Trench isolated integrated circuits including voids

Abstract

A trench isolated integrated circuit includes at least one void in the trench at the trench corner. The trench comprises a trench wall, a trench floor and a trench corner between the trench wall and the trench floor. An insulating region is included in the trench, including on the trench floor and on the trench wall. The insulating region is spaced apart from the trench corner to define a void at the trench corner. The insulating region may also be spaced apart from a portion of the trench wall, to define a second void on the trench wall that is spaced apart from the void at the trench corner. The voids may reduce stresses cased by the thermal mismatch between the insulating region and the integrated circuit substrate, to thereby improve integrated circuit reliability and/or performance. Methods of forming trench isolated integrated circuits according to invention include the steps of forming a trench in an integrated circuit substrate. The trench comprises a trench wall, a trench floor and a trench corner between the trench wall and the trench floor. A first insulating layer is formed on the trench wall and on the trench floor. A second insulating layer is formed on the first insulating layer opposite the trench wall and spaced apart from the trench floor. The first insulating layer is isotropically etched using the second insulating layer as a mask to form a void in the first insulating layer between the second insulating layer and the trench corner. A third insulating layer is formed on the second insulating layer, opposite the first insulating layer.