Tribological, Thermal, and Wear Characteristics of Poly(phenylene sulfide) and Polyetheretherketone Retaining Rings in Interlayer Dielectric CMP

The fabrication of InGaAs n-channels in CMOS devices requires an intervening buffer layer of GaAs or InP between a Si substrate and the InGaAs channel layer, which has to be planarized to enable the growth of a channel that is free of defects due to uneven surface topography. This report discusses the material removal rates (RRs) and AsH 3 evolution observed during chemical mechanical polishing (CMP) of GaAs using aq. solutions of hydrogen peroxide (H 2 O 2 ) and silica slurries containing H 2 O 2 . GaAs RRs were negligible with deionized water or with silica slurries alone. They were relatively high in aq. solutions of H 2 O 2 alone and showed a strong pH-dependence, with significantly higher RRs in the alkaline region. The addition of silica particles to aq. H 2 O 2 did not increase the GaAs RRs significantly. The evolution of arsenic trihydride (AsH 3 ) during the dissolution of GaAs in aq. H 2 O 2 solution was similarly higher in the basic pH range than in neutral pH or in the acidic pH range. However, no AsH 3 was measured during polishing, evidently because of the relatively high water solubility of AsH 3 . In this report, GaAs removal rates and AsH 3 formation are analyzed using data from contact angle measurements, X-Ray photoelectron spectroscopy (XPS), and X-Ray fluorescence (XRF) spectroscopy. Reaction pathways leading to material removal are proposed.The quest for faster devices in the microelectronic industry has renewed interest in III-V materials such as InP, GaAs, and InGaAs as n-channel candidates because of their high electron mobility. 1,2 During the fabrication of n-channels in CMOS devices, chemical mechanical polishing (CMP) of these materials is required to achieve a smooth and planar surface to enable further processing. There are several environmental health and safety (EHS) issues associated with polishing and wet processing of these III-V materials. 2-5 The EHS concerns for As containing materials include the evolution of toxic arsenic trihydride (AsH 3 ) gas, and the handling of arsenic contaminated slurry waste and used consumables (e.g., polishing pads). For InP, the major concern has been the generation of toxic phosphine gas during polishing. 3,4 In this work, the focus is on the chemical mechanical polishing of GaAs and evolution of AsH 3 .There are several reports on the CMP of GaAs using slurries that contain oxidizers such as hydrogen peroxide (H 2 O 2 ), sodium hypochlorite (NaOCl), and dibromine (Br 2 ). 6-9 McGhee et al. 6 proposed a three step mechanism for GaAs removal in an aqueous solution containing H 2 O 2 and ammonia. An oxohydroxyl layer, consisting of sparingly soluble oxohydroxides of Ga and As, was first formed on the surface. These oxohydroxides were converted to soluble species upon complexation with aq. NH 3 . The soluble species were then removed from the surface by mechanical wiping. In Br 2 -MeOH solutions, they proposed that an adsorbed Br layer was formed on the GaAs surface. The adsorption of bromine was followed by a redox reaction, which continued as lo...

Section: Methodsmentioning

confidence: 99%

Fundamental Investigation of Chemical Mechanical Polishing of GaAs in Silica Dispersions: Material Removal and Arsenic Trihydride Formation Pathways

Matovu

Ong

Leunissen

et al. 2013

“…The solution was stirred using a magnetic stirrer at 500 rpm rotational speed to minimize mass transfer effects and the temperature was maintained at 40 • C to mimic more closely the anticipated temperature during CMP. 16,17 The coupon was removed, washed repeatedly with deionized (DI) water, dried in a N 2 stream, and reweighed. The weight loss was used to calculate the dissolution rate and the reported rates were obtained by averaging over three experiments, each spanning at least 1 min.…”

Section: Experimental Techniquesmentioning

confidence: 99%

Chemical Mechanical Polishing of InP

Peddeti

Ong

Leunissen

et al. 2012

Results of a detailed study of different parameters of the polishing process and their influence on the removal rates (RRs) of InP are presented. RRs with silica-based slurries as well as generation of PH 3 were much higher in the acidic pH regions compared to those in basic pH regions. RRs were also higher than those obtained with harder alumina particles. Smaller silica particles led to higher RRs than larger particles at the same wt% loading, presumably due to the higher total particle surface area. These characteristics suggest an affinity between silica particles and InP similar to that observed earlier between Ta and silica. However, unlike with Ta, replacing the surface silanol groups of the silica particles with dimethyl silane did not suppress the RRs completely. It is proposed that InP removal by silica abrasives is facilitated by the formation of -Si-O-In-, -Si-In-and -Si-P-structures due not only to the reactivity of the silanol groups but also due to the combined effect of the electronegativity of Si atoms, the presence of lone pairs of electrons on In atoms on the InP surface and the electronegativity difference between Si and P.

“…10 With lower frictional forces generated at the retaining ring-slurry abrasives-pad interface, the PEEK retaining ring induces a lower pad wear rate and provides benefits with a longer pad life and lower cost of ownership for CMP processes.…”

Section: Resultsmentioning

confidence: 99%

“…In the previous study, similar frictional forces were reported for the PEEK-1 and PEEK-2 retaining rings. 10 As the PEEK-1 and PEEK-2 retaining rings generate similar frictional forces among the retaining ring surface, slurry abrasives, and pad surface, they result in similar pad wear rates. Figure 3 also shows that for both retaining rings, the wear rate for the D100 pad is significantly lower than that for the IC1000 pad.…”

Section: Methodsmentioning

confidence: 99%

Pad Wear Analysis during Interlayer Dielectric Chemical Mechanical Planarization

Jiao

Zhuang

Wei

et al. 2012

Self Cite

In this study, pad wear during interlayer dielectric (ILD) chemical mechanical planarization (CMP) was investigated using retaining rings with different materials and slot designs as well as pads with different materials at different platen temperatures. Results showed that the retaining ring slot design did not significantly affect the pad wear rate. On the other hand, the polyether ether ketone (PEEK) retaining ring exhibited a significantly lower pad wear rate (by 31%) than the polyphenylene sulfide (PPS) retaining ring. At both platen temperatures (25 and 50 • C), the thermoplastic D100 pad exhibited lower pad wear rates than the thermoset IC1000 pad.Chemical mechanical planarization (CMP) has been widely used in the semiconductor industry to provide both local and global planarity through the synergism between chemical and mechanical actions. During a CMP process, a slurry containing abrasive particles is injected onto a polishing pad. A wafer securely held by a retaining ring is pressed down and rotated against the pad under an applied pressure. Before polishing, the pad has a rough surface with protruding asperities. As these asperities make contacts with the slurry abrasives as well as the wafer and retaining ring surfaces during polishing, they collapse after the mechanical contacts. To regenerate pad asperities and prevent material removal rate decay, a disk embedded with diamonds is typically used to condition the pad surface under an applied down force. As the disk rotates and sweeps across the pad, the embedded diamonds plow and cut into the pad surface reviving the collapsed pad asperities. In summary, pad conditioning, as well as direct contacts among pad surface, slurry abrasives, wafer and retaining ring surfaces result in pad wear. Pad wear not only reduces pad life, but also generates negative effects on polishing performance. 1-4 While the effects of pad conditioning and slurry abrasives on pad wear have been extensively investigated, 5-8 to date, no study has been published to illustrate how retaining ring material and slot design impact pad wear rate. In this study, retaining rings made of polyether ether ketone (PEEK) and polyphenylene sulfide (PPS) with two different slot designs were polished for 6 hours and their pad wear rates were compared. In addition, tests were performed on different pads at different platen temperatures to demonstrate their effects on the pad wear rate. ExperimentalAll pad wear tests were performed on an Araca APD-800 polisher and tribometer. The polisher and its accessories were described in detail elsewhere. 9 Three retaining rings with two different materials and two slot designs manufactured by Entegris, Inc. were used in this study. These retaining rings were designed for 300 mm wafer CMP processes. The first retaining ring made of PEEK with slot design-1 was referred to as the PEEK-1 retaining ring, the second retaining ring made of PEEK with slot design-2 was referred to as the PEEK-2 retaining ring, and the third retaining ring made of PPS with slot design-...