Multilayer Semiconductor Fault Detection Using Laser Thermal Stimulation
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Solution Overview
Problem
Conventional methods for detecting faults in deep layers of multilayer semiconductors face challenges such as heat diffusion, reduced precision due to lateral and vertical heat spread, and spatial shifts between the hottest location and the irradiated zone, making it difficult to accurately locate and measure faults in deep layers.
Innovation Solution
A noninvasive thermal-stimulation apparatus and method using a laser beam to selectively heat preselected target regions in multilayer semiconductors, with an optical system to direct the beam and a computer system to control and amplify thermally induced electrical signal changes, allowing for precise alignment and detection of fault locations and depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional OBIRCH technique is used to detect faults in deep layers, then the detection can be performed nondestructively, but the measurement precision deteriorates due to heat diffusion and spatial shifts
Solution Approach 1:
The patent applies parameter changes by modifying the laser heating parameters (pulse width, intensity, and timing) to achieve transient thermal stimulation that minimizes heat diffusion effects. By controlling the thermal parameters in the time domain, the system can detect faults in deep layers with improved spatial precision while maintaining nondestructive operation.
Solution Approach 2:
The patent employs periodic laser pulsing to create time-resolved thermal stimulation. By applying periodic heating and measuring the response at specific time intervals, the system can distinguish between heat generated at the irradiation point versus heat that has diffused to adjacent areas, thereby improving fault location precision while maintaining nondestructive detection.
2Difficulty of detecting and measuring
If laser beam is used to heat deep layers, then fault detection in deep layers becomes possible, but heat diffusion causes spatial shift between hottest location and irradiated zone
Solution Approach 1:
The patent introduces a reference measurement system that acts as an intermediary to map the relationship between laser irradiation position and actual hottest location. By measuring the thermal response at multiple positions and creating a calibration model, the system can compensate for spatial shifts caused by heat diffusion and accurately locate faults in deep layers.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the thermal response and adjusting the laser irradiation position based on the measured temperature distribution. This feedback mechanism compensates for spatial shifts caused by heat diffusion, ensuring that the hottest location aligns with the intended target region for accurate fault detection.
3Productivity
If multilayer stacking is increased to improve transistor density, then IC performance increases, but fault detection complexity increases due to multiple layers
Solution Approach 1:
The patent applies segmentation by dividing the multilayer semiconductor into individual layer sections and detecting faults layer-by-layer using time-resolved thermal measurement. By analyzing the temporal characteristics of heat diffusion, the system can identify which specific layer contains a fault, thereby reducing detection complexity despite the increased number of layers.
Solution Approach 2:
The patent adds the time dimension to the fault detection process by measuring thermal response as a function of time after laser irradiation. This time-resolved measurement approach allows the system to distinguish between faults in different layers based on their different thermal diffusion time constants, effectively converting a complex spatial problem into a more manageable temporal analysis.
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
Improves the accuracy and sensitivity of fault detection in deep layers, enabling more precise manufacturing processes and potentially increasing the number of layers in semiconductor devices, thus enhancing their functionality and performance.
Implementation Method 1
determining a location and a depth of the fault in the MLS by irradiating the shallow layers of the MLS with a laser beam to heat a preselected target region
Implementation Method 2
the infrared light is usually absorbed in the shallow transistor layers (or first layer for a single-laver semiconductor)
Implementation Method 3
measures the electrical resistance change caused by an increase of temperature; the laser-induced electrical resistance changes are significantly different for faulty locations than for functional locations
Implementation Method 4
the accumulated heat in these shallow layers is transported to the deep layer by heat conduction
Data Source
AI summary
An apparatus according to embodiments detects locations of faults in a multilayer semiconductor (MLS). The apparatus comprises a laser source that outputs a laser beam, an optical system that directs the laser beam selectively onto a target region in the MLS to generate an irradiated zone in the MLS, a stage and a scanner that control a relative position between the irradiated zone and the MLS so that the irradiated zone moves along the target region, a controller system that measures electrical signals or electrical signal changes induced by a temperature increase in the MLS, and identifies a location of the target region and locations of faults in the MLS based on the measured electrical signal or the measured electrical signal changes. The target region is made of a material of which thermal conductivity is higher than that of a material around the target region and has a structure penetrating from shallow layers to deep layers of the MLS.