Electrochemical Coupling Effects on the Corrosion of Silicon Samples in  HF  Solutions

Torcheux, L.; Mayeux, Annabelle; Chemla, M.

doi:10.1149/1.2044237

Cited by 36 publications

(38 citation statements)

References 4 publications

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“…2͒, consistent with previous measurements of first-order Cu deposition kinetics in galvanic displacement. 11,26,27 In more dilute HF solutions, however, deposition rates no longer increased linearly with increasing ͓CuSO 4 ͔, reaching maximum constant values at high CuSO 4 concentrations. The deposition rates at these plateaus increased with increasing ͓HF͔, suggesting that Si dissolution limits deposition rates under these conditions.…”

Section: Resultsmentioning

confidence: 99%

Copper Deposition onto Silicon by Galvanic Displacement: Effect of Silicon Dissolution Rate

daRosa

Maboudian

Iglesia

2008

J. Electrochem. Soc.

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The rates of Cu deposition onto rotating Si electrodes were measured to probe the effects of mass transfer, Cu 2+ reduction, and Si oxidation and dissolution on deposition dynamics. Cu deposition rates were proportional to CuSO 4 concentration and limited by Cu 2+ diffusion and subsequent reduction at high HF concentrations ͓͑HF͔/͓CuSO 4 ͔ Ͼ 20͒. In contrast, Si dissolution limited film growth at low HF concentrations ͓͑HF͔/͓CuSO 4 ͔ Ͻ 10͒, and HF 2 − was identified as the most active Si etchant. The observed effects of rotation rate indicate that mass transfer of Cu 2+ limits deposition rates, but mass transfer of HF does not. Open-circuit potential measurements and mixed-potential theory were used to develop a reaction-transport model that accurately predicts deposition rates over a broad range of Cu and HF concentrations. The structure of the films formed was probed by atomic force microscopy. The roughness of the Cu films decreased with increasing ͓HF͔/͓CuSO 4 ͔ ratios, as Si surfaces became less oxidized, and lateral connectivity between Cu nuclei increased.Galvanic displacement has been used for metal deposition on Si for applications including microelectromechanical system, 1,2 surface-enhanced Raman spectroscopy, 3-5 and catalysis. 6,7 Galvanic displacement offers the advantage of selective deposition because reduction of metal ions is coupled with oxidation and dissolution of the substrate. A schematic diagram of galvanic displacement of Cu onto Si is shown in Fig. 1, indicating the mass transfer and kinetic processes required for deposition. Fluoride species, HF in this case, must be added to dissolve oxidized Si and expose additional Si to continue galvanic displacement. Galvanic displacement occurs spontaneously when the depositing metal is more noble ͑easier to reduce͒ than both the substrate and hydrogen. Thus, Cu can be deposited by galvanic displacement because of its favorable reduction potential 8where NHE is the potential of the normal hydrogen electrode. Si is easily oxidized ͑Si 2+ /Si E 0 = −0.81 V 9 ͒, making it a suitable substrate for galvanic displacement. In this work, the concentrations of Cu 2+ and HF are varied to determine the effects of the oxidation and reduction half-reactions on Cu deposition rates and the structure Cu films. Several studies have examined the effects of Cu 2+ concentration on galvanic displacement rates. Deposition rates were found to be first-order in Cu 2+ concentration for deposition on substrates including Si, Fe, and Zn. [10][11][12][13][14] Less is known about the effect of HF concentration on deposition rates. Deposition rates increased with increasing HF concentration for deposition of Cu and Ag on Si, but few HF concentrations were studied, and the relationship between HF concentration and Cu deposition rates was not quantified. 10,15 In this work, we investigate the effect of Si dissolution on Cu deposition rates by systematically varying the HF concentration.In addition to the effects of formal HF concentration, the fluoride species responsible for Si...

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Section: Resultsmentioning

confidence: 99%

Copper Deposition onto Silicon by Galvanic Displacement: Effect of Silicon Dissolution Rate

daRosa

Maboudian

Iglesia

2008

J. Electrochem. Soc.

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“…However, attack by buffered HF on poly-silicon, leading to surface roughening, has been reported under various conditions, and has been correlated with the presence of contaminants, such as metals, as well as the deposition conditions or structure of the poly-silicon 24–27 . Microroughening of single-crystal silicon during immersion in buffered HF solutions for very long times (1–5 days) has also been described 28 .…”

Section: Resultsmentioning

confidence: 98%

Optimized process for fabrication of free-standing silicon nanophotonic devices

Seidler

2017

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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A detailed procedure is presented for fabrication of free-standing silicon photonic devices that accurately reproduces design dimensions while minimizing surface roughness. By reducing charging effects during inductively coupled-plasma reactive ion etching, undercutting in small, high-aspect ratio openings is reduced. Slot structures with a width as small as 40 nm and an aspect ratio of 5.5:1 can be produced with a nearly straight, vertical sidewall profile. Subsequent removal of an underlying sacrificial silicon dioxide layer by wet-etching to create free-standing devices is performed under conditions which suppress attack of the silicon. Slotted one-dimensional photonic crystal cavities are used as sensitive test structures to demonstrate that performance specifications can be reached without iteratively adapting design dimensions; optical resonance frequencies are within 1% of the simulated values and quality factors on the order of 105 are routinely attained.

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“…This result is in contrast with the diffusion-limited deposition of Cu on Si(100) surfaces found in 1-5% HF. 8,9 We used misoriented Si(111) wafers to investigate the relationship between Cu deposition and step density on Si(111) surfaces. Figure 3a shows the Brewster angle p-polarized transmission FTIR spectra of differently misoriented H-Si(111) surfaces.…”

Section: Resultsmentioning

confidence: 99%

Effect of Silicon Surface Termination on Copper Deposition in Deionized Water

Lim¹,

Mo²,

Pianetta

et al. 2001

J. Electrochem. Soc.

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The prevention of metal contamination on silicon wafer surfaces is a stringent issue in the semiconductor fabrication industry, because metals induce device degradation. Particularly, it has been reported that Cu contaminants on silicon surfaces deteriorate the integrity of gate oxide formed on that surface. We have investigated the relationship between Cu deposition and silicon surface termination in order to suggest a way to suppress Cu contamination during the wafer cleaning process. The effect of the microroughness and kink site density of silicon ( 111) and ( 100) surfaces on Cu deposition has been elucidated, using as a model system hydrogen-terminated samples exposed to deionized water with a known amount of dissolved Cu 2ϩ to simulate a contaminated rinse bath. Under identical contamination conditions, the hydrogen-terminated Si( 111) surface ] with its flat monohydride terraces has an order-of-magnitude lower Cu coverage than the microscopically rough, hydrogen-terminated Si(100) surface [H x -Si(100)]. Si(111) wafers that were misoriented between 1 and 8Њ from the (111) plane toward the (110) plane were used to investigate the effect of step density on Cu deposition. The results showed the change in Cu coverage as a function of step density on H-Si( 111) surfaces was negligible compared to that shown between H-Si( 111) and H x -Si(100) surfaces. We suggest that the difference in the densities of dihydride (Si-H 2 ) sites on the H-Si( 111) and H x -Si(100) surfaces is the cause of the difference in Cu coverage. The dihydride densities of misoriented H-Si(111) surfaces are expected to be very low compared with those on H x -Si(100). Hydrogen and methoxy-terminated surfaces were also compared to understand the effect of alternative terminations on Cu nucleation. The methoxy-terminated Si(100) surface had lower Cu coverage than H x -Si(100). Deactivation of dihydride sites on the methoxy-terminated surface may be the reason for its better resistance to Cu contaminants.

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Electrochemical Coupling Effects on the Corrosion of Silicon Samples in HF Solutions

Cited by 36 publications

References 4 publications

Copper Deposition onto Silicon by Galvanic Displacement: Effect of Silicon Dissolution Rate

Copper Deposition onto Silicon by Galvanic Displacement: Effect of Silicon Dissolution Rate

Optimized process for fabrication of free-standing silicon nanophotonic devices

Effect of Silicon Surface Termination on Copper Deposition in Deionized Water

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