Integrated Reflectometer Aperture Plate Beam Separation
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Solution Overview
Problem
Integrating optical metrology tools with processing tools in semiconductor manufacturing is challenging due to space and footprint limitations, leading to compromised optical performance, instability, and measurement drift caused by environmental fluctuations, especially when measuring film thickness and pattern critical dimensions on patterned samples.
Innovation Solution
A compact reflectometer or ellipsometer is integrated with processing tools, featuring a source module, illumination fiber, mirrors, an aperture plate, and a detection module, which includes a broadband input beam, measurement and reference beams, and a lens to compensate for aberrations, allowing precise measurements within a vacuum chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If optical metrology tools are integrated with processing tools, then measurement speed and feedback capability are improved, but optical performance and measurement precision are compromised due to space and footprint limitations
Solution Approach 1:
The optical metrology tool is divided into separate functional modules (light source module, beam shaping module with mirrors and aperture plate, measurement module, reference module, detection module) that can be independently optimized and arranged. This segmentation allows each module to perform its specific function efficiently while fitting within the constrained space of the processing tool, thereby maintaining measurement precision despite integration.
Solution Approach 2:
The patent employs multiple mirrors (first mirror, second mirror, third mirror) to redirect light beams along different spatial paths, effectively utilizing three-dimensional space within the compact integration. The aperture plate with multiple apertures creates separate optical paths for measurement and reference beams, allowing parallel processing without interfering with each other, thus maintaining precision in a limited footprint.
2Area of stationary object
If smaller and lighter components are used to reduce footprint, then device size is reduced, but stability and sensitivity to environmental variables increase
Solution Approach 1:
The patent combines the measurement optical path and reference optical path into a single integrated system sharing common components (light source, detection module, mirrors). This merging allows for better thermal management and mechanical stability within the compact footprint, as the shared components can be rigidly mounted and thermally coupled, reducing sensitivity to environmental variations despite the reduced size.
Solution Approach 2:
The reference beam acts as an intermediary that compensates for environmental fluctuations. By comparing the measurement beam with the reference beam in the detection module, the system can distinguish between changes caused by the sample and changes caused by environmental factors (temperature, vibration), thereby maintaining stability and reliability within the compact integrated design.
3Area of stationary object
If measurement windows in vacuum chambers are made thick to cover large area, then coverage is improved, but optical spot quality degrades and working distance is limited
Solution Approach 1:
The patent replaces the conventional approach of using a single large thick window with an optical system using mirrors and an aperture plate to define and focus the measurement beam. The first mirror collimates the input beam, the aperture plate defines a small precise measurement spot, and the second mirror focuses it through the window. This optical substitution allows for precise spot control and adequate working distance while using a thinner window that covers the required area.
Solution Approach 2:
The aperture plate creates a localized measurement region with a small, well-defined spot size at the sample location, rather than attempting to illuminate the entire window area. This local quality approach concentrates the optical energy into a precise spot, maintaining high optical quality and measurement precision while allowing the window to be thinner and cover a larger overall area.
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 solution provides precise film thickness and pattern critical dimension measurements by stabilizing the optical path, reducing measurement drift, and improving sensitivity through polarization filtering and aberration compensation, enabling high-resolution measurements in challenging environments.
Implementation Method 1
The first mirror is configured to collimate the broadband input beam and direct the broadband input beam toward an aperture plate
Implementation Method 2
The second mirror is arranged to receive the measurement beam and focus the measurement beam through a window and onto a surface of a sample
Implementation Method 3
A lens is arranged between the second mirror and the window. The lens is configured to compensate for aberration introduced by the window on the measurement beam
Implementation Method 4
The second mirror focuses the measurement beam onto the surface of the sample at an angle so that at least a portion of the measurement beam is reflected from the surface of the sample as a reflected beam
Implementation Method 5
The third mirror is arranged to receive the reference beam and the reflected beam and focus the reference beam and the reflected beam onto a collection fiber
Data Source
AI summary
A reflectometer or ellipsometer integrated with a processing tool includes a source module configured to generate a input beam, and a first mirror arranged to receive the input beam. The first mirror is configured to collimate the input beam and direct the input beam toward an aperture plate. The aperture plate has at least two apertures. One of the at least two apertures is arranged to define a measurement beam from a portion of the input beam, and one of the at least two apertures is arranged to define a reference beam from a portion of the input beam. An optical element is arranged within an optical path of the reference beam and outside an optical path of the measurement beam. The optical element is configured to direct the reference beam toward a third mirror. A second mirror is arranged to receive the measurement beam and focus the measurement beam through a window and onto a surface of a sample. The window forms part of a chamber of the processing tool and the sample is disposed within the chamber. At least a portion of the measurement beam is reflected from the surface of the sample as a reflected beam. The second mirror is arranged to receive the reflected beam and direct the reflected beam toward the optical element. The optical element is configured to direct the reflected beam toward the third mirror. The third mirror is arranged to receive the reference beam and the reflected beam and focus the reference beam and the reflected beam onto a collection plane.