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The chemical composition of surface oxides grown on p-type InP(100) after etching in H 2 SO 4 /H 2 O and in H 2 SO 4 /H 2 O 2 /H 2 O etchants was investigated using X-ray wide angle diffraction and glancing angle diffraction techniques. Diffraction from only one lattice set in the matrix oxide was detected in etching with H 2 SO 4 /H 2 O solution by wide angle diffraction. Each diffraction line appeared as an interference pattern, possibly caused by beams reflected from thin layers of indium phosphate hydrate having a single-crystal structure, and showing an extremely preferred orientation and coherent with respect to the substrate. Only one set of reflection peaks was observed in wide angle diffraction, and an interference oscillation was observed in each reflected beam. The dissolution rates of InP in H 2 SO 4 /H 2 O and in H 2 SO 4 /H 2 O 2 /H 2 O were determined quantitatively by inductively coupled plasma emission spectrometry. The mixed component oxides and single component products were observed on the oxidized InP. The dissolution rates of InP were almost indiscernible under either illumination or dark. The addition of H 2 O 2 in H 2 SO 4 /H 2 O solution does not play any critical role in the dissolution of InP.

The etching of GaP, whether in strong HNO 3 or in strong HCl is severely inhibited, whereas mixtures of HNO 3 /HCl are commonly employed as etchants for chemical polishing. The etching mechanism of n-GaP in aqua regia (3HCl/ 1HNO 3 ) has been investigated. Aqua regia etching may occur by accomplishing both the following two processes:(1) oxidation and (2) dissolution. First, the nascent chlorine and nitrate ions obtained from the vigorous interaction between HCl and HNO 3 , may easily oxidize the surface atoms of GaP, then nucleophilic attacked by Cl ) on the electron-poor trivalent gallium ions of the oxide lattice generally takes place over the passive surface. Moreover, the remaining phosphate or phosphorus oxide is very soluble. Ga and P atoms are thus carried away from the surface by the etchant system. In HNO 3 -etch, the nitrate ion formed is a weak nucleophile and the amount of its production is very small. In the HCl-etch, Cl ) causes a direct attack on GaP substrate via an Ga (I) chloro intermediate whose thermodynamics is very unfavorable. Thus, the experimental observations are in good agreement with the mechanistic concepts presented.

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The removal selectivity control of aluminum and titanium metal barrier during aluminum chemical mechanical polishing in the Damascene process is known to be critical for surface planarity without metal dishing and dielectric erosion. Unfortunately, the electrochemical behaviors of aluminum and titanium are dissimilar, as one may expect. In this study, in situ electrochemical impedance spectroscopy was carried out to investigate the influences of H 2 O 2 concentration, slurry pH, and metal oxide formation through the passivation on aluminum and titanium. As H 2 O 2 concentration increases, the measured impedance of aluminum and titanium decreases, or the oxidation rates of these two metals are enhanced upon increasing the oxidizer concentration. As the slurry pH increases, the removal rate of polished titanium increases, but it decreases for polished aluminum. The removal rate of titanium was limited to its oxidation rate and aluminum was limited to its oxide dissolution rate.Chemical mechanical polishing ͑CMP͒ has long been recognized as a promising technique for global planarization to delineate metal patterns for submicrometer integrated circuit ͑IC͒ processing. 1-3 Aluminum ͑Al͒ and its alloys have traditionally been used as multilevel interconnects and have emerged as the most important material for such applications. On the other hand, it is well known that titanium ͑Ti͒ is an effective metal barrier. 4 The total process time for Al CMP is also controlled by the removal of the Ti diffusion barrier. Little research has been devoted to the CMP of this barrier film. Since Ti is harder than Al, a lower Ti removal rate is therefore expected.Because Al is soft and easily scratched, polishing on a softer pad has therefore been suggested to avoid severe surface damage, but this technique can produce unwanted pattern geometry effects like metal dishing and interlevel dielectric ͑ILD͒ erosion. 5 Therefore, a two-step CMP process has usually been implemented. For the first step, the overburden Al would be planarized for the step-high reduction, be removed faster and uniformly, and stopped as Ti exposed. For the second step, both Al and Ti outside of trenches would be removed simultaneously and stopped as the ILD exposed. The control of removal selectivity is therefore very critical in the second step. In the ideal case, Al, Ti, or TiN and ILD would be expected to remove at the same rate, or it would result in metal dishing, oxide erosion, and surface nonplanarity. Overpolishing for the complete removal of overburden metals outside of trenches would further induce surface nonplanarity.Kaufman et al. 6 has proposed a desirable removal mechanism for metal CMP which involves the oxidation of metal to form passive surface oxide and dissolution of this metal oxide under polishing stress. No direct metal corrosion to form soluble metallic ions or direct mechanical abrasion on nonoxidized metal substrates would be allowed for CMP, and it would result in the issues of metal corrosion and surface scratching. The formation and di...