Laser Dicing Semiconductor Chips with Backside Metal Layer
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Solution Overview
Problem
Conventional semiconductor chip dicing methods result in inadequate die strength due to metal fragment adhesion and cracking, leading to poor chip performance and increased fabrication costs.
Innovation Solution
A fabrication method involving laser dicing with a backside metal layer fully covering the substrate, eliminating the need for back etching and allowing for thinner substrate thickness, which enhances die strength and heat dissipation while reducing material usage and processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional dicing methods are used with backside metal layer deposition, then die strength should be improved, but metal fragments are sprayed and adhere to integrated circuits causing damage
Solution Approach 1:
The patent replaces the conventional mechanical sawing dicing method with a laser-based dicing method. The laser beam ablates the substrate and metal layer without mechanical contact, eliminating metal fragment generation and adhesion to integrated circuits while maintaining die strength enhancement from the backside metal layer
Solution Approach 2:
The laser dicing process utilizes phase transition of materials through ablation. The laser energy transforms solid substrate and metal layer material directly into vapor or plasma state, removing material cleanly without mechanical fragmentation, thus preventing metal fragment contamination
2Temperature
If substrate is thinned to less than 100 μm before backside metal deposition, then heat dissipation efficiency is improved, but substrate becomes more fragile during processing
Solution Approach 1:
The patent performs substrate thinning as a preliminary action before depositing the backside metal layer. By thinning the substrate first to less than 100 μm, the thermal path is shortened for improved heat dissipation, and the subsequent metal layer deposition provides structural reinforcement to compensate for the reduced substrate thickness
Solution Approach 2:
The patent creates a composite structure by combining the thinned substrate with a deposited metal layer on the backside. This composite construction provides both the thermal management benefits of thin substrate and the mechanical strength of the metal layer, resolving the contradiction between heat dissipation and structural integrity
3Manufacturing precision
If backside metal layer streets are etched to form scribe lines, then dicing precision is improved, but process complexity and cycle time increase
Solution Approach 1:
The patent extracts and eliminates the complex multi-step etching process for creating scribe lines. By using laser dicing directly on the backside metal layer, the method removes the intermediate steps of photoresist coating, etching, and development, achieving precise dicing through a single laser processing step
Solution Approach 2:
The patent replaces the mechanical and chemical etching process with laser-based processing. The laser directly ablates the backside metal layer and substrate along scribe lines with high precision, eliminating the need for photoresist application, etching chemistry, and multiple processing steps
4Loss of substance
If conventional sawing dicing is used, then material usage is higher due to wider scribe lines, but tool capacity and productivity are reduced
Solution Approach 1:
The patent replaces mechanical sawing with laser dicing, which creates narrower kerf widths during cutting. This reduces the amount of substrate and metal layer material removed as waste, improving material utilization while the continuous laser processing maintains high tool capacity and productivity
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 significantly enhances die strength, reduces material waste, and decreases fabrication costs by ensuring tidy cutting and improved chip performance without metal fragment adhesion, thus increasing tool capacity and product yield.
Implementation Method 1
the laser beam 137 passes through areas 161 next to street 127 and reaches the focal point 157 of the laser beam 137. The focal point 157 of the laser beam 137 is at location 125, which is located inside the substrate 149 closer to the backside 131 of the semiconductor wafer 133. When the laser beam 137 reaches the focal point 157, the high intensity laser beam 137 can scribe and weaken the crystal lattice at point 157.
Data Source
AI summary
A fabrication method for producing semiconductor chips with enhanced die strength comprises following steps: forming a semiconductor wafer with enhanced die strength by comprising the substrate, the active layer on the front side of the substrate and the backside metal layer on the backside of the substrate, wherein at least one integrated circuit forms in the active layer; forming a protection layer on a front side of the semiconductor wafer; dicing the semiconductor wafer by at least one laser dicing process and removing the laser dicing residues and removing said protection layer by at least one etching process, whereby plural semiconductor chips with enhanced die strength are produced, and wherein the backside metal layer of said semiconductor chip fully covers the backside of said semiconductor chip after dicing.