Supercritical CO2 Drying for High Aspect Ratio Features
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Solution Overview
Problem
Current wet cleaning techniques for semiconductor substrates with high-aspect-ratio features face challenges in preventing line stiction and residue due to capillary forces during drying, especially with high-aspect-ratio semiconductor device structures, which can lead to damage and process inefficiencies.
Innovation Solution
A substrate processing apparatus and method utilizing a small thermal mass pressurized chamber that employs supercritical CO2 to dry substrates, eliminating capillary forces by transitioning the cleaning fluid into a supercritical state, thereby preventing line stiction and residue formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wet cleaning techniques with liquid spraying or immersion are used, then cleaning liquid can be applied to remove contaminants, but capillary forces cause deformation of high-aspect-ratio structures leading to line stiction and damage
Solution Approach 1:
The patent changes the physical parameters of the cleaning medium by transitioning from liquid to supercritical state. By adjusting temperature and pressure parameters beyond the critical point of CO2 (31.1°C and 73 atm), the cleaning medium eliminates surface tension and capillary forces while maintaining cleaning effectiveness, thus preventing line stiction and structure deformation
Solution Approach 2:
The patent utilizes phase transition of CO2 from gas to supercritical fluid state. This phase transition enables the cleaning medium to penetrate porous structures without generating capillary forces, as supercritical fluids have no distinct liquid-gas interface. The transition is achieved by heating and pressurizing CO2 within the processing chamber
2Loss of substance
If conventional drying methods are used to remove cleaning liquid, then liquid removal is achieved, but residue from cleaning solution remains on the substrate
Solution Approach 1:
The patent employs phase transition of supercritical CO2 to gas state for drying. By depressurizing the supercritical fluid, it transitions directly to gas phase, evaporating and removing all cleaning liquid and residues from the substrate surface and porous structures without leaving any contamination, achieving complete substrate cleanliness
3Stability of the object's composition
If standard chamber design with large thermal mass is used, then structural stability is maintained, but temperature cycling for supercritical processing is slow and inefficient
Solution Approach 1:
The patent segments the chamber into two distinct components: a large outer chamber body for structural stability and pressure containment, and a small inner liner with small thermal mass for rapid temperature cycling. The liner is positioned concentrically within the chamber body, allowing independent thermal response while maintaining overall structural integrity
Solution Approach 2:
The patent extracts the thermal mass function from the overall chamber structure by creating a separate, small thermal mass liner. This liner can be rapidly heated and cooled independently from the large chamber body, enabling fast temperature cycling for supercritical processing while the outer chamber body maintains structural stability and pressure containment
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 use of supercritical CO2 effectively removes liquid and particles from substrates with high-aspect-ratio features, preventing line stiction and residue, while maintaining the integrity of semiconductor substrates, even with complex structures like 3D/vertical NAND flash devices.
Implementation Method 1
an insulation element disposed within the chamber body adjacent the liner
Implementation Method 2
supercritical CO2 may be generated in the processing chamber, and the substrate may be exposed to the supercritical CO2
Implementation Method 3
employs supercritical CO2 to dry substrates, eliminating capillary forces by transitioning the cleaning fluid into a supercritical state
Implementation Method 4
a baffle plate disposed in the processing volume may be coupled to an actuator configured to move the baffle plate within the processing volume
Data Source
AI summary
Embodiments described herein generally relate to a processing chamber incorporating a small thermal mass which enable efficient temperature cycling for supercritical drying processes. The chamber generally includes a body, a liner, and an insulation element which enables the liner to exhibit a small thermal mass relative to the body. The chamber is also configured with suitable apparatus for generating and/or maintaining supercritical fluid within a processing volume of the chamber.