Laser-Assisted Cleaving for Stacked Die Singulation
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Solution Overview
Problem
Conventional stacked die assembly methods using reconstituted wafers often damage or contaminate the periphery bond pads of top semiconductor dies due to mechanical dicing, especially when the dies are thin and the gap between them is small, leading to unreliable wirebonding.
Innovation Solution
Laser-assisted cleaving of reconstituted wafers is used to singulate stacked die devices without damaging or contaminating the periphery bond pads, employing a method where a laser weakens the wafer at intended dicing locations without cutting through, followed by dicing tape separation to create singulated portions attached to a support tape, which are then removed and wire-bonded to a package substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional mechanical dicing operations are used for forming stacked die assemblies using the reconstituted wafer method, then the wafer can be singulated into individual stacked die devices, but the dicing blade comes in close proximity to the periphery bond pads on the top semiconductor die and deposits debris-comprising slurry that damages or contaminates the bond pads, preventing reliable wirebonding
Solution Approach 1:
The patent replaces the conventional mechanical dicing blade system with a laser-based system. The laser irradiates the carrier wafer to create weakened regions along intended dicing lanes without physical contact, eliminating the mechanical blade that generates slurry debris. This substitution resolves the contradiction by maintaining singulation capability while removing the source of bond pad contamination that compromises wirebonding reliability
Solution Approach 2:
The patent introduces an intermediary mechanism where the laser creates a weakened region in the carrier wafer that acts as a predetermined fracture path. This intermediary weakened zone allows the dicing tape to separate the stacked die devices along the intended lanes without the blade needing to physically cut through the bond pad areas, thus protecting the bond pads from debris contamination while enabling efficient singulation
2Manufacturing precision
If the dicing blade operates close to the periphery bond pads to singulate thin stacked die devices, then singulation can be achieved, but the bond pads are damaged or contaminated by debris-comprising slurry
Solution Approach 1:
The patent applies preliminary action by using the laser to pre-weaken the carrier wafer along the intended dicing lanes before the actual separation process. This pre-created weakened region serves as a guided fracture path that directs the separation away from the bond pad areas, achieving precise singulation without the blade needing to operate close to the bond pads, thus preventing contamination while maintaining manufacturing precision
Solution Approach 2:
The patent replaces the mechanical dicing blade with a laser-based weakening system that creates predetermined fracture paths without physical contact. This substitution eliminates the slurry debris generation mechanism while maintaining the ability to achieve precise singulation along intended lanes, resolving the contradiction between singulation precision and bond pad contamination
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 prevents damage and contamination of periphery bond pads, enhancing the reliability of wirebonding and eliminating the need for conventional dicing blades, thereby improving the assembly process by ensuring the integrity of the bond pads.
Implementation Method 1
A laser is used to irradiate the carrier wafer at intended dicing locations that align with gaps between the plurality of first semiconductor die under conditions that mechanically weaken the wafer
Data Source
AI summary
A method of forming stacked die devices includes attaching first semiconductor die onto a wafer to form a reconstituted wafer, and then bonding second semiconductor die onto the first semiconductor die to form a plurality of singulated stacked die devices on the wafer. A support tape is attached to a bottomside of the second semiconductor die. A dicing tape is attached to the wafer. The wafer is laser irradiated before or after attachment of the dicing tape at intended dicing lanes that align with gaps between the first semiconductor die to mechanically weaken the wafer at the intended dicing lanes, but not cut through the wafer. The dicing tape is pulled to cleave the wafer into a plurality of singulated portions to form a plurality of singulated stacked die devices attached to the singulated wafer portions by the dicing tape. The support tape is removed prior to cleaving.