Nested Two Trench P+ Contact
Original Publication Date: 1988-Oct-01
Included in the Prior Art Database: 2005-Feb-15
Disclosed is a method to form a deep substrate contact trench within a trench in semiconductor devices. This provides a way to contact the p+ substrate when p- and n- epitaxial silicon are grown atop it. In bipolar technology p+ substrates are used for substrate noise and ionizing radiation soft error reduction. In some structures, it is necessary to contact the substrate through about 10-15 mm thickness of n- and p- episilicon. As illustrated in Fig. 1, a shallow trench 1 is formed by a reactive ion etch (RIE) followed by nesting within that trench another trench 2, which is the standard deep trench. The shallow trench has no impact on the functionality of the deep trench, which is provided as a means for alignment. The trenches are filled with p+ polysilicon or p+ episilicon.