Laser Ablation for Thinning Semiconductor Wafers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for thinning semiconductor wafers, such as mechanical grinding and wet etching, are complex, time-consuming, and expensive, and can result in fragile wafers that break easily due to excessive or incorrect thinning, leading to high electrical resistance (RDSON).
Innovation Solution
A method involving laser ablation to form deep and wide trenches on the bottom surface of semiconductor wafers, which are then filled with conductive materials like aluminum, allowing for reduced wafer thickness while maintaining mechanical strength, thereby reducing RDSON.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mechanical grinding or wet etching is used to thin the wafer, then the wafer thickness is reduced to lower RDSON, but the wafer becomes fragile and breaks easily
Solution Approach 1:
The patent replaces mechanical grinding and wet etching processes with laser ablation to thin the wafer. The laser beam selectively removes material from the wafer back surface to create precise thickness reduction without mechanical contact, thereby achieving the desired thinness while preserving wafer structural integrity and avoiding fragility issues associated with mechanical methods.
Solution Approach 2:
The patent changes the physical state and properties of the wafer through controlled laser ablation. By adjusting laser parameters (power, pulse duration, scanning speed), the process achieves precise thickness control while maintaining the wafer's mechanical strength. The laser energy selectively removes material at the molecular level rather than through mechanical force, preserving the remaining wafer structure.
2Manufacturing precision
If mechanical grinding or wet etching is used to thin the wafer, then the wafer thickness is reduced, but the process becomes complex and time-consuming
Solution Approach 1:
The patent replaces complex multi-step mechanical grinding and wet etching processes with a single laser ablation process. This substitution simplifies the manufacturing workflow by eliminating the need for multiple process stages, intermediate handling, and complex process control systems associated with mechanical methods, while achieving superior thickness precision.
Solution Approach 2:
The patent extracts and eliminates the intermediate steps and auxiliary processes inherent in mechanical grinding and wet etching methods. By using laser ablation directly on the wafer back surface, the process removes the need for grinding wheels, slurry systems, chemical baths, and multiple processing stages, thereby simplifying the overall device complexity.
3Manufacturing precision
If mechanical grinding or wet etching is used to thin the wafer, then the wafer thickness is reduced, but the process becomes expensive
Solution Approach 1:
The patent replaces expensive mechanical grinding equipment and wet etching chemical systems with laser ablation technology. While laser equipment represents a capital investment, it eliminates ongoing costs associated with grinding wheels, slurry materials, chemical baths, and waste disposal, resulting in lower overall manufacturing costs and improved ease of manufacture.
4Reliability
If the wafer is thinned excessively to reduce RDSON, then the electrical resistance decreases, but the wafer becomes fragile and breaks easily
Solution Approach 1:
The patent uses laser ablation to achieve precise thickness control that optimizes the balance between electrical resistance and mechanical strength. The laser process removes material layer by layer with atomic-level precision, allowing the wafer to be thinned to the exact minimum thickness required for low RDSON while maintaining sufficient mechanical strength to prevent fragility and breakage.
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 effectively reduces electrical resistance by creating a thinner wafer with improved mechanical strength, facilitating better connection and coverage during metal deposition, thus enhancing the performance and reliability of semiconductor devices.
Implementation Method 1
focusing a laser to form holes or trenches on a bottom surface of the wafer
Data Source
AI summary
A laser ablated wafer for a semiconductor device, such as a MOSFET or other power device, and a method of producing such a wafer to achieve a lower electrical resistance are provided. The method includes forming first holes, slots or trenches on a first surface of the wafer and focusing a laser beam to form second trenches on a bottom surface of the wafer, and filling the trenches, for example using aluminum or other metallic filling, to provide conductive electrodes or conductive surfaces for the semiconductor device. In such a wafer each trench on the second surface may be deeper, for example more than one hundred microns deep and tens of microns wide.