The single crystal silicon growth furnace is a key equipment for producing single crystal silicon. The temperature field control accuracy has a vital impact on the quality of silicon crystals. Among them, oxygen content and dislocation density are important indicators for measuring the quality of silicon crystals. Understanding the quantitative relationship between temperature field control accuracy and them is of great significance for improving the production quality and performance of single crystal silicon.
During the growth of single crystal silicon, the temperature field control accuracy directly affects the interaction between silicon melt and quartz crucible. When the temperature field control accuracy is high, the temperature distribution of silicon melt is uniform, the reaction rate with the quartz crucible is relatively stable, and the amount of oxygen dissolved from the quartz crucible into the silicon melt is also relatively stable. Generally speaking, when the temperature field control accuracy is within ±0.1℃, the oxygen content in the silicon crystal can be controlled within the range of 10^17 - 10^18 atoms/cm³. However, if the temperature field control accuracy decreases, for example, the fluctuation reaches ±1℃, the temperature change at the interface between the silicon melt and the quartz crucible will cause the reaction rate to change, and the amount of oxygen dissolved may increase by 20% - 50%, causing the oxygen content in the silicon crystal to increase to 10^18 - 0^19 atoms/cm³.
The change in oxygen content will have many effects on the performance of silicon crystals. The right amount of oxygen can enhance the mechanical strength of silicon crystals, but too high an oxygen content will cause the silicon crystal to form oxygen precipitation during the subsequent heat treatment process, which will affect the electrical properties of the silicon wafer. For example, when the oxygen content exceeds 10^18 atoms/cm³, the minority carrier lifetime of the silicon wafer may decrease by 20% - 50%, which is extremely unfavorable for the performance and reliability of semiconductor devices.
The temperature field control accuracy also has a significant effect on the dislocation density of silicon crystals. Accurate temperature field control can keep a relatively uniform temperature gradient in the growth process of silicon crystals, and the crystal growth interface is flat, thereby reducing the generation of dislocations. Studies have shown that when the temperature field control accuracy reaches ±0.05℃, the dislocation density of silicon crystals can be controlled within 10² - 10³ cm⁻². On the contrary, if the temperature field control accuracy is poor and the temperature gradient fluctuates greatly, the crystal growth interface will be unstable, resulting in greater thermal stress, which will in turn promote the formation and proliferation of dislocations. When the temperature field fluctuation reaches ±0.5℃, the dislocation density may increase by an order of magnitude to 10³ - 10⁴ cm⁻².
The increase in dislocation density will seriously reduce the quality and performance of silicon crystals. Dislocations will scatter carriers, increase resistivity, and reduce electron mobility, thereby affecting the switching speed and signal transmission efficiency of semiconductor devices. In addition, dislocations may also become the center of impurity aggregation, further affecting the electrical uniformity of silicon crystals. In areas with high dislocation density, the breakdown voltage of silicon wafers may be reduced by 10% - 30%, which is a serious problem for the manufacture of high-voltage, high-power devices.
In order to improve the temperature field control accuracy and thus reduce the oxygen content and dislocation density of silicon crystals, a series of optimization measures need to be taken. First, the use of high-precision temperature sensors and advanced temperature control algorithms, such as PID control algorithm combined with fuzzy control algorithm, can achieve precise control of the temperature field. Secondly, optimize the thermal field structure of the growth furnace, use efficient insulation materials and reasonable heater layout to reduce heat loss and temperature non-uniformity. In addition, regular maintenance and calibration of the single crystal silicon growth furnace to ensure the stability and accuracy of the equipment is also an important part of improving the accuracy of temperature field control.
The temperature field control accuracy of the single crystal silicon growth furnace has an important quantitative influence on the oxygen content and dislocation density of silicon crystals. Accurate temperature field control can effectively reduce the oxygen content and dislocation density, and improve the quality and performance of silicon crystals. By taking a series of optimization measures, continuously improving the accuracy of temperature field control is the key to producing high-quality single crystal silicon, which is of great significance to promoting the development of the semiconductor industry.
