Low-Temperature Metal Boride Deposition via Halide ALD
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Solution Overview
Problem
Current methods for forming metal boride and metal silicide films, such as CVD and PVD, face challenges with high substrate temperatures and non-uniform deposition, especially in semiconductor fabrication, while existing ALD solutions do not support low-temperature deposition of these films.
Innovation Solution
The method involves pulsing metal halide and reducing precursors into a reaction chamber, followed by purging, to form metal boride or silicide films at low temperatures using specific precursors like tantalum pentabromide, niobium tetraiodide, and molybdenum hexafluoride, within an atomic layer deposition process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If CVD methods are used to deposit metal boride and silicide films, then deposition can be achieved, but high substrate temperatures (up to 1200°C) are required which exceed thermal budgets for state-of-the-art semiconductor fabrication
Solution Approach 1:
The patent changes the chemical parameters of the deposition process by using metal halide precursors with specific reactivity characteristics that enable low-temperature decomposition and reaction. The use of highly reactive halide precursors (e.g., TaBr5, NbBr5, ZrCl4) allows the deposition to proceed at temperatures below 400°C, fundamentally changing the thermal parameter requirements compared to conventional CVD methods
Solution Approach 2:
The deposition process is segmented into distinct sequential steps: metal halide precursor deposition, reducing precursor deposition, and reaction/formation steps. This segmentation allows each step to be optimized independently, with the metal halide layer being deposited first at low temperature, then reacted with the reducing precursor to form the final metal boride or silicide film
2Manufacturing precision
If PVD methods are used to deposit metal films, then deposition can be achieved, but line-of-sight deposition results in insufficient thin film coverage in areas with complex substrate contours
Solution Approach 1:
The patent replaces the mechanical line-of-sight deposition mechanism of PVD with a chemical vapor deposition mechanism where gaseous precursors diffuse and react on the substrate surface. This chemical approach allows the precursor molecules to reach all surfaces including sidewalls and recesses, achieving conformal coverage on complex substrate contours that cannot be accessed by line-of-sight deposition
3Manufacturing precision
If PVD methods are used for deposition, then deposition can be achieved, but low-volatility precursors deposit on the first solid surface encountered, leading to low-conformality coverage
Solution Approach 1:
The patent changes the volatility parameter by selecting metal halide precursors with appropriate vapor pressures at low temperatures. The precursors are chosen to have sufficient volatility to remain in the gas phase during transport and deposition, yet low enough volatility to allow controlled deposition at temperatures below 400°C. This resolves the contradiction between precursor volatility and conformal coverage
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 metal boride and silicide films with low thermal budgets, achieving conformal coverage and suitable for applications in semiconductor devices like n-metal gates and patterning layers, with improved chemical resistance and low resistivity.
Implementation Method 1
Metal boride and metal silicide films have been formed using various chemical vapor deposition (CVD) methods. In the CVD methods, gaseous source chemicals are introduced into a reaction space at the same time, resulting in a deposition of a metal film on the substrate.
Implementation Method 2
Atomic layer deposition (ALD) has been used to form metal carbide films. For example, U.S. Pat. No. 7,611,751 to Elers discloses methods for forming a metal carbide film through spatially and temporally separated vapor phase pulses of a metal source chemical, a reducing agent, and a carbon source chemical.
Data Source
AI summary
A method for depositing a metal film onto a substrate is disclosed. In particular, the method comprises pulsing a metal halide precursor onto the substrate and pulsing a reducing precursor onto the substrate. A reaction between the metal halide precursor and the reducing precursor forms a metal film. Specifically, the method discloses forming a metal boride or a metal silicide film.