Reflective Endpoint Detection for Mask-Independent Etch Alignment
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Solution Overview
Problem
Existing etch processing systems face inaccuracies in endpoint detection due to masking layer effects, which obscure measurements and limit the accuracy of wafer and photomask processing.
Innovation Solution
An etch processing system with reflective endpoint detection that emits light toward an alignment region on the substrate, using a camera to align the light and measure reflections from the underlying base layer, independent of the masking layer, employing focusing optics with reflective wavelengths and a photodetector to detect changes in reflectance for endpoint determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reflectance monitoring measures reflections from the mask layer, then the measurement signal is obtained, but the accuracy of endpoint detection deteriorates due to masking layer effects obscuring the signal
Solution Approach 1:
The substrate is divided into two distinct regions: a mask layer region and an alignment region. The alignment region is specifically designed to be free of mask layer material, allowing reflectance measurements to be taken from this clean substrate surface. This segmentation enables the optical monitoring system to obtain an unobscured signal from the alignment region while the mask layer remains intact in its region, thereby resolving the contradiction between obtaining a measurement signal and avoiding masking layer interference.
Solution Approach 2:
The alignment region acts as an intermediary area between the mask layer and the measurement system. It provides a中介 zone where light can interact with the substrate surface without being blocked or distorted by the mask layer. This intermediary region enables accurate reflectance measurements to be taken that truly represent the substrate etching state, rather than being confounded by mask layer effects.
2Measurement precision
If the light beam is focused to a small spot size for precise measurement, then the measurement precision improves, but the alignment difficulty increases
Solution Approach 1:
The substrate is divided into a mask layer region and a separate alignment region. This segmentation provides a dedicated target area that is easily identifiable and free from mask layer interference. The well-defined boundaries of the alignment region make it straightforward to locate and align the focused beam spot, even though the spot itself is small. The alignment region serves as a clear visual and optical target that simplifies the alignment process while maintaining precise measurement capability.
3Ease of operation
If the alignment region is made larger to facilitate beam alignment, then the ease of operation improves, but the measurement precision may deteriorate due to larger measurement area
Solution Approach 1:
The alignment region is made larger than the minimum necessary for a single measurement point, providing an excess of alignment target area. This larger region makes it easier to locate and align the beam spot, as there is more target area to work with. However, the measurement process itself is configured to sample from a specific portion or center of this alignment region, ensuring that the measurement precision is maintained by focusing on a representative point within the larger, easier-to-align region.
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 provides accurate and precise endpoint detection, unobscured by masking layer effects, enhancing the accuracy of wafer and photomask processing by focusing on the substrate surface without interference from the masking layer.
Implementation Method 1
the endpoint detection system can include a photodetector to receive a reflection of the light from substantially within the alignment region
Implementation Method 2
The focusing optics can incorporate reflective optics, which are wavelength-independent
Implementation Method 3
light emitted by a light source of the endpoint detection system is focused into a beam spot on the substrate surface
Data Source
AI summary
Embodiments include wafer and photomask processing equipment. An etch processing system including an endpoint detection system having a light source and a photodetector is described. In an example, the light source emits light toward an alignment region over a substrate support member of an etch chamber, and the photodetector receives a reflection of the light from the alignment region. The reflection is monitored for endpoint and process control. A second light source emits light toward the alignment region, and a camera receives the light to image the alignment region. The image can be used to align the light emitted by the endpoint detection system to a spot location within the alignment region, e.g., within an alignment opening of a substrate mounted on the substrate support member.