Polycrystalline Silicon Thin Film Crystallization via Metal Nuclei
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Solution Overview
Problem
The existing methods for forming polycrystalline silicon thin films in LCD manufacturing face challenges such as low electron mobility in amorphous silicon, contamination from metal impurities, and difficulty in adjusting grain size, which affect the quality and uniformity of the thin films, particularly due to the limitations of sputtering and high temperature constraints.
Innovation Solution
A method using atomic layer deposition (ALD) to distribute metal nuclei at a low concentration on an amorphous silicon layer, followed by thermal treatment to control grain size and suppress metal silicide formation, allowing for the formation of a polycrystalline silicon thin film with improved crystallization rate and reduced contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sputtering is used to deposit metal layer on amorphous silicon, then metal nuclei are distributed on the surface, but metal contamination increases and grain size control becomes difficult
Solution Approach 1:
The patent changes the deposition method from sputtering to chemical vapor deposition (CVD), altering the physical-chemical parameters of the process. This enables precise control of metal nuclei concentration and distribution while reducing metal contamination, as CVD allows for lower deposition rates and better control over the amount of metal introduced into the amorphous silicon layer.
Solution Approach 2:
The patent replaces the mechanical sputtering process with a chemical vapor deposition process. Instead of using physical sputtering to deposit metal atoms, the invention uses chemical reactions of metal-organic precursors in the vapor phase, which provides better control over deposition rate and reduces mechanical impacts that cause unwanted metal accumulation and contamination.
2Speed
If high temperature thermal treatment is applied to crystallize amorphous silicon, then crystallization rate increases, but glass substrate deformation occurs
Solution Approach 1:
The patent changes the temperature parameter from high temperature (600-900°C) to low temperature (200-450°C) range. This parameter change enables crystallization of amorphous silicon into polycrystalline silicon without causing glass substrate deformation, while still achieving adequate crystallization rate through optimized low-temperature processing conditions and controlled metal nuclei distribution.
Solution Approach 2:
The patent performs preliminary distribution of metal nuclei in the amorphous silicon layer before thermal treatment. These pre-distributed metal particles act as nucleation sites that facilitate crystallization at lower temperatures, enabling the crystallization process to proceed efficiently at 200-450°C without requiring high temperatures that would deform the glass substrate.
3Temperature
If amorphous silicon is used in LCD manufacturing, then low temperature processing is enabled, but electron mobility is too low for high-speed circuits
Solution Approach 1:
The patent performs preliminary distribution of metal nuclei (such as nickel, cobalt, or copper particles) within the amorphous silicon layer before thermal treatment. These metal particles serve as nucleation sites that enable crystallization to occur at low temperatures (200-450°C), transforming the amorphous silicon into polycrystalline silicon with significantly higher electron mobility while maintaining low processing temperatures that are compatible with glass substrates.
Solution Approach 2:
The patent induces a phase transition from amorphous silicon to polycrystalline silicon through low-temperature thermal treatment (200-450°C) facilitated by pre-distributed metal nuclei. This phase transition dramatically improves electron mobility from the amorphous state (10^-6 to 10^-4 cm²/Vs) to the polycrystalline state (10^-3 to 10^-1 cm²/Vs), enabling high-speed circuit operation while maintaining compatibility with low-temperature glass substrate processing.
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 enhances the crystallization rate of amorphous silicon, decreases metal contamination, and allows for precise control of grain size, resulting in improved electrical properties and uniformity of the polycrystalline silicon thin films, suitable for large-sized LCDs.
Implementation Method 1
introducing a vapor phase metal compound into a process space where a glass substrate having an amorphous silicon layer formed thereon is disposed, to adsorb a metal nucleus contained in the metal compound into the amorphous silicon layer
Implementation Method 2
performing a thermal treatment for crystallization in a reaction chamber, to crystallize the amorphous silicon layer
Implementation Method 3
performing a thermal treatment for crystallization in a reaction chamber, to crystallize the amorphous silicon layer
Data Source
AI summary
Apparatus and method for forming a polycrystalline silicon thin film by converting an amorphous silicon thin film into the polycrystalline silicon thin film using a metal are provided. The method includes: a metal nucleus adsorbing step of introducing a vapor phase metal compound into a process space where the glass substrate having the amorphous silicon formed thereon is disposed, to adsorb a metal nucleus contained in the metal compound into the amorphous silicon layer; a metal nucleus distribution region-forming step of forming a community region including a plurality of silicon particles every metal nucleus in a plane boundary region occupied by the metal compound by a self-limited mechanism due to the adsorption of the metal nucleus; and an excess gas removing step of purging and removing an excess gas which is not adsorbed in the metal nucleus distribution region-forming step.