Semiconductor Wafer Oxygen Profiling for Stable Withstand Voltage
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Solution Overview
Problem
The instability of the impurity profile in the donor layer due to oxygen diffusion during the manufacturing process of semiconductor devices leads to unstable withstand voltage and switching characteristics, affecting the performance of semiconductor devices like IGBTs and diodes.
Innovation Solution
The semiconductor device is designed with a specific relationship between the maximum oxygen concentration and impurity concentration in the drift layer, ensuring that maximum [Oi]=9.40×1016×ln(Cdrift)−2.27×1018 is satisfied, stabilizing the impurity profile and preventing thermal donor phenomena.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment is performed in an atmosphere containing oxygen or after a thermal oxide film is formed, then the semiconductor substrate undergoes oxygen diffusion, but the oxygen concentration decreases in the depth direction causing unstable impurity profile in the donor layer
Solution Approach 1:
The patent applies preliminary anti-action by controlling the oxygen concentration in the drift layer before the heat treatment process. By pre-establishing a specific oxygen concentration range (5×10^16 to 2×10^17 atoms/cm³) in the drift layer through the conversion factor method, the patent prevents the thermal donor phenomenon from occurring during subsequent heat treatment, thereby counteracting the harmful effect of oxygen diffusion on the donor layer impurity profile.
Solution Approach 2:
The patent employs parameter changes by precisely controlling the oxygen concentration parameter in the drift layer. By converting the oxygen concentration measured by FTIR to the equivalent phosphorus impurity concentration using a specific conversion factor, and then adjusting this parameter to fall within a predetermined range, the patent stabilizes the impurity profile of the donor layer during heat treatment processes.
2Manufacturing precision
If the oxygen concentration in the semiconductor substrate is high, then the thermal donor phenomenon occurs causing increased impurity concentration in the donor layer, but the withstand voltage characteristic becomes unstable
Solution Approach 1:
The patent applies parameter changes by establishing a specific relationship between oxygen concentration and impurity concentration. By controlling the oxygen concentration in the drift layer to correspond to a phosphorus impurity concentration of 5×10^16 to 2×10^17 atoms/cm³ (using the conversion factor), the patent prevents excessive thermal donor formation while maintaining stable withstand voltage characteristics.
Solution Approach 2:
The patent implements feedback by using FTIR measurement to detect the oxygen concentration in the drift layer, converting this measurement to an equivalent impurity concentration using a predetermined conversion factor, and then adjusting the oxygen concentration based on this feedback to achieve the target range, thereby stabilizing both manufacturing precision and reliability.
3Strength
If the impurity concentration of the drift layer is increased to improve withstand voltage, then the oxygen diffusion effect is amplified causing greater instability in the donor layer impurity profile
Solution Approach 1:
The patent applies parameter changes by establishing a proportional relationship between drift layer impurity concentration and oxygen concentration. By controlling the oxygen concentration to correspond to a specific phosphorus impurity concentration range in the drift layer, the patent maintains stable donor layer impurity profiles even when the drift layer impurity concentration is increased for higher withstand voltage applications.
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 configuration stabilizes the withstand voltage and switching characteristics, enhancing the electrostatic breakdown voltage, time-zero dielectric breakdown, and operational reliability of IGBTs and diodes, improving their performance under various operating conditions.
Implementation Method 1
heat treatment in an atmosphere containing oxygen or heat treatment after a thermal oxide film is formed forms a profile in which an oxygen concentration decreases in a depth direction of the semiconductor wafer because oxygen is diffused into the semiconductor wafer
Implementation Method 2
heat treatment after a thermal oxide film is formed
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, a first electrode, and a second electrode. The semiconductor substrate includes a drift layer, a semiconductor layer, a first buffer layer, and a second buffer layer. When a maximum value of an oxygen concentration of the semiconductor substrate calculated using a conversion factor of Old ASTM is maximum [Oi] and an impurity concentration of a first conductive type of the drift layer is Cdrift, maximum [Oi]=9.40×1016×ln(Cdrift)−2.27×1018 is satisfied.