Scratch defects

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]. 

Remsen EE, Anjur S, Boldridge D, Kamiti M, Li S, Johns T, Dowell C. Analysis of large particle count in fumed silica slurries and its correlation with scratch defects generated by CMP. J Electrochem Soc 2006 153(5) G453-G461. 

Fig. 19 Number of scratch defects vs. number of grocery items scanned for uncoated float glass window, Diamonex DLC-1 and Diamonex DLC-2 coated fioat giass windows and the corresponding estimated average iifetimes. ...

Fig. 11 Passivating effect of a phosphate layer. Distribution of vertical component of current over a scratched phosphated galvanized steel surface measured by the SVET method. The scratch penetrates down to the steel surface. Cathodic zones (current < 0) are indicated by the filled areas, while anodic zones (current > 0) are transparent. Because of the passivating properties of the phosphate layer, the anodic reaction remains localized in the vicinity of the scratch defect. Each isocurrent line represents lOpAcm. Original data Irsid.

These opposite conclusions are because slurry formulation and material removal mechanisms are different depending on the types of materials to be polished. In any case, the large abrasive sizes can produce the scratch defects on films during CMP (Remsen et al., 2005, 2006). Since the number of maximum permissible defects is continually lowered with decreasing device dimensions, CMP slurries containing smaller abrasive sizes have been investigated. 

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... 

Figure 17.10 Evolution of scratch defects, (a) A scratch post-CMP at current level transforms into a puddle and missing pattern to cause a short circuit at above level (b) a light scratch at current level can still be detected as a nonvisual defect at tbe level above and consumes part of the defect detection budget.

While CMP facilitates mass production of PCM devices, it also poses new challenges like composition control, thickness control of the small device region, imperfections (e.g., scratches, defects, and corrosion), and minimization [1]. 

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)). 

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. 

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. 

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