Non-Linear Crystal Shifting for Stable UV Beam Parameters
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing solutions for stabilizing UV beam parameters in laser apparatuses fail to address the issue of beam parameter drift caused by non-linear crystal degradation, leading to unstable beam quality and performance issues in semiconductor wafer inspection processes.
Innovation Solution
A UV laser apparatus comprising a non-linear crystal, a beam-crystal displacer, a beam parameter monitor, and a laser control unit that shifts the crystal at varying speeds to steer beam parameters toward target values, measured and adjusted in real-time to maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the non-linear crystal is continuously shifted relative to the incident beam, then crystal lifetime is prolonged, but beam parameters become unstable
Solution Approach 1:
The patent implements periodic spot shifting where the beam is shifted to a new location on the crystal after a predetermined number of shots or time interval, rather than continuous shifting. This periodic action allows the crystal to recover between shifts, maintaining both extended lifetime and beam parameter stability by preventing continuous degradation at any single location.
Solution Approach 2:
The system dynamically adjusts the shifting frequency and spot selection based on real-time monitoring of beam parameters and crystal degradation patterns. By making the shifting pattern adaptive rather than fixed, the system optimizes the balance between extending crystal life and maintaining stable beam output quality.
2Duration of action of stationary object
If the source beam is shifted to a new spot on the crystal, then crystal life is extended, but beam parameters exhibit step-wise changes
Solution Approach 1:
The patent incorporates real-time monitoring of beam parameters with feedback control that detects degradation trends and adjusts the spot shifting strategy accordingly. When beam parameters approach specification limits, the system proactively shifts spots before critical degradation occurs, preventing step-wise changes by maintaining continuous stability through adaptive control.
Solution Approach 2:
The system performs preliminary spot shifting before beam parameters actually hit specification limits, based on predictive monitoring of degradation trends. This preliminary action prevents the occurrence of step-wise changes by proactively relocating the beam to a fresh crystal region before significant degradation accumulates at the current spot.
3Productivity
If the non-linear crystal is used at high UV power, then processing efficiency is improved, but beam parameter drift increases due to crystal degradation
Solution Approach 1:
The patent implements periodic spot shifting that allows the crystal to recover between high-power irradiation events. By cycling through multiple spots and allowing rest periods, the crystal can dissipate accumulated damage and thermal effects, enabling sustained high-power operation while maintaining beam parameter stability within specification limits.
Solution Approach 2:
The system changes operational parameters including spot location, irradiation duration, and rest intervals to optimize the balance between high-power processing and crystal health. By dynamically adjusting these parameters based on crystal degradation state, the system maintains both high productivity and beam stability.
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 effectively prolongs crystal lifetime, reduces beam parameter drift, and maintains stable beam quality, even at high UV power levels, with minimal initial and long-term degradation, thereby enhancing laser tool performance.
Implementation Method 1
Within the crystal, the source beam is frequency converted to a higher frequency, producing a shorter wavelength beam. For example, a 532 nm beam can be directed to a non-linear crystal to generate a 266 nm beam (the second harmonic wavelength of the 532 nm beam).
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
This disclosure provides methods and apparatuses which advantageously stabilize beam parameters and elongate crystal lifetime. In one aspect, a UV laser apparatus (100) includes a non-linear crystal(104), a laser source(102), a beam- crystal displacer(106), a beam parameter monitor(108), and a laser control unit (110). The laser source (102) directs a source beam (1021) to the non-linear crystal (104) to produce a UV beam and the beam-crystal displacer(106) shifts the non- linear crystal (104) relative to the source beam (1021) at a plurality of shift speeds. The beam parameter monitor (108) measures the UV beam and outputs a measurement of a beam parameter. The laser control unit(110): receives the measurement; determines, based on the measurement, an adjustment in shift speed that steers the beam parameter toward a target value; and outputs the adjustment to the beam-crystal displacer(106).