Differential Epitaxy for Simultaneous Crystalline and Amorphous Silicon Deposition
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Solution Overview
Problem
Current semiconductor processing methods face challenges in simultaneously depositing multiple crystalline structures with uniform in-situ doping, particularly due to limitations in epitaxial deposition rates and dopant concentration, which affect the electrical characteristics of semiconductor devices.
Innovation Solution
The method involves differential epitaxy, where a monocrystalline silicon layer and an amorphous silicon layer are concurrently formed on a semiconductor body using in-situ doping, with varying process parameters for each sub-layer to optimize deposition characteristics, allowing for the simultaneous growth of multiple crystalline structures without the need for additional seed layers and enabling high dopant concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If in-situ doping is used during epitaxial growth, then layer integrity is improved, but deposition rate decreases considerably
Solution Approach 1:
The patent segments the deposition process into multiple sub-layers with different process parameters. By dividing the epitaxial growth into distinct stages (first sub-layer with initial parameters, second sub-layer with modified parameters), the process achieves both high deposition rate and high dopant concentration in different regions, resolving the contradiction between productivity and reliability
Solution Approach 2:
The patent changes process parameters between sub-layers to optimize different objectives. The first sub-layer uses parameters optimized for high deposition rate, while the second sub-layer uses parameters optimized for high dopant concentration. This parameter variation allows the system to achieve both fast deposition and reliable doping without the trade-off that limits conventional single-parameter processes
2Manufacturing precision
If in-situ doping is used during epitaxial growth, then uniform doping is improved, but dopant concentration is limited below 1e20/cm3
Solution Approach 1:
The patent divides the doping process into segments corresponding to different sub-layers. The first sub-layer provides uniform doping at moderate concentrations, while the second sub-layer achieves high dopant concentrations (exceeding 1e20/cm3). This segmentation allows each layer to be optimized for its specific doping requirements, achieving both uniformity and high concentration
Solution Approach 2:
The patent employs parameter changes between sub-layers to overcome the dopant concentration limit. By modifying deposition conditions (such as dopant gas flow rate, temperature, or pressure) in the second sub-layer, the process achieves dopant concentrations exceeding 1e20/cm3 while maintaining the uniform doping quality established in the first sub-layer
3Quantity of substance
If implantation doping is used after depositing undoped silicon, then dopant concentration can be controlled, but device issues occur due to incomplete doping in faults
Solution Approach 1:
The patent performs doping during the epitaxial growth process itself (in-situ doping) rather than as a subsequent step. This preliminary action ensures that dopant atoms are incorporated uniformly throughout the crystal lattice as the layer forms, including in regions that would later become faults. This prevents the device issues associated with incomplete doping that occur with post-deposition implantation methods
4Productivity
If multiple crystalline structures are deposited simultaneously, then process efficiency is improved, but manufacturing precision deteriorates due to difficulty in controlling uniform doping
Solution Approach 1:
The patent segments the simultaneous deposition process into distinct sub-layers, each with optimized parameters for their specific requirements. This segmentation allows different crystalline structures to be deposited concurrently while maintaining precise control over doping uniformity in each layer, resolving the contradiction between productivity and manufacturing precision
Solution Approach 2:
The patent applies local quality by assigning different process parameters to different sub-layers and regions. Each sub-layer is optimized for its specific crystalline structure and doping requirements, allowing simultaneous deposition of multiple structures with各自 optimized doping uniformity, thereby maintaining manufacturing precision while improving process efficiency
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 enables high-rate deposition of multiple crystalline layers with high dopant concentrations, improving the electrical properties of semiconductor devices by eliminating the need for subsequent thermal activation of dopants and allowing direct growth on isolating layers without additional seed layers.
Implementation Method 1
a deposition gas and a dopant gas are supplied to a process chamber of a CVD reactor
Implementation Method 2
The deposition gas and the dopant gas thermally decompose and deposit onto the substrate
Implementation Method 3
A suitable deposition gas for depositing polysilicon is silane. In general, the silane decomposes under the vacuum and the high temperature of the process chamber and deposits onto the substrate
Implementation Method 4
The dopant atoms move by filling empty crystal positions (i.e. vacancies) or alternately move through the spaces between the crystal sites (i.e. interstitial)
Implementation Method 5
epitaxially growing a layer with the same crystalline structure on top of the seed layer
Data Source
AI summary
One embodiment of the present invention relates to method for the concurrent deposition of multiple different crystalline structures on a semiconductor body utilizing in-situ differential epitaxy. In one embodiment of the present invention a preparation surface is formed, resulting in two distinct crystalline regions, a monocrystalline silicon substrate region and an isolating layer region. A monocrystalline silicon layer and an amorphous silicon layer are concurrently formed directly onto the preparation surface in the monocrystalline silicon substrate region and the isolating layer region, respectively. Deposition comprises the formation of two or more sub-layers. The process parameters can be varied for each individual sub-layer to optimize deposition characteristics.