Titanium Precursor Ligand Design for High-Temperature ALD
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Solution Overview
Problem
The semiconductor industry faces challenges in developing new gate dielectric materials as silicon dioxide reaches its physical limits, and existing titanium-containing precursors for atomic layer deposition (ALD) have poor reactivity and stability, especially with moisture, requiring low substrate temperatures and strong oxidizers, which can result in contaminated films with limited process windows.
Innovation Solution
Development of novel titanium-containing precursors with specific ligand structures, such as Ti(R1—N—C(R3)—N—R2)(OR4)x(NR5R6)y(O2CR7)z, which offer improved thermal stability and reactivity with water, enabling higher temperature ALD processes for depositing high-quality TiO2 and strontium titanate (STO) films with high dielectric constants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If standard Ti precursors (TTIP, TDMAT, TDEAT, TEMAT) are used in water ALD process, then deposition can occur, but deposition rates are below 0.6 Å/cycle and process windows do not exceed 250°C
Solution Approach 1:
The patent modifies the molecular structure of titanium precursors by replacing standard ligands with bulky alkyl groups (tert-butyl, adamantyl) and heteroatom-containing groups (amino, alkoxy). These structural parameter changes increase thermal stability while maintaining reactivity, enabling deposition at temperatures above 250°C with rates exceeding 0.6 Å/cycle
Solution Approach 2:
The patent creates composite precursor molecules combining titanium center with multiple types of ligands (alkyl, amino, alkoxy) in specific configurations. This composite structure provides both thermal stability for high-temperature processing and controlled reactivity for efficient deposition, resolving the contradiction between temperature window and deposition rate
2Reliability
If low substrate temperatures and strong oxidizers are used to compensate for poor precursor stability, then film deposition can occur, but films are contaminated with carbon or nitrogen
Solution Approach 1:
The patent uses precursors with labile ligands that decompose cleanly during the ALD process, leaving no persistent carbon or nitrogen contamination. The precursor molecules are designed to break down into volatile products, ensuring high film purity without requiring aggressive oxidizers that could damage the substrate or underlying layers
3Ease of manufacture
If existing Ti precursors are used, then deposition process can be implemented, but reactivity with moisture is poor requiring strong oxidizers
Solution Approach 1:
The patent incorporates hydrolytically labile groups directly into the precursor molecular structure before deposition. These pre-installed reactive groups enable immediate and efficient reaction with water vapor upon precursor introduction, eliminating the need for separate strong oxidizer steps and simplifying the overall ALD process
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
These precursors allow for the deposition of titanium-containing layers with enhanced thermal stability and reactivity, enabling the formation of high-quality TiO2 and STO films with high dielectric constants at higher temperatures, addressing the limitations of existing materials and processes.
Implementation Method 1
contacting the vapor with the substrate to form a titanium-containing layer on at least one surface of the substrate using a vapor deposition process
Data Source
AI summary
Disclosed are titanium-containing precursors and methods of synthesizing the same. The compounds may be used to deposit titanium, titanium oxide, strontium-titanium oxide, and barium strontium titanate containing layers using vapor deposition methods such as chemical vapor deposition or atomic layer deposition.