Pre-patterned Mask for Plasma Wafer Dicing
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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 limitations like high costs and production issues with metals like copper.
Innovation Solution
A method involving a pre-patterned mask is used to protect integrated circuits during plasma etching, allowing for clean separation of dice without damaging the circuits, using a combination of laser scribing and plasma etching to singulate the wafers, eliminating the need for additional patterning steps and reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If scribing or sawing is used to dice wafers, then separation of dice is achieved, but chipping and cracking occur along severed edges and additional spacing is required between dice
Solution Approach 1:
The patent replaces mechanical scribing and sawing processes with plasma etching. The plasma process uses reactive ions to chemically remove material along the streets between dice, eliminating mechanical contact that causes chipping and cracking. This substitution of mechanical action with chemical/physical plasma action resolves the contradiction by achieving clean separation without damaging the dice edges.
Solution Approach 2:
The patent changes the fundamental parameter of the dicing process from mechanical force to plasma energy. By controlling plasma power, gas flow, and etch chemistry, the process achieves precise material removal without mechanical stress. This parameter change allows separation without the chipping and cracking inherent in mechanical methods, improving both separation quality and dice integrity.
2Reliability
If additional spacing is required between dice to prevent damage, then dice integrity is maintained, but wafer real estate is wasted and fewer dice can be formed
Solution Approach 1:
By replacing mechanical scribing/sawing with plasma etching, the patent eliminates the need for large safety margins between dice. The plasma process confines material removal precisely to the street regions through selective masking and directional ion bombardment, allowing dice to be placed closer together while maintaining integrity. This increases the number of dice per wafer.
Solution Approach 2:
The plasma etching process applies different conditions to different regions: masked regions protect dice while unmasked street regions undergo etching. This local differentiation allows tight spacing between dice while maintaining their integrity, as the plasma action is confined to intended separation zones without affecting adjacent dice structures.
3Reliability
If plasma dicing is implemented, then chipping and cracking are minimized, but costs increase due to additional patterning steps and production issues arise with metals like copper
Solution Approach 1:
The patent applies a pre-patterned mask before plasma etching, defining the streets to be etched in advance. This preliminary patterning step, when combined with plasma etching, eliminates the need for separate lithography and patterning steps that would otherwise be required. The mask is designed to align with the crystal orientation, enabling direct plasma dicing without additional complex processing.
Solution Approach 2:
The pre-patterned mask serves multiple functions: it defines the etch pattern, protects dice during plasma processing, and can be designed to account for crystal orientation requirements. This multi-functionality consolidates several process considerations into a single element, reducing overall process complexity despite the use of plasma technology.
4Manufacturing precision
If sawing is used with a thick blade, then separation is achieved, but three to five hundred microns must separate the circuitry and substantial cleaning is required
Solution Approach 1:
The patent replaces the mechanical saw blade with a plasma etching process. Plasma removes material through chemical reactions and physical sputtering, achieving separation without the need for a physical blade. This eliminates the kerf width constraint of saw blades (15 microns) and allows for much tighter spacing between dice, maximizing wafer real estate utilization.
Solution Approach 2:
By changing from mechanical cutting to plasma etching, the effective removal width can be precisely controlled through plasma power, gas flow, and exposure time parameters. This enables sub-micron precision in street width, allowing minimal spacing between dice while ensuring complete separation. The process also eliminates the need for substantial post-processing cleaning required by mechanical methods.
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 minimizes chipping and cracking, increases wafer efficiency by allowing closer spacing of dice, and reduces the costs associated with plasma dicing by eliminating the need for separate patterning steps, thereby enhancing the yield and reliability of the dicing process.
Implementation Method 1
The pre-patterned mask covers the integrated circuits and exposes streets between the integrated circuits. The pre-patterned mask protects the integrated circuits during the plasma etching.
Implementation Method 2
plasma etching the semiconductor wafer through the streets to singulate the integrated circuits
Implementation Method 3
laser scribing the streets to provide scribe lines between the integrated circuits
Data Source
AI summary
Approaches for protecting a wafer during plasma etching wafer dicing processes are described. In an example, a method of dicing a semiconductor wafer with a front surface having a plurality of integrated circuits thereon involves laminating a pre-patterned mask on the front surface of the semiconductor wafer. The pre-patterned mask covers the integrated circuits and exposes streets between the integrated circuits. The method also involves plasma etching the semiconductor wafer through the streets to singulate the integrated circuits. The pre-patterned mask protects the integrated circuits during the plasma etching.