Trap-Rich Isolation Structure for RF Switch Parasitic Charge
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Solution Overview
Problem
High-frequency RF switch devices in RF integrated circuits are sensitive to parasitic surface charges, leading to harmonic effects, which existing wafer process technologies, such as semiconductor-on-insulator wafers, fail to adequately address.
Innovation Solution
A method for fabricating semiconductor devices that includes forming deep trench isolation and trap rich isolation structures in a substrate, where the trap rich isolation structure is deeper than the deep trench isolation structure, with a liner and insulating layer, using silicon oxide and undoped polysilicon or silicon nitride materials, to mitigate parasitic surface charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If semiconductor-on-insulator (SOI) wafer is used to isolate charges from the high resistivity wafer substrate, then parasitic surface charge isolation is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The isolation structure is segmented into two distinct parts: a deep trench isolation structure extending to a first depth, and a trap-rich isolation structure extending to a greater second depth. This segmentation allows each structure to perform its specific function - the deep trench provides primary charge isolation while the trap-rich structure provides additional parasitic charge trapping capability, thereby improving overall isolation effectiveness without requiring a complete SOI wafer approach
Solution Approach 2:
The solution transitions from a two-dimensional surface isolation approach to a three-dimensional vertical isolation approach by creating trenches that extend deep into the substrate. The trap-rich isolation structure extends even deeper than the deep trench isolation structure, creating a hierarchical vertical arrangement that effectively isolates parasitic charges at different depths, avoiding the need for complex SOI wafer structures
2Reliability
If deeper isolation trenches are formed to improve charge isolation, then parasitic surface charge mitigation is improved, but manufacturing precision and process difficulty increase
Solution Approach 1:
The deep isolation trench is segmented into two distinct structures with different depths and materials: the deep trench isolation structure with a liner and insulating layer extending to a first depth, and the trap-rich isolation structure extending to a greater second depth. This segmentation simplifies manufacturing by allowing each structure to be formed with standard precision requirements rather than requiring one extremely precise deep trench, as each can be optimized independently
Solution Approach 2:
The deep trench isolation structure is formed first as a preliminary step, creating a foundation that guides subsequent processing. The trap-rich isolation structure is then formed to extend deeper in specific regions. This preliminary action approach allows manufacturers to use the first structure as a reference and mask for forming the second structure, thereby maintaining manufacturing precision while achieving the benefits of varying trench depths
Data Source
AI summary
A method for fabricating semiconductor device includes the steps of: forming a first trench and a second trench in a substrate as a depth of the first trench is greater than a depth of the second trench; forming a liner in the first trench and the second trench; forming a first patterned mask on the substrate to cover the second trench; removing the liner in the first trench; removing the first patterned mask; and forming an insulating layer in the first trench and the second trench to form a trap rich isolation structure in the first trench and a deep trench isolation structure in the second trench.