Semiconductor Die Singulation via Plasma Etching and Thinning
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Solution Overview
Problem
Current semiconductor die singulation methods, such as sawing, lead to defects like chipouts and cracking, especially as die thickness decreases, and alternative methods like laser singulation do not produce die with equivalent strength to sawn die due to reformation of silicon side walls into a non-single crystal structure.
Innovation Solution
The method involves etching trenches into the semiconductor wafer from one side using plasma etching, with a depth greater than the die thickness, and then thinning the opposite side to expose the trenches, allowing for singulation without the need for full-thickness cutting, which can help prevent defects and maintain die strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sawing is used to singulate semiconductor die, then the die can be separated from the wafer, but chipouts and cracking occur especially as die thickness decreases
Solution Approach 1:
The singulation process is divided into two distinct stages: first, etching trenches through the full wafer thickness to create separation channels, and second, thinning the wafer to the desired die thickness. This segmentation allows the cutting and thinning operations to be performed separately, preventing the mechanical stress that causes chipouts and cracking during traditional single-pass sawing.
Solution Approach 2:
The trenches are etched through the full wafer thickness before the thinning process begins. This preliminary action creates pre-defined separation paths that guide the subsequent thinning operation, ensuring that the die separate cleanly without generating the mechanical stresses that lead to defects during cutting.
2Ease of manufacture
If laser singulation is used, then the process is simpler, but the die strength is reduced due to reformation of silicon side walls into a non-single crystal structure
Solution Approach 1:
The patent replaces the mechanical sawing process with a combination of plasma etching (chemical process) and controlled thinning. This substitution eliminates the mechanical contact that causes chipouts and cracking, while the etched trenches provide clean separation paths that maintain the single-crystal structure of the silicon side walls.
3Manufacturing precision
If traditional sawing is used, then full-thickness cutting is achieved, but the process is capital-intensive and less manufacturable
Solution Approach 1:
The patent replaces capital-intensive mechanical sawing equipment with plasma etching and controlled thinning processes. The etching process uses chemical reactions to remove material, eliminating the need for expensive saw blades and mechanical cutting systems, while achieving precise trench formation and clean die separation.
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 effectively prevents chipouts and cracking, maintaining die strength and allowing for efficient visual inspection and processing of thinned die, while being less capital-intensive and more manufacturable than traditional methods.
Implementation Method 1
Etching the plurality of trenches may include plasma etching
Implementation Method 2
The semiconductor wafer may include silicon and etching the plurality of trenches may further include using a deep reactive ion etch (DRIE) process
Data Source
AI summary
Implementations of a method of singulating a plurality of die may include: providing a semiconductor wafer including a plurality of die where the plurality of die include a desired thickness. A passivation material may cover at least a portion of the plurality of die and the semiconductor wafer. The method may include clearing the passivation material from one or more die streets located between each of the plurality of die. The method may also include etching a plurality of trenches into the semiconductor wafer only from the first side of the semiconductor wafer. A depth of the plurality of trenches may be greater than the desired thickness of the plurality of die. The method may also include thinning a second side of the semiconductor wafer to a predetermined distance to the depth of the plurality of trenches to singulate the plurality of die.