Low-Temperature Polysilicon Planarization via Polyimide Coating
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Solution Overview
Problem
Low-temperature polysilicon devices face issues with surface roughness due to protrusions formed during crystallization, leading to problems like broken films, unclean etching, and tip discharge, which reduce production yield.
Innovation Solution
A method involving crystallization of the polysilicon layer, followed by a polyimide coating process to form a flat layer, curing, and then removing the coating and protrusions using a dry or wet etching process to achieve planarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If polysilicon layer is crystallized by conventional vapor deposition method, then polysilicon grains grow and form device structure, but adjacent grains extrude each other to form protrusions causing surface roughness
Solution Approach 1:
A flat coating layer is formed on the uneven polysilicon surface before subsequent processing steps. This preliminary coating action allows the rough surface to be covered and planarized, preventing the protrusions from causing broken films, unclean etching, or tip discharge in later stages, thereby maintaining high production yield while achieving smooth surface
Solution Approach 2:
The flat coating layer acts as an intermediary substance between the rough polysilicon surface and the subsequent processing steps. This intermediate layer absorbs the surface irregularities and provides a flat working surface for etching and other processes, resolving the contradiction between maintaining the crystallized grain structure and achieving surface flatness
2Reliability
If polysilicon grains are made larger to improve electrical properties, then device performance improves, but protrusions become higher and surface roughness increases
Solution Approach 1:
The flat coating layer serves as a mediator that allows large polysilicon grains to maintain their electrical properties while providing a flat surface for subsequent processing. The coating layer compensates for the height differences caused by large grain protrusions, enabling both good electrical performance and surface flatness
3Reliability
If more grain boundaries are present to improve device structure, then electrical properties improve, but intersecting grain boundaries create higher protrusions and larger surface roughness
Solution Approach 1:
The flat coating layer acts as an intermediary that covers the complex grain boundary structures and their associated protrusions. This allows the device to benefit from multiple grain boundaries for improved electrical properties while the coating layer provides a uniform flat surface that eliminates the surface roughness problems caused by intersecting grain boundaries
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 method effectively mitigates surface roughness issues, improving the production yield and operational efficiency of low-temperature polysilicon devices by creating a smooth polysilicon layer.
Implementation Method 1
Step S3: Curing the flat coating layer
Implementation Method 2
Step S1: Crystallizing the low-temperature polysilicon device
Implementation Method 3
the removing process is a dry etching method
Data Source
AI summary
A method for planarizing a polysilicon layer of a low-temperature polysilicon device is provided. The method includes: Step S1: Crystallizing the low-temperature polysilicon device. Step S2: Forming a flat coating layer on an uneven surface of the polysilicon layer of the crystallized low-temperature polysilicon device through a coating process. Step S3: Curing the flat coating layer. Step S4: Removing the cured flat coating layer and the polysilicon protrusion through a removing process to form a flat surface of the polysilicon layer. By the foregoing method, the surface of the rough and uneven polysilicon layer can be well-planarized. As a result, the problems of a broken film, unclean etching, or tip discharge, which would be induced by a rough polysilicon layer, are mitigated. Therefore, the production yield of the low-temperature polysilicon device is improved.