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Why Do Foot Shaped Patterns Appear In UV Lithography?
Release time:
2024-08-21
UV Lithography Refers To A Series Of Process Steps Such As Uniform Coating, Exposure, And Development To Remove Specific Parts Of The Wafer Surface And Leave A Thin Film With Micro Patterned Structures. Through The Photolithography Process Steps, The Final Feature Patterned Parts Are Retained On The Wafer. Lithography Technology Is The Center Of The Semiconductor Manufacturing Process, And The Wafer Needs To Undergo Multiple Photolithography Processes During The Manufacturing Process. The Quality Of The Photolithography Process Largely Determines The Graphic Resolution, Yield, And Quality Of Semiconductor Devices. Therefore, Photolithography Is Considered The Most Critical Step In The Semiconductor Manufacturing Industry.
The UV Lithography Process May Seem Simple, But In Actual Operation, Any Small Error In Any Step Can Lead To Defects, Distortion, Or Even Damage To The Pattern. Below Are Some Solutions To The Problem Of Foot Shaped Patterns In UV Lithography.
Foot Shaped Pattern: After Development, There Are Obvious Photoresist Residues At The Bottom Edge Of The Pattern, Which Is Called A Foot Shaped Pattern.
Reason For Occurrence: The Photosensitive Agent Of Positive Photoresist Is A Photosensitive Compound, The Most Common Of Which Is Diazonaphthoquinone (DNQ). Before Exposure, DNQ Is A Strong Dissolution Inhibitor That Can Reduce The Dissolution Rate Of The Resin. After UV Exposure, DNQ Chemically Decomposes In The Photoresist To Become A Solubility Enhancer, Significantly Increasing The Solubility Factor In The Developing Solution. This Exposure Reaction Produces Carboxylic Acid In DNQ, Making It Highly Soluble In The Developing Solution. But If There Are Alkaline Substances Remaining On The Surface Of The Substrate, The Carboxylic Acid Produced After Exposure Will Undergo A Neutralization Reaction With The Alkaline Substances, Generating Substances Insoluble In The Developing Solution, Resulting In The Appearance Of Foot Like Patterns After Development.
Solution: Before Applying Photoresist, The Surface Of The Silicon Wafer Should Be Cleaned Thoroughly To Prevent Residual Alkaline Substances On The Substrate. Secondly, The Photoresist Should Be Properly Stored And Not Exposed To Alkaline Environments For A Long Time.
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