Influence of C4F8/Ar-based etching and H2-based remote plasma ashing processes on ultralow k materials modifications

Abstract

Articles you may be interested inMechanistic study of ultralow k -compatible carbon dioxide in situ photoresist ashing processes. I. Process performance and influence on ULK material modification J. Vac. Sci. Technol. B 28, 952 (2010); 10.1116/1.3482343 Numerical simulation of dual frequency etching reactors: Influence of the external process parameters on the plasma characteristics J. Appl. Phys. 98, 023308 (2005); 10.1063/1.1989439 Study of C 4 F 8 / CO and C 4 F 8 / Ar/CO plasmas for highly selective etching of organosilicate glass over Si 3 N 4 and SiCThe authors evaluated photoresist ͑PR͒ stripping processes that are compatible with ultralow dielectric constant ͑ULK͒ materials using H 2 -based remote plasmas generated in an inductively coupled plasma reactor. The materials used were 193 nm PR and nanoporous SiCOH-based ULK ͑JSR LKD 5109͒. PR ashing rates and ULK damage ͑carbon depletion͒ were measured for H 2 , H 2 / N 2 , and H 2 / Ar discharges as a function of substrate temperature over the range of 200-275°C. They employed ellipsometry, x-ray photoelectron spectroscopy ͑XPS͒, optical emission spectroscopy, and time-of-flight secondary ion mass spectroscopy ͑ToF-SIMS͒ for analysis. For their H 2 remote plasmas and a substrate temperature in the range of 200-275°C, the PR ashing rate varied from 270 to 880 nm/min, whereas 3-5 nm of ULK damage was measured for 20 s remote plasma exposure. As a useful process metric, they defined ashing efficiency as the thickness of PR removed over the thickness of ULK simultaneously damaged. PR stripping processes can be optimized to an ashing efficiency of ϳ60 for substrate temperatures above 250°C, if pure H 2 discharges are employed. The addition of N 2 or Ar to H 2 did not improve the ashing rate and, especially for N 2 , such additions dramatically increased ULK damage. This resulted in reduced ashing efficiency for these cases. To clarify the impact of etching/ashing process interactions on ULK modification, they exposed blanket ULK film to C 4 F 8 / Ar-based etching plasmas employing a dual frequency ͑40.68/4 MHz͒ capacitively coupled plasma ͑CCP͒ reactor. Plasma exposures of the ULK were performed utilizing a silicon roof, which shielded the ULK film located underneath from direct ion bombardment. Since the aspect ratio of the small gap structure was selected to be equal to that of an actual trench structure, trench sidewall-like surface modifications induced by etching processes along with their impact on ashing damage that were introduced during a subsequent PR stripping process can be simulated and studied on blanket films with appropriate size. XPS revealed fluorocarbon ͑FC͒ deposition together with ϳ3 nm of ULK damage on the ULK film surface after the FC plasma etching process. Most of the deposited FC material was removed during a subsequent H 2 -based remote plasma treatment at 275°C. The influence of surface modifications introduced by the prior C 4 F 8 / Ar-based etching exposure on hydrogen permeation of the ULK material during a subsequent H 2 remote pla...

Comparison of the effects of downstream H2- and O2-based plasmas on the removal of photoresist, silicon, and silicon nitride

“…1, the ash rate corresponding to the pure-N 2 plasma is zero, suggesting that N atoms alone cannot etch the photoresist in a remote-plasma environment. This is because the N radical density was found to increase continuously with increasing N 2 addition, 18,19 and this behavior is inconsistent with the trend for the photoresist ash rate as a function of N 2 concentration [ Fig. Further addition of N 2 , however, causes [H] to decrease.…”

“…Nagai et al found that the total electron density in the plasma environment increased substantially when a small amount of N 2 was added to H 2 plasma. 19 Regardless of the exact mechanism, the addition of a small amount of N 2 results in the enhanced dissociation of H 2 and, ultimately, gives rise to an increase in [H], which in turn increases the photoresist ash rate. The high electron density in turn enhances the dissociation of the H 2 into H atoms.…”

Ashing of photoresists using dielectric barrier discharge cryoplasmas

“…One is using different plasma gas chemistries to limit the low-j dielectric damage due to photoresist ashing by remote H 2 plasmas 12,13 or different combinations of Ar-and N 2 -containing plasmas. To mitigate these problems, several approaches have been investigated.…”

Analysis of water adsorption in plasma-damaged porous low-k dielectric by controlled-atmosphere infrared spectroscopy

“…[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] Many groups have investigated the mechanisms of porous organosilicate modification during the exposure to fluorocarbon-based, 7,[10][11][12][13][14]16,18,21 oxygenbased, [7][8][9]11,15,17 and hydrogen-based [7][8][9]11,14,15,17 plasmas. 1-6 Porous organosilicate materials (SiCOH) are currently used in the most advanced integrated circuits.…”