Back-Illumination Inspection for Semiconductor Die Integrity
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Solution Overview
Problem
Current semiconductor packaging processes face challenges in reliably detecting and handling very thin semiconductor chips, leading to significant yield losses due to defects like broken, cracked, or chipped dies, especially during wafer preparation and die picking, which can result in the loss of entire packages during stacked die bonding.
Innovation Solution
A chip handling tool and process that utilize back-illumination imaging to inspect dies for damages by illuminating them from one side and analyzing light transmission, allowing for the identification of cracks and other defects before attachment, thereby ensuring only undamaged dies are placed on substrates or stacks, and enhancing the signal-to-noise ratio for improved crack detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface illumination inspection is used to detect die defects, then the inspection can be performed before picking, but the detection reliability is limited due to low crack contrast and interference from other patterns
Solution Approach 1:
The patent inverts the inspection approach by using backside illumination instead of surface illumination. Light is shone through the backside of the die, and cracks are detected as they block or scatter the transmitted light. This inversion provides much higher contrast for crack detection compared to surface illumination, directly resolving the technical contradiction between detection reliability and measurement difficulty.
Solution Approach 2:
The patent changes the illumination parameter from surface-based to transmission-based through backside lighting. This parameter change fundamentally alters how cracks are visualized, transforming them from low-contrast features to high-contrast obstacles against the light path, thereby improving both reliability and reducing detection difficulty.
2Ease of manufacture
If very thin wafers are processed without lamination, then manufacturing cost is reduced, but yield losses increase due to broken, cracked, or chipped dies during handling
Solution Approach 1:
The patent implements preliminary inspection of die integrity through backside illumination before the dies undergo handling processes. By detecting cracks and defects early in the process flow, the system prevents damaged dies from being further processed or attached, thereby maintaining high yield without requiring lamination for protection.
Solution Approach 2:
The inspection system provides feedback on die integrity status, enabling real-time identification and removal of defective dies. This feedback mechanism allows the manufacturing process to maintain high reliability without additional protective measures like lamination, thus keeping manufacturing costs low while preventing yield losses.
3Productivity
If a broken die is attached to a stack during stacked die bonding, then the attachment process is complete, but the entire package is lost requiring complete rework
Solution Approach 1:
The patent performs preliminary inspection of each die's integrity status before it is attached to a stack. By identifying and removing cracked or broken dies prior to attachment, the system ensures that only sound dies are bonded into packages, preventing catastrophic package loss while maintaining attachment process efficiency.
Solution Approach 2:
The backside illumination inspection system acts as an intermediary between die fabrication and die attachment processes. It provides a quality gate that filters out defective dies, ensuring that only inspected and approved dies proceed to stacking and bonding, thereby protecting package integrity without slowing down the overall attachment productivity.
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 significantly reduces yield losses by allowing for real-time inspection and identification of damaged dies, maximizing the success rate of crack detection, and ensuring accurate alignment and integrity of chip patterns, thereby preventing the attachment of broken dies and maintaining package integrity.
Implementation Method 1
A chip handling tool (10) and a process for handling a chip (5), in particular a semiconductor die, utilize back-illumination imaging to inspect dies for damages by illuminating them from one side and analyzing light transmission
Implementation Method 2
generating a back-illumination image of the die - also referred to as an absorption image - in which cracks, missing parts, patterns, etc. are identified as areas of substantial change of the light intensity transmitter through the die
Data Source
Figure 1
Figure 2a)~2d)
Figure 3
AI summary
The invention pertains to the field of automation technology and relates to an apparatus and a method for handling chips, in particular semiconductor dies. A chip handling tool is configured to receive a chip, in particular a semiconductor die, at a takeover location and to hand over said chip to a delivery location, and comprises a work surface configured to be brought into connection with a first surface on a first side of the chip. The chip handling tool further comprises illumination means for illuminating the chip from its first side while said first side of the chip is in connection with the work surface. A chip handling process is also presented.