Shallow Trench Isolation Liner Height Control via Wet Etching
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Solution Overview
Problem
Current dry etching methods fail to consistently achieve a uniform height for the silicon nitride liner in shallow trench isolation (STI) structures, leading to voids when the liner is too high or loss of protection for the spin-on-glass layer when it's too low, making it difficult to form an ideal STI.
Innovation Solution
The method employs sequential wet etching steps to control the etching intensity, forming a first and second liner layer, followed by selective wet etching to expose the substrate and adjust the liner height, ensuring uniformity, and then fills the trench with a second oxide using high-density plasma to form a shallow trench isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If dry etching method is used to form the silicon nitride liner, then the etching process can be performed, but the liner height becomes non-uniform
Solution Approach 1:
The patent changes the etching method from dry etching to wet etching, altering the process parameters to achieve both manufacturability and uniform liner height. The wet etching process uses chemical solutions that provide more uniform etching rates across the substrate surface, resolving the contradiction between process capability and precision.
Solution Approach 2:
The patent replaces the physical/mechanical dry etching process with a chemical wet etching process. This substitution allows the etching to proceed through chemical reactions that are more uniform and controllable, thereby achieving better liner height uniformity while maintaining the etching function.
2Reliability
If the silicon nitride liner level is too high, then the liner provides adequate protection, but voids appear in the oxide filling
Solution Approach 1:
By changing from dry to wet etching, the patent achieves more precise control over liner height, preventing it from being too high. This parameter control ensures that the oxide filling can proceed without creating voids, while the liner still maintains adequate protective function.
3Ease of manufacture
If the silicon nitride liner level is too low, then the oxide filling is easier, but the spin-on-glass layer loses protection and is damaged
Solution Approach 1:
The patent uses wet etching to precisely control the liner height parameter, ensuring it is neither too high nor too low. This precise parameter control maintains the protective function for the spin-on-glass layer while still allowing proper oxide filling, resolving the contradiction between ease of manufacture and reliability.
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
This approach allows for the formation of a shallow trench isolation with a uniform and ideal liner height, preventing voids and protecting the spin-on-glass layer, thereby improving the reliability of the STI structure.
Implementation Method 1
performing a first wet etching to remove part of the first oxide and part of the first liner layer to expose the substrate
Implementation Method 2
performing a second wet etching to remove part of the second liner layer so that the second liner layer is lower than the surface of the substrate
Implementation Method 3
performing a third wet etching to remove part of the first oxide and part of the first liner layer
Implementation Method 4
the high-density plasma would usually fail to fill the trench with an oxide
Data Source
AI summary
A method for forming a shallow trench isolation includes providing a substrate with a trench, a first liner layer and a second liner layer sequentially in the trench with a first oxide filling the trench, performing a first wet etching to remove part of the first oxide and part of the first liner layer to expose the substrate, performing a second wet etching to remove part of the second liner layer so that the second liner layer is lower than surface of the substrate, performing a third wet etching to remove part of the first oxide and part of the first liner layer, and filling the trench with a second oxide to form a shallow trench isolation.