MEMS Eutectic Bonding Oxide Removal Without Preclean
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Solution Overview
Problem
The use of a preclean process in eutectic bonding sequences for semiconductor wafers can cause RF generators to resonate with suspended mechanical components, leading to defects and inoperability in MEMS structures.
Innovation Solution
An extended acid-based etch process is used to remove oxides without a preclean step, increasing the duration of the acid-based etch to at least 20 seconds, ensuring effective oxide removal while minimizing material etching and reducing the risk of stiction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a preclean process is used in eutectic bonding sequence, then oxide removal is effective, but RF generators resonate with suspended mechanical components causing defects
Solution Approach 1:
The patent removes the preclean process from the eutectic bonding sequence, extracting the problematic step that causes RF generator resonance. The oxide removal function is retained through extended acid-based etching during the bonding process itself, eliminating the harmful resonance effect while maintaining oxide removal effectiveness.
Solution Approach 2:
The patent performs oxide removal准备工作 in advance by extending the acid-based etch duration before bonding. This preliminary action ensures oxides are adequately removed without requiring a separate preclean step, preventing the resonance issue while achieving the necessary surface preparation.
2Reliability
If acid-based etch duration is extended to at least 20 seconds, then oxide removal is effective without preclean, but material etching increases
Solution Approach 1:
The patent changes the duration parameter of the acid-based etch process to at least 20 seconds, optimizing it to achieve complete oxide removal without preclean. This parameter adjustment balances oxide removal effectiveness with minimal material loss by extending the etch just enough to remove oxides thoroughly.
Solution Approach 2:
The acid-based etch is applied selectively to remove oxides from specific bonding surfaces. The extended duration ensures complete oxide removal from the bonding interfaces while the localized application minimizes overall material loss to only where etching is necessary for bonding quality.
3Device complexity
If preclean process is removed from bonding sequence, then process complexity is reduced, but oxide removal effectiveness may be compromised
Solution Approach 1:
The patent merges the oxide removal function with the acid-based etching step in the bonding sequence. By combining these functions into a single extended etch step rather than separate preclean and etch steps, the process complexity is reduced while oxide removal effectiveness is maintained through the extended duration.
Solution Approach 2:
The acid-based etching action continues for an extended duration of at least 20 seconds without interruption. This continuous action ensures complete oxide removal throughout the bonding preparation, maintaining manufacturing precision while simplifying the overall process by eliminating the preclean step.
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 simplifies the eutectic bonding sequence, reduces defects, and enhances process yield by preventing mechanical components from sticking to the cavity walls, thus maintaining the functionality of MEMS structures.
Implementation Method 1
etching, using an acidic etchant, a first wafer for a time duration to remove an oxide from one or more portions of the first wafer
Data Source
AI summary
A preclean process may be omitted from a eutectic bonding sequence. To remove oxide from one or more surfaces of a device wafer of a micro-electromechanical-system (MEMS) structure, a duration of an acid-based etch process in the eutectic bonding sequence may be increased relative to the duration of the acid-based etch process when the preclean process is performed. The increased duration of the acid-based etch process enables the acid-based etch process to remove the oxide from the one or more surfaces of the device wafer without the use of a preceding preclean process. This reduces the complexity and cycle time of the eutectic bonding sequence, reduces the risk of stiction between suspended mechanical components of the MEMS structure, and/or reduces the likelihood that the MEMS structure may be rendered defective or inoperable during manufacturing, which increases process yield.