Semiconductor Wafer Drying Centrifugal Force Control
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Solution Overview
Problem
Conventional semiconductor manufacturing techniques face challenges with positioning accuracy and chip size due to the use of thick photoresist films as shielding masks, leading to increased chip size and reduced yield, as well as cracking issues during the drying process which affects the shielding performance and introduces defects as carrier lifetime killers.
Innovation Solution
A method involving the use of a photoresist film as a mask with controlled thickness and rotational speed during the drying process to prevent cracking, ensuring precise ion implantation and maintaining the integrity of the photoresist film, thereby preventing helium defects in unintended regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick photoresist film is used as a shielding mask to prevent helium irradiation in unintended regions, then the shielding performance is improved, but the photoresist film cracks during the drying process due to centrifugal force, reducing manufacturing reliability
Solution Approach 1:
The patent applies parameter changes by controlling the thickness of the photoresist film to be 5 μm or less, and by controlling the rotational speed during drying to be 5000 rpm or less. These parameter optimizations prevent cracking while maintaining adequate shielding performance for the intended helium irradiation depth.
2Reliability
If the photoresist film thickness is increased to improve shielding performance, then deeper helium irradiation can be prevented, but the positioning accuracy and chip size are adversely affected
Solution Approach 1:
The patent optimizes the photoresist film thickness to be 5 μm or less, which provides sufficient shielding for the required helium irradiation depth while maintaining good positioning accuracy and preventing excessive chip size expansion.
3Productivity
If high rotational speed is used during drying to remove water quickly, then productivity is improved, but the photoresist film cracks due to excessive centrifugal force
Solution Approach 1:
The patent controls the rotational speed during drying to be 5000 rpm or less, which generates sufficient centrifugal force for efficient water removal while preventing cracking of the photoresist film. This optimized parameter balances productivity with film integrity.
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 enhances the positioning accuracy and reduces chip size, preventing helium defects in the IGBT regions and maintaining the shielding performance of the photoresist film, thus improving the characteristics of semiconductor devices like RC-IGBTs by ensuring helium defects are only induced in the FWD regions.
Implementation Method 1
drying the semiconductor wafer by rotating the semiconductor wafer around a center axis that is orthogonal to the first main surface of the semiconductor wafer, to thereby generate a centrifugal force to cause the water that is left in the openings of the photoresist film after the cleaning process to fly off the semiconductor wafer
Implementation Method 2
an injection process including ion-implanting a predetermined impurity by a predetermined acceleration energy from the first main surface of the semiconductor wafer, using the photoresist film as a mask, after the drying process
Data Source
AI summary
A method of manufacturing a semiconductor device, including preparing a semiconductor wafer having first and second main surfaces opposite to each other, forming a photoresist film on the first main surface of the semiconductor wafer, forming a plurality of openings at predetermined positions in the photoresist film, cleaning the semiconductor wafer with water after the openings are formed, drying the semiconductor wafer by rotating the semiconductor wafer around a center axis that is orthogonal to the first main surface of the semiconductor wafer, to thereby generate a centrifugal force to cause the water that is left in the openings of the photoresist film to fly off the semiconductor wafer, and ion-implanting a predetermined impurity by a predetermined acceleration energy from the first main surface of the semiconductor wafer, using the photoresist film as a mask, after the drying. The drying process includes setting a rotational speed of the semiconductor wafer to be at most an upper limit value.