Smartphones, cloud computing, Internet of Things and other technologies and the development of self-driving cars continue to drive the demand for semiconductor materials. In order to meet the higher performance of semiconductor devices and improve the quality of devices, it is necessary to control the pollution of silicon wafers during the production process.
The pollution route may come from water, air, equipment, various chemical reagents and pollution caused by human processing. In order to reduce pollution, there are generally higher requirements for the environment, water, equipment, chemical reagents and human operations.
The meaning of the word trace has changed with the development of trace analysis technology. Trace analysis includes the determination of the total concentration of trace elements in the sample, and the use of probe technology to determine the distribution of trace elements in the sample or on the surface of the sample.
Since the content of the measured element in the sample is very low or the distribution is very uneven, it often fluctuates greatly with time and space, so it is necessary to pay full attention to the representativeness of sampling and ensure a certain sample amount.
Reagents used in the semiconductor industry are generally “electronic grade reagents”, “ultra-clean high-purity chemical reagents”, etc., that is, wet electronic chemicals. The purity of its main components is greater than 99.99%, and the number of impurity ions and particles meets strict requirements. Reagents, in which the content of impurity ions is controlled at the ppb or even ppt level, so the selection of instruments for testing trace substances is very important.
Trace analysis is generally divided into three basic steps: sampling, sample preparation and determination. The purpose of the pretreatment is to transform the trace components into the most suitable form for final measurement; for some materials with better solubility, they can be directly measured after being diluted with water or other solvents; In order to enhance the detection ability of trace components and remove the basic interference, the separation and enrichment of trace components is often essential. Generally, there are two schemes:
1) Separate the main components from the sample, leaving the trace components in solution;
2) Separation of trace components leaving the main components in solution.
Common separation and enrichment methods include volatilization, precipitation and co-precipitation, electrolysis, liquid-liquid extraction, ion exchange chromatography, extraction chromatography, electrophoresis, etc. In the process of separation and enrichment, full attention should be paid to the loss of pollution and trace components.