Silicon Nitride Hard Mask Removal via Low-Temperature Phosphoric Acid
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Solution Overview
Problem
Existing methods for removing patterned silicon nitride hard masks in semiconductor fabrication damage either the polysilicon conductive layers or result in slow etching rates, leading to defects and increased costs due to high-temperature phosphoric acid solutions.
Innovation Solution
A method utilizing a patterned silicon nitride layer with a high hydrogen concentration (>1022 atoms/cm3) as a hard mask, which is then removed using a low-temperature phosphoric acid solution, allowing for efficient etching without damaging polysilicon or silicon oxide layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hot phosphoric acid solution (155°C to 170°C) is used to remove the silicon nitride hard mask, then the etching rate of silicon nitride is improved, but the polysilicon conductive layer is damaged
Solution Approach 1:
The patent changes the temperature parameter of the phosphoric acid solution from high temperature (155-170°C) to low temperature (below 155°C) to achieve selective etching. This parameter change allows the etching process to proceed at a acceptable rate while preventing damage to the polysilicon layer, resolving the contradiction between etching efficiency and material protection
Solution Approach 2:
The patent creates a composite hard mask structure by forming a silicon oxide layer between the silicon nitride layer and the polysilicon conductive layer. This composite structure provides chemical selectivity, where the phosphoric acid etches the silicon nitride through the protective silicon oxide barrier without attacking the polysilicon, thus maintaining both high etching rate and polysilicon quality
2Ease of manufacture
If diluted hydrofluoric acid is used to remove the oxide hard mask, then the removal process is simple, but the dielectric layer is damaged due to high etching rate
Solution Approach 1:
The patent uses a disposable silicon oxide protective layer that is intentionally designed to be consumed during the etching process. This thin oxide layer serves as a sacrificial barrier that protects the main dielectric layer from HF acid attack while allowing efficient removal of the silicon nitride mask, balancing process simplicity with layer integrity
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 removes the silicon nitride layer at a higher rate than traditional methods, reducing processing time and preventing damage to the polysilicon and oxide layers, thereby improving the quality and reliability of semiconductor devices.
Implementation Method 1
removing the patterned silicon nitride layer utilizing a low-temperature phosphoric acid solution
Implementation Method 2
utilizing a patterned silicon nitride layer with high hydrogen concentration as a hard mask
Data Source
AI summary
A method for forming a gate and a method for etching a conductive layer are provided. First, a substrate is provided, including a dielectric layer and a conductive layer on its surface in order. Subsequently, a patterned silicon nitride layer is formed on the conductive layer as a hard mask, and the hydrogen concentration of the patterned silicon nitride layer is more than 1022 atoms/cm3. Thereafter, the conductive layer and the dielectric layer are etched utilizing the hard mask as a mask. Finally, an etching solution is utilized to remove the hard mask.