Etch rate control in a 27 MHz reactive ion etching system for ultralarge scale integrated circuit processing

Abstract

Plasma enhanced chemical vapor deposition Si-rich silicon oxynitride films for advanced self-aligned contact oxide etching in sub-0.25 μm ultralarge scale integration technology and beyond Fully large-scale integration-process-compatible Si field emitter technology with high controllability of emitter height and sharpness J. Vac. Sci. Technol. B 15, 488 (1997); 10.1116/1.589605 Pattern profile control of polysilicon in magnetron reactive ion etching J. Vac. Sci. Technol. B 15, 221 (1997); 10.1116/1.589268 Effect of plasma polymerization film on reducing damage of reactive ion etched silicon substrates with CHF3+O2 plasmas J.The etch rates of SiO 2 , photoresist, Si, and SiN in a 27 MHz reactive ion etching system at constant ion flux of 6ϫ10 16 cm Ϫ2 s Ϫ1 and ion energy of 1450 V were studied. Typical incident flux densities of CF 2 and CF ϩ were on the order of 10 17 and 10 16 cm Ϫ2 s Ϫ1 , respectively. The SiO 2 etch rate was determined by the balance of the energy supplied by the total ion flux and the amount of the C-F reactive species supplied by radicals and ions. When we roughly assumed the surface reaction probabilities of F, CF, CF 2 and CF 3 to be 0.1, 0.1, 0.1, and 0.5, the SiO 2 etch rate could be expressed well as a function of the total number of F in the net radical fluxes. To clarify the dominant flux including radicals and ions, however, further research on surface reaction probabilities on the actual etched surface must be conducted because the incident fluxes strongly depend on these constants of the surface reaction probability. Lowering the total ion flux or ion energy decreased the etch rate of SiO 2 . A higher ion flux or higher ion energy is required to obtain higher etch yields. When excess C-F reactive species exist on the etched surface, they disturb the etching reaction by wasting the energy of incident ions. Under these conditions, a reactive species is no longer an ''etchant,'' but an ''inhibitor.'' Therefore, it is important to control the amount of total reactive species according to the ion conditions. Oxygen contributed to the removal of these excess C-F species, resulting in a higher etch yield. In contrast, the etch rates of a photoresist, Si, and SiN did not depend on flux of the C-F reactive species, but on the oxygen concentration. It is concluded that a process with high selectivity requires low oxygen concentration, high ion flux, and optimized flux of C-F reactive species.

Mechanism for difference in etched depth between isolated and dense via holes of SiOCH film

“…The role of additional O 2 in SiO 2 etching [24][25][26][27][28][29] and SiOCH etching 29 associated with fluorocarbon radicals was reported. The etching mechanism of SiOCH is similar to that of SiO 2 .…”

Plasma-etching profile model for SiO/sub 2/ contact holes

“…As a result, CF radicals can be viewed as the etching neutrals and CHF radicals play the role of the deposition neutrals. On the other hand, when CF radicals are excessive in the etching surface, they can waste the incident-ion energy and cause the deposition of the polymer [8], [10].…”

“…The dominant ion is CF in the CF plasma, but the relative abundance of CF , CF , or CF depends on pressure and magnetic field [7]. Various radicals are present: CF , 1-3, C H F (high-molecular-weight radicals), etc., but the CF radical has been reported as the dominant species in the fluorocarbon plasmas by many authors [8], [9]. The Ar gas dilutes the radical densities.…”

“…The thickness of the fluorocarbon polymer layer is an important factor governing the etch rate and the etching profile. In an etching mode, a SiO F layer less than 1-nm thick is present above the SiO substrate surface since the CF ( 1-3) radicals attached to the etching surface react with SiO surface with the assistance of ion bombardment [4], [5], [8]. However, depending on the surface chemical reactions and ion-bombarding energy, a polymer layer can develop on the SiO surface, which contains CF ( 1-3) bonds [13].…”

Study of Surface Reaction and Gas Phase Chemistries in High Density C4F8/O2/Ar and C4F8/O2/Ar/CH2F2Plasma for Contact Hole Etching

“…This deposit enhances the etching selectivity of oxide over silicon or nitride. However, in the patterning of high-aspect-ratio contact holes or self-aligned contacts, these plasmas have serious problems related to the low selectivity of the underlying or mask material, the micro-loading effect, and the etch stop interrupting the etching [1].…”