Alignment Mark Measurement Using Relative Position Signal Selection
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Solution Overview
Problem
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 Solution
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.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
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
Solution Approach 1:
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
Solution Approach 2:
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
2Measurement precision
If a laser beam is scanned to detect reflected light for mark position, then the signal-to-noise ratio is improved, but multiple mark candidate signals are measured making it difficult to identify the true mark
Solution Approach 1:
The patent performs preliminary scanning to identify multiple mark candidate signals before final mark position determination. By预先 detecting all potential mark locations and their relative positions, the system can then apply relative position information to correctly identify which candidate signals correspond to true alignment marks, resolving the ambiguity among multiple candidates
Solution Approach 2:
The patent uses relative position information between multiple detected mark candidates as feedback to verify and confirm the true mark positions. By comparing the measured relative positions with expected geometric relationships, the system can identify and select the correct mark signals from among multiple candidates, ensuring accurate mark identification
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 detection and specification of alignment marks, reducing resist dispersion and improving the signal-to-noise ratio, thereby enhancing the precision of mark positioning in semiconductor manufacturing.
Implementation Method 1
an irradiator which irradiates the target object with a laser beam, and a photoreceiver which receives a reflected light from the target object irradiated with the laser beam
Data Source
AI summary
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.