Polysilicon Layer Uniformity in High Aspect Ratio Structures
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Solution Overview
Problem
Forming a polysilicon layer with a uniform profile within high aspect ratio structures, such as holes or trenches, is challenging using conventional atomic layer deposition (ALD) processes, as it often results in non-uniform thickness and surface diffusion issues.
Innovation Solution
A method involving the use of nitrogen-containing and chlorine-containing silicon precursors, such as Bis(ethylmethylamino)silane and dichlorosilane, is employed to form a seed layer, followed by a silicon source, within an ALD process chamber, with heat treatment and purge processes to activate atoms and prevent surface diffusion, ensuring a uniform polysilicon layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional ALD process is used to form polysilicon layer in high aspect ratio structures, then the polysilicon layer can be formed, but the uniformity of thickness and profile is poor
Solution Approach 1:
The polysilicon layer formation is segmented into multiple sequential ALD cycles with different precursors (nitrogen-containing silicon precursor and chlorine-containing silicon precursor) and different processing conditions. Each cycle deposits a portion of the final layer with specific properties, allowing control over thickness uniformity and composition in high aspect ratio structures.
Solution Approach 2:
The ALD process parameters are changed between cycles, including precursor types, deposition temperatures, and cycle durations. These parameter variations enable precise control of the polysilicon layer's deposition rate and uniformity, particularly in challenging high aspect ratio geometries where conventional single-step ALD fails.
2Area of stationary object
If polysilicon layer is formed in high aspect ratio hole or trench, then the layer can cover the structure, but surface diffusion occurs and uniform profile is not obtained
Solution Approach 1:
A nitrogen-containing silicon precursor is used as an intermediary material that deposits first and forms a controlled interface layer. This intermediary layer prevents direct surface diffusion of subsequent chlorine-containing precursor, enabling uniform polysilicon deposition even in high aspect ratio structures where surface diffusion would normally cause non-uniform profiles.
Solution Approach 2:
The nitrogen-containing silicon precursor is deposited in preliminary ALD cycles before the main polysilicon deposition. This preliminary action prepares the surface by creating a controlled initial layer that prevents unwanted surface diffusion during subsequent deposition steps, ensuring uniform profile development throughout the high aspect ratio structure.
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 the formation of a polysilicon layer with a uniform thickness and single atomic layer structure, even in high aspect ratio features, enhancing the uniformity and density of silicon atoms, thus improving the polysilicon layer's quality and consistency.
Implementation Method 1
a silicon precursor is provided onto an object loaded in a process chamber to form a seed layer. The silicon precursor includes a nitrogen containing silicon precursor and a chlorine containing silicon precursor.
Implementation Method 2
a first purge process and a heat treatment may be further performed after forming the preliminary seed layer. nitrogen atoms or silicon atoms of the nitrogen containing silicon precursor may be activated by the first purge process and the heat treatment.
Implementation Method 3
providing a silicon source on the seed layer. A silicon source may be introduced onto the seed layer to form a polysilicon layer having a uniform thickness.
Data Source
AI summary
A method of forming a polysilicon layer includes providing a silicon precursor onto an object loaded in a process chamber to form a seed layer. The silicon precursor includes a nitrogen containing silicon precursor and a chlorine containing silicon precursor. The method further includes providing a silicon source on the seed layer.