ALD Precursor Selectivity via Alkyl Chain Tuning
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Solution Overview
Problem
Current area-selective atomic layer deposition (AS-ALD) processes face challenges in achieving high selectivity due to the limitations of traditional precursors, such as trimethylaluminum (TMA), which lose selectivity after a few tens of cycles, and diethylzinc (DEZ) provides limited blocking selectivity for aluminum oxide (Al2O3) and zinc oxide (ZnO) films.
Innovation Solution
The use of novel ALD precursors with specific design parameters, such as aluminum alkyl chloride compounds, aluminum alkyl compounds, and aluminum alkyl alkoxides, along with optimized process parameters like growth temperature, precursor partial pressure, and purging time, to achieve high selectivity and effective blocking of Al2O3 deposition on self-assembled monolayer (SAM)-coated surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional precursors like trimethylaluminum (TMA) are used for AS-ALD, then the process is simple and widely applicable, but selectivity is lost after a few tens of cycles due to precursor adsorption on SAM layers
Solution Approach 1:
The patent changes the chemical parameters of the precursor by using aluminum alkyl compounds with different alkyl chain lengths (methyl, ethyl, propyl, butyl groups) instead of traditional TMA. This parameter change reduces the precursor's affinity for SAM layers while maintaining reactivity with hydroxyl groups, thereby extending selectivity duration beyond tens of cycles.
Solution Approach 2:
The patent employs precursors with shorter effective lifetimes on SAM surfaces - the aluminum alkyl compounds are designed to react quickly with exposed hydroxyl groups before having time to adsorb significantly on SAM layers. This disposable approach ensures that each precursor molecule contributes to selective deposition rather than accumulating on inhibited surfaces.
2Adaptability or versatility
If diethylzinc (DEZ) is used to improve blocking selectivity for Al2O3 and ZnO films, then blocking capability is enhanced, but the growth per cycle is limited to only 6 nanometers
Solution Approach 1:
The patent optimizes multiple process parameters including temperature (100-200°C), pressure (0.1-10 Torr), and precursor dosage to maximize both blocking selectivity and growth per cycle. By carefully tuning these parameters for aluminum alkyl compounds, the patent achieves superior blocking compared to DEZ while maintaining high productivity through enhanced reaction efficiency.
Solution Approach 2:
The patent employs a composite approach combining aluminum alkyl compounds with water or oxygen as co-reactants. This composite reaction system enables both excellent blocking selectivity on SAM-coated surfaces and high growth rates on exposed surfaces, overcoming the limitations of single-reactant systems like DEZ.
3Reliability
If aluminum alkyl chloride compounds are used as precursors, then Lewis acidity increases improving reactivity, but purging time must be significantly extended to maintain selectivity
Solution Approach 1:
The patent uses aluminum alkyl compounds with partial chloride substitution (AlR2Cl, AlRCl2) rather than fully chlorinated AlCl3. This partial substitution provides sufficient Lewis acidity for high reactivity while reducing the excessive time required for purging, as the alkyl groups modulate the precursor's surface interaction characteristics compared to fully chlorinated variants.
Solution Approach 2:
The patent optimizes the ratio of alkyl to chloride groups in the precursor structure, along with tuning temperature and pressure parameters, to achieve the right balance between reactivity and purging requirements. This parameter optimization allows shorter purging times compared to traditional aluminum alkyl chlorides while maintaining high reaction efficiency.
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 proposed solution achieves selectivity exceeding 0.98 for up to 75 ALD cycles with Al(C2H5)3, allowing for selective growth of 6 nanometers of Al2O3 film on silicon dioxide-covered Si, demonstrating improved blocking and selectivity compared to traditional precursors like Al(CH3)3.
Implementation Method 1
TMA adsorbs on or within the SAM after a few tens of cycles, leading to selectivity loss
Implementation Method 2
self-assembled monolayers (SAMs)
Implementation Method 3
Area-selective atomic layer deposition (AS-ALD) is a bottom-up fabrication process that employs surface chemistry to deposit thin-film material
Data Source
AI summary
Advanced precursors for selective atomic layer deposition (ALD) of aluminum oxide (Al2O3) using self-assembled monolayers (SAM) are provided. Area selective atomic layer deposition (AS-ALD) is a highly sought-after strategy for the fabrication of next-generation electronics. Embodiments described herein provide a process of selective ALD of Al2O3 that achieves an excellent selectivity between an SAM-coated surface and non-coated surface by adopting one of several novel ALD precursors. Some embodiments further optimize process parameters (e.g., growth temperature, precursor partial pressure, precursor dosing time, purging time, reactant dosing time, and number of cycles) to further improve selectivity of the ALD precursor.