Cyclic Amorphous Silicon Gapfill for High Aspect Ratio Trenches
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Solution Overview
Problem
Conventional amorphous silicon deposition methods fail to effectively gapfill high aspect ratio trenches in semiconductor devices, leading to seam and void formation due to uneven deposition rates, which can cause decreased throughput and device failure.
Innovation Solution
A method involving the deposition of amorphous silicon, followed by annealing to heal seams and etching to remove voids, with repeated cycles to achieve seamless and void-free gapfilling in high aspect ratio trenches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional PECVD or conformal deposition methods are used to deposit amorphous silicon, then deposition speed is improved, but uneven deposition rates occur (higher at top, lower at bottom of trenches) resulting in seam formation
Solution Approach 1:
The deposition process is divided into multiple sequential cycles, each depositing a thin layer (e.g., 50-200 nm). After each cycle, an annealing step heals seams formed during that cycle's deposition. This segmentation allows control of seam formation at each stage while maintaining overall deposition speed.
Solution Approach 2:
The process employs periodic alternation between deposition and annealing steps. Deposition creates the film layer by layer, while periodic annealing intervals heal seams before they propagate. This rhythmic cycle maintains both productivity and uniformity.
2Manufacturing precision
If thermal annealing is performed to heal seams in deposited film, then seam healing is improved, but film shrinking occurs and voids form inside trenches
Solution Approach 1:
Annealing parameters (temperature, time, atmosphere) are precisely controlled and optimized to achieve seam healing while minimizing film shrinkage. The annealing temperature is maintained below the film's glass transition temperature where possible, and annealing time is limited to the minimum required for seam closure.
Solution Approach 2:
The process creates a composite structure where multiple deposited layers are interleaved with annealed regions. Each cycle produces a layered composite of deposited material and healed material, building up the trench fill with controlled internal structure that minimizes void formation.
3Adaptability or versatility
If aspect ratio of trenches increases to accommodate smaller device dimensions, then device scaling is improved, but post-curing becomes increasingly difficult and film composition varies throughout the trench
Solution Approach 1:
The trench filling is segmented into multiple thin deposition cycles rather than attempting to fill the entire high aspect ratio trench in one step. Each cycle deposits a manageable thickness that can be properly cured and annealed, ensuring uniform composition throughout the trench depth.
Solution Approach 2:
Each deposition cycle is followed by preliminary annealing and seam healing before the next layer is deposited. This preliminary treatment of each layer ensures proper curing and composition uniformity is established early, preventing composition variations from propagating through the entire trench fill.
4Manufacturing precision
If multiple deposition cycles are performed to achieve uniform fill, then seam reduction is improved, but process time increases and throughput decreases
Solution Approach 1:
Each deposition cycle deposits slightly more material than strictly necessary to cover the previous layer, ensuring complete seam coverage. The annealing step is performed for the minimum time required to heal seams effectively. This balance achieves seam elimination while minimizing unnecessary process cycles.
Solution Approach 2:
Deposition parameters (rate, temperature, pressure) and annealing parameters are optimized to achieve the desired film quality in the minimum number of cycles. By improving the efficiency of each individual cycle, the total process time is reduced while maintaining seam elimination 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 ensures seamless and void-free gapfilling in high aspect ratio trenches, enhancing the performance and reliability of semiconductor devices by eliminating defects caused by seam and void formation.
Implementation Method 1
depositing amorphous silicon over a semiconductor device having one or more features thereon
Implementation Method 2
depositing amorphous silicon over a semiconductor device having one or more features thereon
Implementation Method 3
annealing the deposited amorphous silicon to heal one or more seams in the deposited amorphous silicon between the one or more features
Implementation Method 4
annealing the deposited amorphous silicon to heal one or more seams
Implementation Method 5
etching the annealed amorphous silicon to remove one or more voids in the annealed amorphous silicon between the one or more features
Data Source
AI summary
Methods for seam and void-free gapfilling, such as gapfilling high aspect ratio trenches with amorphous silicon, are provided. A method generally includes depositing amorphous silicon over a semiconductor device having one or more features thereon, annealing the deposited amorphous silicon to heal one or more seams in the deposited amorphous silicon between the one or more features, and etching the annealed amorphous silicon to remove one or more voids in the annealed amorphous silicon between the one or more features. The deposition, anneal, and etch processes are generally repeated any suitable number of times to achieve amorphous silicon gapfill without any seam or void between the one or more features.