Vacuum Inductive Sensor Capsules for In-Situ Layer Measurement
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Solution Overview
Problem
Current eddy current sensors are not suitable for direct measurement of layer characterization in high-vacuum cluster tool process chambers due to space constraints, integration issues, and thermal sensitivity, leading to measurement inaccuracies and the need for ex-situ testing with test wafers, which are costly and time-consuming.
Innovation Solution
A measuring device with inductive sensors, where transmitting and receiving coils are positioned outside the vacuum chamber, connected via capsules or vacuum-compatible materials, allowing for large distance measurements and avoiding heat-generating components within the vacuum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If eddy current sensors are integrated into vacuum chambers for direct measurement, then real-time layer characterization is enabled, but space constraints and thermal sensitivity cause measurement inaccuracies
Solution Approach 1:
The measuring device is divided into two separate parts: a sensor head containing the inductive sensor that can be positioned in or near the vacuum chamber, and a separate evaluation unit that performs signal processing and characterization outside the vacuum chamber. This segmentation allows the sensitive measurement components to be isolated from thermal interference while maintaining measurement capability.
Solution Approach 2:
A vacuum-compatible cable or waveguide acts as an intermediary to transmit electromagnetic signals between the sensor head in the vacuum chamber and the evaluation unit outside the vacuum chamber. This intermediary enables signal transmission without requiring thermal or electrical connections that would introduce thermal sensitivity into the measurement system.
2Ease of operation
If test wafers are used for ex-situ measurement, then measurement can be performed outside vacuum, but process feedback is delayed by hours or days
Solution Approach 1:
The inductive sensor is pre-positioned within or near the vacuum chamber before the coating process, enabling immediate measurement of layer characteristics as they are formed. This preliminary positioning eliminates the need to wait for ex-situ measurement after the process completes, providing real-time feedback.
Solution Approach 2:
The measurement system operates continuously within the vacuum chamber during the coating process, providing ongoing real-time characterization. This continuous measurement action eliminates the discontinuous nature of ex-situ testing, where measurement occurs only after the process is complete, thereby eliminating delays.
3Measurement precision
If signal processing is performed inside vacuum chamber, then measurement can be done directly, but heat dissipation is limited causing thermal drift
Solution Approach 1:
The heat-generating signal processing and evaluation functions are extracted from the vacuum chamber and placed in an external evaluation unit. Only the minimal sensor head remains in the vacuum chamber, while all computational and thermal management functions occur outside, where heat can be effectively dissipated through conventional cooling mechanisms.
4Measurement precision
If coils are positioned close to the measurement object, then measurement sensitivity is improved, but collision risk increases in vacuum
Solution Approach 1:
The sensor head is designed with adjustable positioning capabilities, allowing dynamic optimization of the distance between the coil and the measurement object. This dynamic adjustment enables the system to achieve maximum measurement sensitivity at each moment while maintaining sufficient clearance to prevent collisions with the object or surrounding components.
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
Enables accurate, real-time, and collision-free measurement of layer thickness and resistance on production wafers without interrupting the vacuum, reducing operational costs and time by eliminating the need for test wafers and providing immediate process feedback.
Implementation Method 1
at least one inductive sensor, which has at least one transmitting coil for generating an alternating electromagnetic field
Implementation Method 2
This primary field induces eddy currents in the object being measured. The eddy current flowing in the object generates a secondary electromagnetic field
Implementation Method 3
The eddy current flowing in the object generates a secondary electromagnetic field, which opposes the primary field generated by the coil and therefore influences the combined field formed by the primary and secondary fields. Changes in this combined field can be detected using inductive sensors
Data Source
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Figure 3a~4
AI summary
The invention relates to a measuring device for characterizing a measurement object in a vacuum, wherein the measuring device comprises at least one inductive sensor, which has at least one transmitting coil for generating an alternating electromagnetic field and one receiving coil for detecting an impedance change, as well as a signal amplifier and/or a signal processing unit for evaluating the measurement signals.The object of the present invention is to provide a measuring device that can be integrated into a vacuum system with minimal additional space requirements and enables measurement with high accuracy and high spatial resolution with precise repeatability on a static and/or moving object past the measuring device, by arranging both the transmitting and receiving coils as well as the signal amplifier and/or the signal processing unit outside a vacuum region, wherein the transmitting and receiving coils can each be inserted into a capsule and the capsules are designed as an integral part of a chamber wall of a vacuum chamber and project into the vacuum, the chamber wall separating the vacuum region from an atmospheric side.