Laser-Based Mark Detection for Precise Semiconductor Alignment
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Summary
Problems
Current methods for aligning marks on semiconductor substrates face challenges in accurately detecting fine alignment marks due to low electron yield and resist dispersion when using electron beams, and difficulties in distinguishing true marks from noise signals when using laser beams.
Innovation solutions
A mark position measurement apparatus that uses a laser beam to scan and measure the height distribution of a target object's surface, generating combinations of mark candidate signals and selecting the correct alignment marks by comparing relative position information with a predetermined reference value, allowing for precise identification of mark positions.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If the dose of electron beam is increased to acquire contrast, then the signal-to-noise ratio is improved, but the resist is dispersed to contaminate the writing chamber
Why choose this principle:
The patent introduces a laser beam as an intermediary measurement tool that indirectly detects mark positions through reflected light intensity variations, rather than directly irradiating marks with electron beams. This mediator approach allows mark position detection without requiring high electron beam doses, thereby preventing resist dispersion while maintaining measurement capability
Principle concept:
If the dose of electron beam is increased to acquire contrast, then the signal-to-noise ratio is improved, but the resist is dispersed to contaminate the writing chamber
Why choose this principle:
The patent replaces the electron beam-based mechanical/electrical detection system with an optical detection system using laser beams. By substituting the electron beam irradiation method with optical reflection measurement, the system achieves mark position detection without the harmful side effect of resist dispersion caused by high-dose electron beam irradiation
Application Domain
Data Source
AI summary:
A mark position measurement apparatus that uses a laser beam to scan and measure the height distribution of a target object's surface, generating combinations of mark candidate signals and selecting the correct alignment marks by comparing relative position information with a predetermined reference value, allowing for precise identification of mark positions.
Abstract
A mark-position-measurement-apparatus includes a stage with an object having plural marks thereon, a sensor including an irradiator irradiating beams to the object, and a photoreceiver receiving a reflected light from the object and outputting a height-position distribution of the object surface, a position-calculation-circuit to calculate, for each mark, a position of a mark-candidate-signal acquired in a scanned region, by using the height-position distribution, for each mark, obtained by scanning the beam over the plural marks to be intersected with one of the plural marks, a combination-generation-circuit to generate plural combinations by combining mark-candidate-signals selected from the plural marks when plural mark-candidate-signals are acquired, in a scanning direction, for at least one mark, and a selection-circuit to select a combination of mark-candidate-signals, being mark signals of the plural marks, from the plural combinations, by comparing, with a predetermined reference value, relative position information regarding mark-candidate-signals in the same combination.