AFM Probe Alignment System for Substrate-Independent Distance Control
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Solution Overview
Problem
Current alignment systems in nano-manufacturing and metrology face challenges in accurately maintaining high precision distance between objects, as existing methods are substrate-dependent and lack sufficient resolution and speed, particularly when dealing with minute variations in wafer thickness, tilting, or waviness.
Innovation Solution
An alignment and tracking system utilizing a sensor device with a probe tip for atomic force measurement, connected to an object stage actuator, which adjusts the distance between objects based on measured force, allowing for precise control and independence from substrate properties, using a feedback loop to maintain the desired distance with nanometer resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical measurement techniques are used to measure distance, then measurement can be performed, but the measurement is substrate dependent and affected by reflection behavior
Solution Approach 1:
The patent replaces optical measurement techniques with atomic force microscopy (AFM) based measurement. Instead of using light reflection and optical interference patterns that are substrate-dependent, the system uses a physical probe tip to directly measure atomic forces between the probe and substrate surface, providing substrate-independent distance measurements with nanometer resolution.
Solution Approach 2:
The patent introduces an AFM probe tip as an intermediary between the measurement system and the substrate. The probe tip physically contacts or nears the substrate surface to measure atomic forces, serving as a universal mediator that can interact with any substrate material regardless of its optical properties, thereby eliminating substrate dependence.
2Measurement precision
If capacitive sensors are used to measure distance, then measurement can be performed, but the measurement is substrate dependent and affected by conductivity
Solution Approach 1:
The patent replaces capacitive sensing with direct atomic force measurement using AFM. Instead of measuring electrical capacitance changes that depend on substrate conductivity, the system uses a mechanical probe to directly sense atomic forces at the nanometer scale, providing measurements that are independent of electrical properties.
3Adaptability or versatility
If gas gauge proximity sensors are used, then substrate independence is improved, but the system complexity increases and vacuum conditions are affected
Solution Approach 1:
The patent replaces complex gas-based proximity sensing with a simpler AFM-based atomic force measurement system. The AFM probe directly measures distances through atomic interactions, eliminating the need for complex gas flow control, pressure regulation, and vacuum maintenance systems required by gas gauge sensors.
4Ease of operation
If level sensor measurement is performed initially, then positioning can be achieved, but minute variations in wafer thickness cannot be compensated during movement
Solution Approach 1:
The patent implements continuous distance measurement and adjustment using AFM during the entire wafer movement process, rather than performing a single initial measurement with a level sensor. The AFM probe continuously monitors the distance between the lens and wafer surface, enabling real-time compensation for thickness variations, tilting, and waviness to maintain constant focus.
Solution Approach 2:
The patent employs a feedback control system where the AFM probe continuously measures the actual distance between the lens and wafer surface, and this measurement is fed back to the positioning system to dynamically adjust the lens or wafer position, ensuring constant focus despite variations in wafer geometry during movement.
5Loss of information
If multiple AFMs and location correction elements are used, then spatial relationship information can be obtained, but the relative distance cannot be accurately controlled for different circumstances
Solution Approach 1:
The patent makes the AFM-based measurement system universal by decoupling the measurement function from the positioning control. The AFM probe can measure distances at multiple locations on the wafer surface, and the controller uses this information to dynamically adjust positioning for different circumstances, making the system adaptable to various measurement and control requirements.
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
The system effectively maintains high precision distance between objects, independent of substrate properties, enabling accurate alignment and tracking even with microscopic variations, enhancing precision and speed in nano-manufacturing and metrology applications.
Implementation Method 1
The probe tip is configured to perform an atomic force measurement of a force exerted via the probe tip on a surface of the second object
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
An alignment system (100) and method for positioning and/or keeping a first object (1) at a controlled distanced (D1) with respect to a second object (2). An object stage (11) is configured to hold a surface (1a) of the first object (1) at a distance (D1) over a surface (2a) of the second object (2). A sensor device (31) comprising a probe tip (31a) is connected at a predetermined probe level distance (Dp) relative to the surface (1a) of the first object (1). The probe tip (31a) is configured to perform an atomic force measurement (AFM) of a force (F1) exerted via the probe tip (31a) on a surface (2a) of the second object (2). A controller (80) is configured to control an object stage actuator (21) as a function of the probe level distance (Dp) and the measured force (F1) to maintain the controlled distanced (D1).