Semiconductor Structure with Varying Depth Isolation Trenches
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Solution Overview
Problem
Existing shallow trench isolation (STI) methods in semiconductor fabrication are inadequate for scaled-down device geometries, leading to unsatisfactory electrical isolation and increased etching damage, particularly in sensitive regions like image sensor devices.
Innovation Solution
The method involves forming semiconductor structures with isolation structures of varying depths by embedding etching stop features of different depths in the substrate, allowing for precise control of trench depths through single etching processes, reducing etching damage and improving electrical isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional STI methods are used with uniform trench depths, then fabrication process is simple, but electrical isolation is insufficient for scaled-down devices and etching damage increases
Solution Approach 1:
The patent applies local quality by creating isolation structures with different depths in different regions of the semiconductor device. First isolation structures have a first depth in a first region, while second isolation structures have a second depth in a second region. This allows optimization of electrical isolation for scaled-down devices in specific areas without requiring uniform complex structures across the entire device, thereby improving reliability while managing device complexity.
2Reliability
If deeper trenches are etched to improve isolation, then electrical isolation improves, but etching damage increases in sensitive regions
Solution Approach 1:
The patent implements local quality by varying the depth of isolation structures based on regional requirements. In regions where deep isolation is needed for electrical performance, deeper trenches are created. In sensitive regions where etching damage would be problematic, shallower trenches are formed. This spatially differentiated approach allows the device to achieve necessary electrical isolation while minimizing etching damage in vulnerable areas.
Solution Approach 2:
The patent segments the isolation structure formation into distinct regions with different trench depths. First isolation structures are formed in a first region with a first depth, while second isolation structures are formed in a second region with a second depth. This segmentation allows independent optimization of isolation depth for each region, balancing electrical isolation requirements against etching damage concerns in different parts of the device.
Data Source
AI summary
A semiconductor structure includes a substrate having a front surface and a back surface. The semiconductor structure further includes a first isolation structure extending from the front surface into the substrate, the first isolation structure having a depth D1 from the front surface. The semiconductor structure further includes a second isolation structure extending from the front surface into the substrate, the second isolation structure having a depth D2 from the front surface. The semiconductor structure further includes a first etching stop feature in the substrate and contacting the first isolation structure. The semiconductor structure further includes a second etching stop feature in the substrate and contacting the second isolation structure.