This invention relates to methods of forming trench isolation in the fabrication of integrated circuitry and to methods of fabricating integrated circuitry.
In the fabrication of integrated circuitry, numerous devices are packed onto a single small area of a semiconductor substrate to create an integrated circuit. Many of the individual devices are electrically isolated from one another. Accordingly, electrical isolation is an integral part of semiconductor device design for preventing unwanted electrical coupling between adjacent components and devices.
As the size of integrated circuits is reduced, the devices that make up the circuits are positioned closer together. Conventional methods of isolating circuit components use trench isolation. Such is typically formed by etching trenches into a semiconductor substrate and filling the trenches with insulative material. As the density of components on the semiconductor substrate increased, the widths of the trenches have decreased. Further, it is not uncommon to find different areas of a substrate as having different width and/or different depth isolation trenches. Also and regardless, some areas of integrated circuitry have greater minimum active area spacing between isolation trenches than do other areas.
Insulative materials that are commonly utilized for electrical isolation within isolation trenches include silicon dioxide and silicon nitride. For example, it is common to thermally oxidize trench sidewalls within a silicon-comprising semiconductor substrate, and provide a thin silicon nitride layer thereover. The remaining volume of the trenches is then filled with an insulative material, for example high density plasma deposited silicon dioxide. Yet as trenches have become deeper and narrower, high density plasma deposited oxides can result in undesired void formation within the trenches during filling. Alternate techniques which provide better conformal deposition within isolation trenches include spin-on-dielectrics and chemical vapor deposition utilizing ozone and tetraethylorthosilicate (TEOS). Such latter processes, while resulting in good void-free gap filling, typically result in a silicon dioxide deposition which is not as dense as desired. Accordingly, a steam anneal at very high temperatures is typically utilized to densify the deposited silicon dioxide. To preclude undesired oxide formation of underlying material, a silicon nitride oxidation barrier layer is typically employed within all of the trenches to shield underlying material from being oxidized during the steam anneal.
Further and regardless, deposition using ozone/TEOS or high density plasma oxides typically requires deposition thicknesses much greater than the depths of the trenches themselves to get adequate fill within the trenches. This of course adds to the time required to later remove such material from laterally outward of the trenches. Further even with spin-on-dielectrics, it is sometimes very difficult to get the material to deep within high aspect ratio trenches, and to densify such material at the bases of such trenches.
While the invention was motivated in addressing the above identified issues, it is in no way so limited. The invention is only limited by the accompanying claims as literally worded, without interpretative or other limiting reference to the specification, and in accordance with the doctrine of equivalents.
The invention includes methods of forming trench isolation in the fabrication of integrated circuitry, and methods of fabricating integrated circuitry. In one implementation, first and second isolation trenches are formed into semiconductive material of a semiconductor substrate. The first isolation trench has a narrowest outermost cross sectional dimension which is less than that of the second isolation trench. An insulative layer is deposited to within the first and second isolation trenches effective to fill remaining volume of the first isolation trench within the semiconductive material but not that of the second isolation trench within the semiconductive material. The insulative layer comprises silicon dioxide deposited from flowing TEOS to the first and second isolation trenches. In one aspect, a spin-on-dielectric is deposited over the silicon dioxide deposited from flowing the TEOS within the second isolation trench within the semiconductive material, but not within the first isolation trench within the semiconductive material. In one aspect, a spin-on-dielectric is deposited on the silicon dioxide deposited from flowing the TEOS within the second isolation trench within the semiconductive material (with “on” in the context of this document meaning in at least some direct, touching, physical contact therewith), but not within the first isolation trench within the semiconductive material. The spin-on-dielectric is deposited effective to fill remaining volume of the second isolation trench within the semiconductive material. The spin-on-dielectric is densified within the second isolation trench.
In one implementation, the first isolation trench has a largest aspect ratio of at least 25. In one implementation, the spin-on-dielectric is deposited over the semiconductor substrate laterally outward of the first and second isolation trenches to a thickness no greater than 4,500 Angstroms. In one implementation, the insulative layer comprising silicon dioxide deposited by flowing TEOS has a seam which extends at least partially into the first isolation trench. The densifying is preferably effective to remove such seam.
Other implementations and aspects are contemplated.
Preferred embodiments of the invention are described below with reference to the following accompanying drawings.
This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8).
The invention contemplates methods of forming trench isolation in the fabrication of integrated circuitry and, in one exemplary preferred embodiment, in the fabricating of memory circuitry. Referring initially to
Semiconductor substrate 10 is depicted as comprising bulk semiconductive material 16, for example lightly doped monocrystalline silicon. Of course, semiconductor-on-insulator constructions and other substrates, whether existing or yet-to-be developed, are also contemplated. A pad oxide layer 18 has been formed over semiconductive material 16, and a silicon nitride masking layer 20 formed over pad oxide layer 18.
Referring to
In the depicted exemplary embodiment, at least one of first isolation trenches 22, 22a has a narrowest outermost cross sectional dimension “A” which is less than that of at least one of second isolation trenches 24, 24a and which is depicted by dimension “B”. By way of example only, an exemplary narrowest outermost dimension A for first isolation trenches 22, 22a is from 80 Angstroms to 100 Angstroms, while that for narrowest dimension B of second isolation trenches 24, 24a is from 1,020 Angstroms to 10,020 Angstroms. Such trenches might taper inwardly as shown, with an exemplary width at the trench bases being from 40 Angstroms to 60 Angstroms for isolation trenches 22, 22a, and from 1,000 Angstroms to 10,020 Angstroms for second isolation trenches 24, 24a. An exemplary depth range from the outermost surface of material 16 for trenches 22, 22a, 24 and 24a is from 3,000 Angstroms to 5,000 Angstroms, with 4,000 Angstroms being a specific preferred example. In one exemplary implementation, the first isolation trenches have respective largest aspect ratios of at least 25. In the context of this document, a “largest aspect ratio” is the maximum depth of the trench divided by its narrowest outermost cross sectional dimension. In further preferred embodiments, the first isolation trenches have respective largest aspect ratios of at least 30, of at least 40, and of at least 50.
Further and regardless, in one exemplary aspect of the invention, first circuitry area 12 comprises a first minimum active area spacing C between isolation trenches 22, 22a received therein and the second circuitry area comprises a second minimum active area spacing D between isolation trenches 24, 24a received therein. The first minimum active area spacing is less than the second minimum active area spacing. By way of example only, an exemplary first minimum active area spacing C is from 10 to 110 nanometers, while that for second minimum active area spacing D is from 200 to 800 nanometers.
Referring to
Referring to
Referring to
In one preferred implementation, the spin-on-dielectric is deposited over the semiconductor substrate laterally outward of the first and second isolation trenches to a thickness “Z” which is no greater than 4,500 Angstroms, and more preferably to no greater than 4,000 Angstroms. Such can facilitate reduction in the amount of material over substrate material 16 that will typically be removed subsequently.
Referring to
In one exemplary aspect, the invention also contemplates a method of fabricating integrated circuitry which includes forming isolation trenches within semiconductive material of a first circuitry area of a semiconductor substrate and within semiconductive material of a second circuitry area of the semiconductor substrate, by way of example only as described above in connection with
In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.
This patent resulted from a continuation of U.S. patent application Ser. No. 11/097,876 which was filed Apr. 1, 2005 and which is incorporated herein by reference in its entirety.
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Number | Date | Country | |
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Parent | 11097876 | Apr 2005 | US |
Child | 13211174 | US |