RF Device Cavity Wafer Bonding for Interference Reduction
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Solution Overview
Problem
Conventional semiconductor device manufacturing using double-sided thin SOI processes results in performance issues due to the close proximity of the carrier wafer to the RF device, failing to meet the requirements of certain RF applications.
Innovation Solution
A semiconductor device structure and manufacturing method involving a first substrate with a front-end device, including a transistor and RF device, bonded to a second substrate with a cavity positioned over the RF device, reducing the impact of the carrier wafer on the RF device performance through wafer bonding and thinning processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a carrier wafer is formed on the SOI substrate in conventional manufacturing, then the substrate provides mechanical support and handling capability, but the close proximity of the carrier wafer to the RF device negatively affects RF performance
Solution Approach 1:
The patent removes the carrier wafer entirely from the final device structure. Instead of bonding a carrier wafer to the SOI substrate, the process forms through-silicon vias directly through the thinned SOI substrate to create interconnects to the back surface, eliminating the need for a carrier wafer and thus removing the source of RF interference while maintaining mechanical support through the substrate itself
Solution Approach 2:
The patent introduces a thinning process as an intermediary step between substrate preparation and device formation. By thinning the SOI substrate to a specific thickness range (5-20 micrometers), the substrate itself becomes the mediator that provides mechanical support while being thin enough to minimize RF interference, replacing the need for a separate carrier wafer
2Reliability
If the SOI substrate is thinned to reduce carrier wafer impact, then RF performance improves, but substrate mechanical strength decreases
Solution Approach 1:
The patent optimizes the substrate thickness parameter to a specific range (5-20 micrometers) that balances two competing requirements: thinning enough to reduce RF interference from the back surface, but thick enough to maintain adequate mechanical strength. This parameter optimization allows the substrate to serve both as a structural support and as an RF-friendly platform without requiring a carrier wafer
3Reliability
If through-silicon vias are formed to eliminate carrier wafer, then RF performance improves, but manufacturing complexity increases
Solution Approach 1:
The patent performs substrate thinning as a preliminary action before forming the through-silicon vias. By thinning the substrate first to the optimal thickness range, subsequent via formation becomes easier and more precise, as the reduced thickness allows for better via control and reduces the risk of drilling through defects. This sequencing of operations manages manufacturing complexity by preparing the substrate in advance
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 configuration improves the RF performance by increasing the distance between the carrier wafer and the RF device, enhancing the semiconductor device's performance to meet the requirements of various RF applications.
Implementation Method 1
The first substrate and the second substrate are bonded together such that the first surface of the first substrate is facing the cavity in the second substrate
Implementation Method 2
performing a thinning process on the second surface of the first substrate
Data Source
AI summary
A semiconductor device and method of fabricating the semiconductor device are provided. The semiconductor device includes a first substrate including a front-end device containing a transistor, a radio frequency (RF) device and a first interconnect structure, and a second substrate containing a cavity disposed at a location corresponding to a location of the RF device. The first substrate and the second substrate are bonded together such that the first surface of the first substrate is facing the cavity in the second substrate, and the cavity is over the RF device. Because of the cavity, the distance between the second substrate and the RF device is relatively large so that the second substrate has less impact on the performance of the RF device, thereby improving the performance of the semiconductor device.