Semi-Amorphous Polysilicon Trench Fill to Reduce Seams and Voids
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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 then 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 segments the polysilicon structure by introducing an amorphous dielectric seed layer that divides the trench into multiple regions, preventing the formation of continuous columnar grains that cause seams and voids. The polysilicon is deposited in segments rather than as a single continuous structure.
Solution Approach 2:
The amorphous dielectric material serves as an intermediary layer between the trench walls and the polysilicon deposit. This intermediary prevents direct contact and grain formation across the entire trench width, eliminating the harmful seam and void formation mechanism.
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 the amorphous dielectric seed layer before polysilicon deposition. This pre-formed structure prevents seam and void formation during the fill process itself, eliminating the need for subsequent oxide strip and regrowth loops to clean voids.
Solution Approach 2:
The invention extracts and removes the problematic oxide strip and regrowth loop steps from the process flow. By using the amorphous dielectric seed layer approach, the method achieves void reduction without requiring these additional complex cleaning steps.
3Manufacturing precision
If trench etch profile is tapered to improve fill process, then polysilicon fill is improved, but process complexity, cycle-time and cost increase and control is difficult for high depth-to-width ratios
Solution Approach 1:
The invention applies local quality by forming the amorphous dielectric material specifically at the trench bottom and lower sidewalls where it is most needed to prevent void formation. This localized approach improves fill quality without requiring global process changes like tapering the entire trench profile.
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 creating a polysilicon core with silicon grains larger than half the trench's minimum lateral dimension, thus improving the fill 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 a seed layer in the trench, the seed layer including an amorphous dielectric material; and 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.