Active solid-state devices (e.g. – transistors – solid-state diode – Integrated circuit structure with electrically isolated... – Passive components in ics
Reexamination Certificate
2002-02-04
2002-11-26
Tsai, Jey (Department: 2812)
Active solid-state devices (e.g., transistors, solid-state diode
Integrated circuit structure with electrically isolated...
Passive components in ics
C257S532000, C257S306000
Reexamination Certificate
active
06486529
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly, to a method and structure for the creation of a combined inductor and multiple capacitors structure.
(2) Description of the Prior Art
Developments in the semiconductor industry have over the years been aimed at creating higher performance devices for competitive or lower prices. These developments have resulted in extreme miniaturization of semiconductor devices that has been made possible by numerous and mutually supporting advances in semiconductor processes and by materials that are used for the creation of semiconductor devices, this in combination with new and sophisticated device designs. While most semiconductor devices are aimed at processing digital data, there has also been a broad stream of developments that is aimed at incorporating analog functions into circuits that process digital and analog data or analog data only. It is thereby the objective to create analog data processing devices using digital processing procedures and equipment. One of the major challenges in the creation of analog processing circuitry is that a number of the components that are used for analog circuitry are large in size and are therefore not readily integrated into digital devices that typically have feature sizes in the sub-micron range. The main components that offer a challenge in this respect are capacitors and inductors since both these components are, for typical analog processing circuit, of considerable size. The creation of inductive or capacitive components must therefore emphasize that these components can be created on a relatively small surface area of a semiconductor substrate while using methods and procedures that are well know in the art for the creation of semiconductor devices. The created inductor and capacitor must further be high quality components that can be used in high frequency applications while incurring minimum loss of power.
It is clear that, by combining the creation on one semiconductor monolithic substrate of circuitry that is aimed at the functions of digital and analog data manipulation and storage, a number of significant advantages are achieved. Such advantages include the reduction of manufacturing costs and the reduction of power consumption by the combined functions.
Capacitors and inductors are typically applied in the field of modern mobile communication applications that make use of compact high-frequency semiconductor devices. These devices have over the years continually improved in its performance characteristics, such as lower power consumption, smaller size of the device, wider frequency range of the applications, and lower noise levels. One of the main applications of semiconductor devices in the field of mobile communication is the creation of Radio Frequency (RF) amplifiers and oscillators. RF amplifiers or oscillators contain a number of standard components whereby however a major component of a typical RF amplifier is a tuned circuit that contains inductive and capacitive components. The electrical characteristic of a tuned circuit are such that, dependent on and determined by the magnitudes of its inductive and capacitive components, the tuned circuit forms an impedance that is frequency dependent, thereby enabling the tuned circuit to either be high or a low impedance for signals of a certain frequency. The tuned circuit can therefore either reject or pass and further amplify components of an analog signal based on the operating frequency range of that component. The tuned circuit can in this manner be used as a filter to filter out or remove signals of certain frequencies or to remove noise from a circuit configuration. One commonly used tuned circuit is the LC resonance circuit. One of the problems that is encountered when creating an inductor on the surface of a semiconductor substrate is that the self-resonance caused by the parasitic capacitance between the (spiral) inductor and the underlying substrate as well as the power consumption by parasitic resistances will limit the use of the inductor at high frequencies. As part of the design of such an inductor it is therefore of importance to reduce the capacitive coupling between the created inductor and the underlying substrate and resistive power loss.
Typically, inductors that are created on the surface of a substrate are of a spiral shape whereby the spiral is created in a plane that is parallel with the plane of the surface of the substrate. Conventional methods that are used to create the inductor on the surface of a substrate suffer several limitations. Most high quality factor (Q) inductors form part of a hybrid device configuration or of Monolithic Microwave Integrated Circuits (MMIC's) are created as discrete components, the creation of which is not readily integratable into a typical process of Integrated Circuit manufacturing.
The parameter by which the applicability of an inductor is indicated is the Quality (Q) factor of the inductor. The quality factor Q of an inductor is defined as Q=Es/El, wherein Es is the energy that is stored in the reactive (i.e. inductive) portion of the component while El is the energy that is lost as heat in the resistive portion of the component. The higher the Q factor of the component, the closer the resistive value of the component approaches zero. For components, the quality factor serves as a measure of the purity of the reactance (or the susceptance) of the component, which can be degraded due to parasitics. In an actual configuration, there are always some physical resistors that will dissipate power, thereby decreasing the power that can be recovered. The quality factor Q is dimensionless. A Q value of greater than 100 is considered high enough for discrete inductors that are mounted on the surface of Printed Circuit Boards. For inductors that form part of an integrated circuit, the Q value is typically in the low range between about 3 and 20.
In creating an inductor on a monolithic substrate on which additional semiconductor devices are created, the parasitic capacitances that occur as part of this creation also limit the Q that can be achieved for the inductor to a value of 20 or less. This limitation, which is due to the smaller current flowing through the inductor as a consequence of the charging current of the parasitic capacitances, is for many applications not acceptable. Dependent on the frequency at which the LC circuit is designed to resonate, significantly larger values of Q, such as 100 or more, must be available. Prior Art has in this been limited to creating high values of Q as separate units, and in integrating these separate units with the surrounding device functions. This negates the advantages that can be obtained when using the monolithic construction of creating both the inductor and the surrounding devices on one and the same semiconductor substrate. The non-monolithic approach also has the disadvantage that additional wiring is required to interconnect the sub-components of the assembly, thereby again introducing additional parasitic capacitances and resistive losses over the interconnecting wiring network. For many of the applications of the RF amplifier, such as portable battery powered applications, power consumption is at a premium and must therefore be as low as possible. These problems take on even greater urgency with the rapid expansion of wireless applications such as portable telephones and the like. Wireless communications form a rapidly expanding market, where the integration of RF integrated circuits is one of the most important challenges. One of the approaches is to significantly increase the frequency of operation to for instance the range of 10 to 100 GHz. For such high frequencies, the value of the quality factor obtained from silicon-based inductors is significantly degraded. For applications in this frequency range, monolithic inductors have been created using sapphire or GaAs as a base. These inductors have a considerably lower
Chi Min-Hwa
Tsai Chia-Shiung
Tu Yeur-Luen
Ackerman Stephen B.
Saile George O.
Taiwan Semiconductor Manufacturing Company
Tsai Jey
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