Time, effect etch rate

Many of the above described features are quite different to published and our own data for polyimide. Polyimide (PI) has a linear absorption coefficient at 308 nm similar to the designed polymers (around 95,000 cm-1). The first pronounced differences between the ablation characteristics between PI and our polymers are the higher threshold of ablation (three times), lower etch rates, and an effective absorption coefficient which is similar to the linear absorption coefficient. A comparison of the ablation quality between a designed polymer (TP) and the standard polymer (PI) is shown in Fig. 74. 

EPM > CO > TP > CB. The highly crystalline TB had an etch rate about six times that of CB, ascribable to a morphology difference, while the partially crystalline TO had an etch rate somewhat higher than that of amorphous CO. Cis/trans content had little or no effect on the etch rate of the polyalkenamers. A mechanism involving crosslinking through vinyl units is proposed to explain the unexpected protection imparted to vinylene-rich polybutadienes by the presence of 1,2 double bonds. 

A second method of local planarization involves spinning photoresist onto the SiOj ILD to obtain local planarity. The resist is then hard baked and etched with an RIE etch tailored to remove SiOz (or ILD) at the same rate as the photoresist. Because the etch rate of the two materials is equal, the planarity of the resist film transfers into the SiOz film. However, a precise match in SiOj and photoresist etch rates is difficult to maintain because the relative ratio of SiOj to photoresist exposed increases as the etch back proceeds. Loading effects then result in a decrease in the Si02 etch rate and increase in the photoresist etch rate. Furthermore, polymer deposits build up on the etch reactor chamber walls over time etching of this polymer depletes the chemicals used to etch the photoresist, which slows the photoresist etch rate. If the etch rates are not matched, the planarity of the photoresist layer will not transfer well to the SiOz. 

Solution composition has a stronger effect on the etch rate of doped oxides than thermal oxides in BHF solutions as shown in Fig. 4.19 and in HNO3-HF solutions." Also, the etch rate difference between doped oxides and thermal oxides depends on solution composition in the HF-HNO3 solution the etch rate of a PSG film is 100 to 300 times higher than thermal silicon oxide, but in the BHF solution it is only about 10 to 30 times higher. 

This expression indicates that the Ti etching rate is constant thus we would expect the thickness of a Ti plate undergoing active gas corrosion to decrease linearly with time. The expression also indicates that the etching rate will increase linearly with increasing HCl(g) pressure. Since HCl is the etchant, this makes sense The effect of temperature is less obvious. While temperature appears directly in the denominator of this expression, recall that the rate constant A is an exponentially temperature-activated quantity. Thus, the exponential increase in k with increasing temperature dominates over the T term in this expression the overall effect is that the etching rate will increase rapidly with increasing temperature. 

Sa.tura.tion Index. Materials of constmction used in pools are subject to the corrosive effects of water, eg, iron and copper equipment can corrode whereas concrete and plaster can undergo dissolution, ie, etching. The corrosion rate of metallic surfaces has been shown to be a function of the concentrations of Cl ,, dissolved O2, alkalinity, and Ca hardness as well as buffer intensity, time, and the calcium carbonate saturation index (35). 

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