| 摘要 |
1,035,089. Masking methods. INTERNATIONAL BUSINESS MACHINES CORPORATION. June 4, 1965 [June 9, 1964], No. 23904/65. Heading H1K. When a body such as a gallium arsenide crystal is coated with a substance of different thermal expansion coefficient such as silicon dioxide, rapid heating of the coated body produces cracks in the coating and these cracks tend to be orientated parallel to the grain of the body: in the case of a crystal whose surface plane is in the 111 direction the cracks are in the 112 direction (Fig. 1, not shown). This property provides a technique for masking such a body, e.g. to allow deposition of a set of parallel narrow strips of material on to a semiconductor body. In Figs. 2 and 3 (not shown) a gallium arsenide crystal 1 has its surface coated with silicon dioxide 2 and narrow channels 3, parallel to the grain of the underlying crystal, are cut in the oxide surface to about half its depth. On heating, cracks 5 form preferentially in these channels and break through to the semi-conductor surface. Typically the oxide coating is 10,000 Š thick, the channels 5000 Š deep and the cracks 0À1 Á wide. As an alternative to forming channels in the oxide, the latter may be covered with a layer of another material weakened-by thinning or cutting through-at the sites selected for preferential development of cracks in the oxide. It is also possible to control the location of these cracks by electric, magnetic or mechanical forces acting on the semi-conductor crystal during the heating, these forces may be oscillatory and such as to set up standing waves in the crystal. Fig. 4 (not shown) depicts an N-type crystal, masked by the above method, provided with a PN junction by epitaxial deposition of P-type material through one of the cracks. Fig. 5 (not shown) depicts an apparatus in which the coated crystal is first heated to produce the cracks and then exposed to the vapour of the substance to be epitaxially deposited through the cracks. |
