Motorola Corporation

F J Robinson

Francine Y Robb

Thomas E Wood

Bridget Svechovsky

A new method is used to fabricate an isolation trench to prevent spurious epitaxial growth at the top edge of the trench opening and at pin holes in oxide over the active area. The method involves etching a deep trench into a semiconductor wafer that is patterned with a mask oxide layer, and then depositing a low temperature oxide, followed by growing a thermal oxide layer under the mask oxide and in the trench. When the oxide at the bottom of the trench is removed to provide a seed for the growth of selective epitaxial silicon, an oxide layer thick enough to leave a protective coating over the active area and at the trench opening is provided which prevents spruious epitaxial silicon growth.

Method of forming an oxide liner and active area mask for selective

Filled trenches useful in semiconductor devices for isolation or other purposes are provided by etching a trench in the semiconductor substrate, lining the trench with a first material (e.g., silicon dioxide), covering the first material with a seed layer (e.g., polysilicon) for nucleating a further material, removing a part of the seed layer on the first material in an upper part of the trench, and then filling the trench by selectively depositing the further material (e.g., polysilicon) on the remaining seed layer. Thermally grown silicon dioxide is convenient for the first material. The first material and seed layer may extend over the substrate surface. The upper portion of the seed layer is conveniently removed by first covering the seed layer with a mask (e.g., photoresist) and then etching back the mask to expose the seed layer above the substrate surface and in the upper portion of the trench, leaving part of the mask in the lower portion of the trench. The exposed portion of the seed layer is then etched away. The remaining portion of the mask is removed before growing the trench filling material on the remaining part of the seed layer in the trench.

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Scottsdale, AZ, United States of America

F J Robinson