Laser Illumination Apparatus Energy Control Feedback
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Solution Overview
Problem
Existing laser annealing processes for converting amorphous silicon to polycrystalline silicon, such as TDX, face challenges in maintaining uniform energy density along the laser line due to variations in beam parameters, leading to poor crystal quality.
Innovation Solution
An illuminating apparatus with a beam shaping optical system, an energy measuring device, and an energy control system that measures and controls the energy output of the laser source to maintain uniform energy density along the laser line, using a beam splitter and photodiodes to detect and average the energy, and generate a control signal for feedback loop stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a pulsed narrow narrowly focused laser line is used for TDX process, then the laser can melt the thin Si layer effectively, but energy density variations along the laser line occur due to beam parameter fluctuations, leading to poor crystal quality
Solution Approach 1:
The patent implements a feedback control system that continuously monitors the actual energy delivered to the sample and adjusts the laser source energy output in real-time. The control system receives feedback about the energy that actually reaches the sample and modifies the laser parameters to compensate for variations in optical transmission, thereby maintaining uniform energy density along the laser line and improving crystal quality
Solution Approach 2:
The patent performs preliminary measurement of the energy reaching the sample before the actual laser annealing process. By measuring the energy transmission through the optical system in advance and using this information to pre-adjust the laser source energy, the system compensates for transmission variations before they affect the crystal formation process
2Shape
If beam shaping optics are used to create a line-shaped beam, then the laser can illuminate the sample with the required geometry, but variations in optical transmission cause energy density fluctuations along the laser line
Solution Approach 1:
The feedback control system monitors the actual energy reaching the sample after it has passed through the beam shaping optics and adjusts the laser source energy accordingly. This compensates for transmission variations introduced by the optical system while maintaining the required line-shaped beam geometry
Solution Approach 2:
The system performs preliminary energy measurement at the sample location to determine the actual transmission characteristics of the beam shaping optics. This information is used to pre-adjust the laser source energy before the actual processing, compensating for optical transmission variations
3Reliability
If laser energy is stabilized by feedback loop measuring energy close to the exit window, then the laser source energy is controlled, but this does not prevent variations of energy density along the laser line on the silicon layer
Solution Approach 1:
The patent moves the energy measurement location from the laser exit window to the sample plane, adding a spatial dimension to the feedback control. By measuring energy at the actual processing location rather than at the source, the system captures the cumulative effect of all transmission variations along the beam path and compensates accordingly
Solution Approach 2:
The patent introduces an intermediary energy measurement system at the sample location that acts as a mediator between the laser source and the sample. This intermediary measurement provides direct feedback about the actual energy reaching the sample, enabling more accurate compensation than source-side measurement alone
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 solution significantly reduces energy density variations on the sample, improving crystal quality and expanding the process window by stabilizing the energy output of the laser source during the annealing process.
Implementation Method 1
a beam shaping optical system configured to shape a laser beam into a line-shaped laser beam
Implementation Method 2
an energy measuring device configured to measure an energy of the line-shaped laser beam
Implementation Method 3
the laser beam being emitted during use by a laser source
Data Source
AI summary
The disclosure relates to an illuminating apparatus for illuminating a sample on a work stage, optionally with a relatively narrow illuminating line of relatively controlled energy, as well as methods for controlling energy of a laser source when illuminating a sample on a work stage with a relatively narrow illuminating line.