Silicon Nitride Film Stress Reduction via Hydrogen Radical Purge
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Solution Overview
Problem
Silicon nitride films formed by atomic layer deposition (ALD) methods exhibit high tensile stress and bending issues due to the attraction between spacers, particularly as devices miniaturize, making it difficult to achieve the required low temperature film formation and uniformity.
Innovation Solution
A method involving a hydrogen radical purge step between the film-forming raw material gas adsorbing and nitriding steps in a batch process vessel, using a chlorine-containing silicon compound and nitrogen gas, to promote Si—N bonds and reduce tensile stress in the silicon nitride film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an SiN film is formed by the ALD method using a batch-type vertical film forming apparatus, then the film can be formed at low temperature with uniform and good coverage and good electric characteristics, but the film exhibits high tensile stress and bending issues due to the attraction between spacers
Solution Approach 1:
A hydrogen radical purge step is introduced as an intermediary process between the DCS gas adsorption step and the NH3 gas nitriding step. This hydrogen radical treatment acts as a mediator that modifies the film formation process, promoting Si-N bond formation and reducing tensile stress in the SiN film while maintaining the low temperature ALD process benefits
Solution Approach 2:
The patent changes the process parameters by introducing hydrogen radicals through a plasma discharge process during the purge step. This parameter change (adding hydrogen radical treatment) modifies the chemical environment during film formation, enabling stress reduction without compromising the low temperature process advantage
2Length of moving object
If the SiN spacer becomes thinner according to miniaturization of a device, then the coverage performance is improved, but bending due to the attraction between spacers becomes a more severe problem
Solution Approach 1:
The hydrogen radical purge step serves as an intermediary treatment that strengthens the Si-N bonds in the spacer film. This mediator process reduces the internal tensile stress that causes spacer bending, enabling thinner spacers to maintain structural integrity even as device dimensions are miniaturized
3Stress or pressure
If the SiN film is formed by the plasma CVD method, then the stress in the film can be adjusted by adjusting the hydrogen concentration or composition, but the film contains more impurities compared to the ALD method
Solution Approach 1:
The hydrogen radical purge step introduces a controlled amount of hydrogen radicals as a mediator during the ALD process. This enables stress adjustment similar to plasma CVD, but without the continuous plasma exposure that introduces impurities, thus maintaining the high purity advantage of ALD while achieving stress control
Solution Approach 2:
Instead of using continuous plasma treatment (excessive action) as in plasma CVD, the patent applies hydrogen radical treatment only during the purge step (partial action). This limited application is sufficient to promote Si-N bond formation and reduce stress, while avoiding the impurity introduction associated with continuous plasma processing
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 hydrogen radical purge effectively reduces tensile stress in the silicon nitride film, achieving a more uniform and stress-reduced film suitable for advanced semiconductor applications, such as double patterning techniques.
Implementation Method 1
a hydrogen radical purge step of performing a hydrogen radical purge by generating hydrogen radicals in the process vessel is performed between the film-forming raw material gas adsorbing step and the nitriding step to promote an Si—N bond of the silicon nitride film to be formed so as to reduce a tensile stress of the silicon nitride film to be formed
Implementation Method 2
a process of firstly supplying a dichlorosilane (DCS; SiH2Cl2) gas to a semiconductor wafer as a substrate using, for example, the DCS gas as a raw material gas and an NH3 gas as a nitriding gas to chemically adsorb Si of a single atomic layer
Data Source
AI summary
There is provided a method of forming a silicon nitride film including: arranging substrates in a process vessel; and forming a silicon nitride film on the substrates in a batch by repeating a cycle including: a first purge step of purging the process vessel while heating the process vessel and making an interior of the process vessel be in a predetermined depressurized state; a film-forming raw material gas adsorbing step of adsorbing a chlorine-containing silicon compound to the substrates by supplying a film-forming raw material gas composed of the chlorine-containing silicon compound into the process vessel; a second purge step of purging the process vessel; and a nitriding step of nitriding the substrates by supplying a nitriding gas into the process vessel, and wherein in each of the cycle, a hydrogen radical purge step is performed between the film-forming raw material gas adsorbing step and the nitriding step.