Dynamic Surface Annealing Laser Array with Pyrometry Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Dynamic surface annealing of semiconductor substrates faces challenges in compensating for absorption and reflectivity variations across the substrate surface and variations in laser array output, leading to non-uniform temperature distributions during thermal processing.
Innovation Solution
An apparatus utilizing an array of adjustable lasers focused into a narrow line beam, combined with an imaging pyrometer and emissometer, adjusts individual laser outputs to compensate for temperature variations, ensuring uniform heating across the substrate surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If wide-angle pyrometers are used to monitor large portions of the wafer, then large area temperature monitoring is achieved, but the bulk of the wafer remains near ambient temperature and cannot detect localized temperature variations under the focused laser beam
Solution Approach 1:
The patent segments the monitoring function by using multiple pyrometers, each focused on specific zones under the laser beam. Instead of one wide-angle pyrometer monitoring a large area with poor precision, multiple pyrometers are positioned to monitor smaller, localized areas with high precision, collectively covering the entire laser-irradiated region.
Solution Approach 2:
The patent introduces optical elements (lenses, mirrors) as intermediaries to redirect and focus thermal radiation from the wafer surface into the pyrometers. These optical elements concentrate the thermal radiation signals from specific wafer zones onto the pyrometer detectors, enabling precise localized temperature measurement while maintaining coverage of the entire processing area.
2Productivity
If the laser array output is increased to compensate for absorption variations, then heating efficiency improves, but non-uniform temperature distribution worsens
Solution Approach 1:
The patent implements a feedback control system where pyrometers continuously monitor the temperature distribution across the wafer surface under the laser beam. The measured temperature data is fed back to the control system, which dynamically adjusts the laser power output to compensate for absorption variations. This closed-loop feedback enables high heating efficiency while maintaining uniform temperature distribution.
Solution Approach 2:
The patent applies local quality control by allowing different regions of the laser array to operate at different power levels based on local absorption characteristics and temperature measurements. Each laser element or group of elements can be independently controlled to provide the exact heating power needed for its specific zone, ensuring uniform overall temperature distribution while maintaining high heating efficiency.
3Loss of time
If rapid thermal processing is used to reduce thermal budget, then processing time is reduced, but the entire bulk of the wafer must be heated which limits anneal time
Solution Approach 1:
The patent applies local quality by concentrating laser heating only on the surface layer and specific regions of the wafer where processing is needed, rather than heating the entire bulk. The focused laser beam delivers intense localized heating to the surface, achieving rapid thermal processing and reduced thermal budget without requiring the entire wafer bulk to reach high temperatures.
Solution Approach 2:
The patent uses periodic or pulsed laser action to deliver thermal energy in controlled bursts to the wafer surface. This periodic heating allows the surface layer to reach high temperatures rapidly for processing while the bulk remains cooler, enabling shorter anneal times and reduced thermal budget compared to continuous bulk heating methods.
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 solution achieves a more uniform wafer surface temperature distribution, effectively minimizing thermal budget and optimizing thermal processing by dynamically adjusting laser power based on real-time temperature measurements.
Implementation Method 1
a source of laser radiation emitting at a laser wavelength
Implementation Method 2
compensating for absorption and reflectivity variations across the substrate surface
Implementation Method 3
A pyrometer sensor is provided that is sensitive to a pyrometer wavelength
Implementation Method 4
temperature measurement is desirable because the amount of light coupled into the wafer strongly depends upon the surface structure already formed in the wafer
Data Source
AI summary
Apparatus for dynamic surface annealing of a semiconductor wafer includes a source of laser radiation emitting at a laser wavelength and comprising an array of lasers arranged in rows and columns, the optical power of each the laser being individual adjustable and optics for focusing the radiation from the array of lasers into a narrow line beam in a workpiece plane corresponding to a workpiece surface, whereby the optics images respective columns of the laser array onto respective sections of the narrow line beam. A pyrometer sensor is provided that is sensitive to a pyrometer wavelength. An optical element in an optical path of the optics is tuned to divert radiation emanating from the workpiece plane to the pyrometry sensor. As a result, the optics images each of the respective section of the narrow line beam onto a corresponding portion of the pyrometer sensor. The apparatus further includes a controller responsive to the pyrometry sensor and coupled to adjust individual optical outputs of respective columns of the laser array in accordance with outputs of corresponding portions of the pyrometry sensor.