Interconnect Surface Inspection Using Elongated Fluorescence Excitation
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Solution Overview
Problem
Existing methods for inspecting redistribution layers in integrated circuits face challenges due to the blocking of excitation light by the uppermost metal layer, leading to weakened fluorescence signals from dielectric layers and inaccurate determination of metal and dielectric layer distributions, especially with decreasing line widths and large field-of-view scans.
Innovation Solution
Adjusting the excitation light beam to form an elongated light spot with a long axis perpendicular to its direction of incidence on the interconnect structure surface, allowing uniform illumination of the dielectric layer and enhancing fluorescence signal reception, thereby facilitating accurate determination of the metal layer planar pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional illumination methods are used to inspect dielectric layers, then the inspection process is simple, but the metal layer blocks excitation light causing weakened fluorescence signals and inaccurate determination of layer distribution
Solution Approach 1:
The patent applies asymmetry by forming an elongated light spot where the long axis is perpendicular to the direction of light incidence. This asymmetric configuration allows excitation light to enter the dielectric layer from the side, bypassing the blocking effect of the overlying metal layer while still achieving uniform excitation of the dielectric material for accurate fluorescence-based inspection
Solution Approach 2:
The patent changes the illumination geometry from conventional normal incidence to oblique incidence with a specific angular relationship. By making the long axis of the elongated light spot perpendicular to the direction of incidence, the excitation light penetrates the dielectric layer from a different spatial dimension, avoiding the blocking path of the metal layer
2Productivity
If line widths are decreased to increase circuit density, then more components can be integrated, but fluorescence signal intensity decreases making inspection more difficult
Solution Approach 1:
The patent applies local quality by creating a highly localized and intense elongated light spot that concentrates excitation energy precisely where needed in the dielectric layer. This localized intense illumination compensates for the reduced fluorescence signal from narrower metal lines, enabling accurate inspection of high-density interconnect structures
Solution Approach 2:
The asymmetric elongated light spot configuration with the long axis perpendicular to the incidence direction creates a concentrated excitation region that enhances fluorescence signal collection efficiency, thereby maintaining measurement precision even when metal line widths are reduced for higher integration density
3Area of stationary object
If large field-of-view scans are used to cover entire interconnect structures, then complete inspection is achieved, but signal uniformity across the scan area deteriorates
Solution Approach 1:
The patent segments the illumination into a controlled elongated light spot that can be systematically scanned across the interconnect structure. By maintaining the specific geometric relationship where the long axis is perpendicular to the incidence direction throughout the scan, uniform excitation conditions are preserved across the entire field of view, ensuring consistent fluorescence signal quality throughout the large inspection area
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
The method ensures uniform excitation light distribution, reducing blockage by metal layers and improving the accuracy of determining the planar pattern of metal layers in interconnect structures, even with narrow line widths and large field-of-view scans.
Implementation Method 1
receiving a plurality of fluorescent signals generated from the dielectric layer upon excitation thereof by the elongated light spot
Data Source
AI summary
A method and device of inspecting a surface of an interconnect structure are provided. The interconnect structure includes a metal layer and a dielectric layer having fluorescence characteristics. The method includes: generating an excitation light beam from an excitation light source; adjusting the excitation light beam to cause the excitation light beam to form an elongated light spot having a long axis and a short axis on a surface of the interconnect structure, and cause the excitation light beams for forming the elongated light spot to be incident on the surface of the interconnect structure along a direction perpendicular to the long axis of the elongated light spot; receiving a plurality of fluorescent signals generated from the dielectric layer upon excitation thereof by the elongated light spot; and determining a portion of a planar pattern of the metal layer according to the fluorescence signals.