High-Ohmic Semiconductor Substrate Stabilization via Deep Level Impurities
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Solution Overview
Problem
The manufacturing of high-ohmic silicon substrates for high-frequency devices is challenging due to the formation of thermal donors from interstitial oxygen, leading to unstable resistivity and poor RF performance, especially in 200 mm production technologies where Czochralski or Magnetic Czochralski wafers have higher oxygen concentrations, causing a significant decrease in quality factor Q.
Innovation Solution
Incorporating acceptor or donor impurity atoms with deep energy levels, such as gold, indium, sulfur, or selenium, into the semiconductor substrate to compensate for thermal donors and maintain high resistivity, using techniques like CZ growing or ion implantation, ensuring at least 50% of the wafer volume is doped with these atoms to stabilize the substrate's resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Czochralski or Magnetic Czochralski wafers are used for 200 mm production technology, then productivity and manufacturing capability are improved, but interstitial oxygen concentration increases causing thermal donor formation and resistivity instability
Solution Approach 1:
The patent converts the harmful effect of thermal donors into a beneficial compensation mechanism by introducing deep level impurities. These impurities preferentially bind with thermal donors, transforming the harmful resistivity-decreasing effect into a controlled compensation process that maintains stable high resistivity. The thermal donors, instead of degrading performance, become part of a balanced doping system where their negative effect is counteracted by the deep level impurities.
Solution Approach 2:
The patent changes the doping parameters by introducing deep level impurities with specific energy levels (at least 120 meV from band edges) and controlled concentrations (1×10^12 to 1×10^17 cm^-3). This parameter change creates a new doping regime where deep level impurities dominate the electrical characteristics, compensating for thermal donor effects and enabling stable high resistivity in CZ/MCZ wafers.
2Manufacturing precision
If high-ohmic silicon substrates are manufactured with conventional doping, then initial high resistivity is achieved, but thermal donors form during processing causing resistivity to decrease and RF performance to deteriorate
Solution Approach 1:
The patent applies preliminary action by introducing deep level impurities into the substrate before thermal processing. This preliminary doping ensures that when thermal donors form during subsequent processing, the deep level impurities are already in position to compensate for them. The compensation mechanism is pre-established, preventing resistivity degradation before it occurs rather than attempting to correct it afterward.
Solution Approach 2:
The patent applies preliminary anti-action by introducing deep level impurities that will counteract the harmful effect of thermal donors before the thermal donors can significantly degrade the resistivity. The deep level impurities act as a preemptive countermeasure, binding with thermal donors as they form and preventing the n-type doping effect that would otherwise occur.
3Stability of the object's composition
If float zone wafers are used to avoid thermal donors, then resistivity stability is improved, but availability for 200 mm production is limited and cost increases
Solution Approach 1:
The patent introduces deep level impurities as an intermediary between the thermal donors and the electrical properties of the substrate. Instead of trying to eliminate thermal donors (as in float zone processing), the deep level impurities act as a mediator that binds with thermal donors and prevents them from exerting their harmful n-type doping effect. This allows the use of readily available CZ/MCZ wafers while achieving resistivity stability comparable to float zone wafers.
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 resistivity of the semiconductor substrate, reducing parasitic substrate influences and maintaining high-frequency performance by effectively compensating thermal donors, thus ensuring reproducible high-ohmic substrates and improved RF device quality factors.
Implementation Method 1
Incorporating acceptor or donor impurity atoms with deep energy levels, such as gold, indium, sulfur, or selenium, into the semiconductor substrate to compensate for thermal donors and maintain high resistivity
Implementation Method 2
using techniques like CZ growing or ion implantation, ensuring at least 50% of the wafer volume is doped with these atoms to stabilize the substrate's resistivity
Data Source
AI summary
The semiconductor substrate includes a high-ohmic semiconductor material with a conduction band edge and a valence band edge, separated by a bandgap, wherein the semiconductor material includes acceptor or donor impurity atoms or crystal defects, whose energy levels are located at least 120 meV from the conduction band edge, as well as from the valence band edge in the bandgap; and wherein the concentration of the impurity atoms or crystal defects is larger than 1×1012 cm−3.