Substrate Outgassing Control via Load Lock Oxidation
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Solution Overview
Problem
Current methods for controlling substrate outgassing, particularly after III-V epitaxial growth or etch processes, are inefficient, leading to residual arsenic contamination and reduced throughput due to prolonged baking and inadequate N2 purge cycles, which fail to achieve absolute zero parts per billion (ppb) outgassing.
Innovation Solution
A method involving the delivery of a substrate to a load lock chamber where an oxygen-containing gas is flowed to oxidize residual arsenic species, followed by a non-reactive gas to drive down outgassing, with specific pressure controls and cycles to ensure complete removal of hazardous gases before further processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If thermal back process (>200 degrees Celsius) is used in process chamber or etch chamber to remove outgassing, then outgassing control is improved, but throughput is reduced due to longer bake times required for each substrate
Solution Approach 1:
The patent extracts the thermal back process from the process/etch chambers and relocates it to a dedicated load lock chamber. This separation allows the main processing chambers to maintain vacuum and operational readiness while the load lock chamber performs extended thermal processing without impacting throughput. The load lock chamber becomes a specialized facility for outgassing control that operates independently from the main production flow.
Solution Approach 2:
The patent applies preliminary thermal back process (>200°C) to substrates in the load lock chamber before they enter the main processing chambers. This pre-treatment removes arsenic-related outgassing contaminants in advance, ensuring that substrates are clean before entering the production line. The extended bake times are performed beforehand, so they do not delay subsequent processing steps.
2Object-affected harmful factors
If long N2 purge/pump cycle is used to remove outgassing, then outgassing control is improved, but throughput is reduced and arsenic outgassing remains at 1.9 ppb after ten cycles
Solution Approach 1:
The patent changes the fundamental parameter from chemical purging (N2 cycles) to thermal processing (>200°C). Instead of relying on repeated nitrogen purging cycles that require ten or more iterations to achieve 1.9 ppb reduction, the system uses elevated temperature to actively drive out arsenic contaminants. This parameter change achieves complete arsenic removal in a single extended thermal cycle without compromising throughput.
Solution Approach 2:
The patent uses thermal energy as a strong driving force to accelerate the removal of arsenic contaminants. The extended thermal back process at >200°C provides sufficient energy to break chemical bonds and drive volatile arsenic species off the substrate surface, achieving absolute zero ppb outgassing levels that cannot be attained through gentle nitrogen purging alone.
3Object-affected harmful factors
If extended bake time is used for each substrate to drive out arsenic outgassing, then outgassing control is improved, but throughput is lowered
Solution Approach 1:
The patent extracts the time-consuming extended bake process from the main production line and places it in a dedicated load lock chamber. This allows the bake process to occur in parallel with other substrate processing activities, eliminating the sequential time penalty. While one substrate undergoes extended baking, other substrates can be processed simultaneously in the main chambers, maintaining overall throughput.
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 effectively reduces outgassing to zero ppb, improving substrate throughput and eliminating the need for fume hoods, while minimizing contamination and cross-contamination, and can be applied to various arsenic and phosphate implantations.
Implementation Method 1
flowing an oxygen containing gas into the substrate access chamber... removing a material from a surface of the substrate by reacting the oxygen containing gas with the surface of the substrate
Implementation Method 2
flowing a non-reactive gas into the substrate access chamber... removing the non-reactive gas from the substrate access chamber via a pump cycle
Data Source
AI summary
Embodiments disclosed herein generally relate to methods for controlling substrate outgassing such that hazardous gasses are eliminated from a surface of a substrate after a III-V epitaxial growth process or an etch clean process, and prior to additional processing. An oxygen containing gas is flowed to a substrate in a load lock chamber, and subsequently a non-reactive gas is flowed to the substrate in the load lock chamber. As such, hazardous gases and outgassing residuals are decreased and/or removed from the substrate such that further processing may be performed.