AlN Layer Defect Suppression on Silicon Substrates
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Solution Overview
Problem
The formation of pit-like defects on the surface of AlN layers grown on silicon substrates can lead to unreliable electrode formation and degradation of crystal quality in GaN-based semiconductor layers, affecting the characteristics of high-frequency semiconductor devices like HEMTs.
Innovation Solution
A method involving thermal cleaning of silicon substrates in a hydrogen atmosphere at temperatures between 700° C. and 1060° C. for 5 to 15 minutes, followed by forming a first AlN layer without a nitrogen source and then a second AlN layer with a higher V/III source ratio, to suppress the occurrence of pit-like defects and improve crystal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an AlN layer is formed on a silicon substrate to prevent reaction between Si and Ga, then the barrier function is improved, but pit-like defects occur on the AlN surface
Solution Approach 1:
Thermal cleaning is performed on the silicon substrate surface before forming the AlN layer to remove organic contaminants and oxides. This preliminary treatment prevents pit-like defects from forming during subsequent AlN layer growth, while maintaining the barrier function against Si-Ga reaction.
Solution Approach 2:
The V/III source ratio is optimized during AlN layer formation, and the nitrogen source temperature is controlled within specific ranges (600-1060°C). These parameter changes ensure high-quality AlN layer formation with minimal surface defects while maintaining effective barrier properties.
2Manufacturing precision
If the thermal cleaning temperature is increased to improve surface cleanliness, then the surface quality improves, but excessive cleaning time or temperature causes substrate damage
Solution Approach 1:
The thermal cleaning temperature is precisely controlled within the range of 700-1060°C, and the cleaning time is limited to 5-15 minutes. These optimized parameters achieve thorough surface cleaning and oxide removal without causing substrate damage or excessive silicon evaporation.
3Manufacturing precision
If a high V/III source ratio is used to improve AlN layer quality, then the crystal quality improves, but the formation time increases
Solution Approach 1:
The V/III source ratio is optimized to achieve high crystal quality AlN layers efficiently. By controlling the aluminum and nitrogen source flow rates and temperatures, the patent achieves superior crystal quality without excessive formation time, balancing quality and productivity.
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 effectively reduces the number of pit-like defects and enhances the crystal quality of the AlN layer, thereby improving the fabrication process and transistor characteristics by minimizing crystal degradation and leakage current.
Implementation Method 1
performing thermal cleaning for a surface of a silicon substrate in an atmosphere including hydrogen under a condition that a thermal cleaning temperature is higher than or equal to 700° C. and is lower than or equal to 1060° C.
Implementation Method 2
forming a first AlN layer on the silicon substrate with a first V/III source ratio, the forming of the first AlN layer including supplying an Al source to the surface of the silicon substrate without supplying a N source thereto after the thermal cleaning
Data Source
AI summary
A method for fabricating a semiconductor device includes performing thermal cleaning for a surface of a silicon substrate in an atmosphere including hydrogen under a condition that a thermal cleaning temperature is higher than or equal to 700° C. and is lower than or equal to 1060° C., and a thermal cleaning time is longer than or equal to 5 minutes and is shorter than or equal to 15 minutes; forming a first AlN layer on the substrate with a first V/III source ratio, the forming of the first AlN layer including supplying an Al source to the surface of the substrate without supplying a N source, and supplying both the Al source and the N source; forming a second AlN layer on the first AlN layer with a second V/III source ratio that is greater than the first ratio; and forming a GaN-based semiconductor layer on the second AlN layer.