Browse Prior Art Database

Self Aligning IGFET with Refractory Metal Gate

IP.com Disclosure Number: IPCOM000076074D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Kaplan, LH: AUTHOR

Abstract

This is a process for fabrication of insulated-gate field-effect transistor (IGFET) device circuits, which involves only noncritical photolithographic alignment steps and which has the added advantage of reducing overlap capacitance via a self-aligned gate. The scheme involves the use of a patterned refractory metal to form a source-drain opening, allowing diffusion to be done in automatic alignment with the patterned gate metal edge. Further use of the metal as an oxidation mask (after repatterning) allows the growth of thick passivating oxide without the need for any critical alignment steps.

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Self Aligning IGFET with Refractory Metal Gate

This is a process for fabrication of insulated-gate field-effect transistor (IGFET) device circuits, which involves only noncritical photolithographic alignment steps and which has the added advantage of reducing overlap capacitance via a self-aligned gate. The scheme involves the use of a patterned refractory metal to form a source-drain opening, allowing diffusion to be done in automatic alignment with the patterned gate metal edge. Further use of the metal as an oxidation mask (after repatterning) allows the growth of thick passivating oxide without the need for any critical alignment steps.

A more specific description of the process is as follows. A thin silicon dioxide layer is grown over the wafer. A coating of inert refractory metal is deposited thereover. The metal is patterned by conventional photoresist and etching techniques. The resulting metal pattern is used for mask etching of the silicon dioxide layer for subsequent source/drain diffusion. After the diffusion step, a block-out mask is used to remove metal from nongate areas (no critical alignment). The metal is used to mask the gate oxide while growing a thick thermal oxide elsewhere. Contact holes are formed over the source/drain (no critical alignment). Aluminum is deposited and patterned, using a mask which provides only a small connecting line over the gate (no critical alignment). The resulting structure is shown in the figure wherein the element...