Bird’s beak

Figure 1. SEM of the cross section through a 6000 A bird s beak showing the planarizing effect of 1.6 nm PI2545.

FIGURE 12.23 REM cross section image of a wafer with EXTIGATE. The mini bird s beak can be seen at the active area comer. 

One of the main motivations for the development of the STI process is to eliminate the bird s beak phenomenon. With STI, the field oxide is well embedded into the Si and is clearly distinctive from the active-area regions. It allows very narrow active-area pitches and a higher device-packing density. 

Among other process tq)plications are the use of CMP to improve shallow trench isolation. Bird s beak planarization, and stacked or trench capacitor. 

L(XIOS isolation introduces nonplanarity, and a bird s beak at the edge of the active region reduces the packing density of the circuitry, both of which make LOCOS undesirable at sub-0.5 pm dimensions. As a result, new isolation schemes are being intro-... 

The Plague doctors wore full, leather coats and a hat and crystal goggles to ensure they did not catch the disease from patients, and to be doubly sure touched them only with examining wands. They wore large cones, or nosegays, resembling a bird s beak or bill, and thus it is believed the derogative quack applied to fake doctors. 

The oxide isolation methodology has found wide acceptance in the process industry as the preferred device isolation scheme, despite some major shortcomings. For one, it has evolved as a still more complicated process, requiring several additional processes (see Table 1). The oxide isolation region is characterized by two unique features - the so-called "bird s beak" and the "bird s head" (18,19). The beak tends to prevent fully butted junction formation of the base and emitter. Thus, the full benefits of device density cannot be realized. More importantly, the bird s beak generation represents a real limitation to achieve much smaller (narrower) device isolation regions, and therefore, ultimate device densities. 

Avoidance of Lateral Epitaxial Autodoping Elimination of Sub-isolation Diffusion Single Mask Isolation and Subcollector Definition Absence of Bird s Beak... 

Maximum stress, for instance, is produced at film edges a particularly critical system is the nitride-edge during local oxidation /14,15/ (fig.9). Not only does the nitride-layer inherently create stress in the Si-substrate (which only is partially relieved by the buffer oxide), but the oxide-growth introduces even more stress because the nitride-cover at the edge has to bend upwards to accomodate the volume expansion of the growing oxide (bird s beak phenomenon) /16/. 

But if you want a really interesting candle, you ll have to get hold of a dried stormy petrel, a Shetland Islands bird that has a very high fat content. Islanders fashion candles out of them — they thread a wick through a dead bird s beak, fix its feet in clay, and then set the thing alight. But I bet the bird drips. 

Bird s Beak. A special type of wall tile (see Fig. 7, p350). 

---