Sacrificial Liner Formation for Dual-Channel STI Oxidation Control
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Solution Overview
Problem
The fabrication of semiconductor devices using shallow trench isolation techniques often results in channel oxidation and damage during steam anneal, particularly in dual channel devices with different materials, leading to inconsistent channel widths and potential fixed charge issues from silicon nitride liners.
Innovation Solution
A sacrificial liner is formed over the dual channel regions to protect the channels from oxidation, using a single-layer or dual-layer liner configuration, which can be made from materials like silicon nitride or polysilicon, to ensure consistent channel widths and prevent damage during the oxide anneal process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a steam anneal is used to solidify the oxide material in STI structures, then the oxide is solidified and the STI structure is formed, but the channel structure is oxidized and damaged
Solution Approach 1:
A sacrificial liner layer is introduced as an intermediary between the channel structure and the oxide layer. This liner prevents direct contact between the channel and oxidizing steam during anneal, protecting the channel from oxidation while allowing the oxide to solidify and form the STI structure.
Solution Approach 2:
The sacrificial liner is designed as a temporary, disposable protective layer that is removed after serving its protective function. It is intentionally consumed or removed after the anneal process to eliminate the need for additional cleaning steps and to avoid introducing fixed charges into the channel.
2Object-affected harmful factors
If a silicon nitride liner is used to prevent channel oxidation, then the channel is protected from oxidation, but fixed charge is induced in the device
Solution Approach 1:
The invention changes the material parameter of the sacrificial liner from silicon nitride (which induces fixed charge) to materials such as silicon oxide or silicon oxynitride that do not induce fixed charge. This parameter change maintains oxidation protection while eliminating the harmful fixed charge effect.
Solution Approach 2:
The sacrificial liner is designed to be temporarily present during the anneal process and then completely removed afterward. This discarding approach allows the liner to provide necessary protection during processing without remaining in the final device structure to cause fixed charge issues.
3Reliability
If dual channel devices with different materials are subjected to steam anneal, then the oxide is solidified, but the two channels oxidize at different rates causing inconsistent channel widths
Solution Approach 1:
The sacrificial liner serves as a uniform intermediary layer between the oxide and all channel structures, regardless of channel material. This liner prevents direct oxidation of different channel materials at different rates, ensuring that all channels maintain their intended widths after the anneal process.
Solution Approach 2:
The sacrificial liner provides a homogeneous protective interface between the oxide and diverse channel materials. By creating this uniform intermediate layer, the system achieves consistent protection across different channel materials, resulting in uniform channel widths despite material differences.
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
The sacrificial liner effectively prevents channel oxidation and maintains consistent channel widths between different materials, reducing the risk of fixed charge induction and enhancing the reliability of semiconductor devices.
Implementation Method 1
If the channel structure of the device(s) is exposed to the steam anneal, this can oxidize the channel and damage or alter the properties of the device. A sacrificial liner is formed over the dual channel regions to protect the channels from oxidation
Implementation Method 2
a steam anneal is generally used to solidify the oxide material
Data Source
AI summary
A semiconductor device includes one or more fins. Each fin includes a top channel portion formed from a channel material, a middle portion, and a bottom substrate portion formed from a same material as an underlying substrate. An oxide layer is formed between the bottom substrate portion of each fin and the isolation layer, with a space between a sidewall of at least a top portion of the isolation dielectric layer and an adjacent sidewall of the one or more fins, above the oxide layer. A gate dielectric, protruding into the space and in contact with the middle portion, is formed over the one or more fins and has a portion formed from a material different from the oxide layer.