Interactions of chlorine plasmas with silicon chloride-coated reactor walls during and after silicon etching

Abstract

Mass and Auger electron spectroscopy studies of the interactions of atomic and molecular chlorine on a plasma reactor wallHigh temperature reaction of nitric oxide with Si surfaces: Formation of Si nanopillars through nitride masking and oxygen etching Modification of a high vacuum, crossed molecular beam scattering system to perform angle-resolved, gassurface scattering studies under ultrahigh vacuum conditions Rev.The interplay between chlorine inductively coupled plasmas (ICP) and reactor walls coated with silicon etching products has been studied in situ by Auger electron spectroscopy and line-of-sight mass spectrometry using the spinning wall method. A bare silicon wafer mounted on a radio frequency powered electrode (À108 V dc self-bias) was etched in a 13.56 MHz, 400 W ICP. Etching products, along with some oxygen due to erosion of the discharge tube, deposit a Si-oxychloride layer on the plasma reactor walls, including the rotating substrate surface. Without Si-substrate bias, the layer that was previously deposited on the walls with Si-substrate bias reacts with Cl-atoms in the chlorine plasma, forming products that desorb, fragment in the plasma, stick on the spinning wall and sometimes react, and then desorb and are detected by the mass spectrometer. In addition to mass-to-charge (m/e) signals at 63, 98, 133, and 168, corresponding to SiCl x (x ¼ 1 -4), many Si-oxychloride fragments with m/e ¼ 107, 177, 196, 212, 231, 247, 275, 291, 294, 307, 329, 345, 361, and 392 were also observed from what appear to be major products desorbing from the spinning wall. It is shown that the evolution of etching products is a complex "recycling" process in which these species deposit and desorb from the walls many times, and repeatedly fragment in the plasma before being detected by the mass spectrometer. SiCl 3 sticks on the walls and appears to desorb for at least milliseconds after exposure to the chlorine plasma. Notably absent are signals at m/e ¼ 70 and 72, indicating little or no Langmuir-Hinshelwood recombination of Cl on this surface, in contrast to previous studies done in the absence of Si etching.

Plasma etching: Yesterday, today, and tomorrow

“…It is much better to detect these species directly by UV absorption spectroscopy 120 or mass spectrometry. 121,122 Weak emission from Cl þ in the UV and visible regions is also observed in high-density Cl 2 plasma emission spectra, as shown in the expanded spectrum in Fig. 11 (blue, upper trace).…”

“…Another approach, called the "spinning wall" method inserts a cylindrical substrate into the reactor wall. 109,121,122,[140][141][142][143][144][145][146] Part of the cylinder is in the plasma while another section is in a differentially pumped chamber with a mass spectrometer and Auger electron spectrometer (AES) facing the surface. By rapidly rotating the substrate, portions of the surface that were in the plasma as little as 1 ms ago can be diagnosed.…”

“…449 While pulsed gas valves and fast switching mass flow controllers have improved in recent years, the cycle time is too low for this process to be widely applicable. Even with very fast, stable flow switching, the sticky halogen compounds [etching products 121,122 and even Cl 2 (Ref. 143)] demand long purging times.…”

Influence of the carrier wafer during GaN etching in Cl2 plasma

“…In literature, it has been observed a higher selectivity for GaN:SiO 2 (mask) than for GaN:photoresist (mask) [46][47][48] . respectively 49 . This confirms the production of SiCl etch byproducts during the Si etching in Cl 2 plasma.…”

Resolving critical dimension drift over time in plasma etching through virtual metrology based wafer-to-wafer control

“…It is reported that these phenomena come from plasma to wall environment interaction. [1][2][3][4][5][6][7][8][9][10][11][12] Plasma to wall environment interaction is affected by chamber wall conditioning, 1) recombination characteristics of etchant toward chamber wall material, [2][3][4][5] degassing of etch by-products on chamber wall, 6,7) secondary electron emission change, 8) and so on. In order to maintain constant chamber wall environment, in-situ plasma cleaning after etching has been developed.…”