Monocrystalline Silicon Wafer Nitrogen Doping for Defect Control
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Solution Overview
Problem
High-performance semiconductor wafers composed of monocrystalline silicon face challenges in minimizing defects such as OSF nuclei and COPs in the region relevant to electronic device integration, while also requiring economical production methods that maintain high yields and control nitrogen concentration to prevent excessive OSF formation.
Innovation Solution
A semiconductor wafer is grown using the CZ method with controlled V/G conditions, incorporating both a Pv region and an OSF region, and doped with oxygen and nitrogen, followed by specific heat treatment to achieve a uniform BMD distribution and low OSF density, ensuring a defect-free 'denuded zone' for electronic devices and high BMD density in the bulk for effective gettering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the single crystal is doped with nitrogen to promote oxygen precipitation and formation of thermally stable oxygen precipitates, then gettering properties are improved, but OSF nuclei formation is intensified and OSF density increases
Solution Approach 1:
The patent creates different nitrogen concentration zones within the semiconductor wafer. The central region has lower nitrogen concentration to minimize OSF nuclei formation, while the peripheral region has higher nitrogen concentration to provide adequate gettering capacity. This spatial differentiation of nitrogen distribution allows simultaneous optimization of both defect reduction and impurity gettering.
Solution Approach 2:
The patent controls the nitrogen concentration parameter within specific ranges (1×10^13 to 1×10^14 atoms/cm³ in the central region, 1×10^14 to 1×10^15 atoms/cm³ in the peripheral region) to achieve the desired balance between gettering properties and OSF suppression. By precisely adjusting these concentration parameters, the patent resolves the contradiction between needing nitrogen for gettering and avoiding excessive nitrogen for OSF prevention.
2Manufacturing precision
If the V/G quotient is increased to create a Pv region with excess vacancies for COP formation, then defect distribution is improved, but OSF nuclei formation is intensified
Solution Approach 1:
The patent creates a specific radial defect distribution pattern where the Pv region (excess vacancies) is confined to the peripheral area, while the central region maintains lower vacancy concentration. This is achieved by controlling the V/G quotient during crystal growth to establish different local conditions in different radial zones, thereby suppressing OSF nuclei in the center while maintaining acceptable defect distribution overall.
Solution Approach 2:
The patent divides the semiconductor wafer into distinct radial zones with different defect characteristics: a central region with lower vacancy concentration and minimal OSF nuclei, and a peripheral region with higher vacancy concentration and acceptable Pv defects. This segmentation allows the system to tolerate defects in non-critical peripheral areas while maintaining high purity in the central device region.
3Reliability
If cooling rate is slowed to allow oxygen accumulation and OSF nuclei formation, then gettering capacity is improved, but OSF density increases
Solution Approach 1:
The patent controls the cooling rate parameter to achieve a balance between oxygen accumulation for gettering and OSF nuclei formation. By maintaining the cooling rate within specific ranges and implementing controlled thermal processing, the patent ensures sufficient oxygen precipitation for gettering capacity while preventing excessive OSF density, particularly in the central region where devices are integrated.
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 results in semiconductor wafers with a surface region free from defects, low OSF density, and high BMD density in the bulk, enhancing gettering properties and enabling high-yield, economical production with a reduced thermal budget.
Implementation Method 1
pulling a single crystal from a melt in accordance with the CZ method
Implementation Method 2
pulling a single crystal from a melt
Implementation Method 3
controlling the oxygen concentration in such a way that the oxygen concentration in the section that is provided for the production of semiconductor wafers is 4.4 to 5.2×10^17 atoms/cm³
Implementation Method 4
heat treatment of the semiconductor wafers composed of monocrystalline silicon at the holding temperature
Implementation Method 5
heat treatment ('anneal') of the semiconductor wafer
Implementation Method 6
BMDs are precipitates of supersaturated oxygen which grow from smaller nuclei as a result of a thermal treatment
Implementation Method 7
BMDs are precipitates of supersaturated oxygen
Implementation Method 8
OSF nuclei arise during the cooling of a silicon single crystal pulled from a melt
Data Source
AI summary
Semiconductor wafers composed of monocrystalline silicon and doped with nitrogen contain an OSF region and a Pv region, wherein the OSF region extends from the center radially toward the edge of the wafer as far as the Pv region; the wafer has an OSF density of less than 10 cm−2, a BMD density in the bulk of at least 3.5×108 cm−3, and a radial distribution of the BMD density with a fluctuation range BMDmax/BMDmin of not more than 3. The wafers are produced by controlling initial nitrogen content and maintaining oxygen within a narrow window, followed by a heat treatment.