Laser Doping Apparatus Bubble Interference Control
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Solution Overview
Problem
Laser doping of semiconductor substrates faces interference from bubbles generated during previous shots, leading to uneven impurity element distribution and concentration, as these bubbles remain at the irradiation site and affect subsequent laser light irradiation.
Innovation Solution
An impurity-doping apparatus and method that includes a liquid reservoir, a liquid transport device, and a laser optical system, where the liquid flow rate and scanning velocity are controlled to prevent bubble interference by determining the minimum movement distance and flow rate necessary to move bubbles away from the irradiation area, ensuring consistent impurity element doping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser light is repeatedly irradiated onto the semiconductor substrate surface, then impurity elements can be doped into the substrate, but bubbles generated in previous shots remain at the irradiation site and interfere with subsequent shots
Solution Approach 1:
The patent applies dynamics by making the liquid environment movable rather than static. The liquid is circulated at a controlled flow rate to dynamically clear bubbles from the irradiation area between laser shots, ensuring that each laser pulse interacts with a bubble-free liquid medium for consistent impurity doping.
Solution Approach 2:
The patent uses hydraulics by introducing a liquid circulation system that flows liquid through the irradiation area. The liquid flow rate is specifically controlled to move bubbles away from the laser irradiation path, using fluid dynamics to eliminate the harmful bubble effect without requiring mechanical bubble removal devices.
2Reliability
If the liquid flow rate is increased to move bubbles away from the irradiation area, then bubble interference is reduced, but the complexity of controlling the liquid transport increases
Solution Approach 1:
The patent implements feedback control by monitoring the liquid flow rate and adjusting it to maintain optimal bubble removal. The system controls the liquid transport device to keep the liquid flowing at a rate that ensures bubbles are cleared from the irradiation area while maintaining stable doping conditions, creating a self-regulating system.
Solution Approach 2:
The patent applies parameter changes by controlling the liquid flow rate as a key parameter. By adjusting this parameter within an optimal range, the system achieves effective bubble removal without excessive complexity. The flow rate is set to balance bubble clearance efficiency with system simplicity.
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 allows for precise control of impurity element distribution, preventing bubble interference and achieving desired concentrations and depths of impurity elements in semiconductor substrates, enhancing the efficiency and accuracy of the laser doping process.
Implementation Method 1
a laser optical system which scans and irradiates light pulses onto the surface of the semiconductor substrate through the liquid
Implementation Method 2
The laser lights used in the methods proposed by Ikeda et al. and Nishi et al. are optical beams of having wavelength in the ultraviolet region, which cause a large absorption coefficient in SiC
Implementation Method 3
a liquid transport device transporting the liquid on the surface of the semiconductor substrate at a fixed flow rate
Data Source
AI summary
An apparatus for doping impurities includes: a bath reserving liquid containing impurity elements; a liquid transport device transporting the liquid on a surface of a semiconductor substrate; a laser optical system which scans and irradiates light pulses of laser onto the surface of the semiconductor substrate; an X-Y manipulator moving the semiconductor substrate; and an arithmetic and control unit which controls the liquid transport device and X-Y manipulator. Flow rate of the liquid and scanning velocity of the light pulses are determined, by a characteristic dimension of the irradiation area along the flow direction of the liquid, an overlapping ratio of the irradiation area, and the radius of a bubble generated in the liquid. The impurity elements are doped into a part of the inside of the semiconductor substrate at the determined flow rate and scanning velocity.