Passivation native oxide

Silicon is stable in acidic solutions that do not contain fluoride because the silicon surface is passivated by a native oxide. If only H F is present in an aqueous solution the etch rate remains low, showing values below 0.1 rim miri 1 on single crystalline silicon depending on the OFT concentration [Hu2]. This low etch rate... 

It is not too surprising that vapor-phase HMDS also improves adhesion to this substrate. The native oxide has been shown on Y58 wafers to be easily treated and/or passivated. Actual resist image lift testing on vapor promoted polysilicon wafers produced superior results and no image lifting occurred even for first generation resists known to be susceptible to lifting . 

HPM (SC2) HCI/H2O2/H2O Removal of metallic ions, surface passivation by native oxide formation... 

The materials discussed in this chapter are limited to the relatively thick oxides formed at potentials greater than several volts. It thus concerns mainly the growth and the bulk properties of anodic oxides. The data on thin oxide films are presented in other chapters. In particular, the oxide films involved in passivation at potentials within a few volts above OCP are dealt with in Chapter 5. Native oxides, which are almost always present on the surface of silicon electrodes, are discussed in Chapter 2. 

The silicon surface in nonfluoride and nonalkaline solutions is spontaneously passivated due to the formation of a thin native oxide film at a rate depending on many factors as discussed in Chapter 2. For n-Si samples in aqueous solutions under illumination the occurrence of passivation causes a decrease of the photocurrent as shown in Fig. 5.11. " In the absence of HF, photocurrent rapidly reduces to near zero due to the formation of an oxide film. The stationary photocurrent increases with increasing HF concentration. For a given light intensity, there is a HF concentration above which the photocurrent does not decrease from the initial value. The surface is free of oxide film at this HF concentration. 

The summation of the various observations described in the preceeding paragraph leads to the conclusion that the nature of the residual surface "native" oxide strongly affects the subsequent phase that forms. If GeO is present then an active molecular species is available in the near-surface gases to promote a-Ge3N4 formation and subsequent condensation. On the other hand, if Ge02 is present a passive surface condition exists requiring nitridation to proceed via the solid diffusion of a nitridant into the surface. Furthermore if a uniform passive oxide layer is present on the surface, subsequent a-nitride can only be produced in the vicinity of oxide disruptions. 

The thickness d of passive films ranges from monomolecular films in case of Pt and Au to thick films in the micrometer range in case of Al. The initial or native oxide thickness do is often in the nm range (Table 1). It decreases with increasing Uox-... 

While the native oxide layer on conventional metal superconductors passivates the surface, this is not the case for HTSC. A short-circuit in a native or artificial insulating layer has been considered to be responsible for the appearance of zero-bias peaks accompanied by the proximity effect. Mechanical damage at the interface may also create small particles, causing a charging effect, which then gives rise to various spurious features in the spectrum such as multi-peak conductance. Another difficulty in point-contact methods is the arbitrariness of the results due to the dependence on the contact pressure. 

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