Bonded Wafer Substrate Removal Using a Sacrificial Etch Layer
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Solution Overview
Problem
The existing methods for removing a bulk substrate from a bonded assembly of wafers, such as grinding, are time-consuming, costly, and generate fine particles that are difficult to manage, necessitating a more economical and efficient approach.
Innovation Solution
A method involving the formation of a sacrificial material layer on a second wafer, attaching it to a first wafer, creating voids through the second substrate to expose the sacrificial material layer, and using an etchant to remove the sacrificial material layer, thereby detaching the second substrate from the bonded assembly without generating fine particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If grinding is used to remove bulk substrate, then substrate removal is achieved, but the process is time-consuming and costly
Solution Approach 1:
A sacrificial material layer is formed over the second substrate before bonding to the first wafer. This preliminary action enables selective removal of the sacrificial layer through etching after bonding, allowing the second substrate to be detached from the bonded assembly without requiring time-consuming grinding operations
Solution Approach 2:
The sacrificial material layer acts as an intermediary between the first wafer and the second substrate. It facilitates the bonding process while enabling subsequent selective removal through chemical etching, replacing the need for mechanical grinding and significantly reducing processing time
2Productivity
If grinding is used to remove bulk substrate, then substrate removal is achieved, but fine particles are generated that are difficult to manage
Solution Approach 1:
The mechanical grinding process is replaced with a chemical etching process. Instead of using mechanical abrasion that generates fine particles, an etchant is used to chemically remove the sacrificial material layer, eliminating the generation of difficult-to-manage fine particles while maintaining high substrate removal efficiency
3Productivity
If grinding is used to remove bulk substrate, then substrate removal is achieved, but the process is costly
Solution Approach 1:
The expensive mechanical grinding process is replaced with a more cost-effective chemical etching process. The etching method using sacrificial material layer removal reduces manufacturing costs while maintaining high substrate removal rates, making the overall process more economical
Solution Approach 2:
The process transitions from mechanical parameters (grinding speed, pressure) to chemical parameters (etchant concentration, temperature, exposure time). This parameter change enables a more cost-effective approach with comparable or superior substrate removal efficiency
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 allows for the efficient and cost-effective removal of a significant portion of the second substrate, minimizing material removal and avoiding the generation of fine particles, thus being more economical and environmentally friendly compared to grinding.
Implementation Method 1
removing the sacrificial material layer by providing an etchant that etches a material of the sacrificial material layer through the plurality of voids
Data Source
Figure 1A
Figure 1B~1C
Figure 2A
AI summary
A first wafer including a first substrate, first semiconductor devices overlying the first substrate, and first dielectric material layers overlying the first semiconductor devices is provided. A sacrificial material layer is formed over a top surface of a second wafer including a second substrate. Second semiconductor devices and second dielectric material layers are formed over a top surface of the sacrificial material layer. The second wafer is attached to the first wafer such that the second dielectric material layers face the first dielectric material layers. A plurality of voids is formed through the second substrate. The sacrificial material layer is removed by providing an etchant that etches a material of the sacrificial material layer through the plurality of voids. The substrate is detached from a bonded assembly including the first wafer, the second semiconductor devices, and the second dielectric material layers upon removal of the sacrificial material layer.