Transistor Isolation Etching for Epi Damage Prevention
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Solution Overview
Problem
Etching processes during the isolation of semiconductor transistors can cause damage to the devices, leading to issues such as unintended short-circuits and current leakage.
Innovation Solution
A controlled and multi-stage etching process, known as CPODE, is employed to safely remove material from transistor structures without damaging them, utilizing specific etching parameters at different depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etching processes are used to isolate transistors, then isolation can be achieved, but damage to the transistors occurs causing unintended short-circuits and current leakage
Solution Approach 1:
The etching process is divided into multiple stages with different etching parameters for different depth regions. The first etching stage uses parameters optimized for removing upper layers, while the second etching stage uses different parameters for removing deeper layers, preventing damage to the transistor structures at any single depth
Solution Approach 2:
Different etching parameters are applied to different depth regions of the substrate. The method specifies that a first set of etching parameters is used for a first depth region and a second set of etching parameters is used for a second depth region, allowing localized optimization to protect transistor structures while achieving isolation
2Productivity
If single-stage etching is used, then the process is simple and fast, but it causes damage to transistor structures
Solution Approach 1:
The etching process is segmented into multiple sequential stages, each with specific parameters optimized for the depth region being processed. This segmentation allows precise control over material removal at different depths while maintaining overall process efficiency
Solution Approach 2:
The etching process dynamically adjusts parameters between stages. The method specifies that etching parameters change from the first stage to the second stage, allowing the process to adapt to different depth requirements and protect transistor structures while maintaining productivity
Data Source
AI summary
Methods for fabricating semiconductor devices are disclosed. The method can include forming a plurality of channel regions over a substrate, where each channel region comprises multiple semiconductor layers vertically spaced from one another and in contact with a pair of epitaxial structures, with the channel regions extending in parallel along a first lateral direction. A gate structure can be formed over the channel structures, extending along a second lateral direction. The method can further include removing, through a first etching process, a portion of the gate structure over at least one channel region; removing, through a second etching process, first portions of the corresponding semiconductor layers of the at least one channel region while at least second portions of the semiconductor layers remain along the pair of epitaxial structures; and removing, through a third etching process, a portion of the substrate disposed below the removed semiconductor layers.