Epitaxial Silicon Base Body Oxygen Profiling for Breakdown Voltage
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Solution Overview
Problem
Existing semiconductor manufacturing methods using the Czochralski method result in oxygen in silicon substrates becoming thermal donors, leading to conductivity inversion from p-type to n-type and increased specific resistance, which decreases breakdown voltage in high-voltage power ICs.
Innovation Solution
A semiconductor device with a semiconductor base body having a thickness of 200 to 400 micrometers and an epitaxial growth layer, where oxygen is outwardly diffused and transformed into a donor through controlled thermal treatments, maintaining a peak concentration below 1×10^18 atoms/cm^3 to prevent conductivity inversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxygen in silicon substrate is activated by annealing treatment at 350-500°C, then oxygen is turned into a donor, but conductivity inverts from p-type to n-type in deep regions and specific resistance increases, causing breakdown voltage to decrease
Solution Approach 1:
The patent applies preliminary action by performing outward diffusion of oxygen at high temperature (900-1200°C) before the annealing treatment that converts oxygen to donors. This pre-diffusion reduces the peak oxygen concentration in the depth direction to 1×10^18 atoms/cm³ or less, ensuring that subsequent donor conversion does not cause harmful conductivity inversion or breakdown voltage decrease. The high-temperature diffusion treatment is performed in advance to create a safe oxygen distribution profile.
2Quantity of substance
If oxygen concentration in silicon substrate is increased, then more donors can be formed, but breakdown voltage decreases due to conductivity inversion in deep regions
Solution Approach 1:
The patent applies parameter changes by controlling the peak oxygen concentration in the depth direction to be 1×10^18 atoms/cm³ or less through high-temperature outward diffusion treatment. This parameter control allows the silicon substrate to maintain its p-type conductivity and achieve the required breakdown voltage of 600V or more, while still containing sufficient oxygen for donor formation. The oxygen concentration parameter is precisely managed to balance donor formation needs with breakdown voltage requirements.
3Reliability
If thermal treatment is applied to activate oxygen, then oxygen turns into donors, but oxygen outwardly diffuses from surface regions causing concentration decrease near surfaces
Solution Approach 1:
The patent applies preliminary action by performing outward diffusion at high temperature (900-1200°C) before the annealing treatment. This sequence ensures that oxygen is first redistributed to achieve a safe peak concentration in the depth direction, and only then is the annealing treatment applied to convert oxygen to donors. This preliminary diffusion step prevents excessive oxygen accumulation in deep regions while maintaining sufficient oxygen for donor formation.
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
The method effectively suppresses conductivity inversion and specific resistance increase, maintaining stable breakdown voltage in high-voltage power ICs by managing oxygen distribution and concentration.
Implementation Method 1
decreasing a peak concentration of oxygen in the semiconductor base body by outwardly difussing the oxygen toward a top surface and a bottom surface of the semiconductor base body by first thermal treatment
Implementation Method 2
turning the oxygen in the silicon substrate to a donor by second thermal treatment
Data Source
AI summary
A semiconductor device includes a semiconductor base body having: a semiconductor substrate of a first conductivity-type; and an epitaxial growth layer of the first conductivity-type provided on the semiconductor substrate, wherein the semiconductor base body has a thickness of 200 micrometers or greater and 400 micrometers or less, and a position of a peak concentration of oxygen in the semiconductor base body is located in a depth of 50 micrometers or greater and 250 micrometers or less from a top surface of the semiconductor base body.