Plasma etching metals

Plasma etching is widely used in semiconductor device manufacturing to etch patterns in thin layers of polycrystaUine siUcon often used for metal oxide semiconductor (MOS) device gates and interconnects (see Plasma TECHNOLOGY). 

Born in London, Paul May grew up in Redditch, Worcestershire. He went on to study at Bristol University, where he graduated with a first class honours in chemistry in 1985. He then joined GEC Hirst Research Centre in Wembley where he worked on semiconductor processing for three years, before returning to Bristol to study for a PhD in plasma etching of semiconductors. His PhD was awarded in 1991, and he then remained at Bristol to co-found the CVD diamond research group. In 1992 he was awarded a Ramsay Memorial Fellowship to continue the diamond work, and after that a Royal Society University Fellowship. In October 1999 he became a full-time lecturer in the School of Chemistry at Bristol. He is currently 36 years old. His scientific interests include diamond films, plasma chemistry, interstellar space dust, the internet and web technology. His recreational interests include table-tennis, science fiction, and heavy metal music. 

Etching- metal and oxide etch equipment are used to remove excess parts of the deposited film. High density plasma sources... 

Very little will be said here concerning the equipment aspects of plasma etching. There are three basic types of equipment which have been used a) barrel systems, b) planar systems, and c) systems in which the wafers are located downstream from the plasma to be referred to in this paper as downstream etching systems. These plasma etching configurations are shown schematically in Fig. 3.1. Often the barrel systems are used with a perforated metal tube called an etch tunnel which is shown in Fig. 3.1 a and b. The purpose of the etch tunnel is to protect the wafers from the energetic ion and electron bombardment to which waters immersed directly... 

The determination of structure and bonding of polymer anchored catalysts is another area where the insolubility of the materials often precludes solution spectroscopic studies and one is limited to techniques that can be applied to irregular solids (57). In addition, combining oxygen plasma etching and surface analysis allows investigation of the depth of penetration of the metal into the polymer and allows detection of components that require concentration to allow detection. 

Figure 38 illustrates accumulated surface scans in the rhodium 3d and phosphorus 2p region taken from granules of the rhodium anchored catalyst. The surface concentration is low enough that scan accumulation was necessary to detect these elements. These particles were oxygen plasma etched for thirty minutes and Figure 39 includes a survey spectrum as well as Rh 3d and P 2p spectra taken from the sample after OPE. The intensity of the rhodium and phosphorus lines is enhanced considerably as a result of etching. To investigate the depth of penetration of the anchored metal into the surface of the particles, surface spectra were obtained as a function of OPE times. This data is given in Table VIII and the phosphorus and rhodium spectra as a function of etch time in minutes is shown in Figure 40. The intensity of the rhodium and phosphorus lines increases up to twenty minutes of etching or equivalent to penetration of 160 nm into the surface of the particles. This analysis indicates that rhodium is fairly uniformly distributed into the particles at least 160 nm into the interior.

Figure 4. AES spectrum of nonvolatile Cu residue from 4% Cu-doped A l metallization on Si after plasma etching in CClt (55).

Studies were also performed with an artificial fixed bed composed of an array of microstructured columns made by a plasma etch process. These columns were made porous to increase the surface area to 100 m2, which is not far from the porosity of catalyst particles in fixed beds, and then coated with a catalyst [278]. The performance of such catalytic microcolumns was compared with that of a catalytic fixed bed reactor. When normalized to the metal content, the reaction rates of the columnar and the particle-containing reactor are similar with 6.5 x 10 5 and 4.5 x 10-5 mol/(minm2), respectively. 

---