Self-Aligned Metal Silicide via Controlled Volumetric Expansion
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Solution Overview
Problem
Existing methods for forming self-aligned metal oxide pillars face challenges such as rapid volume expansion leading to structural degradation, adhesion issues, and residual metal at the bottom of trenches, necessitating alternative methods for controlled formation and expansion.
Innovation Solution
The method involves forming a metal-containing film within a substrate feature, exposing it to a silicon precursor to create a self-aligned metal silicide structure that expands at a controlled rate, and using a tungsten film with hydrogen and a metal fluoride etchant to form self-aligned structures and vias with improved adhesion and shape fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal is oxidized to form metal oxide pillars, then self-aligned structures are formed, but rapid volume expansion leads to structural degradation and bending of columns
Solution Approach 1:
The patent changes the chemical reaction parameters by using silicidation instead of oxidation, and further modifies the process by controlling the silicon precursor exposure to achieve gradual volume expansion. This transforms the rapid oxidation process into a more controlled silicidation process with manageable expansion rates.
Solution Approach 2:
The patent employs periodic or staged exposure to silicon precursor, allowing the silicidation reaction to proceed in controlled increments rather than all at once. This periodic action enables manageable volume expansion while maintaining structural integrity.
2Reliability
If metal is rapidly oxidized to form pillars, then self-aligned structures are created, but adhesion issues occur between metal oxide pillar and substrate
Solution Approach 1:
The patent changes the reaction kinetics by substituting oxidation with silicidation, a process that proceeds at a different rate and produces different adhesion characteristics. The controlled silicidation process improves adhesion between the resulting structure and substrate.
Solution Approach 2:
The patent introduces a silicon precursor as an intermediary substance that mediates the transformation of metal to metal silicide. This intermediary enables a more controlled reaction process that maintains better adhesion to the substrate compared to direct oxidation.
3Quantity of substance
If metal is oxidized to form pillars, then self-aligned structures are produced, but residual un-oxidized metal remains at the bottom of the trench
Solution Approach 1:
The patent changes the chemical reaction parameters by using silicidation instead of oxidation. This alternative reaction pathway achieves more complete conversion of the metal film without leaving residual unreacted metal, while still maintaining process control through controlled silicon precursor exposure.
4Productivity
If rapid volume expansion occurs during oxidation, then pillars are formed quickly, but bending of tall columns occurs when CD is small
Solution Approach 1:
The patent uses periodic or staged exposure to silicon precursor, allowing the silicidation and volume expansion to occur in controlled increments. This periodic action prevents rapid expansion-induced bending while maintaining efficient formation speed.
Solution Approach 2:
The patent changes the reaction parameters from rapid oxidation to controlled silicidation, fundamentally altering the expansion kinetics. This parameter change enables tall columns to maintain straightness during formation while still achieving acceptable productivity.
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 allows for the formation of self-aligned structures with reduced volumetric expansion, improved adhesion to the substrate, and straight growth from the substrate, addressing the limitations of existing methods by providing more controlled and stable expansion.
Implementation Method 1
The metal-containing film is exposed to a silicon precursor to form a self-aligned structure of metal silicide that expands from the at least one feature
Implementation Method 2
The self-aligned structure is exposed to a hydrogen plasma and a metal fluoride etchant to remove the self-aligned structure and form a self-aligned via
Data Source
AI summary
Methods of producing a self-aligned structure are described. The methods comprise forming a metal-containing film in a substrate feature and silicidizing the metal-containing film to form a self-aligned structure comprising metal silicide. In some embodiments, the rate of formation of the self-aligned structure is controlled. In some embodiments, the amount of volumetric expansion of the metal-containing film to form the self-aligned structure is controlled. Methods of forming self-aligned vias are also described.