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A Device and Implementation Procedures for Increasing and Tuning the Quality Factor of Varactors

IP.com Disclosure Number: IPCOM000202450D
Publication Date: 2010-Dec-15
Document File: 7 page(s) / 750K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method to achieve a high adjustable quality factor without the need to implement special or complex circuit techniques during the design of on-chip integrated low pass and bandpass filters. The core idea is to utilize a hyper abrupt (HA) junction varactor with the appropriate layout dimensions to increase the quality factor of the as-produced device.

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A Device and Implementation Procedures for Increasing and Tuning the Quality Factor of Varactors

Design of on-chip integrated low pass and bandpass filters requires special and sometimes extensive or complicated circuit techniques. These circuit techniques provide a high and adjustable quality factor (Q). Some of these circuit techniques employ novel methods of controlled positive feedback along with an on-chip circuit transformer [1]. Various other circuit innovations exist in the art where adjustable high quality factors are obtained [2-8]. A high quality factor is also desirable in designing resonant cavities and resonator circuits, as well as for the design of atomic force microscopes [9-12].

Engineers and developers need more complex and extensive circuit special techniques or special devices to achieve a high and adjustable quality factor during the design of on-chip integrated low pass and bandpass filters.

The disclosed invention provides the means to achieve a high adjustable quality factor without the need to implement special or complex circuit techniques. This invention achieves these objectives without the need to utilize special or additional process mask levels in complementary metal-oxide semiconductor (CMOS) integrated technologies.

The invention employs a hyper abrupt (HA)

integrated CMOS Radio Frequency (RF) circuits [13, 14]. With choosing the appropriate Layout dimensions for the varactor, the quality factor of the as-produced device can be increased selectively and significantly to the desired value within a wide range. This is accomplished by applying a predetermined voltage, for a specified length of time, to the varactor in a reverse bias procedure.

There are multiple techniques to achieve the operation of increasing the Q for the HA

r. One procedure utilizes a special and relatively inexpensive process

mask level, and implements the increase in Q by applying a predetermined voltage for a specified length of time to a number of varactors wired to a common terminal. Other implementation procedures are also given.

Figure 1 illustrates a cross section of the HA junction varactor. A top view of the layout is shown in Figure 2 with the different appropriate process mask levels. A key element of this device in this invention is the anode width W.

Figure 1: Cross Section of HA Varactor

1

junction varacto

r, which is widely used in

junction varacto


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Cathode contact

N+ contact region from nfet s/d and NWell

Anode contact

n+ ii

P & N ii n+ ii

width


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n+

p+

n+

STI

STI

n

STI

STI

STI

STI

nwell

N cathode

nwell

Hyperabrupt P+ & N junction

N cathode implant region

Figure 2: Top View of Varactor Layout

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