Silicon Nitride PECVD Plasma Stabilization
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Solution Overview
Problem
Low temperature plasma-enhanced chemical vapour deposition (PECVD) processes for silicon nitride film deposition often result in the formation of unwanted silicon-rich particles, which can impact electrical and thermal properties and cause substrate topography irregularities, and existing methods to mitigate this issue are time-consuming and costly.
Innovation Solution
A method involving a PECVD process where high frequency (HF) and low frequency (LF) RF powers are applied to stabilize the plasma before introducing the silane precursor, with the LF power being reduced or removed shortly after to prevent the formation of silicon-rich particles, allowing for a more stable plasma regime and reduced processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If low temperature PECVD process with high deposition rate is used, then deposition efficiency is improved, but silicon-rich particles are formed on substrate surface
Solution Approach 1:
The patent applies preliminary action by introducing the silane precursor into the plasma before the main deposition process begins. The silane is introduced during a plasma conditioning phase where the plasma is already established and stable, allowing the precursor to be incorporated into the growing film from the earliest stages rather than being introduced during conditions that would cause particle formation.
Solution Approach 2:
The patent employs parameter changes by carefully controlling the plasma power, pressure, and precursor flow rates during different phases of the deposition process. The plasma power is adjusted to maintain optimal conditions for silicon nitride deposition while preventing the formation of silicon-rich particles, and the silane flow rate is controlled to ensure proper incorporation into the film structure.
2Object-generated harmful factors
If successive thin layers are deposited to control silicon-rich particles, then particle prevalence is reduced, but processing time and cost increase
Solution Approach 1:
The patent implements continuous useful action by maintaining a stable plasma throughout the entire deposition process and continuously introducing the silane precursor at controlled rates. This continuous process allows for uniform film formation without the need to interrupt for particle removal or to deposit multiple separate layers, thereby reducing processing time while still preventing particle formation.
Solution Approach 2:
The patent uses preliminary action by establishing a stable plasma regime before introducing the silane precursor and maintaining optimal plasma conditions throughout the deposition. This preliminary plasma conditioning prevents particle formation from the outset, eliminating the need for subsequent particle removal steps or multiple deposition cycles.
3Temperature
If low temperature PECVD is used, then thermal budget is maintained low, but electrical properties of film are compromised
Solution Approach 1:
The patent applies parameter changes by optimizing the plasma power density, pressure, and gas flow rates to achieve films with excellent electrical properties at low temperatures. The plasma power is carefully controlled to provide sufficient energy for good film quality without exceeding the thermal budget, and the pressure and flow rates are adjusted to enhance film densification and reduce defects that would degrade electrical properties.
Solution Approach 2:
The patent employs local quality by creating regions of enhanced plasma activity and precursor incorporation within the film structure. The controlled introduction of silane during plasma exposure creates local variations in film composition and density that improve electrical properties such as breakdown voltage and leakage current while maintaining overall low temperature 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
This approach effectively eradicates the formation of silicon-rich particles, maintaining excellent electrical properties while achieving a high deposition rate and reducing processing time, thereby improving substrate throughput and film quality.
Implementation Method 1
applying a high frequency (HF) RF power and a low frequency (LF) RF power to sustain a plasma in the chamber
Implementation Method 2
depositing silicon nitride onto a substrate by plasma-enhanced chemical vapour deposition (PECVD)
Data Source
Figure 1A~1B
Figure 2
Figure 3~4
AI summary
According to the invention there is provided a method of depositing silicon nitride by plasma-enhanced chemical vapour deposition (PECVD), the method comprising the steps of: providing a PECVD apparatus comprising a chamber and a substrate support disposed within the chamber; positioning a substrate on the substrate support; introducing a nitrogen gas (N2) precursor into the chamber; applying a high frequency (HF) RF power and a low frequency (LF) RF power to sustain a plasma in the chamber; introducing a silane precursor into the chamber while the HF and LF RF powers are being applied so that the silane precursor forms part of the plasma being sustained; and subsequently removing the LF RF power or reducing the LF RF power by at least 90 % while continuing to sustain the plasma so that silicon nitride is deposited onto the substrate by PECVD.