Ultrathin SiON Interface Layer for p-TOPCon Boron Diffusion Control
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Solution Overview
Problem
The existing tunnel oxide passivated contact (TOPCon) solar cells face challenges in large-scale manufacturing due to high costs and suboptimal passivation effects, particularly in p-TOPCon cells, where the plasma-assisted nitrous oxide oxidation method results in low nitrogen concentration in silicon oxide layers, leading to boron diffusion issues and ion bombardment damage.
Innovation Solution
An ultrathin silicon oxynitride (SiON) interface material with a thickness of 1 nm to 4 nm and 1% to 40% nitrogen content is developed, using an ion-free bombardment oxidation method followed by plasma-enhanced chemical vapor deposition with nitrogen-containing and oxygen-containing gases to reduce boron diffusion and ion damage, enhancing chemical passivation and hole transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If plasma-assisted nitrous oxide oxidation method is used to prepare silicon oxide layer, then the passivation effect is improved, but ion bombardment damage defects are introduced on silicon wafer surfaces
Solution Approach 1:
The patent introduces an ultrathin SiON interface material as an intermediary layer between the silicon wafer and the tunnel oxide. This SiON layer acts as a mediator that provides effective passivation while avoiding the ion bombardment damage caused by direct plasma treatment of the silicon surface. The SiON layer absorbs the harmful plasma effects while maintaining the desired passivation functionality.
Solution Approach 2:
The patent changes the chemical composition parameters of the interface material from pure silicon oxide (SiO2) to silicon oxynitride (SiON) with specific nitrogen content (1% to 40% N atoms). This parameter change allows the material to achieve better passivation performance while reducing sensitivity to plasma-induced damage, thereby resolving the contradiction between passivation quality and ion damage resistance.
2Reliability
If nitrogen concentration in SiON film is low, then the passivation effect is maintained, but boron diffusion stopping and enrichment effect cannot be achieved
Solution Approach 1:
The patent optimizes the nitrogen concentration parameter in the SiON film to a specific range (1% to 40% N atoms). This parameter optimization creates a balance where the nitrogen content is sufficient to provide boron diffusion stopping and enrichment effects, while not exceeding the threshold that would compromise the passivation quality. The ultrathin thickness (1 nm to 4 nm) further fine-tunes this parameter balance.
Solution Approach 2:
The patent applies a moderate amount of nitrogen (not excessive) in the SiON interface layer to achieve the desired boron diffusion control. By using partial nitrogen incorporation rather than high nitrogen content, the patent achieves sufficient boron enrichment and diffusion stopping while maintaining good passivation properties.
3Ease of manufacture
If p-TOPCon technology is used to reduce manufacturing costs, then cost compatibility is improved, but passivation quality and iVoc performance are reduced compared to n-TOPCon
Solution Approach 1:
The patent changes the interface material composition to SiON with optimized nitrogen content and controls the layer thickness in the ultrathin range of 1 nm to 4 nm. These parameter changes enable p-TOPCon structures to achieve passivation quality and iVoc performance comparable to n-TOPCon, while maintaining the cost advantages of p-type silicon compatibility with aluminum paste materials.
Solution Approach 2:
The patent uses a composite structure consisting of SiON interface material combined with tunnel oxide and doped polycrystalline silicon. This composite material approach enables the p-TOPCon structure to achieve performance levels previously only attainable with n-TOPCon, while maintaining cost effectiveness through p-type silicon compatibility.
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 high nitrogen content SiON film improves passivation quality, reduces boron-induced defects, and increases hole transport efficiency, achieving open-circuit voltage (iVoc) above 720 mV and contact resistivity less than 5 mΩcm², making the technology more compatible with existing production equipment and cost-effective.
Implementation Method 1
growing a layer of SiO2 film on a silicon wafer by ion-free bombardment oxidation method
Implementation Method 2
performing surface nitriding treatment on the SiO2 film in the plasma enhanced chemical vapor deposition (PECVD) with a nitrogen-containing gas and an oxygen-containing gas filled treatment atmosphere to generate an SiON film
Implementation Method 3
performing surface nitriding treatment on the SiO2 film
Data Source
AI summary
An ultrathin silicon oxynitride interface material, a tunnel oxide passivated structure and preparation methods and applications thereof are provided. The ultrathin silicon oxynitride interface material is an SiON film with a thickness of 1 nm to 4 nm, and the percentage content of N atoms is 1% to 40%. Compared with silicon oxide, the diffusion rate of boron in the SiON film of the present disclosure is low, which effectively reduces the damaging effect of boron, improves the integrity of the SiON film and maintains the chemical passivation effect. The SiON film with high nitrogen concentration can noticeably lower the concentration of boron on the silicon surface so as to lessen the boron-induced defects. Furthermore, the SiON film has an energy band structure approximate to silicon nitride, which increases the hole transport efficiency and hole selectivity, and further improves the passivation quality and reduces the contact resistivity.