Time-Resolved Reflectivity Metrology for Buried Structures
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Solution Overview
Problem
Conventional microscopy techniques face challenges in aligning and overlaying layers during semiconductor processing, especially when optically opaque materials are present, as they require additional patterning operations and cannot detect buried structures like voids or inclusions effectively, limiting their accuracy and increasing process costs.
Innovation Solution
A time-resolved reflectivity metrology device using a pulsed pump beam and a pulsed probe beam with modulated pulses, captured by a multi-pixel array camera with independent phase locking, allows for non-destructive imaging of underlying structures by recording changes in reflectivity or surface deformation as a function of time delay, enabling characterization of alignment, overlay, and detection of buried structures without the need for scanning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical imaging techniques are used to image underlying structures, then alignment and overlay measurements can be performed, but optically opaque layers block the light and prevent detection of buried structures
Solution Approach 1:
The patent replaces optical detection methods with acoustic detection methods. Instead of using light to image underlying structures, the system uses picosecond laser pulses to generate acoustic waves that propagate through the sample and are detected by acoustic transducers. This acoustic approach allows detection of buried structures through opaque layers that would block optical methods.
Solution Approach 2:
The patent changes the detection parameter from optical reflectivity to acoustic signal transmission. By using picosecond laser pulses to generate acoustic waves and detecting their transmission through the sample, the system can penetrate optically opaque layers and image underlying structures that were previously inaccessible to optical methods.
2Measurement precision
If scanning microscopy techniques are used to detect underlying structures, then detailed imaging can be achieved, but the imaging time increases from seconds to minutes or hours
Solution Approach 1:
The patent performs preliminary action by generating acoustic waves that propagate through the entire sample volume simultaneously. Instead of scanning point-by-point, the picosecond laser pulses create acoustic waves that travel through the sample and are detected across the entire field of view at once, enabling parallel acquisition of transient signals from all pixels.
Solution Approach 2:
The patent adds a time dimension to the imaging process by using time-resolved acoustic detection. The picosecond laser pulses generate acoustic waves that propagate through the sample, and by detecting the acoustic signals at different time delays, the system can image structures at different depths, enabling three-dimensional imaging without mechanical scanning.
3Manufacturing precision
If conventional microscopy is used for alignment and overlay control, then layer alignment can be measured, but additional patterning operations are required which increase process cost
Solution Approach 1:
The patent creates a universal measurement technique that can detect both desired structures (for alignment and overlay measurements) and undesired structures (such as voids and inclusions) using the same acoustic detection system. This eliminates the need for separate measurement operations and additional patterning steps that would be required with conventional optical methods.
Solution Approach 2:
The patent uses acoustic waves as an intermediary to transfer information from buried structures to the detector. The picosecond laser pulses generate acoustic waves that propagate through the sample, carrying information about both the desired alignment structures and undesired voids or inclusions, allowing simultaneous measurement of multiple parameters without additional patterning.
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 significantly reduces imaging time from minutes or hours to seconds, enabling high-volume manufacturing capabilities and accurate detection of structures beneath opaque layers, including small voids, without the need for optical penetration, thus improving alignment and overlay precision and reducing process costs.
Implementation Method 1
irradiate the sample with a pump beam having at least one pump pulse to cause transient perturbation in material in the sample
Implementation Method 2
cause transient perturbation in material in the sample
Implementation Method 3
irradiate the sample with a probe beam having at least one probe pulse to produce a reflected probe beam that is modulated based on the transient perturbation in the material in the sample
Implementation Method 4
produce a reflected probe beam that is modulated based on the transient perturbation
Implementation Method 5
The camera is configured for parallel acquisition of transient signals from the images of the sample using a multi-pixel array and independent phase locking for each pixel in the multi-pixel array
Implementation Method 6
receive and demodulate the reflected probe beam to generate images
Data Source
AI summary
A time resolved reflectivity metrology device images structures underlying layers using a pulsed pump beam and pulsed probe beam with at least one time delay between the pulses. One or both beams are modulated. A camera with a multi-pixel array and independent phase locking for each pixel in the multi-pixel array receives and demodulates the reflected probe beam to generate images. The camera may record a change in reflectivity or surface deformation of the target sample at every pixel as a function of at least one time delay between the pump pulses and the probe pulses, with which at least one property of the target sample may be characterized.