Hot Phosphoric Acid Nitride Etching for Semiconductor Oxide Preservation
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Solution Overview
Problem
Conventional semiconductor manufacturing processes face issues with spacer damage and increased leakage current due to the removal of nitride layers at low temperatures, which affects the integrity of the oxide layer and results in transistor kink effects and reduced process windows.
Innovation Solution
The method involves using high concentration H3PO4 at elevated temperatures to selectively remove nitride layers, preserving the base oxide and eliminating the need for subsequent oxide redeposition, thereby reducing manufacturing faults and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional wet etching is used to remove nitride layer at low temperature (110-130°C), then adequate etching rate is achieved, but the oxide layer is damaged and spacers are compromised causing leakage current
Solution Approach 1:
The patent changes the etching parameters by using hot phosphoric acid at elevated temperatures (150-200°C) instead of conventional low temperature (110-130°C) processing. This parameter change enables selective removal of nitride while preserving the oxide layer, resolving the contradiction between achieving adequate etching rate and maintaining oxide layer integrity.
Solution Approach 2:
The patent employs a disposable nitride layer that is intentionally designed to be removed by the hot phosphoric acid etching process. This sacrificial layer approach allows the oxide layer to be preserved during etching, as the nitride serves its purpose and is then discarded through selective removal.
2Ease of manufacture
If conventional SPM clean process is used to strip organic material, then effective cleaning is achieved, but the native silicon dioxide layer is removed causing deep divot and transistor kink effect
Solution Approach 1:
The patent applies local quality by making the cleaning process selective - the hot phosphoric acid solution cleans organic material and photoresist from specific areas while leaving the native silicon dioxide layer intact. This localized action preserves critical oxide regions while achieving effective cleaning where needed.
Solution Approach 2:
The patent changes the cleaning parameters by using hot phosphoric acid at 150-200°C instead of conventional SPM solution at lower temperatures. This parameter change enables effective removal of organic contaminants while preserving the silicon dioxide layer, eliminating deep divot formation and transistor kink effects.
3Productivity
If multiple deposition and etching steps are performed, then complete layer removal is achieved, but process complexity increases and leakage current is induced
Solution Approach 1:
The patent merges multiple functions into a single etching step using hot phosphoric acid. This single process simultaneously removes the nitride layer and cleans organic material without damaging the oxide layer, eliminating the need for separate SPM cleaning and oxide redeposition steps, thus reducing overall process complexity.
Solution Approach 2:
The patent extracts the oxide layer preservation function from the conventional multi-step process. By using hot phosphoric acid that selectively attacks nitride while preserving oxide, the need for subsequent oxide redeposition is eliminated, simplifying the overall manufacturing 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 approach effectively reduces spacer damage, minimizes transistor kink effects, and enhances the Vmin window by maintaining the integrity of the oxide layer, leading to improved semiconductor device performance and manufacturing efficiency.
Implementation Method 1
processing the silicide region using a high selection H3PO4 to remove the nitride at a high temperature with high silicon concentration to preserve the base oxide
Implementation Method 2
SPM is used to clean the oxide layer, but without DHF; oxide is preserved thus reducing the divot and improving Vmin and Kink Effect
Data Source
AI summary
A new method for fabricating a semiconductor device with high selection phosphoric acid solution and eliminating the step of oxide removal and thus reducing oxide loss to improve yield gain and cost saving.