Semiconductor Depression Filling via Segmented Epitaxial Layers
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Solution Overview
Problem
In the process of filling depressions in semiconductor devices, such as through-holes or contact holes, the annealing of amorphous silicon leads to agglomeration, resulting in the formation of cavities or voids, which need to be suppressed to ensure effective filling and prevent defects.
Innovation Solution
A depression filling method involving the formation of an impurity-doped first semiconductor layer along the depression walls, followed by a second semiconductor layer with lower impurity concentration and thickness, and subsequent annealing to form an epitaxial region at the depression bottom, along with etching of the amorphous semiconductor regions to prevent agglomeration and fill the depression effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If amorphous silicon is moved by annealing toward the bottom portion of the depression, then the depression is filled with amorphous silicon, but the amorphous silicon agglomerates and cavities called voids or seams are formed
Solution Approach 1:
The semiconductor layer is divided into multiple layers with different impurity concentrations. The first semiconductor layer has a first impurity concentration and the second semiconductor layer has a second impurity concentration different from the first. This segmentation allows different regions to serve different functions: the higher impurity concentration region suppresses void formation while the lower impurity concentration region enables complete depression filling.
Solution Approach 2:
Different impurity concentrations are applied to different layers of the semiconductor material. The first semiconductor layer contains impurities at a concentration optimized for preventing void formation during annealing, while the second semiconductor layer contains impurities at a different concentration optimized for filling the depression. This local quality variation resolves the contradiction between preventing cavities and achieving complete filling.
2Reliability
If a single amorphous silicon layer is annealed to fill the depression, then the depression is filled, but agglomeration occurs resulting in voids and seams
Solution Approach 1:
The single amorphous silicon layer is segmented into multiple layers with different impurity concentrations. This segmentation prevents uniform agglomeration that occurs in a single-layer structure, as the different impurity concentrations create distinct annealing behaviors in each layer that collectively prevent void formation while ensuring complete filling.
Solution Approach 2:
The semiconductor structure uses a composite of multiple amorphous silicon layers with different impurity concentrations. This composite structure combines the benefits of each layer: the first layer with its specific impurity concentration prevents void formation, while the second layer with different impurity concentration ensures complete depression filling, achieving both reliability and compositional stability.
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 suppresses the formation of cavities, improves crystal quality, and reduces contact resistance between the epitaxial region and the semiconductor substrate, ensuring a more reliable and defect-free filling process.
Implementation Method 1
a heating unit configured to heat an internal space of the vessel
Implementation Method 2
the workpiece is annealed. In this process, by annealing the workpiece, amorphous silicon is moved toward the bottom portion of the depression
Implementation Method 3
amorphous silicon is moved toward the bottom portion of the depression, whereby the depression is filled with the amorphous silicon
Implementation Method 4
etching the first amorphous semiconductor region and the second amorphous semiconductor region
Data Source
AI summary
A depression filling method for filling a depression of a workpiece including a semiconductor substrate and an insulating film formed on the semiconductor substrate includes: forming an impurity-doped first semiconductor layer along a wall surface which defines the depression; forming, on the first semiconductor layer, a second semiconductor layer which is lower in impurity concentration than the first semiconductor layer and which is smaller in thickness than the first semiconductor layer; annealing the workpiece to form an epitaxial region at the bottom of the depression corresponding to crystals of the semiconductor substrate from the first semiconductor layer and the second semiconductor layer; and etching the first amorphous semiconductor region and the second amorphous semiconductor region.