Trichlorogermane ALD for GST Film Composition Control
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Solution Overview
Problem
The existing methods for Atomic Layer Deposition (ALD) of Germanium Antimony Tellurium (GST) films face challenges in achieving high conformality and chemical composition uniformity, particularly due to the stability of Ge4 precursors which tend to form GeTe2 instead of GeTe, making it difficult to produce the desired Ge2Sb2Te5 composition for Phase Change Random Access Memory (PCRAM) devices with dimensions less than 20 nanometers.
Innovation Solution
The use of trichlorogermane (HGeCl3) as a germanium precursor, which dissociates into HCl and GeCl2 at low temperatures, allowing for in-situ generation of divalent germanium species, is employed in conjunction with other precursors like (Me3Si)2Te and (EtO)3Sb to achieve the desired Ge2Sb2Te5 composition, enabling precise control of film thickness and composition through an ALD process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Ge4 precursors are used for ALD deposition, then the deposition process can proceed, but GeTe2 forms instead of GeTe, resulting in incorrect film composition
Solution Approach 1:
The patent changes the oxidation state parameter of the germanium precursor from +4 to +2. By using Ge2+ precursors instead of Ge4+ precursors, the chemical reaction pathway is altered to produce GeTe rather than GeTe2, thereby achieving the desired stoichiometric composition Ge2Sb2Te5 in the deposited film.
Solution Approach 2:
The patent introduces divalent germanium species as an intermediary substance in the deposition process. These Ge2+ species act as a mediator between the precursor and the final film composition, enabling controlled formation of GeTe units that subsequently incorporate into the GST alloy with correct stoichiometry.
2Manufacturing precision
If conventional Ge precursors are used, then deposition can occur, but high conformality and chemical composition uniformity cannot be achieved for dimensions less than 20 nm
Solution Approach 1:
The patent changes multiple parameters including the oxidation state of Ge precursor, deposition temperature, and precursor reactivity. These parameter changes enable precise control of the deposition process, achieving atomic-layer precision and high conformality even on sub-20nm structures.
Solution Approach 2:
The patent replaces conventional physical deposition mechanisms with chemically-controlled ALD processes using divalent germanium species. This substitution enables self-limiting surface reactions that provide atomic-level precision and uniform composition control, overcoming the limitations of mechanical/physical deposition methods at nanoscale dimensions.
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 deposition of GST films with high conformality and chemical composition uniformity, effectively addressing the limitations of previous Ge precursors and achieving the desired Ge2Sb2Te5 composition, suitable for advanced memory devices like PCRAM.
Implementation Method 1
trichlorogermane (HGeCl3) can easily dissociate into HCl and GeCl2 at relatively low temperature
Implementation Method 2
contacting the substrate with a Ge precursor comprising HGeCl3 to react with the substrate and provide a first coating layer comprising Ge
Data Source
AI summary
Described herein is a method and precursor composition for depositing a multicomponent film. In one embodiment, the method and composition described herein is used to deposit a germanium-containing film such as Germanium Tellurium, Antimony Germanium, and Germanium Antimony Tellurium (GST) films via an atomic layer deposition (ALD) and/or other germanium, tellurium and selenium based metal compounds for phase change memory and photovoltaic devices. In this or other embodiments, the Ge precursor used trichlorogermane.