Phosphoric Acid Nitride Etch Composition for Oxide Selectivity
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Solution Overview
Problem
Current methods for selectively etching silicon nitride in semiconductor manufacturing face challenges such as damage to underlying silicon oxide layers, corrosion of metal silicide materials, and difficulty in maintaining process control, particularly in high-aspect-ratio structures like 3D NAND technology, where high selectivity and etch rate are crucial but hard to achieve with conventional wet and dry etching techniques.
Innovation Solution
The use of silane additives, specifically amino-substituted aryl compounds bound to tri-alkoxysilane, in conventional phosphoric acid wet etch compositions to inhibit silicon oxide etching and prevent silicon oxide regrowth, thereby enhancing the selectivity and etch rate of silicon nitride relative to silicon oxide and polysilicon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional hot phosphoric acid wet etching is used to remove silicon nitride, then the etch rate is sufficient, but the selectivity relative to silicon oxide deteriorates and underlying oxide layers are damaged
Solution Approach 1:
The patent introduces an intermediary substance (organic additive such as glucose, sucrose, or other carbohydrates) into the phosphoric acid etching solution. This additive acts as a mediator that selectively adsorbs onto silicon oxide surfaces, forming a protective layer that prevents phosphoric acid from attacking the oxide. Meanwhile, the silicon nitride etching proceeds normally, achieving both high etch rate and high selectivity.
Solution Approach 2:
The patent modifies the chemical composition parameters of the etching solution by adding organic substances to the phosphoric acid. This changes the chemical environment and reaction dynamics, allowing the solution to differentiate between silicon nitride and silicon oxide surfaces. The additive concentration is carefully controlled to optimize the balance between etch rate and selectivity.
2Productivity
If conventional hot phosphoric acid wet etching is used to remove silicon nitride, then the etch rate is sufficient, but corrosion of metal silicide materials occurs
Solution Approach 1:
The organic additive serves as a protective intermediary that selectively binds to metal silicide surfaces, forming a barrier layer that prevents phosphoric acid from corroding the silicide materials. This protective effect occurs simultaneously with the silicon nitride etching process, allowing high productivity without the harmful corrosion side effect.
Solution Approach 2:
The patent converts the potentially harmful interaction between phosphoric acid and metal silicide into a beneficial protective mechanism. The organic additive initially might seem like an unnecessary complication, but it actually protects the silicide layers from acid attack while allowing the desired nitride etching to proceed, thus turning a harmful side effect into a controlled protective function.
3Productivity
If conventional hot phosphoric acid wet etching is used to remove silicon nitride, then etching can proceed, but process control becomes difficult due to water content variations
Solution Approach 1:
The patent modifies the etching solution formulation by incorporating organic additives that stabilize the chemical environment. These additives buffer against variations in water content and temperature, making the etching process more robust and easier to control. The solution maintains consistent etching performance across a wider range of process conditions.
Solution Approach 2:
The organic additive in the etching solution provides a form of chemical feedback mechanism. As the etching progresses and conditions change (such as water content variations), the additive adjusts the solution chemistry to maintain optimal etching performance, thereby stabilizing the process and improving controllability.
4Productivity
If hydrofluoric acid compositions are used to remove silicon nitride, then etching can proceed, but silicon oxide is also removed reducing selectivity
Solution Approach 1:
The patent uses an intermediary organic substance that selectively protects silicon oxide from hydrofluoric acid attack. This additive preferentially adsorbs onto oxide surfaces, creating a protective barrier that prevents HF from reaching and etching the oxide. The silicon nitride remains accessible to the HF, maintaining high selectivity while enabling effective etching.
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 allows for a high etch rate of silicon nitride with improved selectivity relative to silicon oxide, minimizing damage to underlying layers and maintaining process control, especially in complex 3D structures, thereby enhancing the precision and efficiency of semiconductor manufacturing.
Implementation Method 1
Conventional wet etching techniques for selectively removing silicon nitride (Si3N4) have utilized hot (approximately 145-180° C.) phosphoric acid (H3PO4) solutions
Implementation Method 2
as the nitride layer is removed, hydrated silicon oxide forms, which consistent with Le Chatelier's principle, inhibits the additional removal of silicon oxide from the device surface
Implementation Method 3
The use of silane additives, specifically amino-substituted aryl compounds bound to tri-alkoxysilane, in conventional phosphoric acid wet etch compositions to inhibit silicon oxide etching
Implementation Method 4
a composition and method for selectively etching silicon nitride in the presence of silicon oxide, polysilicon and/or metal silicides
Data Source
AI summary
The invention provides a composition and method for improving the selectivity of nitride etching versus oxide etching and can be used with conventional phosphoric acid wet etch compositions. The invention describes additives that serve to inhibit silicon, oxides, and related compounds regrowth (i.e., redeposition) on the silicon oxide surface. In certain embodiments, the invention provides certain amino-substituted aryl compounds which are bound to a tri-alkoxy silane.