Annealed Silicon Wafer Defect Control
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Solution Overview
Problem
Existing methods for manufacturing annealed silicon wafers face challenges with residual voids and deteriorated Time Dependent Dielectric Breakdown (TDDB) characteristics due to narrow nitrogen concentration ranges, leading to reduced crystal yield and increased manufacturing costs.
Innovation Solution
A method involving the Czochralski growth of silicon single crystals with controlled nitrogen, carbon, and hydrogen concentrations, along with specific temperature and hydrogen partial pressure conditions, to expand the applicable nitrogen concentration range and suppress defect occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If nitrogen concentration is increased to eliminate void defects and improve surface quality, then void defects are reduced, but TDDB characteristics of oxide film deteriorate
Solution Approach 1:
The patent changes the concentration parameters of multiple elements (nitrogen, carbon, hydrogen) simultaneously rather than adjusting nitrogen alone. By controlling nitrogen at 1×10^15 to 5×10^15 atoms/cm³, carbon at 1×10^16 to 1×10^17 atoms/cm³, and hydrogen at 1×10^17 to 1×10^18 atoms/cm³, the patent achieves both void defect elimination and TDDB characteristic maintenance through multi-parameter optimization
Solution Approach 2:
The patent creates a composite doping strategy by combining nitrogen, carbon, and hydrogen in specific concentration ratios. This composite approach allows the elements to work synergistically: nitrogen eliminates voids, while carbon and hydrogen prevent oxide film deterioration, achieving what single-element doping cannot accomplish
2Reliability
If nitrogen concentration is decreased to maintain TDDB characteristics, then oxide film quality is preserved, but residual voids remain in the wafer surface
Solution Approach 1:
The patent adjusts nitrogen concentration to a moderate range (1×10^15 to 5×10^15 atoms/cm³) rather than using high concentrations, and compensates by introducing carbon and hydrogen at controlled levels. This parameter redistribution maintains TDDB characteristics while preventing void defects through the combined effect of all three elements
Solution Approach 2:
Carbon and hydrogen act as intermediary elements that mediate between nitrogen's void-eliminating effect and the need to preserve TDDB characteristics. These intermediaries allow the system to achieve both goals by buffering the impact of nitrogen doping
3Reliability
If nitrogen concentration range is restricted to avoid defects, then oxide film quality is maintained, but crystal yield and operational flexibility are reduced
Solution Approach 1:
The patent expands the acceptable nitrogen concentration range by introducing carbon and hydrogen as controlling parameters. This multi-parameter approach allows broader nitrogen doping ranges to be tolerated while maintaining oxide film quality, thereby increasing crystal yield and operational flexibility
Solution Approach 2:
Hydrogen creates a protective atmospheric environment during crystal growth that suppresses unwanted chemical reactions and defect formation. This inert-like environment allows broader doping ranges to be explored without compromising oxide film quality
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 reduces residual voids and improves TDDB characteristics, allowing for a wider nitrogen concentration range, increased operational flexibility, and lower manufacturing costs by controlling carbon concentration and hydrogen partial pressure.
Implementation Method 1
growing a silicon single crystal to which nitrogen, carbon, and hydrogen are added, by Czochralski method
Implementation Method 2
subjecting the silicon single crystal wafer to heat treatment at a high temperature of, for example, not less than 1100°C
Implementation Method 3
Annealed wafers obtained by subjecting silicon single crystal wafers to heat treatment at a high temperature
Data Source
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AI summary
Method of Manufacturing Annealed Wafer To provide a method of manufacturing an annealed wafer capable of avoiding residual voids after annealing and deterioration of TDDB characteristics of an oxide film formed on the annealed wafer, and extending the range of nitrogen concentration that can be contained in a silicon single crystal. In a method of manufacturing an annealed wafer, crystal pulling conditions are controlled such that a ratio V/G between a crystal pulling rate V and an average temperature gradient G in a crystal growth axis direction is not less than 0.9x(V/G)crit and not more than 2.5x(V/G)crit, and a hydrogen partial pressure within a crystal pulling furnace is set to not less than 3 Pa and less than 40 Pa. A silicon single crystal has a nitrogen concentration of more than 5x1014 atoms/cm3 and not more than 6x1015 atoms/cm3, and a carbon concentration of not less than 1x1015 atoms/cm3 and not more than 9x1015 atoms/cm3, and heat treatment is performed in a noble gas atmosphere having an impurity concentration of not more than 5 ppma, or in a non-oxidizing atmosphere.