Vacuum Drying for TEOS Wafer Bow Reduction
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Solution Overview
Problem
Semiconductor wafers with LPCVD TEOS layers exhibit severe outgassing, leading to azimuthally asymmetric wafer bow, which impairs vacuum chucking and results in non-uniform film deposition, rendering the wafers unusable due to humidity incorporation and reabsorption.
Innovation Solution
The method involves drying the wafer with a TEOS oxide layer in a vacuum chamber at a pressure lower than atmospheric pressure, preventing reabsorption of humidity and reducing wafer bow, allowing for uniform deposition of subsequent layers like SABPSG by maintaining the wafer in a vacuum environment throughout the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the wafer is dried at atmospheric pressure, then the drying process is simple and fast, but humidity is reabsorbed leading to severe wafer bow and non-uniform film deposition
Solution Approach 1:
The patent applies vacuum environment (inert atmosphere) during the drying process to prevent humidity reabsorption. The wafer is dried at reduced pressure (1-100 mbar) instead of atmospheric pressure, creating an environment where water vapor cannot recondense on the hot wafer surface, thus preventing wafer bow and ensuring uniform film deposition.
Solution Approach 2:
The patent implements continuous processing where the drying step is performed immediately before deposition without breaking vacuum. The wafer remains in the vacuum chamber throughout, eliminating exposure to atmospheric humidity and maintaining continuous control over the wafer surface condition.
2Reliability
If the wafer is dried at elevated temperatures, then water outgassing is enhanced, but vacuum buildup is inhibited due to severe outgassing
Solution Approach 1:
The patent uses vacuum environment to manage outgassing. By maintaining reduced pressure (1-100 mbar) during drying, the system allows water vapor to be pumped away continuously without reaching atmospheric pressure, preventing vacuum chuck failure while managing the outgassing load.
Solution Approach 2:
The patent optimizes pressure parameters during drying, maintaining it between 1-100 mbar rather than full vacuum or atmospheric pressure. This parameter optimization balances outgassing removal with vacuum maintenance, ensuring reliable vacuum chucking while managing pump load.
3Manufacturing precision
If the wafer is exposed to atmosphere between drying and deposition, then process steps can be separated, but humidity reabsorption causes azimuthally asymmetric wafer bow
Solution Approach 1:
The patent implements continuous vacuum processing where drying and deposition occur back-to-back without breaking vacuum. The wafer never暴露在 atmospheric humidity, eliminating the wafer bow problem while maintaining process efficiency through uninterrupted processing.
Solution Approach 2:
The patent combines drying and deposition steps in the same vacuum chamber, merging two process steps that could be performed separately. This integration eliminates the need to break vacuum for intermediate handling, preventing humidity reabsorption and wafer bow while streamlining the overall process.
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 wafer bow and ensures uniform layer deposition with non-uniformity below 5%, enhancing the reliability of the vacuum chucking mechanism and preventing film non-uniformity issues.
Implementation Method 1
the workpiece is continuously subject to a pressure which is lower than atmospheric pressure during the drying process and during the depositing process
Implementation Method 2
The outgassing of water from TEOS oxide during the chucking procedure at elevated temperatures in a SA-CVD (sub-atmospheric CVD) chamber
Implementation Method 3
vacuum chucks for fastening the semiconductor wafer to be processed
Implementation Method 4
depositing a dielectric layer over the uppermost layer of the dried workpiece
Data Source
AI summary
In various embodiments, a method for coating a workpiece is provided. The method may include drying a workpiece, the workpiece being coated with at least one oxide layer as an uppermost layer; depositing a dielectric layer over the uppermost layer of the dried workpiece; wherein the workpiece is continuously subject to a pressure which is lower than atmospheric pressure during the drying process and during the depositing process.