Semiconductor Wafer Dicing with Laser Scribing and Plasma Etching
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Solution Overview
Problem
Current semiconductor wafer dicing methods, such as scribing and sawing, result in chipping, cracking, and waste of wafer real estate due to jagged separation lines and the need for significant spacing between dice, while plasma dicing faces cost and throughput limitations, especially with thick passivation layers and complex metal layers.
Innovation Solution
A hybrid method combining femtosecond-based laser scribing with dual focus lenses and subsequent plasma etching to singulate integrated circuits, which allows for precise, non-thermal cutting through thick passivation layers and device layers without delamination or microcracking, eliminating the need for lithography patterning and reducing waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If scribing or sawing is used to dice wafers, then the wafer can be separated into individual dice, but chipping and cracking occur along the severed edges and additional spacing is required between dice
Solution Approach 1:
The patent replaces mechanical scribing and sawing systems with a plasma-based dicing system. The plasma process uses ion bombardment and chemical reactions to remove material, eliminating the mechanical contact that causes chipping and cracking. This substitution allows for cleaner cuts with minimal damage to the dice edges, thereby reducing the required spacing between dice and increasing wafer real estate utilization.
Solution Approach 2:
The patent changes the fundamental parameter of the dicing process from mechanical force to plasma energy. By controlling plasma parameters such as power, pressure, and gas composition, the process achieves precise material removal without the mechanical stresses that cause edge damage. This parameter change enables high-precision dicing with minimal spacing requirements.
2Length of stationary object
If a diamond saw is used for dicing, then thick wafers can be cut, but the blade thickness requires three to five hundred microns separation between circuitry
Solution Approach 1:
The patent replaces the mechanical diamond saw with a plasma dicing system. The plasma process can handle thick wafers through controlled material removal via ion bombardment and chemical reactions, eliminating the need for a physical blade. This allows for ultra-precise cutting with minimal kerf width, reducing the separation distance between dice to minimal levels and maximizing wafer utilization.
Solution Approach 2:
The plasma dicing process uses periodic pulsed plasma application to progressively remove material through thick wafers. The pulsed nature of the plasma allows for controlled ablation, preventing excessive heat buildup and enabling precise depth control. This periodic action achieves clean cuts through thick substrates with minimal lateral damage, reducing required spacing between dice.
3Ease of manufacture
If scribing is used for dicing, then the process is simple, but only one side of a die can be scribed in the direction of the crystalline structure resulting in jagged separation lines
Solution Approach 1:
The patent replaces mechanical scribing with plasma-based dicing. The plasma process is not constrained by crystallographic directions and can etch material uniformly in any orientation. This substitution maintains process simplicity while eliminating the fundamental limitation of mechanical scribing, producing smooth, clean separation lines regardless of the dice orientation on the wafer.
Solution Approach 2:
The plasma dicing system provides universal cutting capability that works effectively for all dice orientations and wafer configurations. Unlike mechanical scribing which is directionally limited, the plasma process can accommodate any layout pattern, making it universally applicable to different device geometries and wafer designs while maintaining simple operation.
4Reliability
If plasma dicing is used, then cost and throughput limitations exist, but the patent addresses these with specific process optimizations
Solution Approach 1:
The patent applies preliminary laser scribing to create initial grooves or patterns in the wafer before applying plasma dicing. This preliminary action reduces the total material removal required during the plasma process, thereby decreasing processing time and increasing throughput while maintaining the damage-free advantages of plasma dicing. The pre-formed structures guide the plasma etching process for more efficient material removal.
Solution Approach 2:
The patent employs periodic pulsed plasma dicing with optimized duty cycles to balance etching efficiency and heat management. By using short plasma pulses with appropriate intervals, the process achieves high removal rates while preventing excessive heat buildup that could cause damage. This periodic action optimizes both throughput and reliability, addressing the trade-off between speed and damage-free operation.
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 approach enables efficient, precise, and cost-effective dicing of semiconductor wafers with minimal damage, allowing for closer spacing of integrated circuits and increased wafer utilization, while maintaining high throughput and reducing post-dicing cleaning requirements.
Implementation Method 1
laser scribing the mask layer and the front surface of the semiconductor wafer to provide scribe lines
Implementation Method 2
etching the semiconductor wafer through the scribe lines to singulate the integrated circuits
Data Source
AI summary
Methods of and apparatuses for dicing semiconductor wafers, each wafer having a plurality of integrated circuits, are described. In an example, a method of dicing a semiconductor wafer having a front surface having a plurality of integrated circuits thereon involves forming a mask layer above the front surface of the semiconductor wafer. The method also involves laser scribing the mask layer and the front surface of the semiconductor wafer to provide scribe lines in the mask layer and partially into the semiconductor wafer. The laser scribing involves use of a dual focus lens to provide a dual focus spot beam. The method also involves etching the semiconductor wafer through the scribe lines to singulate the integrated circuits.