Semiconductor Laser Wavelength Control for Two-Wavelength Exposure
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Solution Overview
Problem
Semiconductor exposure apparatuses face challenges in maintaining resolution due to chromatic aberrations caused by wide spectral linewidths of KrF and ArF excimer laser light, which necessitate the use of line narrowing modules to reduce spectral linewidth and prevent decreases in resolution.
Innovation Solution
A laser apparatus with a first wavelength variable semiconductor laser, a pulse amplifier, a wavelength conversion system, a monitor module, and a processor that alternately changes the target wavelength of the laser light to achieve a two-wavelength exposure, calculating and controlling current values to minimize wavelength differences and maintain a desired center wavelength, thereby stabilizing the output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a line narrowing module is provided in the laser resonator to narrow the spectral linewidth, then chromatic aberrations are reduced and resolution is maintained, but the device complexity increases
Solution Approach 1:
The patent changes the fundamental parameter of spectral linewidth by using a wavelength variable semiconductor laser that inherently outputs light with a narrow spectral linewidth. This eliminates the need for additional line narrowing modules while maintaining the resolution required for semiconductor exposure, thus resolving the contradiction between manufacturing precision and device complexity
Solution Approach 2:
The patent extracts and removes the line narrowing module from the laser system by using a semiconductor laser source that naturally provides narrow linewidth output. This extraction eliminates the harmful factor of device complexity while preserving the beneficial effect of reduced chromatic aberrations
2Manufacturing precision
If the target wavelength is changed alternately to achieve two-wavelength exposure, then manufacturing precision is improved, but the control complexity increases
Solution Approach 1:
The patent employs dynamic wavelength switching capability of the wavelength variable semiconductor laser, which can alternately change between two wavelengths under program control. This dynamic parameter change enables two-wavelength exposure that improves manufacturing precision while the programmable nature of the control keeps the system manageable
Solution Approach 2:
The patent implements a feedback control mechanism where the processor monitors the actual wavelength output and adjusts the laser parameters to maintain precise wavelength control during alternating wavelength operation. This feedback loop ensures high exposure precision while automating the control process to manage complexity
3Productivity
If high repetition frequency operation is implemented, then productivity is improved, but wavelength stability deteriorates
Solution Approach 1:
The patent replaces traditional mechanical wavelength tuning mechanisms with electrically controlled wavelength modulation in the semiconductor laser. This substitution enables rapid wavelength switching at high repetition frequencies while maintaining wavelength stability through precise electrical control, resolving the contradiction between productivity and wavelength 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 enables highly accurate two-wavelength exposure even at high repetition frequencies, effectively reducing chromatic aberrations and maintaining resolution in semiconductor manufacturing processes.
Implementation Method 1
a wavelength conversion system configured to convert a wavelength of the first pulse laser light and output resultant second pulse laser light
Implementation Method 2
a first wavelength variable semiconductor laser configured to output first continuous-wave laser light
Implementation Method 3
a first amplifier configured to pulse and amplify the first laser light
Implementation Method 4
a monitor module configured to measure a wavelength of the third pulse laser light
Data Source
AI summary
A laser apparatus includes a first semiconductor laser outputting first continuous-wave laser light; a first amplifier a wavelength conversion system outputting second pulse laser light; an excimer amplifier amplifying the second pulse laser light; a monitor module; and a processor calculating a center wavelength being an average of a measured value of the wavelength of the third pulse laser light output at the first target wavelength and a measured value of the wavelength thereof output at the second target wavelength, calculating a wavelength difference of the measurement values, calculating an average current value of a current flowing through the first semiconductor laser, calculating a current value difference such that a difference between a target wavelength difference and the wavelength difference decreases, and calculating a first current value at the first target wavelength and a second current value at the second target wavelength to control the first semiconductor laser.