Amorphous Silicon Thin Film Deposition via Cyclical Plasma
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for forming amorphous silicon thin films, such as plasma CVD and PEALD, face challenges in achieving uniform thickness and good step-coverage over high aspect ratio features, and often result in films with high surface roughness or low deposition rates.
Innovation Solution
A cyclical deposition process using silicon precursors and hydrogen plasma, where the hydrogen plasma is supplied during and after the precursor supply, with RF power applied to generate plasma, and purge gases used to remove excess reactants and by-products, allowing for effective adsorption and deposition of amorphous silicon at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If plasma CVD or PEALD is used to form amorphous silicon thin films, then deposition can occur at low temperatures, but the films exhibit high surface roughness and poor step-coverage over high aspect ratio features
Solution Approach 1:
The deposition process is divided into multiple sequential cycles, each consisting of precursor exposure, purge, and plasma treatment stages. This segmentation allows precise control over film formation, enabling uniform deposition and good step-coverage even at low temperatures by repeating the cycle multiple times to build up the film layer by layer
Solution Approach 2:
The method employs periodic pulsing of the silicon precursor and hydrogen plasma during deposition cycles. The precursor is supplied in pulses followed by purge steps and plasma treatment steps, creating a periodic action that ensures uniform precursor distribution and reaction control, resulting in films with improved uniformity and step-coverage
2Manufacturing precision
If conventional CVD methods are used to achieve uniform film thickness, then good step-coverage is obtained, but surface roughness increases
Solution Approach 1:
By using periodic pulsing of precursor and plasma treatment steps instead of continuous deposition, the method achieves uniform film thickness through controlled sequential deposition cycles, while the intermittent plasma treatment smooths the surface, reducing roughness compared to conventional continuous CVD
Solution Approach 2:
The method changes the deposition parameters by using low precursor flow rates during pulsing and applying plasma treatment at controlled power levels. These parameter changes enable uniform film formation with reduced surface roughness by controlling the deposition rate and surface treatment conditions
3Temperature
If sputtering is used for physical vapor deposition, then deposition occurs at low temperatures, but step-coverage is poor on surfaces with protrusions and depressions
Solution Approach 1:
Hydrogen plasma is introduced as an intermediary between precursor supply steps to enhance precursor activation and improve film conformality. The plasma acts as a mediator that promotes uniform decomposition of precursors and improves step-coverage, enabling low-temperature deposition with good conformality on high aspect ratio structures
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 method achieves amorphous silicon films with improved uniformity, step-coverage, and reduced roughness compared to conventional CVD processes, while maintaining a low deposition temperature, enabling the formation of high-quality thin films for semiconductor applications.
Implementation Method 1
supplying hydrogen plasma to the reaction chamber at least partly during the first time period
Implementation Method 2
supplying a silicon precursor to the reaction chamber during a first time period
Implementation Method 3
applying radio frequency power to the reaction chamber at least partly during the first time period
Data Source
AI summary
A method for forming an amorphous silicon thin film is disclosed. In some embodiments, a method includes loading a substrate into a reaction chamber; and conducting a plurality of deposition cycles on the substrate. Each of at least two of the cycles includes: supplying a silicon precursor to the reaction chamber during a first time period; applying radio frequency power to the reaction chamber at least partly during the first time period; stopping supplying of the silicon precursor and applying of the radio frequency power during a second time period between the first time period and an immediately subsequent deposition cycle; and supplying hydrogen plasma to the reaction chamber during a third time period between the second time period and the immediately subsequent deposition cycle. The method allows formation of an amorphous silicon film having an excellent step-coverage and a low roughness at a relatively low deposition temperature.