Massachusetts Institute of Technology

Stephen E Bernacki

Jack I Raffel

Jack I Raffai

A process is described which combine polycrystalline isolation of collectors and shallow oxide isolation of bases. This approach is capable of providing deep dielectric isolation, surface planarity and the high density of walled emitter geometries, a combination heretofore unobtainable by any other means. This isolation scheme has been used to fabricate ECL gate chains. The transistors were located in 2.5 micron thick n epi islands surrounded by 5.times.10.sup.5 ohm-cm polysilicon selectively oxidized with silicon nitride masking to a thickness of one micron. The oxide 'bump' at the nitride mask was typically 3000 A and the epi-poly step height was as small as 2600 A. The circuits have polysilicon resistors and were fabricated using both thermal diffusion and ion implantation. The power-delay product of these circuits was approximately one-half that of junction isolated circuits.

Dielectric isolation using shallow oxide and polycrystalline silicon

A process is described which combines polycrystalline isolation of collectors and shallow oxide isolation of bases. This approach is capable of providing deep dielectric isolation, surface planarity and the high density of walled emitter geometries, a combination heretofore unobtainable by any other means. This isolation scheme has been used to fabricate ECL gate chains. The transistors were located in 2.5 micron thick n epi islands surrounded by 5.times.10.sup.5 ohm-cm polysilicon selectively oxidized with silicon nitride masking to a thickness of one micron. The oxide 'bump' at the nitride mask was typically 3000 A and the epi-poly step height was as small as 2600 A. The circuits have polysilicon resistors and were fabricated using both thermal diffusion and ion implantation. The power-delay product of these circuits was approximately one-half that of junction isolated circuits.

Dielectric isolation method using shallow oxide and polycrystalline

A process is described which combines polycrystalline isolation of collectors and shallow oxide isolation of bases. This approach is capable of providing deep dielectric isolation, surface planarity and the high density of walled emitter geometries, a combination heretofore unobtainable by any other means. This isolation scheme has been used to fabricate ECL gate chains. The transistors were located in 2.5 micron thick n-epi islands surrounded by 5.times.10.sup.5 ohm-cm polysilicon selectively oxidized with silicon nitride masking to a thickness of one micron. The oxide 'bump' at the nitride mask was typically 3000 A and the epi-poly step height was as small as 2600 A. The circuits have polysilicon resistors and were fabricated using both thermal diffusion and ion implantation. The power-delay product of these circuits was approximately one-half that of junction isolated circuits.

A source of electrons or charged particles is contained in a baffled enclosure at less than atmospheric pressure. The source projects the electrons or charged particles to strike a target with a velocity which generates soft x-rays. The target is in a chamber at substantially atmospheric pressure in a gaseous environment which is only slightly dispersive and absorptive of the soft x-rays. Access to this chamber is provided to insert a mask and substrate for lithographing by the soft x-rays.

Non vacuum soft x-ray lithographic source

An electrical voltage is connected between a flexible soft-X-ray mask and a substrate causing the mask to make intimate contact and thereby conform to slight irregularities of the surface of the X-ray sensitive polymer on the substrate to minimize the effect of these irregularities during exposure to soft-X-rays.

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Worcester, MA, United States of America

Stephen E Bernacki