Silicon Wafer Etching Rate Characteristics with Burst Width Using 150 kHz Band High-Power Burst Inductively Coupled Plasma

Abstract

The high-speed etching of a silicon wafer was experimentally investigated, focusing on the duty factor of 150 kHz band high-power burst inductively coupled plasma. The pulse burst width was varied in the range of 400–1000 µs and the repetition rate was set to 10 Hz. A mixture of argon (Ar) and carbon tetrafluoride (CF4) gas was used as the etching gas and injected into the vacuum chamber. The impedance was changed with time, and the coil voltage and current were changed to follow it. During the discharge, about 3 kW of power was applied. The electron temperature and plasma density were measured by the double probe method. The plasma density in the etching region was 1018–1019 m−3. The target current increased with t burst width. The etching rate of Ar discharge at burst width of 1000 µs was 0.005 µm/min. Adding CF4 into Ar, the etching rate became 0.05 µm/min, which was about 10 times higher. The etching rate increased with burst width.

Time-resolved observation of 150 kHz high-power pulse burst high-frequency discharge using a high-speed video camera and an intensified charge coupled device camera

“…The plasma density was obtained by floating double probe measurements. 28) The probe tip was a cylindrical tungsten electrode (j 0.4) with an exposed length of 3 mm and a tip-to-tip distance of 8 mm. The double probe was inserted from the downstream direction.…”

“…24,25) This method has advantages such as eliminating the impedance matching device, high plasma density of 10 19 to 10 20 m −3 generated by high-power input to the plasmas, and easy process optimization by flexible adjustment of the burst width and duty cycle. Although sputtering and etching applications using combined burst and pulse power sources have been reported, [26][27][28] fundamental reports on plasma characteristics and discharge principles are lacking. In contrast to the steadystate illumination of plasma in a normal 13.56 MHz band ICP, burst-type RF discharges are transient phenomena and have a different discharge principle from that of normal ICP.…”

Fluid models calculation of Ar/CF4 radiofrequency capacitively coupled plasmas

“…They are a current topic for plasma simulation tools [1].The atomic layer etching to produce nanostructures in semiconductor substrates is very important for the micro-and nanoelectronics industry. CF 4 is one of the popular gases that is used in plasma etching [2][3][4][5][6]. The discharge of CF 4 is electronegative; negative ions are produced in the discharge; however, the electronegativity is weak at low pressures [7,8].…”

Editorial for the Special Issue on Recent Advances in Reactive Ion Etching and Applications of High-Aspect-Ratio Microfabrication

“…Different techniques, such as Bosch and STiGer, are compared [ 5 ] and reviewed [ 1 ] in order to provide a wider overview of their new capabilities. New plasma sources such as ICP systems using burst waves are explored to increase the silicon etching rate [ 6 ]. Advanced microsystems that are widely used in integrated optoelectronic devices, energy harvesting components, and microfluidic lab-on-chips require high-aspect silicon microstructures with a precisely controlled profile.…”