Epitaxial Layer Resistivity Control in Trench Structures
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Solution Overview
Problem
Conventional semiconductor wafer manufacturing methods face issues with resistivity changes in epitaxial layers due to auto-doping, slow growth rates, poor throughput, and deteriorated trench filling properties, especially when growing epitaxial layers at constant high temperatures.
Innovation Solution
A method involving gradual temperature reduction during vapor growth, forming multiple layers at different temperatures to control impurity diffusion and improve trench filling, while removing native oxide or organic matter to stabilize and homogenize the epitaxial layer growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If epitaxial growth is carried out at high temperature to improve growth rate, then productivity is improved, but auto-doping from the semiconductor substrate increases and resistivity control deteriorates
Solution Approach 1:
The epitaxial growth process is divided into multiple stages with different temperature profiles. The growth is performed in steps: initially at higher temperature to achieve adequate growth rate, then temperature is reduced during subsequent growth stages to suppress auto-doping. This segmentation allows simultaneous achievement of productivity and resistivity control.
Solution Approach 2:
The growth temperature is made dynamic rather than constant. The temperature is adjusted during the epitaxial growth process - starting at higher temperatures for rapid growth and then reducing temperature to control impurity diffusion. This dynamic temperature control resolves the contradiction between growth rate and resistivity control.
2Ease of manufacture
If constant temperature growth is used to simplify the process, then ease of manufacture is improved, but resistivity uniformity and trench filling properties deteriorate
Solution Approach 1:
The temperature profile is changed from static (constant) to dynamic (time-dependent). By implementing a temperature profile that varies during growth, the process achieves better resistivity uniformity and trench filling while maintaining reasonable manufacturing complexity through automated temperature control.
3Manufacturing precision
If high temperature growth is used to fill trenches effectively, then trench filling is improved initially, but as growth progresses the trench width narrows and filling becomes harder
Solution Approach 1:
The growth temperature is dynamically adjusted based on growth progress. Higher temperatures are used initially when trench width is larger to maintain good filling properties, then temperature is reduced as growth progresses to prevent excessive narrowing and maintain filling efficiency throughout the process.
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 allows for stepwise resistivity control of epitaxial layers, reduces auto-doping effects, enhances growth efficiency, and improves trench filling properties, resulting in semiconductor wafers with desired electrical characteristics and reduced void formation.
Implementation Method 1
an epitaxial layer is grown on a surface of a semiconductor wafer and in a trench by gradually reducing a temperature in a temperature range of 400 to 1150° C. based on a vapor growth method
Implementation Method 2
a quantity of an impurity diffused in the epitaxial layer from the semiconductor wafer is reduced in a stepwise manner
Data Source
AI summary
A resistivity of an epitaxial layer in a trench is changed in a stepwise manner by reducing a quantity of an impurity diffused into the epitaxial layer in the trench from a semiconductor wafer in a stepwise manner, thereby suppressing an influence of auto-doping from the semiconductor wafer.An epitaxial layer 17 is grown in a trench 16 of a semiconductor wafer 10 having a trench structure by gradually reducing a temperature in a temperature in the range of 400 to 1150° C. by a vapor growth method while supplying a silane gas as a raw material gas, thereby filling the epitaxial layer 17 in the trench 16.