Polysilicon Plasma Etching Shape Control
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Solution Overview
Problem
In semiconductor manufacturing, particularly for DRAM and 3D-NAND flash memory, deep hole or groove shapes with high aspect ratios are difficult to form without etching shape abnormalities, such as increased opening dimensions and etching stop issues, when using polysilicon films as mask layers in plasma etching processes.
Innovation Solution
A plasma processing method using a mixed gas comprising a halogen gas, a fluorocarbon gas, an oxygen gas, and a carbonyl sulfide gas is employed to etch polysilicon films, controlling gas flow rates and bias power to prevent etching shape abnormalities and achieve precise etching depths without enlarging the opening dimension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a polysilicon film mask layer is used to form deep hole shapes with high aspect ratios, then the mask layer can maintain structural integrity during etching, but the opening dimension increases due to etching, causing shape abnormality
Solution Approach 1:
The invention changes the chemical composition parameters of the etching gas from conventional single-gas or two-gas systems to a four-component mixed gas system comprising HBr, O2, CO2, and SO2. This parameter change modifies the etching chemistry to achieve selective removal of polysilicon while protecting the mask layer, thereby maintaining the opening dimension and achieving high aspect ratios without shape abnormality
Solution Approach 2:
The invention uses a composite gas mixture combining four different gases (HBr, O2, CO2, SO2) that work synergistically. HBr provides the primary etching action on polysilicon, while O2, CO2, and SO2 components work together to protect the mask layer and control the etching profile, resulting in precise control of both depth and opening dimension
2Reliability
If the mask layer is made thick to prevent disappearance during etching, then the mask layer maintains protection, but etching stop occurs and desired deep hole shape cannot be formed
Solution Approach 1:
The invention changes the etching selectivity parameters by introducing a four-component gas mixture where HBr selectively etches polysilicon at a controlled rate, while the O2, CO2, and SO2 components provide protective effects on the mask layer. This parameter optimization allows the etching process to penetrate through thick mask layers to form desired deep hole shapes without premature etching stop
Solution Approach 2:
The invention creates a dynamic etching environment where the mixed gas components continuously interact with the etching front, adjusting the chemical reactions in real-time. The combination of reactive HBr and protective O2/CO2/SO2 creates a self-regulating etching process that maintains appropriate etching rates throughout the depth, enabling formation of deep holes with high aspect ratios
3Device complexity
If conventional plasma etching methods are used, then the etching process is simple, but etching shape abnormality occurs with adjacent patterns connecting
Solution Approach 1:
The invention modifies the gas composition parameters from conventional simple mixtures to a specific four-component mixture (HBr, O2, CO2, SO2) with optimized ratios. This parameter change fundamentally alters the etching chemistry to produce vertical sidewalls and prevent lateral etching that causes pattern connection, thereby maintaining pattern separation while using a still-relatively-simple plasma process
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 method effectively prevents etching shape abnormalities, allowing for the formation of desired deep hole or groove shapes with high aspect ratios by optimizing the etching process parameters, ensuring accurate control over etching depth and opening dimensions.
Implementation Method 1
plasma-etching the polysilicon film using a mixed gas includes a halogen gas, a fluorocarbon gas, an oxygen gas, and a carbonyl sulfide gas
Data Source
AI summary
The invention has been made in view of the above problems, and provides a plasma processing method capable of preventing etching shape abnormality in a plasma processing method for forming a mask layer of a polysilicon film. The invention relates to a plasma processing method for plasma-etching a polysilicon film, the plasma processing method comprising plasma-etching the polysilicon film using a mixed gas including a halogen gas, a fluorocarbon gas, an oxygen gas, and a carbonyl sulfide gas.