Semiconductive Stack Design for Select Devices
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Solution Overview
Problem
Current methods for crystallizing amorphous silicon into polycrystalline silicon for semiconductor devices face issues such as long processing times, high temperatures, expensive equipment requirements, and increased leakage current due to residual crystallization-inducing metals.
Innovation Solution
A semiconductive stack with a thickness of 700 Å or less, featuring materials with a band gap of 4 eV or less, is used in select devices, allowing for tunable current densities and reduced fatigue failure through a bipolar select device structure with electrodes and semiconductive materials like silicon, germanium, and gallium nitride, and employing low-temperature annealing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If solid phase crystallization (SPC) is used to crystallize amorphous silicon into polycrystalline silicon, then the substrate can be processed at relatively low temperatures (700°C or less), but the processing time becomes very long (several to several tens of hours) and there is a risk of substrate transformation
Solution Approach 1:
The patent changes the crystallization method from solid phase crystallization to excimer laser crystallization, fundamentally altering the processing parameters. This enables crystallization in seconds rather than hours, resolving the time contradiction while maintaining substrate integrity through localized heating
Solution Approach 2:
The patent replaces the thermal field-based SPC method with a laser field-based ELC method. This substitution of energy field type enables rapid localized heating and cooling cycles that achieve crystallization without the prolonged thermal exposure required by SPC
2Loss of time
If excimer laser crystallization (ELC) is used to crystallize amorphous silicon, then the processing time is greatly reduced, but expensive laser equipment is required and interfacial characteristics between semiconductor material and gate insulating material may be poor due to protrusions on the crystallized surface
Solution Approach 1:
The patent applies selective laser irradiation to specific regions requiring crystallization, rather than uniform treatment. This localized approach reduces overall processing time while minimizing surface protrusions that affect interface quality, and avoids unnecessary heating of already-crystallized or non-requiring areas
3Productivity
If metal induced crystallization (MIC) or metal induced lateral crystallization (MILC) is used to crystallize amorphous silicon, then the crystallization process can be achieved, but a large amount of crystallization-inducing metal remains on the material increasing leakage current
Solution Approach 1:
The patent extracts and eliminates the metal-induced crystallization step entirely, replacing it with direct laser-induced crystallization. This removes the source of residual metal contamination that causes leakage current, while maintaining efficient crystallization through the excimer laser method
Solution Approach 2:
The patent introduces the excimer laser as an intermediary energy source that directly induces crystallization without requiring metal catalysts. This intermediary mechanism achieves the desired crystallization outcome while avoiding the harmful byproduct of residual metal
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
The solution enables select devices to support higher current densities and withstand a large number of loading cycles without premature fatigue, while avoiding the drawbacks of existing methods by optimizing the semiconductive stack configuration and processing conditions.
Implementation Method 1
ELC is a method of crystallizing an amorphous silicon material by irradiating the amorphous silicon material with an excimer laser and locally heating the amorphous silicon material to a high temperature for a very short time
Implementation Method 2
SPC is a method of annealing an amorphous silicon material for several to several tens of hours at a temperature at or below the transition temperature of the glass used as a substrate
Implementation Method 3
MIC is a method of using phase transfer induction from amorphous silicon to polysilicon by contacting the amorphous silicon material with metals such as nickel (Ni), palladium (Pd), gold (Au), and aluminium (Al), or implanting such metals into the amorphous silicon material
Data Source
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AI summary
Methods, devices, and systems are provided for a select device that can include a semiconductive stack of at least one semiconductive material formed on a first electrode, where the semiconductive stack can have a thickness of about 700 angstroms () or less. Each of the at least one semiconductive material can have an associated band gap of about 4 electron volts (eV) or less and a second electrode can be formed on the semiconductive stack.