Damage of ultralow k materials during photoresist mask stripping process

Hua, Xin‐Min; Kuo, Ming-Shu; Oehrlein, G. S.; Lazzeri, P.; Iacob, Erica; Anderle, M.; Inoki, C. K.; Kuan, T. S.; Jiang, Ping; Wu, Wen‐Li

doi:10.1116/1.2194947

Cited by 65 publications

(45 citation statements)

References 24 publications

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“…The modifications to the porous low-k materials lead to increased k-values from densification and hydrophilization. [2][3][4][5] The CO 2 -based plasma has been reported to be less damaging with respect to the O 2 counterpart. Fuller et al proposed the use of CO 2 based RIE plasma for photoresist stripping.…”

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confidence: 99%

Modification of Ultra Low-k Dielectric Films by O₂and CO₂Plasmas

Olawumi

Levrau

Krishtab

et al. 2014

ECS J. Solid State Sci. Technol.

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Low-k materials developed for ULSI interconnects should have sufficient resistance to processing plasma. CO 2 plasma is being considered as a promising candidate for low damage photoresist ash and as a surface activation chemistry for self-assembled monolayers and atomic layer deposition on low-k materials. This article explores the interaction of two organosilicate (OSG) based low-k materials with different k-values (OSG2.4 and OSG2.2) with CO 2 plasma in both CCP and ICP-remote plasma chambers. Time dependent exposure of the materials to CO 2 plasma revealed quick and effective sealing of OSG2.4 surface whereas it takes longer time for OSG2.2. The sealing reduces further plasma damage and leads to accumulation of CO 2 in the pores of both materials. The same behavior occurs in ICP-remote plasma but without a complete sealing of the surface. This suggests the important role of ion bombardment. Damage to low-k by conventional O 2 plasma was studied alongside and it was found that for t < 60 s, O 2 plasma exerts more damage on OSG2.2 than CO 2 . This trend is reversed at t > 60 s. Furthermore, lesser time exposure to CO 2 plasma was investigated with respect to source power at constant pressure and it was discovered that damage although small, increases with varying source power. The performance enhancement of electronic circuits was majorly centered on reducing the transistor sizes, increasing transistor speed and density. However, in advanced technology nodes the performance of the resulting integrated circuits (IC) is greatly hindered by the resistance -capacitance (RC) delay experienced during the signal propagation within the interconnects.1 In order to solve this problem, the traditional Al was replaced by Cu, which has lower resistivity and SiO 2 with k = 4.0 was replaced by low dielectric constants (low-k) materials. Organosilicate glasses (OSG) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) and/or by Spin-on Glass technology (SOG) are presently the most popular low-k materials.Photoresist strip using O 2 based plasma is a conventionally used processing technique but this has been found to be severely damaging to porous low-k materials. The modifications to the porous low-k materials lead to increased k-values from densification and hydrophilization.2-5 The CO 2 -based plasma has been reported to be less damaging with respect to the O 2 counterpart. Fuller et al. proposed the use of CO 2 based RIE plasma for photoresist stripping. Ming-Shu Kuo et al. and Hualiang Shi extensively studied the surface modification of ultralow-k materials by CO 2 plasma and the results are published in their PhD dissertations 7,8 and in several papers. 9-13 They reported that i) CO 2 and O 2 plasma damage to ultralow-k films are comparable ii) there is lower atomic oxygen density in CO 2 discharge than O 2 discharge because of higher activation energy (11.5 eV) required to liberate atomic oxygen from CO 2 than from O 2 molecules (6 eV) -this is why there is supposedly a reduction in damage by CO 2 discharge wi...

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confidence: 99%

Modification of Ultra Low-k Dielectric Films by O₂and CO₂Plasmas

Olawumi

Levrau

Krishtab

et al. 2014

ECS J. Solid State Sci. Technol.

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“…Plasma treatment is most frequently used [4][5][6][7][8][9][10][11][12]. For instance, it was reported in [11,12] that plasma treatment causes pore closing, which results in a decrease in the reactivity of the layers.…”

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confidence: 98%

Effect of preliminary VUV irradiation on the reactivity of alkyl-doped silicon dioxide layers

Dultsev

Sitnikov

2010

Surface and Coatings Technology

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“…This increase in the wall density is probably due to a depletion of carbon in the material. 12 Interestingly, the porosity of the second layer remains unchanged ͑if anything slightly higher͒, while wall density of the second layer increases approximately 24% relative to that of the third layer. Therefore, the most significant factor affecting the increased film density during the plasma treatment should be the densification of wall material; the pore collapse appears to be a secondary effect here.…”

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confidence: 95%