Browse Prior Art Database

Forming Openings in an Insulating Layer

IP.com Disclosure Number: IPCOM000093333D
Original Publication Date: 1967-Aug-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Gates, HR: AUTHOR [+3]

Abstract

This process forms openings in a composite insulating layer. The latter contains an intermediate layer of a rapidly etchable material that is desired to be maintained or preserved as part of the composite insulating layer.

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Forming Openings in an Insulating Layer

This process forms openings in a composite insulating layer. The latter contains an intermediate layer of a rapidly etchable material that is desired to be maintained or preserved as part of the composite insulating layer.

Openings 1 are formed in a composite insulating layer. This contains thermal silicon dioxide layer 2, thin phosphosilicate glass layer 3, and sputtered or deposited protective glass layer 4. All are located on the surface of semiconductor body 5 preferably formed of silicon. During the semiconductor fabrication process of, for example, an NPN transistor device, layer 3 is formed during the emitter diffusion process. The formation of layer 3 is used as the doping source. Since it is desirable to maintain layer 3, layer 4 is formed on layer
3. This is in order to preserve layer 3 which provides stability for the semiconductor device.

This process prevents rapid lateral etching away of glass layer 3 which is caused during the formation of openings through the composite insulating layer in making ohmic contacts, for example. After the emitter diffusion process and before layer 4 is deposited on layer 3, openings are rapidly formed in layer 3 by using photolithographic masking and etching technique. An etchant that rapidly etches through the layer 3, but does not undercut this layer, is used. Subsequently, layer 4 is deposited by pyrolitic or RF sputtering devices to cover layer 3. Layer 4 is deposited in the...