Low-Temperature Conformal Silicon Nitride Deposition
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Solution Overview
Problem
Conventional silicon nitride films are typically deposited at high temperatures, which is not suitable for the shrinking device dimensions and late-stage semiconductor fabrication processes, necessitating the development of methods to form silicon nitride films at lower temperatures, such as less than 600°C, while maintaining their unique properties and avoiding contamination.
Innovation Solution
A method involving atomic layer deposition (ALD) using halogen-free, carbon-free, and nitrogen (N—H bond-free silicon-containing precursors, where the substrate is exposed to a silicon-containing precursor and then a nitrogen plasma to form a silicon nitride film, with optional periodic exposure to a hydrogen-containing plasma, at temperatures below 250°C, ensuring conformal and low-contamination deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional CVD method is used to deposit silicon nitride films, then the films can be formed with good quality, but the deposition temperature must be greater than 750°C which is too high for late-stage fabrication
Solution Approach 1:
The patent changes the chemical parameters of the deposition process by using novel silicon precursors (such as silane, disilane, trisilane, tetrasilane, and trisilylamine) that enable low-temperature deposition. These precursors have different molecular structures and reactivities compared to conventional dichlorosilane, allowing the reaction to proceed at temperatures below 250°C while maintaining film quality. The process also uses nitrogen plasma instead of ammonia, changing the chemical reaction pathway to enable lower temperature operation.
Solution Approach 2:
The patent substitutes the thermal field with a plasma field. Instead of relying solely on high thermal energy to drive the chemical reactions, the invention uses nitrogen plasma to provide the necessary activation energy. The plasma generates reactive nitrogen species that can react with the silicon precursor at much lower temperatures, replacing the need for high-temperature thermal processing.
2Manufacturing precision
If conventional precursors are used, then deposition can proceed, but carbon and halogen contamination occurs in the deposited films
Solution Approach 1:
The patent extracts and eliminates the harmful elements (carbon and halogens) from the precursor molecules. The selected silicon precursors are specifically chosen to be free of carbon-halogen bonds and excessive carbon content. For example, silane (SiH4), disilane (Si2H6), and other silicon hydrides are used because they contain only silicon and hydrogen, completely eliminating carbon and halogen contamination sources.
Solution Approach 2:
The patent applies local quality by ensuring that only the necessary elements (silicon and nitrogen) are present in the precursor and reactant materials. The silicon precursors are selected to have specific compositional qualities - being free from carbon, halogens, and N-H bonds. This localized control of material composition at the molecular level ensures that the deposited film contains only the desired elements without contamination.
3Manufacturing precision
If high temperature deposition is used, then films can be formed, but step coverage and conformality are compromised for advanced device dimensions
Solution Approach 1:
The patent employs periodic action through the sequential deposition process where silicon precursor is deposited first to form an adsorbed layer, then nitrogen plasma is introduced to react and form silicon nitride. This cyclic, step-by-step approach allows for excellent conformal coverage. The process can be repeated multiple times to build up the desired film thickness while maintaining uniform step coverage on complex three-dimensional structures.
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 highly conformal, carbon-free, and halogen-free silicon nitride films at lower temperatures, improving step coverage and reducing contamination, making them suitable for advanced semiconductor applications like memory encapsulation layers.
Implementation Method 1
exposing the substrate to a silicon-containing precursor under conditions allowing formation of an adsorbed layer of the silicon containing precursor on the substrate surface
Implementation Method 2
exposing the adsorbed layer to a nitrogen (N2) plasma to thereby form a silicon nitride film
Implementation Method 3
exposing the adsorbed layer to a nitrogen (N2) plasma to thereby form a silicon nitride film
Implementation Method 4
periodically exposing the substrate to a hydrogen-containing plasma
Data Source
AI summary
Provided herein are methods of depositing conformal silicon nitride films using atomic layer deposition by exposure to a halogen-free, N—H-bond-free, and carbon-free silicon-containing precursor such as disilane, purging of the precursor, exposure to a nitrogen plasma, and purging of the plasma at low temperatures. A high frequency plasma is used, such as a plasma having a frequency of at least 13.56 MHz or at least 27 MHz. Methods yield substantially pure conformal silicon nitride films suitable for deposition in semiconductor devices, such as in trenches or features, or for memory encapsulation.