Wafer Processing with Protective Member for Accurate Dicing
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Solution Overview
Problem
The DBG process faces challenges in maintaining the layout of device chips on a wafer, as the soft die-attach film tends to become misshapen, making it difficult to accurately separate the chips, leading to increased processing time when trying to position a laser beam for severance.
Innovation Solution
A method involving forming grooves on the wafer, covering it with a protective film and curing a liquid resin to create a protective member, grinding the reverse side to expose the grooves, bonding a die-attach film, and using a laser to divide the film along projected dicing lines while keeping the chips in position with the protective member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a soft die-attach film is applied to the reverse side of the wafer, then chipping of the reverse side is restrained, but the layout of device chips becomes out of shape in subsequent steps
Solution Approach 1:
A rigid protective member is formed on the face side of the wafer before applying the soft die-attach film to the reverse side. This preliminary protective structure prevents the soft film from causing layout distortion during subsequent handling and processing steps, while still allowing the film to provide its chip protection function.
Solution Approach 2:
The protective member is formed only on the face side of the wafer where devices are located, while the reverse side receives the die-attach film. This localized application allows each side to have different mechanical properties - rigid protection on the face side and soft cushioning on the reverse side - without interfering with each other's functions.
2Measurement precision
If the layout of device chips varies, then it is difficult to sever the die-attach film at accurate positions, but performing laser positioning on wafers with large layout variations requires very long processing time
Solution Approach 1:
The rigid protective member replaces the need for complex laser positioning and detection systems. By providing a stable reference structure that prevents layout variation, the system eliminates the time-consuming laser positioning step while maintaining high severance accuracy through the protective member's structural stability.
Solution Approach 2:
The protective member is formed in advance to establish a stable reference framework before the die-attach film is applied. This preliminary structural establishment ensures that subsequent severance operations can proceed quickly and accurately without requiring time-consuming layout detection and positioning adjustments.
3Ease of manufacture
If grooves are formed to a depth exceeding finished thickness, then the grooves can be exposed after grinding to divide the wafer, but the face side becomes vulnerable to damage before protective measures are applied
Solution Approach 1:
The protective member is formed on the face side of the wafer before grooves are etched to exceed the finished thickness. This preliminary protection ensures that the face side remains intact and undamaged during the deep groove formation process, while still allowing the grooves to be exposed later for wafer division.
Solution Approach 2:
The protective member is applied specifically to the face side where devices are located, providing localized protection during groove formation. This allows the grooves to be etched deeply for easy wafer division while the protective member prevents damage to the device-bearing face side during the process.
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 ensures the device chips remain in their intended layout even after the protective member is removed, allowing for accurate division of the die-attach film without lengthy positioning processes, thus improving efficiency in the wafer processing.
Implementation Method 1
producing a protective-member-combined wafer that includes the wafer whose face side is covered with the protective member by covering the protective film with a protective member formed by curing a liquid resin that is curable by an external stimulus
Implementation Method 2
applying a laser beam having a wavelength absorbable by the die-attach film to portions of the die-attach film that are exposed between the device chips
Implementation Method 3
applying a laser beam having a wavelength absorbable by the die-attach film to portions of the die-attach film that are exposed between the device chips, while the device chips are being kept in their layouts by the wafer being held under suction on the chuck table, thereby dividing the die-attach film along the projected dicing lines
Implementation Method 4
holding the dicing tape bonded to the protective-member-combined wafer where the device chips are kept in their layouts by the protective member, under suction on a chuck table of a laser processing apparatus
Data Source
AI summary
A method of processing a wafer having a face side where devices are formed in respective areas demarcated by a grid of projected dicing lines includes a groove forming step, a protective film sticking step, a protective-member-combined wafer forming step, a grinding step, a tape bonding step, a holding step, a peeling step, and a die-attach film dividing step.