Boron-Doped Polysilicon Plasma Etching With Mixed Halogen Gas
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Solution Overview
Problem
Boron-doped polysilicon etching in semiconductor manufacturing faces issues such as etching defects like etching stop, taper shape formation, side etching, and bowing shape due to limited etching rate and selectivity, particularly when using fluorine gases.
Innovation Solution
A plasma processing method using a mixed gas of halogen gases, fluorine-containing gases, and boron trichloride gas, such as chlorine, nitrogen trifluoride, oxygen, and hydrogen bromide, to improve etching rates and reduce defects in silicon or polysilicon films containing boron.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If boron-doped polysilicon is etched with fluorine gas, then etching rate is improved, but etching defects such as side etching and bowing shape formation occur
Solution Approach 1:
The patent changes the chemical composition parameters of the etching gas from pure fluorine gas to a mixed gas containing chlorine, fluorine, and boron trichloride. This parameter change allows the etching process to achieve high etching rates while preventing side etching and bowing defects through the synergistic effects of the gas components
Solution Approach 2:
The patent uses a composite gas mixture (chlorine gas + fluorine-containing gas + boron trichloride gas) instead of a single gas. The composite gas provides multiple functions: chlorine contributes to etching rate, fluorine enhances selectivity, and boron trichloride prevents defect formation, thereby resolving the contradiction between etching rate and etching quality
2Productivity
If boron-doped polysilicon is etched under related art conditions, then etching can be performed, but etching stop and taper shape formation occur with decreased etching rate
Solution Approach 1:
The patent modifies the etching gas composition parameters by introducing a specific mixture of chlorine gas, fluorine-containing gas, and boron trichloride gas. This parameter optimization enables consistent etching performance across the substrate, preventing etching stop and taper formation while maintaining high etching rates
Solution Approach 2:
Boron trichloride acts as an intermediary substance in the etching process. It mediates between the aggressive etching action of chlorine and fluorine gases and the substrate, preventing direct harmful interactions that cause etching stop and taper defects while maintaining efficient material removal
3Ease of manufacture
If polysilicon is used as hard mask material, then etching of insulating film can be performed, but selectivity with insulating film is limited
Solution Approach 1:
The patent changes the selectivity parameter by optimizing the gas composition ratios, particularly the chlorine-to-fluorine ratio and the addition of boron trichloride. This creates an etching environment where polysilicon is etched at a controlled rate while insulating films remain protected, achieving the required selectivity for precise pattern transfer
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 enhances etching rates and minimizes defects, allowing for precise control of opening sizes and selection ratios, preventing side etching and bowing shapes, and ensuring effective pattern transfer in semiconductor manufacturing.
Implementation Method 1
a first plasma process in which a mixed gas including a halogen gas, a fluorine-containing gas, and boron trichloride gas is used to etch the silicon film containing boron
Implementation Method 2
etching the silicon film containing boron by using a mixed gas of a halogen gas, a fluorine-containing gas, and a boron trichloride gas
Data Source
AI summary
In a plasma processing method for plasma etching a silicon film or polysilicon film containing boron, the polysilicon film containing boron is etched by using a mixed gas of a halogen gas, a fluorine-containing gas, and a boron trichloride gas. According to plasma processing method, it is possible to improve the etching rate and reduce etching defects when plasma etching a silicon film or polysilicon film containing boron.