US 7,320,912 B2
Trench capacitors with buried isolation layer formed by an oxidation process and methods for manufacturing the same
Yueh-Chuan Lee, Nantou (Taiwan); and Ming-Sheng Tung, Hualien (Taiwan)
Assigned to PROMOS Technologies Inc., Hsinchu (Taiwan)
Filed on May 10, 2005, as Appl. No. 11/125,676.
Prior Publication US 2006/0255388 A1, Nov. 16, 2006
Int. Cl. H01L 21/8242 (2006.01)
U.S. Cl. 438—243  [438/244; 438/245; 438/386; 438/387; 438/388; 257/E29.346] 11 Claims
OG exemplary drawing
 
1. A method for forming a trench capacitor in a substrate, the method comprising:
removing a portion of the substrate to form a trench within the substrate;
forming at least one buried isolation layer within the substrate, the buried isolation layer intersecting with the trench and having at least one gap providing body contact between a first substrate area above the buried isolation layer and a second substrate area below the buried isolation layer, the step of forming the at least one buried isolation layer within the substrate further including:
a) forming at least a first epitaxial layer over the substrate;
b) forming at least a second epitaxial layer over the first epitaxial layer;
c) defining a body contact area by removing a portion of the first epitaxial layer and the second epitaxial layer;
d) forming a third epitaxial layer at least in the body contact area;
e) removing the first epitaxial layer; and
f) forming the buried isolation layer in or near a space provided by removing the first epitaxial layer, the buried isolation layer being a dielectric layer formed by an oxidation process;
forming in the substrate a first electrode of the trench capacitor at least in areas surrounding a lower portion of the trench;
forming a dielectric layer of the trench capacitor, the dielectric layer covering a surface of the trench at least for the portion below the buried isolation layer; and
forming a second electrode of the trench capacitor in the trench.