Patent Application
20130221478
1. Field of the Invention
Generally, the present disclosure relates to the manufacturing of sophisticated semiconductor devices, and, more specifically, to various methods of forming isolation structures, such as trench isolation structures, for semiconductor devices using a spin-on glass material or a flowable oxide material.
2. Description of the Related Art
The fabrication of advanced integrated circuits, such as CPU's, storage devices, ASIC's (application specific integrated circuits) and the like, requires the formation of a large number of circuit elements in a given chip area according to a specified circuit layout, wherein field effect transistors (NMOS and PMOS transistors) represent one important type of circuit element used in manufacturing such integrated circuit devices. A field effect transistor, irrespective of whether an NMOS transistor or a PMOS transistor is considered, typically comprises doped source and drain regions that are formed in a semiconducting substrate that are separated by a channel region. A gate insulation layer is positioned above the channel region and a conductive gate electrode is positioned above the gate insulation layer. By applying an appropriate voltage to the gate electrode, the channel region becomes conductive and current is allowed to flow from the source region to the drain region.
To make an integrated circuit on a semiconducting substrate, the various semiconductor devices, e.g., transistors, capacitors, etc., are electrically isolated from one another by so-called isolation structures. Currently, most sophisticated integrated circuit devices employ so-called shallow trench isolation (STI) structures. As the name implies, STI structures are made by forming a relatively shallow trench in the substrate and thereafter filling the trench with an insulating material, such as silicon dioxide. One technique used to form STI structures initially involves growing a pad oxide layer on the substrate and depositing a pad nitride layer on the pad oxide layer. Thereafter, using traditional photolithography and etching processes, the pad oxide layer and the pad nitride layer are patterned. Then, an etching process is performed to form trenches in the substrate for the STI structure using the patterned pad oxide layer and pad nitride layer as an etch mask. Thereafter, a deposition process is performed to overfill the trenches with an insulating material such as silicon dioxide. A chemical mechanical polishing (CMP) process is then performed using the pad nitride layer as a polish stop layer to remove the excess insulation material. Then, a subsequent deglazing (etching) process may be performed to insure that the insulating material is removed from the surface of the pad nitride layer. This deglaze process removes some of the STI structures.
Numerous processing operations are performed in a very detailed sequence, or process flow, to form such integrated circuit devices, e.g., deposition processes, etching processes, heating processes, masking operations, etc. One problem that arises with current processing techniques is that, after the STI regions are formed, at least portions of the STI regions are exposed to many subsequent etching or cleaning processes that tend to consume, at least to some degree, portions of the STI structures subjected to such etching processes. As a result, the STI structures may not perform their isolation function as intended, which may result in problems such as increased leakage currents, etc. Furthermore, since the erosion of the STI structures is not uniform across a die or a wafer, such structures may have differing heights, which can lead to problems in subsequent processing operations. For example, such height differences may lead to uneven surfaces on subsequently deposited layers of material, which may require additional polishing time in an attempt to planarize the surface of such layers. Such additional polishing may lead to the formation of additional particle defects, which may reduce device yields.
The present disclosure is directed to various methods of forming isolation structures that may eliminate or at least reduce one or more of the problems identified above.
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an exhaustive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.
Generally, the present disclosure is directed to various methods of forming isolation structures, such as trench isolation structures, for semiconductor devices. In one example, the method includes forming a trench in a semiconducting substrate, forming a lower isolation structure comprised of an insulating material in at least the trench, wherein the lower isolation structure has an upper surface that is below an upper surface of the substrate, and forming an upper isolation structure above the lower isolation structure, wherein a portion of the upper isolation structure is positioned within the trench. In some embodiments, the insulating material may be a spin-on glass material or a flowable oxide material.
Another illustrative method disclosed herein includes the steps of forming a trench in a semiconducting substrate, performing a spin-coating process to position either a spin-on glass material or a flowable oxide material in the trench, after performing the spin-coating process, performing at least one heating process to at least partially cure the spin-on glass material or the flowable oxide material and thereby define a lower isolation structure in the trench, wherein the lower isolation structure has an upper surface that is below an upper surface of the substrate, and forming an upper isolation structure above the lower isolation structure, wherein a portion of the upper isolation structure is positioned within the trench.
An illustrative device disclosed herein includes a trench formed in a semiconducting substrate, a lower isolation structure comprised of a spin-on glass material or a flowable oxide material positioned in the trench, wherein the lower isolation structure has an upper surface that is below an upper surface of the substrate, and an upper isolation structure positioned above the lower isolation structure, wherein a portion of the upper isolation structure is positioned within the trench.
The disclosure may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:
While the subject matter disclosed herein is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Various illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
The present subject matter will now be described with reference to the attached figures. Various structures, systems and devices are schematically depicted in the drawings for purposes of explanation only and so as to not obscure the present disclosure with details that are well known to those skilled in the art. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the present disclosure. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.
The present disclosure is directed to various methods of forming isolation structures, such as trench isolation structures, for semiconductor devices using a spin-on glass and/or a flowable oxide material. As will be readily apparent to those skilled in the art upon a complete reading of the present application, the present method is applicable to a variety of devices, including, but not limited to, logic devices, memory devices, etc. With reference to the attached drawings, various illustrative embodiments of the methods and devices disclosed herein will now be described in more detail.
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In the illustrative example depicted herein, the novel STI structure 30 disclosed herein comprises the upper isolation structure 26R and the lower isolation structure 22R made of a spin-on glass material or a flowable oxide material. In one illustrative example, the upper isolation structure 26R has a higher etch resistance to an etchant, such as a dilute HF acid, than does the lower isolation structure 22R. In a more specific example, where the upper isolation structure 26R and the lower isolation structure 22R are comprised of the same material, e.g., silicon dioxide, the upper isolation structure 26R has a higher etch resistance to a dilute HF acid etchant than does the lower isolation structure 22R. Thus, the novel STI structure 30 disclosed herein is better able to resist degradation in subsequent processing operations that are performed on the device 100. That is, the integrity of the STI structure 30 disclosed herein is greater than the integrity of prior art STI structures.
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The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the process steps set forth above may be performed in a different order. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.
