Adaptive Camera System for VLSI Photon Emission Testing
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Solution Overview
Problem
Backside Photon Emission Microscopy (PEM) for VLSI devices faces challenges in achieving a high signal-to-noise ratio (SNR) due to faint 'Hot Carrier' (HC) emissions and significant thermal noise, especially at longer wavelengths, leading to long exposure times and limited observation range.
Innovation Solution
An adaptive camera system that selects an optimal wavelength by inserting a shortpass filter in the optical path, optimizing SNR and resolution by characterizing the signal-to-noise ratio across the observation spectrum and using multiple swappable objective lenses and cold apertures to minimize thermal noise, allowing investigation of HC emissions up to 3 um.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If observation wavelength is extended beyond 1.55 um to capture more HC emissions, then the observation range is improved, but thermal noise increases significantly
Solution Approach 1:
A cold aperture is introduced as an intermediary component in the optical path between the objective lens and detector. This cold aperture acts as a mediator that blocks thermal radiation from reaching the detector while allowing HC photons to pass through, thereby separating the useful signal from harmful thermal noise
Solution Approach 2:
The system changes the temperature parameter of the aperture (cooling it to cryogenic temperatures) to alter its thermal emission characteristics. By lowering the aperture temperature, its thermal radiation is suppressed, enabling observation at longer wavelengths where thermal noise would otherwise dominate
2Measurement precision
If exposure time is increased to improve SNR for faint HC emissions, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The cold aperture serves as a mediator that selectively blocks thermal noise while transmitting HC photons, thereby improving the SNR without requiring longer exposure times. This allows for faster acquisition of high-quality images
Solution Approach 2:
The harmful thermal noise is extracted and blocked by the cold aperture from reaching the detector, isolating the useful HC photon signal. This extraction of noise enables faster detection with improved SNR
3Device complexity
If passive designs are used to mitigate thermal noise, then device complexity is reduced, but thermal noise cannot be completely eliminated
Solution Approach 1:
The cold aperture introduces a new active element (requiring cooling system) that provides superior thermal noise rejection compared to passive designs. While it increases device complexity, it effectively eliminates thermal noise interference
Solution Approach 2:
The cold aperture creates a thermally inert environment in the optical path by blocking thermal radiation from reaching the detector. This inert thermal field allows sensitive detection at longer wavelengths without thermal interference
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 adaptive camera system significantly reduces exposure times and enhances observation capabilities by maximizing SNR, enabling effective imaging of VLSI devices with HC emissions in longer wavelengths, while minimizing thermal noise interference.
Implementation Method 1
inserting an appropriate filter in the optical path... a plurality of shortpass optical filters with high blocking capabilities beyond their cut-off wavelength
Implementation Method 2
a detector sensitive to electromagnetic radiation having wavelengths of at least from 1000 nm to 2200 nm... cameras (detector arrays) sensitive across the IR range
Implementation Method 3
thermal emissions (which follows the black body radiation spectral distribution)... a cold aperture is placed between the relay lens and the detector
Data Source
AI summary
A method for emission testing of a semiconductor device (DUT), by mounting the DUT onto an test bench of an emission tester, the emission tester having an optical detector; electrically connecting the DUT to an electrical tester; applying electrical test signals to the DUT while keeping test parameters constant; serially inserting one of a plurality of shortpass filters into an optical path of the emission tester and collecting emission test signal from the optical detector until all available shortpass filters have been inserted into the optical path; determining appropriate shortpass filter providing highest signal to noise ratio of the emission signal; inserting the appropriate shortpass filter into the optical path; and, performing emission testing on the DUT.