Continuous Clocking of TDI Sensors Using Sinusoidal Waveforms
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Solution Overview
Problem
Existing TDI sensors face issues with suboptimal functionality due to burst clocking, leading to high power dissipation, low charge transfer efficiency, and sensitivity to timing jitter, which affects the accuracy and speed of semiconductor wafer and photomask inspections.
Innovation Solution
The implementation of continuous clocking using sinusoidal voltage waveforms to transfer charge between pixels, reducing electronic noise and enabling faster data rates and higher resolution by controlling voltage waveforms to minimize substrate noise and optimize signal-to-noise ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If burst clocking is used to transfer charge between pixels, then charge transfer can be achieved, but power dissipation increases and charge transfer efficiency decreases
Solution Approach 1:
The patent applies periodic action by using continuous sinusoidal voltage waveforms to clock the charge through the TDI sensor. Instead of burst clocking with sharp transitions, the invention uses continuous periodic sinusoidal signals at frequencies matching the sensor's charge transfer requirements. This continuous periodic action eliminates the high peak currents and power dissipation associated with burst clocking while maintaining efficient charge transfer through the imaging region and serial register.
Solution Approach 2:
The patent changes the clocking parameter from square wave bursts to continuous sinusoidal waveforms. By changing the waveform shape and continuity parameters, the invention achieves smooth charge transfer with reduced power dissipation. The sinusoidal parameters (frequency, amplitude, phase) are optimized to match the sensor's charge transfer characteristics, eliminating the harmful effects of burst clocking while maintaining productivity.
2Speed
If burst clocking with sharp voltage transitions is used, then charge transfer speed can be achieved, but timing jitter sensitivity increases and measurement precision decreases
Solution Approach 1:
The patent uses continuous periodic sinusoidal clocking at frequencies precisely matched to the sensor's charge transfer rate. This periodic action provides smooth, predictable voltage transitions that are far less sensitive to timing jitter than burst clocking. The continuous nature of the sinusoidal waveform ensures that charge transfer proceeds at the required speed without the sharp transitions that amplify timing errors.
Solution Approach 2:
The invention changes the clocking waveform parameter from square wave to sinusoidal, fundamentally altering the transition characteristics. The sinusoidal waveform provides gradual, smooth voltage changes that reduce sensitivity to timing variations. By optimizing the frequency and phase parameters of the sinusoidal clocking, the patent achieves both fast charge transfer and high measurement precision, eliminating the trade-off present in burst clocking systems.
3Loss of energy
If continuous clocking with sinusoidal waveforms is used, then power dissipation is reduced and signal accuracy improves, but device complexity increases due to waveform generation requirements
Solution Approach 1:
The patent replaces complex analog waveform generation circuits with digital signal processing. Field-programmable gate arrays (FPGAs) generate the sinusoidal clocking waveforms digitally, converting digital values to analog voltages through digital-to-analog converters. This substitution of digital for analog complexity reduces overall device complexity while enabling precise control of the sinusoidal parameters. The digital approach allows easy adjustment of frequency and phase without changing physical circuitry.
Solution Approach 2:
The patent uses a universal digital waveform generation approach that can produce multiple clocking patterns and frequencies from a single FPGA system. This multi-functional digital core can generate sinusoidal waveforms for different sensor configurations and operating conditions, eliminating the need for separate analog circuitry for each waveform type. The universal digital platform reduces device complexity by consolidating waveform generation functionality.
4Ease of manufacture
If burst clocking is used, then simple waveform generation is possible, but modulation transfer function decreases and electromigration risk increases
Solution Approach 1:
The patent replaces simple burst clocking circuitry with digital FPGA-based sinusoidal waveform generation. While the digital approach may seem more complex initially, it provides precise control over voltage amplitudes and frequencies, enabling optimized clocking that reduces electromigration. The digital system can generate smooth sinusoidal waveforms that eliminate the high peak currents causing electromigration, while the FPGAs are commercially available and easy to program, maintaining ease of manufacture.
Solution Approach 2:
The invention changes the clocking parameters from burst square waves to continuous sinusoidal waves with optimized amplitude and frequency. This parameter change eliminates the high peak-to-average current ratios that cause electromigration. The sinusoidal parameters are tuned to match the sensor's charge transfer characteristics, providing reliable operation without excessive current stress. The digital control allows easy adjustment of these parameters to optimize reliability for different operating conditions.
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 enhances the modulation transfer function, reduces power dissipation, and improves signal accuracy by minimizing voltage fluctuations and electromigration effects, allowing for more precise and efficient inspection of semiconductor wafers and photomasks.
Implementation Method 1
The wafer surface reflects light onto the TDI sensor, and at the points where light strikes the sensor the sensor may generate photoelectrons
Data Source
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AI summary
A method and apparatus for propagating charge through a sensor and implementation thereof is provided. The method and apparatus may be used to inspect specimens, the sensor operating to advance an accumulated charge between gates of the TDI sensor. The design implementation provides a set of values representing a plurality of out of phase signals, such as sinusoidal or trapezoidal signals. These out of phase signals are converted and transmitted to the sensor. The converted signals cause the sensor to transfer charges in the sensor toward an end of the sensor. Aspects such as feed through correction and correction of nonlinearities are addressed.