Brief description of the superfinishing of the surfaces of semi-finished - conductors, in particular of the surfaces of gallium arsenide of orientation (111)

摘要

1493905 Polishing semi-conductor surfaces WACKER-CHEMITRONIC GES FUR ELEKTRONIK-GRUNDSTOFFE mbH 26 July 1976 [1 Sept 1975] 31056/76 Heading B3D [Also in Division C4] A process for polishing a surface of a semiconductor body comprises polishing the surface by means of a polishing agent comprising a mixture of (i) an aqueous suspension containing one or more of the following: quartz, a silicon, a silicate and a fluorosilicate, and having a pH within the range from 6 to 8, and (ii) an aqueous solution of hydrogen peroxide having a pH within the range from 6 to 8. The aqueous suspension (i) is prepared by mixing 1 part by weight of the quartz, silica, silicate or fluorosilicate with from 1 to 10, preferably 3 to 5, parts of water and adjusting the pH value to 6 to 8, and preferably 6À5 to 7À5, using an acid such as phosphoric, sulphuric, acetic, oxalic or hydrochloric acid. The silicates may be of metals of Groups IIa (Be, Mg, Ca, Sr, Ba), IIb (Zn, Cd), IIIa (Sc, Y, La) and IIIb (B, Al, Ga, In) or heavy metal silicates of zirconium, iron, lead, nickel, cobalt, magnesium, calcium, strontium, barium, zinc, and aluminium, and the fluorosilicates be of metals of Groups Ia (Li, Na, K, Rb, Cs, Fr), Ib (Cu, Ag, Au), IIa, IIb, IIIa and IIIb, e.g. sodium, potassium, magnesium, calcium, barium, aluminium, and zinc. Silica gels and solutions, and quartz powder may be used in the polishing agent. The aqueous solution (ii) may contain from 5 to 30% by weight hydrogen peroxide, the pH value being adjusted to 6 to 8, preferably 6À5 to 7À5 by using an alkali such as aqueous sodium hydroxide, aqueous potassium hydroxide or aqueous ammonia. The suspension (i) and solution (ii) may be raised and stored or, preferably, supplied by pumps to the polishing machine and mixed immediately prior to use, the mixture containing 2 to 15%, preferably 4 to 8%, by weight hydrogen peroxide. The polishing machine may have either polishing discs or cloths. The semiconductors to be polished may be of gallium arsenide, silicon and germanium which may or may not contain a dopant such as tellurium, chromium or selenium. In an example of the polishing agent, 5 litres of waterglass having 30% by weight SiO 2 and 2À5 kg of calcium chloride hexahydrate were suspended in 40 litres of water and the pH adjusted to 7 using concentrated hydrochloric acid. Thirty litres of a 30% by weight aqueous hydrogen peroxide solution were then adjusted to a pH of 7 using an aqueous ammonia solution. The two solutions were conveyed separately to the polishing machine and mixed immediately before flowing on to the semi-conductor discs to be polished.