Semiconductor Interconnect Reaction Layer Control
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Solution Overview
Problem
Conventional semiconductor device manufacturing methods result in unintended thick CuSix layers due to surface temperature and crystal condition variations, leading to increased interconnect resistance and reduced operating speed, especially in miniaturized devices, while attempting to prevent electromigration by forming a copper silicide layer.
Innovation Solution
A method of precisely controlling the thickness of the reaction layer by forming a protective film on the interconnect and exposing it to reactive gas, such as a silicon compound, to create a controlled reaction layer between the interconnect and the protective film, which improves adhesion and electromigration resistance without increasing interconnect resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the semiconductor substrate is heated and exposed to silicon compound to form CuSix layer, then adhesion between interconnect and film is improved, but the reaction layer thickness becomes uncontrolled and interconnect resistance increases
Solution Approach 1:
A protective film is introduced as an intermediary layer between the Cu film and the external environment. This protective film controls the reaction between SiH4 and Cu by allowing selective diffusion of silicon atoms through the film to reach the Cu surface, thereby mediating the formation of CuSix layer with controlled thickness and preventing uncontrolled thick layer formation
Solution Approach 2:
The protective film's properties (thickness, composition, permeability) are adjusted as parameters to control the reaction rate and CuSix layer thickness. By changing the protective film thickness or silicon content, the amount of silicon reaching the Cu surface is controlled, thus controlling the CuSix layer thickness while maintaining adhesion improvement
2Reliability
If the CuSix layer thickness is increased to improve adhesion, then electromigration resistance is improved, but interconnect resistance increases and operating speed is reduced
Solution Approach 1:
The protective film acts as a mediator that controls silicon diffusion to the Cu surface, enabling formation of a thin but sufficient CuSix layer that provides necessary electromigration resistance without excessive thickness that would increase interconnect resistance and reduce operating speed
Solution Approach 2:
The CuSix layer is formed locally only where the protective film allows silicon diffusion, creating a localized reaction layer with optimal thickness at the Cu surface interface. This local formation ensures adequate electromigration resistance at the critical interface without adding unnecessary resistance along the entire interconnect path
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
The method achieves high electromigration resistance and operating speed for semiconductor devices by precisely controlling the reaction layer thickness, ensuring effective adhesion between interconnects and films, even in miniaturized devices.
Implementation Method 1
the reaction between a Cu film and SiH4 further proceeds than expected due to variation of surface temperatures and crystal conditions of the Cu film, and a CuSix layer having a thickness larger than an expected thickness may be formed
Implementation Method 2
exposing it to reactive gas, such as a silicon compound, to create a controlled reaction layer between the interconnect and the protective film
Data Source
AI summary
A first insulating film is formed on a semiconductor substrate, an interconnect groove is formed in the first insulating film, the inside of the interconnect groove is filled with a metal film, thereby forming a first interconnect. Then, a protective film is formed on the first insulating film and the first interconnect, and the surface of the protective film is exposed to reactive gas, thereby forming a reaction layer on an interface between the first interconnect and the protective film.