Wafer Testing With Vacuum-Release Substrate for Warpage Control
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Solution Overview
Problem
Thin wafers with thicknesses less than 200 microns experience significant warpage due to differing thermal expansion rates of the wafer, coatings, and elements, making subsequent detection and testing procedures difficult.
Innovation Solution
A wafer testing method involving a vacuum-release substrate that attaches to the wafer with an air pressure-sensitive force, allowing for warpage detection and subsequent removal of the substrate to expose the wafer for testing, using a robotic arm and multiple stages to manage the wafer's orientation and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the wafer is ground to a thin thickness to meet product specifications, then the thickness requirement is satisfied, but warpage becomes more pronounced and detection becomes difficult
Solution Approach 1:
A support substrate is introduced as an intermediary component between the wafer and the detection/testing equipment. The wafer is bonded to this substrate to form a wafer assembly, which provides mechanical support and stabilizes the wafer's flatness during handling, detection, and testing processes, thereby enabling accurate measurement of thin wafers that would otherwise be too warped to detect
Solution Approach 2:
The wafer is preliminarily bonded to the support substrate before detection and testing procedures. This preliminary bonding action ensures the wafer maintains its flatness during subsequent operations, allowing detection to proceed accurately without the wafer warping during the measurement process
2Length of moving object
If the wafer is made thinner to meet specifications, then the thickness specification is met, but the wafer becomes more susceptible to warpage and damage
Solution Approach 1:
The support substrate acts as a mediator that compensates for the inherent instability of thin wafers. By bonding the thin wafer to the more rigid substrate, the assembly gains structural stability and reliability during handling, transport, and processing, while the wafer itself remains thin to meet product specifications
Solution Approach 2:
The wafer assembly functions as a composite structure combining the thin wafer with the support substrate. This composite construction leverages the substrate's mechanical properties to enhance the overall stability and reliability of the assembly, allowing the thin wafer to maintain its required thickness while gaining structural support
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
Enables accurate detection and testing of warped wafers by minimizing damage and maintaining wafer flatness during the detection and testing process, addressing the challenge of warpage in thin wafers.
Implementation Method 1
providing a negative pressure to the wafer assembly to eliminate the attaching force between the vacuum-release substrate and the wafer
Data Source
AI summary
A wafer testing method adapted to test a thin wafer. The thin wafer is combined with a vacuum-release substrate to form a wafer-assembly, and the wafer-assembly is placed in a wafer cassette. The vacuum-release substrate is attached to a front surface of the wafer with an attaching force which is sensitive to air pressure. The method includes the following steps. First, taking out the wafer-assembly from the wafer cassette, then transferring the wafer-assembly to a warpage-detection-device and placing the wafer-assembly on a first stage of the warpage-detection-device. Then, detecting warpage of the wafer. If the warpage of the wafer is less than a warpage threshold, the wafer-assembly is taken out from the first stage, and the wafer-assembly is turned over to place the wafer-assembly on a second stage. Then, applying negative pressure to the vacuum-release substrate to eliminate the attaching force. Then, removing the vacuum-release substrate.