Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
1998-01-20
2001-09-11
Hiteshew, Felisa (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C438S742000
Reexamination Certificate
active
06287975
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a method for minimizing and containing the critical dimension growth of a feature on a semiconductor wafer and any other product, such as for example, the magnetic head for a disk drive and a flat panel display, which could be constructed using semiconductor processing techniques.
BACKGROUND OF THE INVENTION
The critical dimension (CD) of a feature on a semiconductor wafer, or any product fabricated using semiconductor processing techniques, is a width of that feature. The pitch is generally defined as a critical dimension plus the distance to the next feature.
For semiconductor process methods using etch techniques, lithographic masking layers, such as for example photoresist layers, can be formed on top of the material to be etched. Photoresist layers define the desired features, masking the portion of underlying layer which is not to be etched, and leaving exposed the portion to be etched. During the etching process, materials from a portion of the layer which is etched, as well as compounds formed by various combinations of the etchant gases, the lithographic mask, and the materials of the layer to be etched, can tend to coat the sides of the desired feature, and the lithographic mask, and thereby increase the critical dimension of the feature beyond that defined immediately under the lithographic mask. Such growth of the critical dimension can disadvantageously diminish the space between the features and thereby adversely affect the functionality of the features.
As is known in the art, lithographic masks can include by way of example only, (i) soft masks such as photoresist masks, e-beam resist masks, x-ray resist masks, and syncotron particle acceleration resist masks, and (ii) hard masks, such as metals and oxides of metals such as silicon dioxide (SiO
2
). However, such soft and hard masks have not been found to be particularly useful in controlling the critical dimension growth.
Accordingly, there is a need to provide a semiconductor processing methodology which allows for the desired features to be appropriately etched without causing a growth of the critical dimension of the feature during the etching process.
SUMMARY OF THE INVENTION
The present invention provides for a methodology which allows for etching the features while controlling or minimizing the growth of the critical dimension of the feature during the etching process. The method is useful for fabricating semiconductor wafers in order to produce chip products, magnetic heads for disk drives, and flat panel displays, by way of example only.
The method for critical dimension growth containment includes placing a wafer with a hard mask comprised of a reactive metal, deposited over a layer to be etched in a reactor and etching the wafer in the reactor. The placing step further includes placing a hard mask which is comprised of a reactive metal of an oxide, nitride, fluoride, carbide, boride, or some combination of an oxide, nitride, fluoride, carbide, and/or boride of a reactive metal. Such combination could include, by way of example only, an oxinitride, oxiboride, oxifluoride or oxicarbide, of a reactive metal or any other combination or compound formed by exposing a reactive metal to ions or radicals of any combinations of oxygen, nitrogen, fluorine, boride, and/or carbon.
The placing step further includes placing a wafer having a hard mask which is comprised of one of titanium, aluminum, tantalum, tungsten, cobalt, or molybdenum, or an oxide, nitride fluoride carbide or boride of said reactive metals.
The hard mask could include other reactive metals such as copper, iron and nickel and their compounds.
The method also includes exposing a hard mask to a stream of oxidizing gas such as oxygen, nitrogen, fluorine, boron or carbon in the reactor prior to or during the etch step in order to form a compound with the reactive metal.
The method also includes exposing a hard mask to an ion or radical of oxygen, nitrogen, fluorine, boron or carbon in the reactor prior to or during the etch step in order to form an oxide, a nitride, a fluoride, a boride or a carbide or some combination of the preceding on the reactive metal.
The hard mask can also include any materials that are compatible with semiconductor fabrication processes, and semiconductor manufacturing tools and equipment which have the characteristics described herein.
The invention further includes selecting a hard mask which has or can develop an oxide, nitride, fluoride, carbide, or boride, or some combination of a reactive metal.
In another aspect of the invention, the method includes increasing the rate that one of an oxide, a nitride, a fluoride, a boride or a carbide forms on the hard mask in order to slow down the rate of erosion of the hard mask.
The invention further includes selecting a hard mask that is comprised of a metal which has a low sputter yield.
A further aspect of the present invention is to provide a method for containing critical dimension growth during an etching process including the step for placing a wafer or other substrate, for making by way of example only, a semiconductor product, a magnetic head or a flat panel display, with a hard mask disposed over a layer to be etched in a reactor, wherein the hard mask has at least one of a low sputter yield and a low reactivity to the etch chemistry of the etch process.
Accordingly, it is an object of the present invention to contain, control and minimize the growth of the critical dimension of a feature being etched.
It is still a further object of the present invention to perform the methodology of controlling and minimizing the critical dimension growth of a feature during an etch process, whether the process be conducted at low (below atmospheric) pressure, atmospheric pressure, or high (above atmospheric) pressure.
Other objects, advantages and features of the invention will be described herein and evidenced in the claims and figures.
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Chemistry of titanium dry etching in fluorinated and chlorinated gases, Pure & Appl. Chem., vol. 64, No. 5, pp. 703-707, 1992; Printed in Great Britain, © 1992 IUPAC; Francesco Fracassi and Riccardo d'Agostino.
Cofer Alferd
DeOrnellas Stephen P.
Jerde Leslie G.
Fliesler Dubb Meyer & Lovejoy LLP
Hiteshew Felisa
Tegal Corporation
Umez-Eronini Lynette T.
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