Chemical polishing of single crystal dielectrics

Details Chemical polishing of single crystal dielectrics Chemical polishing of single crystal dielectrics

1970-10-16

1976-06-22

McCamish, Marion E.

Adhesive bonding and miscellaneous chemical manufacture

Methods

156 20, 252 792, 357 4, 357 60, C23G 136

Patent

active

039649423

ABSTRACT:
A polishing method for single crystal dielectrics such as sapphire and magnesium spinel is disclosed. A single crystal wafer of sapphire or magnesium spinel is immersed in a mixture of sulphuric and phosphoric acid in a range of mixtures of 9 parts sulphuric acid to 1 part phosphoric acid to 1 part sulphuric acid to 9 parts phosphoric acid by volume while the mixture is held at a temperature in the range of 200.degree.-325.degree.C. The rate of polishing as well as the quality of polishing of the wafers of sapphire or magnesium spinel is orientation sensitive and polishing is achieved for magnesium spinel having the orientations (100) and (110). Polishing is achieved for sapphire having the orientations (0001), (1123), (1100), (1124), (1120) and (0112). A wafer to be polished is suspended in the heated solution and may be rotated slowly. Nonpreferential material removal rates of fractions of a micron per minute are obtained. Crystals of both sapphire and spinel having the above-mentioned orientations may be polished in a preferred temperature range of 250.degree.-300.degree.C. The preferred polishing mixture for sapphire is 1 part sulphuric acid to 1 part phosphoric acid by volume at a temperature of 285.degree.C. For magnesium spinel, the preferred mixture is 3 parts sulphuric acid to 1 part phosphoric acid at a temperature of 250.degree.C. The polishing technique of the present invention provides planar, polished surfaces which are free of insoluble residues on the polished surface.

REFERENCES:
patent: 1482793 (1924-02-01), Hartman
patent: 2967136 (1961-01-01), Cybriwsky et al.
patent: 3042566 (1962-07-01), Hardy
patent: 3106499 (1963-10-01), Kendall
Scheuplein et al. Surface Structure of Corundum, Jour. Amer. Ceramic Soc., pp. 458-472, Sept., 1960. (vol. 43).

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