Stealth Laser Wafer Thinning Without Cracks or Debris
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Solution Overview
Problem
Conventional backgrinding processes for thinning semiconductor wafers are prone to generating cracks, reducing yield and requiring additional inspection steps, and produce debris that can impair dies, especially at thinner thicknesses.
Innovation Solution
A stealth lasing process that focuses a laser at discrete points beneath the wafer surface to thin the substrate, creating voids that allow for controlled removal of material without cracking the wafer, followed by polishing and dicing into individual dies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional backgrinding processes are used to thin semiconductor wafers, then wafer thickness is reduced, but cracks are generated in the wafer
Solution Approach 1:
The patent replaces the mechanical backgrinding system with a laser-based system. The laser beam focuses energy at discrete points beneath the wafer surface, creating voids that allow controlled material removal without mechanical contact. This substitution eliminates the mechanical forces that cause cracking while achieving the same thinning objective.
Solution Approach 2:
The patent introduces an intermediary medium (laser energy) to transfer the thinning action from the surface to subsurface points. By focusing laser energy at discrete points beneath the surface, the system creates voids that facilitate material removal without direct mechanical contact, preventing crack propagation while maintaining wafer integrity.
2Length of stationary object
If conventional backgrinding processes are used to thin semiconductor wafers, then wafer thickness is reduced, but additional inspection steps are required
Solution Approach 1:
The laser-based system replaces mechanical grinding with optical energy delivery, enabling precise control of material removal. The laser can be programmed to create voids at specific locations and depths, eliminating the need for multiple grinding wheels and intermediate inspection steps to detect cracks.
Solution Approach 2:
The patent changes the fundamental parameter of material removal from mechanical abrasion to laser-induced void formation. By controlling laser power, pulse duration, and focal depth, the system achieves precise thickness reduction without generating cracks, thereby simplifying the overall process and eliminating inspection requirements.
3Length of stationary object
If conventional backgrinding processes are used to thin semiconductor wafers, then wafer thickness is reduced, but debris is generated that impairs dies
Solution Approach 1:
The patent replaces mechanical grinding with laser-based void formation. Instead of mechanically abrading material that generates debris, the laser energy creates vaporization and voids at discrete points, allowing material to be removed without contact. This eliminates the generation of foreign particles and debris that would otherwise contaminate and impair the dies.
Solution Approach 2:
The laser process induces phase transitions in the wafer material at the focal points, transforming solid material into vapor or liquid that can be evacuated through the created voids. This phase change mechanism removes material without mechanical contact, preventing debris generation while achieving the required thickness reduction.
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 eliminates wafer cracking, improves yield and die quality by preventing debris generation, and simplifies the packaging process by eliminating the need for backgrinding wheels.
Implementation Method 1
a stealth lasing process that focuses a laser at discrete points beneath the wafer surface to thin the substrate, creating voids that allow for controlled removal of material
Data Source
AI summary
A semiconductor wafer thinned by a stealth lasing process, and semiconductor dies formed therefrom. After formation of an integrated circuit layer on a semiconductor wafer, the wafer may be thinned by focusing a laser at discrete points in the wafer substrate beneath the surface of the wafer. Upon completion of stealth lasing in one or more planar layers in the substrate, a portion of the substrate may be removed, leaving the wafer thinned to a desired final thickness.