STRUCTURE AND A METHOD FOR FORMING SCALABLE TRENCH CAPACITORS AND SUBSTRATE CONTACTS USING SINGLE TRENCH ETCH PROCESS HAVING TRENCH SIDEWALL SPACERS
Publication Date: 2002-Oct-17
The IP.com Prior Art Database
Key Words Trench, substrate contact, trench capacitor, coupling, bypass
structure and a method for FORMING scalable trench CAPACITORS AND substrate contacts USING single trench etch process HAVING trench sidewall spacers
Trench, substrate contact, trench capacitor, coupling, bypass
High-density bypass capacitors are of great importance in modern integrated circuits as they help reduce costs, help reduce variability associated with external components and also provide for more flexible design methodology. Trench capacitors are possible candidates for high-density, on-chip bypass applications.
In addition, low-resistance, top-side contacts to a highly doped substrate are also desirable, and quite common in bipolar and BiCMOS technology platforms. The availability of a good substrate contact also helps improve the quality factor (Q) of trench bypass capacitors.
For semiconductor processing, the substrate contacts and the trench capacitors are typically created from two separate trench etch modules. A reason for this is to avoid coating the open trench with photoresist when defining the substrate contacts from the trench capacitors. The “two-etch” approach increases both the processing time and the manufacturing cost for the product. The “single-trench-etch” approach involving photoresist can contaminate the trenches if any residual resist remains after cleaning. In addition, photoresist is an expensive material and can add to the manufacturing cost. Furthermore, from a device engineering perspective, one node of the conventional trench capacitor is necessarily tied to the substrate. This restricts one of the capacitor terminals to a fixed bias, and thereby reduces the range of circuit applications.
There is a need to create trench capacitors and substrate contacts using one trench etch process, in order to reduce both the process cycle time and the manufacturing cost. Also, if a trench capacitor can be constructed to permit the free biasing of both electrodes, it may be used for coupling applications in addition to bypass applications. Coupling capacitors need to have good isolation from the substrate (a high Q value), and a high specific capacitance. Trench capacitors, by construction, have a high capacitance per footprint area. Without loss of generality, consider a BiCMOS technology platform consisting of a highly doped buried layer (which may be localized or blanket across the wafer), and beneath it a lightly-doped region that separates it from a highly-doped substrate. Isolation of the floating capacitor from the substrate region may be improved by suitably controlling the thickness and doping concentration in the m-layer. Thus, availability of a high-density “floating” trench capacitor can add a lot of value to a technology platform.
It must be noted that typical capacitance density for integrated coupling capacitors (such as a planar metal-insulator-metal capacitor) is in the range of 1-5fF/m-m2, depending on the nature of the dielectric used and on various other ge...