Laser Soft Marking Depth Control via Pulse Width
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Solution Overview
Problem
Current laser marking technologies for semiconductor wafers have a limited process window for adjusting the depth of soft marks, making it difficult to achieve specific mark depths, especially beyond the narrow energy range of 10 μj, which restricts the flexibility in accommodating evolving semiconductor fabrication processes.
Innovation Solution
A method and system that adjust the laser pulse width and energy to control the depth of soft marks on semiconductor wafers, allowing for a range of mark depths from about 1 micron to 6 microns by setting the pulse width and energy within an acceptable process energy window, thereby modifying the energy density to achieve predetermined mark depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser energy is increased to achieve deeper mark depths, then mark depth is improved, but susceptibility to subsurface damage increases
Solution Approach 1:
The patent changes the temporal parameter (pulse width) of the laser output in addition to energy adjustments. By extending the pulse width from nanosecond to microsecond range, the laser energy is delivered over a longer duration, allowing deeper marks (up to 10 micrometers) to be achieved without concentrating excessive peak power that causes subsurface damage. This parameter change enables operation outside the narrow conventional energy window.
Solution Approach 2:
The system dynamically adjusts both pulse energy and pulse width as independent variables. The controller can independently vary pulse width while maintaining energy within acceptable limits, or adjust energy while keeping pulse width constant. This dynamic control allows navigation through the parameter space to achieve desired mark depths while avoiding subsurface damage thresholds.
2Manufacturing precision
If laser energy window is narrowed to produce acceptable soft marks, then mark quality is improved, but flexibility in adjusting mark depth is reduced
Solution Approach 1:
The patent introduces pulse width as an additional controllable parameter beyond pulse energy. This transforms the system from having one degree of freedom (energy only) to two degrees of freedom (energy and pulse width). The controller can now adjust mark depth by varying pulse width while keeping energy constant, or by combining both adjustments, providing continuous and flexible control over mark depth without being constrained by the narrow energy window.
Solution Approach 2:
The invention adds a temporal dimension (pulse width) to the existing energy dimension. Instead of only adjusting energy magnitude, the system now controls both the magnitude and duration of energy delivery. This dimensional expansion creates a broader process window that enables flexible adjustment of mark depth while maintaining mark quality, as different combinations of energy and pulse width can achieve the same marking effect.
3Illumination intensity
If conventional laser marking is used to achieve deep marks, then mark visibility is improved, but subsurface damage increases
Solution Approach 1:
The patent changes the pulse width parameter from nanosecond to microsecond range, which fundamentally alters the material interaction mechanism. The extended pulse duration allows for more controlled heating and material removal, achieving sufficient mark depth for visibility (1-10 micrometers) while distributing the energy input over time to prevent the sudden stress spikes that cause subsurface damage in conventional short-pulse marking.
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 enables precise control over mark depth, allowing for finer adjustments and broader range of mark depths, enhancing the flexibility and effectiveness of laser soft marking for semiconductor wafers.
Implementation Method 1
irradiating by means of a laser pulse, a surface segment which has a surface area corresponding to 1.5 times to 6.5 times the surface area of the desired surface pattern
Implementation Method 2
the semiconductor material is melted and partially vaporized
Data Source
AI summary
Methods and systems for laser soft marking, especially for semiconductor wafers and devices, are provided. A laser-marking system for marking a semiconductor wafer to form a softmark on the wafer is provided. The system includes a laser subsystem for generating one or more laser pulses and a controller operatively connected to the laser subsystem. The controller sets a laser pulse width of the one or more laser pulses to selectively provide one or more laser output pulses having one or more set pulse widths that affect the depth of a softmark that is to be formed. The mark depth is substantially dependent on the one or more set pulse widths. The controller further sets a pulse energy of the one or more output pulses to selectively provide the one or more output pulses having a set total output energy that is within an acceptable process energy window for producing the softmark.