Browse Prior Art Database

Fabrication of Self Aligned High Frequency MOSFET or MISFET

IP.com Disclosure Number: IPCOM000074860D
Original Publication Date: 1971-Jun-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Yu, HN: AUTHOR

Abstract

This description relates to a method of fabrication of a MOSFET with self-aligned gate metal. The technique minimizes the overlap region of the gate relative to the source and drain regions so that overlap capacitance can be kept to a minimum. The fabrication steps of such a structure are shown in Figs. A-e.

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Fabrication of Self Aligned High Frequency MOSFET or MISFET

This description relates to a method of fabrication of a MOSFET with self- aligned gate metal. The technique minimizes the overlap region of the gate relative to the source and drain regions so that overlap capacitance can be kept to a minimum. The fabrication steps of such a structure are shown in Figs. A-e.

Starting with a p-type substrate 1 in Fig. A, into which n-type diffusions 2 have been made, polycrystalline silicon or a refractory metal such as molybdenum or tungsten is formed as a gate electrode 3 on top of gate oxide 4, which has been grown after forming n-diffusions 2. In the next step, both the gate electrode 3 and the gate oxide 4 are etched as shown in Fig. B, using etchants well known in semiconductor fabrication. An insulating layer 5 (SiO(2), Al(2)O(3), Si(3)N(4), for example) doped with an appropriate dopant, such as arsenic phosphorous or antimony is deposited on the surface of substrate 1, as shown in Fig. C. Doped insulating layer 5 now serves as a diffusion source. The substrate is heated in another diffusion cycle at a suitable temperature. Source and drain regions 2 are now extended to the edge of gate oxide 4 and gate metal 3, as shown in Fig. D. The overlap region between the gate 3 and source and drain regions 2 is kept to a minimum, since diffusion from insulating layer 5 can be controlled to a very shallow depth, e.g., 1,000 angstroms to less than 2,000 angstroms, with a she...