Harold G. Linde

Catalytic control of anisotropic silicon etching

Abstract A wide variety of oxidative catalysts have been tested in altering the wet chemical etching of the three major crystal faces of silicon, using a solution of gallic acid—ethanolamine—water. Significant variations in etch selectivity occur, where both the concentration and the nature of the catalyst are important. The results are useful in the micromachining of silicon.

A study of post-chemical-mechanical polish cleaning strategies

Chemical-mechanical polishing (CMP) has emerged as the premier technique for achieving both local and global planarization. One of the primary concerns in the use of CMP, however, is the efficient and complete removal of CMP contaminants such as slurry and residual hydrocarbons. This paper discusses the removal of silica-based slurries utilized for polysilicon and oxide CMP processes. The effects of mechanical brush cleaning, chemical treatments, and polish processes on defect density for a 16 Mb memory technology are presented. In addition, the chemical compatibility of polishing slurries with various brush and polishing pad materials is discussed.

heterocyclic catalysts for enhanced silicon oxidation and wet chemical etching

Abstract Heterocyclic amine catalysts used to accelerate the wet oxidation of 〈100〉 silicon in gallate-complexed aqueous amine etchant formulations include pyrazines, pyridazines, and N -conjugated triazoles, tetrazoles, and triazines. Faster oxidation results in faster etch rates, where 2- and 2,3-disubstituted pyrazines produce aggressive etchants. Steric factors seem to control catalytic activity: large substituents in the 2- or 2,3- positions may enhance catalyst dissociation from the oxidized silicon surface, but 2,3,5,6-substitution may inhibit association of the catalyst with the bare substrate. Etch rates greater than 125 μm h −1 are obtained on 〈100〉 Si with quinoxaline, but unconjugated 1,2-diazines or diazoles do not show catalytic activity.

Effect of Humidity on Photoresist Performance

This paper discusses the effect of varied humidity on lithographic performance during photoresist exposure. In the presence of water, exposure causes the sensitizer to be converted into acid; without water, a less soluble ester forms. The effect of humidity on the resist chemistry was measured using infrared spectroscopy. To completely convert the sensitizer to acid, humidities exceeding 40% were needed. At lower humidities, significant amounts of ester, rather than acid, were formed. The effect of humidity during exposure was also measured using lithographic techniques. As humidity decreased from 40 to 20%, the dissolution rate decreased by up to 65%, dose-to-clear (E 0 ) increased by up to 25%, the dose-to-print increased by up to 15%, and contrast decreased by up to 10%. The magnitude of these effects was resist-dependent. The time of equilibration of water into and out of the resist film was less than 30 s.

Etch characteristics of various materials in ethanolamine etchants

Abstract Data for the etch rates of passivating and non-passivating films are presented for the anisotropic etchant ethanolamine-gallic acid-water. Thesedataidentifyusefulmasking and conductive layers for

Development of a membrane-etch wet station for x-ray masks

This paper describes the evolution of a simple recirculating etch station into a successful x-ray mask membrane-etch station. The manufacturing etch station consists of a large, heated mix tank in which she ethanolamine solution is brought to reaction temperature. The etchant is then pumped into a smaller heated process tank and is continuously recirculated through a filter between the two tanks. Up to 50 substrates can be processed during one product run. Both tanks and wetted parts are made of Teflon. Salient features of the membrane-etch station include dual Pyrex reflux columns, a nitrogen blanket throughout the systems to prevent oxygen infiltration, special high-temperature Teflon and Gore-tex seals for the mix and process tank lids, and a Teflon filter in the recirculating line between the mix and process tanks. Subsequent tooling improvements included improving the thermal sensors and installing more powerful heaters. Tool qualification tests have demonstrated the membrane-etch station ready for manufacturing use. The manufacturing etch station has increased our etch capacity by almost an order of magnitude and is currently being used to produce silicon membranes for x-ray mask substrates.