Wafer Thinning via Groove Etching and Rear Surface Processing
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Solution Overview
Problem
The challenge in semiconductor wafer processing is to maintain device quality when wafers are thinned to 100 μm or less, as conventional cutting methods often result in chipping at the periphery of devices and make it difficult to handle due to reduced stiffness, and projecting electrodes from the rear surface is complicated.
Innovation Solution
A method involving forming dividing grooves and annular grooves on the wafer's front surface, followed by protective member affixing, rear surface grinding to expose these grooves, and subsequent rear surface etching to project electrodes, which improves handling and reduces chipping by maintaining the wafer's shape and enhancing bending strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the wafer thickness is reduced to 100 μm or less to form a laminate of devices, then the device size is reduced, but the stiffness of the wafer degrades and it becomes difficult to handle
Solution Approach 1:
Dividing grooves are formed in advance along the streets from the front surface side before the final thinning process. These pre-formed grooves serve as stress relief features that prevent chipping during subsequent handling and processing, allowing the wafer to be thinned to 100 μm or less while maintaining sufficient mechanical strength for handling.
Solution Approach 2:
The wafer is segmented into individual device regions by forming dividing grooves along the streets. This segmentation creates isolated support zones for each device area, preventing the entire thin wafer from bending simultaneously and thus maintaining handling stiffness even when the overall wafer thickness is reduced to 100 μm or less.
2Productivity
If the wafer is cut along the streets by using a cutting machine to be divided into individual devices, then the devices are separated, but the periphery of each device is chipped at many positions, thereby reducing its quality
Solution Approach 1:
Dividing grooves are formed in advance along the streets from the front surface side before the final separation process. These pre-formed grooves guide the separation process and prevent uncontrolled chipping at the device peripheries, enabling high-quality device extraction without compromising manufacturing precision.
Solution Approach 2:
The conventional mechanical cutting method that causes chipping is replaced by a chemical etching process. The dividing grooves are formed by etching along the streets, which chemically separates the devices without the mechanical stress and chipping associated with traditional cutting machines, thereby maintaining device periphery quality.
3Manufacturing precision
If the rear surface of the wafer is ground to a predetermined thickness and then etched to project the electrodes, then the electrodes are projected from the rear surface, but grinding distortion is generated on the rear surfaces of the devices
Solution Approach 1:
The mechanical grinding process that causes distortion is replaced by chemical etching. The rear surface is etched to project the electrodes without the mechanical stress and distortion associated with grinding, thereby achieving electrode projection while maintaining rear surface flatness and device shape integrity.
Solution Approach 2:
The processing method is changed from mechanical (grinding) to chemical (etching). This parameter change in the processing mechanism eliminates grinding distortion while still achieving the desired electrode projection, as chemical etching proceeds uniformly without the mechanical forces that cause surface distortion.
4Volume of moving object
If the wafer is made thin to form a laminate of devices, then the device size is reduced, but the periphery of each device is chipped when cut with a cutting machine
Solution Approach 1:
The mechanical cutting process is replaced by chemical etching to form the dividing grooves and separate devices. This substitution eliminates the chipping problem that occurs when thin wafers are mechanically cut, allowing wafers to be made thin for laminate device formation while maintaining high device quality and reliability.
Solution Approach 2:
Dividing grooves are formed in advance along the streets from the front surface side before the wafer is thinned and before device separation. These pre-formed grooves provide controlled separation paths that prevent chipping during subsequent processing, enabling thin wafer processing while maintaining device quality and reliability.
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 method allows for secure division of thin wafers into individual devices without chipping, enables effective projection of electrodes, and improves the bending strength of devices by removing grinding distortion, facilitating easy handling and maintaining the wafer's shape.
Implementation Method 1
a dividing groove forming step for forming dividing grooves having a depth corresponding to the final thickness of each device along the streets from the front surface side of the substrate of the wafer
Implementation Method 2
an annular groove forming step for forming an annular groove having a depth corresponding to the final thickness of each device along the boundary between the device area and the peripheral extra area from the front surface side of the substrate
Implementation Method 3
a rear surface grinding step for grinding a rear surface corresponding to the device area of the substrate of the wafer which has undergone the protective member affixing step to expose the dividing grooves and the annular groove to the rear surface of the substrate of the wafer and form an annular reinforcing portion
Implementation Method 4
a rear surface etching step for etching the rear surface of the substrate of the wafer which has undergone the rear surface grinding step to project the electrodes from the rear surface of the substrate
Data Source
AI summary
A wafer processing method for dividing, along streets, a wafer having a device area where devices are formed in a plurality of areas sectioned by the plurality of streets arranged in a lattice pattern on the front surface of a substrate and a peripheral extra area and comprising electrodes which are embedded in the substrate of the device area, comprising a dividing groove forming step for forming dividing grooves having a depth corresponding to the final thickness of each device along the streets; an annular groove forming step for forming an annular groove having a depth corresponding to the final thickness of each device along the boundary between the device area and the peripheral extra area; a protective member affixing step for affixing a protective member to the front surface of the wafer; a rear surface grinding step for grinding a rear surface corresponding to the device area of the substrate of the wafer to expose the dividing grooves and the annular groove to the rear surface of the substrate of the wafer and form an annular reinforcing portion in an area corresponding to the peripheral extra area; and a rear surface etching step for etching the rear surface of the substrate of the wafer to project the electrodes from the rear surface of the substrate.