Capping Substrate Thinning via Handle Wafer Bonding
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Solution Overview
Problem
Traditional wafer bonding processes for capping wafers introduce mechanical shock defects and require wet dicing, leading to contamination and processing concerns due to the thinness of capping wafers and the need for access to individual dies.
Innovation Solution
A handle substrate is used to bond a capping substrate to an active substrate, allowing pre-thinning and etching of the capping substrate before bonding, which avoids mechanical shock and wet processing issues, and enables the reuse of the handle substrate by selectively removing bonding materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the capping wafer is thinned after bonding to the active wafer, then the capping wafer can be handled individually, but mechanical shock defects are introduced in the die
Solution Approach 1:
The capping wafer is thinned before bonding to the active wafer, rather than after bonding. This preliminary thinning action allows the wafer to be handled individually without introducing mechanical shock defects to the bonded die, as the thinning operation is completed while the wafer is still mechanically robust and separate from the sensitive bonded structure.
2Ease of operation
If wet dicing is performed on the capping wafer to access individual dies, then individual dies can be tested, but mechanical shock defects and wet processing contamination occur
Solution Approach 1:
The capping wafer is thinned before bonding, which enables alternative access methods for individual dies that do not require wet dicing. This preliminary preparation allows for non-destructive access techniques while maintaining die integrity and avoiding contamination.
Solution Approach 2:
The patent replaces the mechanical wet dicing process with an alternative approach where the thinned capping wafer structure itself enables access to individual dies through means other than physical cutting, such as through the thinned regions or via the handle substrate interface, thereby eliminating mechanical shock and wet processing contamination.
3Ease of operation
If the capping wafer is kept thin for handling, then individual handling is possible, but the wafer becomes too thin to handle individually without support
Solution Approach 1:
The capping wafer is thinned before bonding to the active wafer, at which point it has the mechanical support needed to maintain strength. After bonding, the combined structure provides the necessary mechanical reinforcement, allowing the thinned capping wafer to be handled individually without compromising its structural integrity.
Solution Approach 2:
The active wafer serves as an intermediary mechanical support structure that reinforces the thinned capping wafer. By bonding the thin capping wafer to the thicker active wafer, the system achieves both individual handleability and sufficient mechanical strength through the composite structure.
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 method reduces mechanical shock defects and avoids wet processing-induced contamination, allowing for robust, efficient, and cost-effective capping of devices while enabling access to individual dies for testing without dicing the capping wafer.
Implementation Method 1
Through wafer bonding, semiconductor devices may be able to achieve advantageous features that they otherwise would not be able to achieve
Implementation Method 2
The removing comprises providing an etchant through the opening to separate the handle substrate from the capping substrate
Data Source
AI summary
An embodiment is a method for bonding. The method comprises bonding a handle substrate to a capping substrate; thinning the capping substrate; etching the capping substrate; and after the thinning and the etching the capping substrate, bonding the capping substrate to an active substrate. The handle substrate has an opening therethrough. The method also comprises removing the handle substrate from the capping substrate. The removing comprises providing an etchant through the opening to separate the handle substrate from the capping substrate. Other embodiments further include forming a bonding material on a surface of at least one of the handle substrate and the capping substrate such that the capping substrate is bonded to the handle substrate by the bonding material. The bonding material may be removed by using a dry etching to remove the handle substrate from the capping substrate.