Semiconductor Substrate Surface Assessment via Reverse-Side Light Scattering
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Solution Overview
Problem
Existing methods for assessing semiconductor substrates are time-consuming and costly due to the need to divide and polish the substrate for measurement, and they struggle with accurately controlling the thickness of the substrate during measurement, especially when measuring distortions in the surface layer before device formation.
Innovation Solution
A method involving a sticking step to attach the device layer to a support substrate, followed by thinning from the reverse side to a reduced thickness, and then applying light or X-rays from the reverse side to measure scattered or diffracted radiation, allowing for the assessment of surface layer properties without fully exposing the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the semiconductor substrate is divided and polished to create a cross-sectional surface for measurement, then measurement can be performed, but the process becomes time-consuming and costly
Solution Approach 1:
Instead of dividing and polishing the substrate to expose the surface layer for measurement, the patent applies measurement light from the reverse side of the substrate. This inverted approach allows measurement of the surface layer through the substrate without physical sectioning, thereby eliminating the time-consuming division and polishing steps while maintaining measurement capability
Solution Approach 2:
The patent uses the substrate itself as an intermediary medium to transmit measurement light to the surface layer and carry scattered light back. By utilizing the substrate's transparency to measurement wavelengths, the method enables indirect observation of the surface layer without physical access from the front side, avoiding the need for substrate division and polishing
2Measurement precision
If the semiconductor substrate is divided and polished to create a cross-sectional surface for measurement, then measurement can be performed, but the cost increases
Solution Approach 1:
The patent inverts the measurement approach by illuminating from the reverse side rather than requiring front-side access. This eliminates complex substrate preparation steps including division and polishing, significantly reducing manufacturing complexity and cost while enabling surface layer measurement through the substrate
Solution Approach 2:
The patent extracts the measurement function from the physical cross-section preparation process. By using optical scattering through the substrate, the method separates the measurement capability from the need for physical substrate sectioning and polishing, thereby eliminating costly and complex manufacturing steps
3Measurement precision
If the substrate is thinned until the surface of the semiconductor film is exposed, then the surface layer can be measured, but it is difficult to accurately control the thickness
Solution Approach 1:
Instead of thinning the substrate from the front side to expose the surface layer, the patent measures from the reverse side through the substrate. This approach eliminates the need for precise thickness control during thinning, as the substrate maintains its normal thickness while still allowing measurement light to penetrate and scatter from the surface layer
Solution Approach 2:
The substrate acts as an intermediary that transmits measurement light without requiring the light path to terminate at the surface layer. This intermediary approach allows measurement through the substrate at its normal thickness, eliminating the difficulty of controlling thinning precision to expose the surface
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 reduces the time and cost of measurement by enabling the assessment of surface layer distortions and properties with greater accuracy and ease, allowing for the measurement of distortions without exposing the surface layer, thus simplifying the process and improving control over electronic characteristics.
Implementation Method 1
applying light to the semiconductor substrate from the reverse side and measuring scattered light from the semiconductor substrate
Implementation Method 2
applying X-rays to the semiconductor substrate from the reverse side and measuring diffracted X-rays produced as a result of dispersion and interference from the semiconductor substrate
Data Source
AI summary
A method of assessing a semiconductor substrate includes a sticking step of sticking a device layer of the semiconductor substrate to a support substrate, a thinning step of thinning the semiconductor substrate from a reverse side thereof to a thickness smaller than a finished thickness after the sticking step is carried out, and an assessing step of applying light to the semiconductor substrate from the reverse side thereof and measuring scattered light from the semiconductor substrate thereby to assess a property of the semiconductor substrate.