Continuous Wafer Imaging With TDI Scanning for Height Variations
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Solution Overview
Problem
Traditional wafer inspection tools struggle to properly inspect populated wafers with chiplets due to height variations and misalignment, leading to reduced throughput and accuracy in defect detection.
Innovation Solution
The use of a time delay integrated (TDI) linear sensor combined with multiple optical assemblies and a motion assembly allows for fast, continuous inspection scanning, addressing height variations and misalignment by focusing on segments of the TDI linear sensor and adjusting the Z-profile of the surface under examination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional wafer inspection tools are used to inspect populated wafers with chiplets, then the inspection process can detect particles and defects on uniform surfaces, but the tools cannot properly inspect surfaces with height variations between wafer and chiplet surfaces
Solution Approach 1:
The patent employs a tunable lens that can dynamically adjust its focal length to accommodate different height levels on the wafer surface. This dynamic focusing capability allows the inspection system to switch between inspecting the wafer surface and chiplet surfaces without physical repositioning, resolving the contradiction between measurement precision and adaptability to height variations
Solution Approach 2:
The system changes optical parameters by adjusting the focal length of the tunable lens based on the detected height profile. By modifying the optical focal parameter in response to surface topography, the system maintains accurate defect detection across surfaces with varying heights, bridging the gap between precision measurement and surface adaptability
2Measurement precision
If traditional step and repeat acquisition type inspection processes are used, then inspection data can be obtained, but the throughput of the inspection process is substantially impacted
Solution Approach 1:
The patent implements continuous scanning inspection that moves the wafer continuously through the inspection field while the tunable lens and illumination system track and inspect features in real-time. This continuous action eliminates the stop-and-go nature of step-and-repeat methods, maintaining inspection accuracy while dramatically improving throughput
Solution Approach 2:
The system performs preliminary height mapping using the tunable lens to identify surface topography before the main inspection scan. This preliminary action allows the system to pre-adjust focal settings and anticipate height changes, enabling continuous high-speed inspection without sacrificing measurement precision
3Adaptability or versatility
If chiplets are bonded to the wafer surface, then the wafer becomes populated with functional components, but the substantially different heights between wafer surface and chiplet surfaces make inspection difficult
Solution Approach 1:
The tunable lens dynamically adjusts its focal length in response to the height differences between wafer and chiplet surfaces. This dynamic focusing maintains sharp image capture across the varied topography, enabling the system to adapt to bonded wafer configurations while preserving defect detection accuracy
Solution Approach 2:
The tunable lens acts as an intermediary optical element that mediates between the varied height levels of wafer and chiplet surfaces. By adjusting its focal properties, it creates a unified focal plane that captures both surfaces accurately, resolving the inspection difficulty caused by height variations
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 solution enables rapid and accurate inspection of wafers and chiplets, improving throughput and defect detection capabilities, particularly in hybrid bonding processes where height variations and misalignment are significant challenges.
Implementation Method 1
at least one time delay integrated (TDI) linear sensor that has a TDI linear sensor length
Implementation Method 2
each of the plurality of optical assemblies is positioned with an optical output focused on a segment of the TDI linear sensor length
Implementation Method 3
an integrated Z-profiler with a laser-based auto-focus module configured to determine a Z-profile of the surface under examination
Data Source
AI summary
A scanning inspection apparatus detects anomalies on surfaces of objects such as substrates, substrates with bonded chiplets, and carriers with singulated chiplets and the like. In some embodiments, the inspection apparatus includes a time delay integrated (TDI) linear sensor with an optical input and a data output where more than one optical assembly is positioned adjacent to each other with an optical output focused on a different segment of the TDI linear sensor and with an optical input positioned to receive a portion of a surface under examination. The apparatus may further include a platform with an upper surface for supporting an object with the surface under examination and with a motion assembly to move the platform and with a controller in communication with the motion assembly to move the platform in relation to the optical input of the optical assembly.