Semiconductor Die Singulation via Trench Etching and Thinning
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Solution Overview
Problem
Current semiconductor die singulation methods, particularly sawing, lead to defects like chipouts and cracking, which increase as die thickness decreases, and alternative methods like laser singulation do not produce die with equivalent strength to sawn die due to reformation of molten silicon side walls into a non-single crystal structure.
Innovation Solution
The method involves etching trenches around the perimeter of semiconductor wafers using a Bosch deep reactive ion etch process, followed by thinning and exposing these trenches to singulate the die, allowing for effective separation without the need for full-thickness cutting, thereby reducing defects and maintaining die strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sawing is used for singulation, then die can be separated from the wafer, but defects like chipouts and cracking increase as die thickness decreases
Solution Approach 1:
The patent divides the singulation process into two stages: first creating deep trenches that remove the majority of material connecting adjacent die, then completing the separation through thinning or additional etching. This segmentation allows most cutting to occur when die are thicker and stronger, while final separation happens when die are thinner but already partially isolated, reducing stress and defect formation
Solution Approach 2:
The patent performs preliminary trench etching before final thinning or completion of singulation. By removing the bulk of the connecting material in advance while die are still at full thickness, the structure is pre-weakened in a controlled manner, making the final separation easier and less prone to causing chipouts or cracking
2Ease of operation
If laser singulation is used, then die can be separated without mechanical contact, but the molten silicon side walls reform into a non-single crystal structure reducing die strength
Solution Approach 1:
The patent replaces mechanical sawing with a chemical etching process (Bosch deep reactive ion etch) that uses plasma and chemical reactions to remove material. This substitution eliminates mechanical contact and associated defects like chipouts, while the controlled etching process avoids the molten silicon reformation problem of laser singulation, preserving the single crystal structure
Solution Approach 2:
The patent changes the physical state and removal mechanism from mechanical cutting or laser melting to chemical vapor deposition-based etching. The Bosch process uses alternating etching and deposition cycles in a plasma environment, allowing precise material removal without melting, thereby maintaining the crystalline structure of the silicon
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 reduces defects such as chipouts and cracking, maintaining the strength of the die and enabling reliable semiconductor packaging by avoiding the reformation of non-single crystal structures during singulation.
Implementation Method 1
etching a plurality of trenches into the semiconductor wafer from the first side of the semiconductor wafer... using a Bosch deep reactive ion etch process
Data Source
AI summary
Methods of singulating semiconductor die. Specific implementations may include: providing a semiconductor wafer including a plurality of die located on a first side of the semiconductor wafer where the plurality of die include a desired thickness. The method may include etching a plurality of trenches into the semiconductor wafer from the first side of the semiconductor wafer where the plurality of trenches is located adjacent to a perimeter of the plurality of die. A depth of the plurality of trenches may be greater than the desired thickness of the plurality of die. The method may also include mounting the first side of the semiconductor wafer to a tape, thinning a second side of the semiconductor wafer, exposing the plurality of trenches while thinning the second side, and singulating the plurality of die through exposing the plurality of trenches.