Bonded Wafer Thinning via Preliminary Grinding and Chamfer Removal
Solution Overview
Problem
Existing methods for manufacturing SOI wafers with thick SOI layers face issues of chipping and delamination at the outer circumference portion of the bond wafer during thinning, leading to changes in base wafer shape and reduction in wafer diameter, along with increased processing time.
Innovation Solution
A method involving surface grinding in two steps, with a first step setting the bond wafer thickness to create an explementary angle of 40° or more to prevent chipping, followed by removal of the outer circumference portion using a chamfering wheel matching the base wafer's chamfered shape, and a third step of fine surface grinding to achieve the desired thickness without altering the base wafer shape or reducing the bond wafer diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the bond wafer is thinned by surface grinding and polishing to achieve a thickness of 50 μm or more, then the SOI layer thickness is increased, but the outer circumference portion of the bond wafer becomes prone to chipping and delamination due to the sharp tip angle of the chamfered portion
Solution Approach 1:
The patent applies preliminary action by performing a first surface grinding process before the main thinning process. This initial grinding creates a rounded outer circumference portion with a controlled tip angle, which prevents chipping during subsequent thinning operations. The preliminary shaping of the outer circumference ensures that when the bond wafer is thinned to achieve thick SOI layers (50 μm or more), the outer circumference maintains structural integrity and resistance to chipping and delamination.
2Reliability
If the outer circumference portion of the bond wafer is ground to remove the chamfered portion to prevent chipping, then chip resistance is improved, but the base wafer shape changes and the bond wafer diameter is reduced
Solution Approach 1:
The patent applies local quality by selectively modifying only the outer circumference portion of the bond wafer through controlled surface grinding, while preserving the overall wafer shape and dimensions. The grinding process is localized to create a rounded profile at the outer circumference with a specific tip angle, without removing excessive material that would alter the base wafer shape or significantly reduce the bond wafer diameter. This localized modification achieves chip resistance while maintaining the necessary geometric characteristics for device fabrication.
3Ease of manufacture
If conventional surface grinding and polishing processes are used to thin the bond wafer, then manufacturing simplicity is maintained, but processing time increases and chipping occurs at the outer circumference
Solution Approach 1:
The patent reduces processing time by implementing preliminary surface grinding that simultaneously achieves two objectives: shaping the outer circumference portion with an appropriate tip angle to prevent chipping, and removing a portion of the intended thinning amount. This preliminary action reduces the material removal burden in subsequent polishing steps, thereby shortening the overall processing time while maintaining manufacturing process simplicity and preventing chipping.
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 effectively prevents chipping and delamination at the outer circumference of the bond wafer, reduces processing time, and maintains the base wafer's shape and bond wafer diameter, allowing for efficient manufacturing of SOI wafers with minimal reduction in device regions.
Implementation Method 1
performing surface grinding on a bond wafer so that a thickness of the bond wafer reaches a first predetermined value
Implementation Method 2
removing an outer circumference portion of the ground bond wafer by using a chamfering wheel formed into a shape corresponding to the chamfered portion of the base wafer
Implementation Method 3
performing surface grinding on the bond wafer so that a thickness of the bond wafer reaches a second predetermined value
Data Source
Figure 1(A)~1(C)
Figure 2
Figure 3
AI summary
The present invention is a method for manufacturing a bonded wafer comprising bonding together a bond wafer and a base wafer each having a chamfered portion at an outer circumference and thinning the bond wafer, wherein the thinning of the bond wafer includes: a first step of performing surface grinding on the bond wafer such that a thickness of the bond wafer reaches a first predetermined thickness; a second step of removing an outer circumference portion of the ground bond wafer; and a third step of performing surface grinding on the bond wafer such that the thickness of the bond wafer reaches a second predetermined thickness. As a result, there is provided a method for manufacturing a bonded wafer by which a bonded wafer with no chipping at the outer circumference portion of the thinned bond wafer, such as an SOI layer, and no delamination can be manufactured for a short time, while the shape of the base wafer is prevented from changing and the diameter of the bond wafer is significantly inhibited from decreasing.