Kelvin Test Structure for 3DIC Bond Connection Integrity
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Solution Overview
Problem
Existing methods for testing the quality of connections in three-dimensional integrated circuits (3DICs) between top chips and passive interposers, and between interposers and substrates, are inadequate in ensuring reliable electrical connections and detecting potential damage during the bonding process.
Innovation Solution
The implementation of Kelvin structures with conductive lines and testing sites on both the top chip and interposer, allowing for the measurement of resistance to determine the integrity of connections and detect warping or fracturing during the bonding process, thereby ensuring sufficient electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional testing methods are used to test connection quality in 3DICs, then the testing process is simple, but the measurement precision and reliability of connection quality assessment are insufficient
Solution Approach 1:
The testing structure is segmented into four distinct testing sites (first, second, third, and fourth testing sites) arranged in a Kelvin configuration. This segmentation allows separate current injection and voltage measurement paths, enabling precise resistance measurement of solder bumps while eliminating lead resistance interference. The segmentation of testing functions into distinct sites directly resolves the contradiction by providing high measurement precision through structural division.
Solution Approach 2:
The Kelvin structure introduces intermediate testing sites that act as mediators between the solder bumps and the measurement system. The first and second testing sites serve as current injection points, while the third and fourth testing sites serve as voltage measurement points. These intermediary sites enable accurate measurement of connection quality without being affected by external factors, thus improving measurement precision while maintaining manageable device complexity.
2Reliability
If bonding force is increased to ensure connection quality, then the electrical connectivity is improved, but the risk of warping or fracturing during bonding increases
Solution Approach 1:
The Kelvin testing structure is formed preliminarily on both the top chip and the interposer before the bonding process. This preliminary configuration of testing sites and conductive lines allows for real-time monitoring of connection quality during bonding. By having the testing infrastructure in place beforehand, the system can detect connection issues early and adjust bonding parameters to prevent warping or fracturing, thus ensuring reliability without compromising structural integrity.
Solution Approach 2:
The testing structure provides real-time feedback on connection quality during the bonding process by measuring resistance between testing sites. This feedback mechanism allows dynamic adjustment of bonding force and parameters to achieve reliable electrical connectivity while preventing excessive force that could cause warping or fracturing. The feedback loop ensures both reliability and structural integrity are maintained throughout the bonding process.
3Reliability
If real-time detection of connection quality is implemented, then the reliability of electrical connections is ensured, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The testing structure is merged with the existing chip and interposer fabrication processes. The Kelvin testing sites and conductive lines are integrated into the standard manufacturing flow, forming testing structures during normal production rather than as separate post-processing steps. This merging approach enables real-time connection quality detection while minimizing additional manufacturing complexity, as the testing infrastructure is created using the same process steps used for the functional components.
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 enables reliable detection of electrical connectivity and potential damage, preventing unnecessary force application during bonding, which reduces the risk of short circuits and ensures the quality of connections between top chips and interposers in 3DICs.
Implementation Method 1
By passing a voltage through two of the testing sites of the Kelvin structure and measuring a resulting current in the other two testing sites of the Kelvin structure, a resistance value of the micro solder bumps and/or the solder bumps between the passive interposer and the substrate can be determined.
Data Source
AI summary
A circuit test structure includes an interposer for electrically connecting to a chip, wherein the interposer includes a conductive line, and the conductive line extends along at least two side of the interposer. The circuit test structure further includes a plurality of electrical connections to the conductive line. The circuit test structure further includes a testing site electrically connected to the conductive line, wherein the testing site is on an opposite surface of the interposer from the plurality of electrical connections.