The trench is filled with a cured aerogel. For a further embodiment, the invention provides an integrated circuit device. The trench is filled with an air gap. For one embodiment, the invention provides a method of isolating a first active region from a second active region in an integrated circuit device. The method includes forming a substrate by forming a dielectric layer, and coupling a semiconductor layer to the dielectric layer. The method further includes forming a trench in the substrate, wherein the first active region is on a first side of the trench and the second active region is on a second side of the trench.
Dielectric Polymers | SpringerLink
The method further includes filling the trench with a polymeric material and foaming the polymeric material. For another embodiment, the invention provides a method of isolating a first active region from a second active region in an integrated circuit device. The method further includes filling the trench with an aerogel material and curing the aerogel material. For yet another embodiment, the invention provides a method of isolating a first active region from a second active region in an integrated circuit device.
The method further includes filling the trench with a polymeric material, defining additional structures in the integrated circuit device, and removing the polymeric material. For a further embodiment, the invention provides a method of isolating a first active region from a second active region in an integrated circuit device. The method further includes filling the trench with a first fill material and defining additional structures in the integrated circuit device. The method still further includes removing the first fill material and filling the trench with a second fill material.
Further embodiments of the invention include integrated circuit devices and methods of varying scope, as well as apparatus, devices, modules and systems making use of such integrated circuit devices and methods.
Bulk material physics
In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the inventions may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that process, electrical or mechanical changes may be made without departing from the scope of the present invention. The terms wafer and substrate used in the following description include any base semiconductor structure.
Both are to be understood as including silicon-on-sapphire SOS technology, silicon-on-insulator SOI technology, silicon-on-nothing SON technology, thin film transistor TFT technology, doped and undoped semiconductors, epitaxial layers of a silicon supported by a base semiconductor structure, as well as other semiconductor structures well known to one skilled in the art. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims and equivalents thereof.
In accordance with some embodiments of the invention, foamed polymeric material is utilized as an insulating material within an integrated circuit IC. Polymeric materials are meant to include organic polymers i. For example, organic polymers are often characterized by having at least one of the following properties: high ductility; a low elastic modulus also referred to as Young's Modulus E ; or a low compressive yield strength.
In comparison, polymeric materials, as referred to herein, do not include brittle materials, such as ceramics, that are often characterized by their high compressive yield strength. Furthermore, polymeric materials will exhibit a tendency to flow more readily, making their application much easier than, for example, ceramic materials.
Any of the above polymeric materials capable of being foamed, however, is suitable for use in accordance with the present invention. The use of foamed polymeric material advantageously provides a lower dielectric constant insulating material within an integrated circuit relative to conventional silicon dioxide SiO 2. Foamed polymeric material combines the minimal dielectric constant of air, 1. The polymeric material behaves as a matrix for porous structures containing air.
The lower dielectric constant of such foamed polymeric material allows its advantageous use in integrated circuits where capacitive coupling has typically been problematic. Foamed polymeric material provides relief for capacitive coupling problems. Foamed polymeric material has many advantages. For example, unlike conventional SiO 2 , which has a dielectric constant of about 4. For one embodiment, the polymeric material utilized is able to withstand high subsequent processing temperatures in order to maximize the situations in which it can be utilized in an integrated circuit.
Such polymeric materials include polyimides due to their relative stability at higher temperatures. Polyimides may also be able to withstand exposure to higher temperatures for shorter durations. There are a wide variety of suitable polyimides available. Polyimides are usually prepared by reacting a dianhydride and an aromatic diamine. The resulting polyimide is classified according to the type of dianhydride used.
Type I polyimide has an elastic modulus of about 1. Type III polyimide has an elastic modulus of about 2. Type V polyimide has an elastic modulus of about 8. When such polymeric material is foamed, the elastic modulus should be reduced, while the coefficient of thermal expansion should remain about the same as that of the unfoamed polymeric material. Other suitable polymeric materials include, for example, parylene, polynorbornenes and fluorinated polymers. Parylene is based on p-xylyene and is prepared by vapor-phase polymerization.
Silane may be added to polynorbornenes to further lower the dielectric constant. The use of fluorinated polymers, preferably fluorinated polyimides, and more preferably fluorinated Type I polyimides have certain advantages.
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It is well known that the fluorine containing polymers have lower dielectric constants than similar polymers without fluorine additions. An additional advantage of the fluorine containing polymers is based on such polymers tending to be hydrophobic by nature.
ISBN 10: 0125139055
Such a tendency insures that even if water diffuses through the foamed polymer it will not condense in the voids so as to increase the dielectric constant of the foamed material. In addition to polymeric matrix materials, aerogels, such as silica aerogel, may be utilized to provide porous insulating material of the various embodiments.
Aerogels are generally a gel material that forms a porous matrix when liquid or solvent in the gel is replaced by air or another gaseous component. Aerogels generally experience only minimal volumetric change upon such curing. The general processing described herein can be adapted to a variety of integrated circuit devices. As one example, additional processing steps well understood by those skilled in the art may be utilized to define field-effect transistors FETs for such integrated circuit devices as a memory device. In FIG. A polysilicon layer is formed as a second layer overlying the substrate and the gate oxide layer For one embodiment, fill layer contains a polymer as defined herein.
For another embodiment, fill layer contains a silica aerogel. For a further embodiment, fill layer contains a methylsilsesquioxane MSSQ material. A wide variety of methods are available for applying the fill layer to the substrate For example, spin-on coating, spraying, and dipping may be utilized to apply polymers or aerogels to the substrate Furthermore, a combination of such application techniques or any other techniques known to one skilled in the art may be used. For embodiments utilizing a polymeric material for fill layer , the polymeric material is generally cured, or crosslinked, following formation.
For one embodiment, curing can include an optional low temperature bake to drive off most of the solvents that may be present in the polymer prior to crosslinking. In the case of an organic polymer, curing may further include baking in a furnace e. Other conventional polymers can be cured by exposing them to visible or ultraviolet light.
Still other conventional polymers can be cured by adding curing e. It is preferred, when using Type I polymers, to use a multiple step cure to achieve maximum effectiveness. It should be readily apparent to one skilled in the art that the times and temperatures may vary depending upon various factors, including the desired properties of the materials used, and that the present invention is in no manner limited to the illustrative multiple step cure presented above.
Various multiple step curing methods may be suitable. For one embodiment, hot plate curing is used. In the case of a polymer fill layer , cells are formed by foaming the fill layer In the case of an aerogel fill layer , cells are formed by driving off the liquid in the aerogel. Fill layer , as illustrated in FIG. Cell, as used herein, refers to an enclosed region of air or other gaseous component, e.
The size of a cell is determined by the nominal diameter of the enclosed region of gas. Preferably, the size of cells according to the present invention is no greater than about 3. More preferably, the size of cells according to the present invention is less than about 1. In some applications, the size of cells according to the present invention is below 0. It is desirable to have small cell sizes so that the fill layer can be utilized in extremely small trenches.
As long as the maximum cell size of the fill layer is smaller than the width of the trenches , adequate electrical insulation can be provided without a potentially detrimental reduction in mechanical integrity of the trenches For embodiments containing polymeric material in fill layer , a supercritical fluid is utilized to convert at least a portion of the polymeric material, into a foamed polymeric material.
Such use of supercritical fluids is known to facilitate formation of sub-micron cells in the foamed polymeric material. A gas is determined to be in a supercritical state and is referred to as a supercritical fluid when it is subjected to a combination of pressure and temperature above its critical point, such that its density approaches that of a liquid i. A wide variety of compounds and elements can be converted to the supercritical state in order to be used to form the foamed polymeric material of fill layer Although these and other fluids may be used, it is preferable to have a fluid with a low critical pressure, preferably below about atmospheres, and a low critical temperature of at or near room temperature.
Further, it is preferred that the fluids be nontoxic and nonflammable. Likewise, the fluids should not degrade the properties of the polymeric material used nor surrounding structures of the integrated circuit device For one embodiment, supercritical fluid CO 2 is utilized, due to the relatively inert nature of CO 2 with respect to most polymeric materials as well as other materials utilized in integrated circuit fabrication. Thus, when CO 2 is subjected to a combination of pressure and temperature above about 7.
Related Handbook of Low and High Dielectric Constant Materials and Their Applications
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