Defectivity scratches

Polishing is an abrading operation used to remove or smooth out surface defects (scratches, pits, tool marks, etc.) that adversely affect the appearance or function of a part. The operation usually referred to as buffing is included in the polishing operation. 

While some of the WEB drawbacks can be eliminated by W CMP, W CMP itself generates new problems. Because W CMP uses alumina (AI2O3, one of the hardest materials known) abrasive in a Fe(N03)3-based slurry to polish, defectivity (scratches) and Fe contamination become issues. For the former, oxide buff can be used to reduce defects. However, this may lead to an oxide erosion problem, as discussed in a later section. 

The brittle-ductile transition temperature depends on the characteristics of the sample such as thickness, surface defects, and the presence of flaws or notches. Increasing the thickness of the sample favors brittle fracture a typical example is polycarbonate at room temperature. The presence of surface defects (scratches) or the introduction of flaws and notches in the sample increases Tg. A polymer that displays ductile behavior at a particular temperature can break in the brittle mode if a notch is made in it examples are PVC and nylon. This type of behavior is explained by analyzing the distribution of stresses in the zone of the notch. When a sample is subjected to a uniaxial tension, a complex state of stresses is created at the tip of the notch and the yield stress brittle behavior known as notch brittleness. Brittle behavior is favored by sharp notches and thick samples where plane strain deformation prevails over plane stress deformation. 

Different from FM and PR defects, scratch defects can appear with unique spatial signature on a wafer surface. Long arcs of scratches spanning across multiple dies on... 

The character and quality of the electrode surface are of utmost importance, because any kind of defect, scratch, impurity, or kink may function as a nucleation center. Film morphology is at least partly determined by the nucleation and entirely by the growth mechanism. 

Filiform corrosion may occur on products coated with paint or lacquer, especially on lacquered products for buildings. It develops preferentially at coating defects (scratches, lacerations). Meteorological factors are of paramount importance because filiform corrosion occurs especially in marine and humid atmospheres and develops rather quickly, before the fifth year of exposure. While it does not affect the mechanical characteristics of aluminium semi-products, it degrades the overall appearance of a building (see Section B.2.6). 

FI G U RE 14.4 SVET current density map showing cathodic protection of A A 2024-T3 by a n-doped poly(2,3 -dihexylthieno[3,4-ij]pyrazine) film containing an artificial defect (scratch) after 5 min immersion in 0.35 wt% (NH4>2S04. 0.05 wt% NaCl (reduction current is negative). (Reprinted from Yan, M.C. et aL, J. Electrochem. Soc., 156, C360 (color online). 2009. Reproduced with permission of The Electrochemical Society.)... 

Qualitative examples abound. Perfect crystals of sodium carbonate, sulfate, or phosphate may be kept for years without efflorescing, although if scratched, they begin to do so immediately. Too strongly heated or burned lime or plaster of Paris takes up the first traces of water only with difficulty. Reactions of this type tend to be autocat-alytic. The initial rate is slow, due to the absence of the necessary linear interface, but the rate accelerates as more and more product is formed. See Refs. 147-153 for other examples. Ruckenstein [154] has discussed a kinetic model based on nucleation theory. There is certainly evidence that patches of product may be present, as in the oxidation of Mo(lOO) surfaces [155], and that surface defects are important [156]. There may be catalysis thus reaction VII-27 is catalyzed by water vapor [157]. A topotactic reaction is one where the product or products retain the external crystalline shape of the reactant crystal [158]. More often, however, there is a complicated morphology with pitting, cracking, and pore formation, as with calcium carbonate [159]. 

A careful inspection of both shaft ends must be made to ensure that no burrs, nicks, or scratches are present that will damage the hubs. Potentially damaging conditions must be corrected before coupling installation. Emery cloth should be used to remove any burrs, scratches, or oxidation that may be present. A light film of oil should be applied to the shafts prior to installation. Keys and key-ways (discussed in Section 59.3) also should be checked for similar defects and to ensure that the keys fit properly. Properly sized key stock must be used with all keyways do not use bar stock or other material. 

Salt solutions When a zinc sheet is immersed in a solution of a salt, such as potassium chloride or potassium sulphate, corrosion usually starts at a number of points on the surface of the metal, probably where there are defects or impurities present. From these it spreads downwards in streams, if the plate is vertical. Corrosion will start at a scratch or abrasion made on the surface but it is observed that it does not necessarily occur at all such places. In the case of potassium chloride (or sodium chloride) the corrosion spreads downwards and outwards to cover a parabolic area. Evans explains this in terms of the dissolution of the protective layer of zinc oxide by zinc chloride to form a basic zinc chloride which remains in solution. 

Global planeness and large scale scratches are usually evaluated by HDI instruments as shown in Fig. 3(a) [8], which is a surface reflectance analyzer to measure flatness, waviness, roughness of a surface, and observe scratches (Fig. 3(h)), pits (Fig. 3(c)), particles (Fig. 3(d)) on a global surface. These surface defects can also be observed by SEM, TEM, and AFM. Shapes of slurry particles can be observed by SEM and TEM, and their movement in liquid by the fluorometry technique as shown in Chapter2. 

As shown in Fig. 39 [43], it is found that the surface before polishing is uneven and there are a large number of scratches (Fig. 39(a)). After polishing in the slurry I, the surface becomes smoother, and scratches as well as other micro defects could hardly be observed (Fig. 39(h)), by comparison with the surface polished in the slurry II (Fig. 39(c)). 

If an n-type electrode is kept in the dark, the anodic dark current depends on properties of the semiconductor as well as on the chemical composition of the electrolyte. Measurements of dark current density need a defect-free Si surface. Scratches, barely visible to the eye, may increase the dark current by orders of magnitude. For the dark current density of a defect-free silicon electrode a dependence on the chemical environment is observed. 

Fig. 10.6 A p-type Si wafer with a 20 nm thick thermal oxide has been contaminated by scratching the backside with metal wires (Ni, Cu, Fe), according to the pattern shown in (a) and later annealed at 1200°C for 30 s. (e) Under cathodic bias in acetic acid, oxide defects become decorated by hydrogen bubbles. (c, d) After oxide removal junction defects caused by metal precipitates are decorated by hydrogen bubbles, if sufficient catho...

Figure 7 Types of defects commonly encountered on a process line, (l) contamination, (2) opaque spot, (3) large hole, (4) pin hole, (5) excess material, (6) lack of adhesion, (7) intrusion (mouse nip) and (8) scratch.

Physical deterioration includes compaction by creeping and surface deteriorations by scratching and vibration. Creeping is accelerated at higher temperatures and pressures, resulting in the membrane compaction. This phenomenon is well analyzed and the membrane characteristics of compaction can be estimated in terms of m-value. Scratching and vibration can develop the microscopic defects in the surface structure of membranes, and give poor performances. We discussed this type of deterioration in Mexico in 1976 ( ). 

Avoid CMP chemistry that involves multicharged cations. Such chemicals compress the double charge layer and activate slurry agglomeration and process defectivity. Ions such as Al and Fe may initiate agglomeration and scratching at concentrations as low as lO to 10 M. 

Filtration can reduce the particles adhered to the wafer, but only slightly. Filtration will, however, reduce scratch defects. Slurry particles can be more effectively cleaned if more elaborate post-CMP clean chemistry is used [8]. 

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