Kelvin Test Structure for 3DIC Bond Connection Detection
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Solution Overview
Problem
Current 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 top chips and interposers, which allow for the measurement of resistance to determine the sufficiency of electrical connections and detect potential warping or fracturing during the bonding process by applying a voltage and measuring current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional connection testing methods are used in 3DICs, then the testing process is simple, but the reliability of detecting sufficient electrical connections and potential damage is inadequate
Solution Approach 1:
The test structure is segmented into four distinct testing sites (first, second, third, and fourth sites) arranged in a Kelvin configuration. This segmentation allows separate current injection and voltage measurement paths, enabling reliable resistance measurement of interposer connections without measuring lead resistance, thus resolving the contradiction between detection reliability and device complexity.
Solution Approach 2:
The Kelvin test structure acts as an intermediary testing mechanism that indirectly assesses the quality of solder bump connections and interposer integrity. By measuring resistance through the Kelvin structure, the system can detect potential warping or fracturing during bonding without directly interfering with the bonding process, thereby improving detection reliability while maintaining manageable device complexity.
2Productivity
If bonding force is applied without prior detection, then the bonding process is fast, but the risk of causing warping or fracturing increases
Solution Approach 1:
The Kelvin test structure is formed and configured before the bonding process begins. This preliminary setup allows for pre-bonding resistance measurements to be taken, establishing a baseline for connection quality. By performing this detection action before applying bonding force, the system can identify potential issues early, enabling faster bonding processes while reducing the risk of warping or fracturing through early detection and process adjustment.
Solution Approach 2:
The test structure provides real-time feedback on the quality of electrical connections through resistance measurements. During and after the bonding process, changes in resistance values indicate potential warping or fracturing of the interposer. This feedback mechanism allows the bonding process to be monitored and adjusted, ensuring productivity while minimizing harmful effects like warping and fracturing.
3Measurement precision
If resistance measurement is performed to detect connection quality, then the electrical connection sufficiency is accurately determined, but the measurement process becomes more complex
Solution Approach 1:
The Kelvin test structure merges the testing function directly into the interposer structure itself. The four testing sites are integrated into the interposer, and the conductive paths are formed as part of the interposer fabrication process. This merging eliminates the need for separate external testing equipment and complex measurement setups, achieving accurate resistance measurement while keeping the overall system complexity manageable.
Solution Approach 2:
The Kelvin test structure serves multiple functions: it tests the electrical connection quality of solder bumps, monitors interposer integrity during bonding, and provides baseline measurements for comparison. This multi-functionality allows a single structure to perform various measurement tasks with high precision, reducing the need for multiple separate testing systems and thereby managing device complexity while maintaining measurement accuracy.
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 sufficient electrical connections and potential damage, preventing unnecessary force application during bonding, thus reducing the risk of short circuits and ensuring the integrity of the 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.
Implementation Method 2
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 a chip including a conductive line which traces a perimeter of the chip. The circuit test structure further includes an interposer electrically connected to the chip, wherein the conductive line is over both the chip and the interposer. The circuit test structure further includes a test structure connected to the conductive line. The circuit test structure further includes a testing site, wherein the test structure is configured to electrically connect the testing site to the conductive line.