Germanium ALD Using Sequential Precursor Pulses for Film Growth
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Solution Overview
Problem
Existing atomic layer deposition (ALD) processes have not been successful in depositing germanium, which is a promising material for semiconductor and optoelectronic devices due to its high mobility and transport properties.
Innovation Solution
A process involving sequential exposure of a substrate to a Ge-containing precursor and a reducing precursor, such as tetrakis(dimethylamino)Ge and hydrogen, respectively, within a temperature range of 50°C-350°C, using ALD to achieve self-saturating surface reactions and deposit germanium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ALD processes are used for germanium deposition, then the process follows standard ALD methodology, but germanium deposition is not successful
Solution Approach 1:
The patent changes the chemical parameters of the ALD process by using novel precursor combinations: germanium precursors (such as GeCl4, Ge(OEt)4, or Ge(acac)3) combined with sulfur-based precursors (such as H2S, DS, or DMDS). This parameter change in precursor chemistry enables successful germanium deposition where conventional ALD processes failed.
Solution Approach 2:
The patent introduces sulfur-based compounds as intermediary species that facilitate germanium deposition. The sulfur precursors react with germanium precursors to form intermediate species that enable controlled germanium film growth, acting as a mediator between the germanium source and the substrate.
2Reliability
If standard ALD temperature ranges are used, then the process maintains typical ALD conditions, but germanium deposition fails
Solution Approach 1:
The patent optimizes the temperature parameter within a specific range of 60°C to 350°C, with preferred ranges of 80°C to 250°C. This temperature parameter change, combined with the novel precursor system, enables successful germanium deposition at controlled temperatures that prevent precursor decomposition while ensuring adequate reaction kinetics.
3Manufacturing precision
If sequential precursor exposure is implemented, then self-saturating surface reactions occur, but process complexity increases
Solution Approach 1:
The patent divides the deposition process into distinct sequential segments: germanium precursor pulse, purge, sulfur precursor pulse, and purge. This segmentation of the deposition cycle into discrete, well-defined steps enables precise control over film thickness and composition while maintaining processability through clear process boundaries.
Solution Approach 2:
The patent employs periodic cyclic exposure of germanium and sulfur precursors in alternating pulses. This periodic action creates self-saturating surface reactions where each precursor cycle completes a full reaction sequence, enabling precise thickness control through the number of cycles while maintaining systematic process control.
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 method effectively deposits elemental germanium or germanium oxide layers on substrates, overcoming previous ALD process failures and enabling the use of germanium in semiconductor and optoelectronic devices.
Implementation Method 1
Precursor species form a chemical bond to reactive sites of the heated surfaces through chemisorption. Reaction conditions are typically arranged in such a way that no more than a molecular or atomic monolayer of a solid material forms on the surfaces during one precursor pulse. Thus, the growth process is self-terminating, i.e. saturative growth.
Implementation Method 2
the reducing precursor is H2 or hydrogen plasma
Data Source
Figure 1
AI summary
A process of depositing germanium on a substrate comprising sequentially exposing in at least one deposition cycle the substrate inside a chamber with a Ge-containing precursor and a reducing or oxidizing precursor. The object is to provide an industrially applicable method for depositing germanium and germanium oxide on various substrates. This is achieved by sequentially exposing in at least one deposition cycle the substrate inside a chamber to a Ge-containing precursor and a reducing or oxidizing precursor. The invention also relates to a Ge-deposited article and to the use of tetrakis(dimethylamino)germanium in ALD.