Void-Free Polysilicon Contact Hole Fill via Air Gap Seam Removal
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Solution Overview
Problem
In semiconductor device fabrication, high aspect ratio contact holes filled with polysilicon often develop voids due to seam formation, which increase interface and bulk resistance, leading to resistive failures as the voids can move during thermal processes.
Innovation Solution
A method involving the formation of a sacrificial layer, etching to create an open portion, depositing a polysilicon layer, removing the sacrificial layer to form an air gap, and performing a thermal process to remove seams in the polysilicon layer pattern, preventing void formation by leveraging surface tension differences between the air gap and polysilicon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If polysilicon is deposited to gap-fill a high aspect ratio contact hole, then the contact hole is completely filled with polysilicon, but seams form and develop into voids during thermal processing
Solution Approach 1:
A sacrificial layer is formed on the sidewalls of the contact hole before polysilicon deposition. This preliminary structure enables subsequent formation of an air gap that will facilitate seam removal during thermal processing, preventing void formation while maintaining complete contact hole fill
Solution Approach 2:
An air gap is introduced as an intermediary space between the polysilicon and the surrounding structure. This air gap serves as a pathway for seams to escape during thermal processing without forming voids within the polysilicon, thus mediating between the need for complete fill and the prevention of defect formation
2Manufacturing precision
If polysilicon is deposited in a high aspect ratio contact hole, then the contact hole is filled, but interface resistance increases due to void formation
Solution Approach 1:
The air gap acts as an intermediary that allows seams to be removed during thermal processing without forming voids at critical interfaces. This prevents the formation of high resistance paths while maintaining complete contact hole fill
Solution Approach 2:
The sacrificial layer is selectively removed to create the air gap, extracting material that would otherwise constrain the polysilicon structure. This extraction enables seam removal pathways while preserving the filled contact hole structure
3Manufacturing precision
If polysilicon is deposited in a high aspect ratio contact hole, then the contact hole is filled, but bulk resistance increases due to void formation
Solution Approach 1:
The air gap serves as a mediator that enables internal seams within the polysilicon to be removed during thermal processing. This prevents the formation of voids that would increase bulk resistance, while maintaining complete contact hole fill
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 forms void-free polysilicon layers, reducing interface and bulk resistance, and preventing resistive failures by ensuring seams are removed without developing into voids, thus enhancing semiconductor device performance.
Implementation Method 1
forming an air gap by removing the sacrificial layer
Implementation Method 2
performing a thermal process to remove a seam in the polysilicon layer pattern
Implementation Method 3
removing the seam in the polysilicon layer pattern, preventing void formation by leveraging surface tension differences between the air gap and polysilicon
Data Source
AI summary
A method for fabricating a semiconductor device includes forming a buried gate electrode in a semiconductor substrate. An insulating layer is formed over the buried gate electrode and is etched to form a contact hole exposing the semiconductor substrate. A sacrificial spacer is formed on sidewalls of the insulating layer defining the contact hole. A polysilicon layer pattern is formed in the contact hole. The sacrificial spacer is removed to form an air gap around the polysilicon layer pattern. A thermal process is performed to remove a seam existing in the polysilicon layer pattern.