Etching discharges

The siuface kinetics of etching (Section 8.2.7) is controlled by concentrations of ions and active neutrals near the surface. Determination of these parameters reqttires a detailed consideration of etching discharges (Sections 8.2.8 and 8.2.9). Some nseful relations, however, can be derived from general kinetics of the low-pressme discharges applied for etching. In this section, we make such estimations for the concentration and flux of ions concentration and flux of neutral chemically active etchants will be estimated in the next section. A balance of charged particles in plasma between electrodes with area A (characteristic radius R) and narrow gap / between them (/ R), controlled by ionization and losses to the electrodes,... 

In the steady-state conditions dno /dt = 0), the O-atom density in the etching discharge... 

Non-reactive gases like N2, Ar, He, and so forth. The non-reactive additives are sometimes used to control electrical properties of etching discharges and thermal properties of a substrate. 

The kinetics of surface recombination of F atoms can be characterized by the recombination probability per incident atom, Prec, and depends on the surface material. These probabilities, with some exceptions, are small at substrate temperatures and atontic fluxes typical for the etching discharges. Numerical values of the F-atom surface recombination coefficients are presented in Table 8-2. Surface recombination coefficients for Cl and O atoms are larger and reach values of about 0.1 for mat r surfaces. It is also important to notice that the probability of an etching reaction of one F atom per one silicon surface collision is Pr 1-7 10 and is negligible for most of other surfaces. The reaction probability, however, can be very high and even reach Pr 1 in some specific cases, for example, in F etching of a BN surface. 

Figure C2.18.3. Relationship between ion-assisted etching and directionality in plasma etching, (a) Demonstration of the synergy between ion bombardment and reactive species during ion-assisted etching, (b) Ions incident on an etched feature. This situation prevails in glow discharges when the feature dimensions are much less than the plasma sheath thickness. Reproduced from [35]...

Atz-ammoniak, n. caustic ammonia (ammonium hydroxide), ammonia water. artikel, m. (Calico) discharge style. bad, n. etching bath. 

AtZ bild, n., etching figure, etched figure, boden, m. (Calico) discharge ground, -druck, n. discharge printing. 

X.tze,/. corrosion etching cauterization etching liquid, esp. aqua fortis (Calico) discharge. 

B. Chapman, Glow Discharge Processes—Sputtering and Plasma Etching. Wiley, New York, 1980. 

The 0 atom flow rate was measured by N02 titration as described elsewhere (21). At an 02 flow rate of 6.5 x 10-2 cm3 (STP)/s, reactor pressure of 73 Pa (0.55 torr) with the discharge off, and a power level of 15 W, the flow rate of 0 atoms was found to be 2.4 x 10-2 cm3 (STP)/s the latter figure represented an 18 conversion of 02 to 0 atoms. Assuming complete 0(3P)-induced oxidation of the polymer samples to C02 and H20, the flow rate of 0 atoms was at least eight times that required to maintain the highest etch rate observed (0.8 mg/cm2-h, in TB). 

Thirty plants in the aluminum forming industry use etch or cleaning lines. Rinsing is usually required following successive chemical treatments within these etch or cleaning lines. Wastewater discharge values tend to increase as the number of rinses increase. Table 5.11 summarizes the classical and toxic pollutant data for etch line rinses. 

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