Method to form a buried implanted plate for DRAM trench storage capacitors

US5908310A · kind A · utility

Assignees

• International Business Machines Corporation · US
• Siemens Aktiengesellschaft · DE

Inventors

• Gary B. Bronner · Stormville, US
• Wilfried Hansch · South Burlington, US
• Wendell P. Noble · Colchester, US

Key dates

• Filing date: Dec 27, 1995
• Grant date: Jun 1, 1999
• Expiry date: Dec 27, 2015

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10D1/047

Abstract

A buried plate particularly suitable for formation of a common plate of a plurality of trench capacitors, such as are employed in dynamic random access memories, is formed by implantation of impurities in one or more regions of a wafer or semiconductor layer, epitaxially growing a layer of semiconductor material over the implanted regions and diffusing the implanted impurities into the wafer or semiconductor layer and into the epitaxial layer. Diffusion from such a source avoids process complexity compared with provision of diffusion sources within capacitor trenches and further provides an impurity concentration profile which varies with depth within the resulting body of semiconductor material, resulting in a well-defined boundary of the buried plate and an isolation region both above and below the buried plate. The structure allows biasing of the buried plate as desired, such as for reducing electrical stress on the capacitor dielectric to allow reduction in thickness thereof and reduction of area required for the trench capacitor.