Germanide Interconnect Structures for Sub-30 nm Resistivity Control
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Solution Overview
Problem
As interconnect technology scales below 30 nm, traditional copper interconnects experience significant resistivity increases due to grain boundary and surface scattering, necessitating a replacement material with slower resistivity growth.
Innovation Solution
The method involves forming metal germanides, such as copper germanide (Cu3Ge), nickel germanide (NiGe), or cobalt germanide (CoGe2), through a solid vapor reaction, known as germanidation, which occurs even in narrow pitch structures, using plasma-assisted cleaning and germane gas in a reducing atmosphere to achieve low resistivity and suitable phase control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional copper interconnects are used in sub-30 nm dimensions, then manufacturing simplicity is maintained, but resistivity increases dramatically due to grain boundary and surface scattering
Solution Approach 1:
The patent changes the material parameter from pure copper to metal germanides (Cu3Ge, NiGe, CoGe2), which fundamentally alters the resistivity characteristics. These germanides maintain slower resistivity increase in sub-30 nm dimensions compared to copper, directly addressing the reliability issue while being integrated through modified fabrication parameters
Solution Approach 2:
The patent employs composite material structures by forming metal germanides through solid vapor reaction between metal layers and germanium precursors. The resulting interconnect structures combine metal and germanium elements to create compounds (Cu3Ge, NiGe, CoGe2) that exhibit superior electrical properties at nanoscale dimensions compared to pure metals
2Manufacturing precision
If plasma assisted pre-clean is performed at high temperature to remove native oxide, then cleaning effectiveness improves, but damage to dielectric material increases
Solution Approach 1:
The patent optimizes plasma processing parameters by conducting pre-clean at reduced temperatures (250-400°C range) compared to conventional high-temperature plasma. This parameter adjustment maintains sufficient cleaning effectiveness to remove native oxides while significantly reducing thermal and physical damage to low-k dielectric materials
Solution Approach 2:
The patent replaces aggressive mechanical/thermal cleaning methods with plasma-based chemical cleaning. The plasma assists in removing native oxides through chemical reactions rather than purely thermal or mechanical means, enabling effective cleaning at lower temperatures that protect dielectric integrity
3Reliability
If germanidation reaction is performed to achieve desired metal germanide phase, then resistivity control improves, but selectivity becomes challenging in narrow pitch structures
Solution Approach 1:
The patent applies local quality control by optimizing germanidation parameters specifically for narrow pitch structures. The solid vapor reaction conditions (temperature, pressure, germanium precursor flow) are tuned to achieve uniform metal germanide phase formation (Cu3Ge, NiGe, CoGe2) within confined geometries, ensuring consistent resistivity control across different structure dimensions
Solution Approach 2:
The patent performs preliminary plasma assisted pre-clean to remove native oxides before germanidation. This preliminary action prepares the metal surface for uniform germanium reaction, ensuring consistent phase formation and selectivity in subsequent germanidation steps, particularly critical for narrow pitch structures where uniformity is challenging
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 results in interconnect structures with lower sheet resistance and improved adhesion, corrosion resistance, and reduced damage to dielectric materials, effectively addressing the resistivity challenges in sub-30 nm dimensions.
Implementation Method 1
plasma assisted pre-clean performed in-situ at a reducing atmosphere
Implementation Method 2
plasma assisted pre-clean performed in-situ at a reducing atmosphere
Implementation Method 3
solid vapour reaction between the metal and the germanide
Implementation Method 4
solid vapour reaction between copper and the germane gas
Implementation Method 5
The in-situ plasma assisted clean is performed in a reducing atmosphere environment to minimize the damage caused to the dielectric material
Data Source
AI summary
Method for forming an interconnect structure, comprising the steps of: forming a recessed structure in a dielectric material on a substrate; at least partially filling said recessed structure with a metal chosen from the group consisting of copper, nickel and cobalt; introducing the substrate in a CVD reactor; bringing the substrate in the CVD reactor to a soak temperature and subsequently performing a soak treatment by supplying a germanium precursor gas to the CVD reactor at the soak temperature, thereby substantially completely converting the metal in the recessed structure to a germanide.