Effect of material properties on integration damage in organosilicate glass films
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Kurt Junker Motorola, APRDL, 3501 Ed Bluestein Boulevard, Austin, Texas 78721
Jeff Wetzel International SEMATECH, 2706 Montopolis Drive, Austin, Texas 78757
David W. Gidley and Jianing Sun Department of Physics, University of Michigan, Ann Arbor, Michigan 48109
Most organosilicate glass1 (OSG), low dielectric constant (low-) films contain Si–R groups, where R is an organic moiety such as –CH3. The organic component is susceptible to the chemically reactive plasmas used to deposit cap layers, etch patterns, and ash photoresist. This study compares a spin-on, mesoporous OSG film with a completely connected pore structure to both its nonmesoporous counterpart and to another low-density OSG film deposited by plasma-enhanced chemical vapor deposition. The results show that the film with connected pores was much more susceptible to integration damage than were the nonmesoporous OSG films. As integrated circuit device and interconnect dimensions continue to scale smaller, low dielectric constant () interlayer dielectric (ILD) materials will become necessary to mitigate RC (product of resistance and capacitance) propagation delay and reduce power consumption and crosstalk.1 Lowering the -value of a material requires either altering the chemical bonding to reduce the bond polarizability or decreasing the number of bonds (density) in a material.2 To reduce the -value below 2.2, most dielectric materials will require a density decrease by introducing free volume (micropores < 2 nm in diameter) or mesoporosity (2–50 nm diameter pores). Unfortunately, lowering the density also compromises the mechanical strength and other properties of the material.2 The material properties of mesoporous dielectric films, such as connected pores and low mechanical strength, create a host of integration problems including integration damage to the film.3,4 The Si–R groups make organosilicate glass (OSG) films hydrophobic and they lower the density by breaking up the tetrahedral Si–O bonding. However, the carbon component is susceptibleto degradation when exposed to the reactive plasmas used for capping, etching, and ashing processes, especially
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Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 16, No. 12, Dec 2001
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oxidizing plasmas that induce silanol formation. Such plasma-induced chemical modifications can cause film densification, dangling bonds and defects, and moisture uptake.5,6 Recently, International SEMATECH monitored several OSG films for change in caused by integration damage (ID) while integrating the films into SEMATECH’s Cu/Damascene test chip using their standard processing flow (Table I).7 Mesoporous OSG films with connected pores exhibited a large increase in due to ID during integration. In contrast, nonmesoporous OSG films showed much smaller changes in . Thus, connected mesoporosity appears to facilitate film damage during processing by allowing reactive species to more easily penetrate the film. Various pl
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