Backside Isolation Structure for STI-Free 3DSFET Isolation
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Solution Overview
Problem
The formation of shallow trench isolation (STI) structures in semiconductor devices, especially in three-dimensionally-stacked field-effect transistors (3DSFETs), is complex and resource-intensive, requiring long oxidation times at high temperatures, which increases manufacturing costs and complexity.
Innovation Solution
A semiconductor device with a backside isolation structure and placeholder isolation structure is introduced, eliminating the need for STI structures by using a backside contact structure and placeholder isolation structures formed from different materials like silicon oxide and silicon nitride, respectively, to isolate devices and reduce manufacturing time and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shallow trench isolation (STI) structures are formed in the substrate, then device isolation is achieved, but manufacturing time and costs increase due to long oxidation processes at high temperature
Solution Approach 1:
The patent moves the isolation structure from the traditional horizontal plane (within the substrate) to the vertical dimension (backside of the substrate). By forming isolation structures on the backside surface, the patent achieves device isolation without requiring lengthy oxidation processes within the substrate, thus reducing manufacturing time while maintaining isolation effectiveness.
Solution Approach 2:
Instead of forming isolation structures from the front side of the substrate (conventional approach), the patent inverts the approach by forming isolation structures on the backside of the substrate. This inversion eliminates the need for deep trench oxidation and allows for faster, more cost-effective manufacturing while achieving the same isolation function.
2Reliability
If shallow trench isolation (STI) structures are formed in the substrate, then device isolation is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent simplifies manufacturing by inverting the isolation formation approach - instead of creating complex deep trenches and performing long oxidation processes within the substrate, the method forms isolation structures on the backside surface. This inversion reduces process complexity while maintaining effective device isolation.
Solution Approach 2:
The patent segments the isolation function from the active device region by placing isolation structures on the backside of the substrate. This segmentation allows independent formation and optimization of isolation structures without interfering with the complex front-side device fabrication processes, thereby reducing overall manufacturing complexity.
3Reliability
If placeholder isolation structures are formed using different materials, then device isolation is improved, but material selection and process complexity increase
Solution Approach 1:
The patent applies different materials (such as silicon oxide or silicon nitride) for placeholder isolation structures at specific locations on the backside of the substrate. This local differentiation of material properties allows optimization of isolation performance in different regions while maintaining ease of manufacture through targeted material selection rather than uniform material application across the entire substrate.
Data Source
Figure 1A
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Figure 1C
AI summary
Provided is a semiconductor device including: a 1st source/drain region and a 1st backside contact structure, vertically below the 1st source/drain region, connected to the 1st source/drain region; a 2nd source/drain region and a 1st placeholder isolation structure vertically below the 2nd source/drain region; and a backside isolation structure, on a back side of the semiconductor device, surrounding the 1st backside contact structure and the 1st placeholder isolation structure.