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Removal of Microscopic Polishing Damage from Sapphire and Spinel

IP.com Disclosure Number: IPCOM000074648D
Original Publication Date: 1971-May-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Berkenblit, M: AUTHOR [+3]

Abstract

Polishing methods for single-crystal dielectrics, such as, sapphire and magnesium spinel are known. One known method, for example, involves immersing a single-crystal wafer of sapphire or magnesium spinel in a heated mixture of sulfuric and phosphoric acid. This mixture may range from 9 parts sulfuric acid to 1 part phosphoric acid by volume, at one end, to 1 part sulfuric acid to 9 parts phosphoric acid by volume, at the other end, while the mixture is held at a temperature in the range of 200-325 degrees C.

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Removal of Microscopic Polishing Damage from Sapphire and Spinel

Polishing methods for single-crystal dielectrics, such as, sapphire and magnesium spinel are known. One known method, for example, involves immersing a single-crystal wafer of sapphire or magnesium spinel in a heated mixture of sulfuric and phosphoric acid. This mixture may range from 9 parts sulfuric acid to 1 part phosphoric acid by volume, at one end, to 1 part sulfuric acid to 9 parts phosphoric acid by volume, at the other end, while the mixture is held at a temperature in the range of 200-325 degrees C.

The rate of polishing, as well as the quality of polishing, of the wafers of sapphire or magnesium spinel have been found to be orientation sensitive and, accordingly, effective polishing is achieved for magnesium spinel having the orientations (100) and (110). Effective polishing is achieved for sapphire having the orientations (0001), (1123), (1100), (1124), (1120) and (0112). The sapphire or magnesium spinel 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 thereby obtained.

A preferred polishing mixture for sapphire is 1 part sulfuric acid to 1 part phosphoric acid by volume at a temperature of 285 degrees C. For magnesium spinel, the preferred mixture is 3 parts sulfuric acid to 1 part phosphoric acid at a temperature of 250 degrees C.

While the above described method can be employed to remove the damage introduced into the bulk of the wafers, a...