Low-Temperature Copper Interconnect Doping via Metal Liner Interface
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for doping copper (Cu) interconnects face limitations due to thickness requirements, doping levels, conformality, and fill performance, especially at narrow dimensions where high temperatures cause via structure degradation.
Innovation Solution
Low-temperature interfacially-assisted thermal diffusion techniques for doping Cu interconnects, involving patterning trenches, forming barrier and metal liners, depositing Cu seed layers, plating Cu fills, removing overburden, and diffusing dopants along the metal liner-Cu fill interface to form a doping layer, allowing for variable doping levels and avoiding damage at narrow dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional high-temperature thermal diffusion is used to dope Cu interconnects, then doping levels can be achieved, but via structures degrade due to stress migration at narrow dimensions
Solution Approach 1:
The patent changes the temperature parameter from conventional high temperatures to low temperatures (below 200°C) for the thermal diffusion process. This parameter change enables doping to proceed at temperatures that do not cause stress migration and via structure degradation, while still achieving effective dopant diffusion through the Cu interconnects
Solution Approach 2:
The patent introduces a metal liner layer as an intermediary between the Cu fill and the dopant source. This metal liner facilitates the thermal diffusion process by serving as a diffusion pathway, enabling effective doping at low temperatures without requiring high thermal energy that would damage the via structures
2Reliability
If doping is performed at low temperatures to prevent via structure degradation, then via integrity is maintained, but achieving sufficient doping levels becomes difficult
Solution Approach 1:
The metal liner acts as a diffusion mediator that enhances dopant transport efficiency at low temperatures. By depositing the dopant on or near the metal liner, the diffusion process is facilitated through this intermediary layer, achieving sufficient doping levels without requiring high temperatures that would compromise via structure integrity
Solution Approach 2:
The patent applies doping locally at the metal liner-Cu interface rather than attempting uniform bulk doping. This localized approach at the interface, where the metal liner is in contact with the Cu, enables effective doping with reduced thermal requirements, maintaining via integrity while achieving necessary doping levels at the critical interface region
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
Enables effective doping of Cu interconnects at low temperatures below 200°C, preventing via structure damage and allowing for variable doping levels, thereby improving the performance of Cu interconnects in narrow trench structures.
Implementation Method 1
diffusing at least one dopant from the dopant layer along the interface between the metal liner and the Cu fill to form a Cu interconnect doping layer between the metal liner and the Cu fill
Data Source
AI summary
Low-temperature techniques for doping of Cu interconnects based on interfacially-assisted thermal diffusion are provided. In one aspect, a method of forming doped copper interconnects includes the steps of: patterning at least one trench in a dielectric material; forming a barrier layer lining the trench; forming a metal liner on the barrier layer; depositing a seed layer on the metal liner; plating a Cu fill into the trench to form Cu interconnects; removing a portion of a Cu overburden to access an interface between the metal liner and the Cu fill; depositing a dopant layer; and diffusing a dopant(s) from the dopant layer along the interface to form a Cu interconnect doping layer between the metal liner and the Cu fill. Alternatively, the overburden and the barrier layer/metal liner can be completely removed, and the dopant layer deposited selectively on the Cu fill. An interconnect structure is also provided.