STRUCTURE FOR PICKING UP A BURIED LAYER AND METHOD THEREOF
A structure for picking up a buried layer is disclosed. The buried layer is formed in a substrate and has an epitaxial layer formed thereon. One or more isolation regions are formed in the epitaxial layer. The structure for picking up the buried layer includes a contact-hole electrode formed in each of the isolation regions. A bottom of the contact-hole electrode is in contact with the buried layer. As the structure of the present invention is formed in the isolation region without occupying any portion of the active region, its size is much smaller than that of a sinker region of the prior art. Therefore, device area is tremendously reduced. Moreover, as the contact-hole electrode picks up the buried layer by a metal contact, the series resistance of the device can be greatly reduced. A method of forming the above structure is also disclosed.
1 . A structure for picking up a buried layer, the buried layer being formed in a substrate and having an epitaxial layer formed thereon, the epitaxial layer having one or more isolation regions formed therein, the structure comprising a contact-hole electrode formed in each of the isolation regions, a bottom of the contact-hole electrode being in contact with the buried layer.
2 . The structure according to claim 1 , wherein the contact-hole electrode is formed of tungsten.
3 . The structure according to claim 2 , wherein the contact-hole electrode further comprises a titanium and/or titanium nitride barrier layer formed on its bottom.
4 . The structure according to claim 1 , wherein the buried layer has a doping concentration of higher than 1×10 18 atoms/cm 3 .
5 . A method of forming the structure for picking up a buried layer according to claim 1 , comprising:
forming a doped region in a substrate by performing an ion implantation process;
growing a single crystal silicon epitaxial layer on the doped region via an epitaxial process such that the doped region becomes a buried layer;
forming one or more isolation regions in the epitaxial layer;
etching each of the isolation regions to form a hole therein, a bottom of the hole being in contact with the buried layer; and
filling a metal into the hole to form a contact-hole electrode.
6 . The method according to claim 5 , wherein each of the isolation regions is formed by using a local oxidation of silicon (LOCOS) process or a shallow trench isolation (STI) process.
7 . The method according to claim 5 , wherein etching each of the isolation regions to form a hole comprises:
etching the isolation region until the boundary between the isolation region and the epitaxial layer is reached; and
etching the epitaxial layer until a surface of the buried layer is exposed.
8 . The method according to claim 5 , wherein filling a metal into the hole comprises filling tungsten into the hole via a chemical vapor deposition (CVD) process.
9 . The method according to claim 5 , wherein filling a metal into the hole comprises:
forming a titanium and/or titanium nitride barrier layer over the bottom of the hole; and
filling a metal into the hole to form a contact-hole electrode therein.
10 . The method according to claim 9 , wherein the metal is tungsten and is filled via a CVD process.