. In one step, a metal contact layer is deposited over the metal seed layer to form the contact plug in the contact hole.