Silicon Oxide Film Deposition for Low-Impurity High-Aspect Coverage
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Solution Overview
Problem
Existing methods for depositing silicon oxide films in semiconductor devices, such as CVD and PECVD, suffer from defects like interface oxidation, dopant diffusion, and impurities like hydrogen and nitrogen, which affect electrical characteristics and result in inconsistent refractive indices and etch selectivity, particularly for high aspect ratio features with increased circuit density and geometry.
Innovation Solution
A method involving cyclical deposition cycles using a silicon source gas and oxygen-containing gases in a CVD or ALD reactor, with specific precursors like diaminosilane and ozone, to achieve a silicon-rich silicon oxide film with controlled refractive index and improved step coverage over high aspect ratio features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high temperature CVD process (LPCVD or APCVD) is used to deposit silicon oxide films, then deposition temperature is improved (500-850°C), but interface oxidation and dopant diffusion defects occur which degrade electrical characteristics
Solution Approach 1:
The patent changes the deposition temperature parameter from conventional high temperature (500-850°C) to low temperature (200-450°C) range, and modifies the chemical composition by using diaminosilane precursor with controlled oxygen exposure to achieve Si-rich silicon oxide films with reduced interface oxidation and dopant diffusion while maintaining electrical characteristics
Solution Approach 2:
The patent uses oxygen-containing gas (ozone or molecular oxygen) supplied in controlled pulses after silicon precursor deposition to oxidize the silicon-rich film in-situ, forming Si-rich silicon oxide with reduced interface oxidation defects compared to conventional high-temperature processes
2Temperature
If PECVD process is used to deposit silicon oxide films, then deposition temperature is reduced, but hydrogen and nitrogen impurities (2-9 atomic %) are incorporated which adversely affect film processing and result in deviated refractive index and inconsistent etch selectivity
Solution Approach 1:
The patent extracts harmful impurities (hydrogen and nitrogen) from the film composition by using a pure silicon precursor (diaminosilane) without hydrogen-containing co-reactants, and by controlling the deposition environment to prevent nitrogen incorporation, achieving films with <1 atomic % impurities and consistent refractive index
Solution Approach 2:
The patent changes the chemical composition parameters by selecting diaminosilane as precursor and controlling oxygen exposure to form Si-rich silicon oxide with specific atomic ratios (Si:O = 1:1), achieving precise control of refractive index (1.459-1.483) and etch selectivity
3Productivity
If conventional CVD methods are used for deposition, then deposition rate is maintained, but step coverage over high aspect ratio features is insufficient for thin and uniformly thick films
Solution Approach 1:
The patent segments the deposition process into sequential pulses: silicon precursor pulse followed by oxygen-containing gas pulse, repeating this cycle to build up the film layer by layer. This segmented approach allows excellent step coverage over high aspect ratio features while maintaining reasonable deposition rate
Solution Approach 2:
The patent employs periodic cyclic deposition where silicon precursor and oxygen-containing gas are supplied in alternating pulses. This periodic action enables conformal coverage on complex topographies by allowing reactants to reach all surfaces during each cycle, achieving uniform thickness even on high aspect ratio features
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 produces silicon oxide films with a 1:1 atomic ratio of silicon to oxygen, low impurity levels, and a refractive index between 1.459 and 1.483, providing enhanced step coverage and thickness uniformity, reducing defects and improving electrical characteristics.
Implementation Method 1
chemical vapor deposition (CVD) methods, such as low pressure CVD (LPCVD), atmospheric pressure CVD (APCVD)
Implementation Method 2
supplying ozone gas to the substrate during supplying the vapor phase silicon precursor and after purging
Data Source
AI summary
Methods of depositing a silicon oxide film are disclosed. One embodiment is a plasma enhanced atomic layer deposition (PEALD) process that includes supplying a vapor phase silicon precursor, such as a diaminosilane compound, to a substrate, and supplying oxygen plasma to the substrate. Another embodiment is a pulsed hybrid method between atomic layer deposition (ALD) and chemical vapor deposition (CVD). In the other embodiment, a vapor phase silicon precursor, such as a diaminosilane compound, is supplied to a substrate while ozone gas is continuously or discontinuously supplied to the substrate.