Atomic Layer Clean for Photoresist Scum Removal
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Solution Overview
Problem
In semiconductor manufacturing, incomplete ashing during lithographic processing leaves residues known as 'scum' on patterning mandrel structures, which are difficult to remove without damaging other features, posing a challenge for patterning precision.
Innovation Solution
The method involves using atomic layer cleaning (ALC) processes that expose carbon-containing features to an oxidant or reductant without plasma, followed by exposure to an inert gas and a low-power plasma to remove scum without modifying critical feature dimensions, utilizing specific pressure and power settings to achieve directional and controlled etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional plasma ashing is used to remove photoresist scum, then scum removal effectiveness is improved, but damage to underlying features and critical dimensions occurs
Solution Approach 1:
The patent segments the scum removal process into two distinct stages: (1) selective chemical modification of scum using oxidant/reductant exposure without plasma, and (2) controlled plasma activation only after scum modification. This segmentation allows differential treatment of scum versus underlying features, removing scum while preserving critical dimensions.
Solution Approach 2:
The patent applies preliminary chemical modification to the scum using oxidants (e.g., O2, N2O, O3) or reductants before plasma exposure. This preliminary action converts the scum into a more reactive or volatile state, enabling subsequent selective removal without requiring aggressive plasma conditions that would damage underlying features.
2Object-generated harmful factors
If aggressive plasma treatment is applied to remove scum, then cleaning effectiveness is improved, but isotropic damage to features occurs
Solution Approach 1:
The patent changes the chemical and physical parameters of the plasma process by first exposing scum to oxidants or reductants, which modify the scum's chemical composition and reactivity. This parameter change enables subsequent plasma treatment to be less aggressive while achieving the same cleaning effect, thereby preserving feature geometry.
Solution Approach 2:
The oxidant or reductant acts as an intermediary substance that mediates between the scum and the plasma. By introducing this intermediary, the scum is chemically transformed into a state that is more easily removed by mild plasma, avoiding the need for aggressive plasma that would cause isotropic damage.
3Manufacturing precision
If thermal or chemical cleaning methods are used, then feature damage is reduced, but scum removal completeness deteriorates
Solution Approach 1:
The patent employs a composite cleaning approach combining chemical treatment (oxidant/reductant exposure) with physical plasma activation. This composite method leverages the gentle nature of chemical cleaning to preserve features while using plasma to ensure complete scum removal, achieving both feature integrity and cleaning completeness.
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 effectively removes scum from semiconductor substrates while preserving the integrity of underlying features, improving patterning precision and fidelity by preferentially targeting and removing scum without isotropic damage.
Implementation Method 1
exposing the carbon-containing features to an oxidant or reductant in absence of a plasma or other energetic activation to modify scum on a surface of the carbon-containing features
Implementation Method 2
exposing the carbon-containing features to an oxidant or reductant in absence of a plasma or other energetic activation to modify scum on a surface of the carbon-containing features
Implementation Method 3
exposing the modified scum on the surface of the carbon-containing features to an inert gas and igniting a plasma at a pressure greater than 0.1 Torr and less than 10 Torr and a power of less than 200 W to remove the modified scum from the surface of the carbon-containing features
Implementation Method 4
Exposing the modified surface of the carbon-containing features to the ignited plasma may energetically activate the saturated monolayer to liberate volatile byproducts
Data Source
AI summary
Methods and apparatuses for removing photoresist patterning scum from patterning mandrel structures without damaging other features or structures on a semiconductor substrate are desirable for patterning precision. Methods involve cleaning carbon-containing features on a semiconductor substrate by an atomic layer cleaning (ALC) process to descum the carbon-containing features without substantially modifying feature critical dimensions. The ALC process involves exposing the carbon-containing features to an oxidant or reductant in absence of a plasma, or other energetic activation, to modify scum on the surface of the carbon-containing features. The modified scum on the surface of the carbon-containing features is then exposed to an inert gas along with a plasma ignited at a pressure between 0.1 Torr and 10 Torr and a power of less than 200 W to remove the modified scum from the surface of the carbon-containing features.