Wafer-to-Wafer Bonding Connectivity Detection for Misalignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor memory devices, wafer-to-wafer bonding for aligning memory arrays with control circuits is challenging due to the difficulty in detecting misalignment, which can lead to poor electrical connectivity and increased scrap rates during the bonding process.
Innovation Solution
The implementation of connectivity detection circuits, both on-chip and off-chip, using test pads and conductive paths to rapidly identify misalignment by measuring electrical connectivity between corresponding pads on memory and control circuit wafers, allowing for corrective actions during the bonding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wafer-to-wafer bonding is performed without connectivity detection, then the bonding process can proceed quickly, but misalignment cannot be detected leading to poor electrical connectivity and increased scrap rates
Solution Approach 1:
The patent applies preliminary action by performing connectivity detection before final bonding completion. Test pads are bonded first, then electrical connectivity is measured to detect misalignment before the entire wafer bonding process is finalized. This allows early detection and correction of alignment issues without completing the full bonding process on misaligned wafers.
Solution Approach 2:
The patent uses test pads as an intermediary element to detect alignment issues. These dedicated test pads are separately bonded and measured for electrical connectivity, serving as a proxy indicator for overall alignment quality without requiring measurement of all bonding interfaces.
2Measurement precision
If connectivity detection is performed after bonding, then alignment issues can be identified, but testing time is increased and scrap rates rise due to delayed detection
Solution Approach 1:
The patent performs connectivity detection as a preliminary step during the bonding process itself, rather than as a post-bonding inspection. By measuring electrical connectivity through test pads while the bonding is still in progress, the system enables early detection of misalignment before final bonding completion, reducing both testing time and scrap rates.
Solution Approach 2:
The patent allows the bonding process to proceed rapidly through the initial stages, then performs quick connectivity measurement on test pads to identify misalignment. This selective rushing through of non-critical bonding steps followed by rapid detection enables time-efficient misalignment identification without compromising measurement precision.
3Ease of manufacture
If misalignment is not detected during bonding, then the bonding process remains simple, but the number of scrapped dies increases due to poor electrical connectivity
Solution Approach 1:
The patent introduces test pads as intermediary elements that simplify the overall manufacturing process by providing a dedicated, simple mechanism for detecting misalignment. These test pads require minimal additional structure or complexity but enable effective detection of bonding quality, thereby reducing scrap rates without significantly complicating the manufacturing process.
Solution Approach 2:
The bonding process performs self-diagnosis through electrical connectivity measurement on test pads. The system uses its own electrical properties to detect alignment issues, eliminating the need for external complex inspection equipment or procedures. This self-service approach maintains manufacturing simplicity while effectively reducing scrap through automated detection.
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 rapid detection and correction of misalignment, reducing the number of scrapped dies and saving testing time by providing immediate feedback on alignment issues, thus improving the efficiency of the bonding process.
Implementation Method 1
detecting electrical conductivity between test pads to detect misalignment of the memory array with the control circuits
Data Source
AI summary
A first workpiece includes first active pads, a first test pad, and a second test pad on a primary surface of the first workpiece, the first test pad electrically connected to the second test pad. A second workpiece includes second active pads, a third test pad, and a fourth test pad on a primary surface of the second workpiece. The first and second workpieces are bonded along an interface between the primary surface of the first workpiece and the primary surface of the second workpiece to bond the first active pads with the second active pads, bond the first test pad with the third test pad, and bond the second test pad with the fourth test pad. Connectivity detection circuits test electrical connectivity between the third test pad and the fourth test pad.