DRAM Trench Isolation Liner Void Reduction
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Solution Overview
Problem
Current DRAM units with buried gate structures face limitations in fabrication capability, leading to performance and reliability issues due to incomplete filling of trenches during the formation of isolation structures, resulting in voids and inefficiencies.
Innovation Solution
Reversing the order of the atomic layer deposition (ALD) and in-situ steam generation (ISSG) processes to first form a first liner in trenches and then a second liner, ensuring complete filling of narrower trenches while only partially filling wider ones, thereby reducing void formation and improving isolation structure fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional single-layer liner formation is used in trenches, then the process is simple, but narrower trenches cannot be completely filled resulting in voids
Solution Approach 1:
The liner structure is segmented into multiple layers: a first liner layer deposited conformally on trench walls, and a second liner layer deposited subsequently to fill remaining spaces. This segmentation allows each layer to serve specific functions - the first layer provides initial coverage while the second layer ensures complete filling of narrower trenches, thereby eliminating voids without requiring an overly complex single-layer structure
Solution Approach 2:
The first liner layer is deposited as a preliminary action before the second liner layer. This preliminary conformal deposition prepares the trench surfaces and establishes a foundation that enables the subsequent second liner layer to completely fill narrower trenches, ensuring complete filling before final planarization occurs
2Manufacturing precision
If uniform liner deposition is applied to all trenches, then the process is straightforward, but wider trenches receive excessive material and narrower trenches remain incompletely filled
Solution Approach 1:
The second liner layer is deposited with controlled thickness to partially fill wider trenches while completely filling narrower trenches. By controlling the deposition thickness to be greater than the remaining gap in narrower trenches but less than the full depth of wider trenches, the process achieves uniform filling precision without excessive material consumption in wider trenches
3Reliability
If multi-layer liner structure is implemented, then complete trench filling is achieved, but the fabrication process becomes more complex
Solution Approach 1:
The first liner layer serves as a preliminary conformal coating that prepares the trench surfaces and provides initial coverage. This preliminary action simplifies the overall process by establishing a foundation that enables the second layer to achieve complete filling, thereby maintaining fabrication simplicity while ensuring isolation structure integrity through the multi-layer approach
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 void formation and enhances the reliability and performance of DRAM device fabrication by ensuring complete filling of narrower trenches and controlled filling of wider trenches, improving the overall integrity of isolation structures.
Implementation Method 1
Reversing the order of the atomic layer deposition (ALD) and in-situ steam generation (ISSG) processes to first form a first liner in trenches
Implementation Method 2
Reversing the order of the atomic layer deposition (ALD) and in-situ steam generation (ISSG) processes to first form a first liner in trenches and then a second liner
Data Source
AI summary
A method for fabricating semiconductor device includes the steps of: providing a substrate having a memory region and a periphery region; forming a first trench and a second trench in substrate on the memory region, in which a width of the second trench is greater than a width of the first trench; forming a first liner in the first trench and the second trench; forming a second liner on the first liner as the second liner completely fills the first trench and partly fills the second trench; and planarizing the second liner and the first liner to form a first isolation structure and a second isolation structure.