Silicon Nitride Film Reforming With Low-Ion-Energy DC Pulses
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Solution Overview
Problem
Conventional nitride film forming methods struggle to effectively control the film stress of silicon nitride films, often resulting in shifts from tensile to compressive stress due to high ion energy during hydrogen radical purges, which affects film quality and can lead to blister-like peeling.
Innovation Solution
A plasma processing method using a DC pulse voltage with controlled overshoot to generate hydrogen radicals, reducing ion energy and maintaining tensile stress in silicon nitride films by performing hydrogen radical purges between raw material gas adsorption and nitridation cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydrogen radical purges are performed using conventional plasma processing methods, then chlorine removal is effective, but ion energy becomes too high causing film stress to shift from tensile to compressive
Solution Approach 1:
The patent changes the voltage parameter from conventional RF plasma to DC pulse voltage with controlled overshoot. By setting the peak voltage to 150V or less and controlling the pulse width to 1ms or less, the method generates hydrogen radicals with sufficiently low ion energy to prevent film stress from shifting to compressive, while still achieving effective chlorine removal and film reforming.
Solution Approach 2:
The patent employs periodic DC pulse voltage application with controlled pulse widths (1ms or less) and duty cycles (10% or more). This periodic action allows hydrogen radicals to be generated in controlled bursts, enabling effective chlorine removal during the pulse phase while the off-phase allows stress relaxation, preventing cumulative compressive stress buildup.
2Manufacturing precision
If DC pulse voltage with low peak voltage is used to reduce ion energy, then film stress is maintained as tensile, but hydrogen radical generation efficiency may be reduced
Solution Approach 1:
The patent uses periodic DC pulse voltage with optimized pulse widths of 1ms or less and duty cycles of 10% or more. This periodic structure allows the plasma to be generated in controlled bursts, achieving sufficient hydrogen radical generation during the pulse phase while maintaining low average power and keeping ion energy low enough to preserve tensile stress.
Solution Approach 2:
The patent dynamically controls the voltage waveform by adjusting pulse width and duty cycle parameters. By making the pulse width 1ms or less and duty cycle 10% or more, the system adapts the hydrogen radical generation rate to balance between achieving sufficient chlorine removal and maintaining low ion energy to preserve tensile film stress.
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 method achieves high-quality silicon nitride films with maintained tensile stress, improving film quality and preventing blister-like peeling, while reducing hardware modifications and costs.
Implementation Method 1
supplying a hydrogen-containing gas to the processing container to generate a hydrogen radical by a direct current (DC) pulse voltage
Implementation Method 2
dichlorosilane is supplied to form a reactant reacted with dichlorosilane on a wafer. Next, hydrogen radicals are supplied to remove chlorine contained in the reactant. Subsequently, ammonia radicals are supplied into a reaction tube to form a silicon nitride film on a substrate W
Data Source
AI summary
A method of forming a nitride film includes: (a) preparing a substrate; (b) supplying a halogen-containing raw material gas into a processing container; (c) supplying a nitrogen-containing gas into the processing container, wherein the nitride film is formed by repeating a cycle including (b) and (c) a set number of times; and (d) reforming the nitride film by supplying a hydrogen-containing gas to the processing container to generate a hydrogen radical by a direct current (DC) pulse voltage, between (b) and (c).