Semiconductor Epitaxial Layer Surface Smoothing via Dilute Hydrofluoric Acid Cleaning
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Solution Overview
Problem
The existing methods for removing nitride spacers in semiconductor fabrication often damage the epitaxial layer, leading to uneven surfaces and potential device malfunctions due to over-etching during the cleaning process.
Innovation Solution
A method involving a dilute hydrofluoric (DHF) cleaning process followed by a standard clean (SC) process, with an additional DHF rinse step before the SC process, to effectively remove the nitride spacer while minimizing damage to the epitaxial layer and smoothing the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional cleaning process is used to remove the nitride spacer, then the nitride spacer is effectively removed, but the epitaxial layer is damaged and the surface becomes uneven
Solution Approach 1:
The cleaning process is divided into multiple sequential steps: preliminary DHF cleaning, H3PO4 cleaning to remove nitride, additional DHF cleaning to smooth the surface, and final SC process. This segmentation allows each step to address specific requirements without compromising the epitaxial layer
Solution Approach 2:
A preliminary DHF cleaning process is performed before the main nitride removal to prepare the surface and minimize subsequent damage to the epitaxial layer. This preliminary action prevents excessive etching in later steps
2Ease of manufacture
If the nitride spacer is removed using aggressive cleaning methods, then complete removal is achieved, but concaves are formed on the epitaxial layer surface
Solution Approach 1:
The H3PO4 cleaning solution acts as an intermediary that selectively removes nitride material while being less aggressive to the epitaxial layer. This intermediary substance enables complete nitride removal without forming deep concaves
Solution Approach 2:
The cleaning process uses multiple chemical solutions with different properties (DHF, H3PO4, SC) and controls exposure times to precisely control the etching rate. By adjusting these parameters, complete nitride removal is achieved while maintaining surface uniformity
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 reduces the depth of concaves on the epitaxial layer's surface, resulting in a smoother and more stable surface, thereby enhancing the semiconductor device's performance and reliability.
Implementation Method 1
a dilute hydrofluoric (DHF) cleaning process is performed over the substrate, wherein a top surficial portion of the epitaxial layer is removed
Implementation Method 2
a standard clean (SC) process is performed over the substrate, wherein a native oxide layer is formed on an expose surface of the epitaxial layer
Data Source
AI summary
A method for processing a semiconductor device is provided. The semiconductor device includes a protruding structure on a substrate, the protruding structure having a nitride spacer at a sidewall, and an epitaxial layer is formed in the substrate adjacent to the protruding structure. The method includes removing the nitride spacer on the protruding structure. Then, a dilute hydrofluoric (DHF) cleaning process is performed over the substrate, wherein a top surficial portion of the epitaxial layer is removed. A standard clean (SC) process is performed over the substrate, wherein a native oxide layer is formed on an expose surface of the epitaxial layer.