Semiconductor Wafer Backside Drying Using Pressurized Gas Jets
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Solution Overview
Problem
Spin coating of semiconductor wafers faces challenges with edge effects and non-uniform coating thickness due to surface tension and airflow issues, and existing methods are inefficient in drying the backside of wafers without reintroducing contamination or significantly increasing processing time and costs.
Innovation Solution
The method involves using one or more jets of pressurized gas, preferably purified nitrogen, to evaporatively dry the backside of the wafer during the spin coating process, with the gas ports positioned to promote even evaporation and integrated into a spin mechanism with a wafer chuck and spin cup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the spin rate is increased to reduce edge effects, then coating uniformity is improved, but processing time increases and production efficiency decreases
Solution Approach 1:
The drying process is segmented into two independent parts: frontside drying through conventional spin evaporation and backside drying through pressurized gas jets. This segmentation allows the backside to be dried independently, enabling faster removal of solvent without compromising frontside coating quality, thus resolving the contradiction between coating uniformity and production efficiency
Solution Approach 2:
The invention addresses the drying problem by transitioning from a single-dimension (frontside-only) drying approach to a multi-dimensional approach that includes both frontside and backside drying. By applying pressurized gas to the backside, solvent removal occurs from both surfaces simultaneously, significantly reducing total drying time while maintaining coating uniformity
2Loss of time
If slower spin rates are used to reduce edge effects, then processing time is reduced, but coating uniformity deteriorates
Solution Approach 1:
The drying function is segmented between spin-induced frontside evaporation and gas jet backside evaporation. This allows use of slower spin rates for improved coating uniformity while the backside gas jets compensate for reduced overall evaporation rate, maintaining acceptable processing times
Solution Approach 2:
Pressurized gas acts as an intermediary drying mechanism that supplements the reduced evaporation from slower spinning. The gas jets provide an additional drying pathway from the backside, compensating for the slower frontside evaporation and preventing excessive processing times
3Device complexity
If conventional drying methods are used, then equipment complexity is minimized, but drying speed is insufficient and production efficiency is low
Solution Approach 1:
The spin coating system is enhanced with multi-functionality by integrating backside gas jet drying capability. The gas delivery system can be incorporated into existing spin coating equipment, allowing the same apparatus to perform both coating and accelerated drying functions, thereby improving productivity without requiring entirely new equipment
Solution Approach 2:
The invention introduces a pneumatic drying mechanism using pressurized gas jets directed at the backside of the wafer. This pneumatic system provides controlled, high-speed drying by forcing gas through small orifices to create focused jets that rapidly evaporate solvent, significantly improving drying speed while adding relatively simple pneumatic components to the system
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 enables faster and cleaner drying of semiconductor wafers at slower spin speeds, reducing production time and costs while maintaining uniformity, and can be applied to both new and existing spin coating systems.
Implementation Method 1
spraying the backside of the wafer with one or more jets of pressurized gas to evaporatively dry the backside of the wafer
Implementation Method 2
Spin coating is a procedure that utilizes centrifugal forces created by a spinning substrate to uniformly spread a coating solution over a surface
Data Source
AI summary
The invention provides methods and apparatus for drying the backside of semiconductor wafers in a spin-coating environment. Solvent is evaporatively dried from a semiconductor wafer held in a spin mechanism. The undried wafer is sprayed with one or more jets of pressurized gas from gas ports disposed about the spin mechanism.