Fiber-Based Optical Alignment for Semiconductor Wafer Pads
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Solution Overview
Problem
The decreasing size of conductive pads on semiconductor wafers makes conventional probe card alignment difficult and time-consuming, necessitating a more efficient and cost-effective alignment method for integrated circuit testing.
Innovation Solution
A fiber-based optical alignment system using a bundle of optical fibers with a known spatial relationship, where at least one fiber delivers illumination to the alignment target and multiple receiver fibers detect reflected light to determine alignment, ensuring an unobstructed optical path between the wafer and the fibers, and coupling with a light source and sensor for precise alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional probe card alignment methods are used, then alignment can be achieved, but the process becomes difficult and time-consuming due to decreasing pad dimensions
Solution Approach 1:
The patent replaces conventional mechanical probe card alignment methods with an optical fiber-based alignment system. The system uses optical fibers to deliver light to alignment targets on the wafer and receive reflected light, enabling non-contact, high-precision alignment that is not limited by mechanical constraints and is faster than traditional methods
Solution Approach 2:
The patent introduces optical fibers as intermediary elements between the light source and the alignment targets on the wafer. The fibers act as mediators that transmit light to illuminate the targets and carry reflected light back to detectors, enabling precise alignment measurements without direct mechanical contact
2Measurement precision
If conventional alignment methods are used, then alignment can be achieved, but the complexity and cost of the system increases
Solution Approach 1:
The patent creates a multi-functional alignment system where optical fibers serve multiple purposes: delivering illumination light to targets, receiving reflected light for detection, and providing a known spatial relationship for coordinate transformation. This universal use of optical fibers simplifies the overall system architecture compared to dedicated separate systems for each function
Solution Approach 2:
The patent uses optical fibers to create optical copies or images of the alignment targets on the wafer. By projecting light through the fibers onto the targets and detecting the reflected light, the system creates optical representations that can be measured and used for alignment without requiring direct physical measurement of the tiny pad features
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 method allows for efficient and accurate alignment of semiconductor wafers by ensuring that the optical fiber bundle is centered over the pads, enabling reliable electrical contact and reducing the complexity and cost of the alignment process.
Implementation Method 1
a bundle of optical fibers wherein at least one fiber serves to deliver illumination to the alignment target from an end thereof
Implementation Method 2
a plurality of receiver fibers, each having ends with a known spatial relationship to the end of the illuminator fiber
Data Source
AI summary
A low-cost alignment system suitable for aligning a wafer to a test fixture includes a bundle of optical fibers wherein at least one fiber serves to deliver illumination to the alignment target from an end thereof, and a plurality of receiver fibers, each having ends with a known spatial relationship to the end of the illuminator fiber. The ends of the fiber bundle have a known spatial relationship to the fixture. In some embodiments, the fiber bundle is disposed within the fixture such that there is an unobscured optical path between the wafer and the receiving and illuminating ends of the fibers. In some embodiments, the fiber bundle is coupled to a light source and a light sensor mounted on the fixture. In some embodiments the alignment target is one or more bonding pads disposed on a wafer.