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The potential application of germanium in integrated circuits and its etching method (I)

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29 Mar,2021

The potential application of germanium in integrated circuits and its etching method (I) :
Using germanium instead of silicon seems like an ironic twist. The transistor invented at Bell Labs in 1947 was made from plates of germanium, the element below silicon in the periodic table. Germanium was chosen because current flows through it quickly, a characteristic of transistors. But when engineers considered making integrated circuits on a large scale, germanium was ignored because silicon was easier to handle. Now, as manufacturers face the problem of silicon not being able to be miniaturized any further, germanium is being used again. The germanium circuits demonstrated by Professor Peide Ye of Purdue University and his colleagues suggest that germanium materials will be commercialized in the coming years. The tiny transistors currently made are just 14nm in diameter and are extremely tightly packed together. Further reduction in the size of transistors would pose a serious challenge to the semiconductor industry.

CRF plasma etching
During a panel session at the Electronics Devices Conference 2016, Intel researcher Mark Bohr said that it will be impossible to shrink silicon transistors any further in 10 years. "I'm usually more interested in new ideas," says Bohr. Germanium has good electrical properties, so the circuit speed is always better than silicon. However, engineers cannot use germanium to make compact but energy-efficient circuits based on the current production technology used in the industry, called complementary metal oxide semiconductor (CMOS) or complementary gold oxide semiconductor. The circuit made of complementary AO semiconductor adopts the transistor which transmits negative charge at the same time, namely the negative electric field effect transistor. Transistors that transmit positive charges, known as positive field effect transistors, "but germanium transistor technology with negative field effect is hitting a bottleneck". Ye Peide proposed a new design of germanium transistor with negative electric field effect to improve its performance significantly. Saraswat was instrumental in bringing germanium back into the spotlight.


In 2002, he published a paper showing that germanium transistors were two to three times as high as silicon transistors. "We have done the basic science work and now we are focusing on the basic engineering," Saraswat said. Other materials available, such as carbon nanotubes or multielement composite semiconductors, are promising to replace silicon, but they are used in more complex ways that make them difficult to use in the chip industry. Chip makers, by contrast, have used germanium for positive field effect silicon transistors.

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