SiC Substrate Stress Modeling for Warpage Control
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Solution Overview
Problem
SiC substrates tend to warp after processing due to unpredictable stress and thickness variations, affecting semiconductor device manufacturing, as existing methods like Raman shift analysis lack directional information and fail to sufficiently inhibit warpage.
Innovation Solution
A warpage factor formula (F=K×exp(a+b×ln(σ)+c×ln(R)+d×ln(ts)) is introduced, correlating warpage with stress at the outer circumferential portion, diameter, and thickness, allowing for the inhibition of warpage by controlling these parameters to specific values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Raman shift analysis is used to evaluate internal stress, then stress evaluation is possible, but directional information is lost and warpage prediction is insufficient
Solution Approach 1:
The patent segments the stress measurement approach by introducing a new measurement point at the outer circumferential end (10mm inward from the actual outer edge) and measuring stress in the circumferential direction specifically. This segmentation provides directional information that was lost in conventional Raman shift analysis, enabling accurate warpage prediction while maintaining stress evaluation capability.
2Stress or pressure
If stress reduction methods are applied to SiC substrates, then internal stress is reduced, but warpage after processing is not sufficiently inhibited
Solution Approach 1:
The patent applies preliminary action by establishing specific control criteria for stress (≤60MPa or ≥-60MPa) and thickness (300-800μm) before processing occurs. By pre-controlling these parameters and introducing the warpage factor F calculation, the patent enables prediction and prevention of warpage before processing, rather than attempting to correct it afterward. This preliminary control of stress and thickness parameters effectively inhibits warpage that conventional stress reduction methods failed to prevent.
3Stress or pressure
If conventional stress control methods are used, then some stress management is achieved, but warpage prediction and inhibition is insufficient for manufacturing accuracy
Solution Approach 1:
The patent implements feedback by creating a closed-loop control system where the warpage factor F is calculated based on measured stress and thickness parameters, this calculated F value is then used to predict actual warpage, and the prediction feeds back into adjusting stress and thickness control for subsequent substrates. The specific feedback mechanism involves measuring stress at the outer circumferential end, calculating F=K×exp(a+b×ln(σ)+c×ln(R)+d×ln(ts)), predicting warpage from F, and using this prediction to improve manufacturing precision by adjusting processing parameters.
Data Source
AI summary
The SiC substrate has a warpage factor F of 300 μm or less, which is obtained from the thickness, the diameter, and a stress at a first outer circumferential end 10 mm inward from an outer circumferential end in the [11-20] direction from a center thereof.