Vacancy-Oxygen Complexes Stabilize Silicon Wafer Resistivity
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Solution Overview
Problem
High-ohmic silicon wafers used in semiconductor devices face instability due to the formation of thermal donors during processing, which alters resistivity and affects the performance of RF devices and power semiconductors, particularly in larger diameters where FZ-wafers are scarce and expensive.
Innovation Solution
The formation of vacancy-oxygen complexes, such as VO2 centers, in the wafer substrate through electron or proton irradiation and subsequent annealing, which reduces interstitial oxygen concentration and prevents thermal donor formation, maintaining high-ohmic resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional high-ohmic silicon wafers are used in semiconductor processing, then the substrate provides necessary electrical resistance, but thermal donors form during processing which alters resistivity and destabilizes device performance
Solution Approach 1:
The patent applies preliminary action by forming vacancy-oxygen complexes (VO2 centers) in the silicon substrate before device fabrication begins. This pre-treatment stabilizes the interstitial oxygen concentration and prevents thermal donor formation during subsequent processing steps, thereby maintaining consistent high-ohmic resistivity throughout manufacturing
Solution Approach 2:
The patent changes the physical-chemical parameters of the silicon substrate by introducing controlled vacancy-oxygen complexes. This modifies the oxygen distribution and binding states in the crystal lattice, transforming the substrate from an unstable state (prone to thermal donor formation) to a stable high-ohmic state with predictable resistivity
2Reliability
If FZ-wafers are used to avoid thermal donors, then resistivity stability improves, but availability decreases and cost increases for larger diameter wafers
Solution Approach 1:
The patent employs a cost-effective approach by treating conventional Czochralski (CZ) wafers with a relatively simple pre-processing step (forming vacancy-oxygen complexes) to achieve FZ-wafer-like stability. This avoids the need for expensive and scarce FZ-wafers, making high-reliability substrates accessible for large-diameter wafers used in modern semiconductor manufacturing
3Reliability
If electron or proton irradiation is applied to form vacancy-oxygen complexes, then thermal donor formation is prevented, but additional processing steps are required
Solution Approach 1:
The patent utilizes parameter changes by applying controlled electron or proton irradiation to transform the oxygen distribution in the silicon lattice. This creates vacancy-oxygen complexes that act as oxygen sinks, preventing thermal donor formation. The irradiation parameters (energy, dose) are optimized to achieve the desired effect with minimal additional processing
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 stabilizes the high-ohmic substrate, enhancing RF device performance by reducing temperature-dependent resistivity fluctuations and increasing blocking capability in power semiconductors, while avoiding the limitations of conventional methods.
Implementation Method 1
The formation of vacancy-oxygen complexes, such as VO2 centers, in the wafer substrate through electron or proton irradiation
Implementation Method 2
The formation of vacancy-oxygen complexes, such as VO2 centers, in the wafer substrate through electron or proton irradiation
Implementation Method 3
subsequent annealing, which reduces interstitial oxygen concentration and prevents thermal donor formation
Data Source
AI summary
A wafer includes a wafer frontside and a region adjacent to the device surface, wherein the region includes vacancy-oxygen complexes and the wafer frontside includes a predetermined surface structure to form thereon a device with a desired property.