Semi-Amorphous Polysilicon Trench Fill to Reduce Voids and Seams
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Solution Overview
Problem
Conventional polysilicon deposition processes in trench structures of microelectronic devices often result in seam and void formation, which can trap contaminants and degrade device yield and reliability, increasing process complexity and cost.
Innovation Solution
A method involving the formation of a trench structure with a seed layer of amorphous dielectric material and semi-amorphous polysilicon, where the semi-amorphous polysilicon includes amorphous silicon regions separated by polycrystalline silicon, which is converted to a polysilicon core through thermal processes, reducing seam and void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polysilicon deposition process is used, then large columnar grains are formed, but seam and void formation occurs which degrades yield and reliability
Solution Approach 1:
The invention changes the deposition parameters to form semi-amorphous polysilicon instead of conventional crystalline polysilicon. By controlling the deposition conditions to create a semi-amorphous structure with smaller grains, the process eliminates seam and void formation while maintaining complete trench filling, thus improving both manufacturing precision and device reliability
Solution Approach 2:
The invention uses a composite structure consisting of amorphous dielectric material and semi-amorphous polysilicon. The amorphous dielectric material serves as a seed layer that promotes uniform nucleation, resulting in semi-amorphous polysilicon with fine-grained structure that prevents defect formation during trench filling
2Reliability
If oxide strip and oxide regrowth loop is added to clean voids, then seam and void effects are reduced, but process complexity, cycle-time and cost increase
Solution Approach 1:
The invention performs preliminary action by forming amorphous dielectric material as a seed layer before polysilicon deposition. This pre-prepared seed layer creates uniform nucleation sites that ensure defect-free polysilicon growth from the beginning, eliminating the need for subsequent oxide strip and regrowth steps to clean voids
Solution Approach 2:
The invention extracts and removes the problematic oxide strip and regrowth steps from the process flow. By using semi-amorphous polysilicon deposition directly on amorphous dielectric seed layers, the method achieves void-free filling without requiring the additional cleaning cycles, thus reducing process complexity and cycle-time
3Manufacturing precision
If trench etch profile is tapered to improve fill process, then polysilicon filling is improved, but process complexity, cycle-time and cost increase
Solution Approach 1:
The invention changes the material parameters by using semi-amorphous polysilicon with different deposition characteristics compared to conventional polysilicon. This material change allows for uniform filling of high aspect ratio trenches with standard etch profiles, eliminating the need for complex tapered etching while maintaining excellent fill quality
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 minimizes seam and void formation within the trench structure, enhancing the reliability and yield of microelectronic devices by using a polysilicon core with silicon grains larger than half the trench's minimum lateral dimension, thus improving the filling process and reducing process complexity and cost.
Implementation Method 1
Subsequent thermal processes used in fabrication of the microelectronic device may convert the semi-amorphous polysilicon in the trench to a polysilicon core
Implementation Method 2
forming semi-amorphous polysilicon on the amorphous dielectric material
Data Source
AI summary
A microelectronic device with a trench structure is formed by forming a trench in a substrate, forming a seed layer in the trench, the seed layer including an amorphous dielectric material; and forming semi-amorphous polysilicon on the amorphous dielectric material. The semi-amorphous polysilicon has amorphous silicon regions separated by polycrystalline silicon. Subsequent thermal processes used in fabrication of the microelectronic device may convert the semi-amorphous polysilicon in the trench to a polysilicon core. In one aspect, the seed layer may be formed on sidewalls of the trench, contacting the substrate. In another aspect, a polysilicon outer layer may be formed in the trench before forming the seed layer, and the seed layer may be formed on the polysilicon layer.