Low Pressure Bake for Semiconductor Surface Cleaning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The semiconductor industry faces challenges in maintaining the purity of substrate surfaces and preventing reoxidation during epitaxial deposition, which affects the quality and throughput of silicon devices, especially in single-wafer processing where processing time is critical.
Innovation Solution
A method involving a low pressure bake in a chemical vapor deposition (CVD) chamber, where the pressure is reduced to between 1×10−6 Torr and 10 Torr, and a reducing gas is introduced to remove impurities and prevent oxide growth, followed by a rapid increase in pressure for deposition, using a system with a reinforced reaction chamber and a robot for substrate handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wafers are cleaned with APM and HF treatments to remove native oxide and contaminants, then the substrate surface purity is improved, but the thermal budget is consumed and reoxidation occurs during storage time
Solution Approach 1:
The patent performs the oxide removal and surface cleaning action immediately before deposition by conducting a low pressure bake that reduces oxide growth and removes contaminants in-situ within the vacuum chamber, eliminating the storage time gap where reoxidation would occur
Solution Approach 2:
The patent uses a vacuum environment (low pressure bake chamber) as an inert atmosphere that prevents oxidation during the cleaning and pre-deposition treatment, allowing the substrate surface to remain oxide-free from cleaning through deposition without exposure to ambient air
2Manufacturing precision
If single wafer processing is used to improve temperature and gas flow distribution control, then manufacturing precision is improved, but processing time increases due to serial processing
Solution Approach 1:
The patent changes the pressure parameter to a low pressure environment (10^-3 to 10^-6 Torr) during the bake and deposition process, which enables faster processing rates and improved surface quality, thereby increasing throughput while maintaining the precision benefits of single-wafer processing
3Manufacturing precision
If low pressure bake is performed to remove impurities and prevent oxide growth, then substrate surface purity is improved, but processing time is added to the sequence
Solution Approach 1:
The patent merges the low pressure bake, oxide removal, and deposition preparation steps into a single integrated process sequence that occurs in-situ within the vacuum chamber, eliminating the need for separate cleaning and storage steps that would consume additional time
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 cleans the substrate surface, maintains oxide-free conditions, and improves wafer throughput without exhausting the thermal budget, ensuring high-quality epitaxial layers and reducing fabrication costs.
Implementation Method 1
introducing a reducing gas to the reaction chamber... to remove impurities and prevent oxide growth
Implementation Method 2
depositing a layer by chemical vapor deposition at the deposition pressure
Data Source
AI summary
Methods and systems are provided for low pressure baking to remove impurities from a semiconductor surface prior to deposition. Advantageously, the short, low temperature processes consume only a small portion of the thermal budget, while still proving effective at removing interfacial oxygen from the semiconductor surface. The methods and systems are particularly well suited for treating semiconductor surfaces before epitaxy.