Wafer Back Concave Grinding for Handling Stiffness
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Solution Overview
Problem
Thin wafers formed by grinding lose stiffness, making them difficult to handle and carry during processing and subsequent steps, especially when metal films are applied.
Innovation Solution
A wafer processing method involving whole-back grinding followed by a back concave-grinding process to create a ring-like reinforcement portion around the device region, allowing for efficient handling and reducing productivity losses, using a grinding apparatus with a chuck table for rotational and movable holding and grindstones that contact the wafer's center.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the wafer thickness is reduced by grinding to achieve size reduction or weight saving, then the electronic device becomes smaller and lighter, but the wafer loses stiffness and becomes difficult to handle and carry
Solution Approach 1:
The wafer back surface is segmented into two distinct regions: a thinned device region (20-100 μm) for weight reduction and a thicker reinforcement region (300-400 μm) at the periphery for mechanical strength. This segmentation allows the wafer to simultaneously achieve weight savings while maintaining handleability through the reinforced border.
Solution Approach 2:
Different thicknesses are applied to different regions of the wafer: the central device region is thinned to reduce weight, while the peripheral region maintains greater thickness to provide structural reinforcement. This local differentiation of properties resolves the contradiction between weight reduction and handling ease.
2Weight of moving object
If the wafer thickness is reduced by grinding, then the electronic device achieves weight saving, but it becomes difficult to carry the wafer between respective steps
Solution Approach 1:
The wafer back surface is segmented into two distinct regions: a thinned device region (20-100 μm) for weight reduction and a thicker reinforcement region (300-400 μm) at the periphery for mechanical strength. This segmentation allows the wafer to simultaneously achieve weight savings while maintaining handleability through the reinforced border.
Solution Approach 2:
Different thicknesses are applied to different regions of the wafer: the central device region is thinned to reduce weight, while the peripheral region maintains greater thickness to provide structural reinforcement. This local differentiation of properties resolves the contradiction between weight reduction and handling ease.
3Reliability
If a metal film is coated on the back of the thinned wafer, then the wafer achieves enhanced properties, but it becomes even more difficult to handle and carry between steps
Solution Approach 1:
The wafer back surface is segmented into two distinct regions: a thinned device region (20-100 μm) for weight reduction and a thicker reinforcement region (300-400 μm) at the periphery for mechanical strength. This segmentation allows the wafer to simultaneously achieve weight savings while maintaining handleability through the reinforced border.
Solution Approach 2:
Different thicknesses are applied to different regions of the wafer: the central device region is thinned to reduce weight, while the peripheral region maintains greater thickness to provide structural reinforcement. This local differentiation of properties resolves the contradiction between weight reduction and handling ease.
4Device complexity
If only whole-back grinding is performed to reduce wafer thickness, then the processing is simple, but the wafer becomes too thin and difficult to handle in subsequent steps
Solution Approach 1:
The wafer back surface is segmented into two distinct regions: a thinned device region (20-100 μm) for weight reduction and a thicker reinforcement region (300-400 μm) at the periphery for mechanical strength. This segmentation allows the wafer to simultaneously achieve weight savings while maintaining handleability through the reinforced border.
Solution Approach 2:
The device region is extracted and thinned to a specific thickness range (20-100 μm) while the peripheral region is maintained at greater thickness (300-400 μm). This extraction of the device region for selective thinning resolves the contradiction between processing simplicity and handling ease.
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 method enables easy handling and carrying of wafers with reduced thickness by forming a ring-like reinforcement, reducing the time required for concave portion formation and maintaining productivity, and facilitates film formation processes.
Implementation Method 1
a back concave-grinding process of grinding a region corresponding to the device region in the back of the wafer after the whole-back grinding process to form a concave portion
Data Source
AI summary
To facilitate handling of a wafer in processing or carrying of the wafer after the wafer has been reduced in thickness by grinding, the whole back of a wafer is ground to provide the wafer with a predetermined thickness. The wafer surface includes a device region, with a plurality of devices formed therein, and a peripheral surplus region enclosing the device region. After grinding of the whole back surface, a region of the back surface corresponding to the device region on the wafer surface is ground to form a concave portion having a predetermined thickness, so that a ring-like reinforcement portion is formed about a periphery of the concave portion, such that the wafer is easily handled in a subsequent step or in wafer carrying between respective steps.