Wafer Edge Trimming via Plasma Etching to Prevent Dust
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Solution Overview
Problem
The existing wafer processing methods using cutting blades for edge trimming generate excessive dust and require frequent blade dressing, leading to reduced processing efficiency and potential damage to the wafer edges, which can affect the quality of device chips.
Innovation Solution
A method involving plasma etching to remove the peripheral marginal area of the wafer, using a protective layer as a mask to prevent dust generation and eliminate the need for blade dressing, followed by grinding to achieve the desired thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cutting blade is used for edge trimming to prevent knife edge shape formation, then edge damage is suppressed, but a large amount of cutting dust is generated and adheres to the wafer, causing defective operation or bonding of devices
Solution Approach 1:
The patent replaces the mechanical cutting blade system with a plasma processing system. Instead of using a physical cutting blade that generates dust, the invention uses plasma to selectively remove material from the peripheral portion of the wafer, forming a step portion without generating cutting dust that would adhere to the wafer surface and cause device defects
Solution Approach 2:
The patent changes the physical state and processing parameters by using plasma processing conditions. By controlling plasma parameters (power, gas flow, processing time), the method achieves precise removal of the peripheral portion to form a step portion, eliminating the dust generation problem associated with mechanical cutting while maintaining edge damage suppression
2Ease of manufacture
If a cutting blade is used for edge trimming, then the peripheral portion is cut to form a step portion, but the cutting blade is subjected to partial wear requiring frequent dressing, reducing processing efficiency
Solution Approach 1:
The patent replaces the mechanical cutting blade with a plasma processing system. This substitution eliminates blade wear and the need for frequent dressing operations, thereby improving processing efficiency while still achieving the desired step portion formation in the peripheral portion of the wafer
Solution Approach 2:
The plasma processing system provides self-regulating material removal through controlled plasma reactions. The process automatically maintains consistent removal rates without requiring external intervention for blade maintenance or dressing, enabling continuous high-efficiency processing
3Manufacturing precision
If the peripheral portion of the wafer is ground to reduce thickness, then the wafer thickness is reduced to predetermined thickness, but the shape becomes a knife edge shape sharply projecting radially outward, causing chipping and breaking
Solution Approach 1:
The patent applies preliminary plasma processing to form a step portion in the peripheral portion before the wafer thinning process. This preliminary action creates a geometric feature that prevents the formation of knife edge shapes during subsequent grinding, thereby preventing chipping and breaking while maintaining precise thickness control
Solution Approach 2:
The plasma-formed step portion acts as a preliminary anti-action against the knife edge formation that would occur during grinding. By pre-creating this geometric feature, the method counteracts the harmful effect of sharp edge projection that would otherwise lead to edge damage
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 simplifies the cleaning process, eliminates the risk of dust adherence, and prevents edge damage, thereby enhancing processing efficiency and maintaining chip quality.
Implementation Method 1
a plasma etching step of supplying an etching gas in a plasma condition to the front side of the wafer by using the protective layer as a mask, thereby removing the peripheral marginal area including the curved peripheral edge
Data Source
AI summary
There is provided a wafer processing method for reducing a thickness of a wafer. The wafer has a front side and a back side opposite to the front side. The wafer has a device area where a plurality of devices are formed on the front side and a peripheral marginal area including a curved peripheral edge. A protective layer for covering the plural devices are formed on the front side in the device area. The wafer processing method includes a plasma etching step of supplying an etching gas in a plasma condition to the front side of the wafer by using the protective layer as a mask, thereby removing the peripheral marginal area including the curved peripheral edge, a protective member attaching step of attaching a protective member to the front side of the wafer, and a grinding step of grinding the back side of the wafer.