Method to Improve Integrated Diffused Resistor Voltage Linearity Using Dielectric Isolation
Original Publication Date: 2003-Apr-16
Included in the Prior Art Database: 2003-Apr-16
Vijay Parthasarathy: AUTHOR [+4]
This publication proposes an innovation to improve the voltage coefficient of an isolated pwell resistor by isolating the sidewalls of the pwell with oxide inside a deep trench instead of a nwell diffusion.
Abstract: This publication proposes an innovation to improve the voltage coefficient of an isolated pwell resistor by isolating the sidewalls of the pwell with oxide inside a deep trench instead of a nwell diffusion.
A diffused resistor is one of the most widely used resistors in smart power and analog mixed-signal applications due to the availability of various types of diffused wells and significantly better matching characteristics compared to poly resistors. Voltage coefficient, temperature coefficient and matching are key resistor analog parameters which require careful optimization. The voltage coefficient of a precision resistor is a measure of the percentage change in resistance when applying a reverse bias between the resistor terminals and the isolation of the resistor. A low value of voltage coefficient is particularly desirable since it limits the maximum voltage that can be applied to the resistor terminals and accuracy of precision analogy circuitry.
The conventional prior art for an isolated diffused resistor is shown in Figure 1. The figure shows a pwell resistor diffusion whose sidewalls are surrounded by an nwell diffusion which links to a N+ buried layer to form the isolation for the pwell. When a reverse bias is applied between the resistor terminals and the nwell isolation, the depleti...